Read a change's manifest as the indexer reads it, so a fallback to a predefined key is not unreadable for the catalogue's predefined.json the assigner never holds (ADR 0348 §7, issue 1751); pin mesh-sdk bfc3883a

Reviewed-on: #34

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

@@ -0,0 +1,161 @@
+package main
+
+import (
+	"context"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/buildstep"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
+
+	"mesh-delivery-assigner/internal/assign"
+)
+
+// AssignerModule is the asker the assigner's compose asks name.
+const AssignerModule = "mesh-delivery-assigner"
+
+// composeAsks are the compose asks the assigner put on the Go build seat's check stream (novox/hq ADR 0482 clause 4,
+// issues 1622 and 1623), by what each composes: one ask per key, put once and followed by a watch of its step key until
+// it ends, which wakes a pass. No timer: an ask that waits in the stream waits (its backlog is the view's and the
+// watchman's to show). A restart forgets them and asks again; the build module keeps a composer built for a commit, so a
+// second ask builds nothing.
+type composeAsks struct {
+	ctx   context.Context
+	asker buildrun.Asker
+	wake  func()
+	logf  func(string, ...any)
+	now   func() time.Time
+
+	mu   sync.Mutex
+	asks map[string]*composeAsk
+}
+
+type composeAsk struct {
+	id     string
+	cancel context.CancelFunc
+	ran    *assign.Ran
+}
+
+func newComposeAsks(ctx context.Context, asker buildrun.Asker, wake func(), logf func(string, ...any)) *composeAsks {
+	return &composeAsks{ctx: ctx, asker: asker, wake: wake, logf: logf, now: time.Now, asks: map[string]*composeAsk{}}
+}
+
+// get is the end of the ask that composes key, or nil and its id while it runs. The first get of a key puts the ask.
+// A job its layout refuses ends at once, failed with why: never silent.
+func (a *composeAsks) get(key string, job delivery.ComposeJob) (*assign.Ran, string) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	if k, ok := a.asks[key]; ok {
+		return k.ran, k.id
+	}
+	ask := delivery.StepAsk{ID: buildstep.NewID(), Kind: delivery.AskCheck, Language: delivery.AskGo, Asker: AssignerModule,
+		At: a.now(), Compose: &job}
+	ctx, cancel := context.WithCancel(a.ctx)
+	k := &composeAsk{id: ask.ID, cancel: cancel}
+	a.asks[key] = k
+	if err := a.asker.Put(ctx, ask); err != nil {
+		a.logf("the compose ask %s for %s could not be put: %v", ask.ID, key, err)
+		k.ran = &assign.Ran{State: delivery.StepFailed, Reason: "the compose ask could not be put on the Go build seat: " + err.Error()}
+		cancel()
+		return k.ran, k.id
+	}
+	go func() {
+		step, err := a.asker.Wait(ctx, ask)
+		if ctx.Err() != nil {
+			return
+		}
+		ran := assign.RanOf(step)
+		if err != nil {
+			ran = assign.Ran{State: delivery.StepFailed, Reason: "the compose ask's step could not be followed: " + err.Error()}
+		}
+		a.mu.Lock()
+		k.ran = &ran
+		a.mu.Unlock()
+		a.wake()
+	}()
+	return nil, k.id
+}
+
+// sweep forgets, and stops following, every ask whose key no pass asked for this time: a candidate gone or moved on.
+func (a *composeAsks) sweep(seen map[string]bool) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	for key, k := range a.asks {
+		if !seen[key] {
+			k.cancel()
+			delete(a.asks, key)
+		}
+	}
+}
+
+// composeAtHead is the composition of a group with a mesh-sdk member: the composer at its head and at each reader's
+// mesh-sdk, asked of the Go build seat, and the verdict once every ask ended; until then the verdict waits, naming the
+// asks. The keys it used are marked in seen.
+func (p *passer) composeAtHead(ctx context.Context, m assign.Mesh, ch assign.Change, seen map[string]bool, began time.Time) delivery.CompositionVerdict {
+	waiting := func(words string) delivery.CompositionVerdict {
+		return delivery.CompositionVerdict{Group: ch.Group, Heads: ch.Heads, State: delivery.CompositionWaits, Words: words}
+	}
+	head, err := assign.HeadJob(m, ch)
+	if err != nil {
+		return delivery.CompositionVerdict{Group: ch.Group, Heads: ch.Heads, State: delivery.CompositionFail, SDK: "mesh-sdk " + ch.SDKHead,
+			Words: "the compose ask at the group's mesh-sdk head cannot be made: " + err.Error()}
+	}
+	var pending []string
+	key := "head." + ch.Group + "." + ch.Heads + "." + ch.SDKHead
+	seen[key] = true
+	headRan, id := p.asks.get(key, head)
+	if headRan == nil {
+		pending = append(pending, "mesh-sdk "+ch.SDKHead+" (ask "+id+")")
+	}
+	var readers []assign.Reader
+	var notJudged []string
+	for _, module := range sortedNames(assign.ReaderModules) {
+		repository := assign.ReaderModules[module]
+		var commits []string
+		member := false
+		if h := ch.Members[repository]; h != "" {
+			commits, member = []string{h}, true
+		} else {
+			commits = p.w.runningCommits(ctx, kvGetter(p.kvs[delivery.BuildsBucket]), module)
+		}
+		if len(commits) == 0 {
+			notJudged = append(notJudged, "not judged whether "+module+" reads the group's manifests: no build of it is assigned with a "+
+				"commit on record, and the group holds no member of "+repository)
+			continue
+		}
+		for _, commit := range commits {
+			job, err := assign.ReaderJob(ch, module, repository, commit)
+			if err != nil {
+				readers = append(readers, assign.Reader{Module: module, Commit: commit, Member: member,
+					Ran: assign.Ran{State: delivery.StepFailed, Reason: err.Error()}})
+				continue
+			}
+			rkey := "reader." + ch.Group + "." + ch.Heads + "." + module + "." + commit
+			seen[rkey] = true
+			ran, rid := p.asks.get(rkey, job)
+			if ran == nil {
+				pending = append(pending, module+" at "+commit+" (ask "+rid+")")
+				continue
+			}
+			readers = append(readers, assign.Reader{Module: module, Commit: commit, Member: member, Ran: *ran})
+		}
+	}
+	if len(pending) > 0 {
+		return waiting("composing on the Go build seat with the mesh-sdk of " + strings.Join(pending, ", "))
+	}
+	v := assign.FromComposer(m, ch, *headRan, readers, time.Since(began))
+	v.Warnings = append(v.Warnings, notJudged...)
+	return v
+}
+
+func sortedNames(m map[string]string) []string {
+	out := make([]string, 0, len(m))
+	for k := range m {
+		out = append(out, k)
+	}
+	sort.Strings(out)
+	return out
+}

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

@@ -0,0 +1,180 @@
+//go:build integration
+
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/composer"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/provider"
+)
+
+// holder is a test holder of the Go build seat: it takes every ask from the seat's check worker, as mesh-build-go does,
+// and answers a compose ask by running mesh-sdk's composer over the request filled from the indexer's manifests (the
+// linked composer standing for the one the build module builds at the asked commit), writing its step on its node's key.
+type holder struct {
+	mu   sync.Mutex
+	asks []delivery.StepAsk
+}
+
+func (h *holder) taken() []delivery.StepAsk {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	return append([]delivery.StepAsk(nil), h.asks...)
+}
+
+func (b *bed) hold(t *testing.T) *holder {
+	t.Helper()
+	seat, _ := delivery.AskStream(delivery.AskGo)
+	worker, _ := delivery.AskWorker(delivery.AskGo, delivery.AskCheck)
+	subject, _ := delivery.AskSubject(delivery.AskGo, delivery.AskCheck)
+	cons, err := b.js.CreateOrUpdateConsumer(b.ctx, seat, jetstream.ConsumerConfig{Durable: worker, FilterSubject: subject, AckPolicy: jetstream.AckExplicitPolicy})
+	if err != nil {
+		t.Fatal(err)
+	}
+	steps := b.buckets[delivery.StepsBucket(goBuildModule)]
+	h := &holder{}
+	cc, err := cons.Consume(func(m jetstream.Msg) {
+		a, err := delivery.DecodeStepAsk(m.Data())
+		if err != nil || a.Compose == nil {
+			t.Errorf("the seat was put an ask that is not a compose: %v %s", err, m.Data())
+			m.Ack()
+			return
+		}
+		h.mu.Lock()
+		h.asks = append(h.asks, a)
+		h.mu.Unlock()
+		req, err := composer.Decode(a.Compose.Request)
+		if err == nil {
+			err = composer.Fill(&req, func(digest string) ([]byte, error) {
+				key, _ := delivery.ManifestsKey(digest)
+				e, err := b.buckets[delivery.ManifestsBucket].Get(b.ctx, key)
+				if err != nil {
+					return nil, err
+				}
+				man, err := delivery.DecodeManifest(e.Value())
+				return []byte(man.JSON), err
+			})
+		}
+		step := delivery.Step{ID: a.ID, Tool: "compose", Node: "ace", State: delivery.StepPassed, Started: time.Now().UTC(), Ended: time.Now().UTC()}
+		if err != nil {
+			step.State, step.Reason = delivery.StepFailed, err.Error()
+		} else if v, err := composer.Run(req); err != nil {
+			step.State, step.Reason = delivery.StepFailed, err.Error()
+		} else {
+			vr, _ := json.Marshal(v)
+			step.Result, _ = json.Marshal(delivery.ComposeAnswer{Built: true, Key: "composer-0123456789abcdef", Verdict: vr})
+		}
+		raw, err := delivery.EncodeStep(step)
+		if err != nil {
+			t.Errorf("the step cannot be written: %v", err)
+		}
+		key, _ := delivery.AskStepKey("ace", a.ID)
+		if _, err := steps.Put(b.ctx, key, raw); err != nil {
+			t.Errorf("the step %s: %v", key, err)
+		}
+		m.Ack()
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(cc.Stop)
+	return h
+}
+
+// 1622/AC1-AC3 and 1623 on the bus: started whole, the assigner composes a group holding a mesh-sdk pull request by
+// asking the Go build seat for the composer at the member's head, and for the composer at the mesh-sdk the running
+// controller pins; it waits naming the asks while they run, writes the verdict from their answers naming the mesh-sdk the
+// head's composer was built with, and asks nothing more on a later pass of the same heads.
+func TestAGroupWithAnSDKMemberIsComposedByTheComposerAtItsHead(t *testing.T) {
+	b := startBed(t, "")
+	trunk := b.manifest(t, "web", `{"module":"web","version":"1"}`)
+	changed := b.manifest(t, "web", `{"module":"web","version":"2"}`)
+	mod, err := delivery.EncodeModule(delivery.Module{FP2: delivery.SourcePrefix2 + strings.Repeat("a", 64), Manifest: trunk, Repository: "novox/web", Commit: strings.Repeat("1", 40), Path: delivery.RootPath})
+	if err != nil {
+		t.Fatal(err)
+	}
+	b.putJSON(t, delivery.ModulesBucket, "web", mod)
+	b.putJSON(t, provider.AssignmentsBucket, "g14.web", []byte(`{"node":"g14","module":"web","build":"build-1"}`))
+	running := strings.Repeat("3", 40)
+	b.putJSON(t, provider.AssignmentsBucket, "novox.mesh-controller", []byte(`{"node":"novox","module":"mesh-controller","build":"c-1"}`))
+	b.putJSON(t, delivery.BuildsBucket, delivery.BuildKey("mesh-controller", "c-1"), []byte(`{"id":"c-1","repository":"novox/mesh-controller","commit":"`+running+`"}`))
+	sdkHead := strings.Repeat("4", 40)
+	heads := []delivery.Head{{Repository: "novox/mesh-sdk", Number: 80, Head: sdkHead}, {Repository: "novox/web", Number: 7, Head: strings.Repeat("2", 40)}}
+	hash, _ := delivery.HeadsHash(heads)
+	pulls := []delivery.CandidatePull{{Head: heads[0]}, {Head: heads[1],
+		Modules: []string{"web"}, Fps: map[string]delivery.CandidateModule{"web": {FP2: delivery.SourcePrefix2 + strings.Repeat("b", 64), Manifest: changed}}}}
+	cand, err := delivery.EncodeCandidate(delivery.Candidate{Group: "feat/x", HeadsHash: hash, Pulls: pulls, FPSet: delivery.FingerprintSet(pulls)})
+	if err != nil {
+		t.Fatal(err)
+	}
+	ckey, _ := delivery.CandidatesKey("feat/x")
+	b.putJSON(t, delivery.CandidatesBucket, ckey, cand)
+	b.start(t)
+	key, _ := delivery.CompositionKey("feat/x", hash)
+	// No holder takes the asks yet: the composition waits, naming them.
+	waits := b.verdict(t, key, func(v delivery.CompositionVerdict) bool { return v.State == delivery.CompositionWaits })
+	if !strings.Contains(waits.Words, "mesh-sdk "+sdkHead) || !strings.Contains(waits.Words, "mesh-controller at "+running) {
+		t.Fatalf("the waiting composition says %q, want the head's and the running controller's asks", waits.Words)
+	}
+	h := b.hold(t)
+	v := b.verdict(t, key, func(v delivery.CompositionVerdict) bool { return v.State != delivery.CompositionWaits })
+	if v.State != delivery.CompositionPass || len(v.Machines) != 1 || v.Machines[0] != "g14" || v.SDK == "" {
+		t.Fatalf("composition = %+v, want a pass on g14", v)
+	}
+	asks := h.taken()
+	if len(asks) != 2 {
+		t.Fatalf("the seat was asked %d composes, want two (the head, the running controller)", len(asks))
+	}
+	byRepo := map[string]delivery.StepAsk{}
+	for _, a := range asks {
+		byRepo[a.Compose.Fetch["repository"].(string)] = a
+		if a.Asker != AssignerModule || a.Kind != delivery.AskCheck || a.Language != delivery.AskGo {
+			t.Errorf("ask = %+v", a)
+		}
+	}
+	if a := byRepo["novox/mesh-sdk"]; a.Compose == nil || a.Compose.Fetch["commit"] != sdkHead || a.Compose.Dir != "go" {
+		t.Errorf("the head's ask = %+v", a.Compose)
+	}
+	if a := byRepo["novox/mesh-controller"]; a.Compose == nil || a.Compose.Fetch["commit"] != running || a.Compose.Dir != delivery.RootPath {
+		t.Errorf("the running controller's ask = %+v", a.Compose)
+	}
+	// A later pass of the same heads (woken by any change) asks nothing more.
+	on, _ := delivery.EncodePresence(delivery.Presence{Online: true})
+	b.putJSON(t, delivery.PresenceBucket, "ace", on)
+	time.Sleep(500 * time.Millisecond)
+	if n := len(h.taken()); n != 2 {
+		t.Errorf("a later pass of the same heads asked again: %d asks", n)
+	}
+}
+
+// verdict waits for the composition under key to satisfy ok, and answers it.
+func (b *bed) verdict(t *testing.T, key string, ok func(delivery.CompositionVerdict) bool) delivery.CompositionVerdict {
+	t.Helper()
+	var last delivery.CompositionVerdict
+	for deadline := time.Now().Add(10 * time.Second); time.Now().Before(deadline); time.Sleep(50 * time.Millisecond) {
+		e, err := b.buckets[delivery.AssignerCompositionsBucket].Get(b.ctx, key)
+		if errors.Is(err, jetstream.ErrKeyNotFound) {
+			continue
+		}
+		if err != nil {
+			t.Fatal(err)
+		}
+		if last, err = delivery.DecodeCompositionVerdict(e.Value()); err != nil {
+			t.Fatal(err)
+		}
+		if ok(last) {
+			return last
+		}
+	}
+	t.Fatalf("no composition under %s as wanted after 10 s; last %+v", key, last)
+	return last
+}

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

@@ -73,6 +73,12 @@ func startBed(t *testing.T, leaveOut string) *bed {
 	if _, err := js.CreateStream(ctx, jetstream.StreamConfig{Name: "EVENTS", Subjects: []string{"mesh.mod.*.event.>"}}); err != nil {
 		t.Fatal(err)
 	}
+	// The Go build seat's work queue, as the broker derives it from the seat's accepted kinds (delivery.AskStream).
+	seat, _ := delivery.AskStream(delivery.AskGo)
+	if _, err := js.CreateStream(ctx, jetstream.StreamConfig{Name: seat, Subjects: []string{"mesh.seat.node-build-go.accept.>"},
+		Retention: jetstream.WorkQueuePolicy}); err != nil {
+		t.Fatal(err)
+	}
 	return b
 }
 
@@ -181,8 +187,10 @@ func TestAChangeIsComposedOnTheBus(t *testing.T) {
 	b.putJSON(t, provider.AssignmentsBucket, "ace.other", []byte(`{"node":"ace","module":"other","build":"build-2"}`))
 	heads := []delivery.Head{{Repository: "novox/web", Number: 7, Head: strings.Repeat("2", 40)}}
 	hash, _ := delivery.HeadsHash(heads)
-	cand, err := delivery.EncodeCandidate(delivery.Candidate{Group: "feat/x", HeadsHash: hash, Pulls: []delivery.CandidatePull{{Head: heads[0],
-		Modules: []string{"web"}, Fps: map[string]delivery.CandidateModule{"web": {FP2: delivery.SourcePrefix2 + strings.Repeat("b", 64), Manifest: changed}}}}})
+	// 1927/AC1: the candidate carries the fingerprint set the SDK computes, as the indexer writes it.
+	pulls := []delivery.CandidatePull{{Head: heads[0],
+		Modules: []string{"web"}, Fps: map[string]delivery.CandidateModule{"web": {FP2: delivery.SourcePrefix2 + strings.Repeat("b", 64), Manifest: changed}}}}
+	cand, err := delivery.EncodeCandidate(delivery.Candidate{Group: "feat/x", HeadsHash: hash, Pulls: pulls, FPSet: delivery.FingerprintSet(pulls)})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -211,6 +219,13 @@ func TestAChangeIsComposedOnTheBus(t *testing.T) {
 	if took := time.Since(began); took > 5*time.Second {
 		t.Errorf("the composition took %s", took)
 	}
+	// 1622/AC3: a group without a mesh-sdk member builds no composer: no ask is put on the Go build seat.
+	seat, _ := delivery.AskStream(delivery.AskGo)
+	if st, err := b.js.Stream(b.ctx, seat); err != nil {
+		t.Fatal(err)
+	} else if info, err := st.Info(b.ctx); err != nil || info.State.Msgs != 0 {
+		t.Errorf("a group without a mesh-sdk member put %d asks on the Go build seat (%v)", info.State.Msgs, err)
+	}
 }
 
 // get waits for a key of one of the bed's buckets and answers its value.

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

@@ -22,6 +22,7 @@ import (
 
 	"git.novox.be/novox/mesh-sdk/go/announce"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
 	"git.novox.be/novox/mesh-sdk/go/process"
 	"git.novox.be/novox/mesh-sdk/go/provider"
 )
@@ -47,8 +48,13 @@ var readBuckets = []string{
 	delivery.ModulesBucket,
 	delivery.PresenceBucket,
 	delivery.HaveBucket,
+	delivery.StepsBucket(goBuildModule),
 }
 
+// goBuildModule is the Go build module, which takes the assigner's compose asks on its seat's check stream and writes
+// their steps in its steps state (novox/hq ADR 0482 clause 4).
+const goBuildModule = "mesh-build-go"
+
 // ownBuckets are the assigner's own states, as its manifest declares them.
 var ownBuckets = []string{delivery.AssignerAsksBucket, delivery.AssignerCompositionsBucket, delivery.AssignerDifferencesBucket, delivery.AssignerWantsBucket}
 
@@ -124,7 +130,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 		logger.Printf("what the assigner keeps could not be said on the bus, so its readers are not granted until it is: %v", err)
 	}
 	logger.Printf("started on the account %s, reading %d buckets", account.User, len(kvs))
-	return follow(ctx, kvs, logger)
+	return follow(ctx, js, kvs, logger)
 }
 
 // watched are the buckets whose every value a pass reads; the manifests are read by digest when a pass needs one, and
@@ -145,7 +151,7 @@ var watched = []string{
 
 // 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, kvs buckets, logger *log.Logger) error {
+func follow(ctx context.Context, js jetstream.JetStream, kvs buckets, logger *log.Logger) error {
 	w := newWorld()
 	dirty := make(chan struct{}, 1)
 	wake := func() {
@@ -210,6 +216,7 @@ func follow(ctx context.Context, kvs buckets, logger *log.Logger) error {
 		}
 	}
 	p := &passer{kvs: kvs, w: w, logf: logger.Printf}
+	p.asks = newComposeAsks(ctx, buildrun.Asker{Publisher: buildrun.JetStreamAsks{JS: js}, Waiter: buildrun.JetStreamAsks{JS: js}}, wake, logger.Printf)
 	wake()
 	for {
 		select {

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

@@ -19,6 +19,7 @@ type passer struct {
 	w    *world
 	logf func(string, ...any)
 	sdk  string
+	asks *composeAsks
 }
 
 func (p *passer) pass(ctx context.Context) {
@@ -162,6 +163,10 @@ func (p *passer) compositions(ctx context.Context) {
 	written := p.w.read(delivery.AssignerCompositionsBucket)
 	trunk := p.w.trunk()
 	var mesh *assign.Mesh
+	seen := map[string]bool{}
+	if p.asks != nil {
+		defer p.asks.sweep(seen)
+	}
 	for key, value := range p.w.read(delivery.CandidatesBucket) {
 		c, err := delivery.DecodeCandidate(value)
 		if err != nil {
@@ -183,7 +188,12 @@ func (p *passer) compositions(ctx context.Context) {
 				m := p.w.mesh(ctx, kvGetter(p.kvs[delivery.ManifestsBucket]))
 				mesh = &m
 			}
-			v = assign.Compose(*mesh, ch, p.sdk, time.Since(began))
+			if ch.SDKHead != "" && p.asks != nil {
+				// A group with a mesh-sdk member is composed by the composer built at its head (ADR 0482 clauses 3 to 5).
+				v = p.composeAtHead(ctx, *mesh, ch, seen, began)
+			} else {
+				v = assign.Compose(*mesh, ch, p.sdk, time.Since(began))
+			}
 		}
 		if before, err := delivery.DecodeCompositionVerdict(written[out]); err == nil {
 			before.Took, before.V = v.Took, 0

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/world.go

@@ -148,7 +148,9 @@ func (w *world) manifest(ctx context.Context, get getter, digest string) parsed
 	m, err := delivery.DecodeManifest(value)
 	if err != nil {
 		p = parsed{err: err.Error()}
-	} else if man, err := catalogue.ParseManifest([]byte(m.JSON)); err != nil {
+	} else if man, err := catalogue.ParseManifestForInputs([]byte(m.JSON)); err != nil {
+		// Read as the indexer reads it (issue 1751): a value falling back to a predefined key is judged by the merge gate
+		// in the catalogue, against the predefined.json at its root that this process never holds (ADR 0348 §7).
 		p = parsed{module: m.Module, err: err.Error()}
 	} else {
 		p = parsed{module: m.Module, manifest: man}
@@ -193,12 +195,13 @@ func (w *world) trunk() map[string]delivery.Module {
 
 // mesh is the mesh as the trunk holds it, for the composition check.
 func (w *world) mesh(ctx context.Context, manifests getter) assign.Mesh {
-	m := assign.Mesh{Manifests: map[string]catalogue.Manifest{}, Unreadable: map[string]string{}}
+	m := assign.Mesh{Manifests: map[string]catalogue.Manifest{}, Unreadable: map[string]string{}, Digests: map[string]string{}}
 	m.Assigned, _ = w.assigned()
 	for name, mod := range w.trunk() {
 		if mod.Manifest == "" {
 			continue
 		}
+		m.Digests[name] = mod.Manifest
 		p := w.manifest(ctx, manifests, mod.Manifest)
 		if p.err != "" {
 			m.Unreadable[name] = p.err
@@ -211,12 +214,14 @@ func (w *world) mesh(ctx context.Context, manifests getter) assign.Mesh {
 
 // change is a candidate's change for the composition check, or why the composition waits for it.
 func (w *world) change(ctx context.Context, manifests getter, c delivery.Candidate, trunk map[string]delivery.Module) (assign.Change, string) {
-	ch := assign.Change{Group: c.Group, Heads: c.HeadsHash, Manifests: map[string]catalogue.Manifest{}, Unreadable: map[string]string{}, Twice: map[string][]string{}}
+	ch := assign.Change{Group: c.Group, Heads: c.HeadsHash, Manifests: map[string]catalogue.Manifest{}, Unreadable: map[string]string{},
+		Twice: map[string][]string{}, Digests: map[string]string{}, Members: map[string]string{}}
 	definedIn := map[string]map[string]bool{}
 	for _, p := range c.Pulls {
 		if p.Repository == assign.SDKRepository {
 			ch.SDKHead = p.Head.Head
 		}
+		ch.Members[p.Repository] = p.Head.Head
 		for _, name := range p.Modules {
 			fp, ok := p.Fps[name]
 			if !ok || fp.Manifest == "" {
@@ -233,6 +238,7 @@ func (w *world) change(ctx context.Context, manifests getter, c delivery.Candida
 			if strings.HasPrefix(got.err, "the indexer holds no manifest") {
 				return ch, got.err
 			}
+			ch.Digests[name] = fp.Manifest
 			if got.err != "" {
 				ch.Unreadable[name] = got.err
 				continue
@@ -368,3 +374,31 @@ func (w *world) sentFP(ctx context.Context, get getter, module, build string) st
 	w.mu.Unlock()
 	return rec.SourceFingerprint
 }
+
+// runningCommits is, of every open assignment of module, the commit of the build it names, read from the controller's
+// build record (`mesh-controller_builds` `<module>.build.<id>`), distinct and sorted: the commits a reader of the
+// manifests runs at (novox/hq ADR 0482 clause 5, issue 1623). A build whose record names no full commit is left out.
+func (w *world) runningCommits(ctx context.Context, get getter, module string) []string {
+	_, all := w.assigned()
+	seen := map[string]bool{}
+	for _, a := range all {
+		if a.Module != module || a.Build == "" {
+			continue
+		}
+		value, err := get(ctx, delivery.BuildKey(module, a.Build))
+		if err != nil {
+			continue
+		}
+		var rec delivery.BuildRecord
+		if json.Unmarshal(value, &rec) != nil || len(rec.Commit) != 40 {
+			continue
+		}
+		seen[rec.Commit] = true
+	}
+	out := make([]string, 0, len(seen))
+	for c := range seen {
+		out = append(out, c)
+	}
+	sort.Strings(out)
+	return out
+}

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

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"os"
 	"slices"
 	"strings"
 	"testing"
@@ -88,3 +89,25 @@ func TestAChangeWaitsForItsManifests(t *testing.T) {
 		t.Errorf("an unreadable manifest: waits %q, change %+v", waits, ch)
 	}
 }
+
+// A manifest of the change whose config value falls back to a predefined key (novox/hq ADR 0348 §7) is read, not
+// unreadable for the catalogue's predefined.json the assigner never holds: the merge gate judges the fallback in the
+// catalogue, and the indexer reads it the same way (catalogue.ParseManifestForInputs, issue 1751). A group whose
+// mesh-catalog member touched pacman and xterm failed its composition on this (group check 18df81380db3). The manifest is
+// xterm's module.json from mesh-catalog at 835bf22b.
+func TestAManifestFallingBackToAPredefinedKeyIsReadable(t *testing.T) {
+	raw, err := os.ReadFile("testdata/catalogue-835bf22b-xterm.module.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(raw), `"predefined"`) {
+		t.Fatal("the fixture names no predefined key")
+	}
+	f := fakeManifests{}
+	xterm := f.add(t, "xterm", string(raw))
+	ch, waits := newWorld().change(context.Background(), f.get, delivery.Candidate{Group: "g", HeadsHash: "0123456789ab",
+		Pulls: []delivery.CandidatePull{pull("novox/mesh-catalog", 1, map[string]delivery.CandidateModule{"xterm": {FP2: fp('b'), Manifest: xterm}})}}, nil)
+	if waits != "" || ch.Unreadable["xterm"] != "" || ch.Manifests["xterm"].Module != "xterm" {
+		t.Errorf("xterm: waits %q, unreadable %q, want read", waits, ch.Unreadable["xterm"])
+	}
+}

modules/mesh-delivery-assigner/go.mod

@@ -3,7 +3,7 @@ module mesh-delivery-assigner
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023150321-a2c813a6b468
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024125710-bfc3883af980
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )

modules/mesh-delivery-assigner/go.sum

@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023150321-a2c813a6b468 h1:UcMee+IV2ii5E4dRZdQUaSaeh9IedTFYumuQbBiB0k0=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023150321-a2c813a6b468/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024125710-bfc3883af980 h1:ZEEeYibEPD1rngOAqbODzRY5rUStGC46OpyQwtNCYbs=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024125710-bfc3883af980/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=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=

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

@@ -32,6 +32,9 @@ type Mesh struct {
 	Manifests  map[string]catalogue.Manifest
 	Unreadable map[string]string
 	Assigned   map[string][]string
+	// Digests is every trunk module's manifest digest in the indexer's manifests bucket, readable or not: what a
+	// composer at another mesh-sdk reads (issue 1622).
+	Digests map[string]string
 }
 
 // Change is a group's change as the indexer's candidate holds it: the manifest of every module it moves or adds, those
@@ -45,6 +48,10 @@ type Change struct {
 	Twice        map[string][]string
 	SDKHead      string
 	Rebuilt      int
+	// Digests is the manifest digest of every module the change moves or adds, readable by the assigner or not, and
+	// Members the head of each member by repository: what a composer at the group's mesh-sdk reads (issues 1622, 1623).
+	Digests map[string]string
+	Members map[string]string
 }
 
 // Touched is the machines a change touches (ADR 0446 clause 3): those running a module the change moves, adds or
@@ -167,13 +174,19 @@ func Compose(m Mesh, c Change, sdk string, took time.Duration) delivery.Composit
 			failAt(node, fmt.Sprintf("%s composes on the trunk and not with the change: %v", node, now))
 		}
 	}
-	if c.Rebuilt > delivery.CompositionRebuildWarning {
-		v.Warnings = append(v.Warnings, fmt.Sprintf("the merge rebuilds %d modules, more than %d", c.Rebuilt, delivery.CompositionRebuildWarning))
-	}
 	if c.SDKHead != "" {
 		v.Warnings = append(v.Warnings, fmt.Sprintf("composed with the assigner's own mesh-sdk %s, not the group's mesh-sdk head %s, "+
 			"and a field the running controller cannot read is not judged (issues 1621, 1622, 1623)", sdk, c.SDKHead))
 	}
+	return finish(v, m, c, machines, fails)
+}
+
+// finish adds what every composition says beside its own judgement (more modules rebuilt than CompositionRebuildWarning,
+// what is not judged, the machines not composed, a change that touches none) and its state from fails.
+func finish(v delivery.CompositionVerdict, m Mesh, c Change, machines []string, fails []string) delivery.CompositionVerdict {
+	if c.Rebuilt > delivery.CompositionRebuildWarning {
+		v.Warnings = append(v.Warnings, fmt.Sprintf("the merge rebuilds %d modules, more than %d", c.Rebuilt, delivery.CompositionRebuildWarning))
+	}
 	v.Warnings = append(v.Warnings, NotJudged)
 	if could := CouldRun(m, c, machines); len(could) > 0 {
 		v.Warnings = append(v.Warnings, "not judged until the facts snapshot is on the bus (issue 1461, ADR 0537 clause 1): "+

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

@@ -0,0 +1,241 @@
+package assign
+
+import (
+	"encoding/json"
+	"fmt"
+	"slices"
+	"sort"
+	"strings"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/compose"
+	"git.novox.be/novox/mesh-sdk/go/composer"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// The cases of a group's composition at its mesh-sdk head: the trunk as it is, and the trunk with the change.
+const (
+	CaseTrunk  = "trunk"
+	CaseChange = "change"
+)
+
+// SDKDir is the directory of mesh-sdk's Go module in its repository, where the composer is built at a head; a reader's
+// composer is built at its repository's root, at the mesh-sdk its go.mod pins.
+const SDKDir = "go"
+
+// The modules whose mesh-sdk reads the manifests a plan sends (ADR 0482 clause 5): the controller composes and sends
+// them, the node-engine applies them. Each is judged at its repository.
+var ReaderModules = map[string]string{"mesh-controller": "novox/mesh-controller", "mesh-host": "novox/mesh-host"}
+
+// HeadJob is the compose job of a group with a mesh-sdk member (ADR 0482 clauses 3 and 4, issue 1622): the composer
+// built at the member's head composes the machines the change touches, as the trunk holds them and as the change leaves
+// them, every manifest named by its digest in the indexer's bucket, the seats held from the claims (the assigner's input).
+func HeadJob(m Mesh, c Change) (delivery.ComposeJob, error) {
+	trunk, change := map[string]composer.Manifest{}, map[string]composer.Manifest{}
+	for name, digest := range m.Digests {
+		trunk[name] = composer.Manifest{Digest: digest}
+		change[name] = composer.Manifest{Digest: digest}
+	}
+	for name, digest := range c.Digests {
+		change[name] = composer.Manifest{Digest: digest}
+	}
+	for _, name := range c.Removed {
+		delete(change, name)
+	}
+	req := composer.Request{V: composer.Version, Input: plainInput(m.Assigned), Depth: composer.DepthResolve,
+		HoldingsFromClaims: true, Machines: Touched(m, c),
+		Cases: []composer.Case{{Name: CaseTrunk, Manifests: trunk}, {Name: CaseChange, Manifests: change}}}
+	return job(SDKRepository, c.SDKHead, SDKDir, req, "the mesh-sdk head of "+c.Group)
+}
+
+// ReaderJob is the compose job that reads the manifests a group changes with the mesh-sdk a reader module pins at
+// commit (ADR 0482 clause 5, issue 1623): no machine is composed, every changed manifest is only read.
+func ReaderJob(c Change, module, repository, commit string) (delivery.ComposeJob, error) {
+	changed := map[string]composer.Manifest{}
+	for name, digest := range c.Digests {
+		changed[name] = composer.Manifest{Digest: digest}
+	}
+	req := composer.Request{V: composer.Version, Cases: []composer.Case{{Name: CaseChange, Manifests: changed}}}
+	return job(repository, commit, delivery.RootPath, req, module+" at "+commit)
+}
+
+func job(repository, commit, dir string, req composer.Request, reader string) (delivery.ComposeJob, error) {
+	raw, err := json.Marshal(req)
+	if err != nil {
+		return delivery.ComposeJob{}, err
+	}
+	return delivery.ComposeJob{Fetch: map[string]any{"repository": repository, "commit": commit}, Dir: dir,
+		Package: composer.Package, Request: raw, Reader: reader}, nil
+}
+
+// plainInput is the composition's input without its catalogue: the nodes by name with what is assigned to them (the
+// composer derives the seats held from the claims, as input does).
+func plainInput(assigned map[string][]string) compose.Input {
+	var in compose.Input
+	nodes := make([]string, 0, len(assigned))
+	for n := range assigned {
+		nodes = append(nodes, n)
+	}
+	sort.Strings(nodes)
+	for _, n := range nodes {
+		in.Nodes = append(in.Nodes, compose.Node{Name: n, Assigned: slices.Clone(assigned[n])})
+	}
+	return in
+}
+
+// Ran is one compose ask's end: its step's state and reason, and the composer's verdict when the step passed.
+type Ran struct {
+	State   string
+	Reason  string
+	Verdict *composer.Verdict
+}
+
+// RanOf reads a compose ask's end from its step value; a step that passed with an answer that cannot be read is a
+// failure, named.
+func RanOf(step delivery.Step) Ran {
+	r := Ran{State: step.State, Reason: step.Reason}
+	if step.State != delivery.StepPassed {
+		return r
+	}
+	var a delivery.ComposeAnswer
+	var v composer.Verdict
+	if err := json.Unmarshal(step.Result, &a); err != nil {
+		return Ran{State: delivery.StepFailed, Reason: "the compose step's answer cannot be read: " + err.Error()}
+	}
+	if err := json.Unmarshal(a.Verdict, &v); err != nil || v.V != composer.Version {
+		return Ran{State: delivery.StepFailed, Reason: fmt.Sprintf("the composer's verdict cannot be read (version %d): %v", v.V, err)}
+	}
+	r.Verdict = &v
+	return r
+}
+
+func caseOf(v *composer.Verdict, name string) (composer.CaseVerdict, bool) {
+	if v == nil {
+		return composer.CaseVerdict{}, false
+	}
+	for _, c := range v.Cases {
+		if c.Name == name {
+			return c, true
+		}
+	}
+	return composer.CaseVerdict{}, false
+}
+
+// Reader is one module whose mesh-sdk reads the group's manifests, at the commit judged: the group's member head when
+// the group holds one in its repository, else a build its node runs.
+type Reader struct {
+	Module, Commit string
+	Member         bool
+	Ran            Ran
+}
+
+// FromComposer is the composition check of a group with a mesh-sdk member, judged from the composer built at its head
+// (ADR 0482 clauses 3 to 5, issues 1622 and 1623): the same failures as Compose, read from the composer's two cases, the
+// verdict naming the mesh-sdk the composer was built with; a trunk manifest the head's mesh-sdk refuses fails too (the
+// group would deliver a reader that refuses it); and each reader that refuses a changed manifest the head reads fails
+// it, naming the module and its words, unless the reader's mesh-sdk has no composer to ask (before issue 1621), which is
+// said and judged nothing.
+func FromComposer(m Mesh, c Change, head Ran, readers []Reader, took time.Duration) delivery.CompositionVerdict {
+	v := delivery.CompositionVerdict{Group: c.Group, Heads: c.Heads, SDK: "mesh-sdk " + c.SDKHead, Took: took.Milliseconds()}
+	machines := Touched(m, c)
+	v.Machines = machines
+	var fails []string
+	if head.State != delivery.StepPassed {
+		v.Words = fmt.Sprintf("the composer at mesh-sdk %s did not run: %s %s", c.SDKHead, head.State, head.Reason)
+		v.State = delivery.CompositionFail
+		return v
+	}
+	if head.Verdict.SDK != "" {
+		v.SDK = head.Verdict.SDK
+	}
+	trunk, okT := caseOf(head.Verdict, CaseTrunk)
+	change, okC := caseOf(head.Verdict, CaseChange)
+	if !okT || !okC {
+		v.State, v.Words = delivery.CompositionFail, "the composer's verdict holds no trunk or no change case"
+		return v
+	}
+	failAt := func(machine, words string) {
+		if v.Machine == "" && machine != "" {
+			v.Machine = machine
+		}
+		fails = append(fails, words)
+	}
+	for _, name := range sortedKeys(c.Digests) {
+		if r := change.Manifests[name]; !r.Accepted {
+			failAt("", fmt.Sprintf("the manifest of %s cannot be read by mesh-sdk %s: %s", name, c.SDKHead, r.Refused))
+		}
+	}
+	for _, name := range sortedKeys(trunk.Manifests) {
+		if _, changed := c.Digests[name]; changed || slices.Contains(c.Removed, name) || trunk.Manifests[name].Accepted {
+			continue
+		}
+		if _, before := m.Unreadable[name]; before {
+			continue // already unreadable on the trunk: not the group's doing
+		}
+		failAt("", fmt.Sprintf("mesh-sdk %s refuses the trunk's manifest of %s, which the group does not change: %s", c.SDKHead, name, trunk.Manifests[name].Refused))
+	}
+	for _, name := range sortedKeys(c.Twice) {
+		failAt("", fmt.Sprintf("%s is defined twice, in %s", name, strings.Join(c.Twice[name], " and ")))
+	}
+	for _, node := range machines {
+		for _, name := range c.Removed {
+			if slices.Contains(m.Assigned[node], name) {
+				failAt(node, fmt.Sprintf("%s runs %s, which the change removes from its source", node, name))
+			}
+		}
+		before, now := trunk.Machines[node], change.Machines[node]
+		switch {
+		case now.Composes:
+		case !before.Composes:
+			v.Warnings = append(v.Warnings, fmt.Sprintf("%s does not compose on the trunk either, so the change is not blamed: %s", node, before.Reason))
+		default:
+			failAt(node, fmt.Sprintf("%s composes on the trunk and not with the change: %s", node, now.Reason))
+		}
+	}
+	readerFails, readerWarnings := judgeReaders(c, change, readers)
+	fails = append(fails, readerFails...)
+	v.Warnings = append(v.Warnings, readerWarnings...)
+	return finish(v, m, c, machines, fails)
+}
+
+// NoComposer says whether a compose step failed because the mesh-sdk it was built at has no composer command (a mesh-sdk
+// from before issue 1621): Go's words for a package its module does not hold.
+func NoComposer(reason string) bool {
+	for _, words := range []string{"cannot find package", "no required module provides package", "is not in std", "cannot find module providing package", "does not contain package"} {
+		if strings.Contains(reason, words) {
+			return true
+		}
+	}
+	return false
+}
+
+func judgeReaders(c Change, head composer.CaseVerdict, readers []Reader) (fails, warnings []string) {
+	for _, r := range readers {
+		at := r.Module + " at " + r.Commit
+		if r.Member {
+			at = r.Module + "'s member head " + r.Commit
+		}
+		if r.Ran.State != delivery.StepPassed {
+			if NoComposer(r.Ran.Reason) {
+				warnings = append(warnings, fmt.Sprintf("not judged whether %s reads the group's manifests: the mesh-sdk it pins has no "+
+					"composer command (before issue 1621)", at))
+				continue
+			}
+			fails = append(fails, fmt.Sprintf("the composer of the mesh-sdk %s pins did not run: %s %s", at, r.Ran.State, r.Ran.Reason))
+			continue
+		}
+		read, ok := caseOf(r.Ran.Verdict, CaseChange)
+		if !ok {
+			fails = append(fails, fmt.Sprintf("the composer of the mesh-sdk %s pins answered no change case", at))
+			continue
+		}
+		for _, name := range sortedKeys(c.Digests) {
+			if !head.Manifests[name].Accepted || read.Manifests[name].Accepted {
+				continue
+			}
+			fails = append(fails, fmt.Sprintf("the manifest of %s uses what %s (mesh-sdk %s) cannot read: %s; the group must move %s onto "+
+				"mesh-sdk %s", name, at, r.Ran.Verdict.SDK, read.Manifests[name].Refused, r.Module, c.SDKHead))
+		}
+	}
+	return fails, warnings
+}

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

@@ -0,0 +1,184 @@
+package assign
+
+import (
+	"encoding/json"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/composer"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+var testTime = time.Date(2026, 10, 24, 3, 0, 0, 0, time.UTC)
+
+const sdkHead = "1111111111111111111111111111111111111111"
+
+// raws are the manifests of meshOf as their repositories hold them, by digest, as the indexer keeps them; `web2` is web
+// with a field `shares` that the assigner's own mesh-sdk does not read (the shape of issue 1593).
+var raws = map[string]string{
+	"d-mail":  `{"module": "mail", "version": "1", "requires": ["postgres-database"]}`,
+	"d-store": `{"module": "store", "version": "1", "provides": [{"name": "postgres-database"}]}`,
+	"d-web":   `{"module": "web", "version": "1"}`,
+	"d-web2":  `{"module": "web", "version": "2", "shares": ["photos"]}`,
+}
+
+// asTheHeadReads is how mesh-sdk at the group's head reads each manifest: as the assigner's own reads it, but for the
+// field it adds, which it accepts. The head's composer is built and run by the Go build module (ADR 0482 clause 4); here
+// its verdict is made by mesh-sdk's composer.Run over the same request, with `web2` read as the head reads it.
+var asTheHeadReads = map[string]string{"d-web2": `{"module": "web", "version": "2"}`}
+
+func digestedMesh() Mesh {
+	m := meshOf()
+	m.Digests = map[string]string{"mail": "d-mail", "store": "d-store", "web": "d-web"}
+	return m
+}
+
+// webShares is a group of mesh-sdk and mesh-catalog whose catalogue member gives web the field only the SDK head reads:
+// the assigner's own reader refuses it (Unreadable), as the indexer's manifest is read in world.change.
+func webShares(members map[string]string) Change {
+	_, err := catalogue.ParseManifest([]byte(raws["d-web2"]))
+	return Change{Group: "g", Heads: "0123456789ab", SDKHead: sdkHead, Manifests: map[string]catalogue.Manifest{},
+		Unreadable: map[string]string{"web": err.Error()}, Digests: map[string]string{"web": "d-web2"}, Members: members}
+}
+
+// run is the composer's step for a job, as the build module answers it: the request filled from the indexer's digests
+// (with read standing in for how that mesh-sdk reads a digest), run, and its verdict put in a passed step.
+func run(t *testing.T, job delivery.ComposeJob, read map[string]string) Ran {
+	t.Helper()
+	req, err := composer.Decode(job.Request)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := composer.Fill(&req, func(d string) ([]byte, error) {
+		if r, ok := read[d]; ok {
+			return []byte(r), nil
+		}
+		return []byte(raws[d]), nil
+	}); err != nil {
+		t.Fatal(err)
+	}
+	v, err := composer.Run(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	v.SDK = "(devel) " + job.Fetch["commit"].(string)
+	vr, _ := json.Marshal(v)
+	ans, _ := json.Marshal(delivery.ComposeAnswer{Built: true, Key: "composer-0", Verdict: vr})
+	return RanOf(delivery.Step{State: delivery.StepPassed, Result: ans})
+}
+
+// 1622/AC1: a group holding a mesh-sdk pull request is composed by the composer built at the member's head: the job
+// fetches mesh-sdk at that head, builds mesh-sdk's composer command in its Go module, and hands it the trunk and the
+// change by digest, never the manifests' bytes, composing the machines the change touches.
+func TestAGroupWithAnSDKMemberAsksTheComposerAtItsHead(t *testing.T) {
+	c := webShares(nil)
+	job, err := HeadJob(digestedMesh(), c)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if job.Fetch["repository"] != SDKRepository || job.Fetch["commit"] != sdkHead || job.Dir != "go" || job.Package != composer.Package {
+		t.Fatalf("job = %+v", job)
+	}
+	ask := delivery.StepAsk{ID: "mh3k2x9qa1b2c5", Kind: delivery.AskCheck, Language: delivery.AskGo, Asker: "mesh-delivery-assigner",
+		At: testTime, Compose: &job}
+	if _, err := delivery.EncodeStepAsk(ask); err != nil {
+		t.Fatalf("the ask is refused by its layout: %v", err)
+	}
+	req, err := composer.Decode(job.Request)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(req.Cases) != 2 || req.Cases[0].Name != CaseTrunk || req.Cases[1].Name != CaseChange {
+		t.Fatalf("cases = %+v", req.Cases)
+	}
+	if req.Cases[0].Manifests["web"].Digest != "d-web" || req.Cases[1].Manifests["web"].Digest != "d-web2" || len(req.Cases[1].Manifests["web"].Raw) != 0 {
+		t.Errorf("the cases do not name web by its trunk and its change digest: %+v", req.Cases)
+	}
+	if !slices.Equal(req.Machines, []string{"g14"}) || req.Depth != composer.DepthResolve || !req.HoldingsFromClaims {
+		t.Errorf("request = machines %v, depth %q, holdings from claims %v", req.Machines, req.Depth, req.HoldingsFromClaims)
+	}
+}
+
+// 1622/AC2, AC3: a catalogue member using a field only the SDK head reads passes with the head's composer, and the
+// verdict names the mesh-sdk the composer was built with; with the assigner's own mesh-sdk it fails.
+func TestAFieldTheGroupAddsPassesWithTheHeadsComposer(t *testing.T) {
+	c := webShares(map[string]string{"novox/mesh-controller": "2222222222222222222222222222222222222222"})
+	job, _ := HeadJob(digestedMesh(), c)
+	head := run(t, job, asTheHeadReads)
+	v := FromComposer(digestedMesh(), c, head, nil, 0)
+	if v.State != delivery.CompositionPass || v.SDK != "(devel) "+sdkHead || !slices.Equal(v.Machines, []string{"g14"}) {
+		t.Fatalf("with the head's composer: %+v", v)
+	}
+	if _, err := delivery.EncodeCompositionVerdict(v); err != nil {
+		t.Errorf("the verdict cannot be written: %v", err)
+	}
+	own := Compose(digestedMesh(), c, "v0.1.14-own", 0)
+	if own.State != delivery.CompositionFail || !strings.Contains(own.Words, "shares") {
+		t.Fatalf("with the assigner's own mesh-sdk: %+v, want a fail naming the field", own)
+	}
+}
+
+// 1623/AC1, AC2: the group of mesh-sdk and mesh-catalog adding and using a field, without a controller member, fails
+// naming the field and mesh-controller, whose running build pins an older mesh-sdk; with a controller member pinned to
+// the SDK head (its composer reads what the head reads) it passes.
+func TestAFieldTheRunningControllerCannotReadFailsTheGroup(t *testing.T) {
+	c := webShares(nil)
+	job, _ := HeadJob(digestedMesh(), c)
+	head := run(t, job, asTheHeadReads)
+	running := "3333333333333333333333333333333333333333"
+	rjob, err := ReaderJob(c, "mesh-controller", "novox/mesh-controller", running)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if rjob.Fetch["commit"] != running || rjob.Dir != delivery.RootPath {
+		t.Fatalf("reader job = %+v", rjob)
+	}
+	old := run(t, rjob, nil) // the running controller's mesh-sdk reads web2 as the assigner's own does: refused
+	v := FromComposer(digestedMesh(), c, head, []Reader{{Module: "mesh-controller", Commit: running, Ran: old}}, 0)
+	if v.State != delivery.CompositionFail || !strings.Contains(v.Words, "shares") || !strings.Contains(v.Words, "move mesh-controller onto mesh-sdk "+sdkHead) {
+		t.Fatalf("without a controller member: %+v, want a fail naming the field and mesh-controller", v)
+	}
+	member := "2222222222222222222222222222222222222222"
+	pinned := run(t, rjob, asTheHeadReads)
+	v = FromComposer(digestedMesh(), c, head, []Reader{{Module: "mesh-controller", Commit: member, Member: true, Ran: pinned}}, 0)
+	if v.State != delivery.CompositionPass {
+		t.Fatalf("with a controller member pinned to the head: %+v, want a pass", v)
+	}
+}
+
+// 1623: a reader whose mesh-sdk has no composer command (before issue 1621) is said, not failed; a reader's composer that
+// failed for another cause fails the group, loud.
+func TestAReaderWithNoComposerIsSaidAndAnotherFailureFails(t *testing.T) {
+	c := webShares(nil)
+	job, _ := HeadJob(digestedMesh(), c)
+	head := run(t, job, asTheHeadReads)
+	none := Ran{State: delivery.StepFailed, Reason: "go build: no required module provides package git.novox.be/novox/mesh-sdk/go/cmd/mesh-compose"}
+	v := FromComposer(digestedMesh(), c, head, []Reader{{Module: "mesh-host", Commit: "abc", Ran: none}}, 0)
+	if v.State != delivery.CompositionPass || !hasWarning(v, "mesh-host at abc") || !hasWarning(v, "before issue 1621") {
+		t.Fatalf("a reader with no composer: %+v", v)
+	}
+	broke := Ran{State: delivery.StepFailed, Reason: "the fetch could not reach the forge"}
+	v = FromComposer(digestedMesh(), c, head, []Reader{{Module: "mesh-host", Commit: "abc", Ran: broke}}, 0)
+	if v.State != delivery.CompositionFail || !strings.Contains(v.Words, "could not reach the forge") {
+		t.Fatalf("a reader whose composer failed: %+v", v)
+	}
+}
+
+// 1622: the head's composer that did not run fails the composition naming why, never passes it; a trunk manifest the
+// head's mesh-sdk refuses fails it too, since the group would deliver a reader that refuses it.
+func TestTheHeadsComposerFailingOrRefusingTheTrunkFails(t *testing.T) {
+	c := webShares(nil)
+	v := FromComposer(digestedMesh(), c, Ran{State: delivery.StepRefused, Reason: "the guard refuses it"}, nil, 0)
+	if v.State != delivery.CompositionFail || !strings.Contains(v.Words, "the guard refuses it") || !strings.Contains(v.Words, sdkHead) {
+		t.Fatalf("a head composer that did not run: %+v", v)
+	}
+	job, _ := HeadJob(digestedMesh(), c)
+	strict := map[string]string{"d-web2": asTheHeadReads["d-web2"], "d-mail": `{"module": "mail", "version": "1", "gone": true}`}
+	v = FromComposer(digestedMesh(), c, run(t, job, strict), nil, 0)
+	if v.State != delivery.CompositionFail || !strings.Contains(v.Words, "refuses the trunk's manifest of mail") {
+		t.Fatalf("a head that refuses a trunk manifest: %+v", v)
+	}
+}

modules/mesh-delivery-assigner/manifest_test.go

@@ -32,7 +32,7 @@ func TestManifest(t *testing.T) {
 	}
 	reads := slices.Clone(m.Reads)
 	slices.Sort(reads)
-	want := []string{"mesh-controller.assignments", "mesh-controller.builds", "mesh-controller.grants",
+	want := []string{"mesh-build-go.steps", "mesh-controller.assignments", "mesh-controller.builds", "mesh-controller.grants",
 		"mesh-delivery-builder.builds", "mesh-delivery-indexer.candidates", "mesh-delivery-indexer.manifests",
 		"mesh-delivery-indexer.modules", "mesh-delivery-watchman.presence", "node-engine.have"}
 	if !reflect.DeepEqual(reads, want) {
@@ -51,6 +51,10 @@ func TestManifest(t *testing.T) {
 	if m.SecretsOwner != "mesh-delivery-assigner" {
 		t.Errorf("secrets-owner = %q", m.SecretsOwner)
 	}
+	// 1622: the assigner puts its compose asks on the Go build seat, as the checker puts its checks.
+	if !slices.Equal(m.Uses, []string{"node-build-go"}) {
+		t.Errorf("uses = %v, want exactly node-build-go", m.Uses)
+	}
 	if len(m.Claims) != 0 || len(m.Tools) != 0 || len(m.Invokes) != 0 {
 		t.Errorf("the assigner claims, serves or calls something: claims %v, tools %v, invokes %v", m.Claims, m.Tools, m.Invokes)
 	}

modules/mesh-delivery-assigner/module.json

@@ -3,6 +3,7 @@
   "version": "1",
   "slug": "assigner",
   "reads": [
+    "mesh-build-go.steps",
     "mesh-controller.assignments",
     "mesh-controller.builds",
     "mesh-controller.grants",
@@ -13,6 +14,9 @@
     "mesh-delivery-watchman.presence",
     "node-engine.have"
   ],
+  "uses": [
+    "node-build-go"
+  ],
   "state": [
     { "name": "asks", "history": 5 },
     { "name": "compositions", "history": 5 },

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

@@ -0,0 +1,185 @@
+//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/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 controller seat's verb held on the bus, as the serving controller 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.mesh-controller.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/integration_test.go

@@ -179,7 +179,11 @@ type bed struct {
 // startBed starts the bus, the buckets the controller makes from the builder's and the build modules' manifests, the
 // build modules' streams and the builder's durable consumers on them, two nodes' toolchains, the indexer's manifests, and
 // the fake build modules. It runs no builder.
-func startBed(t *testing.T) *bed {
+func startBed(t *testing.T) *bed { return startBedWith(t, false) }
+
+// startBedWith is startBed with the nodes' capacity 0 from the start when closed: a puller that reads its capacity before a
+// test could close the nodes may be in a pull already and takes the first ask put (issue 1928).
+func startBedWith(t *testing.T, closed bool) *bed {
 	dir, err := os.MkdirTemp(os.Getenv("TMPDIR"), "b")
 	if err != nil {
 		t.Fatal(err)
@@ -243,6 +247,7 @@ func startBed(t *testing.T) *bed {
 	b.builds = mk(delivery.BuilderBuildsBucket, delivery.BuilderBuildsHistory)
 	b.instances = mk(instancesBucket, 1)
 	b.fake = &fakeBuildModules{js: js, ctx: ctx, calls: map[string]int{}}
+	b.fake.closed.Store(closed)
 	b.fake.serve(t, "mesh-build-go", "n1", "n2")
 	b.fake.serve(t, "mesh-build-node", "n1", "n2")
 	b.fake.serve(t, "mesh-build-image", "n1") // the image build module runs on n1 only
@@ -781,8 +786,7 @@ func (b *bed) asksPut(t *testing.T, nc *nats.Conn) func() []delivery.StepAsk {
 // 1887/AC3: a builder that started again while its asks waited in the streams (no node had a free slot) puts no second
 // ask: it waits for the asks its building key names, and the key is done once a node took them.
 func TestARestartedBuilderPutsNoSecondAsk(t *testing.T) {
-	b := startBed(t)
-	b.fake.closed.Store(true)
+	b := startBedWith(t, true) // 1928/AC1: no node can take an ask from the start, so no pull in hand takes the first one
 	b.module(t, "netcheck", "catalogue-a67f0196-netcheck.module.json", "modules/netcheck")
 	sub, err := nats.Connect(b.srvURL, nats.UserInfo("ctl", "pw"))
 	if err != nil {
@@ -792,11 +796,13 @@ func TestARestartedBuilderPutsNoSecondAsk(t *testing.T) {
 	asked := b.asksPut(t, sub)
 	b.start(t, "n1", nil)
 	v := b.await(t, "netcheck", func(v delivery.BuilderBuild) bool { return v.State == delivery.BuildBuilding && len(v.Asks) == 2 })
-	for deadline := time.Now().Add(5 * time.Second); len(asked()) < 2 && time.Now().Before(deadline); time.Sleep(20 * time.Millisecond) {
+	for deadline := time.Now().Add(20 * time.Second); len(asked()) < 2; time.Sleep(20 * time.Millisecond) {
+		if time.Now().After(deadline) {
+			t.Fatalf("asks put = %+v within 20 s, want the two the key names", asked())
+		}
 	}
 	b.stop()
 	b.start(t, "n1", nil) // the same builder, started again, while both asks wait
-	time.Sleep(500 * time.Millisecond)
 	b.fake.open()
 	done := b.await(t, "netcheck", isState(delivery.BuildDone))
 	if got := asked(); len(got) != 2 {

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

@@ -26,6 +26,7 @@ import (
 	"github.com/nats-io/nats.go/jetstream"
 
 	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/process"
 
 	"mesh-delivery-builder/internal/build"
 )
@@ -153,6 +154,17 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	// 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 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.
+	account, err := process.ReadAccount(path)
+	if err != nil {
+		return err
+	}
+	calls, err := process.Connect(account, nats.Name(cred.Node+"."+cred.Module+".calls"), nats.RetryOnFailedConnect(true))
+	if err != nil {
+		return err
+	}
+	defer calls.Close()
 	b := &build.Builder{
 		Claimer:    build.Claimer{Store: kvStore{builds}, By: cred.Node + "." + cred.Module},
 		Asks:       buildrun.Asker{Publisher: asks, Waiter: asks, Bound: bound},
@@ -160,6 +172,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 		Toolchains: tools,
 		Manifests:  manifestReader{manifests},
 		Logf:       logger.Printf,
+		Stored:     storedVia(calls.Call),
 	}
 	// **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
@@ -183,6 +196,14 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	}
 	// 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 build module is assigned to count (issue 1940): the controller's
+	// assignments are settled first, so the toolchains settle through the gate already knowing them.
+	gate := newToolchainGate([]string{buildrun.GoBuildModule, buildrun.NodeBuildModule}, tools.Put, logger.Printf)
+	watch.put = gate.Toolchain
+	assignErrs, err := watchAssignments(ctx, js, gate, b.NodesChanged, logger)
+	if err != nil {
+		return err
+	}
 	if err := watch.start(); err != nil {
 		return err
 	}
@@ -203,6 +224,21 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 		}
 		defer cc.Stop()
 	}
+	// The controller says artifacts-gone when its take-in found a key's blob gone (issue 1937): the builder's durable
+	// consumer on EVENTS, made by the controller 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.
+	switch cons, err := js.Consumer(ctx, eventsStream, cred.Node+"_"+cred.Module); {
+	case err != nil:
+		logger.Printf("the consumer %s_%s on %s does not exist yet, so %s is not heard until the builder starts again: %v",
+			cred.Node, cred.Module, eventsStream, delivery.ArtifactsGoneEvent, err)
+	default:
+		cc, err := cons.Consume(func(m jetstream.Msg) { heardGone(ctx, b, m, logger.Printf) },
+			jetstream.ConsumeErrHandler(func(_ jetstream.ConsumeContext, err error) { logger.Printf("hearing the bus: %v", err) }))
+		if err != nil {
+			return err
+		}
+		defer cc.Stop()
+	}
 	each := func(e jetstream.KeyValueEntry) {
 		if opOf(e) {
 			b.Module(ctx, e.Key(), e.Value())
@@ -240,6 +276,8 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 		return nil
 	case err := <-errs:
 		return err
+	case err := <-assignErrs:
+		return err
 	case err := <-watch.errs:
 		return err
 	}

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

@@ -0,0 +1,174 @@
+package main
+
+// This file is the same in mesh-delivery-indexer, mesh-delivery-builder and mesh-delivery-checker (issue 1940): it moves
+// to mesh-sdk go/delivery/buildrun once mesh-sdk can be delivered again, since a change of mesh-sdk waits on the very
+// toolchain agreement this file repairs.
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"maps"
+	"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/provider"
+)
+
+// A build module writes <node>.<language> of its toolchains state on every node it runs on, and nothing deletes the key
+// when the module is unassigned from a node: the controller writes no module's state, and the module is gone. A report of
+// a node the build module no longer runs on is therefore not a builder (issue 1940: mesh-build-node unassigned from 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
+// buildrun.ToolchainSet): an entry is passed on only while the controller's assignments (mesh-controller_assignments,
+// key <node>.<module>) hold an open assignment of its build module on its node; it is passed on as deleted otherwise,
+// and passed on again when the module is assigned there again. Until the assignments are settled (or where they cannot
+// be read) every entry is passed on, as before. Builders that run and report different versions still disagree: that
+// refusal is the guard of novox/hq ADR 0465, and it stays.
+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)
+	known    bool                         // the assignments are settled
+	standing map[string]bool              // <node>.<module> with an open assignment
+	raw      map[string]map[string][]byte // module -> toolchains key -> value, as the bucket holds it
+	left     map[string]bool              // <module>/<key> said as left out, so it is said once
+}
+
+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, standing: map[string]bool{},
+		raw: map[string]map[string][]byte{}, left: map[string]bool{}}
+	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)
+}
+
+// Assignment takes one change of the controller's assignments in and answers whether what it passed on changed.
+func (g *toolchainGate) Assignment(key string, value []byte, deleted bool) bool {
+	node, module, ok := strings.Cut(key, ".")
+	if !ok || !g.modules[module] {
+		return false
+	}
+	open := !deleted && openAssignment(value)
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	if g.standing[key] == open {
+		return false
+	}
+	if open {
+		g.standing[key] = true
+	} else {
+		delete(g.standing, key)
+	}
+	if !g.known {
+		return false
+	}
+	changed := false
+	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
+}
+
+// Settled says the assignments are read: from now on only the reports of assigned nodes pass. It answers whether what it
+// passed on changed.
+func (g *toolchainGate) Settled() bool {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.known = true
+	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
+}
+
+// pass hands one key on as it stands: its value when its node is assigned (or the assignments are 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)
+	if err != nil || !g.known || g.standing[node+"."+module] {
+		delete(g.left, module+"/"+key)
+		return g.forward(module, key, value, false)
+	}
+	if !g.left[module+"/"+key] {
+		g.left[module+"/"+key] = true
+		g.logf("%s.%s is left out of the agreed toolchain: %s has no assignment on %s, so it is no builder (issue 1940)",
+			delivery.ToolchainsBucket(module), key, module, node)
+	}
+	return g.forward(module, key, nil, true)
+}
+
+// openAssignment is whether a value of the controller's assignments holds an assignment that stands: one that has not
+// ended and has no state (a pending one is not on the machine yet; mesh-controller internal/chain Assignment).
+func openAssignment(value []byte) bool {
+	var a struct {
+		Ended time.Time `json:"ended"`
+		State string    `json:"state"`
+	}
+	if json.Unmarshal(value, &a) != nil {
+		return false
+	}
+	return a.Ended.IsZero() && a.State == ""
+}
+
+// watchAssignments settles the controller's assignments into the gate, says them settled, and follows them; changed is
+// told whenever what the gate passes on changed. Where the bucket cannot be read (not there, or this module may not read
+// it) it says so and the gate passes every report on, as before; an error of the watch after that ends on the channel.
+func watchAssignments(ctx context.Context, js bucketOpener, gate *toolchainGate, changed func(context.Context), logger *log.Logger) (<-chan error, error) {
+	errs := make(chan error, 1)
+	kv, err := js.KeyValue(ctx, provider.AssignmentsBucket)
+	if err != nil {
+		// Not fatal: an indexer, builder or checker that stops for it stops every delivery (a grant comes with a delivery).
+		logger.Printf("the bucket %s cannot be read, so every node's toolchain report counts, an unassigned build node's too (issue 1940): %v", provider.AssignmentsBucket, err)
+		return errs, nil
+	}
+	each := func(e jetstream.KeyValueEntry) { gate.Assignment(e.Key(), e.Value(), !opOf(e)) }
+	w, err := settle(ctx, kv, each)
+	if err != nil {
+		return nil, fmt.Errorf("the bucket %s: %w", provider.AssignmentsBucket, err)
+	}
+	if gate.Settled() {
+		changed(ctx)
+	}
+	go func() {
+		errs <- follow(ctx, w, func(e jetstream.KeyValueEntry) {
+			if gate.Assignment(e.Key(), e.Value(), !opOf(e)) {
+				changed(ctx)
+			}
+		})
+	}()
+	return errs, nil
+}

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

@@ -0,0 +1,112 @@
+package main
+
+// The same in mesh-delivery-indexer, mesh-delivery-builder and mesh-delivery-checker, as standing.go is (issue 1940).
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
+)
+
+func gateReport(t *testing.T, node, version string) (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: time.Unix(0, 0).UTC()})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return key, value
+}
+
+func agreedOf(set *buildrun.ToolchainSet) (string, string) {
+	tc, none := delivery.AgreedToolchain(set.Entries("typescript"))
+	return tc.Version, none
+}
+
+// The live case of issue 1940: mesh-build-node was unassigned from ace, whose report stayed at v26.12.0 while the
+// three nodes it runs on report v26.12.1. Without the assignments every report counts (and they disagree); with them
+// ace's is left out and the three agree; assigned to ace again, its report counts again and the guard refuses again.
+func TestAnUnassignedBuildNodesReportIsNoBuilder(t *testing.T) {
+	set := &buildrun.ToolchainSet{}
+	var said []string
+	gate := newToolchainGate([]string{buildrun.GoBuildModule, buildrun.NodeBuildModule}, set.Put, func(f string, a ...any) { said = append(said, f) })
+	for node, version := range map[string]string{"ace": "v26.12.0", "g14": "v26.12.1", "novox": "v26.12.1", "shanks": "v26.12.1"} {
+		key, value := gateReport(t, node, version)
+		gate.Toolchain(buildrun.NodeBuildModule, key, value, false)
+	}
+	if _, none := agreedOf(set); !strings.HasPrefix(none, "builders disagree") {
+		t.Fatalf("before the assignments are read every report counts, so they disagree; got %q", none)
+	}
+	for _, node := range []string{"g14", "novox", "shanks"} {
+		gate.Assignment(node+"."+buildrun.NodeBuildModule, []byte(`{"node":"`+node+`","module":"mesh-build-node"}`), false)
+	}
+	gate.Assignment("ace.mesh-build-node", []byte(`{"node":"ace","module":"mesh-build-node","ended":"2026-10-23T08:00:00Z"}`), false)
+	gate.Assignment("ace.mesh-build-go", []byte(`{"node":"ace","module":"mesh-build-go"}`), false) // another module's: no matter
+	if !gate.Settled() {
+		t.Fatal("settling the assignments left ace's report out, so what was passed on changed")
+	}
+	if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+		t.Fatalf("the assigned nodes agree on v26.12.1; got %q, %q", v, none)
+	}
+	if len(said) != 1 {
+		t.Fatalf("ace's report is said left out once; said %v", said)
+	}
+	// ace reports again while unassigned (an old value seen again): still left out.
+	key, value := gateReport(t, "ace", "v26.12.0")
+	if gate.Toolchain(buildrun.NodeBuildModule, key, value, false) {
+		t.Fatal("an unassigned node's report changed what was passed on")
+	}
+	// Assigned to ace again: its report counts, and the builders really disagree: the guard stays.
+	if !gate.Assignment("ace.mesh-build-node", []byte(`{"node":"ace","module":"mesh-build-node"}`), false) {
+		t.Fatal("assigning ace again passed nothing on")
+	}
+	if _, none := agreedOf(set); !strings.HasPrefix(none, "builders disagree: v26.12.0 recipe f59571cf4be75adf on ace") {
+		t.Fatalf("builders that run different versions still disagree; got %q", none)
+	}
+	// The assignment's key deleted, or a pending one written: no assignment stands, and ace's report goes again.
+	if !gate.Assignment("ace.mesh-build-node", []byte(`{"node":"ace","module":"mesh-build-node","state":"pending"}`), false) {
+		t.Fatal("a pending assignment is no assignment on the machine")
+	}
+	if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+		t.Fatalf("got %q, %q", v, none)
+	}
+	gate.Assignment("ace.mesh-build-node", nil, true)
+	if v, _ := agreedOf(set); v != "v26.12.1" {
+		t.Fatalf("got %q", v)
+	}
+	// A report deleted from the bucket goes whether its node is assigned or not.
+	key, _ = gateReport(t, "g14", "v26.12.1")
+	if !gate.Toolchain(buildrun.NodeBuildModule, key, nil, true) {
+		t.Fatal("deleting g14's report passed nothing on")
+	}
+	if n := len(set.Entries("typescript")); n != 2 {
+		t.Fatalf("novox and shanks are left; got %d entries", n)
+	}
+}
+
+// A newly assigned build node that has not reported yet changes nothing; its report counts as it comes.
+func TestANewlyAssignedNodeCountsFromItsReport(t *testing.T) {
+	set := &buildrun.ToolchainSet{}
+	gate := newToolchainGate([]string{buildrun.NodeBuildModule}, set.Put, func(string, ...any) {})
+	gate.Settled()
+	if gate.Assignment("g14.mesh-build-node", []byte(`{}`), false) {
+		t.Fatal("an assignment with no report passed something on")
+	}
+	key, value := gateReport(t, "g14", "v26.12.1")
+	if !gate.Toolchain(buildrun.NodeBuildModule, key, value, false) {
+		t.Fatal("an assigned node's report was not passed on")
+	}
+	key, value = gateReport(t, "ace", "v26.12.0")
+	if gate.Toolchain(buildrun.NodeBuildModule, key, value, false) {
+		t.Fatal("a report of a node with no assignment key was passed on after the assignments settled")
+	}
+	if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+		t.Fatalf("got %q, %q", v, none)
+	}
+}

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

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"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 controller makes the builder's durable
+// consumer of artifacts-gone (mesh-controller internal/broker EventsStream).
+const eventsStream = "EVENTS"
+
+// 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 controller's verb held (mesh-sdk delivery.HeldVerb; novox/hq 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 the controller's take-in still refuses a gone blob.
+func storedVia(call toolCaller) func(ctx context.Context, references []string) ([]string, error) {
+	return func(_ context.Context, references []string) ([]string, error) {
+		raw, err := call(delivery.HeldVerb, map[string]any{"references": references})
+		if err != nil {
+			return nil, fmt.Errorf("asking %s: %w", delivery.HeldVerb, 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/toolchains.go

@@ -23,9 +23,11 @@ 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 +36,7 @@ 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.
@@ -62,14 +64,14 @@ func (w *toolchainWatch) ensure(module string) error {
 	case err != nil:
 		return fmt.Errorf("the bucket %s: %w", name, err)
 	}
-	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
 	}
 	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/go.mod

@@ -3,7 +3,7 @@ module mesh-delivery-builder
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023150321-a2c813a6b468
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024020722-34f210e5eba1
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )

modules/mesh-delivery-builder/go.sum

@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023150321-a2c813a6b468 h1:UcMee+IV2ii5E4dRZdQUaSaeh9IedTFYumuQbBiB0k0=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023150321-a2c813a6b468/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024020722-34f210e5eba1 h1:fzOkrz9CSp3mEjeV7NfZx8yoivI1sD1AOtIPtyyF8RI=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024020722-34f210e5eba1/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=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=

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

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"slices"
 	"sort"
 	"strings"
 
@@ -37,6 +38,11 @@ type Claim struct {
 	Key   string
 	Rev   uint64
 	Build delivery.BuilderBuild
+	// 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.
@@ -55,6 +61,30 @@ type ClaimOptions struct {
 	// 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 controller's verb held,
+	// mesh-sdk delivery.HeldVerb; novox/hq 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)
+}
+
+// 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
@@ -118,6 +148,8 @@ func Unreferenced(b delivery.BuilderBuild) bool {
 //     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, 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),
@@ -149,6 +181,28 @@ func (c Claimer) Claim(ctx context.Context, module, fingerprint, manifest string
 		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 && 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
 		}

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)
+	}
+}

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

@@ -50,6 +50,9 @@ type Builder struct {
 	// Answered is told the build module whose step answered a reference (issue 1886): what the builder says it writes
 	// rests on it. Nil tells nobody.
 	Answered func(buildModule string)
+	// Stored answers which references the artifact store no longer holds (the controller's verb held; issue 1937): a done
+	// key of the trunk's fingerprint is asked before it is left done (ClaimOptions.Stored). Nil asks nothing.
+	Stored func(ctx context.Context, references []string) (gone []string, err error)
 
 	once     sync.Once
 	sem      chan struct{}
@@ -66,6 +69,9 @@ type Builder struct {
 	// published are the package versions `<name>@<version>` a done key of this bucket names as a package's reference: a key
 	// waiting for one is built once it is here (ADR 0500 clause 6).
 	published map[string]bool
+	// held are the done keys' references the store answered held, by `<key> <references>`, asked once per process: a
+	// blob collected later is found by the take-in, whose artifacts-gone forgets the key here (issue 1937).
+	held map[string]bool
 }
 
 type planned struct {
@@ -82,7 +88,7 @@ func (b *Builder) init() {
 		b.sem = make(chan struct{}, limit)
 		b.cands, b.via, b.trunkFP = map[string]delivery.Candidate{}, map[string]via{}, map[string]bool{}
 		b.known, b.inflight, b.again, b.plans, b.tried = map[string]delivery.Module{}, map[string]bool{}, map[string]delivery.Module{}, map[string]planned{}, map[string]bool{}
-		b.published = map[string]bool{}
+		b.published, b.held = map[string]bool{}, map[string]bool{}
 	})
 }
 
@@ -202,6 +208,55 @@ func (b *Builder) Forget(key string) {
 	b.mu.Unlock()
 }
 
+// storedOnce is Stored for one key, asked once per process while the store answers every reference held.
+func (b *Builder) storedOnce(key string) func(ctx context.Context, references []string) ([]string, error) {
+	if b.Stored == nil {
+		return nil
+	}
+	return func(ctx context.Context, references []string) ([]string, error) {
+		id := key + " " + strings.Join(references, " ")
+		b.mu.Lock()
+		known := b.held[id]
+		b.mu.Unlock()
+		if known {
+			return nil, nil
+		}
+		gone, err := b.Stored(ctx, references)
+		if err == nil && len(gone) == 0 {
+			b.mu.Lock()
+			b.held[id] = true
+			b.mu.Unlock()
+		}
+		return gone, err
+	}
+}
+
+// ArtifactsGone takes the controller's event artifacts-gone in (issue 1937): a take-in found that the store does not
+// hold what the module's key names. The module is looked at again, which asks the store (ClaimOptions.Stored) and
+// builds the key again; an event for a fingerprint the module no longer has is said and left. The event only wakes the
+// builder: what is built rests on the store's answer, never on the event alone.
+func (b *Builder) ArtifactsGone(ctx context.Context, e delivery.ArtifactsGone) {
+	b.init()
+	b.mu.Lock()
+	m, ok := b.known[e.Module]
+	if key, err := delivery.BuilderBuildKey(e.Module, e.Fingerprint); err == nil {
+		for id := range b.held {
+			if strings.HasPrefix(id, key+" ") {
+				delete(b.held, id)
+			}
+		}
+	}
+	b.mu.Unlock()
+	if !ok || m.FP2 != e.Fingerprint {
+		b.logf("%s: heard %s for %s, a fingerprint the module does not have now: nothing to build", e.Module,
+			delivery.ArtifactsGoneEvent, e.Fingerprint)
+		return
+	}
+	b.logf("%s: heard %s (%s): asking the artifact store and building the key again", e.Module,
+		delivery.ArtifactsGoneEvent, strings.Join(e.Gone, ", "))
+	b.consider(ctx, e.Module, m)
+}
+
 // Reconsider looks at every module again: the toolchains changed, so a build that failed for them may build now.
 func (b *Builder) Reconsider(ctx context.Context) {
 	b.init()
@@ -312,7 +367,8 @@ func (b *Builder) try(ctx context.Context, module string, m delivery.Module) {
 	first := !b.tried[key]
 	b.tried[key] = true
 	b.mu.Unlock()
-	cl, err := b.Claimer.Claim(ctx, module, m.FP2, m.Manifest, ClaimOptions{TakeOver: first, ImageBuilder: imageSeat, Trunk: trunk, Published: b.isPublished})
+	cl, err := b.Claimer.Claim(ctx, module, m.FP2, m.Manifest, ClaimOptions{TakeOver: first, ImageBuilder: imageSeat, Trunk: trunk, Published: b.isPublished,
+		Stored: b.storedOnce(key)})
 	if err != nil {
 		b.logf("%s: %v", module, err)
 		return
@@ -320,6 +376,13 @@ func (b *Builder) try(ctx context.Context, module string, m delivery.Module) {
 	if cl == nil {
 		return
 	}
+	if cl.Unasked != nil {
+		b.logf("%v", cl.Unasked)
+	}
+	if len(cl.Gone) > 0 {
+		// Said aloud (issue 1937): the key was done, and the store's collector deleted what it names.
+		b.logf("%s: built again: the artifact store no longer holds %s", cl.Key, strings.Join(cl.Gone, ", "))
+	}
 	// A done key taken again builds only what is missing: the image or the package built unpublished as a candidate's; the
 	// other artifacts stay as the done key has them (ADR 0487 clauses 5 and 8, ADR 0498 clause 6).
 	var prior *delivery.BuilderBuild
@@ -350,6 +413,9 @@ func (b *Builder) try(ctx context.Context, module string, m delivery.Module) {
 		return
 	}
 	result.By, result.Manifest = b.Claimer.By, m.Manifest
+	if len(cl.Gone) > 0 && result.State == delivery.BuildDone {
+		result.Step += " (built again: the artifact store no longer held " + strings.Join(cl.Gone, ", ") + ")"
+	}
 	if publishing && result.State == delivery.BuildFailed {
 		// The trunk's image or package was built only as a candidate's and its push or publish failed: the key says so, so the builds view, the
 		// checker and the failed-key retake see it, and a look does not build the image again for nothing.

modules/mesh-delivery-builder/manifest_test.go

@@ -89,18 +89,21 @@ func TestManifestDeclarations(t *testing.T) { // 1607/AC1
 	}
 	// 1887/A4c: the builder chooses no node, so it reads neither presence nor have, invokes no build module's tool and
 	// holds no capacity; it puts asks on the three build seats and reads their steps (ADR 0525 §1, §4, §5).
-	if want := []string{"mesh-build-go.steps", "mesh-build-go.toolchains", "mesh-build-image.steps", "mesh-build-node.steps", "mesh-build-node.toolchains",
+	if want := []string{"mesh-build-go.steps", "mesh-build-go.toolchains", "mesh-build-image.steps", "mesh-build-node.steps", "mesh-build-node.toolchains", "mesh-controller.assignments",
 		"mesh-delivery-indexer.candidates", "mesh-delivery-indexer.manifests", "mesh-delivery-indexer.modules"}; !reflect.DeepEqual(sorted(m.Reads), want) {
 		t.Errorf("reads = %v, want %v", m.Reads, want)
 	}
 	if want := []string{"node-build-go", "node-build-image", "node-build-node"}; !reflect.DeepEqual(sorted(m.Uses), want) {
 		t.Errorf("uses = %v, want the three build seats", m.Uses)
 	}
-	if len(m.Invokes) != 0 || len(m.Config) != 0 {
-		t.Errorf("invokes = %v, config = %v, want none: no tool call from the builder and no capacity", m.Invokes, m.Config)
+	// 1937/AC3: the builder asks the controller whether the artifact store still holds a done key's blobs (held), and no
+	// other tool; it holds no capacity.
+	if want := []string{"seat:mesh-controller.held"}; !reflect.DeepEqual(m.Invokes, want) || len(m.Config) != 0 {
+		t.Errorf("invokes = %v, config = %v, want %v and no config", m.Invokes, m.Config, want)
 	}
-	// The builder is woken by a build module's report of a toolchain, as the indexer is: the bucket may not exist when it starts.
-	if want := []string{"mesh-build-go.toolchain.reported", "mesh-build-node.toolchain.reported"}; !reflect.DeepEqual(sorted(m.Consumes), want) {
+	// The builder is woken by a build module's report of a toolchain, as the indexer is: the bucket may not exist when it
+	// starts; and by the controller's artifacts-gone, a take-in refused for a gone blob (1937/AC4).
+	if want := []string{"mesh-build-go.toolchain.reported", "mesh-build-node.toolchain.reported", "mesh-controller.artifacts-gone"}; !reflect.DeepEqual(sorted(m.Consumes), want) {
 		t.Errorf("consumes = %v, want %v", m.Consumes, want)
 	}
 	if b, ok := m.OwnSecrets["broker"]; !ok || len(m.OwnSecrets) != 1 || b != "${dir:state}/broker" {
@@ -109,7 +112,7 @@ func TestManifestDeclarations(t *testing.T) { // 1607/AC1
 	if m.SecretsOwner != "mesh-delivery-builder" {
 		t.Errorf("secrets-owner = %q", m.SecretsOwner)
 	}
-	for _, k := range []string{"streams", "logs", "emits", "claims", "provides", "requires", "defines-seats", "tools", "seat", "seats", "bus", "invokes", "config"} {
+	for _, k := range []string{"streams", "logs", "emits", "claims", "provides", "requires", "defines-seats", "tools", "seat", "seats", "bus", "config"} {
 		if _, ok := top[k]; ok {
 			t.Errorf("the manifest declares %q: the builder has none", k)
 		}

modules/mesh-delivery-builder/module.json

@@ -4,7 +4,11 @@
   "slug": "builder",
   "consumes": [
     "mesh-build-go.toolchain.reported",
-    "mesh-build-node.toolchain.reported"
+    "mesh-build-node.toolchain.reported",
+    "mesh-controller.artifacts-gone"
+  ],
+  "invokes": [
+    "seat:mesh-controller.held"
   ],
   "state": [
     { "name": "builds", "history": 5 },
@@ -16,6 +20,7 @@
     "mesh-build-image.steps",
     "mesh-build-node.steps",
     "mesh-build-node.toolchains",
+    "mesh-controller.assignments",
     "mesh-delivery-indexer.candidates",
     "mesh-delivery-indexer.manifests",
     "mesh-delivery-indexer.modules"

modules/mesh-delivery-builder/reads-outside

@@ -0,0 +1 @@
+These tests read files outside this directory (the whole catalogue, the repository, or its root files): mesh-build-go never keeps this package's verdict (issue 1935).

modules/mesh-delivery-checker/cmd/mesh-delivery-checker/integration_test.go

@@ -10,6 +10,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -81,6 +82,9 @@ type fakeBuildModules struct {
 	mu       sync.Mutex
 	calls    map[string]int // by `<module>.<tool>`
 	testTool *testing.T
+	// beside is, by workspace, the siblings the fetch placed in it as `<owner/repo> <commit>`, sorted: a digest echoes them
+	// (1929/AC2; mesh-sdk buildstep.besideOf), or the level runs whole and keeps nothing.
+	beside map[string][]string
 }
 
 func (f *fakeBuildModules) count(tool string) int {
@@ -100,10 +104,30 @@ func (f *fakeBuildModules) result(t *testing.T, tool string, args map[string]any
 		}
 		fetched := readCaptured(t, name)
 		fetched["commit"], fetched["base"] = args["commit"], args["base"]
+		var refs []struct {
+			Repository string `json:"repository"`
+			Commit     string `json:"commit"`
+		}
+		raw, _ := json.Marshal(args["beside"])
+		_ = json.Unmarshal(raw, &refs)
+		var lines []string
+		for _, r := range refs {
+			lines = append(lines, r.Repository+" "+r.Commit)
+		}
+		sort.Strings(lines)
+		f.mu.Lock()
+		if f.beside == nil {
+			f.beside = map[string][]string{}
+		}
+		f.beside[fmt.Sprint(fetched["workspace"])] = lines
+		f.mu.Unlock()
 		v = fetched
 	case strings.HasSuffix(tool, "_digest"):
 		d := map[string]string{"unit": digU, "integration": digI}[level]
-		v = map[string]any{"level": level, "packages": map[string]string{"fixture/slow": d}}
+		f.mu.Lock()
+		beside := f.beside[fmt.Sprint(args["workspace"])]
+		f.mu.Unlock()
+		v = map[string]any{"level": level, "packages": map[string]string{"fixture/slow": d}, "beside": beside}
 	case strings.HasSuffix(tool, "_test"):
 		r := readCaptured(t, "go-test-slow")
 		r["level"] = level
@@ -288,6 +312,15 @@ func startBed(t *testing.T) *bed {
 		}
 		b.buckets[name] = kv
 	}
+	// 1929/AC1: the indexer's value of the repository's module, with no TypeScript manifest, so the Go build module alone
+	// judges the repository (an unknown repository is judged by both, issue 1887 A12).
+	known, err := delivery.EncodeModule(delivery.Module{Repository: repo, Commit: trunk, Path: "modules/m", None2: "the fingerprint is computed with its chain"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := b.buckets[delivery.ModulesBucket].Put(ctx, "m", known); err != nil {
+		t.Fatal(err)
+	}
 	b.setOnline(t, "n1", true)
 	for _, module := range []string{"mesh-build-go", "mesh-build-node"} {
 		b.setHealth(t, "n1", module)
@@ -436,7 +469,7 @@ func (b *bed) owed(t *testing.T, number int, head, state string) delivery.Owed {
 // TestCheckerJudgesACandidateAndOwesItsStatus: a candidate the indexer wrote, one pull request of mesh-delivery, is fetched
 // merged onto the trunk the gate names, digested and tested at both levels on the node, kept, previewed; the verdict passes
 // with the counts of both levels and the composition not run, and the status mesh/check is owed on the head as success.
-func TestCheckerJudgesACandidateAndOwesItsStatus(t *testing.T) { // N6/AC5, 1300/AC5, 1445/AC1
+func TestCheckerJudgesACandidateAndOwesItsStatus(t *testing.T) { // N6/AC5, 1300/AC5, 1445/AC1, 1929/AC1
 	b := startBed(t)
 	key := b.candidate(t, "feat/x", pull(repo, 7, head1))
 	b.start(t, nil)
@@ -476,7 +509,7 @@ func TestCheckerJudgesACandidateAndOwesItsStatus(t *testing.T) { // N6/AC5, 1300
 
 // TestACheckOfEqualInputsRunsNothing: a second candidate (another head, the same digests) is checked with every package
 // taken from the first's kept verdicts: no test step runs and no second kept key appears.
-func TestACheckOfEqualInputsRunsNothing(t *testing.T) { // 1287/AC5, 1288/AC6
+func TestACheckOfEqualInputsRunsNothing(t *testing.T) { // 1287/AC5, 1288/AC6, 1929/AC2
 	b := startBed(t)
 	first := b.candidate(t, "feat/x", pull(repo, 7, head1))
 	b.start(t, nil)
@@ -574,7 +607,7 @@ func TestACheckLeftRunningIsTakenOverWhenTheCheckerStarts(t *testing.T) { // N6/
 
 // TestAMemberNamingAMeshSDKCommitOffTheTrunkFailsNamingTheCommit: the go.mod the forge answers names a commit that main does not
 // hold; the verdict fails naming the member and the commit and no test runs (ADR 0484 clause 9).
-func TestAMemberNamingAMeshSDKCommitOffTheTrunkFailsNamingTheCommit(t *testing.T) { // 1624/AC2
+func TestAMemberNamingAMeshSDKCommitOffTheTrunkFailsNamingTheCommit(t *testing.T) { // 1624/AC2, 1929/AC3
 	b := startBed(t)
 	b.stalePin.Store(true)
 	key := b.candidate(t, "feat/x", pull(repo, 7, head1))
@@ -583,9 +616,7 @@ func TestAMemberNamingAMeshSDKCommitOffTheTrunkFailsNamingTheCommit(t *testing.T
 	if v.State != delivery.VerdictFail || !strings.Contains(v.Failed.Words, "9aaa5c80ac5c") || !strings.Contains(v.Failed.Words, repo+"#7") {
 		t.Fatalf("verdict = %+v", v)
 	}
-	if n := b.fake.count("mesh-build-go.build_go_test"); n != 0 {
-		t.Errorf("%d test steps ran after a stale pin", n)
-	}
+	// 1929/AC3: no assertion that no test ran: one ask runs fetch, digest and tests (ADR 0525 §3).
 }
 
 // triesStore is the tries bucket as the tools write it.
@@ -671,7 +702,7 @@ func TestTheCheckerSaysOwedReadableOnTheBus(t *testing.T) { // R2-1
 		break
 	}
 	if said.Module != "mesh-delivery-checker" || said.Node != "n1" || !said.Keeps("owed") || !said.Readable("owed") ||
-		!said.Readable("previews") || !said.Readable("verdicts") || said.Readable("kept") || said.Readable("tries") || len(said.States) != 5 {
-		t.Fatalf("the checker said %+v, want its five states with owed, previews and verdicts readable", said)
+		!said.Readable("previews") || !said.Readable("verdicts") || !said.Readable("kept") || said.Readable("tries") || len(said.States) != 5 {
+		t.Fatalf("the checker said %+v, want its five states with kept, owed, previews and verdicts readable (1929/AC4; 1887 A5b)", said)
 	}
 }

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

@@ -257,6 +257,14 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 
 	// The toolchains first, so a check that starts from the first candidate finds the nodes.
 	watch := newToolchainWatch(ctx, js, tools, ch.NodesChanged, logger)
+	// Only the toolchain reports of nodes the build module is assigned to count (issue 1940): the controller's
+	// assignments are settled first, so the toolchains settle through the gate already knowing them.
+	gate := newToolchainGate([]string{buildrun.GoBuildModule, buildrun.NodeBuildModule}, tools.Put, logger.Printf)
+	watch.put = gate.Toolchain
+	assignErrs, err := watchAssignments(ctx, js, gate, ch.NodesChanged, logger)
+	if err != nil {
+		return err
+	}
 	if err := watch.start(); err != nil {
 		return err
 	}
@@ -369,6 +377,8 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 		return nil
 	case err := <-errs:
 		return err
+	case err := <-assignErrs:
+		return err
 	case err := <-watch.errs:
 		return err
 	}

modules/mesh-delivery-checker/cmd/mesh-delivery-checker/standing.go

@@ -0,0 +1,174 @@
+package main
+
+// This file is the same in mesh-delivery-indexer, mesh-delivery-builder and mesh-delivery-checker (issue 1940): it moves
+// to mesh-sdk go/delivery/buildrun once mesh-sdk can be delivered again, since a change of mesh-sdk waits on the very
+// toolchain agreement this file repairs.
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"maps"
+	"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/provider"
+)
+
+// A build module writes <node>.<language> of its toolchains state on every node it runs on, and nothing deletes the key
+// when the module is unassigned from a node: the controller writes no module's state, and the module is gone. A report of
+// a node the build module no longer runs on is therefore not a builder (issue 1940: mesh-build-node unassigned from 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
+// buildrun.ToolchainSet): an entry is passed on only while the controller's assignments (mesh-controller_assignments,
+// key <node>.<module>) hold an open assignment of its build module on its node; it is passed on as deleted otherwise,
+// and passed on again when the module is assigned there again. Until the assignments are settled (or where they cannot
+// be read) every entry is passed on, as before. Builders that run and report different versions still disagree: that
+// refusal is the guard of novox/hq ADR 0465, and it stays.
+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)
+	known    bool                         // the assignments are settled
+	standing map[string]bool              // <node>.<module> with an open assignment
+	raw      map[string]map[string][]byte // module -> toolchains key -> value, as the bucket holds it
+	left     map[string]bool              // <module>/<key> said as left out, so it is said once
+}
+
+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, standing: map[string]bool{},
+		raw: map[string]map[string][]byte{}, left: map[string]bool{}}
+	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)
+}
+
+// Assignment takes one change of the controller's assignments in and answers whether what it passed on changed.
+func (g *toolchainGate) Assignment(key string, value []byte, deleted bool) bool {
+	node, module, ok := strings.Cut(key, ".")
+	if !ok || !g.modules[module] {
+		return false
+	}
+	open := !deleted && openAssignment(value)
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	if g.standing[key] == open {
+		return false
+	}
+	if open {
+		g.standing[key] = true
+	} else {
+		delete(g.standing, key)
+	}
+	if !g.known {
+		return false
+	}
+	changed := false
+	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
+}
+
+// Settled says the assignments are read: from now on only the reports of assigned nodes pass. It answers whether what it
+// passed on changed.
+func (g *toolchainGate) Settled() bool {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.known = true
+	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
+}
+
+// pass hands one key on as it stands: its value when its node is assigned (or the assignments are 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)
+	if err != nil || !g.known || g.standing[node+"."+module] {
+		delete(g.left, module+"/"+key)
+		return g.forward(module, key, value, false)
+	}
+	if !g.left[module+"/"+key] {
+		g.left[module+"/"+key] = true
+		g.logf("%s.%s is left out of the agreed toolchain: %s has no assignment on %s, so it is no builder (issue 1940)",
+			delivery.ToolchainsBucket(module), key, module, node)
+	}
+	return g.forward(module, key, nil, true)
+}
+
+// openAssignment is whether a value of the controller's assignments holds an assignment that stands: one that has not
+// ended and has no state (a pending one is not on the machine yet; mesh-controller internal/chain Assignment).
+func openAssignment(value []byte) bool {
+	var a struct {
+		Ended time.Time `json:"ended"`
+		State string    `json:"state"`
+	}
+	if json.Unmarshal(value, &a) != nil {
+		return false
+	}
+	return a.Ended.IsZero() && a.State == ""
+}
+
+// watchAssignments settles the controller's assignments into the gate, says them settled, and follows them; changed is
+// told whenever what the gate passes on changed. Where the bucket cannot be read (not there, or this module may not read
+// it) it says so and the gate passes every report on, as before; an error of the watch after that ends on the channel.
+func watchAssignments(ctx context.Context, js bucketOpener, gate *toolchainGate, changed func(context.Context), logger *log.Logger) (<-chan error, error) {
+	errs := make(chan error, 1)
+	kv, err := js.KeyValue(ctx, provider.AssignmentsBucket)
+	if err != nil {
+		// Not fatal: an indexer, builder or checker that stops for it stops every delivery (a grant comes with a delivery).
+		logger.Printf("the bucket %s cannot be read, so every node's toolchain report counts, an unassigned build node's too (issue 1940): %v", provider.AssignmentsBucket, err)
+		return errs, nil
+	}
+	each := func(e jetstream.KeyValueEntry) { gate.Assignment(e.Key(), e.Value(), !opOf(e)) }
+	w, err := settle(ctx, kv, each)
+	if err != nil {
+		return nil, fmt.Errorf("the bucket %s: %w", provider.AssignmentsBucket, err)
+	}
+	if gate.Settled() {
+		changed(ctx)
+	}
+	go func() {
+		errs <- follow(ctx, w, func(e jetstream.KeyValueEntry) {
+			if gate.Assignment(e.Key(), e.Value(), !opOf(e)) {
+				changed(ctx)
+			}
+		})
+	}()
+	return errs, nil
+}

modules/mesh-delivery-checker/cmd/mesh-delivery-checker/standing_test.go

@@ -0,0 +1,112 @@
+package main
+
+// The same in mesh-delivery-indexer, mesh-delivery-builder and mesh-delivery-checker, as standing.go is (issue 1940).
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
+)
+
+func gateReport(t *testing.T, node, version string) (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: time.Unix(0, 0).UTC()})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return key, value
+}
+
+func agreedOf(set *buildrun.ToolchainSet) (string, string) {
+	tc, none := delivery.AgreedToolchain(set.Entries("typescript"))
+	return tc.Version, none
+}
+
+// The live case of issue 1940: mesh-build-node was unassigned from ace, whose report stayed at v26.12.0 while the
+// three nodes it runs on report v26.12.1. Without the assignments every report counts (and they disagree); with them
+// ace's is left out and the three agree; assigned to ace again, its report counts again and the guard refuses again.
+func TestAnUnassignedBuildNodesReportIsNoBuilder(t *testing.T) {
+	set := &buildrun.ToolchainSet{}
+	var said []string
+	gate := newToolchainGate([]string{buildrun.GoBuildModule, buildrun.NodeBuildModule}, set.Put, func(f string, a ...any) { said = append(said, f) })
+	for node, version := range map[string]string{"ace": "v26.12.0", "g14": "v26.12.1", "novox": "v26.12.1", "shanks": "v26.12.1"} {
+		key, value := gateReport(t, node, version)
+		gate.Toolchain(buildrun.NodeBuildModule, key, value, false)
+	}
+	if _, none := agreedOf(set); !strings.HasPrefix(none, "builders disagree") {
+		t.Fatalf("before the assignments are read every report counts, so they disagree; got %q", none)
+	}
+	for _, node := range []string{"g14", "novox", "shanks"} {
+		gate.Assignment(node+"."+buildrun.NodeBuildModule, []byte(`{"node":"`+node+`","module":"mesh-build-node"}`), false)
+	}
+	gate.Assignment("ace.mesh-build-node", []byte(`{"node":"ace","module":"mesh-build-node","ended":"2026-10-23T08:00:00Z"}`), false)
+	gate.Assignment("ace.mesh-build-go", []byte(`{"node":"ace","module":"mesh-build-go"}`), false) // another module's: no matter
+	if !gate.Settled() {
+		t.Fatal("settling the assignments left ace's report out, so what was passed on changed")
+	}
+	if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+		t.Fatalf("the assigned nodes agree on v26.12.1; got %q, %q", v, none)
+	}
+	if len(said) != 1 {
+		t.Fatalf("ace's report is said left out once; said %v", said)
+	}
+	// ace reports again while unassigned (an old value seen again): still left out.
+	key, value := gateReport(t, "ace", "v26.12.0")
+	if gate.Toolchain(buildrun.NodeBuildModule, key, value, false) {
+		t.Fatal("an unassigned node's report changed what was passed on")
+	}
+	// Assigned to ace again: its report counts, and the builders really disagree: the guard stays.
+	if !gate.Assignment("ace.mesh-build-node", []byte(`{"node":"ace","module":"mesh-build-node"}`), false) {
+		t.Fatal("assigning ace again passed nothing on")
+	}
+	if _, none := agreedOf(set); !strings.HasPrefix(none, "builders disagree: v26.12.0 recipe f59571cf4be75adf on ace") {
+		t.Fatalf("builders that run different versions still disagree; got %q", none)
+	}
+	// The assignment's key deleted, or a pending one written: no assignment stands, and ace's report goes again.
+	if !gate.Assignment("ace.mesh-build-node", []byte(`{"node":"ace","module":"mesh-build-node","state":"pending"}`), false) {
+		t.Fatal("a pending assignment is no assignment on the machine")
+	}
+	if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+		t.Fatalf("got %q, %q", v, none)
+	}
+	gate.Assignment("ace.mesh-build-node", nil, true)
+	if v, _ := agreedOf(set); v != "v26.12.1" {
+		t.Fatalf("got %q", v)
+	}
+	// A report deleted from the bucket goes whether its node is assigned or not.
+	key, _ = gateReport(t, "g14", "v26.12.1")
+	if !gate.Toolchain(buildrun.NodeBuildModule, key, nil, true) {
+		t.Fatal("deleting g14's report passed nothing on")
+	}
+	if n := len(set.Entries("typescript")); n != 2 {
+		t.Fatalf("novox and shanks are left; got %d entries", n)
+	}
+}
+
+// A newly assigned build node that has not reported yet changes nothing; its report counts as it comes.
+func TestANewlyAssignedNodeCountsFromItsReport(t *testing.T) {
+	set := &buildrun.ToolchainSet{}
+	gate := newToolchainGate([]string{buildrun.NodeBuildModule}, set.Put, func(string, ...any) {})
+	gate.Settled()
+	if gate.Assignment("g14.mesh-build-node", []byte(`{}`), false) {
+		t.Fatal("an assignment with no report passed something on")
+	}
+	key, value := gateReport(t, "g14", "v26.12.1")
+	if !gate.Toolchain(buildrun.NodeBuildModule, key, value, false) {
+		t.Fatal("an assigned node's report was not passed on")
+	}
+	key, value = gateReport(t, "ace", "v26.12.0")
+	if gate.Toolchain(buildrun.NodeBuildModule, key, value, false) {
+		t.Fatal("a report of a node with no assignment key was passed on after the assignments settled")
+	}
+	if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+		t.Fatalf("got %q, %q", v, none)
+	}
+}

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

@@ -24,9 +24,11 @@ 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
@@ -35,7 +37,7 @@ 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.
@@ -63,14 +65,14 @@ func (w *toolchainWatch) ensure(module string) error {
 	case err != nil:
 		return fmt.Errorf("the bucket %s: %w", name, err)
 	}
-	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
 	}
 	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-checker/go.mod

@@ -3,7 +3,7 @@ module mesh-delivery-checker
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023150321-a2c813a6b468
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023213200-403a5d72ab93
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )

modules/mesh-delivery-checker/go.sum

@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023150321-a2c813a6b468 h1:UcMee+IV2ii5E4dRZdQUaSaeh9IedTFYumuQbBiB0k0=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023150321-a2c813a6b468/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023213200-403a5d72ab93 h1:FAiFY2KBKEoZSH49OZTt7/zRBIQxyl5g/KhYrpggbN4=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261023213200-403a5d72ab93/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=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=

modules/mesh-delivery-checker/internal/check/beside.go

@@ -26,7 +26,7 @@ const (
 // checks/deps). Which commit of each is besideCommit's rule.
 var besideRules = map[string][]string{
 	controllerRepo:        {catalogueRepository, nodeEngineRepo, SDKRepository},
-	nodeEngineRepo:        {catalogueRepository, SDKRepository},
+	nodeEngineRepo:        {catalogueRepository, SDKRepository, controllerRepo},
 	SDKRepository:         {catalogueRepository, nodeEngineRepo},
 	catalogueRepository:   {SDKRepository, controllerRepo},
 	"novox/mesh-delivery": {SDKRepository, catalogueRepository},
@@ -83,6 +83,10 @@ func (j *Examiner) besideFor(ctx context.Context, c *Case, p Pull) ([]BesideRef,
 				out = append(out, BesideRef{Repository: repo, Commit: member.Head, Ref: refOf(member.Number)})
 			} else if head := heads[repo]; head != "" {
 				out = append(out, BesideRef{Repository: repo, Commit: head})
+			} else if repo == controllerRepo && p.Repository == nodeEngineRepo {
+				// The node-engine's step-nine test judges the controller's own manifest and fails without it (issue 1295): a
+				// checker that cannot place it says so, where placing none left that test to skip.
+				return nil, fmt.Errorf("the trunk head of %s is not known, so the controller the tests of %s#%d read cannot be placed beside them", repo, p.Repository, p.Number)
 			}
 		}
 	}

modules/mesh-delivery-checker/internal/check/digestform_test.go

@@ -0,0 +1,83 @@
+package check
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// 1930/AC3: given a check ask whose stored end keeps the digest's packages as a list of {package, digest} (issue 1930),
+// or one stored before it with the packages a map keyed by package path, when the same heads are checked a second time,
+// then the kept verdicts the first check wrote are read from it: every package it passed is kept, none run again.
+func TestKeptVerdictsAreReadFromTheDigestsListForm(t *testing.T) {
+	for _, tc := range []struct {
+		name string
+		old  bool
+	}{{"the list form", false}, {"a map stored before issue 1930", true}} {
+		t.Run(tc.name, func(t *testing.T) {
+			b := newBench(t)
+			var stored []string
+			b.asks.Answer = func(a delivery.StepAsk) delivery.Step {
+				s := b.answer(a)
+				if tc.old && s.State == delivery.StepPassed {
+					s.Result = oldDigestForm(t, s.Result)
+				}
+				stored = append(stored, string(s.Result))
+				return s
+			}
+			first := b.judge(t, caseOf(t, pullOf(repoA, 7, head1))).Verdict
+			u := first.Levels[delivery.LevelUnit]
+			if first.State != delivery.VerdictPass || u.Run == 0 || u.Kept != 0 {
+				t.Fatalf("the first check = %+v", first)
+			}
+			if len(stored) == 0 {
+				t.Fatal("no ask's end was stored")
+			}
+			list := strings.Contains(stored[0], `"packages":[{"package":"fixture/slow"`)
+			if list == tc.old || strings.Contains(stored[0], `"fixture/slow":"`) != tc.old {
+				t.Fatalf("the stored end is not in the form under test: %s", stored[0])
+			}
+			b.steps.calls = nil
+			second := b.judge(t, caseOf(t, pullOf(repoA, 7, head1))).Verdict
+			if s := second.Levels[delivery.LevelUnit]; second.State != delivery.VerdictPass || s.Kept != u.Run || s.Run != 0 {
+				t.Fatalf("the second check's unit level = %+v, want %d kept and none run", s, u.Run)
+			}
+			if n := len(b.steps.tool("test")); n != 0 {
+				t.Errorf("%d test steps ran on the second check", n)
+			}
+		})
+	}
+}
+
+// oldDigestForm rewrites a check answer's level digests to the form stored before issue 1930: packages as a map keyed by
+// package path.
+func oldDigestForm(t *testing.T, result json.RawMessage) json.RawMessage {
+	t.Helper()
+	var a struct {
+		Fetch  json.RawMessage  `json:"fetch"`
+		Levels []map[string]any `json:"levels"`
+	}
+	if err := json.Unmarshal(result, &a); err != nil {
+		t.Fatal(err)
+	}
+	for _, l := range a.Levels {
+		d, ok := l["digest"].(map[string]any)
+		if !ok {
+			continue
+		}
+		m := map[string]any{}
+		list, _ := d["packages"].([]any)
+		for _, p := range list {
+			pd := p.(map[string]any)
+			m[pd["package"].(string)] = pd["digest"]
+		}
+		d["packages"] = m
+	}
+	raw, err := json.Marshal(a)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return raw
+}

modules/mesh-delivery-checker/internal/check/failure_words_test.go

@@ -0,0 +1,73 @@
+package check
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// The failure the build module reported for group r4g on 2026-10-23: the test logged a line, then failed with a multi-line
+// t.Fatalf. Its output is what the build module now sends (its last lines, with the error line as Cause).
+func fatalAfterLog() Failure {
+	return Failure{
+		Package: "github.com/novox/mesh-controller/internal/broker", Test: "TestTheCataloguesDerivedSubjectsMeet",
+		Cause: "3 subscription(s) derive to a subject no emitter owns:",
+		Output: "    agreement_catalogue_test.go:130: judged against /var/lib/mesh-build-go-work/id/beside/mesh-catalog as cloned\n" +
+			"    agreement_catalogue_test.go:186: 3 subscription(s) derive to a subject no emitter owns:\n" +
+			"          a.b.c\n          d.e.f\n          g.h.i\n--- FAIL: TestTheCataloguesDerivedSubjectsMeet (0.00s)",
+	}
+}
+
+func TestAFailedTestsVerdictKeepsItsWholeFailureMessage(t *testing.T) { // 1901/AC1
+	v := levelFailure(&target{}, "unit", Tested{Failed: []Failure{fatalAfterLog()}})
+	for _, want := range []string{"3 subscription(s) derive to a subject no emitter owns:", "a.b.c", "d.e.f", "g.h.i"} {
+		if !strings.Contains(v.Failed.Words, want) {
+			t.Errorf("words lack %q: %q", want, v.Failed.Words)
+		}
+	}
+	if len(v.Failed.Words) > MaxWords+200 {
+		t.Errorf("words are %d bytes, bound %d", len(v.Failed.Words), MaxWords)
+	}
+}
+
+func TestTheStatusLineNamesTheFailureNotTheFirstLoggedLine(t *testing.T) { // 1901/AC2
+	v := levelFailure(&target{}, "unit", Tested{Failed: []Failure{fatalAfterLog()}})
+	got := firstFailed(*v)
+	if !strings.Contains(got, "3 subscription(s) derive to a subject no emitter owns:") || strings.Contains(got, "judged against") || strings.Contains(got, "\n") {
+		t.Errorf("firstFailed = %q", got)
+	}
+	// With no cause told apart (an older build module), the words still start at the first line, as before.
+	f := fatalAfterLog()
+	f.Cause = ""
+	v = levelFailure(&target{}, "unit", Tested{Failed: []Failure{f}})
+	if !strings.HasPrefix(v.Failed.Words, "agreement_catalogue_test.go:130") {
+		t.Errorf("words = %q", v.Failed.Words)
+	}
+}
+
+func TestWordsLongerThanTheBoundKeepTheirLastLines(t *testing.T) { // 1901/AC1
+	f := Failure{Output: strings.Repeat("log line of some length\n", 500) + "the cause is here"}
+	v := levelFailure(&target{}, "unit", Tested{Failed: []Failure{f}})
+	if !strings.HasSuffix(v.Failed.Words, "the cause is here") || len(v.Failed.Words) > MaxWords+200 {
+		t.Errorf("%d bytes, ends %q", len(v.Failed.Words), v.Failed.Words[len(v.Failed.Words)-30:])
+	}
+	_ = delivery.VerdictFail
+}
+
+// An older build module sends no "cause": its answer is still accepted and the verdict's words are its output, as before.
+func TestAnOlderBuildModulesFailureIsAcceptedWithItsWholeOutput(t *testing.T) { // 1901/AC3
+	old := `{"package":"p","test":"TestX","output":"x_test.go:1: logged\nx_test.go:2: the old kept lines"}`
+	var f Failure
+	if err := json.Unmarshal([]byte(old), &f); err != nil || f.Cause != "" {
+		t.Fatalf("1901/AC3: err = %v, cause = %q", err, f.Cause)
+	}
+	v := levelFailure(&target{}, "unit", Tested{Failed: []Failure{f}})
+	if v.Failed.Words != "x_test.go:1: logged\nx_test.go:2: the old kept lines" {
+		t.Errorf("1901/AC3: words = %q", v.Failed.Words)
+	}
+	if got := firstFailed(*v); !strings.Contains(got, "logged") || strings.Contains(got, "\n") {
+		t.Errorf("1901/AC3: status = %q", got)
+	}
+}

modules/mesh-delivery-checker/internal/check/judge.go

@@ -447,13 +447,11 @@ func (st *state) level(ctx context.Context, t *target, la delivery.LevelAnswer)
 		return fail(t.node, fmt.Sprintf("the check of %s#%d answered the level %q, which is no level", t.pull.Repository, t.pull.Number, level)), 0
 	}
 	var digests map[string]string
-	if t.module == buildrun.GoBuildModule && len(la.Digest) > 0 {
-		var d Digested
-		if err := json.Unmarshal(la.Digest, &d); err == nil {
-			digests = d.Packages
-			if t.runner != "" {
-				t.judgedBy(d.JudgedBy) // the installed module judged it: the runner is not used again
-			}
+	if t.module == buildrun.GoBuildModule && la.Digest != nil {
+		// The packages come as a list, never keyed by a package path (issue 1930); an answer stored before reads too.
+		digests = la.Digest.Map()
+		if t.runner != "" {
+			t.judgedBy(la.Digest.JudgedBy) // the installed module judged it: the runner is not used again
 		}
 	}
 	if t.runner != "" && la.Judged != "" {
@@ -525,13 +523,35 @@ func failedName(f Failure) string {
 	return f.Package + "." + f.Test
 }
 
-// firstLine is the first non-empty line of a failure's output, shortened.
+// MaxWords is the most a failed test's words in a verdict hold (issue 1901). **The words keep the failure's last lines**,
+// where a test says why it failed: the first line is often something it logged before (the group r4g verdict kept a
+// "judged against" line and lost the t.Fatalf after it), and the 120 characters kept before cut a docker command's echo
+// before docker's own error. Four kilobytes holds a long message and is small beside a verdict's other parts.
+const MaxWords = 4096
+
+// failureWords is a failure's words: its output's last lines up to MaxWords, with the line the build module told apart as
+// the test's error first when the output does not start with it, so the first line of the words is the cause and the
+// status line, which is cut short, names it.
+func failureWords(f Failure) string {
+	out := strings.TrimSpace(f.Output)
+	if len(out) > MaxWords {
+		out = out[len(out)-MaxWords:]
+		// Start on a whole line, and a whole character.
+		if i := strings.IndexByte(out, '\n'); i >= 0 {
+			out = "... " + strings.TrimLeft(out[i:], "\n")
+		}
+		out = strings.ToValidUTF8(out, "")
+	}
+	if c := strings.TrimSpace(f.Cause); c != "" && !strings.HasPrefix(firstLine(out), c) {
+		out = c + "\n" + out
+	}
+	return out
+}
+
+// firstLine is the first non-empty line of a failure's words.
 func firstLine(s string) string {
 	for _, l := range strings.Split(s, "\n") {
 		if l = strings.TrimSpace(l); l != "" {
-			if len(l) > 120 {
-				l = l[:120]
-			}
 			return l
 		}
 	}
@@ -548,7 +568,7 @@ func levelFailure(t *target, level string, res Tested) *delivery.Verdict {
 		if t.module == buildrun.NodeBuildModule && f.Package == "" {
 			name = res.Module
 		}
-		v.Failed = delivery.FailedFirst{Test: level + ": " + name, Words: firstLine(f.Output)}
+		v.Failed = delivery.FailedFirst{Test: level + ": " + name, Words: failureWords(f)}
 	default:
 		why := res.Why
 		if why == "" {

modules/mesh-delivery-checker/internal/check/line.go

@@ -37,18 +37,21 @@ func firstFailed(v delivery.Verdict) string {
 	f := v.Failed
 	switch {
 	case f.Test != "":
-		if f.Words != "" {
-			return f.Test + ": " + f.Words
+		if w := firstWordsLine(f.Words); w != "" {
+			return f.Test + ": " + w
 		}
 		return f.Test
-	case f.Machine != "" && f.Words != "":
-		return f.Machine + ": " + f.Words
+	case f.Machine != "" && firstWordsLine(f.Words) != "":
+		return f.Machine + ": " + firstWordsLine(f.Words)
 	case f.Machine != "":
 		return f.Machine
 	}
-	return f.Words
+	return firstWordsLine(f.Words)
 }
 
+// firstWordsLine is the first line of a failure's words: the words are several lines (issue 1901) and the status line one.
+func firstWordsLine(w string) string { return firstLine(w) }
+
 // pieces are the parts of a line, from the most to the least needed.
 type pieces struct {
 	head, commits, counts, shortCounts, times, shortTimes, over, builds, composition, shortComposition, group string

modules/mesh-delivery-checker/internal/check/pins_test.go

@@ -244,6 +244,39 @@ func TestTheSiblingsAreWhereTheTestsStateThem(t *testing.T) { // review D2, ADR
 	}
 }
 
+// 1295/R4g: the node-engine's tests read the controller's manifest, so a mesh-host pull request has mesh-controller beside it:
+// at the group member's head when the group holds one, else at its trunk.
+func hostCase(t *testing.T, pulls ...delivery.CandidatePull) *Case {
+	t.Helper()
+	c, err := delivery.DecodeCandidate(candidateOf(t, "feat/x", pulls...))
+	if err != nil {
+		t.Fatal(err)
+	}
+	cs := CaseOf(c, map[string]string{"novox/mesh-host": trunkA, controllerRepo: trunkA2})
+	if cs == nil {
+		t.Fatal("no case")
+	}
+	return cs
+}
+
+func TestTheNodeEnginesTestsHaveTheControllerBesideThem(t *testing.T) {
+	const host = "novox/mesh-host"
+	b := newBench(t)
+	b.ex.Trunks = trunksOf(t, map[string]string{host: trunkA, controllerRepo: trunkA2, catalogueRepository: trunkS, SDKRepository: trunkS})
+	b.judge(t, hostCase(t, pullOf(host, 5, head1)))
+	if c := besideOf(t, b, host)[controllerRepo]; c.Commit != trunkA2 || c.Ref != "" {
+		t.Errorf("the controller beside the node-engine alone = %+v, want its trunk %s", c, trunkA2)
+	}
+	b = newBench(t)
+	b.ex.Trunks = trunksOf(t, map[string]string{host: trunkA, controllerRepo: trunkA2, catalogueRepository: trunkS, SDKRepository: trunkS})
+	b.ex.Forge = &fakeForge{goMods: map[string]string{controllerRepo + " go.mod " + head2: capturedGoMod(t, "cb54756c3865")},
+		onTrunk: map[string]bool{"cb54756c3865": true}}
+	b.judge(t, hostCase(t, pullOf(host, 5, head1), pullOf(controllerRepo, 9, head2)))
+	if c := besideOf(t, b, host)[controllerRepo]; c.Commit != head2 || c.Ref != "refs/pull/9/head" {
+		t.Errorf("the controller beside the node-engine in a group = %+v, want the member's head %s", c, head2)
+	}
+}
+
 func TestThePinOfTheControllerThatCannotBeReadFailsTheCheck(t *testing.T) { // review D2
 	b := newBench(t)
 	b.ex.Trunks = trunksOf(t, map[string]string{"novox/mesh-controller": trunkA})
@@ -313,3 +346,15 @@ func TestAMeshLabHeadGetsACheck(t *testing.T) {
 		t.Fatalf("mesh-lab was not fetched: %+v", fetched)
 	}
 }
+
+// 1295: the node-engine's step-nine test fails without the controller beside it, so a checker that knows no trunk head of the
+// controller fails the check at the placing, loudly, and does not place none.
+func TestTheNodeEnginesCheckFailsWhereTheControllersTrunkIsNotKnown(t *testing.T) {
+	const host = "novox/mesh-host"
+	b := newBench(t)
+	b.ex.Trunks = trunksOf(t, map[string]string{host: trunkA, catalogueRepository: trunkS, SDKRepository: trunkS})
+	v := b.judge(t, hostCase(t, pullOf(host, 5, head1))).Verdict
+	if v.State != delivery.VerdictFail || !strings.Contains(v.Failed.Words, "mesh-controller") || !strings.Contains(v.Failed.Words, "cannot be placed") {
+		t.Fatalf("verdict = %+v", v)
+	}
+}

modules/mesh-delivery-checker/internal/check/results.go

@@ -59,6 +59,8 @@ type Failure struct {
 	Package string `json:"package"`
 	Test    string `json:"test,omitempty"`
 	Output  string `json:"output,omitempty"`
+	// Cause is the first line of what the test reported as its error, when the build module told it apart (issue 1901).
+	Cause string `json:"cause,omitempty"`
 }
 
 // TestTime is one test and the seconds it took.

modules/mesh-delivery-checker/manifest_test.go

@@ -96,7 +96,7 @@ func TestManifestDeclarations(t *testing.T) { // 1678/AC1
 	if want := []state{{Name: "kept", History: 1}, {Name: "owed", History: 5}, {Name: "previews", History: 5}, {Name: "tries", History: 1}, {Name: "verdicts", History: 5}}; !reflect.DeepEqual(m.State, want) {
 		t.Errorf("state = %+v, want %+v", m.State, want)
 	}
-	if want := []string{"mesh-build-go.steps", "mesh-build-go.toolchains", "mesh-build-node.steps", "mesh-build-node.toolchains",
+	if want := []string{"mesh-build-go.steps", "mesh-build-go.toolchains", "mesh-build-node.steps", "mesh-build-node.toolchains", "mesh-controller.assignments",
 		"mesh-delivery-assigner.compositions", "mesh-delivery-builder.builds", "mesh-delivery-gate.source", "mesh-delivery-indexer.candidates",
 		"mesh-delivery-indexer.manifests", "mesh-delivery-indexer.modules", "mesh-delivery-watchman.presence", "node-engine.have"}; !reflect.DeepEqual(sorted(m.Reads), want) {
 		t.Errorf("reads = %v, want %v", m.Reads, want)

modules/mesh-delivery-checker/module.json

@@ -21,6 +21,7 @@
     "mesh-build-go.toolchains",
     "mesh-build-node.steps",
     "mesh-build-node.toolchains",
+    "mesh-controller.assignments",
     "mesh-delivery-assigner.compositions",
     "mesh-delivery-builder.builds",
     "mesh-delivery-gate.source",

modules/mesh-delivery-checker/reads-outside

@@ -0,0 +1 @@
+These tests read files outside this directory (the whole catalogue, the repository, or its root files): mesh-build-go never keeps this package's verdict (issue 1935).

modules/mesh-delivery-forge-bridge/reads-outside

@@ -0,0 +1 @@
+These tests read files outside this directory (the whole catalogue, the repository, or its root files): mesh-build-go never keeps this package's verdict (issue 1935).

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/integration_test.go

@@ -478,3 +478,159 @@ func TestAMergeOfMeshSDKChangingOnlyGoLeavesItsNamedTreeEqual(t *testing.T) {
 		t.Errorf("the new form moved: %q/%q, then %q/%q", first.FP2, first.None2, second.FP2, second.None2)
 	}
 }
+
+// TestIndexerJudgesAnUnreadableVerdictAgainAtStart: the modules bucket holds avahi as an older SDK wrote it, with the reason
+// 'the manifest cannot be read', the inputs the merge carried (the tree, the lock hash by file name) and the digest of its
+// manifest, which manifests.<digest> holds and the running SDK reads; the go toolchain is reported. Within 5 s of the start
+// and with no repository merge the value carries a fingerprint and no reason (issue 1923).
+func TestIndexerJudgesAnUnreadableVerdictAgainAtStart(t *testing.T) { // 1923/AC3
+	manifest, err := os.ReadFile("../../internal/index/testdata/catalogue-a67f0196-avahi.module.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	const goSum = "3b5028f0c1e9bde04dd766abd63eb5931bc516bae695cf46f00abcd8510b0381"
+	digest := delivery.ManifestDigest(manifest)
+	_, ctx, _, modules := startIndexer(t, func(context.Context, jetstream.KeyValue) {}, func(ctx context.Context, js jetstream.JetStream) {
+		mkey, err := delivery.ManifestsKey(digest)
+		if err != nil {
+			t.Fatal(err)
+		}
+		mdata, err := delivery.EncodeManifest(delivery.Manifest{Module: "avahi", JSON: string(manifest)})
+		if err != nil {
+			t.Fatal(err)
+		}
+		manifests, err := js.KeyValue(ctx, delivery.ManifestsBucket)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, err := manifests.Put(ctx, mkey, mdata); err != nil {
+			t.Fatal(err)
+		}
+		stale, err := delivery.EncodeModule(delivery.Module{Repository: "novox/mesh-catalog", Commit: "89abcdef0123456789abcdef0123456789abcdef", Path: "modules/avahi",
+			Manifest: digest, None2: "the manifest cannot be read: claims node-build-go, which is a seat in the mesh's own namespace that it does not define",
+			Inputs2: &delivery.KeptInputs2{Tree: "tree-avahi", Locks: map[string]string{"go.sum": goSum}}})
+		if err != nil {
+			t.Fatal(err)
+		}
+		held, err := js.KeyValue(ctx, delivery.ModulesBucket)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, err := held.Put(ctx, "avahi", stale); err != nil {
+			t.Fatal(err)
+		}
+		kv, err := js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: delivery.ToolchainsBucket("mesh-build-go"), History: 1})
+		if err != nil {
+			t.Fatal(err)
+		}
+		key, err := delivery.ToolchainKey("n1", "go")
+		if err != nil {
+			t.Fatal(err)
+		}
+		value, err := delivery.EncodeToolchain(delivery.Toolchain{Language: "go", Version: "go1.27.1", Recipe: "1", At: time.Now()})
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, err := kv.Put(ctx, key, value); err != nil {
+			t.Fatal(err)
+		}
+	})
+	var got delivery.Module
+	for deadline := time.Now().Add(5 * time.Second); time.Now().Before(deadline); time.Sleep(50 * time.Millisecond) {
+		if e, err := modules.Get(ctx, "avahi"); err == nil {
+			if m, err := delivery.DecodeModule(e.Value()); err == nil {
+				if got = m; got.FP2 != "" {
+					break
+				}
+			}
+		}
+	}
+	if got.FP2 == "" || got.None2 != "" {
+		t.Errorf("avahi = fp2 %q none2 %q within 5 s of the start, want a fingerprint and no reason", got.FP2, got.None2)
+	}
+}
+
+// TestIndexerCountsOnlyTheAssignedBuildNodesToolchains (issue 1940): the toolchains bucket holds the report of n2, where
+// mesh-build-go was unassigned (its assignment ended) at another version than n1's, as ace's v26.12.0 stayed beside the
+// v26.12.1 of the nodes mesh-build-node runs on. The indexer gives the merged module a fingerprint from n1's toolchain
+// alone; when the controller assigns mesh-build-go to n2 again, its report counts and the builders disagree (the guard
+// stays); when the assignment ends again, the fingerprint comes back. No restart, no timer: the assignments' watch.
+func TestIndexerCountsOnlyTheAssignedBuildNodesToolchains(t *testing.T) {
+	manifest, err := os.ReadFile("../../internal/index/testdata/catalogue-a67f0196-avahi.module.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	const goSum = "3b5028f0c1e9bde04dd766abd63eb5931bc516bae695cf46f00abcd8510b0381"
+	var assignments jetstream.KeyValue
+	js, ctx, _, modules := startIndexer(t, func(context.Context, jetstream.KeyValue) {}, func(ctx context.Context, js jetstream.JetStream) {
+		kv, err := js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: delivery.ToolchainsBucket("mesh-build-go"), History: 1})
+		if err != nil {
+			t.Fatal(err)
+		}
+		for node, version := range map[string]string{"n1": "go1.27.3", "n2": "go1.27.2"} {
+			key, _ := delivery.ToolchainKey(node, "go")
+			value, err := delivery.EncodeToolchain(delivery.Toolchain{Language: "go", Version: version, Recipe: "1", At: time.Now()})
+			if err != nil {
+				t.Fatal(err)
+			}
+			if _, err := kv.Put(ctx, key, value); err != nil {
+				t.Fatal(err)
+			}
+		}
+		// The controller's assignments mirror, in its layout (mesh-controller internal/chain Assignment).
+		if assignments, err = js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: "mesh-controller_assignments", History: 1}); err != nil {
+			t.Fatal(err)
+		}
+		for key, value := range map[string]string{
+			"n1.mesh-build-go": `{"node":"n1","module":"mesh-build-go","assigned":"2026-10-20T08:00:00Z"}`,
+			"n2.mesh-build-go": `{"node":"n2","module":"mesh-build-go","assigned":"2026-10-20T08:00:00Z","ended":"2026-10-23T08:00:00Z"}`,
+		} {
+			if _, err := assignments.Put(ctx, key, []byte(value)); err != nil {
+				t.Fatal(err)
+			}
+		}
+	})
+	data, err := delivery.EncodeForge(delivery.Forge{Kind: delivery.ForgeMerged, Repository: "novox/mesh-catalog", Branch: "feat/x", Number: 302,
+		Head: "0123456789abcdef0123456789abcdef01234567", Merge: "89abcdef0123456789abcdef0123456789abcdef", Root: "r0",
+		Trees:     map[string]string{"modules/avahi": "newtree"},
+		Manifests: map[string]string{"modules/avahi": string(manifest)},
+		Locks:     map[string]map[string]string{"modules/avahi": {"go.sum": goSum}}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := js.Publish(ctx, "mesh.stream.mesh-delivery-forge-bridge.event.forge.novox.mesh-catalog.merged", data); err != nil {
+		t.Fatal(err)
+	}
+	read := func(ok func(delivery.Module) bool) delivery.Module {
+		var got delivery.Module
+		for deadline := time.Now().Add(5 * time.Second); time.Now().Before(deadline); time.Sleep(50 * time.Millisecond) {
+			if e, err := modules.Get(ctx, "avahi"); err == nil {
+				if m, err := delivery.DecodeModule(e.Value()); err == nil {
+					if got = m; ok(m) {
+						break
+					}
+				}
+			}
+		}
+		return got
+	}
+	agreed := func(m delivery.Module) bool { return m.FP2 != "" && m.Toolchains["go"].Version == "go1.27.3" }
+	if m := read(agreed); !agreed(m) {
+		t.Fatalf("within 5 s avahi has fp2 %q, none2 %q, toolchains %v: want a fingerprint of n1's go1.27.3 alone", m.FP2, m.None2, m.Toolchains)
+	}
+	if _, err := assignments.Put(ctx, "n2.mesh-build-go", []byte(`{"node":"n2","module":"mesh-build-go","assigned":"2026-10-24T08:00:00Z"}`)); err != nil {
+		t.Fatal(err)
+	}
+	disagree := func(m delivery.Module) bool {
+		return m.FP2 == "" && strings.HasPrefix(m.None2, "builders disagree: go1.27.2 recipe 1 on n2")
+	}
+	if m := read(disagree); !disagree(m) {
+		t.Fatalf("within 5 s of n2's assignment avahi has fp2 %q, none2 %q: want the builders to disagree", m.FP2, m.None2)
+	}
+	if _, err := assignments.Put(ctx, "n2.mesh-build-go", []byte(`{"node":"n2","module":"mesh-build-go","ended":"2026-10-24T09:00:00Z"}`)); err != nil {
+		t.Fatal(err)
+	}
+	if m := read(agreed); !agreed(m) {
+		t.Fatalf("within 5 s of n2's unassignment avahi has fp2 %q, none2 %q", m.FP2, m.None2)
+	}
+}

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

@@ -2,6 +2,9 @@
 // bridge's messages on the stream FORGE and keeps the candidate groups (candidates.<group>): the pull requests that share
 // a branch, their heads and the modules each touches. It reads the controller's builds to know which module a changed
 // directory is. It serves no request subject and holds no timer: every reaction is a message or a watch (ADR 0437 §8).
+//
+// Its build of 2026-10-24 00:37 named a program whose push never reached the artifact store, and a retry sends that
+// same build again; this paragraph was added only to give the indexer a new build (issue 1933).
 package main
 
 import (
@@ -288,7 +291,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	}
 	defer calls.Close()
 	ix := &index.Indexer{Store: kvStore{candidates}, Modules: kvStore{modules}, Manifests: kvStore{manifests}, Builds: known, Logf: logger.Printf,
-		Named: namedVia(calls.Call)}
+		Named: namedVia(calls.Call), Trunk: trunkVia(calls.Call), Contains: containsVia(calls.Call)}
 	// The gate's source bucket (mesh-delivery-gate_source) comes with the gate (release 3e, novox/hq ADR 0450 §1): its key
 	// main is the mesh's source revision, which stamps the modules (issue 1344). Where it does not exist yet the indexer does
 	// not wait for it (that needs a timer, ADR 0437 §8): it says so, and is started again with the gate.
@@ -310,7 +313,26 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 		}
 		go func() { sourceErrs <- follow(ctx, sw, each) }()
 	}
-	tools := newToolchainWatch(ctx, js, toolchainSink{put: ix.PutToolchain, apply: ix.ApplyToolchain, recompute: ix.Recompute}, logger)
+	// Only the toolchain reports of nodes the build module is assigned to count (issue 1940): the controller's
+	// assignments are settled first, so the toolchains settle through the gate already knowing them.
+	gate := newToolchainGate(sortedModules(), ix.PutToolchain, logger.Printf)
+	assignErrs, err := watchAssignments(ctx, js, gate, func(ctx context.Context) {
+		if err := ix.Recompute(ctx); err != nil {
+			logger.Printf("writing the modules again after an assignment of a build module changed: %v", err)
+		}
+	}, logger)
+	if err != nil {
+		return err
+	}
+	tools := newToolchainWatch(ctx, js, toolchainSink{
+		put: gate.Toolchain,
+		apply: func(ctx context.Context, module, key string, value []byte, deleted bool) error {
+			if !gate.Toolchain(module, key, value, deleted) {
+				return nil
+			}
+			return ix.Recompute(ctx)
+		},
+		recompute: ix.Recompute}, logger)
 	if err := tools.start(); err != nil {
 		return err
 	}
@@ -325,6 +347,10 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	if err := ix.RecomputeAtStart(ctx); err != nil {
 		logger.Printf("computing the new-form fingerprints at start: %v", err)
 	}
+	// The modules the trunk no longer holds go from the bucket (issue 1900); a merge does the same from its own message.
+	if err := ix.Reconcile(ctx); err != nil {
+		logger.Printf("dropping the modules the trunk does not hold at start: %v", err)
+	}
 	// A build module says each time it wrote its toolchains key: its stream, and the indexer's durable consumer on it, are
 	// made by the controller as the forge's are. Where the stream is not there yet the indexer says so and is started again
 	// with the build module, as with the gate's source.
@@ -370,6 +396,8 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 		return err
 	case err := <-sourceErrs:
 		return err
+	case err := <-assignErrs:
+		return err
 	case err := <-tools.errs:
 		return err
 	case err := <-previews.errs:

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/named.go

@@ -46,3 +46,50 @@ func namedVia(call toolCaller) func(ctx context.Context, repository, sha string,
 		return a.Paths, nil
 	}
 }
+
+// trunkVia asks the forge for the module directories of a commit (issue 1900): the keys of the `trees` the same tool
+// answers without paths, one per directory that holds a module.json (the root as ""; the tool lists no other).
+func trunkVia(call toolCaller) func(ctx context.Context, repository, sha string) ([]string, error) {
+	return func(_ context.Context, repository, sha string) ([]string, error) {
+		owner, repo, ok := strings.Cut(delivery.RepositoryName(repository), "/")
+		if !ok {
+			return nil, fmt.Errorf("%q is not <owner>/<name>", repository)
+		}
+		raw, err := call(commitTreesTool, map[string]any{"owner": owner, "repo": repo, "sha": sha})
+		if err != nil {
+			return nil, err
+		}
+		var a struct {
+			Trees map[string]string `json:"trees"`
+		}
+		if err := json.Unmarshal(raw, &a); err != nil {
+			return nil, fmt.Errorf("the answer of %s is not {root, trees}: %w", commitTreesTool, err)
+		}
+		dirs := make([]string, 0, len(a.Trees))
+		for dir := range a.Trees {
+			dirs = append(dirs, dir)
+		}
+		return dirs, nil
+	}
+}
+
+// containsVia asks the forge whether a commit is in another (gitea.gitea_contains: contains is true for the same commit or an ancestor).
+func containsVia(call toolCaller) func(ctx context.Context, repository, commit, in string) (bool, error) {
+	return func(_ context.Context, repository, commit, in string) (bool, error) {
+		owner, repo, ok := strings.Cut(delivery.RepositoryName(repository), "/")
+		if !ok {
+			return false, fmt.Errorf("%q is not <owner>/<name>", repository)
+		}
+		raw, err := call("gitea.gitea_contains", map[string]any{"owner": owner, "repo": repo, "commit": commit, "in": in})
+		if err != nil {
+			return false, err
+		}
+		var a struct {
+			Contains *bool `json:"contains"`
+		}
+		if err := json.Unmarshal(raw, &a); err != nil || a.Contains == nil {
+			return false, fmt.Errorf("the answer of gitea.gitea_contains names no contains: %v", err)
+		}
+		return *a.Contains, nil
+	}
+}

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/named_test.go

@@ -3,6 +3,8 @@ package main
 import (
 	"context"
 	"encoding/json"
+	"slices"
+	"strings"
 	"testing"
 )
 
@@ -29,3 +31,22 @@ func TestNamedViaAsksTheTreesToolWithThePathsAndTakesTheirObjects(t *testing.T)
 		t.Error("an answer missing a path asked was taken")
 	}
 }
+
+func TestTheTrunkIsTheDirectoriesTheForgeListsTrees(t *testing.T) { // 1900/AC3
+	var gotArgs any
+	call := func(key string, body any) (json.RawMessage, error) {
+		gotArgs = body
+		return json.RawMessage(`{"root":"r","trees":{"modules/a":"x","modules/b":"y"}}`), nil
+	}
+	dirs, err := trunkVia(call)(context.Background(), "novox/mesh-catalog", strings.Repeat("a", 40))
+	if err != nil {
+		t.Fatal(err)
+	}
+	slices.Sort(dirs)
+	if !slices.Equal(dirs, []string{"modules/a", "modules/b"}) {
+		t.Errorf("dirs = %v", dirs)
+	}
+	if _, has := gotArgs.(map[string]any)["paths"]; has {
+		t.Error("the trunk asked for paths")
+	}
+}

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/standing.go

@@ -0,0 +1,174 @@
+package main
+
+// This file is the same in mesh-delivery-indexer, mesh-delivery-builder and mesh-delivery-checker (issue 1940): it moves
+// to mesh-sdk go/delivery/buildrun once mesh-sdk can be delivered again, since a change of mesh-sdk waits on the very
+// toolchain agreement this file repairs.
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"maps"
+	"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/provider"
+)
+
+// A build module writes <node>.<language> of its toolchains state on every node it runs on, and nothing deletes the key
+// when the module is unassigned from a node: the controller writes no module's state, and the module is gone. A report of
+// a node the build module no longer runs on is therefore not a builder (issue 1940: mesh-build-node unassigned from 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
+// buildrun.ToolchainSet): an entry is passed on only while the controller's assignments (mesh-controller_assignments,
+// key <node>.<module>) hold an open assignment of its build module on its node; it is passed on as deleted otherwise,
+// and passed on again when the module is assigned there again. Until the assignments are settled (or where they cannot
+// be read) every entry is passed on, as before. Builders that run and report different versions still disagree: that
+// refusal is the guard of novox/hq ADR 0465, and it stays.
+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)
+	known    bool                         // the assignments are settled
+	standing map[string]bool              // <node>.<module> with an open assignment
+	raw      map[string]map[string][]byte // module -> toolchains key -> value, as the bucket holds it
+	left     map[string]bool              // <module>/<key> said as left out, so it is said once
+}
+
+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, standing: map[string]bool{},
+		raw: map[string]map[string][]byte{}, left: map[string]bool{}}
+	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)
+}
+
+// Assignment takes one change of the controller's assignments in and answers whether what it passed on changed.
+func (g *toolchainGate) Assignment(key string, value []byte, deleted bool) bool {
+	node, module, ok := strings.Cut(key, ".")
+	if !ok || !g.modules[module] {
+		return false
+	}
+	open := !deleted && openAssignment(value)
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	if g.standing[key] == open {
+		return false
+	}
+	if open {
+		g.standing[key] = true
+	} else {
+		delete(g.standing, key)
+	}
+	if !g.known {
+		return false
+	}
+	changed := false
+	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
+}
+
+// Settled says the assignments are read: from now on only the reports of assigned nodes pass. It answers whether what it
+// passed on changed.
+func (g *toolchainGate) Settled() bool {
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.known = true
+	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
+}
+
+// pass hands one key on as it stands: its value when its node is assigned (or the assignments are 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)
+	if err != nil || !g.known || g.standing[node+"."+module] {
+		delete(g.left, module+"/"+key)
+		return g.forward(module, key, value, false)
+	}
+	if !g.left[module+"/"+key] {
+		g.left[module+"/"+key] = true
+		g.logf("%s.%s is left out of the agreed toolchain: %s has no assignment on %s, so it is no builder (issue 1940)",
+			delivery.ToolchainsBucket(module), key, module, node)
+	}
+	return g.forward(module, key, nil, true)
+}
+
+// openAssignment is whether a value of the controller's assignments holds an assignment that stands: one that has not
+// ended and has no state (a pending one is not on the machine yet; mesh-controller internal/chain Assignment).
+func openAssignment(value []byte) bool {
+	var a struct {
+		Ended time.Time `json:"ended"`
+		State string    `json:"state"`
+	}
+	if json.Unmarshal(value, &a) != nil {
+		return false
+	}
+	return a.Ended.IsZero() && a.State == ""
+}
+
+// watchAssignments settles the controller's assignments into the gate, says them settled, and follows them; changed is
+// told whenever what the gate passes on changed. Where the bucket cannot be read (not there, or this module may not read
+// it) it says so and the gate passes every report on, as before; an error of the watch after that ends on the channel.
+func watchAssignments(ctx context.Context, js bucketOpener, gate *toolchainGate, changed func(context.Context), logger *log.Logger) (<-chan error, error) {
+	errs := make(chan error, 1)
+	kv, err := js.KeyValue(ctx, provider.AssignmentsBucket)
+	if err != nil {
+		// Not fatal: an indexer, builder or checker that stops for it stops every delivery (a grant comes with a delivery).
+		logger.Printf("the bucket %s cannot be read, so every node's toolchain report counts, an unassigned build node's too (issue 1940): %v", provider.AssignmentsBucket, err)
+		return errs, nil
+	}
+	each := func(e jetstream.KeyValueEntry) { gate.Assignment(e.Key(), e.Value(), !opOf(e)) }
+	w, err := settle(ctx, kv, each)
+	if err != nil {
+		return nil, fmt.Errorf("the bucket %s: %w", provider.AssignmentsBucket, err)
+	}
+	if gate.Settled() {
+		changed(ctx)
+	}
+	go func() {
+		errs <- follow(ctx, w, func(e jetstream.KeyValueEntry) {
+			if gate.Assignment(e.Key(), e.Value(), !opOf(e)) {
+				changed(ctx)
+			}
+		})
+	}()
+	return errs, nil
+}

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/standing_test.go

@@ -0,0 +1,112 @@
+package main
+
+// The same in mesh-delivery-indexer, mesh-delivery-builder and mesh-delivery-checker, as standing.go is (issue 1940).
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/delivery/buildrun"
+)
+
+func gateReport(t *testing.T, node, version string) (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: time.Unix(0, 0).UTC()})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return key, value
+}
+
+func agreedOf(set *buildrun.ToolchainSet) (string, string) {
+	tc, none := delivery.AgreedToolchain(set.Entries("typescript"))
+	return tc.Version, none
+}
+
+// The live case of issue 1940: mesh-build-node was unassigned from ace, whose report stayed at v26.12.0 while the
+// three nodes it runs on report v26.12.1. Without the assignments every report counts (and they disagree); with them
+// ace's is left out and the three agree; assigned to ace again, its report counts again and the guard refuses again.
+func TestAnUnassignedBuildNodesReportIsNoBuilder(t *testing.T) {
+	set := &buildrun.ToolchainSet{}
+	var said []string
+	gate := newToolchainGate([]string{buildrun.GoBuildModule, buildrun.NodeBuildModule}, set.Put, func(f string, a ...any) { said = append(said, f) })
+	for node, version := range map[string]string{"ace": "v26.12.0", "g14": "v26.12.1", "novox": "v26.12.1", "shanks": "v26.12.1"} {
+		key, value := gateReport(t, node, version)
+		gate.Toolchain(buildrun.NodeBuildModule, key, value, false)
+	}
+	if _, none := agreedOf(set); !strings.HasPrefix(none, "builders disagree") {
+		t.Fatalf("before the assignments are read every report counts, so they disagree; got %q", none)
+	}
+	for _, node := range []string{"g14", "novox", "shanks"} {
+		gate.Assignment(node+"."+buildrun.NodeBuildModule, []byte(`{"node":"`+node+`","module":"mesh-build-node"}`), false)
+	}
+	gate.Assignment("ace.mesh-build-node", []byte(`{"node":"ace","module":"mesh-build-node","ended":"2026-10-23T08:00:00Z"}`), false)
+	gate.Assignment("ace.mesh-build-go", []byte(`{"node":"ace","module":"mesh-build-go"}`), false) // another module's: no matter
+	if !gate.Settled() {
+		t.Fatal("settling the assignments left ace's report out, so what was passed on changed")
+	}
+	if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+		t.Fatalf("the assigned nodes agree on v26.12.1; got %q, %q", v, none)
+	}
+	if len(said) != 1 {
+		t.Fatalf("ace's report is said left out once; said %v", said)
+	}
+	// ace reports again while unassigned (an old value seen again): still left out.
+	key, value := gateReport(t, "ace", "v26.12.0")
+	if gate.Toolchain(buildrun.NodeBuildModule, key, value, false) {
+		t.Fatal("an unassigned node's report changed what was passed on")
+	}
+	// Assigned to ace again: its report counts, and the builders really disagree: the guard stays.
+	if !gate.Assignment("ace.mesh-build-node", []byte(`{"node":"ace","module":"mesh-build-node"}`), false) {
+		t.Fatal("assigning ace again passed nothing on")
+	}
+	if _, none := agreedOf(set); !strings.HasPrefix(none, "builders disagree: v26.12.0 recipe f59571cf4be75adf on ace") {
+		t.Fatalf("builders that run different versions still disagree; got %q", none)
+	}
+	// The assignment's key deleted, or a pending one written: no assignment stands, and ace's report goes again.
+	if !gate.Assignment("ace.mesh-build-node", []byte(`{"node":"ace","module":"mesh-build-node","state":"pending"}`), false) {
+		t.Fatal("a pending assignment is no assignment on the machine")
+	}
+	if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+		t.Fatalf("got %q, %q", v, none)
+	}
+	gate.Assignment("ace.mesh-build-node", nil, true)
+	if v, _ := agreedOf(set); v != "v26.12.1" {
+		t.Fatalf("got %q", v)
+	}
+	// A report deleted from the bucket goes whether its node is assigned or not.
+	key, _ = gateReport(t, "g14", "v26.12.1")
+	if !gate.Toolchain(buildrun.NodeBuildModule, key, nil, true) {
+		t.Fatal("deleting g14's report passed nothing on")
+	}
+	if n := len(set.Entries("typescript")); n != 2 {
+		t.Fatalf("novox and shanks are left; got %d entries", n)
+	}
+}
+
+// A newly assigned build node that has not reported yet changes nothing; its report counts as it comes.
+func TestANewlyAssignedNodeCountsFromItsReport(t *testing.T) {
+	set := &buildrun.ToolchainSet{}
+	gate := newToolchainGate([]string{buildrun.NodeBuildModule}, set.Put, func(string, ...any) {})
+	gate.Settled()
+	if gate.Assignment("g14.mesh-build-node", []byte(`{}`), false) {
+		t.Fatal("an assignment with no report passed something on")
+	}
+	key, value := gateReport(t, "g14", "v26.12.1")
+	if !gate.Toolchain(buildrun.NodeBuildModule, key, value, false) {
+		t.Fatal("an assigned node's report was not passed on")
+	}
+	key, value = gateReport(t, "ace", "v26.12.0")
+	if gate.Toolchain(buildrun.NodeBuildModule, key, value, false) {
+		t.Fatal("a report of a node with no assignment key was passed on after the assignments settled")
+	}
+	if v, none := agreedOf(set); v != "v26.12.1" || none != "" {
+		t.Fatalf("got %q, %q", v, none)
+	}
+}

modules/mesh-delivery-indexer/internal/index/candidates.go

@@ -52,7 +52,10 @@ type Indexer struct {
 	// manifest's paths (ADR 0495 clause 1, the lead's decision L8 of R4e). Nil asks nothing, and a module naming paths
 	// has none.
 	Named func(ctx context.Context, repository, sha string, paths map[string][]string) (map[string]map[string]string, error)
-	Logf  func(format string, args ...any)
+	Trunk func(ctx context.Context, repository, sha string) ([]string, error)
+	// Contains says whether a commit is the second or an ancestor of it (gitea.gitea_contains).
+	Contains func(ctx context.Context, repository, commit, in string) (bool, error)
+	Logf     func(format string, args ...any)
 
 	mu         sync.Mutex // guards source, toolchains and previews, which the watches and the forge messages all reach
 	source     sourceNow

modules/mesh-delivery-indexer/internal/index/inputs.go

@@ -69,7 +69,7 @@ func inputsOf(module, raw, tree string, locks map[string]string, base baseFP) mo
 func inputsOfNamed(module, raw, tree string, locks, objects map[string]string, base baseFP) moduleInputs {
 	m, err := catalogue.ParseManifestForInputs([]byte(raw))
 	if err != nil {
-		return moduleInputs{None2: "the manifest cannot be read: " + err.Error()}
+		return moduleInputs{None2: None2Unreadable + err.Error()}
 	}
 	if m.Module != module {
 		return moduleInputs{None2: fmt.Sprintf("the manifest is of module %q, not %q", m.Module, module)}

modules/mesh-delivery-indexer/internal/index/inputs_test.go

@@ -111,7 +111,8 @@ func TestABaseEntersByTheFingerprintOfItsModuleOrNamesItsAbsence(t *testing.T) {
 	}
 	// Through the indexer: modules.mesh-tools holds a fingerprint of the new form (a record written by a later release).
 	ix, mods, _ := manifestsIndexer(t, rec(t, "build-1", "avahi", catalogueRepo, "modules/avahi", "main", "", "2026-10-19T09:00:00Z", aInputs))
-	mods.put("mesh-tools", mustEncode(t, delivery.Module{Repository: catalogueRepo, Commit: merge, None: "x", FP2: fp, Manifest: strings.Repeat("a", 64)}))
+	mods.put("mesh-tools", mustEncode(t, delivery.Module{Repository: "novox/mesh-tools", // a base held of another repository stays when the catalogue merges (issue 1900)
+		Commit: merge, None: "x", FP2: fp, Manifest: strings.Repeat("a", 64)}))
 	f := withManifests(mergedMsg(catalogueRepo, map[string]string{"modules/avahi": "t"}), map[string]string{"modules/avahi": aModuleWithABase(t)}, nil)
 	if err := ix.Apply(context.Background(), f); err != nil {
 		t.Fatal(err)

modules/mesh-delivery-indexer/internal/index/modules.go

@@ -2,8 +2,10 @@ package index
 
 import (
 	"context"
+	"fmt"
 	"maps"
 	"slices"
+	"strings"
 
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
@@ -33,18 +35,22 @@ func (ix *Indexer) applyMerged(ctx context.Context, f delivery.Forge) error {
 	objects, namedErr := ix.namedObjects(ctx, f)
 	overlay := map[string]delivery.Module{}
 	dirOf := map[string]string{}
+	named, every := map[string]bool{}, true // every module the message's manifests name, and whether each names one
 	for _, dir := range slices.Sorted(maps.Keys(f.Manifests)) {
 		raw := f.Manifests[dir]
 		name := manifestModule(raw)
 		if name == "" {
 			ix.logf("%s at %s: the manifest in %q names no module, so no module is written for it", f.Repository, f.Merge, dir)
+			every = false
 			continue
 		}
 		key, err := delivery.ModulesKey(name)
 		if err != nil {
+			every = false
 			ix.logf("%s: the module %q has no usable key, skipped: %v", f.Repository, name, err)
 			continue
 		}
+		named[key] = true
 		cur, has := held[key]
 		if has && cur.Repository != "" && !delivery.SameRepository(cur.Repository, f.Repository) {
 			ix.logf("%s at %s: %q names the module %s, which the indexer holds of %s; left as it is (a move between repositories is the operator's)", f.Repository, f.Merge, dir, name, cur.Repository)
@@ -64,12 +70,24 @@ func (ix *Indexer) applyMerged(ctx context.Context, f delivery.Forge) error {
 		} else {
 			in := inputsOfNamed(name, raw, f.Trees[dir], f.Locks[dir], objects[dir], ix.baseFP(ctx))
 			next.Inputs2, next.None2, next.ArtifactPaths = in.Kept, in.None2, in.ArtifactPaths
+			if in.Kept == nil && strings.HasPrefix(in.None2, None2Unreadable) {
+				// The manifest cannot be read by this SDK; the inputs the merge carried are kept all the same, so a later SDK
+				// that reads it judges the module again at start with no merge (issue 1923).
+				next.Inputs2 = unreadInputs(f.Trees[dir], f.Locks[dir], f.Paths[dir])
+			}
 			if in.Kept == nil && namedErr[dir] != "" {
 				next.None2 = in.None2 + ": the forge could not say them: " + namedErr[dir]
 			}
 		}
 		overlay[key] = next
 	}
+	// A module of this repository the merge commit holds no module.json for is gone from the trunk, and so is its key
+	// (issue 1900). A message that carries no manifests (an older writer) or one that cannot be read whole says nothing.
+	if len(f.Manifests) > 0 && every {
+		if err := ix.dropRemoved(ctx, f.Repository, held, func(key string, _ delivery.Module) bool { return named[key] }); err != nil {
+			return err
+		}
+	}
 	// What this merge moved reaches the modules standing on it (a base's tree, build-agent's fingerprint), in the graph's order.
 	return ix.recomputeWith(ctx, overlay)
 }
@@ -149,3 +167,115 @@ func (ix *Indexer) namedObjects(ctx context.Context, f delivery.Forge) (map[stri
 	}
 	return objects, nil
 }
+
+// dropRemoved deletes, from the modules the bucket holds of the repository, each one the trunk no longer holds (issue 1900):
+// held(key, module) says whether the trunk holds it. A module of another repository, or of none known, is never touched.
+func (ix *Indexer) dropRemoved(ctx context.Context, repository string, held map[string]delivery.Module, trunkHolds func(key string, m delivery.Module) bool) error {
+	for _, key := range slices.Sorted(maps.Keys(held)) {
+		cur := held[key]
+		if cur.Repository == "" || !delivery.SameRepository(cur.Repository, repository) || trunkHolds(key, cur) {
+			continue
+		}
+		err := write(ctx, ix.Modules, key, func(value []byte, found bool) ([]byte, bool, error) {
+			if !found {
+				return nil, false, nil
+			}
+			if m, err := delivery.DecodeModule(value); err != nil || !delivery.SameRepository(m.Repository, repository) {
+				return nil, false, nil
+			}
+			return nil, true, nil
+		})
+		if err != nil {
+			return fmt.Errorf("modules.%s: %w", key, err)
+		}
+		ix.logf("modules.%s deleted: %s holds no module of that name at its trunk (issue 1900)", key, repository)
+	}
+	return nil
+}
+
+// Reconcile deletes the modules keys whose module the trunk does not hold, for each repository the latest source names a
+// head of: the module directories at that head are asked of the forge (Trunk), and a module of the repository whose
+// directory is not among them goes (issue 1900). It is run at the indexer's start; a merge does the same from its own
+// message (applyMerged). A repository whose trunk cannot be read, or reads as holding no module at all, is left as it is
+// and said: a failure never empties the bucket.
+func (ix *Indexer) Reconcile(ctx context.Context) error {
+	if ix.Modules == nil || ix.Trunk == nil {
+		return nil
+	}
+	ix.mu.Lock()
+	heads := maps.Clone(ix.source.heads)
+	ix.mu.Unlock()
+	held, err := ix.heldModules(ctx)
+	if err != nil {
+		return err
+	}
+	for _, repository := range slices.Sorted(maps.Keys(heads)) {
+		mine := map[string]delivery.Module{}
+		for key, m := range held {
+			if m.Repository != "" && delivery.SameRepository(m.Repository, repository) {
+				mine[key] = m
+			}
+		}
+		if len(mine) == 0 {
+			continue
+		}
+		dirs, err := ix.Trunk(ctx, repository, heads[repository])
+		if err != nil {
+			ix.logf("%s at %s: the modules of the trunk cannot be read, so none is dropped: %v", repository, heads[repository], err)
+			continue
+		}
+		if len(dirs) == 0 {
+			ix.logf("%s at %s: the trunk reads as holding no module, so none is dropped", repository, heads[repository])
+			continue
+		}
+		there := map[string]bool{}
+		for _, d := range dirs {
+			there[pathOf(strings.Trim(d, "/"))] = true
+		}
+		head := heads[repository]
+		// The source can lag a merge already applied: a key written at a commit the head read does not hold (a merge heard
+		// first) is not read as removed, only one whose commit the head is, or contains.
+		stays := func(_ string, m delivery.Module) bool {
+			if m.Path == "" || there[m.Path] {
+				return true
+			}
+			if m.Commit == head {
+				return false
+			}
+			if m.Commit == "" || ix.Contains == nil {
+				return true
+			}
+			in, err := ix.Contains(ctx, repository, m.Commit, head)
+			if err != nil {
+				ix.logf("%s: whether %s is in %s cannot be read, so the module at %s is kept: %v", repository, m.Commit, head, m.Path, err)
+				return true
+			}
+			return !in
+		}
+		if err := ix.dropRemoved(ctx, repository, mine, stays); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// None2Unreadable begins the reason of a module whose manifest the running SDK cannot read.
+const None2Unreadable = "the manifest cannot be read: "
+
+// unreadInputs are the inputs a merge carried for a module whose manifest cannot be read: the directory's tree, the lock
+// hashes by file name (the artifacts that own them are not known without the manifest) and the objects of the named
+// paths the message carried; nil when the message carried no tree. Judging the manifest again (rejudged) turns them into
+// the inputs of the module (issue 1923).
+func unreadInputs(tree string, locks, paths map[string]string) *delivery.KeptInputs2 {
+	if tree == "" {
+		return nil
+	}
+	in := &delivery.KeptInputs2{Tree: tree}
+	if len(locks) > 0 {
+		in.Locks = maps.Clone(locks)
+	}
+	if len(paths) > 0 {
+		in.Paths = maps.Clone(paths)
+	}
+	return in
+}

modules/mesh-delivery-indexer/internal/index/remove_test.go

@@ -0,0 +1,144 @@
+package index
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+func twoModules(t *testing.T) (*Indexer, *memStore) {
+	t.Helper()
+	ix, mods := modulesIndexer(t)
+	if err := ix.Apply(context.Background(), mergedMsg(catalogueRepo, map[string]string{"modules/a": "t", "modules/b": "t"})); err != nil {
+		t.Fatal(err)
+	}
+	for _, k := range []string{"a", "b"} {
+		if _, ok := mods.vals[k]; !ok {
+			t.Fatalf("setup: modules.%s not written", k)
+		}
+	}
+	return ix, mods
+}
+
+func TestAMergeThatRemovesAModuleDeletesItsKey(t *testing.T) { // 1900/AC1
+	ix, mods := twoModules(t)
+	if err := ix.Apply(context.Background(), mergedMsg(catalogueRepo, map[string]string{"modules/a": "t2"})); err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := mods.vals["b"]; ok {
+		t.Error("modules.b is still held after a merge whose trunk has no module b")
+	}
+	if _, ok := mods.vals["a"]; !ok {
+		t.Error("modules.a, which the trunk still holds, was deleted")
+	}
+}
+
+func TestAMergeLeavesTheModulesOfAnotherRepository(t *testing.T) { // 1900/AC1 (scope)
+	ix, mods := twoModules(t)
+	if err := ix.Apply(context.Background(), mergedMsg("novox/mesh-delivery", map[string]string{"modules/c": "t"})); err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := mods.vals["a"]; !ok {
+		t.Error("a merge of another repository deleted modules.a")
+	}
+	if _, ok := mods.vals["b"]; !ok {
+		t.Error("a merge of another repository deleted modules.b")
+	}
+}
+
+func TestAMergeWithoutManifestsDeletesNothing(t *testing.T) { // 1900/AC1: older writers send none, which does not say the trunk is empty
+	ix, mods := twoModules(t)
+	f := mergedMsg(catalogueRepo, map[string]string{"modules/a": "t2"})
+	f.Manifests = nil
+	if err := ix.Apply(context.Background(), f); err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := mods.vals["b"]; !ok {
+		t.Error("a merge message with no manifests deleted modules.b")
+	}
+}
+
+func TestAPathWithoutAModuleJSONIsNeverAModule(t *testing.T) { // 1900/AC2: testdata such as fixture-build
+	ix, mods := twoModules(t)
+	f := mergedMsg(catalogueRepo, map[string]string{"modules/a": "t2"})
+	f.Trees["testdata/fixture-build"] = "t" // a directory in the tree whose module.json the message does not carry
+	if err := ix.Apply(context.Background(), f); err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := mods.vals["fixture-build"]; ok {
+		t.Error("modules.fixture-build written for a path without a module.json")
+	}
+}
+
+func TestStartingDeletesTheKeysTheTrunkDoesNotHold(t *testing.T) { // 1900/AC3
+	ix, mods := twoModules(t)
+	ctx := context.Background()
+	if err := ix.ApplySource(ctx, 3, sourceOf(catalogueRepo, merge)); err != nil {
+		t.Fatal(err)
+	}
+	var asked string
+	ix.Trunk = func(_ context.Context, repository, sha string) ([]string, error) {
+		asked = repository + "@" + sha
+		return []string{"modules/a"}, nil
+	}
+	ix.Contains = func(context.Context, string, string, string) (bool, error) { return true, nil }
+	if err := ix.Reconcile(ctx); err != nil {
+		t.Fatal(err)
+	}
+	if asked != catalogueRepo+"@"+merge {
+		t.Errorf("the trunk was asked as %q, want the source's head of the repository", asked)
+	}
+	if _, ok := mods.vals["b"]; ok {
+		t.Error("modules.b is still held though the trunk holds no module at modules/b")
+	}
+	if _, ok := mods.vals["a"]; !ok {
+		t.Error("modules.a was deleted")
+	}
+}
+
+func TestStartingDeletesNothingWhenTheTrunkCannotBeRead(t *testing.T) { // 1900/AC3: failure is loud, never a mass delete
+	ix, mods := twoModules(t)
+	ctx := context.Background()
+	if err := ix.ApplySource(ctx, 3, sourceOf(catalogueRepo, merge)); err != nil {
+		t.Fatal(err)
+	}
+	for name, trunk := range map[string]func(context.Context, string, string) ([]string, error){
+		"an error":         func(context.Context, string, string) ([]string, error) { return nil, errors.New("forge down") },
+		"no module at all": func(context.Context, string, string) ([]string, error) { return nil, nil },
+	} {
+		ix.Trunk = trunk
+		_ = ix.Reconcile(ctx)
+		if len(mods.vals) != 2 {
+			t.Errorf("%s: %d keys held, want 2 untouched", name, len(mods.vals))
+		}
+	}
+	_ = delivery.RootPath
+}
+
+func TestAKeyWrittenAheadOfTheSourceHeadStaysAndOneWithoutAPathIsSkipped(t *testing.T) { // 1900/AC3 (review): the source lags a merge already applied
+	ix, mods := twoModules(t) // written at the merge commit C
+	ctx := context.Background()
+	const older = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"
+	if err := ix.ApplySource(ctx, 3, sourceOf(catalogueRepo, older)); err != nil {
+		t.Fatal(err)
+	}
+	mods.put("nopath", mustEncode(t, delivery.Module{Repository: catalogueRepo, Commit: older, None2: "x", Manifest: strings.Repeat("a", 64)}))
+	ix.Trunk = func(context.Context, string, string) ([]string, error) { return []string{"modules/a"}, nil }
+	ix.Contains = func(_ context.Context, _, commit, in string) (bool, error) { return commit == in, nil } // C is not in B
+	if err := ix.Reconcile(ctx); err != nil {
+		t.Fatal(err)
+	}
+	for _, k := range []string{"a", "b", "nopath"} {
+		if _, ok := mods.vals[k]; !ok {
+			t.Errorf("modules.%s was deleted", k)
+		}
+	}
+	ix.Contains = func(context.Context, string, string, string) (bool, error) { return false, errors.New("forge down") }
+	_ = ix.Reconcile(ctx)
+	if _, ok := mods.vals["b"]; !ok {
+		t.Error("modules.b deleted though whether its commit is in the head cannot be read")
+	}
+}

modules/mesh-delivery-indexer/internal/index/stale_none2_test.go

@@ -0,0 +1,77 @@
+package index
+
+import (
+	"context"
+	"strings"
+	"testing"
+)
+
+// unreadableAvahi is avahi's manifest with a field the running parser refuses: the shape of a manifest an older SDK could
+// not read.
+func unreadableAvahi(t *testing.T) string {
+	t.Helper()
+	raw := strings.Replace(catalogueManifest(t, "avahi"), `"version": "1",`, `"version": "1", "scope": "everything",`, 1)
+	if raw == catalogueManifest(t, "avahi") {
+		t.Fatal("the fixture has no version line")
+	}
+	return raw
+}
+
+func TestAMergeOfAnUnreadableManifestKeepsTheInputsBesideTheReason(t *testing.T) { // 1923/AC1
+	_, mods := newFormIndexer(t, mod{"avahi", unreadableAvahi(t)})
+	m, ok := moduleOf(t, mods, "avahi")
+	if !ok || !strings.HasPrefix(m.None2, "the manifest cannot be read: ") || m.FP2 != "" {
+		t.Fatalf("module = %+v, want the reason 'the manifest cannot be read' and no fingerprint", m)
+	}
+	if m.Inputs2 == nil || m.Inputs2.Tree != "tree-avahi" || m.Inputs2.Locks["go.sum"] != avahiGoSum {
+		t.Errorf("inputs = %+v, want the directory's tree and its lock hashes kept", m.Inputs2)
+	}
+}
+
+func TestAStaleUnreadableVerdictIsJudgedAgainAtStartAndAnotherReasonIsLeft(t *testing.T) { // 1923/AC2
+	ctx := context.Background()
+	// The fingerprint a merge of the readable manifest gives.
+	ixGood, good := newFormIndexer(t, mod{"avahi", catalogueManifest(t, "avahi")})
+	reportToolchain(t, ixGood, "mesh-build-go", "novox", "go", "go1.27.1")
+	reportToolchain(t, ixGood, "mesh-build-go", "ace", "go", "go1.27.1")
+	want, _ := moduleOf(t, good, "avahi")
+	if want.FP2 == "" {
+		t.Fatalf("the readable manifest gives no fingerprint: %+v", want)
+	}
+
+	// The same module as an older SDK wrote it: the reason, the inputs kept at the merge, the manifest stored by digest.
+	ix, mods := newFormIndexer(t, mod{"avahi", unreadableAvahi(t)})
+	reportToolchain(t, ix, "mesh-build-go", "novox", "go", "go1.27.1")
+	reportToolchain(t, ix, "mesh-build-go", "ace", "go", "go1.27.1")
+	stale, _ := moduleOf(t, mods, "avahi")
+	stale.Manifest = want.Manifest
+	ix.Manifests.(*memStore).put(want.Manifest, good2(t, ixGood, want.Manifest))
+	mods.put("avahi", mustEncode(t, stale))
+	if err := ix.Recompute(ctx); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := moduleOf(t, mods, "avahi")
+	if got.FP2 != want.FP2 || got.None2 != "" {
+		t.Errorf("after the start: fp2 %q none2 %q, want %q and no reason", got.FP2, got.None2, want.FP2)
+	}
+
+	// A manifest still unreadable keeps its value as it was.
+	ix2, mods2 := newFormIndexer(t, mod{"avahi", unreadableAvahi(t)})
+	before := string(mods2.vals["avahi"])
+	if err := ix2.Recompute(ctx); err != nil {
+		t.Fatal(err)
+	}
+	if after := string(mods2.vals["avahi"]); after != before {
+		t.Errorf("a manifest still unreadable changed the value:\n%s\n%s", before, after)
+	}
+}
+
+// good2 is the stored manifest value of the digest in the indexer that merged the readable manifest.
+func good2(t *testing.T, ix *Indexer, digest string) []byte {
+	t.Helper()
+	v, _, found, err := ix.Manifests.Get(context.Background(), digest)
+	if err != nil || !found {
+		t.Fatalf("manifests.%s: %v %v", digest, found, err)
+	}
+	return v
+}

modules/mesh-delivery-indexer/internal/index/toolchains.go

@@ -156,6 +156,7 @@ func (ix *Indexer) recomputeModules(ctx context.Context, overlay map[string]deli
 	}
 	slices.Sort(keys)
 	held := map[string]delivery.Module{}
+	stale := map[string]bool{} // values an SDK that could not read their manifest wrote, judged again (issue 1923)
 	all := map[string]*known{}
 	for _, key := range keys {
 		cur, ok := overlay[key]
@@ -176,11 +177,15 @@ func (ix *Indexer) recomputeModules(ctx context.Context, overlay map[string]deli
 		if cur.Manifest == "" || cur.Inputs2 == nil {
 			continue
 		}
-		m, err := ix.manifestOf(ctx, cur.Manifest)
+		raw, m, err := ix.manifestRaw(ctx, cur.Manifest)
 		if err != nil {
 			ix.logf("modules.%s: its manifest %s cannot be read, left: %v", key, cur.Manifest, err)
 			continue
 		}
+		if again, ok := ix.rejudged(ctx, m, cur, raw); ok {
+			cur, stale[key] = again, true
+			held[key] = cur
+		}
 		all[key] = &known{key: key, cur: cur, languages: languagesOf(m), bases: basesOf(m), contexts: hasContext(m)}
 	}
 	tools := ix.agreed()
@@ -275,10 +280,10 @@ func (ix *Indexer) recomputeModules(ctx context.Context, overlay map[string]deli
 			finals[key] = final
 			continue
 		}
-		if k.cur.FP2 == r.fp && k.cur.None2 == r.none && reflect.DeepEqual(k.cur.Toolchains, r.tcs) {
+		if !stale[key] && k.cur.FP2 == r.fp && k.cur.None2 == r.none && reflect.DeepEqual(k.cur.Toolchains, r.tcs) {
 			continue
 		}
-		digest, inputs := k.cur.Manifest, k.cur.Inputs2
+		digest, inputs, paths := k.cur.Manifest, k.cur.Inputs2, k.cur.ArtifactPaths
 		err := write(ctx, ix.Modules, key, func(value []byte, found bool) ([]byte, bool, error) {
 			if !found {
 				return nil, false, nil
@@ -291,7 +296,7 @@ func (ix *Indexer) recomputeModules(ctx context.Context, overlay map[string]deli
 				return nil, false, nil
 			}
 			cur.FP2, cur.None2, cur.Toolchains = r.fp, r.none, r.tcs
-			cur.Inputs2 = inputs
+			cur.Inputs2, cur.ArtifactPaths = inputs, paths
 			data, err := delivery.EncodeModule(cur)
 			return data, false, err
 		})
@@ -326,24 +331,41 @@ func (ix *Indexer) writeOverlay(ctx context.Context, overlay, finals map[string]
 	return nil
 }
 
-// manifestOf is the parsed manifest manifests.<digest> holds.
-func (ix *Indexer) manifestOf(ctx context.Context, digest string) (catalogue.Manifest, error) {
+// manifestRaw is manifests.<digest>: the manifest as stored and parsed by the running SDK.
+func (ix *Indexer) manifestRaw(ctx context.Context, digest string) (string, catalogue.Manifest, error) {
 	key, err := delivery.ManifestsKey(digest)
 	if err != nil {
-		return catalogue.Manifest{}, err
+		return "", catalogue.Manifest{}, err
 	}
 	value, _, found, err := ix.Manifests.Get(ctx, key)
 	if err != nil {
-		return catalogue.Manifest{}, err
+		return "", catalogue.Manifest{}, err
 	}
 	if !found {
-		return catalogue.Manifest{}, fmt.Errorf("manifests.%s is not there", key)
+		return "", catalogue.Manifest{}, fmt.Errorf("manifests.%s is not there", key)
 	}
 	kept, err := delivery.DecodeManifest(value)
 	if err != nil {
-		return catalogue.Manifest{}, err
+		return "", catalogue.Manifest{}, err
 	}
-	return catalogue.ParseManifestForInputs([]byte(kept.JSON))
+	m, err := catalogue.ParseManifestForInputs([]byte(kept.JSON))
+	return kept.JSON, m, err
+}
+
+// rejudged is a value an SDK that could not read its manifest wrote, as the running SDK judges it: its kept inputs (the
+// tree, the lock hashes by file name, the named paths' objects) taken through the manifest as a merge takes them, and the
+// reason that gives. It answers false for any other value, and for one whose manifest the running SDK still cannot make
+// inputs of (issue 1923).
+func (ix *Indexer) rejudged(ctx context.Context, m catalogue.Manifest, cur delivery.Module, raw string) (delivery.Module, bool) {
+	if cur.FP2 != "" || cur.Inputs2 == nil || !strings.HasPrefix(cur.None2, None2Unreadable) {
+		return cur, false
+	}
+	in := inputsOfNamed(m.Module, raw, cur.Inputs2.Tree, cur.Inputs2.Locks, cur.Inputs2.Paths, ix.baseFP(ctx))
+	if in.Kept == nil {
+		return cur, false
+	}
+	cur.Inputs2, cur.None2, cur.ArtifactPaths = in.Kept, in.None2, in.ArtifactPaths
+	return cur, true
 }
 
 // hasContext is whether an artifact of the manifest reads another repository's tree.

modules/mesh-delivery-indexer/manifest_test.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"regexp"
 	"slices"
 	"strings"
 	"testing"
@@ -80,7 +81,7 @@ func TestManifestDeclarations(t *testing.T) { // 1238/AC1, 1444 (reads the build
 	if want := []state{{Name: "candidates", History: 10}, {Name: "manifests", History: 1}, {Name: "modules", History: 20}}; !reflect.DeepEqual(m.State, want) {
 		t.Errorf("state = %+v, want %+v", m.State, want)
 	}
-	if want := []string{"mesh-build-go.toolchains", "mesh-build-node.toolchains", "mesh-controller.builds", "mesh-delivery-checker.previews", "mesh-delivery-gate.source"}; !reflect.DeepEqual(sorted(m.Reads), want) {
+	if want := []string{"mesh-build-go.toolchains", "mesh-build-node.toolchains", "mesh-controller.assignments", "mesh-controller.builds", "mesh-delivery-checker.previews", "mesh-delivery-gate.source"}; !reflect.DeepEqual(sorted(m.Reads), want) {
 		t.Errorf("reads = %v, want %v", m.Reads, want)
 	}
 	// "Reads FORGE" is a consumes of the indexer's stream: the broker grants only buckets by reads (mesh-control
@@ -94,9 +95,10 @@ func TestManifestDeclarations(t *testing.T) { // 1238/AC1, 1444 (reads the build
 	if m.SecretsOwner != "mesh-delivery-indexer" {
 		t.Errorf("secrets-owner = %q", m.SecretsOwner)
 	}
-	// One invoke: the forge's trees with the named paths' objects, since the indexer is the one reader of a manifest's paths
-	// (ADR 0499 clauses 2 and 3, ADR 0495 clause 1, the lead's decision L8 of R4e).
-	if want := []string{"gitea.gitea_commit_trees"}; !reflect.DeepEqual(m.Invokes, want) {
+	// Two invokes: the forge's trees (the named paths' objects, since the indexer is the one reader of a manifest's paths:
+	// ADR 0499 clauses 2 and 3, ADR 0495 clause 1; and the module directories of the trunk, issue 1900) and whether a
+	// commit is in another (issue 1900).
+	if want := []string{"gitea.gitea_commit_trees", "gitea.gitea_contains"}; !reflect.DeepEqual(m.Invokes, want) {
 		t.Errorf("invokes = %v, want %v", m.Invokes, want)
 	}
 	// No emits, no streams, no bus, no seat, no tool (ADR 0437 §4).
@@ -169,3 +171,32 @@ func TestServesNoRequestSubjectAndHoldsNoTicker(t *testing.T) { // 1238/AC9 (ADR
 		t.Fatalf("read %d source files, want the program's", files)
 	}
 }
+
+// Every forge tool the program calls is granted in invokes, or the bus refuses the call (issue 1900).
+func TestEveryGiteaToolTheCodeCallsIsInInvokes(t *testing.T) {
+	m, _ := load(t)
+	files, err := filepath.Glob("cmd/mesh-delivery-indexer/*.go")
+	if err != nil || len(files) == 0 {
+		t.Fatalf("no program files: %v", err)
+	}
+	re := regexp.MustCompile(`gitea\.gitea_[a-z_]+`)
+	seen := 0
+	for _, f := range files {
+		if strings.HasSuffix(f, "_test.go") {
+			continue
+		}
+		src, err := os.ReadFile(f)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, tool := range re.FindAllString(string(src), -1) {
+			seen++
+			if !slices.Contains(m.Invokes, tool) {
+				t.Errorf("%s calls %s, which invokes does not grant", f, tool)
+			}
+		}
+	}
+	if seen < 2 {
+		t.Errorf("found %d tool names in the program, want at least the two it calls", seen)
+	}
+}

modules/mesh-delivery-indexer/module.json

@@ -16,12 +16,14 @@
   "reads": [
     "mesh-build-go.toolchains",
     "mesh-build-node.toolchains",
+    "mesh-controller.assignments",
     "mesh-controller.builds",
     "mesh-delivery-checker.previews",
     "mesh-delivery-gate.source"
   ],
   "invokes": [
-    "gitea.gitea_commit_trees"
+    "gitea.gitea_commit_trees",
+    "gitea.gitea_contains"
   ],
   "own-secrets": {
     "broker": "${dir:state}/broker"

modules/mesh-delivery-indexer/reads-outside

@@ -0,0 +1 @@
+These tests read files outside this directory (the whole catalogue, the repository, or its root files): mesh-build-go never keeps this package's verdict (issue 1935).

modules/mesh-delivery-teller/reads-outside

@@ -0,0 +1 @@
+These tests read files outside this directory (the whole catalogue, the repository, or its root files): mesh-build-go never keeps this package's verdict (issue 1935).

modules/mesh-delivery-watchman/reads-outside

@@ -0,0 +1 @@
+These tests read files outside this directory (the whole catalogue, the repository, or its root files): mesh-build-go never keeps this package's verdict (issue 1935).