A runtime that already dropped a carried module's tools serves them again, read from what runs and its build (issue 1126, review)

rev-held2: ToolsRunning took a carried module's bundles from the runtime's MESH_TOOL_MODULES alone, and shanks had
already applied the drop of systemd-resolved, so its runs stayed empty and the drop permanent. Now every bundle
archive that runs at its module's BundlePath is a running bundle; one the runtime loads nothing of takes its loads and
words from the module's build (its built bundles, else its build's artifacts, by catalogue.BundleLoads, the rule a
build's resolution keeps, now one function). The runtime process and each archive are matched by their owning module
too, not only by id and path. A row added: the runtime already dropped it.

.gitignore

@@ -1,2 +1,3 @@
 node_modules/
 dist/
+vendor/

go/announce/announce.go

@@ -0,0 +1,155 @@
+// Package announce is how a module says on the bus which states it keeps and which of them others may read (novox/hq
+// ADR 0495 clauses 2 and 3; issue 1790): the subject it says it on, the value it says, and where the controller keeps
+// the last one said by each module. What a module announced is the truth of what it keeps; a reader is granted a read
+// from it, never from a list or from the owner's manifest.
+//
+// A module announces from its code (process.Conn.Keeps, stdio.Keeps, the TypeScript SDK's keeps), never from its
+// manifest, which only the core reads (clause 1). A module that keeps no state on the bus announces nothing.
+package announce
+
+import (
+	"encoding/json"
+	"fmt"
+	"regexp"
+	"sort"
+)
+
+// Version is the version of the value this package writes.
+const Version = 1
+
+// Event is the event type of an announcement, under the module's own namespace.
+const Event = "states"
+
+// Subject is where module announces what it keeps: its own event subject, mesh.mod.<module>.event.states, which its
+// account may already publish to and the events stream keeps.
+func Subject(module string) string { return "mesh.mod." + module + ".event." + Event }
+
+// SubjectAll is every module's announcement, what the controller consumes.
+const SubjectAll = "mesh.mod.*.event." + Event
+
+// KeptBucket is the controller's bucket of the last announcement of each module, by Key.
+const KeptBucket = "mesh-controller_states-announced"
+
+var name = regexp.MustCompile(`^[a-z0-9][a-z0-9-]*$`)
+
+// Key is module's key in KeptBucket: the module itself, which must be one plain name, since a module's name is part of
+// its buckets' names (catalogue.StateProblems).
+func Key(module string) (string, error) {
+	if !name.MatchString(module) {
+		return "", fmt.Errorf("announce: %q is not a module that keeps state: lower-case letters, digits and hyphens", module)
+	}
+	return module, nil
+}
+
+// State is one state a module keeps, by its local name, and whether others may read it. Others never write it: a
+// state another module writes is the owner's own code's business.
+type State struct {
+	Name     string `json:"name"`
+	Readable bool   `json:"readable,omitempty"`
+	// Readers, when named, are the only modules that may read the state (novox/hq ADR 0547 clause 9, issue 1945): a
+	// state readable by some and not all, such as the vault's bus account hashes. Only ReadableBy grants them; Readable,
+	// which a composer that knows no readers asks, stays false for it, so such a composer grants nobody.
+	Readers []string `json:"readers,omitempty"`
+}
+
+// States is an announcement: the module, the machine whose instance said it, and every state the module keeps, sorted
+// by name. An empty list says the module keeps nothing.
+type States struct {
+	V      int     `json:"v"`
+	Module string  `json:"module"`
+	Node   string  `json:"node,omitempty"`
+	States []State `json:"states"`
+}
+
+// Keeps says whether the module announced keeping the state.
+func (s States) Keeps(state string) bool {
+	for _, k := range s.States {
+		if k.Name == state {
+			return true
+		}
+	}
+	return false
+}
+
+// ReadableBy says whether the module announced the state readable by reader: readable, and reader among the readers
+// when it names any.
+func (s States) ReadableBy(state, reader string) bool {
+	for _, k := range s.States {
+		if k.Name != state {
+			continue
+		}
+		if len(k.Readers) > 0 {
+			for _, r := range k.Readers {
+				if r == reader {
+					return true
+				}
+			}
+			return false
+		}
+		return k.Readable
+	}
+	return false
+}
+
+// Readable says whether the module announced the state readable by others.
+func (s States) Readable(state string) bool {
+	for _, k := range s.States {
+		if k.Name == state {
+			return k.Readable
+		}
+	}
+	return false
+}
+
+func (s *States) check() error {
+	if s.Module == "" {
+		return fmt.Errorf("announce: an announcement names no module")
+	}
+	if _, err := Key(s.Module); err != nil {
+		return err
+	}
+	seen := map[string]bool{}
+	for _, k := range s.States {
+		if !name.MatchString(k.Name) {
+			return fmt.Errorf("announce: %s announces the state %q, and a state is named locally: lower-case letters, digits and hyphens", s.Module, k.Name)
+		}
+		if seen[k.Name] {
+			return fmt.Errorf("announce: %s announces the state %q twice", s.Module, k.Name)
+		}
+		seen[k.Name] = true
+		for _, r := range k.Readers {
+			if !name.MatchString(r) {
+				return fmt.Errorf("announce: %s names %q as a reader of %s, and a reader is a module: lower-case letters, digits and hyphens", s.Module, r, k.Name)
+			}
+		}
+	}
+	return nil
+}
+
+// Encode is s as JSON at Version, its states sorted; it refuses a module or a state no bucket could be named by and a
+// state announced twice, naming it.
+func Encode(s States) ([]byte, error) {
+	if err := s.check(); err != nil {
+		return nil, err
+	}
+	s.V = Version
+	s.States = append([]State{}, s.States...)
+	sort.Slice(s.States, func(i, j int) bool { return s.States[i].Name < s.States[j].Name })
+	return json.Marshal(s)
+}
+
+// Decode reads an announcement; it refuses another version and what Encode refuses.
+func Decode(data []byte) (States, error) {
+	var s States
+	if err := json.Unmarshal(data, &s); err != nil {
+		return States{}, fmt.Errorf("announce: the announcement is not JSON: %w", err)
+	}
+	if s.V != Version {
+		return States{}, fmt.Errorf("announce: the announcement is version %d, and this reads version %d", s.V, Version)
+	}
+	if err := s.check(); err != nil {
+		return States{}, err
+	}
+	sort.Slice(s.States, func(i, j int) bool { return s.States[i].Name < s.States[j].Name })
+	return s, nil
+}

go/announce/announce_test.go

@@ -0,0 +1,78 @@
+package announce
+
+import (
+	"strings"
+	"testing"
+)
+
+// A module says on the bus which states it keeps and which of them others may read (novox/hq ADR 0495 clause 2), on its
+// own event subject, in a versioned value the controller keeps by module.
+func TestAnAnnouncementRoundTripsSortedAndSaysWhatIsReadable(t *testing.T) {
+	data, err := Encode(States{Module: "mesh-controller", Node: "novox", States: []State{
+		{Name: "plans-building", Readable: true}, {Name: "assignments", Readable: true}, {Name: "own"},
+		{Name: "hashes", Readers: []string{"mesh-grants"}}}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	back, err := Decode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if back.V != Version || back.Module != "mesh-controller" || back.Node != "novox" {
+		t.Fatalf("decoded %+v", back)
+	}
+	var names []string
+	for _, s := range back.States {
+		names = append(names, s.Name)
+	}
+	if strings.Join(names, ",") != "assignments,hashes,own,plans-building" {
+		t.Fatalf("the states are not sorted: %v", names)
+	}
+	if !back.Readable("plans-building") || back.Readable("own") || back.Readable("absent") {
+		t.Fatal("Readable does not say what was announced readable")
+	}
+	// Named readers (ADR 0547 clause 9): readable by them alone, and not readable to a composer that knows no readers.
+	if back.Readable("hashes") || !back.ReadableBy("hashes", "mesh-grants") || back.ReadableBy("hashes", "spy") ||
+		!back.ReadableBy("plans-building", "spy") || back.ReadableBy("own", "spy") {
+		t.Fatal("ReadableBy does not say who was named")
+	}
+	if !back.Keeps("own") || back.Keeps("absent") {
+		t.Fatal("Keeps does not say what was announced")
+	}
+	if Subject("mesh-controller") != "mesh.mod.mesh-controller.event.states" || SubjectAll != "mesh.mod.*.event.states" {
+		t.Fatalf("the subjects are %q and %q", Subject("mesh-controller"), SubjectAll)
+	}
+	if KeptBucket != "mesh-controller_states-announced" {
+		t.Fatalf("the kept bucket is %q", KeptBucket)
+	}
+	if k, err := Key("mesh-delivery-builder"); err != nil || k != "mesh-delivery-builder" {
+		t.Fatalf("Key = %q, %v", k, err)
+	}
+	if nothing, err := Encode(States{Module: "quiet"}); err != nil || !strings.Contains(string(nothing), `"states":[]`) {
+		t.Fatalf("a module keeping nothing: %s, %v", nothing, err)
+	}
+}
+
+func TestAnAnnouncementRefusesWhatNoBucketCouldBe(t *testing.T) {
+	for _, c := range []struct {
+		s    States
+		says string
+	}{
+		{States{Module: ""}, "no module"},
+		{States{Module: "a.b"}, `"a.b"`},
+		{States{Module: "a", States: []State{{Name: "x_y"}}}, `"x_y"`},
+		{States{Module: "a", States: []State{{Name: ""}}}, `""`},
+		{States{Module: "a", States: []State{{Name: "x"}, {Name: "x", Readable: true}}}, "twice"},
+		{States{Module: "a", States: []State{{Name: "x", Readers: []string{"b.c"}}}}, `"b.c"`},
+	} {
+		if _, err := Encode(c.s); err == nil || !strings.Contains(err.Error(), c.says) {
+			t.Errorf("%+v: %v, wanted a refusal saying %s", c.s, err, c.says)
+		}
+	}
+	if _, err := Decode([]byte(`{"v":2,"module":"a","states":[]}`)); err == nil {
+		t.Error("an unknown version was read")
+	}
+	if _, err := Key("a.b"); err == nil {
+		t.Error("a module with a dot became a key")
+	}
+}

go/announcetest/announcetest.go

@@ -0,0 +1,91 @@
+// Package announcetest is the test each module runs with its own checks to hold that it announces on the bus every
+// state it keeps (novox/hq ADR 0495 clause 5; issue 1790): it starts the module against a bus of the test's own and
+// compares what the module announced with what its code declares. With the bind guard of process.Conn.Keeps,
+// stdio.Keeps and the TypeScript keeps, which refuses a state the code did not announce, announcement and code agree.
+//
+// It replaces the merge gate's check of one module's reads against another's manifest (clause 5); a test using it
+// carries `//go:build integration`, since it starts a bus.
+package announcetest
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+	"sort"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/announce"
+	"git.novox.be/novox/mesh-sdk/go/testbus"
+)
+
+// Wait is how long Check waits for the module's announcement once it started it.
+var Wait = 10 * time.Second
+
+// Check starts a bus of the test's own, with a stream taking module's events, calls start with its address (start
+// runs the module, or its part that connects, against it, and answers how to stop it), waits for the module's
+// announcement and fails the test unless it is module's and names exactly want (in any order), readable as want says.
+// It answers the announcement.
+func Check(t testing.TB, module string, want []announce.State, start func(url string) (stop func())) announce.States {
+	t.Helper()
+	url := testbus.URL(t)
+	nc, err := nats.Connect(url)
+	if err != nil {
+		t.Fatalf("announcetest: connecting to the test bus: %v", err)
+	}
+	defer nc.Close()
+	js, err := jetstream.New(nc)
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), Wait)
+	defer cancel()
+	stream, err := js.CreateStream(ctx, jetstream.StreamConfig{Name: "ANNOUNCETEST", Subjects: []string{"mesh.mod." + module + ".event.>"}})
+	if err != nil {
+		t.Fatalf("announcetest: making the events stream: %v", err)
+	}
+	stop := start(url)
+	if stop != nil {
+		defer stop()
+	}
+	got, err := waitFor(ctx, stream, module)
+	if err != nil {
+		t.Fatalf("announcetest: %v", err)
+	}
+	if problem := differs(got, module, want); problem != "" {
+		t.Fatalf("announcetest: %s", problem)
+	}
+	return got
+}
+
+// waitFor reads the stream until module's announcement is in it.
+func waitFor(ctx context.Context, stream jetstream.Stream, module string) (announce.States, error) {
+	for {
+		msg, err := stream.GetLastMsgForSubject(ctx, announce.Subject(module))
+		if err == nil {
+			return announce.Decode(msg.Data)
+		}
+		select {
+		case <-ctx.Done():
+			return announce.States{}, fmt.Errorf("%s announced nothing on %s within %s", module, announce.Subject(module), Wait)
+		case <-time.After(50 * time.Millisecond):
+		}
+	}
+}
+
+// differs says how got is not module's announcement of want, or "".
+func differs(got announce.States, module string, want []announce.State) string {
+	if got.Module != module {
+		return fmt.Sprintf("the announcement names the module %q, not %q", got.Module, module)
+	}
+	w := append([]announce.State{}, want...)
+	sort.Slice(w, func(i, j int) bool { return w[i].Name < w[j].Name })
+	g := append([]announce.State{}, got.States...)
+	if !reflect.DeepEqual(g, w) && !(len(g) == 0 && len(w) == 0) {
+		return fmt.Sprintf("%s announced %v, and its code declares %v", module, g, w)
+	}
+	return ""
+}

go/announcetest/announcetest_integration_test.go

@@ -0,0 +1,29 @@
+//go:build integration
+
+package announcetest
+
+import (
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/announce"
+	"git.novox.be/novox/mesh-sdk/go/process"
+)
+
+// 1790/S11: a module started against the test bus announces through process.Conn.Keeps, and Check reads that
+// announcement back against what the code declares.
+func TestCheckReadsTheModulesAnnouncementOffARealBus(t *testing.T) {
+	declared := []announce.State{{Name: "accounts", Readable: true}, {Name: "drafts"}}
+	got := Check(t, "mesh-mail", declared, func(url string) func() {
+		conn, err := process.Connect(process.Account{URL: url, Module: "mesh-mail", Node: "novox", User: "u", Password: "p"})
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := conn.Keeps(declared...); err != nil {
+			t.Fatal(err)
+		}
+		return conn.Close
+	})
+	if got.Node != "novox" {
+		t.Fatalf("announced from %q", got.Node)
+	}
+}

go/announcetest/announcetest_test.go

@@ -0,0 +1,32 @@
+package announcetest
+
+import (
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/announce"
+)
+
+// The comparison is exact up to order: a state missing, one extra, a readability that differs or another module's
+// announcement each fail, naming what differs.
+func TestAnAnnouncementDiffersFromTheCodeByNameAndReadability(t *testing.T) {
+	got := announce.States{Module: "m", States: []announce.State{{Name: "a", Readable: true}, {Name: "b"}}}
+	if p := differs(got, "m", []announce.State{{Name: "b"}, {Name: "a", Readable: true}}); p != "" {
+		t.Fatalf("an equal announcement differs: %s", p)
+	}
+	for _, want := range [][]announce.State{
+		{{Name: "a", Readable: true}},
+		{{Name: "a", Readable: true}, {Name: "b"}, {Name: "c"}},
+		{{Name: "a"}, {Name: "b"}},
+	} {
+		if p := differs(got, "m", want); p == "" || !strings.Contains(p, "declares") {
+			t.Errorf("want %v: %q", want, p)
+		}
+	}
+	if p := differs(got, "other", nil); !strings.Contains(p, `"other"`) {
+		t.Errorf("another module's announcement: %q", p)
+	}
+	if p := differs(announce.States{Module: "m"}, "m", nil); p != "" {
+		t.Errorf("a module keeping nothing: %q", p)
+	}
+}

go/asks/asks.go

@@ -571,3 +571,8 @@ type ProofAnswer struct {
 	Accepted bool   `json:"accepted"`
 	Words    string `json:"words"`
 }
+
+// EngineAsker is the asker name a node's engine asks the operator under (novox/hq ADR 0563 §3, which changes ADR 0259
+// §2 to admit a node's engine as an asker): `node-engine-<node>`, the last token of the by-caller subjects granted to that
+// node's engine account alone, so no engine acts on another node's warrant.
+func EngineAsker(node string) string { return "node-engine-" + node }

go/buildcpu/buildcpu.go

@@ -0,0 +1,215 @@
+// Package buildcpu is how much of a build node's processors its builds may take, and how they yield to everything else
+// there (novox/hq ADR 0553, issue 1806; the operator, 2026-10-26: "limit CPU usage on our build nodes so the total cpu
+// usage never impacts the normal workings of our nodes ... We have 3 build agents so they should share the cpu power").
+//
+// Three parts, each with one owner:
+//
+//   - **Priority.** A build seat's holder (catalogue.Seat.Yields) runs at the lowest priority there is: the composer
+//     gives its runtime process declaration.Yields, and the node-engine places every yielding process of the node in
+//     one slice (declaration.YieldSlice) whose CPU weight is idle, with Nice=19 for every process it starts.
+//     Interactive and service work always comes first; builds take the cycles nothing else wants.
+//   - **One cap per node, shared.** The node's share of its processors is one value, the node-engine's own config
+//     `build-cpu-share` (ShareSetting), set per node through the node's settings layer. The node-engine writes it as the
+//     slice's CPUQuota: one bound the kernel holds for all the node's build modules together, never one per module.
+//   - **Threads.** The quota bounds the total; threads only size each step. A step gets the share divided by its own
+//     module's capacity (Threads), from the share the composer hands as a word (ShareWord): GOMAXPROCS sets every go
+//     command's -p, the compiler's concurrency, a test binary's processors and -parallel. A module given no word sets
+//     no thread limit at all: without the slice there is nothing to size a step to, and a limit then would only slow
+//     builds.
+package buildcpu
+
+import (
+	"os"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+// ShareSetting is the node-engine's config value of the node's processor share for its builds, in percent of the
+// machine's processors, 1 to 100: one value per node, set through the node's settings layer (novox/hq ADR 0553 §3).
+const ShareSetting = "build-cpu-share"
+
+// DefaultPercent is the share where nothing sets one: half the machine, so a desktop keeps half its processors for
+// itself whatever builds.
+const DefaultPercent = 50
+
+// ShareWord is the word the composer gives every yielding module (novox/hq ADR 0553 §4): the node's share, in percent.
+const ShareWord = "MESH_BUILD_CPU_SHARE"
+
+// Quota is a CPUQuota for a share of a machine with cores processors: systemd counts a quota in percent of one
+// processor, so half of 24 is 1200%. At least 100%, one processor, so a share on a small machine never stops a step.
+func Quota(percent, cores int) int {
+	q := percent * cores
+	if q < 100 {
+		q = 100
+	}
+	return q
+}
+
+// Threads is how many threads one step may run at once: its part of the share when its own module runs slots steps at
+// once, at least one. The slice's quota bounds the steps of all the node's build modules together; this only sizes one.
+func Threads(percent, cores, slots int) int {
+	if slots < 1 {
+		slots = 1
+	}
+	if percent < 1 || percent > 100 {
+		percent = DefaultPercent
+	}
+	t := cores * percent / 100 / slots
+	if t < 1 {
+		t = 1
+	}
+	return t
+}
+
+// Limits is what one step is held to on this node, as a status tool says it.
+type Limits struct {
+	// Percent is the node's share in percent of its processors, and From where it was read: ShareWord, or "none" when
+	// the composer gave no share and a step runs without a thread limit.
+	Percent int    `json:"share-percent,omitempty"`
+	From    string `json:"share-from"`
+	// Cores is the machine's processor count.
+	Cores int `json:"cores"`
+	// Slots is this module's own capacity on the node: steps at once.
+	Slots int `json:"slots"`
+	// Threads is what each step is given (Threads); 0 is no limit.
+	Threads int `json:"threads-per-step"`
+}
+
+// FromWords is the limits of a step from the share the composer gave this process (ShareWord) and the module's own
+// capacity. Without a usable share there is no limit: Threads is 0.
+func FromWords(getenv func(string) string, own int) Limits {
+	if own < 1 {
+		own = 1
+	}
+	l := Limits{From: "none", Cores: runtime.NumCPU(), Slots: own}
+	if n, err := strconv.Atoi(strings.TrimSpace(getenv(ShareWord))); err == nil && n >= 1 && n <= 100 {
+		l.Percent, l.From = n, ShareWord
+		l.Threads = Threads(n, l.Cores, own)
+	}
+	return l
+}
+
+// Env is the environment a step's commands are given so they start no more threads than they may: GOMAXPROCS for every
+// Go program (the compiler, a test binary, esbuild, buildah), UV_THREADPOOL_SIZE for Node's worker pool. Returned as
+// KEY=value words to append to a command's environment; nothing for 0 threads, no limit.
+func Env(threads int) []string {
+	if threads < 1 {
+		return nil
+	}
+	t := strconv.Itoa(threads)
+	return []string{"GOMAXPROCS=" + t, "UV_THREADPOOL_SIZE=" + t}
+}
+
+// InForce is what the kernel holds this process to, read rather than assumed (evidence over assertion): its nice
+// level, its cgroup (the unit) and the cgroup's parent (the slice the node-engine placed it in), each one's CPU weight,
+// idle mark and quota. A field the machine does not answer is left empty and Unread says which.
+//
+// The IO weight is read but binds only where the disk's scheduler honours it (bfq, or the io.cost controller); under
+// the scheduler `none`, the usual one for NVMe, it does nothing, and the CPU bound is what holds.
+type InForce struct {
+	Nice   int    `json:"nice"`
+	Cgroup string `json:"cgroup,omitempty"`
+	Unit   Group  `json:"unit"`
+	Slice  Group  `json:"slice"`
+	// Quota is the tighter of the two groups' cpu.max as a percent of one processor, 0 with none.
+	Quota  int      `json:"quota-percent,omitempty"`
+	Unread []string `json:"unread,omitempty"`
+}
+
+// Group is one cgroup's controls.
+type Group struct {
+	Path      string `json:"path,omitempty"`
+	CPUIdle   string `json:"cpu-idle,omitempty"`
+	CPUWeight string `json:"cpu-weight,omitempty"`
+	// CPUMax is the cgroup's cpu.max: "<quota µs> <period µs>", or "max" with no quota.
+	CPUMax   string `json:"cpu-max,omitempty"`
+	IOWeight string `json:"io-weight,omitempty"`
+}
+
+// cgroupRoot is where the unified hierarchy is mounted. A variable so a test can point it elsewhere.
+var cgroupRoot = "/sys/fs/cgroup"
+
+// procSelfCgroup is this process's cgroup file. A variable so a test can point it elsewhere.
+var procSelfCgroup = "/proc/self/cgroup"
+
+// procSelfStat is this process's stat file. A variable so a test can point it elsewhere.
+var procSelfStat = "/proc/self/stat"
+
+// ReadInForce reads what the kernel holds this process to.
+func ReadInForce() InForce {
+	var f InForce
+	f.Nice = nice()
+	raw, err := os.ReadFile(procSelfCgroup)
+	if err != nil {
+		f.Unread = append(f.Unread, "cgroup: "+err.Error())
+		return f
+	}
+	for _, line := range strings.Split(strings.TrimSpace(string(raw)), "\n") {
+		if strings.HasPrefix(line, "0::") {
+			f.Cgroup = strings.TrimPrefix(line, "0::")
+		}
+	}
+	if f.Cgroup == "" {
+		f.Unread = append(f.Unread, "cgroup: not on the unified hierarchy")
+		return f
+	}
+	read := func(path string) Group {
+		g := Group{Path: path}
+		value := func(name string) string {
+			b, err := os.ReadFile(cgroupRoot + path + "/" + name)
+			if err != nil {
+				f.Unread = append(f.Unread, path+"/"+name+": "+err.Error())
+				return ""
+			}
+			return strings.TrimSpace(string(b))
+		}
+		g.CPUIdle, g.CPUWeight, g.CPUMax, g.IOWeight = value("cpu.idle"), value("cpu.weight"), value("cpu.max"), value("io.weight")
+		return g
+	}
+	f.Unit = read(f.Cgroup)
+	if i := strings.LastIndex(f.Cgroup, "/"); i > 0 {
+		f.Slice = read(f.Cgroup[:i])
+	}
+	for _, q := range []int{quotaOf(f.Unit.CPUMax), quotaOf(f.Slice.CPUMax)} {
+		if q > 0 && (f.Quota == 0 || q < f.Quota) {
+			f.Quota = q
+		}
+	}
+	return f
+}
+
+// quotaOf is a cpu.max value as a percent of one processor: "1200000 100000" is 1200; "max ..." or nothing is 0.
+func quotaOf(cpuMax string) int {
+	fields := strings.Fields(cpuMax)
+	if len(fields) != 2 || fields[0] == "max" {
+		return 0
+	}
+	q, err1 := strconv.Atoi(fields[0])
+	p, err2 := strconv.Atoi(fields[1])
+	if err1 != nil || err2 != nil || p <= 0 {
+		return 0
+	}
+	return q * 100 / p
+}
+
+// nice is this process's nice level from its stat file (the 19th field, counted after the command's closing
+// parenthesis, which may itself hold spaces); 0 when it cannot be read.
+func nice() int {
+	raw, err := os.ReadFile(procSelfStat)
+	if err != nil {
+		return 0
+	}
+	s := string(raw)
+	i := strings.LastIndex(s, ")")
+	if i < 0 {
+		return 0
+	}
+	fields := strings.Fields(s[i+1:])
+	// After the command: state is field 3, so nice (field 19) is index 16.
+	if len(fields) < 17 {
+		return 0
+	}
+	n, _ := strconv.Atoi(fields[16])
+	return n
+}

go/buildcpu/buildcpu_test.go

@@ -0,0 +1,90 @@
+package buildcpu
+
+import (
+	"os"
+	"path/filepath"
+	"reflect"
+	"runtime"
+	"testing"
+)
+
+// The node's share as a quota, the threads one step is given for its own module's capacity, and the word the composer
+// hands, in one table (ADR 0553, issue 1806).
+func TestShareQuotaAndThreads(t *testing.T) {
+	for _, c := range []struct {
+		name                  string
+		percent, cores, slots int
+		quota, threads        int
+	}{
+		{"shanks: half of 24, three slots", 50, 24, 3, 1200, 4},
+		{"ace: three quarters of 24, two slots", 75, 24, 2, 1800, 9},
+		{"g14: half of 16, one slot", 50, 16, 1, 800, 8},
+		{"one processor at least", 10, 2, 4, 100, 1},
+		{"no slots counts as one", 100, 4, 0, 400, 4},
+		{"a share out of range is the default", 0, 8, 1, 0, 4},
+	} {
+		if c.quota != 0 {
+			if q := Quota(c.percent, c.cores); q != c.quota {
+				t.Errorf("%s: Quota = %d, want %d", c.name, q, c.quota)
+			}
+		}
+		if th := Threads(c.percent, c.cores, c.slots); th != c.threads {
+			t.Errorf("%s: Threads = %d, want %d", c.name, th, c.threads)
+		}
+	}
+	l := FromWords(func(k string) string { return map[string]string{ShareWord: "75"}[k] }, 2)
+	if l.Percent != 75 || l.From != ShareWord || l.Slots != 2 || l.Threads != Threads(75, runtime.NumCPU(), 2) {
+		t.Errorf("from the word: %+v", l)
+	}
+	// Told nothing usable, a step has no thread limit: nothing in its environment.
+	for _, word := range []string{"", "250", "lots"} {
+		l := FromWords(func(string) string { return word }, 3)
+		if l.Threads != 0 || l.From != "none" || Env(l.Threads) != nil {
+			t.Errorf("share %q: %+v, env %v", word, l, Env(l.Threads))
+		}
+	}
+	if got := Env(3); !reflect.DeepEqual(got, []string{"GOMAXPROCS=3", "UV_THREADPOOL_SIZE=3"}) {
+		t.Errorf("Env = %q", got)
+	}
+}
+
+// What the kernel holds a process to is read from its unit's and its slice's cgroup and its stat file, not assumed.
+func TestReadInForce(t *testing.T) {
+	dir := t.TempDir()
+	cg := filepath.Join(dir, "cg")
+	slice := filepath.Join(cg, "meshyield.slice")
+	unit := filepath.Join(slice, "mesh-build-go-runtime.service")
+	if err := os.MkdirAll(unit, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	for at, files := range map[string]map[string]string{
+		slice: {"cpu.idle": "1\n", "cpu.weight": "0\n", "cpu.max": "1200000 100000\n", "io.weight": "default 1\n"},
+		unit:  {"cpu.idle": "0\n", "cpu.weight": "100\n", "cpu.max": "max 100000\n", "io.weight": "default 100\n"},
+	} {
+		for name, v := range files {
+			if err := os.WriteFile(filepath.Join(at, name), []byte(v), 0o644); err != nil {
+				t.Fatal(err)
+			}
+		}
+	}
+	self := filepath.Join(dir, "cgroup")
+	stat := filepath.Join(dir, "stat")
+	_ = os.WriteFile(self, []byte("0::/meshyield.slice/mesh-build-go-runtime.service\n"), 0o644)
+	// A command with a space and a parenthesis in it, then nice 19 in field 19.
+	_ = os.WriteFile(stat, []byte("42 (mesh (build) go) S 1 42 42 0 -1 4194560 1 0 0 0 0 0 0 0 39 19 8 0 1 2 3\n"), 0o644)
+	cgroupRoot, procSelfCgroup, procSelfStat = cg, self, stat
+	t.Cleanup(func() {
+		cgroupRoot, procSelfCgroup, procSelfStat = "/sys/fs/cgroup", "/proc/self/cgroup", "/proc/self/stat"
+	})
+
+	got := ReadInForce()
+	want := InForce{Nice: 19, Cgroup: "/meshyield.slice/mesh-build-go-runtime.service",
+		Unit: Group{Path: "/meshyield.slice/mesh-build-go-runtime.service", CPUIdle: "0", CPUWeight: "100",
+			CPUMax: "max 100000", IOWeight: "default 100"},
+		Slice: Group{Path: "/meshyield.slice", CPUIdle: "1", CPUWeight: "0", CPUMax: "1200000 100000",
+			IOWeight: "default 1"},
+		Quota: 1200}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("ReadInForce = %+v\nwant %+v", got, want)
+	}
+}

go/buildstep/askrun.go

@@ -0,0 +1,440 @@
+package buildstep
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"path"
+	"slices"
+	"sort"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **One ask, one whole job** (novox/hq ADR 0525 §3). A build module runs a pulled ask with its own step tools' bodies,
+// the same ones its request and reply tools run (ADR 0525 §8), in the order the job names: a build ask fetches, then
+// builds or copies each artifact; a check ask fetches, digests the level, takes the kept verdicts and tests the rest,
+// the packages whose tests the change touches first. The answers are the tools' own, whole, so the asker judges them as
+// it judged the tools' answers.
+
+// StepFunc is one step tool's body: its arguments in, its answer out.
+type StepFunc func(ctx context.Context, args map[string]any) (any, error)
+
+// AskSteps are the step tools a build module runs an ask with. Copy is the image module's alone; Digest the Go module's.
+type AskSteps struct {
+	Fetch, Build, Copy, Digest, Test StepFunc
+	// Toolchain is the toolchain the module builds with now; a build ask naming another is refused. Nil checks nothing
+	// (an image or an archive names none).
+	Toolchain func(ctx context.Context) (delivery.ToolchainUsed, error)
+	// Kept looks up a kept verdict by level and digest (the checker's kept bucket, delivery.KeptKey): whether one is
+	// kept and how many tests it counted. Nil takes none.
+	Kept func(ctx context.Context, level, digest string) (tests int, found bool, err error)
+	// Release removes a workspace once the ask's steps on it ended (the module's release tool's body); nil leaves it to
+	// the module's sweep.
+	Release func(workspace string) error
+	Logf    func(format string, args ...any)
+	// Has says whether this node has a need a package's tests declare (delivery.AskNeeds, issue 890); a package needing
+	// what it lacks is not tested here but named in the level's Unmet, for the asker to place. Nil has nothing.
+	Has func(need string) bool
+}
+
+// RunAsk runs ask's job with steps and answers a delivery.BuildAnswer or a delivery.CheckAnswer.
+func RunAsk(ctx context.Context, steps AskSteps, ask delivery.StepAsk) (any, error) {
+	if ask.Build != nil {
+		return steps.build(ctx, *ask.Build)
+	}
+	if ask.Check != nil {
+		return steps.check(ctx, *ask.Check)
+	}
+	return nil, Refuse("the ask %s holds no job", ask.ID)
+}
+
+func raw(v any) (json.RawMessage, error) {
+	if r, ok := v.(json.RawMessage); ok {
+		return r, nil
+	}
+	return json.Marshal(v)
+}
+
+// fetched is what an ask reads of a fetch's answer.
+type fetched struct {
+	Workspace string   `json:"workspace"`
+	Merge     string   `json:"merge"`
+	Conflicts []string `json:"conflicts"`
+	Changed   []string `json:"changed"`
+	Modules   []string `json:"modules"`
+}
+
+func (s AskSteps) fetch(ctx context.Context, args map[string]any) (json.RawMessage, fetched, error) {
+	if s.Fetch == nil {
+		return nil, fetched{}, Refuse("this build module fetches nothing")
+	}
+	if _, merges := args["base"]; merges {
+		Phase(ctx, "fetch and merge")
+	} else {
+		Phase(ctx, "fetch")
+	}
+	out, err := s.Fetch(ctx, args)
+	if err != nil {
+		return nil, fetched{}, err
+	}
+	r, err := raw(out)
+	if err != nil {
+		return nil, fetched{}, err
+	}
+	var f fetched
+	if err := json.Unmarshal(r, &f); err != nil || f.Workspace == "" {
+		return r, f, fmt.Errorf("the fetch answered no workspace: %s", r)
+	}
+	return r, f, nil
+}
+
+func (s AskSteps) build(ctx context.Context, job delivery.BuildJob) (any, error) {
+	answer := delivery.BuildAnswer{}
+	if job.Toolchain != nil && s.Toolchain != nil {
+		tc, err := s.Toolchain(ctx)
+		if err != nil {
+			return nil, err
+		}
+		if tc.Version != job.Toolchain.Version || tc.Recipe != job.Toolchain.Recipe {
+			return nil, Refuse("the ask is for %s (recipe %s) and this node builds with %s (recipe %s)",
+				job.Toolchain.Version, job.Toolchain.Recipe, tc.Version, tc.Recipe)
+		}
+		answer.Toolchain = &tc
+	}
+	var f fetched
+	defer func() { s.release(f.Workspace) }()
+	for _, a := range job.Artifacts {
+		if a.From == "" && f.Workspace == "" {
+			r, got, err := s.fetch(ctx, job.Fetch)
+			if err != nil {
+				return nil, err
+			}
+			if _, candidate := job.Fetch["base"]; candidate {
+				// A candidate is built from its head merged onto the trunk; a head that does not merge leaves the tree at the
+				// trunk, and building that would store the trunk's build under the candidate's fingerprint.
+				if len(got.Conflicts) > 0 {
+					return nil, fmt.Errorf("the head does not merge into the trunk: files in conflict: %s", strings.Join(got.Conflicts, ", "))
+				}
+				if got.Merge == "" {
+					return nil, fmt.Errorf("the fetch with a base answered no merge: %s", r)
+				}
+			}
+			f = got
+		}
+		var (
+			out any
+			err error
+		)
+		if a.From != "" {
+			if s.Copy == nil {
+				return nil, Refuse("this build module copies no artifact (%s)", a.Artifact)
+			}
+			Phase(ctx, "copy "+a.Artifact)
+			out, err = s.Copy(ctx, map[string]any{"module": job.Module, "artifact": a.Artifact, "from": a.From})
+		} else {
+			if s.Build == nil {
+				return nil, Refuse("this build module builds no artifact (%s)", a.Artifact)
+			}
+			args := map[string]any{"workspace": f.Workspace, "module": job.Path, "artifact": a.Artifact}
+			if job.Publish {
+				args["publish"] = true
+			}
+			Phase(ctx, "build "+a.Artifact)
+			out, err = s.Build(ctx, args)
+		}
+		if err != nil {
+			return nil, fmt.Errorf("%s: %w", a.Artifact, err)
+		}
+		r, err := raw(out)
+		if err != nil {
+			return nil, err
+		}
+		var built struct {
+			Digest    string `json:"digest"`
+			Reference string `json:"reference"`
+		}
+		if err := json.Unmarshal(r, &built); err != nil || built.Digest == "" {
+			return nil, fmt.Errorf("the build of %s answered no digest: %s", a.Artifact, r)
+		}
+		answer.Artifacts = append(answer.Artifacts, delivery.AskBuilt{Artifact: a.Artifact, Digest: built.Digest, Reference: built.Reference})
+	}
+	return answer, nil
+}
+
+func (s AskSteps) check(ctx context.Context, job delivery.CheckJob) (any, error) {
+	r, f, err := s.fetch(ctx, job.Fetch)
+	if err != nil {
+		return nil, err
+	}
+	defer s.release(f.Workspace)
+	answer := delivery.CheckAnswer{Fetch: r}
+	if len(f.Conflicts) > 0 {
+		return answer, nil // the asker reads the conflict from the fetch's answer: a verdict, not an error
+	}
+	if s.Test == nil {
+		return nil, Refuse("this build module tests nothing")
+	}
+	runner := ""
+	if job.Runner != "" && (job.RunnerWhen == "" || changesUnder(f.Changed, job.RunnerWhen)) {
+		runner = job.Runner
+	}
+	for _, level := range job.Levels {
+		la := delivery.LevelAnswer{Level: level}
+		passed, err := s.level(ctx, job, level, f, runner, &la)
+		answer.Levels = append(answer.Levels, la)
+		if err != nil {
+			return nil, err
+		}
+		if !passed {
+			return answer, nil // the first level that did not pass ends the check (ADR 0484 clause 13)
+		}
+	}
+	return answer, nil
+}
+
+// level runs one level of a check ask and says whether it passed.
+func (s AskSteps) level(ctx context.Context, job delivery.CheckJob, level string, f fetched, runner string, la *delivery.LevelAnswer) (bool, error) {
+	withRunner := func(args map[string]any) map[string]any {
+		if runner != "" {
+			args["runner"] = runner
+		}
+		if len(job.NodeNames) > 0 {
+			args[delivery.NodeNamesArg] = job.NodeNames // the names check's (ADR 0567 §12)
+		}
+		return args
+	}
+	test := func(args map[string]any) (bool, error) {
+		what := "the whole level"
+		if dir, _ := args["module"].(string); dir != "" {
+			what = dir
+		} else if pkgs, _ := args["packages"].([]string); len(pkgs) > 0 {
+			what = fmt.Sprintf("%d packages", len(pkgs))
+		}
+		Phase(ctx, fmt.Sprintf("%s: tests of %s", level, what))
+		out, err := s.Test(ctx, args)
+		if err != nil {
+			return false, err
+		}
+		r, err := raw(out)
+		if err != nil {
+			return false, err
+		}
+		la.Tests = append(la.Tests, r)
+		var t struct {
+			Passed bool `json:"passed"`
+		}
+		_ = json.Unmarshal(r, &t)
+		return t.Passed, nil
+	}
+	// Every test step of the level runs, also after one that did not pass, so one check names every failing test of the
+	// level and not only the first (issue 1921); the level as a whole passes only when each of its steps did.
+	all := true
+	if s.Digest == nil {
+		// A module with no digest (Node) tests each module directory of the tree, those whose tests changed first.
+		for _, priority := range []bool{true, false} {
+			for _, dir := range f.Modules {
+				if changesTestIn(f.Changed, dir) != priority {
+					continue
+				}
+				passed, err := test(withRunner(map[string]any{"workspace": f.Workspace, "module": dir, "level": level}))
+				if err != nil {
+					return false, fmt.Errorf("the %s level of %s: %w", level, dir, err)
+				}
+				all = all && passed
+			}
+		}
+		return all, nil
+	}
+	todo, whole, keepRunner := s.plan(ctx, job, level, f, runner, withRunner, la)
+	if !keepRunner {
+		runner = "" // an installed module that ignores the runner judges the level as it judges any other (ADR 0535 §2)
+	}
+	if whole && len(job.Packages) > 0 {
+		todo, whole = job.Packages, false // a placed ask tests its packages alone, whatever the digest said (ADR 0552 §4)
+	}
+	for _, priority := range []bool{true, false} {
+		args := withRunner(map[string]any{"workspace": f.Workspace, "level": level})
+		if job.Run != "" {
+			args["run"] = job.Run
+		}
+		if whole {
+			if priority {
+				continue // nothing to put first: the level runs whole after
+			}
+		} else {
+			var run []string
+			for _, p := range todo {
+				if changesTestOf(f.Changed, p) == priority {
+					run = append(run, p)
+				}
+			}
+			if len(run) == 0 {
+				continue
+			}
+			args["packages"] = run
+		}
+		passed, err := test(args)
+		if err != nil {
+			return false, fmt.Errorf("the %s level: %w", level, err)
+		}
+		all = all && passed // the packages left still run (issue 1921)
+	}
+	return all, nil
+}
+
+// release removes an ask's workspace, saying a failure: the module's sweep removes it later.
+func (s AskSteps) release(workspace string) {
+	if workspace == "" || s.Release == nil {
+		return
+	}
+	if err := s.Release(workspace); err != nil && s.Logf != nil {
+		s.Logf("the workspace %s is left to the sweep: %v", workspace, err)
+	}
+}
+
+// plan digests the level and takes the kept verdicts: the packages left to test, or all when the level runs whole, and
+// whether the runner stays. A try of some tests runs whole, digesting nothing (a partial run proves no package). Under the
+// candidate's runner the digest is asked as the candidate: when the candidate answers it, every package runs and nothing
+// is digested for keeping (ADR 0535 §4); when the installed module answers it (it does not take the runner), the level is
+// planned as any other and the runner is dropped. The level runs whole and takes nothing when the digest names no package
+// or does not cover the siblings the fetch placed (ADR 0444, L5).
+func (s AskSteps) plan(ctx context.Context, job delivery.CheckJob, level string, f fetched, runner string, withRunner func(map[string]any) map[string]any, la *delivery.LevelAnswer) ([]string, bool, bool) {
+	if job.Run != "" {
+		return nil, true, true
+	}
+	Phase(ctx, level+": digest")
+	out, err := s.Digest(ctx, withRunner(map[string]any{"workspace": f.Workspace, "level": level}))
+	if err != nil {
+		if s.Logf != nil {
+			s.Logf("no digest of the %s level, so it runs whole: %v", level, err)
+		}
+		return nil, true, true
+	}
+	r, err := raw(out)
+	if err != nil {
+		return nil, true, true
+	}
+	var d delivery.LevelDigest // packages kept as a sorted list, never keyed by a package path (issue 1930)
+	if err := json.Unmarshal(r, &d); err != nil {
+		return nil, true, true
+	}
+	if runner != "" {
+		if strings.HasPrefix(d.JudgedBy, "candidate ") {
+			la.Judged = d.JudgedBy
+			return nil, true, true // the candidate decides which verdicts would be taken: all run, nothing kept
+		}
+		runner = ""
+	}
+	if len(d.Packages) == 0 || !slices.Equal(d.Beside, besideOf(job.Fetch)) {
+		return nil, true, runner != "" // a digest that names nothing or not the siblings keys no verdict: the level runs whole
+	}
+	la.Digest = &d
+	only := map[string]bool{}
+	for _, p := range job.Packages {
+		only[p] = true
+	}
+	var todo []string
+	for _, pd := range d.Packages {
+		p := pd.Package
+		if len(only) > 0 && !only[p] {
+			continue // a placed ask's other packages were judged by the first ask (ADR 0552 §4)
+		}
+		if job.Kept && s.Kept != nil {
+			tests, found, err := s.Kept(ctx, level, pd.Digest)
+			if err != nil && s.Logf != nil {
+				s.Logf("the kept verdict of %s at %s cannot be read, so it runs: %v", p, level, err)
+			}
+			if err == nil && found {
+				la.Kept = append(la.Kept, delivery.KeptTaken{Package: p, Digest: pd.Digest, Tests: tests})
+				continue
+			}
+		}
+		if needs := d.NeedsOf(p); len(delivery.Lacks(needs, s.Has)) > 0 {
+			// Its tests would only skip here (issue 890): it is left for a node that has what they need.
+			la.Unmet = append(la.Unmet, delivery.PackageNeeds{Package: p, Needs: needs})
+			if s.Logf != nil {
+				s.Logf("the %s level of %s is left to a node with %s: this node lacks %s", level, p,
+					strings.Join(needs, ", "), strings.Join(delivery.Lacks(needs, s.Has), ", "))
+			}
+			continue
+		}
+		todo = append(todo, p)
+	}
+	return todo, false, false
+}
+
+// besideOf are the siblings a fetch's arguments place, as a digest echoes them: `<owner/repo> <commit>`, sorted.
+func besideOf(fetch map[string]any) []string {
+	raw, err := json.Marshal(fetch["beside"])
+	if err != nil {
+		return nil
+	}
+	var refs []struct {
+		Repository string `json:"repository"`
+		Commit     string `json:"commit"`
+	}
+	_ = json.Unmarshal(raw, &refs)
+	var out []string
+	for _, r := range refs {
+		out = append(out, r.Repository+" "+r.Commit)
+	}
+	sort.Strings(out)
+	return out
+}
+
+// changesUnder says whether a path the merge changes is under prefix.
+func changesUnder(changed []string, prefix string) bool {
+	for _, p := range changed {
+		if strings.HasPrefix(p, prefix) {
+			return true
+		}
+	}
+	return false
+}
+
+// isTestFile says whether a repository-relative path is a test file: Go's _test.go, and a TypeScript module's .test.
+// and .spec. files and test directories.
+func isTestFile(p string) bool {
+	switch {
+	case strings.HasSuffix(p, "_test.go"):
+		return true
+	case strings.Contains(p, ".test.") || strings.Contains(p, ".spec."):
+		return true
+	}
+	for _, seg := range strings.Split(path.Dir(p), "/") {
+		if seg == "__tests__" || seg == "test" || seg == "tests" {
+			return true
+		}
+	}
+	return false
+}
+
+// changesTestOf says whether the merge changes a test file of the Go package with the import path pkg: the file's
+// directory and the import path agree on their last segments.
+func changesTestOf(changed []string, pkg string) bool {
+	for _, f := range changed {
+		if !strings.HasSuffix(f, "_test.go") {
+			continue
+		}
+		dir := path.Dir(f)
+		if dir == pkg || strings.HasSuffix(pkg, "/"+dir) || strings.HasSuffix(dir, "/"+pkg) {
+			return true
+		}
+	}
+	return false
+}
+
+// changesTestIn says whether the merge changes a test file inside the directory of a Node module.
+func changesTestIn(changed []string, dir string) bool {
+	for _, f := range changed {
+		if !isTestFile(f) || strings.HasSuffix(f, "_test.go") {
+			continue
+		}
+		if dir == "." || dir == "" || strings.HasPrefix(f, strings.TrimSuffix(dir, "/")+"/") {
+			return true
+		}
+	}
+	return false
+}

go/buildstep/askrun_test.go

@@ -0,0 +1,294 @@
+package buildstep
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+const runCommit = "0123456789abcdef0123456789abcdef01234567"
+
+// recorder is a build module's step tools that record each call.
+type recorder struct {
+	calls   []string
+	fetch   map[string]any
+	tests   map[string]bool // package or module directory -> passed
+	digests map[string]string
+	needs   []delivery.PackageNeeds
+}
+
+func (r *recorder) steps() AskSteps {
+	call := func(name string, answer func(args map[string]any) any) StepFunc {
+		return func(ctx context.Context, args map[string]any) (any, error) {
+			b, _ := json.Marshal(args)
+			r.calls = append(r.calls, name+" "+string(b))
+			return answer(args), nil
+		}
+	}
+	return AskSteps{
+		Fetch: call("fetch", func(map[string]any) any { return r.fetch }),
+		Build: call("build", func(args map[string]any) any {
+			return map[string]any{"digest": "sha256:" + args["artifact"].(string), "reference": "artifact-store://" + args["artifact"].(string)}
+		}),
+		Copy: call("copy", func(args map[string]any) any { return map[string]any{"digest": "sha256:copied"} }),
+		Digest: call("digest", func(map[string]any) any {
+			return map[string]any{"level": "unit", "packages": r.digests, "needs": r.needs}
+		}),
+		Test: call("test", func(args map[string]any) any {
+			passed := true
+			if pkgs, ok := args["packages"].([]string); ok {
+				for _, p := range pkgs {
+					passed = passed && r.tests[p]
+				}
+			}
+			if dir, ok := args["module"].(string); ok {
+				passed = r.tests[dir]
+			}
+			return map[string]any{"passed": passed, "tests": 1}
+		}),
+		Kept: func(ctx context.Context, level, digest string) (int, bool, error) { return 7, digest == "d-kept", nil },
+	}
+}
+
+func ask(job any) delivery.StepAsk {
+	a := delivery.StepAsk{ID: NewID(), Kind: delivery.AskCheck, Language: delivery.AskGo, Asker: "t", At: time.Now()}
+	switch j := job.(type) {
+	case delivery.BuildJob:
+		a.Build = &j
+	case delivery.CheckJob:
+		a.Check = &j
+	}
+	return a
+}
+
+// 1887/A3: a build ask fetches once, builds each artifact from the workspace with publish, copies a pinned one without a
+// fetch, and answers each artifact's digest and reference.
+func TestRunAskBuilds(t *testing.T) {
+	r := &recorder{fetch: map[string]any{"workspace": "/w/1"}}
+	steps := r.steps()
+	var released []string
+	steps.Release = func(ws string) error { released = append(released, ws); return nil }
+	out, err := RunAsk(context.Background(), steps, ask(delivery.BuildJob{Module: "m", Path: "modules/m", Publish: true,
+		Fetch:     map[string]any{"repository": "novox/x", "commit": runCommit},
+		Artifacts: []delivery.AskArtifact{{Artifact: "base", From: "registry/b@sha256:00"}, {Artifact: "bundle"}, {Artifact: "lib"}}}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := strings.Join(r.calls, "\n")
+	want := `copy {"artifact":"base","from":"registry/b@sha256:00","module":"m"}
+fetch {"commit":"` + runCommit + `","repository":"novox/x"}
+build {"artifact":"bundle","module":"modules/m","publish":true,"workspace":"/w/1"}
+build {"artifact":"lib","module":"modules/m","publish":true,"workspace":"/w/1"}`
+	if got != want {
+		t.Fatalf("calls:\n%s\nwant:\n%s", got, want)
+	}
+	if len(released) != 1 || released[0] != "/w/1" {
+		t.Errorf("released %v, want the one workspace", released)
+	}
+	a := out.(delivery.BuildAnswer)
+	if len(a.Artifacts) != 3 || a.Artifacts[1].Reference != "artifact-store://bundle" {
+		t.Fatalf("answer %+v", a)
+	}
+}
+
+// A build ask for another toolchain is refused, so its step ends refused and the asker reads why.
+func TestRunAskRefusesAnotherToolchain(t *testing.T) {
+	r := &recorder{fetch: map[string]any{"workspace": "/w"}}
+	s := r.steps()
+	s.Toolchain = func(context.Context) (delivery.ToolchainUsed, error) {
+		return delivery.ToolchainUsed{Version: "go1.27", Recipe: "3"}, nil
+	}
+	_, err := RunAsk(context.Background(), s, ask(delivery.BuildJob{Module: "m", Path: ".", Fetch: map[string]any{"repository": "novox/x", "commit": runCommit},
+		Artifacts: []delivery.AskArtifact{{Artifact: "bundle"}}, Toolchain: &delivery.ToolchainUsed{Version: "go1.26", Recipe: "3"}}))
+	var ref *Refusal
+	if !errors.As(err, &ref) || len(r.calls) != 0 {
+		t.Fatalf("err %v, calls %v", err, r.calls)
+	}
+}
+
+// 1887/A3, A5a: a check ask runs the levels of one check after one fetch: it digests the unit level, takes the kept
+// verdicts, tests the packages whose tests changed first, then the rest also after a failure (issue 1921), and runs no
+// level after one that did not pass (ADR 0484 clause 13).
+func TestRunAskChecksTheLevelsOfOneCheck(t *testing.T) {
+	r := &recorder{
+		fetch:   map[string]any{"workspace": "/w", "changed": []string{"pkg/b/b_test.go"}},
+		digests: map[string]string{"x/pkg/a": "d-a", "x/pkg/b": "d-b", "x/pkg/k": "d-kept"},
+		tests:   map[string]bool{"x/pkg/a": true, "x/pkg/b": false},
+	}
+	out, err := RunAsk(context.Background(), r.steps(), ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit, delivery.LevelIntegration}, Kept: true,
+		Runner: "workspace", RunnerWhen: "modules/mesh-build-go/", Fetch: map[string]any{"repository": "novox/x", "commit": runCommit, "base": runCommit}}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := strings.Join(r.calls, "\n")
+	want := `fetch {"base":"` + runCommit + `","commit":"` + runCommit + `","repository":"novox/x"}
+digest {"level":"unit","workspace":"/w"}
+test {"level":"unit","packages":["x/pkg/b"],"workspace":"/w"}
+test {"level":"unit","packages":["x/pkg/a"],"workspace":"/w"}`
+	if got != want {
+		t.Fatalf("calls:\n%s\nwant:\n%s", got, want)
+	}
+	a := out.(delivery.CheckAnswer)
+	if len(a.Levels) != 1 {
+		t.Fatalf("levels %+v, want the unit level alone", a.Levels)
+	}
+	u := a.Levels[0]
+	if u.Level != delivery.LevelUnit || len(u.Kept) != 1 || u.Kept[0].Package != "x/pkg/k" || u.Kept[0].Tests != 7 || len(u.Tests) != 2 || u.Digest == nil {
+		t.Fatalf("the unit level %+v", u)
+	}
+
+	// ADR 0567 §12: a check's node names reach the digest and test tools, for the names check (a kept verdict misses when
+	// they change).
+	r.calls = nil
+	if _, err := RunAsk(context.Background(), r.steps(), ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit}, NodeNames: []string{"anchor"},
+		Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}})); err != nil || !strings.Contains(strings.Join(r.calls, "\n"), `digest {"level":"unit","node-names":["anchor"]`) ||
+		!strings.Contains(strings.Join(r.calls, "\n"), `test {"level":"unit","node-names":["anchor"]`) {
+		t.Fatalf("the node names are not handed to the digest and test tools: %v, %v", r.calls, err)
+	}
+
+	// Issue 890/AC2: a package declaring node-build-node is not tested on a node that lacks it but named unmet, and is
+	// tested on a node that has it.
+	for _, has := range []bool{false, true} {
+		r.calls, r.tests["x/pkg/b"] = nil, true
+		r.needs = []delivery.PackageNeeds{{Package: "x/pkg/a", Needs: []string{delivery.NeedNodeBuildNode}}}
+		steps := r.steps()
+		if has {
+			steps.Has = func(n string) bool { return n == delivery.NeedNodeBuildNode }
+		}
+		out, err := RunAsk(context.Background(), steps, ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit}, Kept: true,
+			Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}}))
+		if err != nil {
+			t.Fatal(err)
+		}
+		u := out.(delivery.CheckAnswer).Levels[0]
+		tested := strings.Contains(strings.Join(r.calls, "\n"), `"x/pkg/a"`)
+		if tested != has || (len(u.Unmet) == 0) == !has || (!has && (u.Unmet[0].Package != "x/pkg/a" || delivery.UnmetNeeds([]delivery.LevelAnswer{u})[0] != delivery.NeedNodeBuildNode)) {
+			t.Fatalf("has %v: tested x/pkg/a %v, unmet %+v, calls %v", has, tested, u.Unmet, r.calls)
+		}
+	}
+	// A placed ask naming its packages tests those alone and takes no other's kept verdict, also when the level would
+	// run whole (ADR 0552 §4).
+	for _, digests := range []map[string]string{r.digests, nil} {
+		r.calls, r.digests = nil, digests
+		steps := r.steps()
+		steps.Has = func(string) bool { return true }
+		out, err := RunAsk(context.Background(), steps, ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit}, Kept: true, Packages: []string{"x/pkg/a"},
+			Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}}))
+		if err != nil {
+			t.Fatal(err)
+		}
+		u := out.(delivery.CheckAnswer).Levels[0]
+		if last := r.calls[len(r.calls)-1]; !strings.HasSuffix(last, `"packages":["x/pkg/a"],"workspace":"/w"}`) || len(u.Kept) != 0 || len(u.Tests) != 1 {
+			t.Fatalf("digests %v: calls %v, kept %+v: want x/pkg/a alone tested, nothing taken kept", digests != nil, r.calls, u.Kept)
+		}
+	}
+}
+
+// ADR 0535 §2, §4: a merge that changes the build module's own code is judged by the candidate's runner: its digest says
+// the candidate ran, and every package runs with nothing kept; an installed module that ignores the runner is planned as
+// any other, the runner dropped. A digest that does not cover the fetch's siblings runs the level whole too.
+func TestRunAskRunsWholeUnderTheRunnerOrWithoutTheSiblings(t *testing.T) {
+	for _, tc := range []struct{ judged, want string }{
+		{"candidate 999", `digest {"level":"unit","runner":"workspace","workspace":"/w"}
+test {"level":"unit","runner":"workspace","workspace":"/w"}`},
+		{"installed", `digest {"level":"unit","runner":"workspace","workspace":"/w"}`},
+	} {
+		r := &recorder{fetch: map[string]any{"workspace": "/w", "changed": []string{"modules/mesh-build-go/x.go"}},
+			digests: map[string]string{"x/pkg/a": "d-kept"}, tests: map[string]bool{}}
+		steps := r.steps()
+		digest := steps.Digest
+		steps.Digest = func(ctx context.Context, args map[string]any) (any, error) {
+			_, _ = digest(ctx, args)
+			return map[string]any{"level": "unit", "packages": r.digests, "judged_by": tc.judged}, nil
+		}
+		out, err := RunAsk(context.Background(), steps, ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit}, Kept: true,
+			Runner: "workspace", RunnerWhen: "modules/mesh-build-go/", Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}}))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got := strings.Join(r.calls[1:], "\n"); got != tc.want {
+			t.Errorf("judged by %s: calls\n%s\nwant\n%s", tc.judged, got, tc.want)
+		}
+		l := out.(delivery.CheckAnswer).Levels[0]
+		if tc.judged == "installed" && (len(l.Kept) != 1 || l.Judged != "") {
+			t.Errorf("an installed module's level %+v, want the kept verdict taken", l)
+		}
+		if tc.judged != "installed" && (len(l.Kept) != 0 || l.Digest != nil || l.Judged != tc.judged) {
+			t.Errorf("the candidate's level %+v, want nothing kept and the program named", l)
+		}
+	}
+	r := &recorder{fetch: map[string]any{"workspace": "/w"}, digests: map[string]string{"x/pkg/a": "d-kept"}, tests: map[string]bool{}}
+	out, err := RunAsk(context.Background(), r.steps(), ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit}, Kept: true,
+		Fetch: map[string]any{"repository": "novox/x", "commit": runCommit, "beside": []any{map[string]any{"repository": "novox/mesh-sdk", "commit": runCommit}}}}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if l := out.(delivery.CheckAnswer).Levels[0]; len(l.Kept) != 0 || l.Digest != nil {
+		t.Fatalf("a digest without the siblings kept %+v", l)
+	}
+}
+
+// A Node check tests each module directory, the one whose tests changed first; a conflict ends the ask with the fetch
+// alone, a verdict for the asker.
+func TestRunAskChecksNodeModulesAndConflicts(t *testing.T) {
+	r := &recorder{fetch: map[string]any{"workspace": "/w", "modules": []string{"a", "b"}, "changed": []string{"b/test/x.test.ts"}},
+		tests: map[string]bool{"a": true, "b": true}}
+	s := r.steps()
+	s.Digest = nil
+	if _, err := RunAsk(context.Background(), s, ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit}, Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}})); err != nil {
+		t.Fatal(err)
+	}
+	if fmt.Sprint(r.calls[1:]) != `[test {"level":"unit","module":"b","workspace":"/w"} test {"level":"unit","module":"a","workspace":"/w"}]` {
+		t.Fatalf("calls %v", r.calls)
+	}
+	r = &recorder{fetch: map[string]any{"workspace": "/w", "conflicts": []string{"go.mod"}}}
+	out, err := RunAsk(context.Background(), r.steps(), ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit}, Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}}))
+	if err != nil || len(r.calls) != 1 || len(out.(delivery.CheckAnswer).Levels) != 0 {
+		t.Fatalf("a conflict: %v %v", err, r.calls)
+	}
+}
+
+// Issue 1921: a failure in the packages whose tests changed does not stop the level: the other packages still run, so two
+// failing packages, one changed and one not, are two test results of the one level, and the level does not pass. A Node
+// check runs every module directory after one fails too.
+func TestRunAskRunsEveryPackageAfterAFailure(t *testing.T) {
+	r := &recorder{
+		fetch:   map[string]any{"workspace": "/w", "changed": []string{"pkg/b/b_test.go"}},
+		digests: map[string]string{"x/pkg/a": "d-a", "x/pkg/b": "d-b"},
+		tests:   map[string]bool{"x/pkg/a": false, "x/pkg/b": false},
+	}
+	out, err := RunAsk(context.Background(), r.steps(), ask(delivery.CheckJob{Levels: []string{delivery.LevelIntegration, delivery.LevelUnit},
+		Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	a := out.(delivery.CheckAnswer)
+	if len(a.Levels) != 1 || len(a.Levels[0].Tests) != 2 {
+		t.Fatalf("levels %+v, want the one level with both packages' results", a.Levels)
+	}
+	for i, raw := range a.Levels[0].Tests {
+		var res struct{ Passed bool }
+		if err := json.Unmarshal(raw, &res); err != nil || res.Passed {
+			t.Errorf("result %d %s, want a failure", i, raw)
+		}
+	}
+
+	r = &recorder{fetch: map[string]any{"workspace": "/w", "modules": []string{"a", "b"}, "changed": []string{"b/test/x.test.ts"}},
+		tests: map[string]bool{"a": true, "b": false}}
+	s := r.steps()
+	s.Digest = nil
+	out, err = RunAsk(context.Background(), s, ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit, delivery.LevelIntegration},
+		Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if a := out.(delivery.CheckAnswer); len(r.calls) != 3 || len(a.Levels) != 1 || len(a.Levels[0].Tests) != 2 {
+		t.Fatalf("calls %v, levels %+v: want both directories of the unit level and no integration level", r.calls, a.Levels)
+	}
+}

go/buildstep/blob.go

@@ -0,0 +1,170 @@
+package buildstep
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"syscall"
+	"time"
+)
+
+// RegistryWait is how long a push waits for an artifact store that refuses connections, longer than its nightly
+// collection holds it still (about a minute and a half, issue 457); RegistryFirstPause is the first pause, doubling
+// to RegistryMostPause. Variables so a test shortens them.
+var (
+	RegistryWait       = 5 * time.Minute
+	RegistryFirstPause = time.Second
+	RegistryMostPause  = 10 * time.Second
+)
+
+// BlobReference is where a pushed bundle or archive is, as a done key names it and the controller delivers from
+// (novox/hq ADR 0498 clause 1): artifact-store://<module>/<artifact>/blobs/<digest>, the store's address left out
+// (issue 102).
+func BlobReference(module, artifact, digest string) string {
+	return "artifact-store://" + module + "/" + artifact + "/blobs/" + digest
+}
+
+// PushBlob puts body into the artifact store at registry (host:port) as a blob of repository (<module>/<artifact>) by
+// its digest (`sha256:` and hex), from the build module's own process, after the build step ended (novox/hq ADR 0498
+// clauses 1 and 2): a blob the store already holds is done without an upload; otherwise it is uploaded (POST
+// blobs/uploads/, then PUT with the digest). A store refusing connections is waited out up to RegistryWait; any other
+// refusal fails, naming the store's status and its own words, for the caller's `not stored:` error. Bytes that are not
+// their digest are refused before anything is sent.
+func PushBlob(ctx context.Context, client *http.Client, registry, repository, digest string, body []byte) error {
+	sum := sha256.Sum256(body)
+	if got := "sha256:" + hex.EncodeToString(sum[:]); got != digest {
+		return fmt.Errorf("the blob is %s, not the digest %s it was to be pushed as", got, digest)
+	}
+	if client == nil {
+		client = http.DefaultClient
+	}
+	base := "http://" + registry + "/v2/" + repository + "/blobs/"
+	var present bool
+	if err := waitForStore(ctx, registry, func() error {
+		var err error
+		present, err = blobPresent(ctx, client, base+digest)
+		return err
+	}); err != nil {
+		return err
+	}
+	if present {
+		return nil
+	}
+	var location string
+	if err := waitForStore(ctx, registry, func() error {
+		var err error
+		location, err = startUpload(ctx, client, base+"uploads/")
+		return err
+	}); err != nil {
+		return err
+	}
+	target, err := url.Parse(base)
+	if err != nil {
+		return err
+	}
+	loc, err := target.Parse(location)
+	if err != nil {
+		return fmt.Errorf("the store answered the upload's location %q, which is not a URL: %w", location, err)
+	}
+	q := loc.Query()
+	q.Set("digest", digest)
+	loc.RawQuery = q.Encode()
+	req, err := http.NewRequestWithContext(ctx, http.MethodPut, loc.String(), bytes.NewReader(body))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/octet-stream")
+	resp, err := client.Do(req)
+	if err != nil {
+		return fmt.Errorf("putting %s of %s: %w", digest, repository, err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusCreated {
+		return storeSaid(resp, "putting "+digest+" of "+repository)
+	}
+	return nil
+}
+
+func blobPresent(ctx context.Context, client *http.Client, at string) (bool, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodHead, at, nil)
+	if err != nil {
+		return false, err
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		return false, err
+	}
+	resp.Body.Close()
+	switch resp.StatusCode {
+	case http.StatusOK:
+		return true, nil
+	case http.StatusNotFound:
+		return false, nil
+	}
+	return false, fmt.Errorf("asking the store for %s: it answered %s", at, resp.Status)
+}
+
+func startUpload(ctx context.Context, client *http.Client, at string) (string, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, at, nil)
+	if err != nil {
+		return "", err
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusAccepted {
+		return "", storeSaid(resp, "starting an upload at "+at)
+	}
+	location := resp.Header.Get("Location")
+	if location == "" {
+		return "", fmt.Errorf("starting an upload at %s: the store named no location", at)
+	}
+	return location, nil
+}
+
+// storeSaid is the store's refusal: its status and the first of its own words.
+func storeSaid(resp *http.Response, what string) error {
+	words, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
+	return fmt.Errorf("%s: the store answered %s: %s", what, resp.Status, strings.TrimSpace(string(words)))
+}
+
+// refused is whether an error is a connection refused.
+func refused(err error) bool {
+	return err != nil && (errors.Is(err, syscall.ECONNREFUSED) || strings.Contains(err.Error(), "connection refused"))
+}
+
+// waitForStore runs try, and while it fails because the store refuses connections, tries again with a growing pause
+// until RegistryWait has passed. A refusal is the one error waited for: nothing was sent, so trying again does nothing
+// twice.
+func waitForStore(ctx context.Context, registry string, try func() error) error {
+	err := try()
+	if !refused(err) {
+		return err
+	}
+	started, pause := time.Now(), RegistryFirstPause
+	for {
+		left := RegistryWait - time.Since(started)
+		if left <= 0 {
+			return fmt.Errorf("the artifact store at %s refused every connection for %s, longer than its nightly collection holds it still, so it is down, not paused: %w",
+				registry, time.Since(started).Round(time.Millisecond), err)
+		}
+		select {
+		case <-ctx.Done():
+			return fmt.Errorf("stopped while waiting for the artifact store at %s: %w (last: %v)", registry, ctx.Err(), err)
+		case <-time.After(min(pause, left)):
+		}
+		pause = min(pause*2, RegistryMostPause)
+		if err = try(); !refused(err) {
+			return err
+		}
+	}
+}

go/buildstep/blob_test.go

@@ -0,0 +1,151 @@
+package buildstep
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+func digestOfBytes(b []byte) string {
+	h := sha256.Sum256(b)
+	return "sha256:" + hex.EncodeToString(h[:])
+}
+
+// registry is an artifact store as far as a blob push needs one: HEAD a blob, start an upload, PUT it with its digest.
+type registry struct {
+	mu    sync.Mutex
+	blobs map[string][]byte
+	calls []string
+	put   int // the status a PUT answers, 201 when 0
+}
+
+func (r *registry) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.calls = append(r.calls, req.Method+" "+req.URL.Path)
+	switch {
+	case req.Method == http.MethodHead && strings.Contains(req.URL.Path, "/blobs/sha256:"):
+		if _, ok := r.blobs[req.URL.Path[strings.LastIndex(req.URL.Path, "/")+1:]]; ok {
+			w.WriteHeader(http.StatusOK)
+			return
+		}
+		w.WriteHeader(http.StatusNotFound)
+	case req.Method == http.MethodPost && strings.HasSuffix(req.URL.Path, "/blobs/uploads/"):
+		w.Header().Set("Location", strings.TrimSuffix(req.URL.Path, "/")+"/u1?state=x")
+		w.WriteHeader(http.StatusAccepted)
+	case req.Method == http.MethodPut && strings.Contains(req.URL.Path, "/blobs/uploads/u1"):
+		if r.put != 0 {
+			w.WriteHeader(r.put)
+			_, _ = io.WriteString(w, `{"errors":[{"code":"DIGEST_INVALID","message":"provided digest did not match uploaded content"}]}`)
+			return
+		}
+		body, _ := io.ReadAll(req.Body)
+		d := req.URL.Query().Get("digest")
+		if req.URL.Query().Get("state") != "x" || d != digestOfBytes(body) {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		r.blobs[d] = body
+		w.WriteHeader(http.StatusCreated)
+	default:
+		w.WriteHeader(http.StatusMethodNotAllowed)
+	}
+}
+
+// A done build's bundle or archive is pushed to the artifact store by its build module (novox/hq ADR 0498 clauses 1
+// and 2): a blob the store already holds is done with no upload; one it lacks is uploaded by digest; its reference is
+// the artifact-store form the builder's key and the controller check.
+func TestABlobIsPushedOnceByItsDigest(t *testing.T) {
+	reg := &registry{blobs: map[string][]byte{}}
+	srv := httptest.NewServer(reg)
+	defer srv.Close()
+	addr := strings.TrimPrefix(srv.URL, "http://")
+	body := []byte("the packed bundle")
+	d := digestOfBytes(body)
+	if err := PushBlob(context.Background(), srv.Client(), addr, "mail/code", d, body); err != nil {
+		t.Fatal(err)
+	}
+	if string(reg.blobs[d]) != string(body) {
+		t.Fatalf("the store holds %q", reg.blobs[d])
+	}
+	reg.calls = nil
+	if err := PushBlob(context.Background(), srv.Client(), addr, "mail/code", d, body); err != nil {
+		t.Fatal(err)
+	}
+	if len(reg.calls) != 1 || !strings.HasPrefix(reg.calls[0], "HEAD ") {
+		t.Fatalf("a blob the store holds was uploaded again: %v", reg.calls)
+	}
+	ref := BlobReference("mail", "code", d)
+	if ref != "artifact-store://mail/code/blobs/"+d {
+		t.Fatalf("BlobReference = %q", ref)
+	}
+	b := delivery.BuilderBuild{State: delivery.BuildDone, Manifest: strings.Repeat("4", 64),
+		Artifacts: []delivery.BuiltArtifact{{Name: "code", Kind: "bundle", Digest: d, Reference: ref}}}
+	if _, err := delivery.EncodeBuilderBuild(b); err != nil {
+		t.Fatalf("the key refuses the reference BlobReference gives: %v", err)
+	}
+}
+
+// A store that refuses the upload fails the push naming the store's own words; bytes that are not the digest are
+// refused before anything is sent.
+func TestAPushTheStoreRefusesSaysTheStoresWords(t *testing.T) {
+	reg := &registry{blobs: map[string][]byte{}, put: http.StatusBadRequest}
+	srv := httptest.NewServer(reg)
+	defer srv.Close()
+	addr := strings.TrimPrefix(srv.URL, "http://")
+	body := []byte("x")
+	err := PushBlob(context.Background(), srv.Client(), addr, "mail/code", digestOfBytes(body), body)
+	if err == nil || !strings.Contains(err.Error(), "provided digest did not match") || !strings.Contains(err.Error(), "400") {
+		t.Fatalf("a refused upload said %v", err)
+	}
+	reg.calls = nil
+	err = PushBlob(context.Background(), srv.Client(), addr, "mail/code", digestOfBytes([]byte("other")), body)
+	if err == nil || len(reg.calls) != 0 {
+		t.Fatalf("bytes that are not their digest: %v, calls %v", err, reg.calls)
+	}
+}
+
+// A store refusing connections (its nightly collection holds it still) is waited out, up to RegistryWait (issue 457).
+func TestAPushWaitsOutAStoreRefusingConnections(t *testing.T) {
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	addr := l.Addr().String()
+	l.Close() // refusing now
+	reg := &registry{blobs: map[string][]byte{}}
+	go func() {
+		time.Sleep(300 * time.Millisecond)
+		l2, err := net.Listen("tcp", addr)
+		if err != nil {
+			return
+		}
+		_ = http.Serve(l2, reg)
+	}()
+	beforeWait, beforePause := RegistryWait, RegistryFirstPause
+	RegistryWait, RegistryFirstPause = 3*time.Second, 100*time.Millisecond
+	defer func() { RegistryWait, RegistryFirstPause = beforeWait, beforePause }()
+	body := []byte("late")
+	if err := PushBlob(context.Background(), http.DefaultClient, addr, "mail/code", digestOfBytes(body), body); err != nil {
+		t.Fatalf("a store that came back was not waited for: %v", err)
+	}
+
+	l3, _ := net.Listen("tcp", "127.0.0.1:0")
+	gone := l3.Addr().String()
+	l3.Close()
+	RegistryWait = 300 * time.Millisecond
+	err = PushBlob(context.Background(), http.DefaultClient, gone, "mail/code", digestOfBytes(body), body)
+	if err == nil || !strings.Contains(err.Error(), "refused every connection") {
+		t.Fatalf("a store that stayed down said %v", err)
+	}
+}

go/buildstep/buildhours.go

@@ -0,0 +1,129 @@
+package buildstep
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+)
+
+// **A node may build only within its build hours** (the operator, 2026-10-26 21:18: the laptop builds only outside
+// office hours, "from 18 o'clock until 6 in the morning"). A build module's `build-hours` setting is the node's window
+// in its local time, a config value set on each node's layer of mesh-config (ADR 0567 §12: no repository names a node);
+// outside it the capacity judged by is 0: steps running finish, no new one is taken. An empty value builds at any hour.
+// The puller judges it at every judgement and wakes on one timer to the window's next edge (a clock edge, not a poll of
+// another part).
+
+// BuildHoursSetting is the build modules' setting of the node's build window: HH:MM-HH:MM in the node's local time; an
+// end before its start crosses midnight (18:00-06:00).
+const BuildHoursSetting = "build-hours"
+
+// BuildWindow is one node's build hours: minutes after local midnight, Start inclusive, End exclusive.
+type BuildWindow struct {
+	Start, End int
+}
+
+// String is the window as the setting writes it.
+func (w BuildWindow) String() string {
+	return fmt.Sprintf("%02d:%02d-%02d:%02d", w.Start/60, w.Start%60, w.End/60, w.End%60)
+}
+
+// Open says whether t, in its own location, falls in the window.
+func (w BuildWindow) Open(t time.Time) bool {
+	m := t.Hour()*60 + t.Minute()
+	if w.Start < w.End {
+		return m >= w.Start && m < w.End
+	}
+	return m >= w.Start || m < w.End
+}
+
+// NextEdge is the first time after t, in t's location, at which the window opens or closes.
+func (w BuildWindow) NextEdge(t time.Time) time.Time {
+	var next time.Time
+	for day := 0; day <= 1; day++ {
+		for _, m := range []int{w.Start, w.End} {
+			e := time.Date(t.Year(), t.Month(), t.Day()+day, m/60, m%60, 0, 0, t.Location())
+			if e.After(t) && (next.IsZero() || e.Before(next)) {
+				next = e
+			}
+		}
+	}
+	return next
+}
+
+// ParseBuildWindow reads a build-hours value, HH:MM-HH:MM: nil when it is empty.
+func ParseBuildWindow(setting string) (*BuildWindow, error) {
+	setting = strings.TrimSpace(setting)
+	if setting == "" {
+		return nil, nil
+	}
+	from, to, ok := strings.Cut(setting, "-")
+	if !ok {
+		return nil, fmt.Errorf("the build hours %q are not HH:MM-HH:MM", setting)
+	}
+	start, err := minuteOf(from)
+	if err != nil {
+		return nil, fmt.Errorf("the build hours %q: %v", setting, err)
+	}
+	end, err := minuteOf(to)
+	if err != nil {
+		return nil, fmt.Errorf("the build hours %q: %v", setting, err)
+	}
+	if start == end {
+		return nil, fmt.Errorf("the build hours %q open and close at the same minute", setting)
+	}
+	return &BuildWindow{Start: start, End: end}, nil
+}
+
+// minuteOf reads HH:MM as minutes after midnight.
+func minuteOf(s string) (int, error) {
+	var h, m int
+	s = strings.TrimSpace(s)
+	if n, err := fmt.Sscanf(s, "%d:%d", &h, &m); err != nil || n != 2 || h < 0 || h > 23 || m < 0 || m > 59 || len(s) != 5 {
+		return 0, fmt.Errorf("%q is not a time HH:MM", s)
+	}
+	return h*60 + m, nil
+}
+
+// NodeBuildHours is the node's build window, read from the module's settings file at path at every call, and why it is
+// none when the value cannot be read. No path, no file value or an empty one is no window and no fault. A value that
+// cannot be read is no window too, so the node builds at any hour; the setting is a preference of hours, not a safety
+// bound (a node that must never build has capacity 0). It is loud: the fault is said once per distinct fault through
+// logf, and the puller writes it in the capacity record that build_usage shows.
+func NodeBuildHours(path, node string, logf func(string, ...any)) func() (*BuildWindow, string) {
+	said := ""
+	say := func(why string) {
+		if logf != nil && why != said {
+			said = why
+			logf("%s, so %s builds at any hour", why, node)
+		}
+	}
+	fault := func(why string) (*BuildWindow, string) {
+		say(why)
+		return nil, why
+	}
+	return func() (*BuildWindow, string) {
+		if path == "" {
+			return nil, ""
+		}
+		raw, err := os.ReadFile(path)
+		if err != nil {
+			return fault(fmt.Sprintf("the setting %s cannot be read: %v", BuildHoursSetting, err))
+		}
+		var s map[string]json.RawMessage
+		if err := json.Unmarshal(raw, &s); err != nil {
+			return fault(fmt.Sprintf("the settings file %s is not JSON: %v", path, err))
+		}
+		setting := ""
+		if v, ok := s[BuildHoursSetting]; ok && json.Unmarshal(v, &setting) != nil {
+			return fault(fmt.Sprintf("the setting %s %s is not a string", BuildHoursSetting, v))
+		}
+		w, err := ParseBuildWindow(setting)
+		if err != nil {
+			return fault(err.Error())
+		}
+		said = ""
+		return w, ""
+	}
+}

go/buildstep/capacity.go

@@ -0,0 +1,61 @@
+package buildstep
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+)
+
+// CapacitySetting is the build modules' setting of the node's build capacity (novox/hq ADR 0525 §5, ADR 0567 §12): how
+// many asks the node takes at once, an integer config value set on each node's layer of mesh-config. No repository names
+// a node: each build module declares it with the default 0, which pulls nothing, and the controller (or mesh-config)
+// lays the node's value into the module's settings file.
+const CapacitySetting = "capacity"
+
+// NodeCapacity is the node's build capacity, read from the module's settings file at path at every call, so a change
+// takes effect at the next pull. No path, no file value, or a value that is not a whole number of at least 0 gives 0 and
+// a value that cannot be read says why: pulling on a setting nobody can read could build on a node that must not.
+func NodeCapacity(path, node string, logf func(string, ...any)) func() int {
+	say := func(format string, args ...any) {
+		if logf != nil {
+			logf(format, args...)
+		}
+	}
+	return func() int {
+		n, err := ReadCapacity(path)
+		if err != nil {
+			say("%v, so %s pulls nothing", err, node)
+			return 0
+		}
+		return n
+	}
+}
+
+// ReadCapacity is the capacity the settings file at path holds, and why it cannot be read when it cannot (then 0).
+func ReadCapacity(path string) (int, error) {
+	if path == "" {
+		return 0, nil
+	}
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return 0, fmt.Errorf("the build capacity cannot be read: %w", err)
+	}
+	var s map[string]json.RawMessage
+	if err := json.Unmarshal(raw, &s); err != nil {
+		return 0, fmt.Errorf("the settings file %s is not JSON: %w", path, err)
+	}
+	return capacityOf(s[CapacitySetting])
+}
+
+// capacityOf is the capacity a config value holds: absent or null is 0; anything but a whole number of at least 0 is
+// refused, naming it.
+func capacityOf(value json.RawMessage) (int, error) {
+	if len(value) == 0 || string(value) == "null" {
+		return 0, nil
+	}
+	var n int
+	if err := json.Unmarshal(value, &n); err != nil || n < 0 {
+		return 0, fmt.Errorf("the build capacity %s is not a whole number of asks at once, 0 or more", value)
+	}
+	return n, nil
+}

go/buildstep/capacity_cpu.go

@@ -0,0 +1,141 @@
+package buildstep
+
+import (
+	"encoding/json"
+	"fmt"
+	"math"
+	"os"
+	"runtime"
+	"strconv"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/buildcpu"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **A build seat's capacity follows the CPU its node gives builds** (issue 1806's follow-up; issue 1890, 2026-10-26
+// 19:41: under the 50 % cap the workstation's mesh-build-go kept capacity 3, three full mesh-catalog checks shared 12 cores, and
+// each step ran past the 30-minute step bound with no test run). The configured capacity is an upper bound; the node's
+// build slice bounds it again by the cores a step needs: floor(the slice's quota in cores / cores-per-step), one at
+// least. The quota is read live from the cgroup at every judgement, so a changed cap is followed at the next take
+// without a restart, and the result is said (the seat's current verb, the status tools, `capacity.<node>` in the pauses
+// state that the delivery view's build_usage reads).
+
+// CoresPerStepSetting is a build module's setting of the processors one of its steps needs: a number above zero, the
+// same on every node (a step's need is the module's, not the node's). Each build module declares it with its own default
+// (DefaultCoresPerStep).
+const CoresPerStepSetting = "cores-per-step"
+
+// DefaultCoresPerStep are the build modules' defaults by language, from measured steps (2026-10-26): a full mesh-catalog
+// check on mesh-build-go takes what it is given (three at once took 965 % of the workstation's 1200 % slice, about 4 cores each,
+// and ran past the 30-minute step bound), so a Go step is given 6, half again what starved; a Node step (tsc, esbuild, a
+// test runner: median 15 s) and an image build (buildah, its RUN lines mostly fetches) need 2.
+var DefaultCoresPerStep = map[string]float64{delivery.AskGo: 6, delivery.AskNode: 2, delivery.AskImage: 2}
+
+// Quota is the build slice's CPU quota as this process's cgroup holds it, in percent of one processor (1200 is 12
+// cores), and where it was read: the cgroup's cpu.max (buildcpu.ReadInForce, the tighter of its unit's and its slice's),
+// else the share the composer gave (buildcpu.ShareWord) over the machine's processors, else 0 and why none is known.
+func Quota() (percent int, from string) {
+	f := buildcpu.ReadInForce()
+	if f.Quota > 0 {
+		path := f.Slice.Path
+		if path == "" {
+			path = f.Cgroup
+		}
+		return f.Quota, "the cpu.max of " + path
+	}
+	if n, err := strconv.Atoi(strings.TrimSpace(os.Getenv(buildcpu.ShareWord))); err == nil && n >= 1 && n <= 100 {
+		return buildcpu.Quota(n, runtime.NumCPU()), fmt.Sprintf("the share %d%% the composer gave (%s), of %d processors; no cpu.max is read", n, buildcpu.ShareWord, runtime.NumCPU())
+	}
+	return 0, "no CPU quota: neither a cpu.max on its cgroup nor a share from the composer"
+}
+
+// EffectiveCapacity is the capacity a seat's holder judges by, from its configured capacity, its node's quota (percent of
+// one processor, 0 when none is known) and the cores one of its steps needs. Without a quota it is the configured one;
+// with one, min(configured, floor(quota cores / coresPerStep)), and one at least while the configured one is above
+// zero. A coresPerStep of zero or less is taken as 1.
+func EffectiveCapacity(configured, quotaPercent int, quotaFrom string, coresPerStep float64) delivery.Capacity {
+	if coresPerStep <= 0 || math.IsNaN(coresPerStep) || math.IsInf(coresPerStep, 0) {
+		coresPerStep = 1
+	}
+	c := delivery.Capacity{Configured: configured, Effective: configured, QuotaFrom: quotaFrom, CoresPerStep: coresPerStep}
+	switch {
+	case configured <= 0:
+		c.Effective = 0
+		c.Why = fmt.Sprintf("its configured capacity is %d, so it pulls nothing", configured)
+		return c
+	case quotaPercent <= 0:
+		c.Why = fmt.Sprintf("its configured capacity %d; %s, so the CPU bounds nothing", configured, quotaFrom)
+		return c
+	}
+	c.QuotaCores = float64(quotaPercent) / 100
+	c.ByCPU = int(math.Floor(c.QuotaCores/coresPerStep + 1e-9))
+	if c.ByCPU < 1 {
+		c.ByCPU = 1
+	}
+	byCPU := fmt.Sprintf("%g cores of the build slice (%s) / %g cores a step = %d", c.QuotaCores, quotaFrom, coresPerStep, c.ByCPU)
+	if c.ByCPU < configured {
+		c.Effective = c.ByCPU
+		c.Why = fmt.Sprintf("%d, bounded by the CPU: %s, under its configured %d", c.Effective, byCPU, configured)
+	} else {
+		c.Why = fmt.Sprintf("%d, its configured capacity; the CPU allows %s", configured, byCPU)
+	}
+	return c
+}
+
+// NodeCoresPerStep is the module's cores-per-step, read from its settings file at path at every call so a change is
+// followed at the next judgement; fallback when there is no path, no value or one that is not a number above zero, said
+// once per distinct fault through logf.
+func NodeCoresPerStep(path string, fallback float64, logf func(string, ...any)) func() float64 {
+	said := ""
+	say := func(why string) {
+		if logf != nil && why != said {
+			said = why
+			logf("%s, so a step is taken to need %g cores", why, fallback)
+		}
+	}
+	return func() float64 {
+		if path == "" {
+			return fallback
+		}
+		raw, err := os.ReadFile(path)
+		if err != nil {
+			say(fmt.Sprintf("the setting %s cannot be read: %v", CoresPerStepSetting, err))
+			return fallback
+		}
+		var s map[string]json.RawMessage
+		if err := json.Unmarshal(raw, &s); err != nil {
+			say(fmt.Sprintf("the settings file %s is not JSON: %v", path, err))
+			return fallback
+		}
+		v, ok := s[CoresPerStepSetting]
+		if !ok {
+			return fallback // not declared yet (a module before its manifest names it): the default, nothing to say
+		}
+		n, err := coresOf(v)
+		if err != nil {
+			say(fmt.Sprintf("the setting %s %s: %v", CoresPerStepSetting, v, err))
+			return fallback
+		}
+		said = ""
+		return n
+	}
+}
+
+// coresOf reads a cores-per-step value: a JSON number or a string holding one, above zero.
+func coresOf(v json.RawMessage) (float64, error) {
+	var n float64
+	if err := json.Unmarshal(v, &n); err != nil {
+		var s string
+		if err := json.Unmarshal(v, &s); err != nil {
+			return 0, fmt.Errorf("is neither a number nor a string")
+		}
+		if n, err = strconv.ParseFloat(strings.TrimSpace(s), 64); err != nil {
+			return 0, fmt.Errorf("is not a number")
+		}
+	}
+	if n <= 0 || math.IsNaN(n) || math.IsInf(n, 0) {
+		return 0, fmt.Errorf("is not above zero")
+	}
+	return n, nil
+}

go/buildstep/capacity_test.go

@@ -0,0 +1,135 @@
+package buildstep
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+// 1887/A7: the node's build capacity is the build module's setting, read at every pull: the control-node at 0 pulls
+// nothing, a change takes effect at the next read, and a setting that cannot be read pulls nothing.
+// ADR 0553 §4: a step's threads are the composer's share over the module's own capacity; without the word, none. And
+// issue 1806's follow-up: the capacity judged by is the configured one bounded by the build slice's cores over the cores
+// a step needs (the three build nodes as they stand on 2026-10-26), and cores-per-step is read from the settings file.
+func TestNodeCapacityAndLimits(t *testing.T) {
+	// ADR 0567 §12: the capacity is the node's integer, its default 0, and no default names a node.
+	if got := NodeCapacity("", "laptop", nil)(); got != 0 {
+		t.Errorf("no settings file = %d, want 0", got)
+	}
+	file := filepath.Join(t.TempDir(), "settings.json")
+	capacity := NodeCapacity(file, "anchor", nil)
+	for value, want := range map[string]int{`{"capacity":1}`: 1, `{"capacity":4}`: 4, `{}`: 0, `{"capacity":null}`: 0,
+		`{"capacity":"anchor=3"}`: 0, `{"capacity":-1}`: 0, `{"capacity":1.5}`: 0} {
+		os.WriteFile(file, []byte(value), 0o600)
+		if got := capacity(); got != want {
+			t.Errorf("%s = %d, want %d", value, got, want)
+		}
+	}
+	if got := NodeCapacity(filepath.Join(t.TempDir(), "none"), "anchor", nil)(); got != 0 {
+		t.Errorf("a missing file = %d, want 0", got)
+	}
+	t.Setenv("MESH_BUILD_CPU_SHARE", "")
+	if l := NodeLimits(3); l.Threads != 0 || l.Slots != 3 {
+		t.Errorf("without the word: %+v", l)
+	}
+	t.Setenv("MESH_BUILD_CPU_SHARE", "75")
+	if l := NodeLimits(3); l.Percent != 75 || l.Slots != 3 || l.Threads < 1 {
+		t.Errorf("from the word: %+v", l)
+	}
+	for _, c := range []struct {
+		name              string
+		configured, quota int
+		cores             float64
+		effective, byCPU  int
+	}{
+		{"shanks: 12 cores, configured 3", 3, 1200, 6, 2, 2},
+		{"ace: 18 cores, configured 2", 2, 1800, 6, 2, 3},
+		{"g14: 8 cores, configured 2", 2, 800, 6, 1, 1},
+		{"node on shanks: 12 cores at 2", 3, 1200, 2, 3, 6},
+		{"no quota: the configured one", 3, 0, 6, 3, 0},
+		{"configured 0 pulls nothing", 0, 1200, 6, 0, 0},
+		{"a quota under one step still builds one", 2, 100, 6, 1, 1},
+		{"no cores a step is one", 2, 150, 0, 1, 1},
+	} {
+		got := EffectiveCapacity(c.configured, c.quota, "test", c.cores)
+		if got.Effective != c.effective || got.ByCPU != c.byCPU || got.Why == "" {
+			t.Errorf("%s: %+v, want effective %d, by CPU %d", c.name, got, c.effective, c.byCPU)
+		}
+	}
+	file = filepath.Join(t.TempDir(), "settings.json")
+	var said []string
+	cores := NodeCoresPerStep(file, 6, func(f string, a ...any) { said = append(said, f) })
+	for _, c := range []struct {
+		file string
+		want float64
+	}{{`{"capacity":2}`, 6}, {`{"cores-per-step":4}`, 4}, {`{"cores-per-step":"3.5"}`, 3.5}, {`{"cores-per-step":0}`, 6}, {`{"cores-per-step":0}`, 6}} {
+		os.WriteFile(file, []byte(c.file), 0o600)
+		if got := cores(); got != c.want {
+			t.Errorf("cores-per-step from %s = %g, want %g", c.file, got, c.want)
+		}
+	}
+	if len(said) != 1 {
+		t.Errorf("a value not above zero is said once, said %d times", len(said))
+	}
+
+	// The operator, 2026-10-26 21:18: g14 builds only from 18:00 to 06:00, its local time. Outside its build hours the
+	// capacity judged by is 0, said with the window and when it opens; a node not named, or a bad value, builds at any hour.
+	// And a node its module proves cannot build (ace without /dev/net/tun, 2026-10-28) judges by 0 at every hour, saying
+	// why, so its asks go to a node that can.
+	cet := time.FixedZone("CET", 3600)
+	day := func(hh, mm int) time.Time { return time.Date(2026, 10, 26, hh, mm, 0, 0, cet) }
+	was := now
+	defer func() { now = was }()
+	for _, c := range []struct {
+		name, setting, node string
+		at                  time.Time
+		effective           int
+		edge                string // the window's next edge, HH:MM; "" for no window
+		bad                 bool
+		ineligible          string // what the module's Eligible says; "" for eligible
+	}{
+		{"the laptop in the office", "18:00-06:00", "laptop", day(10, 0), 0, "18:00", false, ""},
+		{"the laptop in the evening", "18:00-06:00", "laptop", day(18, 0), 2, "06:00", false, ""},
+		{"the laptop past midnight", "18:00-06:00", "laptop", day(5, 59), 2, "06:00", false, ""},
+		{"the laptop at the close", "18:00-06:00", "laptop", day(6, 0), 0, "18:00", false, ""},
+		{"a day window", "09:00-17:30", "anchor", day(17, 29), 2, "17:30", false, ""},
+		{"no window", "", "anchor", day(10, 0), 2, "", false, ""},
+		{"a bad time", "18:00-6", "laptop", day(10, 0), 2, "", true, ""},
+		{"no span", "18:00-18:00", "laptop", day(10, 0), 2, "", true, ""},
+		{"the old form naming a node", "laptop=18:00-06:00", "laptop", day(10, 0), 2, "", true, ""},
+		{"a node without /dev/net/tun", "", "anchor", day(10, 0), 0, "", false, "/dev/net/tun cannot be opened: no such device"},
+		{"not eligible within its hours", "18:00-06:00", "laptop", day(19, 0), 0, "06:00", false, "/dev/net/tun cannot be opened: no such device"},
+	} {
+		w, err := ParseBuildWindow(c.setting)
+		if (err != nil) != c.bad {
+			t.Errorf("%s: parse %v", c.name, err)
+		}
+		if edge := ""; w != nil {
+			edge = w.NextEdge(c.at).Format("15:04")
+			if edge != c.edge {
+				t.Errorf("%s: next edge %s, want %s", c.name, edge, c.edge)
+			}
+		} else if c.edge != "" {
+			t.Errorf("%s: no window, want one", c.name)
+		}
+		file := filepath.Join(t.TempDir(), "settings.json")
+		os.WriteFile(file, []byte(`{"build-hours":"`+c.setting+`"}`), 0o600)
+		now = func() time.Time { return c.at }
+		p := &Puller{Language: "go", Node: c.node, Capacity: func() int { return 2 }, BuildHours: NodeBuildHours(file, c.node, nil),
+			Eligible: func() string { return c.ineligible }}
+		got := p.CapacityDetail()
+		outside := c.effective == 0 && c.ineligible == ""
+		if got.Effective != c.effective || got.OutsideHours != outside || (outside && !strings.Contains(got.Why, "outside its build hours 18:00-06:00 CET until 18:00")) {
+			t.Errorf("%s: %+v, want capacity %d", c.name, got, c.effective)
+		}
+		if got.Ineligible != c.ineligible || (c.ineligible != "" && !strings.HasPrefix(got.Why, "0, not eligible: "+c.ineligible+" (otherwise ")) {
+			t.Errorf("%s: not eligible is not said: %+v", c.name, got)
+		}
+		// A value that cannot be read builds at any hour, loudly: the record names the value and says why.
+		if c.bad && (!strings.Contains(got.BuildHoursFault, c.setting) || !strings.Contains(got.Why, "at any hour, because its build hours cannot be read")) {
+			t.Errorf("%s: a bad value is not said in the record: %+v", c.name, got)
+		}
+	}
+}

go/buildstep/conformance/captured/README.md

@@ -0,0 +1,73 @@
+# The conformance kit's captured runner output
+
+Every file here is the real output of a test runner, never written by hand (issue 1901: a fixture that agrees with the
+mistake proves the mistake). The toolchains are the build nodes' own, as `mesh-build-go.build_go_toolchains` and
+`mesh-build-node.build_node_toolchains` reported them on 2026-10-26: go1.27.3-X:nodwarf5 on every build node, node
+v26.12.1 (npm 12.2.1) on shanks, novox and g14, and typescript 5.9.3 from mesh-build-node's toolchain/package.json.
+To capture a case again, make its tiny project in a fresh directory as below and run the command shown; the kit's case
+table (conformance.go) says what each failure must say.
+
+## go/ — `go test -json`
+
+- `passfirst.jsonl` and `subtests.jsonl` (2026-10-26, go1.27.3-X:nodwarf5, for issue 1901's thorough fix): in
+  `/tmp/1901k/go/<case>`, `GOTOOLCHAIN=local GOFLAGS=-mod=mod go test -json -count=1 ./... > ../<case>.jsonl 2>&1`.
+  - passfirst: module `example.com/passfirst`, `go 1.26`. Package `a` has `TestTheFirstPackagePasses` (empty). Package `b`
+    has `TestTheSecondPackagePassesFirst` (empty) and `TestTheSecondPackageFails`, which calls
+    `t.Logf("judged against the seat as it stands")` then `t.Fatalf("the seat has 2 holders, want 1")`: a passing package
+    and a passing test before the failing one.
+  - subtests: module `example.com/subtests`; `TestTheTable` runs `t.Run("passes", func(t *testing.T) {})` and
+    `t.Run("fails", func(t *testing.T) { t.Errorf("got 3 machines, want 4") })`: the parent fails only by its subtest.
+- `subpanic.jsonl` (2026-10-26, go1.27.3-X:nodwarf5, review round 1 of issue 1901's fix), the same way: module
+  `example.com/subpanic`; `TestTable` runs `t.Run("passes", func(t *testing.T) {})` and `t.Run("panics", ...)`, which
+  writes to a nil map. go test -json files the subtest's panic under the parent `TestTable`.
+- `logthenfatal.jsonl`, `panicking`, `timeout`, `deeptimeout`, `buildfail`, `exiting`, `killed`, `passthenfail`,
+  `mainexit`, `race`, `racemain` were captured for issue 1901's first and third meetings (2026-10-23 and 2026-10-25,
+  go1.27.3) in mesh-catalog's mesh-build-go (`testdata/captured/go-test-json-*.jsonl`, named there `go-test-json-pkg-<case>`
+  and `go-test-json-log-then-fatal`) and moved here unchanged. From that README: each is the standard output and error of
+  `go test -json -count=1 ./...` (the timeouts with `-timeout 2s`; race and racemain with `-race`, CGO_ENABLED=1) in a
+  throwaway one-file module that fails without a test's own assertion: panicking (a nil map write in TestPanics), timeout
+  (TestWaitsForever sleeps past the timeout), deeptimeout (two parallel tests and sixty blocked goroutines past the
+  timeout, so the goroutine dump pushes the panic line out of the last 4 KB), buildfail (a type error in a test file),
+  exiting (os.Exit(3) in TestExits), killed (TestKilled sends itself SIGKILL), passthenfail (TestMain panics in a
+  goroutine after m.Run passed), mainexit (TestMain exits 2 after m.Run passed: go test prints "PASS" and then
+  "FAIL <pkg>"), race (TestRacesOnTheSeat writes a package variable from itself and a goroutine), racemain (TestMain does
+  so after m.Run passed). logthenfatal is a test `TestThree` in package `x` that logs a line with t.Logf and then fails
+  with a multi-line t.Fatalf naming three subscriptions.
+
+## node/ — `npm test` running `node --test` under the TAP reporter
+
+Captured 2026-10-26 with node v26.12.1 and npm 12.2.1 (`/usr/bin/node`, `/usr/bin/npm`), in `/tmp/1901k/node/<case>`, the
+way mesh-build-node runs a test script:
+
+    PATH=/usr/bin:$PATH NODE_OPTIONS="--test-reporter=tap --test-reporter-destination=/tmp/1901k/node/<case>.tap" \
+      npm test > ../<case>.stdout 2> ../<case>.stderr
+
+`<case>.tap` is the report file, `<case>.console` the stdout followed by the stderr. Each project's package.json is
+`{"name":"<case>","private":true,"type":"module","scripts":{"test":"node --test --experimental-strip-types 'test/*.test.ts'"}}`
+(the script every TypeScript package of the catalogue and the SDK runs), with these test files:
+
+- two-files: `test/a.test.ts` holds `test('passes in the first file', () => {})`; `test/b.test.ts` holds
+  `test('passes in the second file first', () => {})` and `test('fails in the second file', ...)`, which logs
+  `judged against the seat as it stands` and asserts `assert.strictEqual(1 + 1, 3, 'one plus one is not three')`.
+- suite: `test/a.test.ts` has `describe('the seat', ...)` with `it('passes inside', () => {})` and `it('fails inside', ...)`
+  asserting `assert.deepStrictEqual({ holders: 2 }, { holders: 1 })`.
+- crash: `test/a.test.ts` holds `test('passes before the crash', () => {})`; `test/b.test.ts` holds
+  `test('throws after it returned', ...)`, which throws `new Error('the bus closed under the test')` in a `setTimeout` of
+  1 ms, and `test('waits after the throw', ...)`, which waits 50 ms: node fails the file with an uncaught exception.
+- logcrash (review round 1): `test/a.test.ts` holds `test('passes and logs', ...)`, which logs
+  `retrying after Error: the store was not ready yet`; `test/b.test.ts` is crash's. A passing test's console line
+  holding "Error" comes before the crash's own.
+- timeout: `test/a.test.ts` holds `test('passes before the wait', () => {})` and
+  `test('waits for an answer that never comes', { timeout: 200 }, async () => { await new Promise(() => {}); })`.
+- syntax: `test/a.test.ts` holds `test('passes in the first file', () => {})`; `test/b.test.ts` is
+  `import test from 'node:test';` and `test('never loads', () => {` (cut off): the file does not load.
+
+## tsc/ — the type-check
+
+`typeerror.console` (2026-10-26, typescript 5.9.3 under node v26.12.1): in `/tmp/1901k/tsc/typeerror`, `ok.ts` is
+`export const holders: number = 1;` and `seat.ts` is `import { holders } from './ok.js'; export const name: string = holders;`;
+the command is mesh-build-node's type-check line without a tsconfig.json:
+
+    node <typescript>/bin/tsc --noEmit --module NodeNext --moduleResolution NodeNext --target ES2022 --rootDir . ok.ts seat.ts
+
+and the file is its stdout followed by its stderr.

go/buildstep/conformance/captured/go/buildfail.jsonl

@@ -0,0 +1,6 @@
+{"ImportPath":"example.com/buildfail [example.com/buildfail.test]","Action":"build-output","Output":"# example.com/buildfail [example.com/buildfail.test]\n"}
+{"ImportPath":"example.com/buildfail [example.com/buildfail.test]","Action":"build-output","Output":"./p_test.go:5:40: cannot use \"seat\" (untyped string constant) as int value in variable declaration\n"}
+{"ImportPath":"example.com/buildfail [example.com/buildfail.test]","Action":"build-fail"}
+{"Time":"2026-10-25T15:34:33.261137737+01:00","Action":"start","Package":"example.com/buildfail"}
+{"Time":"2026-10-25T15:34:33.261255019+01:00","Action":"output","Package":"example.com/buildfail","Output":"FAIL\texample.com/buildfail [build failed]\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.261268099+01:00","Action":"fail","Package":"example.com/buildfail","Elapsed":0,"FailedBuild":"example.com/buildfail [example.com/buildfail.test]"}

go/buildstep/conformance/captured/go/deeptimeout.jsonl

@@ -0,0 +1,417 @@
+{"Time":"2026-10-25T15:35:18.991630993+01:00","Action":"start","Package":"example.com/deeptimeout"}
+{"Time":"2026-10-25T15:35:18.993895188+01:00","Action":"run","Package":"example.com/deeptimeout","Test":"TestHoldsTheSeat"}
+{"Time":"2026-10-25T15:35:18.993963909+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestHoldsTheSeat","Output":"=== RUN   TestHoldsTheSeat\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:35:18.99399484+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestHoldsTheSeat","Output":"=== PAUSE TestHoldsTheSeat\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:35:18.9939982+01:00","Action":"pause","Package":"example.com/deeptimeout","Test":"TestHoldsTheSeat"}
+{"Time":"2026-10-25T15:35:18.99400173+01:00","Action":"run","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus"}
+{"Time":"2026-10-25T15:35:18.99400456+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"=== RUN   TestWaitsForTheBus\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:35:18.99400838+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"=== PAUSE TestWaitsForTheBus\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:35:18.99401133+01:00","Action":"pause","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus"}
+{"Time":"2026-10-25T15:35:18.99401441+01:00","Action":"cont","Package":"example.com/deeptimeout","Test":"TestHoldsTheSeat"}
+{"Time":"2026-10-25T15:35:18.99401704+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestHoldsTheSeat","Output":"=== CONT  TestHoldsTheSeat\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:35:18.994074141+01:00","Action":"cont","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus"}
+{"Time":"2026-10-25T15:35:18.994102612+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"=== CONT  TestWaitsForTheBus\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:35:21.00935195+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"panic: test timed out after 2s\n"}
+{"Time":"2026-10-25T15:35:21.00938383+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\trunning tests:\n"}
+{"Time":"2026-10-25T15:35:21.009394391+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t\tTestHoldsTheSeat (2s)\n"}
+{"Time":"2026-10-25T15:35:21.009398021+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t\tTestWaitsForTheBus (2s)\n"}
+{"Time":"2026-10-25T15:35:21.009401801+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.009406481+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 81 [running]:\n"}
+{"Time":"2026-10-25T15:35:21.009409911+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"testing.(*M).startAlarm.func1()\n"}
+{"Time":"2026-10-25T15:35:21.009413361+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/usr/lib/go/src/testing/testing.go:2961 +0x34a\n"}
+{"Time":"2026-10-25T15:35:21.009418341+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"created by time.goFunc\n"}
+{"Time":"2026-10-25T15:35:21.009421781+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/usr/lib/go/src/time/sleep.go:182 +0x2d\n"}
+{"Time":"2026-10-25T15:35:21.009424991+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.009428341+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 1 [chan receive]:\n"}
+{"Time":"2026-10-25T15:35:21.009431721+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"testing.tRunner.func1()\n"}
+{"Time":"2026-10-25T15:35:21.009441811+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/usr/lib/go/src/testing/testing.go:2144 +0x425\n"}
+{"Time":"2026-10-25T15:35:21.009445511+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"testing.tRunner(0x282e9702008, 0x282e9646bc8)\n"}
+{"Time":"2026-10-25T15:35:21.009449641+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/usr/lib/go/src/testing/testing.go:2201 +0x123\n"}
+{"Time":"2026-10-25T15:35:21.009453471+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"testing.runTests({0x55a45d, 0x17}, {0x55a45d, 0x17}, 0x282e95940f0, {0x6f19f0, 0x2, 0x2}, {0xc2afa2ca3b3c0c8d, 0x7737f168, ...})\n"}
+{"Time":"2026-10-25T15:35:21.009462092+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/usr/lib/go/src/testing/testing.go:2742 +0x510\n"}
+{"Time":"2026-10-25T15:35:21.009467222+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"testing.(*M).Run(0x282e96581e0)\n"}
+{"Time":"2026-10-25T15:35:21.009470662+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/usr/lib/go/src/testing/testing.go:2602 +0x6af\n"}
+{"Time":"2026-10-25T15:35:21.009473692+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"main.main()\n"}
+{"Time":"2026-10-25T15:35:21.009476942+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t_testmain.go:48 +0x9b\n"}
+{"Time":"2026-10-25T15:35:21.009480092+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.009483242+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 7 [sleep]:\n"}
+{"Time":"2026-10-25T15:35:21.009486502+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"time.Sleep(0xdf8475800)\n"}
+{"Time":"2026-10-25T15:35:21.009490682+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/usr/lib/go/src/runtime/time.go:368 +0x165\n"}
+{"Time":"2026-10-25T15:35:21.009493812+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"example.com/deeptimeout.TestHoldsTheSeat(0x282e9702248?)\n"}
+{"Time":"2026-10-25T15:35:21.009498842+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:14 +0x9e\n"}
+{"Time":"2026-10-25T15:35:21.009502242+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"testing.tRunner(0x282e9702248, 0x6d5e78)\n"}
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+{"Time":"2026-10-25T15:35:21.010761822+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x37\n"}
+{"Time":"2026-10-25T15:35:21.010764592+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.010767992+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 61 [chan receive]:\n"}
+{"Time":"2026-10-25T15:35:21.010771062+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"example.com/deeptimeout.TestHoldsTheSeat.func1()\n"}
+{"Time":"2026-10-25T15:35:21.010774282+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x19\n"}
+{"Time":"2026-10-25T15:35:21.010779382+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"created by example.com/deeptimeout.TestHoldsTheSeat in goroutine 7\n"}
+{"Time":"2026-10-25T15:35:21.010782942+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x37\n"}
+{"Time":"2026-10-25T15:35:21.010785722+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.010788573+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 62 [chan receive]:\n"}
+{"Time":"2026-10-25T15:35:21.010791893+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"example.com/deeptimeout.TestHoldsTheSeat.func1()\n"}
+{"Time":"2026-10-25T15:35:21.010794943+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x19\n"}
+{"Time":"2026-10-25T15:35:21.010798083+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"created by example.com/deeptimeout.TestHoldsTheSeat in goroutine 7\n"}
+{"Time":"2026-10-25T15:35:21.010801683+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x37\n"}
+{"Time":"2026-10-25T15:35:21.010804293+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.010807283+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 63 [chan receive]:\n"}
+{"Time":"2026-10-25T15:35:21.010810443+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"example.com/deeptimeout.TestHoldsTheSeat.func1()\n"}
+{"Time":"2026-10-25T15:35:21.010813553+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x19\n"}
+{"Time":"2026-10-25T15:35:21.010816793+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"created by example.com/deeptimeout.TestHoldsTheSeat in goroutine 7\n"}
+{"Time":"2026-10-25T15:35:21.010820233+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x37\n"}
+{"Time":"2026-10-25T15:35:21.010823063+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.010829493+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 64 [chan receive]:\n"}
+{"Time":"2026-10-25T15:35:21.010832683+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"example.com/deeptimeout.TestHoldsTheSeat.func1()\n"}
+{"Time":"2026-10-25T15:35:21.010835953+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x19\n"}
+{"Time":"2026-10-25T15:35:21.010839223+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"created by example.com/deeptimeout.TestHoldsTheSeat in goroutine 7\n"}
+{"Time":"2026-10-25T15:35:21.010842463+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x37\n"}
+{"Time":"2026-10-25T15:35:21.010845333+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.010848423+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 65 [chan receive]:\n"}
+{"Time":"2026-10-25T15:35:21.010851663+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"example.com/deeptimeout.TestHoldsTheSeat.func1()\n"}
+{"Time":"2026-10-25T15:35:21.010854964+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x19\n"}
+{"Time":"2026-10-25T15:35:21.010858364+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"created by example.com/deeptimeout.TestHoldsTheSeat in goroutine 7\n"}
+{"Time":"2026-10-25T15:35:21.010861714+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x37\n"}
+{"Time":"2026-10-25T15:35:21.010864914+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.010867984+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 66 [chan receive]:\n"}
+{"Time":"2026-10-25T15:35:21.010870944+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"example.com/deeptimeout.TestHoldsTheSeat.func1()\n"}
+{"Time":"2026-10-25T15:35:21.010874114+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x19\n"}
+{"Time":"2026-10-25T15:35:21.010877464+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"created by example.com/deeptimeout.TestHoldsTheSeat in goroutine 7\n"}
+{"Time":"2026-10-25T15:35:21.010880504+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x37\n"}
+{"Time":"2026-10-25T15:35:21.010883144+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.010886194+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 67 [chan receive]:\n"}
+{"Time":"2026-10-25T15:35:21.010889154+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"example.com/deeptimeout.TestHoldsTheSeat.func1()\n"}
+{"Time":"2026-10-25T15:35:21.010892234+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x19\n"}
+{"Time":"2026-10-25T15:35:21.010895524+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"created by example.com/deeptimeout.TestHoldsTheSeat in goroutine 7\n"}
+{"Time":"2026-10-25T15:35:21.010902154+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x37\n"}
+{"Time":"2026-10-25T15:35:21.010904984+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\n"}
+{"Time":"2026-10-25T15:35:21.010907984+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"goroutine 68 [chan receive]:\n"}
+{"Time":"2026-10-25T15:35:21.010911064+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"example.com/deeptimeout.TestHoldsTheSeat.func1()\n"}
+{"Time":"2026-10-25T15:35:21.010914074+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x19\n"}
+{"Time":"2026-10-25T15:35:21.010917365+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"created by example.com/deeptimeout.TestHoldsTheSeat in goroutine 7\n"}
+{"Time":"2026-10-25T15:35:21.010920505+01:00","Action":"output","Package":"example.com/deeptimeout","Test":"TestWaitsForTheBus","Output":"\t/tmp/fix-1901b/deeptimeout/p_test.go:12 +0x37\n"}
+{"Time":"2026-10-25T15:35:21.013209581+01:00","Action":"output","Package":"example.com/deeptimeout","Output":"FAIL\texample.com/deeptimeout\t2.021s\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:35:21.013258851+01:00","Action":"fail","Package":"example.com/deeptimeout","Elapsed":2.022}

go/buildstep/conformance/captured/go/exiting.jsonl

@@ -0,0 +1,10 @@
+{"Time":"2026-10-25T15:34:33.768742837+01:00","Action":"start","Package":"example.com/exiting"}
+{"Time":"2026-10-25T15:34:33.773822287+01:00","Action":"run","Package":"example.com/exiting","Test":"TestFine"}
+{"Time":"2026-10-25T15:34:33.773896608+01:00","Action":"output","Package":"example.com/exiting","Test":"TestFine","Output":"=== RUN   TestFine\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.773940319+01:00","Action":"output","Package":"example.com/exiting","Test":"TestFine","Output":"--- PASS: TestFine (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.773945359+01:00","Action":"pass","Package":"example.com/exiting","Test":"TestFine","Elapsed":0}
+{"Time":"2026-10-25T15:34:33.773952529+01:00","Action":"run","Package":"example.com/exiting","Test":"TestExits"}
+{"Time":"2026-10-25T15:34:33.773956439+01:00","Action":"output","Package":"example.com/exiting","Test":"TestExits","Output":"=== RUN   TestExits\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.773959829+01:00","Action":"output","Package":"example.com/exiting","Test":"TestExits","Output":"    p_test.go:11: closing the store\n"}
+{"Time":"2026-10-25T15:34:33.775158538+01:00","Action":"output","Package":"example.com/exiting","Output":"FAIL\texample.com/exiting\t0.006s\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.775186509+01:00","Action":"fail","Package":"example.com/exiting","Elapsed":0.006}

go/buildstep/conformance/captured/go/killed.jsonl

@@ -0,0 +1,7 @@
+{"Time":"2026-10-25T15:34:34.328258934+01:00","Action":"start","Package":"example.com/killed"}
+{"Time":"2026-10-25T15:34:34.331465435+01:00","Action":"run","Package":"example.com/killed","Test":"TestKilled"}
+{"Time":"2026-10-25T15:34:34.331699248+01:00","Action":"output","Package":"example.com/killed","Test":"TestKilled","Output":"=== RUN   TestKilled\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:34.331853111+01:00","Action":"output","Package":"example.com/killed","Test":"TestKilled","Output":"    p_test.go:10: the kernel is about to kill this\n"}
+{"Time":"2026-10-25T15:34:34.334563213+01:00","Action":"output","Package":"example.com/killed","Test":"TestKilled","Output":"signal: killed\n"}
+{"Time":"2026-10-25T15:34:34.334611114+01:00","Action":"output","Package":"example.com/killed","Output":"FAIL\texample.com/killed\t0.006s\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:34.334627134+01:00","Action":"fail","Package":"example.com/killed","Elapsed":0.006}

go/buildstep/conformance/captured/go/logthenfatal.jsonl

@@ -0,0 +1,13 @@
+{"Action":"start","Package":"x"}
+{"Action":"run","Package":"x","Test":"TestThree"}
+{"Action":"output","Package":"x","Test":"TestThree","Output":"=== RUN   TestThree\n","OutputType":"frame"}
+{"Action":"output","Package":"x","Test":"TestThree","Output":"    a_test.go:4: judged against /var/lib/mesh-build-go-work/id/beside/mesh-catalog as cloned\n"}
+{"Action":"output","Package":"x","Test":"TestThree","Output":"    a_test.go:5: 3 subscription(s) derive to a subject no emitter owns:\n","OutputType":"error"}
+{"Action":"output","Package":"x","Test":"TestThree","Output":"          a.b.c\n","OutputType":"error-continue"}
+{"Action":"output","Package":"x","Test":"TestThree","Output":"          d.e.f\n","OutputType":"error-continue"}
+{"Action":"output","Package":"x","Test":"TestThree","Output":"          g.h.i\n","OutputType":"error-continue"}
+{"Action":"output","Package":"x","Test":"TestThree","Output":"--- FAIL: TestThree (0.00s)\n","OutputType":"frame"}
+{"Action":"fail","Package":"x","Test":"TestThree","Elapsed":0}
+{"Action":"output","Package":"x","Output":"FAIL\n","OutputType":"frame"}
+{"Action":"output","Package":"x","Output":"FAIL\tx\t0.002s\n","OutputType":"frame"}
+{"Action":"fail","Package":"x","Elapsed":0.002}

go/buildstep/conformance/captured/go/mainexit.jsonl

@@ -0,0 +1,8 @@
+{"Time":"2026-10-25T15:34:35.274953775+01:00","Action":"start","Package":"example.com/mainexit"}
+{"Time":"2026-10-25T15:34:35.278129565+01:00","Action":"run","Package":"example.com/mainexit","Test":"TestFine"}
+{"Time":"2026-10-25T15:34:35.278191516+01:00","Action":"output","Package":"example.com/mainexit","Test":"TestFine","Output":"=== RUN   TestFine\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:35.278341979+01:00","Action":"output","Package":"example.com/mainexit","Test":"TestFine","Output":"--- PASS: TestFine (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:35.278351739+01:00","Action":"pass","Package":"example.com/mainexit","Test":"TestFine","Elapsed":0}
+{"Time":"2026-10-25T15:34:35.278359039+01:00","Action":"output","Package":"example.com/mainexit","Output":"PASS\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:35.279516487+01:00","Action":"output","Package":"example.com/mainexit","Output":"FAIL\texample.com/mainexit\t0.004s\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:35.279539298+01:00","Action":"fail","Package":"example.com/mainexit","Elapsed":0.005}

go/buildstep/conformance/captured/go/panicking.jsonl

@@ -0,0 +1,27 @@
+{"Time":"2026-10-25T15:34:33.031091436+01:00","Action":"start","Package":"example.com/panicking"}
+{"Time":"2026-10-25T15:34:33.036353279+01:00","Action":"run","Package":"example.com/panicking","Test":"TestBefore"}
+{"Time":"2026-10-25T15:34:33.036441781+01:00","Action":"output","Package":"example.com/panicking","Test":"TestBefore","Output":"=== RUN   TestBefore\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.036568163+01:00","Action":"output","Package":"example.com/panicking","Test":"TestBefore","Output":"--- PASS: TestBefore (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.036609863+01:00","Action":"pass","Package":"example.com/panicking","Test":"TestBefore","Elapsed":0}
+{"Time":"2026-10-25T15:34:33.036641304+01:00","Action":"run","Package":"example.com/panicking","Test":"TestPanics"}
+{"Time":"2026-10-25T15:34:33.036645914+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"=== RUN   TestPanics\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.036698995+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"    p_test.go:8: about to look up the seat\n"}
+{"Time":"2026-10-25T15:34:33.036773996+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"--- FAIL: TestPanics (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.03897418+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"panic: assignment to entry in nil map [recovered, repanicked]\n"}
+{"Time":"2026-10-25T15:34:33.040332172+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"\n"}
+{"Time":"2026-10-25T15:34:33.040414493+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"goroutine 8 [running]:\n"}
+{"Time":"2026-10-25T15:34:33.040521475+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"testing.tRunner.func1.2({0x6b8120, 0x6eff80})\n"}
+{"Time":"2026-10-25T15:34:33.040601826+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"\t/usr/lib/go/src/testing/testing.go:2125 +0x232\n"}
+{"Time":"2026-10-25T15:34:33.040641947+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"testing.tRunner.func1()\n"}
+{"Time":"2026-10-25T15:34:33.040720648+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"\t/usr/lib/go/src/testing/testing.go:2128 +0x329\n"}
+{"Time":"2026-10-25T15:34:33.04083286+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"panic({0x6b8120?, 0x6eff80?})\n"}
+{"Time":"2026-10-25T15:34:33.040912921+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"\t/usr/lib/go/src/runtime/panic.go:859 +0x125\n"}
+{"Time":"2026-10-25T15:34:33.040981652+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"example.com/panicking.TestPanics(0x228226cd0488?)\n"}
+{"Time":"2026-10-25T15:34:33.041059903+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"\t/tmp/fix-1901b/panicking/p_test.go:10 +0x53\n"}
+{"Time":"2026-10-25T15:34:33.041132704+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"testing.tRunner(0x228226cd0488, 0x6d5bc8)\n"}
+{"Time":"2026-10-25T15:34:33.041215586+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"\t/usr/lib/go/src/testing/testing.go:2195 +0xea\n"}
+{"Time":"2026-10-25T15:34:33.041221966+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"created by testing.(*T).Run in goroutine 1\n"}
+{"Time":"2026-10-25T15:34:33.041225556+01:00","Action":"output","Package":"example.com/panicking","Test":"TestPanics","Output":"\t/usr/lib/go/src/testing/testing.go:2260 +0x4d4\n"}
+{"Time":"2026-10-25T15:34:33.041984088+01:00","Action":"fail","Package":"example.com/panicking","Test":"TestPanics","Elapsed":0}
+{"Time":"2026-10-25T15:34:33.041996638+01:00","Action":"output","Package":"example.com/panicking","Output":"FAIL\texample.com/panicking\t0.010s\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:33.042044079+01:00","Action":"fail","Package":"example.com/panicking","Elapsed":0.011}

go/buildstep/conformance/captured/go/passfirst.jsonl

@@ -0,0 +1,22 @@
+{"Time":"2026-10-26T19:40:29.574068887+01:00","Action":"start","Package":"example.com/passfirst/a"}
+{"Time":"2026-10-26T19:40:29.574347185+01:00","Action":"start","Package":"example.com/passfirst/b"}
+{"Time":"2026-10-26T19:40:29.576503518+01:00","Action":"run","Package":"example.com/passfirst/a","Test":"TestTheFirstPackagePasses"}
+{"Time":"2026-10-26T19:40:29.576557657+01:00","Action":"output","Package":"example.com/passfirst/a","Test":"TestTheFirstPackagePasses","Output":"=== RUN   TestTheFirstPackagePasses\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.576589367+01:00","Action":"output","Package":"example.com/passfirst/a","Test":"TestTheFirstPackagePasses","Output":"--- PASS: TestTheFirstPackagePasses (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.576594637+01:00","Action":"pass","Package":"example.com/passfirst/a","Test":"TestTheFirstPackagePasses","Elapsed":0}
+{"Time":"2026-10-26T19:40:29.576602487+01:00","Action":"output","Package":"example.com/passfirst/a","Output":"PASS\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.576614477+01:00","Action":"run","Package":"example.com/passfirst/b","Test":"TestTheSecondPackagePassesFirst"}
+{"Time":"2026-10-26T19:40:29.576626897+01:00","Action":"output","Package":"example.com/passfirst/b","Test":"TestTheSecondPackagePassesFirst","Output":"=== RUN   TestTheSecondPackagePassesFirst\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.576631187+01:00","Action":"output","Package":"example.com/passfirst/b","Test":"TestTheSecondPackagePassesFirst","Output":"--- PASS: TestTheSecondPackagePassesFirst (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.576635567+01:00","Action":"pass","Package":"example.com/passfirst/b","Test":"TestTheSecondPackagePassesFirst","Elapsed":0}
+{"Time":"2026-10-26T19:40:29.576638427+01:00","Action":"run","Package":"example.com/passfirst/b","Test":"TestTheSecondPackageFails"}
+{"Time":"2026-10-26T19:40:29.576640647+01:00","Action":"output","Package":"example.com/passfirst/b","Test":"TestTheSecondPackageFails","Output":"=== RUN   TestTheSecondPackageFails\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.576643477+01:00","Action":"output","Package":"example.com/passfirst/b","Test":"TestTheSecondPackageFails","Output":"    b_test.go:8: judged against the seat as it stands\n"}
+{"Time":"2026-10-26T19:40:29.576646497+01:00","Action":"output","Package":"example.com/passfirst/b","Test":"TestTheSecondPackageFails","Output":"    b_test.go:9: the seat has 2 holders, want 1\n","OutputType":"error"}
+{"Time":"2026-10-26T19:40:29.576650087+01:00","Action":"output","Package":"example.com/passfirst/b","Test":"TestTheSecondPackageFails","Output":"--- FAIL: TestTheSecondPackageFails (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.576652797+01:00","Action":"fail","Package":"example.com/passfirst/b","Test":"TestTheSecondPackageFails","Elapsed":0}
+{"Time":"2026-10-26T19:40:29.576655177+01:00","Action":"output","Package":"example.com/passfirst/b","Output":"FAIL\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.577365541+01:00","Action":"output","Package":"example.com/passfirst/a","Output":"ok  \texample.com/passfirst/a\t0.003s\n"}
+{"Time":"2026-10-26T19:40:29.577382561+01:00","Action":"pass","Package":"example.com/passfirst/a","Elapsed":0.003}
+{"Time":"2026-10-26T19:40:29.577380641+01:00","Action":"output","Package":"example.com/passfirst/b","Output":"FAIL\texample.com/passfirst/b\t0.003s\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.5774131+01:00","Action":"fail","Package":"example.com/passfirst/b","Elapsed":0.003}

go/buildstep/conformance/captured/go/passthenfail.jsonl

@@ -0,0 +1,15 @@
+{"Time":"2026-10-25T15:34:34.919624192+01:00","Action":"start","Package":"example.com/passthenfail"}
+{"Time":"2026-10-25T15:34:34.922861224+01:00","Action":"run","Package":"example.com/passthenfail","Test":"TestFine"}
+{"Time":"2026-10-25T15:34:34.922932965+01:00","Action":"output","Package":"example.com/passthenfail","Test":"TestFine","Output":"=== RUN   TestFine\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:34.922969205+01:00","Action":"output","Package":"example.com/passthenfail","Test":"TestFine","Output":"--- PASS: TestFine (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:34.922979956+01:00","Action":"pass","Package":"example.com/passthenfail","Test":"TestFine","Elapsed":0}
+{"Time":"2026-10-25T15:34:34.922989416+01:00","Action":"output","Package":"example.com/passthenfail","Output":"PASS\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:34.925022528+01:00","Action":"output","Package":"example.com/passthenfail","Output":"panic: the bus closed after the tests: nats: connection closed\n"}
+{"Time":"2026-10-25T15:34:34.925043388+01:00","Action":"output","Package":"example.com/passthenfail","Output":"\n"}
+{"Time":"2026-10-25T15:34:34.925046848+01:00","Action":"output","Package":"example.com/passthenfail","Output":"goroutine 20 [running]:\n"}
+{"Time":"2026-10-25T15:34:34.925051338+01:00","Action":"output","Package":"example.com/passthenfail","Output":"example.com/passthenfail.TestMain.func1()\n"}
+{"Time":"2026-10-25T15:34:34.925055878+01:00","Action":"output","Package":"example.com/passthenfail","Output":"\t/tmp/fix-1901b/passthenfail/p_test.go:13 +0x25\n"}
+{"Time":"2026-10-25T15:34:34.925061428+01:00","Action":"output","Package":"example.com/passthenfail","Output":"created by example.com/passthenfail.TestMain in goroutine 1\n"}
+{"Time":"2026-10-25T15:34:34.925065028+01:00","Action":"output","Package":"example.com/passthenfail","Output":"\t/tmp/fix-1901b/passthenfail/p_test.go:13 +0x25\n"}
+{"Time":"2026-10-25T15:34:34.925390203+01:00","Action":"output","Package":"example.com/passthenfail","Output":"FAIL\texample.com/passthenfail\t0.005s\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:34.925402904+01:00","Action":"fail","Package":"example.com/passthenfail","Elapsed":0.006}

go/buildstep/conformance/captured/go/race.jsonl

@@ -0,0 +1,53 @@
+{"Time":"2026-10-25T15:50:42.908557309+01:00","Action":"start","Package":"example.com/race"}
+{"Time":"2026-10-25T15:50:42.924298679+01:00","Action":"run","Package":"example.com/race","Test":"TestBefore"}
+{"Time":"2026-10-25T15:50:42.92438195+01:00","Action":"output","Package":"example.com/race","Test":"TestBefore","Output":"=== RUN   TestBefore\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:42.924648842+01:00","Action":"output","Package":"example.com/race","Test":"TestBefore","Output":"--- PASS: TestBefore (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:42.924685133+01:00","Action":"pass","Package":"example.com/race","Test":"TestBefore","Elapsed":0}
+{"Time":"2026-10-25T15:50:42.924728573+01:00","Action":"run","Package":"example.com/race","Test":"TestRacesOnTheSeat"}
+{"Time":"2026-10-25T15:50:42.924733573+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"=== RUN   TestRacesOnTheSeat\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:42.92637298+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"==================\n"}
+{"Time":"2026-10-25T15:50:42.92641567+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"WARNING: DATA RACE\n"}
+{"Time":"2026-10-25T15:50:42.926444061+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"Write at 0x000000833468 by goroutine 10:\n"}
+{"Time":"2026-10-25T15:50:42.926462621+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  example.com/race.TestRacesOnTheSeat.func1()\n"}
+{"Time":"2026-10-25T15:50:42.926467121+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /tmp/fix-1901b/race/p_test.go:13 +0x24\n"}
+{"Time":"2026-10-25T15:50:42.926483061+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"\n"}
+{"Time":"2026-10-25T15:50:42.926509741+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"Previous write at 0x000000833468 by goroutine 9:\n"}
+{"Time":"2026-10-25T15:50:42.926530142+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  example.com/race.TestRacesOnTheSeat()\n"}
+{"Time":"2026-10-25T15:50:42.926534952+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /tmp/fix-1901b/race/p_test.go:14 +0x30\n"}
+{"Time":"2026-10-25T15:50:42.926550462+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  testing.tRunner()\n"}
+{"Time":"2026-10-25T15:50:42.926554612+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /usr/lib/go/src/testing/testing.go:2195 +0x21c\n"}
+{"Time":"2026-10-25T15:50:42.926571142+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  testing.(*T).Run.gowrap1()\n"}
+{"Time":"2026-10-25T15:50:42.926575812+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /usr/lib/go/src/testing/testing.go:2260 +0x38\n"}
+{"Time":"2026-10-25T15:50:42.926592202+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"\n"}
+{"Time":"2026-10-25T15:50:42.926607792+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"Goroutine 10 (running) created at:\n"}
+{"Time":"2026-10-25T15:50:42.926624292+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  example.com/race.TestRacesOnTheSeat()\n"}
+{"Time":"2026-10-25T15:50:42.926628923+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /tmp/fix-1901b/race/p_test.go:13 +0x24\n"}
+{"Time":"2026-10-25T15:50:42.926643853+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  testing.tRunner()\n"}
+{"Time":"2026-10-25T15:50:42.926648103+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /usr/lib/go/src/testing/testing.go:2195 +0x21c\n"}
+{"Time":"2026-10-25T15:50:42.926674843+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  testing.(*T).Run.gowrap1()\n"}
+{"Time":"2026-10-25T15:50:42.926680673+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /usr/lib/go/src/testing/testing.go:2260 +0x38\n"}
+{"Time":"2026-10-25T15:50:42.926695433+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"\n"}
+{"Time":"2026-10-25T15:50:42.926711063+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"Goroutine 9 (running) created at:\n"}
+{"Time":"2026-10-25T15:50:42.926726614+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  testing.(*T).Run()\n"}
+{"Time":"2026-10-25T15:50:42.926730814+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /usr/lib/go/src/testing/testing.go:2260 +0xb12\n"}
+{"Time":"2026-10-25T15:50:42.926746484+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  testing.runTests.func1()\n"}
+{"Time":"2026-10-25T15:50:42.926750764+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /usr/lib/go/src/testing/testing.go:2744 +0x84\n"}
+{"Time":"2026-10-25T15:50:42.926765354+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  testing.tRunner()\n"}
+{"Time":"2026-10-25T15:50:42.926769844+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /usr/lib/go/src/testing/testing.go:2195 +0x21c\n"}
+{"Time":"2026-10-25T15:50:42.926791794+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  testing.runTests()\n"}
+{"Time":"2026-10-25T15:50:42.926796704+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /usr/lib/go/src/testing/testing.go:2742 +0x9e9\n"}
+{"Time":"2026-10-25T15:50:42.926811544+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  testing.(*M).Run()\n"}
+{"Time":"2026-10-25T15:50:42.926816694+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      /usr/lib/go/src/testing/testing.go:2602 +0xf44\n"}
+{"Time":"2026-10-25T15:50:42.926831695+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"  main.main()\n"}
+{"Time":"2026-10-25T15:50:42.926835935+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"      _testmain.go:50 +0x164\n"}
+{"Time":"2026-10-25T15:50:42.926850905+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"==================\n"}
+{"Time":"2026-10-25T15:50:42.935320241+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"    testing.go:1867: race detected during execution of test\n","OutputType":"error"}
+{"Time":"2026-10-25T15:50:42.935520113+01:00","Action":"output","Package":"example.com/race","Test":"TestRacesOnTheSeat","Output":"--- FAIL: TestRacesOnTheSeat (0.01s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:42.935592973+01:00","Action":"fail","Package":"example.com/race","Test":"TestRacesOnTheSeat","Elapsed":0.01}
+{"Time":"2026-10-25T15:50:42.935722225+01:00","Action":"run","Package":"example.com/race","Test":"TestAfter"}
+{"Time":"2026-10-25T15:50:42.935728845+01:00","Action":"output","Package":"example.com/race","Test":"TestAfter","Output":"=== RUN   TestAfter\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:42.935995928+01:00","Action":"output","Package":"example.com/race","Test":"TestAfter","Output":"--- PASS: TestAfter (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:42.936006328+01:00","Action":"pass","Package":"example.com/race","Test":"TestAfter","Elapsed":0}
+{"Time":"2026-10-25T15:50:42.936009978+01:00","Action":"output","Package":"example.com/race","Output":"FAIL\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:42.937730745+01:00","Action":"output","Package":"example.com/race","Output":"FAIL\texample.com/race\t0.028s\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:42.937802066+01:00","Action":"fail","Package":"example.com/race","Elapsed":0.029}

go/buildstep/conformance/captured/go/racemain.jsonl

@@ -0,0 +1,27 @@
+{"Time":"2026-10-25T15:50:43.551701745+01:00","Action":"start","Package":"example.com/racemain"}
+{"Time":"2026-10-25T15:50:43.570709708+01:00","Action":"run","Package":"example.com/racemain","Test":"TestFine"}
+{"Time":"2026-10-25T15:50:43.570806059+01:00","Action":"output","Package":"example.com/racemain","Test":"TestFine","Output":"=== RUN   TestFine\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:43.57085525+01:00","Action":"output","Package":"example.com/racemain","Test":"TestFine","Output":"--- PASS: TestFine (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:43.57086149+01:00","Action":"pass","Package":"example.com/racemain","Test":"TestFine","Elapsed":0}
+{"Time":"2026-10-25T15:50:43.57086974+01:00","Action":"output","Package":"example.com/racemain","Output":"PASS\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:43.572155623+01:00","Action":"output","Package":"example.com/racemain","Output":"==================\n"}
+{"Time":"2026-10-25T15:50:43.572168083+01:00","Action":"output","Package":"example.com/racemain","Output":"WARNING: DATA RACE\n"}
+{"Time":"2026-10-25T15:50:43.572171933+01:00","Action":"output","Package":"example.com/racemain","Output":"Write at 0x000000836428 by goroutine 9:\n"}
+{"Time":"2026-10-25T15:50:43.572176703+01:00","Action":"output","Package":"example.com/racemain","Output":"  example.com/racemain.TestMain.func1()\n"}
+{"Time":"2026-10-25T15:50:43.572180053+01:00","Action":"output","Package":"example.com/racemain","Output":"      /tmp/fix-1901b/racemain/p_test.go:15 +0x24\n"}
+{"Time":"2026-10-25T15:50:43.572184923+01:00","Action":"output","Package":"example.com/racemain","Output":"\n"}
+{"Time":"2026-10-25T15:50:43.572189613+01:00","Action":"output","Package":"example.com/racemain","Output":"Previous write at 0x000000836428 by main goroutine:\n"}
+{"Time":"2026-10-25T15:50:43.572192993+01:00","Action":"output","Package":"example.com/racemain","Output":"  example.com/racemain.TestMain()\n"}
+{"Time":"2026-10-25T15:50:43.572198573+01:00","Action":"output","Package":"example.com/racemain","Output":"      /tmp/fix-1901b/racemain/p_test.go:16 +0x44\n"}
+{"Time":"2026-10-25T15:50:43.572202433+01:00","Action":"output","Package":"example.com/racemain","Output":"  main.main()\n"}
+{"Time":"2026-10-25T15:50:43.572205623+01:00","Action":"output","Package":"example.com/racemain","Output":"      _testmain.go:48 +0x171\n"}
+{"Time":"2026-10-25T15:50:43.572208443+01:00","Action":"output","Package":"example.com/racemain","Output":"\n"}
+{"Time":"2026-10-25T15:50:43.572211573+01:00","Action":"output","Package":"example.com/racemain","Output":"Goroutine 9 (running) created at:\n"}
+{"Time":"2026-10-25T15:50:43.572214803+01:00","Action":"output","Package":"example.com/racemain","Output":"  example.com/racemain.TestMain()\n"}
+{"Time":"2026-10-25T15:50:43.572218043+01:00","Action":"output","Package":"example.com/racemain","Output":"      /tmp/fix-1901b/racemain/p_test.go:15 +0x37\n"}
+{"Time":"2026-10-25T15:50:43.572225414+01:00","Action":"output","Package":"example.com/racemain","Output":"  main.main()\n"}
+{"Time":"2026-10-25T15:50:43.572228654+01:00","Action":"output","Package":"example.com/racemain","Output":"      _testmain.go:48 +0x171\n"}
+{"Time":"2026-10-25T15:50:43.572231664+01:00","Action":"output","Package":"example.com/racemain","Output":"==================\n"}
+{"Time":"2026-10-25T15:50:44.581262249+01:00","Action":"output","Package":"example.com/racemain","Output":"Found 1 data race(s)\n"}
+{"Time":"2026-10-25T15:50:44.584693204+01:00","Action":"output","Package":"example.com/racemain","Output":"FAIL\texample.com/racemain\t1.031s\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:50:44.584737425+01:00","Action":"fail","Package":"example.com/racemain","Elapsed":1.033}

go/buildstep/conformance/captured/go/subpanic.jsonl

@@ -0,0 +1,30 @@
+{"Time":"2026-10-26T20:15:37.791161045+01:00","Action":"start","Package":"example.com/subpanic"}
+{"Time":"2026-10-26T20:15:37.793205666+01:00","Action":"run","Package":"example.com/subpanic","Test":"TestTable"}
+{"Time":"2026-10-26T20:15:37.793257158+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"=== RUN   TestTable\n","OutputType":"frame"}
+{"Time":"2026-10-26T20:15:37.793288149+01:00","Action":"run","Package":"example.com/subpanic","Test":"TestTable/passes"}
+{"Time":"2026-10-26T20:15:37.793290669+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable/passes","Output":"=== RUN   TestTable/passes\n","OutputType":"frame"}
+{"Time":"2026-10-26T20:15:37.793298009+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable/passes","Output":"--- PASS: TestTable/passes (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-26T20:15:37.793311679+01:00","Action":"pass","Package":"example.com/subpanic","Test":"TestTable/passes","Elapsed":0}
+{"Time":"2026-10-26T20:15:37.79331977+01:00","Action":"run","Package":"example.com/subpanic","Test":"TestTable/panics"}
+{"Time":"2026-10-26T20:15:37.79332377+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable/panics","Output":"=== RUN   TestTable/panics\n","OutputType":"frame"}
+{"Time":"2026-10-26T20:15:37.79332773+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable/panics","Output":"--- FAIL: TestTable/panics (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-26T20:15:37.79333111+01:00","Action":"fail","Package":"example.com/subpanic","Test":"TestTable/panics","Elapsed":0}
+{"Time":"2026-10-26T20:15:37.79333383+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"--- FAIL: TestTable (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-26T20:15:37.795322529+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"panic: assignment to entry in nil map [recovered, repanicked]\n"}
+{"Time":"2026-10-26T20:15:37.795331489+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"\n"}
+{"Time":"2026-10-26T20:15:37.795340579+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"goroutine 9 [running]:\n"}
+{"Time":"2026-10-26T20:15:37.79534387+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"testing.tRunner.func1.2({0x6b7010, 0x6eef80})\n"}
+{"Time":"2026-10-26T20:15:37.79534657+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"\t/usr/lib/go/src/testing/testing.go:2125 +0x232\n"}
+{"Time":"2026-10-26T20:15:37.79534907+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"testing.tRunner.func1()\n"}
+{"Time":"2026-10-26T20:15:37.79535172+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"\t/usr/lib/go/src/testing/testing.go:2128 +0x329\n"}
+{"Time":"2026-10-26T20:15:37.79535625+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"panic({0x6b7010?, 0x6eef80?})\n"}
+{"Time":"2026-10-26T20:15:37.79535879+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"\t/usr/lib/go/src/runtime/panic.go:859 +0x125\n"}
+{"Time":"2026-10-26T20:15:37.79536129+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"example.com/subpanic.TestTable.func2(0x3b39436666c8?)\n"}
+{"Time":"2026-10-26T20:15:37.79536452+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"\t/tmp/1901k/go/subpanic/p_test.go:7 +0x28\n"}
+{"Time":"2026-10-26T20:15:37.79536782+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"testing.tRunner(0x3b39436666c8, 0x6d4b58)\n"}
+{"Time":"2026-10-26T20:15:37.7953704+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"\t/usr/lib/go/src/testing/testing.go:2195 +0xea\n"}
+{"Time":"2026-10-26T20:15:37.79537289+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"created by testing.(*T).Run in goroutine 7\n"}
+{"Time":"2026-10-26T20:15:37.795381681+01:00","Action":"output","Package":"example.com/subpanic","Test":"TestTable","Output":"\t/usr/lib/go/src/testing/testing.go:2260 +0x4d4\n"}
+{"Time":"2026-10-26T20:15:37.795731441+01:00","Action":"fail","Package":"example.com/subpanic","Test":"TestTable","Elapsed":0}
+{"Time":"2026-10-26T20:15:37.795759332+01:00","Action":"output","Package":"example.com/subpanic","Output":"FAIL\texample.com/subpanic\t0.004s\n","OutputType":"frame"}
+{"Time":"2026-10-26T20:15:37.795783503+01:00","Action":"fail","Package":"example.com/subpanic","Elapsed":0.005}

go/buildstep/conformance/captured/go/subtests.jsonl

@@ -0,0 +1,17 @@
+{"Time":"2026-10-26T19:40:29.768101399+01:00","Action":"start","Package":"example.com/subtests"}
+{"Time":"2026-10-26T19:40:29.770109733+01:00","Action":"run","Package":"example.com/subtests","Test":"TestTheTable"}
+{"Time":"2026-10-26T19:40:29.770152272+01:00","Action":"output","Package":"example.com/subtests","Test":"TestTheTable","Output":"=== RUN   TestTheTable\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.770189372+01:00","Action":"run","Package":"example.com/subtests","Test":"TestTheTable/passes"}
+{"Time":"2026-10-26T19:40:29.770191882+01:00","Action":"output","Package":"example.com/subtests","Test":"TestTheTable/passes","Output":"=== RUN   TestTheTable/passes\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.770197442+01:00","Action":"output","Package":"example.com/subtests","Test":"TestTheTable/passes","Output":"--- PASS: TestTheTable/passes (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.770204352+01:00","Action":"pass","Package":"example.com/subtests","Test":"TestTheTable/passes","Elapsed":0}
+{"Time":"2026-10-26T19:40:29.770209622+01:00","Action":"run","Package":"example.com/subtests","Test":"TestTheTable/fails"}
+{"Time":"2026-10-26T19:40:29.770211832+01:00","Action":"output","Package":"example.com/subtests","Test":"TestTheTable/fails","Output":"=== RUN   TestTheTable/fails\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.770214722+01:00","Action":"output","Package":"example.com/subtests","Test":"TestTheTable/fails","Output":"    s_test.go:7: got 3 machines, want 4\n","OutputType":"error"}
+{"Time":"2026-10-26T19:40:29.770218032+01:00","Action":"output","Package":"example.com/subtests","Test":"TestTheTable/fails","Output":"--- FAIL: TestTheTable/fails (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.770220732+01:00","Action":"fail","Package":"example.com/subtests","Test":"TestTheTable/fails","Elapsed":0}
+{"Time":"2026-10-26T19:40:29.770223522+01:00","Action":"output","Package":"example.com/subtests","Test":"TestTheTable","Output":"--- FAIL: TestTheTable (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.770226292+01:00","Action":"fail","Package":"example.com/subtests","Test":"TestTheTable","Elapsed":0}
+{"Time":"2026-10-26T19:40:29.770228582+01:00","Action":"output","Package":"example.com/subtests","Output":"FAIL\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.770561979+01:00","Action":"output","Package":"example.com/subtests","Output":"FAIL\texample.com/subtests\t0.002s\n","OutputType":"frame"}
+{"Time":"2026-10-26T19:40:29.770581629+01:00","Action":"fail","Package":"example.com/subtests","Elapsed":0.002}

go/buildstep/conformance/captured/go/timeout.jsonl

@@ -0,0 +1,43 @@
+{"Time":"2026-10-25T15:34:36.049580618+01:00","Action":"start","Package":"example.com/timeout"}
+{"Time":"2026-10-25T15:34:36.053250986+01:00","Action":"run","Package":"example.com/timeout","Test":"TestQuick"}
+{"Time":"2026-10-25T15:34:36.053354018+01:00","Action":"output","Package":"example.com/timeout","Test":"TestQuick","Output":"=== RUN   TestQuick\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:36.053459789+01:00","Action":"output","Package":"example.com/timeout","Test":"TestQuick","Output":"--- PASS: TestQuick (0.00s)\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:36.05348499+01:00","Action":"pass","Package":"example.com/timeout","Test":"TestQuick","Elapsed":0}
+{"Time":"2026-10-25T15:34:36.0535114+01:00","Action":"run","Package":"example.com/timeout","Test":"TestWaitsForever"}
+{"Time":"2026-10-25T15:34:36.05351549+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"=== RUN   TestWaitsForever\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:36.053567451+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"    p_test.go:11: waiting for the bus\n"}
+{"Time":"2026-10-25T15:34:38.064693307+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"panic: test timed out after 2s\n"}
+{"Time":"2026-10-25T15:34:38.06487122+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\trunning tests:\n"}
+{"Time":"2026-10-25T15:34:38.06491684+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t\tTestWaitsForever (2s)\n"}
+{"Time":"2026-10-25T15:34:38.065034382+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\n"}
+{"Time":"2026-10-25T15:34:38.065108573+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"goroutine 33 [running]:\n"}
+{"Time":"2026-10-25T15:34:38.065154754+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"testing.(*M).startAlarm.func1()\n"}
+{"Time":"2026-10-25T15:34:38.065386208+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/testing/testing.go:2961 +0x34a\n"}
+{"Time":"2026-10-25T15:34:38.065431878+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"created by time.goFunc\n"}
+{"Time":"2026-10-25T15:34:38.0655151+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/time/sleep.go:182 +0x2d\n"}
+{"Time":"2026-10-25T15:34:38.06553471+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\n"}
+{"Time":"2026-10-25T15:34:38.065847805+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"goroutine 1 [chan receive]:\n"}
+{"Time":"2026-10-25T15:34:38.066038298+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"testing.(*T).Run(0x3a0209bc8008, {0x5580aa?, 0x3a0209a9caa0?}, 0x6d5b10)\n"}
+{"Time":"2026-10-25T15:34:38.066047488+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/testing/testing.go:2268 +0x4f2\n"}
+{"Time":"2026-10-25T15:34:38.066051368+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"testing.runTests.func1(0x3a0209bc8008)\n"}
+{"Time":"2026-10-25T15:34:38.066056128+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/testing/testing.go:2744 +0x37\n"}
+{"Time":"2026-10-25T15:34:38.066059478+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"testing.tRunner(0x3a0209bc8008, 0x3a0209a9cbc8)\n"}
+{"Time":"2026-10-25T15:34:38.066064958+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/testing/testing.go:2195 +0xea\n"}
+{"Time":"2026-10-25T15:34:38.066069599+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"testing.runTests({0x559017, 0x13}, {0x559017, 0x13}, 0x3a0209b8e0d8, {0x6f19f0, 0x2, 0x2}, {0xc2afa2bf832a3f56, 0x773908b5, ...})\n"}
+{"Time":"2026-10-25T15:34:38.066083309+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/testing/testing.go:2742 +0x510\n"}
+{"Time":"2026-10-25T15:34:38.066086879+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"testing.(*M).Run(0x3a0209b8c1e0)\n"}
+{"Time":"2026-10-25T15:34:38.066090269+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/testing/testing.go:2602 +0x6af\n"}
+{"Time":"2026-10-25T15:34:38.066093429+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"main.main()\n"}
+{"Time":"2026-10-25T15:34:38.066097569+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t_testmain.go:48 +0x9b\n"}
+{"Time":"2026-10-25T15:34:38.066100639+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\n"}
+{"Time":"2026-10-25T15:34:38.066103769+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"goroutine 20 [sleep]:\n"}
+{"Time":"2026-10-25T15:34:38.066106969+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"time.Sleep(0xdf8475800)\n"}
+{"Time":"2026-10-25T15:34:38.066110279+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/runtime/time.go:368 +0x165\n"}
+{"Time":"2026-10-25T15:34:38.066113639+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"example.com/timeout.TestWaitsForever(0x3a0209bc8488?)\n"}
+{"Time":"2026-10-25T15:34:38.066117109+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/tmp/fix-1901b/timeout/p_test.go:12 +0x48\n"}
+{"Time":"2026-10-25T15:34:38.066120239+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"testing.tRunner(0x3a0209bc8488, 0x6d5b10)\n"}
+{"Time":"2026-10-25T15:34:38.066123509+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/testing/testing.go:2195 +0xea\n"}
+{"Time":"2026-10-25T15:34:38.066126839+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"created by testing.(*T).Run in goroutine 1\n"}
+{"Time":"2026-10-25T15:34:38.066129989+01:00","Action":"output","Package":"example.com/timeout","Test":"TestWaitsForever","Output":"\t/usr/lib/go/src/testing/testing.go:2260 +0x4d4\n"}
+{"Time":"2026-10-25T15:34:38.066986453+01:00","Action":"output","Package":"example.com/timeout","Output":"FAIL\texample.com/timeout\t2.017s\n","OutputType":"frame"}
+{"Time":"2026-10-25T15:34:38.067002113+01:00","Action":"fail","Package":"example.com/timeout","Elapsed":2.017}

go/buildstep/conformance/captured/node/crash.console

@@ -0,0 +1,2 @@
+npm notice run test
+npm notice run node --test --experimental-strip-types 'test/*.test.ts'

go/buildstep/conformance/captured/node/crash.tap

@@ -0,0 +1,41 @@
+TAP version 13
+# Subtest: passes before the crash
+ok 1 - passes before the crash
+  ---
+  duration_ms: 0.746694
+  type: 'test'
+  ...
+# Subtest: throws after it returned
+ok 2 - throws after it returned
+  ---
+  duration_ms: 0.763364
+  type: 'test'
+  ...
+# Subtest: waits after the throw
+ok 3 - waits after the throw
+  ---
+  duration_ms: 49.953893
+  type: 'test'
+  ...
+# Error: Test "throws after it returned" at test/b.test.ts:2:1 generated asynchronous activity after the test ended. This activity created the error "Error: the bus closed under the test" and would have caused the test to fail, but instead triggered an uncaughtException event.
+# Subtest: test/b.test.ts
+not ok 2 - test/b.test.ts
+  ---
+  duration_ms: 155.864774
+  type: 'test'
+  location: '/tmp/1901k/node/crash/test/b.test.ts:1:1'
+  failureType: 'testCodeFailure'
+  exitCode: 1
+  signal: ~
+  error: 'test failed'
+  code: 'ERR_TEST_FAILURE'
+  ...
+1..4
+# tests 4
+# suites 0
+# pass 3
+# fail 1
+# cancelled 0
+# skipped 0
+# todo 0
+# duration_ms 168.479173

go/buildstep/conformance/captured/node/logcrash.console

@@ -0,0 +1,2 @@
+npm notice run test
+npm notice run node --test --experimental-strip-types 'test/*.test.ts'

go/buildstep/conformance/captured/node/logcrash.tap

@@ -0,0 +1,42 @@
+TAP version 13
+# retrying after Error: the store was not ready yet
+# Subtest: passes and logs
+ok 1 - passes and logs
+  ---
+  duration_ms: 1.184595
+  type: 'test'
+  ...
+# Subtest: throws after it returned
+ok 2 - throws after it returned
+  ---
+  duration_ms: 0.748862
+  type: 'test'
+  ...
+# Subtest: waits after the throw
+ok 3 - waits after the throw
+  ---
+  duration_ms: 51.019875
+  type: 'test'
+  ...
+# Error: Test "throws after it returned" at test/b.test.ts:2:1 generated asynchronous activity after the test ended. This activity created the error "Error: the bus closed under the test" and would have caused the test to fail, but instead triggered an uncaughtException event.
+# Subtest: test/b.test.ts
+not ok 2 - test/b.test.ts
+  ---
+  duration_ms: 172.91715
+  type: 'test'
+  location: '/tmp/1901k/node/logcrash/test/b.test.ts:1:1'
+  failureType: 'testCodeFailure'
+  exitCode: 1
+  signal: ~
+  error: 'test failed'
+  code: 'ERR_TEST_FAILURE'
+  ...
+1..4
+# tests 4
+# suites 0
+# pass 3
+# fail 1
+# cancelled 0
+# skipped 0
+# todo 0
+# duration_ms 185.744334

go/buildstep/conformance/captured/node/suite.console

@@ -0,0 +1,2 @@
+npm notice run test
+npm notice run node --test --experimental-strip-types 'test/*.test.ts'

go/buildstep/conformance/captured/node/suite.tap

@@ -0,0 +1,61 @@
+TAP version 13
+# Subtest: the seat
+    # Subtest: passes inside
+    ok 1 - passes inside
+      ---
+      duration_ms: 0.577396
+      type: 'test'
+      ...
+    # Subtest: fails inside
+    not ok 2 - fails inside
+      ---
+      duration_ms: 1.621198
+      type: 'test'
+      location: '/tmp/1901k/node/suite/test/a.test.ts:5:3'
+      failureType: 'testCodeFailure'
+      error: |-
+        Expected values to be strictly deep-equal:
+        + actual - expected
+        
+          {
+        +   holders: 2
+        -   holders: 1
+          }
+        
+      code: 'ERR_ASSERTION'
+      name: 'AssertionError'
+      expected:
+        holders: 1
+      actual:
+        holders: 2
+      operator: 'deepStrictEqual'
+      stack: |-
+        TestContext.<anonymous> (file:///tmp/1901k/node/suite/test/a.test.ts:5:37)
+        Test.runInAsyncScope (node:async_hooks:226:14)
+        Test.run (node:internal/test_runner/test:1402:25)
+        Suite.processPendingSubtests (node:internal/test_runner/test:974:18)
+        Test.postRun (node:internal/test_runner/test:1542:19)
+        Test.run (node:internal/test_runner/test:1467:12)
+        async Promise.all (index 0)
+        async Suite.run (node:internal/test_runner/test:1905:7)
+        async startSubtestAfterBootstrap (node:internal/test_runner/harness:387:3)
+      ...
+    1..2
+not ok 1 - the seat
+  ---
+  duration_ms: 3.295664
+  type: 'suite'
+  location: '/tmp/1901k/node/suite/test/a.test.ts:3:1'
+  failureType: 'subtestsFailed'
+  error: '1 subtest failed'
+  code: 'ERR_TEST_FAILURE'
+  ...
+1..1
+# tests 2
+# suites 1
+# pass 1
+# fail 1
+# cancelled 0
+# skipped 0
+# todo 0
+# duration_ms 115.948112

go/buildstep/conformance/captured/node/syntax.console

@@ -0,0 +1,2 @@
+npm notice run test
+npm notice run node --test --experimental-strip-types 'test/*.test.ts'

go/buildstep/conformance/captured/node/syntax.tap

@@ -0,0 +1,47 @@
+TAP version 13
+# Subtest: passes in the first file
+ok 1 - passes in the first file
+  ---
+  duration_ms: 0.637465
+  type: 'test'
+  ...
+# node:internal/modules/run_main:111
+#     triggerUncaughtException(
+#     ^
+# file:///tmp/1901k/node/syntax/test/b.test.ts:2
+# test('never loads', () => {
+# SyntaxError [ERR_INVALID_TYPESCRIPT_SYNTAX]: Expected ',', got '<eof>'
+#     at parseTypeScript (node:internal/modules/typescript:61:36)
+#     at processTypeScriptCode (node:internal/modules/typescript:129:37)
+#     at Object.stripTypeScriptModuleTypes (node:internal/modules/typescript:172:22)
+#     at stripTypeScriptModuleTypes (node:internal/modules/esm/translators:35:49)
+#     at ModuleLoader.<anonymous> (node:internal/modules/esm/translators:688:29)
+#     at \#translate (node:internal/modules/esm/loader:441:20)
+#     at afterLoad (node:internal/modules/esm/loader:509:29)
+#     at ModuleLoader.loadAndTranslate (node:internal/modules/esm/loader:514:12)
+#     at \#getOrCreateModuleJobAfterResolve (node:internal/modules/esm/loader:567:36)
+#     at afterResolve (node:internal/modules/esm/loader:614:52) {
+#   code: 'ERR_INVALID_TYPESCRIPT_SYNTAX'
+# }
+# Node.js v26.12.1
+# Subtest: test/b.test.ts
+not ok 2 - test/b.test.ts
+  ---
+  duration_ms: 87.629815
+  type: 'test'
+  location: '/tmp/1901k/node/syntax/test/b.test.ts:1:1'
+  failureType: 'testCodeFailure'
+  exitCode: 1
+  signal: ~
+  error: 'test failed'
+  code: 'ERR_TEST_FAILURE'
+  ...
+1..2
+# tests 2
+# suites 0
+# pass 1
+# fail 1
+# cancelled 0
+# skipped 0
+# todo 0
+# duration_ms 106.551435

go/buildstep/conformance/captured/node/timeout.console

@@ -0,0 +1,2 @@
+npm notice run test
+npm notice run node --test --experimental-strip-types 'test/*.test.ts'

go/buildstep/conformance/captured/node/timeout.tap

@@ -0,0 +1,26 @@
+TAP version 13
+# Subtest: passes before the wait
+ok 1 - passes before the wait
+  ---
+  duration_ms: 0.683015
+  type: 'test'
+  ...
+# Subtest: waits for an answer that never comes
+not ok 2 - waits for an answer that never comes
+  ---
+  duration_ms: 201.103775
+  type: 'test'
+  location: '/tmp/1901k/node/timeout/test/a.test.ts:3:1'
+  failureType: 'testTimeoutFailure'
+  error: 'test timed out after 200ms'
+  code: 'ERR_TEST_FAILURE'
+  ...
+1..2
+# tests 2
+# suites 0
+# pass 1
+# fail 0
+# cancelled 1
+# skipped 0
+# todo 0
+# duration_ms 308.920061

go/buildstep/conformance/captured/node/two-files.console

@@ -0,0 +1,2 @@
+npm notice run test
+npm notice run node --test --experimental-strip-types 'test/*.test.ts'

go/buildstep/conformance/captured/node/two-files.tap

@@ -0,0 +1,49 @@
+TAP version 13
+# Subtest: passes in the first file
+ok 1 - passes in the first file
+  ---
+  duration_ms: 0.740124
+  type: 'test'
+  ...
+# judged against the seat as it stands
+# Subtest: passes in the second file first
+ok 2 - passes in the second file first
+  ---
+  duration_ms: 0.916463
+  type: 'test'
+  ...
+# Subtest: fails in the second file
+not ok 3 - fails in the second file
+  ---
+  duration_ms: 1.719236
+  type: 'test'
+  location: '/tmp/1901k/node/two-files/test/b.test.ts:4:1'
+  failureType: 'testCodeFailure'
+  error: |-
+    one plus one is not three
+    
+    2 !== 3
+    
+  code: 'ERR_ASSERTION'
+  name: 'AssertionError'
+  expected: 3
+  actual: 2
+  operator: 'strictEqual'
+  stack: |-
+    TestContext.<anonymous> (file:///tmp/1901k/node/two-files/test/b.test.ts:6:10)
+    Test.runInAsyncScope (node:async_hooks:226:14)
+    Test.run (node:internal/test_runner/test:1402:25)
+    Test.processPendingSubtests (node:internal/test_runner/test:974:18)
+    Test.postRun (node:internal/test_runner/test:1542:19)
+    Test.run (node:internal/test_runner/test:1467:12)
+    async startSubtestAfterBootstrap (node:internal/test_runner/harness:387:3)
+  ...
+1..3
+# tests 3
+# suites 0
+# pass 2
+# fail 1
+# cancelled 0
+# skipped 0
+# todo 0
+# duration_ms 135.931121

go/buildstep/conformance/captured/tsc/typeerror.console

@@ -0,0 +1 @@
+seat.ts(2,14): error TS2322: Type 'number' is not assignable to type 'string'.

go/buildstep/conformance/conformance.go

@@ -0,0 +1,201 @@
+// Package conformance is the kit every build module's tests run (novox/hq issue 1901, its thorough fix): real output of
+// the test runners, captured with the build nodes' own toolchains (captured/README.md), and what a build module must say
+// of each failure in it under the failure contract (buildstep.Failure). A build module's test calls Run with its own parse
+// path, the code that turns a runner's output into the failures of its test result; the kit fails the test when a
+// failure is not named, its cause is missing or wrong, or a passing line stands in its place.
+//
+// A catalogue check (mesh-catalog checks/failurekit) refuses a build module with a test step whose tests do not call Run,
+// and any build module whose tests do not call LeftRunning, the kit's case of steps a previous process left running
+// (leftrunning.go, issue 1890).
+package conformance
+
+import (
+	"embed"
+	"fmt"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/buildstep"
+)
+
+// The runners the kit holds output of.
+const (
+	// GoTest is `go test -json -count=1 ./...`: Output.Stdout is its output (go1.27.3).
+	GoTest = "go test -json"
+	// NodeTest is a package's `npm test` running `node --test --experimental-strip-types` with
+	// NODE_OPTIONS=buildstep.NodeTestOptions(<file>): Output.Report is the TAP file, Output.Stdout the script's own output
+	// and stderr, Output.Dir the package's directory as it was captured (node v26.12.1, npm 12.2.1).
+	NodeTest = "node --test"
+	// TypeCheck is tsc's type-check (`tsc --noEmit`, typescript 5.9.3): Output.Stdout is what it wrote; its failure
+	// names the test "type-check".
+	TypeCheck = "tsc"
+)
+
+// Output is one captured run of a runner, as a build module's parse path takes it.
+type Output struct {
+	Stdout, Stderr string
+	// Report is what a runner wrote to a report file of its own (node --test's TAP), "" for the others.
+	Report string
+	// Dir is the directory the run was captured in: a node test's file is said relative to it.
+	Dir string
+}
+
+// Parse is a build module's own parse path: the failures its test result would carry for one run that failed.
+type Parse func(Output) []buildstep.Failure
+
+// Case is one captured run and what its failure must say.
+type Case struct {
+	Name   string
+	Runner string
+	// Test is the failing test the failure names (for a package that stopped, the tests that were running; "" for none).
+	Test string
+	// File, when set, is where the failing test is.
+	File string
+	// Cause holds what the failure's cause must contain.
+	Cause []string
+	// Passing are the names of tests that passed in the run, and what they logged: no failure's words may hold them.
+	Passing []string
+}
+
+//go:embed captured
+var captured embed.FS
+
+// Cases are the kit's cases of a runner.
+func Cases(runner string) []Case {
+	var out []Case
+	for _, c := range cases {
+		if c.Runner == runner {
+			out = append(out, c)
+		}
+	}
+	return out
+}
+
+var cases = []Case{
+	{Name: "passfirst", Runner: GoTest, Test: "TestTheSecondPackageFails", Cause: []string{"the seat has 2 holders, want 1"},
+		Passing: []string{"TestTheFirstPackagePasses", "TestTheSecondPackagePassesFirst"}},
+	{Name: "subtests", Runner: GoTest, Test: "TestTheTable/fails", Cause: []string{"got 3 machines, want 4"}, Passing: []string{"TestTheTable/passes"}},
+	{Name: "logthenfatal", Runner: GoTest, Test: "TestThree", Cause: []string{"3 subscription(s) derive to a subject no emitter owns:"}},
+	{Name: "panicking", Runner: GoTest, Test: "TestPanics", Cause: []string{"panic: assignment to entry in nil map"}},
+	{Name: "timeout", Runner: GoTest, Test: "TestWaitsForever", Cause: []string{"panic: test timed out after 2s", "TestWaitsForever"}},
+	{Name: "deeptimeout", Runner: GoTest, Test: "TestHoldsTheSeat, TestWaitsForTheBus", Cause: []string{"panic: test timed out after 2s", "TestHoldsTheSeat", "TestWaitsForTheBus"}},
+	{Name: "buildfail", Runner: GoTest, Cause: []string{`cannot use "seat" (untyped string constant) as int value`}},
+	{Name: "exiting", Runner: GoTest, Test: "TestExits", Cause: []string{"exited", "TestExits"}},
+	{Name: "killed", Runner: GoTest, Test: "TestKilled", Cause: []string{"signal: killed"}},
+	{Name: "passthenfail", Runner: GoTest, Cause: []string{"panic: the bus closed after the tests: nats: connection closed"}},
+	{Name: "mainexit", Runner: GoTest, Cause: []string{"passed", "exited"}},
+	{Name: "race", Runner: GoTest, Test: "TestRacesOnTheSeat", Cause: []string{"DATA RACE", "Write at", "example.com/race.TestRacesOnTheSeat.func1()", "p_test.go:13", "created at example.com/race.TestRacesOnTheSeat()"}},
+	{Name: "subpanic", Runner: GoTest, Test: "TestTable/panics", Cause: []string{"panic: assignment to entry in nil map"}, Passing: []string{"TestTable/passes"}},
+	{Name: "racemain", Runner: GoTest, Cause: []string{"DATA RACE", "Write at", "example.com/racemain.TestMain.func1()", "p_test.go:15", "created at example.com/racemain.TestMain()"}},
+
+	{Name: "two-files", Runner: NodeTest, Test: "fails in the second file", File: "test/b.test.ts:4:1", Cause: []string{"one plus one is not three"},
+		Passing: []string{"passes in the first file", "passes in the second file first"}},
+	{Name: "suite", Runner: NodeTest, Test: "fails inside", File: "test/a.test.ts:5:3", Cause: []string{"Expected values to be strictly deep-equal:"},
+		Passing: []string{"passes inside"}},
+	{Name: "crash", Runner: NodeTest, Test: "test/b.test.ts", File: "test/b.test.ts:1:1", Cause: []string{"the bus closed under the test"},
+		Passing: []string{"passes before the crash"}},
+	{Name: "logcrash", Runner: NodeTest, Test: "test/b.test.ts", File: "test/b.test.ts:1:1", Cause: []string{"the bus closed under the test"},
+		Passing: []string{"passes and logs", "retrying after Error: the store was not ready yet"}},
+	{Name: "timeout", Runner: NodeTest, Test: "waits for an answer that never comes", File: "test/a.test.ts:3:1", Cause: []string{"test timed out after 200ms"},
+		Passing: []string{"passes before the wait"}},
+	{Name: "syntax", Runner: NodeTest, Test: "test/b.test.ts", File: "test/b.test.ts:1:1", Cause: []string{"SyntaxError", "Expected ',', got '<eof>'"},
+		Passing: []string{"passes in the first file"}},
+
+	{Name: "typeerror", Runner: TypeCheck, Test: "type-check", Cause: []string{"seat.ts(2,14): error TS2322: Type 'number' is not assignable to type 'string'."}},
+}
+
+// Load is the captured output of a case.
+func Load(c Case) (Output, error) {
+	switch c.Runner {
+	case GoTest:
+		b, err := captured.ReadFile("captured/go/" + c.Name + ".jsonl")
+		return Output{Stdout: string(b)}, err
+	case NodeTest:
+		report, err := captured.ReadFile("captured/node/" + c.Name + ".tap")
+		if err != nil {
+			return Output{}, err
+		}
+		console, err := captured.ReadFile("captured/node/" + c.Name + ".console")
+		return Output{Report: string(report), Stdout: string(console), Dir: "/tmp/1901k/node/" + c.Name}, err
+	default:
+		b, err := captured.ReadFile("captured/tsc/" + c.Name + ".console")
+		return Output{Stdout: string(b), Dir: "/tmp/1901k/tsc/" + c.Name}, err
+	}
+}
+
+// Run runs every case of runner through parse, each as a subtest, and fails a case whose failure does not keep the
+// contract: exactly one failure, naming the failing test (and its file, where the runner says it), with a cause that
+// holds what the case says and is no passing line, an output that starts with the cause, stays within its bound and
+// holds no passing line and no passing test's name.
+func Run(t *testing.T, runner string, parse Parse) {
+	t.Helper()
+	cs := Cases(runner)
+	if len(cs) == 0 {
+		t.Fatalf("the kit holds no case of the runner %q", runner)
+	}
+	for _, c := range cs {
+		t.Run(c.Name, func(t *testing.T) {
+			out, err := Load(c)
+			if err != nil {
+				t.Fatal(err)
+			}
+			for _, problem := range Judge(c, parse(out)) {
+				t.Error(problem)
+			}
+		})
+	}
+}
+
+// Judge says what is wrong with the failures a parse path made of a case; nothing when they keep the contract.
+func Judge(c Case, failed []buildstep.Failure) []string {
+	var problems []string
+	say := func(s string) { problems = append(problems, c.Runner+" "+c.Name+": "+s) }
+	if len(failed) != 1 {
+		say(fmt.Sprintf("want one failure, got %d: %s", len(failed), describe(failed)))
+		if len(failed) == 0 {
+			return problems
+		}
+	}
+	f := failed[0]
+	if f.Test != c.Test {
+		say("the failure names the test " + quote(f.Test) + ", want " + quote(c.Test))
+	}
+	if c.File != "" && f.File != c.File {
+		say("the failure's file is " + quote(f.File) + ", want " + quote(c.File))
+	}
+	if why := buildstep.Hidden(f); why != "" {
+		say("the failure hides its cause: " + why)
+	}
+	for _, want := range c.Cause {
+		if !strings.Contains(f.Cause, want) {
+			say("the cause " + quote(f.Cause) + " does not hold " + quote(want))
+		}
+	}
+	if first := strings.SplitN(f.Output, "\n", 2)[0]; strings.TrimSpace(first) != strings.TrimSpace(f.Cause) {
+		say("the output starts with " + quote(first) + ", not with the cause")
+	}
+	if len(f.Output) > buildstep.OutputBytes+buildstep.LineBytes+64 {
+		say(fmt.Sprintf("the output holds %d bytes, over its bound", len(f.Output)))
+	}
+	for _, l := range strings.Split(f.Output, "\n") {
+		if buildstep.PassingLine(l) {
+			say("the output keeps the passing line " + quote(l))
+		}
+	}
+	for _, p := range c.Passing {
+		if strings.Contains(f.Output, p+"\n") || strings.HasSuffix(f.Output, p) || strings.Contains(f.Cause, p) || strings.Contains(f.Output, "- "+p) {
+			say("the failure's words hold the passing test " + quote(p))
+		}
+	}
+	return problems
+}
+
+func describe(failed []buildstep.Failure) string {
+	var s []string
+	for _, f := range failed {
+		s = append(s, quote(f.Package+" "+f.Test)+" ("+quote(f.Cause)+")")
+	}
+	return strings.Join(s, ", ")
+}
+
+func quote(s string) string { return fmt.Sprintf("%q", s) }

go/buildstep/conformance/conformance_test.go

@@ -0,0 +1,167 @@
+package conformance
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/buildstep"
+)
+
+// The failure contract (issue 1901): the SDK's own parsers keep it on every captured case of the kit (1901/AC6); the
+// kit refuses what the build modules sent before it; the contract's own rules; and the Go reader's older guarantees.
+func TestTheFailureContract(t *testing.T) {
+	t.Run("the SDK parsers keep it", func(t *testing.T) {
+		Run(t, GoTest, func(o Output) []buildstep.Failure { return buildstep.ReadGoTest(o.Stdout, ".").Failed })
+		Run(t, NodeTest, func(o Output) []buildstep.Failure { return buildstep.ReadTAP(".", "test", o.Dir, o.Report, o.Stdout) })
+		Run(t, TypeCheck, func(o Output) []buildstep.Failure {
+			return []buildstep.Failure{buildstep.ConsoleFailure(".", "type-check", o.Stdout+o.Stderr)}
+		})
+	})
+
+	// 1890/AC7: the SDK's start sweep keeps the left-running case, and the kit refuses a sweep that ends nothing or ends
+	// everything.
+	t.Run("the left-running case", func(t *testing.T) {
+		LeftRunning(t, func(ctx context.Context, scan buildstep.Scan, node string, before time.Time, logf func(string, ...any)) {
+			buildstep.EndStaleAtStart(ctx, scan, node, before, logf)
+		})
+		if p := JudgeLeftRunning(func(context.Context, buildstep.Scan, string, time.Time, func(string, ...any)) {}); len(p) != 11 {
+			t.Errorf("a sweep that ends nothing: %d problems, want 11 (three steps not ended and unsaid, one owner unnamed, two asks not deleted and unsaid):\n%s", len(p), strings.Join(p, "\n"))
+		}
+		wrongNode := func(ctx context.Context, scan buildstep.Scan, _ string, before time.Time, logf func(string, ...any)) {
+			buildstep.EndStaleAtStart(ctx, scan, "kitother", before, logf)
+		}
+		if p := JudgeLeftRunning(wrongNode); len(p) == 0 {
+			t.Error("a sweep of another node's steps is not refused")
+		}
+	})
+
+	// node's output cut to its first fifteen lines with no cause, whose first line was a passing test of the first file
+	// (mesh-build-node's lines() before the contract), and a Go failure keeping its first line.
+	t.Run("the kit refuses a failure that hides its cause", func(t *testing.T) {
+		firstLines := func(s string) string {
+			var keep []string
+			for _, l := range strings.Split(s, "\n") {
+				if l = strings.TrimSpace(l); l != "" && len(keep) < 15 {
+					keep = append(keep, l)
+				}
+			}
+			return strings.Join(keep, "\n")
+		}
+		for _, c := range []struct {
+			runner, name string
+			old          func(Output) []buildstep.Failure
+		}{
+			{NodeTest, "two-files", func(o Output) []buildstep.Failure {
+				return []buildstep.Failure{{Package: ".", Test: "test", Output: firstLines(o.Report)}}
+			}},
+			{GoTest, "passfirst", func(o Output) []buildstep.Failure {
+				return []buildstep.Failure{{Package: "example.com/passfirst/b", Test: "TestTheSecondPackageFails", Cause: "ok  \texample.com/passfirst/a", Output: "--- PASS: TestTheSecondPackagePassesFirst"}}
+			}},
+		} {
+			for _, k := range Cases(c.runner) {
+				if k.Name != c.name {
+					continue
+				}
+				out, err := Load(k)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if problems := Judge(k, c.old(out)); len(problems) == 0 {
+					t.Errorf("%s %s: the kit passed a failure that hides its cause", c.runner, c.name)
+				}
+			}
+		}
+	})
+
+	// What a passing line is (a test's own line starting "ok " is none), when a failure hides its cause, and that a long
+	// failure keeps its last lines within the bound and starts with a real line for an older checker, which reads only
+	// the first line of the output cut to 120 characters (1901/AC1, AC3).
+	t.Run("its rules", func(t *testing.T) {
+		for _, c := range []struct {
+			line    string
+			passing bool
+		}{
+			{"✔ the same merge has the same id (8.0ms)", true}, {"ok 1 - passes", true}, {"    ok 3 - inside", true},
+			{"ok  \texample.com/a\t0.01s", true}, {"PASS", true}, {"--- PASS: TestA (0.00s)", true},
+			{"    --- PASS: TestA/sub (0.00s)", true}, {"✖ fails (1ms)", false}, {"not ok 2 - fails", false},
+			{"okay, the seat moved", false}, {"ok then: the store refused the write", false}, {"ok  the seat", false}, {"FAIL", false},
+		} {
+			if buildstep.PassingLine(c.line) != c.passing {
+				t.Errorf("PassingLine(%q) = %v, want %v", c.line, !c.passing, c.passing)
+			}
+		}
+		if buildstep.Hidden(buildstep.Failure{Cause: "the seat has 2 holders"}) != "" || buildstep.Hidden(buildstep.Failure{}) == "" ||
+			buildstep.Hidden(buildstep.Failure{Cause: "✔ passes (1ms)"}) == "" {
+			t.Error("Hidden does not tell a real cause from none and from a passing line")
+		}
+		var lines []string
+		for i := 0; i < 400; i++ {
+			lines = append(lines, "    x_test.go:1: log line "+strings.Repeat("y", 40))
+		}
+		lines = append(lines, "    x_test.go:9: the real cause", "--- FAIL: TestX (0.00s)")
+		oldFirst := func(out string) string { // the older checker's rule (judge.go firstLine before issue 1901)
+			for _, l := range strings.Split(out, "\n") {
+				if l = strings.TrimSpace(l); l != "" {
+					return l[:min(len(l), 120)]
+				}
+			}
+			return ""
+		}
+		for _, cause := range []string{"the real cause", ""} {
+			out := buildstep.Clip(lines, cause)
+			if len(out) > buildstep.OutputBytes+buildstep.LineBytes {
+				t.Errorf("1901/AC1: kept %d bytes, bound is %d", len(out), buildstep.OutputBytes)
+			}
+			if !strings.HasSuffix(out, "the real cause\n--- FAIL: TestX (0.00s)") || !strings.Contains(out, "\n... (") {
+				t.Errorf("1901/AC1: the last lines or the marker are lost: %q...%q", out[:40], out[len(out)-60:])
+			}
+			if got := oldFirst(out); strings.HasPrefix(got, "... (") || got == "" || (cause != "" && got != cause) {
+				t.Errorf("1901/AC3: cause %q: an older checker would read %q", cause, got)
+			}
+		}
+	})
+
+	// The Go reader (moved from mesh-build-go): an older checker, which knows no "cause" field, still reads a failure and
+	// gets at least the lines it kept (1901/AC3); a test's indented log line saying "panic:" is not the cause, go's own at
+	// column 0 is (1901/AC4); and each package counts its own skipped tests (issue 890).
+	t.Run("the Go reader", func(t *testing.T) {
+		read := func(name string) string {
+			raw, err := captured.ReadFile("captured/go/" + name + ".jsonl")
+			if err != nil {
+				t.Fatal(err)
+			}
+			return string(raw)
+		}
+		b, _ := json.Marshal(buildstep.ReadGoTest(read("logthenfatal"), ".").Failed)
+		var old []struct {
+			Output string `json:"output,omitempty"`
+		}
+		if err := json.Unmarshal(b, &old); err != nil || len(old) != 1 || !strings.Contains(old[0].Output, "judged against") || !strings.Contains(old[0].Output, "3 subscription(s)") {
+			t.Errorf("1901/AC3: an older checker reads %+v, %v", old, err)
+		}
+		lines := strings.SplitAfter(read("deeptimeout"), "\n")
+		added := `{"Action":"output","Package":"example.com/deeptimeout","Test":"TestHoldsTheSeat","Output":"    p_test.go:9: the child said:\n"}` + "\n" +
+			`{"Action":"output","Package":"example.com/deeptimeout","Test":"TestHoldsTheSeat","Output":"        panic: child retried and recovered\n"}` + "\n" +
+			`{"Action":"output","Package":"example.com/deeptimeout","Test":"TestHoldsTheSeat","Output":"        WARNING: DATA RACE\n"}` + "\n"
+		if got := buildstep.ReadGoTest(strings.Join(lines[:10], "")+added+strings.Join(lines[10:], ""), ".").Failed; len(got) != 1 || !strings.HasPrefix(got[0].Cause, "panic: test timed out after 2s") {
+			t.Errorf("1901/AC4: failures = %+v, want the timeout's panic as the cause", got)
+		}
+		res := buildstep.ReadGoTest(`{"Action":"run","Package":"m/a","Test":"TestA"}
+{"Action":"skip","Package":"m/a","Test":"TestA","Elapsed":0}
+{"Action":"run","Package":"m/b","Test":"TestB"}
+{"Action":"pass","Package":"m/b","Test":"TestB","Elapsed":0}
+{"Action":"pass","Package":"m/a","Elapsed":0}
+{"Action":"pass","Package":"m/b","Elapsed":0}
+`, ".")
+		got := map[string]int{}
+		for _, p := range res.Packages {
+			got[p.Package] = p.Skipped
+		}
+		if res.Skipped != 1 || got["m/a"] != 1 || got["m/b"] != 0 {
+			t.Errorf("skipped = %d, per package %v, want 1 with m/a 1 and m/b 0", res.Skipped, got)
+		}
+	})
+}

go/buildstep/conformance/leftrunning.go

@@ -0,0 +1,212 @@
+package conformance
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"sort"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/buildstep"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **A step left running by a previous process** (novox/hq issue 1890, note 21): when a delivery replaced mesh-build-go
+// on a node while a check ask ran, the new process's start sweep let the ask's key stand as running, and it held one
+// of the node's build slots until a hand end. Every build module runs this case (LeftRunning) through the start sweep
+// its main runs: the hand-started steps a previous process left are ended at once and loud, its asks' keys deleted (the
+// stream redelivers the ask, novox/hq ADR 0525 §6, and its asker keeps waiting for that), what this process runs kept. A
+// catalogue check (mesh-catalog checks/failurekit) refuses a build module whose tests do not call LeftRunning.
+
+// Sweep is a build module's own start sweep, as its main runs it once at its start: it ends node's steps in scan that
+// no process of the module runs any more (buildstep.EndStaleAtStart, here with the runtime already serving), before
+// being the start of the process, saying each end with logf.
+type Sweep func(ctx context.Context, scan buildstep.Scan, node string, before time.Time, logf func(string, ...any))
+
+// LeftNode is the node the case's steps are of.
+const LeftNode = "kitnode"
+
+// leftCase is one step in the steps state before the sweep, and whether the sweep must end it.
+type leftCase struct {
+	id, tool, owner, state string
+	node                   string
+	age                    time.Duration // started this long before the process began (negative: after it)
+	ended                  bool
+	deleted                bool // a gone process's ask: its key is deleted, not ended
+}
+
+// gone is a previous process's owner on the same node.
+var gone = "b00t-of-the-kit.4242.mvp0000"
+
+func leftCases() []leftCase {
+	return []leftCase{
+		{id: "mvpwlkzi7e6ca8", tool: "check ask", owner: gone, age: 5 * time.Minute, deleted: true}, // note 21's ghost
+		{id: "mvpwlkzi7e6ca9", tool: "delivery ask", owner: gone, age: -time.Second, deleted: true},
+		{id: "gonehand1", tool: "build_x_test", owner: gone, age: time.Minute, ended: true},
+		{id: "oldhand1", tool: "build_x_fetch", age: time.Hour, ended: true},                // no owner: an older build's
+		{id: "mvpwlkzi7e6caa", tool: "check ask", age: time.Hour, ended: true},              // no owner, past the bound
+		{id: "mvpwlkzi7e6cab", tool: "check ask", age: 5 * time.Minute},                     // no owner, the stream's still
+		{id: "mvpwlkzi7e6cac", tool: "check ask", owner: buildstep.Owner, age: time.Minute}, // this process's
+		{id: "minehand1", tool: "build_x_test", owner: buildstep.Owner, age: -time.Second},
+		{id: "donehand1", tool: "build_x_test", owner: gone, age: time.Hour, state: delivery.StepPassed},
+		{id: "otherhand1", tool: "build_x_test", owner: gone, age: time.Hour, node: "kitother"},
+	}
+}
+
+// LeftRunning runs the case through sweep and fails the test for each step the sweep ended or kept wrongly, or ended
+// without saying it.
+func LeftRunning(t *testing.T, sweep Sweep) {
+	t.Helper()
+	for _, problem := range JudgeLeftRunning(sweep) {
+		t.Error(problem)
+	}
+}
+
+// JudgeLeftRunning says what is wrong with what sweep did to the case; nothing when it keeps the rule.
+func JudgeLeftRunning(sweep Sweep) []string {
+	st := &steps{vals: map[string][]byte{}, revs: map[string]uint64{}}
+	before := time.Now()
+	for _, c := range leftCases() {
+		node, state := c.node, c.state
+		if node == "" {
+			node = LeftNode
+		}
+		if state == "" {
+			state = delivery.StepRunning
+		}
+		key, _ := delivery.StepKey(node, c.id)
+		raw, err := delivery.EncodeStep(delivery.Step{ID: c.id, Tool: c.tool, Node: node, State: state, Started: before.Add(-c.age).UTC(), Owner: c.owner})
+		if err != nil {
+			return []string{"the kit's step " + c.id + ": " + err.Error()}
+		}
+		st.set(key, raw)
+	}
+	served := make(chan struct{})
+	close(served)
+	was := buildstep.StaleServed
+	buildstep.StaleServed = func() <-chan struct{} { return served }
+	defer func() { buildstep.StaleServed = was }()
+	var mu sync.Mutex
+	var said []string
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	sweep(ctx, st.scan(), LeftNode, before, func(f string, a ...any) {
+		mu.Lock()
+		defer mu.Unlock()
+		said = append(said, fmt.Sprintf(f, a...))
+	})
+	mu.Lock()
+	log := strings.Join(said, "\n")
+	mu.Unlock()
+	var problems []string
+	for _, c := range leftCases() {
+		node := c.node
+		if node == "" {
+			node = LeftNode
+		}
+		key, _ := delivery.StepKey(node, c.id)
+		raw := st.get(key)
+		if c.deleted {
+			if raw != nil {
+				problems = append(problems, fmt.Sprintf("left running: the ask %s of the gone owner %q is still held after the sweep (%s); "+
+					"its key is deleted, never ended: the stream redelivers it (ADR 0525 §6)", key, c.owner, raw))
+			}
+			if !strings.Contains(log, key) || !strings.Contains(log, c.owner) {
+				problems = append(problems, "left running: the delete of "+key+" is not said with its owner "+c.owner)
+			}
+			continue
+		}
+		if raw == nil {
+			problems = append(problems, "left running: the step "+key+" is gone after the sweep, want it kept or ended")
+			continue
+		}
+		s, err := delivery.DecodeStep(raw)
+		if err != nil {
+			problems = append(problems, key+": "+err.Error())
+			continue
+		}
+		want := c.state
+		if want == "" {
+			want = delivery.StepRunning
+		}
+		if c.ended {
+			want = delivery.StepFailed
+		}
+		if s.State != want {
+			problems = append(problems, fmt.Sprintf("left running: the step %s (%s, owner %q, %s before the start) is %s after the sweep, want %s", key, c.tool, c.owner, c.age, s.State, want))
+		}
+		if c.ended && !strings.Contains(log, key) {
+			problems = append(problems, "left running: the end of "+key+" is not said")
+		}
+		if c.ended && c.owner != "" && !strings.Contains(log, c.owner) {
+			problems = append(problems, "left running: the end of "+key+" does not name its owner "+c.owner)
+		}
+	}
+	sort.Strings(problems)
+	return problems
+}
+
+// steps is a steps state with revisions, whose Update lands only at the revision read (stdio.ErrChanged otherwise).
+type steps struct {
+	mu   sync.Mutex
+	vals map[string][]byte
+	revs map[string]uint64
+}
+
+func (s *steps) set(key string, raw []byte) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.vals[key], s.revs[key] = raw, s.revs[key]+1
+}
+
+func (s *steps) get(key string) []byte {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.vals[key]
+}
+
+func (s *steps) scan() buildstep.Scan {
+	return buildstep.Scan{
+		Keys: func() ([]string, error) {
+			s.mu.Lock()
+			defer s.mu.Unlock()
+			var out []string
+			for k := range s.vals {
+				out = append(out, k)
+			}
+			return out, nil
+		},
+		Get: func(key string) (json.RawMessage, uint64, error) {
+			s.mu.Lock()
+			defer s.mu.Unlock()
+			return s.vals[key], s.revs[key], nil
+		},
+		Delete: func(key string, revision uint64) error {
+			s.mu.Lock()
+			defer s.mu.Unlock()
+			if s.revs[key] != revision {
+				return stdio.ErrChanged
+			}
+			delete(s.vals, key)
+			s.revs[key]++
+			return nil
+		},
+		Update: func(key string, value any, revision uint64) (uint64, error) {
+			raw, err := json.Marshal(value)
+			if err != nil {
+				return 0, err
+			}
+			s.mu.Lock()
+			defer s.mu.Unlock()
+			if s.revs[key] != revision {
+				return 0, stdio.ErrChanged
+			}
+			s.vals[key], s.revs[key] = raw, revision+1
+			return revision + 1, nil
+		},
+	}
+}

go/buildstep/cpu.go

@@ -0,0 +1,14 @@
+package buildstep
+
+import (
+	"os"
+
+	"git.novox.be/novox/mesh-sdk/go/buildcpu"
+)
+
+// NodeLimits is what one step of a build module is held to (novox/hq ADR 0553 §4): the node's processor share from the
+// word the composer gives the module (buildcpu.ShareWord), divided by the module's own capacity, own, over the machine's
+// processors. Without the word, no thread limit: Threads is 0.
+func NodeLimits(own int) buildcpu.Limits {
+	return buildcpu.FromWords(os.Getenv, own)
+}

go/buildstep/digestshape_test.go

@@ -0,0 +1,234 @@
+package buildstep
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// credentialField is the node runtime's rule for a state value (mesh-tools node-tools/internal/bus/state.go, novox/hq
+// ADR 0201), copied whole: the first field anywhere in the value whose name, lower-cased and without - _ and spaces, ends
+// in a credential word, or "". A step's end is refused when it answers a field.
+func credentialField(value json.RawMessage) string {
+	endings := []string{"password", "passwd", "secret", "token", "credential", "credentials",
+		"authorization", "apikey", "privatekey", "accesskey", "cookie"}
+	var v any
+	if json.Unmarshal(value, &v) != nil {
+		return ""
+	}
+	var walk func(any) string
+	walk = func(v any) string {
+		switch t := v.(type) {
+		case map[string]any:
+			keys := make([]string, 0, len(t))
+			for k := range t {
+				keys = append(keys, k)
+			}
+			sort.Strings(keys)
+			for _, k := range keys {
+				norm := strings.NewReplacer("-", "", "_", "", " ", "").Replace(strings.ToLower(k))
+				for _, end := range endings {
+					if strings.HasSuffix(norm, end) {
+						return k
+					}
+				}
+				if found := walk(t[k]); found != "" {
+					return found
+				}
+			}
+		case []any:
+			for _, x := range t {
+				if found := walk(x); found != "" {
+					return found
+				}
+			}
+		}
+		return ""
+	}
+	return walk(v)
+}
+
+// runtimeState is a steps state that refuses a value as the node runtime does, and keeps every value it took.
+type runtimeState struct {
+	mu      sync.Mutex
+	took    map[string][]delivery.Step
+	refused int
+}
+
+func newRuntimeState() *runtimeState { return &runtimeState{took: map[string][]delivery.Step{}} }
+
+func (s *runtimeState) put(key string, value any) (uint64, error) {
+	raw, _ := value.(json.RawMessage)
+	if f := credentialField(raw); f != "" {
+		s.mu.Lock()
+		s.refused++
+		s.mu.Unlock()
+		return 0, fmt.Errorf("steps.%s carries a field %q, which names a credential", key, f)
+	}
+	st, err := delivery.DecodeStep(raw)
+	if err != nil {
+		return 0, err
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.took[key] = append(s.took[key], st)
+	return uint64(len(s.took[key])), nil
+}
+
+func (s *runtimeState) last(key string) (delivery.Step, bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	t := s.took[key]
+	if len(t) == 0 {
+		return delivery.Step{}, false
+	}
+	return t[len(t)-1], true
+}
+
+func fastEnds(t *testing.T) {
+	attempts, retry := EndAttempts, EndRetry
+	EndAttempts, EndRetry = 2, time.Millisecond
+	t.Cleanup(func() { EndAttempts, EndRetry = attempts, retry })
+}
+
+// 1930/AC1: given a check of a repository with the package .../internal/token, when its ask's answer is stored as the
+// step's end, then no field is keyed by a package path: the runtime's credential rule takes the value, and the package
+// and its digest read back from the stored end.
+func TestADigestOfAPackageNamedTokenIsStoredAsAList(t *testing.T) {
+	fastEnds(t)
+	r := &recorder{
+		fetch:   map[string]any{"workspace": "/w"},
+		digests: map[string]string{"x/internal/token": "d-token", "x/pkg/a": "d-a"},
+		tests:   map[string]bool{"x/internal/token": true, "x/pkg/a": true},
+	}
+	out, err := RunAsk(context.Background(), r.steps(), ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit},
+		Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	old, _ := json.Marshal(map[string]any{"levels": []any{map[string]any{"level": "unit", "digest": map[string]any{"packages": r.digests}}}})
+	if credentialField(old) != "x/internal/token" {
+		t.Fatalf("the rule does not refuse the form before issue 1930 (%s): the test proves nothing", old)
+	}
+	st := newRuntimeState()
+	if err := finish(st.put, "shanks.a1", delivery.Step{ID: "a1", Tool: "check ask", Node: "shanks", State: delivery.StepRunning, Started: time.Now()}, out, nil, t.Logf); err != nil {
+		t.Fatal(err)
+	}
+	s, ok := st.last("shanks.a1")
+	if !ok || s.State != delivery.StepPassed || st.refused != 0 {
+		t.Fatalf("the end %+v (written %v, refused %d), want it passed and taken at once", s, ok, st.refused)
+	}
+	var a delivery.CheckAnswer
+	if err := json.Unmarshal(s.Result, &a); err != nil {
+		t.Fatal(err)
+	}
+	if len(a.Levels) != 1 || a.Levels[0].Digest == nil {
+		t.Fatalf("levels %+v, want the unit level with its digest", a.Levels)
+	}
+	want := []delivery.PackageDigest{{Package: "x/internal/token", Digest: "d-token"}, {Package: "x/pkg/a", Digest: "d-a"}}
+	if got := a.Levels[0].Digest.Packages; fmt.Sprint(got) != fmt.Sprint(want) {
+		t.Errorf("packages %v, want %v", got, want)
+	}
+	if !strings.Contains(string(s.Result), `"package":"x/internal/token"`) {
+		t.Errorf("the stored end does not name the package as a value: %s", s.Result)
+	}
+}
+
+// 1930/AC2: given an end the state refuses every time, when finish writes it, then it logs the refusal and writes a small
+// failed end without the result that names the write's error; and when no end can be written at all it answers an error.
+func TestARefusedEndIsSaidAndEndsTheStepFailed(t *testing.T) {
+	fastEnds(t)
+	big := errors.New("the value carries a field \"x/internal/token\", which names a credential")
+	var refused int
+	var stored []delivery.Step
+	put := func(key string, value any) (uint64, error) {
+		st, _ := delivery.DecodeStep(value.(json.RawMessage))
+		if len(st.Result) > 0 {
+			refused++
+			return 0, big
+		}
+		stored = append(stored, st)
+		return 1, nil
+	}
+	var logged []string
+	logf := func(format string, args ...any) { logged = append(logged, fmt.Sprintf(format, args...)) }
+	err := finish(put, "shanks.a2", delivery.Step{ID: "a2", Tool: "check ask", Node: "shanks", State: delivery.StepRunning, Started: time.Now()}, map[string]any{"levels": 1}, nil, logf)
+	if err != nil {
+		t.Fatalf("finish answered %v, want the small end written", err)
+	}
+	if refused != EndAttempts || len(stored) != 1 {
+		t.Fatalf("refused %d, stored %d, want %d refusals and one small end", refused, len(stored), EndAttempts)
+	}
+	s := stored[0]
+	if s.State != delivery.StepFailed || len(s.Result) != 0 || !strings.Contains(s.Reason, "could not be written") ||
+		!strings.Contains(s.Reason, big.Error()) || !strings.Contains(s.Reason, "passed") {
+		t.Errorf("the small end %+v, want failed, no result, naming the write's error and that it passed", s)
+	}
+	if len(logged) == 0 || !strings.Contains(logged[0], big.Error()) {
+		t.Errorf("logged %q, want the refusal said", logged)
+	}
+	none := func(string, any) (uint64, error) { return 0, errors.New("the bus is gone") }
+	if err := finish(none, "shanks.a3", delivery.Step{ID: "a3", Tool: "check ask", Node: "shanks", Started: time.Now()}, nil, nil, logf); err == nil || !strings.Contains(err.Error(), "the bus is gone") {
+		t.Errorf("finish with no write possible answered %v, want the error", err)
+	}
+}
+
+// 1930/AC2: given an ask whose end the state refuses, when it runs, then the ask is acknowledged only once its small
+// failed end is written; when no end can be written at all, it is given back, never acknowledged as done.
+func TestAnAskWhoseEndCannotBeWrittenIsNotAcked(t *testing.T) {
+	fastEnds(t)
+	for _, tc := range []struct {
+		name      string
+		smallOK   bool
+		wantAcked bool
+	}{{"the small end written", true, true}, {"no end written", false, false}} {
+		t.Run(tc.name, func(t *testing.T) {
+			src := NewFakeAsks()
+			a := testAsk(delivery.AskCheck)
+			_ = src.PublishAsk(a)
+			var mu sync.Mutex
+			var ends []delivery.Step
+			put := func(key string, value any) (uint64, error) {
+				st, err := delivery.DecodeStep(value.(json.RawMessage))
+				if err != nil {
+					return 0, err
+				}
+				if st.State != delivery.StepRunning && (len(st.Result) > 0 || !tc.smallOK) {
+					return 0, errors.New("refused")
+				}
+				mu.Lock()
+				ends = append(ends, st)
+				mu.Unlock()
+				return 1, nil
+			}
+			p := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: put, Capacity: func() int { return 1 },
+				PullWait: 10 * time.Millisecond, Logf: t.Logf,
+				Run: func(ctx context.Context, a delivery.StepAsk) (any, error) { return map[string]any{"ran": true}, nil }}
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+			go p.Pull(ctx)
+			waitFor(t, "the ask's fate", func() bool { ac, tm, nk := src.Fates(); return len(ac)+len(tm)+len(nk) > 0 })
+			cancel()
+			acked, termed, naked := src.Fates()
+			if tc.wantAcked && (len(acked) != 1 || len(naked) != 0) || !tc.wantAcked && (len(acked) != 0 || len(naked) == 0) || len(termed) != 0 {
+				t.Fatalf("acked %v naked %v termed %v", acked, naked, termed)
+			}
+			mu.Lock()
+			defer mu.Unlock()
+			if tc.smallOK {
+				last := ends[len(ends)-1]
+				if last.State != delivery.StepFailed || !strings.Contains(last.Reason, "refused") {
+					t.Errorf("the end %+v, want the small failed end", last)
+				}
+			}
+		})
+	}
+}

go/buildstep/failure.go

@@ -0,0 +1,147 @@
+package buildstep
+
+// The failure contract of a build step's test level (novox/hq issue 1901, its thorough fix): what a build module says of
+// each test that failed, the same for every language. Each build module used to parse its own test runner's output, and
+// a fix in one never reached the others: a failed Go test kept a t.Logf line, a failed node --test run kept a passing
+// '✔' line of its first file. The parsers that fill the contract live here (gotest.go, tap.go) and the conformance kit
+// (package conformance) holds every build module to them with captured runner output.
+
+import (
+	"fmt"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/sdkversion"
+)
+
+// Failure is one test that failed, or a package or file that failed with no test to name (a build that failed, a test
+// program that panicked, a test file that did not load). The JSON names are the ones mesh-build-go and the checker have
+// always used; File is new and an older reader ignores it.
+type Failure struct {
+	// Package is the Go package's import path, or the TypeScript package's directory in the workspace.
+	Package string `json:"package"`
+	// Test names the failing test, or the tests that were running when the program stopped; "" when none can be named.
+	Test string `json:"test,omitempty"`
+	// File is where the failing test is (a Go test's file and line is in its Cause; node names the test's file:line:col).
+	File string `json:"file,omitempty"`
+	// Cause is the one line that says why: the assertion's or the error's first line, a "panic:" line, a build's first
+	// error, or words saying how the program stopped. **Never empty, and never a passing line** (PassingLine).
+	Cause string `json:"cause,omitempty"`
+	// Output is the failing test's own output, its last lines up to OutputBytes, Cause first: an older checker reads
+	// only its first line.
+	Output string `json:"output,omitempty"`
+}
+
+// OutputBytes is the most a failure keeps of its output, and LineBytes the most of one line: four kilobytes holds a long
+// assertion message and stays far under a bus message's or a verdict's bound.
+const (
+	OutputBytes = 4096
+	LineBytes   = 1024
+)
+
+// By names a build module and the SDK it was built with, for a result's "by": the checker names it when a failure hides
+// its cause ("the build module hid the failure (<by>)").
+func By(module string) string {
+	return module + " with mesh-sdk " + sdkversion.Version()
+}
+
+// PassingLine says a line is a test runner's word for a test or a package that passed: node's '✔', TAP's "ok N" (at any
+// indent), go test's "ok  \t<pkg>", "PASS" and "--- PASS". A line of a test's own that starts "ok " is none of these. Such a line is never a failure's cause, nor part of a failure's output.
+func PassingLine(l string) bool {
+	if strings.HasPrefix(l, "ok  \t") { // go test's package line, at column 0
+		return true
+	}
+	t := strings.TrimSpace(l)
+	switch {
+	case t == "PASS", strings.HasPrefix(t, "✔"), strings.HasPrefix(t, "--- PASS"):
+		return true
+	}
+	return tapOk(t)
+}
+
+// Hidden says how a failure hides why it failed, or "" when it does not: it has no cause, or its cause is a passing line.
+// The checker says it loudly (issue 1901): a build module that sends such a failure does not keep the contract.
+func Hidden(f Failure) string {
+	c := strings.TrimSpace(f.Cause)
+	switch {
+	case c == "":
+		return "it sent no cause"
+	case PassingLine(c):
+		return fmt.Sprintf("its cause is a passing line (%q)", CutLine(c))
+	}
+	return ""
+}
+
+// Clip joins the last lines of a failure's output that fit OutputBytes, each cut to LineBytes, and says how many earlier
+// lines it left out. **Its first line is the cause**, put ahead when the kept lines do not start with it, or, with no
+// cause and lines left out, the first non-empty line, then the marker: an older checker reads only the first line.
+// Passing lines are dropped.
+func Clip(lines []string, cause string) string {
+	own := make([]string, 0, len(lines))
+	for _, l := range lines {
+		if !PassingLine(l) {
+			own = append(own, l)
+		}
+	}
+	lines = own
+	size, from := 0, len(lines)
+	for from > 0 {
+		n := len(CutLine(lines[from-1])) + 1
+		if size+n > OutputBytes && from < len(lines) {
+			break
+		}
+		size += n
+		from--
+	}
+	kept := make([]string, 0, len(lines)-from+2)
+	head := strings.TrimSpace(cause)
+	for i := 0; head == "" && i < from; i++ {
+		head = strings.TrimSpace(lines[i])
+	}
+	if head != "" && (from > 0 || len(lines) == 0 || strings.TrimSpace(lines[from]) != head) {
+		kept = append(kept, CutLine(head))
+	}
+	if from > 0 {
+		kept = append(kept, fmt.Sprintf("... (%d earlier lines)", from))
+	}
+	for _, l := range lines[from:] {
+		kept = append(kept, CutLine(l))
+	}
+	return strings.Join(kept, "\n")
+}
+
+// CutLine cuts a line to LineBytes, on a character boundary.
+func CutLine(l string) string {
+	if len(l) <= LineBytes {
+		return l
+	}
+	return strings.ToValidUTF8(l[:LineBytes], "") + "..."
+}
+
+// ConsoleFailure is the failure of a command that is no test runner (go vet, gofmt, tsc, a build script): its cause is the
+// first line that names an error (tsc's "error TS", go vet's "file.go:12:3: ..."), else the first line that is not a
+// heading ("# <package>", npm's "> script"), and its output the command's lines without passing ones.
+func ConsoleFailure(pkg, test, out string) Failure {
+	var lines []string
+	for _, l := range strings.Split(strings.ReplaceAll(stripANSI(out), "\r\n", "\n"), "\n") {
+		if t := strings.TrimSpace(l); t != "" && !PassingLine(t) {
+			lines = append(lines, strings.TrimRight(l, " \t"))
+		}
+	}
+	cause := ""
+	for _, l := range lines {
+		if t := strings.TrimSpace(l); strings.Contains(t, "error") || strings.Contains(t, "Error") || goPosition.MatchString(t) {
+			cause = t
+			break
+		}
+	}
+	for _, l := range lines {
+		if t := strings.TrimSpace(l); cause == "" && !strings.HasPrefix(t, "# ") && !strings.HasPrefix(t, "> ") && !strings.HasPrefix(t, "npm ") {
+			cause = t
+		}
+	}
+	if cause == "" {
+		cause = test + " failed and wrote nothing that says why"
+	}
+	cause = CutLine(cause)
+	return Failure{Package: pkg, Test: test, Cause: cause, Output: Clip(lines, cause)}
+}

go/buildstep/fetch.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"net/url"
+	"os"
+	"path/filepath"
 	"regexp"
 	"strings"
 
@@ -13,12 +15,37 @@ import (
 // Option changes FetchCommit.
 type Option func(*fetchOptions)
 
-type fetchOptions struct{ allowFile bool }
+type fetchOptions struct {
+	allowFile bool
+	mirror    string
+}
 
 // AllowFileRemote lets FetchCommit take a file:// remote. It is for a test's local repository; production
 // code does not pass it, and FetchCommit then refuses anything but ssh://.
 func AllowFileRemote() Option { return func(o *fetchOptions) { o.allowFile = true } }
 
+// WithMirror makes FetchCommit (and MergeInto) borrow objects from mirror, a bare repository that UpdateMirror keeps
+// in the build module's own cache (novox/hq ADR 0536 §2; issue 890): the workspace's .git/objects/info/alternates
+// names the mirror's objects directory, so git transfers only the objects the mirror lacks. It is a plain file, never
+// a symlink. mirror must be an absolute path of an existing directory; the workspace never writes to it.
+func WithMirror(mirror string) Option { return func(o *fetchOptions) { o.mirror = mirror } }
+
+// useMirror writes the alternates file of the repository in dir, when a mirror is set.
+func useMirror(o fetchOptions, dir string) error {
+	if o.mirror == "" {
+		return nil
+	}
+	info := filepath.Join(dir, ".git", "objects", "info")
+	if err := os.MkdirAll(info, 0o755); err != nil {
+		return fmt.Errorf("buildstep: the mirror cannot be used: %w", err)
+	}
+	line := filepath.Join(o.mirror, "objects") + "\n"
+	if err := os.WriteFile(filepath.Join(info, "alternates"), []byte(line), 0o644); err != nil {
+		return fmt.Errorf("buildstep: the mirror cannot be used: %w", err)
+	}
+	return nil
+}
+
 var (
 	commitOK = regexp.MustCompile(`^[0-9a-f]{40}$`)
 	refOK    = regexp.MustCompile(`^refs/[A-Za-z0-9._/-]+$`)
@@ -44,13 +71,16 @@ func FetchCommit(ctx context.Context, run forgekey.Runner, dir, remote, commit,
 		full := append([]string{"-c", "credential.helper=", "-C", dir}, args...)
 		r := run(ctx, env, "git", full...)
 		if r.Status != 0 || r.Err != "" {
-			return "", fmt.Errorf("git %s: %s", args[0], firstLine(r.Err+" "+r.Stderr))
+			return "", fmt.Errorf("git %s: %s", args[0], forgekey.Said(r.Err+"\n"+r.Stderr))
 		}
 		return r.Stdout, nil
 	}
 	if _, err := git("init", "-q"); err != nil {
 		return err
 	}
+	if err := useMirror(o, dir); err != nil {
+		return err
+	}
 	if _, err := git("remote", "add", "origin", remote); err != nil {
 		return err
 	}
@@ -78,10 +108,71 @@ func FetchCommit(ctx context.Context, run forgekey.Runner, dir, remote, commit,
 	return nil
 }
 
+// UpdateMirror brings the bare repository mirror to commit: it makes the mirror when it is absent (git init --bare,
+// origin set to remote), then fetches the commit, or the ref when only the ref holds it, with the same rules as
+// FetchCommit (no prompt, no credential helper, ssh:// or an allowed file:// remote, a 40-hex commit). The mirror
+// keeps every commit it was brought to, so later fetches through WithMirror transfer only what is new. Callers
+// serialise updates of one mirror.
+func UpdateMirror(ctx context.Context, run forgekey.Runner, mirror, remote, commit, ref string, opts ...Option) error {
+	var o fetchOptions
+	for _, opt := range opts {
+		opt(&o)
+	}
+	if !filepath.IsAbs(mirror) {
+		return fmt.Errorf("buildstep: the mirror %q is not an absolute path", mirror)
+	}
+	if err := checkFetch(o, mirror, remote, commit, ref); err != nil {
+		return err
+	}
+	env := []string{"GIT_TERMINAL_PROMPT=0"}
+	git := func(args ...string) error {
+		r := run(ctx, env, "git", append([]string{"-c", "credential.helper="}, args...)...)
+		if r.Status != 0 || r.Err != "" {
+			verb := args[0]
+			if verb == "-C" && len(args) > 2 { // the mirror's commands are named by what they do, not by -C
+				verb = args[2]
+			}
+			return fmt.Errorf("git %s: %s", verb, forgekey.Said(r.Err+"\n"+r.Stderr))
+		}
+		return nil
+	}
+	in := func(args ...string) error { return git(append([]string{"-C", mirror}, args...)...) }
+	if _, err := os.Stat(filepath.Join(mirror, "HEAD")); err != nil {
+		if err := git("init", "-q", "--bare", mirror); err != nil {
+			return err
+		}
+		if err := in("remote", "add", "origin", remote); err != nil {
+			return err
+		}
+	} else if err := in("remote", "set-url", "origin", remote); err != nil {
+		return err
+	}
+	if err := in("fetch", "--no-tags", "origin", commit); err != nil {
+		if ref == "" {
+			return err
+		}
+		if rerr := in("fetch", "--no-tags", "origin", ref); rerr != nil {
+			return fmt.Errorf("%v; then the ref %s: %w", err, ref, rerr)
+		}
+	}
+	if err := in("cat-file", "-e", commit+"^{commit}"); err != nil {
+		return fmt.Errorf("the commit %s is not in the mirror: %w", commit, err)
+	}
+	return nil
+}
+
 func checkFetch(o fetchOptions, dir, remote, commit, ref string) error {
 	if dir == "" {
 		return fmt.Errorf("buildstep: no workspace directory")
 	}
+	if o.mirror != "" {
+		if !filepath.IsAbs(o.mirror) {
+			return fmt.Errorf("buildstep: the mirror %q is not an absolute path", o.mirror)
+		}
+		if fi, err := os.Stat(o.mirror); err != nil || !fi.IsDir() {
+			return fmt.Errorf("buildstep: the mirror %q is not an existing directory", o.mirror)
+		}
+	}
 	if !commitOK.MatchString(commit) {
 		return fmt.Errorf("buildstep: %q is not a full commit (40 hex digits)", commit)
 	}
@@ -103,12 +194,3 @@ func checkFetch(o fetchOptions, dir, remote, commit, ref string) error {
 	}
 	return nil
 }
-
-func firstLine(s string) string {
-	for _, l := range strings.Split(s, "\n") {
-		if l = strings.TrimSpace(l); l != "" {
-			return l
-		}
-	}
-	return ""
-}

go/buildstep/gotest.go

@@ -0,0 +1,409 @@
+package buildstep
+
+// The reader of `go test -json` (moved whole from mesh-catalog's mesh-build-go, issue 1901's thorough fix): per package
+// what ran and for how long, and each failure under the contract (failure.go), its real cause too when the failure is no
+// test's assertion (a panic, a timeout, a build error, an exit, a kill, a race).
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"regexp"
+	"slices"
+	"strings"
+)
+
+// GoPackage is one package's part of a Go test level.
+type GoPackage struct {
+	Dir     string  `json:"dir"`
+	Package string  `json:"package"`
+	Passed  bool    `json:"passed"`
+	Elapsed float64 `json:"elapsed"`
+	Tests   int     `json:"tests"`
+	// Skipped is how many of the package's tests skipped.
+	Skipped int `json:"skipped,omitempty"`
+	// NoTests is a package with no test files (at this level: a file with the other level's build tag is none).
+	NoTests bool `json:"no_tests,omitempty"`
+}
+
+// TestTime is one test and the seconds it took.
+type TestTime struct {
+	Package string  `json:"package"`
+	Test    string  `json:"test"`
+	Elapsed float64 `json:"elapsed"`
+}
+
+// GoTest is what one go.mod directory's `go test -json` said.
+type GoTest struct {
+	Packages []GoPackage
+	Tests    int
+	Skipped  int
+	Times    []TestTime
+	Failed   []Failure
+	// Elapsed is the slowest package's running time in seconds.
+	Elapsed float64
+	// Noise is the lines that were no event: what go said when it could not run the tests at all.
+	Noise []string
+}
+
+// ReadGoTest reads the output of `go test -json` run in the go.mod directory dir.
+func ReadGoTest(out, dir string) GoTest {
+	r := &goReader{dir: dir, pkgs: map[string]*GoPackage{}, builds: map[string][]string{}, pkgOut: map[string][]string{},
+		testOut: map[string][]string{}, causes: map[string]string{}, failedIn: map[string]bool{},
+		running: map[string][]string{}, passed: map[string]bool{}, built: map[string]bool{}}
+	sc := bufio.NewScanner(strings.NewReader(out))
+	sc.Buffer(make([]byte, 1<<20), 1<<26)
+	for sc.Scan() {
+		var ev goEvent
+		if err := json.Unmarshal(sc.Bytes(), &ev); err != nil {
+			if l := strings.TrimSpace(sc.Text()); l != "" {
+				r.res.Noise = append(r.res.Noise, l)
+			}
+			continue
+		}
+		r.event(ev)
+	}
+	r.finish()
+	return r.res
+}
+
+// goEvent is one line of `go test -json` (test2json, and the build events go test adds).
+type goEvent struct {
+	Action      string
+	Package     string
+	Test        string
+	Output      string
+	OutputType  string // "error" for a t.Error or t.Fatal message, "error-continue" for its further lines
+	ImportPath  string
+	FailedBuild string
+	Elapsed     float64
+}
+
+type goReader struct {
+	res      GoTest
+	dir      string
+	pkgs     map[string]*GoPackage
+	order    []string
+	builds   map[string][]string // build output by import path
+	pkgOut   map[string][]string
+	testOut  map[string][]string // by package + "\x00" + test
+	causes   map[string]string   // the first error line of a test, by the same key
+	failedIn map[string]bool     // packages with a failed test
+	// running is the tests that started and have not ended, by package, in the order they started: when a package
+	// fails with no failed test, these were running when its test program stopped.
+	running map[string][]string
+	// passed says a package's test program printed "PASS" before it failed; built says it failed to build.
+	passed, built map[string]bool
+}
+
+func (r *goReader) pkg(name string) *GoPackage {
+	p := r.pkgs[name]
+	if p == nil {
+		p = &GoPackage{Dir: r.dir, Package: name}
+		r.pkgs[name] = p
+		r.order = append(r.order, name)
+	}
+	return p
+}
+
+func keepLine(lines []string, out string) []string {
+	if t := strings.TrimRight(out, "\r\n"); t != "" && !strings.HasPrefix(t, "=== ") {
+		lines = append(lines, t)
+	}
+	return lines
+}
+
+func (r *goReader) event(ev goEvent) {
+	switch {
+	case ev.Package == "" && ev.ImportPath != "":
+		if ev.Action == "build-output" {
+			r.builds[ev.ImportPath] = keepLine(r.builds[ev.ImportPath], ev.Output)
+		}
+	case ev.Package == "":
+	case ev.Test == "":
+		p := r.pkg(ev.Package)
+		switch ev.Action {
+		case "output":
+			// go test's own summary of a package is never a failure's words: a "PASS" before a "FAIL <pkg>" says only
+			// that the tests passed and the program failed after them.
+			switch l := strings.TrimRight(ev.Output, "\r\n"); {
+			case l == "PASS":
+				r.passed[ev.Package] = true
+			case goSummaryLine(l):
+			default:
+				r.pkgOut[ev.Package] = keepLine(r.pkgOut[ev.Package], ev.Output)
+			}
+		case "pass":
+			p.Passed, p.Elapsed = true, ev.Elapsed
+		case "fail":
+			p.Passed, p.Elapsed = false, ev.Elapsed
+			if ev.FailedBuild != "" {
+				r.built[ev.Package] = true
+				r.pkgOut[ev.Package] = append(r.builds[ev.FailedBuild], r.pkgOut[ev.Package]...)
+			}
+		case "skip":
+			p.Passed, p.NoTests = true, true
+		}
+	default:
+		key := ev.Package + "\x00" + ev.Test
+		switch ev.Action {
+		case "output":
+			r.testOut[key] = keepLine(r.testOut[key], ev.Output)
+			if ev.OutputType == "error" && r.causes[key] == "" {
+				r.causes[key] = goErrorWords(ev.Output)
+			}
+		case "run":
+			r.running[ev.Package] = append(r.running[ev.Package], ev.Test)
+		case "pass", "fail", "skip":
+			r.running[ev.Package] = slices.DeleteFunc(r.running[ev.Package], func(t string) bool { return t == ev.Test })
+			p := r.pkg(ev.Package)
+			p.Tests++
+			r.res.Tests++
+			if ev.Action == "skip" {
+				r.res.Skipped++
+				p.Skipped++
+			}
+			r.res.Times = append(r.res.Times, TestTime{Package: ev.Package, Test: ev.Test, Elapsed: ev.Elapsed})
+			if ev.Action == "fail" {
+				r.failedIn[ev.Package] = true
+				if r.subtestFailed(ev.Package, ev.Test) {
+					return // a parent failed only by its subtest is that subtest's failure, said once
+				}
+				if r.subtestTakesTheCause(ev.Package, ev.Test) {
+					return // a subtest's panic, which go files under its parent, is said on the subtest
+				}
+				r.res.Failed = append(r.res.Failed, r.testFailure(ev.Package, ev.Test))
+			}
+		}
+	}
+}
+
+// subtestFailed says a failure of test under pkg was already reported for one of its subtests (they end first), each with
+// a cause of its own, and the test reported no error and no runtime cause (a subtest's panic) of its own.
+func (r *goReader) subtestFailed(pkg, test string) bool {
+	key := pkg + "\x00" + test
+	if r.causes[key] != "" || goRuntimeCause(r.testOut[key]) != "" {
+		return false
+	}
+	for _, f := range r.res.Failed {
+		if f.Package == pkg && strings.HasPrefix(f.Test, test+"/") {
+			return true
+		}
+	}
+	return false
+}
+
+// noMessage is the cause of a test that failed and said nothing of why.
+const noMessage = "the test failed without an error message (t.Fail or t.FailNow)"
+
+// subtestTakesTheCause gives a parent's runtime cause (a subtest's panic: go test -json files its lines under the
+// parent) to the subtests of that parent that failed with no message of their own, and says it did. A parent with an
+// error line of its own, or whose failed subtests each said why, is reported as itself.
+func (r *goReader) subtestTakesTheCause(pkg, test string) bool {
+	key := pkg + "\x00" + test
+	if r.causes[key] != "" {
+		return false
+	}
+	cause := goRuntimeCause(r.testOut[key])
+	if cause == "" {
+		return false
+	}
+	took := false
+	for i, f := range r.res.Failed {
+		if f.Package == pkg && strings.HasPrefix(f.Test, test+"/") && f.Cause == noMessage {
+			r.res.Failed[i].Cause, r.res.Failed[i].Output = cause, Clip(r.testOut[key], cause)
+			took = true
+		}
+	}
+	return took
+}
+
+// testFailure is a test that failed: its cause is its first error line, the race it ran into, the runtime's line, or
+// words saying it failed without a message.
+func (r *goReader) testFailure(pkg, test string) Failure {
+	key := pkg + "\x00" + test
+	cause := r.causes[key]
+	if race := goRaceCause(r.testOut[key]); race != "" && (cause == "" || strings.HasPrefix(cause, "race detected")) {
+		cause = race // the race itself, not testing's "race detected during execution of test"
+	} else if cause == "" {
+		cause = goRuntimeCause(r.testOut[key])
+	}
+	if cause == "" {
+		cause = noMessage
+	}
+	return Failure{Package: pkg, Test: test, Output: Clip(r.testOut[key], cause), Cause: cause}
+}
+
+// goSummaryLine says a line is go test's summary of a package, in go's exact forms only: "PASS" or "FAIL" alone,
+// "ok  \t<pkg>\t<time>" and "FAIL\t<pkg>\t<time>" (a line of the package's own that starts "ok " is kept).
+func goSummaryLine(l string) bool {
+	return l == "PASS" || l == "FAIL" || strings.HasPrefix(l, "ok  \t") || strings.HasPrefix(l, "FAIL\t")
+}
+
+// goRuntimeCause is the cause in a failure's output that is not a test's assertion: a race the race detector reported;
+// else the first "panic:" line, a timeout's with the tests it names as running; else the first "fatal error:" or
+// "signal:" line; "" when there is none. It reads every line, so a long goroutine dump cannot hide it. **It matches only
+// lines at column 0**, where go prints the runtime's: a test's indented log line holding the same words is not the cause.
+func goRuntimeCause(lines []string) string {
+	if race := goRaceCause(lines); race != "" {
+		return race
+	}
+	for _, prefix := range []string{"panic: ", "fatal error: ", "signal: "} {
+		for i, l := range lines {
+			l = strings.TrimRight(l, "\r\n")
+			if !strings.HasPrefix(l, prefix) {
+				continue
+			}
+			if strings.HasPrefix(l, "panic: test timed out after") {
+				var names []string
+				for _, n := range lines[i+1:] {
+					if !strings.HasPrefix(n, "\t\t") {
+						if strings.TrimSpace(n) == "running tests:" {
+							continue
+						}
+						break
+					}
+					names = append(names, strings.TrimSpace(n))
+				}
+				if len(names) > 0 {
+					l += "; running tests: " + strings.Join(names, ", ")
+				}
+			}
+			return CutLine(l)
+		}
+	}
+	return ""
+}
+
+// goRaceCause is the first race the race detector reported in a failure's output, in one line: its access and the frame
+// that made it, and where the goroutine that made it was created. "" when the output holds no race.
+func goRaceCause(lines []string) string {
+	at := -1
+	for i, l := range lines {
+		if strings.TrimRight(l, "\r\n") == "WARNING: DATA RACE" {
+			at = i
+			break
+		}
+	}
+	if at < 0 {
+		return ""
+	}
+	frame := func(i int) string {
+		var fn, file string
+		for _, l := range lines[i+1:] {
+			if l = strings.TrimSpace(l); l == "" {
+				break
+			}
+			if fn == "" {
+				fn = l
+				continue
+			}
+			file = l
+			if j := strings.LastIndexByte(file, '/'); j >= 0 {
+				file = file[j+1:]
+			}
+			if j := strings.Index(file, " +0x"); j >= 0 {
+				file = file[:j]
+			}
+			break
+		}
+		if file != "" {
+			return fn + " (" + file + ")"
+		}
+		return fn
+	}
+	words := "WARNING: DATA RACE"
+	for i := at + 1; i < len(lines); i++ {
+		l := strings.TrimSpace(lines[i])
+		if l == "" || strings.HasPrefix(l, "===") {
+			continue
+		}
+		words += ": " + strings.TrimSuffix(l, ":")
+		if f := frame(i); f != "" {
+			words += " in " + f
+		}
+		break
+	}
+	for i := at + 1; i < len(lines); i++ {
+		l := strings.TrimSpace(lines[i])
+		if strings.HasPrefix(l, "==================") {
+			break
+		}
+		if strings.HasPrefix(l, "Goroutine ") && strings.HasSuffix(l, " created at:") {
+			if f := frame(i); f != "" {
+				words += "; its goroutine created at " + f
+			}
+			break
+		}
+	}
+	return CutLine(words)
+}
+
+// goBuildCause is the first error line of a failed build: the first line that is not go's "# <package>" heading.
+func goBuildCause(lines []string) string {
+	for _, l := range lines {
+		if l = strings.TrimSpace(l); l != "" && !strings.HasPrefix(l, "# ") {
+			return CutLine(l)
+		}
+	}
+	return ""
+}
+
+// goTestNames names the tests that were running, at most three, and how many more.
+func goTestNames(tests []string) string {
+	if len(tests) <= 3 {
+		return strings.Join(tests, ", ")
+	}
+	return fmt.Sprintf("%s and %d more", strings.Join(tests[:3], ", "), len(tests)-3)
+}
+
+// packageFailure is a package that failed with no failed test to name it: its test program did not build, panicked,
+// timed out, was killed or exited. It names the tests that were running, keeps their output with the package's, and
+// says the cause.
+func (r *goReader) packageFailure(name string) Failure {
+	running := r.running[name]
+	var lines []string
+	for _, t := range running {
+		lines = append(lines, r.testOut[name+"\x00"+t]...)
+	}
+	lines = append(lines, r.pkgOut[name]...)
+	cause := goRuntimeCause(lines)
+	switch {
+	case cause != "":
+	case r.built[name]:
+		cause = goBuildCause(lines)
+	case len(running) > 0:
+		cause = "the test program exited while " + goTestNames(running) + " ran, with no panic: an os.Exit or a signal (go test -json reports no exit status)"
+	case r.passed[name]:
+		cause = "the tests passed, then the test program exited with a failure: an os.Exit or a panic in TestMain or after the tests (go test -json reports no exit status)"
+	}
+	if cause == "" {
+		cause = "the package failed with no test to name and no panic, signal or build error in its output"
+	}
+	return Failure{Package: name, Test: goTestNames(running), Output: Clip(lines, cause), Cause: cause}
+}
+
+var goFileAndLine = regexp.MustCompile(`^\S+\.go:\d+: `)
+
+// goPosition matches a line that starts with a Go file's position, as go vet and the compiler write an error.
+var goPosition = regexp.MustCompile(`^\S+\.go:\d+(:\d+)?: `)
+
+// goErrorWords is the words of an error line of a test: trimmed, without the file and line go test put before them.
+func goErrorWords(out string) string {
+	return strings.TrimSpace(goFileAndLine.ReplaceAllString(strings.TrimSpace(out), ""))
+}
+
+// finish moves what was read into the result: the packages in order, a failure for each failed package that has no
+// failed test to name it.
+func (r *goReader) finish() {
+	for _, name := range r.order {
+		p := r.pkgs[name]
+		if !p.Passed && !r.failedIn[name] {
+			r.res.Failed = append(r.res.Failed, r.packageFailure(name))
+		}
+		if !p.NoTests && p.Elapsed > r.res.Elapsed {
+			r.res.Elapsed = p.Elapsed
+		}
+		r.res.Packages = append(r.res.Packages, *p)
+	}
+}

go/buildstep/isolate.go

@@ -0,0 +1,175 @@
+package buildstep
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// Bubblewrap is the program a run step runs in (novox/hq ADR 0448): a build module declares its package, which needs
+// unprivileged user namespaces (issue 1308).
+const Bubblewrap = "bwrap"
+
+// Isolation is how a run step's command is shut off (novox/hq ADR 0448; issue 1309, the lead's decision L2 of R4e: one
+// runner in the SDK for every build module). The fetch step holds the forge key and the network and runs none of the
+// change's code; the run step runs the change's build and tests in bubblewrap with:
+//
+//   - no network: its own network namespace, with only a loopback, so a test may start a bus or a store of its own but
+//     resolves no name and reaches no socket of the machine;
+//   - none of the account: not its home, not the forge key, not a bus login, not the runtime directory (/run), since
+//     none of them is bound; HOME is a directory in the step's own /tmp unless Env names one;
+//   - an environment of exactly Env and the runner's env: nothing of the build module's own passes;
+//   - the system's programs and libraries read-only, and of /etc only what a program needs to run (users, libraries,
+//     certificates, time zone), with a hosts file naming only the loopback;
+//   - the Workspace and Writable directories read-write, the ReadOnly ones (the toolchain, the modules the fetch step
+//     downloaded) read-only;
+//   - the shared warm Caches read-only under a throwaway writable layer (S18), or read-write for a trunk build alone
+//     (WriteCaches), so a candidate's code never changes what a later build reads.
+type Isolation struct {
+	Workspace   string
+	Writable    []string
+	ReadOnly    []string
+	Caches      []string
+	WriteCaches bool
+	Env         []string
+	// Hosts is the file bound as /etc/hosts; Isolated writes one naming only the loopback.
+	Hosts string
+}
+
+// etcNeeded is what of /etc a program in the step may read: who the users are, where the libraries are, the
+// certificates, the time zone. Not resolv.conf, not hosts: the step resolves no name.
+var etcNeeded = []string{"/etc/passwd", "/etc/group", "/etc/nsswitch.conf", "/etc/ld.so.cache", "/etc/ld.so.conf",
+	"/etc/ld.so.conf.d", "/etc/ssl", "/etc/ca-certificates", "/etc/pki", "/etc/localtime", "/etc/os-release", "/etc/alternatives"}
+
+// systemArgs binds the system's programs and libraries read-only: /usr, and /bin, /sbin, /lib, /lib64 as the symlinks
+// they are on a merged-usr system, or bound when they are directories. A variable so a unit test fixes it.
+var systemArgs = func() []string {
+	args := []string{"--ro-bind", "/usr", "/usr"}
+	for _, d := range []string{"/bin", "/sbin", "/lib", "/lib64"} {
+		info, err := os.Lstat(d)
+		switch {
+		case err != nil:
+		case info.Mode()&os.ModeSymlink != 0:
+			if target, err := os.Readlink(d); err == nil {
+				args = append(args, "--symlink", target, d)
+			}
+		case info.IsDir():
+			args = append(args, "--ro-bind", d, d)
+		}
+	}
+	for _, e := range etcNeeded {
+		args = append(args, "--ro-bind-try", e, e)
+	}
+	return args
+}
+
+// stepHome is the HOME of a step that is given none: inside its own /tmp, gone with it.
+const stepHome = "/tmp/home"
+
+func checkDir(what, dir string) error {
+	if dir == "" || !strings.HasPrefix(dir, "/") || path.Clean(dir) != dir || dir == "/" {
+		return fmt.Errorf("buildstep: the %s %q is not an absolute, clean directory other than the root", what, dir)
+	}
+	return nil
+}
+
+// Command is the bubblewrap command line that runs name with args shut off as iso says, env added to iso.Env. It
+// refuses a directory that is not absolute and clean, or is the root, and an environment word without "=".
+func (iso Isolation) Command(name string, args ...string) ([]string, error) {
+	return iso.command(nil, name, args...)
+}
+
+func (iso Isolation) command(env []string, name string, args ...string) ([]string, error) {
+	if err := checkDir("workspace", iso.Workspace); err != nil {
+		return nil, err
+	}
+	for _, group := range []struct {
+		what string
+		dirs []string
+	}{{"writable directory", iso.Writable}, {"read-only directory", iso.ReadOnly}, {"cache", iso.Caches}} {
+		for _, d := range group.dirs {
+			if err := checkDir(group.what, d); err != nil {
+				return nil, err
+			}
+		}
+	}
+	words := append(append([]string{}, iso.Env...), env...)
+	home := false
+	for _, w := range words {
+		k, _, ok := strings.Cut(w, "=")
+		if !ok || k == "" {
+			return nil, fmt.Errorf("buildstep: the environment word %q is not NAME=value", w)
+		}
+		home = home || k == "HOME"
+	}
+	argv := []string{"--unshare-all", "--die-with-parent", "--new-session", "--clearenv",
+		"--proc", "/proc", "--dev", "/dev", "--tmpfs", "/tmp", "--dir", stepHome}
+	argv = append(argv, systemArgs()...)
+	for _, d := range iso.ReadOnly {
+		argv = append(argv, "--ro-bind", d, d)
+	}
+	argv = append(argv, cacheArgs(iso.Caches, iso.WriteCaches)...)
+	argv = append(argv, "--bind", iso.Workspace, iso.Workspace)
+	for _, d := range iso.Writable {
+		argv = append(argv, "--bind", d, d)
+	}
+	if iso.Hosts != "" {
+		argv = append(argv, "--ro-bind", iso.Hosts, "/etc/hosts")
+	}
+	for _, w := range words {
+		k, v, _ := strings.Cut(w, "=")
+		argv = append(argv, "--setenv", k, v)
+	}
+	if !home {
+		argv = append(argv, "--setenv", "HOME", stepHome)
+	}
+	argv = append(argv, "--chdir", iso.Workspace, "--", name)
+	return append(argv, args...), nil
+}
+
+// cacheArgs binds the shared warm caches (S18): for a trunk build read-write, so the next build is warm; for any other
+// read-only beneath an overlay whose writes go to a tmpfs of the step's own, so the step writes as a build does and
+// nothing it wrote outlives it (bubblewrap's --tmp-overlay, an overlay mount in the step's user namespace).
+func cacheArgs(caches []string, write bool) []string {
+	var argv []string
+	for _, c := range caches {
+		if write {
+			argv = append(argv, "--bind", c, c)
+			continue
+		}
+		argv = append(argv, "--overlay-src", c, "--tmp-overlay", c)
+	}
+	return argv
+}
+
+// loopbackHosts is the hosts file of a step: the loopback and nothing else.
+const loopbackHosts = "127.0.0.1 localhost\n::1 localhost\n"
+
+// Isolated is run with every command shut off as iso says (Command), run's env going inside the step: the build modules'
+// run steps call their test, build and digest commands through it, never run itself. Each command gets a hosts file of
+// its own, naming only the loopback, removed when it ends.
+func Isolated(run forgekey.Runner, iso Isolation) forgekey.Runner {
+	return func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		dir, err := os.MkdirTemp("", "step-hosts-")
+		if err != nil {
+			return forgekey.Ran{Status: 1, Err: "the step's hosts file: " + err.Error()}
+		}
+		defer os.RemoveAll(dir)
+		hosts := filepath.Join(dir, "hosts")
+		if err := os.WriteFile(hosts, []byte(loopbackHosts), 0o644); err != nil {
+			return forgekey.Ran{Status: 1, Err: "the step's hosts file: " + err.Error()}
+		}
+		iso := iso
+		iso.Hosts = hosts
+		argv, err := iso.command(env, name, args...)
+		if err != nil {
+			return forgekey.Ran{Status: 1, Err: err.Error()}
+		}
+		return run(ctx, nil, Bubblewrap, argv...)
+	}
+}

go/buildstep/isolate_caches_test.go

@@ -0,0 +1,30 @@
+package buildstep
+
+import "testing"
+
+// The shared warm caches are read under a throwaway writable layer (novox/hq ADR 0448; issue 1309): a candidate's step
+// writes into them as a build does, and nothing it writes outlives it or reaches a later build; only a trunk build
+// writes them.
+func TestACandidatesStepWritesTheCachesOnlyIntoAThrowawayLayer(t *testing.T) {
+	fixedSystem(t)
+	iso := Isolation{Workspace: "/w", Caches: []string{"/var/cache/go-build", "/var/cache/npm"}}
+	argv, err := iso.Command("go", "test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, c := range iso.Caches {
+		if !holds(argv, "--overlay-src", c, "--tmp-overlay", c) {
+			t.Errorf("the cache %s is not under a throwaway layer: %v", c, argv)
+		}
+		if holds(argv, "--bind", c, c) {
+			t.Errorf("a candidate's step writes the cache %s: %v", c, argv)
+		}
+	}
+	iso.WriteCaches = true
+	argv, _ = iso.Command("go", "build")
+	for _, c := range iso.Caches {
+		if !holds(argv, "--bind", c, c) || holds(argv, "--tmp-overlay", c) {
+			t.Errorf("a trunk build does not write the cache %s: %v", c, argv)
+		}
+	}
+}

go/buildstep/isolate_integration_test.go

@@ -0,0 +1,66 @@
+//go:build integration && isolation
+
+package buildstep
+
+import (
+	"context"
+	"net"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// 1309/S19, the issue's proof: a run step, in bubblewrap as Isolated runs it, reads no key and no login, resolves no
+// name, reaches no TCP or unix socket of the machine, finds no home of the account, and leaves the shared cache it
+// wrote unchanged; the workspace it writes keeps what it wrote. It needs bubblewrap and unprivileged user namespaces
+// (issue 1308) on the machine that runs it, and fails naming them when they are not there.
+func TestARunStepReachesNothingAndLeavesTheCachesUnchanged(t *testing.T) {
+	if _, err := exec.LookPath(Bubblewrap); err != nil {
+		t.Fatalf("bubblewrap is not installed here, so the isolation of a run step cannot be proved (issue 1309): %v", err)
+	}
+	root := t.TempDir()
+	account := filepath.Join(root, "account")
+	key, login := filepath.Join(account, ".ssh", "id_ed25519"), filepath.Join(account, "bus-login.json")
+	writeFile(t, filepath.Dir(key), filepath.Base(key), "PRIVATE KEY")
+	writeFile(t, account, "bus-login.json", `{"password":"secret"}`)
+	cacheDir := filepath.Join(root, "cache")
+	writeFile(t, cacheDir, "warm", "warm\n")
+	workspace := filepath.Join(root, "work", "tree")
+	if err := os.MkdirAll(workspace, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	probe := filepath.Join(workspace, "probe")
+	if out, err := exec.Command("go", "build", "-o", probe, "./testdata/isolated-probe").CombinedOutput(); err != nil {
+		t.Fatalf("building the probe: %v\n%s", err, out)
+	}
+	tcp, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tcp.Close()
+	socket := filepath.Join(account, "bus.sock")
+	unix, err := net.Listen("unix", socket)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer unix.Close()
+
+	run := Isolated(forgekey.ExecRunnerFor(0), Isolation{Workspace: workspace, Caches: []string{cacheDir}})
+	r := run(context.Background(), []string{"PATH=/usr/bin:/bin"}, probe, key, login, tcp.Addr().String(), socket, "localhost.localdomain.invalid", filepath.Join(cacheDir, "warm"))
+	if r.Status != 0 || r.Err != "" || strings.TrimSpace(r.Stdout) != "shut off" {
+		t.Fatalf("the run step was not shut off (status %d, %s):\n%s%s", r.Status, r.Err, r.Stdout, r.Stderr)
+	}
+	if b, _ := os.ReadFile(filepath.Join(cacheDir, "warm")); string(b) != "warm\n" {
+		t.Fatalf("the step changed the shared cache: %q", b)
+	}
+
+	// The workspace is the step's own: what it writes there stays.
+	r = run(context.Background(), nil, "/bin/sh", "-c", "echo built > out")
+	if b, err := os.ReadFile(filepath.Join(workspace, "out")); r.Status != 0 || err != nil || string(b) != "built\n" {
+		t.Fatalf("the step's write to its workspace did not stay (status %d, %s%s): %q %v", r.Status, r.Stderr, r.Err, b, err)
+	}
+}

go/buildstep/isolate_test.go

@@ -0,0 +1,115 @@
+package buildstep
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// pairs says whether argv holds the words of want one after another.
+func holds(argv []string, want ...string) bool {
+	for i := 0; i+len(want) <= len(argv); i++ {
+		match := true
+		for j, w := range want {
+			if argv[i+j] != w {
+				match = false
+				break
+			}
+		}
+		if match {
+			return true
+		}
+	}
+	return false
+}
+
+func fixedSystem(t *testing.T) {
+	t.Helper()
+	before := systemArgs
+	systemArgs = func() []string { return []string{"--ro-bind", "/usr", "/usr", "--symlink", "usr/bin", "/bin"} }
+	t.Cleanup(func() { systemArgs = before })
+}
+
+// A run step's command runs in bubblewrap (novox/hq ADR 0448; issue 1309): no network, no namespace shared, an
+// environment of exactly what the step is given, the workspace the one tree it writes, the toolchain read-only, and
+// nothing else of the machine's: not the account's home, not the forge key or a bus login, not the runtime directory,
+// and no name service.
+func TestARunStepRunsShutOffInBubblewrap(t *testing.T) {
+	fixedSystem(t)
+	iso := Isolation{Workspace: "/work/ab12/tree", ReadOnly: []string{"/usr/lib/go"}, Writable: []string{"/work/ab12/out"},
+		Env: []string{"GOFLAGS=-mod=mod", "PATH=/usr/bin"}, Hosts: "/work/ab12/hosts"}
+	argv, err := iso.Command("go", "test", "./...")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range [][]string{
+		{"--unshare-all"}, {"--die-with-parent"}, {"--new-session"}, {"--clearenv"},
+		{"--proc", "/proc"}, {"--dev", "/dev"}, {"--tmpfs", "/tmp"},
+		{"--ro-bind", "/usr", "/usr"}, {"--symlink", "usr/bin", "/bin"},
+		{"--ro-bind", "/usr/lib/go", "/usr/lib/go"},
+		{"--bind", "/work/ab12/tree", "/work/ab12/tree"}, {"--bind", "/work/ab12/out", "/work/ab12/out"},
+		{"--ro-bind", "/work/ab12/hosts", "/etc/hosts"},
+		{"--setenv", "GOFLAGS", "-mod=mod"}, {"--setenv", "PATH", "/usr/bin"}, {"--setenv", "HOME", "/tmp/home"},
+		{"--chdir", "/work/ab12/tree"},
+		{"--", "go", "test", "./..."},
+	} {
+		if !holds(argv, want...) {
+			t.Errorf("the command has no %v: %v", want, argv)
+		}
+	}
+	if holds(argv, "--share-net") || strings.Contains(strings.Join(argv, " "), "resolv.conf") || strings.Contains(strings.Join(argv, " "), "/run") {
+		t.Errorf("the command reaches the network, the name service or the runtime directory: %v", argv)
+	}
+	// The workspace is mounted after /tmp's tmpfs, so a workspace under /tmp is not hidden by it.
+	if strings.Index(strings.Join(argv, "\x00"), "--tmpfs\x00/tmp") > strings.Index(strings.Join(argv, "\x00"), "--bind\x00/work/ab12/tree") {
+		t.Errorf("the tmpfs of /tmp comes after the workspace: %v", argv)
+	}
+	// A HOME the step is given is its own.
+	iso.Env = append(iso.Env, "HOME=/work/ab12/home")
+	argv, _ = iso.Command("true")
+	if holds(argv, "--setenv", "HOME", "/tmp/home") || !holds(argv, "--setenv", "HOME", "/work/ab12/home") {
+		t.Errorf("the step's own HOME was replaced: %v", argv)
+	}
+}
+
+func TestAnIsolationNamesNoPathItCannotPin(t *testing.T) {
+	for _, iso := range []Isolation{
+		{Workspace: ""},
+		{Workspace: "tree"},
+		{Workspace: "/"},
+		{Workspace: "/w", ReadOnly: []string{"relative"}},
+		{Workspace: "/w", Writable: []string{"/"}},
+		{Workspace: "/w", Caches: []string{"/a/../b"}},
+		{Workspace: "/w", Env: []string{"NOEQUALS"}},
+	} {
+		if _, err := iso.Command("true"); err == nil {
+			t.Errorf("%+v was accepted", iso)
+		}
+	}
+}
+
+// Isolated runs every command through bwrap, with the step's environment inside and a hosts file that names only the
+// loopback, removed after.
+func TestIsolatedRunsEachCommandThroughBubblewrap(t *testing.T) {
+	fixedSystem(t)
+	var ran []string
+	var hosts string
+	inner := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		ran = append([]string{name}, args...)
+		for i, a := range args {
+			if a == "/etc/hosts" && i > 0 {
+				hosts = args[i-1]
+			}
+		}
+		return forgekey.Ran{Stdout: "ok"}
+	}
+	r := Isolated(inner, Isolation{Workspace: "/w"})(context.Background(), []string{"A=1"}, "go", "build")
+	if r.Stdout != "ok" || ran[0] != Bubblewrap || !holds(ran, "--setenv", "A", "1") || !holds(ran, "--", "go", "build") {
+		t.Fatalf("ran %v: %+v", ran, r)
+	}
+	if hosts == "" {
+		t.Fatalf("no hosts file was bound: %v", ran)
+	}
+}

go/buildstep/launchers.go

@@ -0,0 +1,14 @@
+package buildstep
+
+import "git.novox.be/novox/mesh-sdk/go/catalogue"
+
+// LauncherSuffix is what a TypeScript entrypoint's launcher is called beside it: index.js is started as
+// index.serve.mjs (novox/hq ADR 0193), an ES module by its own extension whatever the bundle's package.json says.
+const LauncherSuffix = catalogue.LauncherSuffix
+
+// Launchers are the launchers a bundle's build writes, by entrypoint, relative to the bundle's root
+// (catalogue.Launchers): the one rule mesh-build-node, build-agent, the controller and a node taking in a build share
+// (R4e, issue 1126), so the name a build writes is the name a reader expects.
+func Launchers(language string, entrypoints []string) map[string]string {
+	return catalogue.Launchers(language, entrypoints)
+}

go/buildstep/launchers_test.go

@@ -0,0 +1,22 @@
+package buildstep
+
+import (
+	"reflect"
+	"testing"
+)
+
+// A TypeScript bundle's entrypoint x.js is started as x.serve.mjs beside it (novox/hq ADR 0193), the rule mesh-build-node
+// and build-agent both apply; an entrypoint that is not .js gets none, and another language gets none.
+func TestATypeScriptEntrypointIsStartedByTheLauncherBesideIt(t *testing.T) {
+	got := Launchers("typescript", []string{"index.js", "tools/x.js", "data.json"})
+	want := map[string]string{"index.js": "index.serve.mjs", "tools/x.js": "tools/x.serve.mjs"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("Launchers(typescript) = %v, want %v", got, want)
+	}
+	if got := Launchers("go", []string{"index.js"}); len(got) != 0 {
+		t.Fatalf("a Go bundle got launchers: %v", got)
+	}
+	if got := Launchers("typescript", nil); len(got) != 0 {
+		t.Fatalf("a bundle with no entrypoint got launchers: %v", got)
+	}
+}

go/buildstep/merge.go

@@ -0,0 +1,128 @@
+package buildstep
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// MergeResult is what MergeInto made of a head and a trunk commit: the trunk commit (Base) and the head, whole, and the
+// merge commit and the paths the merge changes against the trunk commit; or, when the head does not merge cleanly, the
+// files in conflict, with Merge and Changed empty.
+type MergeResult struct {
+	Base, Head, Merge string
+	Conflicts         []string
+	Changed           []string
+	// Programs are the changed files that are compiled programs (ExecutableKind of their first bytes, read in the workspace
+	// at the merge); never nil for a clean merge, so a caller tells none from a module that reports none (issue 1577).
+	Programs []Program
+}
+
+// MergeInto makes, in the workspace dir that FetchCommit left at commit, the merge of commit into the trunk commit
+// base, as the forge's default merge would (a merge commit, never a fast-forward), and leaves the workspace at the merge
+// (novox/hq ADR 0484 clause 3, ADR 0323). It is the one merge the build modules' fetch steps make, with the identity
+// and flags of the controller's check merge (mesh-controller internal/builder/check_merge.go): a name nobody owns, no
+// signature, no hook, nothing of the machine's git configuration that changes a merge. Nothing is pushed.
+//
+// A merge needs both histories, so it makes the fetch whole (the shallow clone FetchCommit made is deepened) and
+// fetches base by its sha. A head that does not merge cleanly is an answer, not an error: the files in conflict, the
+// merge undone and the workspace left at base. A head already in base answers a Merge equal to Base and no changed
+// paths. An error is that the merge could not be tried: a base or commit that is not a full sha, no base, a workspace
+// not at commit, or a fetch or git command that failed. remote and the options are those of FetchCommit; the runner's
+// bound must allow a whole fetch.
+func MergeInto(ctx context.Context, run forgekey.Runner, dir, remote, base, commit string, opts ...Option) (MergeResult, error) {
+	var o fetchOptions
+	for _, opt := range opts {
+		opt(&o)
+	}
+	res := MergeResult{Base: base, Head: commit}
+	if base == "" {
+		return res, fmt.Errorf("buildstep: no base: a merge needs the trunk commit it is made onto")
+	}
+	if err := checkFetch(o, dir, remote, base, ""); err != nil {
+		return res, err
+	}
+	if err := checkFetch(o, dir, remote, commit, ""); err != nil {
+		return res, err
+	}
+	if err := useMirror(o, dir); err != nil {
+		return res, err
+	}
+	env := []string{"GIT_TERMINAL_PROMPT=0"}
+	git := func(args ...string) (string, error) {
+		full := append([]string{"-c", "credential.helper=", "-C", dir}, args...)
+		r := run(ctx, env, "git", full...)
+		if r.Status != 0 || r.Err != "" {
+			return "", fmt.Errorf("git %s: %s", args[0], forgekey.Said(r.Err+"\n"+r.Stderr))
+		}
+		return r.Stdout, nil
+	}
+	at, err := git("rev-parse", "HEAD")
+	if err != nil {
+		return res, err
+	}
+	if head := strings.TrimSpace(at); head != commit {
+		return res, fmt.Errorf("buildstep: the workspace is at %s, not at the commit %s", head, commit)
+	}
+	shallow, err := git("rev-parse", "--is-shallow-repository")
+	if err != nil {
+		return res, err
+	}
+	fetch := []string{"fetch", "--no-tags", "origin", base}
+	if strings.TrimSpace(shallow) == "true" {
+		fetch = []string{"fetch", "--no-tags", "--unshallow", "origin", base}
+	}
+	if _, err := git(fetch...); err != nil {
+		return res, fmt.Errorf("the trunk commit %s: %w", base, err)
+	}
+	if _, err := git("checkout", "-q", "--detach", base); err != nil {
+		return res, fmt.Errorf("the trunk commit %s cannot be checked out: %w", base, err)
+	}
+	message := fmt.Sprintf("Check the merge of %s into %s (made for a check, never pushed)", short(commit), short(base))
+	args := append(append([]string{}, mergeIdentity...), "merge", "--no-ff", "--no-edit", "--no-verify", "--quiet", "-m", message, commit)
+	if _, err := git(args...); err != nil {
+		out, _ := git("diff", "--name-only", "--diff-filter=U")
+		res.Conflicts = strings.Fields(out)
+		_, _ = git("merge", "--abort")
+		if len(res.Conflicts) == 0 {
+			return res, fmt.Errorf("the head %s could not be merged into the trunk commit %s: %w", short(commit), short(base), err)
+		}
+		return res, nil
+	}
+	merge, err := git("rev-parse", "HEAD")
+	if err != nil {
+		return res, fmt.Errorf("the merge cannot be read: %w", err)
+	}
+	res.Merge = strings.TrimSpace(merge)
+	changed, err := git("diff", "--name-only", "--no-renames", base, res.Merge)
+	if err != nil {
+		return res, fmt.Errorf("the paths the merge changes cannot be read: %w", err)
+	}
+	res.Changed = strings.Fields(changed)
+	raw, err := git("diff", "--raw", "-z", "--no-renames", "--diff-filter=AM", base, res.Merge)
+	if err != nil {
+		return res, fmt.Errorf("the files the merge adds or modifies cannot be read: %w", err)
+	}
+	res.Programs = programsIn(dir, raw)
+	history, err := historyPrograms(git, base, commit, res.Programs)
+	if err != nil {
+		return res, fmt.Errorf("the commits of the branch cannot be read for compiled programs: %w", err)
+	}
+	res.Programs = append(res.Programs, history...)
+	return res, nil
+}
+
+// mergeIdentity is who a check's merge is made as: it is never pushed, so it names nobody's account. No hook of the
+// clone's or the build machine's git configuration runs, and no setting there changes the merge (the controller's
+// check merge, internal/builder/check_merge.go).
+var mergeIdentity = []string{"-c", "user.name=mesh merge check", "-c", "user.email=merge-check@mesh.invalid",
+	"-c", "commit.gpgsign=false", "-c", "core.hooksPath=/dev/null", "-c", "merge.verifySignatures=false"}
+
+func short(commit string) string {
+	if len(commit) > 12 {
+		return commit[:12]
+	}
+	return commit
+}

go/buildstep/merge_integration_test.go

@@ -0,0 +1,199 @@
+//go:build integration
+
+package buildstep
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// The merge on real git repositories starts git processes, so it is an integration test (the unit level keeps its bound,
+// issue 895); the unit tests of merge_test.go prove the commands and the refusals with a fake runner.
+
+func realGit(t *testing.T, dir string, args ...string) string {
+	t.Helper()
+	cmd := exec.Command("git", append([]string{"-C", dir, "-c", "user.name=t", "-c", "user.email=t@example.invalid", "-c", "commit.gpgsign=false"}, args...)...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("git %v: %v\n%s", args, err, out)
+	}
+	return strings.TrimSpace(string(out))
+}
+
+func writeFile(t *testing.T, dir, name, content string) {
+	t.Helper()
+	p := filepath.Join(dir, name)
+	if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(p, []byte(content), 0o644); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// mergeRig is a local bare repository standing in for the forge, a work repository that pushes to it, and an empty
+// workspace: the fetch step's shape (FetchCommit of the head into the workspace, then MergeInto).
+type mergeRig struct {
+	t              *testing.T
+	bare, work, ws string
+	fork, trunk    string // the commit both histories share, and the trunk's head
+	remote         string
+}
+
+func newMergeRig(t *testing.T) *mergeRig {
+	root := t.TempDir()
+	r := &mergeRig{t: t, bare: filepath.Join(root, "r.git"), work: filepath.Join(root, "work"), ws: filepath.Join(root, "ws")}
+	for _, d := range []string{r.bare, r.work, r.ws} {
+		if err := os.MkdirAll(d, 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	r.remote = "file://" + r.bare
+	realGit(t, r.bare, "init", "-q", "--bare")
+	realGit(t, r.work, "init", "-q", "-b", "main")
+	writeFile(t, r.work, "a.txt", "one\ntwo\nthree\n")
+	writeFile(t, r.work, "modules/m/module.json", "{}\n")
+	realGit(t, r.work, "add", ".")
+	realGit(t, r.work, "commit", "-q", "-m", "fork point")
+	r.fork = realGit(t, r.work, "rev-parse", "HEAD")
+	return r
+}
+
+// head makes a commit on a branch off the fork point, pushes it as the pull request's head ref and answers its sha.
+func (r *mergeRig) head(files map[string]string) string {
+	realGit(r.t, r.work, "checkout", "-q", "-B", "pr", r.fork)
+	for n, c := range files {
+		writeFile(r.t, r.work, n, c)
+	}
+	realGit(r.t, r.work, "add", ".")
+	realGit(r.t, r.work, "commit", "-q", "-m", "head")
+	h := realGit(r.t, r.work, "rev-parse", "HEAD")
+	realGit(r.t, r.work, "push", "-q", r.bare, "HEAD:refs/pull/1/head")
+	return h
+}
+
+// headThatAddsAndRemoves is head with an earlier commit on the branch that adds a program and a later one that removes it: the
+// branch's tree is clean, its history is not. It answers the head and the earlier commit.
+func (r *mergeRig) headThatAddsAndRemoves(files map[string]string) (head, added string) {
+	realGit(r.t, r.work, "checkout", "-q", "-B", "pr", r.fork)
+	writeFile(r.t, r.work, "gone/prog", "\x7fELF\x02\x01")
+	realGit(r.t, r.work, "add", ".")
+	realGit(r.t, r.work, "commit", "-q", "-m", "oops")
+	added = realGit(r.t, r.work, "rev-parse", "HEAD")
+	realGit(r.t, r.work, "rm", "-q", "gone/prog")
+	return r.head2(files), added
+}
+
+// head2 commits files on the current branch and pushes it as the pull request's head.
+func (r *mergeRig) head2(files map[string]string) string {
+	for n, c := range files {
+		writeFile(r.t, r.work, n, c)
+	}
+	realGit(r.t, r.work, "add", ".")
+	realGit(r.t, r.work, "commit", "-q", "-m", "head")
+	h := realGit(r.t, r.work, "rev-parse", "HEAD")
+	realGit(r.t, r.work, "push", "-q", r.bare, "HEAD:refs/pull/1/head")
+	return h
+}
+
+// advance moves the trunk past the fork point with a commit changing files, pushes it and answers its sha.
+func (r *mergeRig) advance(files map[string]string) string {
+	realGit(r.t, r.work, "checkout", "-q", "-B", "main", r.fork)
+	for n, c := range files {
+		writeFile(r.t, r.work, n, c)
+	}
+	realGit(r.t, r.work, "add", ".")
+	realGit(r.t, r.work, "commit", "-q", "-m", "trunk moves")
+	r.trunk = realGit(r.t, r.work, "rev-parse", "HEAD")
+	realGit(r.t, r.work, "push", "-q", "-f", r.bare, "HEAD:refs/heads/main")
+	return r.trunk
+}
+
+func (r *mergeRig) fetch(head string) {
+	if err := FetchCommit(context.Background(), forgekey.ExecRunner, r.ws, r.remote, head, "refs/pull/1/head", AllowFileRemote()); err != nil {
+		r.t.Fatal(err)
+	}
+}
+
+// 1674/AC1: a clean merge answers the merge commit and the changed files, and leaves the workspace at the merge, which
+// holds both sides' changes.
+func TestMergeIntoACleanMergeAnswersTheMergeCommitAndTheChangedFiles(t *testing.T) {
+	r := newMergeRig(t)
+	head, added := r.headThatAddsAndRemoves(map[string]string{"b.txt": "head\n", "prog": "\x7fELF\x02\x01"})
+	base := r.advance(map[string]string{"a.txt": "one\ntwo\nthree\nfour\n"})
+	r.fetch(head)
+	res, err := MergeInto(context.Background(), forgekey.ExecRunner, r.ws, r.remote, base, head, AllowFileRemote())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.Base != base || res.Head != head || len(res.Merge) != 40 || res.Merge == base || res.Merge == head || len(res.Conflicts) != 0 {
+		t.Fatalf("result = %+v", res)
+	}
+	if !reflect.DeepEqual(res.Changed, []string{"b.txt", "prog"}) {
+		t.Errorf("changed = %v, want only what the head adds to the trunk: b.txt, prog", res.Changed)
+	}
+	if !reflect.DeepEqual(res.Programs, []Program{{"prog", "ELF", ""}, {"gone/prog", "ELF", added}}) { // issue 1577
+		t.Errorf("programs = %v, want the ELF the head adds and the one an earlier commit added and a later one removed", res.Programs)
+	}
+	if at := realGit(t, r.ws, "rev-parse", "HEAD"); at != res.Merge {
+		t.Errorf("the workspace is at %s, not at the merge %s", at, res.Merge)
+	}
+	for f, want := range map[string]string{"b.txt": "head\n", "a.txt": "one\ntwo\nthree\nfour\n"} {
+		if got, _ := os.ReadFile(filepath.Join(r.ws, f)); string(got) != want {
+			t.Errorf("%s = %q, want %q", f, got, want)
+		}
+	}
+	if parents := strings.Fields(realGit(t, r.ws, "rev-list", "--parents", "-n", "1", res.Merge)); len(parents) != 3 || parents[1] != base || parents[2] != head {
+		t.Errorf("the merge commit's parents = %v, want the trunk commit and the head", parents)
+	}
+	if author := realGit(t, r.ws, "log", "-1", "--format=%an <%ae>", res.Merge); author != "mesh merge check <merge-check@mesh.invalid>" {
+		t.Errorf("the merge is made as %q", author)
+	}
+}
+
+// 1674/AC2: a conflict is an answer: the files in conflict, no merge commit, and the workspace left at the trunk commit.
+func TestMergeIntoAConflictAnswersTheFilesAndLeavesTheTreeAtTheTrunk(t *testing.T) {
+	r := newMergeRig(t)
+	head := r.head(map[string]string{"a.txt": "one\nHEAD\nthree\n", "c.txt": "c\n"})
+	base := r.advance(map[string]string{"a.txt": "one\nTRUNK\nthree\n"})
+	r.fetch(head)
+	res, err := MergeInto(context.Background(), forgekey.ExecRunner, r.ws, r.remote, base, head, AllowFileRemote())
+	if err != nil {
+		t.Fatalf("a conflict is an answer, not an error: %v", err)
+	}
+	if !reflect.DeepEqual(res.Conflicts, []string{"a.txt"}) || res.Merge != "" || len(res.Changed) != 0 || res.Base != base || res.Head != head {
+		t.Fatalf("result = %+v", res)
+	}
+	if at := realGit(t, r.ws, "rev-parse", "HEAD"); at != base {
+		t.Errorf("the workspace is at %s, not at the trunk commit %s", at, base)
+	}
+	if got, _ := os.ReadFile(filepath.Join(r.ws, "a.txt")); string(got) != "one\nTRUNK\nthree\n" {
+		t.Errorf("a.txt = %q, want the trunk's", got)
+	}
+	if st := realGit(t, r.ws, "status", "--porcelain"); st != "" {
+		t.Errorf("the tree is not clean after the aborted merge: %q", st)
+	}
+	if _, err := os.Stat(filepath.Join(r.ws, "c.txt")); err == nil {
+		t.Error("a file of the head is in a tree left at the trunk")
+	}
+}
+
+// A head already in the trunk merges into nothing: the merge is the trunk commit and no path changes.
+func TestMergeIntoAHeadAlreadyInTheTrunkChangesNothing(t *testing.T) {
+	r := newMergeRig(t)
+	head := r.head(map[string]string{"b.txt": "head\n"})
+	r.fork = head // the trunk continues from the head
+	base := r.advance(map[string]string{"a.txt": "one\ntwo\nthree\nfour\n"})
+	r.fetch(head)
+	res, err := MergeInto(context.Background(), forgekey.ExecRunner, r.ws, r.remote, base, head, AllowFileRemote())
+	if err != nil || res.Merge != base || len(res.Changed) != 0 || len(res.Conflicts) != 0 {
+		t.Errorf("result = %+v, %v", res, err)
+	}
+}

go/buildstep/merge_test.go

@@ -0,0 +1,74 @@
+package buildstep
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// 1674/AC3: no base is refused before anything runs; so is a base or a commit that is not a full sha, a workspace that
+// is not at the commit, and a remote that is not ssh://.
+func TestMergeIntoRefusesWhatIsNotAMerge(t *testing.T) {
+	f := &fakeGit{}
+	for name, c := range map[string]struct{ remote, base, commit string }{
+		"no base":          {"ssh://mesh-forge/o/r.git", "", sha},
+		"a short base":     {"ssh://mesh-forge/o/r.git", "abc123", sha},
+		"a branch as base": {"ssh://mesh-forge/o/r.git", "main", sha},
+		"a short commit":   {"ssh://mesh-forge/o/r.git", sha, "abc"},
+		"an https remote":  {"https://forge.example/o/r.git", sha, sha},
+	} {
+		_, err := MergeInto(context.Background(), f.run, "/w", c.remote, c.base, c.commit)
+		if err == nil {
+			t.Errorf("%s accepted", name)
+		}
+	}
+	if len(f.calls) != 0 {
+		t.Errorf("git ran for a refused merge: %v", f.calls)
+	}
+	g := &fakeGit{rule: func(l string) forgekey.Ran {
+		if strings.Contains(l, "rev-parse HEAD") {
+			return forgekey.Ran{Stdout: strings.Repeat("f", 40) + "\n"}
+		}
+		return forgekey.Ran{}
+	}}
+	_, err := MergeInto(context.Background(), g.run, "/w", "ssh://mesh-forge/o/r.git", strings.Repeat("a", 40), sha)
+	if err == nil || !strings.Contains(err.Error(), "not at the commit") || len(g.calls) != 1 {
+		t.Errorf("a workspace at another commit: %v after %d commands", err, len(g.calls))
+	}
+}
+
+// 1674/AC4: the merge is made with the check merge's identity and flags, hooks off, and fetches with no credential.
+func TestMergeIntoRunsTheCheckMergesCommands(t *testing.T) {
+	base := strings.Repeat("b", 40)
+	f := &fakeGit{rule: func(l string) forgekey.Ran {
+		switch {
+		case strings.HasSuffix(l, "rev-parse HEAD"):
+			return forgekey.Ran{Stdout: sha + "\n"}
+		case strings.Contains(l, "--is-shallow-repository"):
+			return forgekey.Ran{Stdout: "true\n"}
+		}
+		return forgekey.Ran{}
+	}}
+	if _, err := MergeInto(context.Background(), f.run, "/w", "ssh://mesh-forge/o/r.git", base, sha); err != nil {
+		t.Fatal(err)
+	}
+	all := strings.Join(f.calls, "\n")
+	for _, want := range []string{
+		pre + "fetch --no-tags --unshallow origin " + base,
+		pre + "checkout -q --detach " + base,
+		"user.name=mesh merge check", "user.email=merge-check@mesh.invalid", "commit.gpgsign=false", "core.hooksPath=/dev/null",
+		"merge --no-ff --no-edit --no-verify --quiet -m",
+		pre + "diff --name-only --no-renames " + base,
+	} {
+		if !strings.Contains(all, want) {
+			t.Errorf("the commands lack %q:\n%s", want, all)
+		}
+	}
+	for _, c := range f.calls {
+		if strings.Contains(c, "https://") || !strings.Contains(c, "credential.helper= ") {
+			t.Errorf("command %q carries a credential or https", c)
+		}
+	}
+}

go/buildstep/mirror_integration_test.go

@@ -0,0 +1,65 @@
+//go:build integration
+
+package buildstep
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// Issue 890 C1 (AC3): a mirror brought to two commits in turn; a fetch through it checks out each commit, the
+// alternates name the mirror, and no symlink is in the workspace.
+func TestMirrorServesTwoCommitsWithoutSymlinks(t *testing.T) {
+	root := t.TempDir()
+	src := filepath.Join(root, "src.git")
+	work := filepath.Join(root, "work")
+	for _, d := range []string{src, work} {
+		if err := os.MkdirAll(d, 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	gitIn(t, src, "init", "-q", "--bare")
+	gitIn(t, work, "init", "-q")
+	var commits []string
+	for _, c := range []string{"one", "two"} {
+		if err := os.WriteFile(filepath.Join(work, "f"), []byte(c), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		gitIn(t, work, "add", "f")
+		gitIn(t, work, "commit", "-q", "-m", c)
+		commits = append(commits, gitIn(t, work, "rev-parse", "HEAD"))
+		gitIn(t, work, "push", "-q", src, "HEAD:refs/heads/main")
+	}
+	remote := "file://" + src
+	mirror := filepath.Join(root, "mirror.git")
+	for i, commit := range commits {
+		if err := UpdateMirror(context.Background(), forgekey.ExecRunner, mirror, remote, commit, "", AllowFileRemote()); err != nil {
+			t.Fatal(err)
+		}
+		ws := filepath.Join(root, "ws"+string(rune('0'+i)))
+		if err := os.MkdirAll(ws, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		if err := FetchCommit(context.Background(), forgekey.ExecRunner, ws, remote, commit, "", AllowFileRemote(), WithMirror(mirror)); err != nil {
+			t.Fatal(err)
+		}
+		if head := gitIn(t, ws, "rev-parse", "HEAD"); head != commit {
+			t.Errorf("HEAD = %s, want %s", head, commit)
+		}
+		b, _ := os.ReadFile(filepath.Join(ws, ".git", "objects", "info", "alternates"))
+		if !strings.Contains(string(b), filepath.Join(mirror, "objects")) {
+			t.Errorf("alternates %q", b)
+		}
+		_ = filepath.Walk(ws, func(p string, fi os.FileInfo, err error) error {
+			if err == nil && fi.Mode()&os.ModeSymlink != 0 {
+				t.Errorf("symlink %s", p)
+			}
+			return nil
+		})
+	}
+}

go/buildstep/mirror_test.go

@@ -0,0 +1,124 @@
+package buildstep
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// Issue 890 C1 (ADR 0536 §2): a fetch through a bare mirror names the mirror in .git/objects/info/alternates, a
+// plain file, and never links it.
+func TestFetchCommitWithMirrorWritesAlternates(t *testing.T) {
+	mirror := t.TempDir()
+	ws := t.TempDir()
+	f := &fakeGit{}
+	// the fake's init does not create .git; make the objects directory as git init would.
+	if err := os.MkdirAll(filepath.Join(ws, ".git", "objects", "info"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	err := FetchCommit(context.Background(), f.run, ws, "ssh://mesh-forge/novox/mesh-sdk.git", sha, "", WithMirror(mirror))
+	if err != nil {
+		t.Fatal(err)
+	}
+	p := filepath.Join(ws, ".git", "objects", "info", "alternates")
+	b, err := os.ReadFile(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got, want := strings.TrimSpace(string(b)), filepath.Join(mirror, "objects"); got != want {
+		t.Errorf("alternates %q, want %q", got, want)
+	}
+	if fi, err := os.Lstat(p); err != nil || !fi.Mode().IsRegular() {
+		t.Errorf("alternates is not a plain file: %v %v", fi, err)
+	}
+	// the alternates exist before the fetch runs
+	if len(f.calls) < 3 || !strings.Contains(f.calls[2], "fetch") {
+		t.Errorf("calls %v", f.calls)
+	}
+}
+
+func TestWithMirrorRefusesARelativeOrMissingMirror(t *testing.T) {
+	for _, m := range []string{"rel/mirror", filepath.Join(t.TempDir(), "absent")} {
+		f := &fakeGit{}
+		err := FetchCommit(context.Background(), f.run, t.TempDir(), "ssh://mesh-forge/novox/x.git", sha, "", WithMirror(m))
+		if err == nil || len(f.calls) != 0 {
+			t.Errorf("mirror %q: err %v, calls %v", m, err, f.calls)
+		}
+	}
+}
+
+func TestUpdateMirrorInitsBareThenFetches(t *testing.T) {
+	mirror := filepath.Join(t.TempDir(), "mirror.git")
+	f := &fakeGit{}
+	if err := UpdateMirror(context.Background(), f.run, mirror, "ssh://mesh-forge/novox/x.git", sha, ""); err != nil {
+		t.Fatal(err)
+	}
+	pm := "git -c credential.helper= -C " + mirror + " "
+	want := []string{
+		"git -c credential.helper= init -q --bare " + mirror,
+		pm + "remote add origin ssh://mesh-forge/novox/x.git",
+		pm + "fetch --no-tags origin " + sha,
+		pm + "cat-file -e " + sha + "^{commit}",
+	}
+	if strings.Join(f.calls, "\n") != strings.Join(want, "\n") {
+		t.Errorf("commands:\n%s\nwant:\n%s", strings.Join(f.calls, "\n"), strings.Join(want, "\n"))
+	}
+}
+
+func TestUpdateMirrorKeepsAnExistingMirrorAndFallsBackToTheRef(t *testing.T) {
+	mirror := t.TempDir() // exists: no init
+	if err := os.WriteFile(filepath.Join(mirror, "HEAD"), []byte("ref: refs/heads/main\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	f := &fakeGit{}
+	f.rule = func(args string) (r forgekey.Ran) {
+		if strings.HasSuffix(args, "origin "+sha) {
+			r.Status = 1
+			r.Stderr = "not our ref"
+		}
+		return
+	}
+	if err := UpdateMirror(context.Background(), f.run, mirror, "ssh://mesh-forge/novox/x.git", sha, "refs/pull/3/head"); err != nil {
+		t.Fatal(err)
+	}
+	all := strings.Join(f.calls, "\n")
+	if strings.Contains(all, "init") || strings.Contains(all, "remote add") || !strings.Contains(all, "fetch --no-tags origin refs/pull/3/head") {
+		t.Errorf("commands:\n%s", all)
+	}
+}
+
+func TestUpdateMirrorRefusesBeforeRunning(t *testing.T) {
+	f := &fakeGit{}
+	for _, c := range []struct{ remote, commit string }{
+		{"https://x/y.git", sha}, {"ssh://u@h/o/r.git", sha}, {"ssh://h/o/r.git", "abc"},
+	} {
+		if err := UpdateMirror(context.Background(), f.run, t.TempDir(), c.remote, c.commit, ""); err == nil {
+			t.Errorf("%v accepted", c)
+		}
+	}
+	if len(f.calls) != 0 {
+		t.Errorf("ran %v", f.calls)
+	}
+}
+
+// The forge's refusal reaches the reason in git's own words: the mirror of a repository its account cannot read said
+// only "git -C: error:" (2026-10-26), since git writes a bare "error:" line before the forge's message.
+func TestUpdateMirrorSaysTheForgesRefusal(t *testing.T) {
+	f := &fakeGit{}
+	f.rule = func(args string) (r forgekey.Ran) {
+		if strings.Contains(args, "fetch") {
+			r.Status = 128
+			r.Stderr = "error: \nerror: User: 22:nox-builder with Key: 30:mesh:ace.mesh-build-go is not authorized to read o/r.\nerror: \nfatal: Could not read from remote repository.\n"
+		}
+		return
+	}
+	err := UpdateMirror(context.Background(), f.run, filepath.Join(t.TempDir(), "m.git"), "ssh://mesh-forge/o/r.git", sha, "")
+	if err == nil || !strings.Contains(err.Error(), "nox-builder with Key: 30:mesh:ace.mesh-build-go is not authorized to read o/r.") ||
+		!strings.Contains(err.Error(), "Could not read from remote repository") || !strings.HasPrefix(err.Error(), "git fetch: ") {
+		t.Errorf("err = %v", err)
+	}
+}

go/buildstep/narrow.go

@@ -0,0 +1,71 @@
+package buildstep
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+// narrowKept are the files of a module's directory a narrowed build keeps beside its named paths: its manifest and
+// its lock files, each an input of the module's key (ModuleTree's Manifest and Locks). package.json and go.mod are
+// not kept: neither is in the named tree, so a build that needs one names it among its artifact's paths, which puts
+// it in the key (novox/hq ADR 0499 clause 4).
+var narrowKept = append([]string{"module.json"}, lockFiles...)
+
+// Narrow leaves in the fetched tree only what a build of an artifact that names its paths may see (novox/hq ADR 0499
+// clause 4): r.Dir's named paths, its manifest and lock files, and .git; everything else is removed, so a file outside
+// them cannot change what is built without changing its key. A named path absent at the tree is an error naming it,
+// and nothing is removed then. With no paths in r it changes nothing. Both build modules' fetch steps call it.
+func Narrow(tree string, r FetchRequest) error {
+	if len(r.Paths) == 0 {
+		return nil
+	}
+	keep := map[string]bool{".git": true}
+	for _, p := range r.Paths {
+		rel := path.Join(r.Dir, p)
+		if strings.HasPrefix(rel, "../") || rel == ".." || path.IsAbs(p) {
+			return fmt.Errorf("the named path %q leaves the module's directory", p)
+		}
+		if _, err := os.Lstat(filepath.Join(tree, filepath.FromSlash(rel))); err != nil {
+			return fmt.Errorf("the named path %q is not in the fetched tree: %w", p, err)
+		}
+		keep[rel] = true
+	}
+	for _, f := range narrowKept {
+		keep[path.Join(r.Dir, f)] = true
+	}
+	return prune(tree, "", keep)
+}
+
+// prune removes from dir (rel within the tree) every entry that is neither kept nor on the way to one.
+func prune(root, rel string, keep map[string]bool) error {
+	entries, err := os.ReadDir(filepath.Join(root, filepath.FromSlash(rel)))
+	if err != nil {
+		return err
+	}
+	for _, e := range entries {
+		p := path.Join(rel, e.Name())
+		if keep[p] {
+			continue
+		}
+		ancestor := false
+		for k := range keep {
+			if strings.HasPrefix(k, p+"/") {
+				ancestor = true
+				break
+			}
+		}
+		if ancestor && e.IsDir() {
+			if err := prune(root, p, keep); err != nil {
+				return err
+			}
+			continue
+		}
+		if err := os.RemoveAll(filepath.Join(root, filepath.FromSlash(p))); err != nil {
+			return err
+		}
+	}
+	return nil
+}

go/buildstep/narrow_test.go

@@ -0,0 +1,82 @@
+package buildstep
+
+import (
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"testing"
+)
+
+func filesUnder(t *testing.T, root string) []string {
+	t.Helper()
+	var out []string
+	_ = filepath.Walk(root, func(p string, info os.FileInfo, err error) error {
+		if err == nil && !info.IsDir() {
+			rel, _ := filepath.Rel(root, p)
+			out = append(out, filepath.ToSlash(rel))
+		}
+		return nil
+	})
+	sort.Strings(out)
+	return out
+}
+
+// A build of an artifact that names its paths sees only those paths, its manifest and its lock files (novox/hq ADR 0499
+// clause 4): Narrow removes everything else of the fetched tree but .git, package.json and go.mod among it, since
+// neither is in the named tree nor among the lock files; with no paths it changes nothing.
+func TestNarrowLeavesOnlyTheNamedPathsTheManifestAndTheLocks(t *testing.T) {
+	tree := t.TempDir()
+	for _, f := range []string{".git/HEAD", "module.json", "package.json", "package-lock.json", "go.sum", "src/index.ts",
+		"src/deep/a.ts", "test/a.test.ts", "tsconfig.json", "go/delivery/x.go", "README.md", "other/module.json"} {
+		writeTreeFile(t, tree, f, "x")
+	}
+	if err := Narrow(tree, FetchRequest{}); err != nil {
+		t.Fatal(err)
+	}
+	if got := len(filesUnder(t, tree)); got != 12 {
+		t.Fatalf("a request without paths changed the tree: %d files", got)
+	}
+	if err := Narrow(tree, FetchRequest{Dir: ".", Paths: []string{"src", "test", "tsconfig.json"}}); err != nil {
+		t.Fatal(err)
+	}
+	want := ".git/HEAD,go.sum,module.json,package-lock.json,src/deep/a.ts,src/index.ts,test/a.test.ts,tsconfig.json"
+	if got := strings.Join(filesUnder(t, tree), ","); got != want {
+		t.Fatalf("the narrowed tree holds %s\nwant %s", got, want)
+	}
+}
+
+func TestNarrowKeepsAModuleDirectorysPathsAndFailsOnAnAbsentOne(t *testing.T) {
+	tree := t.TempDir()
+	for _, f := range []string{".git/config", "modules/a/module.json", "modules/a/go.mod", "modules/a/src/x.ts",
+		"modules/a/notes.md", "modules/b/module.json", "root.txt"} {
+		writeTreeFile(t, tree, f, "x")
+	}
+	err := Narrow(tree, FetchRequest{Dir: "modules/a", Paths: []string{"src", "gone"}})
+	if err == nil || !strings.Contains(err.Error(), `"gone"`) {
+		t.Fatalf("an absent named path gave %v", err)
+	}
+	if len(filesUnder(t, tree)) != 7 {
+		t.Fatal("a refused narrowing removed files")
+	}
+	if err := Narrow(tree, FetchRequest{Dir: "modules/a", Paths: []string{"src"}}); err != nil {
+		t.Fatal(err)
+	}
+	if got := strings.Join(filesUnder(t, tree), ","); got != ".git/config,modules/a/module.json,modules/a/src/x.ts" {
+		t.Fatalf("the narrowed tree holds %s", got)
+	}
+}
+
+// A build that needs package.json or go.mod names it among its paths, and so keys on it (ADR 0499 clause 4).
+func TestNarrowKeepsAManifestOfTheLanguageOnlyWhenNamed(t *testing.T) {
+	tree := t.TempDir()
+	for _, f := range []string{"module.json", "package.json", "go.mod", "src/a.ts"} {
+		writeTreeFile(t, tree, f, "x")
+	}
+	if err := Narrow(tree, FetchRequest{Dir: ".", Paths: []string{"src", "package.json"}}); err != nil {
+		t.Fatal(err)
+	}
+	if got := strings.Join(filesUnder(t, tree), ","); got != "module.json,package.json,src/a.ts" {
+		t.Fatalf("the narrowed tree holds %s", got)
+	}
+}

go/buildstep/phase.go

@@ -0,0 +1,67 @@
+package buildstep
+
+import (
+	"context"
+	"strings"
+	"sync"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **A running ask says its phases** (issue 1890, 2026-10-26 19:09: a mesh-catalog try's step on the workstation ran 30 minutes
+// and its module's journal held no line naming its ask, so nobody could tell whether it fetched, linted or tested). The
+// puller hands every ask's run a phase reporter in its context; RunAsk and a module's own step bodies call Phase as they
+// move (fetch and merge, a level's digest, lint, a level's tests), and each phase is logged with the ask's id and its
+// time since the start, and written to the ask's running step key (delivery.Step.Phase), so its asker and the delivery
+// view read where it stands from the bus.
+
+type phaseKey struct{}
+
+// Phase says that the ask whose run ctx belongs to entered phase; nothing outside an ask's run (a tool called by hand).
+func Phase(ctx context.Context, phase string) {
+	if r, ok := ctx.Value(phaseKey{}).(*phases); ok && r != nil {
+		r.enter(strings.TrimSpace(phase))
+	}
+}
+
+// phases is one running ask's reporter: it writes the step key again with each new phase until the step ends.
+type phases struct {
+	mu     sync.Mutex
+	put    Put
+	key    string
+	step   delivery.Step
+	ended  bool
+	logf   func(format string, args ...any)
+	prefix string
+}
+
+func (r *phases) enter(phase string) {
+	if phase == "" {
+		return
+	}
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.ended || phase == r.step.Phase {
+		return
+	}
+	at := now().UTC()
+	r.step.Phase, r.step.PhaseAt = phase, at
+	if r.logf != nil {
+		r.logf("%s: %s, %s after its start", r.prefix, phase, at.Sub(r.step.Started).Round(time.Second))
+	}
+	if r.put == nil {
+		return
+	}
+	if err := write(r.put, r.key, r.step); err != nil && r.logf != nil {
+		r.logf("%s: the phase %s could not be written to %s: %v", r.prefix, phase, r.key, err)
+	}
+}
+
+// end stops the writes (the step's end is written after it) and answers the step with its last phase, for the end.
+func (r *phases) end() delivery.Step {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.ended = true
+	return r.step
+}

go/buildstep/programs.go

@@ -0,0 +1,115 @@
+package buildstep
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Program is a changed file whose first bytes are an executable binary: a compiled program, which is build output and not
+// source (novox/hq issue 1577: `go build` in a module's folder writes one beside go.mod, and `git add -A` takes it).
+type Program struct {
+	Path string `json:"path"`
+	Kind string `json:"kind"` // ELF, Mach-O or PE
+	// Commit is set for a program a commit of the branch added and a later one removed (or replaced): the merge's tree is clean,
+	// but the merge commit carries the blob into the trunk's history for good. Empty for a program the merge's tree holds.
+	Commit string `json:"commit,omitempty"`
+}
+
+// ExecutableKind says what executable format the first bytes of a file are, or "" when they are none. A PE needs its header
+// ("PE\0\0" at the offset in bytes 0x3c) so a text starting with "MZ" is not one; a fat Mach-O (0xCAFEBABE) is told from a
+// Java class by its architecture count (bytes 4 to 7, fewer than 0x20; a class has its version there).
+func ExecutableKind(head []byte) string {
+	switch {
+	case bytes.HasPrefix(head, []byte("\x7fELF")):
+		return "ELF"
+	case bytes.HasPrefix(head, []byte("MZ")):
+		if len(head) >= 0x40 {
+			off := int(head[0x3c]) | int(head[0x3d])<<8 | int(head[0x3e])<<16 | int(head[0x3f])<<24
+			if off >= 0 && off+4 <= len(head) && bytes.Equal(head[off:off+4], []byte("PE\x00\x00")) {
+				return "PE"
+			}
+		}
+	case bytes.HasPrefix(head, []byte{0xcf, 0xfa, 0xed, 0xfe}), bytes.HasPrefix(head, []byte{0xce, 0xfa, 0xed, 0xfe}),
+		bytes.HasPrefix(head, []byte{0xfe, 0xed, 0xfa, 0xcf}), bytes.HasPrefix(head, []byte{0xfe, 0xed, 0xfa, 0xce}),
+		bytes.HasPrefix(head, []byte{0xca, 0xfe, 0xba, 0xbe}) && len(head) >= 8 && head[4] == 0 && head[5] == 0 && head[6] == 0 && head[7] < 0x20:
+		return "Mach-O"
+	}
+	return ""
+}
+
+// programHeadSize is how many bytes of a file are read to tell its format: enough for a PE header at its usual offsets.
+const programHeadSize = 0x100
+
+// historyPrograms names the compiled programs that a commit of base..head added or modified and the merge's tree no longer
+// holds at that path (those it holds are in final already): each with the commit that added it. git is the merge's git runner.
+func historyPrograms(git func(args ...string) (string, error), base, head string, final []Program) ([]Program, error) {
+	revs, err := git("rev-list", "--no-merges", "--reverse", base+".."+head)
+	if err != nil {
+		return nil, err
+	}
+	held := map[string]bool{}
+	for _, p := range final {
+		held[p.Path] = true
+	}
+	out, seen := []Program{}, map[string]bool{}
+	for _, c := range strings.Fields(revs) {
+		raw, err := git("diff-tree", "-r", "-z", "--no-commit-id", "--no-renames", "--root", "--diff-filter=AM", c)
+		if err != nil {
+			return nil, err
+		}
+		f := strings.Split(raw, "\x00")
+		for i := 0; i+1 < len(f); i += 2 {
+			meta := strings.Fields(strings.TrimPrefix(f[i], ":"))
+			if len(meta) < 4 || (meta[1] != "100644" && meta[1] != "100755") || held[f[i+1]] || seen[meta[3]] {
+				continue
+			}
+			seen[meta[3]] = true
+			blob, err := git("cat-file", "blob", meta[3])
+			if err != nil {
+				return nil, err
+			}
+			head := []byte(blob)
+			if len(head) > programHeadSize {
+				head = head[:programHeadSize]
+			}
+			if k := ExecutableKind(head); k != "" {
+				out = append(out, Program{Path: f[i+1], Kind: k, Commit: c})
+			}
+		}
+	}
+	return out, nil
+}
+
+// programsIn reads the output of `git diff --raw -z --no-renames --diff-filter=AM` (":<old mode> <new mode> <old sha> <new
+// sha> <status>\0<path>\0" per file) and names each added or modified regular file of the tree dir that is a compiled
+// program, from its first bytes read locally. A symlink (mode 120000) and a submodule (160000) are not read. It never
+// answers nil, so a caller can tell no programs from none reported.
+func programsIn(dir, raw string) []Program {
+	out := []Program{}
+	f := strings.Split(raw, "\x00")
+	for i := 0; i+1 < len(f); i += 2 {
+		meta := strings.Fields(strings.TrimPrefix(f[i], ":"))
+		if len(meta) < 2 || (meta[1] != "100644" && meta[1] != "100755") {
+			continue
+		}
+		p := f[i+1]
+		full := filepath.Join(dir, filepath.FromSlash(p))
+		if st, err := os.Lstat(full); err != nil || !st.Mode().IsRegular() {
+			continue
+		}
+		fh, err := os.Open(full)
+		if err != nil {
+			continue
+		}
+		head := make([]byte, programHeadSize)
+		n, _ := io.ReadFull(fh, head)
+		fh.Close()
+		if k := ExecutableKind(head[:n]); k != "" {
+			out = append(out, Program{Path: p, Kind: k})
+		}
+	}
+	return out
+}

go/buildstep/programs_test.go

@@ -0,0 +1,72 @@
+package buildstep
+
+import (
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+)
+
+func pe(offset int, magic string) []byte {
+	b := make([]byte, 0x100)
+	copy(b, "MZ")
+	b[0x3c] = byte(offset)
+	copy(b[offset:], magic)
+	return b
+}
+
+func TestExecutableKindTellsProgramsFromText(t *testing.T) { // issue 1577
+	for _, c := range []struct {
+		name string
+		head []byte
+		want string
+	}{
+		{"elf", []byte("\x7fELF\x02\x01\x01"), "ELF"},
+		{"mach-o 64", []byte{0xcf, 0xfa, 0xed, 0xfe, 7, 0, 0, 1}, "Mach-O"},
+		{"mach-o 32 big", []byte{0xfe, 0xed, 0xfa, 0xce, 0, 0, 0, 7}, "Mach-O"},
+		{"fat mach-o", []byte{0xca, 0xfe, 0xba, 0xbe, 0, 0, 0, 2}, "Mach-O"},
+		{"java class", []byte{0xca, 0xfe, 0xba, 0xbe, 0, 0, 0, 0x34}, ""},
+		{"pe", pe(0x80, "PE\x00\x00"), "PE"},
+		{"mz text", []byte("MZ is a text file starting with two letters"), ""},
+		{"mz without a pe header", pe(0x80, "XX\x00\x00"), ""},
+		{"text", []byte("package main"), ""},
+		{"empty", nil, ""},
+	} {
+		if got := ExecutableKind(c.head); got != c.want {
+			t.Errorf("%s: kind = %q, want %q", c.name, got, c.want)
+		}
+	}
+}
+
+func TestProgramsInNamesTheAddedAndModifiedRegularFilesThatArePrograms(t *testing.T) { // issue 1577
+	dir := t.TempDir()
+	write := func(name string, b []byte) {
+		if err := os.MkdirAll(filepath.Dir(filepath.Join(dir, name)), 0o755); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(filepath.Join(dir, name), b, 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	write("m/prog", []byte("\x7fELF\x02\x01"))
+	write("m/notes", []byte("plain text"))
+	write("m/mac", []byte{0xcf, 0xfa, 0xed, 0xfe, 7, 0, 0, 1})
+	if err := os.Symlink("prog", filepath.Join(dir, "m/link")); err != nil {
+		t.Fatal(err)
+	}
+	line := func(mode, path string) string { return ":000000 " + mode + " 0000 1111 A\x00" + path + "\x00" }
+	for _, c := range []struct {
+		name, raw string
+		want      []Program
+	}{
+		{"none", "", []Program{}},
+		{"a program and a text", line("100755", "m/prog") + line("100644", "m/notes"), []Program{{"m/prog", "ELF", ""}}},
+		{"two programs", line("100644", "m/prog") + line("100755", "m/mac"), []Program{{"m/prog", "ELF", ""}, {"m/mac", "Mach-O", ""}}},
+		{"a symlink and a submodule are not read", line("120000", "m/link") + line("160000", "m/sub"), []Program{}},
+		{"a path the tree lacks", line("100644", "m/gone"), []Program{}},
+	} {
+		if got := programsIn(dir, c.raw); !reflect.DeepEqual(got, c.want) {
+			t.Errorf("%s: programs = %v, want %v", c.name, got, c.want)
+		}
+	}
+}

go/buildstep/pull.go

@@ -0,0 +1,771 @@
+package buildstep
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **The pull loop the build modules share** (novox/hq ADR 0525 §4-§6, ADR 0536 §4; issue 1887). A build module on a node
+// whose build capacity is above zero pulls the asks of its language's seat: from the delivery worker first, then check,
+// then recheck, holding at most its capacity at once. Each ask runs as a step under the ask's own id, so its end is the
+// key <node>.<ask id> in the module's steps state, which the asker watches; the ask is acknowledged when that end is
+// written, kept alive while it runs by an in-progress signal, and redelivered by the stream to another node if this one
+// stops. No part keeps a timer for an ask: the pull's own wait and the stream's acknowledgement wait are the bus's.
+
+// Pulled is one ask a source handed over, with what decides its fate on the bus.
+type Pulled struct {
+	// Kind is the worker it came from, filled by the puller.
+	Kind string
+	Data []byte
+	// Delivered is how many times the bus has handed it over, this time included.
+	Delivered uint64
+	// Ack ends it: it is never delivered again. InProgress tells the bus it is still being worked, restarting its
+	// acknowledgement wait. Nak hands it back to be delivered again at once (to this node or another). Term drops it.
+	Ack, InProgress, Nak, Term func() error
+}
+
+// AskSource is where a puller takes asks from: the seat's workers on the bus (JetStreamAsks) or a test double
+// (FakeAsks).
+type AskSource interface {
+	// Next takes one ask of kind: with wait 0 only one already waiting, else waiting for one at most wait. It answers
+	// nil and no error when none came.
+	Next(ctx context.Context, kind string, wait time.Duration) (*Pulled, error)
+}
+
+// Defaults of a Puller.
+var (
+	// DefaultPullWait is how long one pull of the delivery worker waits for an ask while every worker is empty: the
+	// pull's own wait (as process.Consume's), after which the check and recheck workers are looked at again.
+	DefaultPullWait = 5 * time.Second
+	// DefaultHeartbeat is how often a running ask tells the bus it is still being worked; under the seat worker's
+	// acknowledgement wait of 60 s (mesh-controller internal/broker HolderConsumerFor).
+	DefaultHeartbeat = 20 * time.Second
+)
+
+// Puller pulls a build seat's asks and runs them.
+type Puller struct {
+	Source   AskSource
+	Language string // the seat's language: delivery.AskGo, AskNode or AskImage
+	Node     string // the node this holder runs on, the first part of its step keys
+	Put      Put    // writes the module's steps state
+	// Capacity is how many asks the node runs at once; read before every pull, so a change takes effect at the next
+	// one. 0 pulls nothing.
+	Capacity func() int
+	// Run runs one ask's job; a *Refusal ends its step refused. Its result is the step's result.
+	Run func(ctx context.Context, ask delivery.StepAsk) (any, error)
+	// PullWait and Heartbeat default to DefaultPullWait and DefaultHeartbeat.
+	PullWait  time.Duration
+	Heartbeat time.Duration
+	Logf      func(format string, args ...any)
+	// Load reads one key of the state the node's pause is kept in (nil and no error when it is absent). When set, Pull
+	// reads the node's pause key (delivery.PauseKey) before it pulls, and Pause and Resume write it with PausePut, so a
+	// pause outlives a restart.
+	Load func(key string) ([]byte, error)
+	// PausePut writes the node's pause key: the module's pauses state (delivery.PausesState), which has no age, so a
+	// pause never ends by itself while the steps state drops its old keys. Put when nil.
+	PausePut Put
+	// WatchConfig, when set, follows the module's config value `capacity` (CapacitySetting) as mesh-config resolves it
+	// for this node, and wakes the puller on each change (watchCapacity): WatchConfigServed in a module, a test's own
+	// double. Until it hands a value the puller judges by Capacity.
+	WatchConfig func(key string, handle func(stdio.ProvisionChange) error) error
+	// CoresPerStep is what one ask of this module needs, read at every judgement (NodeCoresPerStep); with it the capacity
+	// judged by is bounded by the node's build slice: min(the configured capacity, floor(the quota's cores / CoresPerStep))
+	// (EffectiveCapacity). Nil bounds nothing by the CPU. Quota reads the quota (Quota when nil; a test's own).
+	CoresPerStep func() float64
+	Quota        func() (percent int, from string)
+	// BuildHours is the node's build window, read at every judgement (NodeBuildHours); with WatchConfig set the value
+	// mesh-config resolves for `build-hours` takes its place once handed. Outside the window the capacity judged by is 0:
+	// steps running finish, no new one is taken; the puller wakes at the window's next edge. Nil builds at any hour.
+	BuildHours func() (*BuildWindow, string)
+	// Eligible says why this node cannot run the seat's asks at all now, and "" when it can: what the module proves of
+	// its machine and finds missing (mesh-build-image: /dev/net/tun cannot be opened, so buildah's network for a RUN line
+	// cannot be made; 2026-10-28 on ace). Read at every judgement, so it is cheap (a module answers its last look).
+	// While it says a reason the capacity judged by is 0, said with the reason: steps running finish, no new one is
+	// taken, and the asks go to a node that can run them instead of failing here. The module calls Wake when its answer
+	// changes. Nil is always eligible.
+	Eligible func() string
+	// Has says whether this node has a need an ask names (delivery.AskNeeds, issue 890). An ask needing what it lacks is
+	// declined: its step ends refused as declined (delivery.StepDeclined), the message is dropped for its asker to put
+	// again, and the worker it came from is not looked at again until the next pull's wait, so a node lacking the need
+	// does not take the asker's next copy at once. Nil has nothing.
+	Has func(need string) bool
+	// SettingsFile is the module's settings file. With it set the puller wakes whenever the file is written (a file event,
+	// WatchSettings), and reads Capacity from it itself, keeping why it cannot be read (CapacityNote); a parked puller at
+	// capacity 0 therefore wakes when the node-engine refills the file, and a failed config follow is tried again then.
+	SettingsFile string
+	// watching, when set, is called each time the settings file's watch is (re)armed: a test waits on it, not on a sleep.
+	watching func()
+
+	mu      sync.Mutex
+	inHand  int
+	running map[string]RunningAsk
+	paused  bool
+	wake    chan struct{}
+	once    sync.Once
+	// watched is the capacity the config watch handed last, used in place of Capacity once hasWatched.
+	watched    int
+	hasWatched bool
+	// capFollow and hoursFollow are the state of the two config follows: followed once WatchConfig took them, trying
+	// while a start is in flight; followFault is the last failure said, so each failure is said once.
+	capFollowed, capTrying, hoursFollowed, hoursTrying bool
+	followFault                                        string
+	// fileFault is why the settings file's capacity cannot be read, "" when it can.
+	fileFault string
+	// capWhy is why the config watch's last value could not be read, "" when it could.
+	capWhy string
+	// hours is the build window the config watch handed last, and hoursFault why its value cannot be read; used in place
+	// of BuildHours once hasHours.
+	hours      *BuildWindow
+	hoursFault string
+	hasHours   bool
+	// judged is the capacity said last (log and capacity.<node>), so a change is said once.
+	judged     delivery.Capacity
+	hasJudged  bool
+	capWritten bool
+	capFault   string
+	// declined are the kinds whose worker handed an ask this node declined, left out of the pulls without a wait until
+	// the next pull's wait ends.
+	declined map[string]bool
+}
+
+func (p *Puller) init() {
+	p.once.Do(func() { p.wake = make(chan struct{}, 1) })
+}
+
+func (p *Puller) logf(format string, args ...any) {
+	if p.Logf != nil {
+		p.Logf(format, args...)
+	}
+}
+
+// Wake makes a waiting puller look again: after a capacity change, a resume, or a step's end.
+func (p *Puller) Wake() {
+	p.init()
+	select {
+	case p.wake <- struct{}{}:
+	default:
+	}
+}
+
+// Pause stops the puller taking asks; the asks it holds run to their end. by names who paused it. With Load set the
+// pause is written on the node's pause key first, and an error there leaves the puller as it was.
+func (p *Puller) Pause(by string) error { return p.setPaused(true, by) }
+
+// Resume lets the puller take asks again, written as Pause's is.
+func (p *Puller) Resume(by string) error { return p.setPaused(false, by) }
+
+func (p *Puller) setPaused(paused bool, by string) error {
+	if p.Load != nil {
+		key, err := delivery.PauseKey(p.Node)
+		if err != nil {
+			return err
+		}
+		raw, err := delivery.EncodePause(delivery.Pause{Paused: paused, By: by, At: now()})
+		if err != nil {
+			return err
+		}
+		put := p.PausePut
+		if put == nil {
+			put = p.Put
+		}
+		if _, err := put(key, json.RawMessage(raw)); err != nil {
+			return fmt.Errorf("buildstep: writing the pause of %s: %w", p.Node, err)
+		}
+	}
+	p.mu.Lock()
+	p.paused = paused
+	p.mu.Unlock()
+	p.Wake()
+	return nil
+}
+
+// restore reads the node's pause key, when Load is set.
+func (p *Puller) restore() error {
+	if p.Load == nil {
+		return nil
+	}
+	key, err := delivery.PauseKey(p.Node)
+	if err != nil {
+		return err
+	}
+	raw, err := p.Load(key)
+	if err != nil {
+		return fmt.Errorf("buildstep: reading the pause of %s: %w", p.Node, err)
+	}
+	if raw == nil {
+		return nil
+	}
+	v, err := delivery.DecodePause(raw)
+	if err != nil {
+		return fmt.Errorf("buildstep: the pause of %s: %w", p.Node, err)
+	}
+	p.mu.Lock()
+	p.paused = v.Paused
+	p.mu.Unlock()
+	return nil
+}
+
+// Paused says whether the puller takes no asks.
+func (p *Puller) Paused() bool {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	return p.paused
+}
+
+// InHand is how many asks run now.
+func (p *Puller) InHand() int {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	return p.inHand
+}
+
+// RunningAsk is an ask a puller runs now, as its seat's current verb says it.
+type RunningAsk struct {
+	ID      string    `json:"id"`
+	Kind    string    `json:"kind"`
+	Module  string    `json:"module,omitempty"`
+	Started time.Time `json:"started"`
+}
+
+// Running are the asks the puller runs now, oldest first.
+func (p *Puller) Running() []RunningAsk {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	out := make([]RunningAsk, 0, len(p.running))
+	for _, r := range p.running {
+		out = append(out, r)
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Started.Before(out[j].Started) })
+	return out
+}
+
+// room says whether the puller may take one more ask now.
+func (p *Puller) room() bool {
+	ok, _, _ := p.roomNow()
+	return ok
+}
+
+// roomNow is room, with the capacity and the asks in hand it was judged on.
+func (p *Puller) roomNow() (ok bool, capacity, inHand int) {
+	capacity = p.CapacityDetail().Effective
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	return !p.paused && p.inHand < capacity, capacity, p.inHand
+}
+
+// CapacityNote says when the puller takes nothing for want of a capacity: why, and whether it is a fault (a setting that
+// cannot be read or is refused, so a person must look) and not a choice (a capacity set to 0). "" when it pulls.
+func (p *Puller) CapacityNote() (why string, fault bool) {
+	c := p.CapacityDetail()
+	if c.Effective > 0 {
+		return "", false
+	}
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if p.fileFault != "" && !p.hasWatched {
+		return "the " + p.Language + " build capacity of " + p.Node + " is 0 because it cannot be read: " + p.fileFault, true
+	}
+	return "the " + p.Language + " build capacity of " + p.Node + " is " + c.Why, p.hasWatched && p.capWhy != ""
+}
+
+// CapacityNow is the capacity the puller judges by (CapacityDetail's Effective).
+func (p *Puller) CapacityNow() int {
+	return p.CapacityDetail().Effective
+}
+
+// CapacityDetail is the capacity the puller judges by now and why: the configured one (the config watch's last value,
+// else Capacity), bounded by the node's build slice when CoresPerStep is set (EffectiveCapacity), its quota read now. A
+// change from what it said last is logged and written to `capacity.<node>` of the pauses state (PausePut), so the
+// delivery view says it too.
+func (p *Puller) CapacityDetail() delivery.Capacity {
+	p.mu.Lock()
+	watched, has := p.watched, p.hasWatched
+	p.mu.Unlock()
+	configured, from := 0, "the settings file"
+	switch {
+	case has:
+		configured, from = watched, "mesh-config, as the config watch handed it"
+	case p.SettingsFile != "":
+		n, err := ReadCapacity(p.SettingsFile)
+		configured = n
+		p.mu.Lock()
+		p.fileFault = ""
+		if err != nil {
+			p.fileFault = err.Error()
+		}
+		p.mu.Unlock()
+	case p.Capacity != nil:
+		configured = p.Capacity()
+	}
+	var c delivery.Capacity
+	if p.CoresPerStep == nil {
+		c = delivery.Capacity{Configured: configured, Effective: configured, QuotaFrom: "not judged: the module names no cores a step needs",
+			Why: fmt.Sprintf("its configured capacity %d", configured)}
+	} else {
+		quota := p.Quota
+		if quota == nil {
+			quota = Quota
+		}
+		percent, qfrom := quota()
+		c = EffectiveCapacity(configured, percent, qfrom, p.CoresPerStep())
+	}
+	c.ConfiguredFrom = from
+	w, fault := p.window()
+	if fault != "" {
+		c.BuildHoursFault = fault
+		c.Why = fmt.Sprintf("%s; at any hour, because its build hours cannot be read: %s", c.Why, fault)
+	}
+	if w != nil {
+		at := now()
+		zone, _ := at.Zone()
+		c.BuildHours = w.String() + " " + zone
+		if !w.Open(at) && c.Effective > 0 {
+			c.OutsideHours = true
+			c.Why = fmt.Sprintf("0, outside its build hours %s until %s (otherwise %s)", c.BuildHours, w.NextEdge(at).Format("15:04"), c.Why)
+			c.Effective = 0
+		} else if c.Effective > 0 {
+			c.Why = fmt.Sprintf("%s; within its build hours %s until %s", c.Why, c.BuildHours, w.NextEdge(at).Format("15:04"))
+		}
+	}
+	if p.Eligible != nil {
+		if why := p.Eligible(); why != "" {
+			c.Ineligible = why
+			c.Why = fmt.Sprintf("0, not eligible: %s (otherwise %s)", why, c.Why)
+			c.Effective = 0
+		}
+	}
+	p.sayCapacity(c)
+	return c
+}
+
+// window is the node's build window now (the config watch's last value, else BuildHours, else none), and why its value
+// cannot be read when it cannot.
+func (p *Puller) window() (*BuildWindow, string) {
+	p.mu.Lock()
+	w, fault, has := p.hours, p.hoursFault, p.hasHours
+	p.mu.Unlock()
+	if has {
+		return w, fault
+	}
+	if p.BuildHours != nil {
+		return p.BuildHours()
+	}
+	return nil, ""
+}
+
+// untilEdge is how long until the build window's next edge, and false when the node has no window.
+func (p *Puller) untilEdge() (time.Duration, bool) {
+	w, _ := p.window()
+	if w == nil {
+		return 0, false
+	}
+	at := now()
+	return w.NextEdge(at).Sub(at), true
+}
+
+// sayCapacity logs c when it differs from what was said last, and writes it to the node's capacity key until a write
+// lands (a failed write is tried again at the next judgement, its error said once).
+func (p *Puller) sayCapacity(c delivery.Capacity) {
+	p.mu.Lock()
+	same := p.hasJudged && p.judged.Effective == c.Effective && p.judged.Configured == c.Configured && p.judged.ByCPU == c.ByCPU &&
+		p.judged.CoresPerStep == c.CoresPerStep && p.judged.QuotaCores == c.QuotaCores && p.judged.OutsideHours == c.OutsideHours &&
+		p.judged.BuildHours == c.BuildHours && p.judged.BuildHoursFault == c.BuildHoursFault &&
+		p.judged.Ineligible == c.Ineligible
+	if !same {
+		p.judged, p.hasJudged, p.capWritten = c, true, false
+	}
+	write := !p.capWritten && p.PausePut != nil
+	p.mu.Unlock()
+	if !same {
+		p.logf("the %s build capacity of %s is %s (configured from %s)", p.Language, p.Node, c.Why, c.ConfiguredFrom)
+	}
+	if !write {
+		return
+	}
+	key, err := delivery.CapacityKey(p.Node)
+	if err != nil {
+		return
+	}
+	c.At = now()
+	raw, err := delivery.EncodeCapacity(c)
+	if err == nil {
+		_, err = p.PausePut(key, json.RawMessage(raw))
+	}
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if err == nil {
+		p.capWritten, p.capFault = true, ""
+		return
+	}
+	if err.Error() != p.capFault {
+		p.capFault = err.Error()
+		p.logf("the %s build capacity of %s could not be written to %s (tried again at the next judgement): %v", p.Language, p.Node, key, err)
+	}
+}
+
+// Pull takes and runs asks until ctx ends. An ask still running then is neither ended nor acknowledged: the stream
+// delivers it again, to another node or to this one restarted.
+func (p *Puller) Pull(ctx context.Context) error {
+	p.init()
+	if p.Source == nil || p.Put == nil || p.Run == nil {
+		return errors.New("buildstep: a puller needs its source, its steps' put and its run")
+	}
+	if err := p.restore(); err != nil {
+		// An unreadable pause degrades to not paused, said once: a puller that stops silently is the worse failure, and a
+		// node kept from building is held by its capacity (0), not by a pause.
+		p.logf("the pause of %s cannot be read: %v; pulling as not paused", p.Node, err)
+	}
+	p.follow() // WatchConfigServed waits for Serve, which a module starts after its pull
+	go p.watchSettings(ctx)
+	wait := p.PullWait
+	if wait <= 0 {
+		wait = DefaultPullWait
+	}
+	for {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+		if ok, capacity, inHand := p.roomNow(); !ok {
+			// Parked until something wakes it: a capacity change (the config watch), a resume, or a step's end. Every
+			// park logs once, so a puller that sits idle says why (issue 1887).
+			p.logf("the %s puller on %s parks: %d of capacity %d in hand, paused %v", p.Language, p.Node, inHand, capacity, p.Paused())
+			var edge <-chan time.Time // the build window's next edge, when the node has one: one timer, not a poll
+			stop := func() bool { return false }
+			if d, ok := p.untilEdge(); ok {
+				t := time.NewTimer(d + time.Second)
+				edge, stop = t.C, t.Stop
+			}
+			select {
+			case <-ctx.Done():
+				stop()
+				return ctx.Err()
+			case <-p.wake:
+			case <-edge:
+			}
+			stop()
+			p.follow() // a follow that failed is tried again at the next event
+			_, capacity, inHand = p.roomNow()
+			p.logf("the %s puller on %s wakes: %d of capacity %d in hand, paused %v", p.Language, p.Node, inHand, capacity, p.Paused())
+			continue
+		}
+		pullWait := wait
+		if d, ok := p.untilEdge(); ok && d < pullWait {
+			pullWait = d // a pull does not wait past the window's close
+		}
+		msg, err := p.next(ctx, pullWait)
+		if err != nil {
+			if ctx.Err() != nil {
+				return ctx.Err()
+			}
+			p.logf("the %s asks cannot be pulled: %v", p.Language, err)
+			select { // the pull's own wait before the next try, as an empty pull's
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-p.wake:
+				p.follow()
+			case <-time.After(wait):
+			}
+			continue
+		}
+		if msg == nil {
+			continue
+		}
+		p.take(ctx, msg)
+	}
+}
+
+// next is one ask from the workers in their order: one already waiting on delivery, check or recheck, and when none
+// waits, a pull of the delivery worker that waits for one.
+//
+// A kind whose worker handed an ask this node declined is left out until that wait ended (issue 890): the pull's own
+// wait, no timer of its own.
+func (p *Puller) next(ctx context.Context, wait time.Duration) (*Pulled, error) {
+	p.mu.Lock()
+	declined := p.declined
+	p.mu.Unlock()
+	for _, kind := range delivery.AskKinds {
+		if declined[kind] {
+			continue
+		}
+		msg, err := p.Source.Next(ctx, kind, 0)
+		if err != nil || msg != nil {
+			return withKind(msg, kind), err
+		}
+	}
+	msg, err := p.Source.Next(ctx, delivery.AskDelivery, wait)
+	p.mu.Lock()
+	p.declined = nil
+	p.mu.Unlock()
+	return withKind(msg, delivery.AskDelivery), err
+}
+
+// decline ends the step of an ask this node lacks a need of, refused as declined with what it lacks, and drops the
+// message: the asker puts the ask again under a new id (issue 890). A message whose decline cannot be written is handed
+// back, as one whose start cannot be.
+func (p *Puller) decline(msg *Pulled, ask delivery.StepAsk, lacks []string) {
+	step, key, err := begin(p.Put, p.Node, ask.Kind+" ask", ask.ID, AskWhat(ask))
+	if err == nil {
+		why := Refuse("the ask %s needs %s, and %s lacks %s: it is left to a node that has it", ask.ID,
+			strings.Join(ask.Needs, ", "), p.Node, strings.Join(lacks, ", "))
+		step.Ended = now().UTC()
+		step.State, step.Reason = delivery.StepRefused, why.Error()
+		step.Result, err = json.Marshal(delivery.StepDeclined{Declined: true, Needs: ask.Needs, Lacks: lacks})
+		if err == nil {
+			err = writeEnd(p.Put, key, step)
+		}
+	}
+	if err != nil {
+		p.logf("the ask %s cannot be declined on %s, so it is given back: %v", ask.ID, p.Node, err)
+		_ = msg.Nak()
+		return
+	}
+	p.logf("the ask %s is declined on %s: it needs %s, and this node lacks %s", ask.ID, p.Node, strings.Join(ask.Needs, ", "), strings.Join(lacks, ", "))
+	_ = msg.Term()
+	p.mu.Lock()
+	if p.declined == nil {
+		p.declined = map[string]bool{}
+	}
+	p.declined[msg.Kind] = true
+	p.mu.Unlock()
+}
+
+func withKind(msg *Pulled, kind string) *Pulled {
+	if msg != nil {
+		msg.Kind = kind
+	}
+	return msg
+}
+
+// take starts one ask: it decodes it, refuses one that is not of this seat, and runs it as a step under its own id.
+func (p *Puller) take(ctx context.Context, msg *Pulled) {
+	kind := msg.Kind
+	ask, err := delivery.DecodeStepAsk(msg.Data)
+	if err == nil && (ask.Language != p.Language || (kind != "" && ask.Kind != kind)) {
+		err = fmt.Errorf("the ask %s is a %s ask of %s, pulled from the %s %s worker", ask.ID, ask.Kind, ask.Language, p.Language, kind)
+	}
+	if err != nil {
+		// An ask that is not one runs nowhere: delivering it again would only fail again.
+		p.logf("an ask dropped: %v", err)
+		_ = msg.Term()
+		return
+	}
+	if lacks := delivery.Lacks(ask.Needs, p.Has); len(lacks) > 0 {
+		p.decline(msg, ask, lacks)
+		return
+	}
+	step, key, err := begin(p.Put, p.Node, ask.Kind+" ask", ask.ID, AskWhat(ask))
+	if err != nil {
+		p.logf("the ask %s cannot start on %s: %v", ask.ID, p.Node, err)
+		_ = msg.Nak()
+		return
+	}
+	if msg.Delivered > delivery.AskRuns {
+		// Run AskRuns times and never ended: each run took its node down or died with it. It is run no more, and said
+		// (issue 1907): the asker's key fails with why.
+		why := fmt.Errorf("the ask was taken %d times and no run of it ended: each took its build node down or died with it, so it is run no more (poison)", msg.Delivered-1)
+		p.logf("the ask %s is ended on %s: %v", ask.ID, p.Node, why)
+		_ = finish(p.Put, key, step, nil, why, p.Logf) // run no more either way: the asker's bound says it then
+		_ = msg.Term()
+		return
+	}
+	module := ""
+	if ask.Build != nil {
+		module = ask.Build.Module
+	}
+	p.mu.Lock()
+	p.inHand++
+	if p.running == nil {
+		p.running = map[string]RunningAsk{}
+	}
+	p.running[ask.ID] = RunningAsk{ID: ask.ID, Kind: ask.Kind, Module: module, Started: step.Started}
+	p.mu.Unlock()
+	p.logf("the %s ask %s starts on %s: %s", ask.Kind, ask.ID, p.Node, step.What)
+	go p.run(ctx, msg, ask, key, step)
+}
+
+func (p *Puller) run(ctx context.Context, msg *Pulled, ask delivery.StepAsk, key string, step delivery.Step) {
+	defer func() {
+		p.mu.Lock()
+		p.inHand--
+		delete(p.running, ask.ID)
+		p.mu.Unlock()
+		p.Wake()
+	}()
+	beat := p.Heartbeat
+	if beat <= 0 {
+		beat = DefaultHeartbeat
+	}
+	done := make(chan struct{})
+	go func() {
+		t := time.NewTicker(beat)
+		defer t.Stop()
+		for {
+			select {
+			case <-done:
+				return
+			case <-t.C:
+				if msg.InProgress != nil {
+					_ = msg.InProgress()
+				}
+			}
+		}
+	}()
+	ph := &phases{put: p.Put, key: key, step: step, logf: p.Logf, prefix: fmt.Sprintf("the %s ask %s on %s", ask.Kind, ask.ID, p.Node)}
+	result, err := protect(ctx, func(ctx context.Context) (any, error) {
+		return p.Run(context.WithValue(ctx, phaseKey{}, ph), ask)
+	})
+	step = ph.end() // its end keeps the phase it ended in
+	close(done)
+	if ctx.Err() != nil {
+		// The process stops: the ask is neither ended nor acknowledged here, so the stream gives it to a node that runs.
+		return
+	}
+	if ferr := finish(p.Put, key, step, result, err, p.Logf); ferr != nil {
+		// No end was written: the ask is not acknowledged as done, so the stream gives it again and a run that can
+		// write its end (or the poison rule, issue 1907) ends it where its asker sees it (issue 1930).
+		p.logf("the ask %s ran on %s and no end of it could be written, so it is given back: %v", ask.ID, p.Node, ferr)
+		_ = msg.Nak()
+		return
+	}
+	outcome := "passed"
+	if err != nil {
+		outcome = "did not pass: " + err.Error()
+		if len(outcome) > 300 {
+			outcome = outcome[:300] + "..."
+		}
+	}
+	p.logf("the %s ask %s ended on %s after %s, in its phase %q; %s", ask.Kind, ask.ID, p.Node,
+		now().Sub(step.Started).Round(time.Second), step.Phase, outcome)
+	if aerr := msg.Ack(); aerr != nil {
+		p.logf("the ask %s ended on %s and its acknowledgement failed: %v", ask.ID, p.Node, aerr)
+	}
+}
+
+// watchCapacity follows the module's config value `capacity` when WatchConfig is set (issue 1887, 2026-10-25: the laptop's
+// puller started at capacity 0 sat parked with capacity 2 set, because nothing woke it to read its settings file
+// again). The value comes as mesh-config resolved it for this node, the event of the change itself: the runtime hands
+// the value now and then each change its machine's provisioner client says moved, so nothing polls, and the puller does
+// not wait for the node-engine to fill its settings file again. Each value handed is kept, used in place of Capacity,
+// and wakes the puller. A watch that cannot start leaves the puller on Capacity, said once.
+func (p *Puller) watchCapacity() {
+	if p.WatchConfig == nil {
+		return
+	}
+	p.mu.Lock()
+	if p.capFollowed || p.capTrying {
+		p.mu.Unlock()
+		return
+	}
+	p.capTrying = true
+	p.mu.Unlock()
+	err := p.WatchConfig(CapacitySetting, func(c stdio.ProvisionChange) error {
+		n, why := p.capacityFrom(c)
+		p.mu.Lock()
+		before, had := p.watched, p.hasWatched
+		p.watched, p.hasWatched, p.capWhy = n, true, why
+		p.mu.Unlock()
+		switch {
+		case why != "":
+			p.logf("the %s puller on %s pulls nothing: %s", p.Language, p.Node, why)
+		case !had || before != n:
+			p.logf("the %s build capacity of %s is %d, as mesh-config resolved it", p.Language, p.Node, n)
+		}
+		p.Wake()
+		return nil
+	})
+	p.followed(&p.capFollowed, &p.capTrying, err, "build capacity")
+}
+
+// follow starts each config follow that is not running: at the start, and at every wake after (a file event, a resume, a
+// step's end), so a follow that failed is tried again by the next event and not given up for good.
+func (p *Puller) follow() {
+	go p.watchCapacity()
+	go p.watchHours()
+}
+
+// followed records the end of one follow's start. A failure is said once per distinct error, with that it is tried again.
+func (p *Puller) followed(done, trying *bool, err error, what string) {
+	p.mu.Lock()
+	*trying = false
+	*done = err == nil
+	said := err != nil && err.Error() == p.followFault
+	if err != nil {
+		p.followFault = err.Error()
+	} else {
+		p.followFault = ""
+	}
+	p.mu.Unlock()
+	if err != nil && !said {
+		p.logf("the %s %s of %s cannot be followed on the bus, so it is read from the settings file; the follow is tried "+
+			"again at the next event: %v", p.Language, what, p.Node, err)
+	}
+}
+
+// watchHours follows the module's config value `build-hours` when WatchConfig and BuildHours are set, as watchCapacity
+// follows `capacity`: each value handed is kept, used in place of BuildHours, and wakes the puller. A value that cannot
+// be read is no window, said; a watch that cannot start leaves the puller on BuildHours, said once.
+func (p *Puller) watchHours() {
+	if p.WatchConfig == nil || p.BuildHours == nil {
+		return
+	}
+	p.mu.Lock()
+	if p.hoursFollowed || p.hoursTrying {
+		p.mu.Unlock()
+		return
+	}
+	p.hoursTrying = true
+	p.mu.Unlock()
+	err := p.WatchConfig(BuildHoursSetting, func(c stdio.ProvisionChange) error {
+		setting := ""
+		var w *BuildWindow
+		var why string
+		switch {
+		case c.Refused != "":
+			why = "its build hours are no longer answered: " + c.Refused
+		case len(c.Value) > 0 && string(c.Value) != "null" && json.Unmarshal(c.Value, &setting) != nil:
+			why = fmt.Sprintf("the setting %s %s is not a string", BuildHoursSetting, c.Value)
+		default:
+			var err error
+			if w, err = ParseBuildWindow(setting); err != nil {
+				why = err.Error()
+			}
+		}
+		p.mu.Lock()
+		p.hours, p.hoursFault, p.hasHours = w, why, true
+		p.mu.Unlock()
+		if why != "" {
+			p.logf("the %s puller on %s builds at any hour: %s", p.Language, p.Node, why)
+		}
+		p.Wake()
+		return nil
+	})
+	p.followed(&p.hoursFollowed, &p.hoursTrying, err, "build hours")
+}
+
+// WatchConfigServed is stdio.WatchConfig once Serve has the runtime's channel (stdio.Served): a build module starts its
+// pull before it serves, and a watch asked before that would be refused.
+func WatchConfigServed(key string, handle func(stdio.ProvisionChange) error) error {
+	<-stdio.Served()
+	return stdio.WatchConfig(key, handle)
+}
+
+// capacityFrom is the node's capacity in one value the watch handed, and why it is 0 when it cannot be read.
+func (p *Puller) capacityFrom(c stdio.ProvisionChange) (int, string) {
+	if c.Refused != "" {
+		return 0, "its capacity is no longer answered: " + c.Refused
+	}
+	n, err := capacityOf(c.Value)
+	if err != nil {
+		return 0, err.Error()
+	}
+	return n, ""
+}

go/buildstep/pull_bus.go

@@ -0,0 +1,102 @@
+package buildstep
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// JetStreamAsks is a build seat's workers on the bus: the shared pull consumer of each kind on the seat's stream
+// (delivery.AskStream, AskWorker), which the broker makes when the seat is declared; a holder only binds them.
+type JetStreamAsks struct {
+	JS       jetstream.JetStream
+	Language string
+
+	mu   sync.Mutex
+	cons map[string]jetstream.Consumer
+}
+
+func (s *JetStreamAsks) consumer(ctx context.Context, kind string) (jetstream.Consumer, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if c, ok := s.cons[kind]; ok {
+		return c, nil
+	}
+	stream, err := delivery.AskStream(s.Language)
+	if err != nil {
+		return nil, err
+	}
+	worker, err := delivery.AskWorker(s.Language, kind)
+	if err != nil {
+		return nil, err
+	}
+	c, err := s.JS.Consumer(ctx, stream, worker)
+	if err != nil {
+		return nil, fmt.Errorf("binding the %s worker %s on %s: %w", kind, worker, stream, err)
+	}
+	if s.cons == nil {
+		s.cons = map[string]jetstream.Consumer{}
+	}
+	s.cons[kind] = c
+	return c, nil
+}
+
+// Next is AskSource's: a fetch of one with no wait when wait is 0, else one that waits at most wait.
+func (s *JetStreamAsks) Next(ctx context.Context, kind string, wait time.Duration) (*Pulled, error) {
+	c, err := s.consumer(ctx, kind)
+	if err != nil {
+		return nil, err
+	}
+	var batch jetstream.MessageBatch
+	if wait <= 0 {
+		batch, err = c.FetchNoWait(1)
+	} else {
+		batch, err = c.Fetch(1, jetstream.FetchMaxWait(wait))
+	}
+	if err != nil {
+		return nil, err
+	}
+	select {
+	case msg, ok := <-batch.Messages():
+		if !ok {
+			return nil, batch.Error()
+		}
+		var delivered uint64 = 1
+		if meta, err := msg.Metadata(); err == nil && meta != nil {
+			delivered = meta.NumDelivered
+		}
+		return &Pulled{Data: append([]byte(nil), msg.Data()...), Delivered: delivered,
+			Ack: msg.Ack, InProgress: msg.InProgress, Nak: msg.Nak, Term: msg.Term}, nil
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+}
+
+// DeclareAskWorkers makes language's seat stream and its three workers on a bus with no broker: a test's (the build
+// modules' integration tests start one). On the mesh the broker declares them from the seat, as it declares every
+// seat's stream (mesh-controller internal/broker SeatStreams); a holder never does.
+func DeclareAskWorkers(ctx context.Context, js jetstream.JetStream, language string, ackWait time.Duration) error {
+	stream, err := delivery.AskStream(language)
+	if err != nil {
+		return err
+	}
+	seat, _ := delivery.BuildSeat(language)
+	if _, err := js.CreateOrUpdateStream(ctx, jetstream.StreamConfig{Name: stream, Subjects: []string{"mesh.seat." + seat + ".accept.>"},
+		Retention: jetstream.WorkQueuePolicy}); err != nil {
+		return fmt.Errorf("the stream %s: %w", stream, err)
+	}
+	for _, kind := range delivery.AskKinds {
+		worker, _ := delivery.AskWorker(language, kind)
+		subject, _ := delivery.AskSubject(language, kind)
+		if _, err := js.CreateOrUpdateConsumer(ctx, stream, jetstream.ConsumerConfig{Durable: worker, FilterSubject: subject,
+			AckPolicy: jetstream.AckExplicitPolicy, AckWait: ackWait, MaxDeliver: 5}); err != nil {
+			return fmt.Errorf("the worker %s: %w", worker, err)
+		}
+	}
+	return nil
+}

go/buildstep/pull_capacity_test.go

@@ -0,0 +1,39 @@
+package buildstep
+
+import (
+	"encoding/json"
+	"sync"
+	"testing"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// configWatch is a double of stdio.WatchConfig: it hands the value now at the start, as the runtime does, and a test
+// hands each change after with set.
+type configWatch struct {
+	mu     sync.Mutex
+	value  string
+	handle func(stdio.ProvisionChange) error
+	asked  string
+}
+
+func (w *configWatch) watch(key string, handle func(stdio.ProvisionChange) error) error {
+	w.mu.Lock()
+	w.asked, w.handle = key, handle
+	value := w.value
+	w.mu.Unlock()
+	return handle(stdio.ProvisionChange{Kind: "config", Key: key, Value: json.RawMessage(value)})
+}
+
+func (w *configWatch) set(t *testing.T, value string) {
+	t.Helper()
+	w.mu.Lock()
+	handle, key := w.handle, w.asked
+	w.mu.Unlock()
+	if handle == nil {
+		t.Fatal("the puller watches no config value")
+	}
+	if err := handle(stdio.ProvisionChange{Kind: "config", Key: key, Value: json.RawMessage(value)}); err != nil {
+		t.Fatal(err)
+	}
+}

go/buildstep/pull_fake.go

@@ -0,0 +1,113 @@
+package buildstep
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// FakeAsks is a test double of a seat's workers for the build modules' unit tests: Publish puts an ask on a kind's
+// worker, Next hands them out in their order, and the fates the puller gives them are counted. Safe for concurrent use.
+type FakeAsks struct {
+	mu      sync.Mutex
+	waiting map[string][][]byte
+	added   chan struct{}
+	// Acked, Termed and Naked are the asks' ids or data by fate, InProgress how many heartbeats were given.
+	Acked, Termed, Naked []string
+	InProgress           int
+	// Delivered, when set, is the delivery count every ask handed over says (1 when 0): a test of a poisoned ask sets it.
+	Delivered uint64
+}
+
+// NewFakeAsks is an empty double.
+func NewFakeAsks() *FakeAsks {
+	return &FakeAsks{waiting: map[string][][]byte{}, added: make(chan struct{}, 1)}
+}
+
+// Publish puts an encoded ask on kind's worker.
+func (f *FakeAsks) Publish(kind string, data []byte) {
+	f.mu.Lock()
+	f.waiting[kind] = append(f.waiting[kind], data)
+	f.mu.Unlock()
+	select {
+	case f.added <- struct{}{}:
+	default:
+	}
+}
+
+// PublishAsk encodes a and puts it on its kind's worker.
+func (f *FakeAsks) PublishAsk(a delivery.StepAsk) error {
+	raw, err := delivery.EncodeStepAsk(a)
+	if err != nil {
+		return err
+	}
+	f.Publish(a.Kind, raw)
+	return nil
+}
+
+// Waiting is how many asks wait on kind's worker.
+func (f *FakeAsks) Waiting(kind string) int {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return len(f.waiting[kind])
+}
+
+// Fates is a copy of the acked, termed and naked lists.
+func (f *FakeAsks) Fates() (acked, termed, naked []string) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return append([]string(nil), f.Acked...), append([]string(nil), f.Termed...), append([]string(nil), f.Naked...)
+}
+
+// Next is AskSource's.
+func (f *FakeAsks) Next(ctx context.Context, kind string, wait time.Duration) (*Pulled, error) {
+	var deadline <-chan time.Time
+	if wait > 0 {
+		t := time.NewTimer(wait)
+		defer t.Stop()
+		deadline = t.C
+	}
+	for {
+		f.mu.Lock()
+		if q := f.waiting[kind]; len(q) > 0 {
+			data := q[0]
+			f.waiting[kind] = q[1:]
+			f.mu.Unlock()
+			return f.pulled(data), nil
+		}
+		f.mu.Unlock()
+		if wait <= 0 {
+			return nil, nil
+		}
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case <-deadline:
+			return nil, nil
+		case <-f.added:
+		}
+	}
+}
+
+func (f *FakeAsks) pulled(data []byte) *Pulled {
+	id := string(data)
+	if a, err := delivery.DecodeStepAsk(data); err == nil {
+		id = a.ID
+	}
+	fate := func(list *[]string) func() error {
+		return func() error {
+			f.mu.Lock()
+			*list = append(*list, id)
+			f.mu.Unlock()
+			return nil
+		}
+	}
+	delivered := f.Delivered
+	if delivered == 0 {
+		delivered = 1
+	}
+	return &Pulled{Data: data, Delivered: delivered, Ack: fate(&f.Acked), Nak: fate(&f.Naked), Term: fate(&f.Termed),
+		InProgress: func() error { f.mu.Lock(); f.InProgress++; f.mu.Unlock(); return nil }}
+}

go/buildstep/pull_integration_test.go

@@ -0,0 +1,144 @@
+//go:build integration
+
+package buildstep
+
+import (
+	"context"
+	"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"
+	"git.novox.be/novox/mesh-sdk/go/testbus"
+)
+
+func askBus(t *testing.T, ackWait time.Duration) jetstream.JetStream {
+	t.Helper()
+	nc, err := nats.Connect(testbus.URL(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(nc.Close)
+	js, err := jetstream.New(nc)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := DeclareAskWorkers(context.Background(), js, delivery.AskGo, ackWait); err != nil {
+		t.Fatal(err)
+	}
+	return js
+}
+
+func publishAsk(t *testing.T, js jetstream.JetStream, a delivery.StepAsk) {
+	t.Helper()
+	raw, err := delivery.EncodeStepAsk(a)
+	if err != nil {
+		t.Fatal(err)
+	}
+	subject, _ := delivery.AskSubject(a.Language, a.Kind)
+	if _, err := js.Publish(context.Background(), subject, raw); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// 1887/A2a, 1887/AC-order, 1887/AC-pull on the real server: a check ask published before a delivery ask runs after it;
+// with capacity 2 and three asks two run, the third waits in the stream and starts when one ends.
+func TestPullOrderAndCapacityOnTheBus(t *testing.T) {
+	js := askBus(t, 30*time.Second)
+	check, first, second := testAsk(delivery.AskCheck), testAsk(delivery.AskDelivery), testAsk(delivery.AskDelivery)
+	publishAsk(t, js, check)
+	publishAsk(t, js, first)
+	publishAsk(t, js, second)
+	release := make(chan struct{})
+	var mu sync.Mutex
+	var order []string
+	st := newSteps()
+	p := &Puller{Source: &JetStreamAsks{JS: js, Language: delivery.AskGo}, Language: delivery.AskGo, Node: "shanks", Put: st.put,
+		Capacity: func() int { return 2 }, PullWait: 200 * time.Millisecond,
+		Run: func(ctx context.Context, a delivery.StepAsk) (any, error) {
+			mu.Lock()
+			order = append(order, a.ID)
+			mu.Unlock()
+			<-release
+			return nil, nil
+		}}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go p.Pull(ctx)
+	waitFor(t, "two in hand", func() bool { return p.InHand() == 2 })
+	time.Sleep(500 * time.Millisecond)
+	mu.Lock()
+	if len(order) != 2 || order[0] != first.ID || order[1] != second.ID {
+		t.Fatalf("ran %v, want the two delivery asks %s %s first", order, first.ID, second.ID)
+	}
+	mu.Unlock()
+	release <- struct{}{}
+	waitFor(t, "the check taken", func() bool { mu.Lock(); defer mu.Unlock(); return len(order) == 3 })
+	close(release)
+	waitFor(t, "every step ended", func() bool {
+		for _, a := range []delivery.StepAsk{check, first, second} {
+			key, _ := delivery.AskStepKey("shanks", a.ID)
+			if s, ok := st.get(key); !ok || s.State != delivery.StepPassed {
+				return false
+			}
+		}
+		return true
+	})
+	info, err := js.Stream(ctx, "SEAT_NODE_BUILD_GO")
+	if err != nil {
+		t.Fatal(err)
+	}
+	waitFor(t, "the stream empty (every ask acknowledged)", func() bool {
+		si, err := info.Info(ctx)
+		return err == nil && si.State.Msgs == 0
+	})
+}
+
+// 1887/A2c, ADR 0525 §6: a killed puller's ask is redelivered by the stream's acknowledgement wait to the other node,
+// whose step key names the reference.
+func TestPullRedeliversAKilledPullersAsk(t *testing.T) {
+	js := askBus(t, 2*time.Second)
+	a := testAsk(delivery.AskDelivery)
+	publishAsk(t, js, a)
+	st := newSteps()
+	taken := make(chan struct{})
+	dying := &Puller{Source: &JetStreamAsks{JS: js, Language: delivery.AskGo}, Language: delivery.AskGo, Node: "ace", Put: st.put,
+		Capacity: func() int { return 1 }, PullWait: 200 * time.Millisecond, Heartbeat: time.Hour,
+		Run: func(ctx context.Context, a delivery.StepAsk) (any, error) {
+			close(taken)
+			<-ctx.Done()
+			return nil, ctx.Err()
+		}}
+	kill, killed := context.WithCancel(context.Background())
+	go dying.Pull(kill)
+	<-taken
+	killed()
+	other := &Puller{Source: &JetStreamAsks{JS: js, Language: delivery.AskGo}, Language: delivery.AskGo, Node: "shanks", Put: st.put,
+		Capacity: func() int { return 1 }, PullWait: 200 * time.Millisecond,
+		Run: func(ctx context.Context, a delivery.StepAsk) (any, error) {
+			return delivery.BuildAnswer{Artifacts: []delivery.AskBuilt{{Artifact: "bundle", Digest: "sha256:00", Reference: "artifact-store://x"}}}, nil
+		}}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go other.Pull(ctx)
+	key, _ := delivery.AskStepKey("shanks", a.ID)
+	deadline := time.Now().Add(10 * time.Second)
+	for {
+		if s, ok := st.get(key); ok && s.State == delivery.StepPassed {
+			if want := `artifact-store://x`; !contains(string(s.Result), want) {
+				t.Fatalf("the step's result %s names no %s", s.Result, want)
+			}
+			return
+		}
+		if time.Now().After(deadline) {
+			t.Fatalf("the killed puller's ask was not taken by shanks within 10 s")
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+}
+
+func contains(s, sub string) bool { return strings.Contains(s, sub) }

go/buildstep/pull_seat.go

@@ -0,0 +1,44 @@
+package buildstep
+
+import (
+	"context"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// SeatAsks is a build seat's workers as a tools bundle reaches them: through its runtime's seat pull and settle
+// (stdio.SeatPull, SeatSettle; issue 1887 A11), one message per pull, only from the workers the module's membership
+// lists.
+type SeatAsks struct {
+	Language string
+	// Pull and Settle are stdio.SeatPull and stdio.SeatSettle when nil; a test gives its own.
+	Pull   func(worker string, wait time.Duration) (*stdio.Pulled, error)
+	Settle func(id, fate string) error
+}
+
+// Next is AskSource's.
+func (s SeatAsks) Next(ctx context.Context, kind string, wait time.Duration) (*Pulled, error) {
+	pull, settle := s.Pull, s.Settle
+	if pull == nil {
+		pull = stdio.SeatPull
+	}
+	if settle == nil {
+		settle = stdio.SeatSettle
+	}
+	worker, err := delivery.AskWorker(s.Language, kind)
+	if err != nil {
+		return nil, err
+	}
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	p, err := pull(worker, wait)
+	if err != nil || p == nil {
+		return nil, err
+	}
+	fate := func(f string) func() error { return func() error { return settle(p.ID, f) } }
+	return &Pulled{Data: p.Body, Delivered: p.Delivered, Ack: fate(stdio.SettleAck), InProgress: fate(stdio.SettleProgress),
+		Nak: fate(stdio.SettleNak), Term: fate(stdio.SettleTerm)}, nil
+}

go/buildstep/pull_seat_test.go

@@ -0,0 +1,40 @@
+package buildstep
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// 1887/A11: a bundle's source pulls the kind's worker by its seat's name and settles each ask by the runtime's id.
+func TestSeatAsksPullsTheKindsWorkerAndSettlesByID(t *testing.T) {
+	var pulled []string
+	var settled []string
+	src := SeatAsks{Language: delivery.AskGo,
+		Pull: func(worker string, wait time.Duration) (*stdio.Pulled, error) {
+			pulled = append(pulled, worker)
+			if worker != "SEAT_NODE_BUILD_GO_CHECK_worker" {
+				return nil, nil
+			}
+			return &stdio.Pulled{ID: "p9", Worker: worker, Body: []byte(`{"v":1}`), Delivered: 2}, nil
+		},
+		Settle: func(id, fate string) error { settled = append(settled, id+" "+fate); return nil }}
+	if p, err := src.Next(context.Background(), delivery.AskDelivery, 0); err != nil || p != nil {
+		t.Fatalf("delivery = %+v, %v", p, err)
+	}
+	p, err := src.Next(context.Background(), delivery.AskCheck, time.Second)
+	if err != nil || p == nil || string(p.Data) != `{"v":1}` || p.Delivered != 2 {
+		t.Fatalf("check = %+v, %v", p, err)
+	}
+	_ = p.InProgress()
+	_ = p.Ack()
+	if len(pulled) != 2 || pulled[0] != "SEAT_NODE_BUILD_GO_DELIVERY_worker" {
+		t.Errorf("pulled %v", pulled)
+	}
+	if len(settled) != 2 || settled[0] != "p9 progress" || settled[1] != "p9 ack" {
+		t.Errorf("settled %v", settled)
+	}
+}

go/buildstep/pull_test.go

@@ -0,0 +1,505 @@
+package buildstep
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// steps records a steps state's puts: the last value of each key.
+type steps struct {
+	mu   sync.Mutex
+	keys map[string]delivery.Step
+}
+
+func newSteps() *steps { return &steps{keys: map[string]delivery.Step{}} }
+
+func (s *steps) put(key string, value any) (uint64, error) {
+	raw, _ := value.(json.RawMessage)
+	st, err := delivery.DecodeStep(raw)
+	if err != nil {
+		return 0, err
+	}
+	s.mu.Lock()
+	s.keys[key] = st
+	s.mu.Unlock()
+	return 1, nil
+}
+
+func (s *steps) get(key string) (delivery.Step, bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	st, ok := s.keys[key]
+	return st, ok
+}
+
+func testAsk(kind string) delivery.StepAsk {
+	id := NewID()
+	a := delivery.StepAsk{ID: id, Kind: kind, Language: delivery.AskGo, Asker: "mesh-delivery-builder", At: time.Now()}
+	fetch := map[string]any{"repository": "novox/x", "commit": "0123456789abcdef0123456789abcdef01234567"}
+	if kind == delivery.AskDelivery {
+		b := buildJobFixture
+		b.Fetch = fetch
+		a.Build = &b
+	} else {
+		a.Check = &delivery.CheckJob{Fetch: fetch, Levels: []string{delivery.LevelUnit}}
+	}
+	return a
+}
+
+var buildJobFixture = delivery.BuildJob{Module: "m", Path: ".", Artifacts: []delivery.AskArtifact{{Artifact: "bundle"}}}
+
+func waitFor(t *testing.T, what string, cond func() bool) {
+	t.Helper()
+	deadline := time.Now().Add(2 * time.Second)
+	for !cond() {
+		if time.Now().After(deadline) {
+			t.Fatalf("waited 2 s for %s", what)
+		}
+		time.Sleep(time.Millisecond)
+	}
+}
+
+// 1887/A2a: given a check ask published before a delivery ask and one slot, the delivery ask runs first.
+func TestPullTakesDeliveryBeforeCheck(t *testing.T) {
+	src, st := NewFakeAsks(), newSteps()
+	check, recheck, deliver := testAsk(delivery.AskCheck), testAsk(delivery.AskRecheck), testAsk(delivery.AskDelivery)
+	for _, a := range []delivery.StepAsk{recheck, check, deliver} {
+		if err := src.PublishAsk(a); err != nil {
+			t.Fatal(err)
+		}
+	}
+	var mu sync.Mutex
+	var order []string
+	p := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: st.put, Capacity: func() int { return 1 },
+		PullWait: 10 * time.Millisecond, Run: func(ctx context.Context, a delivery.StepAsk) (any, error) {
+			mu.Lock()
+			order = append(order, a.Kind)
+			mu.Unlock()
+			return map[string]string{"ran": a.ID}, nil
+		}}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go p.Pull(ctx)
+	waitFor(t, "three asks acked", func() bool { a, _, _ := src.Fates(); return len(a) == 3 })
+	mu.Lock()
+	defer mu.Unlock()
+	if want := []string{delivery.AskDelivery, delivery.AskCheck, delivery.AskRecheck}; len(order) != 3 || order[0] != want[0] || order[1] != want[1] || order[2] != want[2] {
+		t.Fatalf("order = %v, want %v", order, want)
+	}
+	key, _ := delivery.AskStepKey("shanks", deliver.ID)
+	s, ok := st.get(key)
+	if !ok || s.State != delivery.StepPassed || string(s.Result) != `{"ran":"`+deliver.ID+`"}` {
+		t.Fatalf("the step %s = %+v (%v)", key, s, ok)
+	}
+}
+
+// 1887/A2a, 1887/AC-pull: given capacity 2 and three asks waiting, two run and the third waits, and it starts when
+// one ends, with no timer. Issue 1806's follow-up: the 2 is the CPU's, a configured 3 bounded by a 12-core slice at 6
+// cores a step, said once in capacity.<node>; and issue 1890: a run's phase is written to its step key and logged with
+// its ask id, and its end keeps the last phase.
+func TestPullHoldsAtMostItsCapacity(t *testing.T) {
+	src, st := NewFakeAsks(), newSteps()
+	asks := []delivery.StepAsk{}
+	for i := 0; i < 3; i++ {
+		a := testAsk(delivery.AskDelivery)
+		asks = append(asks, a)
+		_ = src.PublishAsk(a)
+	}
+	release := make(chan struct{})
+	var mu sync.Mutex
+	started := 0
+	var said []string
+	capacities := map[string][]byte{}
+	quota := 1200
+	p := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: st.put, Capacity: func() int { return 3 },
+		CoresPerStep: func() float64 { return 6 },
+		Quota:        func() (int, string) { mu.Lock(); defer mu.Unlock(); return quota, "a test's slice" },
+		PausePut: func(key string, v any) (uint64, error) {
+			mu.Lock()
+			capacities[key] = v.(json.RawMessage)
+			mu.Unlock()
+			return 1, nil
+		},
+		Logf:     func(f string, a ...any) { mu.Lock(); said = append(said, fmt.Sprintf(f, a...)); mu.Unlock() },
+		PullWait: 10 * time.Millisecond, Run: func(ctx context.Context, a delivery.StepAsk) (any, error) {
+			mu.Lock()
+			started++
+			mu.Unlock()
+			Phase(ctx, "unit: tests of 3 packages")
+			<-release
+			return nil, nil
+		}}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go p.Pull(ctx)
+	waitFor(t, "two in hand", func() bool { return p.InHand() == 2 })
+	time.Sleep(30 * time.Millisecond) // three pull waits: the third must still wait
+	if p.InHand() != 2 || src.Waiting(delivery.AskDelivery) != 1 {
+		t.Fatalf("in hand %d, waiting %d; want 2 and 1", p.InHand(), src.Waiting(delivery.AskDelivery))
+	}
+	c := p.CapacityDetail()
+	if c.Effective != 2 || c.Configured != 3 || c.ByCPU != 2 || c.QuotaCores != 12 || !strings.Contains(c.Why, "bounded by the CPU") {
+		t.Fatalf("the capacity judged by = %+v, want 2 of a configured 3 bounded by 12 cores / 6", c)
+	}
+	mu.Lock()
+	raw := capacities["capacity.shanks"]
+	capLines := 0
+	for _, l := range said {
+		if strings.Contains(l, "build capacity of shanks is 2, bounded by the CPU") {
+			capLines++
+		}
+	}
+	mu.Unlock()
+	if got, err := delivery.DecodeCapacity(raw); err != nil || got.Effective != 2 || capLines != 1 {
+		t.Fatalf("capacity.shanks = %s (%v), said %d times; want effective 2, said once", raw, err, capLines)
+	}
+	waitFor(t, "a phase on the step key", func() bool {
+		key, _ := delivery.AskStepKey("shanks", p.Running()[0].ID)
+		s, _ := st.get(key)
+		return s.State == delivery.StepRunning && s.Phase == "unit: tests of 3 packages" && !s.PhaseAt.IsZero() && s.Owner == Owner // 1890/AC5
+	})
+	release <- struct{}{}
+	waitFor(t, "the third taken", func() bool { return src.Waiting(delivery.AskDelivery) == 0 })
+	// Taken from the source comes a moment before its run starts: wait for the start, not only the take.
+	waitFor(t, "the third started", func() bool { mu.Lock(); defer mu.Unlock(); return started == 3 })
+	close(release)
+	waitFor(t, "all acked", func() bool { a, _, _ := src.Fates(); return len(a) == 3 })
+	for _, a := range asks {
+		key, _ := delivery.AskStepKey("shanks", a.ID)
+		if s, _ := st.get(key); s.State != delivery.StepPassed || s.Phase != "unit: tests of 3 packages" || s.Owner != Owner {
+			t.Errorf("the end of %s = %+v, want passed in its last phase", a.ID, s)
+		}
+	}
+	mu.Lock()
+	logged := strings.Join(said, "\n")
+	quota = 600 // the cap lowered: one step at 6 cores, followed at the next judgement
+	mu.Unlock()
+	if !strings.Contains(logged, "the delivery ask "+asks[0].ID+" on shanks: unit: tests of 3 packages") {
+		t.Errorf("no journal line names the ask's phase: %s", logged)
+	}
+	if c := p.CapacityDetail(); c.Effective != 1 {
+		t.Errorf("after the quota fell to 6 cores, capacity %+v, want 1", c)
+	}
+}
+
+// An ask that is not one, or not this seat's, is dropped and runs nowhere. And issue 890/AC1: a check ask needing
+// node-build-node is declined on a node that lacks it (its step refused as declined, naming what it lacks, the message
+// dropped for the asker to put again), and runs on a node that has it.
+func TestPullDropsWhatIsNoAsk(t *testing.T) {
+	src, st := NewFakeAsks(), newSteps()
+	src.Publish(delivery.AskDelivery, []byte(`{"v":1}`))
+	other := testAsk(delivery.AskDelivery)
+	other.Language = delivery.AskNode
+	_ = src.PublishAsk(other)
+	placed := testAsk(delivery.AskCheck)
+	placed.Needs = []string{delivery.NeedNodeBuildNode}
+	if err := src.PublishAsk(placed); err != nil {
+		t.Fatal(err)
+	}
+	ran := false
+	p := &Puller{Source: src, Language: delivery.AskGo, Node: "ace", Put: st.put, Capacity: func() int { return 1 },
+		PullWait: 10 * time.Millisecond, Run: func(ctx context.Context, a delivery.StepAsk) (any, error) { ran = true; return nil, nil }}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go p.Pull(ctx)
+	waitFor(t, "three termed", func() bool { _, tm, _ := src.Fates(); return len(tm) == 3 })
+	if ran {
+		t.Fatal("a wrong or a declined ask ran")
+	}
+	key, _ := delivery.AskStepKey("ace", placed.ID)
+	s, _ := st.get(key)
+	if d, ok := delivery.DeclinedOf(s); !ok || len(d.Lacks) != 1 || d.Lacks[0] != delivery.NeedNodeBuildNode || !strings.Contains(s.Reason, "lacks node-build-node") {
+		t.Fatalf("the declined step = %+v", s)
+	}
+	has, hasSteps := NewFakeAsks(), newSteps()
+	_ = has.PublishAsk(placed)
+	q := &Puller{Source: has, Language: delivery.AskGo, Node: "g14", Put: hasSteps.put, Capacity: func() int { return 1 },
+		PullWait: 10 * time.Millisecond, Has: func(n string) bool { return n == delivery.NeedNodeBuildNode },
+		Run: func(ctx context.Context, a delivery.StepAsk) (any, error) { return nil, nil }}
+	go q.Pull(ctx)
+	waitFor(t, "the placed ask acked where its need is met", func() bool { a, _, _ := has.Fates(); return len(a) == 1 })
+}
+
+// load reads the recorded steps state's raw values: the pause key is not a step, so it is kept apart.
+type kv struct {
+	mu   sync.Mutex
+	vals map[string][]byte
+}
+
+func (k *kv) put(key string, value any) (uint64, error) {
+	raw, _ := value.(json.RawMessage)
+	k.mu.Lock()
+	defer k.mu.Unlock()
+	if k.vals == nil {
+		k.vals = map[string][]byte{}
+	}
+	k.vals[key] = append([]byte(nil), raw...)
+	return 1, nil
+}
+
+func (k *kv) load(key string) ([]byte, error) {
+	k.mu.Lock()
+	defer k.mu.Unlock()
+	return k.vals[key], nil
+}
+
+// 1887/A2b, 1887/AC-zero, 1887/AC-wake: at capacity 0 the puller takes nothing; a capacity raised takes effect at the
+// next pull, or, with the config watch (g14 idle at capacity 2, 2026-10-25), at once when the value moves, with no
+// pause, resume or step end to wake it; a refused value pulls nothing, and a watch that cannot start leaves the
+// settings file's capacity.
+func TestPullAtCapacityZeroTakesNothing(t *testing.T) {
+	t.Run("settings file", func(t *testing.T) {
+		src, st := NewFakeAsks(), &kv{}
+		_ = src.PublishAsk(testAsk(delivery.AskDelivery))
+		var mu sync.Mutex
+		capacity := 0
+		p := &Puller{Source: src, Language: delivery.AskGo, Node: "novox", Put: st.put, PullWait: 10 * time.Millisecond,
+			Capacity: func() int { mu.Lock(); defer mu.Unlock(); return capacity },
+			Run:      func(ctx context.Context, a delivery.StepAsk) (any, error) { return nil, nil }}
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		go p.Pull(ctx)
+		time.Sleep(50 * time.Millisecond)
+		if src.Waiting(delivery.AskDelivery) != 1 {
+			t.Fatal("a node at capacity 0 took an ask")
+		}
+		mu.Lock()
+		capacity = 1
+		mu.Unlock()
+		p.Wake()
+		waitFor(t, "the ask taken at capacity 1", func() bool { a, _, _ := src.Fates(); return len(a) == 1 })
+	})
+	t.Run("config watch wakes", func(t *testing.T) {
+		src, st := NewFakeAsks(), newSteps()
+		_ = src.PublishAsk(testAsk(delivery.AskDelivery))
+		w := &configWatch{value: "0"}
+		p := &Puller{Source: src, Language: delivery.AskGo, Node: "g14", Put: st.put, PullWait: 10 * time.Millisecond,
+			Capacity:    func() int { return 0 }, // the settings file, not refilled yet
+			WatchConfig: w.watch,
+			Run:         func(ctx context.Context, a delivery.StepAsk) (any, error) { return nil, nil }}
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		go p.Pull(ctx)
+		waitFor(t, "the watch of the capacity", func() bool { w.mu.Lock(); defer w.mu.Unlock(); return w.handle != nil })
+		time.Sleep(30 * time.Millisecond)
+		if src.Waiting(delivery.AskDelivery) != 1 {
+			t.Fatal("a node at capacity 0 took an ask")
+		}
+		if w.asked != CapacitySetting {
+			t.Fatalf("the puller watches %q, want %q", w.asked, CapacitySetting)
+		}
+		w.set(t, "2")
+		waitFor(t, "the ask taken once the capacity moved to 2", func() bool { a, _, _ := src.Fates(); return len(a) == 1 })
+	})
+	t.Run("settings refill wakes a parked puller and retries a failed follow", func(t *testing.T) {
+		// 2026-10-28: a replaced builder held the old "shanks=2,..." in its settings file, its config follow timed out, and
+		// the puller parked at 0 with nothing to wake it when the node-engine refilled the file.
+		src, st := NewFakeAsks(), newSteps()
+		_ = src.PublishAsk(testAsk(delivery.AskDelivery))
+		file := filepath.Join(t.TempDir(), "settings.json")
+		if err := os.WriteFile(file, []byte(`{"capacity":"shanks=2,ace=2"}`), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		var mu sync.Mutex
+		attempts := 0
+		watch := func(key string, handle func(stdio.ProvisionChange) error) error {
+			mu.Lock()
+			defer mu.Unlock()
+			attempts++
+			if attempts == 1 {
+				return errors.New("nats: timeout")
+			}
+			return nil // followed; no value handed yet
+		}
+		armed := make(chan struct{}, 8)
+		var parked atomic.Int32
+		parks := func() int32 { return parked.Load() }
+		logf := func(format string, args ...any) {
+			if strings.Contains(format, "parks") {
+				parked.Add(1)
+			}
+		}
+		p := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: st.put, PullWait: 10 * time.Millisecond,
+			SettingsFile: file, WatchConfig: watch, Logf: logf, watching: func() { armed <- struct{}{} },
+			Run: func(ctx context.Context, a delivery.StepAsk) (any, error) { return nil, nil }}
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		go p.Pull(ctx)
+		waitFor(t, "the parked puller to say why", func() bool { why, fault := p.CapacityNote(); return fault && why != "" })
+		if src.Waiting(delivery.AskDelivery) != 1 {
+			t.Fatal("a node whose capacity cannot be read took an ask")
+		}
+		<-armed // the file watch is in place
+		tmp := file + ".new"
+		if err := os.WriteFile(tmp, []byte(`{"capacity":2}`), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.Rename(tmp, file); err != nil {
+			t.Fatal(err)
+		}
+		waitFor(t, "the ask taken once the file was refilled", func() bool { a, _, _ := src.Fates(); return len(a) == 1 })
+		// and the directory itself replaced (IN_IGNORED): the watch is armed again and a later refill still wakes the puller
+		dir := filepath.Dir(file)
+		before := parks()
+		if err := os.RemoveAll(dir); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.Mkdir(dir, 0o700); err != nil {
+			t.Fatal(err)
+		}
+		<-armed // armed again
+		waitFor(t, "the puller parked with no settings file", func() bool { return parks() > before })
+		_ = src.PublishAsk(testAsk(delivery.AskDelivery))
+		if err := os.WriteFile(file, []byte(`{"capacity":2}`), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		waitFor(t, "the second ask taken after the directory was replaced", func() bool { a, _, _ := src.Fates(); return len(a) == 2 })
+		waitFor(t, "the failed follow tried again", func() bool { mu.Lock(); defer mu.Unlock(); return attempts >= 2 })
+	})
+	for _, c := range []struct {
+		name  string
+		watch func(string, func(stdio.ProvisionChange) error) error
+		room  bool
+	}{
+		{"refused value leaves no room", func(key string, handle func(stdio.ProvisionChange) error) error {
+			return handle(stdio.ProvisionChange{Kind: "config", Key: key, Refused: "the module is no longer on g14"})
+		}, false},
+		{"watch that cannot start keeps the settings file", func(string, func(stdio.ProvisionChange) error) error {
+			return errors.New("no runtime")
+		}, true},
+	} {
+		t.Run(c.name, func(t *testing.T) {
+			p := &Puller{Source: NewFakeAsks(), Language: delivery.AskGo, Node: "g14", Put: newSteps().put,
+				Capacity: func() int { return 1 }, WatchConfig: c.watch,
+				Run: func(ctx context.Context, a delivery.StepAsk) (any, error) { return nil, nil }}
+			p.watchCapacity()
+			if p.room() != c.room {
+				t.Fatalf("room = %v, want %v", p.room(), c.room)
+			}
+		})
+	}
+}
+
+// 1887/A2b: a paused puller takes nothing, its pause is kept on the pause key, and a puller started again on that state
+// stays paused until resumed.
+func TestPullPauseOutlivesARestart(t *testing.T) {
+	src, st, steps := NewFakeAsks(), &kv{}, &kv{}
+	run := func(ctx context.Context, a delivery.StepAsk) (any, error) { return nil, nil }
+	p := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: steps.put, PausePut: st.put, Load: st.load,
+		PullWait: 10 * time.Millisecond, Capacity: func() int { return 2 }, Run: run}
+	if err := p.Pause("the operator"); err != nil {
+		t.Fatal(err)
+	}
+	key, _ := delivery.PauseKey("shanks")
+	raw, _ := st.load(key)
+	if v, err := delivery.DecodePause(raw); err != nil || !v.Paused || v.By != "the operator" {
+		t.Fatalf("the pause key holds %s (%v)", raw, err)
+	}
+	if raw, _ := steps.load(key); raw != nil {
+		t.Fatalf("the pause was written in the steps state, whose keys age out: %s", raw)
+	}
+	// The restart: a new puller on the same state.
+	again := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: steps.put, PausePut: st.put, Load: st.load,
+		PullWait: 10 * time.Millisecond, Capacity: func() int { return 2 }, Run: run}
+	_ = src.PublishAsk(testAsk(delivery.AskDelivery))
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go again.Pull(ctx)
+	time.Sleep(50 * time.Millisecond)
+	if !again.Paused() || src.Waiting(delivery.AskDelivery) != 1 {
+		t.Fatalf("restarted: paused %v, waiting %d; want paused and 1", again.Paused(), src.Waiting(delivery.AskDelivery))
+	}
+	if err := again.Resume("the operator"); err != nil {
+		t.Fatal(err)
+	}
+	waitFor(t, "the ask taken after the resume", func() bool { a, _, _ := src.Fates(); return len(a) == 1 })
+
+	t.Run("a pause that cannot be read is said and pulled as not paused", func(t *testing.T) {
+		src := NewFakeAsks()
+		var said atomic.Value
+		p := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: steps.put, PausePut: st.put,
+			Load:     func(string) ([]byte, error) { return nil, errors.New("no runtime yet") },
+			PullWait: 10 * time.Millisecond, Capacity: func() int { return 2 }, Run: run,
+			Logf: func(f string, a ...any) {
+				if m := fmt.Sprintf(f, a...); strings.Contains(m, "cannot be read") {
+					said.Store(m)
+				}
+			}}
+		_ = src.PublishAsk(testAsk(delivery.AskDelivery))
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		go p.Pull(ctx)
+		waitFor(t, "the ask taken", func() bool { a, _, _ := src.Fates(); return len(a) == 1 })
+		if m, _ := said.Load().(string); !strings.Contains(m, "pulling as not paused") {
+			t.Fatalf("the unreadable pause was not said: %q", m)
+		}
+	})
+}
+
+// 1887/A2c: a long step tells the bus it is still being worked; a holder that stops mid-step neither ends nor
+// acknowledges its ask, so the stream gives it to another node.
+func TestPullHeartbeatAndStop(t *testing.T) {
+	src, st := NewFakeAsks(), newSteps()
+	a := testAsk(delivery.AskDelivery)
+	_ = src.PublishAsk(a)
+	running := make(chan struct{})
+	p := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: st.put, Capacity: func() int { return 1 },
+		PullWait: 10 * time.Millisecond, Heartbeat: 5 * time.Millisecond,
+		Run: func(ctx context.Context, a delivery.StepAsk) (any, error) {
+			close(running)
+			<-ctx.Done()
+			return nil, ctx.Err()
+		}}
+	ctx, cancel := context.WithCancel(context.Background())
+	stopped := make(chan struct{})
+	go func() { p.Pull(ctx); close(stopped) }()
+	<-running
+	waitFor(t, "two heartbeats", func() bool { src.mu.Lock(); defer src.mu.Unlock(); return src.InProgress >= 2 })
+	cancel()
+	<-stopped
+	waitFor(t, "the step's goroutine gone", func() bool { return p.InHand() == 0 })
+	acked, termed, naked := src.Fates()
+	if len(acked)+len(termed)+len(naked) != 0 {
+		t.Fatalf("a stopped holder gave its ask a fate: acked %v termed %v naked %v", acked, termed, naked)
+	}
+	key, _ := delivery.AskStepKey("shanks", a.ID)
+	if s, ok := st.get(key); !ok || s.State != delivery.StepRunning {
+		t.Fatalf("the step %s = %+v, want left running", key, s)
+	}
+}
+
+// 1907: an ask taken past AskRuns (each run took its node down) is run no more: its step ends failed saying why, so the
+// asker's key fails, and it is ended on the stream, not offered to another node.
+func TestAPoisonedAskIsSaidAndRunNoMore(t *testing.T) {
+	src, st := NewFakeAsks(), newSteps()
+	src.Delivered = delivery.AskRuns + 1
+	a := testAsk(delivery.AskDelivery)
+	_ = src.PublishAsk(a)
+	ran := false
+	p := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: st.put, Capacity: func() int { return 1 },
+		PullWait: 10 * time.Millisecond, Run: func(ctx context.Context, a delivery.StepAsk) (any, error) { ran = true; return nil, nil }}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go p.Pull(ctx)
+	waitFor(t, "the ask termed", func() bool { _, tm, _ := src.Fates(); return len(tm) == 1 })
+	key, _ := delivery.AskStepKey("shanks", a.ID)
+	s, ok := st.get(key)
+	if ran || !ok || s.State != delivery.StepFailed || !strings.Contains(s.Reason, "taken 3 times") || !strings.Contains(s.Reason, "poison") {
+		t.Fatalf("ran %v, step %+v", ran, s)
+	}
+	if acked, _, naked := src.Fates(); len(acked)+len(naked) != 0 {
+		t.Errorf("acked %v naked %v, want it termed alone", acked, naked)
+	}
+}

go/buildstep/refusal.go

@@ -1,5 +1,7 @@
 package buildstep
 
+import "fmt"
+
 // Refusal is a step that is not run on purpose, as against one that failed: the toolchain installed is not the
 // recipe's, the integration level's postgres major is not the one it is built for (novox/hq ADR 0469 §1, ADR 0470
 // §4; issue 1473). A step's run returns one and the runner ends the step refused with its text.
@@ -11,3 +13,6 @@ type Refusal struct {
 }
 
 func (r *Refusal) Error() string { return r.Text }
+
+// Refuse is a Refusal with its text formatted.
+func Refuse(format string, args ...any) *Refusal { return &Refusal{Text: fmt.Sprintf(format, args...)} }

go/buildstep/request.go

@@ -0,0 +1,115 @@
+package buildstep
+
+import (
+	"fmt"
+	"path"
+	"regexp"
+	"strings"
+)
+
+var (
+	requestCommitOK     = regexp.MustCompile(`^[0-9a-f]{40}$`)
+	requestRepositoryOK = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._-]*/[A-Za-z0-9][A-Za-z0-9._-]*$`)
+)
+
+// FetchRequest is what a build module's fetch tool is asked: the repository and the full commit, the pull request's
+// ref when only its head carries the commit, the trunk commit to merge onto for a merge preview, and, for a build of a
+// module whose every artifact names its paths, that module's directory and its named paths (novox/hq ADR 0499 clause 4).
+//
+// **The paths come from the builder, not from a manifest** (ADR 0495 clause 1; the lead's decision L8 of R4e): the
+// builder fills Dir and Paths from the indexer's Module value (Path, and KeptInputs2.Paths' keys), and the build module
+// gives the build and test steps a workspace holding those paths, the manifest and its lock files. A request without
+// them builds from the module's directory, as before.
+type FetchRequest struct {
+	Repository string   `json:"repository"`
+	Commit     string   `json:"commit"`
+	Ref        string   `json:"ref,omitempty"`
+	Base       string   `json:"base,omitempty"`
+	Dir        string   `json:"dir,omitempty"`
+	Paths      []string `json:"paths,omitempty"`
+}
+
+// FetchRequestProperties are the JSON schema properties of FetchRequest's dir and paths, for a fetch tool's Input.
+func FetchRequestProperties() map[string]any {
+	return map[string]any{
+		"dir": map[string]any{"type": "string", "description": "the module's directory in the repository (\".\" for its root), with paths"},
+		"paths": map[string]any{"type": "array", "items": map[string]any{"type": "string"},
+			"description": "the paths the module names, relative to dir, from the indexer's kept inputs: the build sees only these, the manifest and its lock files"},
+	}
+}
+
+// Args is r as a tool call's arguments.
+func (r FetchRequest) Args() map[string]any {
+	args := map[string]any{"repository": r.Repository, "commit": r.Commit}
+	for k, v := range map[string]string{"ref": r.Ref, "base": r.Base, "dir": r.Dir} {
+		if v != "" {
+			args[k] = v
+		}
+	}
+	if len(r.Paths) > 0 {
+		args["paths"] = append([]string(nil), r.Paths...)
+	}
+	return args
+}
+
+// ParseFetchRequest reads a fetch tool's arguments; arguments it does not know (a build module's own) are left to the
+// caller. It refuses a repository that is not <owner>/<name>, a commit or a base that is not 40 hex digits, paths with no
+// module directory or a directory with no path, a directory leaving the repository and a path leaving the directory,
+// naming each.
+func ParseFetchRequest(args map[string]any) (FetchRequest, error) {
+	var r FetchRequest
+	r.Repository, _ = args["repository"].(string)
+	r.Commit, _ = args["commit"].(string)
+	r.Ref, _ = args["ref"].(string)
+	r.Base, _ = args["base"].(string)
+	r.Dir, _ = args["dir"].(string)
+	switch v := args["paths"].(type) {
+	case nil:
+	case []string:
+		r.Paths = append([]string(nil), v...)
+	case []any:
+		for _, p := range v {
+			s, ok := p.(string)
+			if !ok {
+				return FetchRequest{}, fmt.Errorf("paths is a list of strings")
+			}
+			r.Paths = append(r.Paths, s)
+		}
+	default:
+		return FetchRequest{}, fmt.Errorf("paths is a list of strings")
+	}
+	return r, r.Check()
+}
+
+// Check is what ParseFetchRequest refuses.
+func (r FetchRequest) Check() error {
+	if !requestRepositoryOK.MatchString(r.Repository) || strings.Contains(r.Repository, "..") {
+		return fmt.Errorf("%q is not a repository, <owner>/<name>", r.Repository)
+	}
+	if !requestCommitOK.MatchString(r.Commit) {
+		return fmt.Errorf("%q is not a full commit (40 hex digits)", r.Commit)
+	}
+	if r.Base != "" && !requestCommitOK.MatchString(r.Base) {
+		return fmt.Errorf("%q is not a trunk commit (40 hex digits)", r.Base)
+	}
+	switch {
+	case len(r.Paths) > 0 && r.Dir == "":
+		return fmt.Errorf("the request names paths and names no module directory (dir) they are relative to")
+	case len(r.Paths) == 0 && r.Dir != "":
+		return fmt.Errorf("the request names a module directory and no path")
+	}
+	if r.Dir != "" && (outside(r.Dir) || strings.HasPrefix(r.Dir, "/")) {
+		return fmt.Errorf("the module directory %q leaves the repository", r.Dir)
+	}
+	for _, p := range r.Paths {
+		if p == "" || strings.HasPrefix(p, "/") || outside(p) || path.Clean(p) == "." {
+			return fmt.Errorf("the path %q leaves the module's directory or is not a path in it", p)
+		}
+	}
+	return nil
+}
+
+func outside(p string) bool {
+	c := path.Clean(p)
+	return c == ".." || strings.HasPrefix(c, "../")
+}

go/buildstep/request_test.go

@@ -0,0 +1,57 @@
+package buildstep
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// A build's fetch is handed the paths of a module that names them (novox/hq ADR 0499 clause 4): the builder fills them
+// from the indexer's kept inputs and the build module reads them from the call, never from the manifest (ADR 0495
+// clause 1). The request survives the trip through a tool call's arguments.
+func TestAFetchRequestCarriesTheNamedPathsThroughTheToolCall(t *testing.T) {
+	req := FetchRequest{Repository: "novox/mesh-sdk", Commit: strings.Repeat("a", 40), Ref: "refs/pull/7/head",
+		Dir: ".", Paths: []string{"package.json", "src"}}
+	args := req.Args()
+	// A tool call's arguments arrive as JSON: lists of any.
+	args["paths"] = []any{"package.json", "src"}
+	got, err := ParseFetchRequest(args)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(got, req) {
+		t.Fatalf("got %+v, want %+v", got, req)
+	}
+	plain, err := ParseFetchRequest(map[string]any{"repository": "novox/x", "commit": strings.Repeat("b", 40),
+		"base": strings.Repeat("c", 40), "beside": []any{}})
+	if err != nil || plain.Paths != nil || plain.Base != strings.Repeat("c", 40) {
+		t.Fatalf("a request without paths: %+v, %v", plain, err)
+	}
+
+	ok := map[string]any{"repository": "novox/x", "commit": strings.Repeat("b", 40)}
+	for _, c := range []struct {
+		set  map[string]any
+		says string
+	}{
+		{map[string]any{"repository": "novox"}, "is not a repository"},
+		{map[string]any{"repository": "novox/../x"}, "is not a repository"},
+		{map[string]any{"commit": "abc"}, "is not a full commit"},
+		{map[string]any{"base": "abc"}, "is not a trunk commit"},
+		{map[string]any{"paths": []any{"src"}}, "names no module directory"},
+		{map[string]any{"dir": "modules/a", "paths": []any{"../b"}}, "leaves the module's directory"},
+		{map[string]any{"dir": "../a", "paths": []any{"src"}}, "leaves the repository"},
+		{map[string]any{"dir": "modules/a", "paths": []any{3}}, "paths is a list of strings"},
+		{map[string]any{"dir": "modules/a"}, "names a module directory and no path"},
+	} {
+		args := map[string]any{}
+		for k, v := range ok {
+			args[k] = v
+		}
+		for k, v := range c.set {
+			args[k] = v
+		}
+		if _, err := ParseFetchRequest(args); err == nil || !strings.Contains(err.Error(), c.says) {
+			t.Errorf("%v: %v, wanted a refusal saying %q", c.set, err, c.says)
+		}
+	}
+}

go/buildstep/seat_tools.go

@@ -0,0 +1,39 @@
+package buildstep
+
+import (
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// SeatTools are a build seat's verbs on one node, as its holder serves them (novox/hq ADR 0525 §10; mesh-sdk catalogue
+// buildSeatVerbs): `<seat>.current` (what the node runs, its capacity, whether it is paused), `<seat>.pause` and
+// `<seat>.resume`, the pause kept on the node's pause key by the puller. what names the asks in the descriptions ("Go").
+func SeatTools(seat, what string, p *Puller) []stdio.Tool {
+	verb := func(name, description string, run func() (any, error)) stdio.Tool {
+		return stdio.Tool{Name: seat + "." + name, Description: description,
+			Input: map[string]any{"type": "object", "properties": map[string]any{}},
+			Run:   func(map[string]any) (any, error) { return run() }}
+	}
+	current := func() (any, error) {
+		c := p.CapacityDetail()
+		return map[string]any{"node": p.Node, "capacity": c.Effective, "capacity_why": c.Why, "capacity_detail": c,
+			"running": p.Running(), "paused": p.Paused()}, nil
+	}
+	return []stdio.Tool{
+		verb("current", "The "+what+" asks this node runs now (each one's id, kind and when it started), its build capacity (the configured one, "+
+			"bounded by the cores its node's build slice gives over the cores a step needs) and why, "+
+			"and whether it is paused.", current),
+		verb("pause", "Take no new "+what+" ask on this node until resumed; an ask running here ends in its place. Kept "+
+			"across a restart (the node's pause key).", func() (any, error) {
+			if err := p.Pause("the seat's pause verb"); err != nil {
+				return nil, err
+			}
+			return current()
+		}),
+		verb("resume", "Take "+what+" asks again on this node.", func() (any, error) {
+			if err := p.Resume("the seat's resume verb"); err != nil {
+				return nil, err
+			}
+			return current()
+		}),
+	}
+}

go/buildstep/seat_tools_test.go

@@ -0,0 +1,52 @@
+package buildstep
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// 1887/A9a, ADR 0525 §10: a build seat's verbs are <seat>.current, .pause and .resume; current names the ask running,
+// pause stops the puller taking asks, resume lets it take them again.
+func TestSeatToolsCurrentPauseResume(t *testing.T) {
+	src, st := NewFakeAsks(), newSteps()
+	release := make(chan struct{})
+	p := &Puller{Source: src, Language: delivery.AskGo, Node: "shanks", Put: st.put, Capacity: func() int { return 1 },
+		PullWait: 10 * time.Millisecond, Run: func(ctx context.Context, a delivery.StepAsk) (any, error) { <-release; return nil, nil }}
+	tools := map[string]func(map[string]any) (any, error){}
+	for _, tool := range SeatTools("node-build-go", "Go", p) {
+		tools[tool.Name] = tool.Run
+	}
+	for _, name := range []string{"node-build-go.current", "node-build-go.pause", "node-build-go.resume"} {
+		if tools[name] == nil {
+			t.Fatalf("no %s", name)
+		}
+	}
+	a := testAsk(delivery.AskDelivery)
+	_ = src.PublishAsk(a)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go p.Pull(ctx)
+	waitFor(t, "the ask running", func() bool { return p.InHand() == 1 })
+	out, _ := tools["node-build-go.current"](nil)
+	cur := out.(map[string]any)
+	running := cur["running"].([]RunningAsk)
+	if len(running) != 1 || running[0].ID != a.ID || running[0].Module != "m" || cur["capacity"] != 1 || cur["paused"] != false {
+		t.Fatalf("current = %+v", cur)
+	}
+	if out, err := tools["node-build-go.pause"](nil); err != nil || out.(map[string]any)["paused"] != true {
+		t.Fatalf("pause = %v, %v", out, err)
+	}
+	close(release)
+	_ = src.PublishAsk(testAsk(delivery.AskDelivery))
+	time.Sleep(50 * time.Millisecond)
+	if src.Waiting(delivery.AskDelivery) != 1 {
+		t.Fatal("a paused node took an ask")
+	}
+	if _, err := tools["node-build-go.resume"](nil); err != nil {
+		t.Fatal(err)
+	}
+	waitFor(t, "the ask taken after the resume", func() bool { return src.Waiting(delivery.AskDelivery) == 0 })
+}

go/buildstep/stale.go

@@ -0,0 +1,365 @@
+package buildstep
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// **A step left running** (novox/hq issue 1890, note 5). A build module that stops while a step runs leaves its key in
+// state running for good: nothing else writes that key's end, and the stream's redelivery only rewrites it when the same
+// ask comes back. At its start a module ends the steps its node left running by another process (EndStale: every step
+// names its owner, delivery.Step.Owner; note 21), and its step-end tool ends one by hand (EndOne). The conformance kit's
+// left-running case holds every build module to the start sweep (conformance.LeftRunning).
+
+// RestartReason is why a step a previous process left running is ended.
+const RestartReason = "the build module restarted while it ran"
+
+// Boot is when this process began. A step with no owner (written by an older build) started at or after it is taken
+// for this process's, which may still run it, so EndOne refuses it.
+var Boot = time.Now()
+
+// Owner is this process as a step's owner (delivery.Step.Owner): `<boot id>.<pid>.<start>`, the node's boot id
+// (/proc/sys/kernel/random/boot_id), the pid and Boot in milliseconds, base 36. The start keeps two processes apart
+// that a reboot or a pid namespace gave the same pid. A running step whose owner is another is a previous process's.
+var Owner = ownerOf(bootID, os.Getpid(), Boot)
+
+// bootID is the node's boot id as Owner holds it; noBootID when it could not be read, which EndStaleAtStart says once.
+var bootID = readBootID()
+
+const noBootID = "no-boot-id"
+
+func ownerOf(bootID string, pid int, start time.Time) string {
+	return bootID + "." + strconv.Itoa(pid) + "." + strconv.FormatInt(start.UnixMilli(), 36)
+}
+
+// readBootID is the node's boot id, or noBootID where it cannot be read (the pid and the start then tell the processes
+// apart).
+func readBootID() string {
+	b, err := os.ReadFile("/proc/sys/kernel/random/boot_id")
+	if id := strings.TrimSpace(string(b)); err == nil && id != "" {
+		return id
+	}
+	return noBootID
+}
+
+// Scan reads and writes a steps state with its revisions: its keys, a key's stored value and revision (nil and 0 for
+// none), a write that lands only while the key is still at the revision read (KeptState.Update), and a delete of a key
+// still at the revision read; both fail with stdio.ErrChanged when another writer was first.
+type Scan struct {
+	Keys   func() ([]string, error)
+	Get    func(key string) (json.RawMessage, uint64, error)
+	Update func(key string, value any, revision uint64) (uint64, error)
+	Delete func(key string, revision uint64) error
+}
+
+// ScanOf is the Scan of a state the process keeps.
+//
+// Its Delete reads the key again and deletes it only while it is still at the revision read: the runtime's
+// mesh/state.delete takes no revision yet, so a write landing between that read and the delete (a few milliseconds) is
+// deleted with it. For a step key that is a redelivered ask begun on this node in that moment: its running key leaves
+// the steps state until its run writes its end, which its asker still reads (a watch takes puts only).
+func ScanOf(s stdio.KeptState) Scan {
+	get := func(key string) (json.RawMessage, uint64, error) {
+		e, err := s.Get(key)
+		if err != nil || e == nil {
+			return nil, 0, err
+		}
+		return e.Value, e.Revision, nil
+	}
+	return Scan{Keys: s.Keys, Update: s.Update, Get: get, Delete: func(key string, revision uint64) error {
+		_, rev, err := get(key)
+		if err != nil {
+			return err
+		}
+		if rev != revision {
+			return stdio.ErrChanged
+		}
+		return s.Delete(key)
+	}}
+}
+
+// isAsk says a step is a pulled ask's: its key is <node>.<ask id> and its tool is "<kind> ask" (a hand-started step
+// has the tool's name). An ask's key is the stream's to settle, never a restart's: the puller leaves an ask it was
+// running unacknowledged so the stream redelivers it, and the asker's wait takes the first end it reads on the key.
+// A key a gone process owns is deleted, never ended (EndStale); one with no owner is ended only once the asker's bound
+// has passed (delivery.StepBound), when it is nobody's.
+func isAsk(key string, s delivery.Step) bool {
+	_, _, err := delivery.ParseAskStepKey(key)
+	return err == nil && strings.HasSuffix(s.Tool, " ask")
+}
+
+// AskWhat says what an ask is, in one line: its kind, and its repository, head and levels, or its module and
+// fingerprint.
+func AskWhat(a delivery.StepAsk) string {
+	short := func(s string) string {
+		if len(s) > 12 {
+			return s[:12]
+		}
+		return s
+	}
+	str := func(m map[string]any, k string) string { v, _ := m[k].(string); return v }
+	parts := []string{a.Kind + " ask"}
+	switch {
+	case a.Check != nil:
+		parts = append(parts, str(a.Check.Fetch, "repository")+"@"+short(str(a.Check.Fetch, "commit")), "levels "+strings.Join(a.Check.Levels, ","))
+		if a.Check.Run != "" {
+			parts = append(parts, "run "+a.Check.Run)
+		}
+	case a.Build != nil:
+		parts = append(parts, "module "+a.Build.Module)
+		if r := str(a.Build.Fetch, "repository"); r != "" {
+			parts = append(parts, r+"@"+short(str(a.Build.Fetch, "commit")))
+		}
+		if a.Build.FP != "" {
+			parts = append(parts, "fp "+short(a.Build.FP))
+		}
+	case a.Compose != nil:
+		parts = append(parts, "compose", str(a.Compose.Fetch, "repository")+"@"+short(str(a.Compose.Fetch, "commit")))
+	}
+	return strings.Join(parts, ", ")
+}
+
+// endRunning writes step ended failed with why, only while its key is still at revision.
+func endRunning(scan Scan, key string, step delivery.Step, revision uint64, why string) error {
+	step.State, step.Reason, step.Ended, step.Result = delivery.StepFailed, why, now().UTC(), nil
+	raw, err := delivery.EncodeStep(step)
+	if err != nil {
+		return err
+	}
+	_, err = scan.Update(key, json.RawMessage(raw), revision)
+	return err
+}
+
+// EndStale ends this node's running steps that no process of this module runs any more, and answers their ids. Only keys
+// of node are read; a value that is no step is left alone.
+//   - A hand-started step with an owner (delivery.Step.Owner) that is not this process (Owner) is ended failed with
+//     RestartReason at once, whatever its age: its process is gone and nothing redelivers it, so nothing else would
+//     write its end (issue 1890, note 21).
+//   - A pulled ask's step with an owner that is not this process is deleted, not ended (novox/hq ADR 0525 §6): the
+//     stream redelivers an ask whose node stopped (the puller neither ends nor acknowledges one at its stop), and its
+//     asker takes the first end it reads, so an end written here would fail a check the redelivery would still run. Its
+//     asker's watch takes puts only and keeps waiting for the redelivery's key, its bound the backstop; the stale running
+//     key leaves the steps state, and with it the delivery view's and the checker's count of what runs (note 21: it
+//     held one of a build node's two slots).
+//   - A step owned by this process is left: it may run now. A redelivered ask begun on this node is owned by it.
+//   - A step with no owner (written by an older build) keeps the earlier rule: a hand-started step started before
+//     `before` (the start of this process) is ended; a pulled ask is left to the stream's redelivery (isAsk) until its
+//     start is older than delivery.StepBound, and then ended "past the step bound: its asker stopped waiting at <time>".
+//
+// Each end and delete is logged, naming the step, its owner and why. A key written by another writer since it was read
+// (a redelivered ask's start, a real end) is skipped.
+func EndStale(scan Scan, node string, before time.Time, logf func(string, ...any)) ([]string, error) {
+	keys, err := scan.Keys()
+	if err != nil {
+		return nil, fmt.Errorf("buildstep: listing the steps of %s: %w", node, err)
+	}
+	var ended []string
+	for _, k := range keys {
+		n, _, perr := delivery.ParseStepKey(k)
+		if perr != nil || n != node {
+			continue
+		}
+		raw, rev, err := scan.Get(k)
+		if err != nil {
+			return ended, fmt.Errorf("buildstep: reading the step %s: %w", k, err)
+		}
+		if len(raw) == 0 {
+			continue
+		}
+		step, err := delivery.DecodeStep(raw)
+		if err != nil || step.State != delivery.StepRunning {
+			continue
+		}
+		why, said := staleWhy(k, step, before)
+		if why == "" {
+			continue
+		}
+		done := "ended"
+		if step.Owner != "" && isAsk(k, step) {
+			done = "deleted, left to the stream's redelivery"
+			if scan.Delete == nil {
+				err = fmt.Errorf("the steps state takes no delete")
+			} else {
+				err = scan.Delete(k, rev)
+			}
+		} else {
+			err = endRunning(scan, k, step, rev, why)
+		}
+		if err != nil {
+			if errors.Is(err, stdio.ErrChanged) {
+				continue
+			}
+			return ended, fmt.Errorf("buildstep: ending the step %s: %w", k, err)
+		}
+		if logf != nil {
+			logf("the step %s (%s, started %s) was left running and is %s: %s; %s", k, step.Tool,
+				step.Started.UTC().Format(time.RFC3339), done, why, said)
+		}
+		ended = append(ended, step.ID)
+	}
+	return ended, nil
+}
+
+// staleWhy is why a running step is ended (or, for an ask with an owner, deleted) by EndStale and what the log says of
+// its owner, or "" to leave it.
+func staleWhy(key string, step delivery.Step, before time.Time) (why, said string) {
+	switch {
+	case step.Owner == Owner:
+		return "", ""
+	case step.Owner != "":
+		return RestartReason, "its owner " + step.Owner + " is not this process " + Owner
+	case isAsk(key, step):
+		if !step.Started.Add(delivery.StepBound).Before(now()) {
+			return "", ""
+		}
+		return "past the step bound: its asker stopped waiting at " + step.Started.Add(delivery.StepBound).UTC().Format("2006-01-02T15:04:05Z"),
+			"it names no owner (an older build wrote it)"
+	case step.Started.Before(before):
+		return RestartReason, "it names no owner (an older build wrote it) and started before this process"
+	}
+	return "", ""
+}
+
+// EndOne ends this node's running step id (or the key <node>.<id>) as failed with why. A step that is not running is
+// refused, and so is one this process owns (Owner; for a step with no owner, one started since Boot: it may still run,
+// whether a pulled ask or a step a tool started), one live reports as held, and one whose key changed since it was read.
+func EndOne(scan Scan, node, id, why string, live func(id string) bool) (delivery.Step, error) {
+	id = strings.TrimSpace(id)
+	if n, rest, ok := strings.Cut(id, "."); ok {
+		if n != node {
+			return delivery.Step{}, fmt.Errorf("the step %q is of node %q, this module runs on %q", id, n, node)
+		}
+		id = rest
+	}
+	if strings.TrimSpace(why) == "" {
+		return delivery.Step{}, fmt.Errorf("say why the step is ended (why)")
+	}
+	key, err := delivery.StepKey(node, id)
+	if err != nil {
+		return delivery.Step{}, err
+	}
+	raw, rev, err := scan.Get(key)
+	if err != nil {
+		return delivery.Step{}, err
+	}
+	if len(raw) == 0 {
+		return delivery.Step{}, fmt.Errorf("no step %s in the steps state", key)
+	}
+	step, err := delivery.DecodeStep(raw)
+	if err != nil {
+		return delivery.Step{}, err
+	}
+	if step.State != delivery.StepRunning {
+		return delivery.Step{}, fmt.Errorf("the step %s is %s, not running", key, step.State)
+	}
+	if step.Owner == Owner || (step.Owner == "" && !step.Started.Before(Boot)) || (live != nil && live(id)) {
+		return delivery.Step{}, fmt.Errorf("the step %s was started by this process and may run now; only a step a previous process left is ended", key)
+	}
+	if err := endRunning(scan, key, step, rev, why); err != nil {
+		if errors.Is(err, stdio.ErrChanged) {
+			return delivery.Step{}, fmt.Errorf("the step %s changed while it was being ended; read it again", key)
+		}
+		return delivery.Step{}, err
+	}
+	step.State, step.Reason = delivery.StepFailed, why
+	return step, nil
+}
+
+// StepEndTool is the module's step-end tool, named name (build_go_step_end): it ends one step left running, with a
+// reason, refusing one this process started. p may be nil.
+func StepEndTool(name string, node string, scan Scan, p *Puller) stdio.Tool {
+	return stdio.Tool{Name: name,
+		Description: "End one step of this machine that is stuck in state running (for instance left by a restart of the module) " +
+			"as failed, with the reason given; its asker then sees it over, so ending an ask still in its stream fails its asker. " +
+			"A step not running, or one this process started, is refused. " +
+			"id is the step id or the key <node>.<id>.",
+		Input: map[string]any{"type": "object", "required": []string{"id", "why"}, "properties": map[string]any{
+			"id":  map[string]any{"type": "string", "description": "the step id, or the key <node>.<id>"},
+			"why": map[string]any{"type": "string", "description": "why it is ended; it becomes the step's reason"}}},
+		Run: func(args map[string]any) (any, error) {
+			id, _ := args["id"].(string)
+			why, _ := args["why"].(string)
+			var live func(string) bool
+			if p != nil {
+				live = func(id string) bool {
+					for _, r := range p.Running() {
+						if r.ID == id {
+							return true
+						}
+					}
+					return false
+				}
+			}
+			return EndOne(scan, node, id, why, live)
+		}}
+}
+
+// StaleAttempts and StaleRetry bound EndStaleAtStart's tries: the steps state is readable once the runtime serves.
+var (
+	StaleAttempts = 6
+	StaleRetry    = 5 * time.Second
+)
+
+// StaleServed is what EndStaleAtStart waits for before it reads the steps state: the runtime serving (stdio.Served).
+// The conformance kit's left-running case (conformance.LeftRunning) hands it a closed channel, to run a module's own
+// start sweep in its test.
+var StaleServed = stdio.Served
+
+// EndStaleAtStart is what a build module runs once at its start, in a goroutine: it waits for the runtime to serve,
+// then ends this node's steps a previous process left running (EndStale), trying again when the state cannot be read
+// yet. A step names its owner, so `before` (the start of this process) matters only for a step with no owner, written
+// by an older build: such a step started before it is a previous process's. When the node's boot id cannot be read it
+// says so once: Owner then tells processes apart by their pid and start only.
+func EndStaleAtStart(ctx context.Context, scan Scan, node string, before time.Time, logf func(string, ...any)) {
+	select {
+	case <-ctx.Done():
+		return
+	case <-StaleServed():
+	}
+	if bootID == noBootID && logf != nil {
+		logf("the boot id of %s cannot be read (/proc/sys/kernel/random/boot_id): its steps' owner is %s, told apart by pid and start only", node, Owner)
+	}
+	for attempt := 1; ; attempt++ {
+		ended, err := EndStale(scan, node, before, logf)
+		if err == nil {
+			if logf != nil {
+				logf("%d steps of %s left running by a previous process ended", len(ended), node)
+			}
+			return
+		}
+		if logf != nil {
+			logf("ending the steps left running (try %d of %d): %v", attempt, StaleAttempts, err)
+		}
+		if attempt >= StaleAttempts {
+			return
+		}
+		select {
+		case <-ctx.Done():
+			return
+		case <-time.After(StaleRetry):
+		}
+	}
+}
+
+// EndStaleRound is EndStale as the module's periodic round runs it: at once, and only when the runtime serves (a round
+// before that is skipped, the start's EndStaleAtStart and the next round cover it). It ends the steps a previous
+// process left and the asks past delivery.StepBound.
+func EndStaleRound(scan Scan, node string, logf func(string, ...any)) {
+	select {
+	case <-stdio.Served():
+	default:
+		return
+	}
+	if _, err := EndStale(scan, node, Boot, logf); err != nil && logf != nil {
+		logf("ending the steps left running: %v", err)
+	}
+}

go/buildstep/stale_test.go

@@ -0,0 +1,161 @@
+package buildstep
+
+import (
+	"encoding/json"
+	"fmt"
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"strings"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// scanOf is the steps a keys double holds, last value per key, its revision the count of its puts; a write through
+// Update lands only at the revision read, as the state's does. race, when set, runs once before the next Update's check.
+func scanOf(k *keys, race func(key string)) Scan {
+	return Scan{
+		Keys: func() ([]string, error) {
+			k.mu.Lock()
+			defer k.mu.Unlock()
+			var out []string
+			for key := range k.puts {
+				out = append(out, key)
+			}
+			return out, nil
+		},
+		Get: func(key string) (json.RawMessage, uint64, error) {
+			k.mu.Lock()
+			defer k.mu.Unlock()
+			s, ok := k.puts[key]
+			if !ok {
+				return nil, 0, nil
+			}
+			raw, err := delivery.EncodeStep(s[len(s)-1])
+			return raw, uint64(len(s)), err
+		},
+		Delete: func(key string, revision uint64) error {
+			k.mu.Lock()
+			defer k.mu.Unlock()
+			if uint64(len(k.puts[key])) != revision {
+				return stdio.ErrChanged
+			}
+			delete(k.puts, key)
+			return nil
+		},
+		Update: func(key string, value any, revision uint64) (uint64, error) {
+			if race != nil {
+				race(key)
+			}
+			k.mu.Lock()
+			n := uint64(len(k.puts[key]))
+			k.mu.Unlock()
+			if n != revision {
+				return 0, stdio.ErrChanged
+			}
+			return k.put(key, value)
+		},
+	}
+}
+
+// 1890 and 1890/AC6: EndStale ends this node's hand-started running steps of another owner at once, whatever their age,
+// and deletes its asks of another owner (the stream redelivers them, ADR 0525 §6); of
+// the steps with no owner (an older build's), the hand-started ones left running before the process began and the asks
+// past the step bound (a younger ask is the stream's to redeliver); never a step this process owns or a key written
+// meanwhile. EndOne ends one by hand, never one this process owns or started.
+func TestEndStaleAndEndOne(t *testing.T) {
+	k := newKeys()
+	boot := time.Now()
+	oldBoot := Boot
+	Boot = boot
+	defer func() { Boot = oldBoot }()
+	gone := ownerOf("b00t", 4242, boot.Add(-time.Hour))
+	put := func(node, id, tool, state string, started time.Time, owner string) {
+		key, _ := delivery.StepKey(node, id)
+		_, _ = k.put(key, json.RawMessage(mustStep(t, delivery.Step{ID: id, Tool: tool, Node: node, State: state, Started: started, Owner: owner})))
+	}
+	put("ace", "old1", "build_go_fetch", delivery.StepRunning, boot.Add(-time.Hour), "")
+	put("ace", "mjk3l9x0abcdef", "check ask", delivery.StepRunning, boot.Add(-time.Hour), "")
+	put("ace", "mjk3l9x0abcdee", "check ask", delivery.StepRunning, time.Now().Add(-5*time.Minute), "")
+	put("ace", "mjk3l9x0abcded", "check ask", delivery.StepRunning, time.Now().Add(-5*time.Minute), gone) // note 21's ghost
+	put("ace", "gone2", "build_go_test", delivery.StepRunning, boot.Add(time.Second), gone)
+	put("ace", "mine1", "check ask", delivery.StepRunning, boot.Add(-time.Hour), Owner)
+	put("ace", "raced1", "build_go_test", delivery.StepRunning, boot.Add(-time.Hour), "")
+	put("ace", "new1", "build_go_fetch", delivery.StepRunning, boot.Add(time.Second), "")
+	put("ace", "done1", "build_go_fetch", delivery.StepPassed, boot.Add(-time.Hour), gone)
+	put("g14", "other1", "build_go_fetch", delivery.StepRunning, boot.Add(-time.Hour), gone)
+	// raced1 is ended by its own run between the read and the write.
+	raced := false
+	scan := scanOf(k, func(key string) {
+		if key == "ace.raced1" && !raced {
+			raced = true
+			put("ace", "raced1", "build_go_test", delivery.StepPassed, boot.Add(-time.Hour), "")
+		}
+	})
+	var said []string
+	ended, err := EndStale(scan, "ace", boot, func(f string, a ...any) { said = append(said, fmt.Sprintf(f, a...)) })
+	if err != nil || len(ended) != 4 {
+		t.Fatalf("ended %v, %v", ended, err)
+	}
+	if _, held := k.puts["ace.mjk3l9x0abcded"]; held {
+		t.Errorf("the ghost ask's key is still held: %+v", k.last("ace.mjk3l9x0abcded"))
+	}
+	for _, key := range []string{"ace.old1", "ace.gone2"} {
+		if s := k.last(key); s.State != delivery.StepFailed || s.Reason != RestartReason || s.Ended.IsZero() {
+			t.Errorf("%s = %+v", key, s)
+		}
+	}
+	if s := k.last("ace.mjk3l9x0abcdef"); s.State != delivery.StepFailed || !strings.HasPrefix(s.Reason, "past the step bound: its asker stopped waiting at ") {
+		t.Errorf("the old ask = %+v", s)
+	}
+	if log := strings.Join(said, "\n"); !strings.Contains(log, "ace.mjk3l9x0abcded") || !strings.Contains(log, "deleted, left to the stream's redelivery") || !strings.Contains(log, "its owner "+gone+" is not this process "+Owner) {
+		t.Errorf("the log does not name the ghost and its owner:\n%s", log)
+	}
+	for key, state := range map[string]string{"ace.mjk3l9x0abcdee": delivery.StepRunning, "ace.mine1": delivery.StepRunning, "ace.raced1": delivery.StepPassed,
+		"ace.new1": delivery.StepRunning, "ace.done1": delivery.StepPassed, "g14.other1": delivery.StepRunning} {
+		if s := k.last(key); s.State != state {
+			t.Errorf("%s = %s, want %s", key, s.State, state)
+		}
+	}
+	// EndOne: refuses without why, a held step, one this process owns or (with no owner) started, a step not running and
+	// another node's; ends a step a previous process left.
+	for _, c := range []struct{ id, why string }{{"old1", ""}, {"new1", "stuck"}, {"mine1", "stuck"}, {"done1", "x"}, {"g14.other1", "x"}} {
+		if _, err := EndOne(scan, "ace", c.id, c.why, nil); err == nil {
+			t.Errorf("ended %s with why %q", c.id, c.why)
+		}
+	}
+	put("ace", "old2", "build_go_fetch", delivery.StepRunning, boot.Add(time.Second), gone)
+	if _, err := EndOne(scan, "ace", "old2", "x", func(string) bool { return true }); err == nil {
+		t.Error("ended a held step")
+	}
+	if _, err := EndOne(scan, "ace", "ace.old2", "stuck for good", nil); err != nil {
+		t.Fatal(err)
+	}
+	if s := k.last("ace.old2"); s.State != delivery.StepFailed || s.Reason != "stuck for good" || s.Owner != gone {
+		t.Errorf("old2 = %+v", s)
+	}
+	if a, b := ownerOf("b", 1, boot), ownerOf("b", 1, boot.Add(time.Second)); a == b {
+		t.Errorf("two starts of one pid share the owner %q", a)
+	}
+}
+
+func mustStep(t *testing.T, s delivery.Step) []byte {
+	t.Helper()
+	raw, err := delivery.EncodeStep(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return raw
+}
+
+// 1890: AskWhat names the repository, head and levels of a check ask and the module of a build ask.
+func TestAskWhat(t *testing.T) {
+	check := delivery.StepAsk{Kind: "check", Check: &delivery.CheckJob{Fetch: map[string]any{"repository": "novox/mesh-sdk", "commit": "0123456789abcdef0123"}, Levels: []string{"unit", "integration"}}}
+	if got, want := AskWhat(check), "check ask, novox/mesh-sdk@0123456789ab, levels unit,integration"; got != want {
+		t.Errorf("check = %q", got)
+	}
+	build := delivery.StepAsk{Kind: "delivery", Build: &delivery.BuildJob{Module: "mesh-x", FP: "abcdef0123456789"}}
+	if got, want := AskWhat(build), "delivery ask, module mesh-x, fp abcdef012345"; got != want {
+		t.Errorf("build = %q", got)
+	}
+}

go/buildstep/step.go

@@ -1,6 +1,7 @@
 // Package buildstep is what both build modules share: the runner of a long step that answers a tool call at once
 // and ends on its key in the module's `steps` state (novox/hq ADR 0469 §2; issue 1471), the toolchain guard
-// (issue 1473) and the fetch of one commit over SSH (issue 1474).
+// (issue 1473), the fetch of one commit over SSH (issue 1474), and the failure contract of a test level with the parsers
+// of go test -json and node --test's TAP that fill it (failure.go, issue 1901; its conformance kit is package conformance).
 package buildstep
 
 import (
@@ -10,6 +11,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"log"
 	"strconv"
 	"time"
 
@@ -42,43 +44,89 @@ func NewID() string {
 // the error's text, or refused when the error is a *Refusal; a panic in run ends the step failed, naming it, and
 // the process goes on. If the running write fails, nothing was started and Start answers the error.
 func Start(ctx context.Context, put Put, node, tool string, run func(ctx context.Context) (result any, err error)) (string, error) {
-	step := delivery.Step{ID: NewID(), Tool: tool, Node: node, State: delivery.StepRunning, Started: now().UTC()}
-	key, err := delivery.StepKey(node, step.ID)
+	step, key, err := begin(put, node, tool, NewID(), "")
 	if err != nil {
 		return "", err
 	}
-	if err := write(put, key, step); err != nil {
-		return "", fmt.Errorf("buildstep: writing the running step %s: %w", key, err)
-	}
-	go func() {
-		result, err := protect(ctx, run)
-		step.Ended = now().UTC()
-		switch ref := (*Refusal)(nil); {
-		case err == nil:
-			step.State = delivery.StepPassed
-			if result != nil {
-				raw, merr := json.Marshal(result)
-				if merr != nil {
-					step.State, step.Reason = delivery.StepFailed, "the result is not JSON: "+merr.Error()
-				} else {
-					step.Result = raw
-				}
-			}
-		case errors.As(err, &ref):
-			step.State, step.Reason = delivery.StepRefused, err.Error()
-		default:
-			step.State, step.Reason = delivery.StepFailed, err.Error()
-		}
-		for attempt := 1; ; attempt++ {
-			if werr := write(put, key, step); werr == nil || attempt >= EndAttempts {
-				return
-			}
-			time.Sleep(EndRetry)
-		}
-	}()
+	go end(ctx, put, key, step, run)
 	return step.ID, nil
 }
 
+// begin writes the step running under id, owned by this process (Owner).
+func begin(put Put, node, tool, id, what string) (delivery.Step, string, error) {
+	step := delivery.Step{ID: id, Tool: tool, Node: node, State: delivery.StepRunning, Started: now().UTC(), What: what, Owner: Owner}
+	key, err := delivery.StepKey(node, step.ID)
+	if err != nil {
+		return delivery.Step{}, "", err
+	}
+	if err := write(put, key, step); err != nil {
+		return delivery.Step{}, "", fmt.Errorf("buildstep: writing the running step %s: %w", key, err)
+	}
+	return step, key, nil
+}
+
+// end runs run and writes the step's end.
+func end(ctx context.Context, put Put, key string, step delivery.Step, run func(ctx context.Context) (any, error)) {
+	result, err := protect(ctx, run)
+	_ = finish(put, key, step, result, err, log.Printf) // finish says a refused end itself
+}
+
+// finish writes the step's end from run's result or error: passed, failed or refused (a *Refusal). A write that fails is
+// tried EndAttempts times. When the whole end is refused every time (a result the state will not take: issue 1930), the
+// refusal is logged and a small failed end without the result is written instead, naming the write's error, so the
+// step's reader learns it is over and why. finish answers an error only when no end could be written at all, and then
+// the step's ask is not acknowledged as done.
+func finish(put Put, key string, step delivery.Step, result any, err error, logf func(format string, args ...any)) error {
+	step.Ended = now().UTC()
+	switch ref := (*Refusal)(nil); {
+	case err == nil:
+		step.State = delivery.StepPassed
+		if result != nil {
+			raw, merr := json.Marshal(result)
+			if merr != nil {
+				step.State, step.Reason = delivery.StepFailed, "the result is not JSON: "+merr.Error()
+			} else {
+				step.Result = raw
+			}
+		}
+	case errors.As(err, &ref):
+		step.State, step.Reason = delivery.StepRefused, err.Error()
+	default:
+		step.State, step.Reason = delivery.StepFailed, err.Error()
+	}
+	werr := writeEnd(put, key, step)
+	if werr == nil {
+		return nil
+	}
+	if logf != nil {
+		logf("the end of the step %s (%s) could not be written in %d tries: %v", key, step.State, EndAttempts, werr)
+	}
+	ended := step.State
+	why := fmt.Sprintf("the step ended %s, and its end could not be written: %v", ended, werr)
+	if step.Reason != "" {
+		why = fmt.Sprintf("the step ended %s (%s), and its end could not be written: %v", ended, step.Reason, werr)
+	}
+	step.State, step.Reason, step.Result = delivery.StepFailed, why, nil
+	if ferr := writeEnd(put, key, step); ferr != nil {
+		if logf != nil {
+			logf("the failed end of the step %s could not be written either: %v", key, ferr)
+		}
+		return fmt.Errorf("buildstep: no end of the step %s could be written: %w", key, ferr)
+	}
+	return nil
+}
+
+// writeEnd writes the step's end, trying EndAttempts times.
+func writeEnd(put Put, key string, step delivery.Step) error {
+	for attempt := 1; ; attempt++ {
+		werr := write(put, key, step)
+		if werr == nil || attempt >= EndAttempts {
+			return werr
+		}
+		time.Sleep(EndRetry)
+	}
+}
+
 // protect is run with a panic turned into the error that ends the step.
 func protect(ctx context.Context, run func(ctx context.Context) (any, error)) (result any, err error) {
 	defer func() {

go/buildstep/step_test.go

@@ -70,8 +70,9 @@ func TestStartAnswersAtOnceWithTheStepRunning(t *testing.T) {
 		t.Errorf("Start took %v", d)
 	}
 	s := k.last("ace." + id)
-	if s.State != delivery.StepRunning || s.Tool != "fetch" || s.Node != "ace" || s.ID != id || s.Started.IsZero() {
-		t.Errorf("step = %+v", s)
+	// 1890/AC5: the running key names this process as its owner.
+	if s.State != delivery.StepRunning || s.Tool != "fetch" || s.Node != "ace" || s.ID != id || s.Started.IsZero() || s.Owner != Owner || Owner == "" {
+		t.Errorf("step = %+v, want owner %q", s, Owner)
 	}
 }
 
@@ -100,7 +101,7 @@ func TestStepEndsPassedFailedOrRefusedOnItsKey(t *testing.T) {
 				t.Fatalf("ended key %q", got)
 			}
 			s := k.last("ace." + id)
-			if s.State != c.state || s.Reason != c.reason || string(s.Result) != c.result || s.Ended.IsZero() {
+			if s.State != c.state || s.Reason != c.reason || string(s.Result) != c.result || s.Ended.IsZero() || s.Owner != Owner {
 				t.Errorf("step = %+v", s)
 			}
 		})

go/buildstep/tap.go

@@ -0,0 +1,192 @@
+package buildstep
+
+// The reader of `node --test` under its TAP reporter (issue 1901's thorough fix; first written in mesh-build-node by
+// fix-1901ts): each failing test with its name, its file, its cause and its own block, never a passing line of an
+// earlier file, which is what node's default reporter left the first fifteen lines of.
+
+import (
+	"regexp"
+	"strings"
+)
+
+// NodeTestOptions is the NODE_OPTIONS a build module runs a package's test script with: node's TAP reporter, written to
+// the file dest, so whatever the script prints on its own output the report is whole and machine-readable. A script
+// that names a reporter of its own makes node refuse the run loudly ("--test-reporter must match the number of
+// --test-reporter-destination"), never quietly.
+func NodeTestOptions(dest string) string {
+	return "--test-reporter=tap --test-reporter-destination=" + dest
+}
+
+var ansiEscape = regexp.MustCompile("\x1b\\[[0-9;]*m")
+
+func stripANSI(s string) string { return ansiEscape.ReplaceAllString(s, "") }
+
+// ReadTAP reads the failing tests of a `node --test` run: report is what the TAP reporter wrote (NodeTestOptions'
+// file), console the script's own stdout and stderr, script the name of the script that ran and dir the package's
+// directory, which a test's file is made relative to. A suite that failed only because a test inside it did is not
+// reported twice. A test file that did not load (a syntax error, a crash, an error after its test ended) takes its
+// cause from the lines node wrote before it. When the report holds no failing test (node itself failed, or the script
+// failed before its tests ran: a build, a reporter refused) the failure is the console's (ConsoleFailure).
+func ReadTAP(pkg, script, dir, report, console string) []Failure {
+	var failed []Failure
+	all := strings.Split(stripANSI(strings.ReplaceAll(report, "\r\n", "\n")), "\n")
+	var cancelled []Failure // failed because a suite around them did: said after the failure that carries the cause
+	prev := 0               // the line after the last test block, passing or not: what the run wrote since belongs to the next test
+	for i := 0; i < len(all); i++ {
+		name, ok := tapNotOk(all[i])
+		if !ok {
+			if tapOk(all[i]) {
+				i = tapBlockEnd(all, i) - 1
+				prev = i + 1
+			}
+			continue
+		}
+		indent := len(all[i]) - len(strings.TrimLeft(all[i], " "))
+		block := []string{strings.TrimSpace(all[i])}
+		fields := map[string]string{}
+		var key string
+		inYAML := false
+		j := i + 1
+		for ; j < len(all); j++ {
+			t := strings.TrimSpace(all[j])
+			if !inYAML {
+				if t == "---" {
+					inYAML = true
+					continue
+				}
+				break
+			}
+			if t == "..." {
+				j++
+				break
+			}
+			block = append(block, strings.TrimRight(all[j], " \t"))
+			if k, v, found := tapKey(all[j], indent); found {
+				key = k
+				if v != "|-" && v != "|" {
+					fields[k] = strings.Trim(v, "'")
+				}
+			} else if key != "" && fields[key] == "" && t != "" {
+				fields[key] = t // the first line of a block scalar
+			}
+		}
+		from, at := prev, i
+		i, prev = j-1, j
+		if fields["failureType"] == "subtestsFailed" {
+			continue
+		}
+		cause := fields["error"]
+		if cause == "test failed" || cause == "" {
+			// a file that did not load, or an error after a test ended: node says only "test failed" and wrote the
+			// error as comment lines before it
+			var own []string
+			for _, l := range all[from:at] {
+				if t := strings.TrimSpace(l); strings.HasPrefix(t, "# ") && !strings.HasPrefix(t, "# Subtest") {
+					own = append(own, strings.TrimPrefix(t, "# "))
+				}
+			}
+			for _, l := range own {
+				if strings.Contains(l, "Error") {
+					cause = l
+					break
+				}
+			}
+			if cause == "" && len(own) > 0 {
+				cause = own[0]
+			}
+			block = append(own, block...)
+		}
+		if cause == "" {
+			cause = fields["failureType"]
+		}
+		if cause == "" {
+			cause = "the test failed and node said no error"
+		}
+		cause = CutLine(cause)
+		file := strings.TrimPrefix(fields["location"], "file://")
+		if dir != "" {
+			file = strings.TrimPrefix(file, strings.TrimSuffix(dir, "/")+"/")
+		}
+		f := Failure{Package: pkg, Test: name, File: file, Cause: cause, Output: Clip(block, cause)}
+		if fields["failureType"] == "cancelledByParent" {
+			cancelled = append(cancelled, f)
+			continue
+		}
+		failed = append(failed, f)
+	}
+	if failed = append(failed, cancelled...); len(failed) > 0 {
+		return failed
+	}
+	var comments []string
+	for _, l := range all {
+		if t := strings.TrimSpace(l); strings.HasPrefix(t, "# ") && !strings.HasPrefix(t, "# Subtest") && !tapCount(t) {
+			comments = append(comments, strings.TrimPrefix(t, "# "))
+		}
+	}
+	return []Failure{ConsoleFailure(pkg, script, strings.Join(comments, "\n")+"\n"+console)}
+}
+
+// tapCount says a comment is TAP's closing count ("# tests 3", "# pass 2", "# duration_ms 1.2").
+func tapCount(t string) bool {
+	for _, w := range []string{"tests", "suites", "pass", "fail", "cancelled", "skipped", "todo", "duration_ms"} {
+		if strings.HasPrefix(t, "# "+w+" ") {
+			return true
+		}
+	}
+	return false
+}
+
+// tapOk says a line is a passing test's "ok N - name", indented or not.
+func tapOk(l string) bool {
+	rest, ok := strings.CutPrefix(strings.TrimSpace(l), "ok ")
+	return ok && rest != "" && rest[0] >= '0' && rest[0] <= '9'
+}
+
+// tapBlockEnd is the line after the test line at i and its YAML block ("---" to "...").
+func tapBlockEnd(all []string, i int) int {
+	j := i + 1
+	if j >= len(all) || strings.TrimSpace(all[j]) != "---" {
+		return j
+	}
+	for j++; j < len(all); j++ {
+		if strings.TrimSpace(all[j]) == "..." {
+			return j + 1
+		}
+	}
+	return j
+}
+
+// tapNotOk is the test name of a "not ok N - name" line, indented or not; a TODO or SKIP directive fails nothing.
+func tapNotOk(l string) (string, bool) {
+	t := strings.TrimSpace(l)
+	rest, ok := strings.CutPrefix(t, "not ok ")
+	if !ok {
+		return "", false
+	}
+	if u := strings.ToUpper(rest); strings.Contains(u, " # TODO") || strings.Contains(u, " # SKIP") {
+		return "", false
+	}
+	if _, after, found := strings.Cut(rest, " - "); found {
+		rest = after
+	}
+	return strings.TrimSpace(rest), true
+}
+
+// tapKey is "key: value" of a field of a TAP block, whose lines sit two spaces deeper than their "not ok" line; a deeper
+// line is part of a block scalar (an error's lines, a stack).
+func tapKey(l string, indent int) (key, val string, ok bool) {
+	t := strings.TrimLeft(l, " ")
+	if len(l)-len(t) != indent+2 {
+		return "", "", false
+	}
+	k, v, found := strings.Cut(t, ": ")
+	if !found {
+		if k, found = strings.CutSuffix(t, ":"); !found {
+			return "", "", false
+		}
+	}
+	if k == "" || strings.ContainsAny(k, " ()/") {
+		return "", "", false
+	}
+	return k, strings.TrimSpace(v), true
+}

go/buildstep/testdata/isolated-probe/main.go

@@ -0,0 +1,49 @@
+// The probe a run step's isolation is proved with (novox/hq ADR 0448; issue 1309, S19): run inside the step, it says
+// on stdout every way it reached what a step must not, and "shut off" when it reached none. Its arguments: the files
+// it must not read (the forge key, a bus login), a TCP address and a unix socket of the machine it must not reach, a
+// name it must not resolve, and a cache file it writes, which must be unchanged after the step.
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"time"
+)
+
+func main() {
+	if len(os.Args) != 7 {
+		fmt.Println("usage: probe <key> <login> <tcp address> <unix socket> <name> <cache file>")
+		os.Exit(2)
+	}
+	key, login, tcp, socket, name, cache := os.Args[1], os.Args[2], os.Args[3], os.Args[4], os.Args[5], os.Args[6]
+	reached := 0
+	say := func(f string, a ...any) { reached++; fmt.Printf(f+"\n", a...) }
+	for _, f := range []string{key, login} {
+		if _, err := os.ReadFile(f); err == nil {
+			say("read %s", f)
+		}
+	}
+	if c, err := net.DialTimeout("tcp", tcp, 2*time.Second); err == nil {
+		c.Close()
+		say("reached %s", tcp)
+	}
+	if c, err := net.DialTimeout("unix", socket, 2*time.Second); err == nil {
+		c.Close()
+		say("reached %s", socket)
+	}
+	if addrs, err := net.LookupHost(name); err == nil {
+		say("resolved %s to %v", name, addrs)
+	}
+	if home, err := os.UserHomeDir(); err == nil {
+		if entries, err := os.ReadDir(home); err == nil && len(entries) > 0 {
+			say("the home %s holds %d entries", home, len(entries))
+		}
+	}
+	if err := os.WriteFile(cache, []byte("written by the step\n"), 0o644); err != nil {
+		say("could not write the cache under its throwaway layer: %v", err)
+	}
+	if reached == 0 {
+		fmt.Println("shut off")
+	}
+}

go/buildstep/trees.go

@@ -0,0 +1,123 @@
+package buildstep
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// ModuleTree is what a merge holds of one module directory: its tree id, the sha256 of its module.json and the sha256
+// of each lock file it has (go.sum, package-lock.json), from which the checker and the indexer take the module's inputs
+// (novox/hq ADR 0484 clause 3).
+type ModuleTree struct {
+	Tree     string            `json:"tree"`
+	Manifest string            `json:"manifest"`
+	Locks    map[string]string `json:"locks,omitempty"`
+	// Paths are, of a module whose every artifact names its paths, each named path's git object id at the commit; Tree
+	// is then their delivery.NamedTree with Manifest (novox/hq ADR 0499 clause 2). Absent otherwise.
+	Paths map[string]string `json:"paths,omitempty"`
+}
+
+var lockFiles = []string{"go.sum", "package-lock.json"}
+
+// ModuleTrees are the trees, in commit, of every directory of the workspace dir that holds a module.json, by directory
+// (the repository's root is "."); for a module whose every artifact names its paths, the named tree of those paths and
+// their objects (novox/hq ADR 0499 clause 2). The workspace is at commit, so the manifests and the lock files are read from it. env is
+// the environment git runs with (nil for none). Both build modules' fetch steps answer it for a merge.
+func ModuleTrees(ctx context.Context, run forgekey.Runner, env []string, dir, commit string) (map[string]ModuleTree, error) {
+	r := run(ctx, env, "git", "-C", dir, "ls-files", "--", "module.json", "*/module.json")
+	if r.Status != 0 || r.Err != "" {
+		return nil, fmt.Errorf("git ls-files: %s", forgekey.Said(r.Err+"\n"+r.Stderr))
+	}
+	trees := map[string]ModuleTree{}
+	for _, l := range strings.Split(r.Stdout, "\n") {
+		if l = strings.TrimSpace(l); l == "" {
+			continue
+		}
+		mdir := filepath.ToSlash(filepath.Dir(l))
+		spec := commit + ":" + mdir
+		if mdir == "." {
+			spec = commit + "^{tree}"
+		}
+		t := run(ctx, env, "git", "-C", dir, "rev-parse", spec)
+		if t.Status != 0 || t.Err != "" {
+			return nil, fmt.Errorf("git rev-parse %s: %s", spec, forgekey.Said(t.Err+"\n"+t.Stderr))
+		}
+		mt := ModuleTree{Tree: strings.TrimSpace(t.Stdout)}
+		raw, err := os.ReadFile(filepath.Join(dir, filepath.FromSlash(l)))
+		if err != nil {
+			return nil, err
+		}
+		mt.Manifest = sha256Hex(raw)
+		if err := narrow(ctx, run, env, dir, commit, mdir, raw, &mt); err != nil {
+			return nil, err
+		}
+		for _, lock := range lockFiles {
+			if raw, err := os.ReadFile(filepath.Join(dir, filepath.FromSlash(mdir), lock)); err == nil {
+				if mt.Locks == nil {
+					mt.Locks = map[string]string{}
+				}
+				mt.Locks[lock] = sha256Hex(raw)
+			}
+		}
+		trees[mdir] = mt
+	}
+	return trees, nil
+}
+
+// narrow sets mt's Paths and its named Tree when the module's manifest names paths on every artifact (novox/hq ADR 0499
+// clause 2): one `git ls-tree -z` gives each named path's object at commit. The merge preview reads the manifest here, as
+// the indexer does, with catalogue.ParseManifestForInputs (issue 1751), and no other build step reads paths from one (ADR 0495 clause 1). A manifest that does not parse
+// is not narrowed: the indexer gives it none. A named path absent at commit fails, naming the module and the path.
+func narrow(ctx context.Context, run forgekey.Runner, env []string, dir, commit, mdir string, raw []byte, mt *ModuleTree) error {
+	m, err := catalogue.ParseManifestForInputs(raw)
+	if err != nil {
+		return nil
+	}
+	paths, every := m.NamedPaths()
+	if !every {
+		return nil
+	}
+	full := make([]string, len(paths))
+	for i, p := range paths {
+		full[i] = path.Join(mdir, p)
+	}
+	r := run(ctx, env, "git", append([]string{"-C", dir, "ls-tree", "-z", commit, "--"}, full...)...)
+	if r.Status != 0 || r.Err != "" {
+		return fmt.Errorf("git ls-tree %s of the module %s: %s", commit, mdir, forgekey.Said(r.Err+"\n"+r.Stderr))
+	}
+	objects := map[string]string{}
+	for _, l := range strings.Split(r.Stdout, "\x00") {
+		meta, name, ok := strings.Cut(l, "\t")
+		fields := strings.Fields(meta)
+		if !ok || len(fields) != 3 {
+			continue
+		}
+		objects[name] = fields[2]
+	}
+	mt.Paths = map[string]string{}
+	for i, p := range paths {
+		object := objects[full[i]]
+		if object == "" {
+			return fmt.Errorf("the module %s names the path %q, which is not in %s", mdir, p, commit)
+		}
+		mt.Paths[p] = object
+	}
+	named, err := delivery.NamedTree(mt.Manifest, mt.Paths)
+	if err != nil {
+		return fmt.Errorf("the module %s: %w", mdir, err)
+	}
+	mt.Tree = named
+	return nil
+}
+
+func sha256Hex(b []byte) string { h := sha256.Sum256(b); return hex.EncodeToString(h[:]) }

go/buildstep/trees_integration_test.go

@@ -0,0 +1,63 @@
+//go:build integration
+
+package buildstep
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// On a real repository shaped like mesh-sdk (novox/hq ADR 0499 clauses 2 and 6), a commit touching only the Go package
+// leaves the TypeScript package's tree value equal, and a commit touching its source changes it; a module that names no
+// path keeps its directory's tree id.
+func TestAGoOnlyCommitLeavesTheNamedTreeEqualOnRealGit(t *testing.T) {
+	repo := t.TempDir()
+	realGit(t, repo, "init", "-q", "-b", "main")
+	writeFile(t, repo, "module.json", `{"module":"mesh-sdk","version":"1","build":{"artifacts":[`+
+		`{"name":"lib","kind":"package","language":"typescript","paths":["src","test","package.json","package-lock.json","tsconfig.json"]}]}}`)
+	writeFile(t, repo, "src/index.ts", "export const a = 1\n")
+	writeFile(t, repo, "test/a.test.ts", "// a\n")
+	writeFile(t, repo, "package.json", "{}\n")
+	writeFile(t, repo, "package-lock.json", "{}\n")
+	writeFile(t, repo, "tsconfig.json", "{}\n")
+	writeFile(t, repo, "go/delivery/x.go", "package delivery\n")
+	writeFile(t, repo, "other/module.json", `{"module":"other","version":"1"}`)
+	writeFile(t, repo, "other/a.txt", "a\n")
+	commit := func(msg string) string {
+		realGit(t, repo, "add", "-A")
+		realGit(t, repo, "commit", "-q", "-m", msg)
+		return realGit(t, repo, "rev-parse", "HEAD")
+	}
+	trees := func(c string) map[string]ModuleTree {
+		got, err := ModuleTrees(context.Background(), forgekey.ExecRunner, nil, repo, c)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return got
+	}
+	first := trees(commit("first"))
+	if !strings.HasPrefix(first["."].Tree, "named:") || len(first["."].Paths) != 5 {
+		t.Fatalf("the root module was not narrowed: %+v", first["."])
+	}
+	if want := realGit(t, repo, "rev-parse", "HEAD:other"); first["other"].Tree != want || first["other"].Paths != nil {
+		t.Fatalf("a module naming no path: %+v, want its directory's tree %s", first["other"], want)
+	}
+
+	writeFile(t, repo, "go/delivery/x.go", "package delivery\n\nconst B = 2\n")
+	goOnly := trees(commit("go only"))
+	if goOnly["."].Tree != first["."].Tree {
+		t.Fatalf("a Go-only commit changed the TypeScript package's tree: %s, was %s", goOnly["."].Tree, first["."].Tree)
+	}
+
+	writeFile(t, repo, "src/index.ts", "export const a = 2\n")
+	src := trees(commit("src"))
+	if src["."].Tree == first["."].Tree {
+		t.Fatal("a commit to src/ left the TypeScript package's tree equal")
+	}
+	if src["."].Paths["src"] != realGit(t, repo, "rev-parse", "HEAD:src") {
+		t.Fatalf("the object of src is %s, git says %s", src["."].Paths["src"], realGit(t, repo, "rev-parse", "HEAD:src"))
+	}
+}

go/buildstep/trees_named_test.go

@@ -0,0 +1,113 @@
+package buildstep
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// A module whose every artifact names its paths takes its tree from them (novox/hq ADR 0499 clause 2): ModuleTrees asks
+// git for each named path's object at the commit, keeps them in Paths and answers their delivery.NamedTree as Tree; a
+// module naming none keeps its directory's tree, as before.
+func TestModuleTreesNarrowsAModuleWhoseArtifactsNameTheirPaths(t *testing.T) {
+	root := t.TempDir()
+	sdk := `{"module":"mesh-sdk","version":"1","build":{"artifacts":[{"name":"lib","kind":"package","language":"typescript","paths":["src","package.json"]}]}}`
+	writeTreeFile(t, root, "module.json", sdk)
+	writeTreeFile(t, root, "modules/b/module.json", `{"module":"b","version":"1"}`)
+	merge := strings.Repeat("c", 40)
+	var lsTree []string
+	run := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		switch args[2] {
+		case "ls-files":
+			return forgekey.Ran{Stdout: "module.json\nmodules/b/module.json\n"}
+		case "rev-parse":
+			return forgekey.Ran{Stdout: "tree-of-" + args[3] + "\n"}
+		case "ls-tree":
+			lsTree = append(lsTree, strings.Join(args[4:], " "))
+			return forgekey.Ran{Stdout: "100644 blob " + strings.Repeat("b", 40) + "\tpackage.json\x00" +
+				"040000 tree " + strings.Repeat("a", 40) + "\tsrc\x00"}
+		}
+		return forgekey.Ran{Status: 1, Stderr: "unexpected " + args[2]}
+	}
+	got, err := ModuleTrees(context.Background(), run, nil, root, merge)
+	if err != nil {
+		t.Fatal(err)
+	}
+	paths := map[string]string{"src": strings.Repeat("a", 40), "package.json": strings.Repeat("b", 40)}
+	want, _ := delivery.NamedTree(hexOf(sdk), paths)
+	if g := got["."]; g.Tree != want || len(g.Paths) != 2 || g.Paths["src"] != paths["src"] || g.Paths["package.json"] != paths["package.json"] {
+		t.Fatalf("the root module = %+v, want tree %s and paths %v", g, want, paths)
+	}
+	if len(lsTree) != 1 || lsTree[0] != merge+" -- package.json src" {
+		t.Fatalf("git ls-tree ran as %v", lsTree)
+	}
+	if g := got["modules/b"]; g.Tree != "tree-of-"+merge+":modules/b" || g.Paths != nil {
+		t.Fatalf("a module naming no path was narrowed: %+v", g)
+	}
+}
+
+// A named path absent at the commit fails the answer, naming the module and the path: a tree computed without it would
+// pin a build source that does not exist.
+func TestModuleTreesFailsNamingANamedPathAbsentAtTheCommit(t *testing.T) {
+	root := t.TempDir()
+	writeTreeFile(t, root, "modules/a/module.json", `{"module":"a","version":"1","build":{"artifacts":[{"name":"lib","kind":"package","language":"typescript","paths":["src","gone"]}]}}`)
+	run := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		switch args[2] {
+		case "ls-files":
+			return forgekey.Ran{Stdout: "modules/a/module.json\n"}
+		case "rev-parse":
+			return forgekey.Ran{Stdout: "t\n"}
+		case "ls-tree":
+			if strings.Join(args[4:], " ") != strings.Repeat("c", 40)+" -- modules/a/gone modules/a/src" {
+				return forgekey.Ran{Status: 1, Stderr: "wrong arguments " + strings.Join(args[3:], " ")}
+			}
+			return forgekey.Ran{Stdout: "040000 tree " + strings.Repeat("a", 40) + "\tmodules/a/src\x00"}
+		}
+		return forgekey.Ran{Status: 1}
+	}
+	_, err := ModuleTrees(context.Background(), run, nil, root, strings.Repeat("c", 40))
+	if err == nil || !strings.Contains(err.Error(), `"gone"`) || !strings.Contains(err.Error(), "modules/a") {
+		t.Fatalf("an absent named path gave %v", err)
+	}
+}
+
+// A manifest whose config value falls back to a predefined key is narrowed here as the indexer narrows it: both read it
+// with catalogue.ParseManifestForInputs (issue 1751), so a build module holding no published list computes the same
+// tree (ADR 0499 clause 2).
+func TestModuleTreesNarrowsAManifestFallingBackToAPredefinedKey(t *testing.T) {
+	was := catalogue.ReplacePublished(nil) // the build modules' case: no published list
+	defer catalogue.ReplacePublished(was)
+	root := t.TempDir()
+	raw := `{"module":"xterm","version":"1","config":{"size":{"type":"number","description":"The text size.","predefined":"font-size","default":12,"runtime":true}},` +
+		`"build":{"artifacts":[{"name":"lib","kind":"package","language":"typescript","paths":["src"]}]}}`
+	if _, err := catalogue.ParseManifest([]byte(raw)); err == nil {
+		t.Fatal("ParseManifest reads the manifest with no list; the test proves nothing")
+	}
+	if _, err := catalogue.ParseManifestForInputs([]byte(raw)); err != nil {
+		t.Fatalf("the indexer's read refuses the manifest: %v", err)
+	}
+	writeTreeFile(t, root, "module.json", raw)
+	run := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		switch args[2] {
+		case "ls-files":
+			return forgekey.Ran{Stdout: "module.json\n"}
+		case "rev-parse":
+			return forgekey.Ran{Stdout: "whole\n"}
+		case "ls-tree":
+			return forgekey.Ran{Stdout: "040000 tree " + strings.Repeat("a", 40) + "\tsrc\x00"}
+		}
+		return forgekey.Ran{Status: 1}
+	}
+	got, err := ModuleTrees(context.Background(), run, nil, root, strings.Repeat("c", 40))
+	if err != nil {
+		t.Fatal(err)
+	}
+	want, _ := delivery.NamedTree(hexOf(raw), map[string]string{"src": strings.Repeat("a", 40)})
+	if g := got["."]; g.Tree != want || g.Paths["src"] == "" {
+		t.Fatalf("the module = %+v, want the named tree %s", g, want)
+	}
+}

go/buildstep/trees_test.go

@@ -0,0 +1,93 @@
+package buildstep
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+func hexOf(s string) string { h := sha256.Sum256([]byte(s)); return hex.EncodeToString(h[:]) }
+
+func writeTreeFile(t *testing.T, root, name, content string) {
+	t.Helper()
+	p := filepath.Join(root, filepath.FromSlash(name))
+	if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(p, []byte(content), 0o644); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// ModuleTrees answers, for each directory holding a module.json (the root as "."), the tree id git gives, the sha256 of
+// module.json and of each lock file present, and reads them from the workspace.
+func TestModuleTreesAnswersTreeManifestAndLocksPerModuleDirectory(t *testing.T) {
+	root := t.TempDir()
+	writeTreeFile(t, root, "module.json", `{"root":1}`)
+	writeTreeFile(t, root, "go.sum", "rootsum")
+	writeTreeFile(t, root, "modules/a/module.json", `{"a":1}`)
+	writeTreeFile(t, root, "modules/a/go.sum", "asum")
+	writeTreeFile(t, root, "modules/a/package-lock.json", "alock")
+	writeTreeFile(t, root, "modules/b/module.json", `{"b":1}`)
+	merge := strings.Repeat("c", 40)
+	var calls []string
+	var envs [][]string
+	run := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		calls = append(calls, name+" "+strings.Join(args[2:], " "))
+		envs = append(envs, env)
+		switch args[2] {
+		case "ls-files":
+			return forgekey.Ran{Stdout: "module.json\nmodules/a/module.json\nmodules/b/module.json\n"}
+		case "rev-parse":
+			return forgekey.Ran{Stdout: "tree-of-" + args[3] + "\n"}
+		}
+		return forgekey.Ran{Status: 1, Stderr: "unexpected"}
+	}
+	got, err := ModuleTrees(context.Background(), run, []string{"X=1"}, root, merge)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := map[string]ModuleTree{
+		".":         {Tree: "tree-of-" + merge + "^{tree}", Manifest: hexOf(`{"root":1}`), Locks: map[string]string{"go.sum": hexOf("rootsum")}},
+		"modules/a": {Tree: "tree-of-" + merge + ":modules/a", Manifest: hexOf(`{"a":1}`), Locks: map[string]string{"go.sum": hexOf("asum"), "package-lock.json": hexOf("alock")}},
+		"modules/b": {Tree: "tree-of-" + merge + ":modules/b", Manifest: hexOf(`{"b":1}`)},
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("trees = %+v\nwant %+v", got, want)
+	}
+	if got["modules/b"].Locks != nil {
+		t.Error("a module with no lock file carries a lock map")
+	}
+	for _, e := range envs {
+		if len(e) != 1 || e[0] != "X=1" {
+			t.Errorf("git ran with env %v, want the one given", e)
+		}
+	}
+}
+
+func TestModuleTreesFailsNamingTheGitCommandOrTheUnreadableManifest(t *testing.T) {
+	root := t.TempDir()
+	fail := func(on string) forgekey.Runner {
+		return func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+			if args[2] == on {
+				return forgekey.Ran{Status: 128, Stderr: "fatal: no\n"}
+			}
+			return forgekey.Ran{Stdout: "modules/a/module.json\n"}
+		}
+	}
+	for _, on := range []string{"ls-files", "rev-parse"} {
+		if _, err := ModuleTrees(context.Background(), fail(on), nil, root, sha); err == nil || !strings.Contains(err.Error(), on) || !strings.Contains(err.Error(), "fatal: no") {
+			t.Errorf("%s failing: %v", on, err)
+		}
+	}
+	if _, err := ModuleTrees(context.Background(), fail("none"), nil, root, sha); err == nil {
+		t.Error("a module.json that is not in the workspace was read")
+	}
+}

go/buildstep/watch_settings_linux.go

@@ -0,0 +1,112 @@
+//go:build linux
+
+package buildstep
+
+import (
+	"context"
+	"encoding/binary"
+	"os"
+	"path/filepath"
+	"syscall"
+)
+
+const settingsMask = syscall.IN_CLOSE_WRITE | syscall.IN_MOVED_TO | syscall.IN_CREATE
+
+// watchSettings wakes the puller each time its settings file is written or replaced (inotify on the file's directory, so
+// a rename over it counts): the event the node-engine's refill of the file is, which a parked puller at capacity 0
+// otherwise never sees. No timer: it blocks on the kernel's event. When the kernel drops the watch (IN_IGNORED: the
+// directory was replaced or removed) it is added again, said once; while the directory is missing the nearest existing
+// ancestor is watched for the directory's return. A watch that cannot start is said once.
+func (p *Puller) watchSettings(ctx context.Context) {
+	if p.SettingsFile == "" {
+		return
+	}
+	fd, err := syscall.InotifyInit1(syscall.IN_CLOEXEC | syscall.IN_NONBLOCK)
+	if err != nil {
+		p.logf("the settings file %s cannot be watched, so a refill of it wakes the puller only at another event: %v", p.SettingsFile, err)
+		return
+	}
+	f := os.NewFile(uintptr(fd), "inotify")
+	defer f.Close()
+	dir, base := filepath.Split(p.SettingsFile)
+	dir = filepath.Clean(dir)
+	// arm watches dir, or when it is missing its nearest existing ancestor; it returns the watch descriptor and whether it
+	// is the directory's own.
+	arm := func() (int, bool, error) {
+		wd, err := syscall.InotifyAddWatch(fd, dir, settingsMask)
+		if err == nil {
+			return wd, true, nil
+		}
+		for up := filepath.Dir(dir); ; up = filepath.Dir(up) {
+			wd, aerr := syscall.InotifyAddWatch(fd, up, settingsMask)
+			if aerr == nil {
+				// the directory may have come back between the two calls: look once more, now that the ancestor is watched
+				if own, oerr := syscall.InotifyAddWatch(fd, dir, settingsMask); oerr == nil {
+					return own, true, nil
+				}
+				return wd, false, nil
+			}
+			if up == filepath.Dir(up) {
+				return 0, false, err
+			}
+		}
+	}
+	wd, own, err := arm()
+	if err != nil {
+		p.logf("the settings file %s cannot be watched, so a refill of it wakes the puller only at another event: %v", p.SettingsFile, err)
+		return
+	}
+	if p.watching != nil {
+		p.watching()
+	}
+	go func() { <-ctx.Done(); f.Close() }()
+	buf := make([]byte, 4096)
+	for {
+		n, err := f.Read(buf)
+		if err != nil {
+			return
+		}
+		hit, rearm := false, false
+		for off := 0; off+16 <= n; {
+			ewd := int(int32(binary.LittleEndian.Uint32(buf[off:])))
+			mask := binary.LittleEndian.Uint32(buf[off+4:])
+			l := int(binary.LittleEndian.Uint32(buf[off+12:]))
+			name := buf[off+16 : off+16+l]
+			for i, c := range name {
+				if c == 0 {
+					name = name[:i]
+					break
+				}
+			}
+			switch {
+			case mask&syscall.IN_IGNORED != 0 && ewd == wd:
+				rearm = true
+			case ewd == wd && own && string(name) == base:
+				hit = true
+			case ewd == wd && !own:
+				rearm = true // something appeared where the directory was: look again
+			}
+			off += 16 + l
+		}
+		if rearm {
+			nwd, nown, err := arm()
+			if err != nil {
+				p.logf("the settings file %s is no longer watched, so a refill of it wakes the puller only at another event: %v", p.SettingsFile, err)
+				return
+			}
+			if own || nown { // said once per loss of the watch on the directory itself
+				if own {
+					p.logf("the watch of the settings file %s was dropped (its directory was replaced); watching again", p.SettingsFile)
+				}
+			}
+			wd, own = nwd, nown
+			if p.watching != nil {
+				p.watching()
+			}
+			hit = true // the file may have been refilled meanwhile
+		}
+		if hit {
+			p.Wake()
+		}
+	}
+}

go/buildstep/watch_settings_other.go

@@ -0,0 +1,8 @@
+//go:build !linux
+
+package buildstep
+
+import "context"
+
+// watchSettings watches nothing off Linux: the puller wakes at its other events.
+func (p *Puller) watchSettings(ctx context.Context) {}

go/buildstep/workspaces.go

@@ -0,0 +1,160 @@
+package buildstep
+
+// A build module's room to work and its workspaces (novox/hq issue 1839, ADR 0509): a step is refused while the
+// filesystem it writes to has less free than the floor, and a workspace is removed when its caller releases it, or,
+// unheld, once its last use is past a bound (a lost caller's), never while a running step holds it.
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"sync"
+	"syscall"
+	"time"
+)
+
+// FreeSpaceFloor is the free space a build module needs on its work and cache filesystems to take a step: the floor
+// build-agent keeps (mesh-controller internal/builder/floor.go, issue 1834).
+const FreeSpaceFloor uint64 = 20 << 30
+
+// UnheldBound is how long a workspace no step holds is kept after its last use, when its caller never released it
+// (ADR 0509: a lost caller's workspace goes after two hours).
+const UnheldBound = 2 * time.Hour
+
+// FreeBytes reads the bytes an unprivileged writer can still use on the filesystem holding path.
+func FreeBytes(path string) (uint64, error) {
+	var s syscall.Statfs_t
+	if err := syscall.Statfs(path, &s); err != nil {
+		return 0, err
+	}
+	return s.Bavail * uint64(s.Bsize), nil
+}
+
+// Floor refuses a step while a filesystem it writes to has less free than Bytes. A zero Bytes checks nothing.
+type Floor struct {
+	// Node is named in the refusal.
+	Node  string
+	Bytes uint64
+	// Free reads a path's free bytes; FreeBytes when nil. A test answers for a disk it does not have.
+	Free func(path string) (uint64, error)
+}
+
+// Check answers a *Refusal, "refused: <node> has N GiB free under the floor of F GiB (on <path>)", when any path's
+// filesystem has less free than the floor, or its free space cannot be read; nil otherwise. A path not made yet is
+// read at its nearest folder that is; an empty path is skipped.
+func (f Floor) Check(paths ...string) error {
+	if f.Bytes == 0 {
+		return nil
+	}
+	free := f.Free
+	if free == nil {
+		free = FreeBytes
+	}
+	for _, p := range paths {
+		if p == "" {
+			continue
+		}
+		at := p
+		for {
+			if _, err := os.Stat(at); err == nil || filepath.Dir(at) == at {
+				break
+			}
+			at = filepath.Dir(at)
+		}
+		n, err := free(at)
+		if err != nil {
+			return &Refusal{Text: fmt.Sprintf("refused: the free space of %s on %s cannot be read: %v", p, f.Node, err)}
+		}
+		if n < f.Bytes {
+			return &Refusal{Text: fmt.Sprintf("refused: %s has %d GiB free under the floor of %d GiB (on %s)", f.Node, n>>30, f.Bytes>>30, p),
+				Want: fmt.Sprintf("%d GiB", f.Bytes>>30), Have: fmt.Sprintf("%d GiB", n>>30)}
+		}
+	}
+	return nil
+}
+
+var workspaceID = regexp.MustCompile(`^[a-z0-9]+$`)
+
+// Workspaces are a build module's workspaces, each <Dir>/<id>, and which of them running steps hold.
+type Workspaces struct {
+	Dir string
+
+	mu   sync.Mutex
+	held map[string]int
+}
+
+// Hold marks the workspace held by a running step until the answered func is called; both mark it used now, so the
+// sweep counts its bound from the step's end. An id that is not a workspace's holds nothing.
+func (w *Workspaces) Hold(id string) func() {
+	if !workspaceID.MatchString(id) {
+		return func() {}
+	}
+	w.mu.Lock()
+	if w.held == nil {
+		w.held = map[string]int{}
+	}
+	w.held[id]++
+	w.mu.Unlock()
+	w.touch(id)
+	var once sync.Once
+	return func() {
+		once.Do(func() {
+			w.touch(id)
+			w.mu.Lock()
+			if w.held[id]--; w.held[id] <= 0 {
+				delete(w.held, id)
+			}
+			w.mu.Unlock()
+		})
+	}
+}
+
+func (w *Workspaces) touch(id string) {
+	now := time.Now()
+	_ = os.Chtimes(filepath.Join(w.Dir, id), now, now) // a workspace not made yet has nothing to mark
+}
+
+// Release removes the workspace at once: its caller's chain of steps has ended. One already gone is no error; one a
+// running step holds is refused and kept; an id that is not a workspace's is refused.
+func (w *Workspaces) Release(id string) error {
+	if !workspaceID.MatchString(id) {
+		return fmt.Errorf("%q is not a workspace id", id)
+	}
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	if w.held[id] > 0 {
+		return fmt.Errorf("the workspace %s is held by a running step", id)
+	}
+	if err := os.RemoveAll(filepath.Join(w.Dir, id)); err != nil {
+		return fmt.Errorf("the workspace %s could not be removed: %w", id, err)
+	}
+	return nil
+}
+
+// Sweep removes every workspace no step holds whose last use is older than bound, and answers the ids it removed,
+// sorted. It is the safety net for a caller that never released its workspace.
+func (w *Workspaces) Sweep(now time.Time, bound time.Duration) []string {
+	entries, err := os.ReadDir(w.Dir)
+	if err != nil {
+		return nil
+	}
+	removed := []string{}
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	for _, e := range entries {
+		if !e.IsDir() || !workspaceID.MatchString(e.Name()) || w.held[e.Name()] > 0 {
+			continue
+		}
+		info, err := e.Info()
+		if err != nil || now.Sub(info.ModTime()) < bound {
+			continue
+		}
+		if os.RemoveAll(filepath.Join(w.Dir, e.Name())) == nil {
+			removed = append(removed, e.Name())
+		}
+	}
+	sort.Strings(removed)
+	return removed
+}

go/buildstep/workspaces_test.go

@@ -0,0 +1,113 @@
+package buildstep
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+// 1839/AC1: a filesystem under the floor refuses the step, naming the node, what is free and the floor.
+func TestAFilesystemUnderTheFloorRefusesNamingNodeFreeAndFloor(t *testing.T) {
+	dir := t.TempDir()
+	f := Floor{Node: "ace", Bytes: 20 << 30, Free: func(string) (uint64, error) { return 4<<30 + 5, nil }}
+	err := f.Check(dir)
+	var ref *Refusal
+	if !errors.As(err, &ref) {
+		t.Fatalf("Check = %v, want a *Refusal", err)
+	}
+	if want := "refused: ace has 4 GiB free under the floor of 20 GiB (on " + dir + ")"; err.Error() != want {
+		t.Errorf("Check = %q, want %q", err, want)
+	}
+}
+
+// 1839/AC1: at or above the floor, and with no floor set, nothing is refused.
+func TestAtTheFloorOrWithNoFloorNothingIsRefused(t *testing.T) {
+	dir := t.TempDir()
+	if err := (Floor{Node: "ace", Bytes: 20 << 30, Free: func(string) (uint64, error) { return 20 << 30, nil }}).Check(dir); err != nil {
+		t.Errorf("at the floor: %v", err)
+	}
+	if err := (Floor{Node: "ace", Free: func(string) (uint64, error) { return 0, nil }}).Check(dir); err != nil {
+		t.Errorf("no floor: %v", err)
+	}
+}
+
+// 1839/AC1: a path not made yet is read at its nearest folder that is; a free space that cannot be read is a refusal.
+func TestAPathNotMadeIsReadAtItsParentAndAnUnreadableOneRefuses(t *testing.T) {
+	dir := t.TempDir()
+	var read string
+	f := Floor{Node: "ace", Bytes: 1, Free: func(p string) (uint64, error) { read = p; return 2, nil }}
+	if err := f.Check(filepath.Join(dir, "not", "made")); err != nil || read != dir {
+		t.Errorf("Check = %v, read %q, want nil and %q", err, read, dir)
+	}
+	f.Free = func(string) (uint64, error) { return 0, errors.New("statfs: boom") }
+	var ref *Refusal
+	if err := f.Check(dir); !errors.As(err, &ref) {
+		t.Errorf("Check = %v, want a refusal", err)
+	}
+}
+
+func makeWorkspace(t *testing.T, w *Workspaces, id string, age time.Duration) string {
+	t.Helper()
+	p := filepath.Join(w.Dir, id)
+	if err := os.MkdirAll(filepath.Join(p, "tree"), 0o700); err != nil {
+		t.Fatal(err)
+	}
+	at := time.Now().Add(-age)
+	if err := os.Chtimes(p, at, at); err != nil {
+		t.Fatal(err)
+	}
+	return p
+}
+
+func gone(p string) bool { _, err := os.Stat(p); return os.IsNotExist(err) }
+
+// 1839/AC2: a released workspace is gone at once; one already gone is no error; one a running step holds is refused
+// and kept; an id that is not a workspace's is refused.
+func TestReleaseRemovesAWorkspaceAtOnce(t *testing.T) {
+	w := &Workspaces{Dir: t.TempDir()}
+	p := makeWorkspace(t, w, "abc1", 0)
+	if err := w.Release("abc1"); err != nil || !gone(p) {
+		t.Fatalf("Release = %v, gone %v", err, gone(p))
+	}
+	if err := w.Release("abc1"); err != nil {
+		t.Errorf("a second release = %v, want nil", err)
+	}
+	held := makeWorkspace(t, w, "abc2", 0)
+	done := w.Hold("abc2")
+	if err := w.Release("abc2"); err == nil || gone(held) {
+		t.Errorf("Release of a held workspace = %v, gone %v; want refused and kept", err, gone(held))
+	}
+	done()
+	if err := w.Release("abc2"); err != nil || !gone(held) {
+		t.Errorf("Release after the hold ended = %v, gone %v", err, gone(held))
+	}
+	if err := w.Release("../etc"); err == nil {
+		t.Errorf("Release of ../etc answered nil")
+	}
+}
+
+// 1839/AC3: the sweep removes a workspace no step holds whose last use is past the bound, and keeps a held one and a
+// recent one; a hold ending counts as a use.
+func TestSweepRemovesUnheldWorkspacesPastTheBound(t *testing.T) {
+	w := &Workspaces{Dir: t.TempDir()}
+	old := makeWorkspace(t, w, "old1", 3*time.Hour)
+	heldOld := makeWorkspace(t, w, "held1", 3*time.Hour)
+	recent := makeWorkspace(t, w, "new1", time.Minute)
+	if err := os.WriteFile(filepath.Join(w.Dir, "not-a-workspace.txt"), nil, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	done := w.Hold("held1")
+	removed := w.Sweep(time.Now(), 2*time.Hour)
+	if !gone(old) || gone(heldOld) || gone(recent) {
+		t.Errorf("after the sweep: old gone %v, held kept %v, recent kept %v", gone(old), !gone(heldOld), !gone(recent))
+	}
+	if len(removed) != 1 || removed[0] != "old1" {
+		t.Errorf("Sweep answered %v, want [old1]", removed)
+	}
+	done()
+	if w.Sweep(time.Now(), 2*time.Hour); gone(heldOld) {
+		t.Errorf("a workspace whose hold just ended was swept: its end is a use")
+	}
+}

go/buscompose/accounts.go

@@ -0,0 +1,244 @@
+package buscompose
+
+import (
+	"encoding/json"
+	"fmt"
+	"slices"
+	"strings"
+	"time"
+)
+
+// **The accounts the grants part wants, and the one shape a held account takes** (novox/hq ADR 0561 §1, §2; issue 774).
+//
+// The bus composer derives every user from placement, the manifests and the wants. For each account the mesh mints (a
+// module's, a module's process's, a machine's provisioner client's), the grants part writes one key of its state
+// `accounts`, keyed by the bus user, holding the account's fields that are not secret: what the controller's credential
+// carries today beside the password. The vault watches that state, mints the user it holds no value for, and keeps the
+// value as the module's own secret on that node, built by HeldCredential, which gives byte for byte the controller's
+// shape, so a runtime reads it unchanged. The state is read by the vault alone (NamedReaders), as `bus-accounts` is read
+// by the grants part alone.
+//
+// The node accounts, the controller's own, an enrolment user and a person are never wanted here: the vault mints none
+// of them (ADR 0561 §4, §5).
+
+// AccountsState is the grants part's state of wanted accounts, by bus user.
+const AccountsState = "accounts"
+
+// GrantsAccounts is that state as a reader names it (`<owner>.<name>`).
+const GrantsAccounts = GrantsModule + "." + AccountsState
+
+// AccountsBucket is the bucket the state lives in.
+var AccountsBucket = BucketName(GrantsModule, AccountsState)
+
+// AccountsSubject is the subject of one wanted account's key: `$KV.mesh-grants_accounts.<user>`.
+func AccountsSubject(user string) string { return "$KV." + AccountsBucket + "." + user }
+
+// AccountIssuedEvent is what the vault says when it minted an account: AccountIssued, never a value or a hash.
+const AccountIssuedEvent = "account-issued"
+
+// AccountIssuedSubject is where it says it, as the runtime addresses mesh-vault's events.
+const AccountIssuedSubject = "mesh.mod." + VaultSeat + ".event." + AccountIssuedEvent
+
+// ClaimedSeat is one seat a module claims, as its runtime needs it (the controller's seatClaimed): the name, the scope (a
+// node-scoped seat's verb carries the machine) and the verbs the runtime serves for it.
+type ClaimedSeat struct {
+	Seat   string   `json:"seat"`
+	Scope  string   `json:"scope"`
+	Serves []string `json:"serves,omitempty"`
+}
+
+// WantedAccount is one key of the grants part's state `accounts`: an account the mesh needs, without its password.
+type WantedAccount struct {
+	User string `json:"user"`
+	// Kind is KindModule (KindNodeTools for the runtime, named as a module is), KindProcess or KindProvisioner.
+	Kind   Kind   `json:"kind"`
+	Node   string `json:"node"`
+	Module string `json:"module"`
+	// Process is a KindProcess account's process id.
+	Process string `json:"process,omitempty"`
+	// URL is the bus's address as that node reaches it, `nats://<host>:<port>`; Fingerprint the bus certificate's.
+	URL         string `json:"url"`
+	Fingerprint string `json:"fingerprint,omitempty"`
+	// Claims are a module's claims with the verbs each seat promises: none for a process or a provisioner client.
+	Claims []ClaimedSeat `json:"claims,omitempty"`
+	// At is when the grants part wrote the key: not compared (Same).
+	At time.Time `json:"at"`
+}
+
+// mintedKinds are the kinds of account the vault mints (ADR 0561 §1).
+var mintedKinds = []Kind{KindModule, KindNodeTools, KindProcess, KindProvisioner}
+
+// principal is the account as the composer names it.
+func (w WantedAccount) principal() Principal {
+	return Principal{Kind: w.Kind, Node: w.Node, Module: w.Module, Process: w.Process}
+}
+
+// Valid says why w is not an account the vault may mint, or nil: a kind it mints, every name a subject token, the user
+// the one the composer derives from them, and an address to reach the bus at.
+func (w WantedAccount) Valid() error {
+	if !slices.Contains(mintedKinds, w.Kind) {
+		return fmt.Errorf("%s is a %s account, which the vault never mints (ADR 0561 §4)", w.User, w.Kind)
+	}
+	for what, v := range map[string]string{"node": w.Node, "module": w.Module} {
+		if !safeSubject.MatchString(v) {
+			return fmt.Errorf("%s: the %s %q is not a name the mesh writes", w.User, what, v)
+		}
+	}
+	if w.Kind == KindProcess && !safeSubject.MatchString(w.Process) {
+		return fmt.Errorf("%s: the process %q is not a name the mesh writes", w.User, w.Process)
+	}
+	if w.Kind != KindProcess && w.Process != "" {
+		return fmt.Errorf("%s: only a process's account names a process", w.User)
+	}
+	if want := w.principal().Username(); w.User != want {
+		return fmt.Errorf("%s is not the user of a %s account of %s on %s (that is %s)", w.User, w.Kind, w.Module, w.Node, want)
+	}
+	if !strings.HasPrefix(w.URL, "nats://") || len(w.URL) == len("nats://") {
+		return fmt.Errorf("%s names no bus address (url, nats://<host>:<port>)", w.User)
+	}
+	if len(w.Claims) > 0 && w.Kind != KindModule && w.Kind != KindNodeTools {
+		return fmt.Errorf("%s: a %s account holds no seat, so it carries no claims", w.User, w.Kind)
+	}
+	return nil
+}
+
+// Same says whether two wanted accounts want the same account: every field but when it was written.
+func (w WantedAccount) Same(o WantedAccount) bool {
+	a, b := w, o
+	a.At, b.At = time.Time{}, time.Time{}
+	ra, _ := json.Marshal(a)
+	rb, _ := json.Marshal(b)
+	return string(ra) == string(rb)
+}
+
+// OwnSecret is the module's own secret the account is held in: `broker`, `broker-<process id>` or `provisioner-broker`
+// (the controller's names, ADR 0436 §2, ADR 0349 §11).
+func (w WantedAccount) OwnSecret() string {
+	switch w.Kind {
+	case KindProcess:
+		return "broker-" + w.Process
+	case KindProvisioner:
+		return "provisioner-broker"
+	}
+	return "broker"
+}
+
+// ReadWantedAccount reads the key user of the state: refused when it is not a valid wanted account of that user.
+func ReadWantedAccount(user string, raw []byte) (WantedAccount, error) {
+	var w WantedAccount
+	if err := json.Unmarshal(raw, &w); err != nil {
+		return WantedAccount{}, fmt.Errorf("%s %s is not a wanted account: %w", GrantsAccounts, user, err)
+	}
+	if w.User != user {
+		return WantedAccount{}, fmt.Errorf("%s %s names the user %q", GrantsAccounts, user, w.User)
+	}
+	return w, w.Valid()
+}
+
+// AccountIssued is the vault's account-issued: which account it minted, and its generation. Never a value or a hash.
+type AccountIssued struct {
+	User       string    `json:"user"`
+	Kind       Kind      `json:"kind"`
+	Node       string    `json:"node"`
+	Module     string    `json:"module"`
+	Process    string    `json:"process,omitempty"`
+	Generation int       `json:"generation"`
+	At         time.Time `json:"at"`
+}
+
+// HeldCredential is the value the account's holder reads, exactly as the controller builds it today (issueWith,
+// sealProcess and sealProvisionerClient): a module's `{url, fingerprint, node, module, user, password, claims}`, a
+// process's without claims, a provisioner client's without module or claims; an empty fingerprint or claims left out.
+func HeldCredential(w WantedAccount, password string) ([]byte, error) {
+	if err := w.Valid(); err != nil {
+		return nil, err
+	}
+	if password == "" {
+		return nil, fmt.Errorf("%s: an account is held with its password", w.User)
+	}
+	switch w.Kind {
+	case KindProcess:
+		return json.Marshal(struct {
+			URL         string `json:"url"`
+			Fingerprint string `json:"fingerprint,omitempty"`
+			Node        string `json:"node"`
+			Module      string `json:"module"`
+			User        string `json:"user"`
+			Password    string `json:"password"`
+		}{URL: w.URL, Fingerprint: w.Fingerprint, Node: w.Node, Module: w.Module, User: w.User, Password: password})
+	case KindProvisioner:
+		return json.Marshal(struct {
+			URL         string `json:"url"`
+			Fingerprint string `json:"fingerprint,omitempty"`
+			Node        string `json:"node"`
+			User        string `json:"user"`
+			Password    string `json:"password"`
+		}{URL: w.URL, Fingerprint: w.Fingerprint, Node: w.Node, User: w.User, Password: password})
+	}
+	return json.Marshal(struct {
+		URL         string        `json:"url"`
+		Fingerprint string        `json:"fingerprint,omitempty"`
+		Node        string        `json:"node"`
+		Module      string        `json:"module"`
+		User        string        `json:"user"`
+		Password    string        `json:"password"`
+		Claims      []ClaimedSeat `json:"claims,omitempty"`
+	}{URL: w.URL, Fingerprint: w.Fingerprint, Node: w.Node, Module: w.Module, User: w.User, Password: password,
+		Claims: w.Claims})
+}
+
+// **One issuer at every moment: minting turns on at the lease write** (novox/hq ADR 0561 §3, §6). The controller's lease
+// is the one key `holder` of its bucket (LeaseBucket). The operator's credential hands it away by writing a value that
+// names its new holder in `handed-to`; while the key holds that, the vault mints and the grants part creates the durable
+// consumers an account needs. A controller's value, a key deleted or expired, or one that cannot be read or parsed, turn
+// both off: when in doubt nothing is minted, so the controller and the vault never both mint one account. No clock and
+// no setting turns it.
+
+// ControllerLease is the lease's bucket as a reader names it; the vault and the grants part alone read it
+// (NamedReaders), the controller's announcement marking it readable by nobody.
+const ControllerLease = ControllerSeat + ".lease"
+
+// ControllerLeaseKey is the lease's one key.
+const ControllerLeaseKey = leaseKey
+
+// LeaseHolder is the lease key's value: a controller instance's (mesh-controller internal/lease Holder), or, once handed
+// away, one naming its holder in HandedTo.
+type LeaseHolder struct {
+	Instance string    `json:"instance,omitempty"`
+	Host     string    `json:"host,omitempty"`
+	Epoch    uint64    `json:"epoch,omitempty"`
+	Taken    time.Time `json:"taken,omitzero"`
+	Renewed  time.Time `json:"renewed,omitzero"`
+	// HandedTo is who holds the lease once the controller handed it away: never a controller instance.
+	HandedTo string `json:"handed-to,omitempty"`
+	// HandedBy is the credential that wrote it (the operator's), and Why its reason.
+	HandedBy string `json:"handed-by,omitempty"`
+	Why      string `json:"why,omitempty"`
+}
+
+// LeaseHandedAway reads the lease key as a getter answered it (its value, whether it was there, the read's error) and
+// says whether it is handed to a holder that is no controller, with why either way.
+func LeaseHandedAway(raw []byte, found bool, readErr error) (bool, string) {
+	switch {
+	case readErr != nil:
+		return false, "the controller's lease cannot be read (" + readErr.Error() + "), so nothing is minted"
+	case !found || len(raw) == 0 || string(raw) == "null":
+		return false, "no lease is written (expired, deleted, or never taken): a controller may take it, so nothing is minted"
+	}
+	var h LeaseHolder
+	if err := json.Unmarshal(raw, &h); err != nil {
+		return false, "the controller's lease is not readable as a holder (" + err.Error() + "), so nothing is minted"
+	}
+	if strings.TrimSpace(h.HandedTo) == "" {
+		who := h.Instance
+		if who == "" {
+			who = "an instance that names itself not"
+		}
+		return false, "the controller holds the lease (" + who + "): it mints, so the vault mints nothing (ADR 0561 §3)"
+	}
+	if h.Instance != "" {
+		return false, "the lease names both a controller instance (" + h.Instance + ") and a holder it is handed to (" +
+			h.HandedTo + "), so nothing is minted"
+	}
+	return true, "the lease is handed to " + h.HandedTo + ": the vault mints every new account (ADR 0561 §1, §3)"
+}

go/buscompose/agreement.go

@@ -0,0 +1,125 @@
+package buscompose
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// Do the emitters and the consumers of a catalogue agree?
+//
+// **The check that was missing** (novox/hq 04-ISSUES/127). Every manifest was individually
+// well-formed and every derivation individually correct, and no cross-module subscription in the
+// mesh matched anything: a consumer's declaration derived into a namespace nobody publishes to.
+// Nothing failed, because a subscription that matches nothing is not an error — it is silence.
+//
+// The comparison has to be over the whole catalogue, because the two halves live in different
+// manifests, and it cannot simply demand that every consumed event have a live emitter: a module
+// may be installed long before the one whose events it wants. So the rule is narrower and still
+// catches this: **where the emitter is present, it must emit what the consumer asked for.**
+
+// AConsumer is one module's interest in another's events, as this check needs it.
+type AConsumer struct {
+	Module   string
+	Consumes []string
+}
+
+// AnEmitter is one module's events.
+type AnEmitter struct {
+	Module string
+	Emits  []string
+}
+
+// Disagreements are the consumed events whose emitter is in the catalogue and does not emit them.
+//
+// Returned as sentences rather than as structs: every one of them is read by a person deciding
+// whether a manifest or a catalogue is wrong, and a pair of names without the reason is a puzzle.
+func Disagreements(emitters []AnEmitter, consumers []AConsumer, seats []DeclaredSeat) []string {
+	emits := map[string]map[string]bool{}
+	for _, e := range emitters {
+		if emits[e.Module] == nil {
+			emits[e.Module] = map[string]bool{}
+		}
+		for _, name := range e.Emits {
+			emits[e.Module][name] = true
+		}
+	}
+	// A seat's events are published by its holder under the seat's name, so a consumer naming the
+	// seat is naming something real even though no module declares it as its own.
+	for _, s := range seats {
+		if len(s.Emits) == 0 {
+			continue
+		}
+		if emits[s.Name] == nil {
+			emits[s.Name] = map[string]bool{}
+		}
+		for _, name := range s.Emits {
+			emits[s.Name][name] = true
+		}
+	}
+
+	var out []string
+	for _, c := range consumers {
+		for _, pattern := range c.Consumes {
+			emitter, event, named := strings.Cut(pattern, ".")
+			// Every event from everyone, or every event from one module: both are deliberate and
+			// neither names a particular event to check.
+			if !named || emitter == "*" || emitter == catalogueTheRest || event == catalogueTheRest {
+				continue
+			}
+			known, present := emits[emitter]
+			if !present {
+				// Not installed here, which is ordinary: a module lives in its own repository and
+				// may be registered later. Nothing to compare, so nothing to say.
+				continue
+			}
+			if matchesAny(event, known) {
+				continue
+			}
+			out = append(out, fmt.Sprintf(
+				"%s consumes %q and %s emits %s — so that subscription would match nothing, and "+
+					"nothing would report it",
+				c.Module, pattern, emitter, listOf(known)))
+		}
+	}
+	sort.Strings(out)
+	return out
+}
+
+// matchesAny says whether one of an emitter's event names satisfies a consumer's pattern.
+func matchesAny(pattern string, emitted map[string]bool) bool {
+	want := strings.Split(pattern, ".")
+	for name := range emitted {
+		if matches(want, strings.Split(name, ".")) {
+			return true
+		}
+	}
+	return false
+}
+
+func matches(pattern, name []string) bool {
+	for i, part := range pattern {
+		if part == catalogueTheRest {
+			return i < len(name)
+		}
+		if i >= len(name) {
+			return false
+		}
+		if part != "*" && part != name[i] {
+			return false
+		}
+	}
+	return len(pattern) == len(name)
+}
+
+func listOf(names map[string]bool) string {
+	if len(names) == 0 {
+		return "nothing"
+	}
+	out := make([]string, 0, len(names))
+	for n := range names {
+		out = append(out, n)
+	}
+	sort.Strings(out)
+	return strings.Join(out, ", ")
+}

go/buscompose/announced.go

@@ -0,0 +1,107 @@
+package buscompose
+
+import (
+	"slices"
+	"sort"
+	"strings"
+
+	"git.novox.be/novox/mesh-sdk/go/announce"
+)
+
+// Who may read a module's state is what the module announced (novox/hq ADR 0495 clauses 2 and 3, ADR 0513 §3; issue
+// 1790). A module says on the bus which states it keeps and which others may read (announce.Subject); the controller
+// keeps the last word of each (announce.KeptBucket) and grants a reader's `reads: <owner>.<name>` only when the owner
+// announced that state readable. An owner that has announced nothing yet is read as before, from the reader's `reads`
+// (the transition, until every module announces), and is named as not yet announced.
+
+// StatesAnnouncedBucket is the controller's bucket of the last announcement of each module (announce.KeptBucket).
+const StatesAnnouncedBucket = announce.KeptBucket
+
+// controllerReadable are the controller's states others may read: the record mirrors (the packages each node declares
+// among them, which the pacman module reads, ADR 0507 §5), the chain's buckets, and the grants issued and the
+// compositions' digests, which the assigner reads (ADR 0528 clause 2, ADR 0539 clause 6).
+var controllerReadable = []string{MirrorAssignments, MirrorDeclaredConfig, MirrorPredefined, ChainBuilds, ChainRollouts,
+	MirrorDeclaredPackages, ControllerGrants, ControllerComposed}
+
+// ControllerAnnouncement is what the controller announces it keeps (ADR 0495 clause 2): every bucket of its own by its local
+// name, the ones others may read marked readable. It announces itself, as any module does from its code.
+func ControllerAnnouncement(node string) announce.States {
+	s := announce.States{Module: ControllerSeat, Node: node}
+	readable := map[string]bool{}
+	for _, n := range controllerReadable {
+		readable[n] = true
+	}
+	for _, bucket := range ControllerBuckets() {
+		local, mine := strings.CutPrefix(bucket, ControllerSeat+"_")
+		if !mine {
+			continue
+		}
+		s.States = append(s.States, announce.State{Name: local, Readable: readable[local]})
+	}
+	sort.Slice(s.States, func(i, j int) bool { return s.States[i].Name < s.States[j].Name })
+	return s
+}
+
+// ReadsAnnounced splits a reader's `reads` (`<owner>.<name>`) by what each owner announced: granted when the owner
+// announced the state readable, or announced nothing yet (the transition); refused when the owner announced and did
+// not announce that state readable.
+func ReadsAnnounced(reads []string, announced map[string]announce.States) (granted, refused []string) {
+	return ReadsAnnouncedBy("", reads, announced)
+}
+
+// ReadsAnnouncedBy is ReadsAnnounced for one reader module, which also honours the readers an owner named for a state
+// (announce.State.Readers) and the composer's named readers (NamedReaders, ADR 0547 clause 9): a read named for other
+// modules is refused. An empty reader is judged by the readable mark alone.
+func ReadsAnnouncedBy(reader string, reads []string, announced map[string]announce.States) (granted, refused []string) {
+	for _, r := range reads {
+		owner, name, ok := strings.Cut(r, ".")
+		s, said := announced[owner]
+		switch {
+		case reader != "" && !ReaderMay(reader, r):
+			refused = append(refused, r)
+		case reader != "" && namedReader(reader, r):
+			// A state the composer names its readers for is theirs whatever its owner announced (ADR 0561 §3: the
+			// controller's lease, which its announcement marks readable by nobody).
+			granted = append(granted, r)
+		case reader != "" && ok && said && s.Keeps(name):
+			if s.ReadableBy(name, reader) {
+				granted = append(granted, r)
+			} else {
+				refused = append(refused, r)
+			}
+		case !ok || !said || s.Readable(name):
+			granted = append(granted, r)
+		default:
+			refused = append(refused, r)
+		}
+	}
+	return granted, refused
+}
+
+// NotAnnounced are the owners some module reads the state of and that have announced nothing yet, sorted: read from the
+// readers' `reads` as before, until they announce.
+func NotAnnounced(r Records) []string {
+	seen := map[string]bool{}
+	var out []string
+	for _, ds := range r.Assigned {
+		for _, d := range ds {
+			for _, read := range append(append([]string(nil), d.Reads...), d.ReadsRefused...) {
+				owner, _, ok := strings.Cut(read, ".")
+				if !ok || seen[owner] {
+					continue
+				}
+				if _, said := r.Announced[owner]; !said {
+					seen[owner] = true
+					out = append(out, owner)
+				}
+			}
+		}
+	}
+	sort.Strings(out)
+	return out
+}
+
+// namedReader says the composer names module among the readers of read (NamedReaders).
+func namedReader(module, read string) bool {
+	return slices.Contains(NamedReaders[strings.TrimSpace(read)], module)
+}

go/buscompose/buildbacklog.go

@@ -0,0 +1,47 @@
+package buscompose
+
+import "git.novox.be/novox/mesh-sdk/go/delivery"
+
+// The view alone reads the build seats' queues (novox/hq ADR 0525 §2, issue 1887 A8a): the shared workers' counts and the
+// oldest waiting ask, to show the backlog. It may not publish an ask: only the builder and the checker ask, by their seat use.
+// The watchman is granted nothing here: a waiting ask has no pulse, a taken one is read from the build module's steps (issue
+// 1908). Nothing is a wildcard over a stream or a worker.
+const (
+	// ViewModule is the module of the delivery view (mesh-delivery-view).
+	ViewModule = "mesh-delivery-view"
+	// BuilderModule is the module of the builder (mesh-delivery-builder).
+	BuilderModule = "mesh-delivery-builder"
+)
+
+// BuildAskReads are the API subjects the builder requests when it takes over, at its start, a key naming an ask (issue
+// 1910): each build seat's stream's information and its messages by sequence, to tell whether the ask is on its stream.
+// Reads only: no consumer, no pull, no acknowledgement; the builder puts its asks by its seat use, as before.
+func BuildAskReads() []string {
+	var out []string
+	for _, lang := range delivery.AskLanguages {
+		if stream, err := delivery.AskStream(lang); err == nil {
+			out = append(out, "$JS.API.STREAM.INFO."+stream, "$JS.API.STREAM.MSG.GET."+stream)
+		}
+	}
+	return out
+}
+
+// BuildBacklogReads are the API subjects the view requests: the information of each build seat's stream and of each of its
+// shared workers (delivery.AskStream, delivery.AskWorker), and the message of the stream by sequence. Reads only: no
+// message is pulled, none acknowledged, none published.
+func BuildBacklogReads() []string {
+	var out []string
+	for _, lang := range delivery.AskLanguages {
+		stream, err := delivery.AskStream(lang)
+		if err != nil {
+			continue
+		}
+		out = append(out, "$JS.API.STREAM.INFO."+stream, "$JS.API.STREAM.MSG.GET."+stream)
+		for _, kind := range delivery.AskKinds {
+			if w, err := delivery.AskWorker(lang, kind); err == nil {
+				out = append(out, "$JS.API.CONSUMER.INFO."+stream+"."+w)
+			}
+		}
+	}
+	return out
+}