Pin mesh-sdk 05b3e2e1b94f, mesh-contracts ae5266e77639 and mesh-catalog's buildstep 125929dbc459, the group's final heads (issue 1966)

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

.gitignore

@@ -1 +1,4 @@
 vendor/
+# A compiled program never enters a commit (issue 1577): `go build .` in a command directory leaves one there.
+modules/*/cmd/*/mesh-*
+!modules/*/cmd/*/mesh-*.go

merge-check.sh

@@ -1,74 +0,0 @@
-#!/bin/sh
-# mesh-check-toolchain: go
-#
-# This repository's own check, mesh/repo-check (novox/hq ADR 0238 §4), written with its first commit (ADR 0428 §4):
-# every Go module in the tree is vetted, its unit tests run, and then its integration tests (-tags integration).
-# A tree with no Go module has nothing to test, and the check says so and passes.
-#
-# No module commits its dependencies (no vendor directory: .gitignore). A module's dependencies are fetched, or a
-# requirement of the mesh's own forge (the pinned mesh-sdk commit) is taken from its repository's clone beside the check
-# (MESH_CHECK_BESIDE), through a go.mod of its own (-modfile), by mesh-catalog's helper checks/deps, built from the
-# clone of mesh-catalog beside this check and not copied here: the build seat forgets the forge credential before the
-# check runs, so a commit the seat's module cache does not hold cannot be fetched from the forge (novox/hq issue 385). A
-# module whose dependencies cannot be had **fails the check**, by name and why: its tests could not run, and a test that
-# could not run is a failure, never a note. Run by hand, without MESH_CHECK_BESIDE, the dependencies are fetched.
-set -eu
-cd "$(dirname "$0")"
-
-# The toolchain the check runs in sets -mod=vendor; there is no vendor directory, so the modules are used as they are.
-GOFLAGS="$(printf '%s' "${GOFLAGS:-}" | sed 's/-mod=[a-z]*//g') -mod=mod"
-export GOFLAGS
-export GOPRIVATE=git.novox.be
-
-modules=$(find . -name go.mod -not -path '*/vendor/*' -not -path './.git/*' | sort)
-if [ -z "$modules" ]; then
-  echo "This tree holds no Go module, so there are no tests to run; the check passes."
-  exit 0
-fi
-
-work=$(mktemp -d)
-trap 'rm -rf "$work"' EXIT
-deps=""
-helper="${MESH_CHECK_BESIDE:-}/mesh-catalog/checks/deps"
-if [ -n "${MESH_CHECK_BESIDE:-}" ] && [ -f "$helper/main.go" ]; then
-  if ! (cd "$helper" && go build -o "$work/deps" .); then
-    echo "FAILED: the dependency helper of mesh-catalog beside this check could not be built"
-    exit 1
-  fi
-  deps="$work/deps"
-elif [ -n "${MESH_CHECK_BESIDE:-}" ]; then
-  echo "NOT TAKEN FROM BESIDE: no mesh-catalog/checks/deps beside this check ($MESH_CHECK_BESIDE); the dependencies are fetched"
-fi
-
-untestable=""
-for mod in $modules; do
-  dir=$(dirname "$mod")
-  modfile=""
-  if [ -n "$deps" ]; then
-    if ! modfile=$("$deps" -beside "$MESH_CHECK_BESIDE" -work "$work" "$dir"); then
-      echo "FAILED: $dir could not be tested: $modfile"
-      untestable="$untestable $dir"
-      continue
-    fi
-    [ -n "$modfile" ] && echo "$dir takes its forge dependencies from the clones beside the check"
-  elif ! fetched=$(cd "$dir" && go mod download 2>&1); then
-    echo "FAILED: $dir could not be tested: its dependencies cannot be fetched: $(printf '%s\n' "$fetched" | tail -n 1)"
-    untestable="$untestable $dir"
-    continue
-  fi
-  mf=""
-  [ -n "$modfile" ] && mf="-modfile=$modfile"
-  unformatted=$(cd "$dir" && gofmt -l .)
-  if [ -n "$unformatted" ]; then
-    echo "$dir is not gofmt'd: $unformatted"
-    exit 1
-  fi
-  echo "== $dir: go vet and the unit tests"
-  (cd "$dir" && go vet $mf ./... && go test $mf ./...)
-  echo "== $dir: the integration tests (-tags integration)"
-  (cd "$dir" && go vet $mf -tags integration ./... && go test $mf -tags integration ./...)
-done
-if [ -n "$untestable" ]; then
-  echo "the check fails: the tests of$untestable could not run (novox/hq issue 385)"
-  exit 1
-fi

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/composed.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"sort"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// Every node's published compositions, read only to compare (novox/hq ADR 0593 §8): each node's engine writes its own
+// `composed-<node>` (delivery.ComposedRead, one bucket per node), and `mesh-wants.upgrade` with compare names, for every
+// node, the composition its own have runs beside the newest it published of each module and of the node, so a person sees
+// where they part. The assigner composes nothing and never writes these.
+
+// publishedRow is one composition a node published: the module ("node" for its own), the fingerprint, the digest, or why
+// it was refused or cannot be read.
+type publishedRow struct {
+	Key     string `json:"key"`
+	Module  string `json:"module"`
+	FP      string `json:"fp,omitempty"`
+	Digest  string `json:"digest,omitempty"`
+	Refused string `json:"refused,omitempty"`
+	Unread  string `json:"unread,omitempty"`
+}
+
+// published is, by node, every composition it published, sorted by key, from every key of the per-node state (a key
+// names its node first): each value decoded and digested here, as the node-engine digests it (delivery.ComposedDigestOf).
+// A value or key that does not read is named with why, never left out.
+func published(values map[string][]byte) map[string][]publishedRow {
+	byNode := map[string]map[string][]byte{}
+	for key, raw := range values {
+		node, _, _ := strings.Cut(key, ".")
+		if byNode[node] == nil {
+			byNode[node] = map[string][]byte{}
+		}
+		byNode[node][key] = raw
+	}
+	out := map[string][]publishedRow{}
+	for node, keys := range byNode {
+		var rows []publishedRow
+		for key, raw := range keys {
+			row := publishedRow{Key: key}
+			_, module, fp, isNode, err := delivery.ParseComposedKey(key)
+			switch {
+			case err != nil:
+				row.Unread = err.Error()
+			case isNode:
+				row.Module = "node"
+			default:
+				row.Module, row.FP = module, fp
+			}
+			if err == nil {
+				c, derr := delivery.DecodeComposed(raw)
+				switch {
+				case derr != nil:
+					row.Unread = derr.Error()
+				case c.Refused != "":
+					row.Refused = c.Refused
+				default:
+					if d, err := delivery.ComposedDigestOf(c); err != nil {
+						row.Unread = err.Error()
+					} else {
+						row.Digest = d
+					}
+				}
+			}
+			rows = append(rows, row)
+		}
+		sort.Slice(rows, func(i, j int) bool { return rows[i].Key < rows[j].Key })
+		out[node] = rows
+	}
+	return out
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go

@@ -0,0 +1,555 @@
+// Command mesh-delivery-assigner is delivery's assigner (novox/hq ADR 0429 §1 and §6, ADR 0446, ADR 0528, issue 1297): a
+// process on its own bus credential that watches what the indexer, the builder, the controller, the node-engines and
+// the watchman write, and writes what each node should run (`want.<node>.<module>`, by the six rules), the
+// fingerprints it holds, every difference between a want and what the controller sends, and the composition check's
+// verdict of each group the checker judges. In release 5 the wants are only compared: the controller still sends what
+// each node runs (ADR 0429 §7). It holds no timer: every pass is started by a change it watched.
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"os/signal"
+	"slices"
+	"syscall"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	oc "git.novox.be/novox/mesh-contracts/go/seats/operatorchannel"
+	"git.novox.be/novox/mesh-sdk/go/announce"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+	"git.novox.be/novox/mesh-sdk/go/process"
+	"git.novox.be/novox/mesh-sdk/go/provisions"
+
+	"git.novox.be/novox/mesh-delivery/sdk/enginereads"
+	"git.novox.be/novox/mesh-sdk/go/views"
+
+	"mesh-delivery-assigner/internal/assign"
+)
+
+func main() {
+	if os.Getenv(process.BrokerFileEnv) == "" {
+		// Started by the tool runner, with no credential of its own: the put's tools (ADR 0546), served through the runtime,
+		// since a process never serves (ADR 0436). The process the manifest runs names its credential.
+		if err := serveTools(); err != nil {
+			fmt.Fprintln(os.Stderr, "mesh-delivery-assigner:", err)
+			os.Exit(1)
+		}
+		return
+	}
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+	if err := run(ctx, os.Getenv, os.Stderr); err != nil {
+		fmt.Fprintln(os.Stderr, "mesh-delivery-assigner:", err)
+		os.Exit(1)
+	}
+}
+
+// readBuckets are the buckets of other parts the assigner reads, each named in its manifest's reads (the manifest test
+// holds the two lists equal), so the controller's broker grants exactly these.
+var readBuckets = []string{
+	delivery.PartGrantsBucket,
+	delivery.AnswersBucket,
+	delivery.BuilderBuildsBucket,
+	delivery.PresenceBucket,
+	delivery.HaveBucket,
+	provisions.ProvisionsBucket,
+	delivery.SourceBucket,
+	delivery.MergesBucket,
+}
+
+// readFamilies are the states kept one bucket per node the assigner reads, each named in its manifest's reads: every
+// node's compositions, which mesh-wants.upgrade compares (novox/hq ADR 0593 §8).
+var readFamilies = []string{delivery.ComposedRead}
+
+// ownBuckets are the assigner's own states, as its manifest declares them: the seat mesh-placement's three among them
+// (ADR 0567 §1), named after the assigner as every module state is.
+var ownBuckets = []string{delivery.AssignerAsksBucket, delivery.AssignerDifferencesBucket,
+	delivery.AssignerPutsBucket, delivery.AssignerWantsBucket, delivery.PlacementBucket, delivery.PlacementProposalsBucket,
+	delivery.PlacementCandidatesBucket, delivery.PlacementPulsesBucket, assign.FindingsBucket, assign.PoliciesBucket, delivery.SeatHoldersBucket,
+	engineReadsBucket}
+
+// engineReadsState is the assigner's state of what each node's engine states it reads (ADR 0618 §3), one key `<node>`, as
+// the verb manifest-reads last answered it or the fallback read it: what assigner_engine_reads lists and asks again.
+const engineReadsState = "engine-reads"
+
+// engineReadsBucket is that state's bucket.
+const engineReadsBucket = delivery.AssignerModule + "_" + engineReadsState
+
+// seatBuckets are the seat's states, new with it: until the controller has made them from the manifest and the bus grants
+// them, the assigner starts without them and binds each once the bus says it was created (issue 1790's kind).
+var seatBuckets = []string{delivery.PlacementBucket, delivery.PlacementProposalsBucket, delivery.PlacementCandidatesBucket,
+	delivery.PlacementPulsesBucket}
+
+// keptStates is what the assigner keeps and who may read it (ADR 0495 §2-§3): its wants by the watchman and the view
+// (and the node agent from release 6), its differences by the view, its asks by the view
+// and the teller, its puts by whoever follows one (ADR 0546), and the seat mesh-placement's placement, proposals and
+// candidates by the node agents, the grants part, mesh-config and the view (ADR 0567 §9), and its placement by
+// the builder, the checker and the indexer, through mesh-sdk's toolchain gate (issue 774, ADR 0549 §3).
+var keptStates = []announce.State{
+	{Name: delivery.PlacementState, Readable: true},
+	{Name: delivery.PlacementProposalsState, Readable: true},
+	{Name: delivery.PlacementCandidatesState, Readable: true},
+	{Name: delivery.PlacementPulsesState, Readable: true},
+	{Name: "asks", Readable: true},
+	{Name: "differences", Readable: true},
+	{Name: "puts", Readable: true},
+	{Name: "wants", Readable: true},
+	{Name: health.FindingsState, Readable: true},
+	{Name: delivery.AssignerPoliciesState, Readable: true},
+	{Name: delivery.SeatHoldersState, Readable: true},
+	{Name: views.MarksState, Readable: true},  // what its views family said each state up to (views.go)
+	{Name: views.StatusState, Readable: true}, // its first views of the indexer's states (views.go)
+	{Name: engineReadsState, Readable: true},
+}
+
+// buckets is every bucket the assigner opened, by name.
+type buckets map[string]jetstream.KeyValue
+
+// open opens every bucket the assigner reads and writes; a bucket it cannot open stops the start, named with its grant (issue 1945),
+// since a pass without it would write wants from half the mesh. The puts' bucket is the exception: whatever keeps it from opening (it
+// does not exist yet, the credential is not granted it yet, the bus does not answer in time), the assigner writes wants
+// without it and takes no put further until it starts again (ADR 0546).
+func open(ctx context.Context, js process.BucketOpener, logf func(string, ...any)) (buckets, error) {
+	out := buckets{}
+	for _, name := range append(append([]string{}, readBuckets...), ownBuckets...) {
+		kv, err := js.KeyValue(ctx, name)
+		if name == delivery.AssignerPutsBucket && err != nil {
+			logf("the bucket %s cannot be opened (%v): no put is taken further until the assigner starts again", name, err)
+			continue
+		}
+		if slices.Contains(seatBuckets, name) && err != nil {
+			// The seat's states come in the same delivery as this assigner (ADR 0567 §1): without placement no module is placed.
+			logf("the bucket %s cannot be opened (%v): it is bound once the bus says it was made", name, err)
+			continue
+		}
+		if name == delivery.SeatHoldersBucket && err != nil {
+			// The seat's state, new with ADR 0571 §4: bound once the bus says it was made; until then nobody is told who
+			// holds which seat here, and the controller's seats still answer.
+			logf("the bucket %s cannot be opened (%v): it is bound once the bus says it was made", name, err)
+			continue
+		}
+		if name == provisions.ProvisionsBucket && err != nil {
+			// The seat mesh-provisioner's state, with its own delivery (ADR 0570 §4): bound once the bus says it was made;
+			// until then no want waits for a provision, as before.
+			logf("the bucket %s cannot be opened (%v): it is bound once the bus says it was made", name, err)
+			continue
+		}
+		if name == assign.PoliciesBucket && err != nil {
+			// The seat mesh-wants' state, new with it (ADR 0565 §7): bound once the bus says it was made; until then no
+			// person's policy is read, so the controller's beside each composition holds, as before.
+			logf("the bucket %s cannot be opened (%v): it is bound once the bus says it was made", name, err)
+			continue
+		}
+		if name == assign.FindingsBucket && err != nil {
+			// New with health leaving the controller (issue 1952 WM6): without it the conditions are said straight to the
+			// router and kept as no finding.
+			logf("the bucket %s cannot be opened (%v): the assigner's conditions are said straight to the router until it starts again", name, err)
+			continue
+		}
+		if (name == delivery.SourceBucket || name == delivery.MergesBucket) && err != nil {
+			// The gate's source and merges (ADR 0601 §1): without them no release is known to carry a build, so every move of
+			// a record module is asked of a person, as before.
+			logf("the bucket %s cannot be opened (%v): no release's Approve answers a record ask until it is bound", name, err)
+			continue
+		}
+		if name == engineReadsBucket && err != nil {
+			// New with ADR 0618 §3: without it the statements the verb answers are kept in memory only, and
+			// assigner_engine_reads lists nothing.
+			logf("the bucket %s cannot be opened (%v): what each node's engine reads is kept in memory only until it starts again", name, err)
+			continue
+		}
+		if name == delivery.PartGrantsBucket && err != nil {
+			// The grants part's grants (ADR 0571 clause 9): without them no module counts as granted until it is bound.
+			logf("the bucket %s cannot be opened (%v): no grant is read until it is bound once the bus says it was made", name, err)
+			continue
+		}
+		if err != nil {
+			return nil, process.EssentialErr("assigner", name, "write a want from the whole mesh", err)
+		}
+		out[name] = kv
+	}
+	return out, nil
+}
+
+// startsWithout says the assigner starts without the bucket when it cannot be opened (open says why for each): the seat's
+// states and those new with a delivery of their own, bound once made, and the two that choose the grants' source.
+func startsWithout(name string) bool {
+	switch name {
+	case delivery.SeatHoldersBucket, provisions.ProvisionsBucket, assign.PoliciesBucket, assign.FindingsBucket,
+		delivery.AssignerPutsBucket, delivery.SourceBucket, delivery.MergesBucket, engineReadsBucket:
+		return true
+	}
+	return slices.Contains(seatBuckets, name) || name == delivery.PartGrantsBucket
+}
+
+// run is the program: it returns when ctx ends or the bus cannot be used.
+func run(ctx context.Context, getenv func(string) string, logOut io.Writer) error {
+	logger := log.New(logOut, "mesh-delivery-assigner: ", log.LstdFlags)
+	account, err := process.ReadBrokerAccount(getenv)
+	if err != nil {
+		return err
+	}
+	conn, js, err := account.Dial()
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+	kvs, err := open(ctx, js, logger.Printf)
+	if err != nil {
+		return err
+	}
+	// What the assigner keeps, said on the bus (ADR 0495 §2-§3): a reader is granted from it. Not fatal when it cannot
+	// be said now: process.Conn says it again at every reconnect.
+	said, err := process.Connect(account, nats.Name(account.Node+"."+account.Module+".keeps"), nats.RetryOnFailedConnect(true))
+	if err != nil {
+		return err
+	}
+	defer said.Close()
+	if err := said.Keeps(keptStates...); err != nil {
+		logger.Printf("what the assigner keeps could not be said on the bus, so its readers are not granted until it is: %v", err)
+	}
+	thisNode = account.Node
+	logger.Printf("started on the account %s, reading %d buckets", account.User, len(kvs))
+	findings := findingsOf(ctx, kvs, logger.Printf)
+	// Each change of the states its readers read is said on its views family (ADR 0615 §5, ADR 0619 §2); a watch of it
+	// that ends stops the program, as a watch of what a pass reads does.
+	viewErrs := make(chan error, len(viewedStates))
+	startViews(ctx, js, conn, account, kvs, findings, viewErrs, logger.Printf)
+	go func() {
+		select {
+		case <-ctx.Done():
+		case err := <-viewErrs:
+			logger.Printf("%v: the assigner stops, and is started again", err)
+			conn.Close()
+		}
+	}()
+	iv := &indexerViews{js: js, account: account, call: said.Call, findings: findings, logf: logger.Printf,
+		status: process.AwaitBucket(ctx, js, conn, firstViewsBucket, "assigner_first_views reads nothing and assigner_first_view_again is not heard", logger.Printf)}
+	return follow(ctx, js, conn, kvs, findings.Say(sayVia(ctx, js)), findings, emitting{said}, iv, logger)
+}
+
+// findingsOf is where the assigner's said conditions go as findings (issue 1952 WM6): its findings bucket, which the
+// condition keeper carries (novox/hq ADR 0590 §3). Without it the conditions are said straight to the router.
+func findingsOf(ctx context.Context, kvs buckets, logf func(string, ...any)) assign.Findings {
+	var f assign.Findings
+	if kv := kvs[assign.FindingsBucket]; kv != nil {
+		f.Put = func(key string, value []byte) error { _, err := kv.Put(ctx, key, value); return err }
+		f.Delete = func(key string) error { return kv.Delete(ctx, key) }
+		f.Keys = func() ([]string, error) {
+			keys, err := kv.Keys(ctx)
+			if errors.Is(err, jetstream.ErrNoKeysFound) {
+				return nil, nil
+			}
+			return keys, err
+		}
+	}
+	return f
+}
+
+// thisNode is the node this process runs on, as its credential names it: said with each of the seat's events.
+var thisNode string
+
+// emitting is the process connection as the puts' caller: its calls, and its events with no options.
+type emitting struct{ *process.Conn }
+
+func (e emitting) Emit(eventType string, body any) error { return e.Conn.Emit(eventType, body) }
+
+// watched are the buckets whose every value a pass reads; the manifests are read by digest when a pass needs one, and
+// watched only for keys, so a manifest that arrives wakes a composition that waits for it.
+var watched = []string{
+	delivery.PartGrantsBucket,
+	delivery.AnswersBucket,
+	delivery.BuilderBuildsBucket,
+	delivery.PlacementBucket,
+	delivery.PlacementProposalsBucket,
+	delivery.PlacementCandidatesBucket,
+	delivery.PlacementPulsesBucket,
+	delivery.PresenceBucket,
+	delivery.HaveBucket,
+	delivery.AssignerAsksBucket,
+	delivery.AssignerDifferencesBucket,
+	delivery.AssignerWantsBucket,
+	assign.PoliciesBucket,
+	provisions.ProvisionsBucket,
+	delivery.SeatHoldersBucket,
+	delivery.SourceBucket,
+	delivery.MergesBucket,
+	engineReadsBucket,
+}
+
+// follow watches every bucket a pass reads and makes a pass at start, once every watch handed what stands, and after
+// each change; changes that come during a pass make one more. It returns when ctx ends or a watch ends.
+func follow(ctx context.Context, js jetstream.JetStream, nc process.Subscriber, kvs buckets, say func(oc.Condition) error, findings assign.Findings, bus caller, iv *indexerViews, logger *log.Logger) error {
+	w := newWorld()
+	dirty := make(chan struct{}, 1)
+	wake := func() {
+		select {
+		case dirty <- struct{}{}:
+		default:
+		}
+	}
+	errs := make(chan error, len(watched)+2)
+	settled := make(chan struct{}, len(watched)+2)
+	// What each node's engine reads (ADR 0618 §3, §4): asked through the seat's verb, kept in the state engine-reads, read
+	// from the node's record where the engine does not answer (the fallback, said in the journal).
+	reads := &enginereads.Keeper{Fallback: w.recordReads, Changed: wake, Logf: logger.Printf}
+	if bus != nil {
+		reads.Call = bus.CallOn
+	}
+	if kv := kvs[engineReadsBucket]; kv != nil {
+		reads.Put = func(node string, v []byte) error { _, err := kv.Put(ctx, node, v); return err }
+		reads.Delete = func(node string) error { return kv.Delete(ctx, node) }
+	}
+	watch := func(name string, opts ...jetstream.WatchOpt) error {
+		kw, err := kvs[name].WatchAll(ctx, opts...)
+		if err != nil {
+			return fmt.Errorf("the bucket %s cannot be watched: %w", name, err)
+		}
+		// The puts' watch never stops the wants (ADR 0546): when it ends, the puts are no longer heard, said in the journal.
+		optional := name == delivery.AssignerPutsBucket
+		go func() {
+			defer kw.Stop()
+			for {
+				select {
+				case <-ctx.Done():
+					errs <- nil
+					return
+				case e, ok := <-kw.Updates():
+					if !ok {
+						if optional {
+							logger.Printf("the watch of %s ended: no put is taken further until the assigner starts again", name)
+							return
+						}
+						errs <- fmt.Errorf("the watch of %s ended", name)
+						return
+					}
+					if e == nil {
+						if !optional { // the puts never gate the first pass, so never the wants (ADR 0546)
+							settled <- struct{}{}
+						}
+						continue
+					}
+					var value []byte
+					if e.Operation() == jetstream.KeyValuePut {
+						value = e.Value()
+					}
+					if name == engineReadsBucket {
+						reads.Heard(e.Key(), value, value == nil) // it wakes a pass when a statement changed
+						continue
+					}
+					w.putEntry(name, e.Key(), value, e.Revision(), e.Created())
+					wake()
+				}
+			}
+		}()
+		return nil
+	}
+	// The puts' watch is not waited for before the first pass: a watch of them that ends before it handed what stands only
+	// stops the puts, never the wants.
+	if kvs[delivery.AssignerPutsBucket] != nil {
+		if err := watch(delivery.AssignerPutsBucket); err != nil {
+			logger.Printf("%v: no put is taken further until it is opened again", err)
+			delete(kvs, delivery.AssignerPutsBucket)
+		}
+	}
+	// The puts' bucket is made by the controller from the manifest's states at its start (ADR 0201), and the assigner's
+	// credential reads it once the bus's user list carries the grant: neither waits for the assigner. So while it is not open,
+	// a pass started by a change opens it again, at most once a minute, and from then on the puts are watched and taken
+	// further, without a restart.
+	var triedPuts time.Time
+	reopenPuts := func(p *passer) {
+		if kvs[delivery.AssignerPutsBucket] != nil || time.Since(triedPuts) < PutsReopenEvery {
+			return
+		}
+		triedPuts = time.Now()
+		kv, err := js.KeyValue(ctx, delivery.AssignerPutsBucket)
+		if err != nil {
+			return
+		}
+		kvs[delivery.AssignerPutsBucket] = kv
+		if err := watch(delivery.AssignerPutsBucket); err != nil {
+			logger.Printf("%v: no put is taken further until it is opened again", err)
+			delete(kvs, delivery.AssignerPutsBucket)
+			return
+		}
+		if bus != nil {
+			p.acts = newPutActs(bus, wake, logger.Printf)
+		}
+		logger.Printf("the bucket %s is open: puts are taken further", delivery.AssignerPutsBucket)
+	}
+	started := 0
+	for _, name := range watched {
+		if kvs[name] == nil && startsWithout(name) {
+			continue // not on the bus at this start (open said so)
+		}
+		started++
+		var opts []jetstream.WatchOpt
+		if name == delivery.HaveBucket || name == delivery.SourceBucket {
+			// what each node ran healthy before, for a set-back; and the release behind each source revision (ADR 0601 §1)
+			opts = append(opts, jetstream.IncludeHistory())
+		}
+		if err := watch(name, opts...); err != nil {
+			return err
+		}
+	}
+	// The indexer's manifests, modules and module graph, through its first views and views family, never its buckets
+	// (DLV-F2r, ADR 0631): the first pass waits for the three answers, as it waits for every watch to hand what stands.
+	if iv != nil {
+		started += iv.start(ctx, w, wake, settled)
+	}
+	// The seat's states arrive with the same delivery as this assigner (ADR 0567 §1): one not on the bus at this start is
+	// bound once the bus says it was created, and watched from then on, with no restart (issue 1790's kind). Until then no
+	// module is placed.
+	type appeared struct {
+		name string
+		kv   jetstream.KeyValue
+	}
+	placementAppeared := make(chan appeared, len(seatBuckets)+2)
+	for _, name := range seatBuckets {
+		if kvs[name] == nil && js != nil {
+			process.AwaitBucket(ctx, js, nc, name, "the seat mesh-placement waits for it",
+				logger.Printf).Ready(func(kv jetstream.KeyValue) { placementAppeared <- appeared{name, kv} })
+		}
+	}
+	// And the two that choose where grants are read from, with the same delivery as the grants part that writes one.
+	for _, name := range []string{delivery.PartGrantsBucket, assign.PoliciesBucket, provisions.ProvisionsBucket, delivery.SeatHoldersBucket} {
+		if kvs[name] == nil && js != nil {
+			name := name
+			process.AwaitBucket(ctx, js, nc, name, "until then the bucket is not read",
+				logger.Printf).Ready(func(kv jetstream.KeyValue) { placementAppeared <- appeared{name, kv} })
+		}
+	}
+	takePlacement := func(a appeared) error {
+		if kvs[a.name] != nil {
+			return nil // bound already, by the other of its two events
+		}
+		kvs[a.name] = a.kv
+		logger.Printf("the bucket %s is open and watched", a.name)
+		return watch(a.name)
+	}
+	for range started {
+		select {
+		case <-ctx.Done():
+			return nil
+		case err := <-errs:
+			return err
+		case <-settled:
+		}
+	}
+	p := &passer{kvs: kvs, w: w, logf: logger.Printf, say: say, findings: findings, said: map[string]bool{}, answeredAt: map[string]uint64{},
+		reads: reads}
+	// The node-engine seat's manifest-reads-changed, for one node (ADR 0618 §4): that node is asked again, with no timer.
+	// Heard on the assigner's durable consumer on EVENTS, which the grants part makes from the manifest's consumes; where it
+	// is not there yet, a node is asked again only when it comes back online.
+	if js != nil {
+		hearReadsChanged(ctx, js, reads, findings, logger.Printf)
+	}
+	if bus != nil && kvs[delivery.AssignerPutsBucket] != nil {
+		p.acts = newPutActs(bus, wake, logger.Printf)
+	}
+	if bus != nil {
+		p.seat = newSeatActs(bus, wake, logger.Printf)
+	}
+	if js != nil {
+		p.publish = streamPublisher(ctx, js, thisNode)
+	}
+	wake()
+	for {
+		select {
+		case <-ctx.Done():
+			return nil
+		case err := <-errs:
+			return err
+		case <-settled:
+		case kv := <-placementAppeared:
+			if err := takePlacement(kv); err != nil {
+				return err
+			}
+		case <-dirty:
+			reopenPuts(p)
+			// The grants part makes the seat's buckets in the pass that seals the list granting them, so their creation can
+			// be said before this credential may hear it: every pass, itself started by a watched change, binds each one the
+			// bus now holds, and says the seat waits while one is missing.
+			var unbound []string
+			for _, name := range seatBuckets {
+				if kvs[name] != nil || js == nil {
+					continue
+				}
+				if kv, err := js.KeyValue(ctx, name); err == nil {
+					if err := takePlacement(appeared{name, kv}); err != nil {
+						return err
+					}
+					continue
+				}
+				unbound = append(unbound, name)
+			}
+			p.sayWaits(unbound)
+			p.pass(ctx)
+		}
+	}
+}
+
+// PutsReopenEvery is how often, at most, a pass opens the puts' bucket again while it is not open.
+var PutsReopenEvery = time.Minute
+
+// sayVia publishes a condition on the operator-channel seat's one subject for conditions, under the assigner's own name
+// (ADR 0437 clause 9).
+func sayVia(ctx context.Context, js jetstream.JetStream) func(oc.Condition) error {
+	return func(c oc.Condition) error {
+		subject, err := occ.ConditionSubject(delivery.AssignerModule)
+		if err != nil {
+			return err
+		}
+		data, err := occ.EncodeCondition(c)
+		if err != nil {
+			return err
+		}
+		_, err = js.Publish(ctx, subject, data)
+		return err
+	}
+}
+
+// hearReadsChanged hears the node-engine seat's event manifest-reads-changed on the assigner's durable consumer on EVENTS,
+// and asks the node it names again. Any other event the consumer hands is acknowledged and left.
+func hearReadsChanged(ctx context.Context, js jetstream.JetStream, reads *enginereads.Keeper, findings assign.Findings, logf func(string, ...any)) {
+	account := process.Account{Node: thisNode, Module: delivery.AssignerModule}
+	w := notHeardWriter(findings, logf)
+	cons, err := account.EventConsumer(ctx, js, process.EventsStream)
+	if err != nil {
+		w.NotHeard(process.EventsStream, enginereads.Event+" is not heard until the assigner starts again (a node is asked again when it comes back online)",
+			fmt.Errorf("the consumer %s on %s does not exist yet: %w", account.EventConsumerName(), process.EventsStream, err))
+		return
+	}
+	cc, err := process.HearEvents(cons, func(m jetstream.Msg) {
+		if err := m.Ack(); err != nil {
+			logf("acknowledging %s: %v", m.Subject(), err)
+		}
+		node, ours, err := enginereads.NodeOf(m.Subject(), m.Data())
+		switch {
+		case !ours:
+		case err != nil:
+			logf("%s holds what is not %s, and %s is asked again all the same: %v", m.Subject(), enginereads.Event, node, err)
+			reads.AskNode(node, enginereads.Event+" that does not read")
+		default:
+			reads.AskNode(node, enginereads.Event)
+		}
+	}, logf)
+	if err != nil {
+		w.NotHeard(process.EventsStream, enginereads.Event+" is not heard until the assigner starts again", err)
+		return
+	}
+	w.Heard(process.EventsStream)
+	go func() {
+		<-ctx.Done()
+		cc.Stop()
+	}()
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main_test.go

@@ -0,0 +1,191 @@
+package main
+
+import (
+	"mesh-delivery-assigner/internal/assign"
+
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+	"reflect"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	oc "git.novox.be/novox/mesh-contracts/go/seats/operatorchannel"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/process"
+)
+
+// 1297/B2a: the buckets the program opens are exactly the manifest's reads and states, as the broker names them
+// (`<module>.<state>` read as the bucket `<module>_<state>`), so it is granted what it reads and reads nothing else.
+func TestOpensWhatItsManifestNames(t *testing.T) {
+	// Review round 2: the assigner's views emitter writes its finding view-unsaid (Emitter.Findings set) when it keeps findings.
+	findings := assign.Findings{Put: func(string, []byte) error { return nil }, Delete: func(string) error { return nil }}
+	if viewsEmitter(nil, process.Account{}, nil, findings, nil, t.Logf).Findings == nil {
+		t.Error("the assigner's views emitter writes no view-unsaid finding")
+	}
+	// 1297/B2a: without a credential the program does not start, and says why.
+	if err := run(context.Background(), func(string) string { return "" }, io.Discard); err == nil || !strings.Contains(err.Error(), "MESH_BROKER_FILE") {
+		t.Errorf("run without a credential = %v", err)
+	}
+	raw, err := os.ReadFile(filepath.Join("..", "..", "module.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	m, err := catalogue.Decode(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var reads []string
+	for _, r := range m.Reads {
+		if slices.Contains(readFamilies, r) {
+			continue // a state kept one bucket per node, read by its prefix (ADR 0593 §6), not one bucket
+		}
+		reads = append(reads, strings.Replace(r, ".", "_", 1))
+	}
+	for _, l := range readFamilies {
+		if !slices.Contains(m.Reads, l) {
+			t.Errorf("the program reads the per-node state %s, the manifest does not name it", l)
+		}
+	}
+	var states []string
+	for _, s := range m.State {
+		states = append(states, m.Module+"_"+s.Name)
+	}
+	for _, pair := range []struct {
+		what       string
+		code, want []string
+	}{{"reads", readBuckets, reads}, {"states", append(slices.Clone(ownBuckets), marksBucket, firstViewsBucket), states}} { // the marks are bound by the views family (views.go)
+		got, want := slices.Sorted(slices.Values(pair.code)), slices.Sorted(slices.Values(pair.want))
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("the program's %s are %v, the manifest's %v", pair.what, got, want)
+		}
+	}
+	var kept []string
+	for _, s := range keptStates {
+		kept = append(kept, m.Module+"_"+s.Name)
+	}
+	if got, want := slices.Sorted(slices.Values(kept)), slices.Sorted(slices.Values(append(slices.Clone(ownBuckets), marksBucket, firstViewsBucket))); !reflect.DeepEqual(got, want) {
+		t.Errorf("the program announces %v, keeps %v", got, want)
+	}
+	// ADR 0546: whatever keeps the puts' bucket from opening (not there, not granted, no answer in time), the assigner opens
+	// the rest and starts, writing wants; any other bucket it cannot open stops the start, named.
+	for _, c := range []struct {
+		missing string
+		err     error
+		starts  bool
+		said    string
+	}{
+		{delivery.AssignerPutsBucket, jetstream.ErrBucketNotFound, true, "no put is taken further"},
+		{delivery.AssignerPutsBucket, errors.New("nats: permissions violation for subscription to \"$JS.API.STREAM.INFO.KV_mesh-delivery-assigner_puts\""), true, "no put is taken further"},
+		{delivery.AssignerPutsBucket, context.DeadlineExceeded, true, "no put is taken further"},
+		{delivery.AssignerWantsBucket, errors.New("nats: permissions violation"), false, ""},
+		// Issue 774: the grants part's grants not there do not stop the start.
+		{delivery.PartGrantsBucket, jetstream.ErrBucketNotFound, true, "no grant is read"},
+	} {
+		var logged string
+		kvs, err := open(context.Background(), refusingJS{missing: c.missing, err: c.err}, func(f string, a ...any) { logged += fmt.Sprintf(f, a...) })
+		switch {
+		case c.starts && (err != nil || kvs[c.missing] != nil || len(kvs) != len(readBuckets)+len(ownBuckets)-1 || !strings.Contains(logged, c.said)):
+			t.Errorf("%s refused with %v: the start answered %v, %d buckets, logged %q", c.missing, c.err, err, len(kvs), logged)
+		case !c.starts && (err == nil || !strings.Contains(err.Error(), "grant of "+c.missing)): // 1945: named with its grant
+			t.Errorf("%s refused with %v: the start answered %v", c.missing, c.err, err)
+		}
+	}
+	// And a watch of the puts that ends before it handed what stands (its subscription closed, its grant withdrawn) does not
+	// keep the first pass from being made: the wants are written all the same.
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	wrote := make(chan string, 8)
+	kvs := buckets{}
+	for _, name := range append(append([]string{}, readBuckets...), ownBuckets...) {
+		kvs[name] = &watchKV{memKV: &memKV{values: map[string][]byte{}}}
+	}
+	placed, err := delivery.PlacementValues(delivery.Placement{Node: "ace"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	for key, raw := range placed {
+		kv := kvs[delivery.PlacementBucket].(*watchKV)
+		kv.entries = append(kv.entries, kvEntry{key: key, value: raw})
+	}
+	kvs[delivery.AssignerPutsBucket].(*watchKV).closed = true
+	kvs[delivery.AssignerWantsBucket].(*watchKV).wrote = wrote
+	go follow(ctx, nil, nil, kvs, func(oc.Condition) error { return nil }, assign.Findings{}, nil, nil, log.New(io.Discard, "", 0))
+	select {
+	case key := <-wrote:
+		if key != "want.ace.node" {
+			t.Errorf("the first pass wrote %s", key)
+		}
+	case <-ctx.Done():
+		t.Error("a puts watch that ended before its first marker kept the first pass from being made: no want was written")
+	}
+}
+
+// refusingJS opens every bucket but one, which it refuses with err.
+type refusingJS struct {
+	jetstream.JetStream
+	missing string
+	err     error
+}
+
+func (r refusingJS) KeyValue(_ context.Context, name string) (jetstream.KeyValue, error) {
+	if name == r.missing {
+		return nil, r.err
+	}
+	return &memKV{values: map[string][]byte{}}, nil
+}
+
+// watchKV is a memKV whose watch hands its entries and then the marker that all stands was handed, or ends at once when
+// closed; a put on it is said on wrote.
+type watchKV struct {
+	*memKV
+	entries []kvEntry
+	closed  bool
+	wrote   chan string
+}
+
+func (w *watchKV) WatchAll(context.Context, ...jetstream.WatchOpt) (jetstream.KeyWatcher, error) {
+	ch := make(chan jetstream.KeyValueEntry, len(w.entries)+1)
+	if w.closed {
+		close(ch)
+		return keyWatcher{ch}, nil
+	}
+	for _, e := range w.entries {
+		ch <- e
+	}
+	ch <- nil
+	return keyWatcher{ch}, nil
+}
+
+func (w *watchKV) Put(ctx context.Context, key string, value []byte) (uint64, error) {
+	if w.wrote != nil {
+		w.wrote <- key
+	}
+	return 1, nil
+}
+
+type keyWatcher struct{ ch chan jetstream.KeyValueEntry }
+
+func (k keyWatcher) Updates() <-chan jetstream.KeyValueEntry { return k.ch }
+func (k keyWatcher) Stop() error                             { return nil }
+
+type kvEntry struct {
+	jetstream.KeyValueEntry
+	key   string
+	value []byte
+}
+
+func (e kvEntry) Key() string                     { return e.key }
+func (e kvEntry) Value() []byte                   { return e.value }
+func (e kvEntry) Operation() jetstream.KeyValueOp { return jetstream.KeyValuePut }
+func (e kvEntry) Revision() uint64                { return 1 }
+func (e kvEntry) Created() time.Time              { return time.Time{} }

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/puts.go

@@ -0,0 +1,456 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/handacts"
+
+	"mesh-delivery-assigner/internal/assign"
+)
+
+// The puts (novox/hq ADR 0546): the tool `assigner_put` writes the key `<node>.<module>` of the assigner's puts, and each pass
+// takes every put that has not ended one step further (assign.StepPut), doing the acts the step asks for: the put's ask, the
+// bus's snapshot, the warranted record. Each act's outcome is heard back as a change of the world (the composition, the grant,
+// the answer) or, for the calls, as a wake once they answer; nothing polls but the snapshot's read-back of the backup holder,
+// as the controller's bus step reads it (ADR 0235), bounded. Every step is said as the event mesh-delivery-assigner.put, so a
+// caller waits on it.
+
+// PutEvent is the event a put's every step is said as: mesh.mod.mesh-delivery-assigner.event.put.
+const PutEvent = "put"
+
+// caller is what the puts need of the bus as the assigner's own process account: a call of a seat's verb, on one node or on
+// the seat held once, and an event said. process.Conn, or a test's.
+type caller interface {
+	Call(key string, body any) (json.RawMessage, error)
+	CallOn(node, key string, body any) (json.RawMessage, error)
+	Emit(eventType string, body any) error
+}
+
+// putActs keeps, by put (its key and when it was asked), what the acts of a put came to while this process runs: a restart
+// takes the snapshot again, without harm.
+type putActs struct {
+	mu        sync.Mutex
+	bus       caller
+	wake      func()
+	logf      func(string, ...any)
+	snapping  map[string]bool
+	snapped   map[string]string
+	snapNo    map[string]string
+	warranted map[string]bool
+	// rec records the put's warrant in the hand-act log (ADR 0565 §11).
+	rec       handacts.Recorder
+	warrantNo map[string]string
+	said      map[string]string
+	// snapshot takes the bus's snapshot on node; a variable so a test takes none.
+	snapshot func(ctx context.Context, node, module string) (string, error)
+}
+
+func newPutActs(bus caller, wake func(), logf func(string, ...any)) *putActs {
+	a := &putActs{rec: handacts.Recorder{Ask: bus.Call}, bus: bus, wake: wake, logf: logf, snapping: map[string]bool{}, snapped: map[string]string{}, snapNo: map[string]string{}, warranted: map[string]bool{}, warrantNo: map[string]string{},
+		said: map[string]string{}}
+	a.snapshot = a.snapshotTheBus
+	return a
+}
+
+// identity names one put: its key and when it was asked, so a put asked again under the key is another.
+func identity(key string, p delivery.Put) string {
+	return key + "@" + p.At.UTC().Format(time.RFC3339Nano)
+}
+
+// putsByModule is every put the assigner holds, by module then node.
+func (p *passer) putsByModule() map[string]map[string]delivery.Put {
+	out := map[string]map[string]delivery.Put{}
+	for key, value := range p.w.read(delivery.AssignerPutsBucket) {
+		node, module, err := delivery.ParsePutKey(key)
+		if err != nil {
+			continue
+		}
+		put, err := delivery.DecodePut(value)
+		if err != nil {
+			p.logf("the put %s cannot be read, and is left: %v", key, err)
+			continue
+		}
+		if out[module] == nil {
+			out[module] = map[string]delivery.Put{}
+		}
+		out[module][node] = put
+	}
+	return out
+}
+
+// puts takes every put that has not ended one step further.
+func (p *passer) puts(ctx context.Context) {
+	if p.acts == nil {
+		return
+	}
+	all := p.putsByModule()
+	if len(all) == 0 {
+		return
+	}
+	assigned := p.w.assigned()
+	trunk := p.w.trunk()
+	get := p.w.getter(delivery.ManifestsBucket) // the indexer's manifests, as its first view and views family say them
+	wanted := p.w.wantsOf()
+	modules := make([]string, 0, len(all))
+	for m := range all {
+		modules = append(modules, m)
+	}
+	sort.Strings(modules)
+	for _, module := range modules {
+		var manifest catalogue.Manifest
+		if mod, ok := trunk[module]; ok && mod.Manifest != "" {
+			if got := p.w.manifest(ctx, get, mod.Manifest); got.err == "" {
+				manifest = got.manifest
+			}
+		}
+		for node, put := range all[module] {
+			if delivery.PutEnded(put.Step) {
+				continue
+			}
+			key, _ := delivery.PutKey(node, module)
+			id := identity(key, put)
+			world := p.putWorld(node, module, put, manifest, assigned[node])
+			world.Snapshot, world.Snapshotting, world.SnapshotFailed = p.acts.state(id)
+			next := assign.StepPut(world)
+			// A held bus whose user list the rules moved on (ADR 0539 §7): the put follows the composition its want names.
+			if w, ok := wanted[module][node]; ok && w.Put && w.FP == next.Put.FP && w.Composed != "" && w.Composed != next.Put.Composed &&
+				(next.Put.Step == delivery.PutWanted || next.Put.Step == delivery.PutHolding) {
+				if d, _ := p.composedFor(node, module, w.FP); d != nil && d.UserListOnly && d.Digest == w.Composed {
+					next.Put = next.Put.Said(world.Now, next.Put.Step, fmt.Sprintf("the bus's user list changed: the want names composition %s", shortHex(w.Composed)))
+					next.Put.Composed = w.Composed
+				}
+			}
+			// The bus's want is written only for the act the operator's yes bound (ADR 0546 clause 8).
+			if next.Put.Step == delivery.PutWanted && put.Step != delivery.PutWanted && world.Bus && next.Put.Ask != "" {
+				if err := p.performs(next.Put.Ask, assign.PutAct(node, module, next.Put.FP, next.Put.Composed)); err != nil {
+					next = assign.PutNext{Put: next.Put.Said(world.Now, delivery.PutRefused, "the bus's want is not written: "+err.Error())}
+				}
+			}
+			if failed := p.acts.warrantFailed(id); failed != "" && (next.Put.Step == delivery.PutWanted || next.Put.Step == delivery.PutHolding) &&
+				!strings.Contains(next.Put.Words, failed) {
+				next.Put = next.Put.Said(world.Now, next.Put.Step, next.Put.Words+"; "+failed)
+			}
+			p.actOn(ctx, node, module, id, world, next)
+			written := samePut(put, next.Put) || p.writePut(ctx, key, put, next.Put)
+			if !written {
+				continue // released or put again meanwhile: nothing is done for the put that no longer stands
+			}
+			if next.Put.Step == delivery.PutWanted && put.Step != delivery.PutWanted {
+				// The want is written in this pass too, before the next one would: Module.Puts writes the same.
+				if wkey, err := delivery.WantKey(node, module); err == nil {
+					want := assign.PutWant(next.Put)
+					if before, ok := wanted[module][node]; !ok || !delivery.SameWant(normalWant(before), normalWant(want)) {
+						p.put(ctx, delivery.AssignerWantsBucket, wkey, func() ([]byte, error) { return delivery.EncodeWant(want) })
+					}
+				}
+				if next.Warranted {
+					p.acts.warrant(id, delivery.AskingID(next.Put.Ask, assign.PutAsking(next.Put)))
+				}
+			}
+		}
+	}
+}
+
+func normalWant(w delivery.Want) delivery.Want {
+	w.V = 0
+	return w
+}
+
+// putWorld is what one step of a put reads from the world.
+func (p *passer) putWorld(node, module string, put delivery.Put, manifest catalogue.Manifest, assignedHere []string) assign.PutWorld {
+	w := assign.PutWorld{Node: node, Module: module, Put: put, Now: p.clock(), Bus: catalogue.ProvidesBus(manifest), Newest: p.w.trunk()[module].FP2}
+	for _, m := range assignedHere {
+		if m == module {
+			w.Assigned = true
+		}
+	}
+	if bkey, err := delivery.BuilderBuildKey(module, put.FP); err == nil {
+		if raw := p.w.value(delivery.BuilderBuildsBucket, bkey); raw != nil {
+			if b, err := delivery.DecodeBuilderBuild(raw); err == nil {
+				w.Build, w.BuildWords = b.State, b.Error
+			} else {
+				w.Build = "unreadable: " + err.Error()
+			}
+		}
+	}
+	w.Composed, w.Granted = p.composedFor(node, module, put.FP)
+	if d := w.Composed; d != nil {
+		policy := d.Policy
+		chosen, _ := assign.DecodePolicies(p.w.read(assign.PoliciesBucket))
+		if c, ok := chosen[module]; ok {
+			policy, _, _, _ = catalogue.Upgrade(manifest, &c) // a person's choice at the assigner (ADR 0565 §7)
+		} else if policy == "" {
+			policy, _, _ = catalogue.DerivedUpgrade(manifest)
+		}
+		w.Recorded = policy == catalogue.PolicyRecord
+		if akey, err := delivery.RecordAskKey(node, module, d.Digest); err == nil && put.Ask == akey {
+			// Only this put's own ask counts: an ask (and its answer) of an earlier put under the same key is another asking.
+			if a, ask, err := assign.DecodeAsk(akey, p.w.value(delivery.AssignerAsksBucket, akey)); err == nil && a.Asking == assign.PutAsking(put) {
+				switch {
+				case p.answeredWith(akey, assign.OptionYes):
+					w.Answer = assign.OptionYes
+				case p.answeredWith(akey, assign.OptionNo):
+					w.Answer = assign.OptionNo
+				default:
+					expires := assign.ExpiresAt(ask)
+					w.AskExpired = !expires.IsZero() && w.Now.After(expires)
+				}
+			}
+		}
+	}
+	if hkey, err := delivery.HaveKey(node, module); err == nil {
+		if raw := p.w.value(delivery.HaveBucket, hkey); raw != nil {
+			if h, err := delivery.DecodeHave(raw); err == nil {
+				w.Have = &h
+			}
+		}
+	}
+	return w
+}
+
+// composedFor is the composition of module for node at fp and whether the grant at fp names the node's accounts: the one
+// place a put reads them (ADR 0546 clause 4). Today their writer is the controller (mesh-controller_composed and
+// mesh-controller_grants); the grants are the grants part's while the controller's lease is handed away (grantsBucket).
+func (p *passer) composedFor(node, module, fp string) (*delivery.ComposedDigest, bool) {
+	var out *delivery.ComposedDigest
+	if d, ok := p.w.composed(node, module, fp); ok {
+		out = &d
+	}
+	granted := false
+	if gkey, err := delivery.PartGrantKey(module, fp); err == nil {
+		if raw := p.w.value(p.w.grantsBucket(), gkey); raw != nil {
+			if g, err := delivery.DecodeGrant(raw); err == nil {
+				granted = g.NamesNode(node, module)
+			}
+		}
+	}
+	return out, granted
+}
+
+// actOn does the acts a step asks for.
+func (p *passer) actOn(ctx context.Context, node, module, id string, w assign.PutWorld, next assign.PutNext) {
+	if next.Put.Step == delivery.PutPerson && next.Put.Ask != "" && w.Composed != nil {
+		// The put's own ask, written again over one an earlier put left under the key (its asking differs), so the teller
+		// raises it anew under its own id.
+		akey := next.Put.Ask
+		current, _, err := assign.DecodeAsk(akey, p.w.value(delivery.AssignerAsksBucket, akey))
+		if err != nil || current.Asking != assign.PutAsking(next.Put) {
+			a, err := assign.PutAsk(akey, node, module, next.Put, *w.Composed, w.Bus, w.Now)
+			if err != nil {
+				p.logf("the ask about putting %s on %s is not written: %v", module, node, err)
+			} else {
+				p.put(ctx, delivery.AssignerAsksBucket, akey, func() ([]byte, error) { return assign.EncodeAsk(akey, a) })
+			}
+		}
+	}
+	if next.Snapshot {
+		p.acts.snap(ctx, id, node, module)
+	}
+}
+
+// performs checks that the act about to be performed is the one the yes of the ask at key bound (occ.Performs).
+func (p *passer) performs(key string, act occ.Act) error {
+	_, ask, err := assign.DecodeAsk(key, p.w.value(delivery.AssignerAsksBucket, key))
+	if err != nil {
+		return fmt.Errorf("the ask %s cannot be read: %w", key, err)
+	}
+	for _, o := range ask.Options {
+		if o.ID == assign.OptionYes {
+			return occ.Performs(o, act)
+		}
+	}
+	return fmt.Errorf("the ask %s offers no yes", key)
+}
+
+// samePut says two puts say the same: their step, words and what they found.
+func samePut(a, b delivery.Put) bool {
+	return a.Step == b.Step && a.Words == b.Words && a.Composed == b.Composed && a.Ask == b.Ask && a.Snapshot == b.Snapshot
+}
+
+// writePut writes a put's next value over the one the pass read, by compare-and-set, unless the tool has put again or
+// released it since; and says it as the event put. It says whether it wrote.
+func (p *passer) writePut(ctx context.Context, key string, read, next delivery.Put) bool {
+	kv := p.kvs[delivery.AssignerPutsBucket]
+	if kv == nil {
+		return false
+	}
+	e, err := kv.Get(ctx, key)
+	if err != nil {
+		p.logf("the put %s cannot be read again, and is taken further at the next pass: %v", key, err)
+		return false
+	}
+	now, err := delivery.DecodePut(e.Value())
+	if err != nil || !now.At.Equal(read.At) || now.Step != read.Step {
+		return false // asked again or released meanwhile: the next pass reads that
+	}
+	data, err := delivery.EncodePut(next)
+	if err != nil {
+		p.logf("the put %s is not written: %v", key, err)
+		return false
+	}
+	if _, err := kv.Update(ctx, key, data, e.Revision()); err != nil {
+		if !errors.Is(err, context.Canceled) {
+			p.logf("the put %s could not be written, and is taken further at the next pass: %v", key, err)
+		}
+		return false
+	}
+	p.w.put(delivery.AssignerPutsBucket, key, data)
+	p.logf("put %s: %s: %s", key, next.Step, next.Words)
+	p.acts.say(key, next)
+	return true
+}
+
+// state is what this process knows of a put's acts.
+func (a *putActs) state(id string) (snapshot string, snapping bool, snapNo string) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	return a.snapped[id], a.snapping[id], a.snapNo[id]
+}
+
+// snap has the bus's snapshot taken once for a put, in the background.
+func (a *putActs) snap(ctx context.Context, id, node, module string) {
+	a.mu.Lock()
+	if a.snapping[id] || a.snapped[id] != "" || a.snapNo[id] != "" {
+		a.mu.Unlock()
+		return
+	}
+	a.snapping[id] = true
+	a.mu.Unlock()
+	go func() {
+		defer a.wake()
+		where, err := a.snapshot(ctx, node, module)
+		a.mu.Lock()
+		defer a.mu.Unlock()
+		a.snapping[id] = false
+		if err != nil {
+			a.snapNo[id] = err.Error()
+			return
+		}
+		a.snapped[id] = where
+	}()
+}
+
+// SnapshotWithin is how long the bus node's backup holder is given to take the bus's snapshot (as the controller's bus step).
+var SnapshotWithin = 15 * time.Minute
+
+// snapshotLook is how often the backup holder's record is read back while the snapshot is taken.
+var snapshotLook = 10 * time.Second
+
+// backedUp is one module as the backup holder's `backed-up` answers it.
+type backedUp struct {
+	Module string `json:"module"`
+	Data   []struct {
+		Item       string     `json:"item"`
+		LastBackup *time.Time `json:"last_backup"`
+		Error      string     `json:"error"`
+	} `json:"data"`
+}
+
+// snapshotTheBus asks the bus node's backup holder to back the bus module up now, whose dump is the streams' snapshot
+// (ADR 0235), and reads its record back until it names a backup newer than the ask: where the snapshot is.
+func (a *putActs) snapshotTheBus(ctx context.Context, node, module string) (string, error) {
+	asked := time.Now()
+	if _, err := a.bus.CallOn(node, "seat:"+catalogue.BackupSeat+".now", map[string]any{"module": module}); err != nil {
+		return "", fmt.Errorf("%s's backup holder was not asked to take the bus's snapshot: %w", node, err)
+	}
+	deadline := asked.Add(SnapshotWithin)
+	for {
+		if raw, err := a.bus.CallOn(node, "seat:"+catalogue.BackupSeat+".backed-up", map[string]any{}); err == nil {
+			var modules []backedUp
+			if json.Unmarshal(raw, &modules) == nil {
+				for _, m := range modules {
+					for _, it := range m.Data {
+						if m.Module == module && it.LastBackup != nil && it.LastBackup.After(asked) && it.Error == "" {
+							return fmt.Sprintf("%s's restore point of %s (%s) taken %s", node, module, it.Item, it.LastBackup.UTC().Format(time.RFC3339)), nil
+						}
+					}
+				}
+			}
+		}
+		if time.Now().After(deadline) {
+			return "", fmt.Errorf("%s's backup holder did not say the bus's snapshot was taken within %s", node, SnapshotWithin)
+		}
+		select {
+		case <-ctx.Done():
+			return "", ctx.Err()
+		case <-time.After(snapshotLook):
+		}
+	}
+}
+
+// warrant records once, in the hand-act log (the seat mesh-hand-acts', or the controller's while that seat has no holder and
+// the controller holds its lease, ADR 0565 §11), that the bus's want was written on the operator's warrant: the router's
+// record of the teller's ask says who chose and how (ADR 0274).
+func (a *putActs) warrant(id, ask string) {
+	a.mu.Lock()
+	if a.warranted[id] {
+		a.mu.Unlock()
+		return
+	}
+	a.warranted[id] = true
+	a.mu.Unlock()
+	go func() {
+		if _, err := a.rec.RecordWarrant(delivery.TellerModule, ask); err != nil {
+			a.logf("the put's warrant %s is not recorded in the hand-act log: %v", ask, err)
+			a.mu.Lock()
+			a.warrantNo[id] = fmt.Sprintf("the warrant %s is not recorded in the hand-act log: %v", ask, err)
+			a.mu.Unlock()
+			a.wake()
+		}
+	}()
+}
+
+// warrantFailed says why the put's warrant was not recorded, "" when it was or is not yet known.
+func (a *putActs) warrantFailed(id string) string {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	return a.warrantNo[id]
+}
+
+// putSaid is the body of the event put.
+type putSaid struct {
+	Node     string `json:"node"`
+	Module   string `json:"module"`
+	FP       string `json:"fp"`
+	Hold     bool   `json:"hold"`
+	Step     string `json:"step"`
+	Words    string `json:"words"`
+	Composed string `json:"composed,omitempty"`
+}
+
+// say says a put's step as the event put, once per step and words.
+func (a *putActs) say(key string, p delivery.Put) {
+	node, module, err := delivery.ParsePutKey(key)
+	if err != nil || a.bus == nil {
+		return
+	}
+	a.mu.Lock()
+	if a.said[key] == p.Step+p.Words {
+		a.mu.Unlock()
+		return
+	}
+	a.said[key] = p.Step + p.Words
+	a.mu.Unlock()
+	if err := a.bus.Emit(PutEvent, putSaid{Node: node, Module: module, FP: p.FP, Hold: p.Hold, Step: p.Step, Words: p.Words, Composed: p.Composed}); err != nil {
+		a.logf("the put %s's step %s is not said as an event: %v", key, p.Step, err)
+	}
+}
+
+// shortHex is a digest's first twelve hex digits.
+func shortHex(digest string) string {
+	h := strings.TrimPrefix(digest, "sha256:")
+	if len(h) > 12 {
+		return h[:12]
+	}
+	return h
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seat.go

@@ -0,0 +1,753 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"maps"
+	"reflect"
+	"slices"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/handacts"
+	"git.novox.be/novox/mesh-sdk/go/process"
+
+	"mesh-delivery-assigner/internal/assign"
+	"mesh-delivery-assigner/internal/judge"
+)
+
+// The seat mesh-placement's holder in the assigner's process (novox/hq ADR 0567 §2-§8): each pass follows every open
+// proposal one step, from what the world holds. A proposal the verbs wrote is said (placement-proposed); the nodes it
+// must hear from are found by composing every node with and without it, and those its key does not change get a reached
+// candidate; their answers are judged (placement-judged) and, on a passing verdict, the operator is asked to approve it;
+// on the warrant each changed key is written by compare-and-set at the revision it was laid over (placement-changed),
+// and the controller's assignments are kept in step through its verbs until the lease write. A key moved meanwhile
+// lays the proposal again; a decline, an expiry or a withdrawal ends it (placement-withdrawn). Every event is said on the
+// assigner's own stream, so only this process says them. Nothing polls: the wake at an answer's bound is the one wake.
+
+// publisher says one of the seat's events on the assigner's stream, under a message id the bus keeps one of.
+type publisher func(event string, body any, id string) error
+
+// streamPublisher publishes on mesh.stream.mesh-delivery-assigner.event.<event>, with the headers an emit carries.
+func streamPublisher(ctx context.Context, js jetstream.JetStream, node string) publisher {
+	return func(event string, body any, id string) error {
+		data, err := json.Marshal(body)
+		if err != nil {
+			return err
+		}
+		msg := nats.NewMsg(process.ModuleStreamSubject(delivery.AssignerModule, event))
+		msg.Header.Set("x-event-id", id)
+		msg.Header.Set("x-source", delivery.AssignerModule)
+		msg.Header.Set("x-node", node)
+		msg.Header.Set("x-time", time.Now().UTC().Format(time.RFC3339Nano))
+		msg.Header.Set("content-type", "application/json")
+		msg.Data = data
+		_, err = js.PublishMsg(ctx, msg, jetstream.WithMsgID(id))
+		return err
+	}
+}
+
+// seatActs keeps the seat's acts while this process runs: the warrant recorded in the hand-act log. The seat calls no verb of
+// the controller: placement is the one source (ADR 0567 §8, issue 774).
+type seatActs struct {
+	bus  caller
+	wake func()
+	logf func(string, ...any)
+	// rec records the seat's acts in the hand-act log (ADR 0565 §11).
+	rec handacts.Recorder
+}
+
+func newSeatActs(bus caller, wake func(), logf func(string, ...any)) *seatActs {
+	return &seatActs{bus: bus, wake: wake, logf: logf, rec: handacts.Recorder{Ask: bus.Call}}
+}
+
+// record records once, in the hand-act log, that placement was written on the operator's warrant (§5): the router's
+// record of the teller's ask says who chose and how (ADR 0274). The log is the seat mesh-hand-acts' from its delivery, and
+// the controller's while that seat has no holder (ADR 0565 §11, handacts.Recorder).
+func (a *seatActs) record(warrant string) {
+	if a == nil || warrant == "" {
+		return
+	}
+	ask, _, _ := strings.Cut(warrant, "@")
+	go func() {
+		if taken, err := a.rec.RecordWarrant(delivery.TellerModule, ask); err != nil {
+			a.logf("the placement's warrant %s is not recorded in the hand-act log: %v", ask, err)
+		} else {
+			a.logf("the placement's warrant %s is recorded in the log of %s", ask, taken.Log)
+		}
+	}()
+}
+
+// clearStaleCalls clears, once, the conditions of the refused controller calls a previous process raised (findings of the
+// kinds controller-call and controller-pin): the assigner calls no verb of the controller any more (ADR 0567 §8, issue 774),
+// so nothing would clear them. It is tried again at the next pass while the findings cannot be read.
+func (p *passer) clearStaleCalls() {
+	if p.callsCleared || p.say == nil || p.findings.Keys == nil {
+		return
+	}
+	keys, err := p.findings.Keys()
+	if err != nil {
+		p.logf("the findings were not read, so the refused controller calls a previous process raised are cleared at the next pass: %v", err)
+		return
+	}
+	p.callsCleared = true
+	for _, k := range keys {
+		rest, ok := strings.CutPrefix(k, "module.")
+		if !ok {
+			continue
+		}
+		for _, kind := range []string{assign.KindControllerCall, assign.KindControllerPin} {
+			if pair, ok := strings.CutSuffix(rest, "."+kind); ok {
+				if node, module, two := strings.Cut(pair, "."); two {
+					if err := p.say(assign.CallClearedCondition(kind, node, module)); err != nil {
+						p.callsCleared = false
+						p.logf("the condition of the old %s call for %s on %s could not be cleared, and is cleared at the next pass: %v", kind, module, node, err)
+					}
+				}
+			}
+		}
+	}
+}
+
+// sayWaits raises, once, that the seat waits for the states not yet bound, and clears it once, when all are.
+func (p *passer) sayWaits(unbound []string) {
+	c := assign.SeatWaitsCondition(unbound)
+	state := string(c.State) + c.Summary
+	if p.say == nil || p.said[c.Key] && p.saidWaits == state {
+		return
+	}
+	if c.State == occ.StateCleared && p.saidWaits == "" {
+		return // nothing was raised by this process
+	}
+	if err := p.say(c); err != nil {
+		p.logf("that the seat waits for its states could not be said, and is said at the next pass: %v", err)
+		return
+	}
+	p.said[c.Key], p.saidWaits = true, state
+}
+
+// seatPlacements is every node's placement and the revision of its node key (its legacy key's for a node not yet
+// converted), as the watch holds them: the revision a proposal is laid over (§2, research 072 row 37).
+func (p *passer) seatPlacements() (map[string]delivery.Placement, map[string]uint64) {
+	return p.w.placement.AllRevisions()
+}
+
+// candidatesOf is a proposal's candidates by node, with their keys' revisions and the newest write.
+func (p *passer) candidatesOf(id string) (map[string]delivery.PlacementCandidate, map[string]uint64, time.Time) {
+	out, revs := map[string]delivery.PlacementCandidate{}, map[string]uint64{}
+	var newest time.Time
+	for key, value := range p.w.read(delivery.PlacementCandidatesBucket) {
+		pid, node, err := delivery.ParsePlacementCandidateKey(key)
+		if err != nil || pid != id {
+			continue
+		}
+		c, err := delivery.DecodePlacementCandidate(value)
+		if err != nil {
+			continue
+		}
+		meta := p.w.metaOf(delivery.PlacementCandidatesBucket, key)
+		out[node], revs[node] = c, meta.revision
+		if meta.at.After(newest) {
+			newest = meta.at
+		}
+	}
+	return out, revs, newest
+}
+
+// answersTo is, by node, each node's answer to the proposal in its `<node>.node` have.
+func (p *passer) answersTo(id string) map[string]*delivery.CandidateAnswer {
+	out := map[string]*delivery.CandidateAnswer{}
+	for key, value := range p.w.read(delivery.HaveBucket) {
+		node, _, isNode, err := delivery.ParseHaveKey(key)
+		if err != nil || !isNode {
+			continue
+		}
+		h, err := delivery.DecodeHaveNode(value)
+		if err != nil {
+			continue
+		}
+		if a, ok := h.Candidates[id]; ok {
+			out[node] = &a
+		}
+	}
+	return out
+}
+
+// placementSeat takes every open proposal one step further.
+func (p *passer) placementSeat(ctx context.Context) {
+	for _, b := range seatBuckets {
+		if p.kvs[b] == nil {
+			return
+		}
+	}
+	if p.saidProposed == nil {
+		p.saidProposed, p.intended = map[string]bool{}, map[string]map[string]map[string]bool{}
+	}
+	p.convertPlacement(ctx)
+	current, revs := p.seatPlacements()
+	ids := make([]string, 0)
+	raws := p.w.read(delivery.PlacementProposalsBucket)
+	for id := range raws {
+		ids = append(ids, id)
+	}
+	sort.Strings(ids)
+	for _, id := range ids {
+		prop, err := delivery.DecodePlacementProposal(raws[id])
+		if err != nil || prop.ID != id {
+			p.logf("the proposal %s cannot be read, so it is left: %v", id, err)
+			continue
+		}
+		p.stepProposal(ctx, prop, p.w.metaOf(delivery.PlacementProposalsBucket, id).revision, current, revs)
+	}
+}
+
+// pulse writes a bound's key with its time to live (§4): its expiry, heard on the watch as the server's delete marker,
+// is the event that ends the wait. Written again over one that stands, so its time starts anew.
+func (p *passer) pulse(ctx context.Context, key string, ttl time.Duration) {
+	kv := p.kvs[delivery.PlacementPulsesBucket]
+	_ = kv.Delete(ctx, key)
+	rev, err := kv.Create(ctx, key, []byte(`{}`), jetstream.KeyTTL(ttl))
+	if err != nil {
+		p.logf("the bound %s is not written, so its wait ends at once: %v", key, err)
+		return
+	}
+	p.w.putEntry(delivery.PlacementPulsesBucket, key, []byte(`{}`), rev, p.clock())
+}
+
+// pulsing says whether a bound's key stands.
+func (p *passer) pulsing(key string) bool { return p.w.has(delivery.PlacementPulsesBucket, key) }
+
+// deletePulses deletes every bound of a proposal.
+func (p *passer) deletePulses(ctx context.Context, id string) {
+	for key := range p.w.read(delivery.PlacementPulsesBucket) {
+		if strings.HasSuffix(key, "."+id) || strings.Contains(key, "."+id+".") {
+			if err := p.kvs[delivery.PlacementPulsesBucket].Delete(ctx, key); err == nil {
+				p.w.put(delivery.PlacementPulsesBucket, key, nil)
+			}
+		}
+	}
+}
+
+// ask raises (or raises again) a proposal's authorising ask and its bound, and answers the proposal asked.
+func (p *passer) ask(ctx context.Context, prop delivery.PlacementProposal, akey, brief string) (delivery.PlacementProposal, bool) {
+	a, err := assign.PlacementAsk(akey, prop, brief, assign.PlacementAsking(prop, p.clock()), p.clock())
+	if err != nil {
+		p.logf("the ask about the proposal %s is not written: %v", prop.ID, err)
+		return prop, false
+	}
+	placed, err := assign.AskOf(a)
+	if err != nil {
+		p.logf("the ask about the proposal %s is not written: %v", prop.ID, err)
+		return prop, false
+	}
+	p.put(ctx, delivery.AssignerAsksBucket, akey, func() ([]byte, error) { return assign.EncodeAsk(akey, a) })
+	if pk, err := delivery.PulseAskKey(prop.ID); err == nil {
+		p.pulse(ctx, pk, assign.ExpiresAt(placed).Sub(p.clock()))
+	}
+	prop.State, prop.Ask = delivery.ProposalAsked, placed.ID
+	return prop, true
+}
+
+// stepProposal takes one proposal one step further.
+func (p *passer) stepProposal(ctx context.Context, prop delivery.PlacementProposal, rev uint64, current map[string]delivery.Placement, revs map[string]uint64) {
+	if !p.saidProposed[prop.ID] && prop.State == delivery.ProposalAnswering && prop.Verdict == nil {
+		p.sayEvent(delivery.PlacementProposedEvent, delivery.PlacementEvent{Proposal: prop}, prop.ID)
+		p.saidProposed[prop.ID] = true
+	}
+	if prop.Withdrawn != "" {
+		p.endProposal(ctx, prop, prop.Withdrawn)
+		return
+	}
+	if prop.Seed || prop.HandBack {
+		// Adopt and hand-back are gone since the lease write (ADR 0547 §11, ADR 0567 §11): a proposal one left open ends.
+		p.endProposal(ctx, prop, "adopt and hand-back are gone since the lease write: placement is the mesh's alone")
+		return
+	}
+	if prop.Warrant != nil {
+		p.addNode(ctx, prop, revs)
+		return
+	}
+	akey, _ := delivery.PlacementAskKey(prop.ID)
+	again := !prop.Again.IsZero() && (prop.Verdict == nil || prop.Again.After(prop.Verdict.At))
+	if prop.State == delivery.ProposalAsked {
+		askPulse, _ := delivery.PulseAskKey(prop.ID)
+		switch {
+		case p.answeredWith(akey, assign.OptionYes):
+			p.warranted(ctx, prop, rev, akey, current, revs)
+			return
+		case p.answeredWith(akey, assign.OptionNo):
+			p.endProposal(ctx, prop, "declined by the operator")
+			return
+		case !p.pulsing(askPulse) && !again:
+			p.endProposal(ctx, prop, "its ask expired unanswered")
+			return
+		}
+	}
+	if moved(prop, revs) {
+		p.layAgain(ctx, prop, rev, current, revs, "a key it was laid over moved since")
+		return
+	}
+	cands, candRevs, written := p.candidatesOf(prop.ID)
+	if len(prop.Must) == 0 {
+		p.mustAnswer(ctx, prop, rev, current, cands)
+		return
+	}
+	for _, node := range prop.Must {
+		if _, ok := cands[node]; !ok {
+			return // a candidate just written is not heard yet: its watch wakes the next pass
+		}
+	}
+	if written.After(prop.Written) {
+		prop.Written = written
+	}
+	pulsing := map[string]bool{}
+	for _, node := range prop.Must {
+		if k, err := delivery.PulseAnswerKey(prop.ID, node); err == nil {
+			pulsing[node] = p.pulsing(k)
+		}
+	}
+	v := judge.JudgeAnswers(prop, p.intendedOf(prop, current, cands), p.answersTo(prop.ID), candRevs, p.w.online(), pulsing, p.clock())
+	if prop.Verdict != nil && sameVerdict(*prop.Verdict, v) && !again {
+		return
+	}
+	prop.Verdict = &v
+	switch v.State {
+	case delivery.VerdictFail:
+		prop.State, prop.Ask = delivery.ProposalFailed, ""
+	case delivery.VerdictWaits:
+		prop.State, prop.Ask = delivery.ProposalAnswering, ""
+	case delivery.VerdictPass:
+		if prop.State != delivery.ProposalAsked || again {
+			var ok bool
+			if prop, ok = p.ask(ctx, prop, akey, judge.Brief(prop, v)); !ok {
+				return
+			}
+			if again {
+				prop.Words = "judged and asked again (again)"
+			}
+		}
+	}
+	if p.writeProposal(ctx, prop, rev) {
+		p.sayEvent(delivery.PlacementJudgedEvent, delivery.PlacementEvent{Proposal: prop},
+			fmt.Sprintf("%s.judged.%d", prop.ID, v.At.UnixNano()))
+	}
+}
+
+// sameVerdict says two verdicts say the same, their time aside.
+func sameVerdict(a, b delivery.PlacementVerdict) bool {
+	a.At, b.At = time.Time{}, time.Time{}
+	return reflect.DeepEqual(a, b)
+}
+
+// moved says whether a key the proposal changes is no longer at the revision it was laid over.
+func moved(prop delivery.PlacementProposal, revs map[string]uint64) bool {
+	for node, base := range prop.Base {
+		if revs[node] != base {
+			return true
+		}
+	}
+	return false
+}
+
+// intendedOf is, by proposal and the revisions it was laid over, what Intended computed, kept while this process runs.
+func (p *passer) intendedOf(prop delivery.PlacementProposal, current map[string]delivery.Placement, cands map[string]delivery.PlacementCandidate) map[string]map[string]bool {
+	key := fmt.Sprint(prop.ID, prop.Base)
+	if got, ok := p.intended[key]; ok {
+		return got
+	}
+	got, _ := p.compute(prop, current, cands)
+	p.intended[key] = got
+	return got
+}
+
+// compute is what the proposal changes on each node by its placement, and the nodes that answer it: every node with a
+// placement or a record (judge.Intended, ADR 0593 §8). The holder composes nothing: each node says what its compositions
+// change in its answer.
+func (p *passer) compute(prop delivery.PlacementProposal, current map[string]delivery.Placement, cands map[string]delivery.PlacementCandidate) (map[string]map[string]bool, []string) {
+	laid := map[string]*delivery.Placement{}
+	for _, node := range prop.Nodes() {
+		if c, ok := cands[node]; ok && !c.Reached {
+			laid[node] = c.Placement
+		}
+	}
+	nodes := map[string]bool{}
+	for n := range current {
+		nodes[n] = true
+	}
+	for n := range p.w.records() {
+		nodes[n] = true
+	}
+	return judge.Intended(current, laid, slices.Sorted(maps.Keys(nodes)))
+}
+
+// mustAnswer finds the nodes the proposal must hear from (§3), writes a reached candidate for each whose key it does not
+// change, and writes them into the proposal.
+func (p *passer) mustAnswer(ctx context.Context, prop delivery.PlacementProposal, rev uint64, current map[string]delivery.Placement, cands map[string]delivery.PlacementCandidate) {
+	for _, node := range prop.Nodes() {
+		if _, ok := cands[node]; !ok {
+			return // the verbs write the candidates before the proposal: wait to hear them
+		}
+	}
+	intended, must := p.compute(prop, current, cands)
+	p.intended[fmt.Sprint(prop.ID, prop.Base)] = intended
+	for _, node := range must {
+		if _, ok := cands[node]; ok {
+			continue
+		}
+		key, err := delivery.PlacementCandidateKey(prop.ID, node)
+		if err != nil {
+			continue
+		}
+		c := delivery.PlacementCandidate{Proposal: prop.ID, Reached: true}
+		if pl, ok := current[node]; ok {
+			c.Placement = &pl
+		}
+		p.put(ctx, delivery.PlacementCandidatesBucket, key, func() ([]byte, error) { return delivery.EncodePlacementCandidate(c) })
+	}
+	for _, node := range must {
+		if k, err := delivery.PulseAnswerKey(prop.ID, node); err == nil {
+			p.pulse(ctx, k, judge.AnswerBound)
+		}
+	}
+	prop.Must = must
+	p.writeProposal(ctx, prop, rev)
+}
+
+// layAgain lays a proposal over the keys as they stand now (§5: a key moved): its candidates are written again, the
+// nodes that must answer found again, and it is judged and asked again; a proposal that no longer lays ends.
+func (p *passer) layAgain(ctx context.Context, prop delivery.PlacementProposal, rev uint64, current map[string]delivery.Placement, revs map[string]uint64, why string) {
+	held, recorded := p.lays(ctx)
+	again, laid, findings := assign.Propose(assign.ProposeIn{ID: prop.ID, By: prop.By, Why: prop.Why, At: prop.At, Changes: prop.Changes,
+		Current: current, Revisions: revs, Held: held, Recorded: recorded})
+	if len(findings) > 0 {
+		p.endProposal(ctx, prop, why+", and laid over the keys now it is refused: "+strings.Join(findings, "; "))
+		return
+	}
+	p.deleteCandidates(ctx, prop.ID)
+	p.deletePulses(ctx, prop.ID)
+	for _, node := range again.Nodes() {
+		key, _ := delivery.PlacementCandidateKey(prop.ID, node)
+		c := delivery.PlacementCandidate{Proposal: prop.ID, Placement: laid[node]}
+		p.put(ctx, delivery.PlacementCandidatesBucket, key, func() ([]byte, error) { return delivery.EncodePlacementCandidate(c) })
+	}
+	again.Written, again.Words = p.clock().UTC(), why+": laid again over the keys as they stand, to be judged and asked again"
+	p.writeProposal(ctx, again, rev)
+}
+
+// lays is what a proposal is checked against, as the verbs check it: the modules the indexer holds, by key, and the
+// nodes with a record.
+func (p *passer) lays(ctx context.Context) (func(string) bool, func(string) bool) {
+	held := map[string]bool{}
+	for key := range p.w.read(delivery.ModulesBucket) {
+		if name, err := delivery.ParseModulesKey(key); err == nil {
+			held[name] = true
+		}
+	}
+	records := p.w.records()
+	return func(m string) bool { return held[m] }, func(n string) bool { _, ok := records[n]; return ok }
+}
+
+// warranted writes an approved proposal (§5): each changed key by compare-and-set at the revision it was laid over; then the warrant recorded, the candidates and the
+// proposal deleted, and placement-changed said.
+func (p *passer) warranted(ctx context.Context, prop delivery.PlacementProposal, rev uint64, akey string, current map[string]delivery.Placement, revs map[string]uint64) {
+	if err := p.performs(akey, assign.PlacementAct(prop)); err != nil {
+		p.endProposal(ctx, prop, "its warrant does not bind these changes, so nothing is written: "+err.Error())
+		return
+	}
+	answer, _ := p.w.answer(akey)
+	if moved(prop, revs) {
+		p.layAgain(ctx, prop, rev, current, revs, "a key moved since it was approved, so its warrant is spent")
+		return
+	}
+	cands, _, _ := p.candidatesOf(prop.ID)
+	laid := map[string]*delivery.Placement{}
+	for _, node := range prop.Nodes() {
+		laid[node] = cands[node].Placement
+	}
+	writes, err := assign.Writes(prop, laid)
+	if err != nil {
+		p.logf("the proposal %s cannot be written: %v", prop.ID, err)
+		return
+	}
+	var changes []delivery.PlacementChange
+	writtenLaid := map[string]*delivery.Placement{}
+	after := maps.Clone(current)
+	afterRevs := maps.Clone(revs)
+	for _, w := range writes {
+		rev2, err := p.writeNode(ctx, w.Node, w.Value)
+		if err != nil {
+			// Another writer came first (a hand-back): what is written stands and is followed through; the rest is laid
+			// again over the keys as this write left them.
+			p.logf("placement %s is not written at revision %d (%v): the rest of the proposal %s is laid again", w.Key, w.Base, err, prop.ID)
+			p.followWrite(prop, answer, changes)
+			if rest, ok := assign.Rest(prop, writtenLaid); ok {
+				p.layAgain(ctx, rest, rev, after, afterRevs, "a key moved while it was written, after "+strings.Join(sortedNodes(writtenLaid), ", ")+" were")
+			} else {
+				p.endProposal(ctx, prop, "a key moved while it was written: "+err.Error())
+			}
+			return
+		}
+		before := current[w.Node]
+		now := delivery.Placement{Node: w.Node}
+		if w.Value != nil {
+			now = *w.Value
+			after[w.Node] = *w.Value
+		} else {
+			delete(after, w.Node)
+		}
+		afterRevs[w.Node] = rev2
+		c := delivery.ChangeOf(before, now)
+		c.Before, c.After = w.Base, rev2
+		changes = append(changes, c)
+		writtenLaid[w.Node] = w.Value
+	}
+	p.deleteCandidates(ctx, prop.ID)
+	p.deletePulses(ctx, prop.ID)
+	_ = p.kvs[delivery.PlacementProposalsBucket].Delete(ctx, prop.ID)
+	p.w.put(delivery.PlacementProposalsBucket, prop.ID, nil)
+	p.followWrite(prop, answer, changes)
+}
+
+// addNode writes a joining node on the warrant of the enrolment that issued its token (ADR 0587 §7): the operator's Approve
+// was the issue's, so no node is waited on and no ask is raised. The key is created at the revision it was laid over (none: a
+// node with a key is no joining node); the enrolment recorded the warrant in the hand-act log when it was given, so this does
+// not record it again; placement-changed carries the warrant. A key written meanwhile ends the proposal, saying so.
+func (p *passer) addNode(ctx context.Context, prop delivery.PlacementProposal, revs map[string]uint64) {
+	current, _ := p.seatPlacements()
+	if moved(prop, revs) {
+		p.endProposal(ctx, prop, "a key it was laid over was written since: the enrolment proposes the node again")
+		return
+	}
+	laid, findings := delivery.LayChanges(current, prop.Changes)
+	findings = append(findings, assign.ControllerRefusals(prop.Changes, laid)...)
+	node := prop.Changes[0].Node
+	if prop.Changes[0].Op == delivery.OpRemoveNode {
+		p.removeNode(ctx, prop, current, findings)
+		return
+	}
+	value, ok := laid[node]
+	if len(findings) > 0 || !ok {
+		p.endProposal(ctx, prop, "the node cannot be added: "+strings.Join(findings, "; "))
+		return
+	}
+	rev, err := p.writeNode(ctx, node, &value)
+	if err != nil {
+		p.endProposal(ctx, prop, "the node's key was not written: "+err.Error())
+		return
+	}
+	c := delivery.ChangeOf(delivery.Placement{Node: node}, value)
+	c.Before, c.After = prop.Base[node], rev
+	p.deleteCandidates(ctx, prop.ID)
+	p.deletePulses(ctx, prop.ID)
+	_ = p.kvs[delivery.PlacementProposalsBucket].Delete(ctx, prop.ID)
+	p.w.put(delivery.PlacementProposalsBucket, prop.ID, nil)
+	w := prop.Warrant
+	p.sayChanged(prop, delivery.Answer{Option: assign.OptionYes, Warrant: w.Warrant,
+		Words: fmt.Sprintf("the operator approved the machine %s at %s through the enrolment's ask %s", w.Node, w.Address, w.Ask)},
+		[]delivery.PlacementChange{c})
+}
+
+// removeNode deletes the key of a joining node whose enrolment ended unconfirmed, on that enrolment's warrant (the operator's
+// decision of 2026-11-02 01:05): no node answers and no ask is raised, as for its add-node; placement-changed carries the warrant.
+// A node that runs modules or holds seats is no joining node and stays (LayChanges' finding ends the proposal).
+func (p *passer) removeNode(ctx context.Context, prop delivery.PlacementProposal, current map[string]delivery.Placement, findings []string) {
+	node := prop.Changes[0].Node
+	before, ok := current[node]
+	if len(findings) > 0 || !ok {
+		p.endProposal(ctx, prop, "the node cannot be taken off: "+strings.Join(findings, "; "))
+		return
+	}
+	rev, err := p.writeNode(ctx, node, nil)
+	if err != nil {
+		p.endProposal(ctx, prop, "the node's key was not deleted: "+err.Error())
+		return
+	}
+	c := delivery.ChangeOf(before, delivery.Placement{Node: node})
+	c.Before, c.After = prop.Base[node], rev
+	p.deleteCandidates(ctx, prop.ID)
+	p.deletePulses(ctx, prop.ID)
+	_ = p.kvs[delivery.PlacementProposalsBucket].Delete(ctx, prop.ID)
+	p.w.put(delivery.PlacementProposalsBucket, prop.ID, nil)
+	w := prop.Warrant
+	p.sayChanged(prop, delivery.Answer{Option: assign.OptionYes, Warrant: w.Warrant,
+		Words: fmt.Sprintf("the machine %s left placement: its enrolment (ask %s) ended before it confirmed", w.Node, w.Ask)},
+		[]delivery.PlacementChange{c})
+}
+
+// followWrite follows the keys a warrant wrote: the warrant recorded and placement-changed said. No verb of the
+// controller is called: the placement is the one source of where modules run (ADR 0567 §8, issue 774).
+func (p *passer) followWrite(prop delivery.PlacementProposal, answer delivery.Answer, changes []delivery.PlacementChange) {
+	if len(changes) == 0 {
+		return
+	}
+	p.seat.record(answer.Warrant)
+	p.sayChanged(prop, answer, changes)
+}
+
+func sortedNodes(m map[string]*delivery.Placement) []string {
+	out := make([]string, 0, len(m))
+	for n := range m {
+		out = append(out, n)
+	}
+	sort.Strings(out)
+	return out
+}
+
+// sayChanged says placement-changed for the keys written.
+func (p *passer) sayChanged(prop delivery.PlacementProposal, answer delivery.Answer, changes []delivery.PlacementChange) {
+	if len(changes) == 0 {
+		return
+	}
+	at := p.clock().UTC()
+	if _, when, ok := strings.Cut(answer.Warrant, "@"); ok {
+		if t, err := time.Parse(time.RFC3339Nano, when); err == nil {
+			at = t
+		}
+	}
+	delivery.SortChanges(changes)
+	p.sayEvent(delivery.PlacementChangedEvent, delivery.PlacementEvent{Proposal: prop, Nodes: changes,
+		Warrant: &delivery.PlacementWarrant{Warrant: answer.Warrant, Words: answer.Words, At: at}}, prop.ID+".changed")
+}
+
+// endProposal ends a proposal: its ask, its candidates and its key deleted, and placement-withdrawn said carrying it
+// whole with why it ended.
+func (p *passer) endProposal(ctx context.Context, prop delivery.PlacementProposal, why string) {
+	if akey, err := delivery.PlacementAskKey(prop.ID); err == nil && p.w.has(delivery.AssignerAsksBucket, akey) {
+		if err := p.kvs[delivery.AssignerAsksBucket].Delete(ctx, akey); err == nil {
+			p.w.put(delivery.AssignerAsksBucket, akey, nil)
+		}
+	}
+	p.deleteCandidates(ctx, prop.ID)
+	p.deletePulses(ctx, prop.ID)
+	if err := p.kvs[delivery.PlacementProposalsBucket].Delete(ctx, prop.ID); err != nil && !errors.Is(err, context.Canceled) {
+		p.logf("the proposal %s is not deleted, and is ended at the next pass: %v", prop.ID, err)
+		return
+	}
+	p.w.put(delivery.PlacementProposalsBucket, prop.ID, nil)
+	p.logf("the proposal %s ends: %s", prop.ID, why)
+	p.sayEvent(delivery.PlacementWithdrawnEvent, delivery.PlacementEvent{Proposal: prop, Ended: why}, prop.ID+".withdrawn")
+}
+
+// deleteCandidates deletes every candidate of a proposal.
+func (p *passer) deleteCandidates(ctx context.Context, id string) {
+	for key := range p.w.read(delivery.PlacementCandidatesBucket) {
+		if pid, _, err := delivery.ParsePlacementCandidateKey(key); err == nil && pid == id {
+			if err := p.kvs[delivery.PlacementCandidatesBucket].Delete(ctx, key); err == nil {
+				p.w.put(delivery.PlacementCandidatesBucket, key, nil)
+			}
+		}
+	}
+}
+
+// writeProposal writes a proposal over the revision the pass read, by compare-and-set: a verb that marked it meanwhile
+// (withdraw, again) wins, and the next pass reads that. It says whether it wrote.
+func (p *passer) writeProposal(ctx context.Context, prop delivery.PlacementProposal, rev uint64) bool {
+	raw, err := delivery.EncodePlacementProposal(prop)
+	if err != nil {
+		p.logf("the proposal %s is not written: %v", prop.ID, err)
+		return false
+	}
+	kv := p.kvs[delivery.PlacementProposalsBucket]
+	var at uint64
+	if rev == 0 {
+		at, err = kv.Create(ctx, prop.ID, raw)
+	} else {
+		at, err = kv.Update(ctx, prop.ID, raw, rev)
+	}
+	if err != nil {
+		if !errors.Is(err, context.Canceled) {
+			p.logf("the proposal %s is not written, and is taken further at the next pass: %v", prop.ID, err)
+		}
+		return false
+	}
+	p.w.putEntry(delivery.PlacementProposalsBucket, prop.ID, raw, at, p.clock())
+	return true
+}
+
+// say says one of the seat's events, said in the journal when the bus refuses it.
+func (p *passer) sayEvent(event string, body delivery.PlacementEvent, id string) {
+	if p.publish == nil {
+		return
+	}
+	if err := p.publish(event, body, id); err != nil {
+		p.logf("%s of %s is not said: %v", event, body.Proposal.ID, err)
+	}
+}
+
+// writeNode writes one node's placement after (nil: none) as its keys (mesh-sdk delivery.PlacementKeys.Writes; research
+// 072 row 37): the module keys that change, each carrying the value it replaces, then the node key, the commit, then the
+// module keys no longer placed. It answers the node key's revision after (0: deleted). A write that fails up to the
+// commit ends it with nothing changed for any reader, the module keys written before it read at their previous values;
+// a delete after the commit that fails leaves a module key the node key does not name, which places nothing and is
+// deleted at the node's next write. Each key written is taken into the world at once, so the next write of the pass
+// reads it.
+func (p *passer) writeNode(ctx context.Context, node string, after *delivery.Placement) (uint64, error) {
+	writes, err := p.w.placement.Writes(node, after)
+	if err != nil {
+		return 0, err
+	}
+	kv := p.kvs[delivery.PlacementBucket]
+	committed, rev := false, uint64(0)
+	for _, w := range writes {
+		got, err := writeKey(ctx, kv, w)
+		if err != nil {
+			if committed {
+				p.logf("placement %s is not deleted after %s's write (%v): it places nothing, and goes at the node's next write", w.Key, node, err)
+				continue
+			}
+			return 0, fmt.Errorf("placement %s at revision %d: %w", w.Key, w.Base, err)
+		}
+		p.w.putEntry(delivery.PlacementBucket, w.Key, w.Value, got, p.clock())
+		if w.Commit {
+			committed, rev = true, got
+		}
+	}
+	return rev, nil
+}
+
+// writeKey makes one write of a placement key by compare-and-set and answers the key's revision after (0: deleted).
+func writeKey(ctx context.Context, kv jetstream.KeyValue, w delivery.PlacementKeyWrite) (uint64, error) {
+	switch {
+	case w.Value == nil:
+		return 0, kv.Delete(ctx, w.Key, jetstream.LastRevision(w.Base))
+	case w.Base == 0:
+		return kv.Create(ctx, w.Key, w.Value)
+	default:
+		return kv.Update(ctx, w.Key, w.Value, w.Base)
+	}
+}
+
+// convertPlacement converts every node the state holds only in the form before, `placement.<node>`, into its node key
+// and module keys (research 072 row 37), once: each node converted is said, and a node whose conversion fails is said
+// and tried again at the next pass. The legacy key is left for the readers not yet delivered; a node key wins over it
+// for every reader that reads both, and it is deleted with the node key when the node's placement is.
+func (p *passer) convertPlacement(ctx context.Context) {
+	if p.convertedAll {
+		return
+	}
+	migrations, err := p.w.placement.Migrations()
+	if err != nil {
+		p.logf("placement: some nodes in the form before cannot be converted, and stay read from it: %v", err)
+	}
+	failed := false
+	for _, node := range slices.Sorted(maps.Keys(migrations)) {
+		before, rev, _ := p.w.placement.Of(node)
+		got, err := p.writeNode(ctx, node, &before)
+		if err != nil {
+			failed = true
+			p.logf("placement: %s is not converted from placement.%s (revision %d) to its node and module keys, and is tried again at the next pass: %v", node, node, rev, err)
+			continue
+		}
+		p.logf("placement: %s converted from placement.%s (revision %d) to %s.node (revision %d) and %d module keys (research 072 row 37); placement.%s stays for readers not yet delivered",
+			node, node, rev, node, got, len(before.Modules), node)
+	}
+	p.convertedAll = !failed && err == nil
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seat_tools.go

@@ -0,0 +1,620 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"slices"
+	"sort"
+	"strings"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+
+	"mesh-delivery-assigner/internal/assign"
+)
+
+// The seat mesh-placement's seven verbs (novox/hq ADR 0567 §10), served through the tool runner beside the put tools: a
+// process never serves (ADR 0436). They read every state the seat keeps and write what a person asks of it: a proposal
+// and its candidates (propose, adopt), a proposal marked to end (withdraw) or to be judged again (again), and the keys
+// deleted (hand-back). Everything that follows a proposal — composing it, judging the answers, the ask, the write at the
+// warrant and the seat's events on its stream — is the assigner's process's (seat.go), started by these writes.
+
+// seatStore is what the seat's verbs need of the states: the runtime's, or a test's.
+type seatStore interface {
+	store
+	del(state, key string) error
+	history(state, key string) ([]stdio.StateRevision, error)
+}
+
+func (runtimeStore) del(state, key string) error { return stdio.State(state).Delete(key) }
+
+func (runtimeStore) history(state, key string) ([]stdio.StateRevision, error) {
+	return stdio.State(state).History(key)
+}
+
+// The states the verbs read, as the runtime names them: the seat's own by their local names, the others'
+// `<module>.<state>`.
+const (
+	modulesState = delivery.IndexerModule + ".modules"
+	haveState    = "node-engine.have"
+)
+
+// seatTools serves the seat's verbs over a store, asking the controller through ask (stdio.Ask, or a test's).
+type seatTools struct {
+	st  seatStore
+	ask func(key string, body any) (json.RawMessage, error)
+	now func() time.Time
+}
+
+func newSeatTools(st seatStore, ask func(string, any) (json.RawMessage, error)) *seatTools {
+	return &seatTools{st: st, ask: ask, now: time.Now}
+}
+
+// keyed is one placement key as a verb answers it.
+type keyed struct {
+	Placement delivery.Placement `json:"placement"`
+	Revision  uint64             `json:"revision"`
+}
+
+// placements reads every node's placement and the revision of its node key (its legacy key's before it is converted),
+// assembled from its keys in either form (delivery.PlacementKeys; research 072 row 37).
+func (s *seatTools) placements() (map[string]delivery.Placement, map[string]uint64, error) {
+	keys, err := s.st.keys(delivery.PlacementState)
+	if err != nil {
+		return nil, nil, fmt.Errorf("placement cannot be listed: %w", err)
+	}
+	sort.Strings(keys)
+	held := delivery.NewPlacementKeys()
+	var bad []string
+	for _, key := range keys {
+		if _, _, _, err := delivery.ParsePlacementKey(key); err != nil {
+			continue
+		}
+		raw, rev, found, err := s.st.get(delivery.PlacementState, key)
+		if err != nil {
+			return nil, nil, fmt.Errorf("placement key %s cannot be read: %w", key, err)
+		}
+		if !found {
+			continue
+		}
+		if _, err := held.Put(key, raw, rev, false); err != nil {
+			bad = append(bad, err.Error())
+		}
+	}
+	out, revs := held.AllRevisions()
+	if len(bad) > 0 && len(out) == 0 {
+		return nil, nil, fmt.Errorf("placement cannot be read: %s", strings.Join(bad, "; "))
+	}
+	return out, revs, nil
+}
+
+// lays is what a proposal is checked against: the modules the indexer holds and the nodes with a record.
+func (s *seatTools) lays() (func(string) bool, func(string) bool, error) {
+	mods, err := s.st.keys(modulesState)
+	if err != nil {
+		return nil, nil, fmt.Errorf("the indexer's modules cannot be listed: %w", err)
+	}
+	held := map[string]bool{}
+	for _, k := range mods {
+		if name, err := delivery.ParseModulesKey(k); err == nil {
+			held[name] = true
+		}
+	}
+	haves, err := s.st.keys(haveState)
+	if err != nil {
+		return nil, nil, fmt.Errorf("the nodes' records cannot be listed: %w", err)
+	}
+	recorded := map[string]bool{}
+	for _, k := range haves {
+		node, _, isNode, err := delivery.ParseHaveKey(k)
+		if err != nil || !isNode {
+			continue
+		}
+		if raw, _, found, err := s.st.get(haveState, k); err == nil && found {
+			if h, err := delivery.DecodeHaveNode(raw); err == nil && h.Record != nil {
+				recorded[node] = true
+			}
+		}
+	}
+	return func(m string) bool { return held[m] }, func(n string) bool { return recorded[n] }, nil
+}
+
+// proposal reads one open proposal.
+func (s *seatTools) proposal(id string) (delivery.PlacementProposal, error) {
+	if err := delivery.CheckProposalID(id); err != nil {
+		return delivery.PlacementProposal{}, err
+	}
+	raw, _, found, err := s.st.get(delivery.PlacementProposalsState, id)
+	if err != nil {
+		return delivery.PlacementProposal{}, fmt.Errorf("the proposal %s cannot be read: %w", id, err)
+	}
+	if !found {
+		return delivery.PlacementProposal{}, fmt.Errorf("no proposal %s is open: mesh-placement.proposals lists those that are", id)
+	}
+	return delivery.DecodePlacementProposal(raw)
+}
+
+// write writes a proposal laid by assign.Propose: each candidate, then the proposal, whose write the assigner's process
+// takes as the event to compose and judge it.
+func (s *seatTools) write(p delivery.PlacementProposal, laid map[string]*delivery.Placement) error {
+	p.Written = s.now().UTC()
+	for _, node := range p.Nodes() {
+		key, err := delivery.PlacementCandidateKey(p.ID, node)
+		if err != nil {
+			return err
+		}
+		raw, err := delivery.EncodePlacementCandidate(delivery.PlacementCandidate{Proposal: p.ID, Placement: laid[node]})
+		if err != nil {
+			return err
+		}
+		if err := s.st.put(delivery.PlacementCandidatesState, key, raw); err != nil {
+			return fmt.Errorf("the candidate %s is not written: %w", key, err)
+		}
+	}
+	raw, err := delivery.EncodePlacementProposal(p)
+	if err != nil {
+		return err
+	}
+	if err := s.st.put(delivery.PlacementProposalsState, p.ID, raw); err != nil {
+		return fmt.Errorf("the proposal %s is not written: %w", p.ID, err)
+	}
+	return nil
+}
+
+// proposed is what propose and adopt answer.
+type proposed struct {
+	Proposal delivery.PlacementProposal `json:"proposal"`
+	Follow   string                     `json:"follow"`
+}
+
+func followProposal(id string) string {
+	return fmt.Sprintf("the nodes it touches answer it; mesh-placement.proposals with id %q says where it stands, and the "+
+		"operator is asked to approve it once its verdict passes", id)
+}
+
+// changesOf reads propose's changes: a JSON array, given as one or as its text.
+func changesOf(v any) ([]delivery.PlacementProposalChange, error) {
+	var raw []byte
+	switch c := v.(type) {
+	case string:
+		raw = []byte(c)
+	case nil:
+		return nil, errors.New("propose names its changes")
+	default:
+		var err error
+		if raw, err = json.Marshal(c); err != nil {
+			return nil, err
+		}
+	}
+	var out []delivery.PlacementProposalChange
+	dec := json.NewDecoder(strings.NewReader(string(raw)))
+	dec.DisallowUnknownFields()
+	if err := dec.Decode(&out); err != nil {
+		return nil, fmt.Errorf("the changes are no list of changes: %w", err)
+	}
+	return out, nil
+}
+
+// doPropose is the verb propose (§2).
+func (s *seatTools) doPropose(args map[string]any, by string) (any, error) {
+	changes, err := changesOf(args["changes"])
+	if err != nil {
+		return nil, err
+	}
+	for _, c := range changes {
+		if c.Op == delivery.OpSeed {
+			return nil, errors.New("the seed is gone with adopt: propose takes place, take-off, pin, unpin, hold, unhold, decide and config")
+		}
+	}
+	current, revs, err := s.placements()
+	if err != nil {
+		return nil, err
+	}
+	held, recorded, err := s.lays()
+	if err != nil {
+		return nil, err
+	}
+	warrant, err := warrantOf(args["warrant"])
+	if err != nil {
+		return nil, err
+	}
+	now := s.now()
+	p, laid, findings := assign.Propose(assign.ProposeIn{ID: delivery.NewProposalID(now), By: by, Why: arg(args, "why"), At: now,
+		Changes: changes, Current: current, Revisions: revs, Held: held, Recorded: recorded, Warrant: warrant})
+	if refusal := delivery.AddNodeRefusal(p, moduleOfCaller(by)); refusal != "" {
+		findings = append(findings, refusal)
+	}
+	if len(findings) > 0 {
+		return nil, fmt.Errorf("the proposal is refused: %s", strings.Join(findings, "; "))
+	}
+	if err := s.write(p, laid); err != nil {
+		return nil, err
+	}
+	return proposed{Proposal: p, Follow: followProposal(p.ID)}, nil
+}
+
+// warrantOf reads propose's warrant, an enrolment's for an add-node: an object, given as one or as its text; none is none.
+func warrantOf(v any) (*delivery.AddNodeWarrant, error) {
+	var raw []byte
+	switch w := v.(type) {
+	case nil:
+		return nil, nil
+	case string:
+		if strings.TrimSpace(w) == "" {
+			return nil, nil
+		}
+		raw = []byte(w)
+	default:
+		var err error
+		if raw, err = json.Marshal(w); err != nil {
+			return nil, err
+		}
+	}
+	var out delivery.AddNodeWarrant
+	dec := json.NewDecoder(strings.NewReader(string(raw)))
+	dec.DisallowUnknownFields()
+	if err := dec.Decode(&out); err != nil {
+		return nil, fmt.Errorf("the warrant is no enrolment's warrant {node, address, ask, warrant}: %w", err)
+	}
+	return &out, nil
+}
+
+// moduleOfCaller is the module a caller is, as the runtime proves it, for AddNodeRefusal: mesh-enrolment when the proven
+// caller is that module's (its bus user `<node>.mesh-enrolment`, never a person's `person.mesh-enrolment`), else the caller
+// as proven, which the refusal names.
+func moduleOfCaller(by string) string {
+	if (stdio.Callers{delivery.EnrolmentModule}).Allows(by) {
+		return delivery.EnrolmentModule
+	}
+	return by
+}
+
+// doWithdraw is the verb withdraw (§2): the proposal is marked, and the assigner deletes it and its candidates and says
+// placement-withdrawn carrying it whole.
+func (s *seatTools) doWithdraw(args map[string]any, by string) (any, error) {
+	why := arg(args, "why")
+	if why == "" {
+		return nil, errors.New("withdraw says why: it is kept in the event that ends the proposal")
+	}
+	p, err := s.proposal(arg(args, "id"))
+	if err != nil {
+		return nil, err
+	}
+	p.Withdrawn = fmt.Sprintf("withdrawn by %s: %s", by, why)
+	raw, err := delivery.EncodePlacementProposal(p)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.st.put(delivery.PlacementProposalsState, p.ID, raw); err != nil {
+		return nil, fmt.Errorf("the proposal %s is not withdrawn: %w", p.ID, err)
+	}
+	return map[string]any{"proposal": p.ID, "withdrawn": p.Withdrawn}, nil
+}
+
+// doAgain is the verb again (§10): the proposal is marked, and the assigner judges it now and raises its ask again
+// when its verdict passes.
+func (s *seatTools) doAgain(args map[string]any) (any, error) {
+	p, err := s.proposal(arg(args, "id"))
+	if err != nil {
+		return nil, err
+	}
+	p.Again = s.now().UTC()
+	raw, err := delivery.EncodePlacementProposal(p)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.st.put(delivery.PlacementProposalsState, p.ID, raw); err != nil {
+		return nil, fmt.Errorf("the proposal %s is not asked again: %w", p.ID, err)
+	}
+	return map[string]any{"proposal": p.ID, "again": p.Again, "follow": followProposal(p.ID)}, nil
+}
+
+// placementAnswer is what the verb placement answers.
+type placementAnswer struct {
+	Keys    map[string]keyed `json:"keys,omitempty"`
+	Nodes   []string         `json:"nodes,omitempty"`
+	Count   int              `json:"count"`
+	History int              `json:"history-per-key"`
+	Changes []historyEntry   `json:"changes,omitempty"`
+	Older   string           `json:"older,omitempty"`
+}
+
+// historyEntry is one change of a key in the state's revisions.
+type historyEntry struct {
+	Node     string                   `json:"node"`
+	Revision uint64                   `json:"revision"`
+	At       time.Time                `json:"at"`
+	Change   delivery.PlacementChange `json:"change"`
+	Deleted  bool                     `json:"deleted,omitempty"`
+}
+
+// doPlacement is the verb placement (§10, §6): one node's key, one module's nodes, or every key; with history, the
+// changes in order from the revisions the state keeps.
+func (s *seatTools) doPlacement(args map[string]any) (any, error) {
+	if arg(args, "seats") == "true" {
+		return s.seats(arg(args, "node"))
+	}
+	all, revs, err := s.placements()
+	if err != nil {
+		return nil, err
+	}
+	node, module := arg(args, "node"), arg(args, "module")
+	out := placementAnswer{Keys: map[string]keyed{}, Count: len(all), History: delivery.PlacementHistory}
+	for n, p := range all {
+		if node != "" && n != node {
+			continue
+		}
+		if module != "" && !strings.Contains(" "+strings.Join(p.Assigned(), " ")+" ", " "+module+" ") {
+			continue
+		}
+		out.Keys[n] = keyed{Placement: p, Revision: revs[n]}
+		out.Nodes = append(out.Nodes, n)
+	}
+	sort.Strings(out.Nodes)
+	if node != "" && len(out.Keys) == 0 && arg(args, "history") != "true" {
+		return nil, fmt.Errorf("%s has no placement key", node)
+	}
+	if arg(args, "history") != "true" {
+		return out, nil
+	}
+	nodes := out.Nodes
+	if node != "" {
+		nodes = []string{node}
+	} else if module == "" {
+		nodes = nil
+		for n := range all {
+			nodes = append(nodes, n)
+		}
+		sort.Strings(nodes)
+	}
+	for _, n := range nodes {
+		revisions, err := s.nodeHistory(n)
+		if err != nil {
+			return nil, err
+		}
+		var before sketch
+		for _, r := range revisions {
+			e := historyEntry{Node: n, Revision: r.Revision, At: r.At}
+			after := sketch{}
+			if r.Op == "" || r.Op == "put" || r.Op == "PUT" {
+				after = sketchOf(r.Key, r.Value)
+			} else {
+				e.Deleted = true
+			}
+			e.Change = after.changeFrom(n, before)
+			e.Change.Before, e.Change.After = 0, r.Revision
+			before = after
+			if module != "" && !strings.Contains(" "+strings.Join(append(append(e.Change.Added, e.Change.Removed...), e.Change.Changed...), " ")+" ", " "+module+" ") {
+				continue
+			}
+			out.Changes = append(out.Changes, e)
+		}
+	}
+	out.Older = fmt.Sprintf("the state keeps %d revisions of each key; an older change is in its placement-changed event on "+
+		"the assigner's stream %s, kept %d days", delivery.PlacementHistory, delivery.PlacementStream, delivery.PlacementStreamDays)
+	return out, nil
+}
+
+// openProposal is one open proposal as the verb proposals answers it: the proposal (its changes, base revisions,
+// verdict with the differences and the answers it judged, its ask), its candidates by node with their revisions, and
+// every node's answer now.
+type openProposal struct {
+	Proposal   delivery.PlacementProposal          `json:"proposal"`
+	Candidates map[string]uint64                   `json:"candidates"`
+	Answers    map[string]delivery.CandidateAnswer `json:"answers,omitempty"`
+}
+
+// doProposals is the verb proposals (§10).
+func (s *seatTools) doProposals(args map[string]any) (any, error) {
+	ids, err := s.st.keys(delivery.PlacementProposalsState)
+	if err != nil {
+		return nil, fmt.Errorf("the proposals cannot be listed: %w", err)
+	}
+	cands, err := s.st.keys(delivery.PlacementCandidatesState)
+	if err != nil {
+		return nil, fmt.Errorf("the candidates cannot be listed: %w", err)
+	}
+	haves, err := s.st.keys(haveState)
+	if err != nil {
+		return nil, fmt.Errorf("the nodes' haves cannot be listed: %w", err)
+	}
+	answers := map[string]map[string]delivery.CandidateAnswer{} // by proposal, then node
+	for _, k := range haves {
+		node, _, isNode, err := delivery.ParseHaveKey(k)
+		if err != nil || !isNode {
+			continue
+		}
+		raw, _, found, err := s.st.get(haveState, k)
+		if err != nil || !found {
+			continue
+		}
+		h, err := delivery.DecodeHaveNode(raw)
+		if err != nil {
+			continue
+		}
+		for id, a := range h.Candidates {
+			if answers[id] == nil {
+				answers[id] = map[string]delivery.CandidateAnswer{}
+			}
+			answers[id][node] = a
+		}
+	}
+	sort.Strings(ids)
+	out := []openProposal{}
+	for _, id := range ids {
+		if want := arg(args, "id"); want != "" && want != id {
+			continue
+		}
+		p, err := s.proposal(id)
+		if err != nil {
+			return nil, err
+		}
+		o := openProposal{Proposal: p, Candidates: map[string]uint64{}, Answers: answers[id]}
+		for _, k := range cands {
+			pid, node, err := delivery.ParsePlacementCandidateKey(k)
+			if err != nil || pid != id {
+				continue
+			}
+			if _, rev, found, err := s.st.get(delivery.PlacementCandidatesState, k); err == nil && found {
+				o.Candidates[node] = rev
+			}
+		}
+		out = append(out, o)
+	}
+	if arg(args, "id") != "" && len(out) == 0 {
+		return nil, fmt.Errorf("no proposal %s is open", arg(args, "id"))
+	}
+	return map[string]any{"proposals": out}, nil
+}
+
+// tools are the seat's verbs as the runtime serves them, each named <seat>.<verb> (the tool runner serves a seat's verb
+// only from a tool of that name), with the seat's own schemas.
+func (s *seatTools) tools() []stdio.Tool {
+	seat, _ := catalogue.SeatNamed(catalogue.PlacementSeat)
+	input := map[string]map[string]any{}
+	description := map[string]string{}
+	for _, v := range seat.Serves {
+		input[v.Name], description[v.Name] = v.Input, v.Description
+	}
+	run := map[string]func(map[string]any) (any, error){
+		catalogue.PlacementVerbPlacement: s.doPlacement,
+		catalogue.PlacementVerbProposals: s.doProposals,
+		catalogue.PlacementVerbPropose:   func(a map[string]any) (any, error) { return s.doPropose(a, stdio.CallerOf(a)) },
+		catalogue.PlacementVerbWithdraw:  func(a map[string]any) (any, error) { return s.doWithdraw(a, stdio.CallerOf(a)) },
+		catalogue.PlacementVerbAgain:     s.doAgain,
+	}
+	var out []stdio.Tool
+	for _, v := range seat.Serves {
+		out = append(out, stdio.Tool{Name: catalogue.PlacementSeat + "." + v.Name, Description: description[v.Name], Input: input[v.Name], Run: run[v.Name]})
+	}
+	return out
+}
+
+// seats is the verb placement with seats (ADR 0571 §4): who holds each seat and on which node, as the state seat-holders
+// holds it; with node, the keys of seats held on that node.
+func (s *seatTools) seats(node string) (any, error) {
+	keys, err := s.st.keys(delivery.SeatHoldersState)
+	if err != nil {
+		return nil, fmt.Errorf("seat-holders cannot be listed: %w", err)
+	}
+	sort.Strings(keys)
+	out := []delivery.SeatHolders{}
+	for _, key := range keys {
+		raw, _, found, err := s.st.get(delivery.SeatHoldersState, key)
+		if err != nil {
+			return nil, fmt.Errorf("seat-holders %s cannot be read: %w", key, err)
+		}
+		if !found {
+			continue
+		}
+		var sh delivery.SeatHolders
+		if json.Unmarshal(raw, &sh) != nil {
+			continue
+		}
+		if node != "" && sh.Node != node && !slices.ContainsFunc(sh.Holders, func(h delivery.SeatHolder) bool { return h.Node == node }) {
+			continue
+		}
+		out = append(out, sh)
+	}
+	return map[string]any{"seats": out, "holds": len(keys)}, nil
+}
+
+// keyedRevision is one revision of a node's placement key, the key it is of beside it.
+type keyedRevision struct {
+	stdio.StateRevision
+	Key string
+}
+
+// nodeHistory is the revisions of a node's placement, in the order the bus wrote them: its legacy key's
+// `placement.<node>` before it was converted, then its node key's `<node>.node`, whose every revision is one write of
+// the node (research 072 row 37: the node key is a write's commit, so its history is the node's placement history).
+func (s *seatTools) nodeHistory(node string) ([]keyedRevision, error) {
+	legacy, err := delivery.LegacyPlacementKey(node)
+	if err != nil {
+		return nil, err
+	}
+	nodeKey, err := delivery.PlacementNodeKey(node)
+	if err != nil {
+		return nil, err
+	}
+	var out []keyedRevision
+	for _, key := range []string{legacy, nodeKey} {
+		revisions, err := s.st.history(delivery.PlacementState, key)
+		if err != nil {
+			return nil, fmt.Errorf("the history of %s cannot be read: %w", key, err)
+		}
+		for _, r := range revisions {
+			out = append(out, keyedRevision{StateRevision: r, Key: key})
+		}
+	}
+	sort.SliceStable(out, func(i, j int) bool { return out[i].Revision < out[j].Revision })
+	return out, nil
+}
+
+// sketch is a revision of a node's placement as far as its history says a change: each module's digest, and its pins
+// and holdings, which change every module (delivery.ChangeOf).
+type sketch struct {
+	modules  []delivery.PlacementRef
+	nodeWide string
+}
+
+// sketchOf reads one revision of a node key or a legacy key; a value that does not read places nothing.
+func sketchOf(key string, value []byte) sketch {
+	_, _, kind, err := delivery.ParsePlacementKey(key)
+	if err != nil {
+		return sketch{}
+	}
+	wide := func(pins map[string]delivery.Provider, holds []delivery.Holding) string {
+		raw, _ := json.Marshal([]any{pins, holds})
+		return string(raw)
+	}
+	if kind == delivery.PlacementNodeKind {
+		n, err := delivery.DecodePlacementNode(value)
+		if err != nil {
+			return sketch{}
+		}
+		return sketch{modules: n.Modules, nodeWide: wide(n.Pins, n.Holds)}
+	}
+	p, err := delivery.DecodePlacement(value)
+	if err != nil {
+		return sketch{}
+	}
+	out := sketch{nodeWide: wide(p.Pins, p.Holds)}
+	for _, m := range p.Modules {
+		out.modules = append(out.modules, delivery.PlacementRef{Module: m.Module, Digest: m.Digest()})
+	}
+	return out
+}
+
+// changeFrom is what changed from before to s on node, as delivery.ChangeOf says it.
+func (s sketch) changeFrom(node string, before sketch) delivery.PlacementChange {
+	c := delivery.PlacementChange{Node: node}
+	was := map[string]string{}
+	for _, r := range before.modules {
+		was[r.Module] = r.Digest
+	}
+	now := map[string]bool{}
+	nodeWide := before.nodeWide != s.nodeWide && len(before.modules) > 0
+	for _, r := range s.modules {
+		now[r.Module] = true
+		d, ok := was[r.Module]
+		switch {
+		case !ok:
+			c.Added = append(c.Added, r.Module)
+		case nodeWide || d != r.Digest:
+			c.Changed = append(c.Changed, r.Module)
+		}
+	}
+	for _, r := range before.modules {
+		if !now[r.Module] {
+			c.Removed = append(c.Removed, r.Module)
+		}
+	}
+	sort.Strings(c.Added)
+	sort.Strings(c.Removed)
+	sort.Strings(c.Changed)
+	return c
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seat_tools_test.go

@@ -0,0 +1,573 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"reflect"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+	"git.novox.be/novox/mesh-sdk/go/provisions"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"mesh-delivery-assigner/internal/assign"
+)
+
+func (s memStore) del(state, key string) error {
+	delete(s[state].values, key)
+	return nil
+}
+
+func (s memStore) history(state, key string) ([]stdio.StateRevision, error) {
+	v, ok := s[state].values[key]
+	if !ok {
+		return nil, nil
+	}
+	return []stdio.StateRevision{{Key: key, Value: v, Revision: uint64(len(v)), Op: "put"}}, nil
+}
+
+// ADR 0567 §2, §7, §10: the seat's five verbs over the states. propose lays a proposal and writes it with its candidates,
+// or refuses naming every finding and writes nothing; withdraw and again mark it for the holder; placement and
+// proposals read every state the seat keeps, and history names the stream for what the state no longer keeps.
+func TestTheSeatsVerbs(t *testing.T) {
+	anchor := delivery.Placement{V: delivery.Version, Node: "anchor", Modules: []delivery.PlacedModule{{Module: "web"}}}
+	st := memStore{}
+	for _, state := range []string{delivery.PlacementState, delivery.PlacementProposalsState, delivery.PlacementCandidatesState, modulesState, haveState} {
+		st[state] = &memKV{values: map[string][]byte{}}
+	}
+	for _, m := range []string{"web", "shell"} {
+		st[modulesState].values[m] = []byte("{}")
+	}
+	for _, n := range []string{"anchor", "laptop"} {
+		raw, _ := delivery.EncodeHaveNode(delivery.HaveNode{Record: &delivery.NodeRecord{Node: n}})
+		st[haveState].values[n+".node"] = raw
+	}
+	var asked []string
+	s := newSeatTools(st, func(key string, body any) (json.RawMessage, error) {
+		asked = append(asked, key)
+		return json.RawMessage(`{"ok":true}`), nil
+	})
+	s.now = func() time.Time { return time.Date(2026, 10, 28, 20, 0, 0, 0, time.UTC) }
+
+	raw, _ := delivery.EncodePlacement(anchor)
+	st[delivery.PlacementState].values["placement.anchor"] = raw
+
+	// withdraw and again mark the proposal; the holder ends or judges it.
+	got, err := s.doPropose(map[string]any{"why": "hold", "changes": `[{"op":"hold","node":"anchor","module":"web","claim":"node-shell","scope":"node"}]`}, "op")
+	if err != nil {
+		t.Fatal(err)
+	}
+	seed := got.(proposed).Proposal
+	if _, err := s.doWithdraw(map[string]any{"id": seed.ID, "why": "not yet"}, "op"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := s.doAgain(map[string]any{"id": seed.ID}); err != nil {
+		t.Fatal(err)
+	}
+	if p, err := s.proposal(seed.ID); err != nil || !strings.Contains(p.Withdrawn, "not yet") || p.Again.IsZero() {
+		t.Errorf("marked = %+v, %v", p, err)
+	}
+	if _, err := s.doWithdraw(map[string]any{"id": "p-none", "why": "x"}, "op"); err == nil {
+		t.Error("an unknown proposal was withdrawn")
+	}
+	delete(st[delivery.PlacementProposalsState].values, seed.ID) // the holder ended it
+	st[delivery.PlacementCandidatesState].values = map[string][]byte{}
+
+	// propose: refused whole, naming every finding; a valid move laid over the keys at their revisions.
+	if _, err := s.doPropose(map[string]any{"why": "x", "changes": `[{"op":"place","node":"anchor","module":"ghost"},{"op":"hold","node":"anchor","module":"web","claim":"x"}]`}, "op"); err == nil ||
+		!strings.Contains(err.Error(), "ghost") || len(st[delivery.PlacementProposalsState].values) != 0 {
+		t.Errorf("a refused proposal: %v", err)
+	}
+	if _, err := s.doPropose(map[string]any{"why": "x", "changes": `[{"op":"swap","node":"anchor"}]`}, "op"); err == nil {
+		t.Error("an unknown change was taken")
+	}
+	got, err = s.doPropose(map[string]any{"why": "move web", "changes": []any{
+		map[string]any{"op": "take-off", "node": "anchor", "module": "web"}, map[string]any{"op": "place", "node": "laptop", "module": "web"}}}, "operator@laptop")
+	if err != nil {
+		t.Fatal(err)
+	}
+	move := got.(proposed).Proposal
+	if move.By != "operator@laptop" || move.Base["anchor"] != uint64(len(raw)) || move.Base["laptop"] != 0 || len(st[delivery.PlacementCandidatesState].values) != 2 {
+		t.Fatalf("propose = %+v", move)
+	}
+
+	// placement and proposals read every state the seat keeps (§10); history names the stream for what is older.
+	reads := map[string]bool{}
+	pa, err := s.doPlacement(map[string]any{"module": "web", "history": "true"})
+	if a := pa.(placementAnswer); err != nil || !slices.Equal(a.Nodes, []string{"anchor"}) || len(a.Changes) != 1 || !strings.Contains(a.Older, delivery.PlacementStream) {
+		t.Errorf("placement of web = %+v, %v", pa, err)
+	} else {
+		reads[delivery.PlacementState], reads["stream "+delivery.PlacementStream] = true, true
+	}
+	if _, err := s.doPlacement(map[string]any{"node": "laptop"}); err == nil {
+		t.Error("a node with no key was answered")
+	}
+	ps, err := s.doProposals(map[string]any{"id": move.ID})
+	if list := ps.(map[string]any)["proposals"].([]openProposal); err != nil || len(list) != 1 || len(list[0].Candidates) != 2 {
+		t.Errorf("proposals = %+v, %v", ps, err)
+	} else {
+		reads[delivery.PlacementProposalsState], reads[delivery.PlacementCandidatesState] = true, true
+	}
+	raw0, err := readManifest()
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, state := range raw0.State {
+		if slices.Contains([]string{delivery.PlacementState, delivery.PlacementProposalsState, delivery.PlacementCandidatesState}, state.Name) && !reads[state.Name] {
+			t.Errorf("no verb reads the seat's state %s", state.Name)
+		}
+	}
+	for _, stream := range raw0.Streams {
+		// The views family is no seat's stream: the readers of the assigner's states follow it (ADR 0615 §5).
+		if stream.Name != viewsStream && !reads["stream "+stream.Name] {
+			t.Errorf("no verb reads the seat's stream %s", stream.Name)
+		}
+	}
+
+	// Issue 774 (ADR 0567 §8): every kind of change is proposed, and there is no controller to hand placement back to.
+	if _, err := s.doPropose(map[string]any{"why": "hold", "changes": `[{"op":"hold","node":"anchor","module":"web","claim":"node-shell","scope":"node"}]`}, "op"); err != nil {
+		t.Errorf("a hold: %v", err)
+	}
+	// 774/S59/AC1 (ADR 0587 §7): an add-node from mesh-enrolment whose warrant names this node and this address is proposed, with
+	// the node a joining one with no record; from another caller, naming another node or address, or with no warrant it is refused.
+	addNode := func(by, warrant string) error {
+		_, err := s.doPropose(map[string]any{"why": "enrolment of ace", "warrant": warrant, "changes": []any{map[string]any{"op": "add-node", "node": "ace",
+			"decided": map[string]any{"address": "10.9.0.2"}, "keys": map[string]any{"overlay": "dHVubmVs"}}}}, by)
+		return err
+	}
+	good := `{"node":"ace","address":"10.9.0.2","ask":"enrol-ace-1","warrant":"enrol-ace-1@2026-10-28T20:00:00Z"}`
+	for _, c := range []struct{ by, warrant, want string }{
+		{"novox.mesh-grants", good, "mesh-enrolment's alone"},
+		{"person.mesh-enrolment", good, "mesh-enrolment's alone"},
+		{"novox.mesh-enrolment", `{"node":"g14","address":"10.9.0.2","ask":"a","warrant":"a@t"}`, "carries the warrant of g14"},
+		{"novox.mesh-enrolment", `{"node":"ace","address":"10.9.0.9","ask":"a","warrant":"a@t"}`, "carries the warrant of ace at 10.9.0.9"},
+		{"novox.mesh-enrolment", "", "carries no warrant"},
+	} {
+		if err := addNode(c.by, c.warrant); err == nil || !strings.Contains(err.Error(), c.want) {
+			t.Errorf("an add-node by %s with warrant %q: %v, want a refusal saying %q", c.by, c.warrant, err, c.want)
+		}
+	}
+	if err := addNode("novox.mesh-enrolment", good); err != nil {
+		t.Errorf("an add-node from mesh-enrolment: %v", err)
+	}
+	// A remove-node (the operator's decision of 2026-11-02 01:05) takes a joining node that never confirmed off placement: from
+	// mesh-enrolment, on the warrant naming that node, of a node running nothing, it is proposed with the node's key to delete;
+	// of a node running modules, or with another node's warrant, it is refused.
+	joiner, _ := delivery.EncodePlacement(delivery.Placement{V: delivery.Version, Node: "joiner", Decided: delivery.NodeDecided{Address: "10.9.0.7"}, Modules: []delivery.PlacedModule{}})
+	st[delivery.PlacementState].values["placement.joiner"] = joiner
+	removeNode := func(node, warrant string) (any, error) {
+		return s.doPropose(map[string]any{"why": "enrolment ended", "warrant": warrant,
+			"changes": []any{map[string]any{"op": "remove-node", "node": node}}}, "novox.mesh-enrolment")
+	}
+	for _, c := range []struct{ node, warrant, want string }{
+		{"anchor", `{"node":"anchor","address":"10.9.0.1","ask":"a","warrant":"a@t"}`, "runs modules or holds seats"},
+		{"joiner", `{"node":"g14","address":"10.9.0.7","ask":"a","warrant":"a@t"}`, "carries the warrant of g14"},
+	} {
+		if _, err := removeNode(c.node, c.warrant); err == nil || !strings.Contains(err.Error(), c.want) {
+			t.Errorf("a remove-node of %s: %v, want a refusal saying %q", c.node, err, c.want)
+		}
+	}
+	if got, err := removeNode("joiner", `{"node":"joiner","address":"10.9.0.7","ask":"a","warrant":"a@t"}`); err != nil {
+		t.Errorf("a remove-node from mesh-enrolment: %v", err)
+	} else if rm := got.(proposed).Proposal; !slices.Equal(rm.Nodes(), []string{"joiner"}) || !slices.Equal(rm.RemovedNodes(), []string{"joiner"}) {
+		t.Errorf("the remove-node proposed %+v", rm)
+	}
+	// 1126/B8: the seat serves its five verbs; adopt and hand-back went with the controller (ADR 0590).
+	if tools := s.tools(); len(tools) != 5 || tools[2].Name != "mesh-placement.propose" || tools[2].Run == nil || tools[2].Input == nil {
+		t.Errorf("the seat's verbs as served: %+v", tools)
+	}
+	t.Run("1953/D4-D6: the seat mesh-wants' upgrade and bus", wantsVerbs)
+	t.Run("1955/L7 (ADR 0571 §6): rule 7 reads the node's own composition; an unplaced node is said", func(t *testing.T) {
+		w := newWorld()
+		fp := delivery.SourcePrefix2 + strings.Repeat("2", 64)
+		pl, _ := delivery.EncodePlacement(delivery.Placement{V: delivery.Version, Node: "ace", Modules: []delivery.PlacedModule{{Module: "web"}}})
+		pkey, _ := delivery.LegacyPlacementKey("ace")
+		w.putEntry(delivery.PlacementBucket, pkey, pl, 1, time.Now())
+		for node, digest := range map[string]string{"ace": "sha256:" + strings.Repeat("a", 64), "g14": ""} {
+			hn, _ := delivery.EncodeHaveNode(delivery.HaveNode{Composed: digest})
+			hk, _ := delivery.HaveNodeKey(node)
+			w.putEntry(delivery.HaveBucket, hk, hn, 1, time.Now())
+		}
+		if d, ok := w.composed("ace", "web", fp); !ok || d.Digest != "sha256:"+strings.Repeat("a", 64) {
+			t.Errorf("ace: %+v %v", d, ok)
+		}
+		if _, ok := w.composed("g14", "web", fp); ok || !slices.Equal(w.unplacedNodes(), []string{"g14"}) {
+			t.Errorf("g14 unplaced: composed %v, unplaced %v", ok, w.unplacedNodes())
+		}
+		findings := map[string][]byte{}
+		p := &passer{w: w, logf: func(string, ...any) {}, findings: assign.Findings{
+			Put:    func(k string, v []byte) error { findings[k] = v; return nil },
+			Delete: func(k string) error { delete(findings, k); return nil }}}
+		p.unplacedFindings()
+		if _, ok := findings[assign.UnplacedKey("g14")]; !ok || len(findings) != 1 {
+			t.Fatalf("findings = %v", findings)
+		}
+		pl2, _ := delivery.EncodePlacement(delivery.Placement{V: delivery.Version, Node: "g14", Modules: []delivery.PlacedModule{{Module: "web"}}})
+		pkey2, _ := delivery.LegacyPlacementKey("g14")
+		w.putEntry(delivery.PlacementBucket, pkey2, pl2, 1, time.Now())
+		p.unplacedFindings()
+		if len(findings) != 0 {
+			t.Errorf("placed again: findings %v", findings)
+		}
+	})
+	t.Run("1955/L7 (ADR 0571 §4): seat-holders is written from placement, only the keys a change moves, and answered by placement seats", func(t *testing.T) {
+		writes := 0
+		kv := &countingKV{memKV: memKV{values: map[string][]byte{}}, writes: &writes}
+		p := &passer{w: newWorld(), logf: t.Logf, kvs: buckets{delivery.SeatHoldersBucket: kv}}
+		place := func(node string, holds ...delivery.Holding) {
+			pl, err := delivery.EncodePlacement(delivery.Placement{V: delivery.Version, Node: node, Modules: []delivery.PlacedModule{{Module: "web"}, {Module: "nats"}}, Holds: holds})
+			if err != nil {
+				t.Fatal(err)
+			}
+			k, _ := delivery.LegacyPlacementKey(node)
+			p.w.putEntry(delivery.PlacementBucket, k, pl, 1, time.Now())
+		}
+		place("ace", delivery.Holding{Claim: "mesh-broker", Scope: "mesh", Module: "nats"}, delivery.Holding{Claim: "node-shell", Scope: "node", Module: "web"})
+		place("g14", delivery.Holding{Claim: "node-shell", Scope: "node", Module: "web"})
+		ctx := context.Background()
+		p.seatHolders(ctx)
+		if writes != 3 || kv.values["mesh-broker"] == nil || kv.values["node-shell.ace"] == nil || kv.values["node-shell.g14"] == nil {
+			t.Fatalf("%d writes: %v", writes, kv.values)
+		}
+		p.seatHolders(ctx)
+		if writes != 3 {
+			t.Errorf("an unchanged placement wrote %d keys", writes-3)
+		}
+		place("g14") // g14 holds nothing now
+		p.seatHolders(ctx)
+		if writes != 3 || kv.values["node-shell.g14"] != nil || kv.values["node-shell.ace"] == nil {
+			t.Errorf("after g14's change: %d writes, %v", writes, kv.values)
+		}
+		st := memStore{delivery.SeatHoldersState: &memKV{values: kv.values}}
+		out, err := newSeatTools(st, nil).seats("ace")
+		if err != nil || len(out.(map[string]any)["seats"].([]delivery.SeatHolders)) != 2 {
+			t.Errorf("seats on ace = %+v, %v", out, err)
+		}
+	})
+	t.Run("research 072 row 37: the form before is converted once, a node is written as its keys, and history reads both", func(t *testing.T) {
+		ctx := context.Background()
+		kv := &revKV{values: map[string][]byte{}, revs: map[string]uint64{}}
+		var logs []string
+		p := &passer{w: newWorld(), kvs: buckets{delivery.PlacementBucket: kv}, now: time.Now,
+			logf: func(f string, a ...any) { logs = append(logs, fmt.Sprintf(f, a...)) }}
+		put := func(key string, value []byte, rev uint64) {
+			p.w.putEntry(delivery.PlacementBucket, key, value, rev, time.Now())
+		}
+		was := delivery.Placement{Node: "anchor", Modules: []delivery.PlacedModule{{Module: "web"}}}
+		raw, _ := delivery.EncodePlacement(was)
+		put("placement.anchor", raw, kv.write("placement.anchor", raw))
+		p.convertPlacement(ctx)
+		if strings.Join(kv.log, " ") != "create anchor.web create anchor.node" || !p.convertedAll ||
+			!strings.Contains(strings.Join(logs, "\n"), "anchor converted from placement.anchor") {
+			t.Fatalf("the conversion wrote %v, said %v", kv.log, logs)
+		}
+		p.convertPlacement(ctx)
+		if len(kv.log) != 2 {
+			t.Errorf("a converted node is converted again: %v", kv.log)
+		}
+		// A write: the module keys, the node key (its commit), the mirror, then the module key no longer placed.
+		after := delivery.Placement{Node: "anchor", Modules: []delivery.PlacedModule{{Module: "shell", Ports: map[string]int{"22": 2222}}}}
+		kv.log = nil
+		rev, err := p.writeNode(ctx, "anchor", &after)
+		if err != nil || strings.Join(kv.log, " ") != "create anchor.shell update anchor.node update placement.anchor delete anchor.web" || rev != kv.revs["anchor.node"] {
+			t.Fatalf("the write = %v, %d, %v", kv.log, rev, err)
+		}
+		if got, _ := p.seatPlacements(); !delivery.SamePlacement(got["anchor"], after) {
+			t.Errorf("the write is not read back at once: %+v", got)
+		}
+		// A commit refused leaves every reader on what stood: the module key written before it carries the value it replaced.
+		kv.refuse, kv.log = "anchor.node", nil
+		moved := delivery.Placement{Node: "anchor", Modules: []delivery.PlacedModule{{Module: "shell", Ports: map[string]int{"22": 2223}}}}
+		if _, err := p.writeNode(ctx, "anchor", &moved); err == nil || strings.Join(kv.log, " ") != "update anchor.shell" {
+			t.Fatalf("a refused commit = %v, %v", kv.log, err)
+		}
+		fresh, err := delivery.PlacementsOf(kv.values)
+		if err != nil || !delivery.SamePlacement(fresh["anchor"], after) {
+			t.Errorf("a reader of the keys after a refused commit reads %+v, %v", fresh["anchor"], err)
+		}
+		kv.refuse = ""
+		// The verb's history reads the form before, then the node key.
+		st := memStore{delivery.PlacementState: &memKV{values: kv.values}}
+		hs := newSeatTools(st, nil)
+		hs.st = historyStore{memStore: st, revisions: map[string][]stdio.StateRevision{
+			"placement.anchor": {{Key: "placement.anchor", Value: raw, Revision: 1, Op: "put"}},
+			"anchor.node":      {{Key: "anchor.node", Value: kv.values["anchor.node"], Revision: 5, Op: "put"}, {Key: "anchor.node", Revision: 9, Op: "del"}},
+		}}
+		pa, err := hs.doPlacement(map[string]any{"node": "anchor", "history": "true"})
+		a, _ := pa.(placementAnswer)
+		if err != nil || len(a.Changes) != 3 || !slices.Equal(a.Changes[0].Change.Added, []string{"web"}) ||
+			!slices.Equal(a.Changes[1].Change.Added, []string{"shell"}) || !slices.Equal(a.Changes[1].Change.Removed, []string{"web"}) ||
+			!a.Changes[2].Deleted || !slices.Equal(a.Changes[2].Change.Removed, []string{"shell"}) {
+			t.Errorf("history = %+v, %v", pa, err)
+		}
+		// No placement: the mirror first, then the node key, then the module keys.
+		kv.log = nil
+		if _, err := p.writeNode(ctx, "anchor", nil); err != nil || strings.Join(kv.log, " ") != "delete placement.anchor delete anchor.node delete anchor.shell" {
+			t.Errorf("the delete = %v, %v", kv.log, err)
+		}
+	})
+	t.Run("1954/D1: a failed provision is the assigner's finding until it is provided", func(t *testing.T) {
+		findings := map[string][]byte{}
+		p := &passer{w: newWorld(), logf: func(string, ...any) {}, kvs: buckets{provisions.ProvisionsBucket: nil}, findings: assign.Findings{
+			Put:    func(k string, v []byte) error { findings[k] = v; return nil },
+			Delete: func(k string) error { delete(findings, k); return nil }}}
+		failed, _ := provisions.Encode(provisions.Provision{Provision: "db", Consumer: provisions.End{Module: "photos", Node: "ace"},
+			Provider: provisions.End{Module: "postgres", Node: "novox"}, State: provisions.Failed, Why: "the role exists already"})
+		p.w.putEntry(provisions.ProvisionsBucket, "ace.photos.db", failed, 1, time.Now())
+		p.kvs[provisions.ProvisionsBucket] = &memKV{}
+		of := p.provisionsOf()
+		if got := of("photos")("ace"); got["ace.photos.db"].State != provisions.Failed {
+			t.Fatalf("provisions = %+v", got)
+		}
+		if _, ok := findings[assign.ProvisionFailedKey("ace.photos.db")]; !ok || len(findings) != 1 {
+			t.Fatalf("findings = %v", findings)
+		}
+		provided, _ := provisions.Encode(provisions.Provision{Provision: "db", Consumer: provisions.End{Module: "photos", Node: "ace"},
+			Provider: provisions.End{Module: "postgres", Node: "novox"}, State: provisions.Provided})
+		p.w.putEntry(provisions.ProvisionsBucket, "ace.photos.db", provided, 2, time.Now())
+		p.provisionsOf()
+		if len(findings) != 0 {
+			t.Errorf("findings after provided = %v", findings)
+		}
+		// A required provision with no key: pulsed with the bound first, said once the pulse expired, ended once keyed.
+		ctx := context.Background()
+		p.kvs[delivery.PlacementPulsesBucket] = &memKV{values: map[string][]byte{}}
+		gone := map[string]bool{"ace.photos.s3": true}
+		p.provisionsMissing(ctx, gone)
+		if !p.pulsing("provision-missing.ace.photos.s3") || len(findings) != 0 {
+			t.Fatalf("first seen: pulsing %v, findings %v", p.pulsing("provision-missing.ace.photos.s3"), findings)
+		}
+		p.provisionsMissing(ctx, gone)
+		if len(findings) != 0 {
+			t.Fatal("said before its bound")
+		}
+		p.w.put(delivery.PlacementPulsesBucket, "provision-missing.ace.photos.s3", nil) // the server expired it
+		p.provisionsMissing(ctx, gone)
+		if _, ok := findings[assign.ProvisionMissingKey("ace.photos.s3")]; !ok {
+			t.Fatalf("past its bound: findings %v", findings)
+		}
+		p.provisionsMissing(ctx, map[string]bool{})
+		if len(findings) != 0 {
+			t.Errorf("keyed again: findings %v", findings)
+		}
+	})
+}
+
+// wantsVerbs (novox/hq ADR 0565 §7, §8, §9): upgrade answers each module's policy and its source; a person's choice is
+// written with who and why, recorded as a hand act in the seat's log and said as policy-changed, and default takes it back;
+// the bus is refused; compare lists each node's composition and the findings; bus names the node behind the indexer's newest.
+func wantsVerbs(t *testing.T) {
+	fpOld, fpNew := delivery.SourcePrefix2+strings.Repeat("1", 64), delivery.SourcePrefix2+strings.Repeat("2", 64)
+	st := memStore{}
+	for _, state := range []string{modulesState, manifestsState, policiesState, haveState, putsState, "findings", delivery.ComposedRead} {
+		st[state] = &memKV{values: map[string][]byte{}}
+	}
+	// ADR 0593 §6, §8: what each node published, every node's bucket as one state: anchor's own composition and its web at
+	// a fingerprint, and laptop's web refused there.
+	webKey, _ := delivery.ComposedKey("anchor", "web", fpNew)
+	refusedKey, _ := delivery.ComposedKey("laptop", "web", fpNew)
+	st[delivery.ComposedRead].values["anchor.node"], _ = delivery.EncodeComposed(delivery.Composed{Node: "anchor"})
+	st[delivery.ComposedRead].values[webKey], _ = delivery.EncodeComposed(delivery.Composed{Node: "anchor", Module: "web", FP: fpNew})
+	st[delivery.ComposedRead].values[refusedKey], _ = delivery.EncodeComposed(delivery.Composed{Node: "laptop", Module: "web", FP: fpNew, Refused: "a required value is unset"})
+	manifest := func(name, extra string) {
+		raw := `{"module":"` + name + `","version":"1"` + extra + `}`
+		digest := delivery.ManifestDigest([]byte(raw))
+		st[manifestsState].values[digest], _ = delivery.EncodeManifest(delivery.Manifest{V: delivery.Version, Module: name, JSON: raw})
+		st[modulesState].values[name], _ = delivery.EncodeModule(delivery.Module{V: delivery.Version, FP2: fpNew, Manifest: digest, Repository: "novox/x", Commit: "c"})
+	}
+	manifest("web", "")
+	manifest("photos", `,"upgrade":{"policy":"record","why":"a person checks the albums"}`)
+	manifest("nats", `,"provides":[{"name":"mesh-bus","scope":"mesh"}],"upgrade":{"policy":"record","why":"its streams"}`)
+	for node, fp := range map[string]string{"anchor": fpOld, "laptop": fpNew} {
+		st[haveState].values[node+".nats"], _ = delivery.EncodeHave(delivery.Have{FP: fp, Phase: delivery.PhaseRunning, Health: delivery.HealthOK})
+	}
+	st[haveState].values["anchor.node"], _ = delivery.EncodeHaveNode(delivery.HaveNode{Composed: "sha256:" + strings.Repeat("c", 64)})
+	var asked []string
+	var said []string
+	w := newWantsTools(st, func(key string, body any) (json.RawMessage, error) {
+		asked = append(asked, key)
+		return json.RawMessage(`{"ok":true}`), nil
+	}, func(event, id string, body any) error { said = append(said, event+" "+id); return nil })
+	policyOf := func(module string) policyRow {
+		out, err := w.doUpgrade(map[string]any{"module": module}, "op")
+		if err != nil {
+			t.Fatal(err)
+		}
+		return out.(map[string]any)["modules"].([]policyRow)[0]
+	}
+	if p := policyOf("photos"); p.Policy != catalogue.PolicyRecord || p.From != catalogue.FromModule {
+		t.Errorf("photos = %+v", p)
+	}
+	if p := policyOf("nats"); p.Policy != catalogue.PolicyRecord || p.From != catalogue.FromModule { // the policy its manifest says (issue 774)
+		t.Errorf("nats = %+v", p)
+	}
+	// compare: each node's own composition is the digest its have names, and the assigner's findings; nothing splits, the
+	// controller being gone (1126/B8).
+	out, _ := w.doUpgrade(map[string]any{"compare": "true"}, "op")
+	if got := out.(map[string]any); got["splits"] != nil || got["findings"] == nil ||
+		got["composed"].(map[string]string)["anchor"] != "sha256:"+strings.Repeat("c", 64) || len(got["composed"].(map[string]string)) != 1 {
+		t.Errorf("compare = %+v", got)
+	}
+	pub, _ := out.(map[string]any)["published"].(map[string][]publishedRow)
+	if a, l := pub["anchor"], pub["laptop"]; len(a) != 2 || a[0].Module != "node" || a[1].Module != "web" || a[1].FP != fpNew ||
+		!strings.HasPrefix(a[1].Digest, "sha256:") || len(l) != 1 || l[0].Refused != "a required value is unset" || l[0].Digest != "" {
+		t.Errorf("published = %+v (unread %v)", pub, out.(map[string]any)["published-unread"])
+	}
+	// Read by watch (issue 1953 L5f): the same answer, each watched state started once, and no get per key of the
+	// large states (the modules, their manifests, the composed record).
+	watches := map[string]int{}
+	byWatch := newWantsTools(st, nil, nil)
+	byWatch.watched = stdio.WatchedStatesOver(func(state string, handle func(stdio.StateChange) error) error {
+		watches[state]++
+		for k, v := range st[state].values {
+			_ = handle(stdio.StateChange{Key: k, Op: stdio.OpPut, Value: v, Current: true})
+		}
+		return nil
+	}, func(state, key string) ([]byte, bool, error) {
+		watches[state+" by key"]++
+		v, ok := st[state].values[key]
+		return v, ok, nil
+	})
+	for range 2 {
+		wout, werr := byWatch.doUpgrade(map[string]any{"compare": "true"}, "op")
+		if werr != nil {
+			t.Fatal(werr)
+		}
+		if got := wout.(map[string]any); got["composed"].(map[string]string)["anchor"] != "sha256:"+strings.Repeat("c", 64) {
+			t.Errorf("compare by watch = %+v", got)
+		}
+	}
+	if n := watches[manifestsState+" by key"]; n == 0 || n > len(st[manifestsState].values) {
+		t.Errorf("the manifests were read by key %d times, want each once", n)
+	}
+	for _, state := range []string{modulesState, haveState, health.FindingsState} {
+		if watches[state] != 1 {
+			t.Errorf("%s was watched %d times, want once", state, watches[state])
+		}
+	}
+	// ADR 0580 clause 3: the compare reads through mesh-sdk's watched reader and the seat keeps no mirror of its own.
+	for f := range reflect.TypeFor[wantsTools]().Fields() {
+		if f.Type.Kind() == reflect.Map || (f.Type.Kind() == reflect.Pointer && f.Type.Elem().Kind() == reflect.Map) {
+			t.Errorf("wantsTools keeps %s, a copy of its own beside the watched reader", f.Name)
+		}
+	}
+	if watches[policiesState] != 0 {
+		t.Errorf("the seat's own small policies state was watched: %v", watches)
+	}
+	// a person's record for web: written, recorded, said.
+	if _, err := w.doUpgrade(map[string]any{"module": "web", "policy": "record", "why": "the operator checks it"}, "person.jochen"); err != nil {
+		t.Fatal(err)
+	}
+	chosen, _ := assign.DecodePolicies(st[policiesState].values)
+	if c := chosen["web"]; c.Policy != catalogue.PolicyRecord || c.By != "person.jochen" || !slices.Contains(asked, "seat:mesh-hand-acts.hand-act") ||
+		len(said) != 1 || !strings.HasPrefix(said[0], "policy-changed policy-changed.web.") {
+		t.Errorf("chosen %+v, asked %v, said %v", c, asked, said)
+	}
+	// A person may choose the bus's policy as any module's (ADR 0601 §1: no part treats the module that provides the bus apart).
+	if _, err := w.doUpgrade(map[string]any{"module": "nats", "policy": "roll", "why": "x"}, "op"); err != nil {
+		t.Errorf("a person's policy for the bus was refused: %v", err)
+	}
+	if _, err := w.doUpgrade(map[string]any{"module": "nats", "policy": "default", "why": "back to the module"}, "op"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := w.doUpgrade(map[string]any{"module": "web", "policy": "roll"}, "op"); err == nil {
+		t.Error("a policy without why was set")
+	}
+	if _, err := w.doUpgrade(map[string]any{"module": "web", "policy": "default", "why": "back to the module"}, "op"); err != nil || len(st[policiesState].values) != 0 {
+		t.Errorf("default left %v (%v)", st[policiesState].values, err)
+	}
+	// bus: the node behind the indexer's newest.
+	b, err := w.doBus(nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	nodes := b.(map[string]any)["nodes"].([]busNode)
+	if b.(map[string]any)["module"] != "nats" || len(nodes) != 2 || !nodes[0].Behind || nodes[1].Behind || !slices.Contains(asked, "seat:mesh-hand-acts.hand-acts") {
+		t.Errorf("bus = %+v, asked %v", b, asked)
+	}
+	if tools := w.tools(); len(tools) != 2 || tools[0].Name != "mesh-wants.upgrade" || tools[1].Run == nil {
+		t.Errorf("the seat's verbs as served: %+v", tools)
+	}
+}
+
+// readManifest is the module's manifest, read as the controller reads it.
+func readManifest() (catalogue.Manifest, error) {
+	raw, err := os.ReadFile("../../module.json")
+	if err != nil {
+		return catalogue.Manifest{}, err
+	}
+	return catalogue.Decode(raw)
+}
+
+// countingKV is a memKV that counts its puts.
+type countingKV struct {
+	memKV
+	writes *int
+}
+
+func (c *countingKV) Put(ctx context.Context, key string, value []byte) (uint64, error) {
+	*c.writes++
+	return c.memKV.Put(ctx, key, value)
+}
+
+// revKV is a bucket with real revisions, refusing a write at a revision that is not the key's, and a write of refuse;
+// log is every write in order.
+type revKV struct {
+	jetstream.KeyValue
+	rev    uint64
+	values map[string][]byte
+	revs   map[string]uint64
+	log    []string
+	refuse string
+}
+
+func (k *revKV) write(key string, value []byte) uint64 {
+	k.rev++
+	k.values[key], k.revs[key] = value, k.rev
+	return k.rev
+}
+
+func (k *revKV) Create(_ context.Context, key string, value []byte, _ ...jetstream.KVCreateOpt) (uint64, error) {
+	if _, ok := k.values[key]; ok || key == k.refuse {
+		return 0, errors.New("key exists")
+	}
+	k.log = append(k.log, "create "+key)
+	return k.write(key, value), nil
+}
+
+func (k *revKV) Update(_ context.Context, key string, value []byte, revision uint64) (uint64, error) {
+	if k.revs[key] != revision || key == k.refuse {
+		return 0, errors.New("wrong last sequence")
+	}
+	k.log = append(k.log, "update "+key)
+	return k.write(key, value), nil
+}
+
+func (k *revKV) Delete(_ context.Context, key string, _ ...jetstream.KVDeleteOpt) error {
+	if key == k.refuse {
+		return errors.New("wrong last sequence")
+	}
+	k.log = append(k.log, "delete "+key)
+	delete(k.values, key)
+	delete(k.revs, key)
+	return nil
+}
+
+// historyStore is a memStore whose history is given.
+type historyStore struct {
+	memStore
+	revisions map[string][]stdio.StateRevision
+}
+
+func (s historyStore) history(_, key string) ([]stdio.StateRevision, error) {
+	return s.revisions[key], nil
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/testdata/catalogue-835bf22b-xterm.module.json

@@ -0,0 +1,236 @@
+{
+  "module": "xterm",
+  "version": "1",
+  "moved": true,
+  "capabilities": [
+    "package-manager"
+  ],
+  "requires": [
+    "x11-display"
+  ],
+  "claims": [
+    {
+      "name": "node-terminal-emulator",
+      "scope": "node",
+      "serves": [
+        "open"
+      ]
+    }
+  ],
+  "tools": [
+    "xterm_font",
+    "xterm_colours"
+  ],
+  "config": {
+    "face": {
+      "type": "string",
+      "description": "The font family xterm draws with, as fc-list names it: JetBrainsMono Nerd Font, because research 026/04 chose it for its glyphs the prompt uses. A family the machine does not have falls back to the nearest installed face (xterm_font says which).",
+      "pattern": "[A-Za-z0-9 ._-]{1,64}",
+      "default": "JetBrainsMono Nerd Font"
+    },
+    "size": {
+      "type": "number",
+      "description": "The size of xterm's text, in points: 12 reads well on a screen of about 100 DPI, and a denser screen needs a larger size.",
+      "minimum": 6,
+      "maximum": 72,
+      "predefined": "font-size",
+      "default": 12
+    },
+    "save-lines": {
+      "type": "number",
+      "description": "How many lines of scrollback xterm keeps per terminal: 10000 holds a long build log, and each line costs memory in every open terminal.",
+      "minimum": 0,
+      "maximum": 1000000,
+      "default": 10000
+    },
+    "term-name": {
+      "type": "string",
+      "description": "The TERM value xterm sets for the programs it runs: xterm-256color, because the palette has 256 colours and every program knows the name.",
+      "pattern": "[A-Za-z0-9._-]{1,64}",
+      "default": "xterm-256color"
+    },
+    "render-font": {
+      "type": "boolean",
+      "description": "Whether xterm draws with fontconfig faces (true) or the old X core fonts (false): true, because the face is a fontconfig family and core fonts cannot show it.",
+      "default": true
+    },
+    "bold-mode": {
+      "type": "boolean",
+      "description": "Whether xterm draws bold text by overstriking the normal face (true): false, because the face has a real bold style and overstriking blurs it.",
+      "default": false
+    },
+    "always-bold-mode": {
+      "type": "boolean",
+      "description": "Whether xterm overstrikes bold even where the face has a bold style (true): false, for the same reason as bold-mode.",
+      "default": false
+    },
+    "allow-bold-fonts": {
+      "type": "boolean",
+      "description": "Whether xterm may use the face's bold style for bold text (true): true, so bold text is drawn with the real bold weight.",
+      "default": true
+    },
+    "background": {
+      "type": "string",
+      "description": "The terminal's background colour, as #rrggbb: black, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#000000"
+    },
+    "foreground": {
+      "type": "string",
+      "description": "The terminal's text colour, as #rrggbb: a light grey, easier on the eyes than white on black.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#a8a8a8"
+    },
+    "color0": {
+      "type": "string",
+      "description": "Palette entry 0, the normal black, as #rrggbb: #000000, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#000000"
+    },
+    "color1": {
+      "type": "string",
+      "description": "Palette entry 1, the normal red, as #rrggbb: #9e1828, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#9e1828"
+    },
+    "color2": {
+      "type": "string",
+      "description": "Palette entry 2, the normal green, as #rrggbb: #008800, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#008800"
+    },
+    "color3": {
+      "type": "string",
+      "description": "Palette entry 3, the normal yellow, as #rrggbb: #d2bb4b, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#d2bb4b"
+    },
+    "color4": {
+      "type": "string",
+      "description": "Palette entry 4, the normal blue, as #rrggbb: #414171, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#414171"
+    },
+    "color5": {
+      "type": "string",
+      "description": "Palette entry 5, the normal magenta, as #rrggbb: #963c59, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#963c59"
+    },
+    "color6": {
+      "type": "string",
+      "description": "Palette entry 6, the normal cyan, as #rrggbb: #418179, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#418179"
+    },
+    "color7": {
+      "type": "string",
+      "description": "Palette entry 7, the normal white, as #rrggbb: #bebebe, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#bebebe"
+    },
+    "color8": {
+      "type": "string",
+      "description": "Palette entry 8, the bright black, as #rrggbb: #666666, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#666666"
+    },
+    "color9": {
+      "type": "string",
+      "description": "Palette entry 9, the bright red, as #rrggbb: #bc5766, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#bc5766"
+    },
+    "color10": {
+      "type": "string",
+      "description": "Palette entry 10, the bright green, as #rrggbb: #61a171, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#61a171"
+    },
+    "color11": {
+      "type": "string",
+      "description": "Palette entry 11, the bright yellow, as #rrggbb: #e7db52, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#e7db52"
+    },
+    "color12": {
+      "type": "string",
+      "description": "Palette entry 12, the bright blue, as #rrggbb: #5085af, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#5085af"
+    },
+    "color13": {
+      "type": "string",
+      "description": "Palette entry 13, the bright magenta, as #rrggbb: #a97a99, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#a97a99"
+    },
+    "color14": {
+      "type": "string",
+      "description": "Palette entry 14, the bright cyan, as #rrggbb: #6ba4a4, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#6ba4a4"
+    },
+    "color15": {
+      "type": "string",
+      "description": "Palette entry 15, the bright white, as #rrggbb: #ffffff, as both workstations ran it.",
+      "pattern": "#[0-9a-fA-F]{6}",
+      "default": "#ffffff"
+    },
+    "copy-binding": {
+      "type": "string",
+      "description": "The key combination that copies the selection to the clipboard, in X translation syntax: Ctrl Shift ~Alt <Key> C, so a plain Ctrl+C still interrupts the program. It holds no colon, backslash or line break, which would end the resource.",
+      "pattern": "[^:\\\\\\n]+",
+      "default": "Ctrl Shift ~Alt <Key> C"
+    },
+    "paste-binding": {
+      "type": "string",
+      "description": "The key combination that pastes the clipboard, in X translation syntax: Ctrl Shift ~Alt <Key> V, the pair of copy-binding. It holds no colon, backslash or line break, which would end the resource.",
+      "pattern": "[^:\\\\\\n]+",
+      "default": "Ctrl Shift ~Alt <Key> V"
+    }
+  },
+  "items": [
+    {
+      "collection": "environment",
+      "name": "terminal",
+      "attributes": {
+        "kind": "variable",
+        "name": "TERMINAL"
+      },
+      "template": "files/env-terminal"
+    },
+    {
+      "collection": "shell:xresources:normal",
+      "name": "xresources-normal",
+      "template": "files/xresources-normal"
+    }
+  ],
+  "resources": [
+    {
+      "id": "package",
+      "type": "package",
+      "package": "xterm"
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/xterm-tools",
+        "binary": "xterm-tools",
+        "loads": [
+          "xterm-tools"
+        ]
+      },
+      {
+        "name": "files",
+        "kind": "archive",
+        "from": "files"
+      }
+    ]
+  }
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/tools.go

@@ -0,0 +1,379 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"regexp"
+	"slices"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+
+	"git.novox.be/novox/mesh-delivery/sdk/enginereads"
+)
+
+// The assigner's tools (novox/hq ADR 0546), served through the tool runner from its bundle: a process never serves (ADR
+// 0436, mesh-sdk process). They write and read the puts; the assigner's process takes each put further (puts.go) and says
+// every step as the event put. They are the module's own tools; the seat mesh-placement's verbs are served beside them
+// (seat_tools.go, ADR 0567 §10).
+
+// engineReadsTool lists what each node's engine reads, as the assigner uses it, and asks one node's engine again.
+const engineReadsTool = "assigner_engine_reads"
+
+// putsState is the assigner's state of puts, as the runtime names a module's own state.
+const putsState = "puts"
+
+// answerWithin is how long assigner_put waits for the assigner's process to take the put up before it answers what stands.
+var answerWithin = 20 * time.Second
+
+// store is what the tools need of the states: the runtime's (stdio.State), or a test's.
+type store interface {
+	get(state, key string) ([]byte, uint64, bool, error)
+	put(state, key string, value []byte) error
+	keys(state string) ([]string, error)
+}
+
+// putTools serves the tools over a store, and keeps the newest value of every put it heard, to wait on.
+type putTools struct {
+	st  store
+	now func() time.Time
+	mu  sync.Mutex
+	// heard is every put the watch handed, by key; changed is closed and replaced at each.
+	heard   map[string][]byte
+	changed chan struct{}
+}
+
+func newPutTools(st store) *putTools {
+	return &putTools{st: st, now: time.Now, heard: map[string][]byte{}, changed: make(chan struct{})}
+}
+
+// hear takes a put's change in from the watch.
+func (s *putTools) hear(key string, value []byte) {
+	s.mu.Lock()
+	s.heard[key] = value
+	close(s.changed)
+	s.changed = make(chan struct{})
+	s.mu.Unlock()
+}
+
+// fullFP is a fingerprint of the new form, whole; prefix at least its first twelve hex digits.
+var (
+	fullFP = regexp.MustCompile(`^src2:[0-9a-f]{64}$`)
+	prefix = regexp.MustCompile(`^(src2:)?[0-9a-f]{12,63}$`)
+)
+
+// version reads the version a put names: newest (the indexer's fingerprint at the trunk), a whole fingerprint, or the start
+// of one the builder built, which must name one build alone.
+func (s *putTools) version(module, version string) (string, error) {
+	v := strings.ToLower(strings.TrimSpace(version))
+	switch {
+	case v == "newest":
+		raw, _, found, err := s.st.get(delivery.IndexerModule+".modules", module)
+		if err != nil {
+			return "", fmt.Errorf("the indexer's modules cannot be read: %w", err)
+		}
+		if !found {
+			return "", fmt.Errorf("the indexer holds no module %s at the trunk", module)
+		}
+		m, err := delivery.DecodeModule(raw)
+		if err != nil {
+			return "", fmt.Errorf("the indexer's %s cannot be read: %w", module, err)
+		}
+		if m.FP2 == "" {
+			return "", fmt.Errorf("the indexer holds no fingerprint of the new form for %s: %s", module, m.None2)
+		}
+		return m.FP2, nil
+	case fullFP.MatchString(v):
+		return v, nil
+	case prefix.MatchString(v):
+		start := strings.TrimPrefix(v, delivery.SourcePrefix2)
+		keys, err := s.st.keys(delivery.BuilderModule + ".builds")
+		if err != nil {
+			return "", fmt.Errorf("the builder's builds cannot be listed: %w", err)
+		}
+		var found []string
+		for _, k := range keys {
+			m, fp, err := delivery.ParseBuilderBuildKey(k)
+			if err == nil && m == module && strings.HasPrefix(strings.TrimPrefix(fp, delivery.SourcePrefix2), start) {
+				found = append(found, fp)
+			}
+		}
+		switch len(found) {
+		case 0:
+			return "", fmt.Errorf("the builder built no %s whose fingerprint starts %s: give it whole", module, start)
+		case 1:
+			return found[0], nil
+		}
+		sort.Strings(found)
+		return "", fmt.Errorf("%s starts %d fingerprints of %s the builder built (%s): give more of it", start, len(found), module, strings.Join(found, ", "))
+	}
+	return "", fmt.Errorf("%q is no version: newest, a fingerprint (src2: and 64 hex digits) or at least its first 12 hex digits", version)
+}
+
+// putAnswer is what assigner_put and assigner_puts answer of one put.
+type putAnswer struct {
+	Node   string `json:"node"`
+	Module string `json:"module"`
+	delivery.Put
+	Follow string `json:"follow,omitempty"`
+}
+
+// doPut is the tool assigner_put.
+func (s *putTools) doPut(args map[string]any, by string) (any, error) {
+	node, module, why := arg(args, "node"), arg(args, "module"), arg(args, "why")
+	key, err := delivery.PutKey(node, module)
+	if err != nil {
+		return nil, err
+	}
+	if why == "" {
+		return nil, errors.New("put says why: it is kept with the put and said in any ask")
+	}
+	hold := false
+	switch arg(args, "hold") {
+	case "true":
+		hold = true
+	case "", "false":
+	default:
+		return nil, fmt.Errorf("hold is true or false, not %q", arg(args, "hold"))
+	}
+	fp, err := s.version(module, arg(args, "version"))
+	if err != nil {
+		return nil, err
+	}
+	now := s.now().UTC()
+	words := fmt.Sprintf("asked by %s: %s", by, why)
+	if raw, _, found, err := s.st.get(putsState, key); err != nil {
+		return nil, fmt.Errorf("the put of %s on %s cannot be read: %w", module, node, err)
+	} else if found {
+		if before, err := delivery.DecodePut(raw); err == nil && !delivery.PutEnded(before.Step) {
+			if before.FP == fp && before.Hold == hold {
+				return putAnswer{Node: node, Module: module, Put: before, Follow: followPut(node, module)}, nil
+			}
+			words += fmt.Sprintf("; it replaces the put of %s at %s, which stood at %s", module, shortFP(before.FP), before.Step)
+		}
+	}
+	p := delivery.Put{FP: fp, Hold: hold, Why: why, By: by, At: now}.Said(now, delivery.PutAsked, words)
+	data, err := delivery.EncodePut(p)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.st.put(putsState, key, data); err != nil {
+		return nil, fmt.Errorf("the put of %s on %s is not written: %w", module, node, err)
+	}
+	s.hear(key, data)
+	return putAnswer{Node: node, Module: module, Put: s.await(key, p), Follow: followPut(node, module)}, nil
+}
+
+// await is the put at key once the assigner's process took it up past its asking, or as it stands after answerWithin.
+func (s *putTools) await(key string, p delivery.Put) delivery.Put {
+	deadline := time.After(answerWithin)
+	for {
+		s.mu.Lock()
+		raw, changed := s.heard[key], s.changed
+		s.mu.Unlock()
+		if now, err := delivery.DecodePut(raw); err == nil && now.At.Equal(p.At) {
+			p = now
+			if now.Step != delivery.PutAsked && now.Step != delivery.PutBuild && now.Step != delivery.PutCompose {
+				return p // it waits on a person or the node, or ended
+			}
+		}
+		select {
+		case <-changed:
+		case <-deadline:
+			return p
+		}
+	}
+}
+
+// followPut says how a caller follows a put after the answer.
+func followPut(node, module string) string {
+	return fmt.Sprintf("the put goes on: mesh_wait on mesh-delivery-assigner.put with filter {\"node\": %q, \"module\": %q}, then "+
+		"mesh-delivery-assigner.assigner_puts for where it stands", node, module)
+}
+
+// doRelease is the tool assigner_release.
+func (s *putTools) doRelease(args map[string]any, by string) (any, error) {
+	node, module, why := arg(args, "node"), arg(args, "module"), arg(args, "why")
+	key, err := delivery.PutKey(node, module)
+	if err != nil {
+		return nil, err
+	}
+	if why == "" {
+		return nil, errors.New("release says why: it is kept with the put")
+	}
+	raw, _, found, err := s.st.get(putsState, key)
+	if err != nil {
+		return nil, fmt.Errorf("the put of %s on %s cannot be read: %w", module, node, err)
+	}
+	if !found {
+		return nil, fmt.Errorf("%s holds no put of %s: nothing to release", node, module)
+	}
+	p, err := delivery.DecodePut(raw)
+	if err != nil {
+		return nil, fmt.Errorf("the put of %s on %s cannot be read: %w", module, node, err)
+	}
+	if delivery.PutEnded(p.Step) {
+		return nil, fmt.Errorf("the put of %s on %s ended already (%s: %s): nothing to release", module, node, p.Step, p.Words)
+	}
+	p = p.Said(s.now(), delivery.PutReleased, fmt.Sprintf("released by %s: %s; the assigner's rules write the want again", by, why))
+	data, err := delivery.EncodePut(p)
+	if err != nil {
+		return nil, err
+	}
+	if err := s.st.put(putsState, key, data); err != nil {
+		return nil, fmt.Errorf("the release of %s on %s is not written: %w", module, node, err)
+	}
+	s.hear(key, data)
+	return putAnswer{Node: node, Module: module, Put: p}, nil
+}
+
+// doPuts is the tool assigner_puts.
+func (s *putTools) doPuts(args map[string]any) (any, error) {
+	keys, err := s.st.keys(putsState)
+	if err != nil {
+		return nil, fmt.Errorf("the puts cannot be listed: %w", err)
+	}
+	sort.Strings(keys)
+	out := []putAnswer{}
+	for _, key := range keys {
+		node, module, err := delivery.ParsePutKey(key)
+		if err != nil || (arg(args, "node") != "" && node != arg(args, "node")) || (arg(args, "module") != "" && module != arg(args, "module")) {
+			continue
+		}
+		raw, _, found, err := s.st.get(putsState, key)
+		if err != nil || !found {
+			continue
+		}
+		p, err := delivery.DecodePut(raw)
+		if err != nil {
+			continue
+		}
+		out = append(out, putAnswer{Node: node, Module: module, Put: p})
+	}
+	return map[string]any{"puts": out}, nil
+}
+
+func arg(args map[string]any, name string) string {
+	switch v := args[name].(type) {
+	case string:
+		return strings.TrimSpace(v)
+	case bool:
+		return fmt.Sprint(v)
+	}
+	return ""
+}
+
+// The tools' names, as the manifest lists them.
+const (
+	toolPut     = "assigner_put"
+	toolRelease = "assigner_release"
+	toolPuts    = "assigner_puts"
+)
+
+// schema is a tool's arguments, each a string: required ones first named, and switches true or false.
+func schema(properties map[string]string, required []string, switches ...string) map[string]any {
+	props := map[string]any{}
+	for name, description := range properties {
+		p := map[string]any{"type": "string", "description": description}
+		if slices.Contains(switches, name) {
+			p["enum"] = []string{"true", "false"}
+		}
+		props[name] = p
+	}
+	out := map[string]any{"type": "object", "properties": props}
+	if len(required) > 0 {
+		out["required"] = required
+	}
+	return out
+}
+
+// tools are the assigner's tools as the runtime serves them (ADR 0546 clause 1).
+func (s *putTools) tools() []stdio.Tool {
+	return []stdio.Tool{
+		{Name: toolPut, Description: "Put one version of a module on one machine (novox/hq ADR 0546): the build at that fingerprint, " +
+			"the composition and grant the controller wrote for that machine, then the machine's want naming it, held there until " +
+			"released when hold is true. A module whose moves a person takes (the bus, a module of policy record) is asked of the " +
+			"operator first, and the bus has its streams snapshotted after the yes. Answers what was done or what it waits on; the " +
+			"put goes on after the answer, each step said as the event mesh-delivery-assigner.put, and assigner_puts says where it stands.",
+			Input: schema(map[string]string{
+				"node":    "the machine, where the module is assigned",
+				"module":  "the module",
+				"version": "newest, a fingerprint (src2: and 64 hex digits), or at least its first 12 hex digits",
+				"hold":    "\"true\": the want stays at this version until released; \"false\" (the default): the rules move it again once it runs",
+				"why":     "why, kept with the put and said in any ask",
+			}, []string{"node", "module", "version", "why"}, "hold"),
+			Run: func(a map[string]any) (any, error) { return s.doPut(a, stdio.CallerOf(a)) }},
+		{Name: toolRelease, Description: "End a put on one machine (novox/hq ADR 0546): its hold is taken away and the assigner's " +
+			"rules write the machine's want again from their next pass. Nothing changes on the machine until they move it.",
+			Input: schema(map[string]string{"node": "the machine", "module": "the module", "why": "why, kept with the put"},
+				[]string{"node", "module", "why"}),
+			Run: func(a map[string]any) (any, error) { return s.doRelease(a, stdio.CallerOf(a)) }},
+		{Name: toolPuts, Description: "Every put and where it stands (novox/hq ADR 0546): its version, hold, why, each step with " +
+			"its time and words. Narrowed by machine or module. Read-only.",
+			Input: schema(map[string]string{"node": "one machine", "module": "one module"}, nil),
+			Run:   s.doPuts},
+	}
+}
+
+// runtimeStore is the runtime's states.
+type runtimeStore struct{}
+
+func (runtimeStore) get(state, key string) ([]byte, uint64, bool, error) {
+	e, err := stdio.State(state).Get(key)
+	if err != nil || e == nil {
+		return nil, 0, false, err
+	}
+	return e.Value, e.Revision, true, nil
+}
+
+func (runtimeStore) put(state, key string, value []byte) error {
+	_, err := stdio.State(state).Put(key, json.RawMessage(value))
+	return err
+}
+
+func (runtimeStore) keys(state string) ([]string, error) { return stdio.State(state).Keys() }
+
+// serveTools serves the tools to the runtime until it stops, hearing every put to answer assigner_put with its first steps.
+func serveTools() error {
+	s := newPutTools(runtimeStore{})
+	go func() {
+		<-stdio.Served()
+		for wait := 2 * time.Second; ; wait = min(wait*2, time.Minute) {
+			err := stdio.State(putsState).Watch("", func(c stdio.StateChange) error {
+				s.hear(c.Key, c.Value)
+				return nil
+			})
+			if err == nil {
+				return
+			}
+			fmt.Fprintf(os.Stderr, "mesh-delivery-assigner: the puts are not heard yet (%v); asked again in %s\n", err, wait)
+			time.Sleep(wait)
+		}
+	}()
+	tools := append(s.tools(), newSeatTools(runtimeStore{}, stdio.Ask).tools()...)
+	wants := newWantsTools(runtimeStore{}, stdio.Ask, func(e, id string, b any) error {
+		// The seat's event, said on the seat: a claimed seat's event is never the module's own.
+		return stdio.SeatPublish(wantsEventSubject(e), b, id)
+	})
+	wants.watched = stdio.NewWatchedStates() // the large states read whole from one watched copy (ADR 0580 clause 3)
+	tools = append(tools, wants.tools()...)
+	tools = append(tools, viewTools(os.Getenv, keptSource, time.Now)...)
+	// What each node's engine reads, as the assigner uses it (ADR 0618 §3): its own state engine-reads, asked again through it.
+	tools = append(tools, enginereads.Tool(engineReadsTool, "the assigner", enginereads.KeptState(stdio.State(engineReadsState)), false, time.Now))
+	return stdio.Serve("", tools)
+}
+
+// shortFP is a fingerprint's first twelve hex digits.
+func shortFP(fp string) string {
+	part, err := delivery.FingerprintKeyPart(fp)
+	if err != nil || len(part) < 12 {
+		return fp
+	}
+	return part[:12]
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/verbs.go

@@ -0,0 +1,128 @@
+package main
+
+import (
+	"context"
+	"slices"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+
+	"git.novox.be/novox/mesh-delivery/sdk/graph"
+
+	"mesh-delivery-assigner/internal/assign"
+)
+
+// The verb edges a want waits on (novox/hq ADR 0614 §2, §3): the module graph the indexer writes names what each module
+// invokes and serves and which of its verb edges it leaves out on a cycle (one place decides the cycle); a want waits for
+// each kept edge until a build serving its verb runs healthy, read from the haves, the builder's builds and the indexer's
+// manifests, as a provider is counted (ADR 0603 §5).
+
+// moduleGraph is the module graph as the indexer's first view and views family last said it (ADR 0631); a key that
+// does not decode is left out, so its module waits on no verb.
+func (p *passer) moduleGraph() graph.Graph {
+	g := graph.Graph{}
+	for key, raw := range p.w.read(graph.Bucket) {
+		module, err := graph.ParseKey(key)
+		if err != nil {
+			continue
+		}
+		if n, err := graph.Decode(raw); err == nil {
+			g[module] = n
+		}
+	}
+	return g
+}
+
+// keptInvokes are the verbs of module the graph keeps as edges: each it invokes and does not leave out, that a module
+// other than itself serves. A verb no module of the graph serves is no edge, so it holds nothing; nil when the graph holds
+// no node of module.
+func keptInvokes(g graph.Graph, module string) []string {
+	n, ok := g[module]
+	if !ok {
+		return nil
+	}
+	var out []string
+	for _, v := range n.Invokes {
+		if slices.Contains(n.LeftOut, v) {
+			continue
+		}
+		if slices.ContainsFunc(g.Servers(v), func(s string) bool { return s != module }) {
+			out = append(out, v)
+		}
+	}
+	return out
+}
+
+// served is, for this pass, whether a build serving a verb runs healthy on some node (graph.Served): every running healthy
+// have's build (the builder's builds key of its module and fingerprint) names its manifest, and the verbs that manifest
+// serves are served. A healthy build whose manifest cannot be read counts what the graph says its module serves, said in
+// the log, so a build read late never holds its callers for good; nil when the graph holds nothing, and no want waits on
+// a verb.
+func (p *passer) served(ctx context.Context, get getter, g graph.Graph, n assign.Nodes) func(string) bool {
+	if len(g) == 0 {
+		return nil
+	}
+	served, unread := graph.Served(n.Haves, func(module, fp string) ([]string, bool) { return p.servesOf(ctx, get, module, fp) },
+		func(module string) []string { return g[module].Serves })
+	if len(unread) > 0 {
+		p.logf("the manifest of the running build of %v cannot be read, so what the module graph says they serve is counted as served", unread)
+	}
+	return served
+}
+
+// offering is, for this pass, whether a build whose manifest offers a provision runs healthy on a node present (ADR 0603
+// §5, ADR 0614 §5): every running healthy have on an online node, its build's manifest read as servesOf reads it. A
+// healthy build whose manifest cannot be read counts what its module's trunk manifest offers, so a build read late never
+// holds a consumer for good.
+func (p *passer) offering(ctx context.Context, get getter, trunk map[string]catalogue.Manifest, n assign.Nodes) func(string) bool {
+	offered := map[string]bool{}
+	for node, haves := range n.Haves {
+		if !n.Online[node] {
+			continue
+		}
+		for module, h := range haves {
+			if h.Phase != delivery.PhaseRunning || h.Health != delivery.HealthOK {
+				continue
+			}
+			m, ok := p.manifestOf(ctx, get, module, h.FP)
+			if !ok {
+				m = trunk[module]
+			}
+			for _, o := range m.Offers() {
+				offered[o] = true
+			}
+		}
+	}
+	return func(provision string) bool { return offered[provision] }
+}
+
+// servesOf are the verbs the manifest of module's build at fp serves (graph.ServesOf), and whether it could be read.
+func (p *passer) servesOf(ctx context.Context, get getter, module, fp string) ([]string, bool) {
+	m, ok := p.manifestOf(ctx, get, module, fp)
+	if !ok {
+		return nil, false
+	}
+	return graph.ServesOf(m), true
+}
+
+// manifestOf is the manifest of module's build at fp (the builder's build names its digest in the indexer's manifests),
+// and whether it could be read.
+func (p *passer) manifestOf(ctx context.Context, get getter, module, fp string) (catalogue.Manifest, bool) {
+	key, err := delivery.BuilderBuildKey(module, fp)
+	if err != nil {
+		return catalogue.Manifest{}, false
+	}
+	raw := p.w.value(delivery.BuilderBuildsBucket, key)
+	if raw == nil {
+		return catalogue.Manifest{}, false
+	}
+	b, err := delivery.DecodeBuilderBuild(raw)
+	if err != nil || b.Manifest == "" {
+		return catalogue.Manifest{}, false
+	}
+	got := p.w.manifest(ctx, get, b.Manifest)
+	if got.err != "" {
+		return catalogue.Manifest{}, false
+	}
+	return got.manifest, true
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/views.go

@@ -0,0 +1,235 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"slices"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/handacts"
+	"git.novox.be/novox/mesh-sdk/go/health"
+	"git.novox.be/novox/mesh-sdk/go/process"
+
+	"git.novox.be/novox/mesh-sdk/go/views"
+
+	"git.novox.be/novox/mesh-delivery/sdk/graph"
+	"git.novox.be/novox/mesh-delivery/sdk/heard"
+
+	"mesh-delivery-assigner/internal/assign"
+)
+
+// viewsStream is the assigner's views family on its old streams section, beside placement (ADR 0619 §2, ADR 0615 §5),
+// as its manifest's `streams` names it; indexerViewsStream is the indexer's, as the indexer's manifest names it.
+const (
+	viewsStream        = "assigner-views"
+	indexerViewsStream = "indexer-views"
+)
+
+// marksBucket is the assigner's state of what its views family said each state up to.
+var marksBucket = delivery.AssignerModule + "_" + views.MarksState
+
+// viewedTool is one tool over one state of the assigner's.
+type viewedTool struct{ tool, state, words string }
+
+// firstViewTools are the assigner's first-view tools (ADR 0621 §1): each answers only its callers list
+// (views.CallersEnv), which the manifest writes.
+var firstViewTools = []viewedTool{
+	{"placement", delivery.PlacementState, "where each module is placed: the seat mesh-placement's placement, by module."},
+	{"seat-holders", delivery.SeatHoldersState, "who holds which seat on which node."},
+	{"wants", "wants", "what each node should run: want.<node>.<module>, its fingerprint and the rule that gave it."},
+}
+
+// readTools are the assigner's ordinary read tools, one per state its readers read (design 25 § 12.2).
+var readTools = []viewedTool{
+	{"assigner_read_placement", delivery.PlacementState, "where each module is placed, by module."},
+	{"assigner_read_seat_holders", delivery.SeatHoldersState, "who holds which seat on which node."},
+	{"assigner_read_wants", "wants", "what each node should run: want.<node>.<module>."},
+	{"assigner_read_findings", health.FindingsState, "the assigner's findings, which the condition keeper raises and clears."},
+	{"assigner_read_asks", "asks", "the asks the assigner put to a person, and their answers."},
+	{"assigner_read_differences", "differences", "every difference between a want and what a node runs."},
+}
+
+// viewedStates are the states the views family says, each by its bucket: the six its readers read.
+var viewedStates = map[string]string{
+	delivery.PlacementState:   delivery.PlacementBucket,
+	delivery.SeatHoldersState: delivery.SeatHoldersBucket,
+	"wants":                   delivery.AssignerWantsBucket,
+	health.FindingsState:      assign.FindingsBucket,
+	"asks":                    delivery.AssignerAsksBucket,
+	"differences":             delivery.AssignerDifferencesBucket,
+}
+
+// viewTools are the assigner's first-view and read tools, reading only its own states, so they answer as soon as its
+// runtime of its own is connected (ADR 0621 §3).
+func viewTools(getenv func(string) string, state func(string) views.Source, now func() time.Time) []stdio.Tool {
+	marks := state(views.MarksState)
+	var out []stdio.Tool
+	for _, t := range firstViewTools {
+		out = append(out, views.FirstViewTool(delivery.AssignerModule, t.tool, t.state, t.words, views.ParseCallers(getenv(views.CallersEnv(t.tool))), state(t.state), marks, now))
+	}
+	for _, t := range readTools {
+		out = append(out, views.ReadTool(delivery.AssignerModule, t.tool, t.state, t.words, state(t.state), marks, now))
+	}
+	// Its own first views, of the indexer's manifests, modules and graph (DLV-F3r, ADR 0631 §2): read, and asked again by hand.
+	return append(out, views.StatusTools(delivery.AssignerModule, "assigner_first_views", "assigner_first_view_again", stdio.State(views.StatusState), handacts.Recorder{Ask: stdio.Ask}, now)...)
+}
+
+func keptSource(name string) views.Source { return views.KeptSource{State: stdio.State(name)} }
+
+// startViews says each change of the assigner's viewed states on its views family, once its marks state is bound,
+// each state as soon as its bucket is (kvs, or bound once it appears). A watch that ends is sent on errs.
+func startViews(ctx context.Context, js jetstream.JetStream, nc process.Subscriber, account process.Account, kvs buckets, findings assign.Findings, errs chan<- error, logf func(string, ...any)) {
+	tooLarge := func(state, key string, size int) {
+		if findings.Put == nil {
+			return
+		}
+		k, v, err := views.TooLargeFinding(delivery.AssignerModule, state, key, size, time.Now())
+		if err == nil {
+			err = findings.Put(k, v)
+		}
+		if err != nil {
+			logf("views: the finding of %s.%s too large is not written: %v", state, key, err)
+		}
+	}
+	process.AwaitBucket(ctx, js, nc, marksBucket, "no change is said on the views family, so every reader waits on its first view", logf).Ready(func(mk jetstream.KeyValue) {
+		em := viewsEmitter(js, account, mk, findings, tooLarge, logf)
+		for _, state := range []string{"asks", "differences", health.FindingsState, delivery.PlacementState, delivery.SeatHoldersState, "wants"} {
+			state := state
+			start := func(kv jetstream.KeyValue) {
+				if err := em.Start(ctx, state, kv, errs); err != nil {
+					logf("%v: its readers ask its first view at each change until the assigner starts again", err)
+				}
+			}
+			if kv := kvs[viewedStates[state]]; kv != nil {
+				start(kv)
+				continue
+			}
+			process.AwaitBucket(ctx, js, nc, viewedStates[state], "its changes are not said on the views family", logf).Ready(start)
+		}
+	})
+}
+
+// viewsEmitter is the assigner's emitter of its views family: a change not said past views.Bound is its finding
+// view-unsaid, in its findings (review round 2); with no findings state it is said in the log only.
+func viewsEmitter(js jetstream.JetStream, account process.Account, mk jetstream.KeyValue, findings assign.Findings, tooLarge func(string, string, int), logf func(string, ...any)) views.Emitter {
+	em := views.Emitter{Owner: delivery.AssignerModule, Subject: account.StreamSubject, Publish: views.JetStreamPublish(js), Marks: mk, TooLarge: tooLarge, Logf: logf}
+	if findings.Put != nil && findings.Delete != nil {
+		em.Findings = assignerFindings{findings}
+	}
+	return em
+}
+
+// assignerFindings is the assigner's findings as views.Emitter's Findings.
+type assignerFindings struct{ f assign.Findings }
+
+func (a assignerFindings) Put(key string, value []byte) error { return a.f.Put(key, value) }
+func (a assignerFindings) Delete(key string) error            { return a.f.Delete(key) }
+
+// firstViewsBucket is the assigner's own state of its first views (views.StatusState).
+var firstViewsBucket = delivery.AssignerModule + "_" + views.StatusState
+
+// indexerViews are the assigner's first views of the indexer's manifests, modules and module graph (ADR 0615 §1,
+// ADR 0621 §2, ADR 0631; DLV-F2r): asked at the start through the indexer's tools, then followed on indexer-views, asking once more on a gap;
+// past the bound its finding names the indexer and the tool, cleared by the answer.
+type indexerViews struct {
+	js       jetstream.JetStream
+	account  process.Account
+	call     func(string, any) (json.RawMessage, error)
+	findings assign.Findings
+	status   *process.AwaitedBucket
+	logf     func(string, ...any)
+}
+
+// indexerFirstViews are the indexer's states the assigner takes by first view and the views family, each by the name of
+// the indexer's bucket the world keeps it under: manifests and modules (ADR 0621 §2), and the module graph, whose verb
+// edges a want waits on (ADR 0614 §2, §3; ADR 0631 §1).
+var indexerFirstViews = map[string]string{"manifests": delivery.ManifestsBucket, "modules": delivery.ModulesBucket, graph.State: graph.Bucket}
+
+// firstViewBound and firstViewWait are each first view's bound before its condition is raised, and its first wait
+// between two failed asks; zero is the views package's (views.Bound, two minutes, ADR 0615 §6; and a first wait of five
+// seconds). A test shortens them.
+var firstViewBound, firstViewWait time.Duration
+
+// start asks the three first views, each answer taken into w under the indexer's bucket names and settled once (a pass waits
+// for it), and hears the views family; it answers how many settles to wait for.
+func (iv *indexerViews) start(ctx context.Context, w *world, wake func(), settled chan<- struct{}) int {
+	finding := func(s views.Status, raised bool) {
+		if iv.findings.Put == nil {
+			return
+		}
+		key, value, err := views.UnansweredFinding(delivery.AssignerModule, s, time.Now())
+		if err == nil && raised {
+			err = iv.findings.Put(key, value)
+		} else if err == nil {
+			err = iv.findings.Delete(key)
+		}
+		if err != nil {
+			iv.logf("views: the finding of the first view %s is not written: %v", s.Tool, err)
+		}
+	}
+	followers := map[string]*views.Follower{}
+	var all []*views.Follower
+	for state, bucket := range indexerFirstViews {
+		bucket := bucket
+		tool := delivery.IndexerModule + "." + state
+		f := &views.Follower{Owner: delivery.IndexerModule, Tool: tool, State: state, Ask: views.AskVia(iv.call, tool), Logf: iv.logf,
+			Bound: firstViewBound, Wait: firstViewWait,
+			Raise: func(s views.Status) { finding(s, true) }, Clear: func(s views.Status) { finding(s, false) },
+			Changed: func(key string, value json.RawMessage, deleted bool, at time.Time) {
+				if deleted {
+					value = nil
+				}
+				w.putEntry(bucket, key, value, 0, at)
+				wake()
+			}}
+		followers[state] = f
+		all = append(all, f)
+		go func() {
+			if f.Start(ctx) == nil {
+				settled <- struct{}{}
+			}
+		}()
+	}
+	if iv.status != nil {
+		iv.status.Ready(func(kv jetstream.KeyValue) {
+			for _, f := range all {
+				f.Said = views.KeepStatus(ctx, kv, iv.logf)
+			}
+			if err := views.HearAgain(ctx, kv, all, iv.logf); err != nil {
+				iv.logf("views: assigner_first_view_again is not heard (%v) until the assigner starts again", err)
+			}
+		})
+	}
+	// Not heard, the indexer's views family is the finding family-not-heard until it binds (ADR 0615 §5).
+	stream := catalogue.StreamBusName(indexerViewsStream)
+	_ = notHeardWriter(iv.findings, iv.logf).Bind(stream, "the indexer's manifests, modules and graph are the first views' alone until the assigner starts again", func() error {
+		cons, err := iv.account.EventConsumer(ctx, iv.js, stream)
+		if err != nil {
+			return fmt.Errorf("the consumer %s on %s does not exist yet: %w", iv.account.EventConsumerName(), stream, err)
+		}
+		_, err = process.HearEvents(cons, views.Hear(ctx, followers, iv.logf), iv.logf)
+		return err
+	})
+	return len(all)
+}
+
+// notHeardWriter writes the assigner's finding of a family it does not hear into its findings (heard.Writer); with no
+// findings state it is said in the log alone.
+func notHeardWriter(findings assign.Findings, logf func(string, ...any)) heard.Writer {
+	w := heard.Writer{Observer: delivery.AssignerModule, Logf: logf, Put: findings.Put}
+	if findings.Delete != nil {
+		w.Delete = func(key string) error {
+			if keys, err := findings.Keys(); err == nil && !slices.Contains(keys, key) {
+				return nil // none stands
+			}
+			return findings.Delete(key)
+		}
+	}
+	return w
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/wants_tools.go

@@ -0,0 +1,320 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"sort"
+	"strconv"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/handacts"
+	"git.novox.be/novox/mesh-sdk/go/health"
+
+	"mesh-delivery-assigner/internal/assign"
+)
+
+// The seat mesh-wants' verbs (novox/hq ADR 0565 §7, §8, §9, §15; issue 1953 D4-D6), served through the tool runner beside the
+// put tools and mesh-placement's verbs. `upgrade` reads and sets a person's upgrade policy, kept in the state `policies`
+// (each set recorded as a hand act and said as policy-changed), and with compare lists the digest of the composition each node's
+// own have names beside every composition each node published (ADR 0593 §8, composed.go); `bus` says what a bus upgrade would do. The assigner's process reads
+// `policies` when it judges a move and writes the finding policy-split while a split stands.
+
+// The states the verbs read, as the runtime names them.
+const (
+	policiesState  = delivery.AssignerPoliciesState
+	manifestsState = delivery.IndexerModule + ".manifests"
+	// PolicyChangedEvent is the seat's event of a person's policy set or taken back.
+	PolicyChangedEvent = "policy-changed"
+	// busStepCause is the cause the bus's step is recorded under in the hand-act log.
+	busStepCause = "bus-upgrade"
+)
+
+// wantsTools serves the seat's verbs over a store, asking seats through ask and saying events through emit.
+type wantsTools struct {
+	st   seatStore
+	ask  func(key string, body any) (json.RawMessage, error)
+	emit func(event, id string, body any) error
+	now  func() time.Time
+	// watched is the copy of the large states it reads whole, each by one watch started on its first read and kept by
+	// its changes after (mesh-sdk's WatchedStates, novox/hq ADR 0580 clause 3), never a get per key, which timed out on
+	// a large state (issue 1953 L5f). Nil reads key by key.
+	watched *stdio.WatchedStates
+}
+
+// wantsEventSubject is the subject of one of the seat's events.
+func wantsEventSubject(event string) string {
+	return "mesh.seat." + catalogue.WantsSeat + ".event." + event
+}
+
+func newWantsTools(st seatStore, ask func(string, any) (json.RawMessage, error), emit func(event, id string, body any) error) *wantsTools {
+	return &wantsTools{st: st, ask: ask, emit: emit, now: time.Now}
+}
+
+// values reads every key of a state: from the watched copy when there is one, else key by key.
+func (s *wantsTools) values(state string) (map[string][]byte, error) {
+	if s.watched != nil {
+		return s.watched.Values(state)
+	}
+	return s.direct(state)
+}
+
+// direct reads a state key by key, for a small state of the seat's own.
+func (s *wantsTools) direct(state string) (map[string][]byte, error) {
+	keys, err := s.st.keys(state)
+	if err != nil {
+		return nil, fmt.Errorf("%s cannot be listed: %w", state, err)
+	}
+	out := map[string][]byte{}
+	for _, k := range keys {
+		raw, _, found, err := s.st.get(state, k)
+		if err != nil {
+			return nil, fmt.Errorf("%s %s cannot be read: %w", state, k, err)
+		}
+		if found {
+			out[k] = raw
+		}
+	}
+	return out, nil
+}
+
+// manifest reads a manifest by its digest: kept once read when there is a watched copy, a manifest never changing
+// under its digest.
+func (s *wantsTools) manifest(digest string) ([]byte, bool, error) {
+	if s.watched != nil {
+		return s.watched.Once(manifestsState, digest)
+	}
+	raw, _, found, err := s.st.get(manifestsState, digest)
+	return raw, found, err
+}
+
+// manifests is every module the indexer holds, with its trunk manifest and fingerprint.
+func (s *wantsTools) manifests() (map[string]catalogue.Manifest, map[string]delivery.Module, error) {
+	mods, err := s.values(modulesState)
+	if err != nil {
+		return nil, nil, err
+	}
+	out, held := map[string]catalogue.Manifest{}, map[string]delivery.Module{}
+	for name, raw := range mods {
+		m, err := delivery.DecodeModule(raw)
+		if err != nil {
+			continue
+		}
+		held[name] = m
+		if m.Manifest == "" {
+			continue
+		}
+		mraw, found, err := s.manifest(m.Manifest)
+		if err != nil || !found {
+			continue
+		}
+		kept, err := delivery.DecodeManifest(mraw)
+		if err != nil {
+			continue
+		}
+		// Decoded, never judged (ADR 0578 §3); one that does not decode is left out of the answer, as before.
+		if man, err := catalogue.Decode([]byte(kept.JSON)); err == nil {
+			out[name] = man
+		}
+	}
+	return out, held, nil
+}
+
+// policyRow is one module's policy as upgrade answers it.
+type policyRow struct {
+	Module string `json:"module"`
+	Policy string `json:"policy"`
+	From   string `json:"from"`
+	Why    string `json:"why,omitempty"`
+	By     string `json:"by,omitempty"`
+}
+
+// doUpgrade is the verb upgrade: read every module's policy or one's; with policy and why set a person's choice, or take it
+// back with default; with compare each node's composition and the assigner's findings.
+func (s *wantsTools) doUpgrade(args map[string]any, by string) (any, error) {
+	manifests, _, err := s.manifests()
+	if err != nil {
+		return nil, err
+	}
+	raw, err := s.direct(policiesState) // the seat's own small state, read whole after its own writes
+	if err != nil {
+		return nil, err
+	}
+	chosen, unreadable := assign.DecodePolicies(raw)
+	if arg(args, "compare") == "true" {
+		haves, err := s.values(haveState)
+		if err != nil {
+			return nil, err
+		}
+		composed := map[string]string{}
+		for key, raw := range haves {
+			if node, _, isNode, err := delivery.ParseHaveKey(key); err == nil && isNode {
+				if h, err := delivery.DecodeHaveNode(raw); err == nil && h.Composed != "" {
+					composed[node] = h.Composed
+				}
+			}
+		}
+		out := map[string]any{"composed": composed}
+		// And what every node published (ADR 0593 §8), read only to compare.
+		if values, err := s.values(delivery.ComposedRead); err != nil {
+			out["published-unread"] = err.Error()
+		} else {
+			out["published"] = published(values)
+		}
+		// The assigner's findings, its said conditions as the condition keeper reads them (§15).
+		if found, err := s.values(health.FindingsState); err != nil {
+			out["findings-unread"] = err.Error()
+		} else {
+			keys := []string{}
+			for k := range found {
+				keys = append(keys, k)
+			}
+			sort.Strings(keys)
+			out["findings"] = keys
+		}
+		return out, nil
+	}
+	module, policy := arg(args, "module"), arg(args, "policy")
+	if policy != "" {
+		return s.setPolicy(module, policy, arg(args, "why"), by, manifests)
+	}
+	var rows []policyRow
+	for name, m := range manifests {
+		if module != "" && name != module {
+			continue
+		}
+		p, from, why, who := assign.PolicyOf(m, chosen)
+		rows = append(rows, policyRow{Module: name, Policy: p, From: from, Why: why, By: who})
+	}
+	if module != "" && len(rows) == 0 {
+		return nil, fmt.Errorf("the indexer holds no manifest of %s", module)
+	}
+	sort.Slice(rows, func(i, j int) bool { return rows[i].Module < rows[j].Module })
+	return map[string]any{"modules": rows, "unreadable": unreadable}, nil
+}
+
+// setPolicy writes a person's choice of a module's policy, or deletes it for default, records the act in the hand-act log
+// and says policy-changed. The bus's choice is a person's as any module's (ADR 0601 §1).
+func (s *wantsTools) setPolicy(module, policy, why, by string, manifests map[string]catalogue.Manifest) (any, error) {
+	if module == "" {
+		return nil, errors.New("a policy is set for one module: name it")
+	}
+	if _, ok := manifests[module]; !ok {
+		return nil, fmt.Errorf("the indexer holds no manifest of %s", module)
+	}
+	if why == "" {
+		return nil, errors.New("a person's policy says why")
+	}
+	if by == "" || by == stdio.Unproven {
+		return nil, errors.New("a person's policy names who chose it, and the runtime proved no caller")
+	}
+	what := fmt.Sprintf("mesh-wants.upgrade %s %s", module, policy)
+	if policy == "default" {
+		if err := s.st.del(policiesState, module); err != nil {
+			return nil, fmt.Errorf("the choice for %s cannot be taken back: %w", module, err)
+		}
+	} else {
+		p := catalogue.PersonPolicy{V: catalogue.PersonPolicyVersion, Module: module, Policy: policy, Why: why, By: by, At: s.now().UTC()}
+		if err := p.Check(); err != nil {
+			return nil, err
+		}
+		raw, _ := json.Marshal(p)
+		if err := s.st.put(policiesState, module, raw); err != nil {
+			return nil, fmt.Errorf("the choice for %s cannot be written: %w", module, err)
+		}
+	}
+	rec := handacts.Recorder{Ask: s.ask}
+	taken, rerr := rec.Record(handacts.Request{What: what, Why: why, Cause: "upgrade-policy", Verb: "mesh-wants.upgrade"})
+	recorded := taken.Log
+	if rerr != nil {
+		recorded = "not recorded: " + rerr.Error()
+	}
+	body := map[string]any{"module": module, "policy": policy, "why": why, "by": by}
+	said := ""
+	if s.emit != nil {
+		id := PolicyChangedEvent + "." + module + "." + strconv.FormatInt(s.now().UnixNano(), 10)
+		if err := s.emit(PolicyChangedEvent, id, body); err != nil {
+			said = "not said: " + err.Error()
+		}
+	}
+	return map[string]any{"set": body, "hand-act": recorded, "event": said}, nil
+}
+
+// busNode is one node's bus as bus answers it.
+type busNode struct {
+	Node   string `json:"node"`
+	FP     string `json:"fp"`
+	Behind bool   `json:"behind"`
+}
+
+// doBus is the verb bus: the fingerprint of the bus module each node runs against the indexer's newest, the nodes behind,
+// the last bus steps of the hand-act log and the assigner's puts of the bus. Read-only.
+func (s *wantsTools) doBus(map[string]any) (any, error) {
+	manifests, held, err := s.manifests()
+	if err != nil {
+		return nil, err
+	}
+	bus := ""
+	for name, m := range manifests {
+		if catalogue.ProvidesBus(m) {
+			bus = name
+		}
+	}
+	if bus == "" {
+		return nil, errors.New("the indexer holds no module that provides the bus")
+	}
+	newest := held[bus].FP2
+	haves, err := s.values(haveState)
+	if err != nil {
+		return nil, err
+	}
+	var nodes []busNode
+	for key, raw := range haves {
+		node, module, isNode, err := delivery.ParseHaveKey(key)
+		if err != nil || isNode || module != bus {
+			continue
+		}
+		h, err := delivery.DecodeHave(raw)
+		if err != nil || h.Phase == delivery.PhaseRemoved {
+			continue
+		}
+		nodes = append(nodes, busNode{Node: node, FP: h.FP, Behind: newest != "" && h.FP != newest})
+	}
+	sort.Slice(nodes, func(i, j int) bool { return nodes[i].Node < nodes[j].Node })
+	out := map[string]any{"module": bus, "newest": newest, "nodes": nodes}
+	if steps, err := s.ask("seat:"+handacts.Seat+".hand-acts", map[string]any{"cause": busStepCause, "days": 90}); err != nil {
+		out["steps-unread"] = err.Error()
+	} else {
+		out["steps"] = steps
+	}
+	puts, err := s.values(putsState)
+	if err != nil {
+		out["puts-unread"] = err.Error()
+	} else {
+		mine := map[string]json.RawMessage{}
+		for k, v := range puts {
+			if _, module, err := delivery.ParsePutKey(k); err == nil && module == bus {
+				mine[k] = v
+			}
+		}
+		out["puts"] = mine
+	}
+	return out, nil
+}
+
+// tools are the seat's verbs as the runtime serves them, each named <seat>.<verb>, with the seat's own schemas.
+func (s *wantsTools) tools() []stdio.Tool {
+	seat, _ := catalogue.SeatNamed(catalogue.WantsSeat)
+	run := map[string]func(map[string]any) (any, error){
+		"upgrade": func(a map[string]any) (any, error) { return s.doUpgrade(a, stdio.CallerOf(a)) },
+		"bus":     s.doBus,
+	}
+	var out []stdio.Tool
+	for _, v := range seat.Serves {
+		out = append(out, stdio.Tool{Name: catalogue.WantsSeat + "." + v.Name, Description: v.Description, Input: v.Input, Run: run[v.Name]})
+	}
+	return out
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/world.go

@@ -0,0 +1,542 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"maps"
+	"slices"
+	"sort"
+	"sync"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+
+	"mesh-delivery-assigner/internal/assign"
+)
+
+// noModuleWords is the indexer's reason for a module of a candidate whose directory the merge preview holds no manifest
+// for (mesh-sdk delivery.CandidateNoneNoModule, which the indexer writes): the change removes the module.
+const noModuleWords = delivery.CandidateNoneNoModule
+
+// world is what the assigner watched, as it stands now: every value by bucket and key, and the manifests read by
+// digest. The watches write it; a pass reads it.
+type world struct {
+	mu        sync.Mutex
+	values    map[string]map[string][]byte
+	manifests map[string]parsed
+	// healthy is, by have key, every fingerprint the node ran healthy, oldest first, each once: what a set-back goes to.
+	healthy map[string][]string
+	// changes counts, by bucket and key, the values this process has seen the key take: a value written again is another.
+	changes map[string]uint64
+	// meta is, by bucket and key, the revision and the time of the value held now, where the watch said them (putEntry).
+	meta map[string]entryMeta
+	// trunkBuilt is, by module, its newest done trunk build in the builder's log (putBuilt).
+	trunkBuilt map[string]delivery.BuildLogEntry
+	// placement is the seat's state placement assembled node by node from its keys in either form (mesh-sdk
+	// delivery.PlacementKeys; research 072 row 37): the one reader of its keys in the assigner.
+	placement *delivery.PlacementKeys
+	// sourceGroups is, by revision of the gate's source.main, the release (group) that moved it, from every revision its
+	// history keeps (watched with history): a build's source revision names the release that carries it (ADR 0601 §1).
+	sourceGroups map[uint64]string
+}
+
+// entryMeta is a value's revision in its bucket and when it was written.
+type entryMeta struct {
+	revision uint64
+	at       time.Time
+}
+
+// parsed is a manifest read by digest: its module and its manifest, or why it cannot be read.
+type parsed struct {
+	module   string
+	manifest catalogue.Manifest
+	err      string
+}
+
+func newWorld() *world {
+	return &world{values: map[string]map[string][]byte{}, manifests: map[string]parsed{}, healthy: map[string][]string{}, changes: map[string]uint64{},
+		meta: map[string]entryMeta{}, trunkBuilt: map[string]delivery.BuildLogEntry{}, placement: delivery.NewPlacementKeys(),
+		sourceGroups: map[uint64]string{}}
+}
+
+// putEntry is put, keeping the value's revision and the time it was written.
+func (w *world) putEntry(bucket, key string, value []byte, revision uint64, at time.Time) {
+	w.put(bucket, key, value)
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	if value == nil {
+		delete(w.meta, bucket+"|"+key)
+		return
+	}
+	w.meta[bucket+"|"+key] = entryMeta{revision: revision, at: at}
+	if bucket == delivery.PlacementBucket {
+		_, _ = w.placement.Put(key, value, revision, false) // put took it already; this is its revision
+	}
+	if bucket == delivery.SourceBucket && key == delivery.SourceMainKey {
+		if s, err := delivery.DecodeSource(value); err == nil && s.Group != "" {
+			w.sourceGroups[revision] = s.Group
+		}
+	}
+}
+
+// release is the release whose Approve carries module's build fp (ADR 0601 §1), and whether one does: the trunk's value of
+// the module names fp, the source revision at which that fingerprint last changed (FPSrc, never the Src of its last merge,
+// which a recompute with no merge keeps) names the release that moved it, and the gate's merge of that release, which it
+// writes on the operator's Approve, holds the module's own trunk merge among its merged pull requests. Any of them
+// unknown: none, and the move is asked of a person.
+func (w *world) release(module, fp string) (string, bool) {
+	t, ok := w.trunk()[module]
+	if !ok || fp == "" || t.FP2 != fp || t.FPSrc == 0 || t.Commit == "" {
+		return "", false
+	}
+	w.mu.Lock()
+	group := w.sourceGroups[t.FPSrc]
+	w.mu.Unlock()
+	key, err := delivery.MergesKey(group)
+	if group == "" || err != nil {
+		return "", false
+	}
+	raw := w.value(delivery.MergesBucket, key)
+	if raw == nil {
+		return "", false
+	}
+	merge, err := delivery.DecodeMerge(raw)
+	if err != nil {
+		return "", false
+	}
+	for _, pull := range merge.Pulls {
+		if pull.State == delivery.MergeMerged && pull.Commit == t.Commit && delivery.SameRepository(pull.Repository, t.Repository) {
+			return group, true
+		}
+	}
+	return "", false
+}
+
+// metaOf is the revision and time of the value a bucket holds at key, as the watch said them.
+func (w *world) metaOf(bucket, key string) entryMeta {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	return w.meta[bucket+"|"+key]
+}
+
+// put takes a change of a watched bucket in: a value, or nil for a key deleted or purged.
+func (w *world) put(bucket, key string, value []byte) {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	if w.values[bucket] == nil {
+		w.values[bucket] = map[string][]byte{}
+	}
+	w.changes[bucket]++ // the bucket's generation (bucketGen), a delete included
+	if value == nil {
+		delete(w.values[bucket], key)
+		if bucket == delivery.PlacementBucket {
+			_, _ = w.placement.Put(key, nil, 0, true)
+		}
+		return
+	}
+	w.values[bucket][key] = value
+	w.changes[bucket+"|"+key]++
+	if bucket == delivery.PlacementBucket {
+		// A key or value that does not read places nothing new on its node; the indexer's read tool says it.
+		_, _ = w.placement.Put(key, value, 0, false)
+	}
+	if bucket == delivery.HaveBucket {
+		if h, err := delivery.DecodeHave(value); err == nil && h.FP != "" && h.Phase == delivery.PhaseRunning && h.Health == delivery.HealthOK {
+			list := slices.DeleteFunc(w.healthy[key], func(fp string) bool { return fp == h.FP })
+			w.healthy[key] = append(list, h.FP)
+		}
+	}
+}
+
+// lastHealthy is the newest fingerprint other than fp the node ran the module healthy at, or empty.
+func (w *world) lastHealthy(node, module, fp string) string {
+	key, err := delivery.HaveKey(node, module)
+	if err != nil {
+		return ""
+	}
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	list := w.healthy[key]
+	for i := len(list) - 1; i >= 0; i-- {
+		if list[i] != fp {
+			return list[i]
+		}
+	}
+	return ""
+}
+
+// read is a copy of what a bucket holds now.
+func (w *world) read(bucket string) map[string][]byte {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	out := make(map[string][]byte, len(w.values[bucket]))
+	for k, v := range w.values[bucket] {
+		out[k] = v
+	}
+	return out
+}
+
+// getter reads one key's value; errNotThere when the key does not exist.
+type getter func(ctx context.Context, key string) ([]byte, error)
+
+var errNotThere = errors.New("no such key")
+
+// kvGetter reads keys of a bucket.
+func kvGetter(kv jetstream.KeyValue) getter {
+	return func(ctx context.Context, key string) ([]byte, error) {
+		e, err := kv.Get(ctx, key)
+		if errors.Is(err, jetstream.ErrKeyNotFound) {
+			return nil, errNotThere
+		}
+		if err != nil {
+			return nil, err
+		}
+		return e.Value(), nil
+	}
+}
+
+// getter reads a key of a bucket the world holds: errNotThere where it holds none.
+func (w *world) getter(bucket string) getter {
+	return func(_ context.Context, key string) ([]byte, error) {
+		w.mu.Lock()
+		defer w.mu.Unlock()
+		v, ok := w.values[bucket][key]
+		if !ok {
+			return nil, errNotThere
+		}
+		return v, nil
+	}
+}
+
+// manifest reads the manifest of a digest from the indexer's bucket once and keeps it: a digest's manifest never changes.
+func (w *world) manifest(ctx context.Context, get getter, digest string) parsed {
+	w.mu.Lock()
+	p, ok := w.manifests[digest]
+	w.mu.Unlock()
+	if ok {
+		return p
+	}
+	key, err := delivery.ManifestsKey(digest)
+	if err != nil {
+		return parsed{err: err.Error()}
+	}
+	value, err := get(ctx, key)
+	if errors.Is(err, errNotThere) {
+		return parsed{err: "the indexer holds no manifest of digest " + digest + " yet"}
+	}
+	if err != nil {
+		return parsed{err: err.Error()}
+	}
+	m, err := delivery.DecodeManifest(value)
+	if err != nil {
+		p = parsed{err: err.Error()}
+	} else if man, err := catalogue.Decode([]byte(m.JSON)); err != nil {
+		// Decoded, never judged (novox/hq ADR 0578 §3): the indexer's judge judged it, and its verdict is taken from the
+		// module's value where it is read (world.mesh).
+		p = parsed{module: m.Module, err: "it does not decode: " + err.Error()}
+	} else {
+		p = parsed{module: m.Module, manifest: man}
+	}
+	w.mu.Lock()
+	w.manifests[digest] = p
+	w.mu.Unlock()
+	return p
+}
+
+// assigned is each node's modules the seat mesh-placement's placement names, in name order (ADR 0549 §5, ADR 0567 §8): the
+// placement is the one source of where modules run. The controller's assignments are read no more (issue 774).
+func (w *world) assigned() map[string][]string {
+	placed, _ := w.placed()
+	out := make(map[string][]string, len(placed))
+	for node, modules := range placed {
+		out[node] = slices.Sorted(slices.Values(modules))
+	}
+	return out
+}
+
+// placed is each node's modules in the seat's placement (ADR 0567 §1), and whether any placement key was read: a key
+// that does not read places nothing on its node and is said by the indexer's own read tool.
+func (w *world) placed() (map[string][]string, bool) {
+	out := map[string][]string{}
+	for node, p := range w.placements() {
+		out[node] = p.Assigned()
+	}
+	return out, len(w.read(delivery.PlacementBucket)) > 0
+}
+
+// placements is every node's placement, assembled from its keys in either form (delivery.PlacementKeys).
+func (w *world) placements() map[string]delivery.Placement {
+	out, _ := w.placement.AllRevisions()
+	return out
+}
+
+// placedNodes is every node the seat's placement names (ADR 0567 §1): those compose their own modules (ADR 0547 §2),
+// so their wants name the build alone and the seventh rule does not hold them.
+func (w *world) placedNodes() map[string]bool {
+	placed, _ := w.placed()
+	out := make(map[string]bool, len(placed))
+	for node := range placed {
+		out[node] = true
+	}
+	return out
+}
+
+// trunk is every module the indexer holds at the trunk, with its value.
+func (w *world) trunk() map[string]delivery.Module {
+	out := map[string]delivery.Module{}
+	for key, value := range w.read(delivery.ModulesBucket) {
+		name, err := delivery.ParseModulesKey(key)
+		if err != nil {
+			continue
+		}
+		if m, err := delivery.DecodeModule(value); err == nil {
+			out[name] = m
+		}
+	}
+	return out
+}
+
+// records is each node's record in its own have key (`<node>.node`): the nodes a placement proposal is answered by,
+// with those placement names (ADR 0593 §8).
+func (w *world) records() map[string]delivery.NodeRecord {
+	out := map[string]delivery.NodeRecord{}
+	for key, value := range w.read(delivery.HaveBucket) {
+		node, _, isNode, err := delivery.ParseHaveKey(key)
+		if err != nil || !isNode {
+			continue
+		}
+		if h, err := delivery.DecodeHaveNode(value); err == nil && h.Record != nil {
+			out[node] = *h.Record
+		}
+	}
+	return out
+}
+
+// online is, by node, whether the watchman holds the node online.
+func (w *world) online() map[string]bool {
+	out := map[string]bool{}
+	for key, value := range w.read(delivery.PresenceBucket) {
+		node, _, _, err := delivery.ParsePresenceKey(key)
+		if err != nil || node == "" {
+			continue
+		}
+		if p, err := delivery.DecodePresence(value); err == nil {
+			out[node] = p.Online
+		}
+	}
+	return out
+}
+
+// wantsOf is the wants the assigner wrote, by module then node.
+func (w *world) wantsOf() map[string]map[string]delivery.Want {
+	out := map[string]map[string]delivery.Want{}
+	for key, value := range w.read(delivery.AssignerWantsBucket) {
+		node, module, err := delivery.ParseWantKey(key)
+		if err != nil {
+			continue
+		}
+		want, err := delivery.DecodeWant(value)
+		if err != nil {
+			continue
+		}
+		if out[module] == nil {
+			out[module] = map[string]delivery.Want{}
+		}
+		out[module][node] = want
+	}
+	return out
+}
+
+// nodes is what the six rules read of the nodes: presence, haves, and every provision's providers with their nodes.
+func (w *world) nodes(manifests map[string]catalogue.Manifest, assigned map[string][]string) assign.Nodes {
+	n := assign.Nodes{Online: map[string]bool{}, Haves: map[string]map[string]delivery.Have{}, Providers: map[string]map[string][]string{},
+		Reads: map[string][]string{}}
+	for key, value := range w.read(delivery.PresenceBucket) {
+		node, _, _, err := delivery.ParsePresenceKey(key)
+		if err != nil || node == "" {
+			continue
+		}
+		if p, err := delivery.DecodePresence(value); err == nil {
+			n.Online[node] = p.Online
+		}
+	}
+	for key, value := range w.read(delivery.HaveBucket) {
+		node, module, isNode, err := delivery.ParseHaveKey(key)
+		if err != nil {
+			continue
+		}
+		if isNode {
+			// What the node's engine reads (ADR 0614 §4); a record that states none is read as the baseline.
+			if h, err := delivery.DecodeHaveNode(value); err == nil && h.Record != nil {
+				n.Reads[node] = h.Record.ManifestReads
+			}
+			continue
+		}
+		if h, err := delivery.DecodeHave(value); err == nil {
+			if n.Haves[node] == nil {
+				n.Haves[node] = map[string]delivery.Have{}
+			}
+			n.Haves[node][module] = h
+		}
+	}
+	nodesOf := map[string][]string{}
+	for node, modules := range assigned {
+		for _, m := range modules {
+			nodesOf[m] = append(nodesOf[m], node)
+		}
+	}
+	for name, man := range manifests {
+		for _, o := range man.Provides {
+			if n.Providers[o.Name] == nil {
+				n.Providers[o.Name] = map[string][]string{}
+			}
+			n.Providers[o.Name][name] = nodesOf[name]
+		}
+	}
+	return n
+}
+
+// value is what a bucket holds at a key now, nil when nothing.
+func (w *world) value(bucket, key string) []byte {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	return w.values[bucket][key]
+}
+
+// grantsBucket is the bucket the grants are read from: the grants part's state `grants`, always (ADR 0571 clause 9); no
+// manifest but the controller's reads the controller's grants.
+func (w *world) grantsBucket() string { return delivery.PartGrantsBucket }
+
+// has says whether a bucket holds a key now.
+func (w *world) has(bucket, key string) bool {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	_, ok := w.values[bucket][key]
+	return ok
+}
+
+// built says whether the builder's build of a module at a fingerprint is done.
+func (w *world) built(module, fp string) bool {
+	key, err := delivery.BuilderBuildKey(module, fp)
+	if err != nil {
+		return false
+	}
+	w.mu.Lock()
+	value, ok := w.values[delivery.BuilderBuildsBucket][key]
+	w.mu.Unlock()
+	if !ok {
+		return false
+	}
+	b, err := delivery.DecodeBuilderBuild(value)
+	return err == nil && b.State == delivery.BuildDone
+}
+
+// buildNeeds are the reference forms the builder's done build of module at fp is written in (the build key's needs, ADR
+// 0618 §1): nil when it is not done or names none.
+func (w *world) buildNeeds(module, fp string) []string {
+	key, err := delivery.BuilderBuildKey(module, fp)
+	if err != nil {
+		return nil
+	}
+	b, err := delivery.DecodeBuilderBuild(w.value(delivery.BuilderBuildsBucket, key))
+	if err != nil || b.State != delivery.BuildDone {
+		return nil
+	}
+	return b.Needs
+}
+
+// recordReads is what node's record `<node>.node` states its engine reads (ADR 0614 §4), and whether the assigner holds
+// a record of it: the fallback where the engine does not answer the verb manifest-reads (enginereads.FromRecord).
+func (w *world) recordReads(node string) ([]string, bool) {
+	r, ok := w.records()[node]
+	return r.ManifestReads, ok
+}
+
+// knownNodes is every node the assigner hears of: placed, with a record, or with a presence.
+func (w *world) knownNodes() []string {
+	set := map[string]bool{}
+	for node := range w.placedNodes() {
+		set[node] = true
+	}
+	for node := range w.records() {
+		set[node] = true
+	}
+	for node := range w.online() {
+		set[node] = true
+	}
+	return slices.Sorted(maps.Keys(set))
+}
+
+// composed is the composition of module for node: a placed node composes its own, and its composition is the digest its own
+// have names (ADR 0571 §6); an unplaced node has none, so it gets no want (and the pass says so, unplacedFindings). The
+// controller's copy (mesh-controller_composed) is read no more (issue 774).
+func (w *world) composed(node, module, fp string) (delivery.ComposedDigest, bool) {
+	if !w.placedNodes()[node] {
+		return delivery.ComposedDigest{}, false
+	}
+	return w.ownComposed(node)
+}
+
+// answer is the teller's answer to the ask at key (mesh-delivery-teller_answers, the same key), and whether there is one.
+func (w *world) answer(key string) (delivery.Answer, bool) {
+	w.mu.Lock()
+	value, ok := w.values[delivery.AnswersBucket][key]
+	w.mu.Unlock()
+	if !ok {
+		return delivery.Answer{}, false
+	}
+	a, err := delivery.DecodeAnswer(value)
+	return a, err == nil
+}
+
+// bucketGen is how many times any key of the bucket was written or deleted in this process: a read of what it shows
+// elsewhere is asked again only after it moves.
+func (w *world) bucketGen(bucket string) uint64 {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	return w.changes[bucket]
+}
+
+// changed is how many values the key has taken in this process (see world.changes).
+func (w *world) changed(bucket, key string) uint64 {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	return w.changes[bucket+"|"+key]
+}
+
+// ownComposed is a placed node's own composition, as the digest its own have names (`<node>.node` of the haves, Composed):
+// what rule 7 reads. A node whose have names none is not composed yet.
+func (w *world) ownComposed(node string) (delivery.ComposedDigest, bool) {
+	key, err := delivery.HaveNodeKey(node)
+	if err != nil {
+		return delivery.ComposedDigest{}, false
+	}
+	raw, ok := w.read(delivery.HaveBucket)[key]
+	if !ok {
+		return delivery.ComposedDigest{}, false
+	}
+	h, err := delivery.DecodeHaveNode(raw)
+	if err != nil || h.Composed == "" {
+		return delivery.ComposedDigest{}, false
+	}
+	return delivery.ComposedDigest{V: delivery.Version, Digest: h.Composed, Judgement: delivery.JudgedNeither,
+		Words: "the node composes its own"}, true
+}
+
+// unplacedNodes are the nodes whose engine has a have and that no placement names: they get no
+// want, since nothing composes them.
+func (w *world) unplacedNodes() []string {
+	placed := w.placedNodes()
+	var out []string
+	for key := range w.read(delivery.HaveBucket) {
+		node, _, isNode, err := delivery.ParseHaveKey(key)
+		if err == nil && isNode && !placed[node] {
+			out = append(out, node)
+		}
+	}
+	sort.Strings(out)
+	return out
+}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/world_test.go

@@ -0,0 +1,80 @@
+package main
+
+import (
+	"context"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// fakeManifests is the indexer's manifests bucket in memory.
+type fakeManifests map[string][]byte
+
+func (f fakeManifests) add(t *testing.T, module, body string) string {
+	t.Helper()
+	digest := delivery.ManifestDigest([]byte(body))
+	value, err := delivery.EncodeManifest(delivery.Manifest{Module: module, JSON: body})
+	if err != nil {
+		t.Fatal(err)
+	}
+	f[digest] = value
+	return digest
+}
+
+func (f fakeManifests) get(_ context.Context, key string) ([]byte, error) {
+	if v, ok := f[key]; ok {
+		return v, nil
+	}
+	return nil, errNotThere
+}
+
+func fp(c byte) string { return delivery.SourcePrefix2 + strings.Repeat(string(c), 64) }
+
+func pull(repo string, number int, modules map[string]delivery.CandidateModule) delivery.CandidatePull {
+	p := delivery.CandidatePull{Head: delivery.Head{Repository: repo, Number: number, Head: strings.Repeat("3", 40)}, Fps: modules}
+	for m := range modules {
+		p.Modules = append(p.Modules, m)
+	}
+	slices.Sort(p.Modules)
+	return p
+}
+
+// Review round 1 (items 3 and 4): the world counts the values a key takes, so a have written again after an answer is seen.
+func theWorldCountsTheValuesAKeyTakes(t *testing.T) {
+	w := newWorld()
+	w.put(delivery.HaveBucket, "ace.web", []byte(`{"v":1}`))
+	w.put(delivery.HaveBucket, "ace.web", []byte(`{"v":1}`))
+	w.put(delivery.HaveBucket, "ace.mail", []byte(`{"v":1}`))
+	if got := w.changed(delivery.HaveBucket, "ace.web"); got != 2 {
+		t.Errorf("changed = %d, want 2", got)
+	}
+	if got := w.changed(delivery.HaveBucket, "gone"); got != 0 {
+		t.Errorf("changed = %d for a key never seen", got)
+	}
+	// ADR 0571 clause 9: grants are read from the grants part's bucket, the one bucket of grants (ADR 0590).
+	fp := delivery.SourcePrefix2 + strings.Repeat("d", 64)
+	gkey, _ := delivery.PartGrantKey("web", fp)
+	grant, _ := delivery.EncodeGrant(delivery.Grant{Accounts: []string{"ace.web"}})
+	for _, row := range []struct {
+		name    string
+		inPart  bool
+		granted bool
+	}{
+		{"the part's grant", true, true},
+		{"no grant", false, false},
+	} {
+		p := newPasser(buckets{}, time.Now())
+		if row.inPart {
+			p.w.put(delivery.PartGrantsBucket, gkey, grant)
+		}
+		if got := p.w.grantsBucket(); got != delivery.PartGrantsBucket {
+			t.Errorf("%s: grants are read from %s, want the part's", row.name, got)
+		}
+		if _, granted := p.composedFor("ace", "web", fp); granted != row.granted {
+			t.Errorf("%s: granted = %v, want %v", row.name, granted, row.granted)
+		}
+	}
+}

modules/mesh-delivery-assigner/go.mod

@@ -0,0 +1,34 @@
+module mesh-delivery-assigner
+
+go 1.26.0
+
+require (
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261104174359-05b3e2e1b94f
+	github.com/nats-io/nats-server/v2 v2.11.17
+	github.com/nats-io/nats.go v1.54.0
+)
+
+require (
+	git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639 // indirect
+	github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op // indirect
+	github.com/google/go-tpm v0.9.8 // indirect
+	github.com/klauspost/compress v1.20.1 // indirect
+	github.com/minio/highwayhash v1.0.4 // indirect
+	github.com/nats-io/jwt/v2 v2.8.2 // indirect
+	github.com/nats-io/nkeys v0.4.16 // indirect
+	github.com/nats-io/nuid v1.0.1 // indirect
+	golang.org/x/crypto v0.57.0 // indirect
+	golang.org/x/sys v0.48.0 // indirect
+	golang.org/x/time v0.16.0 // indirect
+)
+
+require git.novox.be/novox/mesh-delivery/sdk v0.0.0-00010101000000-000000000000
+
+require (
+	git.novox.be/novox/mesh-contracts/go/clients/nodeengineclient v0.0.0-20261104174344-ae5266e77639
+	git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient v0.0.0-20261104174344-ae5266e77639
+	git.novox.be/novox/mesh-contracts/go/seats/nodeengine v0.0.0-20261104174344-ae5266e77639
+	git.novox.be/novox/mesh-contracts/go/seats/operatorchannel v0.0.0-20261104174344-ae5266e77639
+)
+
+replace git.novox.be/novox/mesh-delivery/sdk => ../../sdk

modules/mesh-delivery-assigner/go.sum

@@ -0,0 +1,37 @@
+git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639 h1:Zt7CfWt2S2W/fVgWNyW2u2+xwz051LXvGxVTNIyfhdM=
+git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639/go.mod h1:0dD1XEJBJ0G5UYDQxSZI84nuujb6m3tOpJl4C8rQVvg=
+git.novox.be/novox/mesh-contracts/go/clients/nodeengineclient v0.0.0-20261104174344-ae5266e77639 h1:3FTxvHrv3Hv+ZUbp/ezTrndqdgiS+Z6EUG2XGYJNJr8=
+git.novox.be/novox/mesh-contracts/go/clients/nodeengineclient v0.0.0-20261104174344-ae5266e77639/go.mod h1:/V/1wfyQwjE9VbPLsFtkf6uX+SHKUXX34s5JscDuGAs=
+git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient v0.0.0-20261104174344-ae5266e77639 h1:19PhtrCOwia711Oqdyafvs5EKTVmmgk5Gdb4leCkq3w=
+git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient v0.0.0-20261104174344-ae5266e77639/go.mod h1:Dj6fbL8Evgy72EWO3Gl3L3Ra8N/nJSzgEVwSGmeRam0=
+git.novox.be/novox/mesh-contracts/go/seats/nodeengine v0.0.0-20261104174344-ae5266e77639 h1:YQ6eJvc+RYUVIVf+oX+R4TC1dYL8TLLMZ0/JPDU1tp4=
+git.novox.be/novox/mesh-contracts/go/seats/nodeengine v0.0.0-20261104174344-ae5266e77639/go.mod h1:TB20TsQuOd5aer+cXL6PbaYyg2RvgL1R4MzD61Oks3A=
+git.novox.be/novox/mesh-contracts/go/seats/operatorchannel v0.0.0-20261104174344-ae5266e77639 h1:K/1yIkqAWKGtLEtJ0PibijIdpo5YATL/9IUVXFoEglM=
+git.novox.be/novox/mesh-contracts/go/seats/operatorchannel v0.0.0-20261104174344-ae5266e77639/go.mod h1:osh0jQyNqYDM27tbxQo6HeUEXgLq9XUewKzNhUXadog=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261104174359-05b3e2e1b94f h1:jDsfDMd48MXY9Zershc3eRxnhmx2sSpUfQkLq5jAIds=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261104174359-05b3e2e1b94f/go.mod h1:08OomDXdwVN8/87nyDtv5R3rH/6LoP8SFFXz30bTYCM=
+github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op h1:1BOWQJweNyvZMlpAHXGLiZQn9S+QXGcz3xh94lC0w6E=
+github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
+github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=
+github.com/google/go-tpm v0.9.8/go.mod h1:h9jEsEECg7gtLis0upRBQU+GhYVH6jMjrFxI8u6bVUY=
+github.com/klauspost/compress v1.20.1 h1:T7kKElXUMXrUJ2E9QhQhxFtcK5rPyLdsGZvdbLMPdiQ=
+github.com/klauspost/compress v1.20.1/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
+github.com/minio/highwayhash v1.0.4 h1:asJizugGgchQod2ja9NJlGOWq4s7KsAWr5XUc9Clgl4=
+github.com/minio/highwayhash v1.0.4/go.mod h1:GGYsuwP/fPD6Y9hMiXuapVvlIUEhFhMTh0rxU3ik1LQ=
+github.com/nats-io/jwt/v2 v2.8.2 h1:XXRgB60MSTnqsRwejQurVDs/hcv2dkt+86GjI+I/bMc=
+github.com/nats-io/jwt/v2 v2.8.2/go.mod h1:Ag/56sq9OblL4JgdYufDd16Egb17Kr/8WwwuO/forVc=
+github.com/nats-io/nats-server/v2 v2.11.17 h1:GKEghcFK6A+aFx11Yf1LjgLC3txAwvyhnYzhBIQZA8I=
+github.com/nats-io/nats-server/v2 v2.11.17/go.mod h1:B1sFVz4StNosQ903ak4N1G01Fl/9f8e06mXpFIE2K24=
+github.com/nats-io/nats.go v1.54.0 h1:vsXoOxjHp/GmPUN+EcI7uOf/uB+iAP+kEsAFNQN0yzA=
+github.com/nats-io/nats.go v1.54.0/go.mod h1:y+DZoD1oBOYfZTU681eTUiUjI0vbqYGixNVFHcjHJ0k=
+github.com/nats-io/nkeys v0.4.16 h1:rd5oAuLOb8mnAycB0xleuEBNS1pVVnN0fv/FF34Eypg=
+github.com/nats-io/nkeys v0.4.16/go.mod h1:llLgWoI0o4z/Q57q2R1kHfmocyhGV6VG/U18Glg1Afs=
+github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
+github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OSON2c=
+golang.org/x/crypto v0.57.0 h1:3ZVCjf8Ggz7zneR/EHRVx68Ctf+2pmIMP2UFhh9cC6M=
+golang.org/x/crypto v0.57.0/go.mod h1:Fdz0i5U6CoizGwLda9DttjSk6qlZo25zYNtR+ycvuZA=
+golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.48.0 h1:bbX/i/6MgT9BVLM9RT1thmxL04yeTAhbEz4SyadbXoo=
+golang.org/x/sys v0.48.0/go.mod h1:hNLxWAXmnKAxqDtdwIYC4bM9oQPEecfsnNMuSxOs3og=
+golang.org/x/time v0.16.0 h1:vMb6ptszcQMkcwiRTAuNNU50gom6++Q/6gY2hDM6VDE=
+golang.org/x/time v0.16.0/go.mod h1:rVKOqvZeKvrDKTQiAHJ7wmwP0RzleSphoEA9RcdLA0s=

modules/mesh-delivery-assigner/internal/assign/askjson.go

@@ -0,0 +1,68 @@
+package assign
+
+import (
+	"encoding/json"
+	"fmt"
+	"time"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	oc "git.novox.be/novox/mesh-contracts/go/seats/operatorchannel"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// assignerAsk is the asking-th ask a, as the asks state holds it: the router's ask as JSON (delivery.AssignerAsk.Ask).
+func assignerAsk(asking int, a oc.Ask) delivery.AssignerAsk {
+	raw, err := json.Marshal(a)
+	if err != nil { // an oc.Ask holds only strings, bools and a slice of them: it cannot fail
+		panic(fmt.Sprintf("assign: the ask %q does not marshal: %v", a.ID, err))
+	}
+	return delivery.AssignerAsk{Asking: asking, Ask: raw}
+}
+
+// AskOf is the router's ask an asks-state value carries.
+func AskOf(a delivery.AssignerAsk) (oc.Ask, error) {
+	var ask oc.Ask
+	if err := json.Unmarshal(a.Ask, &ask); err != nil {
+		return oc.Ask{}, fmt.Errorf("assign: the value carries no router's ask: %w", err)
+	}
+	return ask, nil
+}
+
+// EncodeAsk is delivery.EncodeAssignerAsk at key, after the checks every keeper of an ask owes (occ.Carried, ADR 0627 §4):
+// the ask's id is delivery.AskingID(key, asking), and it offers at least one option.
+func EncodeAsk(key string, a delivery.AssignerAsk) ([]byte, error) {
+	if _, err := checkedAsk(key, a); err != nil {
+		return nil, err
+	}
+	return delivery.EncodeAssignerAsk(key, a)
+}
+
+func checkedAsk(key string, a delivery.AssignerAsk) (oc.Ask, error) {
+	ask, err := occ.Carried(a.Ask, delivery.AskingID(key, a.Asking))
+	if err != nil {
+		return oc.Ask{}, fmt.Errorf("assign: %w", err)
+	}
+	return ask, nil
+}
+
+// DecodeAsk reads the ask at key (delivery.DecodeAssignerAsk) with the router's ask it carries.
+func DecodeAsk(key string, data []byte) (delivery.AssignerAsk, oc.Ask, error) {
+	a, err := delivery.DecodeAssignerAsk(key, data)
+	if err != nil {
+		return delivery.AssignerAsk{}, oc.Ask{}, err
+	}
+	ask, err := checkedAsk(key, a)
+	if err != nil {
+		return delivery.AssignerAsk{}, oc.Ask{}, err
+	}
+	return a, ask, nil
+}
+
+// ExpiresAt is when the ask ends unanswered; the zero time for an ask that names none.
+func ExpiresAt(a oc.Ask) time.Time {
+	t, err := occ.Time(a.Expires)
+	if err != nil {
+		return time.Time{}
+	}
+	return t
+}

modules/mesh-delivery-assigner/internal/assign/asks.go

@@ -0,0 +1,245 @@
+package assign
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+	"time"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	oc "git.novox.be/novox/mesh-contracts/go/seats/operatorchannel"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// HoldAsk is the ask about a module's fingerprint the assigner holds, at its key (delivery.HoldAskKey): keep it held or
+// release it. Releasing writes the held fingerprint's want again by the rules (ADR 0539 §19). node and words are the held
+// record's: the machine whose health check failed and the hold's words (issue 1906). asking numbers the writing: 0 the first, a
+// larger number an ask written again after a hold lifted by itself, so the router takes it as new.
+func HoldAsk(key, module, fp, node, words string, asking int, now time.Time) delivery.AssignerAsk {
+	return assignerAsk(asking, oc.Ask{
+		ID:       delivery.AskingID(key, asking),
+		Headline: fmt.Sprintf("%s is held at %s", module, short(fp)),
+		Explanation: fmt.Sprintf("The health check of %s failed on %s at %s (%s), so the assigner holds that version and wants "+
+			"no node to move to it. It lifts the hold by itself once every node that runs %s runs it healthy; releasing it "+
+			"lets the wants move to it now.", module, node, short(fp), words, module),
+		Options: []oc.Option{
+			{ID: "keep", Label: "Keep it held", Does: "the version stays held", Level: occ.Acknowledge},
+			{ID: "release", Label: "Release it", Does: "the version is released and the wants move to it by the rules again", Level: occ.Acknowledge},
+		},
+		Who:      occ.Operator,
+		Expires:  occ.FormatTime(now.Add(7 * 24 * time.Hour)),
+		OnExpiry: "the version stays held",
+		About:    key,
+	})
+}
+
+// The options of the restore ask (ADR 0537 §3, ADR 0539 §19), and what each does on the node.
+const (
+	OptionRestore      = "restore"
+	OptionLeaveStopped = "leave-stopped"
+)
+
+// RestoreAsk is the ask about a module holding data whose fingerprint failed its health check on a node (ADR 0429 §6): it is
+// not set back by itself, since a set-back would lose the writes made since. words is the check's words. Restore sets the
+// node back to the last healthy fingerprint and loses the newer writes; leaving it stopped keeps the data as it is.
+func RestoreAsk(key, node, module, fp, words string, now time.Time) delivery.AssignerAsk {
+	return assignerAsk(0, oc.Ask{
+		ID:       delivery.AskingID(key, 0),
+		Headline: fmt.Sprintf("%s failed its health check on %s", module, node),
+		Explanation: fmt.Sprintf("%s holds data, and its health check failed on %s at %s: %s. Setting it back to the version that ran healthy "+
+			"would lose the writes made since; leaving it stopped keeps the data as it is.", module, node, short(fp), words),
+		Options: []oc.Option{
+			{ID: OptionRestore, Label: "Restore it", Does: "the node is set back to the last healthy version and the newer writes are lost", Level: occ.Acknowledge},
+			{ID: OptionLeaveStopped, Label: "Leave it stopped", Does: "the module stays as it is on the node and the data is kept", Level: occ.Acknowledge},
+		},
+		Who:      occ.Operator,
+		Expires:  occ.FormatTime(now.Add(7 * 24 * time.Hour)),
+		OnExpiry: "the module stays as it is on the node",
+		About:    key,
+	})
+}
+
+// HeldCondition is the condition the assigner raises when it holds a fingerprint of a module (ADR 0429 §6, ADR 0539 §19), or
+// clears (raised false) when the hold is released. It names the module, the node whose health check failed and the check's
+// words, under the assigner's own name (ADR 0437 clause 9), keyed by the held fingerprint. needsYou is true for a module holding
+// data, whose restore ask waits for the operator.
+func HeldCondition(module, fp, node, words string, raised, needsYou bool) oc.Condition {
+	key := delivery.AssignerModule + ".held." + module + "." + strings.TrimPrefix(fp, delivery.SourcePrefix2)
+	subject := oc.ConditionSubject{Scope: "module", ID: module, Machine: node}
+	if !raised {
+		return oc.Condition{Key: key, Subject: subject, State: occ.StateCleared}
+	}
+	c := oc.Condition{Key: key, Severity: occ.SeverityWarning, Subject: subject, State: occ.StateRaised,
+		Summary:  fmt.Sprintf("%s is held at %s", module, short(fp)),
+		Headline: fmt.Sprintf("%s is held at %s", module, short(fp))}
+	what := fmt.Sprintf("The health check of %s failed on %s at %s: %s. The assigner holds that version and wants no node to move to it.", module, node, short(fp), words)
+	if needsYou {
+		c.Needs = "answer whether to restore " + module + " on " + node
+		c.Explanation = occ.NeedsYou + c.Needs + ". " + what
+	} else {
+		c.Explanation = occ.NothingToDo + " " + what + " Nodes that wanted it are set back to the version that ran healthy."
+	}
+	return c
+}
+
+// NodeFailedCondition is the condition the assigner raises for a module whose newest fingerprint fp failed its health check on
+// node while other nodes run it healthy (ADR 0557 §1, issue 1496): the failure is the node's, so nothing is held or set back and
+// the node keeps its want. It names the node, the module, fp and the have's words, keyed by node and module, and is cleared
+// (raised false) once the node no longer fails alone.
+func NodeFailedCondition(node, module, fp string, f NodeFailure, raised bool) oc.Condition {
+	key := delivery.AssignerModule + ".failed-alone." + node + "." + module
+	subject := oc.ConditionSubject{Scope: "module", ID: module, Machine: node}
+	if !raised {
+		return oc.Condition{Key: key, Subject: subject, State: occ.StateCleared,
+			Resolved: fmt.Sprintf("%s on %s no longer fails its health check alone.", module, node)}
+	}
+	headline := fmt.Sprintf("%s fails on %s alone", module, node)
+	if n := len([]rune(headline)); n > occ.HeadlineLength {
+		headline = string([]rune(headline)[:occ.HeadlineLength])
+	}
+	return oc.Condition{Key: key, Severity: occ.SeverityWarning, Subject: subject, State: occ.StateRaised,
+		Summary: headline, Headline: headline,
+		Explanation: fmt.Sprintf("%s The health check of %s at %s failed on %s (%s), while it runs healthy on %s. The failure is %s's, "+
+			"so the assigner holds nothing and sets no node back, and %s keeps its want. This clears once %s runs it healthy or "+
+			"another version is the newest.", occ.NothingToDo, module, short(fp), node, f.Words, strings.Join(f.Others, ", "), node,
+			node, node)}
+}
+
+// NeitherCondition is the condition of a module assigned to node that holds no want for it (issue 1945): the node's own composition
+// gives up every module with a fingerprint of the new form, so nothing applies it there and its files are gone. It is raised (urgent)
+// naming the module, the node and the rule holding its first want back with the rule's words, under the assigner's own name keyed by
+// node and module, and cleared (raised false) when the node has a want for it again.
+func NeitherCondition(node, module string, h Holding, raised bool) oc.Condition {
+	key := delivery.AssignerModule + ".neither." + node + "." + module
+	subject := oc.ConditionSubject{Scope: "module", ID: module, Machine: node}
+	if !raised {
+		return oc.Condition{Key: key, Subject: subject, State: occ.StateCleared,
+			Resolved: fmt.Sprintf("%s on %s has a want again, so its own composition is applied there.", module, node)}
+	}
+	headline := fmt.Sprintf("%s on %s is on no list", module, node)
+	if n := len([]rune(headline)); n > occ.HeadlineLength {
+		headline = string([]rune(headline)[:occ.HeadlineLength])
+	}
+	return oc.Condition{Key: key, Severity: occ.SeverityUrgent, Subject: subject, State: occ.StateRaised,
+		Summary: headline, Headline: headline,
+		Explanation: fmt.Sprintf("%s %s is assigned to %s, but the node holds no want for it and the node's own composition does not "+
+			"hold it either, so nothing applies it there. The assigner's rule %d holds its first want back: %s. The assigner writes the want once the "+
+			"rule holds, and clears this.", occ.NothingToDo, module, node, h.Rule, h.Words)}
+}
+
+// NeitherLeftCondition clears the neither condition of module on node when it is no longer on neither list: why is "" when the
+// node has a live want for it again, else why it has none (it is held, its move waits for an ask, the node no longer runs it), so
+// the clear never says a want the node does not hold (issue 1945: "nats on novox has a want again" while it had none).
+func NeitherLeftCondition(node, module, why string) oc.Condition {
+	c := NeitherCondition(node, module, Holding{}, false)
+	if why != "" {
+		c.Resolved = fmt.Sprintf("%s on %s is no longer on neither list and has no want: %s.", module, node, why)
+	}
+	return c
+}
+
+// LiftedCondition clears the condition of a held fingerprint the assigner lifted by itself, saying why (issue 1906).
+func LiftedCondition(module, fp string) oc.Condition {
+	c := HeldCondition(module, fp, "", "", false, false)
+	c.Resolved = LiftedWords(module, fp) + "."
+	return c
+}
+
+// The options of the record ask (ADR 0539 §14) and of the backup ask (§16).
+const (
+	OptionYes         = "yes"
+	OptionNo          = "no"
+	OptionBackupAgain = delivery.BackupAgain
+	OptionBackupSkip  = delivery.BackupSkip
+)
+
+// RecordAsk is the ask about a move of a module of policy record on node to the composition with the digest, judged by the
+// controller to recreate a container, to move data, or not to be judgeable (ADR 0539 §14). The want names the composition only
+// after the answer yes. The way the move was judged is in the ask.
+func RecordAsk(key, node, module, fp string, need RecordNeed, now time.Time) delivery.AssignerAsk {
+	what := map[delivery.Judgement]string{
+		delivery.JudgedRecreates: "recreates a container",
+		delivery.JudgedMovesData: "moves the module's data",
+		delivery.JudgedCannot:    "cannot be judged: " + need.Words,
+	}[need.Judgement]
+	return assignerAsk(0, oc.Ask{
+		ID:       delivery.AskingID(key, 0),
+		Headline: fmt.Sprintf("%s waits for your yes on %s", module, node),
+		Explanation: fmt.Sprintf("%s is recorded: a person takes each of its moves. The next one on %s (version %s) %s. "+
+			"The node is told to apply it only after you say yes.", module, node, short(fp), what),
+		Options: []oc.Option{
+			{ID: OptionYes, Label: "Yes, move it", Does: "the node is told to apply the new composition of " + module, Level: occ.Acknowledge},
+			{ID: OptionNo, Label: "No, not now", Does: "the node keeps what it runs", Level: occ.Acknowledge},
+		},
+		Who:      occ.Operator,
+		Expires:  occ.FormatTime(now.Add(7 * 24 * time.Hour)),
+		OnExpiry: "the node keeps what it runs",
+		About:    key,
+	})
+}
+
+// NextBackupAsking is the number of the asking that follows the one numbered after (a negative number: none yet). Numbers 0 and 1
+// give one id (delivery.AskingID), so the first asking is 0 and the next 2.
+func NextBackupAsking(after int) int {
+	if after < 0 {
+		return 0
+	}
+	return max(after+1, 2)
+}
+
+var backupDigest = regexp.MustCompile(`\(composition (sha256:[0-9a-f]{64})\)`)
+
+// BackupAskDigest is the digest of the composition a backup ask was made about, from its explanation; empty for an ask that names
+// none. An answer is taken for the composition of the ask it answers, and a new revision at the same fingerprint is asked again
+// under a new number (ADR 0539 §16).
+func BackupAskDigest(a delivery.AssignerAsk) string {
+	ask, err := AskOf(a)
+	if err != nil {
+		return ""
+	}
+	if m := backupDigest.FindStringSubmatch(ask.Explanation); m != nil {
+		return m[1]
+	}
+	return ""
+}
+
+// BackupAnswerWords are the words of a want carrying the answer to the asking-th ask: each asking's answer is another want
+// value, so a backup that fails again after "back up again" and is answered "again" again changes the key and the node retries.
+func BackupAnswerWords(option string, asking int) string {
+	return fmt.Sprintf("the operator answered %q to the backup ask (asking %d)", option, asking+1)
+}
+
+// BackupAsk is the ask about a backup of a module on node that failed before an apply (ADR 0539 §16): back up again, or go on
+// without a backup. digest is the composition about to be applied and asking the number of the asking, 0 the first; words are the
+// backup's own words, from the node's have.
+func BackupAsk(key, node, module, fp, digest, words string, asking int, now time.Time) delivery.AssignerAsk {
+	return assignerAsk(asking, oc.Ask{
+		ID:       delivery.AskingID(key, asking),
+		Headline: fmt.Sprintf("The backup of %s failed on %s", module, node),
+		Explanation: fmt.Sprintf("The backup before applying %s at %s on %s failed: %s. %s keeps running what it has until you answer. (composition %s)",
+			module, short(fp), node, words, module, digest),
+		Options: []oc.Option{
+			{ID: OptionBackupAgain, Label: "Back up again", Does: "the node tries the backup again before it applies", Level: occ.Acknowledge},
+			{ID: OptionBackupSkip, Label: "Go on without a backup", Does: "the node applies the new version without a backup", Level: occ.Acknowledge},
+		},
+		Who:      occ.Operator,
+		Expires:  occ.FormatTime(now.Add(7 * 24 * time.Hour)),
+		OnExpiry: "the module keeps running what it has",
+		About:    key,
+	})
+}
+
+// BackupCondition is the condition raised when a backup before an apply fails and the module is held on the node (ADR 0539 §16),
+// naming the node, the module and the backup's words; cleared under the same key.
+func BackupCondition(node, module, fp, words string, raised bool) oc.Condition {
+	key := delivery.AssignerModule + ".backup." + node + "." + module + "." + strings.TrimPrefix(fp, delivery.SourcePrefix2)
+	subject := oc.ConditionSubject{Scope: "module", ID: module, Machine: node}
+	if !raised {
+		return oc.Condition{Key: key, Subject: subject, State: occ.StateCleared}
+	}
+	headline := fmt.Sprintf("The backup of %s failed on %s", module, node)
+	needs := "answer whether to back up again or go on without a backup"
+	return oc.Condition{Key: key, Severity: occ.SeverityWarning, Subject: subject, State: occ.StateRaised,
+		Summary: headline, Headline: headline, Needs: needs,
+		Explanation: occ.NeedsYou + needs + ". The backup before applying " + module + " at " + short(fp) + " on " + node + " failed: " + words + "."}
+}

modules/mesh-delivery-assigner/internal/assign/asks_test.go

@@ -0,0 +1,293 @@
+package assign
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	oc "git.novox.be/novox/mesh-contracts/go/seats/operatorchannel"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+)
+
+// 1297/B9 (the assigner's half): the ask about a held fingerprint is a valid ask of the router and of mesh-sdk's layout at
+// its key, of a kind the view may answer.
+func TestTheHoldAskIsValid(t *testing.T) {
+	key, err := delivery.HoldAskKey("mail", fNew)
+	if err != nil {
+		t.Fatal(err)
+	}
+	now := time.Now()
+	a := HoldAsk(key, "mail", fNew, "ace", "health failed, phase running: connection refused", 0, now)
+	if err := occ.Check(mustAsk(t, a), now); err != nil {
+		t.Errorf("the router refuses the ask: %v", err)
+	}
+	if _, err := EncodeAsk(key, a); err != nil {
+		t.Errorf("the ask cannot be written: %v", err)
+	}
+	// 1906/H3: the ask names the machine whose check failed and the hold's words.
+	if !strings.Contains(mustAsk(t, a).Explanation, "on ace") || !strings.Contains(mustAsk(t, a).Explanation, "connection refused") {
+		t.Errorf("the ask does not name the node and the hold's words: %q", mustAsk(t, a).Explanation)
+	}
+	// 1906/H2: an ask written again after a lift is another asking, under an id of its own.
+	again := HoldAsk(key, "mail", fNew, "ace", "x", 7, now)
+	if again.Asking != 7 || mustAsk(t, again).ID != delivery.AskingID(key, 7) || mustAsk(t, again).ID == mustAsk(t, a).ID {
+		t.Errorf("the asking after a lift = %d %s", again.Asking, mustAsk(t, again).ID)
+	}
+	if _, err := EncodeAsk(key, again); err != nil {
+		t.Errorf("the ask asked again cannot be written: %v", err)
+	}
+	if _, err := delivery.ViewAnswerKey(key); err != nil {
+		t.Errorf("the view may not answer it: %v", err)
+	}
+	// The join (A1d ruling 1): mesh-sdk no longer refuses another id, no option or no ask in an assigner's ask; EncodeAsk does.
+	t.Run("EncodeAsk refuses what mesh-sdk no longer does", func(t *testing.T) {
+		good := HoldAsk(key, "mail", fNew, "ace", "x", 0, time.Unix(100, 0))
+		other := good
+		other.Asking = 3 // its id is the asking 0's
+		empty := good
+		ask := mustAsk(t, good)
+		ask.Options = nil
+		empty.Ask = assignerAsk(0, ask).Ask
+		for name, a := range map[string]delivery.AssignerAsk{"another id": other, "no option": empty, "no ask": {}} {
+			if _, err := EncodeAsk(key, a); err == nil {
+				t.Errorf("%s: written", name)
+			}
+		}
+	})
+}
+
+// 1906/D3 (ADR 0539 §19): the ask about a data module held on a node is a valid ask of the router and of mesh-sdk's layout at
+// its restore key, of a kind the view may answer; it offers restoring (losing the newer writes) and leaving it stopped.
+func TestTheRestoreAskIsValid(t *testing.T) {
+	key, err := delivery.RestoreAskKey("ace", "mail", fNew)
+	if err != nil {
+		t.Fatal(err)
+	}
+	now := time.Now()
+	a := RestoreAsk(key, "ace", "mail", fNew, "connection refused", now)
+	if err := occ.Check(mustAsk(t, a), now); err != nil {
+		t.Errorf("the router refuses the ask: %v", err)
+	}
+	if _, err := EncodeAsk(key, a); err != nil {
+		t.Errorf("the ask cannot be written: %v", err)
+	}
+	if _, err := delivery.ViewAnswerKey(key); err != nil {
+		t.Errorf("the view may not answer it: %v", err)
+	}
+	var ids []string
+	for _, o := range mustAsk(t, a).Options {
+		ids = append(ids, o.ID)
+	}
+	if len(ids) != 2 || ids[0] != OptionRestore || ids[1] != OptionLeaveStopped {
+		t.Errorf("options = %v", ids)
+	}
+	if !strings.Contains(mustAsk(t, a).Explanation, "connection refused") || !strings.Contains(mustAsk(t, a).Explanation, "ace") {
+		t.Errorf("the ask does not name the node and the check's words: %q", mustAsk(t, a).Explanation)
+	}
+}
+
+// 1906/D3: the condition for a held fingerprint names the module, the node and the check's words, under the assigner's own
+// name (ADR 0437 clause 9), and is cleared under the same key.
+func TestTheAssignersConditions(t *testing.T) {
+	t.Run("the held condition names module, node and words", heldConditionNamesModuleNodeAndWords)
+	t.Run("a lifted hold clears its condition saying why", liftedHoldClearsItsConditionSayingWhy)
+	t.Run("1952/WM6: each said condition is a finding, its clear deletes it, said straight only with no findings bucket", saidConditionsAreFindings)
+}
+
+func heldConditionNamesModuleNodeAndWords(t *testing.T) {
+	c := HeldCondition("mail", fNew, "ace", "connection refused", true, true)
+	if _, err := occ.EncodeCondition(c); err != nil {
+		t.Fatalf("the condition is refused: %v", err)
+	}
+	if c.State != occ.StateRaised || c.Subject.ID != "mail" || c.Subject.Machine != "ace" || !strings.Contains(c.Explanation, "connection refused") || !strings.Contains(c.Key, "mail") {
+		t.Errorf("condition = %+v", c)
+	}
+	if got := HeldCondition("mail", fNew, "", "", false, false); got.State != occ.StateCleared || got.Key != c.Key {
+		t.Errorf("cleared = %+v", got)
+	}
+}
+
+// 1906/H2: a hold lifted by itself clears the held condition under its key, saying why.
+func liftedHoldClearsItsConditionSayingWhy(t *testing.T) {
+	c := LiftedCondition("mail", fNew)
+	if _, err := occ.EncodeCondition(c); err != nil {
+		t.Fatalf("the condition is refused: %v", err)
+	}
+	if c.State != occ.StateCleared || c.Key != HeldCondition("mail", fNew, "ace", "x", true, false).Key || !strings.Contains(c.Resolved, "lifted its hold by itself") {
+		t.Errorf("condition = %+v", c)
+	}
+}
+
+// 1952/WM6 (ADR 0564 §2, issue 1952 note 16): every condition the assigner says is a finding in its own bucket, under
+// `<scope>.<id>.<kind>`, written at the raise and deleted at the clear, and only as a finding: the keeper is the one
+// source since the controller's end (novox/hq ADR 0590 §3, issue 1126 B8). Said straight to the router only where the
+// findings bucket cannot be written to at all.
+func saidConditionsAreFindings(t *testing.T) {
+	at := time.Date(2026, 10, 29, 21, 0, 0, 0, time.UTC)
+	for _, c := range []struct {
+		raised, cleared oc.Condition
+		key             string
+	}{
+		{HeldCondition("mail", fNew, "ace", "refused", true, true), LiftedCondition("mail", fNew), "module.mail." + strings.TrimPrefix(fNew, delivery.SourcePrefix2) + ".held"},
+		{NodeFailedCondition("ace", "mail", fNew, NodeFailure{Words: "x", Others: []string{"g14"}}, true), NodeFailedCondition("ace", "mail", fNew, NodeFailure{}, false), "module.ace.mail.failed-alone"},
+		{NeitherCondition("ace", "mail", Holding{Rule: 3, Words: "w"}, true), NeitherCondition("ace", "mail", Holding{}, false), "module.ace.mail.neither"},
+		{SeatWaitsCondition([]string{"placement"}), SeatWaitsCondition(nil), "module.mesh-delivery-assigner.seat-states"},
+		{BackupCondition("ace", "mail", fNew, "disk full", true), BackupCondition("ace", "mail", fNew, "", false), "module.ace.mail." + strings.TrimPrefix(fNew, delivery.SourcePrefix2) + ".backup"},
+	} {
+		puts, deletes, said := map[string]health.Finding{}, []string{}, 0
+		f := Findings{Put: func(k string, v []byte) error {
+			got, err := health.DecodeFinding(v)
+			puts[k] = got
+			return err
+		}, Delete: func(k string) error { deletes = append(deletes, k); return nil }, Now: func() time.Time { return at }}
+		say := f.Say(func(oc.Condition) error { said++; return nil })
+		if err := say(c.raised); err != nil {
+			t.Fatalf("%s: %v", c.key, err)
+		}
+		got, ok := puts[c.key]
+		if !ok || got.Severity != health.Severity(c.raised.Severity) || got.Headline != c.raised.Headline || got.Observer != delivery.AssignerModule ||
+			got.Subject.Machine != c.raised.Subject.Machine || said != 0 {
+			t.Fatalf("%s: finding %+v (written %v), said %d", c.key, got, puts, said)
+		}
+		if err := say(c.cleared); err != nil || !slices.Equal(deletes, []string{c.key}) || said != 0 {
+			t.Fatalf("%s: deleted %v, said %d (%v)", c.key, deletes, said, err)
+		}
+		if err := (Findings{}).Say(func(oc.Condition) error { said++; return nil })(c.raised); err != nil || said != 1 {
+			t.Fatalf("%s: with no findings bucket said %d (%v), want straight once", c.key, said, err)
+		}
+	}
+	if _, _, _, err := FindingOf(oc.Condition{Key: "another.x", State: occ.StateRaised}, at); err == nil {
+		t.Error("a condition not the assigner's is a finding")
+	}
+}
+
+// 1906/D4: the record ask and the backup ask are valid asks of the router and of mesh-sdk's layout at their keys, answerable in
+// the view, and name the move and the node.
+func TestTheRecordAndBackupAsksAreValid(t *testing.T) {
+	now := time.Now()
+	rkey, err := delivery.RecordAskKey("ace", "mail", "sha256:"+strings.Repeat("b", 64))
+	if err != nil {
+		t.Fatal(err)
+	}
+	r := RecordAsk(rkey, "ace", "mail", fNew, RecordNeed{Node: "ace", Digest: "sha256:" + strings.Repeat("b", 64), Judgement: delivery.JudgedCannot, Words: "the composition it runs is gone"}, now)
+	bkey, err := delivery.BackupAskKey("ace", "mail", fNew)
+	if err != nil {
+		t.Fatal(err)
+	}
+	dgst := "sha256:" + strings.Repeat("b", 64)
+	b := BackupAsk(bkey, "ace", "mail", fNew, dgst, "no space left", 0, now)
+	for key, a := range map[string]delivery.AssignerAsk{rkey: r, bkey: b} {
+		if err := occ.Check(mustAsk(t, a), now); err != nil {
+			t.Errorf("%s: the router refuses the ask: %v", key, err)
+		}
+		if _, err := EncodeAsk(key, a); err != nil {
+			t.Errorf("%s: cannot be written: %v", key, err)
+		}
+		if _, err := delivery.ViewAnswerKey(key); err != nil {
+			t.Errorf("%s: the view may not answer it: %v", key, err)
+		}
+	}
+	if !strings.Contains(mustAsk(t, r).Explanation, "gone") || mustAsk(t, r).Options[0].ID != OptionYes {
+		t.Errorf("the record ask = %+v", mustAsk(t, r))
+	}
+	if !strings.Contains(mustAsk(t, b).Explanation, "no space left") || mustAsk(t, b).Options[0].ID != delivery.BackupAgain || mustAsk(t, b).Options[1].ID != delivery.BackupSkip {
+		t.Errorf("the backup ask = %+v", mustAsk(t, b))
+	}
+	// the id binds the ask to the composition and to its number (review round 1, items 3 and 4)
+	if again := BackupAsk(bkey, "ace", "mail", fNew, dgst, "x", NextBackupAsking(0), now); mustAsk(t, again).ID == mustAsk(t, b).ID {
+		t.Errorf("asked again under the same id")
+	}
+	if NextBackupAsking(-1) != 0 || NextBackupAsking(0) != 2 || NextBackupAsking(2) != 3 {
+		t.Errorf("the numbers of the askings: %d %d %d", NextBackupAsking(-1), NextBackupAsking(0), NextBackupAsking(2))
+	}
+	if BackupAskDigest(b) != dgst {
+		t.Errorf("the ask names composition %q, want %q", BackupAskDigest(b), dgst)
+	}
+	if BackupAnswerWords("again", 0) == BackupAnswerWords("again", 1) {
+		t.Errorf("two answers of the same option are one want value")
+	}
+	c := BackupCondition("ace", "mail", fNew, "no space left", true)
+	if _, err := occ.EncodeCondition(c); err != nil {
+		t.Errorf("the backup condition is refused: %v", err)
+	}
+	// ADR 0546 clauses 7 and 8: a put's ask is valid at the record ask's key; for the bus its yes approves and binds the act,
+	// so the view cannot answer it, and it lasts no longer than an approving ask may.
+	put := delivery.Put{FP: fNew, Why: "the bus's user list", Hold: true}
+	d := delivery.ComposedDigest{Digest: dgst, Judgement: delivery.JudgedCannot, Words: "the have names no composition"}
+	for _, bus := range []bool{false, true} {
+		a, err := PutAsk(rkey, "ace", "mail", put, d, bus, now)
+		if err != nil {
+			t.Fatalf("bus %v: %v", bus, err)
+		}
+		if err := occ.Check(mustAsk(t, a), now); err != nil {
+			t.Errorf("bus %v: the router refuses the put's ask: %v", bus, err)
+		}
+		if _, err := EncodeAsk(rkey, a); err != nil {
+			t.Errorf("bus %v: the put's ask cannot be written: %v", bus, err)
+		}
+		viewed := delivery.ViewAnswerFits(delivery.ViewAnswer{Asking: mustAsk(t, a).ID, Option: OptionYes}, rkey, a)
+		yes := mustAsk(t, a).Options[0]
+		// mesh-sdk gives no refusal by level any more: the teller refuses an option a view cannot answer (its level is not
+		// acknowledge), as it did through the sdk before.
+		if viewed == nil {
+			if o, ok := occ.OptionOf(mustAsk(t, a), OptionYes); ok && o.Level != "" && o.Level != occ.Acknowledge {
+				viewed = fmt.Errorf("only a channel that proves who answered takes the option %s", o.ID)
+			}
+		}
+		switch {
+		case !strings.Contains(mustAsk(t, a).Explanation, "the bus's user list"):
+			t.Errorf("bus %v: the put's ask does not say why: %s", bus, mustAsk(t, a).Explanation)
+		case bus && (yes.Level != occ.Approve || yes.Binds == "" || viewed == nil || expiresAt(t, a).After(now.Add(occ.ApproveLasts))):
+			t.Errorf("bus: the yes is %+v, the view's answer %v, expiring %s", yes, viewed, expiresAt(t, a))
+		case !bus && (yes.Level != occ.Acknowledge || viewed != nil):
+			t.Errorf("a recorded module: the yes is %+v, the view's answer %v", yes, viewed)
+		}
+		later := put
+		later.At = now.Add(time.Minute)
+		b, _ := PutAsk(rkey, "ace", "mail", later, d, bus, now)
+		if mustAsk(t, b).ID == mustAsk(t, a).ID || b.Asking != PutAsking(later) {
+			t.Errorf("bus %v: a later put's ask is asking %d under id %q, the earlier's %q", bus, b.Asking, mustAsk(t, b).ID, mustAsk(t, a).ID)
+		}
+		if err := occ.Performs(yes, PutAct("ace", "mail", fNew, dgst)); err != nil {
+			t.Errorf("bus %v: the yes does not perform the act it bound: %v", bus, err)
+		}
+		if err := occ.Performs(yes, PutAct("ace", "mail", fNew, dig(fOld))); bus && err == nil {
+			t.Errorf("bus: the yes performs another composition's act")
+		}
+	}
+}
+
+// 1945/AC21: the condition of a module on neither list is urgent, names the module, the node and the rule holding its want back,
+// under the assigner's own name keyed by node and module, and is cleared under the same key.
+func TestTheNeitherConditionNamesModuleNodeAndRule(t *testing.T) {
+	c := NeitherCondition("g14", "i3status-rust", Holding{Rule: delivery.RuleProviders, Words: "no provider of x11-display runs healthy on g14 or at its canary"}, true)
+	if _, err := occ.EncodeCondition(c); err != nil {
+		t.Fatalf("the condition is refused: %v", err)
+	}
+	if c.State != occ.StateRaised || c.Severity != occ.SeverityUrgent || c.Subject.ID != "i3status-rust" || c.Subject.Machine != "g14" ||
+		!strings.Contains(c.Explanation, "x11-display") || !strings.Contains(c.Explanation, "rule 5") || c.Key != "mesh-delivery-assigner.neither.g14.i3status-rust" {
+		t.Errorf("condition = %+v", c)
+	}
+	if got := NeitherCondition("g14", "i3status-rust", Holding{}, false); got.State != occ.StateCleared || got.Key != c.Key {
+		t.Errorf("cleared = %+v", got)
+	}
+}
+
+// mustAsk is the router's ask an asks-state value carries.
+func mustAsk(t *testing.T, a delivery.AssignerAsk) oc.Ask {
+	t.Helper()
+	ask, err := AskOf(a)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return ask
+}
+
+func expiresAt(t *testing.T, a delivery.AssignerAsk) time.Time {
+	t.Helper()
+	return ExpiresAt(mustAsk(t, a))
+}

modules/mesh-delivery-assigner/internal/assign/findings.go

@@ -0,0 +1,105 @@
+package assign
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	oc "git.novox.be/novox/mesh-contracts/go/seats/operatorchannel"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+)
+
+// The assigner's said conditions become findings (novox/hq ADR 0564 §2, issue 1952 WM6, note 16): every condition it says
+// under its own name (ADR 0437 §9) — a hold and its lift, a node failing alone, a module on neither list, a backup, a pair
+// placed by one source, the seat waiting for its states — is also a finding in its own bucket `findings`, written at its
+// raise and deleted at its clear, which the condition keeper raises and clears. Until the operator's take-over the router
+// hears it straight from the assigner, as before; from the take-over the keeper's condition is the one said, so the
+// assigner no longer says it straight (never both).
+
+// FindingsBucket is the assigner's findings.
+var FindingsBucket = health.FindingsBucket(delivery.AssignerModule)
+
+// FindingOf is a said condition as a finding: its key `<scope>.<id>.<kind>`, from the condition's own key
+// `mesh-delivery-assigner.<kind>.<id…>` (the subject's id when the key names none), its words unchanged. raised is false for
+// a clear, whose key is to be deleted; value is nil then.
+func FindingOf(c oc.Condition, at time.Time) (key string, value []byte, raised bool, err error) {
+	rest, ok := strings.CutPrefix(c.Key, delivery.AssignerModule+".")
+	if !ok || rest == "" {
+		return "", nil, false, fmt.Errorf("the condition %q is not the assigner's", c.Key)
+	}
+	kind, id, _ := strings.Cut(rest, ".")
+	if id == "" {
+		id = c.Subject.ID
+	}
+	scope := c.Subject.Scope
+	if scope == "" {
+		scope = health.ScopeModule
+	}
+	key = health.FindingKey(scope, id, kind)
+	if c.State == occ.StateCleared {
+		return key, nil, false, nil
+	}
+	if c.State != occ.StateRaised {
+		return "", nil, false, fmt.Errorf("the condition %s is neither raised nor cleared", c.Key)
+	}
+	summary := c.Summary
+	if summary == "" {
+		summary = c.Headline
+	}
+	var actions []health.Action
+	for _, a := range c.Actions {
+		actions = append(actions, health.Action{Label: a.Label, Verb: a.Verb, Machine: a.Machine, Arguments: a.Arguments, Level: string(a.Level)})
+	}
+	value, err = health.EncodeFinding(health.Finding{Key: key, Kind: kind, Subject: health.Subject{Scope: scope, ID: id, Machine: c.Subject.Machine},
+		Severity: health.Severity(c.Severity), Summary: summary, Headline: c.Headline, Explanation: c.Explanation, Resolved: c.Resolved,
+		Needs: c.Needs, Actions: actions, Evidence: []health.Evidence{{At: at.UTC(), Said: summary}}, Source: "assigner." + kind,
+		Observer: delivery.AssignerModule, At: at.UTC()})
+	return key, value, true, err
+}
+
+// Findings is where the assigner's findings go: the bucket's put and delete.
+type Findings struct {
+	Put    func(key string, value []byte) error
+	Delete func(key string) error
+	Keys   func() ([]string, error)
+	Now    func() time.Time
+}
+
+// Say is say with each condition written as a finding (or its finding deleted), which the condition keeper carries, the
+// one source since the controller's end (novox/hq ADR 0590 §3); said straight to the router only where there is no
+// findings bucket at all. A finding that cannot be written is the error.
+func (f Findings) Say(say func(oc.Condition) error) func(oc.Condition) error {
+	return func(c oc.Condition) error {
+		var errs []error
+		if f.Put != nil {
+			now := time.Now
+			if f.Now != nil {
+				now = f.Now
+			}
+			key, value, raised, err := FindingOf(c, now())
+			switch {
+			case err != nil:
+				errs = append(errs, err)
+			case raised:
+				if err := f.Put(key, value); err != nil {
+					errs = append(errs, fmt.Errorf("the finding %s cannot be written: %w", key, err))
+				}
+			default:
+				if err := f.Delete(key); err != nil {
+					errs = append(errs, fmt.Errorf("the finding %s cannot be deleted: %w", key, err))
+				}
+			}
+		}
+		if f.Put == nil {
+			if say != nil {
+				if err := say(c); err != nil {
+					errs = append(errs, err)
+				}
+			}
+		}
+		return errors.Join(errs...)
+	}
+}

modules/mesh-delivery-assigner/internal/assign/placement.go

@@ -0,0 +1,23 @@
+package assign
+
+import (
+	"strings"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	oc "git.novox.be/novox/mesh-contracts/go/seats/operatorchannel"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// SeatWaitsCondition is the assigner's word on the seat mesh-placement while a state of the seat is not bound (ADR 0567
+// §1): raised naming each, cleared when none is left.
+func SeatWaitsCondition(unbound []string) oc.Condition {
+	key := delivery.AssignerModule + ".seat-states"
+	subject := oc.ConditionSubject{Scope: "module", ID: delivery.AssignerModule}
+	if len(unbound) == 0 {
+		return oc.Condition{Key: key, Subject: subject, State: occ.StateCleared, Resolved: "the seat mesh-placement holds all its states."}
+	}
+	why := "the seat waits for its states: " + strings.Join(unbound, ", ") + " are not on the bus or not granted yet"
+	return oc.Condition{Key: key, Severity: occ.SeverityWarning, Subject: subject, State: occ.StateRaised,
+		Summary: "the seat waits for its states", Headline: "the seat waits for its states",
+		Explanation: occ.NothingToDo + " " + why + "; each is bound at the next pass once it is, with no restart."}
+}

modules/mesh-delivery-assigner/internal/assign/policy.go

@@ -0,0 +1,135 @@
+package assign
+
+import (
+	"encoding/json"
+	"fmt"
+	"sort"
+	"strings"
+	"time"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+	"git.novox.be/novox/mesh-sdk/go/provisions"
+)
+
+// A person's upgrade policy is the assigner's (novox/hq ADR 0565 §7, §8, issue 1953 D4, D5): kept in its state `policies`, one
+// key per module, set and taken back through `mesh-wants.upgrade`. Every reader takes one derivation, mesh-sdk's
+// catalogue.Upgrade: a person's choice over the module's word, its irreplaceable data and the default, the bus as any module (ADR 0601 §1).
+
+// PoliciesBucket is the assigner's state `policies`.
+var PoliciesBucket = delivery.AssignerModule + "_" + delivery.AssignerPoliciesState
+
+// DecodePolicies reads the policies state's values by key (the module); a value that cannot be read is left out, named.
+func DecodePolicies(values map[string][]byte) (map[string]catalogue.PersonPolicy, []string) {
+	out := map[string]catalogue.PersonPolicy{}
+	var bad []string
+	for key, raw := range values {
+		var p catalogue.PersonPolicy
+		if err := json.Unmarshal(raw, &p); err != nil || p.V != catalogue.PersonPolicyVersion || p.Check() != nil || p.Module != key {
+			bad = append(bad, key)
+			continue
+		}
+		out[key] = p
+	}
+	sort.Strings(bad)
+	return out, bad
+}
+
+// PolicyOf is a module's policy and where it comes from, with the person's choice for it when there is one.
+func PolicyOf(m catalogue.Manifest, chosen map[string]catalogue.PersonPolicy) (policy, from, why, by string) {
+	var c *catalogue.PersonPolicy
+	if p, ok := chosen[m.Module]; ok {
+		c = &p
+	}
+	return catalogue.Upgrade(m, c)
+}
+
+func contains(list []string, s string) bool {
+	for _, v := range list {
+		if v == s {
+			return true
+		}
+	}
+	return false
+}
+
+// KindProvisionFailed is the assigner's finding of a provision its module's want waits for that failed (ADR 0570 §4).
+const KindProvisionFailed = "provision-failed"
+
+// ProvisionFailedKey is a failed provision's finding's key, `provider.<node>.<consumer>.<provision>[.<local>].provision-failed`.
+func ProvisionFailedKey(key string) string {
+	return health.FindingKey(health.ScopeProvider, key, KindProvisionFailed)
+}
+
+// ProvisionFailedFinding is the finding of a failed provision, naming its consumer, its provider and why.
+func ProvisionFailedFinding(key string, p provisions.Provision, at time.Time) ([]byte, error) {
+	summary := fmt.Sprintf("%s for %s on %s failed at %s on %s: %s, so %s is not moved there until it is provided", p.Provision,
+		p.Consumer.Module, p.Consumer.Node, p.Provider.Module, p.Provider.Node, p.Why, p.Consumer.Module)
+	return health.EncodeFinding(health.Finding{Key: ProvisionFailedKey(key), Kind: KindProvisionFailed,
+		Subject:  health.Subject{Scope: health.ScopeProvider, ID: key, Machine: p.Consumer.Node, Also: also(p.Provider.Node, p.Consumer.Node)},
+		Severity: health.Warning, Summary: summary, Headline: clipHeadline(p.Consumer.Module + " waits for a provision that failed"),
+		Explanation: occ.NothingToDo + " " + summary + ". It clears once the provider provides it.",
+		Resolved:    p.Provision + " for " + p.Consumer.Module + " is provided", Evidence: []health.Evidence{{At: at.UTC(), Said: p.Why}},
+		Source: "assigner." + KindProvisionFailed, Observer: delivery.AssignerModule, At: at.UTC()})
+}
+
+func also(provider, consumer string) []string {
+	if provider == "" || provider == consumer {
+		return nil
+	}
+	return []string{provider}
+}
+
+// KindProvisionMissing is the assigner's finding of a required provision that has had no key for longer than its bound.
+const KindProvisionMissing = "provision-missing"
+
+// ProvisionMissingKey is its key, `provider.<node>.<module>.<provision>.provision-missing`.
+func ProvisionMissingKey(key string) string {
+	return health.FindingKey(health.ScopeProvider, key, KindProvisionMissing)
+}
+
+// ProvisionMissingFinding is the finding of a required provision with no key past bound (key `<node>.<module>.<provision>`).
+func ProvisionMissingFinding(key string, bound time.Duration, at time.Time) ([]byte, error) {
+	parts := strings.SplitN(key, ".", 3)
+	if len(parts) != 3 {
+		return nil, fmt.Errorf("%q is not <node>.<module>.<provision>", key)
+	}
+	node, module, provision := parts[0], parts[1], parts[2]
+	summary := fmt.Sprintf("%s on %s requires %s and mesh-provisioner has composed no key for it in %s, so %s is not moved there: "+
+		"no provider of it may be placed", module, node, provision, bound, module)
+	return health.EncodeFinding(health.Finding{Key: ProvisionMissingKey(key), Kind: KindProvisionMissing,
+		Subject:  health.Subject{Scope: health.ScopeProvider, ID: key, Machine: node},
+		Severity: health.Warning, Summary: summary, Headline: clipHeadline(module + " on " + node + " lacks " + provision),
+		Explanation: occ.NothingToDo + " " + summary + ". It clears once the provision has its key.",
+		Resolved:    provision + " for " + module + " on " + node + " has its key", Evidence: []health.Evidence{{At: at.UTC(), Said: summary}},
+		Source: "assigner." + KindProvisionMissing, Observer: delivery.AssignerModule, At: at.UTC()})
+}
+
+// KindUnplaced is, from the lease write, a node that runs but no placement names (ADR 0571 §6).
+const KindUnplaced = "unplaced"
+
+// UnplacedKey is its finding's key, `machine.<node>.unplaced`.
+func UnplacedKey(node string) string {
+	return health.FindingKey(health.ScopeMachine, node, KindUnplaced)
+}
+
+// UnplacedFinding is the finding of a node no placement names since the lease write.
+func UnplacedFinding(node string, at time.Time) ([]byte, error) {
+	summary := fmt.Sprintf("%s runs, but no placement names it: since the controller handed its lease away nothing composes it, "+
+		"so the assigner writes it no want", node)
+	return health.EncodeFinding(health.Finding{Key: UnplacedKey(node), Kind: KindUnplaced,
+		Subject: health.Subject{Scope: health.ScopeMachine, ID: node, Machine: node}, Severity: health.Warning, Summary: summary,
+		Headline: clipHeadline(node + " has no placement"), Needs: "place it with mesh-placement.propose.",
+		Explanation: occ.NeedsYou + "place it with mesh-placement.propose. " + summary + ".",
+		Resolved:    node + " is placed", Evidence: []health.Evidence{{At: at.UTC(), Said: summary}},
+		Source: "assigner." + KindUnplaced, Observer: delivery.AssignerModule, At: at.UTC()})
+}
+
+func clipHeadline(s string) string {
+	if len([]rune(s)) <= 60 {
+		return s
+	}
+	return string([]rune(s)[:60])
+}

modules/mesh-delivery-assigner/internal/assign/put.go

@@ -0,0 +1,253 @@
+package assign
+
+import (
+	"fmt"
+	"time"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	oc "git.novox.be/novox/mesh-contracts/go/seats/operatorchannel"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// A put (novox/hq ADR 0546): one version of a module put on one node by the assigner's tool assigner_put. The tool writes the put
+// key; each pass takes it one step further from what the world holds (StepPut), and the rules pass over the node's want for
+// the module from its asking until it ends (Module.Puts).
+
+// ComposeWithin is how long a put waits for the composition and grant it needs (a take-in of a build just done writes them)
+// before it is refused.
+const ComposeWithin = 10 * time.Minute
+
+// PutWorld is what one step of a put reads.
+type PutWorld struct {
+	Node, Module string
+	Put          delivery.Put
+	// Assigned says the module stands assigned to the node.
+	Assigned bool
+	// Bus says the module provides the mesh's bus (ADR 0539 §15); Recorded that it is of policy record (§14).
+	Bus, Recorded bool
+	// Build is the state of the builder's build at the put's fingerprint, "" when no key is written; BuildWords its error.
+	Build, BuildWords string
+	// Newest is the module's newest fingerprint at the trunk, which the builder builds by itself.
+	Newest string
+	// Composed is the composition of the module for the node at the fingerprint, as its writer holds it; nil when there is
+	// none. Granted says the grant at the fingerprint names the node's accounts. Both are read, never asked for (clause 4).
+	Composed *delivery.ComposedDigest
+	Granted  bool
+	// Answer is the option the operator chose on this put's own ask (its asking, PutAsking), "" when none; AskExpired says
+	// that ask expired unanswered.
+	Answer     string
+	AskExpired bool
+	// Snapshot says where the bus's streams were snapshotted for this put, once they were; Snapshotting that it was
+	// asked; SnapshotFailed why it was not taken.
+	Snapshot       string
+	Snapshotting   bool
+	SnapshotFailed string
+	// Have is what the node says it runs of the module; nil when it says nothing.
+	Have *delivery.Have
+	Now  time.Time
+}
+
+// PutNext is what a step decides: the put as it stands after it, and the acts the pass does for it.
+type PutNext struct {
+	Put delivery.Put
+	// Ask writes the put's ask about the move (PutAsk).
+	Ask bool
+	// Snapshot has the bus's node back the bus up now, its dump the streams' snapshot (ADR 0235).
+	Snapshot bool
+	// Warranted records, once, in the controller's hand-act log that the bus's want was written on the operator's warrant.
+	Warranted bool
+}
+
+// StepPut takes a put one step further from what the world holds (ADR 0546 clauses 3 to 8).
+func StepPut(w PutWorld) PutNext {
+	p := w.Put
+	if delivery.PutEnded(p.Step) {
+		return PutNext{Put: p}
+	}
+	say := func(step, format string, args ...any) PutNext {
+		return PutNext{Put: p.Said(w.Now, step, fmt.Sprintf(format, args...))}
+	}
+	fp := short(p.FP)
+	if !w.Assigned {
+		return say(delivery.PutRefused, "%s is not assigned to %s: a put moves a module where it stands assigned (propose its placement first)", w.Module, w.Node)
+	}
+	switch w.Build {
+	case delivery.BuildDone:
+	case delivery.BuildFailed:
+		return say(delivery.PutRefused, "the builder's build of %s at %s failed: %s", w.Module, fp, w.BuildWords)
+	case "":
+		if p.FP != w.Newest {
+			// The builder builds the trunk's newest fingerprint and the candidates', and takes no ask for another yet (ADR 0546
+			// clause 3): an older fingerprint it never built, or whose key it removed, cannot be put.
+			return say(delivery.PutRefused, "the builder holds no build of %s at %s, and builds by itself only the trunk's newest (%s): put that, or a version it built", w.Module, fp, short(w.Newest))
+		}
+		return say(delivery.PutBuild, "waits for the builder's build of %s at %s, the trunk's newest, which it builds by itself", w.Module, fp)
+	default:
+		return say(delivery.PutBuild, "waits for the builder's build of %s at %s, which is %s", w.Module, fp, w.Build)
+	}
+	if w.Composed == nil || !w.Granted {
+		missing := fmt.Sprintf("no composition of %s for %s at %s is written", w.Module, w.Node, fp)
+		if w.Composed != nil {
+			missing = fmt.Sprintf("the grant of %s at %s does not name %s's accounts", w.Module, fp, w.Node)
+		}
+		since := w.Now
+		if p.Step == delivery.PutCompose && len(p.Steps) > 0 {
+			since = p.Steps[len(p.Steps)-1].At
+		}
+		if w.Now.Sub(since) > ComposeWithin {
+			return say(delivery.PutRefused, "%s after %s: only a composition written by the take-in of its build (or one of the five kept) is put; "+
+				"for another the hand path is mesh-hand-compose (ADR 0539 §10)", missing, ComposeWithin)
+		}
+		return say(delivery.PutCompose, "waits up to %s: %s yet", ComposeWithin, missing)
+	}
+	d := *w.Composed
+	if p.Step == delivery.PutWanted || p.Step == delivery.PutHolding {
+		return PutNext{Put: applied(w, p)}
+	}
+	p.Composed = d.Digest
+	if needsPerson(w, d) {
+		switch w.Answer {
+		case OptionNo:
+			return say(delivery.PutRefused, "the operator answered no to putting %s at %s on %s", w.Module, fp, w.Node)
+		case OptionYes:
+		default:
+			if w.AskExpired {
+				return say(delivery.PutRefused, "the operator's ask about putting %s at %s on %s expired unanswered: the node keeps what it runs", w.Module, fp, w.Node)
+			}
+			next := say(delivery.PutPerson, "waits for the operator's yes to putting %s at %s on %s (composition %s, judged %s)", w.Module, fp, w.Node, short(d.Digest), d.Judgement)
+			if p.Ask == "" {
+				next.Ask = true
+				next.Put.Ask, _ = delivery.RecordAskKey(w.Node, w.Module, d.Digest)
+			}
+			return next
+		}
+		if w.Bus {
+			switch {
+			case w.Snapshot != "":
+				p.Snapshot = w.Snapshot
+			case w.SnapshotFailed != "":
+				return say(delivery.PutRefused, "the bus's streams were not snapshotted, so the bus is not put: %s", w.SnapshotFailed)
+			case w.Snapshotting:
+				return say(delivery.PutSnapshot, "the operator said yes; waits for %s's backup holder to snapshot the bus's streams", w.Node)
+			default:
+				next := say(delivery.PutSnapshot, "the operator said yes; asked %s's backup holder to snapshot the bus's streams", w.Node)
+				next.Snapshot = true
+				return next
+			}
+		}
+	}
+	words := fmt.Sprintf("the want of %s on %s names %s (composition %s)", w.Module, w.Node, fp, short(d.Digest))
+	if p.Hold {
+		words += ", held until released"
+	}
+	if p.Snapshot != "" {
+		words += "; the streams were snapshotted: " + p.Snapshot
+	}
+	next := PutNext{Put: applied(w, p.Said(w.Now, delivery.PutWanted, words))}
+	next.Warranted = w.Bus && p.Ask != ""
+	return next
+}
+
+// applied is a wanted put once the node's have says how it went: holding or done when it runs the composition healthy.
+func applied(w PutWorld, p delivery.Put) delivery.Put {
+	h := w.Have
+	if h == nil || h.FP != p.FP || h.Composed != p.Composed {
+		return p
+	}
+	switch {
+	case h.Phase == delivery.PhaseRunning && h.Health == delivery.HealthOK && p.Hold:
+		return p.Said(w.Now, delivery.PutHolding, fmt.Sprintf("%s runs %s at %s healthy; held there until released", w.Node, w.Module, short(p.FP)))
+	case h.Phase == delivery.PhaseRunning && h.Health == delivery.HealthOK:
+		return p.Said(w.Now, delivery.PutDone, fmt.Sprintf("%s runs %s at %s healthy; the rules write its want again", w.Node, w.Module, short(p.FP)))
+	case failed(*h):
+		return p.Said(w.Now, p.Step, fmt.Sprintf("%s runs %s at %s and its health check failed: %s", w.Node, w.Module, short(p.FP), h.Detail))
+	}
+	return p
+}
+
+// needsPerson says whether the put's move waits for the operator: any move of the bus but a revision at the fingerprint the
+// node runs that changes only its user list (ADR 0539 §7, §15), and a move of a module of policy record judged to recreate a
+// container, move data, or that cannot be judged (§14).
+func needsPerson(w PutWorld, d delivery.ComposedDigest) bool {
+	runs := w.Have != nil && w.Have.FP == w.Put.FP
+	if runs && w.Have.Composed == d.Digest {
+		return false // the node runs this composition already: nothing moves
+	}
+	if w.Bus {
+		return !(runs && d.UserListOnly)
+	}
+	if !w.Recorded {
+		return false
+	}
+	return d.Judgement == delivery.JudgedRecreates || d.Judgement == delivery.JudgedMovesData || d.Judgement == delivery.JudgedCannot
+}
+
+// PutWant is the want a put writes once it is wanted: the fingerprint and composition, marked put, and held when it holds.
+func PutWant(p delivery.Put) delivery.Want {
+	return delivery.Want{FP: p.FP, Composed: p.Composed, Put: true, Hold: p.Hold, Words: "put: " + p.Why}
+}
+
+// PutOwns says what a put does to the node's want: owns says the rules pass over it, want the want it writes (nil: what
+// stands stays). A put owns the want from its asking until it ends; a held put ends only when released.
+func PutOwns(p delivery.Put) (want *delivery.Want, owns bool) {
+	switch p.Step {
+	case delivery.PutWanted, delivery.PutHolding:
+		w := PutWant(p)
+		return &w, true
+	case delivery.PutDone, delivery.PutReleased, delivery.PutRefused:
+		return nil, false
+	}
+	return nil, true
+}
+
+// PutAsking is a put's own asking number: when it was asked, in milliseconds. Each put asked under the same key is another
+// asking, so the ask is written again under an id of its own and an answer to an earlier put, whose warrant names that put's
+// asking, never counts for a later one (ADR 0546 clause 8: one approval binds one act).
+func PutAsking(p delivery.Put) int {
+	if n := p.At.UnixMilli(); n > 0 {
+		return int(n)
+	}
+	return 0
+}
+
+// PutAct is the act a bus put's yes binds and that is performed when its want is written.
+func PutAct(node, module, fp, composed string) occ.Act {
+	return occ.Act{"put": "want", "node": node, "module": module, "fp": fp, "composed": composed}
+}
+
+// PutAsk is the ask about a put's move (ADR 0546 clauses 7 and 8), under the record ask's key of the composition so the
+// teller relays it and its answer as any record ask's. For the bus its yes is of level approve and binds the act, so only a
+// channel that proves who answered takes it (ADR 0259), never the view.
+func PutAsk(key, node, module string, p delivery.Put, d delivery.ComposedDigest, bus bool, now time.Time) (delivery.AssignerAsk, error) {
+	yes := oc.Option{ID: OptionYes, Label: "Yes, put it", Does: "the node is told to apply " + module + " at " + short(p.FP), Level: occ.Acknowledge}
+	what := map[delivery.Judgement]string{
+		delivery.JudgedRecreates: "recreates a container",
+		delivery.JudgedMovesData: "moves the module's data",
+		delivery.JudgedCannot:    "cannot be judged: " + d.Words,
+		delivery.JudgedNeither:   "recreates no container and moves no data",
+		delivery.JudgedUnchanged: "changes nothing the node runs",
+	}[d.Judgement]
+	explanation := fmt.Sprintf("Asked to put %s at version %s on %s: %s. The move %s.", module, short(p.FP), node, p.Why, what)
+	expires := occ.FormatTime(now.Add(7 * 24 * time.Hour))
+	if bus {
+		binds, err := occ.ActDigest(PutAct(node, module, p.FP, d.Digest))
+		if err != nil {
+			return delivery.AssignerAsk{}, err
+		}
+		yes.Level, yes.Binds = occ.Approve, binds
+		yes.Does = "the bus's streams are snapshotted, then " + node + " is told to apply the bus at " + short(p.FP)
+		explanation += " It is the mesh's bus: every module reconnects while it restarts, and its streams are snapshotted first."
+		expires = occ.FormatTime(now.Add(occ.ApproveLasts))
+	}
+	return assignerAsk(PutAsking(p), oc.Ask{
+		ID:          delivery.AskingID(key, PutAsking(p)),
+		Headline:    fmt.Sprintf("Put %s on %s?", module, node),
+		Explanation: explanation,
+		Options: []oc.Option{yes,
+			{ID: OptionNo, Label: "No", Does: "the node keeps what it runs, and the put is refused", Level: occ.Acknowledge}},
+		Who:      occ.Operator,
+		Expires:  expires,
+		OnExpiry: "the node keeps what it runs",
+		About:    key,
+	}), nil
+}

modules/mesh-delivery-assigner/internal/assign/seat.go

@@ -0,0 +1,236 @@
+package assign
+
+import (
+	"fmt"
+	"maps"
+	"slices"
+	"strings"
+	"time"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	oc "git.novox.be/novox/mesh-contracts/go/seats/operatorchannel"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// The seat mesh-placement (novox/hq ADR 0567), held by the assigner beside its wants: placement is its state
+// `placement`, changed only by a proposal (§2) the nodes it touches answer (§3), judged (§4) and written on the
+// operator's Approve at the revision it was laid over (§5). What here decides; the tools and the passes do.
+
+// ProposeIn is what a proposal is laid over: its id, who and why, its changes; every node's current placement and the
+// revision of its key; which modules the indexer holds and which nodes have a record; and, for the seed, the export's
+// digest.
+type ProposeIn struct {
+	ID, By, Why string
+	At          time.Time
+	Changes     []delivery.PlacementProposalChange
+	Current     map[string]delivery.Placement
+	Revisions   map[string]uint64
+	Held        func(module string) bool
+	Recorded    func(node string) bool
+	// Warrant is the enrolment's warrant an add-node carries (ADR 0587 §7); only that change has one.
+	Warrant *delivery.AddNodeWarrant
+}
+
+// Propose lays a proposal over the current keys (§2): the proposal (state answering, each changed node's base revision),
+// the laid placement of every node whose key it changes, and every finding, which refuses it whole: a change that does not fit its node, and what
+// CheckPlacements refuses of the result laid over every placement (two modules on one host port, a provider not placed,
+// a seat held once held twice, two nodes with one address, two hubs, a module the indexer does not hold, a node with no
+// record). A key whose value the proposal leaves as it is changes nothing and is not laid.
+func Propose(in ProposeIn) (delivery.PlacementProposal, map[string]*delivery.Placement, []string) {
+	p := delivery.PlacementProposal{ID: in.ID, By: strings.TrimSpace(in.By), Why: strings.TrimSpace(in.Why), At: in.At.UTC(),
+		Changes: in.Changes, Warrant: in.Warrant, Base: map[string]uint64{}, State: delivery.ProposalAnswering}
+	var findings []string
+	if p.By == "" {
+		findings = append(findings, "the runtime names no caller: a proposal is made by someone")
+	}
+	if p.Why == "" {
+		findings = append(findings, "a proposal says why: it is shown to the operator")
+	}
+	if len(in.Changes) == 0 {
+		findings = append(findings, "a proposal changes something: it names no change")
+	}
+	for i, c := range in.Changes {
+		if c.Op == delivery.OpSeed {
+			findings = append(findings, fmt.Sprintf("change %d: the seed is gone with adopt, the controller's export being gone", i+1))
+		}
+	}
+	laid, lay := delivery.LayChanges(in.Current, in.Changes)
+	findings = append(findings, lay...)
+	findings = append(findings, ControllerRefusals(in.Changes, laid)...)
+	all := map[string]delivery.Placement{}
+	for node, pl := range in.Current {
+		all[node] = pl
+	}
+	out := map[string]*delivery.Placement{}
+	for node, pl := range laid {
+		if before, ok := in.Current[node]; ok && delivery.SamePlacement(before, pl) {
+			continue
+		}
+		pl := pl
+		all[node] = pl
+		out[node] = &pl
+		p.Base[node] = in.Revisions[node]
+	}
+	// A remove-node deletes the key of a joining node that never confirmed (the operator's decision of 2026-11-02 01:05): its
+	// candidate is no placement, and the checks across nodes read the mesh without it. LayChanges said why one cannot go.
+	for _, node := range p.RemovedNodes() {
+		if _, ok := in.Current[node]; !ok {
+			continue
+		}
+		delete(all, node)
+		out[node] = nil
+		p.Base[node] = in.Revisions[node]
+	}
+	if len(findings) == 0 && len(out) == 0 {
+		findings = append(findings, "the changes leave every placement as it is")
+	}
+	held, recorded := in.Held, in.Recorded
+	if held == nil {
+		held = func(string) bool { return false }
+	}
+	if recorded == nil {
+		recorded = func(string) bool { return false }
+	}
+	// A joining node writes its record only once it holds its account, which the add-node's write gives it: this one change by
+	// this one caller is the exception to a node with no record (ADR 0587 §7, changing ADR 0567 §2).
+	joining := map[string]bool{}
+	for _, c := range in.Changes {
+		if c.Op == delivery.OpAddNode {
+			joining[c.Node] = true
+		}
+	}
+	if len(joining) > 0 {
+		was := recorded
+		recorded = func(node string) bool { return joining[node] || was(node) }
+	}
+	for _, r := range delivery.CheckPlacements(all, held, recorded) {
+		findings = append(findings, r)
+	}
+	return p, out, findings
+}
+
+// ControllerModule is the controller's module, which nothing places again (issue 1126).
+const ControllerModule = "mesh-controller"
+
+// ControllerEnded is why a placement of the controller is refused: the parts that acted only once its lease was handed
+// (consumers, the user list, enrolment, dead letters) now act without reading the lease, so a controller placed again
+// would write beside them, silently.
+const ControllerEnded = "the controller ended by its unassignment on 2026-11-02; placing it again would make two writers (issue 1126)"
+
+// ControllerRefusals names every change, and every node as laid, that places the controller: by a place, by a seed's
+// whole placement, or in what the changes lay. None when nothing does.
+func ControllerRefusals(changes []delivery.PlacementProposalChange, laid map[string]delivery.Placement) []string {
+	var out []string
+	nodes := map[string]bool{}
+	for i, c := range changes {
+		places := c.Module == ControllerModule && c.Op != delivery.OpTakeOff
+		if c.Whole != nil && slices.Contains(c.Whole.Assigned(), ControllerModule) {
+			places = true
+		}
+		if places {
+			out = append(out, fmt.Sprintf("change %d places %s on %s: %s", i+1, ControllerModule, c.Node, ControllerEnded))
+			nodes[c.Node] = true
+		}
+	}
+	for _, node := range slices.Sorted(maps.Keys(laid)) {
+		if !nodes[node] && slices.Contains(laid[node].Assigned(), ControllerModule) {
+			out = append(out, fmt.Sprintf("%s would run %s: %s", node, ControllerModule, ControllerEnded))
+		}
+	}
+	return out
+}
+
+// Write is one node a warrant writes (§5): the node, its node key `<node>.node` (the commit of the node's keys,
+// mesh-sdk delivery.PlacementKeys.Writes), the revision of the node's placement it is written at (0: it has none, so
+// it is created) and its value (nil: it is deleted).
+type Write struct {
+	Node, Key string
+	Base      uint64
+	Value     *delivery.Placement
+}
+
+// Writes is every key a proposal writes, by node order.
+func Writes(p delivery.PlacementProposal, laid map[string]*delivery.Placement) ([]Write, error) {
+	var out []Write
+	for _, node := range p.Nodes() {
+		key, err := delivery.PlacementNodeKey(node)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, Write{Node: node, Key: key, Base: p.Base[node], Value: laid[node]})
+	}
+	return out, nil
+}
+
+// The kinds of the condition (and finding) of a refused controller call, which the assigner raised until it stopped calling
+// the controller's verbs (ADR 0567 §8, issue 774).
+const (
+	KindControllerCall = "controller-call"
+	KindControllerPin  = "controller-pin"
+)
+
+// CallClearedCondition clears the condition of a refused controller call a previous process raised, for its pair (node and
+// module, or node and provision for a pin).
+func CallClearedCondition(kind, node, module string) oc.Condition {
+	return oc.Condition{Key: delivery.AssignerModule + "." + kind + "." + node + "." + module,
+		Subject: oc.ConditionSubject{Scope: "module", ID: module, Machine: node}, State: occ.StateCleared,
+		Resolved: "the assigner calls no verb of the controller any more: placement is the one source."}
+}
+
+// PlacementAct is the act an approved proposal's yes binds: writing exactly its changes at its base revisions.
+func PlacementAct(p delivery.PlacementProposal) occ.Act {
+	return occ.Act{"placement": "write", "proposal": p.ID, "changes": delivery.ChangesDigest(p)}
+}
+
+// PlacementAsking is a proposal's asking number: each judging that raises its ask again (again, a key moved) is
+// another asking, under an id of its own.
+func PlacementAsking(p delivery.PlacementProposal, at time.Time) int {
+	return int(at.Unix())
+}
+
+// PlacementAsk is the authorising ask about a proposal (§5): an Approve that binds its act, so only a channel that
+// proves who answered takes it, with the brief of the verdict by node (judge.Brief) as its explanation.
+func PlacementAsk(key string, p delivery.PlacementProposal, brief string, asking int, now time.Time) (delivery.AssignerAsk, error) {
+	binds, err := occ.ActDigest(PlacementAct(p))
+	if err != nil {
+		return delivery.AssignerAsk{}, err
+	}
+	nodes := p.Nodes()
+	headline := fmt.Sprintf("Change placement on %s?", strings.Join(nodes, ", "))
+	if n := len([]rune(headline)); n > occ.HeadlineLength {
+		headline = fmt.Sprintf("Change placement on %d machines?", len(nodes))
+	}
+	return assignerAsk(asking, oc.Ask{
+		ID:          delivery.AskingID(key, asking),
+		Headline:    headline,
+		Explanation: brief,
+		Options: []oc.Option{
+			{ID: OptionYes, Label: "Approve", Does: "the placement of " + strings.Join(nodes, ", ") + " is written as proposed",
+				Level: occ.Approve, Binds: binds},
+			{ID: OptionNo, Label: "Decline", Does: "nothing is written, and the proposal ends", Level: occ.Acknowledge},
+		},
+		Who:      occ.Operator,
+		Expires:  occ.FormatTime(now.Add(occ.ApproveLasts)),
+		OnExpiry: "nothing is written, and the proposal ends",
+		About:    key,
+	}), nil
+}
+
+// Rest is what a proposal leaves to write once the keys of written are: its changes of the other nodes, to be laid again
+// over the keys as the write left them (§5: a key moved while it was written). False when nothing is left.
+func Rest(p delivery.PlacementProposal, written map[string]*delivery.Placement) (delivery.PlacementProposal, bool) {
+	rest := p
+	rest.Changes, rest.Base = nil, map[string]uint64{}
+	for _, c := range p.Changes {
+		if _, done := written[c.Node]; !done {
+			rest.Changes = append(rest.Changes, c)
+		}
+	}
+	for node, base := range p.Base {
+		if _, done := written[node]; !done {
+			rest.Base[node] = base
+		}
+	}
+	rest.Must, rest.Verdict, rest.Ask, rest.State = nil, nil, "", delivery.ProposalAnswering
+	return rest, len(rest.Changes) > 0
+}

modules/mesh-delivery-assigner/internal/assign/seat_test.go

@@ -0,0 +1,103 @@
+package assign
+
+import (
+	"encoding/json"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	occ "git.novox.be/novox/mesh-contracts/go/clients/operatorchannelclient"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// ADR 0567 §2, §5, §7, §8: what the seat's holder decides of a proposal: every refusal named at once, a valid one laid
+// with the base revision of each key it changes, the writes at those revisions, the controller's calls that keep its
+// assignments in step, the authorising ask bound to the changes, and the export read as the controller answers it.
+func TestThePlacementSeatDecides(t *testing.T) {
+	anchor := delivery.Placement{V: delivery.Version, Node: "anchor", Decided: delivery.NodeDecided{Hub: true, Address: "10.0.0.1"},
+		Modules: []delivery.PlacedModule{{Module: "store", Ports: map[string]int{"5432": 5432}}, {Module: "web"}}}
+	laptop := delivery.Placement{V: delivery.Version, Node: "laptop", Decided: delivery.NodeDecided{Address: "10.0.0.2"}, Modules: []delivery.PlacedModule{{Module: "shell"}}}
+	in := func(changes ...delivery.PlacementProposalChange) ProposeIn {
+		return ProposeIn{ID: "p-one", By: "operator@laptop", Why: "move web", At: time.Unix(1, 0), Changes: changes,
+			Current: map[string]delivery.Placement{"anchor": anchor, "laptop": laptop}, Revisions: map[string]uint64{"anchor": 4, "laptop": 9},
+			Held:     func(m string) bool { return m != "ghost" },
+			Recorded: func(n string) bool { return n == "anchor" || n == "laptop" }}
+	}
+	move := []delivery.PlacementProposalChange{{Op: delivery.OpTakeOff, Node: "anchor", Module: "web"}, {Op: delivery.OpPlace, Node: "laptop", Module: "web"}}
+	p, laid, findings := Propose(in(move...))
+	if len(findings) != 0 || p.State != delivery.ProposalAnswering || p.Base["anchor"] != 4 || p.Base["laptop"] != 9 ||
+		!slices.Equal(laid["laptop"].Assigned(), []string{"shell", "web"}) || !slices.Equal(laid["anchor"].Assigned(), []string{"store"}) {
+		t.Fatalf("a move: %+v, %+v, %v", p, laid, findings)
+	}
+	if _, err := delivery.EncodePlacementProposal(p); err != nil {
+		t.Fatalf("the proposal cannot be written: %v", err)
+	}
+	for name, c := range map[string]struct {
+		in   ProposeIn
+		want string
+	}{
+		"a module not held":     {in(delivery.PlacementProposalChange{Op: delivery.OpPlace, Node: "laptop", Module: "ghost"}), "the indexer holds no module ghost"},
+		"a node with no record": {in(delivery.PlacementProposalChange{Op: delivery.OpPlace, Node: "stranger", Module: "web"}), "stranger is a node with no record"},
+		"nothing changes":       {in(delivery.PlacementProposalChange{Op: delivery.OpPlace, Node: "anchor", Module: "web"}), "leave every placement as it is"},
+		"no why":                {func() ProposeIn { i := in(move...); i.Why = " "; return i }(), "says why"},
+		"no caller":             {func() ProposeIn { i := in(move...); i.By = ""; return i }(), "names no caller"},
+		"a seed by hand":        {in(delivery.PlacementProposalChange{Op: delivery.OpSeed, Node: "laptop", Whole: &laptop}), "gone with adopt"},
+		// 1126: the controller ended by its unassignment; placed again it would be a second writer beside the parts that
+		// act without its lease.
+		"the controller placed again": {in(delivery.PlacementProposalChange{Op: delivery.OpPlace, Node: "laptop", Module: "mesh-controller"}), "ended by its unassignment"},
+		"the controller seeded whole": {in(delivery.PlacementProposalChange{Op: delivery.OpSeed, Node: "anchor", Whole: &delivery.Placement{V: delivery.Version, Node: "anchor",
+			Decided: anchor.Decided, Modules: []delivery.PlacedModule{{Module: "mesh-controller"}}}}), "two writers (issue 1126)"},
+		"a pin of nobody placed": {in(delivery.PlacementProposalChange{Op: delivery.OpPin, Node: "laptop", Provision: "db", Provider: &delivery.Provider{Node: "laptop", Module: "store"}}), "not placed there"},
+	} {
+		if _, _, f := Propose(c.in); !slices.ContainsFunc(f, func(s string) bool { return strings.Contains(s, c.want) }) {
+			t.Errorf("%s: findings %v, want one naming %q", name, f, c.want)
+		}
+	}
+
+	// Every kind of change is taken: the placement is the one source, and the controller's verbs limit nothing (ADR 0567 §8).
+	for _, c := range []delivery.PlacementProposalChange{
+		{Op: delivery.OpConfig, Node: "anchor", Module: "web", Values: map[string]any{"puid": 1}},
+		{Op: delivery.OpPlace, Node: "laptop", Module: "web", Ports: map[string]int{"80": 8080}, Bindings: map[string]delivery.Provider{"db": {Node: "anchor", Module: "store"}}},
+		{Op: delivery.OpConfig, Node: "anchor", Module: "web", Layer: map[string]any{"places": []any{}}},
+		{Op: delivery.OpConfig, Node: "anchor", Module: "web", MeshWide: map[string]any{"accesses": []any{}}},
+		{Op: delivery.OpDecide, Node: "laptop", Field: "site", Value: json.RawMessage(`"attic"`)},
+		{Op: delivery.OpHold, Node: "anchor", Module: "store", Claim: "node-shell", Scope: "node"},
+	} {
+		if _, _, f := Propose(in(c)); len(f) != 0 {
+			t.Errorf("%s is refused: %v", c.Op, f)
+		}
+	}
+
+	// A key moved while the warrant wrote: what is left to write is the other nodes' changes, to be laid and asked again.
+	if rest, ok := Rest(p, map[string]*delivery.Placement{"anchor": laid["anchor"]}); !ok || len(rest.Changes) != 1 || rest.Changes[0].Node != "laptop" ||
+		len(rest.Base) != 1 || rest.State != delivery.ProposalAnswering || rest.Must != nil {
+		t.Errorf("the rest = %+v, %v", rest, ok)
+	}
+	if _, ok := Rest(p, laid); ok {
+		t.Error("a proposal written whole leaves something to write")
+	}
+
+	// The seat says it waits while one of its states is not bound, naming it, and clears once all are.
+	for _, unbound := range [][]string{{delivery.PlacementPulsesBucket}, nil} {
+		c := SeatWaitsCondition(unbound)
+		if _, err := occ.EncodeCondition(c); err != nil || (len(unbound) > 0) != (c.State == occ.StateRaised) ||
+			(len(unbound) > 0 && !strings.Contains(c.Explanation, "the seat waits for its states: "+delivery.PlacementPulsesBucket)) {
+			t.Errorf("waiting for %v: %+v, %v", unbound, c, err)
+		}
+	}
+
+	writes, err := Writes(p, laid)
+	if err != nil || len(writes) != 2 || writes[0].Key != "anchor.node" || writes[0].Base != 4 || writes[1].Base != 9 {
+		t.Fatalf("writes = %+v, %v", writes, err)
+	}
+	a, err := PlacementAsk("placement.p-one", p, "move web (proposed by operator@laptop)", 7, time.Unix(100, 0))
+	if err != nil || occ.Check(mustAsk(t, a), time.Unix(100, 0)) != nil || mustAsk(t, a).Options[0].Level != occ.Approve || occ.Performs(mustAsk(t, a).Options[0], PlacementAct(p)) != nil {
+		t.Fatalf("the ask = %+v, %v", a, err)
+	}
+	q := p
+	q.Changes = append(slices.Clone(p.Changes), delivery.PlacementProposalChange{Op: delivery.OpUnpin, Node: "laptop", Provision: "x"})
+	if occ.Performs(mustAsk(t, a).Options[0], PlacementAct(q)) == nil {
+		t.Error("the ask's yes binds changes it was not asked about")
+	}
+}

modules/mesh-delivery-assigner/internal/assign/verbs.go

@@ -0,0 +1,38 @@
+package assign
+
+import (
+	"slices"
+
+	"git.novox.be/novox/mesh-delivery/sdk/graph"
+)
+
+// verbWaiting says why the module's want on node waits for a verb it invokes (novox/hq ADR 0614 §2): the first seat verb or
+// module tool of Invokes (the module graph's verb edges, those it leaves out on a cycle not among them, §3) that no
+// running healthy build serves. Nil Served (nothing read of what runs) waits for none, and a verb a running build serves
+// already adds no wait. It holds under the provisions' rule (RuleProvisions): no reader knows a rule number of its own
+// yet, so the words name the edge (graph.VerbWaitWords, which the delivery view reads).
+func (m Module) verbWaiting(node string) (string, bool) {
+	if m.Served == nil {
+		return "", false
+	}
+	for _, v := range slices.Sorted(slices.Values(m.Invokes)) {
+		if !m.Served(v) {
+			return graph.VerbWaitWords(v, m.Name, node), true
+		}
+	}
+	return "", false
+}
+
+// busStateWaiting says why the module's want on node waits for bus state (ADR 0614 §5): its manifest asks bus state (a
+// bus-state entry, as the module graph reads it) and no build whose manifest offers bus-state runs healthy on a node
+// present. The provision bus-state is answered with no credential of a consumer's own, so ADR 0603 §5 counts the
+// provider's own have and no provisioner key is waited for, handed or not. Nil Offering (nothing read of what runs) waits
+// for none, and neither does a module that offers bus-state itself. It holds under the provisions' rule, its words naming bus state (graph.BusStateWaitWords).
+func (m Module) busStateWaiting(node string) (string, bool) {
+	if len(m.Manifest.BusState) == 0 || m.Offering == nil || m.Offering(graph.BusState) ||
+		slices.Contains(m.Manifest.Offers(), graph.BusState) { // the bus module offering it waits on nobody for it
+
+		return "", false
+	}
+	return graph.BusStateWaitWords(m.Name, node), true
+}

modules/mesh-delivery-assigner/internal/assign/wants.go

@@ -0,0 +1,795 @@
+package assign
+
+import (
+	"fmt"
+	"maps"
+	"slices"
+	"sort"
+	"strings"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/provisions"
+
+	"git.novox.be/novox/mesh-delivery/sdk/forms"
+	"git.novox.be/novox/mesh-delivery/sdk/graph"
+)
+
+// Module is what the six rules read of one module (ADR 0429 §6, ADR 0528 clause 3): its newest fingerprint F at the
+// trunk (the indexer's modules), whether the builder's build of F is done, whether F is held, whether the controller
+// issued its credential for F, its manifest at F, and the nodes it is assigned to.
+type Module struct {
+	Name    string
+	FP      string
+	Built   bool
+	Held    bool
+	Granted bool
+	// GrantedAt says whether the controller issued the module's credential for another fingerprint than FP: the first want of a node
+	// that runs an older one names it (issue 1945). Nil: none.
+	GrantedAt func(fp string) bool
+	// GrantedOn says whether the controller's grant of FP names the module's accounts on a node, when the grant names any:
+	// a grant written for the module's other nodes says nothing of a node whose account is not issued and sealed (issue
+	// 1945, live on 2026-10-25 at 20:04: ace's mesh-build-go was wanted with no account on the bus). Nil: the grant alone.
+	GrantedOn func(node string) bool
+	Manifest  catalogue.Manifest
+	// Provisions is the seat mesh-provisioner's provisions this module consumes on a node, by key (ADR 0570 §4): the want
+	// waits until each is provided. Nil: the seat's state is not read (not delivered yet), and nothing waits on it.
+	Provisions func(node string) map[string]provisions.Provision
+	// Answering is the manifests of the modules placed somewhere that provide a provision: what catalogue.Awaited
+	// judges a want's provisions by (issue 774). Nil: none known, and no key is waited for that is not there.
+	Answering func(provision string) []catalogue.Manifest
+	// Offered says whether any module offers a provision by name or by its own name (catalogue.Manifest.Offers) among every
+	// manifest the trunk holds and the modules the mesh provides itself, placed or not. Nil: not known, and no requirement
+	// is waited on for want of an offer.
+	Offered func(provision string) bool
+	// Invokes are the seat verbs and module tools the module graph says the module invokes and keeps as edges to the
+	// modules serving them, those it leaves out on a cycle not among them (ADR 0614 §2, §3): the want waits until each is
+	// served (Served). Nil: no graph node is read, and no want waits on a verb.
+	Invokes []string
+	// Served says whether a build serving a seat verb or module tool runs healthy, counted from its holder's have (ADR 0614
+	// §2, as ADR 0603 §5 counts a provider's). Nil: nothing is read of what runs, and no want waits on a verb.
+	Served func(invoke string) bool
+	// Offering says whether a build whose manifest offers a provision runs healthy on a node present, counted from the
+	// provider's own have (ADR 0603 §5): what a want asking bus state waits for (ADR 0614 §5). Nil: nothing is read of what
+	// runs, and no want waits on bus state.
+	Offering func(provision string) bool
+	// Chosen is a person's choice of the module's upgrade policy (the assigner's `policies`, ADR 0565 §7); nil: none.
+	Chosen *catalogue.PersonPolicy
+	Nodes  []string
+	// Composed answers the composition of the module for a node at a fingerprint: the digest the node's own have names (a
+	// placed node composes its own, ADR 0571 §6), and whether it names one. Nil: none exists (ADR 0539 §1, §6).
+	Composed func(node, fp string) (delivery.ComposedDigest, bool)
+	// Allowed says whether the operator answered yes to the record ask about the move of this module on node to the composition
+	// with this digest (ADR 0539 §14). Nil: none did.
+	Allowed func(node, digest string) bool
+	// Release names the release whose Approve carries the build fp, as mesh-delivery's gate holds it for the release's heads,
+	// read by the build's source revision (ADR 0601 §1): that Approve is the yes to a move of the build alone. False when no
+	// approved release is known to carry it. Nil: none is read.
+	Release func(fp string) (string, bool)
+	// Released is a hold on FP the operator released (ADR 0539 §19): FP is not held again by a health check that failed.
+	Released bool
+	// Restored says whether the operator answered "restore" to the restore ask of this data module on node: it is then set back
+	// as any module is, losing the writes made since (ADR 0539 §19). Nil: none did.
+	Restored func(node string) bool
+	// Kept says the operator answered "keep" to the hold ask of FP: a hold kept so is not lifted by itself.
+	Kept bool
+	// Now is when this pass reads the haves: the held record names it as when the health check was seen to fail. Zero: not said.
+	Now time.Time
+	// Puts are the puts of the module, by node (ADR 0546): while one owns a node's want (PutOwns), the rules pass over it.
+	Puts map[string]delivery.Put
+	// Needs are the reader capabilities the manifest at FP needs (the indexer's modules value, catalogue.ManifestNeeds, ADR
+	// 0614 §4): a node's want moves only while that node's engine states each of them. Nil: none.
+	Needs []string
+	// FormNeeds are the reference forms the module's build at FP is written in (`form:<name>`, the builder's build key's
+	// needs, ADR 0618 §1): a node's want is held only while that node's engine reads none of them (ADR 0624 §2). Nil: the
+	// build names none, and holds nothing.
+	FormNeeds []string
+	// Self says whether node composes the module itself: the catalogue's placement names the node (ADR 0547 §2). It is the one
+	// source of a want's Self: every want the rules write or keep is derived from it (selfDerived), so a want written Self while
+	// the node was placed does not outlive the placement (issue 1126). Nil: no node does.
+	Self func(node string) bool
+}
+
+func (m Module) selfOn(node string) bool { return m.Self != nil && m.Self(node) }
+
+func (m Module) composition(node, fp string) (delivery.ComposedDigest, bool) {
+	if m.Composed == nil {
+		return delivery.ComposedDigest{}, false
+	}
+	return m.Composed(node, fp)
+}
+
+// Node is what the rules read of the nodes: whether each is online (the watchman's presence) and each module's have.
+type Nodes struct {
+	Online map[string]bool
+	Haves  map[string]map[string]delivery.Have
+	// Providers is, by provision, the modules that provide it, with the nodes each is assigned to.
+	Providers map[string]map[string][]string
+	// Reads is, by node, the reader capabilities its node-engine states in its node record (delivery.NodeRecord.ManifestReads,
+	// ADR 0614 §4). A node with none, or none read, is read as stating the baseline (catalogue.StatedManifestReads).
+	Reads map[string][]string
+}
+
+// healthy says whether a have runs fp healthy.
+func healthy(h delivery.Have, fp string) bool {
+	return h.FP == fp && h.Phase == delivery.PhaseRunning && h.Health == delivery.HealthOK
+}
+
+// Canary is the module's canary: the first of its nodes, by name, that is online (ADR 0435 §3; one ring, ordered by
+// name, ADR 0528 clause 3). Empty when none is online.
+func Canary(nodes []string, online map[string]bool) string {
+	sorted := slices.Sorted(slices.Values(nodes))
+	for _, n := range sorted {
+		if online[n] {
+			return n
+		}
+	}
+	return ""
+}
+
+// Holds is whether every rule holds for moving node's want for m to m.FP, and if not, the first rule that does not,
+// with why (ADR 0429 §6). Rule 4, at most `step` others ahead, always holds: the mesh keeps no step, and step 0 is no
+// limit (ADR 0528 clause 3). Rule 5, every provider healthy, holds no want (issue 1960): a module whose provider is down
+// is wanted all the same, and said as not reached (Unreached), since a site runs while the proxy in front of it is
+// down and one module never blocks another.
+func Holds(m Module, node string, n Nodes) (bool, int, string) {
+	return holds(m, node, n, true)
+}
+
+// holds is Holds; with ordering false it leaves out the canary (3), which orders a move among nodes, and keeps those
+// without which there is nothing to want: the build done, not held, the grant and the composition.
+func holds(m Module, node string, n Nodes, ordering bool) (bool, int, string) {
+	switch {
+	case !m.Built:
+		return false, delivery.RuleBuildDone, fmt.Sprintf("the build of %s at %s is not done", m.Name, short(m.FP))
+	case m.Held:
+		return false, delivery.RuleNotHeld, fmt.Sprintf("%s is held at %s", m.Name, short(m.FP))
+	}
+	if ordering {
+		canary := Canary(m.Nodes, n.Online)
+		switch {
+		case canary == "":
+			return false, delivery.RuleCanary, fmt.Sprintf("none of the nodes of %s is online, so it has no canary", m.Name)
+		case node != canary && !healthy(n.Haves[canary][m.Name], m.FP):
+			return false, delivery.RuleCanary, fmt.Sprintf("the canary %s does not run %s healthy yet", canary, short(m.FP))
+		}
+	}
+	if !m.Granted {
+		return false, delivery.RuleGrant, fmt.Sprintf("the controller has not issued the credential of %s for %s", m.Name, short(m.FP))
+	}
+	if m.GrantedOn != nil && !m.GrantedOn(node) {
+		return false, delivery.RuleGrant, fmt.Sprintf("the controller has not issued the credential of %s on %s for %s", m.Name, node,
+			short(m.FP))
+	}
+	if words, lacking := m.readerLacking(node, n); lacking {
+		return false, delivery.RuleComposed, words
+	}
+	if _, ok := m.composition(node, m.FP); !ok {
+		return false, delivery.RuleComposed, fmt.Sprintf("%s has named no composition of its own for %s at %s yet", node, m.Name, short(m.FP))
+	}
+	if words, waiting := m.provisionWaiting(node); waiting {
+		return false, delivery.RuleProvisions, words
+	}
+	if words, waiting := m.verbWaiting(node); waiting {
+		return false, delivery.RuleProvisions, words
+	}
+	if words, waiting := m.busStateWaiting(node); waiting {
+		return false, delivery.RuleProvisions, words
+	}
+	return true, 0, ""
+}
+
+// readerLacking says why the module's want on node is held for the node's engine (ADR 0614 §4): a reader capability its
+// manifest needs that the engine does not state, read as the baseline when it states none. It is held under rule 7 (the
+// composition), since no rule of its own is numbered in this release, with words naming the capability; it moves once the
+// engine states it. The node-engine's own new build is held only by a word of its own manifest no engine states.
+//
+// A build's reference forms hold the want only when the engine reads none of them (ADR 0624 §2): every engine reads a
+// first form, so a build written in one is never held by its forms; the words name the forms it reads none of.
+func (m Module) readerLacking(node string, n Nodes) (string, bool) {
+	missing := catalogue.MissingManifestReads(m.Needs, n.Reads[node])
+	if len(missing) == 0 && forms.Current.Held(m.FormNeeds, n.Reads[node]) {
+		missing = slices.Clone(m.FormNeeds)
+	}
+	if len(missing) == 0 {
+		return "", false
+	}
+	return graph.ReaderWaitWords(node, missing, m.Name, short(m.FP)), true // the words the delivery view names the edge by
+}
+
+// provisionWaiting says why the module's want on node waits for a provision (ADR 0570 §4): a provision it requires that has
+// no key yet, or the first of its keys that is not provided. Nil Provisions (the seat's state not on the bus) waits for none.
+func (m Module) provisionWaiting(node string) (string, bool) {
+	if m.Provisions == nil {
+		return "", false
+	}
+	if missing := m.MissingProvisions(node); len(missing) > 0 {
+		return fmt.Sprintf("provision %s has no key yet for %s on %s", missing[0], m.Name, node), true
+	}
+	keyed := m.Provisions(node)
+	// Only a provision the newest manifest still requires is waited on (ADR 0603 §9): a key of an older revision's edge,
+	// asked or retiring for the operator's answer (ADR 0570 §5), holds nothing. A requirement catalogue.Awaited leaves out is
+	// not waited on when something offers it (a module's own name, a module the mesh provides itself, a provision the
+	// composition does not key: optional, a toolchain on the module's own machine, a login the controller makes). One that
+	// nothing offers is waited on (ADR 0603 §5: an unknown provider has provided nothing), so a consumer never moves ahead of
+	// a provider whose module the indexer has not yet taken in; it holds loudly, since the watchman raises the hold past its
+	// bound (ADR 0603 §8).
+	needed := m.Manifest.Requires
+	if m.Answering != nil {
+		needed = catalogue.Awaited(m.Manifest, m.Answering)
+		have := map[string]bool{}
+		for _, p := range keyed {
+			have[p.Provision] = true
+		}
+		for _, r := range slices.Sorted(slices.Values(m.Manifest.Requires)) {
+			if have[r] && !m.Manifest.OptionalRequires[r] && !slices.Contains(needed, r) {
+				needed = append(needed, r) // the provisioner keys it from the manifests, whoever is placed yet
+				continue
+			}
+			if m.Offered == nil || m.Manifest.OptionalRequires[r] || len(m.Answering(r)) > 0 || m.Offered(r) || slices.Contains(needed, r) {
+				continue
+			}
+			needed = append(needed, r)
+			if !have[r] {
+				return fmt.Sprintf("no module offers %s yet for %s on %s: an unknown provider has provided nothing, so the want waits for one, and the watchman raises it past its bound", r, m.Name, node), true
+			}
+		}
+	}
+	for _, key := range slices.Sorted(maps.Keys(keyed)) {
+		if p := keyed[key]; p.State != provisions.Provided && slices.Contains(needed, p.Provision) {
+			words := fmt.Sprintf("the provision %s of %s on %s is %s, not provided", key, m.Name, node, p.State)
+			if p.Why != "" {
+				words += ": " + p.Why
+			}
+			return words, true
+		}
+	}
+	return "", false
+}
+
+// MissingProvisions are the provisions a want of the module waits for (catalogue.Awaited, the one rule the plan
+// composition and the seat mesh-provisioner key by, issue 774) that have no key on node yet, sorted; none while the
+// seat's state is not read. A requirement the composition keys nothing for (a toolchain on the module's own machine, a
+// login the controller still makes for a module not handed) is not waited for: on 2026-10-30 every new build of
+// grafana, dnsmasq, mesh-knowledge, mesh-mail and the builders waited here for a key nobody would make.
+func (m Module) MissingProvisions(node string) []string {
+	if m.Provisions == nil || m.Answering == nil {
+		return nil
+	}
+	have := map[string]bool{}
+	for _, p := range m.Provisions(node) {
+		have[p.Provision] = true
+	}
+	var out []string
+	for _, r := range catalogue.Awaited(m.Manifest, m.Answering) {
+		if !have[r] {
+			out = append(out, r)
+		}
+	}
+	return out
+}
+
+// providedHealthy is rule 5 for one provision: some module providing it runs healthy on the node, or, assigned
+// elsewhere only, at its canary. A provision no module provides is not a module's to judge (the mesh or the node
+// offers it) and holds.
+func providedHealthy(provision, node string, n Nodes) (bool, string) {
+	providers := n.Providers[provision]
+	if len(providers) == 0 {
+		return true, ""
+	}
+	names := make([]string, 0, len(providers))
+	for p := range providers {
+		names = append(names, p)
+	}
+	sort.Strings(names)
+	for _, p := range names {
+		nodes := providers[p]
+		at := node
+		if !slices.Contains(nodes, node) {
+			at = Canary(nodes, n.Online)
+		}
+		if h, ok := n.Haves[at][p]; ok && at != "" && h.Phase == delivery.PhaseRunning && h.Health == delivery.HealthOK {
+			return true, ""
+		}
+	}
+	return false, fmt.Sprintf("no provider of %s runs healthy on %s or at its canary", provision, node)
+}
+
+// unreached is why m on node may be wanted and not reached: the first provision it requires that no provider runs
+// healthy on node or at its canary (rule 5, said and never holding a want; issue 1960); empty when all do.
+func unreached(m Module, node string, n Nodes) string {
+	for _, provision := range m.Manifest.Requires {
+		if ok, why := providedHealthy(provision, node, n); !ok {
+			return why
+		}
+	}
+	return ""
+}
+
+// keepsData says whether a module holds data a set-back would lose: an own item of a class that keeps (irreplaceable,
+// valuable or rebuildable; cache and none do not).
+func keepsData(m catalogue.Manifest) bool {
+	for _, it := range m.DataItems() {
+		if it.Class == catalogue.ClassIrreplaceable || it.Class == catalogue.ClassValuable || it.Class == catalogue.ClassRebuildable {
+			return true
+		}
+	}
+	return false
+}
+
+// Outcome is what one module's pass decides: each node's want to write (only those that change), and a hold to write.
+type Outcome struct {
+	Wants map[string]delivery.Want
+	// Held is the hold of m.FP to write, when a node's health check failed on it and it is not held yet.
+	Held *delivery.Held
+	// Lifted is the hold of m.FP lifted by itself: every node that runs the module runs m.FP healthy (issue 1906). The held
+	// record and its ask are taken away, and the wants move by the rules again in this pass.
+	Lifted bool
+	// NodeFailed is, by node, a failed health check of m.FP on a node while another node runs m.FP healthy: the failure is
+	// that node's, so m.FP is not held and nothing is set back (ADR 0557 §1, issue 1496). The pass raises its condition once.
+	NodeFailed map[string]NodeFailure
+	// Record is the moves a person must allow before the want names them: each is asked once (ADR 0539 §14).
+	Record []RecordNeed
+	// Restore is the nodes of a module holding data whose held fingerprint failed its health check there and that are not set
+	// back: the operator is asked whether to restore each (ADR 0539 §19).
+	Restore []string
+	// Rules is, by node, the rule holding the node back from m.FP and why.
+	Rules map[string]Holding
+	// Unreached is, by node, why the module may be wanted there and not reached: no provider of a provision it requires runs
+	// healthy (rule 5, issue 1960). It holds no want back; the pass says it.
+	Unreached map[string]string
+	// Neither is, by node, the nodes the module is assigned to that run it (or whose have names it), hold no want for it after this
+	// pass and are not held (a held module is on the held list), with the rule holding the first want back: the node's own composition does not hold a module with a fingerprint of the new form, so such a module is on
+	// neither list and nothing applies it on that node (issue 1945). A module with no fingerprint of the new form goes with the node's
+	// own composition and is never here.
+	Neither map[string]Holding
+}
+
+// RecordNeed is a move of a module of policy record on a node that waits for the operator's yes: the composition's digest, the
+// controller's judgement of the move and its words.
+type RecordNeed struct {
+	Node      string
+	Digest    string
+	Judgement delivery.Judgement
+	Words     string
+}
+
+// Holding is a rule holding a node back, and why. The bus module is held back by the rules alone, as every module (ADR 0601 §1,
+// §2): no bar of its own.
+type Holding struct {
+	Rule  int
+	Words string
+}
+
+// Reason is the holding in words: the rule and its words.
+func (h Holding) Reason() string {
+	return fmt.Sprintf("rule %d: %s", h.Rule, h.Words)
+}
+
+// Wants is the pass of one module m: for each of its nodes, the want by the six rules, starting from the want written
+// before (wants, by node); lastHealthy is, by node, the newest fingerprint other than m.FP the node ran healthy. A failed
+// health check of m.FP on a node holds it: every node wanting m.FP is set back to its last healthy fingerprint, but a
+// module holding data is not set back but asked about (Restore). A
+// node that wants m but is no longer among its nodes gets its want written removed, never deleted (ADR 0408 §4).
+func Wants(m Module, n Nodes, wants map[string]delivery.Want, lastHealthy map[string]string) Outcome {
+	out := Outcome{Wants: map[string]delivery.Want{}, Rules: map[string]Holding{}, Neither: map[string]Holding{}}
+	held := m.Held
+	if held && !m.Kept && m.FP != "" && allRunHealthy(m, n) {
+		out.Lifted, held = true, false
+	}
+	if !held && !out.Lifted && !m.Released && m.FP != "" {
+		for _, node := range slices.Sorted(slices.Values(m.Nodes)) {
+			h, ok := n.Haves[node][m.Name]
+			if !ok || h.FP != m.FP || !failed(h) {
+				continue
+			}
+			if others := healthyElsewhere(m, n, node); len(others) > 0 && !failedElsewhere(m, n, node) {
+				// F runs healthy on another node, so its failure here is this node's, not F's: F is not held, no node is set back,
+				// and the failing node keeps its want (ADR 0557 §1; issue 1496: on ace a newly assigned mesh-build-node failed its
+				// first check and the hold moved shanks, g14 and novox, healthy on F for an hour, back). The pass raises the node's
+				// condition. With no online healthy witness, or with F failed on a second node, the hold and the set-back stand (ADR 0557
+				// §2, ADR 0429 §6).
+				if out.NodeFailed == nil {
+					out.NodeFailed = map[string]NodeFailure{}
+				}
+				out.NodeFailed[node] = NodeFailure{Others: others, Words: HeldWords(h, time.Time{})} // said once: no clock in it
+				continue
+			}
+			out.Held = &delivery.Held{Node: node, Words: HeldWords(h, m.Now)}
+			held = true
+			break
+		}
+	}
+	mm := m
+	mm.Held = held
+	for _, node := range m.Nodes {
+		if m.FP == "" {
+			break
+		}
+		before, had := wants[node]
+		var next delivery.Want
+		p, put := m.Puts[node]
+		if !put && had && before.Put && before.Hold {
+			// The want is the truth (ADR 0546 clause 5): a want marked put and held stands while its put is not heard (the
+			// puts not open, or not yet handed after a start); only a put heard released gives it back to the rules. A put
+			// without hold is not kept this way: its put takes it further once heard.
+			p, put = delivery.Put{FP: before.FP, Composed: before.Composed, Hold: true, Why: strings.TrimPrefix(before.Words, "put: "),
+				Step: delivery.PutHolding}, true
+		}
+		if put {
+			if want, owns := PutOwns(p); owns {
+				if want != nil {
+					w := *want
+					// A held bus still takes a revision of its composition that changes only its user list (ADR 0539 §7).
+					if ul, ok := m.userListRevision(node, before, had, n); ok && ul.FP == w.FP {
+						w.Composed = ul.Composed
+					}
+					if !had || !delivery.SameWant(normal(before), normal(w)) {
+						out.Wants[node] = w
+					}
+				}
+				continue
+			}
+		}
+		// A revision of the bus module's composition that differs only in its user list is written at once, at the fingerprint the
+		// node runs, outside the rules, the record hold and the bar on a new fingerprint: a new module's credential must reach the
+		// bus before the module can connect (ADR 0539 §7). The controller marks it; whatever it judges of the file's mount stands.
+		if w, ok := m.userListRevision(node, before, had, n); ok {
+			if !had || !delivery.SameWant(normal(before), normal(w)) {
+				out.Wants[node] = w
+			}
+			continue
+		}
+		ok, rule, words := Holds(mm, node, n)
+		target := m.FP
+		if have, ran := n.Haves[node][m.Name]; !ok && (!had || before.Removed) && rule == delivery.RuleCanary {
+			// The canary orders a move, never the first want of a node that does not run the module (issue 1960: de-spiegel,
+			// link2pay and photos on novox were left with no want). A node that runs an older fingerprint of the new form,
+			// composed and granted, gets its first want at what it runs, and rule 3 then orders its move to F as from any want.
+			// A node that runs an old-form build, which no want can name, stays under the canary (issue 1945, a design limit):
+			// its first want names F once the canary runs F healthy. Any other node that runs it (F itself, or an older
+			// fingerprint with no composition or grant) gets F by the rules without which there is nothing to want.
+			older := ran && runs(have) && have.FP != m.FP && strings.HasPrefix(have.FP, delivery.SourcePrefix2)
+			if older {
+				_, composed := m.composition(node, have.FP)
+				older = composed && m.GrantedAt != nil && m.GrantedAt(have.FP)
+			}
+			oldForm := ran && runs(have) && have.FP != m.FP && !strings.HasPrefix(have.FP, delivery.SourcePrefix2)
+			switch {
+			case older:
+				ok, target = true, have.FP
+			case oldForm:
+				// held back by rule 3 as written: on neither list until the canary runs F healthy
+			default:
+				ok, rule, words = holds(mm, node, n, false)
+			}
+		}
+		if why := unreached(m, node, n); why != "" {
+			if out.Unreached == nil {
+				out.Unreached = map[string]string{}
+			}
+			out.Unreached[node] = why
+		}
+		if ok && target == m.FP && len(out.NodeFailed) > 0 && !(had && !before.Removed && before.FP == m.FP) &&
+			n.Haves[node][m.Name].FP != m.FP {
+			// While a node fails F alone, F reaches no further node: a node that neither wants nor runs F gets no new want
+			// naming it, and wants already written stay (ADR 0557 §2). A node that runs F with no live want gets its want at F, or
+			// it would be on neither list and its node-engine would give the module up (issue 1945).
+			ok, rule, words = false, delivery.RuleNotHeld, FailedAloneWords(m.Name, m.FP, slices.Sorted(maps.Keys(out.NodeFailed)))
+		}
+		switch {
+		case ok:
+			d, _ := m.composition(node, target)
+			next = delivery.Want{FP: target, Composed: d.Digest}
+			at := m
+			if target != m.FP {
+				// the first want at the older fingerprint the node runs: held back from F by the rule, and judged as a want at it
+				next.Newest, next.Rule, next.Words = m.FP, rule, words
+				at.FP = target
+			}
+			// A placed node's want names the build alone: it is the same target while the build is.
+			if had && !before.Removed && !before.Put && before.FP == target && (before.Composed == d.Digest || (before.Self && m.selfOn(node))) {
+				next.Backup, next.Words = before.Backup, before.Words // the answer to a failed backup stays while its target stays (ADR 0539 §16)
+			}
+			running, ran := n.Haves[node][m.Name]
+			// A removed want is no want: a first want after it goes through the record ask as a first want does.
+			asked, hadLive := before, had
+			if before.Removed {
+				asked, hadLive = delivery.Want{}, false
+			}
+			if need, wait := at.mustAsk(node, asked, hadLive, ran, running.FP, running.Composed == "", d); wait {
+				if need != nil {
+					out.Record = append(out.Record, *need)
+				}
+				continue
+			}
+		case held && had && before.FP == m.FP:
+			out.Rules[node] = Holding{Rule: rule, Words: words}
+			last := lastHealthy[node]
+			switch {
+			case keepsData(m.Manifest) && (m.Restored == nil || !m.Restored(node)):
+				next = before
+				next.Words = fmt.Sprintf("%s holds data, so it is not set back from %s: the operator is asked whether to restore it", m.Name, short(m.FP))
+				out.Restore = append(out.Restore, node)
+			case last == "":
+				next = before
+				next.Words = fmt.Sprintf("%s is held at %s and %s ran no other fingerprint healthy to set it back to", m.Name, short(m.FP), node)
+			default:
+				d, there := m.composition(node, last)
+				if !there {
+					next = before
+					next.Words = fmt.Sprintf("%s is held at %s, and the composition of %s at %s is gone, so %s is not set back", m.Name, short(m.FP), m.Name, short(last), node)
+					break
+				}
+				next = delivery.Want{FP: last, Composed: d.Digest, Newest: m.FP, Rule: rule, Words: words}
+			}
+		default:
+			out.Rules[node] = Holding{Rule: rule, Words: words}
+			if !had || before.Removed {
+				// The node runs the module, or its have names it, and gets no want for it: the module is on neither list (issue 1945), and
+				// the pass says so. A new assignment, with no have, waits for the rules and is on no list yet by design. A held module (rule 2,
+				// held before or by this pass) is on the held list instead, whose hold is said and answered on its own: it is never on neither
+				// list (issue 1945: systemd-resolved, held on shanks by the operator, was said as urgent every hour).
+				h, there := n.Haves[node][m.Name]
+				switch {
+				case there && h.Phase != delivery.PhaseRemoved && !held:
+					out.Neither[node] = Holding{Rule: rule, Words: words}
+				case had && (!there || h.Phase == delivery.PhaseRemoved):
+					// A removed want of a node that does not run the module says why no want follows it (issue 1945), so the view's
+					// assigner_want answers it; it stays removed. A node with no key gets none: a removed want written where none was
+					// would have its node agent remove the module and stop holding its composition's resources back.
+					next = delivery.Want{Removed: true, Words: NoWantWords(rule, words)}
+					if !delivery.SameWant(normal(before), normal(next)) {
+						out.Wants[node] = next
+					}
+				}
+				continue
+			}
+			next = delivery.Want{FP: before.FP, Composed: before.Composed, Newest: m.FP, Rule: rule, Words: words}
+			if before.FP == m.FP {
+				// Held at F by the rules: a new revision of F's composition waits for them, as a new fingerprint does (ADR 0539 §5).
+				next = delivery.Want{FP: m.FP, Composed: before.Composed}
+			} else if d, there := m.composition(node, before.FP); there && d.Digest != "" && d.Digest != before.Composed {
+				// Held back at an earlier fingerprint whose kept composition the controller composed again with today's config
+				// (novox/hq ADR 0545): the want follows its new revision, so the node does not run that build with the config of
+				// the moment it was made (on g14 a capacity of 0 after a rollback). Asked as any move of a record module is.
+				at := m
+				at.FP = before.FP
+				running, ran := n.Haves[node][m.Name]
+				need, wait := at.mustAsk(node, before, true, ran, running.FP, running.Composed == "", d)
+				if need != nil {
+					out.Record = append(out.Record, *need)
+				}
+				if !wait {
+					next.Composed = d.Digest
+				}
+			}
+		}
+		next, write := m.selfDerived(node, before, had, next, n, &out)
+		if !write {
+			continue
+		}
+		if !had || !delivery.SameWant(normal(before), normal(next)) {
+			out.Wants[node] = next
+		}
+	}
+	for node, before := range wants {
+		if !slices.Contains(m.Nodes, node) && !before.Removed {
+			out.Wants[node] = delivery.Want{Removed: true, Words: fmt.Sprintf("%s is no longer assigned to %s", m.Name, node)}
+		}
+	}
+	return out
+}
+
+// selfDerived is next with its Self derived from the placement now (Module.Self), whichever rule made it, and whether it is
+// written. A placed node's want names the build alone (ADR 0547 §2). An unplaced node's want that a rule kept from the want
+// written while the node was placed (held at F, held back by rule 3 or 5, a data module asked about) names the controller's
+// composition of the same fingerprint, asked as any move of a record module is (ADR 0539 §14): on 2026-10-27, after the
+// placement seed's revert, g14's systemd-resolved (held) and forticlient (rule 5), and shanks's forticlient (rule 3), kept
+// their Self wants, which their node agents, no longer placed, could not compose (issue 1126). With no such composition, or
+// while its ask waits, the want written stays and the node's holding says why.
+func (m Module) selfDerived(node string, before delivery.Want, had bool, next delivery.Want, n Nodes, out *Outcome) (delivery.Want, bool) {
+	switch {
+	case next.Removed:
+		return next, true
+	case m.selfOn(node):
+		next.Self, next.Composed = true, ""
+		return next, true
+	case !next.Self && next.Composed != "":
+		return next, true
+	}
+	next.Self, next.Yes = false, ""
+	d, there := m.composition(node, next.FP)
+	if !there || d.Digest == "" {
+		out.Rules[node] = Holding{Rule: delivery.RuleComposed, Words: fmt.Sprintf("%s on %s was composed by the node while it was placed, "+
+			"and no composition of its own is named at %s now, so its want stays", m.Name, node, short(next.FP))}
+		return next, false
+	}
+	at := m
+	at.FP = next.FP
+	running, ran := n.Haves[node][m.Name]
+	if need, wait := at.mustAsk(node, before, had, ran, running.FP, running.Composed == "", d); wait {
+		if need != nil && !slices.Contains(out.Record, *need) { // the branch held back at an older fingerprint may have asked it
+			out.Record = append(out.Record, *need)
+		}
+		return next, false
+	}
+	next.Composed = d.Digest
+	return next, true
+}
+
+// NoWantWords say why a node gets no want for a module: the rule that holds its first want back and why (issue 1945).
+func NoWantWords(rule int, words string) string {
+	return fmt.Sprintf("no want: rule %d: %s", rule, words)
+}
+
+// failed says whether a have's health check failed once the node is done moving: phase running or failed (never removed, held, or
+// moving). A failed health while it
+// backs up, applies or checks is a step of the move, not its outcome (on novox at 15:27:36 on 2026-10-25, "health failed, phase
+// applying" held the controller's canary two seconds before the new build was healthy). Every healthy read (healthy, providedHealthy,
+// the world's lastHealthy) already asks for phase running.
+func failed(h delivery.Have) bool {
+	return h.Health == delivery.HealthFailed && (h.Phase == delivery.PhaseRunning || h.Phase == delivery.PhaseFailed)
+}
+
+// healthyElsewhere is every online node of m but node that runs m.FP healthy, by name.
+func healthyElsewhere(m Module, n Nodes, node string) []string {
+	var out []string
+	for _, other := range slices.Sorted(slices.Values(m.Nodes)) {
+		// A witness is online: a node that sleeps keeps the have it last wrote, and a stale have is no evidence that F runs
+		// healthy now.
+		if other != node && n.Online[other] && healthy(n.Haves[other][m.Name], m.FP) {
+			out = append(out, other)
+		}
+	}
+	return out
+}
+
+// failedElsewhere says whether another node of m has a have naming m.FP failed: then the failure is not one node's alone, and
+// the hold and the set-back stand at the second failure (ADR 0557 §2).
+func failedElsewhere(m Module, n Nodes, node string) bool {
+	for _, other := range m.Nodes {
+		if h, ok := n.Haves[other][m.Name]; ok && other != node && h.FP == m.FP && failed(h) {
+			return true
+		}
+	}
+	return false
+}
+
+// FailedAloneWords say why a node gets no new want naming fp: fp fails its health check on the nodes named, alone.
+func FailedAloneWords(module, fp string, failing []string) string {
+	return fmt.Sprintf("%s at %s fails its health check on %s, so no further node moves to it until that is over", module, short(fp),
+		strings.Join(failing, ", "))
+}
+
+// NodeFailure is a failed health check of a module's newest fingerprint on one node while it runs healthy on Others: the have's
+// health, phase and words (HeldWords without a time), and the healthy witnesses by name.
+type NodeFailure struct {
+	Others []string
+	Words  string
+}
+
+// runs says whether a have is of a module the node runs: running, whatever its health.
+func runs(h delivery.Have) bool {
+	return h.Phase == delivery.PhaseRunning
+}
+
+// allRunHealthy says whether every node of m that runs the module (its have's phase is running, or failed) runs m.FP healthy, and
+// at least one does: a hold whose fingerprint runs healthy wherever the module runs holds nothing back any more (issue 1906: seven
+// modules stayed held on every machine after one transient failed check). A node set back to another fingerprint does not run
+// m.FP, and a failed one does not run it healthy, so the hold stays; a have that is removed, held for its backup or still moving
+// (backing up, applying, checking) is not counted, or it would keep the hold up for ever.
+func allRunHealthy(m Module, n Nodes) bool {
+	ran := 0
+	for _, node := range m.Nodes {
+		h, ok := n.Haves[node][m.Name]
+		if !ok || (h.Phase != delivery.PhaseRunning && h.Phase != delivery.PhaseFailed) {
+			continue
+		}
+		if !healthy(h, m.FP) {
+			return false
+		}
+		ran++
+	}
+	return ran > 0
+}
+
+// HeldWords are the words a hold keeps of its cause (issue 1906): the health and phase the node reported, when the assigner saw
+// it, and the node's own words. The node is the held record's own field.
+func HeldWords(h delivery.Have, at time.Time) string {
+	words := fmt.Sprintf("health %s, phase %s", h.Health, h.Phase)
+	if !at.IsZero() {
+		words += ", seen at " + at.UTC().Format(time.RFC3339)
+	}
+	if d := strings.TrimSpace(h.Detail); d != "" {
+		return words + ": " + d
+	}
+	return words + ": the node gave no words"
+}
+
+// LiftedWords say why a hold was lifted by itself.
+func LiftedWords(module, fp string) string {
+	return fmt.Sprintf("every node that runs %s runs %s healthy, so the assigner lifted its hold by itself", module, short(fp))
+}
+
+// normal is a want without its version, as a decoded and a composed one are compared.
+func normal(w delivery.Want) delivery.Want {
+	w.V = 0
+	return w
+}
+
+func short(fp string) string {
+	part, err := delivery.FingerprintKeyPart(fp)
+	if err != nil || len(part) < 12 {
+		return fp
+	}
+	return part[:12]
+}
+
+// mustAsk says whether the move to the composition d on node waits for the operator's yes (need names the ask, ADR 0539 §14). A
+// module the node never ran (it has no want and no have), a move judged neither, a module that is not of policy record and a want
+// that stays are written as any want. The bus module is no exception: it moves by the rules (ADR 0601 §1), its node backing up its
+// streams before it applies (§2); the assigner asks no snapshot for it.
+func (m Module) mustAsk(node string, before delivery.Want, had, ran bool, running string, haveNamesNoComposition bool, d delivery.ComposedDigest) (*RecordNeed, bool) {
+	if (!had && !ran) || before.Removed || (before.FP == m.FP && before.Composed == d.Digest) {
+		return nil, false
+	}
+	// Right after the switch no node has a readable want, and a have from the old node-engine names a fingerprint and no composition
+	// (ADR 0539 §9, §11): a node running this fingerprint is given its want at it with no hold when the controller judges the composition
+	// unchanged, equal to the declaration the node last applied (ADR 0540 §9), since the node agent then applies nothing. A composition that
+	// differs from it (a changed setting or secret), or that the controller could not judge, waits for the ask. A new fingerprint still waits.
+	if !had && ran && running == m.FP && haveNamesNoComposition && d.Judgement == delivery.JudgedUnchanged {
+		return nil, false
+	}
+	if !m.recorded(d) || d.Judgement == delivery.JudgedNeither || d.Judgement == delivery.JudgedUnchanged {
+		return nil, false
+	}
+	if m.Allowed != nil && m.Allowed(node, d.Digest) {
+		return nil, false
+	}
+	return &RecordNeed{Node: node, Digest: d.Digest, Judgement: d.Judgement, Words: d.Words}, true
+}
+
+// recorded says whether the module is of policy record: a person's choice at the assigner over the manifest's word (ADR
+// 0565 §7, catalogue.Upgrade); for a module with none, as the controller holds it beside the composition's digest until the
+// lease write (ADR 0539 §14); on a composition made by hand, which carries none, as the manifest derives it.
+func (m Module) recorded(d delivery.ComposedDigest) bool {
+	if m.Chosen != nil {
+		policy, _, _, _ := catalogue.Upgrade(m.Manifest, m.Chosen)
+		return policy == catalogue.PolicyRecord
+	}
+	if d.Policy != "" {
+		return d.Policy == delivery.PolicyRecord
+	}
+	policy, _, _ := catalogue.DerivedUpgrade(m.Manifest)
+	return policy == catalogue.PolicyRecord
+}
+
+// userListRevision is the want that names the bus module's composition at the fingerprint the node runs when that composition
+// differs from the one the node runs only in the bus's user list (ComposedDigest.UserListOnly), and whether there is one. A node
+// whose want names another fingerprint than the one it runs, or a module that does not provide the bus, has none.
+func (m Module) userListRevision(node string, before delivery.Want, had bool, n Nodes) (delivery.Want, bool) {
+	if !catalogue.ProvidesBus(m.Manifest) {
+		return delivery.Want{}, false
+	}
+	running, ran := n.Haves[node][m.Name]
+	if !ran || running.FP == "" || (had && (before.Removed || before.FP != running.FP)) {
+		return delivery.Want{}, false
+	}
+	d, ok := m.composition(node, running.FP)
+	if !ok || !d.UserListOnly {
+		return delivery.Want{}, false
+	}
+	w := delivery.Want{FP: running.FP, Composed: d.Digest}
+	if had && before.Composed == d.Digest {
+		w.Backup, w.Words = before.Backup, before.Words
+	}
+	return w, true
+}
+
+// GrantNamesNode says whether a grant of module names its accounts on node (mesh-sdk's Grant.NamesNode, which a
+// put reads by too).
+func GrantNamesNode(g delivery.Grant, node, module string) bool {
+	return g.NamesNode(node, module)
+}

modules/mesh-delivery-assigner/internal/judge/judge.go

@@ -0,0 +1,332 @@
+// Package judge is how the seat mesh-placement's holder judges a proposal (novox/hq ADR 0567 §3, §4, as ADR 0593 §8
+// changes them): what it changes on each node by its placement (Intended), every node answering it, and the verdict of
+// their answers (JudgeAnswers). The assigner's own (ADR 0593 §1), moved back from mesh-sdk's compose/judge: the holder
+// composes nothing, since every composition is its node's engine's, and a node answers through the candidates path
+// with what it composed. It holds no bus client and no timer: the holder gives it what it read.
+package judge
+
+import (
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	nec "git.novox.be/novox/mesh-contracts/go/clients/nodeengineclient"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// AnswerBound is how long the holder waits for a node's answer after its candidate was written: the time to live of the
+// node's pulse key (delivery.PulseAnswerKey), whose expiry names it as giving no answer, never passed. The same answer
+// bound a check gives a node (ADR 0593 §8, §7: 60 seconds, nec.AnswerBound). A variable so a test on the bus
+// can shorten it.
+var AnswerBound = nec.AnswerBound
+
+// Intended is, by node, the modules whose placed entry the proposal changes there, and the nodes that answer it: every
+// node (ADR 0593 §8, changing ADR 0567 §4's list of the nodes that must answer), sorted. current is the placement as it
+// stands, laid the proposal's placements by node (nil removes the node's key) and nodes every node with a record. A
+// node's set holds the modules the proposal adds, removes or whose placed entry differs on that node; a node with no
+// key now gets an empty set (§7: the seed is answered as the same). What a node's compositions change beyond its own
+// placement it says itself in its answer, marked in the brief as not computed.
+func Intended(current map[string]delivery.Placement, laid map[string]*delivery.Placement, nodes []string) (intended map[string]map[string]bool, must []string) {
+	intended = map[string]map[string]bool{}
+	all := map[string]bool{}
+	for _, n := range nodes {
+		all[n] = true
+	}
+	for n := range laid {
+		all[n] = true
+	}
+	for node := range all {
+		must = append(must, node)
+		set := map[string]bool{}
+		intended[node] = set
+		before, placed := current[node]
+		after, changesKey := laid[node]
+		if !changesKey || !placed {
+			continue // untouched, or new to placement: every answer must be the same
+		}
+		var afterModules []delivery.PlacedModule
+		if after != nil {
+			afterModules = after.Modules
+		}
+		entries := map[string]delivery.PlacedModule{}
+		for _, m := range before.Modules {
+			entries[m.Module] = m
+		}
+		seen := map[string]bool{}
+		for _, m := range afterModules {
+			seen[m.Module] = true
+			if e, ok := entries[m.Module]; !ok || !reflect.DeepEqual(e, m) {
+				set[m.Module] = true
+			}
+		}
+		for name := range entries {
+			if !seen[name] {
+				set[name] = true
+			}
+		}
+	}
+	sort.Strings(must)
+	return intended, must
+}
+
+// JudgeAnswers is the verdict of a proposal's answers (§4). answers is by node its HaveNode.Candidates entry for the
+// proposal (nil when it has none) and revisions by node the revision of its candidate key: an answer counts when it
+// names the proposal and that revision. It fails on a refusal by a node that must answer; a node of Must with no answer
+// that counts is waited for while its pulse key stands, and once it has ended (pulsing false: the bound's expiry, heard
+// on the bus) is named as giving no answer and the proposal decided on the answers it has (ADR 0593 §8).
+// A difference fails nothing: one Intended computed is listed under Intended, one it did not under Unintended, both
+// shown in the ask's brief. The seed alone fails on any difference.
+func JudgeAnswers(p delivery.PlacementProposal, intended map[string]map[string]bool, answers map[string]*delivery.CandidateAnswer,
+	revisions map[string]uint64, online map[string]bool, pulsing map[string]bool, now time.Time) delivery.PlacementVerdict {
+	v := delivery.PlacementVerdict{At: now.UTC(), Intended: map[string][]string{}, Unintended: map[string][]string{}, Carried: map[string][]string{},
+		Answers: map[string]delivery.CandidateAnswer{}}
+	for node, set := range intended {
+		for m := range set {
+			v.Intended[node] = append(v.Intended[node], m)
+		}
+		sort.Strings(v.Intended[node])
+	}
+	must := p.Must
+	if len(must) == 0 {
+		must = p.Nodes()
+	}
+	for _, node := range must {
+		a := answers[node]
+		if a == nil || a.Proposal != p.ID || a.Revision == 0 || a.Revision != revisions[node] {
+			v.Silent = append(v.Silent, node)
+			continue
+		}
+		v.Answers[node] = *a
+		if a.Refused != "" {
+			v.Fails = append(v.Fails, fmt.Sprintf("%s cannot compose the proposal: %s", node, a.Refused))
+			continue
+		}
+		for _, r := range a.Refusals {
+			v.Fails = append(v.Fails, fmt.Sprintf("%s refuses the proposal for %s: %s", node, r.Module, r.Why))
+		}
+		want := intended[node]
+		differs := func(module, words string) {
+			if p.Seed {
+				// The seed carries what its nodes found, each named in the brief for the operator who approves it.
+				v.Carried[node] = append(v.Carried[node], words)
+				return
+			}
+			if !want[module] {
+				v.Unintended[node] = append(v.Unintended[node], module)
+			}
+		}
+		for _, d := range a.Differs {
+			differs(d.Module, differenceWords(d))
+		}
+		for _, d := range a.Added {
+			differs(d.Module, "would run "+d.Module)
+		}
+		for _, m := range a.Removed {
+			differs(m, "would stop running "+m)
+		}
+		sort.Strings(v.Unintended[node])
+	}
+	if len(v.Intended) == 0 {
+		v.Intended = nil
+	}
+	if len(v.Unintended) == 0 {
+		v.Unintended = nil
+	}
+	if len(v.Carried) == 0 {
+		v.Carried = nil
+	}
+	if len(v.Answers) == 0 {
+		v.Answers = nil
+	}
+	var waiting, gone []string
+	for _, node := range v.Silent {
+		named := node
+		if online != nil && !online[node] {
+			named += " (offline)"
+		}
+		if pulsing[node] {
+			waiting = append(waiting, named)
+		} else {
+			gone = append(gone, named)
+		}
+	}
+	if len(waiting) > 0 {
+		v.Notes = append(v.Notes, fmt.Sprintf("waits for the answers of %s, each for %s from its candidate's write",
+			strings.Join(waiting, ", "), AnswerBound))
+	}
+	if len(gone) > 0 {
+		// ADR 0593 §8: decided on the answers it has; that node's own composition judges again when it applies (§9).
+		v.Notes = append(v.Notes, fmt.Sprintf("no answer from %s within %s of its candidate's write: decided on the answers "+
+			"it has, and that node's own composition judges again when it applies", strings.Join(gone, ", "), AnswerBound))
+	}
+	switch {
+	case len(v.Fails) > 0:
+		v.State = delivery.VerdictFail
+	case len(waiting) > 0:
+		v.State = delivery.VerdictWaits
+	default:
+		v.State = delivery.VerdictPass
+	}
+	return v
+}
+
+// Brief is the verdict as the ask's brief shows it, by node (§5): what the proposal changes and what each node answered
+// beside it, marked, and what stays held as the node holds it today, with the proposal's why.
+func Brief(p delivery.PlacementProposal, v delivery.PlacementVerdict) string {
+	var b strings.Builder
+	fmt.Fprintf(&b, "%s (proposed by %s)", p.Why, p.By)
+	nodes := map[string]bool{}
+	for n := range v.Intended {
+		nodes[n] = true
+	}
+	for n := range v.Unintended {
+		nodes[n] = true
+	}
+	for _, n := range p.Nodes() {
+		nodes[n] = true
+	}
+	for n, a := range v.Answers {
+		if len(a.Held) > 0 {
+			nodes[n] = true
+		}
+	}
+	for n := range v.Carried {
+		nodes[n] = true
+	}
+	names := make([]string, 0, len(nodes))
+	for n := range nodes {
+		names = append(names, n)
+	}
+	sort.Strings(names)
+	for _, n := range names {
+		fmt.Fprintf(&b, "; %s:", n)
+		if m := v.Intended[n]; len(m) > 0 {
+			fmt.Fprintf(&b, " changes %s", strings.Join(m, ", "))
+		} else {
+			b.WriteString(" composes the same")
+		}
+		if m := v.Unintended[n]; len(m) > 0 {
+			fmt.Fprintf(&b, "; also differs, not computed: %s", strings.Join(m, ", "))
+		}
+		if m := v.Carried[n]; len(m) > 0 {
+			fmt.Fprintf(&b, "; the seed carries: %s", strings.Join(m, "; "))
+		}
+		if held := v.Answers[n].Held; len(held) > 0 {
+			var names []string
+			for _, h := range held {
+				today := h.Today
+				if today == "" {
+					today = "held"
+				}
+				names = append(names, h.Module+" ("+today+")")
+			}
+			fmt.Fprintf(&b, "; stays as today: %s", strings.Join(names, ", "))
+		}
+	}
+	return b.String()
+}
+
+// differenceWords names one module's difference: the module, the first field that differs in it with its value as it
+// runs and as the seed composes it, each cut to about 60 characters ("(value cut)" where a body shown is cut before the
+// field), and how many fields more; or the resource and why when no body is shown.
+func differenceWords(d delivery.ModuleDiffers) string {
+	for _, b := range d.Bodies {
+		if len(b.Paths) == 0 {
+			continue
+		}
+		path := b.Paths[0]
+		words := fmt.Sprintf("%s: %s %s → %s", d.Module, fieldName(b.Running, b.Composed, path),
+			valueAt(b.Running, path), valueAt(b.Composed, path))
+		if n := len(b.Paths) - 1; n > 0 {
+			words += fmt.Sprintf(" (and %d more fields)", n)
+		}
+		return words
+	}
+	if d.Resource != "" {
+		return fmt.Sprintf("%s: %s (%s)", d.Module, d.Resource, d.Why)
+	}
+	return fmt.Sprintf("%s: %s", d.Module, d.Why)
+}
+
+// shownValue bounds a value named in a brief.
+const shownValue = 60
+
+// walk follows a differing path (delivery.DifferingPaths: keys joined by dots, a key may hold dots, and a JSON value
+// written in a string is read as JSON) through a body, answering the keys it passed and the value at its end.
+func walk(body, path string) (keys []string, value any, ok bool) {
+	var v any
+	if json.Unmarshal([]byte(body), &v) != nil {
+		return nil, nil, false
+	}
+	rest := path
+	for rest != "" {
+		if s, isString := v.(string); isString {
+			var inner any
+			if json.Unmarshal([]byte(s), &inner) != nil {
+				return nil, nil, false
+			}
+			v = inner
+		}
+		switch t := v.(type) {
+		case map[string]any:
+			best := ""
+			for k := range t {
+				if (rest == k || strings.HasPrefix(rest, k+".")) && len(k) > len(best) {
+					best = k
+				}
+			}
+			if best == "" {
+				return nil, nil, false
+			}
+			keys, v, rest = append(keys, best), t[best], strings.TrimPrefix(strings.TrimPrefix(rest, best), ".")
+		case []any:
+			seg, after, _ := strings.Cut(rest, ".")
+			n, err := strconv.Atoi(seg)
+			if err != nil || n < 0 || n >= len(t) {
+				return nil, nil, false
+			}
+			keys, v, rest = append(keys, seg), t[n], after
+		default:
+			return nil, nil, false
+		}
+	}
+	return keys, v, true
+}
+
+// valueAt is the value at path in a shown body, cut to shownValue, or why it is not shown.
+func valueAt(body, path string) string {
+	if body == "" {
+		return "(none)"
+	}
+	_, v, ok := walk(body, path)
+	if !ok {
+		return "(value cut)"
+	}
+	s, isString := v.(string)
+	if !isString {
+		raw, _ := json.Marshal(v)
+		s = string(raw)
+	}
+	if r := []rune(s); len(r) > shownValue {
+		s = string(r[:shownValue-1]) + "…"
+	}
+	return s
+}
+
+// fieldName is the differing field as a person reads it: its parent's name and its own, `PARENT[key]`, from whichever
+// body reaches it; the path's end when neither does.
+func fieldName(running, composed, path string) string {
+	for _, body := range []string{running, composed} {
+		if keys, _, ok := walk(body, path); ok && len(keys) > 0 {
+			if len(keys) == 1 {
+				return keys[0]
+			}
+			return keys[len(keys)-2] + "[" + keys[len(keys)-1] + "]"
+		}
+	}
+	return path
+}

modules/mesh-delivery-assigner/internal/judge/judge_test.go

@@ -0,0 +1,91 @@
+package judge
+
+import (
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// ADR 0567 §3, §4 (rows moved from the assigner's check of a pull request's placement, ADR 0559 §5): what a proposal
+// changes by node, and the verdict of the answers: differences shown and failing nothing, a refusal and a silent node
+// failing, a later answer judging again, the seed failing on any difference.
+func TestJudge(t *testing.T) {
+	current := map[string]delivery.Placement{"anchor": {Node: "anchor", Modules: []delivery.PlacedModule{{Module: "mail"}}}, "server": {Node: "server"}}
+	laid := map[string]*delivery.Placement{
+		"anchor": {Node: "anchor", Modules: []delivery.PlacedModule{{Module: "mail", Ports: map[string]int{"25": 2525}}, {Module: "web"}}},
+		"laptop": {Node: "laptop", Modules: []delivery.PlacedModule{{Module: "web"}}}}
+	// ADR 0593 §8: every node answers; what the placement changes is read from the placement alone.
+	got, must := Intended(current, laid, []string{"anchor", "laptop", "server"})
+	if !got["anchor"]["mail"] || !got["anchor"]["web"] || len(got["laptop"]) != 0 || len(got["server"]) != 0 ||
+		!slices.Equal(must, []string{"anchor", "laptop", "server"}) {
+		t.Errorf("intended = %v, must %v: want anchor's mail and web, nothing elsewhere, every node answering", got, must)
+	}
+
+	at := time.Date(2026, 10, 27, 2, 0, 0, 0, time.UTC)
+	p := delivery.PlacementProposal{ID: "p-one", By: "op", Why: "move web", Written: at, Base: map[string]uint64{"anchor": 3, "laptop": 0},
+		Must: []string{"anchor", "laptop"}}
+	revisions := map[string]uint64{"anchor": 7, "laptop": 8}
+	intended := map[string]map[string]bool{"anchor": {"web": true}}
+	same := func(rev uint64) *delivery.CandidateAnswer {
+		return &delivery.CandidateAnswer{Proposal: "p-one", Revision: rev, Verdict: delivery.CandidateSame, Same: []string{"mail"}}
+	}
+	differs := func(rev uint64, module string) *delivery.CandidateAnswer {
+		return &delivery.CandidateAnswer{Proposal: "p-one", Revision: rev, Verdict: delivery.CandidateDiffers,
+			Differs: []delivery.ModuleDiffers{{Module: module, Why: "the port differs"}}}
+	}
+	for _, row := range []struct {
+		name    string
+		seed    bool
+		answers map[string]*delivery.CandidateAnswer
+		pulsing map[string]bool
+		state   string
+		words   string
+		marked  string
+	}{
+		{"all the same", false, map[string]*delivery.CandidateAnswer{"anchor": same(7), "laptop": same(8)}, nil, delivery.VerdictPass, "", ""},
+		{"a module added where intended", false, map[string]*delivery.CandidateAnswer{"anchor": {Proposal: "p-one", Revision: 7, Verdict: delivery.CandidateDiffers,
+			Added: []delivery.ModuleAdded{{Module: "web", Unissued: []string{"its own secret"}}}}, "laptop": same(8)}, nil, delivery.VerdictPass, "", ""},
+		{"a difference not computed passes, marked", false, map[string]*delivery.CandidateAnswer{"anchor": differs(7, "mail"), "laptop": same(8)}, nil, delivery.VerdictPass, "", "mail"},
+		{"the seed carries a difference, named", true, map[string]*delivery.CandidateAnswer{"anchor": same(7), "laptop": {Proposal: "p-one", Revision: 8,
+			Verdict: delivery.CandidateDiffers, Differs: []delivery.ModuleDiffers{{Module: "node-tools", Resource: "node-tools.runtime", Why: "the resource differs",
+				Bodies: []delivery.ResourceBodies{{ID: "node-tools.runtime", Paths: []string{"env.MESH_OWNED_PATHS./etc/resolv.conf", "env.MESH_TOOL_MODULES"},
+					Running:  `{"env":{"MESH_OWNED_PATHS":"{\"/etc/hosts\":\"hostname\",\"/etc/resolv.conf\":\"networkmanager (node-uplink)\"}"}}`,
+					Composed: `{"env":{"MESH_OWNED_PATHS":"{\"/etc/hosts\":\"hostname\",\"/etc/resolv.conf\":\"systemd-resolved (node-resolver)\"}","MESH_TOOL_MODULES":"… (cut at 8192 bytes)`}}}}}}, nil, delivery.VerdictPass, "", ""},
+		{"a refusal", false, map[string]*delivery.CandidateAnswer{"anchor": same(7), "laptop": {Proposal: "p-one", Revision: 8, Verdict: delivery.CandidateRefused,
+			Refusals: []delivery.ModuleRefused{{Module: "web", Why: "no own secret"}}}}, nil, delivery.VerdictFail, "laptop refuses", ""},
+		{"a node not answering, within its bound", false, map[string]*delivery.CandidateAnswer{"anchor": same(7)}, map[string]bool{"laptop": true}, delivery.VerdictWaits, "laptop (offline)", ""},
+		{"an answer of an earlier revision, past its bound, is no answer and decided without it", false, map[string]*delivery.CandidateAnswer{"anchor": same(6), "laptop": same(8)}, nil, delivery.VerdictPass, "no answer from anchor", ""},
+		{"a module held as today passes, shown in the brief", false, map[string]*delivery.CandidateAnswer{"anchor": same(7), "laptop": {Proposal: "p-one", Revision: 8,
+			Verdict: delivery.CandidateSame, Held: []delivery.ModuleRefused{{Module: "spiegel", Why: "a required value is unset"}}}}, nil, delivery.VerdictPass, "", ""},
+		{"its later answer", false, map[string]*delivery.CandidateAnswer{"anchor": same(7), "laptop": same(8)}, nil, delivery.VerdictPass, "", ""},
+	} {
+		q := p
+		q.Seed = row.seed
+		v := JudgeAnswers(q, intended, row.answers, revisions, map[string]bool{"anchor": true}, row.pulsing, at)
+		all := strings.Join(append(append([]string{}, v.Fails...), v.Notes...), "; ")
+		if v.State != row.state || !strings.Contains(all, row.words) {
+			t.Errorf("%s: %s, %q", row.name, v.State, all)
+		}
+		if row.seed && row.state == delivery.VerdictPass && !strings.Contains(Brief(q, v), "the seed carries: node-tools: MESH_OWNED_PATHS[/etc/resolv.conf] networkmanager (node-uplink) → (value cut) (and 1 more fields)") {
+			t.Errorf("%s: the brief does not name it: %s", row.name, Brief(q, v))
+		}
+		if row.seed && row.state == delivery.VerdictPass {
+			whole := row.answers["laptop"].Differs[0]
+			whole.Bodies = []delivery.ResourceBodies{{ID: "r", Paths: []string{"env.MESH_OWNED_PATHS./etc/resolv.conf"},
+				Running:  `{"env":{"MESH_OWNED_PATHS":"{\"/etc/resolv.conf\":\"networkmanager (node-uplink)\"}"}}`,
+				Composed: `{"env":{"MESH_OWNED_PATHS":"{\"/etc/resolv.conf\":\"systemd-resolved (node-resolver)\"}"}}`}}
+			if got := differenceWords(whole); got != "node-tools: MESH_OWNED_PATHS[/etc/resolv.conf] networkmanager (node-uplink) → systemd-resolved (node-resolver)" {
+				t.Errorf("the difference is named %q", got)
+			}
+		}
+		if strings.HasPrefix(row.name, "a module held as today") && !strings.Contains(Brief(q, v), "stays as today: spiegel (held)") {
+			t.Errorf("%s: the brief does not show it: %s", row.name, Brief(q, v))
+		}
+		if row.marked != "" && (!slices.Contains(v.Unintended["anchor"], row.marked) || !strings.Contains(Brief(q, v), "not computed: "+row.marked)) {
+			t.Errorf("%s: the difference is not marked: %+v, %s", row.name, v.Unintended, Brief(q, v))
+		}
+	}
+}

modules/mesh-delivery-assigner/manifest_test.go

@@ -0,0 +1,126 @@
+package manifest
+
+import (
+	"os"
+	"reflect"
+	"slices"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+
+	"git.novox.be/novox/mesh-sdk/go/views"
+)
+
+func load(t *testing.T) catalogue.Manifest {
+	t.Helper()
+	raw, err := os.ReadFile("module.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	m, err := catalogue.Decode(raw)
+	if err != nil {
+		t.Fatalf("mesh-sdk cannot decode the manifest: %v", err)
+	}
+	return m
+}
+
+// 1297/B2a: the controller's reader (mesh-sdk catalogue, which the controller reads manifests with) takes the
+// manifest; it reads exactly the buckets the assigner opens (the program's list, held equal in its own test), keeps
+// the states it declares (the differences kept read-only, 1906/D5), and holds a credential of its own.
+func TestManifest(t *testing.T) {
+	m := load(t)
+	if m.Module != "mesh-delivery-assigner" {
+		t.Errorf("module = %q", m.Module)
+	}
+	reads := slices.Clone(m.Reads)
+	slices.Sort(reads)
+	// ADR 0593 §8: it composes nothing, so it reads no candidate, held or resolved value, compose step or build log; it reads
+	// every node's published compositions to compare them, and the gate's source and merges, for the release that carries a build (ADR 0601 §1).
+	// DLV-F2r (ADR 0615 §1, ADR 0631 §1): the indexer's manifests, modules and module graph (whose verb edges a want waits
+	// on, ADR 0614 §2, §3) are read through its first views and views family, none of the indexer's states by reads.
+	want := []string{"mesh-delivery-builder.builds", "mesh-delivery-gate.merges", "mesh-delivery-gate.source",
+		"mesh-delivery-teller.answers", "mesh-delivery-watchman.presence", "mesh-grants.grants", "mesh-host.composed",
+		"mesh-provisioner.provisions", "node-engine.have"}
+	if !reflect.DeepEqual(reads, want) {
+		t.Errorf("reads = %v, want exactly %v", reads, want)
+	}
+	states := map[string]int{}
+	for _, s := range m.State {
+		states[s.Name] = s.History
+	}
+	if want := map[string]int{"asks": 5, "differences": 64, "puts": 20, "wants": 20,
+		"placement": 64, "proposals": 5, "candidates": 5, "pulses": 0, "findings": 5, "policies": 20, "seat-holders": 5, views.MarksState: 1, views.StatusState: 1,
+		"engine-reads": 1}; !reflect.DeepEqual(states, want) {
+		t.Errorf("state = %v, want %v", states, want)
+	}
+	if _, ok := m.OwnSecrets["broker"]; !ok || len(m.OwnSecrets) != 1 {
+		t.Errorf("own-secrets = %v, want exactly broker (or no credential is issued)", m.OwnSecrets)
+	}
+	if m.SecretsOwner != "mesh-delivery-assigner" {
+		t.Errorf("secrets-owner = %q", m.SecretsOwner)
+	}
+	// 1906/D3: it says its conditions on the operator channel; it asks the Go build seat nothing since the composition is
+	// the node-engine's (ADR 0593 §7).
+	if !slices.Equal(m.Uses, []string{"operator-channel"}) {
+		t.Errorf("uses = %v, want exactly operator-channel", m.Uses)
+	}
+	// ADR 0546: it serves its own tools (put, release, puts) from its bundle through the tool runner (the artifact loads the
+	// module), says each put's step as the event put, and calls the hand-act seat and the bus node's backup holder.
+	// ADR 0567 §1, §6-§10: it holds the seat mesh-placement, serving its five verbs (adopt and hand-back went with the
+	// controller, ADR 0590); keeps the seat's events on its stream placement for 30 days; calls the hand-act log; and reads
+	// mesh-config's resolved values to compose every node a proposal touches.
+	// ADR 0565 §7, §9 (issue 1953 D4): and the seat mesh-wants, serving upgrade and bus.
+	if len(m.Claims) != 2 || m.Claims[0].Name != catalogue.PlacementSeat || m.Claims[0].At() != catalogue.ScopeMesh ||
+		!slices.Equal(m.Claims[0].Serves, []string{"placement", "proposals", "propose", "withdraw", "again"}) ||
+		m.Claims[1].Name != catalogue.WantsSeat || m.Claims[1].At() != catalogue.ScopeMesh || !slices.Equal(m.Claims[1].Serves, []string{"upgrade", "bus"}) {
+		t.Errorf("the assigner claims %+v, want mesh-placement with its five verbs and mesh-wants with its two", m.Claims)
+	}
+	if seat, _ := catalogue.SeatNamed(catalogue.WantsSeat); catalogue.CanHold(m, seat) != nil {
+		t.Errorf("the assigner cannot hold mesh-wants: %v", catalogue.CanHold(m, seat))
+	}
+	if seat, _ := catalogue.SeatNamed(catalogue.PlacementSeat); catalogue.CanHold(m, seat) != nil {
+		t.Errorf("the assigner cannot hold the seat: %v", catalogue.CanHold(m, seat))
+	}
+	// ADR 0621 §1: the first-view tools placement, seat-holders and wants and design 25 § 12.2's six read tools, of the
+	// program's bundle, which runs in a runtime of its own on the assigner's account; ADR 0618 §3: and assigner_engine_reads,
+	// which lists and asks again what each node's engine reads.
+	if !slices.Equal(m.Tools, []string{"assigner_put", "assigner_release", "assigner_puts", "placement", "seat-holders", "wants",
+		"assigner_read_placement", "assigner_read_seat_holders", "assigner_read_wants", "assigner_read_findings", "assigner_read_asks", "assigner_read_differences",
+		"assigner_first_views", "assigner_first_view_again", "assigner_engine_reads"}) {
+		t.Errorf("the assigner serves tools %v, want its three put tools, three first views, six read tools and assigner_engine_reads", m.Tools)
+	}
+	if m.RunsAs != m.Module || m.SecretsOwner != m.RunsAs {
+		t.Errorf("runs-as = %q: the bundle runs on the assigner's own account (ADR 0621 §1)", m.RunsAs)
+	}
+	// ADR 0621 §2: each first-view tool answers exactly its readers, never the assigner.
+	callers := map[string]string{"placement": "mesh-grants,node-tools,mesh-delivery-indexer", "seat-holders": "node-tools", "wants": "mesh-grants"}
+	env := m.Build.Artifacts[0].Env
+	for tool, list := range callers {
+		if env[views.CallersEnv(tool)] != list || views.ParseCallers(env[views.CallersEnv(tool)]).Allows("n1."+m.Module) {
+			t.Errorf("%s callers = %q, want %q", tool, env[views.CallersEnv(tool)], list)
+		}
+	}
+	// ADR 0619 §2, ADR 0615 §5: its views family beside placement on its old streams section.
+	if len(m.Streams) != 2 || m.Streams[1].Name != "assigner-views" || !slices.Equal(m.Streams[1].Events, []string{views.EventPattern}) ||
+		m.Streams[1].MaxAgeDays != views.StreamDays || m.Streams[1].MaxMiB != views.StreamMiB || m.Streams[1].Retention != "" {
+		t.Errorf("streams = %+v, want placement and assigner-views", m.Streams)
+	}
+	if m.Streams[0].Name != delivery.PlacementStream || m.Streams[0].MaxAgeDays != delivery.PlacementStreamDays ||
+		!slices.Equal(slices.Sorted(slices.Values(m.Streams[0].Events)), slices.Sorted(slices.Values(delivery.PlacementEvents))) {
+		t.Errorf("streams = %+v, want placement carrying the seat's four events for %d days", m.Streams, delivery.PlacementStreamDays)
+	}
+	// ADR 0618 §4: and it hears each node's engine say its reads changed.
+	if !slices.Equal(m.Consumes, []string{"mesh-delivery-indexer.views.graph", "mesh-delivery-indexer.views.manifests", "mesh-delivery-indexer.views.modules", "node-engine.manifest-reads-changed"}) {
+		t.Errorf("consumes = %v, want the indexer's views of graph, manifests and modules and the engines' reads changed", m.Consumes)
+	}
+	if want := []string{"mesh-delivery-indexer.graph", "mesh-delivery-indexer.manifests", "mesh-delivery-indexer.modules",
+		"seat:mesh-hand-acts.hand-act", "seat:mesh-hand-acts.hand-acts", "seat:mesh-hand-acts.warranted", // ADR 0565 §9, §11: the seat alone
+		"seat:node-backup.backed-up", "seat:node-backup.now",
+		"seat:node-engine.manifest-reads"}; !slices.Equal(slices.Sorted(slices.Values(m.Invokes)), want) { // ADR 0618 §3
+		t.Errorf("invokes = %v, want %v", m.Invokes, want)
+	}
+	if !slices.Equal(m.Emits, []string{"put"}) {
+		t.Errorf("emits = %v, want put", m.Emits)
+	}
+}

modules/mesh-delivery-assigner/module.json

@@ -0,0 +1,164 @@
+{
+  "module": "mesh-delivery-assigner",
+  "version": "1",
+  "slug": "assigner",
+  "runs-as": "mesh-delivery-assigner",
+  "claims": [
+    {
+      "name": "mesh-placement",
+      "scope": "mesh",
+      "serves": [
+        "placement",
+        "proposals",
+        "propose",
+        "withdraw",
+        "again"
+      ]
+    },
+    {
+      "name": "mesh-wants",
+      "scope": "mesh",
+      "serves": [
+        "upgrade",
+        "bus"
+      ]
+    }
+  ],
+  "reads": [
+    "mesh-delivery-builder.builds",
+    "mesh-delivery-gate.merges",
+    "mesh-delivery-gate.source",
+    "mesh-delivery-teller.answers",
+    "mesh-delivery-watchman.presence",
+    "mesh-grants.grants",
+    "mesh-host.composed",
+    "mesh-provisioner.provisions",
+    "node-engine.have"
+  ],
+  "uses": [
+    "operator-channel"
+  ],
+  "consumes": [
+    "mesh-delivery-indexer.views.graph",
+    "mesh-delivery-indexer.views.manifests",
+    "mesh-delivery-indexer.views.modules",
+    "node-engine.manifest-reads-changed"
+  ],
+  "invokes": [
+    "mesh-delivery-indexer.graph",
+    "mesh-delivery-indexer.manifests",
+    "mesh-delivery-indexer.modules",
+    "seat:mesh-hand-acts.hand-act",
+    "seat:mesh-hand-acts.hand-acts",
+    "seat:mesh-hand-acts.warranted",
+    "seat:node-backup.backed-up",
+    "seat:node-backup.now",
+    "seat:node-engine.manifest-reads"
+  ],
+  "emits": [
+    "put"
+  ],
+  "tools": [
+    "assigner_put",
+    "assigner_release",
+    "assigner_puts",
+    "placement",
+    "seat-holders",
+    "wants",
+    "assigner_read_placement",
+    "assigner_read_seat_holders",
+    "assigner_read_wants",
+    "assigner_read_findings",
+    "assigner_read_asks",
+    "assigner_read_differences",
+    "assigner_first_views",
+    "assigner_first_view_again",
+    "assigner_engine_reads"
+  ],
+  "state": [
+    { "name": "placement", "history": 64 },
+    { "name": "proposals", "history": 5 },
+    { "name": "candidates", "history": 5 },
+    { "name": "pulses", "key-ttl": true },
+    { "name": "asks", "history": 5 },
+    { "name": "differences", "history": 64 },
+    { "name": "puts", "history": 20 },
+    { "name": "wants", "history": 20 },
+    { "name": "findings", "history": 5 },
+    { "name": "policies", "history": 20 },
+    { "name": "seat-holders", "history": 5 },
+    { "name": "view-marks", "history": 1 },
+    { "name": "first-views", "history": 1 },
+    { "name": "engine-reads", "history": 1 }
+  ],
+  "streams": [
+    {
+      "name": "placement",
+      "events": [
+        "placement-proposed",
+        "placement-judged",
+        "placement-changed",
+        "placement-withdrawn"
+      ],
+      "max-age-days": 30
+    },
+    { "name": "assigner-views", "events": ["views.**"], "max-age-days": 7, "max-mib": 256 }
+  ],
+  "own-secrets": {
+    "broker": "${dir:state}/broker"
+  },
+  "secrets-owner": "mesh-delivery-assigner",
+  "resources": [
+    {
+      "id": "account",
+      "type": "user",
+      "name": "mesh-delivery-assigner",
+      "shell": "/usr/bin/nologin",
+      "home": "/var/lib/mesh-delivery-assigner"
+    },
+    {
+      "id": "state",
+      "type": "directory",
+      "mode": "0700",
+      "owner": "mesh-delivery-assigner",
+      "place": ".",
+      "unknown": "program"
+    },
+    {
+      "id": "assigner",
+      "type": "process",
+      "name": "mesh-delivery-assigner",
+      "artifact": "program",
+      "run": [
+        "./mesh-delivery-assigner"
+      ],
+      "env": {
+        "MESH_BROKER_FILE": "${dir:state}/broker"
+      },
+      "user": "mesh-delivery-assigner",
+      "health": {
+        "kind": "unit"
+      }
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "program",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/mesh-delivery-assigner",
+        "binary": "mesh-delivery-assigner",
+        "loads": [
+          "mesh-delivery-assigner"
+        ],
+        "env": {
+          "MESH_VIEW_CALLERS_PLACEMENT": "mesh-grants,node-tools,mesh-delivery-indexer",
+          "MESH_VIEW_CALLERS_SEAT_HOLDERS": "node-tools",
+          "MESH_VIEW_CALLERS_WANTS": "mesh-grants"
+        }
+      }
+    ]
+  }
+}

modules/mesh-delivery-builder/buildrun/asks.go

@@ -0,0 +1,316 @@
+package buildrun
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **An asker puts an ask on its build seat's stream and waits for its step** (novox/hq ADR 0525 §1, §6; issue 1887 A4,
+// A5). It chooses no node: whichever build node pulls the ask writes `<node>.<ask id>` in its build module's steps state,
+// and the asker reads the first such key that is not running. The builder and the checker share it.
+
+// AskPublisher puts an encoded ask on subject, de-duplicated by its id.
+type AskPublisher interface {
+	PublishAsk(ctx context.Context, subject, id string, data []byte) error
+}
+
+// AskWaiter watches an ask's steps: every value a key `*.<ask id>` of the build module's steps state takes, running or
+// ended, on the channel it answers, until ctx ends. A watch, not a poll.
+type AskWaiter interface {
+	WatchAsk(ctx context.Context, module, askID string) (<-chan delivery.Step, error)
+}
+
+// Asker puts asks and waits for their steps.
+type Asker struct {
+	Publisher AskPublisher
+	Waiter    AskWaiter
+	// Bound is how long a running step (a build node took the ask, its key written running) may stand still, with no new phase,
+	// before the asker stops waiting; a step that keeps moving is waited for up to 3 Bounds from its start (issue 1930); zero waits as long as ctx. An ask waiting in its stream is not bounded: the stream's backlog is no fault
+	// (ADR 0525 §6, §9), and the bound starts again when another node takes the ask.
+	Bound time.Duration
+}
+
+// Put puts a on its stream: the seat's accept subject of its language and kind.
+func (k Asker) Put(ctx context.Context, a delivery.StepAsk) error {
+	raw, err := delivery.EncodeStepAsk(a)
+	if err != nil {
+		return err
+	}
+	subject, err := delivery.AskSubject(a.Language, a.Kind)
+	if err != nil {
+		return err
+	}
+	if err := k.Publisher.PublishAsk(ctx, subject, a.ID, raw); err != nil {
+		return fmt.Errorf("putting the %s ask %s: %w", a.Kind, a.ID, err)
+	}
+	return nil
+}
+
+// Wait waits for the step of an ask already put (a builder that started again takes over its own asks with it, never
+// putting them twice) and answers it when it ended, whatever its state. The bound runs from the step's start on the node
+// that took the ask, read from its running key, so an ask that waits in the stream for a free slot waits as long as ctx.
+func (k Asker) Wait(ctx context.Context, a delivery.StepAsk) (delivery.Step, error) {
+	module, err := delivery.BuildModuleOf(a.Language)
+	if err != nil {
+		return delivery.Step{}, err
+	}
+	watch, cancel := context.WithCancel(ctx)
+	defer cancel()
+	steps, err := k.Waiter.WatchAsk(watch, module, a.ID)
+	if err != nil {
+		return delivery.Step{}, err
+	}
+	var bound, outerCap <-chan time.Time
+	var timer, capTimer *time.Timer
+	defer func() {
+		if timer != nil {
+			timer.Stop()
+		}
+		if capTimer != nil {
+			capTimer.Stop()
+		}
+	}()
+	running, since, phase, phaseAt := "", time.Time{}, "", time.Time{}
+	standStill := func() error {
+		if phase == "" {
+			return fmt.Errorf("the ask %s's step on %s did not end within %s of its start: it stood still, saying no phase", a.ID, running, k.Bound)
+		}
+		return fmt.Errorf("the ask %s's step on %s did not end within %s: it stood still in %q since %s",
+			a.ID, running, k.Bound, phase, phaseAt.UTC().Format(time.RFC3339))
+	}
+	for {
+		select {
+		case <-ctx.Done():
+			return delivery.Step{}, ctx.Err()
+		case <-bound:
+			return delivery.Step{}, standStill()
+		case <-outerCap:
+			return delivery.Step{}, fmt.Errorf("the ask %s's step on %s did not end within %s of its start: it kept moving (last phase %q at %s) but never ended",
+				a.ID, running, 3*k.Bound, phase, phaseAt.UTC().Format(time.RFC3339))
+		case step, ok := <-steps:
+			if !ok {
+				return delivery.Step{}, errors.New("the watch of the ask's step ended")
+			}
+			if seen := stepSeenOf(ctx); seen != nil {
+				seen(step)
+			}
+			if step.State != delivery.StepRunning {
+				return step, nil
+			}
+			if k.Bound <= 0 {
+				continue
+			}
+			newRun := step.Node != running || !step.Started.Equal(since)
+			if !newRun && step.Phase == phase && step.PhaseAt.Equal(phaseAt) {
+				continue
+			}
+			// A node took the ask, or took it again after its run stopped (another node, or the same node's build module
+			// replaced mid-run: a new start), or its step entered a phase. The bound is on standing still: it runs from the
+			// step's last movement (its phase's start, else its start), so a step that keeps moving is waited for, up to
+			// three bounds from its start (issue 1930).
+			running, since, phase, phaseAt = step.Node, step.Started, step.Phase, step.PhaseAt
+			last := step.Started
+			if step.PhaseAt.After(last) {
+				last = step.PhaseAt
+			}
+			left := k.Bound
+			if !last.IsZero() {
+				left = time.Until(last.Add(k.Bound))
+			}
+			if timer != nil {
+				timer.Stop()
+			}
+			timer = time.NewTimer(max(left, 0))
+			bound = timer.C
+			if newRun {
+				if capTimer != nil {
+					capTimer.Stop()
+				}
+				outer := 3 * k.Bound
+				if !step.Started.IsZero() {
+					outer = time.Until(step.Started.Add(3 * k.Bound))
+				}
+				capTimer = time.NewTimer(max(outer, 0))
+				outerCap = capTimer.C
+			}
+		}
+	}
+}
+
+type stepSeenKey struct{}
+
+// WithStepSeen is ctx carrying seen, which Asker.Wait hands every value the ask's step key takes while it waits: the node
+// that took it, each phase it says while running (delivery.Step.Phase), and its end. A try names its asks' progress so
+// (issue 1890). seen runs in the waiting goroutine and must not block.
+func WithStepSeen(ctx context.Context, seen func(delivery.Step)) context.Context {
+	return context.WithValue(ctx, stepSeenKey{}, seen)
+}
+
+func stepSeenOf(ctx context.Context) func(delivery.Step) {
+	seen, _ := ctx.Value(stepSeenKey{}).(func(delivery.Step))
+	return seen
+}
+
+// Ask puts a and waits for its step; a step that did not pass is an error naming its node, its state and its reason.
+func (k Asker) Ask(ctx context.Context, a delivery.StepAsk) (delivery.Step, error) {
+	if err := k.Put(ctx, a); err != nil {
+		return delivery.Step{}, err
+	}
+	return k.Passed(k.Wait(ctx, a))
+}
+
+// Passed is step when it passed, else an error naming where it ended and why.
+func (k Asker) Passed(step delivery.Step, err error) (delivery.Step, error) {
+	if err != nil {
+		return step, err
+	}
+	if step.State != delivery.StepPassed {
+		return step, fmt.Errorf("the ask %s on %s %s: %s", step.ID, step.Node, step.State, step.Reason)
+	}
+	return step, nil
+}
+
+// JetStreamAsks is the bus side of an Asker: a JetStream publish de-duplicated by the ask's id (Nats-Msg-Id), and a watch
+// of `*.<ask id>` in the build module's steps bucket.
+type JetStreamAsks struct {
+	JS jetstream.JetStream
+}
+
+// PublishAsk is AskPublisher's.
+func (s JetStreamAsks) PublishAsk(ctx context.Context, subject, id string, data []byte) error {
+	msg := &nats.Msg{Subject: subject, Data: data, Header: nats.Header{}}
+	msg.Header.Set(jetstream.MsgIDHeader, id)
+	_, err := s.JS.PublishMsg(ctx, msg)
+	return err
+}
+
+// WatchAsk is AskWaiter's: the watch hands over what the keys hold now, so a step that ended before it began is read at
+// once, and every change after.
+func (s JetStreamAsks) WatchAsk(ctx context.Context, module, askID string) (<-chan delivery.Step, error) {
+	pattern, err := delivery.AskStepWatch(askID)
+	if err != nil {
+		return nil, err
+	}
+	kv, err := s.JS.KeyValue(ctx, delivery.StepsBucket(module))
+	if err != nil {
+		return nil, fmt.Errorf("the bucket %s: %w", delivery.StepsBucket(module), err)
+	}
+	w, err := kv.Watch(ctx, pattern)
+	if err != nil {
+		return nil, err
+	}
+	out := make(chan delivery.Step)
+	go func() {
+		defer close(out)
+		defer w.Stop()
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case e, ok := <-w.Updates():
+				if !ok {
+					return
+				}
+				if e == nil || e.Operation() != jetstream.KeyValuePut {
+					continue
+				}
+				step, err := delivery.DecodeStep(e.Value())
+				if err != nil {
+					continue // not a step (a node's pause key never matches an ask id; anything else is not this ask's)
+				}
+				select {
+				case out <- step:
+				case <-ctx.Done():
+					return
+				}
+			}
+		}
+	}()
+	return out, nil
+}
+
+// FakeAsks is a test double of the bus for an asker's tests: each ask put is kept and, when Answer is set, its step is
+// written at once with what Answer says a build node wrote (running or ended). Write writes a step later. Safe for
+// concurrent use.
+type FakeAsks struct {
+	Answer func(a delivery.StepAsk) delivery.Step
+
+	mu       sync.Mutex
+	asks     []delivery.StepAsk
+	steps    map[string][]delivery.Step
+	watchers map[string][]chan delivery.Step
+}
+
+// PublishAsk is AskPublisher's.
+func (f *FakeAsks) PublishAsk(_ context.Context, _, id string, data []byte) error {
+	a, err := delivery.DecodeStepAsk(data)
+	if err != nil {
+		return err
+	}
+	f.mu.Lock()
+	f.asks = append(f.asks, a)
+	f.mu.Unlock()
+	if f.Answer != nil {
+		f.Write(f.Answer(a))
+	}
+	return nil
+}
+
+// Write writes an ask's step, as a build node does.
+func (f *FakeAsks) Write(step delivery.Step) {
+	f.mu.Lock()
+	if f.steps == nil {
+		f.steps, f.watchers = map[string][]delivery.Step{}, map[string][]chan delivery.Step{}
+	}
+	f.steps[step.ID] = append(f.steps[step.ID], step)
+	ws := append([]chan delivery.Step(nil), f.watchers[step.ID]...)
+	f.mu.Unlock()
+	for _, w := range ws {
+		w <- step
+	}
+}
+
+// End is Write: kept for the tests that end a step.
+func (f *FakeAsks) End(step delivery.Step) { f.Write(step) }
+
+// WatchAsk is AskWaiter's: what was written so far, then every write.
+func (f *FakeAsks) WatchAsk(ctx context.Context, _ string, askID string) (<-chan delivery.Step, error) {
+	out := make(chan delivery.Step, 64)
+	f.mu.Lock()
+	if f.steps == nil {
+		f.steps, f.watchers = map[string][]delivery.Step{}, map[string][]chan delivery.Step{}
+	}
+	for _, s := range f.steps[askID] {
+		out <- s
+	}
+	f.watchers[askID] = append(f.watchers[askID], out)
+	f.mu.Unlock()
+	go func() {
+		<-ctx.Done()
+		f.mu.Lock()
+		ws := f.watchers[askID]
+		for i, w := range ws {
+			if w == out {
+				f.watchers[askID] = append(ws[:i], ws[i+1:]...)
+				break
+			}
+		}
+		f.mu.Unlock()
+	}()
+	return out, nil
+}
+
+// Asks are the asks put so far.
+func (f *FakeAsks) Asks() []delivery.StepAsk {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return append([]delivery.StepAsk(nil), f.asks...)
+}

modules/mesh-delivery-builder/buildrun/asks_integration_test.go

@@ -0,0 +1,61 @@
+//go:build integration
+
+package buildrun
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/testbus"
+)
+
+// 1887/A4a, 1887/AC3 on the real bus: an ask put twice under one id is one message, and the asker reads the step a node
+// wrote under `<node>.<ask id>`.
+func TestAnAskIsPutOnceAndItsStepIsRead(t *testing.T) {
+	nc, err := nats.Connect(testbus.URL(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer nc.Close()
+	js, _ := jetstream.New(nc)
+	ctx := context.Background()
+	if _, err := js.CreateStream(ctx, jetstream.StreamConfig{Name: "SEAT_NODE_BUILD_GO", Subjects: []string{"mesh.seat.node-build-go.accept.>"},
+		Retention: jetstream.WorkQueuePolicy}); err != nil {
+		t.Fatal(err)
+	}
+	kv, err := js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: delivery.StepsBucket("mesh-build-go")})
+	if err != nil {
+		t.Fatal(err)
+	}
+	bus := JetStreamAsks{JS: js}
+	k := Asker{Publisher: bus, Waiter: bus, Bound: 5 * time.Second}
+	a := goAsk("mvl0frv18d1960")
+	for i := 0; i < 2; i++ {
+		if err := k.Put(ctx, a); err != nil {
+			t.Fatal(err)
+		}
+	}
+	s, _ := js.Stream(ctx, "SEAT_NODE_BUILD_GO")
+	if info, _ := s.Info(ctx); info.State.Msgs != 1 {
+		t.Fatalf("%d messages for one ask put twice", info.State.Msgs)
+	}
+	go func() {
+		time.Sleep(100 * time.Millisecond)
+		key, _ := delivery.AskStepKey("ace", a.ID)
+		running, _ := delivery.EncodeStep(delivery.Step{ID: a.ID, Tool: "delivery ask", Node: "ace", State: delivery.StepRunning, Started: time.Now()})
+		_, _ = kv.Put(ctx, key, running)
+		passed, _ := delivery.EncodeStep(delivery.Step{ID: a.ID, Tool: "delivery ask", Node: "ace", State: delivery.StepPassed, Started: time.Now(),
+			Result: json.RawMessage(`{"artifacts":[]}`)})
+		_, _ = kv.Put(ctx, key, passed)
+	}()
+	step, err := k.Passed(k.Wait(ctx, a))
+	if err != nil || step.Node != "ace" {
+		t.Fatalf("step %+v, %v", step, err)
+	}
+}

modules/mesh-delivery-builder/buildrun/asks_test.go

@@ -0,0 +1,234 @@
+package buildrun
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+)
+
+func goAsk(id string) delivery.StepAsk {
+	return delivery.StepAsk{ID: id, Kind: delivery.AskDelivery, Language: delivery.AskGo, Asker: "mesh-delivery-builder", At: time.Now(),
+		Build: &delivery.BuildJob{Module: "m", Path: ".", Fetch: map[string]any{"repository": "novox/x", "commit": strings.Repeat("a", 40)},
+			Artifacts: []delivery.AskArtifact{{Artifact: "program"}}}}
+}
+
+// 1887/A4a: an asker puts the ask once and answers the step a build node wrote for it, naming the node; one that did not
+// pass is an error naming the node and why; a wait of an ask already put puts nothing.
+func TestAnAskerPutsOnceAndReadsTheStep(t *testing.T) {
+	f := &FakeAsks{Answer: func(a delivery.StepAsk) delivery.Step {
+		return delivery.Step{ID: a.ID, Node: "ace", State: delivery.StepPassed, Result: []byte(`{"artifacts":[]}`)}
+	}}
+	k := Asker{Publisher: f, Waiter: f}
+	var seen []delivery.Step // issue 1890: a waiter that asks to see each value of the step sees it
+	step, err := k.Ask(WithStepSeen(context.Background(), func(s delivery.Step) { seen = append(seen, s) }), goAsk("mvl0frv18d1957"))
+	if err != nil || step.Node != "ace" || len(f.Asks()) != 1 || len(seen) != 1 || seen[0].Node != "ace" {
+		t.Fatalf("step %+v, %v, asks %d, seen %+v", step, err, len(f.Asks()), seen)
+	}
+	f.Answer = func(a delivery.StepAsk) delivery.Step {
+		return delivery.Step{ID: a.ID, Node: "shanks", State: delivery.StepRefused, Reason: "go 1.27 installed"}
+	}
+	if _, err := k.Ask(context.Background(), goAsk("mvl0frv18d1958")); err == nil || !strings.Contains(err.Error(), "shanks refused: go 1.27 installed") {
+		t.Fatalf("a refused step: %v", err)
+	}
+	// review round 2 item 1: an ask that waits in its stream for a free slot is not bounded; once a node writes its step
+	// running, the step is bounded from its start, and the error names the node.
+	g := &FakeAsks{}
+	k = Asker{Publisher: g, Waiter: g, Bound: 20 * time.Millisecond}
+	waiting, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	defer cancel()
+	if _, err := k.Wait(waiting, goAsk("mvl0frv18d1959")); err != context.DeadlineExceeded {
+		t.Fatalf("an ask no node took: %v, want it still waiting when ctx ended", err)
+	}
+	g.Write(delivery.Step{ID: "mvl0frv18d1961", Node: "ace", State: delivery.StepRunning, Started: time.Now()})
+	if _, err := k.Wait(context.Background(), goAsk("mvl0frv18d1961")); err == nil || !strings.Contains(err.Error(), "on ace did not end within") {
+		t.Fatalf("a step that never ends: %v", err)
+	}
+	if len(g.Asks()) != 0 {
+		t.Fatal("a wait put an ask")
+	}
+	// Issue 1930: the bound is on a step that stands still, not on its age. A step past one bound from its start that entered a
+	// new phase inside the bound is waited for until it ends; one that stood a whole bound in a phase fails at once, naming
+	// the phase; one three bounds from its start ends, said as kept moving. The steps' own times stand for the clock, so the
+	// bound is an hour no loaded machine reaches and no case waits on a pause (the check of 2026-11-02 22:35 tripped one
+	// of 60 ms).
+	k = Asker{Publisher: g, Waiter: g, Bound: time.Hour}
+	now := time.Now()
+	g.Write(delivery.Step{ID: "mvl0frv18d1980", Node: "ace", State: delivery.StepRunning, Started: now.Add(-90 * time.Minute), Phase: "pb", PhaseAt: now})
+	g.Write(delivery.Step{ID: "mvl0frv18d1980", Node: "ace", State: delivery.StepPassed})
+	if step, err := k.Wait(context.Background(), goAsk("mvl0frv18d1980")); err != nil || step.State != delivery.StepPassed {
+		t.Fatalf("a step that kept moving past its bound: %+v, %v", step, err)
+	}
+	g.Write(delivery.Step{ID: "mvl0frv18d1981", Node: "ace", State: delivery.StepRunning, Started: now.Add(-time.Hour), Phase: "integration: tests", PhaseAt: now.Add(-time.Hour)})
+	if _, err := k.Wait(context.Background(), goAsk("mvl0frv18d1981")); err == nil || !strings.Contains(err.Error(), `stood still in "integration: tests"`) {
+		t.Fatalf("a step that stood still in a phase: %v", err)
+	}
+	g.Write(delivery.Step{ID: "mvl0frv18d1982", Node: "ace", State: delivery.StepRunning, Started: now.Add(-3 * time.Hour), Phase: "qz", PhaseAt: now})
+	if _, err := k.Wait(context.Background(), goAsk("mvl0frv18d1982")); err == nil || !strings.Contains(err.Error(), "kept moving") {
+		t.Fatalf("a step that never stops moving: %v", err)
+	}
+	// Issue 734: an ask the build seat gave up on (DEAD_LETTERS keeps its copy with the ask's id) ends its wait as failed
+	// with the words, though a node had taken it; under NotTakenBound one no node takes ends at the bound; a step written
+	// first is answered as the node wrote it.
+	dead := &DeadLetters{}
+	lw := LostAskWaiter{Inner: g, Dead: dead}
+	k = Asker{Publisher: g, Waiter: lw, Bound: time.Minute}
+	g.Write(delivery.Step{ID: "mvl0frv18d1970", Node: "ace", State: delivery.StepRunning, Started: time.Now()})
+	given, ok := GivenUpOf(map[string][]string{"Mesh-Dead-Msg-Id": {"mvl0frv18d1970"}, "Mesh-Dead-Deliveries": {"5"},
+		"Mesh-Dead-Stream": {"SEAT_NODE_BUILD_GO"}, "Mesh-Dead-Gave-Up": {"2026-10-26T12:26:40Z"}})
+	if !ok {
+		t.Fatal("a dead letter's headers were not read")
+	}
+	go dead.Heard(given)
+	step, err = k.Wait(context.Background(), goAsk("mvl0frv18d1970"))
+	if err != nil || step.State != delivery.StepFailed || !IsLost(step) ||
+		!strings.Contains(step.Reason, LostWords+" after 5 deliveries at 2026-10-26T12:26:40Z") {
+		t.Fatalf("a given-up ask: %+v, %v", step, err)
+	}
+	if _, err := k.Passed(step, nil); err == nil || !strings.Contains(err.Error(), "on "+LostNode+" failed: "+LostWords) {
+		t.Fatalf("a given-up ask's error: %v", err)
+	}
+	step, err = k.Wait(NotTakenBound(context.Background(), 20*time.Millisecond), goAsk("mvl0frv18d1971"))
+	if err != nil || !IsNotTaken(step) || IsLost(step) {
+		t.Fatalf("an ask no node took: %+v, %v", step, err)
+	}
+	g.Write(delivery.Step{ID: "mvl0frv18d1972", Node: "g14", State: delivery.StepPassed})
+	if step, err = k.Wait(NotTakenBound(context.Background(), time.Minute), goAsk("mvl0frv18d1972")); err != nil || step.Node != "g14" {
+		t.Fatalf("a step written: %+v, %v", step, err)
+	}
+	// Review round 1 of issue 734: a hearing the bus refuses at start is deaf and says so, never holds the start up, and
+	// tries again on the next ask waited for; heard, it says so and hands the given-up asks on.
+	fol := &refusingFollower{refuse: 1}
+	var mu sync.Mutex
+	var told []Hearing
+	hearing := NewDeadLetterHearing(context.Background(), fol, []string{delivery.AskGo}, dead, nil,
+		func(h Hearing) { mu.Lock(); told = append(told, h); mu.Unlock() })
+	hearing.Wait()
+	if why := hearing.Deaf(); !strings.Contains(why, "SEAT_NODE_BUILD_GO: permissions violation") {
+		t.Fatalf("a refused hearing says %q", why)
+	}
+	k = Asker{Publisher: g, Waiter: LostAskWaiter{Inner: g, Dead: dead, Hearing: hearing}, Bound: time.Minute}
+	g.Write(delivery.Step{ID: "mvl0frv18d1973", Node: "g14", State: delivery.StepPassed})
+	if _, err := k.Wait(context.Background(), goAsk("mvl0frv18d1973")); err != nil {
+		t.Fatal(err)
+	}
+	hearing.Wait()
+	mu.Lock()
+	if hearing.Deaf() != "" || len(told) != 2 || told[0].Heard || !told[1].Heard || fol.calls() != 2 {
+		t.Fatalf("after an ask: deaf %q, told %+v, followed %d times", hearing.Deaf(), told, fol.calls())
+	}
+	mu.Unlock()
+	fol.heard(GivenUp{AskID: "mvl0frv18d1974", Deliveries: 5})
+	step, err = k.Wait(context.Background(), goAsk("mvl0frv18d1974"))
+	if err != nil || !IsLost(step) {
+		t.Fatalf("an ask heard given up after the hearing came back: %+v, %v", step, err)
+	}
+	// The lost check of 2026-10-28: a step whose own watch went deaf is read at the next nudge (a step of its build module
+	// ended) and answered; a nudge of another build module reads nothing; a watch that closes is opened again.
+	d := &FakeAsks{}
+	heard := &HeardEnds{Inner: deafWatch{}, Read: d}
+	k = Asker{Publisher: d, Waiter: heard, Bound: time.Minute}
+	d.Write(delivery.Step{ID: "mvl0frv18d1980", Node: "shanks", State: delivery.StepPassed})
+	got := make(chan delivery.Step, 1)
+	go func() { s, _ := k.Wait(context.Background(), goAsk("mvl0frv18d1980")); got <- s }()
+	for heard.Waiting() == 0 {
+		time.Sleep(time.Millisecond)
+	}
+	heard.Nudge(NodeBuildModule)
+	select {
+	case s := <-got:
+		t.Fatalf("a nudge of another build module answered %+v", s)
+	case <-time.After(20 * time.Millisecond):
+	}
+	heard.Nudge(GoBuildModule)
+	if s := <-got; s.State != delivery.StepPassed || s.Node != "shanks" {
+		t.Fatalf("a step its watch never handed over: %+v", s)
+	}
+	closing := &HeardEnds{Inner: &closingWatch{inner: d}, Read: d}
+	if s, err := (Asker{Publisher: d, Waiter: closing}).Wait(context.Background(), goAsk("mvl0frv18d1980")); err != nil || s.State != delivery.StepPassed {
+		t.Fatalf("a watch that closed once: %+v, %v", s, err)
+	}
+	for _, row := range []struct {
+		h    *Hearing
+		want string
+	}{{nil, health.StateUnhealthy}, {&told[0], health.StateUnhealthy}, {&told[1], health.StateHealthy}} {
+		var raw []byte
+		if row.h != nil {
+			raw, _ = json.Marshal(row.h)
+		}
+		if a := HearingHealth(raw); a.State != row.want || a.Why == "" {
+			t.Errorf("health of %+v = %+v, want %s", row.h, a, row.want)
+		}
+	}
+}
+
+// Review (issue 734 path): an ask taken again by the same node (its build module replaced mid-run) is bounded from the
+// new run's start, not the first run's. The steps' own times stand for the clock: the first run started now, the second a
+// whole bound ago, so the wait ends at once on the second run's bound where the first run's would wait an hour; no case
+// waits on a pause a loaded machine can outlast (the check of 2026-11-02 22:35 tripped one of 60 ms). The context's
+// bound is reached only by a wait that kept the first run's start.
+func TestARedeliveryToTheSameNodeRestartsTheBound(t *testing.T) {
+	f := &FakeAsks{}
+	k := Asker{Publisher: f, Waiter: f, Bound: time.Hour}
+	const id = "mvl0frv18d1962"
+	now := time.Now()
+	f.Write(delivery.Step{ID: id, Node: "ace", State: delivery.StepRunning, Started: now})
+	f.Write(delivery.Step{ID: id, Node: "ace", State: delivery.StepRunning, Started: now.Add(-time.Hour)})
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	if _, err := k.Wait(ctx, goAsk(id)); err == nil || !strings.Contains(err.Error(), "on ace did not end within 1h0m0s of its start") {
+		t.Fatalf("a redelivered run a bound old: %v, want its own bound to end the wait", err)
+	}
+}
+
+// refusingFollower refuses the first `refuse` follows, as the bus does before the asker's grant is composed.
+type refusingFollower struct {
+	mu     sync.Mutex
+	refuse int
+	n      int
+	hand   func(GivenUp)
+}
+
+func (f *refusingFollower) Follow(_ context.Context, _ string, _ time.Time, heard func(GivenUp)) (func(), error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.n++
+	if f.n <= f.refuse {
+		return nil, errors.New("permissions violation")
+	}
+	f.hand = heard
+	return func() {}, nil
+}
+
+func (f *refusingFollower) calls() int { f.mu.Lock(); defer f.mu.Unlock(); return f.n }
+
+func (f *refusingFollower) heard(g GivenUp) { f.mu.Lock(); h := f.hand; f.mu.Unlock(); h(g) }
+
+// deafWatch is a watch of an ask's step that stays open and hears nothing.
+type deafWatch struct{}
+
+func (deafWatch) WatchAsk(context.Context, string, string) (<-chan delivery.Step, error) {
+	return make(chan delivery.Step), nil
+}
+
+// closingWatch closes its first watch at once, and hands the later ones to inner.
+type closingWatch struct {
+	inner  AskWaiter
+	closed bool
+}
+
+func (c *closingWatch) WatchAsk(ctx context.Context, module, askID string) (<-chan delivery.Step, error) {
+	if !c.closed {
+		c.closed = true
+		ch := make(chan delivery.Step)
+		close(ch)
+		return ch, nil
+	}
+	return c.inner.WatchAsk(ctx, module, askID)
+}

modules/mesh-delivery-builder/buildrun/choose.go

@@ -0,0 +1,88 @@
+package buildrun
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// ChooseNodes picks up to want build nodes for a language (ADR 0478 clause 3): the nodes whose toolchains key reports the
+// version the nodes agree on, the ones with room under their build capacity first (places), then the fewest lanes the
+// part has running or chosen there, a tie broken by the node's name. A place is reserved on each node chosen, in the
+// same step as the choice, so builds choosing at once do not choose the same full node while another has room; the
+// caller takes the place (Places.Acquire) or gives it up (Places.Cancel). A node at its capacity is still chosen when
+// the others are too (fewer than want have room): its lane waits for a place. A node qualifies only when qualifies is true
+// of it (online and its build module healthy; nil means every node does). It answers the toolchain all the reporting nodes
+// agree on, qualifying or not, as the indexer computes it. When nothing is reported, or the nodes report different
+// versions (so the indexer agreed none), it fails naming the language and why; when no reporting node qualifies it fails
+// naming the nodes. A node whose build module refuses on its toolchain refuses the step, and the build fails naming it.
+func ChooseNodes(language string, entries []delivery.NodeToolchain, places *Places, qualifies func(node string) bool, want int) ([]string, delivery.Toolchain2, error) {
+	tc, none := delivery.AgreedToolchain(entries)
+	if none != "" {
+		return nil, delivery.Toolchain2{}, fmt.Errorf("no %s build node qualifies: %s", language, none)
+	}
+	nodes, err := choose(language, entries, places, qualifies, want)
+	return nodes, tc, err
+}
+
+// ChooseAnyNodes is ChooseNodes for artifacts that need no toolchain, such as an archive (ADR 0478 clause 1): the
+// build module's nodes agree on nothing, so any node of the build module that qualifies is chosen, by capacity and load only.
+func ChooseAnyNodes(language string, entries []delivery.NodeToolchain, places *Places, qualifies func(node string) bool, want int) ([]string, error) {
+	return choose(language, entries, places, qualifies, want)
+}
+
+func choose(language string, entries []delivery.NodeToolchain, places *Places, qualifies func(node string) bool, want int) ([]string, error) {
+	if places == nil {
+		places = &Places{}
+	}
+	nodes := make([]string, 0, len(entries))
+	var reporting []string
+	seen := map[string]bool{}
+	for _, e := range entries {
+		if seen[e.Node] {
+			continue
+		}
+		seen[e.Node] = true
+		reporting = append(reporting, e.Node)
+		if places.CapacityOf(e.Node) > 0 && (qualifies == nil || qualifies(e.Node)) { // a capacity of 0 keeps the part off a node
+			nodes = append(nodes, e.Node)
+		}
+	}
+	if len(nodes) == 0 {
+		sort.Strings(reporting)
+		return nil, fmt.Errorf("no %s build node qualifies: %s report the toolchain, and none is online with a healthy build module and a build capacity", language, strings.Join(reporting, ", "))
+	}
+	return places.choose(nodes, want), nil
+}
+
+// DigestsDifferPrefix opens the error of a build whose nodes built an artifact to different digests (ADR 0478 clause 4):
+// such a key is not built again as a new revision, since the same source on the same toolchains gave two answers and
+// building again settles nothing; it waits for another fingerprint.
+const DigestsDifferPrefix = "digests differ:"
+
+// Agree is the one digest every node built an artifact to (ADR 0478 clause 4), or an error naming each node and its
+// digest when they differ. One node's digest agrees with itself.
+func Agree(artifact string, byNode map[string]string) (string, error) {
+	nodes := make([]string, 0, len(byNode))
+	for n := range byNode {
+		nodes = append(nodes, n)
+	}
+	sort.Strings(nodes)
+	var first string
+	for i, n := range nodes {
+		if i == 0 {
+			first = byNode[n]
+			continue
+		}
+		if byNode[n] != first {
+			msg := fmt.Sprintf("%s the nodes built %s to different digests:", DigestsDifferPrefix, artifact)
+			for _, n := range nodes {
+				msg += fmt.Sprintf(" %s %s;", n, byNode[n])
+			}
+			return "", fmt.Errorf("%s", msg[:len(msg)-1])
+		}
+	}
+	return first, nil
+}

modules/mesh-delivery-builder/buildrun/choose_test.go

@@ -0,0 +1,109 @@
+package buildrun
+
+import (
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+const digest = "sha256:2222222222222222222222222222222222222222222222222222222222222222"
+
+func hex64(c byte) string { return strings.Repeat(string(c), 64) }
+
+func tcs(language, version string, nodes ...string) []delivery.NodeToolchain {
+	var out []delivery.NodeToolchain
+	for _, n := range nodes {
+		out = append(out, delivery.NodeToolchain{Node: n, Toolchain: delivery.Toolchain{Language: language, Version: version, Recipe: "1"}})
+	}
+	return out
+}
+
+func chooseTakesTheAgreedNodesWithFewestRunningStepsTiesByName(t *testing.T) { // 1607/AC4, ADR 0478 clause 3
+	entries := tcs("go", "go1.27.1", "novox", "ace", "g14", "shanks")
+	nodes, tc, err := ChooseNodes("go", entries, placesRunning(map[string]int{"novox": 3, "ace": 1, "g14": 1, "shanks": 0}), nil, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(nodes) != 2 || nodes[0] != "shanks" || nodes[1] != "ace" {
+		t.Errorf("nodes = %v, want [shanks ace]: fewest steps first, a tie by name", nodes)
+	}
+	if tc.Version != "go1.27.1" || tc.Recipe != "1" || tc.Language != "go" {
+		t.Errorf("toolchain = %+v", tc)
+	}
+}
+
+func chooseWithOneNodeAnswersOneNode(t *testing.T) { // 1607/AC4
+	nodes, _, err := ChooseNodes("go", tcs("go", "go1.27.1", "novox"), nil, nil, 2)
+	if err != nil || len(nodes) != 1 || nodes[0] != "novox" {
+		t.Errorf("nodes = %v, err %v, want [novox]", nodes, err)
+	}
+}
+
+func chooseFailsNamingTheLanguageAndTheVersionsWhenNoNodeQualifies(t *testing.T) { // 1607/AC4
+	_, _, err := ChooseNodes("typescript", nil, nil, nil, 2)
+	if err == nil || !strings.Contains(err.Error(), "typescript") || !strings.Contains(err.Error(), delivery.ToolchainNoReport) {
+		t.Errorf("no report: error = %v, want it to name typescript and %q", err, delivery.ToolchainNoReport)
+	}
+	entries := append(tcs("go", "go1.27.1", "novox"), tcs("go", "go1.26.0", "ace")...)
+	_, _, err = ChooseNodes("go", entries, nil, nil, 2)
+	if err == nil || !strings.Contains(err.Error(), "go1.27.1") || !strings.Contains(err.Error(), "go1.26.0") || !strings.Contains(err.Error(), "go") {
+		t.Errorf("disagreeing nodes: error = %v, want both versions named", err)
+	}
+}
+
+func agreeNeedsEqualDigestsAndNamesBothNodesWhenTheyDiffer(t *testing.T) { // 1607/AC4, ADR 0478 clause 4
+	d, err := Agree("tool", map[string]string{"ace": digest, "novox": digest})
+	if err != nil || d != digest {
+		t.Errorf("Agree = %q, %v, want %q", d, err, digest)
+	}
+	_, err = Agree("tool", map[string]string{"ace": digest, "novox": "sha256:" + hex64('9')})
+	if err == nil || !strings.Contains(err.Error(), "ace") || !strings.Contains(err.Error(), "novox") || !strings.Contains(err.Error(), digest) || !strings.Contains(err.Error(), hex64('9')) || !strings.Contains(err.Error(), "tool") {
+		t.Errorf("differing digests: error = %v, want the artifact, both nodes and both digests", err)
+	}
+	if d, err := Agree("tool", map[string]string{"ace": digest}); err != nil || d != digest {
+		t.Errorf("one node: %q, %v", d, err)
+	}
+}
+
+func chooseSkipsNodesThatAreNotOnlineAndFailsNamingThemWhenNoneIs(t *testing.T) { // 1607 review 3, ADR 0478 clause 3
+	entries := tcs("go", "go1.27.1", "ace", "g14", "novox")
+	online := func(n string) bool { return n != "g14" } // a sleeping laptop
+	nodes, tc, err := ChooseNodes("go", entries, placesRunning(map[string]int{"novox": 5}), online, 2)
+	if err != nil || len(nodes) != 2 || nodes[0] != "ace" || nodes[1] != "novox" || tc.Version != "go1.27.1" {
+		t.Errorf("nodes = %v, toolchain %+v, err %v, want [ace novox] with g14 left out although it runs nothing", nodes, tc, err)
+	}
+	_, tc, err = ChooseNodes("go", entries, nil, func(string) bool { return false }, 2)
+	if err == nil || !strings.Contains(err.Error(), "online") || !strings.Contains(err.Error(), "g14") || !strings.Contains(err.Error(), "go") {
+		t.Errorf("none online: error = %v, want it to name the nodes that report and that none is online", err)
+	}
+	if tc.Version != "go1.27.1" {
+		t.Errorf("none online: the agreed toolchain %+v is still answered", tc)
+	}
+}
+
+// placesRunning is Places with these steps counted as running, for a test of the choice.
+func placesRunning(running map[string]int) *Places {
+	return &Places{running: running, changed: make(chan struct{})}
+}
+
+func choosePrefersNodesBelowTheirCapacity(t *testing.T) { // round 3
+	entries := tcs("go", "go1.27.1", "ace", "novox", "shanks")
+	// shanks has capacity 3 with 2 running: room; ace has the default 1 with 1 running: none; novox has none running.
+	p := placesRunning(map[string]int{"shanks": 2, "ace": 1})
+	p.Capacity = map[string]int{"shanks": 3}
+	nodes, _, err := ChooseNodes("go", entries, p, nil, 2)
+	if err != nil || len(nodes) != 2 || nodes[0] != "novox" || nodes[1] != "shanks" {
+		t.Errorf("nodes = %v, err %v, want [novox shanks]: the nodes with room, ace at capacity left out", nodes, err)
+	}
+}
+
+// The choice of the nodes a step runs on and the agreement of their answers, one table of cases (the test budget).
+func TestChoosingTheNodesOfAStep(t *testing.T) {
+	t.Run("choose takes the agreed nodes with fewest running steps ties by name", chooseTakesTheAgreedNodesWithFewestRunningStepsTiesByName)
+	t.Run("choose with one node answers one node", chooseWithOneNodeAnswersOneNode)
+	t.Run("choose fails naming the language and the versions when no node qualifies", chooseFailsNamingTheLanguageAndTheVersionsWhenNoNodeQualifies)
+	t.Run("agree needs equal digests and names both nodes when they differ", agreeNeedsEqualDigestsAndNamesBothNodesWhenTheyDiffer)
+	t.Run("choose skips nodes that are not online and fails naming them when none is", chooseSkipsNodesThatAreNotOnlineAndFailsNamingThemWhenNoneIs)
+	t.Run("choose prefers nodes below their capacity", choosePrefersNodesBelowTheirCapacity)
+}

modules/mesh-delivery-builder/buildrun/doc.go

@@ -0,0 +1,5 @@
+// Package buildrun holds the parts every module that runs steps on the build modules shares: the caller, the steps
+// watch and the runner of a long step (ADR 0469), the sets of presence, toolchains and healthy build modules, the
+// places a node offers by capacity, and the choice of build nodes (ADR 0478). The builder and the checker of the
+// delivery use them; they moved here from the builder's own package so neither keeps a copy (issue 1671, ADR 0484).
+package buildrun

modules/mesh-delivery-builder/buildrun/go.mod

@@ -0,0 +1,23 @@
+module git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun
+
+go 1.26.0
+
+require (
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261104174359-05b3e2e1b94f
+	github.com/nats-io/nats.go v1.54.0
+)
+
+require (
+	git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639 // indirect
+	github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op // indirect
+	github.com/google/go-tpm v0.9.8 // indirect
+	github.com/klauspost/compress v1.20.1 // indirect
+	github.com/minio/highwayhash v1.0.4 // indirect
+	github.com/nats-io/jwt/v2 v2.8.2 // indirect
+	github.com/nats-io/nats-server/v2 v2.11.17 // indirect
+	github.com/nats-io/nkeys v0.4.16 // indirect
+	github.com/nats-io/nuid v1.0.1 // indirect
+	golang.org/x/crypto v0.57.0 // indirect
+	golang.org/x/sys v0.48.0 // indirect
+	golang.org/x/time v0.16.0 // indirect
+)

modules/mesh-delivery-builder/buildrun/go.sum

@@ -0,0 +1,29 @@
+git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639 h1:Zt7CfWt2S2W/fVgWNyW2u2+xwz051LXvGxVTNIyfhdM=
+git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639/go.mod h1:0dD1XEJBJ0G5UYDQxSZI84nuujb6m3tOpJl4C8rQVvg=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261104174359-05b3e2e1b94f h1:jDsfDMd48MXY9Zershc3eRxnhmx2sSpUfQkLq5jAIds=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261104174359-05b3e2e1b94f/go.mod h1:08OomDXdwVN8/87nyDtv5R3rH/6LoP8SFFXz30bTYCM=
+github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op h1:1BOWQJweNyvZMlpAHXGLiZQn9S+QXGcz3xh94lC0w6E=
+github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
+github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=
+github.com/google/go-tpm v0.9.8/go.mod h1:h9jEsEECg7gtLis0upRBQU+GhYVH6jMjrFxI8u6bVUY=
+github.com/klauspost/compress v1.20.1 h1:T7kKElXUMXrUJ2E9QhQhxFtcK5rPyLdsGZvdbLMPdiQ=
+github.com/klauspost/compress v1.20.1/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
+github.com/minio/highwayhash v1.0.4 h1:asJizugGgchQod2ja9NJlGOWq4s7KsAWr5XUc9Clgl4=
+github.com/minio/highwayhash v1.0.4/go.mod h1:GGYsuwP/fPD6Y9hMiXuapVvlIUEhFhMTh0rxU3ik1LQ=
+github.com/nats-io/jwt/v2 v2.8.2 h1:XXRgB60MSTnqsRwejQurVDs/hcv2dkt+86GjI+I/bMc=
+github.com/nats-io/jwt/v2 v2.8.2/go.mod h1:Ag/56sq9OblL4JgdYufDd16Egb17Kr/8WwwuO/forVc=
+github.com/nats-io/nats-server/v2 v2.11.17 h1:GKEghcFK6A+aFx11Yf1LjgLC3txAwvyhnYzhBIQZA8I=
+github.com/nats-io/nats-server/v2 v2.11.17/go.mod h1:B1sFVz4StNosQ903ak4N1G01Fl/9f8e06mXpFIE2K24=
+github.com/nats-io/nats.go v1.54.0 h1:vsXoOxjHp/GmPUN+EcI7uOf/uB+iAP+kEsAFNQN0yzA=
+github.com/nats-io/nats.go v1.54.0/go.mod h1:y+DZoD1oBOYfZTU681eTUiUjI0vbqYGixNVFHcjHJ0k=
+github.com/nats-io/nkeys v0.4.16 h1:rd5oAuLOb8mnAycB0xleuEBNS1pVVnN0fv/FF34Eypg=
+github.com/nats-io/nkeys v0.4.16/go.mod h1:llLgWoI0o4z/Q57q2R1kHfmocyhGV6VG/U18Glg1Afs=
+github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
+github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OSON2c=
+golang.org/x/crypto v0.57.0 h1:3ZVCjf8Ggz7zneR/EHRVx68Ctf+2pmIMP2UFhh9cC6M=
+golang.org/x/crypto v0.57.0/go.mod h1:Fdz0i5U6CoizGwLda9DttjSk6qlZo25zYNtR+ycvuZA=
+golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.48.0 h1:bbX/i/6MgT9BVLM9RT1thmxL04yeTAhbEz4SyadbXoo=
+golang.org/x/sys v0.48.0/go.mod h1:hNLxWAXmnKAxqDtdwIYC4bM9oQPEecfsnNMuSxOs3og=
+golang.org/x/time v0.16.0 h1:vMb6ptszcQMkcwiRTAuNNU50gom6++Q/6gY2hDM6VDE=
+golang.org/x/time v0.16.0/go.mod h1:rVKOqvZeKvrDKTQiAHJ7wmwP0RzleSphoEA9RcdLA0s=

modules/mesh-delivery-builder/buildrun/have.go

@@ -0,0 +1,56 @@
+package buildrun
+
+import (
+	"sync"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// HaveSet holds what each node's node-engine says of each module on it (node-engine_have, key `<node>.<module>`): the
+// builder reads it to know whether a node's build module is running and healthy, since a build module whose installed
+// toolchain is not the one its recipe builds with is unhealthy (mesh-build-go build_go_health) and its steps would
+// refuse (ADR 0478 clause 3). A module the node-engine has written no key of is not healthy. Safe for use from the watch
+// and from a build at once.
+type HaveSet struct {
+	mu      sync.Mutex
+	healthy map[string]bool // by `<node>.<module>`
+}
+
+// Put takes a change of the have bucket in and answers whether a module's healthy state changed. A node's own key
+// (`<node>.node`) and a value that is not a have are left out.
+func (s *HaveSet) Put(key string, value []byte, deleted bool) bool {
+	node, module, isNode, err := delivery.ParseHaveKey(key)
+	if err != nil || isNode {
+		return false
+	}
+	ok := false
+	if !deleted {
+		h, err := delivery.DecodeHave(value)
+		if err != nil {
+			return false
+		}
+		ok = h.Phase == delivery.PhaseRunning && h.Health == delivery.HealthOK
+	}
+	k := node + "." + module
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.healthy[k] == ok {
+		return false
+	}
+	if s.healthy == nil {
+		s.healthy = map[string]bool{}
+	}
+	if ok {
+		s.healthy[k] = true
+	} else {
+		delete(s.healthy, k)
+	}
+	return true
+}
+
+// Healthy is whether the module on the node was last seen running and healthy.
+func (s *HaveSet) Healthy(node, module string) bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.healthy[node+"."+module]
+}

modules/mesh-delivery-builder/buildrun/heardends.go

@@ -0,0 +1,236 @@
+package buildrun
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **A step's end is never only its own watch's to hear** (the lost check of 2026-10-28: mesh-catalog #553's verdict
+// stayed running after its step mvsgthyjed5786 had passed on shanks at 19:09:31Z; the watch of that one key, opened at
+// 18:46:05Z, heard neither the step's start nor its end and never closed, while a watch opened at 18:58:48Z heard its own
+// step end). HeardEnds stands between the asker (Asker) and the watch of each ask's step key: when it is
+// nudged, every ask it waits on reads its step keys now (a read, not the watch) and hands what it reads to its wait, so a
+// step that ended is judged even when its own watch went deaf. A watch that closes under a wait is opened again, at most
+// reopenTries times. It is nudged on an event (Nudge): any step of the same build module ending (one watch of each steps
+// state, HearEnds), a reconnect to the bus, and whatever else the asker hears (the checker: checker_ask_again).
+// It holds no timer. Every asker of the build seats waits through it (the checker and the builder, HearEnds).
+
+// StepReader reads, now, every step a build module's steps state holds for an ask: its keys `*.<ask id>`.
+type StepReader interface {
+	AskSteps(ctx context.Context, module, askID string) ([]delivery.Step, error)
+}
+
+// reopenTries is how often a wait opens its ask's watch again after it closed, before the wait ends failed.
+const reopenTries = 3
+
+// HeardEnds is an AskWaiter over Inner that also reads an ask's steps when nudged. Safe for concurrent use.
+type HeardEnds struct {
+	Inner AskWaiter
+	Read  StepReader
+	Logf  func(format string, args ...any)
+
+	mu      sync.Mutex
+	waiting map[string]*waitedAsk // by ask id
+}
+
+type waitedAsk struct {
+	module string
+	nudge  chan struct{}
+}
+
+func (h *HeardEnds) logf(format string, args ...any) {
+	if h.Logf != nil {
+		h.Logf(format, args...)
+	}
+}
+
+// WatchAsk is AskWaiter's: what Inner's watch hands, and, at each nudge, what the ask's keys hold now.
+func (h *HeardEnds) WatchAsk(ctx context.Context, module, askID string) (<-chan delivery.Step, error) {
+	in, err := h.Inner.WatchAsk(ctx, module, askID)
+	if err != nil {
+		return nil, err
+	}
+	w := &waitedAsk{module: module, nudge: make(chan struct{}, 1)}
+	h.mu.Lock()
+	if h.waiting == nil {
+		h.waiting = map[string]*waitedAsk{}
+	}
+	h.waiting[askID] = w
+	h.mu.Unlock()
+	out := make(chan delivery.Step)
+	go func() {
+		defer close(out)
+		defer func() {
+			h.mu.Lock()
+			if h.waiting[askID] == w {
+				delete(h.waiting, askID)
+			}
+			h.mu.Unlock()
+		}()
+		send := func(s delivery.Step) bool {
+			select {
+			case out <- s:
+				return true
+			case <-ctx.Done():
+				return false
+			}
+		}
+		reopened := 0
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case s, ok := <-in:
+				if !ok {
+					if ctx.Err() != nil || reopened >= reopenTries {
+						h.logf("the watch of the ask %s's step on %s closed %d times; its wait ends", askID, module, reopened+1)
+						return
+					}
+					reopened++
+					if in, err = h.Inner.WatchAsk(ctx, module, askID); err != nil {
+						h.logf("the watch of the ask %s's step on %s closed and cannot be opened again, so its wait ends: %v", askID, module, err)
+						return
+					}
+					h.logf("the watch of the ask %s's step on %s closed; opened again (%d of %d)", askID, module, reopened, reopenTries)
+					continue
+				}
+				if !send(s) {
+					return
+				}
+			case <-w.nudge:
+				if h.Read == nil {
+					continue
+				}
+				steps, err := h.Read.AskSteps(ctx, module, askID)
+				if err != nil {
+					h.logf("the steps of the ask %s on %s cannot be read: %v", askID, module, err)
+					continue
+				}
+				for _, s := range steps {
+					if s.State != delivery.StepRunning {
+						h.logf("the ask %s's step on %s ended %s, read at a nudge: its watch had not handed it over", askID, s.Node, s.State)
+					}
+					if !send(s) {
+						return
+					}
+				}
+			}
+		}
+	}()
+	return out, nil
+}
+
+// Nudge has every ask waited on of module read its steps now; module "" nudges every ask.
+func (h *HeardEnds) Nudge(module string) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	for _, w := range h.waiting {
+		if module == "" || w.module == module {
+			select {
+			case w.nudge <- struct{}{}:
+			default: // a nudge is pending already
+			}
+		}
+	}
+}
+
+// Waiting is how many asks are waited on now.
+func (h *HeardEnds) Waiting() int {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	return len(h.waiting)
+}
+
+// AskSteps is StepReader's: the keys `*.<ask id>` of the build module's steps state, read now.
+func (s JetStreamAsks) AskSteps(ctx context.Context, module, askID string) ([]delivery.Step, error) {
+	pattern, err := delivery.AskStepWatch(askID)
+	if err != nil {
+		return nil, err
+	}
+	kv, err := s.JS.KeyValue(ctx, delivery.StepsBucket(module))
+	if err != nil {
+		return nil, fmt.Errorf("the bucket %s: %w", delivery.StepsBucket(module), err)
+	}
+	lister, err := kv.ListKeysFiltered(ctx, pattern)
+	if err != nil {
+		return nil, err
+	}
+	var out []delivery.Step
+	for key := range lister.Keys() {
+		e, err := kv.Get(ctx, key)
+		if err != nil {
+			continue // deleted between the list and the read
+		}
+		if step, err := delivery.DecodeStep(e.Value()); err == nil {
+			out = append(out, step)
+		}
+	}
+	return out, nil
+}
+
+// HearEnds is the HeardEnds every asker of the build seats waits through: over inner (the asks' own watches, or a
+// LostAskWaiter's inner), reading with asks, and nudged at each step end of each of modules (one watch of each steps state,
+// updates only; one that closes is opened again, and said and left after reopenTries closes in a row that heard nothing). The asker nudges it at a reconnect too (Nudge("")).
+func HearEnds(ctx context.Context, asks JetStreamAsks, inner AskWaiter, modules []string, logf func(string, ...any)) *HeardEnds {
+	if logf == nil {
+		logf = func(string, ...any) {}
+	}
+	h := &HeardEnds{Inner: inner, Read: asks, Logf: logf}
+	for _, module := range modules {
+		kv, err := asks.JS.KeyValue(ctx, delivery.StepsBucket(module))
+		if err != nil {
+			logf("the steps of %s cannot be read (%v): an ask whose own watch goes deaf is read only at a reconnect", module, err)
+			continue
+		}
+		go h.follow(ctx, kv, module)
+	}
+	return h
+}
+
+func (h *HeardEnds) follow(ctx context.Context, kv jetstream.KeyValue, module string) {
+	silent := 0 // closes in a row having heard nothing
+	for ctx.Err() == nil {
+		w, err := kv.WatchAll(ctx, jetstream.UpdatesOnly())
+		if err != nil {
+			h.logf("the steps of %s cannot be watched, so an ask whose own watch goes deaf is read only at a reconnect: %v", module, err)
+			return
+		}
+		heard := false
+		for e := range w.Updates() {
+			if e == nil || e.Operation() != jetstream.KeyValuePut {
+				continue
+			}
+			heard = true
+			if step, err := delivery.DecodeStep(e.Value()); err == nil && step.State != delivery.StepRunning {
+				h.Nudge(module)
+			}
+		}
+		_ = w.Stop()
+		if ctx.Err() != nil {
+			return
+		}
+		h.Nudge(module) // a step may have ended while the watch was closing
+		if heard {
+			silent = 0
+		} else if silent++; silent >= reopenTries {
+			h.logf("the watch of the steps of %s closed %d times in a row having heard nothing, so it is left: an ask whose own watch goes deaf is read only at a reconnect", module, silent)
+			return
+		}
+		h.logf("the watch of the steps of %s closed; opened again", module)
+	}
+}
+
+// AskSteps is StepReader's: the last step written for the ask, if any.
+func (f *FakeAsks) AskSteps(_ context.Context, _ string, askID string) ([]delivery.Step, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if s := f.steps[askID]; len(s) > 0 {
+		return []delivery.Step{s[len(s)-1]}, nil
+	}
+	return nil, nil
+}

modules/mesh-delivery-builder/buildrun/lostask.go

@@ -0,0 +1,503 @@
+package buildrun
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+	"git.novox.be/novox/mesh-sdk/go/process"
+)
+
+// **An ask the build seat gave up on ends its step** (novox/hq issue 734). A build seat's worker offers an ask
+// delivery.AskMaxDeliver times; one handed out that often without an answer (a bus reload that drops every hand-out, a node
+// that dies taking it each time) is given up by the server, and the controller keeps a copy of it in DEAD_LETTERS under
+// mesh.events.dead.<seat stream>.<worker>, with the ask's message id (its ask id), how often it was handed out and when it
+// was given up. No build node writes a step for it, so an asker that waits for the step waits for ever: a try stays
+// running and holds a try place, a check's verdict stays running and its pull request waits.
+//
+// An asker of the build seats (the checker, the builder) hears those copies (DeadLetterHearing: an ordered consumer on
+// DEAD_LETTERS filtered to the build seats' streams, granted to a user of a seat pulled by kind, buscompose
+// DeadLetterReads) into DeadLetters, and LostAskWaiter ends the waiting step at once as failed on the node LostNode, its
+// reason saying LostWords; the asker decides what follows (the checker ends a try as error and asks a check again, the
+// builder asks its part of a build again).
+//
+// Belt and braces, where the asker says so in the context (NotTakenBound; the checker's tries): an ask no build node took
+// within a bound ends the same way, saying NotTakenWords. An ask waits in the stream as long as the backlog is otherwise
+// (ADR 0525 §9): a backlog is no fault.
+
+// LostNode is the node a step ended for a lost ask names: no build node wrote it.
+const LostNode = "bus"
+
+// The words of a step ended for its ask.
+const (
+	LostWords     = "its ask was given up by the build seat"
+	NotTakenWords = "no build node took its ask"
+)
+
+// The headers the controller keeps a given-up message's copy with in DEAD_LETTERS (mesh-controller internal/link
+// deadletters.go): the original message id (an ask's is its ask id), how often it was handed out, when it was given up.
+const (
+	DeadHeaderMsgID      = "Mesh-Dead-Msg-Id"
+	DeadHeaderDeliveries = "Mesh-Dead-Deliveries"
+	DeadHeaderGaveUp     = "Mesh-Dead-Gave-Up"
+	DeadHeaderStream     = "Mesh-Dead-Stream"
+)
+
+// DeadLettersStream is the stream the controller keeps given-up messages in, and DeadLetterFilter the subjects of one seat
+// stream's copies there (buscompose DeadLetterSubject).
+const DeadLettersStream = "DEAD_LETTERS"
+
+// DeadLetterFilter is the subjects DEAD_LETTERS keeps a seat stream's given-up messages under.
+func DeadLetterFilter(stream string) string { return "mesh.events.dead." + stream + ".>" }
+
+// SeatStream is the stream of a build seat's language (buscompose seatStreamName of node-build-<language>).
+func SeatStream(language string) string { return "SEAT_NODE_BUILD_" + strings.ToUpper(language) }
+
+// GivenUp is one ask a build seat gave up on, as DEAD_LETTERS keeps it.
+type GivenUp struct {
+	AskID      string
+	Stream     string
+	Deliveries int
+	At         time.Time
+}
+
+// GivenUpOf reads a DEAD_LETTERS copy's headers; false when it names no message id.
+func GivenUpOf(header map[string][]string) (GivenUp, bool) {
+	get := func(k string) string {
+		if v := header[k]; len(v) > 0 {
+			return strings.TrimSpace(v[0])
+		}
+		return ""
+	}
+	g := GivenUp{AskID: get(DeadHeaderMsgID), Stream: get(DeadHeaderStream)}
+	if g.AskID == "" {
+		return GivenUp{}, false
+	}
+	g.Deliveries, _ = strconv.Atoi(get(DeadHeaderDeliveries))
+	g.At, _ = time.Parse(time.RFC3339Nano, get(DeadHeaderGaveUp))
+	return g, true
+}
+
+// Words are what a step ended for the given-up ask says.
+func (g GivenUp) Words() string {
+	at := "at an unknown time"
+	if !g.At.IsZero() {
+		at = "at " + g.At.UTC().Format(time.RFC3339)
+	}
+	return fmt.Sprintf("%s after %d deliveries %s (kept in %s); ask again", LostWords, g.Deliveries, at, DeadLettersStream)
+}
+
+// keptGivenUp is how many given-up asks DeadLetters remembers for a waiter that starts after the copy was heard.
+const keptGivenUp = 1024
+
+// DeadLetters holds the given-up asks heard, and hands each to the waiter of its ask. Safe for concurrent use.
+type DeadLetters struct {
+	mu       sync.Mutex
+	heard    map[string]GivenUp
+	order    []string
+	watchers map[string][]chan GivenUp
+}
+
+// Heard takes one given-up ask in.
+func (d *DeadLetters) Heard(g GivenUp) {
+	d.mu.Lock()
+	if d.heard == nil {
+		d.heard, d.watchers = map[string]GivenUp{}, map[string][]chan GivenUp{}
+	}
+	if _, ok := d.heard[g.AskID]; !ok {
+		d.order = append(d.order, g.AskID)
+		if len(d.order) > keptGivenUp {
+			delete(d.heard, d.order[0])
+			d.order = d.order[1:]
+		}
+	}
+	d.heard[g.AskID] = g
+	ws := d.watchers[g.AskID]
+	delete(d.watchers, g.AskID)
+	d.mu.Unlock()
+	for _, w := range ws {
+		w <- g // buffered, one each
+	}
+}
+
+// watch answers a channel that gets the ask's given-up copy once (at once when it was heard already), and its cancel.
+func (d *DeadLetters) watch(askID string) (<-chan GivenUp, func()) {
+	ch := make(chan GivenUp, 1)
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	if d.heard == nil {
+		d.heard, d.watchers = map[string]GivenUp{}, map[string][]chan GivenUp{}
+	}
+	if g, ok := d.heard[askID]; ok {
+		ch <- g
+		return ch, func() {}
+	}
+	d.watchers[askID] = append(d.watchers[askID], ch)
+	return ch, func() {
+		d.mu.Lock()
+		defer d.mu.Unlock()
+		ws := d.watchers[askID]
+		for i, w := range ws {
+			if w == ch {
+				d.watchers[askID] = append(ws[:i], ws[i+1:]...)
+				break
+			}
+		}
+		if len(d.watchers[askID]) == 0 {
+			delete(d.watchers, askID)
+		}
+	}
+}
+
+type notTakenKey struct{}
+
+// NotTakenBound says, in ctx, that an ask no build node took within bound ends its step (a try's, never a check's).
+func NotTakenBound(ctx context.Context, bound time.Duration) context.Context {
+	return context.WithValue(ctx, notTakenKey{}, bound)
+}
+
+func notTakenBoundOf(ctx context.Context) time.Duration {
+	d, _ := ctx.Value(notTakenKey{}).(time.Duration)
+	return d
+}
+
+// LostAskWaiter is an AskWaiter that ends an ask's step when the build seat gave the ask up (DeadLetters), or, under
+// NotTakenBound, when no build node took it within the bound: it hands the asker a failed step whose reason says why, on
+// the node "bus". Every step the build module writes is handed on as it is.
+type LostAskWaiter struct {
+	Inner AskWaiter
+	Dead  *DeadLetters
+	// Hearing, when set, is asked to hear DEAD_LETTERS again each time an ask is waited for while it cannot: an ask put is
+	// the event that makes hearing matter.
+	Hearing interface {
+		Deaf() string
+		Again()
+	}
+	Now func() time.Time
+}
+
+func (w LostAskWaiter) now() time.Time {
+	if w.Now != nil {
+		return w.Now()
+	}
+	return time.Now()
+}
+
+// WatchAsk is AskWaiter's.
+func (w LostAskWaiter) WatchAsk(ctx context.Context, module, askID string) (<-chan delivery.Step, error) {
+	if w.Hearing != nil && w.Hearing.Deaf() != "" {
+		w.Hearing.Again()
+	}
+	inner, err := w.Inner.WatchAsk(ctx, module, askID)
+	if err != nil {
+		return nil, err
+	}
+	var dead <-chan GivenUp
+	cancel := func() {}
+	if w.Dead != nil {
+		dead, cancel = w.Dead.watch(askID)
+	}
+	// The not-taken bound is a context's (ADR 0437 §8: no timer), ended when a node takes the ask.
+	var notTaken <-chan struct{}
+	bound := notTakenBoundOf(ctx)
+	stopBound := func() {}
+	if bound > 0 {
+		var nt context.Context
+		nt, stopBound = context.WithTimeout(context.Background(), bound)
+		notTaken = nt.Done()
+	}
+	out := make(chan delivery.Step)
+	go func() {
+		defer close(out)
+		defer cancel()
+		defer func() { stopBound() }()
+		send := func(s delivery.Step) bool {
+			select {
+			case out <- s:
+				return true
+			case <-ctx.Done():
+				return false
+			}
+		}
+		ended := func(reason string) delivery.Step {
+			at := w.now().UTC()
+			return delivery.Step{ID: askID, Node: LostNode, State: delivery.StepFailed, Reason: reason, Ended: at}
+		}
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case s, ok := <-inner:
+				if !ok {
+					return
+				}
+				if notTaken != nil {
+					stopBound() // a node took it: its step is bounded by the asker from its start
+					notTaken = nil
+				}
+				if !send(s) {
+					return
+				}
+			case g := <-dead:
+				dead = nil
+				send(ended(g.Words()))
+				return
+			case <-notTaken:
+				send(ended(fmt.Sprintf("%s within %s of its put; it was lost or waits behind a backlog; ask again", NotTakenWords, bound)))
+				return
+			}
+		}
+	}()
+	return out, nil
+}
+
+// IsLost says whether a step was ended by LostAskWaiter because the build seat gave its ask up (LostWords).
+func IsLost(s delivery.Step) bool { return s.Node == LostNode && strings.Contains(s.Reason, LostWords) }
+
+// IsNotTaken says whether a step was ended by LostAskWaiter because no build node took its ask within the bound.
+func IsNotTaken(s delivery.Step) bool {
+	return s.Node == LostNode && strings.Contains(s.Reason, NotTakenWords)
+}
+
+// **The asker hears DEAD_LETTERS, tries again when it cannot, and says whether it hears** (issue 734). The read is
+// granted with the asker's seat traffic (buscompose DeadLetterReads); an asker started before its grant was composed is
+// refused, and an asker that only tried once would stay deaf until it starts again, silently. DeadLetterHearing tries in
+// the background, never holding the start up, and again on an event (Again): the asker's reconnect to the bus, and every
+// ask waited for while it is deaf (LostAskWaiter.Hearing); no timer. Each change of whether it hears is said (Said), so
+// the module's health tool says it: a deaf asker is not healthy.
+
+// Hearing is what a DeadLetterHearing says: whether it hears every build seat stream it follows, and why not.
+type Hearing struct {
+	Heard   bool      `json:"heard"`
+	Streams []string  `json:"streams"`
+	Why     string    `json:"why,omitempty"`
+	At      time.Time `json:"at"`
+}
+
+// HearingKey is the key a module keeps its Hearing under, in its own state (the checker's and the builder's hearing).
+const HearingKey = "dead-letters"
+
+// DeadLetterFollower starts following one seat stream's copies in DEAD_LETTERS from since, handing each given-up ask to
+// heard; it answers the stop, or why it cannot.
+type DeadLetterFollower interface {
+	Follow(ctx context.Context, stream string, since time.Time, heard func(GivenUp)) (func(), error)
+}
+
+// JetStreamDeadLetters is the bus side of a DeadLetterFollower: an ordered consumer on DEAD_LETTERS filtered to the
+// stream's copies, which resumes where it was after a reconnect and, reset before it heard any, starts at since again.
+type JetStreamDeadLetters struct{ JS jetstream.JetStream }
+
+// Follow is DeadLetterFollower's.
+func (j JetStreamDeadLetters) Follow(ctx context.Context, stream string, since time.Time, heard func(GivenUp)) (func(), error) {
+	cons, err := j.JS.OrderedConsumer(ctx, DeadLettersStream, jetstream.OrderedConsumerConfig{
+		FilterSubjects: []string{DeadLetterFilter(stream)}, DeliverPolicy: jetstream.DeliverByStartTimePolicy, OptStartTime: &since})
+	if err != nil {
+		return nil, err
+	}
+	cc, err := cons.Consume(func(m jetstream.Msg) {
+		if g, ok := GivenUpOf(m.Headers()); ok {
+			heard(g)
+		}
+	})
+	if err != nil {
+		return nil, err
+	}
+	return cc.Stop, nil
+}
+
+// DeadLetterHearing follows the build seats' given-up asks into Dead. Make it with NewDeadLetterHearing.
+type DeadLetterHearing struct {
+	follower DeadLetterFollower
+	streams  []string
+	dead     *DeadLetters
+	logf     func(string, ...any)
+	said     func(Hearing)
+	ctx      context.Context
+	since    time.Time
+
+	mu     sync.Mutex
+	stops  map[string]func()
+	why    map[string]string
+	trying bool
+	again  bool
+	told   *Hearing
+	wg     sync.WaitGroup
+}
+
+// NewDeadLetterHearing starts hearing the given-up asks of each language's build seat stream, in the background. said
+// is told each change of whether it hears (nil tells nothing); ctx ends it.
+func NewDeadLetterHearing(ctx context.Context, follower DeadLetterFollower, languages []string, dead *DeadLetters,
+	logf func(string, ...any), said func(Hearing)) *DeadLetterHearing {
+	h := &DeadLetterHearing{follower: follower, dead: dead, logf: logf, said: said, ctx: ctx, since: time.Now(),
+		stops: map[string]func(){}, why: map[string]string{}}
+	for _, l := range languages {
+		s := SeatStream(l)
+		h.streams = append(h.streams, s)
+		h.why[s] = "not tried yet"
+	}
+	if h.logf == nil {
+		h.logf = func(string, ...any) {}
+	}
+	h.Again()
+	return h
+}
+
+// Deaf says why a stream is not heard, or "" when every one is.
+func (h *DeadLetterHearing) Deaf() string {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	return h.deafLocked()
+}
+
+func (h *DeadLetterHearing) deafLocked() string {
+	var out []string
+	for _, s := range h.streams {
+		if why, deaf := h.why[s]; deaf {
+			out = append(out, s+": "+why)
+		}
+	}
+	if len(out) == 0 {
+		return ""
+	}
+	return DeadLettersStream + " is not heard, so an ask a build seat gives up on is waited for until its bound: " +
+		strings.Join(out, "; ")
+}
+
+// Again tries, in the background, every stream not heard yet; a call while it tries makes it try once more after.
+func (h *DeadLetterHearing) Again() {
+	h.mu.Lock()
+	if h.trying {
+		h.again = true
+		h.mu.Unlock()
+		return
+	}
+	h.trying = true
+	h.mu.Unlock()
+	h.wg.Add(1)
+	go func() {
+		defer h.wg.Done()
+		for {
+			h.try()
+			h.mu.Lock()
+			if !h.again || h.ctx.Err() != nil {
+				h.trying = false
+				h.mu.Unlock()
+				return
+			}
+			h.again = false
+			h.mu.Unlock()
+		}
+	}()
+}
+
+// Wait returns when no try runs.
+func (h *DeadLetterHearing) Wait() { h.wg.Wait() }
+
+// Stop ends every stream's following.
+func (h *DeadLetterHearing) Stop() {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	for s, stop := range h.stops {
+		stop()
+		delete(h.stops, s)
+	}
+}
+
+func (h *DeadLetterHearing) try() {
+	for _, s := range h.streams {
+		h.mu.Lock()
+		_, deaf := h.why[s]
+		h.mu.Unlock()
+		if !deaf || h.ctx.Err() != nil {
+			continue
+		}
+		stream := s
+		stop, err := h.follower.Follow(h.ctx, stream, h.since, func(g GivenUp) {
+			h.logf("the ask %s on %s was given up after %d deliveries at %s: the wait for its step ends", g.AskID, g.Stream,
+				g.Deliveries, g.At.Format(time.RFC3339))
+			h.dead.Heard(g)
+		})
+		h.mu.Lock()
+		if err != nil {
+			h.why[stream] = err.Error()
+			h.logf("the asks %s gives up on are not heard (%s of %s); tried again at the next reconnect or ask: %v",
+				stream, DeadLetterFilter(stream), DeadLettersStream, err)
+		} else {
+			delete(h.why, stream)
+			h.stops[stream] = stop
+			h.logf("the asks %s gives up on are heard from %s", stream, DeadLettersStream)
+		}
+		h.mu.Unlock()
+	}
+	h.tell()
+}
+
+// tell says the hearing when it changed.
+func (h *DeadLetterHearing) tell() {
+	h.mu.Lock()
+	why := h.deafLocked()
+	now := Hearing{Heard: why == "", Streams: append([]string(nil), h.streams...), Why: why, At: time.Now().UTC()}
+	same := h.told != nil && h.told.Heard == now.Heard && h.told.Why == now.Why
+	if !same {
+		h.told = &now
+	}
+	h.mu.Unlock()
+	if !same && h.said != nil {
+		h.said(now)
+	}
+}
+
+// HearingState is the name of the state an asker keeps its Hearing in (`<module>_hearing`, key HearingKey), which its
+// health tool reads.
+const HearingState = "hearing"
+
+// HearingKeeper is where a Hearing is kept: a jetstream.KeyValue, or a process.AwaitedBucket for a state that may not be
+// on the bus at the part's start (issue 1790), which keeps the latest until it appears and answers process.ErrNotYet.
+type HearingKeeper interface {
+	Put(ctx context.Context, key string, value []byte) (uint64, error)
+}
+
+// SayHearing is a DeadLetterHearing's said that keeps each Hearing in kv under HearingKey; nil kv keeps nothing and
+// says so once. A write kv keeps for later (process.ErrNotYet) is not an error: the awaited bucket said it waits.
+func SayHearing(ctx context.Context, kv HearingKeeper, logf func(string, ...any)) func(Hearing) {
+	if kv == nil {
+		if logf != nil {
+			logf("whether %s is heard is not kept: the state %s is not there, so the health tool cannot say it", DeadLettersStream, HearingState)
+		}
+		return nil
+	}
+	return func(h Hearing) {
+		data, err := json.Marshal(h)
+		if err == nil {
+			_, err = kv.Put(ctx, HearingKey, data)
+		}
+		if err != nil && !errors.Is(err, process.ErrNotYet) && logf != nil {
+			logf("whether %s is heard could not be kept: %v", DeadLettersStream, err)
+		}
+	}
+}
+
+// HearingHealth is the health answer of an asker's kept Hearing (raw, empty when none is kept): healthy while it hears
+// DEAD_LETTERS, unhealthy saying why while it does not or has not said.
+func HearingHealth(raw []byte) health.Answer {
+	if len(raw) == 0 {
+		return health.Unhealthy("it has not said whether it hears " + DeadLettersStream + " (issue 734): it is starting, or its state " + HearingState + " is not there")
+	}
+	var h Hearing
+	if err := json.Unmarshal(raw, &h); err != nil {
+		return health.Unhealthy("what it keeps of hearing " + DeadLettersStream + " is not a hearing: " + err.Error())
+	}
+	if !h.Heard {
+		return health.Unhealthy(h.Why + " (since " + h.At.Format(time.RFC3339) + "; tried again at its next reconnect or ask)")
+	}
+	return health.Healthy("it hears " + DeadLettersStream + " for " + strings.Join(h.Streams, ", "))
+}

modules/mesh-delivery-builder/buildrun/modules.go

@@ -0,0 +1,7 @@
+package buildrun
+
+// The build modules the mesh runs, by the language each builds (ADR 0469).
+const (
+	GoBuildModule   = "mesh-build-go"
+	NodeBuildModule = "mesh-build-node"
+)

modules/mesh-delivery-builder/buildrun/places.go

@@ -0,0 +1,145 @@
+package buildrun
+
+import (
+	"context"
+	"fmt"
+	"sort"
+	"sync"
+)
+
+// DefaultCapacity is the build capacity of a node that has no setting: one build step at a time.
+const DefaultCapacity = 1
+
+// Places counts the build steps a part runs on each node and holds a lane back while its node is at its
+// capacity (the operator's decision of 2026-10-21; ADR 0478 clause 3). A lane is the fetch and the builds of one build
+// module on one node, run one step at a time, so a lane holds one place while it runs. A node is chosen for a lane by
+// reserving a place on it at the moment of the choice (ChooseNodes), so that builds choosing at once see each other's
+// choices and none waits on a full node while another has room. A lane waits for its place by watching the ends of the
+// other lanes, not by a timer: ending a lane wakes the waiting ones.
+type Places struct {
+	// Capacity is the number of steps at once by node; a node not in it has DefaultCapacity.
+	Capacity map[string]int
+
+	mu       sync.Mutex
+	running  map[string]int // lanes holding a place
+	reserved map[string]int // lanes chosen for the node that do not hold a place yet
+	changed  chan struct{}  // closed, and replaced, each time a lane ends
+}
+
+// CapacityOf is how many steps the part runs on the node at once: DefaultCapacity for a node the setting does not
+// name, and 0 for one it names so, where the part never builds.
+func (p *Places) CapacityOf(node string) int {
+	if n, ok := p.Capacity[node]; ok && n >= 0 {
+		return n
+	}
+	return DefaultCapacity
+}
+
+// Running is the steps in flight now, by node.
+func (p *Places) Running() map[string]int {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	out := make(map[string]int, len(p.running))
+	for n, c := range p.running {
+		if c > 0 {
+			out[n] = c
+		}
+	}
+	return out
+}
+
+// Reserved is the lanes chosen for a node that hold no place yet, by node.
+func (p *Places) Reserved() map[string]int {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	out := make(map[string]int, len(p.reserved))
+	for n, c := range p.reserved {
+		if c > 0 {
+			out[n] = c
+		}
+	}
+	return out
+}
+
+func (p *Places) init() {
+	if p.running == nil {
+		p.running = map[string]int{}
+	}
+	if p.reserved == nil {
+		p.reserved = map[string]int{}
+	}
+	if p.changed == nil {
+		p.changed = make(chan struct{})
+	}
+}
+
+// Acquire takes a place on the node, waiting while the node is at its capacity, and answers the function that gives it
+// back. A place reserved for the node by a choice is the one taken. It returns an error when ctx ends first, and then
+// gives up the reservation too.
+func (p *Places) Acquire(ctx context.Context, node string) (release func(), err error) {
+	for {
+		p.mu.Lock()
+		p.init()
+		if p.running[node] < p.CapacityOf(node) {
+			p.running[node]++
+			if p.reserved[node] > 0 {
+				p.reserved[node]--
+			}
+			p.mu.Unlock()
+			var once sync.Once
+			return func() {
+				once.Do(func() {
+					p.mu.Lock()
+					p.running[node]--
+					close(p.changed)
+					p.changed = make(chan struct{})
+					p.mu.Unlock()
+				})
+			}, nil
+		}
+		wait := p.changed
+		p.mu.Unlock()
+		select {
+		case <-wait:
+		case <-ctx.Done():
+			p.Cancel(node)
+			return nil, fmt.Errorf("waiting for a place on %s: %w", node, ctx.Err())
+		}
+	}
+}
+
+// Cancel gives up a place reserved for the node that will not be taken.
+func (p *Places) Cancel(node string) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	p.init()
+	if p.reserved[node] > 0 {
+		p.reserved[node]--
+	}
+}
+
+// choose orders the nodes (those with room first, counting the lanes running and the lanes reserved, then the fewest of
+// them, then by name), keeps the first want and reserves a place on each, all at once.
+func (p *Places) choose(nodes []string, want int) []string {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	p.init()
+	load := func(n string) int { return p.running[n] + p.reserved[n] }
+	sort.SliceStable(nodes, func(i, j int) bool {
+		ri, rj := load(nodes[i]) < p.CapacityOf(nodes[i]), load(nodes[j]) < p.CapacityOf(nodes[j])
+		if ri != rj {
+			return ri
+		}
+		if load(nodes[i]) != load(nodes[j]) {
+			return load(nodes[i]) < load(nodes[j])
+		}
+		return nodes[i] < nodes[j]
+	})
+	if len(nodes) > want {
+		nodes = nodes[:want]
+	}
+	for _, n := range nodes {
+		p.reserved[n]++
+	}
+	return nodes
+}

modules/mesh-delivery-builder/buildrun/places_test.go

@@ -0,0 +1,104 @@
+package buildrun
+
+import (
+	"context"
+	"strings"
+	"testing"
+	"time"
+)
+
+func acquireAsync(p *Places, node string) chan func() {
+	got := make(chan func(), 1)
+	go func() {
+		release, err := p.Acquire(context.Background(), node)
+		if err != nil {
+			close(got)
+			return
+		}
+		got <- release
+	}()
+	return got
+}
+
+func TestThreeStepsOnANodeOfCapacityTwoRunTwoAtOnceAndTheThirdStartsWhenOneEnds(t *testing.T) { // round 3
+	p := &Places{Capacity: map[string]int{"ace": 2}}
+	a, b := acquireAsync(p, "ace"), acquireAsync(p, "ace")
+	ra, rb := <-a, <-b
+	third := acquireAsync(p, "ace")
+	select {
+	case <-third:
+		t.Fatal("a third step started on a node of capacity 2 with two running")
+	case <-time.After(10 * time.Millisecond):
+	}
+	if p.Running()["ace"] != 2 {
+		t.Errorf("running = %v, want 2 on ace", p.Running())
+	}
+	ra()
+	select {
+	case r := <-third:
+		r()
+	case <-time.After(2 * time.Second):
+		t.Fatal("the third step did not start when one ended")
+	}
+	rb()
+}
+
+func TestANodeWithNoSettingRunsOneStepAtATime(t *testing.T) { // round 3
+	p := &Places{Capacity: map[string]int{"shanks": 3}}
+	first := <-acquireAsync(p, "g14")
+	second := acquireAsync(p, "g14")
+	select {
+	case <-second:
+		t.Fatal("two steps on a node without a setting")
+	case <-time.After(10 * time.Millisecond):
+	}
+	first()
+	r := <-second
+	r()
+	if p.CapacityOf("g14") != 1 || p.CapacityOf("shanks") != 3 {
+		t.Errorf("capacities = %d, %d", p.CapacityOf("g14"), p.CapacityOf("shanks"))
+	}
+}
+
+func TestAWaitingStepStopsWhenItsContextEnds(t *testing.T) { // round 3
+	p := &Places{}
+	r := <-acquireAsync(p, "ace")
+	defer r()
+	ctx, cancel := context.WithCancel(context.Background())
+	done := make(chan error, 1)
+	go func() { _, err := p.Acquire(ctx, "ace"); done <- err }()
+	cancel()
+	select {
+	case err := <-done:
+		if err == nil {
+			t.Error("Acquire returned no error for a cancelled wait")
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("a cancelled wait did not return")
+	}
+}
+
+// The operator's decision of 2026-10-21 13:40: the builder builds on shanks and ace only; a capacity of 0 keeps it off a node.
+func TestACapacityOfZeroKeepsThePartOffTheNodeAndANodeNotNamedKeepsOne(t *testing.T) { // issue 1661
+	p := &Places{Capacity: map[string]int{"shanks": 3, "ace": 2, "g14": 0, "novox": 0}}
+	if p.CapacityOf("g14") != 0 || p.CapacityOf("novox") != 0 || p.CapacityOf("ace") != 2 || p.CapacityOf("other") != DefaultCapacity {
+		t.Errorf("capacities = %d %d %d %d, want 0 0 2 and the default for a node not named", p.CapacityOf("g14"), p.CapacityOf("novox"), p.CapacityOf("ace"), p.CapacityOf("other"))
+	}
+	entries := tcs("go", "go1.27.1", "ace", "g14", "novox", "shanks", "other")
+	for i := 0; i < 6; i++ {
+		nodes, _, err := ChooseNodes("go", entries, p, nil, 2)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, n := range nodes {
+			if n == "g14" || n == "novox" {
+				t.Fatalf("choice %d: %v includes a node of capacity 0", i, nodes)
+			}
+		}
+	}
+	// Only nodes of capacity 0 report: nothing qualifies, and the build says why.
+	_, _, err := ChooseNodes("go", tcs("go", "go1.27.1", "g14", "novox"), p, nil, 2)
+	if err == nil || !strings.Contains(err.Error(), "capacity") {
+		t.Errorf("only capacity-0 nodes: error = %v, want it to name the capacity", err)
+	}
+}

modules/mesh-delivery-builder/buildrun/presence.go

@@ -0,0 +1,53 @@
+package buildrun
+
+import (
+	"sync"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// PresenceSet holds which nodes are online, as the watchman writes it (mesh-delivery-watchman_presence, key `<node>`, the
+// node-engine's connection): a node asleep or off the bus is offline and its build module cannot answer. A node the
+// watchman has no key of is not online. Safe for use from the watch and from a build at once.
+type PresenceSet struct {
+	mu     sync.Mutex
+	online map[string]bool
+}
+
+// Put takes a change of the presence bucket in and answers whether a node's online state changed. A part's key and a
+// value that is not a presence are left out.
+func (s *PresenceSet) Put(key string, value []byte, deleted bool) bool {
+	node, part, _, err := delivery.ParsePresenceKey(key)
+	if err != nil || part != "" {
+		return false
+	}
+	on := false
+	if !deleted {
+		p, err := delivery.DecodePresence(value)
+		if err != nil {
+			return false
+		}
+		on = p.Online
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.online[node] == on {
+		return false
+	}
+	if s.online == nil {
+		s.online = map[string]bool{}
+	}
+	if on {
+		s.online[node] = true
+	} else {
+		delete(s.online, node)
+	}
+	return true
+}
+
+// Online is whether the watchman last saw the node online.
+func (s *PresenceSet) Online(node string) bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.online[node]
+}

modules/mesh-delivery-builder/buildrun/presence_test.go

@@ -0,0 +1,43 @@
+package buildrun
+
+import (
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+func presenceValue(t *testing.T, online bool) []byte {
+	t.Helper()
+	b, err := delivery.EncodePresence(delivery.Presence{Online: online})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return b
+}
+
+func TestPresenceSetKnowsOnlyNodesTheWatchmanSawOnline(t *testing.T) { // 1607 review 3
+	var s PresenceSet
+	if s.Online("ace") {
+		t.Error("a node the watchman never wrote is online")
+	}
+	if !s.Put("ace", presenceValue(t, true), false) || !s.Online("ace") {
+		t.Error("ace online was not taken in")
+	}
+	if s.Put("ace", presenceValue(t, true), false) {
+		t.Error("the same presence again counted as a change")
+	}
+	if !s.Put("ace", presenceValue(t, false), false) || s.Online("ace") {
+		t.Error("ace going offline was not taken in")
+	}
+	s.Put("g14", presenceValue(t, true), false)
+	if !s.Put("g14", nil, true) || s.Online("g14") {
+		t.Error("a deleted key is still online")
+	}
+	// A part's instance (part.<part>.<instance>) is not a node.
+	if s.Put("part.mesh-delivery-builder.novox", presenceValue(t, true), false) || s.Online("part") {
+		t.Error("a part's key was taken for a node")
+	}
+	if s.Put("novox", []byte("junk"), false) {
+		t.Error("junk counted")
+	}
+}

modules/mesh-delivery-builder/buildrun/standing.go

@@ -0,0 +1,248 @@
+package buildrun
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"maps"
+	"slices"
+	"sort"
+	"sync"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/process"
+)
+
+// A build module writes <node>.<language> of its toolchains state on every node it runs on, and nothing deletes the key
+// when the module leaves a node: no part writes another module's state, and the module is gone. A report of a node the
+// build module no longer runs on is therefore no builder's (issue 1940: mesh-build-node taken off ace on 2026-10-23 left
+// ace.typescript at v26.12.0, and every Node fingerprint said "builders disagree").
+//
+// ToolchainGate stands between the toolchains buckets and what takes their entries in (the indexer's PutToolchain, a
+// ToolchainSet): an entry is passed on only while the placement (the seat mesh-placement's state `placement`, held by
+// the assigner, delivery.PlacementBucket, read by delivery.Placed; ADR 0567, ADR 0549 §3) places its build module on
+// its node, and only once it was written since that placement; it is passed on as deleted otherwise, said once, and
+// passed on when its node writes it again. A report written before the placement is one an earlier run of the module
+// left (issue 1940, 2026-10-25 20:56: mesh-build-node put on ace again brought ace.typescript v26.12.0 of 2026-10-23
+// back into the agreement before the module ran there). Until the placement is settled, and while no node's placement
+// is held (before the assigner's adopt writes the first one, or where the state cannot be read), every entry is passed
+// on. Builders that run and report different versions still disagree: that refusal is the guard of novox/hq ADR 0465,
+// and it stays.
+//
+// This replaces the copies of the gate the indexer, the builder and the checker each kept over the controller's
+// assignments (issue 1940's subtask, issue 774: those go with the controller's lease, ADR 0549 §6).
+type ToolchainGate struct {
+	mu      sync.Mutex
+	modules map[string]bool                                           // the build modules whose toolchains pass the gate
+	forward func(module, key string, value []byte, deleted bool) bool // answers whether it changed what it holds
+	logf    func(format string, a ...any)
+	placed  *delivery.Placed
+	known   bool                         // the placement is settled
+	raw     map[string]map[string][]byte // module -> toolchains key -> value, as the bucket holds it
+	left    map[string]string            // <module>/<key> -> why it was said left out, so each reason is said once
+	// OnPlaced is told, outside the gate's lock, once the placement's history is read and after each revision of it
+	// FollowPlacement hears from then on (the counted nodes, Nodes, may have changed). Nil tells nobody.
+	OnPlaced func()
+}
+
+// NewToolchainGate is a gate over the toolchains of modules, passing what stands on to forward and saying with logf what
+// it leaves out.
+func NewToolchainGate(modules []string, forward func(module, key string, value []byte, deleted bool) bool, logf func(string, ...any)) *ToolchainGate {
+	g := &ToolchainGate{modules: map[string]bool{}, forward: forward, logf: logf, placed: delivery.NewPlaced(),
+		raw: map[string]map[string][]byte{}, left: map[string]string{}}
+	for _, m := range modules {
+		g.modules[m] = true
+	}
+	return g
+}
+
+// Toolchain takes one change of a build module's toolchains bucket in and answers whether what it passed on changed.
+func (g *ToolchainGate) Toolchain(module, key string, value []byte, deleted bool) bool {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	if g.raw[module] == nil {
+		g.raw[module] = map[string][]byte{}
+	}
+	if deleted {
+		delete(g.raw[module], key)
+	} else {
+		g.raw[module][key] = value
+	}
+	return g.pass(module, key)
+}
+
+// Placement takes one revision of the seat mesh-placement's placement in (at is when the bus wrote it) and answers whether what it
+// passed on changed. A value that does not read is said, and places nothing on its node.
+func (g *ToolchainGate) Placement(key string, value []byte, deleted bool, at time.Time) bool {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	was := g.placed.Seeded()
+	node, changed, err := g.placed.Put(key, value, deleted, at)
+	if err != nil {
+		g.logf("%s: %v (issue 1940)", delivery.PlacementBucket, err)
+	}
+	if !g.known {
+		return false
+	}
+	if was != g.placed.Seeded() {
+		// The first placement came, or the last went: every report's standing changed.
+		return g.all()
+	}
+	return g.again(node, changed)
+}
+
+// Nodes are the nodes the placement places any module on, sorted: the nodes the mesh counts (a node leaves the count
+// when the placement no longer names it; ADR 0624 §1). None until the placement is read.
+func (g *ToolchainGate) Nodes() []string {
+	var out []string
+	for node, modules := range g.placed.ByNode() {
+		if len(modules) > 0 {
+			out = append(out, node)
+		}
+	}
+	sort.Strings(out)
+	return out
+}
+
+// Settled says the placement's history is read: from now on only the reports of placed nodes pass, once a node's
+// placement is held. It answers whether what it passed on changed.
+func (g *ToolchainGate) Settled() bool {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.known = true
+	return g.all()
+}
+
+// all passes on every report again. The caller holds mu.
+func (g *ToolchainGate) all() bool {
+	changed := false
+	for _, module := range slices.Sorted(maps.Keys(g.raw)) {
+		for _, k := range slices.Sorted(maps.Keys(g.raw[module])) {
+			changed = g.pass(module, k) || changed
+		}
+	}
+	return changed
+}
+
+// again passes on every report of node by a build module among modules. The caller holds mu.
+func (g *ToolchainGate) again(node string, modules []string) bool {
+	changed := false
+	for _, module := range modules {
+		if !g.modules[module] {
+			continue
+		}
+		for _, k := range slices.Sorted(maps.Keys(g.raw[module])) {
+			if n, _, err := delivery.ParseToolchainKey(k); err == nil && n == node {
+				changed = g.pass(module, k) || changed
+			}
+		}
+	}
+	return changed
+}
+
+// pass hands one key on as it stands: its value when its node is placed and wrote it since (or the placement is not
+// known), deleted otherwise. The caller holds mu.
+func (g *ToolchainGate) pass(module, key string) bool {
+	value, held := g.raw[module][key]
+	if !held {
+		return g.forward(module, key, nil, true)
+	}
+	node, _, err := delivery.ParseToolchainKey(key)
+	why := ""
+	if err == nil && g.known && g.placed.Seeded() {
+		why = g.leftOut(module, node, value)
+	}
+	if why == "" {
+		delete(g.left, module+"/"+key)
+		return g.forward(module, key, value, false)
+	}
+	if g.left[module+"/"+key] != why {
+		g.left[module+"/"+key] = why
+		g.logf("%s.%s is left out of the agreed toolchain: %s (issue 1940)", delivery.ToolchainsBucket(module), key, why)
+	}
+	return g.forward(module, key, nil, true)
+}
+
+// leftOut is why a node's report is no builder's, or empty when it counts: the catalogue does not place the module on its
+// node, or the report was written before it did. A value that is no toolchain is passed on for its reader to refuse.
+// The caller holds mu.
+func (g *ToolchainGate) leftOut(module, node string, value []byte) string {
+	since, placed := g.placed.Since(node, module)
+	if !placed {
+		return fmt.Sprintf("the catalogue does not place %s on %s, so it is no builder", module, node)
+	}
+	tc, err := delivery.DecodeToolchain(value)
+	if err == nil && tc.At.Before(since) {
+		return fmt.Sprintf("it was written at %s, before %s was placed on %s at %s: it counts once %s writes it again",
+			tc.At.UTC().Format(time.RFC3339), module, node, since.UTC().Format(time.RFC3339), node)
+	}
+	return ""
+}
+
+// FollowPlacement reads the seat mesh-placement's placement with its history into gate, says it settled, and follows it; changed
+// is told whenever what the gate passes on changed. Where the state cannot be read or watched (not there, or this part
+// may not read it) it says so and the gate passes every report on: not fatal, since an indexer, builder or checker that
+// stops for it stops every delivery (issue 1945). An error of the watch after that ends on the channel.
+func FollowPlacement(ctx context.Context, js process.BucketOpener, gate *ToolchainGate, changed func(context.Context), logf func(string, ...any)) (<-chan error, error) {
+	errs := make(chan error, 1)
+	kv, err := js.KeyValue(ctx, delivery.PlacementBucket)
+	if err != nil {
+		logf("the state %s cannot be read, so every node's toolchain report counts, a build node's the catalogue does not place too (issue 1940): %v", delivery.PlacementBucket, err)
+		return errs, nil
+	}
+	w, err := kv.WatchAll(ctx, jetstream.IncludeHistory())
+	if err != nil {
+		logf("the state %s cannot be watched, so every node's toolchain report counts, a build node's the catalogue does not place too (issue 1940): %v", delivery.PlacementBucket, err)
+		return errs, nil
+	}
+	put := func(e jetstream.KeyValueEntry) bool {
+		return gate.Placement(e.Key(), e.Value(), e.Operation() != jetstream.KeyValuePut, e.Created())
+	}
+	for settled := false; !settled; {
+		select {
+		case <-ctx.Done():
+			_ = w.Stop()
+			return errs, ctx.Err()
+		case e, ok := <-w.Updates():
+			if !ok {
+				return errs, errors.New("the watch of " + delivery.PlacementBucket + " ended before it settled")
+			}
+			if e == nil {
+				settled = true
+				continue
+			}
+			put(e)
+		}
+	}
+	if gate.Settled() {
+		changed(ctx)
+	}
+	if gate.OnPlaced != nil {
+		gate.OnPlaced()
+	}
+	go func() {
+		defer func() { _ = w.Stop() }()
+		for {
+			select {
+			case <-ctx.Done():
+				errs <- ctx.Err()
+				return
+			case e, ok := <-w.Updates():
+				if !ok {
+					errs <- errors.New("the watch of " + delivery.PlacementBucket + " ended")
+					return
+				}
+				if e != nil && put(e) {
+					changed(ctx)
+				}
+				if e != nil && gate.OnPlaced != nil {
+					gate.OnPlaced()
+				}
+			}
+		}
+	}()
+	return errs, nil
+}

modules/mesh-delivery-builder/buildrun/standing_test.go

@@ -0,0 +1,263 @@
+package buildrun
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+func gateReport(t *testing.T, node, version string, at time.Time) (string, []byte) {
+	t.Helper()
+	key, err := delivery.ToolchainKey(node, "typescript")
+	if err != nil {
+		t.Fatal(err)
+	}
+	value, err := delivery.EncodeToolchain(delivery.Toolchain{Language: "typescript", Version: version, Recipe: "f59571cf4be75adf", At: at})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return key, value
+}
+
+// placing is a value of the state `placement` placing modules on node.
+func placing(t *testing.T, node string, modules ...string) (string, []byte) {
+	t.Helper()
+	p := delivery.Placement{Node: node}
+	for _, m := range modules {
+		p.Modules = append(p.Modules, delivery.PlacedModule{Module: m})
+	}
+	values, err := delivery.PlacementValues(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	key, _ := delivery.PlacementNodeKey(node)
+	return key, values[key]
+}
+
+// placingLegacy is placing in the form before, `placement.<node>` (research 072 row 37).
+func placingLegacy(t *testing.T, node string, modules ...string) (string, []byte) {
+	t.Helper()
+	p := delivery.Placement{Node: node}
+	for _, m := range modules {
+		p.Modules = append(p.Modules, delivery.PlacedModule{Module: m})
+	}
+	key, _ := delivery.LegacyPlacementKey(node)
+	value, err := delivery.EncodePlacement(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return key, value
+}
+
+func agreedOf(set *ToolchainSet) (string, string) {
+	tc, none := delivery.AgreedToolchain(set.Entries("typescript"))
+	return tc.Version, none
+}
+
+// Issue 1940, the gate over the catalogue's placement (issue 774, ADR 0549 §3): a build node's report counts only while
+// the placement places its build module on its node, and only once written since; before the placement is settled, and
+// while no node's placement is held, every report counts. The live cases: mesh-build-node taken off ace left
+// ace.typescript at v26.12.0 against v26.12.1 on the three others; put on ace again, its report of 2026-10-23 06:29 came
+// back before the module ran there.
+func TestToolchainGate(t *testing.T) {
+	old := time.Date(2026, 10, 23, 6, 29, 18, 0, time.UTC)     // ace's report from its earlier run
+	placed := time.Date(2026, 10, 25, 19, 56, 45, 0, time.UTC) // mesh-build-node placed on ace again
+	three := []string{"g14", "novox", "shanks"}
+	start := func(t *testing.T, seeded bool) (*ToolchainGate, *ToolchainSet, *[]string) {
+		set := &ToolchainSet{}
+		said := &[]string{}
+		gate := NewToolchainGate([]string{GoBuildModule, NodeBuildModule}, set.Put, func(f string, a ...any) { *said = append(*said, fmt.Sprintf(f, a...)) })
+		for _, node := range three {
+			if seeded {
+				key, value := placing(t, node, NodeBuildModule)
+				gate.Placement(key, value, false, old.Add(-time.Hour))
+			}
+			key, value := gateReport(t, node, "v26.12.1", placed.Add(time.Minute))
+			gate.Toolchain(NodeBuildModule, key, value, false)
+		}
+		return gate, set, said
+	}
+
+	t.Run("not placed on ace: its report is no builder's", func(t *testing.T) {
+		gate, set, said := start(t, true)
+		key, value := gateReport(t, "ace", "v26.12.0", old)
+		gate.Toolchain(NodeBuildModule, key, value, false)
+		if a := delivery.ToolchainAgreement(set.Entries("typescript")); len(a.SittingOut) != 1 || a.SittingOut[0].Node != "ace" { // ADR 0584: the majority is agreed, ace's report counts as the one that sits out
+			t.Fatalf("before the placement is settled every report counts; got %+v", a)
+		}
+		k, v := placing(t, "ace", GoBuildModule) // another build module on ace: no matter
+		gate.Placement(k, v, false, old)
+		if !gate.Settled() {
+			t.Fatal("settling left ace's report out, so what was passed on changed")
+		}
+		if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+			t.Fatalf("the placed nodes agree on v26.12.1; got %q, %q", v, none)
+		}
+		if len(*said) != 1 || !strings.Contains((*said)[0], "does not place mesh-build-node on ace") {
+			t.Fatalf("ace's report is said left out once; said %q", *said)
+		}
+		if gate.Toolchain(NodeBuildModule, key, value, false) {
+			t.Fatal("a report of a node not placed changed what was passed on")
+		}
+		// Placed on ace with a report written since: it counts, and the builders really disagree.
+		k, v = placing(t, "ace", GoBuildModule, NodeBuildModule)
+		gate.Placement(k, v, false, old.Add(-time.Minute))
+		if a := delivery.ToolchainAgreement(set.Entries("typescript")); a.Toolchain.Version != "v26.12.1" || len(a.SittingOut) != 1 || a.SittingOut[0].Version != "v26.12.0" {
+			t.Fatalf("builders that run different versions: the majority is agreed and ace sits out; got %+v", a)
+		}
+		// Taken off ace again (its key deleted): its report goes again.
+		if !gate.Placement(k, nil, true, placed) {
+			t.Fatal("taking ace's placement away passed nothing on")
+		}
+		if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+			t.Fatalf("got %q, %q", v, none)
+		}
+		// A report deleted from the bucket goes whether its node is placed or not.
+		key, _ = gateReport(t, "g14", "v26.12.1", placed)
+		if !gate.Toolchain(NodeBuildModule, key, nil, true) || len(set.Entries("typescript")) != 2 {
+			t.Fatalf("deleting g14's report: %d entries left, want novox and shanks", len(set.Entries("typescript")))
+		}
+	})
+
+	for _, c := range []struct {
+		name   string
+		at     time.Time // when ace wrote its report
+		counts bool
+	}{
+		{"a report left before the placement", old, false},
+		{"a report written since the placement", placed.Add(30 * time.Second), true},
+	} {
+		t.Run(c.name, func(t *testing.T) {
+			gate, set, said := start(t, true)
+			k, v := placing(t, "ace") // ace's key, first heard placing nothing
+			gate.Placement(k, v, false, old.Add(-time.Hour))
+			gate.Settled()
+			k, v = placing(t, "ace", NodeBuildModule)
+			if gate.Placement(k, v, false, placed) {
+				t.Fatal("a placement with no report passed something on")
+			}
+			key, value := gateReport(t, "ace", "v26.12.0", c.at)
+			if got := gate.Toolchain(NodeBuildModule, key, value, false); got != c.counts {
+				t.Fatalf("ace's report passed on: %v, want %v", got, c.counts)
+			}
+			// ace's placement written again with another module beside: its standing does not move, nothing is said again.
+			k, v = placing(t, "ace", GoBuildModule, NodeBuildModule)
+			if gate.Placement(k, v, false, placed.Add(time.Minute)) {
+				t.Fatal("the same placement of mesh-build-node changed what was passed on")
+			}
+			if c.counts {
+				return
+			}
+			if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+				t.Fatalf("ace's left report is no builder's; got %q, %q", v, none)
+			}
+			if len(*said) != 1 || !strings.Contains((*said)[0], "before mesh-build-node was placed on ace at 2026-10-25T19:56:45Z") {
+				t.Fatalf("said %q, want once why ace's report is left out", *said)
+			}
+			key, value = gateReport(t, "ace", "v26.12.1", placed.Add(time.Minute))
+			if !gate.Toolchain(NodeBuildModule, key, value, false) || len(set.Entries("typescript")) != 4 {
+				t.Fatal("ace's new report was not passed on")
+			}
+		})
+	}
+
+	t.Run("no placement held: every report counts", func(t *testing.T) {
+		gate, set, _ := start(t, false)
+		key, value := gateReport(t, "ace", "v26.12.0", old)
+		gate.Toolchain(NodeBuildModule, key, value, false)
+		gate.Settled()
+		if n := len(set.Entries("typescript")); n != 4 {
+			t.Fatalf("before the first placement file every report counts; got %d", n)
+		}
+		k, v := placing(t, "g14", NodeBuildModule)
+		if !gate.Placement(k, v, false, old.Add(-time.Hour)) || len(set.Entries("typescript")) != 1 {
+			t.Fatalf("the first placement leaves every node it does not place out; got %d", len(set.Entries("typescript")))
+		}
+		if !gate.Placement(k, nil, true, placed) || len(set.Entries("typescript")) != 4 {
+			t.Fatal("the last placement gone: every report counts again")
+		}
+	})
+
+	t.Run("the history: a module in the first revision heard of a key stands since before it", func(t *testing.T) {
+		p := delivery.NewPlaced()
+		// ace in the form before, then converted: its module stands since before, the legacy key read no more.
+		k, v := placingLegacy(t, "ace", NodeBuildModule)
+		p.Put(k, v, false, old)
+		k, v = placing(t, "ace", NodeBuildModule)
+		if _, changed, err := p.Put(k, v, false, placed); len(changed) != 0 || err != nil {
+			t.Errorf("the conversion of ace's key changed %v, %v", changed, err)
+		}
+		if _, changed, _ := p.Put("ace."+NodeBuildModule, []byte("{}"), false, placed); len(changed) != 0 {
+			t.Errorf("a module key says which modules stand: %v", changed)
+		}
+		if k, v := placingLegacy(t, "ace"); true {
+			if _, changed, _ := p.Put(k, v, false, placed); len(changed) != 0 {
+				t.Errorf("the legacy key is read after the node key: %v", changed)
+			}
+		}
+		k2, v2 := placing(t, "g14")
+		p.Put(k2, v2, false, old)
+		k2, v2 = placing(t, "g14", NodeBuildModule)
+		if _, changed, _ := p.Put(k2, v2, false, placed); strings.Join(changed, ",") != NodeBuildModule {
+			t.Errorf("a module placed says changed %v", changed)
+		}
+		if _, _, err := p.Put("placement.novox", []byte("not json"), false, old); err == nil {
+			t.Error("a value that does not read was not said")
+		}
+		if s, ok := p.Since("ace", NodeBuildModule); !ok || !s.IsZero() {
+			t.Errorf("ace's module stands since %v, %v; want the zero time", s, ok)
+		}
+		if s, ok := p.Since("g14", NodeBuildModule); !ok || !s.Equal(placed) {
+			t.Errorf("g14's module stands since %v, %v; want the revision that placed it", s, ok)
+		}
+		if got := p.PlacedNodes(NodeBuildModule); strings.Join(got, ",") != "ace,g14" || len(p.ByNode()) != 2 || !p.Seeded() {
+			t.Errorf("PlacedNodes = %v, ByNode = %v", got, p.ByNode())
+		}
+	})
+
+	t.Run("a placement the bus refuses is said, and the part goes on", func(t *testing.T) {
+		var logs bytes.Buffer
+		logger := log.New(&logs, "", 0)
+		refused := errors.New("nats: permissions violation for publish to $JS.API.CONSUMER.CREATE.KV_mesh-delivery-assigner_placement")
+		gate, _, _ := start(t, false)
+		for _, bus := range []refusingBus{{err: refused}, {refuseOpen: true, err: refused}} {
+			if _, err := FollowPlacement(context.Background(), bus, gate, func(context.Context) {}, logger.Printf); err != nil {
+				t.Errorf("a refused placement stopped the start: %v", err)
+			}
+		}
+		if !strings.Contains(logs.String(), "cannot be watched") || !strings.Contains(logs.String(), "cannot be read") {
+			t.Errorf("the refusals were not said: %q", logs.String())
+		}
+	})
+}
+
+// refusingBus is a bus that refuses: every open (refuseOpen), or every watch of a bucket it opens, with err.
+type refusingBus struct {
+	refuseOpen bool
+	err        error
+}
+
+func (r refusingBus) KeyValue(context.Context, string) (jetstream.KeyValue, error) {
+	if r.refuseOpen {
+		return nil, r.err
+	}
+	return refusedWatch{err: r.err}, nil
+}
+
+type refusedWatch struct {
+	jetstream.KeyValue
+	err error
+}
+
+func (r refusedWatch) WatchAll(context.Context, ...jetstream.WatchOpt) (jetstream.KeyWatcher, error) {
+	return nil, r.err
+}

modules/mesh-delivery-builder/buildrun/steps.go

@@ -0,0 +1,67 @@
+package buildrun
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// Caller calls a tool of a module on one named machine (mesh-sdk process.Conn.CallOn; ADR 0469 clause 3).
+type Caller interface {
+	CallOn(node, key string, body any) (json.RawMessage, error)
+}
+
+// Steps waits for the end of a build module's long step: the value of its key `<node>.<id>` in the module's steps state
+// (ADR 0469 clause 2) once its state is not running. It is a watch of that key, not a poll; it returns when the step
+// ends or ctx does.
+type Steps interface {
+	Wait(ctx context.Context, module, key string) (delivery.Step, error)
+}
+
+// Runner runs a build module's long steps: the call answers at once with the step's key, and the result is read from that
+// key when the step ends (ADR 0469 clause 2).
+type Runner struct {
+	Caller Caller
+	Steps  Steps
+	// Bound is how long a step may run before the builder stops waiting for it.
+	Bound time.Duration
+}
+
+// Run calls tool of the build module on node with args, waits for the step's end and answers its result. A step that
+// failed or was refused is an error naming the node, the state and the reason.
+func (r Runner) Run(ctx context.Context, module, node, tool string, args map[string]any) (json.RawMessage, error) {
+	raw, err := r.Caller.CallOn(node, module+"."+tool, args)
+	if err != nil {
+		return nil, fmt.Errorf("%s on %s: %w", tool, node, err)
+	}
+	var answer struct {
+		Step  string `json:"step"`
+		Key   string `json:"key"`
+		State string `json:"state"`
+	}
+	if err := json.Unmarshal(raw, &answer); err != nil {
+		return nil, fmt.Errorf("%s on %s answered what is not a step: %w", tool, node, err)
+	}
+	if answer.Key == "" {
+		return nil, fmt.Errorf("%s on %s answered no step key: %s", tool, node, raw)
+	}
+	if n, _, err := delivery.ParseStepKey(answer.Key); err != nil || n != node {
+		return nil, fmt.Errorf("%s on %s answered the step key %q, which is not a key of that node", tool, node, answer.Key)
+	}
+	wait, cancel := context.WithTimeoutCause(ctx, r.Bound, fmt.Errorf("the step %s did not end within %s", answer.Key, r.Bound))
+	defer cancel()
+	step, err := r.Steps.Wait(wait, module, answer.Key)
+	if err != nil {
+		if cause := context.Cause(wait); cause != nil && ctx.Err() == nil {
+			err = cause
+		}
+		return nil, fmt.Errorf("%s on %s: %w", tool, node, err)
+	}
+	if step.State != delivery.StepPassed {
+		return nil, fmt.Errorf("%s on %s: the step %s %s: %s", tool, node, answer.Key, step.State, step.Reason)
+	}
+	return step.Result, nil
+}

modules/mesh-delivery-builder/buildrun/steps_test.go

@@ -0,0 +1,125 @@
+package buildrun
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+type call struct {
+	node, key string
+	body      any
+}
+
+// fakeCaller answers a long tool as the build modules do: at once, with the step and its key.
+type fakeCaller struct {
+	calls  []call
+	answer string
+	err    error
+}
+
+func (f *fakeCaller) CallOn(node, key string, body any) (json.RawMessage, error) {
+	f.calls = append(f.calls, call{node, key, body})
+	if f.err != nil {
+		return nil, f.err
+	}
+	return json.RawMessage(f.answer), nil
+}
+
+// fakeSteps holds the steps values by `<module>/<key>`; Wait on a key it does not hold blocks until the context ends.
+type fakeSteps struct {
+	mu    sync.Mutex
+	steps map[string]delivery.Step
+	// during, when set, is called as a wait starts and the function it answers as the wait ends.
+	during func(key string) func()
+}
+
+func (f *fakeSteps) Wait(ctx context.Context, module, key string) (delivery.Step, error) {
+	f.mu.Lock()
+	s, ok := f.steps[module+"/"+key]
+	during := f.during
+	f.mu.Unlock()
+	if ok {
+		if during != nil {
+			defer during(key)()
+		}
+		return s, nil
+	}
+	<-ctx.Done()
+	return delivery.Step{}, context.Cause(ctx)
+}
+
+func stepAt(node, id, state, reason string, result string) delivery.Step {
+	s := delivery.Step{ID: id, Tool: "build_go_fetch", Node: node, State: state, Reason: reason}
+	if result != "" {
+		s.Result = json.RawMessage(result)
+	}
+	return s
+}
+
+func runCallsTheToolOnTheNodeAndReadsTheStepsKey(t *testing.T) { // 1607/AC5
+	caller := &fakeCaller{answer: `{"step":"abc1","key":"ace.abc1","state":"running"}`}
+	steps := &fakeSteps{steps: map[string]delivery.Step{"mesh-build-go/ace.abc1": stepAt("ace", "abc1", delivery.StepPassed, "", `{"workspace":"w1","commit":"c"}`)}}
+	res, err := Runner{Caller: caller, Steps: steps, Bound: time.Second}.Run(context.Background(), "mesh-build-go", "ace", "build_go_fetch", map[string]any{"repository": "novox/r", "commit": "c"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(caller.calls) != 1 || caller.calls[0].node != "ace" || caller.calls[0].key != "mesh-build-go.build_go_fetch" {
+		t.Errorf("calls = %+v, want one on ace for mesh-build-go.build_go_fetch", caller.calls)
+	}
+	var fr struct{ Workspace string }
+	if err := json.Unmarshal(res, &fr); err != nil || fr.Workspace != "w1" {
+		t.Errorf("result = %s (%v), want the step's result", res, err)
+	}
+}
+
+func runFailsOnAFailedOrRefusedStepNamingItsReason(t *testing.T) { // 1607/AC5
+	for _, state := range []string{delivery.StepFailed, delivery.StepRefused} {
+		caller := &fakeCaller{answer: `{"step":"abc1","key":"ace.abc1","state":"running"}`}
+		steps := &fakeSteps{steps: map[string]delivery.Step{"mesh-build-go/ace.abc1": stepAt("ace", "abc1", state, "go is go1.26.0, the recipe builds with go1.27.1", "")}}
+		_, err := Runner{Caller: caller, Steps: steps, Bound: time.Second}.Run(context.Background(), "mesh-build-go", "ace", "build_go_build", nil)
+		if err == nil || !strings.Contains(err.Error(), "go1.27.1") || !strings.Contains(err.Error(), state) || !strings.Contains(err.Error(), "ace") {
+			t.Errorf("%s: error = %v, want the node, the state and the reason", state, err)
+		}
+	}
+}
+
+func runStopsWaitingAtTheBound(t *testing.T) { // 1607/AC5
+	caller := &fakeCaller{answer: `{"step":"abc1","key":"ace.abc1","state":"running"}`}
+	_, err := Runner{Caller: caller, Steps: &fakeSteps{}, Bound: 20 * time.Millisecond}.Run(context.Background(), "mesh-build-go", "ace", "build_go_build", nil)
+	if err == nil || !strings.Contains(err.Error(), "ace.abc1") || !strings.Contains(err.Error(), "did not end") {
+		t.Errorf("error = %v, want the step key and that it did not end within its bound", err)
+	}
+}
+
+func runRefusesAnAnswerWithNoKeyAndAKeyOfAnotherNode(t *testing.T) { // 1607/AC5
+	for _, answer := range []string{`{"state":"running"}`, `{"step":"abc1","key":"novox.abc1","state":"running"}`, `not json`} {
+		_, err := Runner{Caller: &fakeCaller{answer: answer}, Steps: &fakeSteps{}, Bound: time.Second}.Run(context.Background(), "mesh-build-go", "ace", "build_go_fetch", nil)
+		if err == nil {
+			t.Errorf("answer %s: no error", answer)
+		}
+	}
+}
+
+func runReturnsTheCallsOwnError(t *testing.T) { // 1607/AC5
+	boom := errors.New("no responders")
+	_, err := Runner{Caller: &fakeCaller{err: boom}, Steps: &fakeSteps{}, Bound: time.Second}.Run(context.Background(), "mesh-build-go", "ace", "build_go_fetch", nil)
+	if !errors.Is(err, boom) || !strings.Contains(err.Error(), "ace") {
+		t.Errorf("error = %v, want the call's error naming the node", err)
+	}
+}
+
+// A step run on its node and read from its steps key, one table of cases (the test budget).
+func TestRunningAStepOnANode(t *testing.T) {
+	t.Run("run calls the tool on the node and reads the steps key", runCallsTheToolOnTheNodeAndReadsTheStepsKey)
+	t.Run("run fails on a failed or refused step naming its reason", runFailsOnAFailedOrRefusedStepNamingItsReason)
+	t.Run("run stops waiting at the bound", runStopsWaitingAtTheBound)
+	t.Run("run refuses an answer with no key and a key of another node", runRefusesAnAnswerWithNoKeyAndAKeyOfAnotherNode)
+	t.Run("run returns the calls own error", runReturnsTheCallsOwnError)
+}

modules/mesh-delivery-builder/buildrun/toolchains.go

@@ -0,0 +1,64 @@
+package buildrun
+
+import (
+	"sync"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// LanguageOf is the language each build module's toolchains state holds (the indexer's ToolchainModules, reversed).
+var LanguageOf = map[string]string{GoBuildModule: "go", NodeBuildModule: "typescript"}
+
+// ToolchainSet holds what the build modules' toolchains buckets hold: each node's entry of a language, as the watches
+// put them in. Safe for use from the watches and from a build at once.
+type ToolchainSet struct {
+	mu sync.Mutex
+	by map[string]map[string]delivery.Toolchain // language -> node -> entry
+}
+
+// Put takes a change of a build module's toolchains bucket in: a put of a node's entry (key <node>.<language>) or its
+// delete. It answers whether the language's entries changed (a node's version or recipe, or a node appearing or going).
+// A key or a value that is not an entry of the module's language is left out.
+func (s *ToolchainSet) Put(module, key string, value []byte, deleted bool) bool {
+	language, ok := LanguageOf[module]
+	if !ok {
+		return false
+	}
+	node, keyLanguage, err := delivery.ParseToolchainKey(key)
+	if err != nil || keyLanguage != language {
+		return false
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if deleted {
+		if _, had := s.by[language][node]; !had {
+			return false
+		}
+		delete(s.by[language], node)
+		return true
+	}
+	tc, err := delivery.DecodeToolchain(value)
+	if err != nil || tc.Language != language {
+		return false
+	}
+	if s.by == nil {
+		s.by = map[string]map[string]delivery.Toolchain{}
+	}
+	if s.by[language] == nil {
+		s.by[language] = map[string]delivery.Toolchain{}
+	}
+	cur, had := s.by[language][node]
+	s.by[language][node] = tc
+	return !had || cur.Version != tc.Version || cur.Recipe != tc.Recipe
+}
+
+// Entries are the nodes' entries of a language, in no particular order.
+func (s *ToolchainSet) Entries(language string) []delivery.NodeToolchain {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	var out []delivery.NodeToolchain
+	for node, tc := range s.by[language] {
+		out = append(out, delivery.NodeToolchain{Node: node, Toolchain: tc})
+	}
+	return out
+}

modules/mesh-delivery-builder/buildrun/toolchains_test.go

@@ -0,0 +1,49 @@
+package buildrun
+
+import (
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+func tcValue(t *testing.T, language, version string) []byte {
+	t.Helper()
+	b, err := delivery.EncodeToolchain(delivery.Toolchain{Language: language, Version: version, Recipe: "1", At: time.Now()})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return b
+}
+
+func TestToolchainSetKeepsEachNodesEntryByLanguageAndSaysWhenOneChanged(t *testing.T) { // 1607/AC6
+	var s ToolchainSet
+	if !s.Put(GoBuildModule, "novox.go", tcValue(t, "go", "go1.27.1"), false) {
+		t.Error("a first entry did not count as a change")
+	}
+	if s.Put(GoBuildModule, "novox.go", tcValue(t, "go", "go1.27.1"), false) {
+		t.Error("the same entry again counted as a change")
+	}
+	s.Put(GoBuildModule, "ace.go", tcValue(t, "go", "go1.27.1"), false)
+	s.Put(NodeBuildModule, "ace.typescript", tcValue(t, "typescript", "tsc5"), false)
+	if got := s.Entries("go"); len(got) != 2 {
+		t.Errorf("go entries = %+v, want two", got)
+	}
+	if got := s.Entries("typescript"); len(got) != 1 || got[0].Node != "ace" || got[0].Version != "tsc5" {
+		t.Errorf("typescript entries = %+v", got)
+	}
+	if !s.Put(GoBuildModule, "ace.go", nil, true) || len(s.Entries("go")) != 1 {
+		t.Error("a delete did not remove the node's entry")
+	}
+	// What is not a toolchain of the module's language is left out.
+	s = ToolchainSet{}
+	if s.Put(GoBuildModule, "novox.typescript", tcValue(t, "typescript", "x"), false) {
+		t.Error("a typescript toolchain in the go build module's bucket counted")
+	}
+	if s.Put(GoBuildModule, "novox.go", []byte("not json"), false) || s.Put("other-module", "novox.go", tcValue(t, "go", "x"), false) {
+		t.Error("garbage or an unknown module counted")
+	}
+	if len(s.Entries("go")) != 0 {
+		t.Error("an entry was kept")
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder-tools/main.go

@@ -0,0 +1,427 @@
+// Command mesh-delivery-builder-tools serves the builder's tools (novox/hq issue 1945): the runtime launches it for a call.
+// builder_stuck reads the builder's builds and reasks states and the build modules' steps through the builder's state and
+// reads; builder_ask_again writes one value of the reasks state, which the builder watches and answers. The builder is the
+// other program: it serves no tool (ADR 0437 §4).
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+	"sync"
+	"time"
+
+	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/handacts"
+	"git.novox.be/novox/mesh-sdk/go/views"
+
+	"git.novox.be/novox/mesh-delivery/sdk/enginereads"
+
+	"mesh-delivery-builder/internal/build"
+	"mesh-delivery-builder/internal/versions"
+)
+
+// EngineReadsTool lists, asks again and drops what each counted node's engine reads, as the builder keeps it.
+const EngineReadsTool = "builder_engine_reads"
+
+// queueAsker writes a queues value and waits for the builder's answer to it.
+type queueAsker func(key string, value []byte) (json.RawMessage, error)
+
+// Tools are the builder's tools: stuck reads, askAgain writes the reasks value, queue writes a queues value and waits for
+// the builder's read, buildAgain writes a reasks value of mode build and waits for the builder's answer.
+// tags writes a tag-asks value and waits for the builder's answer; ta reads tag-asks.
+func Tools(r build.StuckReader, askAgain func(key string, value []byte) error, queue, buildAgain queueAsker, since build.LogSince, now func() time.Time, vs versions.Reader,
+	tags queueAsker, ta, fw, of versions.Reader) []stdio.Tool {
+	str := func(args map[string]any, k string) string { s, _ := args[k].(string); return strings.TrimSpace(s) }
+	// handAct writes a reasks value of a versions hand act and answers the builder's answer, or its refusal as an error.
+	handAct := func(key string, value []byte, err error) (any, error) {
+		if err != nil {
+			return nil, err
+		}
+		raw, err := buildAgain(key, value)
+		if err != nil {
+			return nil, err
+		}
+		a, err := build.DecodeReAsk(raw)
+		if err != nil {
+			return nil, err
+		}
+		if a.Refused {
+			return nil, errors.New(a.Answer)
+		}
+		return map[string]any{"key": key, "name": a.Name, "do": a.Do, "version": a.Version, "answer": a.Answer}, nil
+	}
+	tagAct := func(key string, value []byte, err error) (any, error) {
+		if err != nil {
+			return nil, err
+		}
+		raw, err := tags(key, value)
+		if err != nil {
+			return nil, err
+		}
+		return versions.DecodeTagAsk(raw)
+	}
+	nameFP := map[string]any{"type": "object", "required": []string{"name", "fp", "why"}, "properties": map[string]any{
+		"name": map[string]any{"type": "string", "description": "the numbered name, <module>/<artifact>, as builder_versions lists it"},
+		"fp":   map[string]any{"type": "string", "description": "the fingerprint, src2:<hex>"},
+		"why":  map[string]any{"type": "string", "description": "why, in plain words"}}}
+	branch := func(head bool) map[string]any {
+		req := []string{"repository", "branch", "why"}
+		props := map[string]any{
+			"repository": map[string]any{"type": "string", "description": "<owner>/<name>"},
+			"branch":     map[string]any{"type": "string", "description": "the branch; its cleaned name is the tag"},
+			"why":        map[string]any{"type": "string", "description": "why, in plain words"}}
+		if head {
+			req = append(req, "head")
+			props["head"] = map[string]any{"type": "string", "description": "the commit the tagged version is built from"}
+		}
+		return map[string]any{"type": "object", "required": req, "properties": props}
+	}
+	return []stdio.Tool{
+		{Name: versions.PublishAgainTool, Description: versions.PublishAgainDescription, Input: nameFP,
+			Run: func(args map[string]any) (any, error) {
+				return handAct(build.NewPublishAgain(str(args, "name"), str(args, "fp"), str(args, "why"), stdio.CallerOf(args), now()))
+			}},
+		{Name: versions.FloorAgainTool, Description: versions.FloorAgainDescription,
+			Input: map[string]any{"type": "object", "required": []string{"name", "why"}, "properties": map[string]any{
+				"name": map[string]any{"type": "string", "description": "the numbered name, <module>/<artifact>"},
+				"why":  map[string]any{"type": "string", "description": "why, in plain words"}}},
+			Run: func(args map[string]any) (any, error) {
+				return handAct(build.NewFloorAgain(str(args, "name"), str(args, "why"), stdio.CallerOf(args), now()))
+			}},
+		{Name: versions.TagTool, Description: versions.TagDescription, Input: branch(true),
+			Run: func(args map[string]any) (any, error) {
+				return tagAct(versions.NewTagAsk(str(args, "repository"), str(args, "branch"), str(args, "head"), str(args, "why"), stdio.CallerOf(args), now()))
+			}},
+		{Name: versions.UntagTool, Description: versions.UntagDescription, Input: branch(false),
+			Run: func(args map[string]any) (any, error) {
+				return tagAct(versions.NewUntag(str(args, "repository"), str(args, "branch"), str(args, "why"), stdio.CallerOf(args), now()))
+			}},
+		{Name: versions.TagAsksTool, Description: versions.TagAsksDescription,
+			Input: map[string]any{"type": "object", "properties": map[string]any{
+				"repository": map[string]any{"type": "string", "description": "only this repository's asks, <owner>/<name>"}}},
+			Run: func(args map[string]any) (any, error) { return versions.AnswerTagAsks(ta, str(args, "repository")) }},
+		{Name: versions.OldFormTool, Description: versions.OldFormDescription,
+			Input: map[string]any{"type": "object", "properties": map[string]any{
+				"drop": map[string]any{"type": "string", "description": "a retired node to drop from the count by hand"},
+				"why":  map[string]any{"type": "string", "description": "with drop: why, in plain words"}}},
+			Run: func(args map[string]any) (any, error) {
+				if node := str(args, "drop"); node != "" {
+					return handAct(build.NewOldFormDrop(node, str(args, "why"), stdio.CallerOf(args), now()))
+				}
+				return versions.AnswerOldForm(of)
+			}},
+		{Name: versions.FloorWaitsTool, Description: versions.FloorWaitsDescription,
+			Input: map[string]any{"type": "object", "properties": map[string]any{}},
+			Run:   func(map[string]any) (any, error) { return versions.AnswerFloorWaits(fw) }},
+		{Name: versions.VersionsTool, Description: versions.VersionsDescription,
+			Input: map[string]any{"type": "object", "required": []string{"name"}, "properties": map[string]any{
+				"name":    map[string]any{"type": "string", "description": "the package, image, bundle or archive name"},
+				"version": map[string]any{"type": "string", "description": "one version, to ask whether it is recorded"},
+				"digest":  map[string]any{"type": "string", "description": "with version: the digest the holder received"}}},
+			Run: func(args map[string]any) (any, error) {
+				return versions.AnswerVersions(context.Background(), vs, str(args, "name"), str(args, "version"), str(args, "digest"))
+			}},
+		{Name: build.StuckTool,
+			Description: "Every build key that waits (building or queued), oldest first: its module, fingerprint, step words and since when, and each ask it " +
+				"waits on by language with its id, when it was put, its asking (1 for the first; the builder asks an ask again when it can no longer be " +
+				"answered, at most 3 times) and what its build module's steps hold of it (none, or its state on its node since its start). The " +
+				"seat workers' delivery counts are not readable by the builder. dead_letters says whether the builder hears the asks the build seats give up " +
+				"on (issue 734), and why not: heard, a given-up ask is asked again at once; deaf, at its check bound. With module, that module's keys only. Read-only.",
+			Input: map[string]any{"type": "object", "properties": map[string]any{
+				"module": map[string]any{"type": "string", "description": "only this module's keys"}}},
+			Run: func(args map[string]any) (any, error) { return r.Stuck(str(args, "module")) }},
+		{Name: build.AskAgainTool,
+			Description: "Ask a waiting build key's asks again now, under new ids the key then names, as the builder does by itself for an ask its build " +
+				"seat's stream gave up on. The builder answers in the reasks state, which " + build.StuckTool + " shows beside the key; a key no ask of " +
+				"which waits is answered so and nothing is asked. An ask whose step already runs on a node is asked again too: it is then " +
+				"built twice, the first run's work wasted and its end read by nobody, never a wrong key; builder_stuck shows whether a step runs.",
+			Input: map[string]any{"type": "object", "required": []string{"module", "fp", "why"}, "properties": map[string]any{
+				"module": map[string]any{"type": "string", "description": "the module's name"},
+				"fp":     map[string]any{"type": "string", "description": "its new-form fingerprint, src2:<hex>, as builder_stuck shows it"},
+				"why":    map[string]any{"type": "string", "description": "why it is asked again, in plain words"}}},
+			Run: func(args map[string]any) (any, error) {
+				key, value, err := build.NewReAsk(str(args, "module"), str(args, "fp"), str(args, "why"), stdio.CallerOf(args), now())
+				if err != nil {
+					return nil, err
+				}
+				if err := askAgain(key, value); err != nil {
+					return nil, fmt.Errorf("the ask could not be written to %s: %w", build.ReAsksBucket, err)
+				}
+				return map[string]any{"key": key, "asked": true,
+					"next": "the builder answers in " + build.ReAsksState + "." + key + "; " + build.StuckTool + " shows the answer and the new ask"}, nil
+			}},
+		{Name: build.BuildAgainTool,
+			Description: "Build a failed key again (rebuild a module, build a failed key again): the builder writes the key of module and " +
+				"fingerprint building as a new revision of the same key and asks the build seats, as it does by itself when it looks at a module " +
+				"again (ADR 0429 clause 18). Answers the new revision and the ask id of each build module (go, node, image). Refuses a key that " +
+				"is not failed, and says why: done (nothing to do), or waiting (building or queued: " + build.AskAgainTool + " asks its waiting asks " +
+				"again); a key failed for a reason the builder never retries on the same fingerprint (a pin missing, a version taken, digests that " +
+				"differ) and a fingerprint its module no longer has are refused too. Use it for a key builder_stuck does not show, which failed.",
+			Input: map[string]any{"type": "object", "required": []string{"module", "fp", "why"}, "properties": map[string]any{
+				"module": map[string]any{"type": "string", "description": "the module's name"},
+				"fp":     map[string]any{"type": "string", "description": "its new-form fingerprint, src2:<hex>"},
+				"why":    map[string]any{"type": "string", "description": "why it is built again, in plain words"}}},
+			Run: func(args map[string]any) (any, error) {
+				key, value, err := build.NewBuildAgain(str(args, "module"), str(args, "fp"), str(args, "why"), stdio.CallerOf(args), now())
+				if err != nil {
+					return nil, err
+				}
+				raw, err := buildAgain(key, value)
+				if err != nil {
+					return nil, err
+				}
+				r, err := build.DecodeReAsk(raw)
+				if err != nil {
+					return nil, err
+				}
+				if r.Refused {
+					return nil, errors.New(r.Answer)
+				}
+				if r.Failed != "" {
+					return nil, errors.New(r.Answer)
+				}
+				if r.Revision == 0 && !r.Pending {
+					return nil, fmt.Errorf("the builder answered neither a new revision nor a refusal (an older builder?): %s", r.Answer)
+				}
+				return map[string]any{"key": key, "revision": r.Revision, "asks": r.Asks, "answer": r.Answer,
+					"next": build.StuckTool + " shows the key and its asks while they wait"}, nil
+			}},
+		{Name: delivery.BuildsSinceTool,
+			Description: "Every build that ended since a time, oldest first, from the builder's log build-log (kept 30 days): per build its module, " +
+				"fingerprint, source revision, repository, directory, commit and ref, the build node, when it ended, its outcome (done, failed or " +
+				"queued), the manifest built, the bases it was built against and each artifact made with its digest and reference. more says the " +
+				"log held more than one answer carries: ask again from the last build's time. What the operator's command nox builds reads. Read-only.",
+			Input: map[string]any{"type": "object", "required": []string{"since"}, "properties": map[string]any{
+				"since": map[string]any{"type": "string", "description": "RFC 3339 time; the builds that ended at or after it"}}},
+			Run: func(args map[string]any) (any, error) {
+				at, err := time.Parse(time.RFC3339Nano, str(args, "since"))
+				if err != nil {
+					return nil, fmt.Errorf("since %q is not an RFC 3339 time: %w", str(args, "since"), err)
+				}
+				return build.BuildsSince(since, at)
+			}},
+		{Name: build.AnnounceAgainTool,
+			Description: "Announce a done build again (take in again, compose again): the builder writes the done key of module and fingerprint " +
+				"again, unchanged, as a new revision of the same key (its content, artifacts and manifest stay identical), so the controller's " +
+				"take-in hears it and composes the module and writes its grant again. Use it when a done build was taken in but its composition " +
+				"or grant is gone and every want is refused for it. Answers the new revision. Refuses a key that is not done: " + build.BuildAgainTool +
+				" builds a failed key again, " + build.AskAgainTool + " asks a waiting key's asks again.",
+			Input: map[string]any{"type": "object", "required": []string{"module", "fp", "why"}, "properties": map[string]any{
+				"module": map[string]any{"type": "string", "description": "the module's name"},
+				"fp":     map[string]any{"type": "string", "description": "its new-form fingerprint, src2:<hex>"},
+				"why":    map[string]any{"type": "string", "description": "why it is announced again, in plain words"}}},
+			Run: func(args map[string]any) (any, error) {
+				key, value, err := build.NewAnnounceAgain(str(args, "module"), str(args, "fp"), str(args, "why"), stdio.CallerOf(args), now())
+				if err != nil {
+					return nil, err
+				}
+				raw, err := buildAgain(key, value)
+				if err != nil {
+					return nil, err
+				}
+				r, err := build.DecodeReAsk(raw)
+				if err != nil {
+					return nil, err
+				}
+				if r.Refused || r.Revision == 0 {
+					return nil, errors.New(r.Answer)
+				}
+				return map[string]any{"key": key, "revision": r.Revision, "answer": r.Answer}, nil
+			}},
+		{Name: build.SeatQueueTool,
+			Description: "What waits on a build seat's stream (SEAT_NODE_BUILD_<LANGUAGE>), as the builder reads it: the stream's message count and " +
+				"sequences, and per kind (delivery, check, recheck) its messages oldest first, at most limit each, with sequence, ask id, when asked " +
+				"and put, age, the state of the step a build node wrote for it, and whether the builder counts it as still waiting or as given up " +
+				"on (its worker delivered it its most times) or taken; and the ask asked last that a node took. The workers' delivery counts are " +
+				"not readable by the builder (nats.nats_streams shows them). Read by the builder, which alone may read the stream; read-only.",
+			Input: map[string]any{"type": "object", "properties": map[string]any{
+				"language": map[string]any{"type": "string", "description": "go, node or image (default go)"},
+				"seat":     map[string]any{"type": "string", "description": "or the seat: node-build-go, node-build-node, node-build-image"},
+				"limit":    map[string]any{"type": "integer", "description": fmt.Sprintf("messages read of each kind (default %d, at most %d)", build.DefaultQueueLimit, build.MaxQueueLimit)}}},
+			Run: func(args map[string]any) (any, error) {
+				language := build.LanguageOf(str(args, "language"))
+				if language == "" {
+					language = build.LanguageOf(str(args, "seat"))
+				}
+				if language == "" {
+					language = delivery.AskGo
+				}
+				limit, _ := args["limit"].(float64)
+				key, value, err := build.NewQueueAsk(language, int(limit), stdio.CallerOf(args), now())
+				if err != nil {
+					return nil, err
+				}
+				return queue(key, value)
+			}},
+	}
+}
+
+// askQueue writes the queues value at key and waits, on a watch of the key, at most bound for the builder's answer.
+func askQueue(s stdio.KeptState, bound time.Duration) queueAsker {
+	return askKept(s, build.QueuesState, build.QueuesBucket, "the read", bound, func(v []byte) bool {
+		a, err := build.DecodeQueueAsk(v)
+		return err == nil && !a.Answered.IsZero()
+	})
+}
+
+// askKept writes a value at key of a state the builder watches and answers there, and waits, on a watch of the key, at most
+// bound for a value written after it that answered says is the builder's answer.
+func askKept(s stdio.KeptState, state, bucket, what string, bound time.Duration, answered func([]byte) bool) queueAsker {
+	return func(key string, value []byte) (json.RawMessage, error) {
+		heard := make(chan json.RawMessage, 1)
+		var rev uint64
+		var mu sync.Mutex
+		if err := s.Watch(key, func(c stdio.StateChange) error {
+			mu.Lock()
+			mine := rev
+			mu.Unlock()
+			if c.Op != "put" || mine == 0 || c.Revision <= mine {
+				return nil
+			}
+			if answered(c.Value) {
+				select {
+				case heard <- c.Value:
+				default:
+				}
+			}
+			return nil
+		}); err != nil {
+			return nil, fmt.Errorf("watching %s.%s: %w", state, key, err)
+		}
+		r, err := s.Put(key, json.RawMessage(value))
+		if err != nil {
+			return nil, fmt.Errorf("%s could not be written to %s: %w", what, bucket, err)
+		}
+		mu.Lock()
+		rev = r
+		mu.Unlock()
+		// The watch may have heard the answer before the revision was known: read it once too.
+		if e, err := s.Get(key); err == nil && e != nil && e.Revision > r && answered(e.Value) {
+			return e.Value, nil
+		}
+		wait, cancel := context.WithTimeout(context.Background(), bound) // a context's bound, no timer (ADR 0437 §8)
+		defer cancel()
+		select {
+		case v := <-heard:
+			return v, nil
+		case <-wait.Done():
+			return nil, fmt.Errorf("the builder did not answer %s.%s within %s: it is not running, or cannot read %s", state, key, bound, bucket)
+		}
+	}
+}
+
+func read(s stdio.KeptState) build.StateRead {
+	return build.StateRead{Keys: s.Keys, Get: func(key string) (json.RawMessage, time.Time, error) {
+		e, err := s.Get(key)
+		if err != nil || e == nil {
+			return nil, time.Time{}, err
+		}
+		return e.Value, time.Time{}, nil
+	}, Written: func(key string) time.Time {
+		e, err := s.Get(key)
+		if err != nil || e == nil {
+			return time.Time{}
+		}
+		return written(s, key, e.Revision)
+	}}
+}
+
+// written is when the key's revision was written, from its history, or zero.
+func written(s stdio.KeptState, key string, revision uint64) time.Time {
+	h, err := s.History(key)
+	if err != nil {
+		return time.Time{}
+	}
+	for _, r := range h {
+		if r.Revision == revision {
+			return r.At
+		}
+	}
+	return time.Time{}
+}
+
+func main() {
+	steps := map[string]build.StateRead{}
+	for _, bm := range build.StuckBuildModules {
+		steps[bm] = read(stdio.State(bm + ".steps"))
+	}
+	reasks := stdio.State(build.ReAsksState)
+	r := build.StuckReader{Logf: func(f string, a ...any) { fmt.Fprintf(os.Stderr, "[mesh-delivery-builder-tools] "+f+"\n", a...) }, Builds: read(stdio.State("builds")), ReAsks: read(reasks), Steps: steps,
+		Hearing: read(stdio.State(buildrun.HearingState))}
+	put := func(key string, value []byte) error {
+		_, err := reasks.Put(key, json.RawMessage(value))
+		return err
+	}
+	buildAgain := askKept(reasks, build.ReAsksState, build.ReAsksBucket, "the request", 25*time.Second, func(v []byte) bool {
+		a, err := build.DecodeReAsk(v)
+		return err == nil && !a.Answered.IsZero()
+	})
+	vs := stdio.State(versions.State)
+	vr := versions.Reader{Keys: vs.Keys, Get: func(key string) (json.RawMessage, bool, error) {
+		e, err := vs.Get(key)
+		if err != nil || e == nil {
+			return nil, false, err
+		}
+		return e.Value, true, nil
+	}}
+	ts := stdio.State(versions.TagAsksState)
+	tags := askKept(ts, versions.TagAsksState, versions.TagAsksBucket, "the ask", 25*time.Second, func(v []byte) bool {
+		a, err := versions.DecodeTagAsk(v)
+		return err == nil && !a.Answered.IsZero()
+	})
+	tr := versions.Reader{Keys: ts.Keys, Get: func(key string) (json.RawMessage, bool, error) {
+		e, err := ts.Get(key)
+		if err != nil || e == nil {
+			return nil, false, err
+		}
+		return e.Value, true, nil
+	}}
+	fs := stdio.State(versions.FloorWaitsState)
+	fr := versions.Reader{Keys: fs.Keys, Get: func(key string) (json.RawMessage, bool, error) {
+		e, err := fs.Get(key)
+		if err != nil || e == nil {
+			return nil, false, err
+		}
+		return e.Value, true, nil
+	}}
+	ofs := stdio.State(versions.OldFormState)
+	ofr := versions.Reader{Keys: ofs.Keys, Get: func(key string) (json.RawMessage, bool, error) {
+		e, err := ofs.Get(key)
+		if err != nil || e == nil {
+			return nil, false, err
+		}
+		return e.Value, true, nil
+	}}
+	bs := stdio.State(versions.BoundsState)
+	br := versions.Reader{Keys: bs.Keys, Get: func(key string) (json.RawMessage, bool, error) {
+		e, err := bs.Get(key)
+		if err != nil || e == nil {
+			return nil, false, err
+		}
+		return e.Value, true, nil
+	}}
+	tools := Tools(r, put, askQueue(stdio.State(build.QueuesState), 25*time.Second), buildAgain, stdio.Log(delivery.BuilderLog).Since, time.Now, vr, tags, tr, fr, ofr)
+	// The builder's expiring keys (state bounds): what each bounds and when it ends.
+	tools = append(tools, stdio.Tool{Name: versions.BoundsTool, Description: versions.BoundsDescription,
+		Input: map[string]any{"type": "object", "properties": map[string]any{}},
+		Run: func(map[string]any) (any, error) {
+			rows, err := versions.AnswerBounds(br, time.Now())
+			return map[string]any{"bounds": rows}, err
+		}})
+	// What each counted node's engine reads, as the builder keeps it (ADR 0618 §2, ADR 0624 §1): listed, one node asked
+	// again, or one node's key dropped.
+	tools = append(tools, enginereads.Tool(EngineReadsTool, "the builder", enginereads.KeptState(stdio.State("engine-reads")), true, time.Now))
+	// builder_first_views and builder_first_view_again: where the builder's first views of the indexer's and the assigner's
+	// states stand, and asking one again by hand (ADR 0615, DLV-M1).
+	tools = append(tools, views.StatusTools(delivery.BuilderModule, "builder_first_views", "builder_first_view_again", stdio.State(views.StatusState), handacts.Recorder{Ask: stdio.Ask}, time.Now)...)
+	if err := stdio.Serve("", tools); err != nil {
+		fmt.Fprintf(os.Stderr, "[mesh-delivery-builder-tools] %v\n", err)
+		os.Exit(1)
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/branchend.go

@@ -0,0 +1,174 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"strings"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+
+	"mesh-delivery-builder/internal/build"
+	"mesh-delivery-builder/internal/versions"
+)
+
+// forgeStream is the forge bridge's stream `forge` as the bus names it, where the builder's durable consumer hears a
+// branch's end (design 51 *Tagged versions*).
+const forgeStream = "FORGE"
+
+// forgeBranchDeleted is the forge bridge's kind for a branch's end (delivery.ForgeBranchDeleted in the group's mesh-sdk).
+const forgeBranchDeleted = "branch-deleted"
+
+// checkerAsksStream is the checker's family `asks` as the bus names it, and tagWantedSubject its event tag-wanted
+// (design 51 *Tagged versions*, DLV-C3): on the checker's own stream, so its subject is mesh.stream.<module>.event.*.
+const (
+	checkerAsksStream = "ASKS"
+	tagWantedSubject  = "mesh.stream." + delivery.CheckerModule + ".event.tag-wanted"
+)
+
+// forgeEnd is the part of a forge message the builder reads.
+type forgeEnd struct {
+	Kind       string `json:"kind"`
+	Repository string `json:"repository"`
+	Branch     string `json:"branch"`
+	Action     string `json:"action"`
+}
+
+// ended says whether the message ends a branch: merged, a pull closed, or branch-deleted.
+func (f forgeEnd) ended() bool {
+	switch f.Kind {
+	case delivery.ForgeMerged, forgeBranchDeleted:
+		return f.Branch != ""
+	case delivery.ForgePull:
+		return f.Action == delivery.PullClosed && f.Branch != ""
+	}
+	return false
+}
+
+// branchEnds hears the forge bridge's stream: every message wakes a floor whose bridge_tags was silent, and a branch's
+// end removes its tagged versions, acknowledged only once all are removed.
+type branchEnds struct {
+	acts     versions.Acts
+	findings *findings
+	tagAsks  func() jetstream.KeyValue
+	wake     func(ctx context.Context)
+	logf     func(string, ...any)
+	now      func() time.Time
+}
+
+func (h *branchEnds) heard(ctx context.Context, m jetstream.Msg) {
+	if h.wake != nil {
+		h.wake(ctx)
+	}
+	var f forgeEnd
+	if err := json.Unmarshal(m.Data(), &f); err != nil || !f.ended() {
+		h.ack(m)
+		return
+	}
+	end, err := h.acts.BranchEnded(ctx, f.Repository, f.Branch)
+	if err != nil {
+		h.logf("the end of %s %s: the versions cannot be read, heard again: %v", f.Repository, f.Branch, err)
+		h.again(m)
+		return
+	}
+	id := f.Repository + "/" + f.Branch
+	if end.Done {
+		h.findings.clear(ctx, versions.RemovalNotDone, health.ScopeModule, id)
+		if kv := h.tagAsks(); kv != nil {
+			if err := kv.Delete(ctx, versions.TagAskKey(f.Repository, f.Branch)); err != nil && !errors.Is(err, jetstream.ErrKeyNotFound) {
+				h.logf("the tag ask of %s %s stays in %s: %v", f.Repository, f.Branch, versions.TagAsksState, err)
+			}
+		}
+		h.ack(m)
+		return
+	}
+	since := h.now()
+	if md, err := m.Metadata(); err == nil {
+		since = md.Timestamp
+	}
+	if h.now().Sub(since) >= versions.RemovalFindingAfter {
+		h.findings.raise(ctx, finding{kind: versions.RemovalNotDone, scope: health.ScopeModule, id: id,
+			summary:     end.Finding(f.Repository, f.Branch, since),
+			headline:    "A branch's tagged versions are not removed",
+			explanation: "The branch ended, and the registry seats did not say removed for every version tagged for it within 15 minutes.",
+			resolved:    "Every seat said removed.",
+			needs:       "Look at the seats named: " + strings.Join(end.Seats(), ", ")})
+	}
+	h.logf("the end of %s %s: remove asked of %d tagged versions, heard again in a minute", f.Repository, f.Branch, len(end.Left))
+	h.again(m)
+}
+
+func (h *branchEnds) ack(m jetstream.Msg) {
+	if err := m.Ack(); err != nil {
+		h.logf("acknowledging %s: %v", m.Subject(), err)
+	}
+}
+
+// again leaves the message for the bus to give again in a minute: the retry is the bus's redelivery, not a timer here.
+func (h *branchEnds) again(m jetstream.Msg) {
+	if err := m.NakWithDelay(versions.RemoveAgainAfter); err != nil {
+		h.logf("leaving %s for the bus to give again: %v", m.Subject(), err)
+	}
+}
+
+// tagWanted takes the checker's tag-wanted in: written to tag-asks as builder_tag writes it, answered by its watch.
+func tagWanted(ctx context.Context, kv jetstream.KeyValue, m jetstream.Msg, by string, now time.Time, logf func(string, ...any)) {
+	if m.Subject() != tagWantedSubject {
+		_ = m.Ack() // the family's other events (the verdicts) are not the builder's
+		return
+	}
+	var t versions.TagWanted
+	err := json.Unmarshal(m.Data(), &t)
+	var key string
+	var value []byte
+	if err == nil {
+		key, value, err = versions.TagWantedAsk(t, by, now)
+	}
+	if err != nil {
+		logf("%s holds what is no tag-wanted, left: %v", m.Subject(), err)
+		_ = m.Ack()
+		return
+	}
+	if kv == nil {
+		logf("tag-wanted of %s %s is heard again: %s is not on the bus yet", t.Repository, t.Branch, versions.TagAsksState)
+		_ = m.NakWithDelay(versions.RemoveAgainAfter)
+		return
+	}
+	if _, err := kv.Put(ctx, key, value); err != nil {
+		logf("tag-wanted of %s %s is heard again: %v", t.Repository, t.Branch, err)
+		_ = m.Nak()
+		return
+	}
+	_ = m.Ack()
+}
+
+// tagsVia is build.Builder.Tags over the state tag-asks: the asks of the repository, read when a check's build is
+// looked at; none while the state is not bound.
+func tagsVia(kv func() jetstream.KeyValue, logf func(string, ...any)) build.TagOf {
+	return func(ctx context.Context, repository, head string) (string, bool) {
+		store := kv()
+		if store == nil {
+			return "", false
+		}
+		lister, err := store.ListKeysFiltered(ctx, versions.EscapeToken(repository)+".>")
+		if err != nil {
+			logf("the tag asks of %s cannot be read, so its check builds no tagged version: %v", repository, err)
+			return "", false
+		}
+		var asks []versions.TagAsk
+		for key := range lister.Keys() {
+			e, err := store.Get(ctx, key)
+			if err != nil {
+				continue
+			}
+			if t, err := versions.DecodeTagAsk(e.Value()); err == nil {
+				asks = append(asks, t)
+			}
+		}
+		return versions.TagFor(asks, repository, head)
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/bus.go

@@ -66,6 +66,11 @@ func settle(ctx context.Context, kv jetstream.KeyValue, each func(jetstream.KeyV
 	if err != nil {
 		return nil, err
 	}
+	return settled(ctx, w, each)
+}
+
+// settled hands each entry the watch delivers before its end-of-initial marker to each, and answers the watch.
+func settled(ctx context.Context, w jetstream.KeyWatcher, each func(jetstream.KeyValueEntry)) (jetstream.KeyWatcher, error) {
 	for {
 		select {
 		case <-ctx.Done():
@@ -102,43 +107,6 @@ func follow(ctx context.Context, w jetstream.KeyWatcher, each func(jetstream.Key
 	}
 }
 
-// stepsWaiter waits for a build module's step by watching its key in the module's steps bucket (ADR 0469 clause 2): the
-// watch hands over the value the key holds now, so a step that ended before the watch began is read at once, and every
-// change after. No timer: the caller bounds the wait with its context.
-type stepsWaiter struct{ js bucketOpener }
-
-func (w stepsWaiter) Wait(ctx context.Context, module, key string) (delivery.Step, error) {
-	kv, err := w.js.KeyValue(ctx, delivery.StepsBucket(module))
-	if err != nil {
-		return delivery.Step{}, fmt.Errorf("the bucket %s: %w", delivery.StepsBucket(module), err)
-	}
-	watch, err := kv.Watch(ctx, key)
-	if err != nil {
-		return delivery.Step{}, err
-	}
-	defer watch.Stop()
-	for {
-		select {
-		case <-ctx.Done():
-			return delivery.Step{}, ctx.Err()
-		case e, ok := <-watch.Updates():
-			if !ok {
-				return delivery.Step{}, errors.New("the watch of the step ended")
-			}
-			if e == nil || !opOf(e) {
-				continue
-			}
-			step, err := delivery.DecodeStep(e.Value())
-			if err != nil {
-				return delivery.Step{}, fmt.Errorf("the step %s is not a step: %w", key, err)
-			}
-			if step.State != delivery.StepRunning {
-				return step, nil
-			}
-		}
-	}
-}
-
 // manifestReader reads manifests.<digest> of the indexer and parses the manifest it holds.
 type manifestReader struct{ kv jetstream.KeyValue }
 
@@ -155,5 +123,6 @@ func (m manifestReader) Manifest(ctx context.Context, digest string) (catalogue.
 	if err != nil {
 		return catalogue.Manifest{}, err
 	}
-	return catalogue.ParseManifest([]byte(kept.JSON))
+	// Decoded, never judged (novox/hq ADR 0578 §3): what a build needs of it is read, a field it does not know set aside.
+	return catalogue.Decode([]byte(kept.JSON))
 }

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/findings.go

@@ -0,0 +1,174 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+	"git.novox.be/novox/mesh-sdk/go/process"
+
+	"git.novox.be/novox/mesh-delivery/sdk/heard"
+
+	"mesh-delivery-builder/internal/versions"
+)
+
+// findingsBucket is the builder's findings (novox/hq ADR 0564 §2): what it sees wrong now, written at its raise and
+// deleted at its clear, which the condition keeper raises and clears.
+var findingsBucket = health.FindingsBucket(delivery.BuilderModule)
+
+// findings writes the builder's findings into its state, once bound; until then each is said in the log only.
+type findings struct {
+	kv   *process.AwaitedBucket
+	logf func(string, ...any)
+	now  func() time.Time
+	// store stands in for kv in a test.
+	store findingStore
+}
+
+// findingStore is the part of the findings bucket written.
+type findingStore interface {
+	Get(ctx context.Context, key string) (jetstream.KeyValueEntry, error)
+	Put(ctx context.Context, key string, value []byte) (uint64, error)
+	Delete(ctx context.Context, key string, opts ...jetstream.KVDeleteOpt) error
+}
+
+// finding is one of the builder's findings: its kind, what it is about, and its words.
+type finding struct {
+	kind, scope, id                                 string
+	summary, headline, explanation, resolved, needs string
+	severity                                        health.Severity
+}
+
+func (f *findings) bucket() findingStore {
+	switch {
+	case f == nil:
+		return nil
+	case f.store != nil:
+		return f.store
+	case f.kv == nil:
+		return nil
+	}
+	if kv := f.kv.KV(); kv != nil {
+		return kv
+	}
+	return nil
+}
+
+// BuildFailed is the finding of a failed trunk build (DLV-B7, design 25), about its module.
+const BuildFailed = "build-failed"
+
+// buildEnded raises the module's build-failed for a trunk build that failed and clears it at a later done one; a
+// candidate's build (its ref named) is the check's to say.
+func (f *findings) buildEnded(ctx context.Context, e delivery.BuildLogEntry) {
+	if e.Event != delivery.BuildEndedEvent || e.Ref != "" {
+		return
+	}
+	switch e.Outcome {
+	case delivery.BuildFailed:
+		f.raise(ctx, finding{kind: BuildFailed, scope: health.ScopeModule, id: e.Module,
+			summary:     "the trunk build of " + e.Module + " at " + e.FP + " (commit " + e.Commit + ") failed",
+			headline:    "A module's trunk build failed",
+			explanation: "The builder built " + e.Module + " from the trunk and the build failed, so its new version is not delivered.",
+			resolved:    "A later trunk build of " + e.Module + " is done.",
+			needs:       "builder_builds_since shows the build; builder_build_again builds it again."})
+	case delivery.BuildDone:
+		f.clear(ctx, BuildFailed, health.ScopeModule, e.Module)
+	}
+}
+
+// raise writes fd; it is written again only when its words changed, so the keeper's condition moves only then.
+func (f *findings) raise(ctx context.Context, fd finding) {
+	key := health.FindingKey(fd.scope, fd.id, fd.kind)
+	kv := f.bucket()
+	if kv == nil {
+		f.logf("finding %s (not written, %s is not on the bus yet): %s", key, findingsBucket, fd.summary)
+		return
+	}
+	if e, err := kv.Get(ctx, key); err == nil {
+		if old, err := health.DecodeFinding(e.Value()); err == nil && old.Summary == fd.summary {
+			return
+		}
+	}
+	at := f.now().UTC()
+	sev := fd.severity
+	if sev == "" {
+		sev = health.Warning
+	}
+	value, err := health.EncodeFinding(health.Finding{Key: key, Kind: fd.kind, Subject: health.Subject{Scope: fd.scope, ID: fd.id},
+		Severity: sev, Summary: fd.summary, Headline: fd.headline, Explanation: fd.explanation, Resolved: fd.resolved, Needs: fd.needs,
+		Evidence: []health.Evidence{{At: at, Said: fd.summary}}, Source: "builder." + fd.kind, Observer: delivery.BuilderModule, At: at})
+	if err == nil {
+		_, err = kv.Put(ctx, key, value)
+	}
+	if err != nil {
+		f.logf("the finding %s cannot be written: %v", key, err)
+	}
+}
+
+// clear deletes the finding of kind about scope and id; one not there is nothing to clear.
+func (f *findings) clear(ctx context.Context, kind, scope, id string) {
+	kv := f.bucket()
+	if kv == nil {
+		return
+	}
+	key := health.FindingKey(scope, id, kind)
+	if _, err := kv.Get(ctx, key); errors.Is(err, jetstream.ErrKeyNotFound) {
+		return
+	}
+	if err := kv.Delete(ctx, key); err != nil && !errors.Is(err, jetstream.ErrKeyNotFound) {
+		f.logf("the finding %s cannot be cleared: %v", key, err)
+	}
+}
+
+// notHeard is the writer of the builder's finding of a family it does not hear (heard.Writer, ADR 0615 §5): written into
+// its findings once bound, said in the log until then.
+func (f *findings) notHeard(ctx context.Context) heard.Writer {
+	on := func(do func(findingStore)) {
+		switch {
+		case f.store != nil:
+			do(f.store)
+		case f.kv != nil:
+			f.kv.Ready(func(kv jetstream.KeyValue) { do(kv) })
+		}
+	}
+	return heard.Writer{Observer: delivery.BuilderModule, Logf: f.logf, Now: f.now,
+		Put: func(key string, value []byte) error {
+			on(func(kv findingStore) {
+				if _, err := kv.Put(ctx, key, value); err != nil {
+					f.logf("the finding %s cannot be written: %v", key, err)
+				}
+			})
+			return nil
+		},
+		Delete: func(key string) error {
+			on(func(kv findingStore) {
+				if _, err := kv.Get(ctx, key); err != nil {
+					return // none stands
+				}
+				if err := kv.Delete(ctx, key); err != nil {
+					f.logf("the finding %s cannot be cleared: %v", key, err)
+				}
+			})
+			return nil
+		}}
+}
+
+// floorSaid is the floor finding (design 51 *Health and conditions*: a floor source silent): raised for a name waiting on
+// its floor, about that name, cleared once all three sources answered.
+func (f *findings) floorSaid(ctx context.Context) func(versions.FloorWait, bool) {
+	return func(w versions.FloorWait, raised bool) {
+		if !raised {
+			f.clear(ctx, versions.FloorSilent, health.ScopeModule, w.Name)
+			return
+		}
+		f.raise(ctx, finding{kind: versions.FloorSilent, scope: health.ScopeModule, id: w.Name, summary: w.Finding(),
+			headline:    "A version's floor is not known",
+			explanation: "The builder numbers a name only once its registry seat, the forge bridge's tags and the indexer's requirements all answered; one of them did not.",
+			resolved:    "All three answered.",
+			needs:       "builder_floor_waits names the silent source; builder_floor_again asks again by hand."})
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/gone_integration_test.go

@@ -0,0 +1,186 @@
+//go:build integration
+
+package main
+
+import (
+	"encoding/json"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// A done key whose blob the artifact store no longer holds is built again, by the builder whole against the bus
+// (novox/hq issue 1937): on 2026-10-24 the store's 03:30 collection deleted the bare blobs of three done keys the
+// controller had never taken in, and the builder kept them done.
+
+// heldVerb answers the seat mesh-artifact-sweep's verb held on the bus, as its holder does: {result: {output, ok,
+// answer}}; a reference is gone while gone says so.
+type heldVerb struct {
+	mu    sync.Mutex
+	gone  func(reference string) bool
+	asked []string
+}
+
+func (h *heldVerb) serve(t *testing.T, b *bed) {
+	t.Helper()
+	sub, err := b.js.Conn().Subscribe("mesh.seat."+catalogue.ArtifactSweepSeat+".call.held.>", func(m *nats.Msg) {
+		var args struct {
+			References []string `json:"references"`
+		}
+		_ = json.Unmarshal(m.Data, &args)
+		a := delivery.HeldAnswer{Store: "store.test:5100", Held: []string{}, Gone: []string{}}
+		h.mu.Lock()
+		for _, r := range args.References {
+			h.asked = append(h.asked, r)
+			if h.gone(r) {
+				a.Gone = append(a.Gone, r)
+			} else {
+				a.Held = append(a.Held, r)
+			}
+		}
+		h.mu.Unlock()
+		reply, _ := json.Marshal(map[string]any{"result": map[string]any{"output": "held", "ok": true, "answer": a}, "node": "ctl"})
+		_ = m.Respond(reply)
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = sub.Unsubscribe() })
+}
+
+func (h *heldVerb) asks() int {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	return len(h.asked)
+}
+
+// eventsConsumer makes EVENTS and the builder's durable consumer of artifacts-gone on it, as the controller makes them
+// from the manifest's consumes.
+func eventsConsumer(t *testing.T, b *bed, node string) {
+	t.Helper()
+	if _, err := b.js.CreateStream(b.ctx, jetstream.StreamConfig{Name: eventsStream, Subjects: []string{delivery.ArtifactsGoneSubject}}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := b.js.CreateOrUpdateConsumer(b.ctx, eventsStream, jetstream.ConsumerConfig{Durable: node + "_mesh-delivery-builder",
+		AckPolicy: jetstream.AckExplicitPolicy, FilterSubjects: []string{delivery.ArtifactsGoneSubject}}); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// doneKey writes builds.<module>.<fp> done, naming one archive at reference, and answers its revision.
+func doneKey(t *testing.T, b *bed, module, manifest, reference, digest string) uint64 {
+	t.Helper()
+	key, _ := delivery.BuilderBuildKey(module, fp)
+	data, err := delivery.EncodeBuilderBuild(delivery.BuilderBuild{State: delivery.BuildDone, By: "n2.mesh-delivery-builder",
+		Manifest: manifest, Step: "built mesh-build-go on n2",
+		Artifacts: []delivery.BuiltArtifact{{Name: "files", Kind: "archive", Digest: digest, Reference: reference}}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	rev, err := b.builds.Put(b.ctx, key, data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return rev
+}
+
+func revisionOf(t *testing.T, b *bed, module string) uint64 {
+	t.Helper()
+	key, _ := delivery.BuilderBuildKey(module, fp)
+	e, err := b.builds.Get(b.ctx, key)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return e.Revision()
+}
+
+// 1937/AC3 (integration): the builder, started whole, finds the done key of the trunk's fingerprint naming a blob held
+// answers gone, builds it again as a new revision whose step says so, and leaves the rebuilt key done.
+func TestADoneKeyWhoseBlobIsGoneIsBuiltAgainAtStart(t *testing.T) {
+	b := startBed(t)
+	eventsConsumer(t, b, "n1")
+	manifest := b.archive(t, "ca-trust", "modules/ca-trust", commit)
+	old := digestOf("collected last night")
+	oldRef := "artifact-store://ca-trust/files/blobs/" + old
+	rev := doneKey(t, b, "ca-trust", manifest, oldRef, old)
+	h := &heldVerb{gone: func(r string) bool { return r == oldRef }}
+	h.serve(t, b)
+
+	b.start(t, "n1", nil)
+	v := b.await(t, "ca-trust", func(v delivery.BuilderBuild) bool {
+		return v.State == delivery.BuildDone && len(v.Artifacts) == 1 && v.Artifacts[0].Digest == digestOf("files")
+	})
+	if !strings.Contains(v.Step, "built again: the artifact store no longer held "+oldRef) {
+		t.Errorf("the rebuilt key's step %q does not say why it was built again", v.Step)
+	}
+	if got := revisionOf(t, b, "ca-trust"); got <= rev {
+		t.Errorf("revision %d, was %d: want a new revision", got, rev)
+	}
+	if n := b.fake.count("mesh-build-go.build_go_build"); n != 1 {
+		t.Errorf("the archive was built %d times, want once", n)
+	}
+	if h.asks() == 0 {
+		t.Error("the builder never asked held")
+	}
+}
+
+// 1937/AC4 (integration): a done key whose blob held answers held at start stays done; when the controller says
+// artifacts-gone for it, the builder asks again and builds it again.
+func TestArtifactsGoneLeadsTheBuilderToBuildTheKeyAgain(t *testing.T) {
+	b := startBed(t)
+	eventsConsumer(t, b, "n1")
+	manifest := b.archive(t, "ca-trust", "modules/ca-trust", commit)
+	d := digestOf("files")
+	ref := "artifact-store://ca-trust/files/blobs/" + d
+	rev := doneKey(t, b, "ca-trust", manifest, ref, d)
+	var mu sync.Mutex
+	collected := false
+	h := &heldVerb{gone: func(r string) bool {
+		mu.Lock()
+		defer mu.Unlock()
+		if r == ref && collected {
+			collected = false // gone once: the rebuild pushes it again
+			return true
+		}
+		return false
+	}}
+	h.serve(t, b)
+
+	b.start(t, "n1", nil)
+	for deadline := time.Now().Add(20 * time.Second); h.asks() == 0 && time.Now().Before(deadline); time.Sleep(50 * time.Millisecond) {
+	}
+	if h.asks() == 0 {
+		t.Fatal("the builder never asked held at its start")
+	}
+	time.Sleep(300 * time.Millisecond)
+	if got := revisionOf(t, b, "ca-trust"); got != rev || b.fake.count("mesh-build-go.build_go_build") != 0 {
+		t.Fatalf("a key whose blob is held was built again (revision %d, was %d)", got, rev)
+	}
+
+	mu.Lock()
+	collected = true
+	mu.Unlock()
+	key, _ := delivery.BuilderBuildKey("ca-trust", fp)
+	body, err := delivery.EncodeArtifactsGone(delivery.ArtifactsGone{Module: "ca-trust", Key: key, Fingerprint: fp,
+		Gone: []string{ref}, At: time.Now().UTC()})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := b.js.Publish(b.ctx, delivery.ArtifactsGoneSubject, body); err != nil {
+		t.Fatal(err)
+	}
+	v := b.await(t, "ca-trust", func(v delivery.BuilderBuild) bool {
+		return v.State == delivery.BuildDone && strings.Contains(v.Step, "built again")
+	})
+	if got := revisionOf(t, b, "ca-trust"); got <= rev || b.fake.count("mesh-build-go.build_go_build") != 1 {
+		t.Errorf("build = %+v at revision %d (was %d), %d builds: want built again once on the event", v, got, rev,
+			b.fake.count("mesh-build-go.build_go_build"))
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/held.go

@@ -0,0 +1,306 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+
+	"mesh-delivery-builder/internal/build"
+)
+
+// heldOnTheBus says whether an ask a build key names is on its build seat's stream, or a build node wrote a step for it
+// (issue 1910), read once at the take-over of a key at start; and, at the builder's check bound, whether an ask can still
+// be answered (issue 1945). Never polled.
+type heldOnTheBus struct{ js jetstream.JetStream }
+
+// Held is build.Builder's Held: a step key `<node>.<ask id>` in the build module's steps, or a message of the stream under
+// the ask's subject whose Nats-Msg-Id is the ask's id.
+func (h heldOnTheBus) Held(ctx context.Context, a delivery.StepAsk) (bool, error) {
+	seen, err := h.seen(ctx, a, false)
+	if err != nil {
+		return false, err
+	}
+	return seen.Step || seen.OnStream, nil
+}
+
+// Gone is build.Builder's Gone: why the ask can no longer be answered (build.AskSeen.Why), or "".
+func (h heldOnTheBus) Gone(ctx context.Context, a delivery.StepAsk) (string, error) {
+	seen, err := h.seen(ctx, a, true)
+	if err != nil {
+		return "", err
+	}
+	return seen.Why(), nil
+}
+
+// maxOnSubject bounds the messages of one subject a read walks (each a read by sequence, next by subject), and maxSteps
+// the steps it reads whole to find the last ask taken: past them the read says it cannot tell, and the ask is waited for.
+const (
+	maxOnSubject = 5000
+	maxSteps     = 200
+)
+
+// seen reads what the bus holds of the ask; with later, the ask asked last that a build node took too (AskSeen.Last), when
+// the ask is on its stream.
+func (h heldOnTheBus) seen(ctx context.Context, a delivery.StepAsk, later bool) (build.AskSeen, error) {
+	seen := build.AskSeen{Kind: a.Kind, At: build.AskedAt(a.ID)}
+	module, err := delivery.BuildModuleOf(a.Language)
+	if err != nil {
+		return seen, err
+	}
+	steps, err := h.js.KeyValue(ctx, delivery.StepsBucket(module))
+	if err != nil {
+		return seen, fmt.Errorf("the bucket %s: %w", delivery.StepsBucket(module), err)
+	}
+	pattern, err := delivery.AskStepWatch(a.ID)
+	if err != nil {
+		return seen, err
+	}
+	keys, err := steps.ListKeysFiltered(ctx, pattern)
+	if err != nil {
+		return seen, err
+	}
+	for range keys.Keys() {
+		keys.Stop()
+		seen.Step = true // a node took it
+		return seen, nil
+	}
+	stream, name, subject, err := h.stream(ctx, a.Language, a.Kind)
+	seen.Stream = name
+	if errors.Is(err, jetstream.ErrStreamNotFound) {
+		return seen, nil
+	}
+	if err != nil {
+		return seen, err
+	}
+	var ahead []build.Queued
+	err = onSubject(ctx, stream, subject, func(q build.Queued) bool {
+		if q.Ask == a.ID {
+			seen.OnStream, seen.PutAt = true, q.PutAt
+			return false
+		}
+		ahead = append(ahead, q)
+		return true
+	})
+	if err != nil || !seen.OnStream || !later {
+		return seen, err
+	}
+	taken, err := stepKeys(ctx, steps)
+	if err != nil {
+		return seen, err
+	}
+	for i := range ahead {
+		ahead[i].Step = stepState(ctx, steps, taken[ahead[i].Ask])
+	}
+	seen.Ahead = ahead
+	since := seen.At
+	if since.IsZero() {
+		since = seen.PutAt
+	}
+	for _, q := range ahead {
+		if q.At.Before(since) {
+			since = q.At
+		}
+	}
+	seen.Last = lastTaken(ctx, steps, taken, a.Kind, since)
+	return seen, nil
+}
+
+// stream is the build seat's stream of language, its name and the subject of kind on it.
+func (h heldOnTheBus) stream(ctx context.Context, language, kind string) (jetstream.Stream, string, string, error) {
+	subject, err := delivery.AskSubject(language, kind)
+	if err != nil {
+		return nil, "", "", err
+	}
+	// The seat's stream by its name (delivery.AskStream), as the broker grants the builder its information and its
+	// messages by sequence and nothing wider (issue 1910).
+	name, err := delivery.AskStream(language)
+	if err != nil {
+		return nil, "", "", err
+	}
+	stream, err := h.js.Stream(ctx, name)
+	return stream, name, subject, err
+}
+
+// onSubject hands each message of subject on stream to each, in order, until each answers false or the subject's
+// messages end. A seat's stream is a work queue, which takes no second consumer over its subjects: its messages are read
+// by sequence instead, each the next of the subject (one read per message, none for the sequences taken between), and
+// none consumed.
+func onSubject(ctx context.Context, stream jetstream.Stream, subject string, each func(build.Queued) bool) error {
+	for seq, n := uint64(1), 0; ; n++ {
+		if n >= maxOnSubject {
+			return fmt.Errorf("%s holds more than %d messages before the one asked after: not read further", subject, maxOnSubject)
+		}
+		m, err := stream.GetMsg(ctx, seq, jetstream.WithGetMsgSubject(subject))
+		if errors.Is(err, jetstream.ErrMsgNotFound) {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+		q := build.Queued{Seq: m.Sequence, Ask: m.Header.Get(jetstream.MsgIDHeader), PutAt: m.Time}
+		if _, kind, err := delivery.ParseAskSubject(m.Subject); err == nil {
+			q.Kind = kind
+		}
+		if q.At = build.AskedAt(q.Ask); q.At.IsZero() {
+			q.At = q.PutAt
+		}
+		if !each(q) {
+			return nil
+		}
+		seq = m.Sequence + 1
+	}
+}
+
+// stepKeys are the build module's step keys by ask id: `<node>.<ask id>` (a node's own key, such as its pause, has no
+// ask id and is left out).
+func stepKeys(ctx context.Context, steps jetstream.KeyValue) (map[string][]string, error) {
+	all, err := steps.ListKeys(ctx)
+	if err != nil {
+		if errors.Is(err, jetstream.ErrNoKeysFound) {
+			return map[string][]string{}, nil
+		}
+		return nil, err
+	}
+	defer all.Stop()
+	out := map[string][]string{}
+	for k := range all.Keys() {
+		if _, id, ok := strings.Cut(k, "."); ok && !build.AskedAt(id).IsZero() {
+			out[id] = append(out[id], k)
+		}
+	}
+	return out, nil
+}
+
+// stepState is the state of the first of keys a node wrote, "" for none.
+func stepState(ctx context.Context, steps jetstream.KeyValue, keys []string) string {
+	for _, k := range keys {
+		e, err := steps.Get(ctx, k)
+		if err != nil {
+			continue
+		}
+		if s, err := delivery.DecodeStep(e.Value()); err == nil {
+			return s.State
+		}
+	}
+	return ""
+}
+
+// lastTaken is the ask asked last after since that a build node took, of a kind whose taking proves kind passed
+// (build.Proves), read newest first and at most maxSteps of them; nil for none. A step's tool is "<kind> ask"
+// (mesh-sdk buildstep).
+func lastTaken(ctx context.Context, steps jetstream.KeyValue, taken map[string][]string, kind string, since time.Time) *build.Taken {
+	var ids []string
+	for id := range taken {
+		if build.AskedAt(id).After(since) {
+			ids = append(ids, id)
+		}
+	}
+	sort.Slice(ids, func(i, j int) bool { return build.AskedAt(ids[i]).After(build.AskedAt(ids[j])) })
+	read := 0
+	for _, id := range ids {
+		for _, k := range taken[id] {
+			if read >= maxSteps {
+				return nil
+			}
+			read++
+			e, err := steps.Get(ctx, k)
+			if err != nil {
+				continue
+			}
+			s, err := delivery.DecodeStep(e.Value())
+			if err != nil {
+				continue
+			}
+			stepKind, ok := strings.CutSuffix(s.Tool, " ask")
+			if !ok || !build.Proves(stepKind, kind) {
+				continue
+			}
+			return &build.Taken{Ask: id, Kind: stepKind, At: build.AskedAt(id), Node: s.Node, Started: s.Started}
+		}
+	}
+	return nil
+}
+
+// Drop is build.Dropper's Drop: it removes the ask's message from its build seat's stream, found by its Nats-Msg-Id on its
+// subject, when the stream still holds it. The builder's account must be granted $JS.API.STREAM.MSG.DELETE.<stream>.
+func (h heldOnTheBus) Drop(ctx context.Context, a delivery.StepAsk) error {
+	stream, name, subject, err := h.stream(ctx, a.Language, a.Kind)
+	if errors.Is(err, jetstream.ErrStreamNotFound) {
+		return nil
+	}
+	if err != nil {
+		return err
+	}
+	var seq uint64
+	if err := onSubject(ctx, stream, subject, func(q build.Queued) bool {
+		if q.Ask == a.ID {
+			seq = q.Seq
+			return false
+		}
+		return true
+	}); err != nil || seq == 0 {
+		return err
+	}
+	if err := stream.DeleteMsg(ctx, seq); err != nil && !errors.Is(err, jetstream.ErrMsgNotFound) {
+		return fmt.Errorf("deleting message %d of %s (is $JS.API.STREAM.MSG.DELETE.%s granted to the builder?): %w", seq, name, name, err)
+	}
+	return nil
+}
+
+// Queue is what the tool builder_seat_queue answers (build.SeatQueue): the messages of language's build seat's stream, of
+// every kind, oldest first and at most limit of each kind, each with its step's state and whether it still waits.
+func (h heldOnTheBus) Queue(ctx context.Context, language string, limit int) (build.SeatQueue, error) {
+	q := build.SeatQueue{Language: language, Note: build.QueueNote}
+	module, err := delivery.BuildModuleOf(language)
+	if err != nil {
+		return q, err
+	}
+	stream, name, _, err := h.stream(ctx, language, delivery.AskDelivery)
+	q.Stream = name
+	if errors.Is(err, jetstream.ErrStreamNotFound) {
+		q.Note = name + " does not exist"
+		return q, nil
+	}
+	if err != nil {
+		return q, err
+	}
+	info, err := stream.Info(ctx)
+	if err != nil {
+		return q, err
+	}
+	q.Messages, q.FirstSeq, q.LastSeq = info.State.Msgs, info.State.FirstSeq, info.State.LastSeq
+	steps, err := h.js.KeyValue(ctx, delivery.StepsBucket(module))
+	if err != nil {
+		return q, fmt.Errorf("the bucket %s: %w", delivery.StepsBucket(module), err)
+	}
+	taken, err := stepKeys(ctx, steps)
+	if err != nil {
+		return q, err
+	}
+	for _, kind := range delivery.AskKinds {
+		subject, _ := delivery.AskSubject(language, kind)
+		var ahead []build.Queued
+		if err := onSubject(ctx, stream, subject, func(m build.Queued) bool {
+			ahead = append(ahead, m)
+			return len(ahead) < limit
+		}); err != nil {
+			return q, err
+		}
+		if len(ahead) == 0 {
+			continue
+		}
+		for i := range ahead {
+			ahead[i].Step = stepState(ctx, steps, taken[ahead[i].Ask])
+		}
+		seen := build.AskSeen{Kind: kind, Ahead: ahead, Last: lastTaken(ctx, steps, taken, kind, ahead[0].At)}
+		q.Kinds = append(q.Kinds, build.NewKindQueue(kind, seen, time.Now()))
+	}
+	return q, nil
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/main.go

@@ -5,38 +5,39 @@
 package main
 
 import (
+	"cmp"
 	"context"
-	"crypto/sha256"
-	"crypto/tls"
-	"crypto/x509"
-	"encoding/hex"
-	"encoding/json"
-	"errors"
 	"fmt"
-	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
 	"io"
 	"log"
+	"maps"
 	"os"
 	"os/signal"
+	"slices"
 	"strings"
+	"sync"
 	"syscall"
 	"time"
 
+	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
+	"git.novox.be/novox/mesh-delivery/sdk/forms"
+
 	"github.com/nats-io/nats.go"
 	"github.com/nats-io/nats.go/jetstream"
 
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/process"
+	"git.novox.be/novox/mesh-sdk/go/views"
 
 	"mesh-delivery-builder/internal/build"
+	"mesh-delivery-builder/internal/versions"
 )
 
 const (
-	// defaultStepBound is how long the builder waits for one step of a build module (a fetch downloads the Go modules, a
-	// build compiles).
+	// defaultStepBound is how long one ask's step may run once a build node took it (a fetch downloads the Go modules, a
+	// build compiles): from its start, never from its put, so an ask waiting in its stream for a free slot is not failed
+	// (buildrun.Asker.Bound; ADR 0525 §3, §6).
 	defaultStepBound = 30 * time.Minute
-	// nodesPerFingerprint is how many build nodes build each fingerprint until release R4e (ADR 0478 clause 4).
-	nodesPerFingerprint = 2
 )
 
 func main() {
@@ -48,202 +49,421 @@ func main() {
 	}
 }
 
-// credential is the broker file the controller issues to the module: JSON of the bus address, the certificate
-// fingerprint to pin, the principal and its password (as the indexer reads it; issue 1242 moves this into the SDK).
-type credential struct {
-	URL         string `json:"url"`
-	Fingerprint string `json:"fingerprint"`
-	Node        string `json:"node"`
-	Module      string `json:"module"`
-	User        string `json:"user"`
-	Password    string `json:"password"`
-}
-
-func readCredential(path string) (credential, error) {
-	raw, err := os.ReadFile(path)
-	if err != nil {
-		return credential{}, err
-	}
-	var c credential
-	if err := json.Unmarshal(raw, &c); err != nil {
-		return credential{}, fmt.Errorf("the broker credential is not one: %w", err)
-	}
-	if c.URL == "" || c.User == "" {
-		return credential{}, errors.New("the broker credential names no bus address or user")
-	}
-	return c, nil
-}
-
-// pinned accepts exactly the certificate with this SHA-256 and no other.
-func pinned(want string) *tls.Config {
-	return &tls.Config{
-		InsecureSkipVerify: true, //nolint:gosec // replaced by the pin below, which is stricter
-		MinVersion:         tls.VersionTLS12,
-		VerifyPeerCertificate: func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
-			if len(rawCerts) == 0 {
-				return errors.New("the bus presented no certificate")
-			}
-			sum := sha256.Sum256(rawCerts[0])
-			if got := "sha256:" + hex.EncodeToString(sum[:]); got != want {
-				return fmt.Errorf("the bus presented a certificate this mesh does not know (%.23s…)", got)
-			}
-			return nil
-		},
-	}
-}
-
 // run is the program: it returns when ctx ends or the bus cannot be used.
 func run(ctx context.Context, getenv func(string) string, logOut io.Writer) error {
 	logger := log.New(logOut, "mesh-delivery-builder: ", log.LstdFlags)
-	path := strings.TrimSpace(getenv("MESH_BROKER_FILE"))
-	if path == "" {
-		return errors.New("MESH_BROKER_FILE is not set, so there is no credential to hear the bus with")
-	}
-	cred, err := readCredential(path)
+	cred, err := process.ReadBrokerAccount(getenv)
 	if err != nil {
 		return err
 	}
-	opts := []nats.Option{
-		nats.Name(cred.Node + "." + cred.Module),
-		nats.UserInfo(cred.User, cred.Password),
-		nats.CustomInboxPrefix("_INBOX." + cred.User),
-		nats.MaxReconnects(-1),
-		nats.RetryOnFailedConnect(true),
-	}
-	if strings.TrimSpace(cred.Fingerprint) != "" {
-		opts = append(opts, nats.Secure(pinned(cred.Fingerprint)))
-	}
-	conn, err := nats.Connect(cred.URL, opts...)
+	conn, js, err := cred.Dial()
 	if err != nil {
-		return fmt.Errorf("connecting to the bus: %w", err)
+		return err
 	}
 	defer conn.Close()
-	js, err := jetstream.New(conn)
+	builds, err := process.EssentialBucket(ctx, js, "builder", delivery.BuilderBuildsBucket, "claim or write a build key")
 	if err != nil {
 		return err
 	}
-	bucket := func(name string) (jetstream.KeyValue, error) {
-		kv, err := js.KeyValue(ctx, name)
-		if err != nil {
-			return nil, fmt.Errorf("the bucket %s: %w", name, err)
-		}
-		return kv, nil
-	}
-	builds, err := bucket(delivery.BuilderBuildsBucket)
+	// The indexer's modules, manifests, candidates and packages and the assigner's placement are their owners' states, read by the
+	// first view of their read tools and then their views families, never their buckets (ADR 0615 §1, DLV-M1). An owner that
+	// is down never holds the start: each is read on a goroutine once its first view is answered, and until then the
+	// unanswered first view is the builder's finding.
+	calls, err := process.Connect(cred, nats.Name(cred.Node+"."+cred.Module+".calls"), nats.RetryOnFailedConnect(true))
 	if err != nil {
 		return err
 	}
-	modules, err := bucket(delivery.ModulesBucket)
+	defer calls.Close()
+	reader := &views.ProcessReader{Module: delivery.BuilderModule, Call: calls.Call, Logf: logger.Printf}
+	findingsKV := process.AwaitBucket(ctx, js, conn, findingsBucket, "the builder's findings, a first view unanswered past its bound among them, are said in its log only", logger.Printf)
+	reader.Findings = findingsKV.KV
+	modules, err := reader.Follow(delivery.IndexerModule, modulesState, delivery.IndexerModule+".indexer_read_modules", indexerViews)
 	if err != nil {
 		return err
 	}
-	manifests, err := bucket(delivery.ManifestsBucket)
+	manifests, err := reader.Follow(delivery.IndexerModule, manifestsState, delivery.IndexerModule+".indexer_read_manifests", indexerViews)
 	if err != nil {
 		return err
 	}
-	candidates, err := bucket(delivery.CandidatesBucket)
+	// The candidates' fingerprints are built too (issue 1684).
+	candidates, err := reader.Follow(delivery.IndexerModule, candidatesState, delivery.IndexerModule+".indexer_read_candidates", indexerViews)
 	if err != nil {
 		return err
 	}
-	// Calls to the build modules go out as this module's own account, naming the machine (mesh-sdk process.CallOn); the
-	// buckets are read and written on the connection above.
-	account, err := process.ReadAccount(path)
+	// The indexer's packages, whose names a package is numbered under (design 32).
+	packages, err := reader.Follow(delivery.IndexerModule, delivery.PackagesState, delivery.IndexerModule+".indexer_read_packages", indexerViews)
 	if err != nil {
 		return err
 	}
-	caller, err := process.Connect(account, nats.Name(cred.Node+"."+cred.Module+".calls"), nats.RetryOnFailedConnect(true))
+	placement, err := reader.Follow(delivery.AssignerModule, delivery.PlacementState, delivery.AssignerModule+".assigner_read_placement", assignerViews)
 	if err != nil {
 		return err
 	}
-	defer caller.Close()
-
 	bound := defaultStepBound
 	if v := strings.TrimSpace(getenv("MESH_BUILDER_STEP_BOUND")); v != "" {
 		if bound, err = time.ParseDuration(v); err != nil {
 			return fmt.Errorf("MESH_BUILDER_STEP_BOUND: %w", err)
 		}
 	}
-	capacity, err := capacityFrom(strings.TrimSpace(getenv("MESH_BUILDER_SETTINGS")), getenv("MESH_BUILDER_CAPACITY"))
-	if err != nil {
-		return fmt.Errorf("the build capacity setting: %w", err)
+	// An unanswered tag ask is narrated every TagAskBound (design 51: five minutes); a test gives a shorter one.
+	tagAskBound := versions.TagAskBound
+	if v := strings.TrimSpace(getenv("MESH_BUILDER_TAG_ASK_BOUND")); v != "" {
+		if tagAskBound, err = time.ParseDuration(v); err != nil {
+			return fmt.Errorf("MESH_BUILDER_TAG_ASK_BOUND: %w", err)
+		}
 	}
 	tools := &buildrun.ToolchainSet{}
-	presence := &buildrun.PresenceSet{}
-	have := &buildrun.HaveSet{}
+	// Each build module's part of a build is an ask on its build seat's stream, pulled by a build node with a free slot
+	// (novox/hq ADR 0525): the builder chooses no node, so it reads neither presence nor have and holds no capacity.
+	asks := buildrun.JetStreamAsks{JS: js}
+	// The asks the build seats gave up on (issue 734): heard from DEAD_LETTERS, each ends the wait for its step at once,
+	// and the lane asks its part again (Builder.waitOnce) instead of waiting for the check bound.
+	// Heard in the background, and again at a reconnect or an ask while it is not; whether it is heard is kept in the
+	// state hearing, which builder_stuck says (dead_letters).
+	dead := &buildrun.DeadLetters{}
+	// The state may not be on the bus yet when a delivery started the builder (the grants part creates it, issue 1790): it
+	// is bound when the bus says it was created, and the latest hearing is written then.
+	hearingKV := process.AwaitBucket(ctx, js, conn, delivery.BuilderModule+"_"+buildrun.HearingState, "builder_stuck cannot say whether DEAD_LETTERS is heard", logger.Printf)
+	hearing := buildrun.NewDeadLetterHearing(ctx, buildrun.JetStreamDeadLetters{JS: js}, delivery.AskLanguages, dead, logger.Printf,
+		buildrun.SayHearing(ctx, hearingKV, logger.Printf))
+	defer hearing.Stop()
+	// Each ask's step is heard by its own watch and, at every step end of its build module and every reconnect, read
+	// (buildrun.HearEnds): a watch that goes deaf loses no end (the lost check of 2026-10-28).
+	var buildModules []string
+	for _, l := range delivery.AskLanguages {
+		if m, err := delivery.BuildModuleOf(l); err == nil {
+			buildModules = append(buildModules, m)
+		}
+	}
+	heard := buildrun.HearEnds(ctx, asks, asks, buildModules, logger.Printf)
+	conn.SetReconnectHandler(func(*nats.Conn) { hearing.Again(); heard.Nudge("") })
+	// The builder asks the controller, as its own account, whether the artifact store still holds a done key's blobs
+	// (the seat verb held, novox/hq issue 1937) before it leaves the key done, on its calls connection.
+	// The builder numbers each trunk build at its claim (novox/hq design 51 *The versions*): its state versions, bound once
+	// the bus holds it; the floor's three sources asked as its own account; each new number said as version.numbered.
+	versionsKV := process.AwaitBucket(ctx, js, conn, versions.Bucket, "no trunk build is numbered: each is built unnumbered and published by its digest", logger.Printf)
+	found := &findings{kv: findingsKV, logf: logger.Printf, now: time.Now}
+	floorWaits := &versions.FloorWaits{Logf: logger.Printf, Said: found.floorSaid(context.WithoutCancel(ctx))}
+	// The names waiting on their floor are kept in the state floor-waits (DLV-B4): a restarted builder takes them in, so
+	// their silent sources' events still wake them; until the state is bound they are kept here only.
+	process.AwaitBucket(ctx, js, conn, versions.FloorWaitsBucket, "the names waiting on their floor are kept in memory only, and builder_floor_waits shows none", logger.Printf).
+		Ready(func(kv jetstream.KeyValue) {
+			floorWaits.Keep(kvKeeper{ctx: ctx, kv: kv}, heldFloorWaits(ctx, kv, logger.Printf))
+		})
+	// A package is numbered under its name in its ecosystem, read from the indexer's packages state (design 32).
+	numberer := &versions.Numberer{Versions: versions.Versions{Store: awaitedVersions{versionsKV}}, Floor: floorVia(calls.Call), Waits: floorWaits,
+		Names: versions.NamesIn(indexerPackages{packages}),
+		Said: func(nb delivery.VersionNumbered) {
+			if err := emitNumbered(context.WithoutCancel(ctx), js, cred, nb); err != nil {
+				logger.Printf("%v", err)
+			}
+		}}
+	// A publish that ends badly is a finding (design 51 *Health and conditions*): a holder's refused, a version no holder
+	// answered within its bound (a key of the state bounds with its own time to live), a seat's outcome that does not read.
+	pubBoundsKV := process.AwaitBucket(ctx, js, conn, versions.BoundsBucket, "a publish no holder answers, and a node holding the old form seven days, are not raised", logger.Printf)
+	pubs := &publishes{bounds: pubBoundsKV.KV, versions: numberer.Versions, findings: found, bound: versions.PublishBound, logf: logger.Printf}
+	numberer.Publishing = pubs.arm
 	b := &build.Builder{
-		Claimer:    build.Claimer{Store: kvStore{builds}, By: cred.Node + "." + cred.Module},
-		Runner:     buildrun.Runner{Caller: caller, Steps: stepsWaiter{js}, Bound: bound},
+		Claimer: build.Claimer{Store: kvStore{builds}, By: cred.Node + "." + cred.Module},
+		Asks:    buildrun.Asker{Publisher: asks, Waiter: buildrun.LostAskWaiter{Inner: heard, Dead: dead, Hearing: hearing}, Bound: bound},
+		Held:    heldOnTheBus{js},
+		// An ask that can no longer be answered is asked again (issue 1945), read at the step bound: a context's bound.
+		Gone:       heldOnTheBus{js},
+		CheckAfter: bound,
 		Toolchains: tools,
-		Presence:   presence,
-		Health:     have,
-		Places:     &buildrun.Places{Capacity: capacity},
 		Manifests:  manifestReader{manifests},
-		Nodes:      nodesPerFingerprint,
 		Logf:       logger.Printf,
+		Stored:     storedVia(calls.Call),
+		Node:       cred.Node,
+	}
+	tagAsksKV := process.AwaitBucket(ctx, js, conn, versions.TagAsksBucket, "builder_tag and builder_untag are not answered", logger.Printf)
+	// A check's build of a head a kept tag ask names numbers its packages tagged (design 51 *Tagged versions*), and the ask
+	// is marked numbered with its versions.
+	b.Tags = tagsVia(tagAsksKV.KV, logger.Printf)
+	b.Numbers = build.VersionNumbers{N: numberer, TagNumbered: tagNumbered(tagAsksKV.KV, logger.Printf, time.Now)}
+	// An ask not answered within five minutes is narrated with what it waits on: its bound's end on the bus says when.
+	boundsKV := process.AwaitBucket(ctx, js, conn, versions.TagAskBoundsBucket, "an unanswered tag ask is not narrated", logger.Printf)
+	bounds := &tagBounds{asks: tagAsksKV.KV, bounds: boundsKV.KV, bound: tagAskBound, waits: floorWaits.Waiting, logf: logger.Printf, now: time.Now,
+		log: func(e delivery.BuildLogEntry) { b.Log(e) }}
+	// A state bound later numbers the builds looked at without it.
+	versionsKV.Ready(func(jetstream.KeyValue) { b.Reconsider(ctx) })
+	// The versions' hand acts (builder_publish_again, builder_floor_again) come through reasks, as builder_build_again.
+	acts := versions.Acts{Numberer: numberer, Done: doneVia(b), Reconsider: b.Reconsider, Remove: removeVia(calls.Call),
+		BuildAgain: func(ctx context.Context, module, fp, why, by string) (string, bool) {
+			r := b.BuildAgain(ctx, module, fp, why, by, buildAgainBound)
+			if r.Refused != "" {
+				return r.Refused, true
+			}
+			if r.Failed != "" {
+				return "built again, and it failed before its asks were put: " + r.Failed, false
+			}
+			return fmt.Sprintf("built again as revision %d", r.Revision), false
+		}}
+	// A candidate's preview is merged onto the trunk head the indexer previewed it onto: source.main at the candidate's base
+	// revision (the gate's source state). The source's revisions are watched with their history (a direct get of one revision
+	// is not what a read grants): a revision heard after the candidate that names it builds that candidate then. Where it
+	// cannot be read the trunk's keys are built and the candidates wait (issue 1945).
+	errs := make(chan error, 10)
+	trunks := &trunkSource{ctx: ctx, js: js, heads: &sourceHeads{}, moved: func(ctx context.Context) {
+		// A source revision heard is the forge's merge: it wakes a floor whose bridge_tags was silent (design 51 *The floor*).
+		(&floorWake{b: b, waits: floorWaits, logf: logger.Printf}).wake(ctx, versions.WakeForge, "", "")
+		b.TrunkMoved(ctx)
+	}, errs: errs, logf: logger.Printf}
+	trunks.start()
+	b.Trunk = trunks.head
+	// The builder's log (ADR 0571 §1): each build's start and end in its module log `build-log`, read by the view, the
+	// indexer and the assigner through their reads, and by the operator's command nox builds through the tool builder_builds_since.
+	b.Log = func(e delivery.BuildLogEntry) {
+		if e.Node == "" { // a narration of no one build (a tag ask, the old form's window) is this instance's
+			e.Node = cred.Node
+		}
+		if err := appendLog(context.WithoutCancel(ctx), js, cred, e); err != nil {
+			logger.Printf("%v", err)
+		}
+		// A failed trunk build is the builder's finding build-failed, cleared by a later done one (DLV-B7).
+		found.buildEnded(context.WithoutCancel(ctx), e)
+	}
+	b.Said = func(e build.AskedAgain) {
+		if err := emitAskedAgain(context.WithoutCancel(ctx), js, cred, e); err != nil {
+			logger.Printf("%v", err)
+		}
+	}
+	// **Said once every build module answered a reference, taken away when stopped** (issue 1886, ADR 0522): the
+	// controller delivers from this builder's keys only while an instance says it writes references. A bucket not there
+	// yet (the manifest's state not made) is said, and the controller's plan waits for the keys, named (no build-agent
+	// is asked since R4g, ADR 0524 §7).
+	switch kv := process.OptionalBucket(ctx, js, instancesBucket, "the controller is not told that this builder writes references until it starts again", logger.Printf); {
+	case kv == nil:
+	default:
+		says := newSayer(ctx, kv, cred.Node, []string{buildrun.GoBuildModule, buildrun.NodeBuildModule, build.ImageBuildModule}, logger.Printf)
+		b.Answered = says.Answered
+		defer func() {
+			stopping, cancel := context.WithTimeout(context.WithoutCancel(ctx), 5*time.Second)
+			defer cancel()
+			if err := says.unsay(stopping); err != nil {
+				logger.Printf("%v", err)
+			}
+		}()
 	}
 	// The toolchains first, so a build that starts from the first modules value finds the nodes.
 	watch := newToolchainWatch(ctx, js, tools, b.NodesChanged, logger)
+	// Only the toolchain reports of nodes the catalogue places the build module on count (issue 1940, ADR 0549 §3): the
+	// placement is settled first, so the toolchains settle through the gate already knowing it.
+	gate := buildrun.NewToolchainGate([]string{buildrun.GoBuildModule, buildrun.NodeBuildModule}, tools.Put, logger.Printf)
+	watch.put = gate.Toolchain
+	// What each counted node's engine reads (ADR 0618 §2, ADR 0624 §1): asked through the node-engine seat's verb as the
+	// builder's own account, for every node the placement names, and kept in the state engine-reads once it is bound.
+	reads := newEngineReads(calls.CallOn, gate, logger.Printf)
+	// The old reference form's window over them (DLV-B9), kept in the state old-form once it is bound; builder_old_form
+	// reads it and drops a retired node by hand.
+	reads.ctx = context.WithoutCancel(ctx)
+	reads.window = &oldForm{forms: forms.Current, findings: found, logf: logger.Printf, now: time.Now, log: func(e delivery.BuildLogEntry) { b.Log(e) },
+		bounds: pubBoundsKV.KV,
+		said: func(body versions.OldFormClosedBody) {
+			if err := emitEvent(context.WithoutCancel(ctx), js, cred, versions.OldFormClosedEvent, "old-form-closed-"+body.At.Format(time.RFC3339Nano), body); err != nil {
+				logger.Printf("saying %s: %v", versions.OldFormClosedEvent, err)
+			}
+		}}
+	acts.DropOldForm = func(ctx context.Context, node, by, why string, at time.Time) (string, error) {
+		answer, err := reads.window.drop(ctx, node, by, why, at)
+		if err == nil {
+			reads.stepWindow()
+		}
+		return answer, err
+	}
+	process.AwaitBucket(ctx, js, conn, versions.OldFormBucket, "the old form's window is kept in memory only, and builder_old_form shows none", logger.Printf).
+		Ready(func(kv jetstream.KeyValue) {
+			reads.window.bind(context.WithoutCancel(ctx), kv)
+			reads.stepWindow()
+		})
+	gate.OnPlaced = reads.placed
+	b.Forms = reads.built
+	// Until the placement's first view is answered the gate passes every report on, as before the placement is settled.
+	placementErrs := make(chan error, 1)
+	go func() {
+		select {
+		case <-ctx.Done():
+			return
+		case <-placement.Follower().Ready():
+		}
+		pe, err := buildrun.FollowPlacement(ctx, reader, gate, b.NodesChanged, logger.Printf)
+		if err != nil {
+			placementErrs <- err
+			return
+		}
+		placementErrs <- <-pe
+	}()
 	if err := watch.start(); err != nil {
 		return err
 	}
 	// A build module says each time it wrote its toolchains key: its stream, and the builder's durable consumer on it, are
 	// made by the controller. Where the stream is not there yet the builder says so and is started again with the build
 	// module.
+	// Each consumer that is not there yet is the finding family-not-heard naming its stream until it binds at a later
+	// start (heard.Writer; ADR 0615 §5); one there that cannot be heard stops the builder, as before.
+	notHeard := found.notHeard(ctx)
+	var stopped error
+	hear := func(stream, consequence string, each func(jetstream.Msg)) {
+		_ = notHeard.Bind(stream, consequence, func() error {
+			cons, err := cred.EventConsumer(ctx, js, stream)
+			if err != nil {
+				return fmt.Errorf("the consumer %s_%s on %s does not exist yet: %w", cred.Node, cred.Module, stream, err)
+			}
+			cc, err := process.HearEvents(cons, each, logger.Printf)
+			if err != nil {
+				stopped = cmp.Or(stopped, err)
+				return err
+			}
+			go func() { <-ctx.Done(); cc.Stop() }()
+			return nil
+		})
+	}
 	for _, module := range []string{buildrun.GoBuildModule, buildrun.NodeBuildModule} {
-		stream := toolchainStreams[module]
-		cons, err := js.Consumer(ctx, stream, cred.Node+"_"+cred.Module)
-		if err != nil {
-			logger.Printf("the consumer %s_%s on %s does not exist yet, so %s's reports are not heard until the builder starts again: %v", cred.Node, cred.Module, stream, module, err)
-			continue
-		}
-		cc, err := cons.Consume(func(m jetstream.Msg) { watch.Reported(m) },
-			jetstream.ConsumeErrHandler(func(_ jetstream.ConsumeContext, err error) { logger.Printf("hearing the bus: %v", err) }))
-		if err != nil {
-			return err
-		}
-		defer cc.Stop()
+		hear(toolchainStreams[module], module+"'s toolchain reports are not heard until the builder starts again", func(m jetstream.Msg) { watch.Reported(m) })
 	}
-	// The watchman's presence says which nodes are asleep. Where its bucket is not there yet no node is online, so nothing
-	// builds; the builder says so and is started again with the watchman.
-	presenceErrs := make(chan error, 1)
-	switch kv, err := js.KeyValue(ctx, delivery.PresenceBucket); {
-	case errors.Is(err, jetstream.ErrBucketNotFound):
-		logger.Printf("the bucket %s does not exist yet: no node counts as online until the builder starts again", delivery.PresenceBucket)
-	case err != nil:
-		return fmt.Errorf("the bucket %s: %w", delivery.PresenceBucket, err)
-	default:
-		pw, err := settle(ctx, kv, func(e jetstream.KeyValueEntry) { presence.Put(e.Key(), e.Value(), !opOf(e)) })
-		if err != nil {
-			return err
+	// The seat mesh-artifact-sweep says artifacts-gone when it found a key's blob gone (issue 1937, ADR 0571 §2): the
+	// builder's durable consumer on EVENTS, made by the grants part from the manifest's consumes. Where it is not there yet the builder says
+	// so; it still asks held at its start and at every module value.
+	// The same consumer carries what wakes a floor (design 51 *The floor*): the indexer's manifest-accepted and the
+	// condition keeper's condition-cleared.
+	floor := floorWake{b: b, waits: floorWaits, logf: logger.Printf}
+	// And the four registry seats' published, refused and removed (DLV-B4), which move a numbered version.
+	seats := seatHearer{n: numberer, b: b, logf: logger.Printf, pub: pubs}
+	hear(eventsStream, delivery.ArtifactsGoneEvent+", what wakes a floor, the registry seats' words and manifest-reads-changed are not heard until the builder starts again", func(m jetstream.Msg) {
+		if reads.heard(m, logger.Printf) || floor.heard(ctx, m) || seats.heard(ctx, m) { // reads: the node-engine seat's manifest-reads-changed (ADR 0618 §4)
+			return
 		}
-		go func() {
-			presenceErrs <- follow(ctx, pw, func(e jetstream.KeyValueEntry) {
-				if presence.Put(e.Key(), e.Value(), !opOf(e)) {
-					b.NodesChanged(ctx) // a node came online or went: a build that waited for one may go on
-				}
-			})
-		}()
+		heardGone(ctx, b, m, logger.Printf)
+	})
+	if stopped != nil {
+		return stopped
 	}
-	// The node-engine's have says whether a node's build module runs and is healthy: a node whose build module is not is not
-	// chosen (ADR 0478 clause 3). Where its bucket is not there yet no build module counts as healthy, so nothing builds.
-	haveErrs := make(chan error, 1)
-	switch kv, err := js.KeyValue(ctx, delivery.HaveBucket); {
-	case errors.Is(err, jetstream.ErrBucketNotFound):
-		logger.Printf("the bucket %s does not exist yet: no build module counts as healthy until the builder starts again", delivery.HaveBucket)
-	case err != nil:
-		return fmt.Errorf("the bucket %s: %w", delivery.HaveBucket, err)
-	default:
-		hw, err := settle(ctx, kv, func(e jetstream.KeyValueEntry) { have.Put(e.Key(), e.Value(), !opOf(e)) })
-		if err != nil {
-			return err
+	reader.Start(ctx, js, cred, process.AwaitBucket(ctx, js, conn, firstViewsBucket, "builder_first_views reads nothing and builder_first_view_again is not heard", logger.Printf))
+	// The modules, once their first views and the manifests' are answered: what a module builds is read from the manifests.
+	go func() { errs <- buildFromModules(ctx, b, modules, manifests, candidates) }()
+	// A package's name heard in the indexer's packages looks at its module again, so a done build is numbered then.
+	go func() { errs <- followPackages(ctx, packages, b, logger.Printf) }()
+	// A person asks a key's build again with builder_ask_again, which writes the reasks state (issue 1945): watched, as
+	// every other input. The builder asks again by itself without it.
+	// A state not on the bus yet at this start is watched once it appears (issue 1790).
+	process.AwaitBucket(ctx, js, conn, build.ReAsksBucket, "builder_ask_again is not heard; an ask that can no longer be answered is still asked again by itself", logger.Printf).Ready(func(kv jetstream.KeyValue) {
+		eachReAsk := func(e jetstream.KeyValueEntry) { reAsked(ctx, b, acts, kv, e, logger.Printf) }
+		if rw, err := settle(ctx, kv, eachReAsk); err != nil {
+			process.NotWatched(logger.Printf, build.ReAsksBucket, err, "builder_ask_again is not heard until the builder starts again")
+		} else {
+			go func() { errs <- follow(ctx, rw, eachReAsk) }()
 		}
-		go func() {
-			haveErrs <- follow(ctx, hw, func(e jetstream.KeyValueEntry) {
-				if have.Put(e.Key(), e.Value(), !opOf(e)) {
-					b.NodesChanged(ctx) // a build module became healthy or stopped being: a build that waited may go on
+	})
+	// A tag ask or a branch's removal by hand (builder_tag, builder_untag) is written to tag-asks and answered there
+	// (design 51 *Tagged versions*); the checker's tag-wanted and the branch's end join it on their consumers (DLV-B6).
+	tagAsksKV.Ready(func(kv jetstream.KeyValue) {
+		each := func(e jetstream.KeyValueEntry) {
+			tagAsked(ctx, acts, kv, e, logger.Printf)
+			if !opOf(e) {
+				bounds.disarm(ctx, e.Key())
+			} else if t, err := versions.DecodeTagAsk(e.Value()); err == nil {
+				bounds.asked(ctx, e.Key(), t)
+			}
+		}
+		if tw, err := settle(ctx, kv, each); err != nil {
+			process.NotWatched(logger.Printf, versions.TagAsksBucket, err, "builder_tag and builder_untag are not answered until the builder starts again")
+		} else {
+			go func() { errs <- follow(ctx, tw, each) }()
+		}
+	})
+	pubBoundsKV.Ready(func(kv jetstream.KeyValue) {
+		each := func(e jetstream.KeyValueEntry) {
+			if versions.IsOldFormBound(e.Key()) {
+				if e.Operation() == jetstream.KeyValuePurge {
+					reads.stepWindow() // a node's seven days ended: the step raises old-form-held now
 				}
-			})
-		}()
+				return
+			}
+			pubs.ended(ctx, e)
+		}
+		watchBounds(ctx, kv, each, found.notHeard(ctx), errs, logger.Printf)
+	})
+	boundsKV.Ready(func(kv jetstream.KeyValue) {
+		each := func(e jetstream.KeyValueEntry) { bounds.ended(ctx, e) }
+		if bw, err := settle(ctx, kv, each); err != nil {
+			process.NotWatched(logger.Printf, versions.TagAskBoundsBucket, err, "an unanswered tag ask is not narrated until the builder starts again")
+		} else {
+			go func() { errs <- follow(ctx, bw, each) }()
+		}
+	})
+	// A person reads a build seat's stream with builder_seat_queue, which writes the queues state (issue 1945 note 62): the
+	// builder alone may read the stream, so it answers there.
+	process.AwaitBucket(ctx, js, conn, build.QueuesBucket, "builder_seat_queue is not answered", logger.Printf).Ready(func(kv jetstream.KeyValue) {
+		eachRead := func(e jetstream.KeyValueEntry) { queueRead(ctx, heldOnTheBus{js}, kv, e, logger.Printf) }
+		if qw, err := settle(ctx, kv, eachRead); err != nil {
+			process.NotWatched(logger.Printf, build.QueuesBucket, err, "builder_seat_queue is not answered until the builder starts again")
+		} else {
+			go func() { errs <- follow(ctx, qw, eachRead) }()
+		}
+	})
+	// A branch's end removes its tagged versions (design 51 *Tagged versions*, DLV-B6): the forge bridge's merged, a pull's
+	// closed or branch-deleted on the builder's durable consumer of its stream; each forge message also wakes a floor whose
+	// bridge_tags was silent. The checker's tag-wanted is kept in tag-asks. A consumer not there yet is said.
+	ends := &branchEnds{acts: acts, findings: found, tagAsks: tagAsksKV.KV, logf: logger.Printf, now: time.Now,
+		wake: func(ctx context.Context) {
+			(&floorWake{b: b, waits: floorWaits, logf: logger.Printf}).wake(ctx, versions.WakeForge, "", "")
+		}}
+	for _, c := range []struct {
+		stream, what string
+		hear         func(jetstream.Msg)
+	}{
+		{forgeStream, "a branch's end", func(m jetstream.Msg) { ends.heard(ctx, m) }},
+		{checkerAsksStream, "the checker's tag-wanted", func(m jetstream.Msg) {
+			tagWanted(ctx, tagAsksKV.KV(), m, delivery.CheckerModule, time.Now(), logger.Printf)
+		}},
+	} {
+		hear(c.stream, c.what+" is not heard until the builder starts again", c.hear)
+	}
+	if stopped != nil {
+		return stopped
+	}
+	// The state engine-reads, new with ADR 0618 (issue 1790's kind): until it is on the bus each statement is kept in memory
+	// only, and builder_engine_reads answers nothing.
+	process.AwaitBucket(ctx, js, conn, engineReadsBucket, "what each node's engine reads is kept in memory only", logger.Printf).Ready(func(kv jetstream.KeyValue) {
+		reads.bind(ctx, kv, errs, logger.Printf)
+	})
+	logger.Printf("started on %s", cred.Node)
+	select {
+	case <-ctx.Done():
+		b.Wait()
+		return nil
+	case err := <-errs:
+		return err
+	case err := <-placementErrs:
+		return err
+	case err := <-watch.errs:
+		return err
+	}
+}
+
+// The builder's own state of its first views (views.StatusState); its findings (findingsBucket) are where the condition
+// keeper raises a first view unanswered past its bound (ADR 0615 §6).
+var firstViewsBucket = delivery.BuilderModule + "_" + views.StatusState
+
+// The indexer's states the builder follows (delivery.ModulesBucket, ManifestsBucket, CandidatesBucket), and the owners'
+// views families as their manifests' `streams` name them.
+const (
+	indexerViews    = "indexer-views"
+	assignerViews   = "assigner-views"
+	modulesState    = "modules"
+	manifestsState  = "manifests"
+	candidatesState = "candidates"
+)
+
+// buildFromModules builds from the indexer's modules and candidates once the first views of the modules, the manifests and
+// the candidates are answered (never at the start: an indexer that is down holds no other part of it), and follows them.
+func buildFromModules(ctx context.Context, b *build.Builder, modules, manifests, candidates *views.Picture) error {
+	for _, p := range []*views.Picture{modules, manifests, candidates} {
+		select {
+		case <-ctx.Done():
+			return nil
+		case <-p.Follower().Ready():
+		}
 	}
 	each := func(e jetstream.KeyValueEntry) {
 		if opOf(e) {
@@ -272,21 +492,53 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	if err != nil {
 		return err
 	}
-	logger.Printf("started on %s", cred.Node)
-	errs := make(chan error, 2)
-	go func() { errs <- follow(ctx, w, each) }()
-	go func() { errs <- follow(ctx, cw, eachCandidate) }()
-	select {
-	case <-ctx.Done():
-		b.Wait()
-		return nil
-	case err := <-errs:
-		return err
-	case err := <-watch.errs:
-		return err
-	case err := <-presenceErrs:
-		return err
-	case err := <-haveErrs:
-		return err
+	go func() { _ = follow(ctx, cw, eachCandidate) }()
+	return follow(ctx, w, each)
+}
+
+// sourceHeads are the trunk heads of each revision of the gate's source.main the watch delivered, the newest
+// delivery.SourceHistory of them: what a candidate's base revision names.
+type sourceHeads struct {
+	mu    sync.Mutex
+	byRev map[uint64]map[string]string
+}
+
+// put takes one revision in and answers whether it is new.
+func (s *sourceHeads) put(e jetstream.KeyValueEntry) bool {
+	if !opOf(e) {
+		return false
 	}
+	src, err := delivery.DecodeSource(e.Value())
+	if err != nil {
+		return false
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.byRev == nil {
+		s.byRev = map[uint64]map[string]string{}
+	}
+	if _, had := s.byRev[e.Revision()]; had {
+		return false
+	}
+	s.byRev[e.Revision()] = src.Heads
+	for len(s.byRev) > delivery.SourceHistory {
+		delete(s.byRev, slices.Min(slices.Collect(maps.Keys(s.byRev))))
+	}
+	return true
+}
+
+// head is the head of repository in revision rev; an error when the revision is not heard (yet, or any more).
+func (s *sourceHeads) head(_ context.Context, rev uint64, repository string) (string, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	heads, ok := s.byRev[rev]
+	if !ok {
+		return "", fmt.Errorf("source revision %d is not heard (it is built once it is)", rev)
+	}
+	for r, head := range heads {
+		if delivery.SameRepository(r, repository) {
+			return head, nil
+		}
+	}
+	return "", nil
 }

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/oldform.go

@@ -0,0 +1,187 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"slices"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+
+	"git.novox.be/novox/mesh-delivery/sdk/forms"
+
+	"mesh-delivery-builder/internal/versions"
+)
+
+// oldForm keeps the old reference form's window (design 51 *Every build keeps the old reference form*, DLV-B9) in the
+// state old-form: stepped on every change of what the counted nodes state, of the placement, on a hand drop and at each
+// build key written, never on a timer. A node holding it seven days is the finding old-form-held; its close is said once
+// as version.old-form-closed and in the builder's log.
+type oldForm struct {
+	forms    forms.ArtifactForms
+	findings *findings
+	// said emits version.old-form-closed.
+	said func(versions.OldFormClosedBody)
+	// log writes the close into the builder's build log (build.said); nil writes none.
+	log  func(delivery.BuildLogEntry)
+	logf func(string, ...any)
+	now  func() time.Time
+
+	// bounds is the builder's state bounds: each node holding the window has a key there whose time to live ends at its
+	// seven days, so old-form-held is raised then, not at the next change (review round 1); nil keeps none.
+	bounds func() jetstream.KeyValue
+
+	mu sync.Mutex
+	w  versions.OldFormWindow
+	kv jetstream.KeyValue
+	// overdue are the nodes the finding is raised for now.
+	overdue []string
+}
+
+// bind takes the kept window in, so a restarted builder keeps each node's since and the nodes dropped by hand, and keeps
+// every later step in kv.
+func (o *oldForm) bind(ctx context.Context, kv jetstream.KeyValue) {
+	e, err := kv.Get(ctx, versions.OldFormKey)
+	o.mu.Lock()
+	defer o.mu.Unlock()
+	switch {
+	case errors.Is(err, jetstream.ErrKeyNotFound):
+	case err != nil:
+		o.logf("%s.%s cannot be read, so the window starts again: %v", versions.OldFormState, versions.OldFormKey, err)
+	default:
+		w, err := versions.DecodeOldFormWindow(e.Value())
+		if err != nil {
+			o.logf("%v; the window starts again", err)
+			break
+		}
+		// Taken in under what was stepped before the state was bound: the kept since and drops are the older truth.
+		for n, s := range o.w.Since {
+			if _, ok := w.Since[n]; !ok && w.Open && slices.Contains(w.Holding, n) {
+				w.Since[n] = s
+			}
+		}
+		for _, d := range o.w.Dropped {
+			w, _ = w.Drop(d.Node, d.By, d.Why, d.At)
+		}
+		o.w = w
+	}
+	o.kv = kv
+	o.keep(ctx)
+}
+
+// dropped is the nodes dropped by hand.
+func (o *oldForm) dropped() map[string]bool {
+	o.mu.Lock()
+	defer o.mu.Unlock()
+	return o.w.DroppedSet()
+}
+
+// step moves the window to what counted states.
+// named is every node the read named (the placement's nodes before any is dropped), counted the statements of those
+// still counted: a read naming no node judges nothing (delivery.StepWindow), so it never closes the window.
+func (o *oldForm) step(ctx context.Context, named []string, counted map[string][]string) {
+	o.mu.Lock()
+	defer o.mu.Unlock()
+	before := o.w
+	next, closed, overdue := o.w.Step(named, versions.Holding(o.forms, counted, o.w.DroppedSet()), o.now())
+	o.w = next
+	if !slices.Equal(before.Holding, next.Holding) || before.Open != next.Open || closed {
+		o.keep(ctx)
+	}
+	for _, n := range o.overdue {
+		if !slices.Contains(overdue, n) {
+			o.findings.clear(ctx, versions.OldFormHeld, health.ScopeMachine, n)
+		}
+	}
+	for _, n := range overdue {
+		o.findings.raise(ctx, finding{kind: versions.OldFormHeld, scope: health.ScopeMachine, id: n,
+			summary: fmt.Sprintf("the node-engine of %s has read only an older reference form since %s, so every build key still carries it",
+				n, next.Since[n].Format(time.RFC3339)),
+			headline:    "A node holds the old reference form",
+			explanation: "The builder writes an older reference form into every build key while a counted node's engine reads none of the newest (ADR 0624 §1); this node has held it seven days.",
+			resolved:    "The node's engine states the newest form, the node leaves the placement, or it is dropped as retired.",
+			needs:       "builder_old_form shows the window; a retired node is dropped there by hand; builder_engine_reads asks the node again."})
+	}
+	o.overdue = overdue
+	o.keepBounds(ctx, before, next, overdue)
+	if closed {
+		body := next.Closing()
+		line := fmt.Sprintf("the old reference form's window closed at %s: no counted node-engine reads only an older form (last held by %s; dropped by hand: %d); new build keys leave it out",
+			body.At.Format(time.RFC3339), strings.Join(body.LastHolding, ", "), len(body.Dropped))
+		o.logf("%s", line)
+		// In the build log too (design 51 *The node-engine's own build*), under the builder's own key, the window's key
+		// standing for the fingerprint: the close is no one build's.
+		if o.log != nil {
+			o.log(delivery.BuildLogEntry{Event: delivery.BuildSaidEvent, Module: delivery.BuilderModule, FP: versions.OldFormKey,
+				At: body.At.UTC(), Line: line, Why: versions.SaidOldFormClosed})
+		}
+		if o.said != nil {
+			o.said(body)
+		}
+	}
+}
+
+// keepBounds writes a bound for each node holding the window and not yet overdue, ending at its seven days, and deletes
+// the bound of each node that no longer holds it. A standing bound keeps its time (a Create). Called with mu held.
+func (o *oldForm) keepBounds(ctx context.Context, before, next versions.OldFormWindow, overdue []string) {
+	if o.bounds == nil {
+		return
+	}
+	kv := o.bounds()
+	if kv == nil {
+		return
+	}
+	for _, n := range before.Holding {
+		if !slices.Contains(next.Holding, n) {
+			if err := kv.Delete(ctx, versions.OldFormBoundKey(n)); err != nil && !errors.Is(err, jetstream.ErrKeyNotFound) {
+				o.logf("the old form's bound of %s is not deleted: %v", n, err)
+			}
+		}
+	}
+	for _, n := range next.Holding {
+		left := next.Since[n].Add(versions.FindingAfter).Sub(o.now())
+		if slices.Contains(overdue, n) || left <= 0 {
+			continue
+		}
+		if left < time.Second {
+			left = time.Second // the bus's least time to live
+		}
+		if _, err := kv.Create(ctx, versions.OldFormBoundKey(n), versions.EncodeBound("the seven days "+n+" holds the old form's window", o.now().Add(left)), jetstream.KeyTTL(left)); err != nil && !errors.Is(err, jetstream.ErrKeyExists) {
+			o.logf("the old form's bound of %s is not written, so its seven days are seen at the next change only: %v", n, err)
+		}
+	}
+}
+
+// drop is builder_old_form's drop: the node leaves the count, the window is stepped by the caller.
+func (o *oldForm) drop(ctx context.Context, node, by, why string, at time.Time) (string, error) {
+	o.mu.Lock()
+	defer o.mu.Unlock()
+	w, err := o.w.Drop(node, by, why, at)
+	if err != nil {
+		return "", err
+	}
+	o.w = w
+	o.keep(ctx)
+	return node + " dropped from the old form's count by hand; the window is stepped now", nil
+}
+
+// keep writes the window, once the state is bound; until then it is kept here only. Called with mu held.
+func (o *oldForm) keep(ctx context.Context) {
+	if o.kv == nil {
+		return
+	}
+	raw, err := json.Marshal(o.w)
+	if err == nil {
+		_, err = o.kv.Put(ctx, versions.OldFormKey, raw)
+	}
+	if err != nil {
+		o.logf("%s.%s cannot be written: %v", versions.OldFormState, versions.OldFormKey, err)
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/optional.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **A part does not stop for a bucket it can work without** (mesh-sdk process.EssentialBucket, OptionalBucket) (novox/hq issue 1945, met twice on 2026-10-25: the builder of
+// mesh-delivery #48 exited on a refused read of the gate's source, and its reasks bucket would have done the same). A grant
+// reaches the bus with a delivery, so a bucket the bus refuses, or times out on, at start is often only not granted yet:
+// exiting for it stops every build until a person's hand. A bucket the builder cannot build at all without (its builds,
+// the indexer's modules and manifests) still stops the start, naming the grant to look at; every other is said and left,
+// and opened again at the next event that needs it where there is one.
+
+// trunkSource is the gate's source history the candidates' previews are merged onto (sourceHeads), opened at start and,
+// while it cannot be, again at the next candidate that asks a trunk head: a builder without it builds the trunk's keys,
+// and a candidate's preview waits, saying why.
+type trunkSource struct {
+	ctx   context.Context
+	js    bucketOpener
+	heads *sourceHeads
+	moved func(context.Context)
+	errs  chan<- error
+	logf  func(string, ...any)
+
+	mu     sync.Mutex
+	opened bool
+}
+
+// ensure opens and settles the source's watch once, and follows it; an error leaves it closed for the next ask.
+func (t *trunkSource) ensure() error {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.opened {
+		return nil
+	}
+	kv, err := t.js.KeyValue(t.ctx, delivery.SourceBucket)
+	if err != nil {
+		return fmt.Errorf("the bucket %s cannot be read (%v)", delivery.SourceBucket, err)
+	}
+	w, err := kv.Watch(t.ctx, delivery.SourceMainKey, jetstream.IncludeHistory())
+	if err != nil {
+		return fmt.Errorf("the bucket %s cannot be watched (%v)", delivery.SourceBucket, err)
+	}
+	sw, err := settled(t.ctx, w, func(e jetstream.KeyValueEntry) { t.heads.put(e) })
+	if err != nil {
+		return fmt.Errorf("the bucket %s: %w", delivery.SourceBucket, err)
+	}
+	t.opened = true
+	go func() {
+		t.errs <- follow(t.ctx, sw, func(e jetstream.KeyValueEntry) {
+			if t.heads.put(e) && t.moved != nil {
+				t.moved(t.ctx)
+			}
+		})
+	}()
+	return nil
+}
+
+// start opens the source at start; one that cannot be is said, and the builder goes on.
+func (t *trunkSource) start() {
+	if err := t.ensure(); err != nil {
+		t.logf("%v: the trunk's keys are built, and a candidate's preview waits until the source can be read, tried again at its next candidate", err)
+	}
+}
+
+// head is Builder.Trunk: the head of repository at source revision rev, opening the source first if it is not yet.
+func (t *trunkSource) head(ctx context.Context, rev uint64, repository string) (string, error) {
+	if err := t.ensure(); err != nil {
+		return "", err
+	}
+	return t.heads.head(ctx, rev, repository)
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/publishbounds.go

@@ -0,0 +1,129 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/health"
+	"git.novox.be/novox/mesh-sdk/go/process"
+
+	"git.novox.be/novox/mesh-delivery/sdk/heard"
+
+	"mesh-delivery-builder/internal/versions"
+)
+
+// publishes raises and clears the builder's findings of a publish that ended badly (versions/publish.go): a holder's
+// refused, a version unanswered past its bound, kept as a key of the state bounds with its own time to live, and a seat's
+// outcome that does not read.
+type publishes struct {
+	bounds   func() jetstream.KeyValue
+	versions versions.Versions
+	findings *findings
+	bound    time.Duration
+	logf     func(string, ...any)
+}
+
+// arm writes the version's bound when none stands, so a standing bound keeps its time. A bound that cannot be written
+// would never end, so the version is publish-unanswered at once (review round 2): the finding says why.
+func (p *publishes) arm(ctx context.Context, e versions.Entry) {
+	kv := p.bounds()
+	var err error
+	if kv == nil {
+		err = fmt.Errorf("%s is not on the bus yet", versions.BoundsBucket)
+	} else if _, err = kv.Create(ctx, versions.PublishBoundKey(e.Name, e.Version), versions.EncodeBound("the publish of "+e.Name+"@"+e.Version+" to "+e.Seat, time.Now().Add(p.bound)), jetstream.KeyTTL(p.bound)); errors.Is(err, jetstream.ErrKeyExists) {
+		err = nil
+	}
+	if err == nil {
+		return
+	}
+	p.logf("the publish bound of %s@%s is not written, so it is raised unanswered now: %v", e.Name, e.Version, err)
+	p.unanswered(ctx, e, fmt.Sprintf("its bound could not be written (%v), so the builder cannot wait on the holder's word", err))
+}
+
+// unanswered raises publish-unanswered about e's name, saying why.
+func (p *publishes) unanswered(ctx context.Context, v versions.Entry, why string) {
+	p.findings.raise(ctx, finding{kind: versions.PublishUnanswered, scope: health.ScopeModule, id: v.Name,
+		summary:     fmt.Sprintf("%s said neither published nor refused of %s@%s: %s", v.Seat, v.Name, v.Version, why),
+		headline:    "A registry seat did not answer a publish",
+		explanation: "The builder built and numbered " + v.Name + " " + v.Version + " and asked " + v.Seat + " to publish it; no word of its holder is known, so the build says done while the version may not be in the registry.",
+		resolved:    "That version is published, or a later version of " + v.Name + " is.",
+		needs:       "a look at the holder of " + v.Seat + " (its health and log); builder_publish_again asks the publish again."})
+}
+
+// heard is told each holder's word the numberer took in: published clears the name's findings, refused raises
+// publish-refused with the holder's reason, and either ends the version's bound.
+func (p *publishes) heard(ctx context.Context, seat, event string, o versions.Outcome) {
+	if o.Version != "" {
+		if kv := p.bounds(); kv != nil {
+			if err := kv.Delete(ctx, versions.PublishBoundKey(o.Name, o.Version)); err != nil && !errors.Is(err, jetstream.ErrKeyNotFound) {
+				p.logf("the publish bound of %s@%s is not ended: %v", o.Name, o.Version, err)
+			}
+		}
+	}
+	switch event {
+	case versions.HeardPublished:
+		p.findings.clear(ctx, versions.PublishRefused, health.ScopeModule, o.Name)
+		p.findings.clear(ctx, versions.PublishUnanswered, health.ScopeModule, o.Name)
+	case versions.HeardRefused:
+		reason := o.Reason
+		if reason == "" {
+			reason = "it gave no reason"
+		}
+		p.findings.raise(ctx, finding{kind: versions.PublishRefused, scope: health.ScopeModule, id: o.Name,
+			summary:     fmt.Sprintf("%s refused to publish %s@%s (digest %s): %s", seat, o.Name, o.Version, o.Digest, reason),
+			headline:    "A registry seat refused a publish",
+			explanation: "The builder built and numbered " + o.Name + " " + o.Version + ", and the holder of " + seat + " refused to store it, so that version is not in the registry.",
+			resolved:    "That version is published, or a later version of " + o.Name + " is.",
+			needs:       "builder_versions shows the version and why; builder_publish_again publishes it again once the cause is mended."})
+	}
+}
+
+// unread raises seat-outcome-unread about seat: what it said on subject is no outcome. read clears it.
+func (p *publishes) unread(ctx context.Context, seat, subject string, why error) {
+	p.findings.raise(ctx, finding{kind: versions.SeatOutcomeUnread, scope: health.ScopeModule, id: seat,
+		summary:     fmt.Sprintf("%s said on %s what is no outcome of a publish: %v", seat, subject, why),
+		headline:    "A registry seat said what the builder cannot read",
+		explanation: "The builder hears each registry seat's published, refused and removed to move a numbered version; this one does not read, so the version it was about does not move.",
+		resolved:    "The next outcome of " + seat + " reads.",
+		needs:       "a look at the seat's holder: the outcome's body is its contract's (mesh-contracts)."})
+}
+
+func (p *publishes) read(ctx context.Context, seat string) {
+	p.findings.clear(ctx, versions.SeatOutcomeUnread, health.ScopeModule, seat)
+}
+
+// ended is told each change of the state bounds: a bound whose time ended (the bus's marker) on a version still numbered
+// raises publish-unanswered.
+func (p *publishes) ended(ctx context.Context, e jetstream.KeyValueEntry) {
+	key, ok := versions.PublishBoundOf(e.Key())
+	if e.Operation() != jetstream.KeyValuePurge || !ok {
+		return
+	}
+	raw, _, found, err := p.versions.Store.Get(ctx, key)
+	if err != nil || !found {
+		return
+	}
+	v, err := versions.Decode(raw)
+	if err != nil || v.State != versions.Numbered {
+		return
+	}
+	p.unanswered(ctx, v, fmt.Sprintf("nothing within %s of its build", p.bound))
+}
+
+// watchBounds watches the state bounds, handing each change to each: a watch that cannot start loses every bound's end,
+// so it is the finding family-not-heard naming the state until a later start watches it (review round 2).
+func watchBounds(ctx context.Context, kv jetstream.KeyValue, each func(jetstream.KeyValueEntry), w heard.Writer, errs chan<- error, logf func(string, ...any)) {
+	const consequence = "a publish no holder answers, and a node holding the old form seven days, are not raised until the builder starts again"
+	pw, err := settle(ctx, kv, each)
+	if err != nil {
+		process.NotWatched(logf, versions.BoundsBucket, err, consequence)
+		w.NotHeard(versions.BoundsState, consequence, err)
+		return
+	}
+	w.Heard(versions.BoundsState)
+	go func() { errs <- follow(ctx, pw, each) }()
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/queues.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"mesh-delivery-builder/internal/build"
+)
+
+// queueReader is the part of the builder a queues value reads through: heldOnTheBus.
+type queueReader interface {
+	Queue(ctx context.Context, language string, limit int) (build.SeatQueue, error)
+}
+
+// queueRead answers one value of the queues state (the tool builder_seat_queue, issue 1945 note 62): a value not yet
+// answered is read now, from the stream the builder's account may read, and written back by compare-and-set at its
+// revision with what was read or why it could not be. A value answered already (this builder's own write, or another
+// instance's) or deleted is left.
+func queueRead(ctx context.Context, r queueReader, kv jetstream.KeyValue, e jetstream.KeyValueEntry, logf func(string, ...any)) {
+	if e.Operation() != jetstream.KeyValuePut {
+		return
+	}
+	a, err := build.DecodeQueueAsk(e.Value())
+	if err != nil {
+		logf("%s.%s holds what is not a queue read, left: %v", build.QueuesState, e.Key(), err)
+		return
+	}
+	if !a.Answered.IsZero() {
+		return
+	}
+	read, cancel := context.WithTimeout(ctx, 20*time.Second)
+	q, err := r.Queue(read, e.Key(), max(1, min(a.Limit, build.MaxQueueLimit)))
+	cancel()
+	if err != nil {
+		a.Error = err.Error()
+	}
+	a.Queue, a.Answered = &q, time.Now().UTC()
+	data, err := json.Marshal(a)
+	if err != nil {
+		return
+	}
+	if _, err := kv.Update(ctx, e.Key(), data, e.Revision()); err != nil && !errors.Is(err, jetstream.ErrKeyExists) && !errors.Is(err, jetstream.ErrKeyRevisionMismatch) {
+		logf("%s.%s: the read could not be written: %v", build.QueuesState, e.Key(), err)
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/reads.go

@@ -0,0 +1,151 @@
+package main
+
+import (
+	"context"
+	"slices"
+	"sync"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/process"
+
+	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
+	"git.novox.be/novox/mesh-delivery/sdk/enginereads"
+)
+
+// EngineReadsState is the builder's state of what each counted node's engine states it reads (novox/hq ADR 0618 §2, ADR
+// 0624 §1): one key `<node>`, written from the node-engine seat's verb manifest-reads at the builder's start, on the
+// seat's event manifest-reads-changed for that node, and when a person asks again (builder_engine_reads); a node that
+// is away keeps its last statement, and its key is removed when the placement no longer names the node. A counted node
+// with no key reads as stating the baseline: its first forms. No node's record is read in its place.
+const EngineReadsState = "engine-reads"
+
+// engineReadsBucket is that state's bucket.
+const engineReadsBucket = delivery.BuilderModule + "_" + EngineReadsState
+
+// engineReads keeps the statements and the counted nodes for the builder's forms (build.Builder.Forms).
+type engineReads struct {
+	keeper  *enginereads.Keeper
+	gate    *buildrun.ToolchainGate
+	mu      sync.Mutex
+	counted []string
+	// window is the old reference form's window over these statements (DLV-B9); nil keeps none.
+	window *oldForm
+	ctx    context.Context
+}
+
+// newEngineReads asks through call (process.Conn.CallOn) and keeps each answer in the state once it is bound.
+func newEngineReads(call enginereads.Caller, gate *buildrun.ToolchainGate, logf func(string, ...any)) *engineReads {
+	r := &engineReads{gate: gate, keeper: &enginereads.Keeper{Call: call, Logf: logf}}
+	r.keeper.Changed = r.stepWindow
+	return r
+}
+
+// stepWindow moves the old form's window to what the counted nodes state now (design 51 *Every build keeps the old
+// reference form*): on a statement's change, the placement's and a hand drop, and at each build key written.
+func (r *engineReads) stepWindow() {
+	if r.window == nil {
+		return
+	}
+	ctx := r.ctx
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	_, counted := r.forms()
+	r.window.step(ctx, r.named(), counted)
+}
+
+// named are the nodes the placement names, none dropped: what the window's step judges a read by.
+func (r *engineReads) named() []string {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	return slices.Clone(r.counted)
+}
+
+// bind keeps the statements in kv and hears it: every node's last statement at the start, a person's ask again and drop
+// later. Bound once the state is on the bus (process.AwaitBucket).
+func (r *engineReads) bind(ctx context.Context, kv jetstream.KeyValue, errs chan<- error, logf func(string, ...any)) {
+	r.keeper.Put = func(node string, v []byte) error { _, err := kv.Put(ctx, node, v); return err }
+	r.keeper.Delete = func(node string) error { return kv.Delete(ctx, node) }
+	each := func(e jetstream.KeyValueEntry) {
+		r.keeper.Heard(e.Key(), e.Value(), e.Operation() != jetstream.KeyValuePut)
+	}
+	w, err := settle(ctx, kv, each)
+	if err != nil {
+		process.NotWatched(logf, engineReadsBucket, err, "builder_engine_reads is not answered until the builder starts again")
+		return
+	}
+	go func() { errs <- follow(ctx, w, each) }()
+	// Every counted node asked again, so what was asked before the state was bound is kept in it too.
+	r.mu.Lock()
+	nodes := slices.Clone(r.counted)
+	r.mu.Unlock()
+	for _, node := range nodes {
+		r.keeper.AskNode(node, "the state engine-reads is bound")
+	}
+}
+
+// placed takes the placement in: a node it names newly is asked, one it no longer names is forgotten, key and all. The
+// first call asks every counted node (the builder's start).
+func (r *engineReads) placed() {
+	nodes := r.gate.Nodes()
+	r.mu.Lock()
+	before, first := r.counted, r.counted == nil
+	r.counted = nodes
+	r.mu.Unlock()
+	for _, node := range nodes {
+		if first || !slices.Contains(before, node) {
+			r.keeper.AskNode(node, "counted: the placement names it")
+		}
+	}
+	for _, node := range before {
+		if !slices.Contains(nodes, node) {
+			r.keeper.Forget(node)
+		}
+	}
+	r.stepWindow()
+}
+
+// heard takes an event of the builder's consumer on EVENTS: manifest-reads-changed asks its node again, and answers true.
+func (r *engineReads) heard(m jetstream.Msg, logf func(string, ...any)) bool {
+	node, ours, err := enginereads.NodeOf(m.Subject(), m.Data())
+	if !ours {
+		return false
+	}
+	if ackErr := m.Ack(); ackErr != nil {
+		logf("acknowledging %s: %v", m.Subject(), ackErr)
+	}
+	if err != nil {
+		logf("%s holds what is not %s, and %s is asked again all the same: %v", m.Subject(), enginereads.Event, node, err)
+	}
+	r.keeper.AskNode(node, enginereads.Event)
+	return true
+}
+
+// forms is the counted nodes' statements, and those of the nodes whose engine answered; a retired node dropped by hand
+// (builder_old_form) counts no more.
+func (r *engineReads) forms() (present, counted map[string][]string) {
+	r.mu.Lock()
+	nodes := slices.Clone(r.counted)
+	r.mu.Unlock()
+	if r.window != nil {
+		dropped := r.window.dropped()
+		nodes = slices.DeleteFunc(nodes, func(n string) bool { return dropped[n] })
+	}
+	return r.keeper.Present(nodes), r.keeper.Reads(nodes)
+}
+
+// built is build.Builder.Forms: forms, and the window stepped with them, so a node's seven days are seen at the next
+// build key at the latest.
+func (r *engineReads) built() (present, counted map[string][]string) {
+	present, counted = r.forms()
+	if r.window != nil {
+		ctx := r.ctx
+		if ctx == nil {
+			ctx = context.Background()
+		}
+		r.window.step(ctx, r.named(), counted)
+	}
+	return present, counted
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/reasks.go

@@ -0,0 +1,187 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/buscompose"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/process"
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"mesh-delivery-builder/internal/build"
+	"mesh-delivery-builder/internal/versions"
+)
+
+// askAgainer is the part of the builder a reasks value asks through.
+type askAgainer interface {
+	AskAgain(key, why string) []string
+	BuildAgain(ctx context.Context, module, fp, why, by string, bound time.Duration) build.BuildAgainResult
+	AnnounceAgain(ctx context.Context, module, fp, why, by string) build.BuildAgainResult
+}
+
+// buildAgainBound is how long the builder waits for the claim and the asks of a key built again by hand; the tool waits
+// longer for the builder's answer.
+const buildAgainBound = 15 * time.Second
+
+// reAsked answers one value of the reasks state (the tool builder_ask_again, issue 1945): a value not yet answered asks the
+// key's waiting lanes again and is written back, by compare-and-set at its revision, with what the builder did. A value
+// answered already (this builder's own write) or deleted is left.
+func reAsked(ctx context.Context, b askAgainer, acts versions.Acts, kv jetstream.KeyValue, e jetstream.KeyValueEntry, logf func(string, ...any)) {
+	if e.Operation() != jetstream.KeyValuePut {
+		return
+	}
+	r, err := build.DecodeReAsk(e.Value())
+	if err != nil {
+		logf("%s.%s holds what is not an ask to ask again, left: %v", build.ReAsksState, e.Key(), err)
+		return
+	}
+	if r.Answer != "" {
+		return
+	}
+	if r.Mode == build.ModeBuild {
+		// The answer comes when the claim and the asks are written, so it is made beside the watch, not in it.
+		go builtAgain(ctx, b, kv, e, r, logf)
+		return
+	}
+	if r.Mode == build.ModeAnnounce {
+		announcedAgain(ctx, b, kv, e, r, logf)
+		return
+	}
+	if r.Mode == build.ModePublishAgain || r.Mode == build.ModeFloorAgain || r.Mode == build.ModeOldFormDrop {
+		// A version's hand act (design 51 *Tools of the builder*) may build again, so it is answered beside the watch.
+		go versionActed(ctx, acts, kv, e, r, logf)
+		return
+	}
+	asked := b.AskAgain(e.Key(), r.Why)
+	if len(asked) == 0 {
+		r.Answer = "no ask of this key waits in this builder now (it is not building, or its build has not reached its ask yet): nothing was asked; builder_stuck shows where it stands"
+	} else {
+		r.Answer = "asked again: the " + strings.Join(asked, ", ") + " ask, under a new id the key names"
+	}
+	r.Answered = time.Now().UTC()
+	logf("%s: asked again by %s (%s): %s", e.Key(), r.By, r.Why, r.Answer)
+	data, err := json.Marshal(r)
+	if err != nil {
+		return
+	}
+	if _, err := kv.Update(ctx, e.Key(), data, e.Revision()); err != nil && !errors.Is(err, jetstream.ErrKeyExists) && !errors.Is(err, jetstream.ErrKeyRevisionMismatch) {
+		logf("%s.%s: the answer could not be written: %v", build.ReAsksState, e.Key(), err)
+	}
+}
+
+// emitAskedAgain says the builder's event build.asked-again (issue 1945): mesh.mod.<module>.event.build.asked-again,
+// with the SDK's envelope headers and the new ask's id as the bus's dedup id.
+func emitAskedAgain(ctx context.Context, js jetstream.JetStream, cred process.Account, e build.AskedAgain) error {
+	if err := emitEvent(ctx, js, cred, build.AskedAgainEvent, "asked-again-"+e.New, e); err != nil {
+		return fmt.Errorf("saying %s for %s: %w", build.AskedAgainEvent, e.Key, err)
+	}
+	return nil
+}
+
+// builtAgain answers a reasks value of mode build (the tool builder_build_again, issue 1126 note 72): the failed key is
+// built again as a new revision, and the value is written back with the revision and the asks put, or why nothing was done.
+func builtAgain(ctx context.Context, b askAgainer, kv jetstream.KeyValue, e jetstream.KeyValueEntry, r build.ReAsk, logf func(string, ...any)) {
+	res := b.BuildAgain(ctx, r.Module, r.FP, r.Why, r.By, buildAgainBound)
+	switch {
+	case res.Refused != "":
+		r.Answer, r.Refused = res.Refused, true
+	case res.Failed != "":
+		r.Answer, r.Revision, r.Failed = fmt.Sprintf("the key is written building as revision %d, and the build failed before any ask was put: %s", res.Revision, res.Failed), res.Revision, res.Failed
+	default:
+		r.Pending = res.Revision == 0
+		r.Answer, r.Revision, r.Asks = "built again: the key is written building as revision "+fmt.Sprint(res.Revision)+" and its asks are put", res.Revision, res.Asks
+		if res.Pending != "" {
+			r.Answer = res.Pending
+			if res.Revision != 0 {
+				r.Answer = "built again: the key is written building as revision " + fmt.Sprint(res.Revision) + "; " + res.Pending
+			}
+		}
+	}
+	r.Answered = time.Now().UTC()
+	logf("%s: build again asked by %s (%s): %s", e.Key(), r.By, r.Why, r.Answer)
+	data, err := json.Marshal(r)
+	if err != nil {
+		return
+	}
+	if _, err := kv.Update(ctx, e.Key(), data, e.Revision()); err != nil && !errors.Is(err, jetstream.ErrKeyExists) && !errors.Is(err, jetstream.ErrKeyRevisionMismatch) {
+		logf("%s.%s: the answer could not be written: %v", build.ReAsksState, e.Key(), err)
+	}
+}
+
+// announcedAgain answers a reasks value of mode announce (the tool builder_announce_again): the done key is written again
+// unchanged, and the value is written back with the new revision, or why nothing was done.
+func announcedAgain(ctx context.Context, b askAgainer, kv jetstream.KeyValue, e jetstream.KeyValueEntry, r build.ReAsk, logf func(string, ...any)) {
+	res := b.AnnounceAgain(ctx, r.Module, r.FP, r.Why, r.By)
+	if res.Refused != "" {
+		r.Answer, r.Refused = res.Refused, true
+	} else {
+		r.Revision, r.Answer = res.Revision, fmt.Sprintf("announced again: the done key is written again, unchanged, as revision %d", res.Revision)
+	}
+	r.Answered = time.Now().UTC()
+	data, err := json.Marshal(r)
+	if err != nil {
+		return
+	}
+	if _, err := kv.Update(ctx, e.Key(), data, e.Revision()); err != nil && !errors.Is(err, jetstream.ErrKeyExists) && !errors.Is(err, jetstream.ErrKeyRevisionMismatch) {
+		logf("%s.%s: the answer could not be written: %v", build.ReAsksState, e.Key(), err)
+	}
+}
+
+// appendLog appends one entry to the builder's module log `build-log` (ADR 0297, ADR 0571 §1) under the module's key
+// (delivery.BuildLogKey), on the log's own subject: a module's program appends to the logs it keeps on its own credential.
+// The id makes a repeated append of one entry one entry.
+func appendLog(ctx context.Context, js jetstream.JetStream, cred process.Account, e delivery.BuildLogEntry) error {
+	data, err := delivery.EncodeBuildLogEntry(e)
+	if err != nil {
+		return err
+	}
+	key, err := delivery.BuildLogKey(e.Module)
+	if err != nil {
+		return err
+	}
+	msg := nats.NewMsg(buscompose.LogSubject(cred.Module, delivery.BuilderLog) + "." + key)
+	msg.Data = data
+	id := e.Event + "." + e.Module + "." + e.FP + "." + e.At.Format(time.RFC3339Nano)
+	pub, cancel := context.WithTimeout(ctx, 10*time.Second)
+	defer cancel()
+	if _, err := js.PublishMsg(pub, msg, jetstream.WithMsgID(id)); err != nil {
+		return fmt.Errorf("logging %s of %s at %s: %w", e.Event, e.Module, e.FP, err)
+	}
+	return nil
+}
+
+// versionActed answers a reasks value of builder_publish_again, builder_floor_again or builder_old_form's drop, a hand act said in the log.
+func versionActed(ctx context.Context, acts versions.Acts, kv jetstream.KeyValue, e jetstream.KeyValueEntry, r build.ReAsk, logf func(string, ...any)) {
+	var err error
+	if r.Mode == build.ModePublishAgain {
+		var ag versions.Again
+		ag, r.Answer, err = acts.PublishAgain(ctx, r.Name, r.FP, r.Why, r.By, r.At)
+		r.Do, r.Version = ag.Do, ag.Entry.Version
+	} else if r.Mode == build.ModeOldFormDrop {
+		if acts.DropOldForm == nil {
+			err = errors.New("this builder keeps no old-form window")
+		} else {
+			r.Answer, err = acts.DropOldForm(ctx, r.Name, r.By, r.Why, r.At)
+		}
+	} else {
+		r.Answer, err = acts.FloorAgain(ctx, r.Name)
+	}
+	if err != nil {
+		r.Answer, r.Refused = err.Error(), true
+	}
+	r.Answered = time.Now().UTC()
+	logf("%s: %s of %s by %s (%s): %s", e.Key(), r.Mode, r.Name, r.By, r.Why, r.Answer)
+	data, err := json.Marshal(r)
+	if err != nil {
+		return
+	}
+	if _, err := kv.Update(ctx, e.Key(), data, e.Revision()); err != nil && !errors.Is(err, jetstream.ErrKeyExists) && !errors.Is(err, jetstream.ErrKeyRevisionMismatch) {
+		logf("%s.%s: the answer could not be written: %v", build.ReAsksState, e.Key(), err)
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/refused_test.go

@@ -0,0 +1,528 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"log"
+	"maps"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/health"
+
+	"git.novox.be/novox/mesh-delivery/sdk/heard"
+	"git.novox.be/novox/mesh-sdk/go/process"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-contracts/go/seats/nodeengine"
+	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
+	"git.novox.be/novox/mesh-delivery/sdk/enginereads"
+	"git.novox.be/novox/mesh-delivery/sdk/forms"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+
+	"mesh-delivery-builder/internal/build"
+	"mesh-delivery-builder/internal/versions"
+)
+
+// 1945 (a part exits at start for a bucket it works without): a bus that refuses every toolchains bucket leaves the
+// watch unstarted and the part running, said; a refused bucket it cannot work without is an error naming the bucket and
+// its grant. The gate over the seat's placement, and its refusal, are mesh-sdk's (buildrun.ToolchainGate,
+// issue 774).
+func TestARefusedBucketIsSaidAndThePartGoesOn(t *testing.T) {
+	t.Run("a floor's wake is heard on the events consumer (design 51 The floor)", aFloorsWakeIsHeard)
+	t.Run("a failed trunk build is a finding until a later done one (DLV-B7)", aFailedTrunkBuildIsAFinding)
+	t.Run("a branch's end is acknowledged once its tagged versions are removed (design 51 Tagged versions)", aBranchsEndIsHeard)
+	set := &buildrun.ToolchainSet{}
+	var logs bytes.Buffer
+	logger := log.New(&logs, "", 0)
+	refused := refusingBus{err: errors.New("nats: permissions violation for publish to $JS.API.CONSUMER.CREATE.KV_mesh-build-node_toolchains")}
+	if err := newToolchainWatch(context.Background(), refusingBus{refuseOpen: true, err: refused.err}, set, func(context.Context) {}, logger).start(); err != nil {
+		t.Errorf("a refused toolchains bucket stopped the start: %v", err)
+	}
+	if !strings.Contains(logs.String(), "cannot be read") {
+		t.Errorf("the refusals were not said: %q", logs.String())
+	}
+	if _, err := process.EssentialBucket(context.Background(), refusingBus{refuseOpen: true, err: refused.err}, "builder", "mesh-delivery-indexer_modules", "work"); err == nil ||
+		!strings.Contains(err.Error(), "grant of mesh-delivery-indexer_modules") {
+		t.Errorf("a refused bucket the part needs: %v, want an error naming its grant", err)
+	}
+	// The gate's source (the previews' trunk heads): refused at start, the builder goes on, and a candidate asking a trunk
+	// head is told why and opens it again then.
+	src := &trunkSource{ctx: context.Background(), js: refusingBus{refuseOpen: true, err: refused.err}, heads: &sourceHeads{}, errs: make(chan error, 1), logf: logger.Printf}
+	src.start()
+	if _, err := src.head(context.Background(), 7, "novox/mesh-catalog"); err == nil || !strings.Contains(err.Error(), delivery.SourceBucket) {
+		t.Errorf("a trunk head with the source refused: %v, want why", err)
+	}
+	if src.opened {
+		t.Error("a refused source counts as opened, so it is never opened again")
+	}
+	t.Run("ADR 0624: the counted nodes' engine reads", theCountedNodesEngineReads)
+}
+
+// theCountedNodesEngineReads: the builder asks the node-engine seat's verb of every node the placement names; a node away
+// and never asked has no statement and reads as the baseline's first forms, with no node record read in its place; an
+// away node keeps its last statement; a node the placement no longer names leaves the count, its key removed; and
+// builder_engine_reads drops one node's key.
+func theCountedNodesEngineReads(t *testing.T) {
+	gate := buildrun.NewToolchainGate(nil, func(string, string, []byte, bool) bool { return false }, t.Logf)
+	place := func(nodes ...string) {
+		for _, node := range []string{"n1", "n2"} {
+			pl := delivery.Placement{Node: node}
+			if slices.Contains(nodes, node) {
+				pl.Modules = []delivery.PlacedModule{{Module: "web"}}
+			}
+			values, err := delivery.PlacementValues(pl)
+			if err != nil {
+				t.Fatal(err)
+			}
+			for key, raw := range values {
+				gate.Placement(key, raw, false, time.Now())
+			}
+			if !slices.Contains(nodes, node) {
+				key, _ := delivery.PlacementModuleKey(node, "web")
+				gate.Placement(key, nil, true, time.Now())
+			}
+		}
+	}
+	away := map[string]bool{"n2": true}
+	asked := map[string]int{}
+	r := newEngineReads(func(node, key string, _ any) (json.RawMessage, error) {
+		asked[node]++
+		if away[node] {
+			return nil, nats.ErrNoResponders
+		}
+		return json.Marshal(nodeengine.ManifestReadsAnswer{V: 1, Node: node, ManifestReads: []string{"form:new"}, StatedAt: time.Now().Format(time.RFC3339Nano)})
+	}, gate, t.Logf)
+	r.keeper.Sync = true
+	kept := map[string][]byte{}
+	r.keeper.Put = func(node string, v []byte) error { kept[node] = v; return nil }
+	r.keeper.Delete = func(node string) error { delete(kept, node); return nil }
+	place("n1", "n2")
+	r.placed()
+	present, counted := r.forms()
+	if !slices.Equal(present["n1"], []string{"form:new"}) || len(present) != 1 || len(counted) != 2 || counted["n2"] != nil {
+		t.Errorf("away and never asked: present %v, counted %v", present, counted)
+	}
+	if s := r.keeper.Statements()["n2"]; s.From != enginereads.FromNone || s.Answered || asked["n2"] != 1 {
+		t.Errorf("n2, away and never asked, is %+v (asked %d)", s, asked["n2"])
+	}
+	// n2 back, stating {word:module}, then away again: it keeps that statement.
+	away["n2"] = false
+	r.keeper.Heard("n2", mustStatement(t, enginereads.Statement{Node: "n2", From: enginereads.FromVerb, Answered: true,
+		AskAgain: &enginereads.Again{By: "n1.ada", Why: "back"}}), false)
+	away["n2"] = true
+	r.keeper.AskNode("n2", "its event")
+	if _, counted = r.forms(); !slices.Equal(counted["n2"], []string{"form:new"}) || r.keeper.Statements()["n2"].Answered {
+		t.Errorf("away again, n2 reads %v (%+v)", counted["n2"], r.keeper.Statements()["n2"])
+	}
+	// n2 retired: it leaves the placement, and its key goes.
+	place("n1")
+	r.placed()
+	if _, counted = r.forms(); len(counted) != 1 || kept["n2"] != nil {
+		t.Errorf("retired n2: counted %v, its key %s", counted, kept["n2"])
+	}
+	// builder_engine_reads drops one key.
+	st := &memReads{v: map[string][]byte{"n1": kept["n1"]}}
+	tool := enginereads.Tool("builder_engine_reads", "the builder", st, true, time.Now)
+	if _, err := tool.Run(map[string]any{"node": "n1", "drop": "true", "why": "a test"}); err != nil || st.v["n1"] != nil {
+		t.Errorf("drop: %v, the key %s", err, st.v["n1"])
+	}
+}
+
+func mustStatement(t *testing.T, s enginereads.Statement) []byte {
+	t.Helper()
+	raw, err := enginereads.Encode(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return raw
+}
+
+// memReads is the builder's state of engine reads in memory, as the tool reads it.
+type memReads struct{ v map[string][]byte }
+
+func (m *memReads) Keys() ([]string, error) { return slices.Collect(maps.Keys(m.v)), nil }
+func (m *memReads) Get(key string) ([]byte, uint64, bool, error) {
+	v, ok := m.v[key]
+	return v, 1, ok, nil
+}
+func (m *memReads) Put(key string, value []byte) (uint64, error) { m.v[key] = value; return 2, nil }
+func (m *memReads) Delete(key string) error                      { delete(m.v, key); return nil }
+func (m *memReads) Await(string, uint64, func([]byte) bool, time.Duration) ([]byte, error) {
+	return nil, errors.New("no part answers here")
+}
+
+// refusingBus is a bus that refuses: every open (refuseOpen), or every watch of a bucket it opens, with err.
+type refusingBus struct {
+	refuseOpen bool
+	err        error
+}
+
+func (r refusingBus) KeyValue(context.Context, string) (jetstream.KeyValue, error) {
+	if r.refuseOpen {
+		return nil, r.err
+	}
+	return refusedWatch{err: r.err}, nil
+}
+
+type refusedWatch struct {
+	jetstream.KeyValue
+	err error
+}
+
+func (r refusedWatch) WatchAll(context.Context, ...jetstream.WatchOpt) (jetstream.KeyWatcher, error) {
+	return nil, r.err
+}
+func (r refusedWatch) Watch(context.Context, string, ...jetstream.WatchOpt) (jetstream.KeyWatcher, error) {
+	return nil, r.err
+}
+
+// wakeMsg is a message of the builder's events consumer: its subject and body, acknowledged.
+type wakeMsg struct {
+	jetstream.Msg
+	subject string
+	data    []byte
+	acked   bool
+	naked   bool
+	delayed time.Duration
+}
+
+func (m *wakeMsg) Subject() string { return m.subject }
+func (m *wakeMsg) Data() []byte    { return m.data }
+func (m *wakeMsg) Ack() error      { m.acked = true; return nil }
+func (m *wakeMsg) Nak() error      { m.naked = true; return nil }
+func (m *wakeMsg) NakWithDelay(d time.Duration) error {
+	m.delayed = d
+	return nil
+}
+func (m *wakeMsg) Metadata() (*jetstream.MsgMetadata, error) {
+	return nil, errors.New("no metadata")
+}
+func (m *wakeMsg) Headers() nats.Header {
+	return nil
+}
+
+func aFloorsWakeIsHeard(t *testing.T) {
+	var logs bytes.Buffer
+	waits := &versions.FloorWaits{}
+	waits.Wait("m/lib", versions.SeatGoPackages, "", versions.Floor{Silent: []string{versions.SourceRequirements}}, nil, time.Unix(0, 0))
+	waits.Wait("m/img", versions.SeatImages, "", versions.Floor{Silent: []string{versions.SourceTags}}, nil, time.Unix(0, 0))
+	f := &floorWake{b: &build.Builder{}, waits: waits, logf: log.New(&logs, "", 0).Printf}
+	accepted := &wakeMsg{subject: manifestAcceptedSubject}
+	if !f.heard(context.Background(), accepted) || !accepted.acked || !strings.Contains(logs.String(), "the floor of m/lib is asked again: manifest-accepted") {
+		t.Fatalf("manifest-accepted: acked %v, log %q", accepted.acked, logs.String())
+	}
+	logs.Reset()
+	cleared := &wakeMsg{subject: conditionClearedSubject, data: []byte(`{"subject":{"scope":"probe","id":"ace/mesh-delivery-forge-bridge"}}`)}
+	if !f.heard(context.Background(), cleared) || !strings.Contains(logs.String(), "the floor of m/img is asked again: condition-cleared") {
+		t.Fatalf("condition-cleared: log %q", logs.String())
+	}
+	if f.heard(context.Background(), &wakeMsg{subject: delivery.ArtifactsGoneSubject}) {
+		t.Fatal("artifacts-gone was taken as a floor's wake")
+	}
+	// DLV-B4: a registry seat's outcome on the same consumer moves a version; a published wakes a name whose seat was
+	// silent; one the state cannot take is left for the bus to give again.
+	logs.Reset()
+	waits.Wait("m/pkg", versions.SeatGoPackages, "", versions.Floor{Silent: []string{versions.SourceSeat}}, nil, time.Unix(0, 0))
+	h := &seatHearer{n: &versions.Numberer{Versions: versions.Versions{Store: noVersions{}}, Waits: waits}, b: &build.Builder{}, logf: log.New(&logs, "", 0).Printf}
+	byDigest := &wakeMsg{subject: "mesh.seat.go-package-registry.event.published", data: []byte(`{"name":"m/other","digest":"sha256:aa","kind":"package","holder":"gitea"}`)}
+	if !h.heard(context.Background(), byDigest) || !byDigest.acked || !strings.Contains(logs.String(), "the floor of m/pkg is asked again: go-package-registry said published") {
+		t.Fatalf("published: acked %v, log %q", byDigest.acked, logs.String())
+	}
+	refused := &wakeMsg{subject: "mesh.seat.oci-artifact-registry.event.refused", data: []byte(`{"name":"m/program","version":"0.1.3","digest":"sha256:bb","reason":"bytes differ"}`)}
+	if !h.heard(context.Background(), refused) || refused.acked || !refused.naked {
+		t.Fatalf("a refusal the state cannot take: acked %v, naked %v, log %q", refused.acked, refused.naked, logs.String())
+	}
+	if h.heard(context.Background(), &wakeMsg{subject: manifestAcceptedSubject}) {
+		t.Fatal("manifest-accepted was taken as a seat's outcome")
+	}
+}
+
+// noVersions is a state versions that holds nothing.
+type noVersions struct{}
+
+func (noVersions) Get(context.Context, string) ([]byte, uint64, bool, error) {
+	return nil, 0, false, nil
+}
+func (noVersions) Create(context.Context, string, []byte) (uint64, error) {
+	return 0, errors.New("read only")
+}
+func (noVersions) Update(context.Context, string, []byte, uint64) (uint64, error) {
+	return 0, errors.New("read only")
+}
+func (noVersions) KeysOf(context.Context, string) ([]string, error) { return nil, nil }
+
+func aBranchsEndIsHeard(t *testing.T) {
+	for _, c := range []struct {
+		f    forgeEnd
+		want bool
+	}{
+		{forgeEnd{Kind: delivery.ForgeMerged, Repository: "o/r", Branch: "feat/x"}, true},
+		{forgeEnd{Kind: forgeBranchDeleted, Repository: "o/r", Branch: "feat/x"}, true},
+		{forgeEnd{Kind: delivery.ForgePull, Repository: "o/r", Branch: "feat/x", Action: delivery.PullClosed}, true},
+		{forgeEnd{Kind: delivery.ForgePull, Repository: "o/r", Branch: "feat/x", Action: delivery.PullOpened}, false},
+		{forgeEnd{Kind: delivery.ForgeMerged, Repository: "o/r"}, false},
+	} {
+		if got := c.f.ended(); got != c.want {
+			t.Errorf("%+v ended = %v, want %v", c.f, got, c.want)
+		}
+	}
+	var logs bytes.Buffer
+	woken := 0
+	h := &branchEnds{acts: versions.Acts{Numberer: &versions.Numberer{Versions: versions.Versions{Store: noVersions{}}}}, findings: &findings{logf: t.Logf},
+		tagAsks: func() jetstream.KeyValue { return nil }, wake: func(context.Context) { woken++ }, logf: log.New(&logs, "", 0).Printf, now: time.Now}
+	open := &wakeMsg{subject: "mesh.mod.mesh-delivery-forge-bridge.event.forge.o.r.pull", data: []byte(`{"kind":"pull","repository":"o/r","branch":"feat/x","action":"opened"}`)}
+	h.heard(context.Background(), open)
+	merged := &wakeMsg{subject: "mesh.mod.mesh-delivery-forge-bridge.event.forge.o.r.merged", data: []byte(`{"kind":"merged","repository":"o/r","branch":"feat/x"}`)}
+	h.heard(context.Background(), merged)
+	if !open.acked || !merged.acked || woken != 2 {
+		t.Errorf("an open pull acked %v, a merge with nothing tagged acked %v, floors woken %d times", open.acked, merged.acked, woken)
+	}
+	// The checker's family holds its verdicts beside tag-wanted: a verdict is acknowledged and not kept; a tag-wanted with
+	// tag-asks not bound is heard again.
+	verdict := &wakeMsg{subject: "mesh.stream.mesh-delivery-checker.event.verdict", data: []byte(`{"repository":"o/r"}`)}
+	wanted := &wakeMsg{subject: tagWantedSubject, data: []byte(`{"repository":"o/r","branch":"feat/x","head":"abc","tag":"feat-x"}`)}
+	for _, m := range []*wakeMsg{verdict, wanted} {
+		tagWanted(context.Background(), nil, m, delivery.CheckerModule, time.Now(), t.Logf)
+	}
+	if !verdict.acked || verdict.delayed != 0 || wanted.acked || wanted.delayed != versions.RemoveAgainAfter || !strings.HasPrefix(tagWantedSubject, "mesh.stream.") {
+		t.Errorf("a verdict acked %v (delayed %v), a tag-wanted acked %v (delayed %v)", verdict.acked, verdict.delayed, wanted.acked, wanted.delayed)
+	}
+	unreadable := &wakeMsg{subject: merged.subject, data: merged.data}
+	h.acts.Numberer.Versions.Store = failingVersions{}
+	h.heard(context.Background(), unreadable)
+	if unreadable.acked || unreadable.delayed != versions.RemoveAgainAfter {
+		t.Errorf("a branch's end the versions cannot answer: acked %v, given again after %v", unreadable.acked, unreadable.delayed)
+	}
+}
+
+// failingVersions is a state versions that cannot be read.
+type failingVersions struct{ noVersions }
+
+func (failingVersions) KeysOf(context.Context, string) ([]string, error) {
+	return nil, errors.New("down")
+}
+
+func aFailedTrunkBuildIsAFinding(t *testing.T) {
+	st := &memFindings{vals: map[string][]byte{}}
+	f := &findings{store: st, logf: t.Logf, now: func() time.Time { return time.Unix(0, 0) }}
+	ended := func(outcome, ref string) delivery.BuildLogEntry {
+		return delivery.BuildLogEntry{Event: delivery.BuildEndedEvent, Module: "m", FP: "f1", Commit: "c", Ref: ref, Outcome: outcome}
+	}
+	key := health.FindingKey(health.ScopeModule, "m", BuildFailed)
+	f.buildEnded(context.Background(), ended(delivery.BuildFailed, "refs/pull/3/head"))
+	if len(st.vals) != 0 {
+		t.Fatalf("a candidate's failed build is a finding: %v", st.vals)
+	}
+	f.buildEnded(context.Background(), ended(delivery.BuildFailed, ""))
+	got, err := health.DecodeFinding(st.vals[key])
+	if err != nil || got.Observer != delivery.BuilderModule || !strings.Contains(got.Summary, "trunk build of m at f1") {
+		t.Fatalf("the finding = %+v, %v", got, err)
+	}
+	f.buildEnded(context.Background(), ended(delivery.BuildDone, ""))
+	if _, ok := st.vals[key]; ok {
+		t.Error("a later done trunk build leaves build-failed")
+	}
+	// The floor finding: raised while a name waits on its floor, cleared once it is known.
+	fw := &versions.FloorWaits{Said: f.floorSaid(context.Background())}
+	fw.Wait("m/lib", versions.SeatGoPackages, "", versions.Floor{Silent: []string{versions.SourceTags}}, nil, time.Unix(0, 0))
+	floorKey := health.FindingKey(health.ScopeModule, "m/lib", versions.FloorSilent)
+	if got, err := health.DecodeFinding(st.vals[floorKey]); err != nil || !strings.Contains(got.Summary, "bridge_tags did not answer") {
+		t.Fatalf("the floor finding = %+v, %v", got, err)
+	}
+	fw.Answered("m/lib")
+	if _, ok := st.vals[floorKey]; ok {
+		t.Error("a known floor leaves floor-silent")
+	}
+	// Design 51 *Health and conditions* (review round 1): a holder's refused is publish-refused with its reason, a version
+	// no holder answered within its bound publish-unanswered, a seat's outcome that does not read seat-outcome-unread;
+	// a later published of the name clears the first two, the seat's next outcome that reads the third.
+	vs := versions.Versions{Store: memVersions{}}
+	for _, v := range []string{"0.1.3", "0.1.4"} {
+		raw, err := versions.Encode(versions.Entry{Name: "m/program", Kind: versions.KindBundle, Series: "0.1", Version: v, Seat: "oci-artifact-registry", State: versions.Numbered})
+		if err != nil {
+			t.Fatal(err)
+		}
+		vs.Store.(memVersions)[versions.Key("m/program", v)] = raw
+	}
+	pubs := &publishes{bounds: func() jetstream.KeyValue { return nil }, versions: vs, findings: f, bound: versions.PublishBound, logf: t.Logf}
+	h := &seatHearer{n: &versions.Numberer{Versions: vs}, b: &build.Builder{}, logf: t.Logf, pub: pubs}
+	refusedKey := health.FindingKey(health.ScopeModule, "m/program", versions.PublishRefused)
+	refused := &wakeMsg{subject: "mesh.seat.oci-artifact-registry.event.refused", data: []byte(`{"name":"m/program","version":"0.1.3","digest":"sha256:bb","reason":"bytes differ"}`)}
+	if !h.heard(context.Background(), refused) || !refused.acked {
+		t.Fatalf("a refusal: acked %v", refused.acked)
+	}
+	if got, err := health.DecodeFinding(st.vals[refusedKey]); err != nil || !strings.Contains(got.Summary, "refused to publish m/program@0.1.3") || !strings.Contains(got.Summary, "bytes differ") {
+		t.Fatalf("a holder's refused: the finding = %+v, %v", got, err)
+	}
+	pubs.ended(context.Background(), purged{key: versions.PublishBoundKey("m/program", "0.1.4")})
+	unansweredKey := health.FindingKey(health.ScopeModule, "m/program", versions.PublishUnanswered)
+	if got, err := health.DecodeFinding(st.vals[unansweredKey]); err != nil || !strings.Contains(got.Summary, "neither published nor refused of m/program@0.1.4") {
+		t.Fatalf("a bound ended unanswered: the finding = %+v, %v", got, err)
+	}
+	// Review round 2: a bound that cannot be written is publish-unanswered at once; a watch of bounds that cannot start
+	// is family-not-heard naming the state.
+	delete(st.vals, unansweredKey)
+	pubs.arm(context.Background(), versions.Entry{Name: "m/program", Version: "0.1.4", Seat: "oci-artifact-registry"})
+	if got, err := health.DecodeFinding(st.vals[unansweredKey]); err != nil || !strings.Contains(got.Summary, "its bound could not be written") {
+		t.Fatalf("a bound not written: the finding = %+v, %v", got, err)
+	}
+	watchBounds(context.Background(), refusedWatch{err: errors.New("permissions violation")}, func(jetstream.KeyValueEntry) {}, f.notHeard(context.Background()), nil, t.Logf)
+	if got, err := health.DecodeFinding(st.vals[heard.Key(delivery.BuilderModule, versions.BoundsState)]); err != nil || !strings.Contains(got.Summary, "permissions violation") {
+		t.Fatalf("bounds not watched: the finding = %+v, %v", got, err)
+	}
+	delete(st.vals, heard.Key(delivery.BuilderModule, versions.BoundsState))
+	malformed := &wakeMsg{subject: "mesh.seat.oci-artifact-registry.event.published", data: []byte(`{"version":"0.1.4"}`)}
+	unreadKey := health.FindingKey(health.ScopeModule, "oci-artifact-registry", versions.SeatOutcomeUnread)
+	if !h.heard(context.Background(), malformed) || !malformed.acked || st.vals[unreadKey] == nil {
+		t.Fatalf("an outcome that does not read: acked %v, findings %v", malformed.acked, st.vals)
+	}
+	published := &wakeMsg{subject: "mesh.seat.oci-artifact-registry.event.published", data: []byte(`{"name":"m/program","version":"0.1.4","digest":"sha256:cc"}`)}
+	if !h.heard(context.Background(), published) || st.vals[refusedKey] != nil || st.vals[unansweredKey] != nil || st.vals[unreadKey] != nil {
+		t.Fatalf("a later published leaves the findings: %v", st.vals)
+	}
+	// ADR 0615 §5 (review round 1): a consumer not there yet is family-not-heard naming its stream, cleared when it binds.
+	notHeard := f.notHeard(context.Background())
+	unheardKey := heard.Key(delivery.BuilderModule, "FORGE")
+	_ = notHeard.Bind("FORGE", "a branch's end is not heard", func() error { return errors.New("consumer not found") })
+	if got, err := health.DecodeFinding(st.vals[unheardKey]); err != nil || got.Kind != heard.Kind || !strings.Contains(got.Summary, "does not hear FORGE") {
+		t.Fatalf("a consumer not there: the finding = %+v, %v", got, err)
+	}
+	_ = notHeard.Bind("FORGE", "a branch's end is not heard", func() error { return nil })
+	if _, ok := st.vals[unheardKey]; ok {
+		t.Error("a consumer bound leaves family-not-heard")
+	}
+	// DLV-B9, the old form's window: one counted node reading only the first form holds it; seven days on it is
+	// old-form-held about that node; the node stating the newest form closes it, said once, the finding cleared; a
+	// retired node dropped by hand leaves the count.
+	now := time.Unix(0, 0)
+	fs := forms.ArtifactForms{{Name: "registry", First: true, Kinds: []string{"image"}}, {Name: "oci", Kinds: []string{"image"}}}
+	var closings []versions.OldFormClosedBody
+	var logged []delivery.BuildLogEntry
+	marks := &memBounds{keys: map[string]bool{}}
+	window := &oldForm{forms: fs, findings: f, logf: t.Logf, now: func() time.Time { return now }, bounds: func() jetstream.KeyValue { return marks },
+		said: func(b versions.OldFormClosedBody) { closings = append(closings, b) },
+		log:  func(e delivery.BuildLogEntry) { logged = append(logged, e) }}
+	reads := &engineReads{keeper: &enginereads.Keeper{}, window: window, counted: []string{"a", "b"}}
+	newest := []string{forms.FormNeed("oci")}
+	counted := map[string][]string{"a": newest, "b": nil}
+	window.step(context.Background(), []string{"a", "b"}, counted)
+	heldKey := health.FindingKey(health.ScopeMachine, "b", versions.OldFormHeld)
+	if !window.w.Open || !slices.Equal(window.w.Holding, []string{"b"}) || st.vals[heldKey] != nil {
+		t.Fatalf("one node lacking the newest form: %+v", window.w)
+	}
+	// Review round 1: the node holding it has a bound in the state bounds ending at its seven days, so old-form-held is
+	// raised then, not at the next change.
+	if !marks.keys[versions.OldFormBoundKey("b")] || marks.keys[versions.OldFormBoundKey("a")] {
+		t.Fatalf("the old form's bounds = %v, want b's alone", marks.keys)
+	}
+	// Security-upgrade F3 (review round 1): an empty node_haves read, naming no node, leaves the window open.
+	window.step(context.Background(), nil, map[string][]string{})
+	if !window.w.Open || !slices.Equal(window.w.Holding, []string{"b"}) || len(closings) != 0 {
+		t.Fatalf("an empty read closed the window: %+v, closings %+v", window.w, closings)
+	}
+	now = now.Add(versions.FindingAfter)
+	window.step(context.Background(), []string{"a", "b"}, counted)
+	if got, err := health.DecodeFinding(st.vals[heldKey]); err != nil || !strings.Contains(got.Summary, "the node-engine of b") {
+		t.Fatalf("seven days held: the finding = %+v, %v", got, err)
+	}
+	counted["b"] = newest
+	window.step(context.Background(), []string{"a", "b"}, counted)
+	window.step(context.Background(), []string{"a", "b"}, counted)
+	if marks.keys[versions.OldFormBoundKey("b")] {
+		t.Error("a node no longer holding the window keeps its bound")
+	}
+	if window.w.Open || len(closings) != 1 || !slices.Equal(closings[0].LastHolding, []string{"b"}) || st.vals[heldKey] != nil {
+		t.Errorf("the node back with the newest form: %+v, closings %+v, finding left %v", window.w, closings, st.vals[heldKey] != nil)
+	}
+	if len(logged) != 1 || logged[0].Event != delivery.BuildSaidEvent || logged[0].Why != versions.SaidOldFormClosed ||
+		!strings.Contains(logged[0].Line, "last held by b") {
+		t.Errorf("the build log = %+v, want the close said once (build.said)", logged)
+	} else if _, err := delivery.EncodeBuildLogEntry(logged[0]); err != nil {
+		t.Errorf("the close is no entry the build log takes: %v", err)
+	}
+	if _, err := window.drop(context.Background(), "b", "op@shanks", "retired", now); err != nil {
+		t.Fatal(err)
+	}
+	if _, c := reads.forms(); len(c) != 1 || c["b"] != nil {
+		t.Errorf("a node dropped by hand is still counted: %v", c)
+	}
+}
+
+// memVersions is a state versions in memory.
+type memVersions map[string][]byte
+
+func (m memVersions) Get(_ context.Context, key string) ([]byte, uint64, bool, error) {
+	v, ok := m[key]
+	return v, 1, ok, nil
+}
+func (m memVersions) Create(_ context.Context, key string, v []byte) (uint64, error) {
+	m[key] = v
+	return 1, nil
+}
+func (m memVersions) Update(_ context.Context, key string, v []byte, _ uint64) (uint64, error) {
+	m[key] = v
+	return 2, nil
+}
+func (m memVersions) KeysOf(context.Context, string) ([]string, error) {
+	return slices.Collect(maps.Keys(m)), nil
+}
+
+// memBounds is the state bounds in memory: which keys stand.
+type memBounds struct {
+	jetstream.KeyValue
+	keys map[string]bool
+}
+
+func (m *memBounds) Create(_ context.Context, key string, _ []byte, _ ...jetstream.KVCreateOpt) (uint64, error) {
+	if m.keys[key] {
+		return 0, jetstream.ErrKeyExists
+	}
+	m.keys[key] = true
+	return 1, nil
+}
+func (m *memBounds) Delete(_ context.Context, key string, _ ...jetstream.KVDeleteOpt) error {
+	delete(m.keys, key)
+	return nil
+}
+
+// purged is the bus's marker of a key whose time to live ended.
+type purged struct {
+	jetstream.KeyValueEntry
+	key string
+}
+
+func (p purged) Key() string                     { return p.key }
+func (p purged) Operation() jetstream.KeyValueOp { return jetstream.KeyValuePurge }
+
+// memFindings is a findings bucket in memory.
+type memFindings struct{ vals map[string][]byte }
+
+type memEntry struct {
+	jetstream.KeyValueEntry
+	v []byte
+}
+
+func (e memEntry) Value() []byte { return e.v }
+
+func (m *memFindings) Get(_ context.Context, key string) (jetstream.KeyValueEntry, error) {
+	v, ok := m.vals[key]
+	if !ok {
+		return nil, jetstream.ErrKeyNotFound
+	}
+	return memEntry{v: v}, nil
+}
+func (m *memFindings) Put(_ context.Context, key string, v []byte) (uint64, error) {
+	m.vals[key] = v
+	return 1, nil
+}
+func (m *memFindings) Delete(_ context.Context, key string, _ ...jetstream.KVDeleteOpt) error {
+	delete(m.vals, key)
+	return nil
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/says.go

@@ -0,0 +1,79 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"github.com/nats-io/nats.go/jetstream"
+)
+
+// What the builder says it writes (novox/hq issue 1886, ADR 0522): each running instance keeps a key, named by its node,
+// in its own bucket of instances (`mesh-delivery-builder_instances`, the manifest's state `instances`), saying that every
+// done key it writes names where its artifacts are (ADR 0498 §1). The references come from the build modules' own pushes,
+// so an instance says it only once a step of every build module it calls answered one since it started: a builder beside
+// a build module from before R4e says nothing. The controller delivers from the builder's keys only while an instance
+// says so; since R4g it asks no build-agent, and a module whose key is not yet done waits, named (ADR 0524 §7). The bucket is read by the controller alone, so its name and shape
+// are not in mesh-sdk.
+const (
+	instancesBucket  = "mesh-delivery-builder_instances"
+	writesReferences = `{"v":1,"writes":["references"]}`
+)
+
+// sayStore is the bucket of instances as the builder writes it.
+type sayStore interface {
+	Put(ctx context.Context, key string, value []byte) (uint64, error)
+	Delete(ctx context.Context, key string, opts ...jetstream.KVDeleteOpt) error
+}
+
+// sayer puts this instance's say once every build module in need answered a reference, and takes it away at the stop.
+type sayer struct {
+	ctx   context.Context
+	store sayStore
+	node  string
+	need  []string
+	logf  func(string, ...any)
+
+	mu       sync.Mutex
+	answered map[string]bool
+	said     bool
+}
+
+func newSayer(ctx context.Context, store sayStore, node string, need []string, logf func(string, ...any)) *sayer {
+	return &sayer{ctx: ctx, store: store, node: node, need: need, logf: logf, answered: map[string]bool{}}
+}
+
+// Answered is told the build module whose step answered a reference (build.Builder.Answered).
+func (s *sayer) Answered(module string) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.answered[module] = true
+	if s.said {
+		return
+	}
+	for _, m := range s.need {
+		if !s.answered[m] {
+			return
+		}
+	}
+	if _, err := s.store.Put(s.ctx, s.node, []byte(writesReferences)); err != nil {
+		s.logf("saying in %s that this builder writes references: %v; said again at the next reference", instancesBucket, err)
+		return
+	}
+	s.said = true
+	s.logf("every build module answered a reference: said in %s that this builder writes references", instancesBucket)
+}
+
+// unsay takes the say away, if it was made: a builder replaced by one that does not write references leaves none.
+func (s *sayer) unsay(ctx context.Context) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if !s.said {
+		return nil
+	}
+	if err := s.store.Delete(ctx, s.node); err != nil {
+		return fmt.Errorf("taking away the say in %s: %w", instancesBucket, err)
+	}
+	s.said = false
+	return nil
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/says_test.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+
+	"github.com/nats-io/nats.go/jetstream"
+)
+
+type saysOf map[string]string
+
+func (s saysOf) Put(_ context.Context, key string, value []byte) (uint64, error) {
+	s[key] = string(value)
+	return 1, nil
+}
+
+func (s saysOf) Delete(_ context.Context, key string, _ ...jetstream.KVDeleteOpt) error {
+	delete(s, key)
+	return nil
+}
+
+// 1886/AC5: a builder says, under its node, that it writes references only once every build module it calls answered
+// one; stopped, it says nothing any more.
+func TestTheBuilderSaysItWritesReferencesOnceEveryBuildModuleAnsweredOne(t *testing.T) {
+	s := saysOf{}
+	say := newSayer(t.Context(), s, "shanks", []string{"mesh-build-go", "mesh-build-node", "mesh-build-image"}, t.Logf)
+	say.Answered("mesh-build-go")
+	say.Answered("mesh-build-node")
+	if v, ok := s["shanks"]; ok {
+		t.Fatalf("said before the image build module answered a reference: %q", v)
+	}
+	say.Answered("mesh-build-image")
+	var v struct {
+		Writes []string `json:"writes"`
+	}
+	if err := json.Unmarshal([]byte(s["shanks"]), &v); err != nil || len(v.Writes) != 1 || v.Writes[0] != "references" {
+		t.Fatalf("the builder's say: %q %v", s["shanks"], err)
+	}
+	if err := say.unsay(t.Context()); err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := s["shanks"]; ok {
+		t.Fatalf("the stopped builder still says: %v", s)
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/seats.go

@@ -0,0 +1,148 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"strings"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-contracts/go/seats/containerimageregistry"
+	"git.novox.be/novox/mesh-contracts/go/seats/gopackageregistry"
+	"git.novox.be/novox/mesh-contracts/go/seats/npmpackageregistry"
+	"git.novox.be/novox/mesh-contracts/go/seats/ociartifactregistry"
+
+	"mesh-delivery-builder/internal/build"
+	"mesh-delivery-builder/internal/versions"
+)
+
+// seatEvent is one registry seat's event the builder hears: the seat and the event's name.
+type seatEvent struct{ seat, event string }
+
+// seatEvents are the four registry seats' published, refused, removed and kept, by subject (design 51 *How a publish ends*,
+// DLV-B4): each a seat event `<seat>.<event>` on the shared events stream, heard on the builder's durable consumer of
+// it through the manifest's consumes. The subjects are the seats' contracts' (mesh-contracts).
+var seatEvents = map[string]seatEvent{
+	containerimageregistry.SubjectPublished: {containerimageregistry.Seat, containerimageregistry.EventPublished},
+	containerimageregistry.SubjectRefused:   {containerimageregistry.Seat, containerimageregistry.EventRefused},
+	containerimageregistry.SubjectRemoved:   {containerimageregistry.Seat, containerimageregistry.EventRemoved},
+	containerimageregistry.SubjectKept:      {containerimageregistry.Seat, containerimageregistry.EventKept},
+	ociartifactregistry.SubjectPublished:    {ociartifactregistry.Seat, ociartifactregistry.EventPublished},
+	ociartifactregistry.SubjectRefused:      {ociartifactregistry.Seat, ociartifactregistry.EventRefused},
+	ociartifactregistry.SubjectRemoved:      {ociartifactregistry.Seat, ociartifactregistry.EventRemoved},
+	ociartifactregistry.SubjectKept:         {ociartifactregistry.Seat, ociartifactregistry.EventKept},
+	gopackageregistry.SubjectPublished:      {gopackageregistry.Seat, gopackageregistry.EventPublished},
+	gopackageregistry.SubjectRefused:        {gopackageregistry.Seat, gopackageregistry.EventRefused},
+	gopackageregistry.SubjectRemoved:        {gopackageregistry.Seat, gopackageregistry.EventRemoved},
+	gopackageregistry.SubjectKept:           {gopackageregistry.Seat, gopackageregistry.EventKept},
+	npmpackageregistry.SubjectPublished:     {npmpackageregistry.Seat, npmpackageregistry.EventPublished},
+	npmpackageregistry.SubjectRefused:       {npmpackageregistry.Seat, npmpackageregistry.EventRefused},
+	npmpackageregistry.SubjectRemoved:       {npmpackageregistry.Seat, npmpackageregistry.EventRemoved},
+	npmpackageregistry.SubjectKept:          {npmpackageregistry.Seat, npmpackageregistry.EventKept},
+}
+
+// seatHearer takes the registry seats' outcomes in: each moves a numbered version (versions.Numberer.Heard), and a
+// `published` that wakes a name waiting on its floor looks at every module again.
+type seatHearer struct {
+	n    *versions.Numberer
+	b    *build.Builder
+	logf func(string, ...any)
+	// pub raises and clears the findings of a publish that ended badly; nil raises none.
+	pub *publishes
+}
+
+// heard takes a message of the events consumer in when it is a registry seat's outcome, and answers whether it was.
+// One the state could not take is left unacknowledged (Nak), so the bus gives it again; one that is no outcome is said
+// and dropped.
+func (h *seatHearer) heard(ctx context.Context, m jetstream.Msg) bool {
+	se, ok := seatEvents[m.Subject()]
+	if !ok {
+		return false
+	}
+	var o versions.Outcome
+	if err := json.Unmarshal(m.Data(), &o); err != nil || o.Name == "" {
+		if err == nil {
+			err = errors.New("it names no name")
+		}
+		h.logf("%s holds what is no outcome of %s, left: %v", m.Subject(), se.seat, err)
+		if h.pub != nil {
+			h.pub.unread(ctx, se.seat, m.Subject(), err)
+		}
+		h.ack(m)
+		return true
+	}
+	if h.pub != nil {
+		h.pub.read(ctx, se.seat)
+	}
+	id := ""
+	if m.Headers() != nil {
+		id = m.Headers().Get("x-event-id")
+	}
+	wake, err := h.n.Heard(ctx, se.seat, se.event, id, o)
+	if err != nil {
+		h.logf("%v; heard again", err)
+		if nakErr := m.Nak(); nakErr != nil {
+			h.logf("leaving %s for the bus to give again: %v", m.Subject(), nakErr)
+		}
+		return true
+	}
+	if h.pub != nil {
+		h.pub.heard(ctx, se.seat, se.event, o)
+	}
+	h.ack(m)
+	if len(wake) > 0 {
+		h.logf("the floor of %s is asked again: %s said %s", strings.Join(wake, ", "), se.seat, se.event)
+		h.b.Reconsider(ctx)
+	}
+	return true
+}
+
+func (h *seatHearer) ack(m jetstream.Msg) {
+	if err := m.Ack(); err != nil {
+		h.logf("acknowledging %s: %v", m.Subject(), err)
+	}
+}
+
+// kvKeeper is the state floor-waits as versions.FloorKeeper.
+type kvKeeper struct {
+	ctx context.Context
+	kv  jetstream.KeyValue
+}
+
+func (k kvKeeper) Put(key string, value []byte) error {
+	_, err := k.kv.Put(k.ctx, key, value)
+	return err
+}
+
+func (k kvKeeper) Delete(key string) error {
+	err := k.kv.Delete(k.ctx, key)
+	if errors.Is(err, jetstream.ErrKeyNotFound) {
+		return nil
+	}
+	return err
+}
+
+// heldFloorWaits are the waits floor-waits holds at the builder's start; a value that is no wait is said and left.
+func heldFloorWaits(ctx context.Context, kv jetstream.KeyValue, logf func(string, ...any)) []versions.FloorWait {
+	l, err := kv.ListKeys(ctx)
+	if err != nil {
+		logf("%s cannot be listed, so a restart's waits are asked at their next claim: %v", versions.FloorWaitsState, err)
+		return nil
+	}
+	defer func() { _ = l.Stop() }()
+	var out []versions.FloorWait
+	for k := range l.Keys() {
+		e, err := kv.Get(ctx, k)
+		if err != nil {
+			continue
+		}
+		w, err := versions.DecodeFloorWait(e.Value())
+		if err != nil {
+			logf("%s.%s holds what is no floor wait, left: %v", versions.FloorWaitsState, k, err)
+			continue
+		}
+		out = append(out, w)
+	}
+	return out
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/settings.go

@@ -1,28 +0,0 @@
-package main
-
-import (
-	"encoding/json"
-	"fmt"
-	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
-	"os"
-)
-
-// capacityFrom is the build capacity of each node (ADR 0478 clause 3): the module's setting `capacity`, `<node>=<steps at
-// once>` pairs separated by commas, laid into the settings file the controller composes (issue 1661); empty is one step at a
-// time on every node. With no settings file named, fallback is read instead, for a run outside the module's launch.
-func capacityFrom(path, fallback string) (map[string]int, error) {
-	if path == "" {
-		return buildrun.ParseCapacity(fallback)
-	}
-	raw, err := os.ReadFile(path)
-	if err != nil {
-		return nil, fmt.Errorf("the settings file: %w", err)
-	}
-	var s struct {
-		Capacity string `json:"capacity"`
-	}
-	if err := json.Unmarshal(raw, &s); err != nil {
-		return nil, fmt.Errorf("the settings file %s is not JSON: %w", path, err)
-	}
-	return buildrun.ParseCapacity(s.Capacity)
-}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/settings_test.go

@@ -1,67 +0,0 @@
-package main
-
-import (
-	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
-	"os"
-	"path/filepath"
-	"testing"
-)
-
-func settingsFile(t *testing.T, body string) string {
-	t.Helper()
-	p := filepath.Join(t.TempDir(), "settings.json")
-	if err := os.WriteFile(p, []byte(body), 0o600); err != nil {
-		t.Fatal(err)
-	}
-	return p
-}
-
-// 1661: the build capacity is the module's setting `capacity`, laid into the settings file: empty is one step at a time everywhere.
-func TestCapacityIsReadFromTheSettingsFile(t *testing.T) {
-	for body, want := range map[string]map[string]int{
-		`{"capacity": "shanks=3,ace=2"}`: {"shanks": 3, "ace": 2},
-		`{"capacity": ""}`:               {},
-		`{}`:                             {},
-	} {
-		got, err := capacityFrom(settingsFile(t, body), "")
-		if err != nil || len(got) != len(want) || got["shanks"] != want["shanks"] || got["ace"] != want["ace"] {
-			t.Errorf("%s: capacity %v, %v, want %v", body, got, err, want)
-		}
-	}
-	p := &buildrun.Places{Capacity: mustCapacity(t, settingsFile(t, `{"capacity": ""}`))}
-	if p.CapacityOf("shanks") != 1 || p.CapacityOf("ace") != 1 {
-		t.Errorf("an empty setting gives %d and %d, want 1 everywhere", p.CapacityOf("shanks"), p.CapacityOf("ace"))
-	}
-}
-
-func mustCapacity(t *testing.T, path string) map[string]int {
-	t.Helper()
-	c, err := capacityFrom(path, "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	return c
-}
-
-func TestACapacitySettingThatIsNotOneIsRefusedNamingIt(t *testing.T) {
-	if _, err := capacityFrom(settingsFile(t, `{"capacity": "shanks=-1"}`), ""); err == nil {
-		t.Error("shanks=-1 accepted")
-	}
-	if c, err := capacityFrom(settingsFile(t, `{"capacity": "shanks=3,ace=2,g14=0,novox=0"}`), ""); err != nil || c["g14"] != 0 || len(c) != 4 {
-		t.Errorf("the starting value: %v, %v", c, err)
-	}
-	if _, err := capacityFrom(settingsFile(t, `not json`), ""); err == nil {
-		t.Error("a file that is not JSON accepted")
-	}
-	if _, err := capacityFrom(filepath.Join(t.TempDir(), "none"), ""); err == nil {
-		t.Error("a settings file that is not there accepted")
-	}
-}
-
-// With no settings file named (a run outside the module's launch, as the tests do), the capacity is the environment's.
-func TestWithNoSettingsFileTheCapacityIsTheEnvironments(t *testing.T) {
-	got, err := capacityFrom("", "ace=2")
-	if err != nil || got["ace"] != 2 {
-		t.Errorf("capacity %v, %v", got, err)
-	}
-}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/stored.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+
+	"mesh-delivery-builder/internal/build"
+)
+
+// eventsStream is the stream every module's and role's events are on, where the grants part makes the builder's durable
+// consumer of artifacts-gone (mesh-sdk buscompose EventsStream).
+const eventsStream = "EVENTS"
+
+// SeatHeld is the seat mesh-artifact-sweep's verb held (ADR 0571 §2).
+const SeatHeld = "seat:" + catalogue.ArtifactSweepSeat + ".held"
+
+// toolCaller calls a tool or a seat verb as the builder's own account (mesh-sdk process.Conn.Call).
+type toolCaller func(key string, body any) (json.RawMessage, error)
+
+// storedVia is build.Builder's Stored: it asks the seat mesh-artifact-sweep's `held` (novox/hq ADR 0571 §2, issue 1937)
+// and answers the references the store no longer holds. One it could not ask about, with none gone, is an error: the key
+// is then left done, and asked again at the next module value or artifacts-gone.
+func storedVia(call toolCaller) func(ctx context.Context, references []string) ([]string, error) {
+	return func(_ context.Context, references []string) ([]string, error) {
+		body := map[string]any{"references": references}
+		raw, err := call(SeatHeld, body)
+		if err != nil {
+			return nil, fmt.Errorf("asking held: %w", err)
+		}
+		a, err := delivery.DecodeHeldAnswer(raw, references)
+		if err != nil {
+			return nil, err
+		}
+		if len(a.Gone) == 0 && len(a.Unknown) > 0 {
+			var why []string
+			for r, w := range a.Unknown {
+				why = append(why, r+": "+w)
+			}
+			sort.Strings(why)
+			return nil, fmt.Errorf("the artifact store could not be asked about %s", strings.Join(why, "; "))
+		}
+		return a.Gone, nil
+	}
+}
+
+// heardGone takes one artifacts-gone event in: acknowledged, then handed to the builder, which asks the store and builds
+// the key again. A body that is not one is said and acknowledged, so it is not handed over again.
+func heardGone(ctx context.Context, b *build.Builder, m jetstream.Msg, logf func(string, ...any)) {
+	e, err := delivery.DecodeArtifactsGone(m.Data())
+	if ackErr := m.Ack(); ackErr != nil {
+		logf("acknowledging %s: %v", m.Subject(), ackErr)
+	}
+	if err != nil {
+		logf("%s holds what is not %s, left: %v", m.Subject(), delivery.ArtifactsGoneEvent, err)
+		return
+	}
+	b.ArtifactsGone(ctx, e)
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/tagbounds.go

@@ -0,0 +1,132 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+
+	"mesh-delivery-builder/internal/versions"
+)
+
+// tagBounds narrates a tag ask the builder has not answered within five minutes, with what it waits on (design 51
+// *Tagged versions*): each unanswered ask has a key in the state tag-ask-bounds written with its own time to live, and
+// the bus's marker of its end, heard on the watch, is what narrates it and writes the bound again. No timer.
+type tagBounds struct {
+	asks   func() jetstream.KeyValue
+	bounds func() jetstream.KeyValue
+	waits  func() []versions.FloorWait
+	logf   func(string, ...any)
+	// log writes a narration into the builder's build log (build.said); nil writes none.
+	log   func(delivery.BuildLogEntry)
+	now   func() time.Time
+	bound time.Duration
+}
+
+// arm writes key's bound when none stands: a Create, so a standing bound keeps its time and a restart arms each
+// unanswered ask whose bound ended while the builder was away.
+func (tb *tagBounds) arm(ctx context.Context, key string) {
+	kv := tb.bounds()
+	if kv == nil {
+		return
+	}
+	if _, err := kv.Create(ctx, key, []byte(`{}`), jetstream.KeyTTL(tb.bound)); err != nil && !errors.Is(err, jetstream.ErrKeyExists) {
+		tb.logf("the bound of the tag ask %s is not written, so it is not narrated past five minutes: %v", key, err)
+	}
+}
+
+// disarm removes key's bound: the ask was answered or ended.
+func (tb *tagBounds) disarm(ctx context.Context, key string) {
+	if kv := tb.bounds(); kv != nil {
+		_ = kv.Delete(ctx, key)
+	}
+}
+
+// asked is told each value of tag-asks: an unanswered ask is armed, any other disarmed.
+func (tb *tagBounds) asked(ctx context.Context, key string, t versions.TagAsk) {
+	if t.Unanswered() {
+		tb.arm(ctx, key)
+		return
+	}
+	tb.disarm(ctx, key)
+}
+
+// ended is told each change of tag-ask-bounds: a bound whose time ended (the bus's marker, a purge on the watch) on an
+// ask still unanswered narrates it and arms it again.
+func (tb *tagBounds) ended(ctx context.Context, e jetstream.KeyValueEntry) {
+	if e.Operation() != jetstream.KeyValuePurge {
+		return
+	}
+	kv := tb.asks()
+	if kv == nil {
+		return
+	}
+	got, err := kv.Get(ctx, e.Key())
+	if err != nil {
+		return // the ask ended with its branch
+	}
+	t, err := versions.DecodeTagAsk(got.Value())
+	if err != nil || !t.Unanswered() {
+		return
+	}
+	var waits []versions.FloorWait
+	if tb.waits != nil {
+		waits = tb.waits()
+	}
+	line := versions.NarrateUnanswered(t, waits, tb.now())
+	tb.logf("%s", line)
+	// In the build log too (design 51 *Tagged versions*): under the builder's own key, no build being claimed yet, the
+	// ask's key standing for the fingerprint.
+	if tb.log != nil {
+		tb.log(delivery.BuildLogEntry{Event: delivery.BuildSaidEvent, Module: delivery.BuilderModule, FP: e.Key(), Commit: t.Head,
+			At: tb.now().UTC(), Line: line, Why: versions.SaidUnanswered})
+	}
+	tb.arm(ctx, e.Key())
+}
+
+// tagNumbered marks the tag ask of a check's build's head numbered with its versions in tag-asks, by compare-and-set.
+func tagNumbered(kv func() jetstream.KeyValue, logf func(string, ...any), now func() time.Time) func(context.Context, versions.BuildClaim, versions.Numbering) {
+	return func(ctx context.Context, c versions.BuildClaim, got versions.Numbering) {
+		store := kv()
+		if store == nil {
+			return
+		}
+		lister, err := store.ListKeysFiltered(ctx, versions.EscapeToken(c.Repository)+".>")
+		if err != nil {
+			logf("the tag ask of %s at %s is not marked numbered: %v", c.Repository, c.Head, err)
+			return
+		}
+		for key := range lister.Keys() {
+			for range 3 {
+				e, err := store.Get(ctx, key)
+				if err != nil {
+					break
+				}
+				t, err := versions.DecodeTagAsk(e.Value())
+				if err != nil {
+					break
+				}
+				t, changed := t.WithNumbered(c.Module, c.Head, got.Versions, got.Names, now())
+				if !changed {
+					break
+				}
+				data, err := json.Marshal(t)
+				if err != nil {
+					break
+				}
+				if _, err = store.Update(ctx, key, data, e.Revision()); err == nil {
+					logf("%s: tag ask of %s %s: %s", key, t.Repository, t.Branch, t.Answer)
+					break
+				}
+				if !errors.Is(err, jetstream.ErrKeyExists) && !errors.Is(err, jetstream.ErrKeyRevisionMismatch) {
+					logf("the tag ask %s is not marked numbered: %v", key, err)
+					break
+				}
+			}
+		}
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/testdata/catalogue-49caf17f-hello-web.module.json

@@ -0,0 +1,82 @@
+{
+  "module": "hello-web",
+  "slug": "hello",
+  "version": "1",
+  "capabilities": [
+    "container-runtime"
+  ],
+  "requires": [
+    "route"
+  ],
+  "contributes": {
+    "route": {
+      "label": "hello",
+      "endpoint": "web"
+    }
+  },
+  "binds": {
+    "route": "${dir:state}/route.json"
+  },
+  "listens": [
+    {
+      "name": "web",
+      "port": 8080,
+      "protocol": "tcp",
+      "from": "mesh",
+      "why": "the demo web page; only the route-proxy reaches it, and the public name is a route grant"
+    }
+  ],
+  "resources": [
+    {
+      "id": "state",
+      "type": "directory",
+      "mode": "0700",
+      "place": ".",
+      "unknown": "program"
+    },
+    {
+      "id": "page",
+      "type": "file",
+      "path": "${dir:state}/index.html",
+      "mode": "0644",
+      "template": "files/index.html"
+    },
+    {
+      "id": "net",
+      "type": "network",
+      "name": "hello-web"
+    },
+    {
+      "id": "server",
+      "type": "container",
+      "name": "hello-web",
+      "network": "hello-web",
+      "ports": [
+        "8080"
+      ],
+      "volumes": [
+        "${dir:state}/index.html:/www/index.html:ro"
+      ],
+      "args": [
+        "sh",
+        "-c",
+        "while true; do { printf 'HTTP/1.1 200 OK\\r\\nContent-Type: text/plain\\r\\nConnection: close\\r\\n\\r\\n'; cat /www/index.html; } | nc -l -p 8080; done"
+      ],
+      "artifact": "server"
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "server",
+        "kind": "upstream",
+        "from": "alpine@sha256:28bd5fe8b56d1bd048e5babf5b10710ebe0bae67db86916198a6eec434943f8b"
+      },
+      {
+        "name": "files",
+        "kind": "archive",
+        "from": "files"
+      }
+    ]
+  }
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/testdata/catalogue-835bf22b-claude-code.module.json

@@ -0,0 +1,249 @@
+{
+  "module": "claude-code",
+  "version": "1",
+  "moved": true,
+  "slug": "agent",
+  "capabilities": [
+    "package-manager"
+  ],
+  "requires": [
+    "mcp-endpoint",
+    {
+      "name": "gitea-read",
+      "optional": true
+    }
+  ],
+  "binds": {
+    "mcp-endpoint": "${dir:state}/mcp-endpoint.json"
+  },
+  "secrets": {
+    "gitea-read": "${dir:state}/gitea-read.secret"
+  },
+  "uses": [
+    "operator-channel"
+  ],
+  "state": [
+    "servers",
+    "holdings",
+    "config",
+    "proposals",
+    "questions",
+    "memory",
+    "waits"
+  ],
+  "reads": [
+    "claude-licence-manager.bindings"
+  ],
+  "tools": [
+    "claude_code_status",
+    "claude_code_render",
+    "claude_code_guard",
+    "claude_code_pull",
+    "claude_code_grant",
+    "claude_code_add_api_key",
+    "claude_code_registrations",
+    "claude_code_memory",
+    "claude_code_mcp_list",
+    "claude_code_mcp_register",
+    "claude_code_mcp_unregister",
+    "claude_code_skill_list",
+    "claude_code_skill_register",
+    "claude_code_skill_unregister",
+    "claude_code_agent_list",
+    "claude_code_agent_register",
+    "claude_code_agent_unregister",
+    "claude_code_command_list",
+    "claude_code_command_register",
+    "claude_code_command_unregister",
+    "claude_code_hook_list",
+    "claude_code_hook_register",
+    "claude_code_hook_unregister",
+    "claude_code_output_style_list",
+    "claude_code_output_style_register",
+    "claude_code_output_style_unregister",
+    "claude_code_instructions_list",
+    "claude_code_instructions_register",
+    "claude_code_instructions_unregister",
+    "claude_code_instructions_propose",
+    "claude_code_proposals",
+    "claude_code_ask",
+    "claude_code_answer",
+    "claude_code_wait",
+    "claude_code_settings_get",
+    "claude_code_settings_set",
+    "claude_code_settings_clear",
+    "claude_code_permission_add",
+    "claude_code_permission_remove",
+    "claude_code_config_list",
+    "claude_code_config_show",
+    "claude_code_config_status",
+    "claude_code_config_import",
+    "claude_code_home_show",
+    "claude_code_home_remove",
+    "claude_code_home_removed",
+    "claude_code_home_restore",
+    "claude_code_judge",
+    "claude_code_judged"
+  ],
+  "data": {
+    "own": [
+      {
+        "id": "agent-home",
+        "path": "${dir:agent-home}",
+        "class": "valuable",
+        "why": "the operator's agent's own files: its memory, history and projects"
+      }
+    ]
+  },
+  "config": {
+    "role": {
+      "type": "string",
+      "description": "What this machine is for, in a sentence, written into the instructions every Claude Code session on it reads; empty says nothing.",
+      "trusted": true,
+      "default": ""
+    },
+    "mcp_servers": {
+      "type": "object",
+      "description": "The tool servers every session on this machine is given beside the mesh's own, by name, each as Claude Code's managed MCP configuration takes it; empty adds none.",
+      "trusted": true,
+      "default": {}
+    },
+    "managed_settings": {
+      "type": "object",
+      "description": "Keys of Claude Code's managed settings every session on this machine obeys, such as spinnerTipsEnabled, laid over the mesh's own; empty adds none. Falls back to agent-managed-settings, the mesh's or this node's.",
+      "trusted": true,
+      "predefined": "agent-managed-settings",
+      "default": {}
+    },
+    "instructions": {
+      "type": "object",
+      "description": "The instructions every session on this machine reads, by name, each a text as one line or a list of its lines; empty adds none.",
+      "trusted": true,
+      "default": {}
+    },
+    "output_styles": {
+      "type": "object",
+      "description": "The output styles offered to every session on this machine, by name, each a text as one line or a list of its lines; empty adds none.",
+      "trusted": true,
+      "default": {}
+    },
+    "skills": {
+      "type": "object",
+      "description": "The skills offered to every session on this machine, by name, each its files by path, a text as one line or a list of its lines; a skill without its SKILL.md is left out; empty adds none.",
+      "trusted": true,
+      "default": {}
+    },
+    "commands": {
+      "type": "object",
+      "description": "The slash commands offered to every session on this machine, by name, each a text as one line or a list of its lines; empty adds none.",
+      "trusted": true,
+      "default": {}
+    },
+    "agents": {
+      "type": "object",
+      "description": "The agents offered to every session on this machine, by name, each a text as one line or a list of its lines; empty adds none.",
+      "trusted": true,
+      "default": {}
+    }
+  },
+  "resources": [
+    {
+      "id": "package",
+      "type": "package",
+      "package": "claude-code"
+    },
+    {
+      "id": "managed",
+      "type": "directory",
+      "path": "/etc/claude-code",
+      "mode": "0755",
+      "unknown": "program"
+    },
+    {
+      "id": "start",
+      "type": "file",
+      "path": "/usr/local/bin/claude-agent",
+      "mode": "0755",
+      "template": "files/claude-agent"
+    },
+    {
+      "id": "agent-account-name",
+      "type": "file",
+      "path": "/etc/claude-code/agent-account",
+      "mode": "0644",
+      "template": "files/agent-account"
+    },
+    {
+      "id": "agent-account",
+      "type": "user",
+      "name": "${machine:agent-account}",
+      "home": "${machine:agent-home}",
+      "root": "${machine:agent-root}"
+    },
+    {
+      "id": "agent-home",
+      "type": "directory",
+      "path": "${machine:agent-home}/.claude",
+      "mode": "0700",
+      "owner": "${machine:agent-account}",
+      "unknown": "module"
+    },
+    {
+      "id": "state",
+      "type": "directory",
+      "mode": "0700",
+      "owner": "${machine:account}",
+      "place": ".",
+      "unknown": "program"
+    },
+    {
+      "id": "facts",
+      "type": "file",
+      "path": "${dir:state}/facts.json",
+      "mode": "0600",
+      "owner": "${machine:account}",
+      "template": "files/facts.json"
+    },
+    {
+      "id": "settings",
+      "type": "file",
+      "path": "${dir:state}/settings.json",
+      "mode": "0600",
+      "owner": "${machine:account}",
+      "takes-config": ["role", "mcp_servers", "managed_settings", "instructions", "output_styles", "skills", "commands", "agents"],
+      "merge": "json",
+      "template": "files/settings.json"
+    }
+  ],
+  "items": [
+    {
+      "collection": "shell:zsh:normal",
+      "template": "files/zsh-normal"
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/claude-code",
+        "binary": "claude-code",
+        "loads": [
+          "claude-code"
+        ],
+        "env": {
+          "MESH_CLAUDE_CODE_STATE": "${dir:state}",
+          "MESH_CLAUDE_CODE_FACTS": "${dir:state}/facts.json",
+          "MESH_CLAUDE_CODE_SETTINGS": "${dir:state}/settings.json"
+        }
+      },
+      {
+        "name": "files",
+        "kind": "archive",
+        "from": "files"
+      }
+    ]
+  }
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/toolchains.go

@@ -4,11 +4,13 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
 	"log"
 	"strings"
 	"sync"
 
+	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
+	"git.novox.be/novox/mesh-sdk/go/process"
+
 	"github.com/nats-io/nats.go/jetstream"
 
 	"git.novox.be/novox/mesh-sdk/go/delivery"
@@ -23,9 +25,11 @@ var toolchainStreams = map[string]string{buildrun.GoBuildModule: "TOOLCHAINS_GO"
 // §8): it watches the buckets that exist at start, and a build module says each time it wrote its toolchains key
 // (toolchain.reported, handled by Reported); a bucket not watched yet is then watched.
 type toolchainWatch struct {
-	ctx     context.Context
-	js      bucketOpener
-	set     *buildrun.ToolchainSet
+	ctx context.Context
+	js  bucketOpener
+	set *buildrun.ToolchainSet
+	// put takes a change of a toolchains bucket in: set.Put, or the gate of the assigned build nodes before it (issue 1940).
+	put     func(module, key string, value []byte, deleted bool) bool
 	changed func(ctx context.Context) // a language's entries changed: the failed builds are tried again
 	logger  *log.Logger
 	errs    chan error
@@ -34,7 +38,7 @@ type toolchainWatch struct {
 }
 
 func newToolchainWatch(ctx context.Context, js bucketOpener, set *buildrun.ToolchainSet, changed func(context.Context), logger *log.Logger) *toolchainWatch {
-	return &toolchainWatch{ctx: ctx, js: js, set: set, changed: changed, logger: logger, errs: make(chan error, len(buildrun.LanguageOf)), watched: map[string]bool{}}
+	return &toolchainWatch{ctx: ctx, js: js, set: set, put: set.Put, changed: changed, logger: logger, errs: make(chan error, len(buildrun.LanguageOf)), watched: map[string]bool{}}
 }
 
 // start watches the buckets that exist now; a missing one is said and waits for its build module's event.
@@ -60,16 +64,19 @@ func (w *toolchainWatch) ensure(module string) error {
 		w.logger.Printf("the bucket %s does not exist yet: it is watched when %s reports a toolchain", name, module)
 		return nil
 	case err != nil:
-		return fmt.Errorf("the bucket %s: %w", name, err)
+		// Refused or not answered (its grant not on the bus yet, issue 1945): said, and opened again at the module's next report.
+		w.logger.Printf("the bucket %s cannot be read (%v): %s's toolchains are not heard until its next report", name, err, module)
+		return nil
 	}
-	watcher, err := settle(w.ctx, kv, func(e jetstream.KeyValueEntry) { w.set.Put(module, e.Key(), e.Value(), !opOf(e)) })
+	watcher, err := settle(w.ctx, kv, func(e jetstream.KeyValueEntry) { w.put(module, e.Key(), e.Value(), !opOf(e)) })
 	if err != nil {
-		return err
+		process.NotWatched(w.logger.Printf, name, err, fmt.Sprintf("%s's toolchains are not heard until its next report", module))
+		return nil
 	}
 	w.watched[module] = true
 	go func() {
 		w.errs <- follow(w.ctx, watcher, func(e jetstream.KeyValueEntry) {
-			if w.set.Put(module, e.Key(), e.Value(), !opOf(e)) {
+			if w.put(module, e.Key(), e.Value(), !opOf(e)) {
 				w.changed(w.ctx)
 			}
 		})

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/versions.go

@@ -0,0 +1,352 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-contracts/go/seats/ociartifactregistry"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/health"
+	"git.novox.be/novox/mesh-sdk/go/process"
+
+	"mesh-delivery-builder/internal/build"
+	"mesh-delivery-builder/internal/versions"
+)
+
+// The floor's two module tools (novox/hq design 51 *The floor*); the seat's is `seat:<registry>.versions`.
+const (
+	bridgeTagsTool   = "mesh-delivery-forge-bridge.bridge_tags"
+	requirementsTool = "mesh-delivery-indexer.indexer_requirements"
+)
+
+// awaitedVersions is the state versions as versions.Store: bound once the bus holds it (the grants part makes it, issue
+// 1790); until then every use is an error, so a trunk build is built unnumbered and said (build.Builder.number).
+type awaitedVersions struct{ b *process.AwaitedBucket }
+
+var errVersionsMissing = errors.New("the state " + versions.Bucket + " is not on the bus yet")
+
+func (s awaitedVersions) kv() (jetstream.KeyValue, error) {
+	if kv := s.b.KV(); kv != nil {
+		return kv, nil
+	}
+	return nil, errVersionsMissing
+}
+
+func (s awaitedVersions) Get(ctx context.Context, key string) ([]byte, uint64, bool, error) {
+	kv, err := s.kv()
+	if err != nil {
+		return nil, 0, false, err
+	}
+	e, err := kv.Get(ctx, key)
+	if errors.Is(err, jetstream.ErrKeyNotFound) {
+		return nil, 0, false, nil
+	}
+	if err != nil {
+		return nil, 0, false, err
+	}
+	return e.Value(), e.Revision(), true, nil
+}
+
+// indexerPackages is the indexer's packages state as the builder reads a package's name in its ecosystem from it (design
+// 32): the picture of its read tool's first view and its views family (ADR 0615 §1), never its bucket. Until the first
+// view is answered a package is built unnumbered and said (versions.Numberer.Names), and numbered once its name is heard
+// (followPackages).
+type indexerPackages struct{ kv jetstream.KeyValue }
+
+func (s indexerPackages) Keys(ctx context.Context) ([]string, error) {
+	keys, err := s.kv.Keys(ctx)
+	if errors.Is(err, jetstream.ErrNoKeysFound) {
+		return nil, nil
+	}
+	return keys, err
+}
+
+func (s indexerPackages) Get(ctx context.Context, key string) ([]byte, bool, error) {
+	e, err := s.kv.Get(ctx, key)
+	if errors.Is(err, jetstream.ErrKeyNotFound) || errors.Is(err, jetstream.ErrKeyDeleted) {
+		return nil, false, nil
+	}
+	if err != nil {
+		return nil, false, err
+	}
+	return e.Value(), true, nil
+}
+
+// followPackages watches the picture of the indexer's packages state: each series key heard that names a package's name
+// (versions.NamedModule), its first view's included, looks at its module again (build.Builder.PackageNamed), so a done
+// build that left the package unnumbered is numbered then with its digests. Woken by the views family, never a timer; a
+// key heard again naming the name and module it named (the indexer writes a series at each publish) looks at nothing.
+func followPackages(ctx context.Context, kv jetstream.KeyValue, b *build.Builder, logf func(string, ...any)) error {
+	w, err := kv.WatchAll(ctx)
+	if err != nil {
+		return err
+	}
+	heard := map[string]string{}
+	return follow(ctx, w, func(e jetstream.KeyValueEntry) {
+		if e.Operation() != jetstream.KeyValuePut {
+			delete(heard, e.Key())
+			return
+		}
+		module, name, named := versions.NamedModule(e.Key(), e.Value())
+		if named && heard[e.Key()] != module+" "+name {
+			heard[e.Key()] = module + " " + name
+			logf("%s.%s names a package of %s: its build is looked at again", delivery.PackagesBucket, e.Key(), module)
+			b.PackageNamed(ctx, module)
+		}
+	})
+}
+
+func versionsConflict(err error) error {
+	if errors.Is(err, jetstream.ErrKeyExists) || errors.Is(err, jetstream.ErrKeyRevisionMismatch) {
+		return versions.ErrConflict
+	}
+	return err
+}
+
+func (s awaitedVersions) Create(ctx context.Context, key string, value []byte) (uint64, error) {
+	kv, err := s.kv()
+	if err != nil {
+		return 0, err
+	}
+	rev, err := kv.Create(ctx, key, value)
+	return rev, versionsConflict(err)
+}
+
+func (s awaitedVersions) Update(ctx context.Context, key string, value []byte, revision uint64) (uint64, error) {
+	kv, err := s.kv()
+	if err != nil {
+		return 0, err
+	}
+	rev, err := kv.Update(ctx, key, value, revision)
+	return rev, versionsConflict(err)
+}
+
+func (s awaitedVersions) KeysOf(ctx context.Context, filter string) ([]string, error) {
+	kv, err := s.kv()
+	if err != nil {
+		return nil, err
+	}
+	l, err := kv.ListKeysFiltered(ctx, filter)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { _ = l.Stop() }()
+	var out []string
+	for k := range l.Keys() {
+		out = append(out, k)
+	}
+	return out, nil
+}
+
+// floorVia is the floor's three sources as calls of the builder's own account (design 51 *The floor*): the seat's verb
+// versions, the forge bridge's bridge_tags and the indexer's indexer_requirements. A call that fails is that source
+// silent.
+func floorVia(call toolCaller) versions.FloorSources {
+	return versions.FloorSources{
+		Seat: func(_ context.Context, seat, name string) ([]string, error) {
+			raw, err := call("seat:"+seat+".versions", map[string]any{"name": name})
+			if err != nil {
+				return nil, err
+			}
+			var a struct {
+				Versions []struct {
+					Version string `json:"version"`
+				} `json:"versions"`
+			}
+			if err := json.Unmarshal(raw, &a); err != nil {
+				return nil, fmt.Errorf("%s's versions answered what is no list of versions: %w", seat, err)
+			}
+			var out []string
+			for _, v := range a.Versions {
+				if v.Version != "" {
+					out = append(out, v.Version)
+				}
+			}
+			return out, nil
+		},
+		Tags: func(_ context.Context, repository, prefix string) ([]string, error) {
+			raw, err := call(bridgeTagsTool, map[string]any{"repository": repository, "prefix": prefix})
+			if err != nil {
+				return nil, err
+			}
+			var a struct {
+				Tags []string `json:"tags"`
+			}
+			if err := json.Unmarshal(raw, &a); err != nil {
+				return nil, fmt.Errorf("bridge_tags answered what is no list of tags: %w", err)
+			}
+			return a.Tags, nil
+		},
+		Requirements: func(_ context.Context, name string) ([]string, error) {
+			raw, err := call(requirementsTool, map[string]any{"package": name})
+			if err != nil {
+				return nil, err
+			}
+			var a struct {
+				Requirements []string `json:"requirements"`
+			}
+			if err := json.Unmarshal(raw, &a); err != nil {
+				return nil, fmt.Errorf("indexer_requirements answered what is no list of versions: %w", err)
+			}
+			return a.Requirements, nil
+		},
+	}
+}
+
+// emitNumbered says the builder's event version.numbered (design 51 *Events of the builder*), on its own family apart
+// from its builds' ends; the name and version are the bus's dedup id.
+func emitNumbered(ctx context.Context, js jetstream.JetStream, cred process.Account, b delivery.VersionNumbered) error {
+	id := "numbered-" + versions.Key(b.Name, b.Version)
+	if b.Again != "" {
+		id += "-again-" + b.Again
+	}
+	if err := emitEvent(ctx, js, cred, delivery.VersionNumberedEvent, id, b); err != nil {
+		return fmt.Errorf("saying %s for %s@%s: %w", delivery.VersionNumberedEvent, b.Name, b.Version, err)
+	}
+	return nil
+}
+
+// emitEvent says one of the builder's events, mesh.mod.<module>.event.<event>, with the SDK's envelope headers and id as
+// the bus's dedup id.
+func emitEvent(ctx context.Context, js jetstream.JetStream, cred process.Account, event, id string, body any) error {
+	data, err := json.Marshal(body)
+	if err != nil {
+		return err
+	}
+	msg := nats.NewMsg(cred.EventSubject(event))
+	msg.Header.Set("x-event-id", id)
+	msg.Header.Set("x-source", cred.Module)
+	msg.Header.Set("x-node", cred.Node)
+	msg.Header.Set("x-time", time.Now().UTC().Format(time.RFC3339Nano))
+	msg.Header.Set("content-type", "application/json")
+	msg.Data = data
+	pub, cancel := context.WithTimeout(ctx, 10*time.Second)
+	defer cancel()
+	_, err = js.PublishMsg(pub, msg, jetstream.WithMsgID(id))
+	return err
+}
+
+// The events on the builder's consumer of EVENTS that wake a floor (design 51 *The floor*, DLV-B3b).
+var (
+	manifestAcceptedSubject = "mesh.mod." + delivery.IndexerModule + ".event." + delivery.ManifestAcceptedEvent
+	conditionClearedSubject = "mesh.mod." + health.KeeperModule + ".event." + health.EventCleared
+)
+
+// floorWake asks the floor of the names an event wakes again, by looking at every module again: a trunk build is
+// numbered before its claim (build.Builder.number).
+type floorWake struct {
+	b     *build.Builder
+	waits *versions.FloorWaits
+	logf  func(string, ...any)
+}
+
+// heard takes a message of the consumer in when it is one that wakes a floor, acknowledged, and answers whether it was.
+func (f *floorWake) heard(ctx context.Context, m jetstream.Msg) bool {
+	switch m.Subject() {
+	case manifestAcceptedSubject:
+		f.ack(m)
+		f.wake(ctx, versions.WakeAccepted, "", "")
+	case conditionClearedSubject:
+		f.ack(m)
+		var e health.Event
+		if err := json.Unmarshal(m.Data(), &e); err != nil {
+			f.logf("%s holds what is no condition, left: %v", m.Subject(), err)
+			return true
+		}
+		for _, module := range conditionModules(e.Subject.ID) {
+			f.wake(ctx, versions.WakeCleared, "", module)
+		}
+	default:
+		return false
+	}
+	return true
+}
+
+func (f *floorWake) ack(m jetstream.Msg) {
+	if err := m.Ack(); err != nil {
+		f.logf("acknowledging %s: %v", m.Subject(), err)
+	}
+}
+
+// wake looks at every module again when the event wakes a name, and says which.
+func (f *floorWake) wake(ctx context.Context, kind, seat, module string) {
+	names := f.waits.Wake(kind, seat, module, "")
+	if len(names) == 0 {
+		return
+	}
+	f.logf("the floor of %s is asked again: %s", strings.Join(names, ", "), kind)
+	f.b.Reconsider(ctx)
+}
+
+// conditionModules are the tokens of a condition's subject id (`<node>/<module>`, `<module>.<check>`): a module named
+// among them is the one whose condition cleared.
+func conditionModules(id string) []string {
+	return strings.FieldsFunc(id, func(r rune) bool { return r == '/' || r == '.' || r == ':' })
+}
+
+// doneVia says whether a build key is done, read from the builder's own builds state: the build's file is held.
+func doneVia(b *build.Builder) func(ctx context.Context, module, fp string) (bool, error) {
+	return func(ctx context.Context, module, fp string) (bool, error) {
+		key, err := delivery.BuilderBuildKey(module, fp)
+		if err != nil {
+			return false, err
+		}
+		raw, _, found, err := b.Claimer.Store.Get(ctx, key)
+		if err != nil || !found {
+			return false, err
+		}
+		cur, err := delivery.DecodeBuilderBuild(raw)
+		if err != nil {
+			return false, err
+		}
+		return cur.State == delivery.BuildDone, nil
+	}
+}
+
+// removeVia calls a registry seat's remove for one tagged version, as the builder's own account (design 51 *Tagged
+// versions*): the reason tag-gone; the seat says removed on its events, or answers kept when another tag names the
+// digest (the registry part's RemoveAnswer: kept, reason, tags), which ends the remove.
+func removeVia(call toolCaller) func(ctx context.Context, seat string, e versions.Entry) (versions.RemoveOutcome, error) {
+	return func(_ context.Context, seat string, e versions.Entry) (versions.RemoveOutcome, error) {
+		raw, err := call("seat:"+seat+".remove", map[string]any{"name": e.Name, "version": e.Version, "tag": e.Tag, "reason": "tag-gone"})
+		if err != nil {
+			return versions.RemoveOutcome{}, err
+		}
+		var a ociartifactregistry.RemoveAnswer // the four registry seats share the part's answer
+		if len(raw) > 0 && json.Unmarshal(raw, &a) != nil {
+			return versions.RemoveOutcome{}, fmt.Errorf("%s's remove answered what is no answer of it: %s", seat, raw)
+		}
+		return versions.RemoveOutcome{Kept: a.Kept, Reason: a.Reason, Tags: a.Tags}, nil
+	}
+}
+
+// tagAsked answers an unanswered value of tag-asks by compare-and-set at its revision, said in the log.
+func tagAsked(ctx context.Context, acts versions.Acts, kv jetstream.KeyValue, e jetstream.KeyValueEntry, logf func(string, ...any)) {
+	if e.Operation() != jetstream.KeyValuePut {
+		return
+	}
+	t, err := versions.DecodeTagAsk(e.Value())
+	if err != nil {
+		logf("%s.%s holds what is not a tag ask, left: %v", versions.TagAsksState, e.Key(), err)
+		return
+	}
+	if !t.Answered.IsZero() {
+		return
+	}
+	t = acts.TagAsked(ctx, t, time.Now())
+	logf("%s: %s of %s %s by %s (%s): %s", e.Key(), map[bool]string{true: "untag", false: "tag ask"}[t.Untag], t.Repository, t.Branch, t.By, t.Why, t.Answer)
+	data, err := json.Marshal(t)
+	if err != nil {
+		return
+	}
+	if _, err := kv.Update(ctx, e.Key(), data, e.Revision()); err != nil && !errors.Is(err, jetstream.ErrKeyExists) && !errors.Is(err, jetstream.ErrKeyRevisionMismatch) {
+		logf("%s.%s: the answer could not be written: %v", versions.TagAsksState, e.Key(), err)
+	}
+}

modules/mesh-delivery-builder/files/settings.json

@@ -1,3 +0,0 @@
-{
-  "capacity": "shanks=3,ace=2,g14=0,novox=0"
-}

modules/mesh-delivery-builder/go.mod

@@ -3,20 +3,44 @@ module mesh-delivery-builder
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261021192148-78364e318bdc
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261104174359-05b3e2e1b94f
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )
 
+require git.novox.be/novox/mesh-catalog/modules/mesh-build-go/buildstep v0.0.0-20261104174638-125929dbc459
+
 require (
-	github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op // indirect
+	git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639 // indirect
+	git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun v0.0.0-00010101000000-000000000000
+	github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op // indirect
 	github.com/google/go-tpm v0.9.8 // indirect
-	github.com/klauspost/compress v1.20.0 // indirect
+	github.com/klauspost/compress v1.20.1 // indirect
 	github.com/minio/highwayhash v1.0.4 // indirect
-	github.com/nats-io/jwt/v2 v2.8.1 // indirect
+	github.com/nats-io/jwt/v2 v2.8.2 // indirect
 	github.com/nats-io/nkeys v0.4.16 // indirect
 	github.com/nats-io/nuid v1.0.1 // indirect
 	golang.org/x/crypto v0.57.0 // indirect
 	golang.org/x/sys v0.48.0 // indirect
-	golang.org/x/time v0.15.0 // indirect
+	golang.org/x/time v0.16.0 // indirect
 )
+
+replace git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun => ./buildrun
+
+require (
+	git.novox.be/novox/mesh-contracts/go/seats/containerimageregistry v0.0.0-20261104174344-ae5266e77639
+	git.novox.be/novox/mesh-contracts/go/seats/gopackageregistry v0.0.0-20261104174344-ae5266e77639
+	git.novox.be/novox/mesh-contracts/go/seats/nodeengine v0.0.0-20261104174344-ae5266e77639
+	git.novox.be/novox/mesh-contracts/go/seats/npmpackageregistry v0.0.0-20261104174344-ae5266e77639
+	git.novox.be/novox/mesh-contracts/go/seats/ociartifactregistry v0.0.0-20261104174344-ae5266e77639
+	git.novox.be/novox/mesh-delivery/sdk v0.0.0-00010101000000-000000000000
+)
+
+require (
+	git.novox.be/novox/mesh-contracts/go/clients/containerimageregistryclient v0.0.0-20261104174344-ae5266e77639 // indirect
+	git.novox.be/novox/mesh-contracts/go/clients/gopackageregistryclient v0.0.0-20261104174344-ae5266e77639 // indirect
+	git.novox.be/novox/mesh-contracts/go/clients/npmpackageregistryclient v0.0.0-20261104174344-ae5266e77639 // indirect
+	git.novox.be/novox/mesh-contracts/go/clients/ociartifactregistryclient v0.0.0-20261104174344-ae5266e77639 // indirect
+)
+
+replace git.novox.be/novox/mesh-delivery/sdk => ../../sdk

modules/mesh-delivery-builder/go.sum

@@ -1,15 +1,37 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261021192148-78364e318bdc h1:ZJScJSnF6LgFl55/VJ9RT/lNroVWun469sXtx0nlVYw=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261021192148-78364e318bdc/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
-github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
-github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
+git.novox.be/novox/mesh-catalog/modules/mesh-build-go/buildstep v0.0.0-20261104174638-125929dbc459 h1:DA4SFG/gKyG+aPJbfUpAUad2VeITIiKjJ6qOPmDhSA8=
+git.novox.be/novox/mesh-catalog/modules/mesh-build-go/buildstep v0.0.0-20261104174638-125929dbc459/go.mod h1:zR1HsAKZVbQsBIY5wPyrqI2WHInK268tITzGl2oqHro=
+git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639 h1:Zt7CfWt2S2W/fVgWNyW2u2+xwz051LXvGxVTNIyfhdM=
+git.novox.be/novox/mesh-contracts/go v0.0.0-20261104174344-ae5266e77639/go.mod h1:0dD1XEJBJ0G5UYDQxSZI84nuujb6m3tOpJl4C8rQVvg=
+git.novox.be/novox/mesh-contracts/go/clients/containerimageregistryclient v0.0.0-20261104174344-ae5266e77639 h1:I6uVDO9E+i3D9/n6KQ2RWYRs3kXYCqueiKXynifQo8w=
+git.novox.be/novox/mesh-contracts/go/clients/containerimageregistryclient v0.0.0-20261104174344-ae5266e77639/go.mod h1:ER2NVrd81uJo1lN0YCGA7OBxL910IHRgWYtxpsnHGF0=
+git.novox.be/novox/mesh-contracts/go/clients/gopackageregistryclient v0.0.0-20261104174344-ae5266e77639 h1:Rs5jOa7EWlpKuaH6+ExyGLN9k9UUi8N7upP9Ac3k+GY=
+git.novox.be/novox/mesh-contracts/go/clients/gopackageregistryclient v0.0.0-20261104174344-ae5266e77639/go.mod h1:fNfjFkP1+suYb12HJkapQe5W3cF98JsTcLBI/syoLHc=
+git.novox.be/novox/mesh-contracts/go/clients/npmpackageregistryclient v0.0.0-20261104174344-ae5266e77639 h1:VG+sZltyBIKrd9cwFJyKkInz04SxWBxUlJWfAuo6774=
+git.novox.be/novox/mesh-contracts/go/clients/npmpackageregistryclient v0.0.0-20261104174344-ae5266e77639/go.mod h1:Nq7glLZSZ8zOLTh1pXDnKZi+MxsMRyHw/bZODC3mvrY=
+git.novox.be/novox/mesh-contracts/go/clients/ociartifactregistryclient v0.0.0-20261104174344-ae5266e77639 h1:ROS9UG/Dg0NpsaDuEmDFV9CsIC1R92sOm3QauF7IvL0=
+git.novox.be/novox/mesh-contracts/go/clients/ociartifactregistryclient v0.0.0-20261104174344-ae5266e77639/go.mod h1:/Pke1v2VnSFcR8ic+fo/kNCg3JFYK6ILTal72Ca9520=
+git.novox.be/novox/mesh-contracts/go/seats/containerimageregistry v0.0.0-20261104174344-ae5266e77639 h1:5HeZzk6tKzcSwVivD3IcIvQ/2WIvysZvNvNKyq/oIBA=
+git.novox.be/novox/mesh-contracts/go/seats/containerimageregistry v0.0.0-20261104174344-ae5266e77639/go.mod h1:pPxwhTMb3hIk7UUrBicJnGQCqfTEoBGJvNFspEK2U18=
+git.novox.be/novox/mesh-contracts/go/seats/gopackageregistry v0.0.0-20261104174344-ae5266e77639 h1:oAXU1t8A1rGIr82JPBaNYSGLicXqhWglKaEAtPmrD0c=
+git.novox.be/novox/mesh-contracts/go/seats/gopackageregistry v0.0.0-20261104174344-ae5266e77639/go.mod h1:Y5kgBh0hBbL/hgc+abCF9Vbhov+vCsB0ckpRzUw1D+0=
+git.novox.be/novox/mesh-contracts/go/seats/nodeengine v0.0.0-20261104174344-ae5266e77639 h1:YQ6eJvc+RYUVIVf+oX+R4TC1dYL8TLLMZ0/JPDU1tp4=
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+git.novox.be/novox/mesh-contracts/go/seats/npmpackageregistry v0.0.0-20261104174344-ae5266e77639 h1:ILh7uctNwgx/89qHoR/H2kz5TpWeKEeIH0O2pDPE7Iw=
+git.novox.be/novox/mesh-contracts/go/seats/npmpackageregistry v0.0.0-20261104174344-ae5266e77639/go.mod h1:JRtTjIjMTkzn59IN4vCYei9ZwJGFnN1Puwame4V/sD0=
+git.novox.be/novox/mesh-contracts/go/seats/ociartifactregistry v0.0.0-20261104174344-ae5266e77639 h1:+bkN8op2yrAlBYrOB+hYnIoIZkbjXsNmc/4//uMnL4E=
+git.novox.be/novox/mesh-contracts/go/seats/ociartifactregistry v0.0.0-20261104174344-ae5266e77639/go.mod h1:ooQa2CiP8JOvhP0bdQvwurV5wskRE7Cm68ecURBbCwU=
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+github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op h1:1BOWQJweNyvZMlpAHXGLiZQn9S+QXGcz3xh94lC0w6E=
+github.com/antithesishq/antithesis-sdk-go v0.8.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=
 github.com/google/go-tpm v0.9.8/go.mod h1:h9jEsEECg7gtLis0upRBQU+GhYVH6jMjrFxI8u6bVUY=
-github.com/klauspost/compress v1.20.0 h1:a3C1ke2ohxFymNlb2HWAHjDeKCI90scRskErZkR0ezA=
-github.com/klauspost/compress v1.20.0/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
+github.com/klauspost/compress v1.20.1 h1:T7kKElXUMXrUJ2E9QhQhxFtcK5rPyLdsGZvdbLMPdiQ=
+github.com/klauspost/compress v1.20.1/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
 github.com/minio/highwayhash v1.0.4 h1:asJizugGgchQod2ja9NJlGOWq4s7KsAWr5XUc9Clgl4=
 github.com/minio/highwayhash v1.0.4/go.mod h1:GGYsuwP/fPD6Y9hMiXuapVvlIUEhFhMTh0rxU3ik1LQ=
-github.com/nats-io/jwt/v2 v2.8.1 h1:V0xpGuD/N8Mi+fQNDynXohVvp7ZztevW5io8CUWlPmU=
-github.com/nats-io/jwt/v2 v2.8.1/go.mod h1:nWnOEEiVMiKHQpnAy4eXlizVEtSfzacZ1Q43LIRavZg=
+github.com/nats-io/jwt/v2 v2.8.2 h1:XXRgB60MSTnqsRwejQurVDs/hcv2dkt+86GjI+I/bMc=
+github.com/nats-io/jwt/v2 v2.8.2/go.mod h1:Ag/56sq9OblL4JgdYufDd16Egb17Kr/8WwwuO/forVc=
 github.com/nats-io/nats-server/v2 v2.11.17 h1:GKEghcFK6A+aFx11Yf1LjgLC3txAwvyhnYzhBIQZA8I=
 github.com/nats-io/nats-server/v2 v2.11.17/go.mod h1:B1sFVz4StNosQ903ak4N1G01Fl/9f8e06mXpFIE2K24=
 github.com/nats-io/nats.go v1.54.0 h1:vsXoOxjHp/GmPUN+EcI7uOf/uB+iAP+kEsAFNQN0yzA=
@@ -23,5 +45,5 @@ golang.org/x/crypto v0.57.0/go.mod h1:Fdz0i5U6CoizGwLda9DttjSk6qlZo25zYNtR+ycvuZ
 golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.48.0 h1:bbX/i/6MgT9BVLM9RT1thmxL04yeTAhbEz4SyadbXoo=
 golang.org/x/sys v0.48.0/go.mod h1:hNLxWAXmnKAxqDtdwIYC4bM9oQPEecfsnNMuSxOs3og=
-golang.org/x/time v0.15.0 h1:bbrp8t3bGUeFOx08pvsMYRTCVSMk89u4tKbNOZbp88U=
-golang.org/x/time v0.15.0/go.mod h1:Y4YMaQmXwGQZoFaVFk4YpCt4FLQMYKZe9oeV/f4MSno=
+golang.org/x/time v0.16.0 h1:vMb6ptszcQMkcwiRTAuNNU50gom6++Q/6gY2hDM6VDE=
+golang.org/x/time v0.16.0/go.mod h1:rVKOqvZeKvrDKTQiAHJ7wmwP0RzleSphoEA9RcdLA0s=

modules/mesh-delivery-builder/internal/build/announce.go

@@ -0,0 +1,53 @@
+package build
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **A done build is announced again by hand** (recovery of photos and link2pay on novox, 2026-10-29). The controller takes a
+// build in when a write of the build key reaches its take-in consumer, and composes then; a done key is never written again
+// by the builder, so a composition or a grant lost afterwards could not be made again by any tool. AnnounceAgain writes the
+// done key again with its own bytes, as a new revision of the same key: its content, state, artifacts and manifest stay
+// identical, and only the write is new. Who asked and why is in the builder's log and in the reasks answer.
+
+// AnnounceAgain rewrites the done key of module at fp unchanged, as a new revision, and answers the revision. A key that is
+// not done is refused with why: failed (builder_build_again builds it) or waiting (builder_ask_again).
+func (b *Builder) AnnounceAgain(ctx context.Context, module, fp, why, by string) BuildAgainResult {
+	b.init()
+	key, err := delivery.BuilderBuildKey(module, fp)
+	if err != nil {
+		return BuildAgainResult{Refused: err.Error()}
+	}
+	value, rev, found, err := b.Claimer.Store.Get(ctx, key)
+	if err != nil {
+		return BuildAgainResult{Refused: fmt.Sprintf("%s cannot be read: %v", key, err)}
+	}
+	if !found {
+		return BuildAgainResult{Refused: fmt.Sprintf("%s has no build key: nothing to announce", key)}
+	}
+	cur, err := delivery.DecodeBuilderBuild(value)
+	if err != nil {
+		return BuildAgainResult{Refused: fmt.Sprintf("%s holds what is not a build: %v", key, err)}
+	}
+	switch cur.State {
+	case delivery.BuildDone:
+	case delivery.BuildFailed:
+		return BuildAgainResult{Refused: fmt.Sprintf("%s is failed, not done: %s builds it again", key, BuildAgainTool)}
+	default:
+		return BuildAgainResult{Refused: fmt.Sprintf("%s is %q, not done: %s asks its waiting asks again", key, cur.State, AskAgainTool)}
+	}
+	// Compare-and-set at the revision read: a build written meanwhile is not overwritten.
+	nrev, err := b.Claimer.Store.Update(ctx, key, value, rev)
+	if err != nil {
+		if errors.Is(err, ErrConflict) {
+			return BuildAgainResult{Refused: fmt.Sprintf("%s changed while it was announced: read it again", key)}
+		}
+		return BuildAgainResult{Refused: fmt.Sprintf("%s could not be written: %v", key, err)}
+	}
+	b.logf("%s: done, announced again by %s (revision %d): %s", key, by, nrev, why)
+	return BuildAgainResult{Revision: nrev}
+}

modules/mesh-delivery-builder/internal/build/announce_test.go

@@ -0,0 +1,49 @@
+package build
+
+import (
+	"bytes"
+	"context"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+func TestAnnounceAgainRewritesOnlyADoneKeyUnchanged(t *testing.T) { // recovery of photos and link2pay, 2026-10-29
+	for _, c := range []struct {
+		name   string
+		key    *delivery.BuilderBuild
+		fp     string
+		refuse string
+	}{
+		{name: "a done key is written again, unchanged, as a new revision", key: &delivery.BuilderBuild{State: delivery.BuildDone, Step: "built"}},
+		{name: "a failed key is refused, builder_build_again is for it", refuse: "builder_build_again", key: &delivery.BuilderBuild{State: delivery.BuildFailed, Error: "x"}},
+		{name: "a building key is refused, builder_ask_again is for it", refuse: "builder_ask_again", key: &delivery.BuilderBuild{State: delivery.BuildBuilding, By: "novox.builder", Step: "asked"}},
+		{name: "a key with no build is refused", refuse: "has no build key"},
+		{name: "a fingerprint that is not one is refused", refuse: "fingerprint", fp: "nope"},
+	} {
+		t.Run(c.name, func(t *testing.T) {
+			r := newRig(t, goBundle)
+			var rev uint64
+			if c.key != nil {
+				c.key.Manifest = manifestD
+				rev = putBuild(t, r.st, r.key, *c.key)
+			}
+			before := bytes.Clone(r.st.vals[r.key])
+			fp := fp1
+			if c.fp != "" {
+				fp = c.fp
+			}
+			res := r.b.AnnounceAgain(context.Background(), "m", fp, "grant lost", "shanks.lead")
+			if c.refuse != "" {
+				if !strings.Contains(res.Refused, c.refuse) || res.Revision != 0 || r.st.revs[r.key] != rev || !bytes.Equal(r.st.vals[r.key], before) {
+					t.Fatalf("answer %+v, key at revision %d (was %d); want refused with %q and nothing written", res, r.st.revs[r.key], rev, c.refuse)
+				}
+				return
+			}
+			if res.Refused != "" || res.Revision <= rev || r.st.revs[r.key] != res.Revision || !bytes.Equal(r.st.vals[r.key], before) {
+				t.Fatalf("answer %+v, key at revision %d (was %d); want a new revision and the same bytes", res, r.st.revs[r.key], rev)
+			}
+		})
+	}
+}

modules/mesh-delivery-builder/internal/build/askagain.go

@@ -0,0 +1,419 @@
+package build
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"regexp"
+	"slices"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
+	"git.novox.be/novox/mesh-sdk/go/buildstep"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **An ask that can no longer be answered is asked again** (novox/hq issue 1945). A build seat's stream gives an ask up
+// once it was delivered as often as its worker may (delivery.AskMaxDeliver), and a message given up on, dropped or
+// terminated with no step written is answered by no build node: the lane waiting for its step would wait for ever, and on
+// restart take over the same id and wait again. The builder notices it at the check bound (CheckAfter, the step bound),
+// a context's bound and no timer of its own: it asks Gone, which reads the bus, and asks such an ask again under a new
+// id, written into the key, said in its log and as the event build.asked-again, at most Askings times; then the key is
+// failed with why. An ask DEAD_LETTERS says the seat gave up (buildrun.LostAskWaiter, issue 734) is asked again at once.
+// A person asks the same by hand with the tool builder_ask_again (AskAgain).
+
+// DefaultAskings is how many times a build module's part of a build is asked, the first included, when Builder.Askings is 0.
+const DefaultAskings = 3
+
+// AskedAgainEvent is the event the builder says when it asked an ask again: mesh.mod.mesh-delivery-builder.event.<this>.
+const AskedAgainEvent = "build.asked-again"
+
+// AskedAgain is the body of AskedAgainEvent.
+type AskedAgain struct {
+	Key         string    `json:"key"`
+	Module      string    `json:"module"`
+	FP          string    `json:"fp"`
+	BuildModule string    `json:"build_module"`
+	Language    string    `json:"language"`
+	Old         string    `json:"old"`
+	New         string    `json:"new"`
+	Asking      int       `json:"asking"`
+	Askings     int       `json:"askings"`
+	Why         string    `json:"why"`
+	At          time.Time `json:"at"`
+}
+
+// AskSeen is what the bus says of an ask whose step has not ended, as the builder may read it: its build seat's stream
+// (information and messages by sequence) and its build module's steps. The builder may not read the seat workers'
+// delivery counts or ack floors (granted to the delivery view alone: $JS.API.CONSUMER.INFO.<stream>.<worker>), so a
+// message given up on is told by what the workers did after it: a build node took an ask asked later, of the same kind or
+// of one pulled after it (issue 1945 note 62: seven messages SEAT_NODE_BUILD_GO had given up on sat ahead of a Go ask for
+// five hours, each counted as waiting, so the ask was never asked again).
+type AskSeen struct {
+	Stream string
+	// Kind is the ask's kind, At when it was asked (its id's time).
+	Kind string
+	At   time.Time
+	// Step is whether a build node wrote a step for the ask (running: the step bound of buildrun.Asker judges it).
+	Step bool
+	// OnStream is whether the stream still holds the ask's message; PutAt is when it was put.
+	OnStream bool
+	PutAt    time.Time
+	// Ahead are the messages of its subject before it on the stream.
+	Ahead []Queued
+	// Last is the ask asked last that a build node took (wrote a step for) of the ask's kind or of a kind pulled after
+	// it, when one was taken: every message of the kind asked before it was then delivered already, or given up on.
+	Last *Taken
+}
+
+// Queued is one message of a build seat's stream: its sequence, its ask's id and kind, when the ask was asked (its id's
+// time, the put time when the id says none) and put, and the state of the step a build node wrote for it ("" for none).
+type Queued struct {
+	Seq   uint64    `json:"seq"`
+	Ask   string    `json:"ask"`
+	Kind  string    `json:"kind"`
+	At    time.Time `json:"asked"`
+	PutAt time.Time `json:"put"`
+	Step  string    `json:"step,omitempty"`
+}
+
+// Taken is an ask a build node took: its id, kind and when it was asked, and the step's node and start.
+type Taken struct {
+	Ask     string    `json:"ask"`
+	Kind    string    `json:"kind"`
+	At      time.Time `json:"asked"`
+	Node    string    `json:"node"`
+	Started time.Time `json:"started"`
+}
+
+// Proves is whether a taken ask of kind taken shows that a message of kind waiting asked before it is no longer
+// delivered: a holder pulls the kinds in delivery.AskKinds' order, so taking one of the same kind or of a later one means
+// its worker had none of waiting's kind left to give.
+func Proves(taken, waiting string) bool {
+	t, w := slices.Index(delivery.AskKinds, taken), slices.Index(delivery.AskKinds, waiting)
+	return t >= 0 && w >= 0 && t >= w
+}
+
+// Waits is whether a message ahead still waits to be delivered: no build node wrote a step for it, and no ask of its
+// kind asked after it was taken. A message its worker gave up on (delivered its most times) stays on a work queue until
+// its age, and is not counted.
+func (s AskSeen) Waits(q Queued) bool {
+	return q.Step == "" && !s.passed(q.At)
+}
+
+func (s AskSeen) passed(at time.Time) bool {
+	return s.Last != nil && Proves(s.Last.Kind, s.Kind) && s.Last.At.After(at)
+}
+
+// Waiting is how many messages ahead still wait to be delivered (Waits).
+func (s AskSeen) Waiting() int {
+	n := 0
+	for _, q := range s.Ahead {
+		if s.Waits(q) {
+			n++
+		}
+	}
+	return n
+}
+
+// Why is why the ask can no longer be answered, or "" when it can: it has a step, waits behind others of its kind still
+// deliverable, or no build node took a later ask of its kind (the nodes are busy or paused: a backlog, never a fault,
+// ADR 0525 §9).
+func (s AskSeen) Why() string {
+	switch {
+	case s.Step:
+		return ""
+	case !s.OnStream:
+		return fmt.Sprintf("no build node wrote a step for it and %s no longer holds it: it was given up on or dropped", s.Stream)
+	case s.Waiting() > 0 || !s.passed(s.at()):
+		return ""
+	default:
+		behind := ""
+		if n := len(s.Ahead); n > 0 {
+			behind = fmt.Sprintf(" behind %d given up on or taken", n)
+		}
+		return fmt.Sprintf("it waits on %s since %s%s while %s took the %s ask %s asked later at %s: its stream no longer delivers it (given up after its most deliveries)",
+			s.Stream, s.PutAt.UTC().Format(time.RFC3339), behind, s.Last.Node, s.Last.Kind, s.Last.Ask, s.Last.At.UTC().Format(time.RFC3339))
+	}
+}
+
+func (s AskSeen) at() time.Time {
+	if s.At.IsZero() {
+		return s.PutAt
+	}
+	return s.At
+}
+
+// AskedAt is when an ask id was made (buildstep.NewID: its milliseconds in base 36 before six hex digits), or zero.
+func AskedAt(id string) time.Time {
+	if len(id) <= 6 {
+		return time.Time{}
+	}
+	ms, err := strconv.ParseInt(id[:len(id)-6], 36, 64)
+	if err != nil || ms <= 0 {
+		return time.Time{}
+	}
+	return time.UnixMilli(ms)
+}
+
+// Dropper removes an ask's message from its build seat's stream (Builder.Gone may be one): the old message of an ask asked
+// again, so a message given up on does not sit ahead of every later ask of its kind until its age (issue 1945 note 62).
+type Dropper interface {
+	Drop(ctx context.Context, a delivery.StepAsk) error
+}
+
+// drop removes the old ask's message when Gone can; a refusal is said and changes nothing else: the new ask is put.
+func (b *Builder) drop(ctx context.Context, ask delivery.StepAsk, old string) {
+	d, ok := b.Gone.(Dropper)
+	if !ok {
+		return
+	}
+	prior := ask
+	prior.ID = old
+	if err := d.Drop(ctx, prior); err != nil {
+		b.logf("the message of the ask %s asked again as %s stays on its stream: %v", old, ask.ID, err)
+	}
+}
+
+// DefaultDeclineBound is how long one ask may go on being declined, from its first decline, before its key fails (the
+// checker's DefaultDeclineBound, issue 890); DefaultDeclinePause is how long the builder waits before it puts a declined
+// ask again, so a lone node off the agreed toolchain cannot spin on it.
+const (
+	DefaultDeclineBound = 30 * time.Minute
+	DefaultDeclinePause = 5 * time.Second
+)
+
+func (b *Builder) declineBound() time.Duration {
+	if b.DeclineBound > 0 {
+		return b.DeclineBound
+	}
+	return DefaultDeclineBound
+}
+
+func (b *Builder) declinePause() time.Duration {
+	if b.DeclinePause != 0 {
+		return max(b.DeclinePause, 0)
+	}
+	return DefaultDeclinePause
+}
+
+// declinedWords names the nodes that declined an ask and why, in the order of their names.
+func declinedWords(by map[string]string) string {
+	nodes := make([]string, 0, len(by))
+	for n := range by {
+		nodes = append(nodes, n)
+	}
+	sort.Strings(nodes)
+	var parts []string
+	for _, n := range nodes {
+		parts = append(parts, n+": "+by[n])
+	}
+	return strings.Join(parts, "; ")
+}
+
+func (b *Builder) askings() int {
+	if b.Askings > 0 {
+		return b.Askings
+	}
+	return DefaultAskings
+}
+
+var askingWords = regexp.MustCompile(`asked (\S+) again \(asking (\d+)\)`)
+
+// askingOf is the asking a key's step words name for a build module's ask, 1 when none.
+func askingOf(step, buildModule string) int {
+	for _, m := range askingWords.FindAllStringSubmatch(step, -1) {
+		if m[1] == buildModule {
+			if n, err := strconv.Atoi(m[2]); err == nil && n > 0 {
+				return n
+			}
+		}
+	}
+	return 1
+}
+
+// AskAgain asks the waiting asks of a build key again now, under new ids (the tool builder_ask_again): it answers the
+// languages whose lane waits, none when no lane of this builder waits on the key.
+func (b *Builder) AskAgain(key, why string) []string {
+	b.init()
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	var asked []string
+	for language, c := range b.waiting[key] {
+		select {
+		case c <- why:
+		default: // one is already asked
+		}
+		asked = append(asked, language)
+	}
+	return asked
+}
+
+// Waiting are the build keys whose lanes wait for a step now, each with its languages.
+func (b *Builder) Waiting() map[string][]string {
+	b.init()
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	out := map[string][]string{}
+	for key, ls := range b.waiting {
+		for l := range ls {
+			out[key] = append(out[key], l)
+		}
+	}
+	return out
+}
+
+func (b *Builder) listen(key, language string) chan string {
+	b.init()
+	c := make(chan string, 1)
+	b.mu.Lock()
+	if b.waiting[key] == nil {
+		b.waiting[key] = map[string]chan string{}
+	}
+	b.waiting[key][language] = c
+	b.mu.Unlock()
+	return c
+}
+
+func (b *Builder) unlisten(key, language string, c chan string) {
+	b.mu.Lock()
+	if b.waiting[key][language] == c {
+		delete(b.waiting[key], language)
+		if len(b.waiting[key]) == 0 {
+			delete(b.waiting, key)
+		}
+	}
+	b.mu.Unlock()
+}
+
+var (
+	errCheck = errors.New("the check bound passed")
+	errAgain = errors.New("asked again")
+	// errDeclined: a build node on another toolchain than the agreed one sat out of the ask (ADR 0584 clause 2).
+	errDeclined = errors.New("declined")
+)
+
+type byHand struct{ why string }
+
+func (h byHand) Error() string { return "asked again by hand: " + h.why }
+
+// answer waits for the step of the lane's ask, and asks it again while it can no longer be answered (Gone) or a person
+// asked it again (AskAgain); it answers the step and the ask that has it.
+func (b *Builder) answer(ctx context.Context, l *lane, ask delivery.StepAsk, asked *askNotes, module, fp string) (delivery.Step, delivery.StepAsk, error) {
+	key, _ := delivery.BuilderBuildKey(module, fp)
+	again := b.listen(key, ask.Language)
+	defer b.unlisten(key, ask.Language, again)
+	asking := askingOf(asked.step, l.module)
+	var firstDecline time.Time
+	declines := map[string]string{} // node -> why it declined, the last
+	for {
+		step, why, err := b.waitOnce(ctx, ask, again)
+		switch {
+		case errors.Is(err, errCheck):
+			continue
+		case errors.Is(err, errDeclined):
+			// Not an asking: a node that sits out would use them all while it idles and pulls the ask again at once.
+			// Bounded by time from the first decline, then failed loudly naming the nodes and their reasons (as the
+			// checker's decline loop is, issue 890).
+			now := b.now()
+			if firstDecline.IsZero() {
+				firstDecline = now
+			}
+			declines[step.Node] = why
+			if bound := b.declineBound(); now.Sub(firstDecline) > bound {
+				return step, ask, fmt.Errorf("the ask %s of %s was declined for %s and no build node took it: %s", ask.ID, l.module, bound.Round(time.Second), declinedWords(declines))
+			}
+			// The pause is a context's bound, not a timer (ADR 0437 §8).
+			pause, stop := context.WithTimeout(ctx, b.declinePause())
+			<-pause.Done()
+			stop()
+			if ctx.Err() != nil {
+				return step, ask, ctx.Err()
+			}
+			old := ask.ID
+			ask.ID, ask.At = buildstep.NewID(), time.Now()
+			if err := asked.note(ctx, ask.Language, ask.ID, fmt.Sprintf("put %s again after %s declined it", l.module, step.Node)); err != nil {
+				return step, ask, fmt.Errorf("the ask of %s put again after a decline could not be written to the key: %w", l.module, err)
+			}
+			if err := b.Asks.Put(ctx, ask); err != nil {
+				return step, ask, err
+			}
+			b.drop(ctx, ask, old)
+			b.logf("%s: the ask %s of %s was declined on %s and is put again as %s: %s", key, old, l.module, step.Node, ask.ID, why)
+		case errors.Is(err, errAgain):
+			if asking >= b.askings() {
+				return step, ask, fmt.Errorf("the ask %s could not be answered and was asked %d times, the most it is: %s", ask.ID, asking, why)
+			}
+			asking++
+			old := ask.ID
+			ask.ID, ask.At = buildstep.NewID(), time.Now()
+			if err := asked.note(ctx, ask.Language, ask.ID, fmt.Sprintf("asked %s again (asking %d): %s", l.module, asking, why)); err != nil {
+				return step, ask, fmt.Errorf("the ask of %s asked again could not be written to the key: %w", l.module, err)
+			}
+			if err := b.Asks.Put(ctx, ask); err != nil {
+				return step, ask, err
+			}
+			b.drop(ctx, ask, old)
+			b.logf("%s: the ask %s of %s is asked again as %s (asking %d of %d): %s", key, old, l.module, ask.ID, asking, b.askings(), why)
+			if b.Said != nil {
+				b.Said(AskedAgain{Key: key, Module: module, FP: fp, BuildModule: l.module, Language: ask.Language, Old: old, New: ask.ID,
+					Asking: asking, Askings: b.askings(), Why: why, At: ask.At})
+			}
+		default:
+			return step, ask, err
+		}
+	}
+}
+
+// waitOnce waits for the ask's step until it ends, a person asks it again, or the check bound passes: then it asks Gone
+// and answers errAgain with why when the ask can no longer be answered, errCheck when it waits on.
+func (b *Builder) waitOnce(ctx context.Context, ask delivery.StepAsk, again <-chan string) (delivery.Step, string, error) {
+	hand, cancel := context.WithCancelCause(ctx)
+	defer cancel(nil)
+	go func() {
+		select {
+		case why := <-again:
+			cancel(byHand{why})
+		case <-hand.Done():
+		}
+	}()
+	wait := hand
+	if b.Gone != nil && b.CheckAfter > 0 {
+		var stop context.CancelFunc
+		wait, stop = context.WithTimeoutCause(hand, b.CheckAfter, errCheck)
+		defer stop()
+	}
+	step, err := b.Asks.Wait(wait, ask)
+	if _, declined := delivery.DeclinedOf(step); err == nil && declined {
+		// A build node off the agreed toolchain sat out (ADR 0584 clause 2). It is no asking: answer() puts the ask again
+		// after a pause, within DeclineBound.
+		return step, step.Reason, errDeclined
+	}
+	if err == nil && buildrun.IsLost(step) {
+		// The build seat gave the ask up (issue 734): it can no longer be answered, so it is asked again now, with the
+		// words of why, not at the check bound.
+		return step, step.Reason, errAgain
+	}
+	if err == nil || ctx.Err() != nil {
+		return step, "", err
+	}
+	var h byHand
+	if errors.As(context.Cause(hand), &h) {
+		return step, strings.TrimSpace("asked again by hand: " + h.why), errAgain
+	}
+	if errors.Is(context.Cause(wait), errCheck) {
+		why, gerr := b.Gone.Gone(ctx, ask)
+		if gerr != nil {
+			b.logf("whether the ask %s can still be answered cannot be read, so it is waited for: %v", ask.ID, gerr)
+			return step, "", errCheck
+		}
+		if why == "" {
+			return step, "", errCheck
+		}
+		return step, why, errAgain
+	}
+	return step, "", err
+}

modules/mesh-delivery-builder/internal/build/askfake_test.go

@@ -0,0 +1,94 @@
+package build
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"maps"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// The build runner a build node runs an ask with is mesh-build-go's (novox/hq ADR 0593 §1), another repository's,
+// which the builder does not import. These tests run an ask as the builder needs it run: fetch once at the job's
+// fetch arguments with its package versions, build or copy each artifact, answer each one's digest and reference. They
+// test the builder, not the runner.
+
+// stepFunc is one step of a build module, as its tool answers it.
+type stepFunc func(ctx context.Context, args map[string]any) (any, error)
+
+// askSteps are a build module's steps an ask is run with.
+type askSteps struct{ Fetch, Build, Copy stepFunc }
+
+// runAsk runs a build ask with steps and answers its delivery.BuildAnswer, or the error that fails the step.
+func runAsk(ctx context.Context, steps askSteps, ask delivery.StepAsk) (any, error) {
+	if ask.Build == nil {
+		return nil, fmt.Errorf("the ask %s holds no build job", ask.ID)
+	}
+	job := *ask.Build
+	fetch := job.Fetch
+	if len(ask.Packages) > 0 && fetch != nil {
+		fetch = maps.Clone(fetch)
+		fetch["packages"] = maps.Clone(ask.Packages)
+	}
+	answer := delivery.BuildAnswer{}
+	workspace := ""
+	for _, a := range job.Artifacts {
+		var out any
+		var err error
+		if a.From != "" {
+			if steps.Copy == nil {
+				return nil, fmt.Errorf("this build module copies no artifact (%s)", a.Artifact)
+			}
+			out, err = steps.Copy(ctx, map[string]any{"module": job.Module, "artifact": a.Artifact, "from": a.From})
+		} else {
+			if workspace == "" {
+				raw, err := asRaw(steps.Fetch(ctx, fetch))
+				if err != nil {
+					return nil, err
+				}
+				var f struct {
+					Workspace string   `json:"workspace"`
+					Merge     string   `json:"merge"`
+					Conflicts []string `json:"conflicts"`
+				}
+				if err := json.Unmarshal(raw, &f); err != nil || f.Workspace == "" {
+					return nil, fmt.Errorf("the fetch answered no workspace: %s", raw)
+				}
+				if _, candidate := fetch["base"]; candidate && (len(f.Conflicts) > 0 || f.Merge == "") {
+					return nil, fmt.Errorf("the head does not merge into the trunk: %s", strings.Join(f.Conflicts, ", "))
+				}
+				workspace = f.Workspace
+			}
+			args := map[string]any{"workspace": workspace, "module": job.Path, "artifact": a.Artifact}
+			if job.Publish {
+				args["publish"] = true
+			}
+			out, err = steps.Build(ctx, args)
+		}
+		raw, err := asRaw(out, err)
+		if err != nil {
+			return nil, fmt.Errorf("%s: %w", a.Artifact, err)
+		}
+		var built struct {
+			Digest    string `json:"digest"`
+			Reference string `json:"reference"`
+		}
+		if err := json.Unmarshal(raw, &built); err != nil || built.Digest == "" {
+			return nil, fmt.Errorf("the build of %s answered no digest: %s", a.Artifact, raw)
+		}
+		answer.Artifacts = append(answer.Artifacts, delivery.AskBuilt{Artifact: a.Artifact, Digest: built.Digest, Reference: built.Reference})
+	}
+	return answer, nil
+}
+
+func asRaw(v any, err error) (json.RawMessage, error) {
+	if err != nil {
+		return nil, err
+	}
+	if r, ok := v.(json.RawMessage); ok {
+		return r, nil
+	}
+	return json.Marshal(v)
+}

modules/mesh-delivery-builder/internal/build/buildagain.go

@@ -0,0 +1,183 @@
+package build
+
+import (
+	"context"
+	"fmt"
+	"maps"
+	"strings"
+	"time"
+
+	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **A failed key is built again by hand** (novox/hq issue 1126 note 72; ADR 0429 clause 18: "a fingerprint is built again
+// only when its build key failed, as a new revision of the same key"). The builder does it by itself whenever it looks at a
+// module again (a modules value, a change of the toolchains, artifacts-gone, a moved trunk): Claimer.Claim writes a failed
+// key building as a new revision and the build asks the build seats. Nothing looks at an unchanged module on its own, so a key
+// that failed (a node refused the build, a toolchain was missing) stayed failed until the module changed. The tool
+// builder_build_again (BuildAgain) makes the builder look at one module now, which does exactly that and no more: it keeps
+// the claim's rules, so a key failed for a reason the builder never retries on the same fingerprint stays refused.
+
+// BuildAgainResult is the builder's answer to a request to build a key again.
+type BuildAgainResult struct {
+	// Refused is why nothing was done, "" when the key was written building as a new revision.
+	Refused string
+	// Revision is the revision the claim wrote; Asks are the ask ids put by language, as far as they were put within the bound.
+	Revision uint64
+	Asks     map[string]string
+	// Pending says the builder had not claimed the key, or not put every ask, when it answered: not a refusal.
+	Pending string
+	// Failed is the error of the key when the build ended failed before its asks were put (a plan that cannot be read, a
+	// toolchain not agreed): the new revision was written, and nothing was asked.
+	Failed string
+}
+
+// handWatch follows one request to build a key again until its asks are put.
+type handWatch struct {
+	rev   uint64
+	lanes int
+	asks  map[string]string
+	done  chan struct{}
+	shut  bool
+	// ended is set when the look ended before the asks were all put.
+	ended bool
+}
+
+// settle closes done once the claim is written and every lane has put its ask. Call with b.mu held.
+func (w *handWatch) settle() {
+	if !w.shut && w.rev > 0 && w.lanes >= 0 && len(w.asks) >= w.lanes {
+		w.shut = true
+		close(w.done)
+	}
+}
+
+func (b *Builder) hand(key string, f func(w *handWatch)) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if w := b.hands[key]; w != nil {
+		f(w)
+	}
+}
+
+func (b *Builder) handClaimed(key string, rev uint64) {
+	b.hand(key, func(w *handWatch) { w.rev = rev; w.settle() })
+}
+
+func (b *Builder) handLanes(key string, n int) {
+	b.hand(key, func(w *handWatch) { w.lanes = n; w.settle() })
+}
+
+func (b *Builder) handAsk(key, language, id string) {
+	b.hand(key, func(w *handWatch) { w.asks[language] = id; w.settle() })
+}
+
+// handEnded ends the watch of a request whose look ended: it wrote no claim, or the build ended.
+func (b *Builder) handEnded(key string) {
+	b.hand(key, func(w *handWatch) {
+		if !w.shut {
+			w.shut, w.ended = true, true
+			close(w.done)
+		}
+	})
+}
+
+// BuildAgain builds the failed key of module at fp again, as the builder does by itself: the key is written building as a
+// new revision and the build module asks are put on the build seats. It answers once the asks are put, or at bound. A key
+// that is not failed is refused with why: done (nothing to do) or waiting (builder_ask_again asks its waiting asks again).
+// ctx is the builder's own context: the build it starts lives on it.
+func (b *Builder) BuildAgain(ctx context.Context, module, fp, why, by string, bound time.Duration) BuildAgainResult {
+	b.init()
+	key, err := delivery.BuilderBuildKey(module, fp)
+	if err != nil {
+		return BuildAgainResult{Refused: err.Error()}
+	}
+	value, _, found, err := b.Claimer.Store.Get(ctx, key)
+	if err != nil {
+		return BuildAgainResult{Refused: fmt.Sprintf("%s cannot be read: %v", key, err)}
+	}
+	if !found {
+		return BuildAgainResult{Refused: fmt.Sprintf("%s has no build key: nothing failed. The builder builds a fingerprint by itself once the indexer writes it to its module", key)}
+	}
+	cur, err := delivery.DecodeBuilderBuild(value)
+	if err != nil {
+		return BuildAgainResult{Refused: fmt.Sprintf("%s holds what is not a build: %v", key, err)}
+	}
+	switch {
+	case cur.State == delivery.BuildDone:
+		return BuildAgainResult{Refused: fmt.Sprintf("%s is done: nothing to do", key)}
+	case cur.State == delivery.BuildBuilding || cur.State == delivery.BuildQueued:
+		return BuildAgainResult{Refused: fmt.Sprintf("%s is waiting (%s: %s): %s asks its waiting asks again", key, cur.State, cur.Step, AskAgainTool)}
+	case cur.State != delivery.BuildFailed:
+		return BuildAgainResult{Refused: fmt.Sprintf("%s is %q, not failed", key, cur.State)}
+	case delivery.FailedUntilChanged(cur.Error) || strings.HasPrefix(cur.Error, buildrun.DigestsDifferPrefix):
+		return BuildAgainResult{Refused: fmt.Sprintf("%s failed for a reason the builder does not retry on the same fingerprint, it waits for another fingerprint: %s", key, cur.Error)}
+	}
+	// One critical section: the key is refused when it is looked at or asked already, the module still has the fingerprint,
+	// and the watch and the look are registered before anything else can take the key.
+	w := &handWatch{lanes: -1, asks: map[string]string{}, done: make(chan struct{})}
+	b.mu.Lock()
+	m, known := b.known[module]
+	switch {
+	case !known || m.FP2 != fp:
+		b.mu.Unlock()
+		return BuildAgainResult{Refused: fmt.Sprintf("module %s does not have the fingerprint %s now (a newer one superseded it, or its modules value is not read yet): the builder builds the module's current fingerprint", module, fp)}
+	case m.Manifest == "":
+		b.mu.Unlock()
+		return BuildAgainResult{Refused: fmt.Sprintf("module %s names no manifest at %s yet, so the builder looks at nothing", module, fp)}
+	case b.inflight[key] || b.hands[key] != nil:
+		b.mu.Unlock()
+		return BuildAgainResult{Refused: fmt.Sprintf("%s is being looked at by this builder now (or asked again by hand): wait for it to end", key)}
+	}
+	b.hands[key] = w
+	b.inflight[key] = true
+	b.mu.Unlock()
+	defer func() {
+		b.mu.Lock()
+		if b.hands[key] == w {
+			delete(b.hands, key)
+		}
+		b.mu.Unlock()
+	}()
+	b.logf("%s: failed (%s); built again by hand, asked by %s: %s", key, cur.Error, by, why)
+	b.startOnce(ctx, key, module, m)
+	wait, stop := context.WithTimeout(ctx, bound) // a context's bound for a person's answer (ADR 0437 §8)
+	defer stop()
+	select {
+	case <-w.done:
+	case <-wait.Done():
+	}
+	b.mu.Lock()
+	res := BuildAgainResult{Revision: w.rev, Asks: maps.Clone(w.asks)}
+	ended, shut, lanes := w.ended, w.shut, w.lanes
+	b.mu.Unlock()
+	switch {
+	case res.Revision == 0 && shut:
+		res.Refused = fmt.Sprintf("the builder looked at %s and wrote nothing (a toolchain moved, the claim was lost or could not be written): its log says why", key)
+	case res.Revision == 0:
+		res.Pending = fmt.Sprintf("the builder has not claimed %s within %s: it waits behind other builds; builder_stuck shows where it stands", key, bound)
+	case ended && len(res.Asks) < max(lanes, 0)+boolInt(lanes < 0):
+		// The look ended before every ask was put: say how the key stands, not that it was asked.
+		if v, _, found, err := b.Claimer.Store.Get(ctx, key); err == nil && found {
+			if cur, err := delivery.DecodeBuilderBuild(v); err == nil {
+				switch cur.State {
+				case delivery.BuildFailed:
+					res.Failed = cur.Error
+				case delivery.BuildDone:
+				default:
+					res.Pending = fmt.Sprintf("the look ended with the key %s (%s) before every ask was put: its log says why", cur.State, cur.Step)
+				}
+			}
+		}
+	case !shut:
+		res.Pending = fmt.Sprintf("the key is building at revision %d, and not every ask was put within %s; builder_stuck shows the asks", res.Revision, bound)
+	}
+	return res
+}
+
+func boolInt(b bool) int {
+	if b {
+		return 1
+	}
+	return 0
+}

modules/mesh-delivery-builder/internal/build/candidates.go

@@ -5,8 +5,8 @@ import (
 	"fmt"
 	"sort"
 
+	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
-	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
 )
 
 // How a candidate's fingerprint is built (novox/hq ADR 0484 clause 3, issue 1684): the indexer writes, for each module a
@@ -68,10 +68,22 @@ func (b *Builder) considerCandidate(ctx context.Context, c delivery.Candidate) {
 				continue
 			}
 			m := delivery.Module{Repository: p.Repository, Commit: p.Head.Head, FP2: cm.FP2, Manifest: cm.Manifest, Path: trunk.Path,
-				Toolchains: b.agreedFor(ctx, cm.Manifest)}
+				Toolchains: b.agreedFor(ctx, cm.Manifest), Packages: cm.Packages} // the group's package heads (ADR 0573 §4)
+			if len(cm.Paths) > 0 {
+				// The named paths' objects the preview gave it: the fetch names the paths (runLane, ADR 0499 clause 4).
+				m.Inputs2 = &delivery.KeptInputs2{Paths: cm.Paths}
+			}
+			// The preview is merged onto the trunk head the candidate was previewed onto: the head of the pull request's
+			// repository in the gate's source revision c.Base (ADR 0484 §3). Never the module's value's commit: that is the
+			// commit its fingerprint first appeared at, and may be many merges behind the trunk.
+			base, err := b.trunkHead(ctx, c.Base, p.Repository)
+			if err != nil {
+				b.logf("candidates.%s: the module %s's fingerprint %s is not built: %v", c.Group, name, cm.FP2, err)
+				continue
+			}
 			b.mu.Lock()
 			if _, onTrunk := b.trunkFP[key]; !onTrunk {
-				b.via[key] = via{Ref: fmt.Sprintf("refs/pull/%d/head", p.Number), Base: trunk.Commit}
+				b.via[key] = via{Ref: fmt.Sprintf("refs/pull/%d/head", p.Number), Base: base}
 			}
 			b.mu.Unlock()
 			b.consider(ctx, name, m)
@@ -102,3 +114,18 @@ func (b *Builder) agreedFor(ctx context.Context, manifest string) map[string]del
 	}
 	return out
 }
+
+// trunkHead is the head of repository in the gate's source revision rev (Builder.Trunk), or why it cannot be said.
+func (b *Builder) trunkHead(ctx context.Context, rev uint64, repository string) (string, error) {
+	if b.Trunk == nil {
+		return "", fmt.Errorf("the gate's source cannot be read here, so the trunk head %s was previewed onto is not known", repository)
+	}
+	head, err := b.Trunk(ctx, rev, repository)
+	if err != nil {
+		return "", fmt.Errorf("the trunk head of %s at source revision %d cannot be read: %w", repository, rev, err)
+	}
+	if head == "" {
+		return "", fmt.Errorf("source revision %d names no trunk head of %s", rev, repository)
+	}
+	return head, nil
+}

modules/mesh-delivery-builder/internal/build/candidates_test.go

@@ -2,9 +2,13 @@ package build
 
 import (
 	"context"
+	"encoding/json"
+	"fmt"
+	"os"
 	"strings"
 	"testing"
 
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
 
@@ -40,11 +44,74 @@ func candidateValue(t *testing.T, group string, number int, head string) []byte
 }
 
 const (
-	headX = "1111111111111111111111111111111111111111"
-	headY = "2222222222222222222222222222222222222222"
+	// trunkHead is the trunk head the rig's source revision names: newer than the module value's commit, which stays at the
+	// commit its fingerprint first appeared at.
+	trunkHead = "3333333333333333333333333333333333333333"
+	headX     = "1111111111111111111111111111111111111111"
+	headY     = "2222222222222222222222222222222222222222"
 )
 
+// indexerCandidate is a candidate as the indexer writes it, with the gate's source revision it names (mesh-delivery-indexer
+// internal/index testdata/candidate-written.json, kept equal to what the indexer writes by its own test).
+func indexerCandidate(t *testing.T) (rev uint64, heads map[string]string, c delivery.Candidate, raw []byte) {
+	t.Helper()
+	data, err := os.ReadFile("../../../mesh-delivery-indexer/internal/index/testdata/candidate-written.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var w struct {
+		Source struct {
+			Rev   uint64            `json:"rev"`
+			Heads map[string]string `json:"heads"`
+		} `json:"source"`
+		Candidate json.RawMessage `json:"candidate"`
+	}
+	if err := json.Unmarshal(data, &w); err != nil {
+		t.Fatal(err)
+	}
+	if c, err = delivery.DecodeCandidate(w.Candidate); err != nil {
+		t.Fatal(err)
+	}
+	return w.Source.Rev, w.Source.Heads, c, w.Candidate
+}
+
 func TestACandidatesFingerprintIsBuiltOnceAsAKeyOfItsOwnFromTheHeadMergedOntoTheTrunk(t *testing.T) { // N7/AC1, N7/AC2 (issue 1684)
+	// The candidate the indexer writes is merged onto the trunk head of the source revision it names, never onto the module
+	// value's commit, which stays at the commit its fingerprint first appeared at (review of the indexer writing on change).
+	{
+		rev, heads, c, raw := indexerCandidate(t)
+		p := c.Pulls[0]
+		cm := p.Fps["avahi"]
+		ir := newRig(t, goBundle)
+		ir.mf.byDigest[cm.Manifest] = catalogue.Manifest{Module: "avahi", Build: &catalogue.Build{Artifacts: []catalogue.Artifact{goBundle}}}
+		ir.b.Trunk = func(_ context.Context, at uint64, repository string) (string, error) {
+			if at != rev {
+				return "", fmt.Errorf("source revision %d is not heard", at)
+			}
+			return heads[repository], nil
+		}
+		const valueCommit = "7a74cee83f88e6585a5511c3cc53bdf0f5303d20"
+		value, err := delivery.EncodeModule(delivery.Module{Repository: p.Repository, Commit: valueCommit, FP2: "src2:" + hex64('e'),
+			Manifest: cm.Manifest, Path: "modules/avahi", Toolchains: agreedToolchains})
+		if err != nil {
+			t.Fatal(err)
+		}
+		ir.b.Module(context.Background(), "avahi", value)
+		ir.b.Wait()
+		ir.bm.mu.Lock()
+		ir.bm.calls = nil
+		ir.bm.mu.Unlock()
+		ir.b.Candidate(context.Background(), "feat%2Fx", raw)
+		ir.b.Wait()
+		fetches := ir.bm.callsOf("build_go_fetch")
+		if len(fetches) != 1 {
+			t.Fatalf("%d fetches of the indexer's candidate, want one", len(fetches))
+		}
+		f := fetches[0].body.(map[string]any)
+		if want := heads[p.Repository]; want == "" || f["base"] != want || f["base"] == valueCommit || f["commit"] != p.Head.Head {
+			t.Errorf("fetch args = %+v, want the head merged onto the trunk head %.8s of source revision %d", f, want, rev)
+		}
+	}
 	r := newRig(t, goBundle)
 	trunkModule(t, r)
 	r.b.Candidate(context.Background(), "feat%2Fx", candidateValue(t, "feat/x", 7, headX))
@@ -54,12 +121,12 @@ func TestACandidatesFingerprintIsBuiltOnceAsAKeyOfItsOwnFromTheHeadMergedOntoThe
 		t.Fatalf("build = %+v, want the candidate's fingerprint built", v)
 	}
 	fetches := r.bm.callsOf("build_go_fetch")
-	if len(fetches) != 2 { // one on each of two nodes
-		t.Fatalf("%d fetches, want one per node", len(fetches))
+	if len(fetches) != 1 { // one node per fingerprint (ADR 0478 clause 4)
+		t.Fatalf("%d fetches, want one", len(fetches))
 	}
 	f := fetches[0].body.(map[string]any)
-	if f["commit"] != headX || f["ref"] != "refs/pull/7/head" || f["base"] != "7a74cee83f88e6585a5511c3cc53bdf0f5303d20" || f["repository"] != "novox/mesh-catalog" {
-		t.Errorf("fetch args = %+v, want the head, its ref and the trunk commit to merge onto", f)
+	if f["commit"] != headX || f["ref"] != "refs/pull/7/head" || f["base"] != trunkHead || f["repository"] != "novox/mesh-catalog" {
+		t.Errorf("fetch args = %+v, want the head, its ref and the trunk head the candidate was previewed onto", f)
 	}
 	if b := r.bm.callsOf("build_go_build")[0].body.(map[string]any); b["module"] != "modules/m" {
 		t.Errorf("build args = %+v", b)
@@ -67,7 +134,7 @@ func TestACandidatesFingerprintIsBuiltOnceAsAKeyOfItsOwnFromTheHeadMergedOntoThe
 	// Two heads carrying one fingerprint are one build.
 	r.b.Candidate(context.Background(), "feat%2Fy", candidateValue(t, "feat/y", 8, headY))
 	r.b.Wait()
-	if n := len(r.bm.callsOf("build_go_fetch")); n != 2 {
+	if n := len(r.bm.callsOf("build_go_fetch")); n != 1 {
 		t.Errorf("%d fetches after a second head with the same fingerprint, want no more", n)
 	}
 }

modules/mesh-delivery-builder/internal/build/claim.go

@@ -4,9 +4,12 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
+	"slices"
+	"sort"
 	"strings"
 
+	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-builder/buildrun"
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
 
@@ -35,23 +38,11 @@ type Claim struct {
 	Key   string
 	Rev   uint64
 	Build delivery.BuilderBuild
-}
-
-// OneNodePrefix opens the Step of a done build that a build module built on one node only, because no second node
-// qualified (ADR 0478 clause 4); the build modules that did so follow in parentheses, then ": ". Claim reads it to build
-// the key again, as a new revision, once a second node qualifies.
-const OneNodePrefix = "one node ("
-
-// OneNodeModules are the build modules a done build built on one node only, or none when it is not such a build.
-func OneNodeModules(b delivery.BuilderBuild) []string {
-	if b.State != delivery.BuildDone || !strings.HasPrefix(b.Step, OneNodePrefix) {
-		return nil
-	}
-	list, _, ok := strings.Cut(strings.TrimPrefix(b.Step, OneNodePrefix), "): ")
-	if !ok || list == "" {
-		return nil
-	}
-	return strings.Split(list, ", ")
+	// Gone are the references of a done key the artifact store no longer holds, for which it was claimed again
+	// (ClaimOptions.Stored; issue 1937): said in the log and the key's step.
+	Gone []string
+	// Unasked is why the store could not be asked about a done key taken as it stands to publish: said in the log.
+	Unasked error
 }
 
 // ClaimOptions say what the builder knows about the moment of a claim.
@@ -59,26 +50,90 @@ type ClaimOptions struct {
 	// TakeOver takes a key found building whoever holds it: the builder has just started and looks at the key for the first
 	// time, and a build left building by a builder that is gone, on this node or another, is nobody's (ADR 0478 clause 6).
 	TakeOver bool
-	// MoreNodes says whether one of these build modules, which built a done key on one node only, has a second node that
-	// qualifies now and the key may be built again (it is not held back after a failed second build, issue 1664). Nil means
-	// none does.
-	MoreNodes func(modules []string) bool
 	// ImageBuilder says whether a node runs a healthy image build module now: a key failed for NoImageBuilderPrefix is taken
 	// again only then. Nil means none does.
 	ImageBuilder func() bool
-	// Trunk is whether the trunk's record names this fingerprint. A done key whose image has no reference was built as a
-	// candidate's, which never pushes (ADR 0487 clause 12); on the trunk it is taken again to publish the image, when an image
-	// builder runs (ImageBuilder).
+	// Trunk is whether the trunk's record names this fingerprint. A done key whose image or package has no reference was
+	// built as a candidate's, which never pushes or publishes (ADR 0487 clause 12, ADR 0498 clauses 5 and 6); on the trunk it
+	// is taken again to publish them, an image only when an image builder runs (ImageBuilder).
 	Trunk bool
+	// Published says whether a package version `<name>@<version>` is published: one of the builder's done keys names it as
+	// a package's reference. A key queued waiting for a version (BuilderBuild.Waits) is taken only once it is (ADR 0500
+	// clause 6). Nil means none is.
+	Published func(ref string) bool
+	// Stored answers which of the references given the artifact store no longer holds (the seat mesh-artifact-sweep's verb held,
+	// novox/hq ADR 0571 §2, issue 1937). A done key of the trunk's fingerprint is asked before it is left
+	// done: the store's nightly collector deletes a blob nothing holds, and a key the controller never took in holds
+	// nothing, so a key whose blob is gone is claimed building as a new revision and built again. Nil asks nothing.
+	Stored func(ctx context.Context, references []string) (gone []string, err error)
 }
 
-// Unpublished is whether a done build holds an image built without a push: it has no reference.
-func Unpublished(b delivery.BuilderBuild) bool {
+// StoredReferences are the references of a done build's bundles and archives that name a blob in the artifact store
+// (`artifact-store://<module>/<artifact>/blobs/<digest>`): what the store's collector can delete. An image or an upstream
+// copy is a manifest, which the collector keeps, and a package lives in the package registry.
+func StoredReferences(b delivery.BuilderBuild) []string {
+	var out []string
+	for _, a := range b.Artifacts {
+		if strings.HasPrefix(a.Reference, "artifact-store://") && strings.Contains(a.Reference, "/blobs/") &&
+			!slices.Contains(out, a.Reference) {
+			out = append(out, a.Reference)
+		}
+	}
+	return out
+}
+
+// GoneStep is the step a key claimed again for gone blobs says (issue 1937).
+func GoneStep(gone []string) string {
+	return "claimed again: the artifact store no longer holds " + strings.Join(gone, ", ")
+}
+
+// Unpublished is whether a done build holds an image built without a push or a package built without a publish: it has
+// no reference (a candidate's, ADR 0487 clause 12, ADR 0498 clauses 5 and 6).
+func Unpublished(b delivery.BuilderBuild) bool { return len(UnpublishedModules(b)) > 0 }
+
+// UnpublishedModules are the build modules that publish what a done build holds unpublished: the image build module for
+// an image, the Node build module for a package; sorted, none when it holds nothing unpublished.
+func UnpublishedModules(b delivery.BuilderBuild) []string {
+	if b.State != delivery.BuildDone {
+		return nil
+	}
+	var image, pkg bool
+	for _, a := range b.Artifacts {
+		image = image || (a.Kind == catalogue.ArtifactImage && a.Reference == "")
+		pkg = pkg || (a.Kind == catalogue.ArtifactPackage && a.Reference == "")
+	}
+	var out []string
+	if image {
+		out = append(out, ImageBuildModule)
+	}
+	if pkg {
+		out = append(out, buildrun.NodeBuildModule)
+	}
+	sort.Strings(out)
+	return out
+}
+
+// publishable are the build modules of UnpublishedModules that can publish now: the image build module only while a node
+// runs it (imageBuilder).
+func publishable(b delivery.BuilderBuild, imageBuilder func() bool) []string {
+	var out []string
+	for _, bm := range UnpublishedModules(b) {
+		if bm != ImageBuildModule || (imageBuilder != nil && imageBuilder()) {
+			out = append(out, bm)
+		}
+	}
+	return out
+}
+
+// Unreferenced is whether a done build holds a bundle, an archive or an upstream copy that names no reference: a key done
+// before R4e, whose artifacts stayed on their build nodes (ADR 0498 clause 8). An artifact of no kind (a key written before
+// kinds) is one too. Claim takes such a key again, once: its new revision names them.
+func Unreferenced(b delivery.BuilderBuild) bool {
 	if b.State != delivery.BuildDone {
 		return false
 	}
 	for _, a := range b.Artifacts {
-		if a.Kind == "image" && a.Reference == "" {
+		if a.Reference == "" && (a.Kind == "" || stored(a.Kind)) {
 			return true
 		}
 	}
@@ -87,13 +142,21 @@ func Unpublished(b delivery.BuilderBuild) bool {
 
 // Claim takes the build of module at fingerprint, or answers nil when it is not this builder's to build now:
 //   - no key: it is created building, by this builder; a create that finds the key made meanwhile gets nothing;
-//   - a done key is not taken again (the same source is never built twice), except one built on one node only (OneNodePrefix)
-//     when a second node qualifies now (ClaimOptions.MoreNodes): that is taken as it stands, with the done value, and its
-//     builder writes the new revision when the second build ends (ADR 0478 clause 4);
+//   - a done key is not taken again (the same source is never built twice), except one whose bundle, archive or upstream
+//     copy names no reference (Unreferenced, a key done before R4e: ADR 0498 clause 8), which is claimed building as a new
+//     revision and built whole, and one whose image or package was built unpublished as a candidate's once the trunk
+//     names it (ClaimOptions.Trunk): that is taken as it stands, with the done value, and its builder writes the new
+//     revision when the publishing build ends (ADR 0498 clause 6). From R4e one node builds each fingerprint (ADR 0478
+//     clause 4), so a key built on one node is never built again for a second;
+//   - a done key of the trunk's fingerprint whose bundle or archive blob the artifact store no longer holds
+//     (ClaimOptions.Stored, issue 1937) is claimed building as a new revision and built whole, its step saying which;
 //   - a failed key is taken again as a new revision of the same key (ADR 0429 clause 18), except one failed for a kind no
-//     builder builds yet (RefusedPrefix, ADR 0478 clause 2) or for digests that differ (buildrun.DigestsDifferPrefix, clause 4),
+//     builder builds, for an upstream pinned by no digest or a package version taken (delivery.FailedUntilChanged: ADR 0478
+//     clause 2, ADR 0498 clauses 4 and 5) or for digests that differ (buildrun.DigestsDifferPrefix, clause 4),
 //     which wait for another fingerprint, and one failed for want of an image builder (NoImageBuilderPrefix), which waits for
 //     another fingerprint or a node that runs the image build module (ClaimOptions.ImageBuilder);
+//   - a key queued waiting for a package version (Waits) is claimed building as a new revision once that version is
+//     published (ClaimOptions.Published, ADR 0500 clause 6), and not before;
 //   - a key left queued or building by this builder is taken as it stands (ADR 0478 clause 5: a stopped builder takes its
 //     own again when it starts), and so is one left by another builder when ClaimOptions.TakeOver (clause 6).
 func (c Claimer) Claim(ctx context.Context, module, fingerprint, manifest string, opt ClaimOptions) (*Claim, error) {
@@ -115,19 +178,46 @@ func (c Claimer) Claim(ctx context.Context, module, fingerprint, manifest string
 	}
 	switch {
 	case cur.State == delivery.BuildDone:
-		if modules := OneNodeModules(cur); len(modules) > 0 && opt.MoreNodes != nil && opt.MoreNodes(modules) {
-			return &Claim{Key: key, Rev: rev, Build: cur}, nil
+		if Unreferenced(cur) {
+			return c.write(ctx, key, building, func(data []byte) (uint64, error) { return c.Store.Update(ctx, key, data, rev) })
 		}
-		if opt.Trunk && Unpublished(cur) && opt.ImageBuilder != nil && opt.ImageBuilder() {
+		if opt.Trunk && opt.Stored != nil {
+			if refs := StoredReferences(cur); len(refs) > 0 {
+				gone, err := opt.Stored(ctx, refs)
+				if err != nil {
+					err = fmt.Errorf("%s: whether the artifact store still holds %s cannot be asked, so the key is "+
+						"left done (the controller's take-in refuses it if one is gone): %w", key, strings.Join(refs, ", "), err)
+					if len(publishable(cur, opt.ImageBuilder)) > 0 {
+						return &Claim{Key: key, Rev: rev, Build: cur, Unasked: err}, nil
+					}
+					return nil, err
+				}
+				if len(gone) > 0 {
+					again := building
+					again.Step = GoneStep(gone)
+					cl, err := c.write(ctx, key, again, func(data []byte) (uint64, error) { return c.Store.Update(ctx, key, data, rev) })
+					if cl != nil {
+						cl.Gone = gone
+					}
+					return cl, err
+				}
+			}
+		}
+		if opt.Trunk && len(publishable(cur, opt.ImageBuilder)) > 0 {
 			return &Claim{Key: key, Rev: rev, Build: cur}, nil
 		}
 		return nil, nil
-	case cur.State == delivery.BuildFailed && (strings.HasPrefix(cur.Error, RefusedPrefix) || strings.HasPrefix(cur.Error, buildrun.DigestsDifferPrefix)):
+	case cur.State == delivery.BuildFailed && (delivery.FailedUntilChanged(cur.Error) || strings.HasPrefix(cur.Error, buildrun.DigestsDifferPrefix)):
 		return nil, nil
 	case cur.State == delivery.BuildFailed && strings.HasPrefix(cur.Error, NoImageBuilderPrefix) && (opt.ImageBuilder == nil || !opt.ImageBuilder()):
 		return nil, nil
 	case cur.State == delivery.BuildFailed:
 		return c.write(ctx, key, building, func(data []byte) (uint64, error) { return c.Store.Update(ctx, key, data, rev) })
+	case cur.State == delivery.BuildQueued && cur.Waits != "":
+		if opt.Published == nil || !opt.Published(cur.Waits) {
+			return nil, nil // the package it waits for is not published yet
+		}
+		return c.write(ctx, key, building, func(data []byte) (uint64, error) { return c.Store.Update(ctx, key, data, rev) })
 	case cur.By == c.By || opt.TakeOver:
 		return &Claim{Key: key, Rev: rev, Build: cur}, nil
 	}

modules/mesh-delivery-builder/internal/build/claim_test.go

@@ -114,20 +114,19 @@ func TestClaimCreatesTheKeyBuildingAndASecondBuilderGetsNothing(t *testing.T) {
 	if second, err := b.Claim(context.Background(), "m", fp1, hex64('a'), ClaimOptions{}); err != nil || second != nil {
 		t.Errorf("second builder's claim = %v, %v, want none: the same source is never built twice", second, err)
 	}
-}
 
-func TestClaimLosingTheCreateRaceGetsNothing(t *testing.T) { // 1607/AC3
-	st := newMem()
+	// A claim losing the create race gets nothing (merged into this test for the test budget, design 51).
+	st = newMem()
 	st.before = func() { seed(t, st, delivery.BuilderBuild{State: delivery.BuildBuilding, By: "novox.b"}) }
-	got, err := Claimer{Store: st, By: "novox.a"}.Claim(context.Background(), "m", fp1, "", ClaimOptions{})
+	got, err = Claimer{Store: st, By: "novox.a"}.Claim(context.Background(), "m", fp1, "", ClaimOptions{})
 	if err != nil || got != nil {
 		t.Errorf("claim = %v, %v, want none: the create failed because the key exists", got, err)
 	}
 }
 
-func TestADoneKeyIsNeverTakenAgain(t *testing.T) { // 1607/AC3
+func TestADoneKeyIsNeverTakenAgain(t *testing.T) { // 1607/AC3; a key whose artifacts name references (ADR 0498 clause 8)
 	st := newMem()
-	seed(t, st, delivery.BuilderBuild{State: delivery.BuildDone, By: "novox.a", Manifest: hex64('a'), Artifacts: []delivery.BuiltArtifact{{Name: "x", Digest: digest}}})
+	seed(t, st, delivery.BuilderBuild{State: delivery.BuildDone, By: "novox.a", Manifest: hex64('a'), Artifacts: []delivery.BuiltArtifact{{Name: "x", Kind: "bundle", Digest: digest, Reference: "artifact-store://m/x/blobs/" + digest}}})
 	writes := st.writes
 	got, err := Claimer{Store: st, By: "novox.a"}.Claim(context.Background(), "m", fp1, hex64('a'), ClaimOptions{})
 	if err != nil || got != nil || st.writes != writes {
@@ -148,11 +147,19 @@ func TestAFailedKeyIsTakenAgainAsANewRevisionExceptARefusedKind(t *testing.T) {
 	}
 
 	st = newMem()
-	key = seed(t, st, delivery.BuilderBuild{State: delivery.BuildFailed, By: "novox.a", Error: RefusedPrefix + " image (artifact x): build-agent builds it"})
+	key = seed(t, st, delivery.BuilderBuild{State: delivery.BuildFailed, By: "novox.a", Error: delivery.RefusedKind + "package of language \"python\" (artifact x)"})
 	writes := st.writes
 	if got, err := (Claimer{Store: st, By: "novox.a"}).Claim(context.Background(), "m", fp1, "", ClaimOptions{}); err != nil || got != nil || st.writes != writes {
 		t.Errorf("a refused kind: claim = %v, %v, writes %d (was %d), want none and no write", got, err, st.writes, writes)
 	}
+	for _, e := range []string{delivery.NotPinned + "up: nats:2 names no digest", delivery.VersionTaken + "@novox/mesh-sdk@0.1.15"} { // B3, B5: ADR 0498 clauses 4, 5
+		st = newMem()
+		seed(t, st, delivery.BuilderBuild{State: delivery.BuildFailed, By: "novox.a", Error: e})
+		writes = st.writes
+		if got, err := (Claimer{Store: st, By: "novox.a"}).Claim(context.Background(), "m", fp1, "", ClaimOptions{}); err != nil || got != nil || st.writes != writes {
+			t.Errorf("%s: claim = %v, %v, writes %d (was %d), want none until the fingerprint changes", e, got, err, st.writes, writes)
+		}
+	}
 }
 
 func TestAKeyFailedForNoImageBuilderIsTakenAgainOnlyWhenANodeHasTheModule(t *testing.T) { // 1705b
@@ -189,12 +196,11 @@ func TestFinishMovesTheKeyByCompareAndSetAndWritesOnlyADifferentValue(t *testing
 	if st.writes != writes {
 		t.Errorf("the same value was written again (%d writes, was %d)", st.writes, writes)
 	}
-}
 
-func TestFinishAfterTheKeyChangedIsAConflictNotAnOverwrite(t *testing.T) { // 1607/AC3
-	st := newMem()
-	c := Claimer{Store: st, By: "novox.a"}
-	got, _ := c.Claim(context.Background(), "m", fp1, "", ClaimOptions{})
+	// Finish after the key changed is a conflict, not an overwrite (merged into this test for the test budget).
+	st = newMem()
+	c = Claimer{Store: st, By: "novox.a"}
+	got, _ = c.Claim(context.Background(), "m", fp1, "", ClaimOptions{})
 	st.put(got.Key, []byte(`{"v":1,"state":"failed","error":"someone else"}`))
 	err := c.Finish(context.Background(), got, delivery.BuilderBuild{State: delivery.BuildFailed, Error: "mine"})
 	if !errors.Is(err, ErrConflict) {

modules/mesh-delivery-builder/internal/build/fixtures_test.go

@@ -1,10 +1,14 @@
 package build
 
 import (
+	"context"
 	"encoding/json"
 	"os"
+	"strings"
 	"testing"
+	"time"
 
+	"git.novox.be/novox/mesh-sdk/go/buildstep"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
 
@@ -25,17 +29,31 @@ func captured(t *testing.T, name string) json.RawMessage {
 	return step.Result
 }
 
+// The captured image steps, run as a pulled ask runs them (runAsk), answer what the builder reads: the trunk's
+// build its digest and reference, a candidate's its digest and no reference (issue 1887 A4a).
 func TestCapturedImageStepsDecodeWithTheBuildersOwnTypes(t *testing.T) { // review r2, mesh-catalog 2; ADR 0487 clause 1
-	var f fetchResult
-	if err := json.Unmarshal(captured(t, "fetch.json"), &f); err != nil || f.Workspace == "" {
-		t.Errorf("fetch = %+v, %v, want a workspace (the field the builder reads)", f, err)
-	}
-	var trunk buildResult
-	if err := json.Unmarshal(captured(t, "build-trunk.json"), &trunk); err != nil || trunk.Digest == "" || trunk.Reference == "" {
-		t.Errorf("trunk build = %+v, %v, want a digest and a reference", trunk, err)
-	}
-	var cand buildResult
-	if err := json.Unmarshal(captured(t, "build-candidate.json"), &cand); err != nil || cand.Digest == "" || cand.Reference != "" {
-		t.Errorf("candidate build = %+v, %v, want a digest and no reference", cand, err)
+	for _, tc := range []struct {
+		build   string
+		publish bool
+		ref     bool
+	}{{"build-trunk.json", true, true}, {"build-candidate.json", false, false}} {
+		steps := askSteps{
+			Fetch: func(context.Context, map[string]any) (any, error) {
+				return json.RawMessage(captured(t, "fetch.json")), nil
+			},
+			Build: func(context.Context, map[string]any) (any, error) { return json.RawMessage(captured(t, tc.build)), nil },
+		}
+		ask := delivery.StepAsk{ID: buildstep.NewID(), Kind: delivery.AskDelivery, Language: delivery.AskImage, Asker: delivery.BuilderModule,
+			At: time.Now(), Build: &delivery.BuildJob{Module: "m", Path: "modules/m", Publish: tc.publish,
+				Fetch:     map[string]any{"repository": "novox/mesh-catalog", "commit": strings.Repeat("a", 40)},
+				Artifacts: []delivery.AskArtifact{{Artifact: "server"}}}}
+		out, err := runAsk(context.Background(), steps, ask)
+		if err != nil {
+			t.Fatalf("%s: %v", tc.build, err)
+		}
+		a := out.(delivery.BuildAnswer)
+		if len(a.Artifacts) != 1 || a.Artifacts[0].Digest == "" || (a.Artifacts[0].Reference != "") != tc.ref {
+			t.Errorf("%s answered %+v, want a digest and a reference only for the trunk", tc.build, a)
+		}
 	}
 }

modules/mesh-delivery-builder/internal/build/followups_test.go

@@ -8,43 +8,6 @@ import (
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
 
-// 1664: a done key built on one node is not built again, over and over, while the second node's build keeps failing.
-func TestASecondNodeBuildThatFailsIsNotRetriedUntilTheNodesChange(t *testing.T) { // issue 1664
-	r := newRig(t, goBundle)
-	r.pres.Put("ace", presenceValue(t, false), false) // only novox qualifies
-	first := r.consider(t, "modules/m")
-	r.bm.fails["ace/build_go_fetch"] = "ace is out of disk"
-	r.pres.Put("ace", presenceValue(t, true), false)
-	r.b.NodesChanged(context.Background()) // ace came online: one more try
-	r.b.Wait()
-	tries := len(r.bm.callsOf("build_go_fetch"))
-	if tries < 2 {
-		t.Fatalf("%d fetches: the second node was never tried", tries)
-	}
-	if v := valueOf(t, r.st, r.key); !delivery.SameBuilderBuild(v, first) {
-		t.Fatalf("the done key changed: %+v", v)
-	}
-	// Nothing about the nodes changed: a modules value, a Reconsider and a start of looking again build nothing.
-	for i := 0; i < 3; i++ {
-		r.b.Module(context.Background(), "m", moduleValue(t, "modules/m"))
-		r.b.Reconsider(context.Background())
-		r.b.Wait()
-	}
-	if n := len(r.bm.callsOf("build_go_fetch")); n != tries {
-		t.Errorf("%d fetches after looking again, was %d: the failed second build was retried in a loop", n, tries)
-	}
-	// A node changing (ace goes and comes back) is a reason to try again, and ace now builds.
-	delete(r.bm.fails, "ace/build_go_fetch")
-	r.pres.Put("ace", presenceValue(t, false), false)
-	r.b.NodesChanged(context.Background())
-	r.pres.Put("ace", presenceValue(t, true), false)
-	r.b.NodesChanged(context.Background())
-	r.b.Wait()
-	if v := valueOf(t, r.st, r.key); v.State != delivery.BuildDone || strings.HasPrefix(v.Step, OneNodePrefix) || !strings.Contains(v.Step, "ace and novox") {
-		t.Errorf("build = %+v, want it built on both nodes once ace could", v)
-	}
-}
-
 // 1660: at start the builder closes a key left building for a fingerprint the module no longer has.
 func TestAKeyLeftBuildingForAFingerprintTheModuleNoLongerHasIsClosedAtStart(t *testing.T) { // issue 1660
 	r := newRig(t, goBundle)

modules/mesh-delivery-builder/internal/build/gone_test.go

@@ -0,0 +1,204 @@
+package build
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"slices"
+	"strings"
+	"sync"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// A done key whose blob the artifact store no longer holds is built again (novox/hq issue 1937): on 2026-10-24 the
+// store's 03:30 collection deleted the bare blobs of node-tools', mesh-host's and the forge bridge's done keys, which the
+// controller had never taken in, and the builder kept them done.
+
+// fakeHeld answers the controller's verb held: the references in gone are gone.
+type fakeHeld struct {
+	mu    sync.Mutex
+	gone  map[string]bool
+	err   error
+	asked [][]string
+}
+
+func (f *fakeHeld) stored(_ context.Context, refs []string) ([]string, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.asked = append(f.asked, slices.Clone(refs))
+	if f.err != nil {
+		return nil, f.err
+	}
+	var out []string
+	for _, r := range refs {
+		if f.gone[r] {
+			out = append(out, r)
+		}
+	}
+	return out, nil
+}
+
+func (f *fakeHeld) asks() int {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return len(f.asked)
+}
+
+// logged keeps what the builder says.
+type logged struct {
+	mu    sync.Mutex
+	lines []string
+}
+
+func (l *logged) logf(format string, args ...any) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.lines = append(l.lines, fmt.Sprintf(format, args...))
+}
+
+func (l *logged) has(words ...string) bool {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	for _, line := range l.lines {
+		all := true
+		for _, w := range words {
+			all = all && strings.Contains(line, w)
+		}
+		if all {
+			return true
+		}
+	}
+	return false
+}
+
+const goneRef = "artifact-store://m/tool/blobs/" + digest
+
+func doneKeyNaming(ref string) delivery.BuilderBuild {
+	return delivery.BuilderBuild{State: delivery.BuildDone, By: "shanks.builder", Manifest: manifestD, Step: "built mesh-build-go on shanks",
+		Artifacts: []delivery.BuiltArtifact{{Name: "tool", Kind: "bundle", Digest: digest, Reference: ref}}}
+}
+
+// 1937/AC3 (unit, the claim): a done key of the trunk's fingerprint whose blob is gone is claimed building as a new
+// revision, its step naming the gone reference; a candidate's done key is not asked about.
+func TestADoneTrunkKeyWhoseBlobIsGoneIsClaimedAgain(t *testing.T) {
+	st := newMem()
+	c := Claimer{Store: st, By: "novox.builder"}
+	key, _ := delivery.BuilderBuildKey("m", fp1)
+	rev := putBuild(t, st, key, doneKeyNaming(goneRef))
+	held := &fakeHeld{gone: map[string]bool{goneRef: true}}
+
+	cl, err := c.Claim(t.Context(), "m", fp1, manifestD, ClaimOptions{Stored: held.stored})
+	if err != nil || cl != nil || held.asks() != 0 {
+		t.Fatalf("a candidate's done key: claim %+v, %v, %d asks; want nothing and no ask", cl, err, held.asks())
+	}
+	cl, err = c.Claim(t.Context(), "m", fp1, manifestD, ClaimOptions{Trunk: true, Stored: held.stored})
+	if err != nil || cl == nil {
+		t.Fatalf("claim = %+v, %v; want the key claimed again", cl, err)
+	}
+	if cl.Rev <= rev || cl.Build.State != delivery.BuildBuilding || !slices.Equal(cl.Gone, []string{goneRef}) {
+		t.Errorf("claim = %+v (revision was %d); want building as a new revision naming the gone reference", cl, rev)
+	}
+	v := valueOf(t, st, key)
+	if v.State != delivery.BuildBuilding || !strings.Contains(v.Step, "no longer holds") || !strings.Contains(v.Step, goneRef) {
+		t.Errorf("the key holds %+v; want building, its step naming the gone reference", v)
+	}
+}
+
+// 1937/AC5 (unit, the claim): a done trunk key whose blobs are all held stays done; a store that cannot be asked leaves
+// it done and says why; images and packages are not asked about.
+func TestADoneTrunkKeyStaysDoneWhileTheStoreHoldsItsBlobs(t *testing.T) {
+	st := newMem()
+	c := Claimer{Store: st, By: "novox.builder"}
+	key, _ := delivery.BuilderBuildKey("m", fp1)
+	b := doneKeyNaming(goneRef)
+	b.Artifacts = append(b.Artifacts, delivery.BuiltArtifact{Name: "img", Kind: "image", Digest: digest, Reference: "registry.example/m/img@" + digest})
+	rev := putBuild(t, st, key, b)
+	held := &fakeHeld{gone: map[string]bool{}}
+	if cl, err := c.Claim(t.Context(), "m", fp1, manifestD, ClaimOptions{Trunk: true, Stored: held.stored}); err != nil || cl != nil {
+		t.Fatalf("claim = %+v, %v; want nothing: the store holds the blob", cl, err)
+	}
+	if len(held.asked) != 1 || !slices.Equal(held.asked[0], []string{goneRef}) {
+		t.Errorf("asked %v; want the bundle's reference alone", held.asked)
+	}
+	held.err = errors.New("the controller did not answer")
+	cl, err := c.Claim(t.Context(), "m", fp1, manifestD, ClaimOptions{Trunk: true, Stored: held.stored})
+	if cl != nil || err == nil || !strings.Contains(err.Error(), "cannot be asked") || !strings.Contains(err.Error(), "left done") {
+		t.Errorf("claim = %+v, %v; want the key left done and said", cl, err)
+	}
+	if st.revs[key] != rev {
+		t.Errorf("the key moved to revision %d (was %d)", st.revs[key], rev)
+	}
+}
+
+// 1937/AC3 (unit, the builder): the builder's look at a module whose done key's blob is gone builds it again, says so
+// in a log line and in the done key's step, and asks the store once per process while it answers held.
+func TestTheBuilderBuildsAgainADoneKeyWhoseBlobIsGone(t *testing.T) {
+	r := newRig(t, goBundle)
+	log := &logged{}
+	r.b.Logf = log.logf
+	held := &fakeHeld{gone: map[string]bool{goneRef: true}}
+	r.b.Stored = held.stored
+	rev := putBuild(t, r.st, r.key, doneKeyNaming(goneRef))
+	v := r.consider(t, "modules/m")
+	if v.State != delivery.BuildDone || r.st.revs[r.key] <= rev || len(r.bm.callsOf("build_go_build")) == 0 {
+		t.Fatalf("build = %+v at revision %d (was %d); want built again", v, r.st.revs[r.key], rev)
+	}
+	if !strings.Contains(v.Step, "built again: the artifact store no longer held "+goneRef) {
+		t.Errorf("the done key's step %q does not say it was built again for the gone blob", v.Step)
+	}
+	if !log.has(r.key, "built again", goneRef) {
+		t.Errorf("no log line says the key was built again: %v", log.lines)
+	}
+	// The new revision's blob is held: asked once, then not again in this process.
+	held.mu.Lock()
+	held.gone = map[string]bool{}
+	held.mu.Unlock()
+	rev = r.st.revs[r.key]
+	asks := held.asks()
+	r.consider(t, "modules/m")
+	r.consider(t, "modules/m")
+	if r.st.revs[r.key] != rev {
+		t.Errorf("a key whose blob is held was built again")
+	}
+	if held.asks() != asks+1 {
+		t.Errorf("asked the store %d times for two looks at a held key; want once", held.asks()-asks)
+	}
+}
+
+// 1937/AC4 (unit, the builder): artifacts-gone for the module's fingerprint makes the builder ask again, even for a key
+// it found held before, and build it again; one for another fingerprint builds nothing.
+func TestArtifactsGoneMakesTheBuilderAskAndBuildAgain(t *testing.T) {
+	r := newRig(t, goBundle)
+	log := &logged{}
+	r.b.Logf = log.logf
+	held := &fakeHeld{gone: map[string]bool{}}
+	r.b.Stored = held.stored
+	putBuild(t, r.st, r.key, doneKeyNaming(goneRef))
+	if v := r.consider(t, "modules/m"); v.State != delivery.BuildDone || len(r.bm.callsOf("build_go_build")) != 0 {
+		t.Fatalf("a key whose blob is held was built: %+v", v)
+	}
+	rev := r.st.revs[r.key]
+
+	held.mu.Lock()
+	held.gone[goneRef] = true // collected after the builder's look; the controller's take-in found it
+	held.mu.Unlock()
+	r.b.ArtifactsGone(context.Background(), delivery.ArtifactsGone{Event: delivery.ArtifactsGoneEvent, Module: "m",
+		Fingerprint: "src2:" + strings.Repeat("9", 64), Gone: []string{goneRef}})
+	r.b.Wait()
+	if r.st.revs[r.key] != rev || !log.has("a fingerprint the module does not have now") {
+		t.Fatalf("an event for another fingerprint moved the key (revision %d, was %d): %v", r.st.revs[r.key], rev, log.lines)
+	}
+
+	r.b.ArtifactsGone(context.Background(), delivery.ArtifactsGone{Event: delivery.ArtifactsGoneEvent, Module: "m",
+		Key: r.key, Fingerprint: fp1, Gone: []string{goneRef}})
+	r.b.Wait()
+	v := valueOf(t, r.st, r.key)
+	if v.State != delivery.BuildDone || r.st.revs[r.key] <= rev || len(r.bm.callsOf("build_go_build")) == 0 {
+		t.Fatalf("build = %+v at revision %d (was %d); want built again on the event", v, r.st.revs[r.key], rev)
+	}
+	if !log.has("heard artifacts-gone") || !log.has(r.key, "built again", goneRef) {
+		t.Errorf("the builder did not say what it heard and did: %v", log.lines)
+	}
+}