Merge remote-tracking branch 'origin/main' into feat/try-speed

Reviewed-on: #79

go/buildstep/askrun.go

@@ -8,6 +8,7 @@ import (
 	"slices"
 	"sort"
 	"strings"
+	"sync"
 
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
@@ -170,16 +171,36 @@ func (s AskSteps) check(ctx context.Context, job delivery.CheckJob) (any, error)
 	if job.Runner != "" && (job.RunnerWhen == "" || changesUnder(f.Changed, job.RunnerWhen)) {
 		runner = job.Runner
 	}
-	for _, level := range job.Levels {
+	// The levels run side by side (issue 1921, try speed S10; the operator's yes to D1, ADR 0541): the integration level
-		la := delivery.LevelAnswer{Level: level}
+	// does not wait for the unit level. They are answered in their order, so the first level that did not pass is still
-		passed, err := s.level(ctx, job, level, f, runner, &la)
+	// the first failure the asker reads (ADR 0484 clause 13); the levels after it are kept in the answer for the log.
-		answer.Levels = append(answer.Levels, la)
+	type ran struct {
-		if err != nil {
+		la     delivery.LevelAnswer
-			return nil, err
+		passed bool
-		}
+		err    error
-		if !passed {
+	}
-			return answer, nil // the first level that did not pass ends the check (ADR 0484 clause 13)
+	runs := make([]ran, len(job.Levels))
+	var wg sync.WaitGroup
+	for i, level := range job.Levels {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			runs[i].la = delivery.LevelAnswer{Level: level}
+			runs[i].passed, runs[i].err = s.level(ctx, job, level, f, runner, &runs[i].la)
+		}()
+	}
+	wg.Wait()
+	failed := false
+	for _, r := range runs {
+		if r.err != nil {
+			if failed {
+				continue // a level after the first failure that could not run: the failure is the answer
+			}
+			answer.Levels = append(answer.Levels, r.la)
+			return nil, r.err
 		}
+		answer.Levels = append(answer.Levels, r.la)
+		failed = failed || !r.passed
 	}
 	return answer, nil
 }

go/buildstep/askrun_levels_test.go

@@ -0,0 +1,60 @@
+package buildstep
+
+import (
+	"context"
+	"encoding/json"
+	"sync"
+	"testing"
+	"time"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// 1921/S10 (the operator's yes to D1, ADR 0541): a check's levels run side by side: the integration level has started
+// before the unit level ends. The answer holds the levels in their order, so with the unit level failing it still names
+// the unit level first; the integration level's answer is kept after it for the log.
+func TestACheckRunsItsLevelsSideBySideAndAnswersThemInOrder(t *testing.T) {
+	integrationStarted := make(chan struct{})
+	var once sync.Once
+	var mu sync.Mutex
+	unitWaited := false
+	steps := AskSteps{
+		Fetch: func(context.Context, map[string]any) (any, error) {
+			return map[string]any{"workspace": "/w", "modules": []string{"."}}, nil
+		},
+		Test: func(ctx context.Context, args map[string]any) (any, error) {
+			switch args["level"] {
+			case delivery.LevelUnit:
+				select {
+				case <-integrationStarted:
+					mu.Lock()
+					unitWaited = true
+					mu.Unlock()
+				case <-time.After(2 * time.Second):
+				}
+				return map[string]any{"passed": false, "level": "unit"}, nil
+			default:
+				once.Do(func() { close(integrationStarted) })
+				return map[string]any{"passed": true, "level": "integration"}, nil
+			}
+		},
+	}
+	out, err := RunAsk(context.Background(), steps, ask(delivery.CheckJob{Levels: []string{delivery.LevelUnit, delivery.LevelIntegration},
+		Fetch: map[string]any{"repository": "novox/x", "commit": runCommit}}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	mu.Lock()
+	defer mu.Unlock()
+	if !unitWaited {
+		t.Error("the integration level did not start while the unit level ran")
+	}
+	a := out.(delivery.CheckAnswer)
+	if len(a.Levels) != 2 || a.Levels[0].Level != delivery.LevelUnit || a.Levels[1].Level != delivery.LevelIntegration {
+		t.Fatalf("levels %+v, want unit then integration", a.Levels)
+	}
+	var first struct{ Passed bool }
+	if err := json.Unmarshal(a.Levels[0].Tests[0], &first); err != nil || first.Passed {
+		t.Errorf("the first level's result %s, want the unit level's failure", a.Levels[0].Tests[0])
+	}
+}

go/buildstep/askrun_test.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 
@@ -16,6 +17,7 @@ const runCommit = "0123456789abcdef0123456789abcdef01234567"
 
 // recorder is a build module's step tools that record each call.
 type recorder struct {
+	mu      sync.Mutex // a check's levels run side by side (issue 1921, S10)
 	calls   []string
 	fetch   map[string]any
 	tests   map[string]bool // package or module directory -> passed
@@ -26,7 +28,9 @@ 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.mu.Lock()
 			r.calls = append(r.calls, name+" "+string(b))
+			r.mu.Unlock()
 			return answer(args), nil
 		}
 	}
@@ -110,8 +114,8 @@ func TestRunAskRefusesAnotherToolchain(t *testing.T) {
 }
 
 // 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
+// verdicts, tests the packages whose tests changed first, then the rest also after a failure (issue 1921); the levels run
-// level after one that did not pass (ADR 0484 clause 13).
+// side by side and are answered in order, the first that did not pass first (ADR 0484 clause 13; issue 1921 S10).
 func TestRunAskChecksTheLevelsOfOneCheck(t *testing.T) {
 	r := &recorder{
 		fetch:   map[string]any{"workspace": "/w", "changed": []string{"pkg/b/b_test.go"}},
@@ -123,7 +127,13 @@ func TestRunAskChecksTheLevelsOfOneCheck(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	got := strings.Join(r.calls, "\n")
+	var unit []string
+	for _, c := range r.calls {
+		if !strings.Contains(c, `"level":"integration"`) {
+			unit = append(unit, c)
+		}
+	}
+	got := strings.Join(unit, "\n")
 	want := `fetch {"base":"` + runCommit + `","commit":"` + runCommit + `","repository":"novox/x"}
 digest {"level":"unit","workspace":"/w"}
 test {"level":"unit","packages":["x/pkg/b"],"workspace":"/w"}
@@ -132,8 +142,8 @@ test {"level":"unit","packages":["x/pkg/a"],"workspace":"/w"}`
 		t.Fatalf("calls:\n%s\nwant:\n%s", got, want)
 	}
 	a := out.(delivery.CheckAnswer)
-	if len(a.Levels) != 1 {
+	if len(a.Levels) != 2 || a.Levels[1].Level != delivery.LevelIntegration {
-		t.Fatalf("levels %+v, want the unit level alone", a.Levels)
+		t.Fatalf("levels %+v, want the unit level first, the integration level after it", 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 {
@@ -220,8 +230,8 @@ func TestRunAskRunsEveryPackageAfterAFailure(t *testing.T) {
 		t.Fatal(err)
 	}
 	a := out.(delivery.CheckAnswer)
-	if len(a.Levels) != 1 || len(a.Levels[0].Tests) != 2 {
+	if len(a.Levels) != 2 || len(a.Levels[0].Tests) != 2 || a.Levels[0].Level != delivery.LevelIntegration {
-		t.Fatalf("levels %+v, want the one level with both packages' results", a.Levels)
+		t.Fatalf("levels %+v, want the first level with both packages' results, in the order asked", a.Levels)
 	}
 	for i, raw := range a.Levels[0].Tests {
 		var res struct{ Passed bool }
@@ -239,7 +249,7 @@ func TestRunAskRunsEveryPackageAfterAFailure(t *testing.T) {
 	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 {
+	if a := out.(delivery.CheckAnswer); len(r.calls) != 5 || len(a.Levels) != 2 || len(a.Levels[0].Tests) != 2 || a.Levels[0].Level != delivery.LevelUnit {
-		t.Fatalf("calls %v, levels %+v: want both directories of the unit level and no integration level", r.calls, a.Levels)
+		t.Fatalf("calls %v, levels %+v: want both directories of each level, the unit level first", r.calls, a.Levels)
 	}
 }

go/buildstep/isolate.go

@@ -3,10 +3,13 @@ package buildstep
 import (
 	"context"
 	"fmt"
+	"io/fs"
 	"os"
 	"path"
 	"path/filepath"
+	"strconv"
 	"strings"
+	"sync"
 
 	"git.novox.be/novox/mesh-sdk/go/forgekey"
 )
@@ -29,16 +32,25 @@ const Bubblewrap = "bwrap"
 //   - 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.
+//     (WriteCaches), so a candidate's code never changes what a later build reads;
+//   - with a CacheLayer, what one command writes into the caches kept for the later commands of the same ask (issue 1921,
+//     the try speed-up): the vet, the unit tests and the integration compile of one ask compile each package once.
 type Isolation struct {
 	Workspace   string
 	Writable    []string
 	ReadOnly    []string
 	Caches      []string
 	WriteCaches bool
-	Env         []string
+	// CacheLayer is a directory of the ask's own, in its workspace and gone with it: each command writes the caches into
+	// a layer of its own beneath it (overlayfs refuses an upper layer two mounts share, and an ask's commands run side by
+	// side), which Isolated moves into the ask's kept layer when the command ends; every later command reads the kept
+	// layer above the shared cache. The shared cache stays unchanged. Empty: what a command writes is thrown away.
+	CacheLayer string
+	Env        []string
 	// Hosts is the file bound as /etc/hosts; Isolated writes one naming only the loopback.
 	Hosts string
+	// run is the directory of this command's own writable layers under CacheLayer; Isolated makes one per command.
+	run string
 }
 
 // etcNeeded is what of /etc a program in the step may read: who the users are, where the libraries are, the
@@ -91,7 +103,7 @@ func (iso Isolation) command(env []string, name string, args ...string) ([]strin
 	for _, group := range []struct {
 		what string
 		dirs []string
-	}{{"writable directory", iso.Writable}, {"read-only directory", iso.ReadOnly}, {"cache", iso.Caches}} {
+	}{{"writable directory", iso.Writable}, {"read-only directory", iso.ReadOnly}, {"cache", iso.Caches}, {"cache layer", layerDirs(iso.CacheLayer)}} {
 		for _, d := range group.dirs {
 			if err := checkDir(group.what, d); err != nil {
 				return nil, err
@@ -113,7 +125,7 @@ func (iso Isolation) command(env []string, name string, args ...string) ([]strin
 	for _, d := range iso.ReadOnly {
 		argv = append(argv, "--ro-bind", d, d)
 	}
-	argv = append(argv, cacheArgs(iso.Caches, iso.WriteCaches)...)
+	argv = append(argv, iso.cacheArgs()...)
 	argv = append(argv, "--bind", iso.Workspace, iso.Workspace)
 	for _, d := range iso.Writable {
 		argv = append(argv, "--bind", d, d)
@@ -134,19 +146,107 @@ func (iso Isolation) command(env []string, name string, args ...string) ([]strin
 
 // 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).
+// nothing it wrote outlives it (bubblewrap's --tmp-overlay, an overlay mount in the step's user namespace). With a
-func cacheArgs(caches []string, write bool) []string {
+// CacheLayer the ask's kept layer lies above the shared cache and the command's writes go to its own layer on disk
+// (--overlay), which Isolated keeps for the ask when the command ends.
+func (iso Isolation) cacheArgs() []string {
 	var argv []string
-	for _, c := range caches {
+	for i, c := range iso.Caches {
-		if write {
+		switch {
+		case iso.WriteCaches:
 			argv = append(argv, "--bind", c, c)
-			continue
+		case iso.CacheLayer != "":
+			upper, work := iso.runLayer(i)
+			argv = append(argv, "--overlay-src", c, "--overlay-src", keptLayer(iso.CacheLayer, i), "--overlay", upper, work, c)
+		default:
+			argv = append(argv, "--overlay-src", c, "--tmp-overlay", c)
 		}
-		argv = append(argv, "--overlay-src", c, "--tmp-overlay", c)
 	}
 	return argv
 }
 
+func layerDirs(layer string) []string {
+	if layer == "" {
+		return nil
+	}
+	return []string{layer}
+}
+
+// keptLayer is where the ask keeps what its commands wrote into the cache i.
+func keptLayer(layer string, i int) string { return filepath.Join(layer, "kept", strconv.Itoa(i)) }
+
+// runLayer is the upper and work directory of this command's writes into the cache i. Command, which makes no
+// directory, names the layer "run"; Isolated gives each command one of its own.
+func (iso Isolation) runLayer(i int) (upper, work string) {
+	run := iso.run
+	if run == "" {
+		run = filepath.Join(iso.CacheLayer, "run")
+	}
+	return filepath.Join(run, strconv.Itoa(i), "upper"), filepath.Join(run, strconv.Itoa(i), "work")
+}
+
+// layerLocks hold one mutex per cache layer, so two commands ending at once keep their writes one after the other.
+var layerLocks sync.Map
+
+// prepareLayer makes the kept layers and a run directory of the command's own under the cache layer.
+func (iso *Isolation) prepareLayer() error {
+	if iso.CacheLayer == "" || iso.WriteCaches || len(iso.Caches) == 0 {
+		return nil
+	}
+	if err := os.MkdirAll(filepath.Join(iso.CacheLayer, "runs"), 0o700); err != nil {
+		return err
+	}
+	run, err := os.MkdirTemp(filepath.Join(iso.CacheLayer, "runs"), "run-")
+	if err != nil {
+		return err
+	}
+	iso.run = run
+	for i := range iso.Caches {
+		upper, work := iso.runLayer(i)
+		for _, d := range []string{keptLayer(iso.CacheLayer, i), upper, work} {
+			if err := os.MkdirAll(d, 0o700); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+// keepLayer moves what the command wrote into the caches into the ask's kept layers, and removes its run directory.
+// A file the command wrote replaces the kept one (a cache's newest write wins); a whiteout (a file the command
+// deleted) is not kept, since a cache entry deleted by one command is no fault of a later one. A write that cannot be
+// kept only means a later command builds it again.
+func (iso Isolation) keepLayer() {
+	if iso.run == "" {
+		return
+	}
+	defer os.RemoveAll(iso.run)
+	mu, _ := layerLocks.LoadOrStore(iso.CacheLayer, &sync.Mutex{})
+	mu.(*sync.Mutex).Lock()
+	defer mu.(*sync.Mutex).Unlock()
+	for i := range iso.Caches {
+		upper, _ := iso.runLayer(i)
+		kept := keptLayer(iso.CacheLayer, i)
+		filepath.WalkDir(upper, func(p string, d fs.DirEntry, err error) error {
+			if err != nil || p == upper {
+				return nil
+			}
+			rel, _ := filepath.Rel(upper, p)
+			to := filepath.Join(kept, rel)
+			switch {
+			case d.IsDir():
+				if fi, err := os.Lstat(to); err == nil && !fi.IsDir() {
+					os.Remove(to)
+				}
+				os.MkdirAll(to, 0o700)
+			case d.Type().IsRegular():
+				os.Rename(p, to)
+			}
+			return nil
+		})
+	}
+}
+
 // loopbackHosts is the hosts file of a step: the loopback and nothing else.
 const loopbackHosts = "127.0.0.1 localhost\n::1 localhost\n"
 
@@ -166,6 +266,10 @@ func Isolated(run forgekey.Runner, iso Isolation) forgekey.Runner {
 		}
 		iso := iso
 		iso.Hosts = hosts
+		if err := iso.prepareLayer(); err != nil {
+			return forgekey.Ran{Status: 1, Err: "the step's cache layer: " + err.Error()}
+		}
+		defer iso.keepLayer()
 		argv, err := iso.command(env, name, args...)
 		if err != nil {
 			return forgekey.Ran{Status: 1, Err: err.Error()}

go/buildstep/isolate_integration_test.go

@@ -64,3 +64,39 @@ func TestARunStepReachesNothingAndLeavesTheCachesUnchanged(t *testing.T) {
 		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)
 	}
 }
+
+// 1921/S2: in one ask (one cache layer), a second go build of the same package does not compile it again, and the
+// shared cache is unchanged afterwards.
+func TestASecondBuildOfTheAskFindsTheFirstsCompiledAndTheSharedCacheIsUnchanged(t *testing.T) {
+	if _, err := exec.LookPath(Bubblewrap); err != nil {
+		t.Fatalf("bubblewrap is not installed here (issue 1309): %v", err)
+	}
+	goBin, err := exec.LookPath("go")
+	if err != nil {
+		t.Fatal(err)
+	}
+	root := t.TempDir()
+	shared := filepath.Join(root, "gobuild")
+	if err := os.MkdirAll(shared, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	workspace := filepath.Join(root, "ws")
+	tree := filepath.Join(workspace, "tree")
+	writeFile(t, tree, "go.mod", "module probe\n\ngo 1.22\n")
+	writeFile(t, tree, "probe.go", "package probe\n\nfunc Probe() int { return 42 }\n")
+	run := Isolated(forgekey.ExecRunnerFor(0), Isolation{Workspace: workspace, Caches: []string{shared},
+		CacheLayer: filepath.Join(workspace, "cachelayer"), ReadOnly: []string{filepath.Dir(filepath.Dir(goBin))}})
+	env := []string{"PATH=" + filepath.Dir(goBin) + ":/usr/bin:/bin", "GOCACHE=" + shared, "GOTOOLCHAIN=local", "GOFLAGS=-mod=mod"}
+	for i, want := range []bool{true, false} {
+		r := run(context.Background(), env, "go", "-C", tree, "build", "-x", "./...")
+		if r.Status != 0 || r.Err != "" {
+			t.Fatalf("build %d: status %d %s\n%s", i+1, r.Status, r.Err, r.Stderr)
+		}
+		if compiled := strings.Contains(r.Stderr, "/compile "); compiled != want {
+			t.Errorf("build %d compiled the package: %v, want %v\n%s", i+1, compiled, want, r.Stderr)
+		}
+	}
+	if entries, _ := os.ReadDir(shared); len(entries) != 0 {
+		t.Errorf("the shared cache was written: %d entries", len(entries))
+	}
+}

go/buildstep/isolate_layer_test.go

@@ -0,0 +1,110 @@
+package buildstep
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"sync"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/forgekey"
+)
+
+// overlayOf answers the upper directory a command line gives the cache c, "" when it gives none.
+func overlayOf(argv []string, c string) string {
+	for i := 0; i+3 < len(argv); i++ {
+		if argv[i] == "--overlay" && argv[i+3] == c {
+			return argv[i+1]
+		}
+	}
+	return ""
+}
+
+// 1921/S2: with a cache layer, a command reads the ask's kept layer above the shared cache and writes into a layer on
+// disk of its own, never into the shared cache and never into a throwaway tmpfs.
+func TestACommandWithACacheLayerReadsTheKeptLayerAndWritesItsOwn(t *testing.T) {
+	fixedSystem(t)
+	iso := Isolation{Workspace: "/w", Caches: []string{"/cache/gomod", "/cache/gobuild"}, CacheLayer: "/w/cachelayer"}
+	argv, err := iso.Command("go", "vet")
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i, c := range iso.Caches {
+		if !holds(argv, "--overlay-src", c, "--overlay-src", keptLayer(iso.CacheLayer, i), "--overlay") {
+			t.Errorf("the cache %s is not read beneath the ask's kept layer: %v", c, argv)
+		}
+		if up := overlayOf(argv, c); up == "" || filepath.Dir(filepath.Dir(filepath.Dir(up))) != "/w/cachelayer" {
+			t.Errorf("the cache %s is written into %q, not a layer of the ask's own: %v", c, up, argv)
+		}
+		if holds(argv, "--tmp-overlay", c) || holds(argv, "--bind", c, c) {
+			t.Errorf("the cache %s is thrown away or written: %v", c, argv)
+		}
+	}
+	if _, err := (Isolation{Workspace: "/w", CacheLayer: "cachelayer"}).Command("go"); err == nil {
+		t.Error("a relative cache layer was taken")
+	}
+}
+
+// 1921/S2: what one command wrote into the caches is kept for the ask's later commands, the shared cache stays
+// unchanged, two commands at once write into layers of their own (overlayfs refuses an upper layer two mounts share),
+// and a command's own layer is gone when it ends.
+func TestWhatOneCommandCompiledIsReadByTheNextOfTheSameAsk(t *testing.T) {
+	fixedSystem(t)
+	root := t.TempDir()
+	shared := filepath.Join(root, "gobuild")
+	if err := os.MkdirAll(shared, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	layer := filepath.Join(root, "ws", "cachelayer")
+	var mu sync.Mutex
+	uppers := map[string]bool{}
+	gate := make(chan struct{})
+	var started sync.WaitGroup
+	started.Add(2)
+	inner := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		up := overlayOf(args, shared)
+		mu.Lock()
+		uppers[up] = true
+		mu.Unlock()
+		if holds(args, "--", "go", "build") {
+			started.Done()
+			<-gate // both commands are running before either ends
+			os.MkdirAll(filepath.Join(up, "ab"), 0o700)
+			os.WriteFile(filepath.Join(up, "ab", args[len(args)-1]+"-d"), []byte("compiled"), 0o600)
+		}
+		return forgekey.Ran{}
+	}
+	run := Isolated(inner, Isolation{Workspace: filepath.Join(root, "ws"), Caches: []string{shared}, CacheLayer: layer})
+	var wg sync.WaitGroup
+	for _, pkg := range []string{"one", "two"} {
+		wg.Add(1)
+		go func() { defer wg.Done(); run(context.Background(), nil, "go", "build", pkg) }()
+	}
+	started.Wait()
+	close(gate)
+	wg.Wait()
+	if len(uppers) != 2 {
+		t.Fatalf("two commands at once wrote into %d layers, want 2 of their own: %v", len(uppers), uppers)
+	}
+	for _, pkg := range []string{"one", "two"} {
+		if b, err := os.ReadFile(filepath.Join(keptLayer(layer, 0), "ab", pkg+"-d")); err != nil || string(b) != "compiled" {
+			t.Errorf("what the build of %s compiled is not kept for the ask: %q %v", pkg, b, err)
+		}
+	}
+	for up := range uppers {
+		if _, err := os.Stat(up); !os.IsNotExist(err) {
+			t.Errorf("the command's own layer %s outlived it: %v", up, err)
+		}
+	}
+	var next []string
+	Isolated(func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		next = args
+		return forgekey.Ran{}
+	}, Isolation{Workspace: filepath.Join(root, "ws"), Caches: []string{shared}, CacheLayer: layer})(context.Background(), nil, "go", "test")
+	if !holds(next, "--overlay-src", shared, "--overlay-src", keptLayer(layer, 0)) {
+		t.Errorf("the next command does not read the kept layer: %v", next)
+	}
+	if entries, _ := os.ReadDir(shared); len(entries) != 0 {
+		t.Errorf("the shared cache was written: %v", entries)
+	}
+}

go/buildstep/merge.go

@@ -24,7 +24,8 @@ type MergeResult struct {
 // 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
+// fetches base by its sha: from the mirror WithMirror names, when it holds base (UpdateMirror to base first), else
+// from remote. 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
@@ -67,12 +68,20 @@ func MergeInto(ctx context.Context, run forgekey.Runner, dir, remote, base, comm
 	if err != nil {
 		return res, err
 	}
-	fetch := []string{"fetch", "--no-tags", "origin", base}
+	fetchFrom := func(source string) error {
-	if strings.TrimSpace(shallow) == "true" {
+		fetch := []string{"fetch", "--no-tags", source, base}
-		fetch = []string{"fetch", "--no-tags", "--unshallow", "origin", base}
+		if strings.TrimSpace(shallow) == "true" {
+			fetch = []string{"fetch", "--no-tags", "--unshallow", source, base}
+		}
+		_, err := git(fetch...)
+		return err
 	}
-	if _, err := git(fetch...); err != nil {
+	// With a mirror brought to the trunk commit, the history is deepened from it, a local fetch (issue 1921, try speed
-		return res, fmt.Errorf("the trunk commit %s: %w", base, err)
+	// S6); a mirror that cannot answer leaves it to the forge, as before.
+	if o.mirror == "" || fetchFrom(o.mirror) != nil {
+		if err := fetchFrom("origin"); 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)

go/buildstep/merge_integration_test.go

@@ -170,3 +170,33 @@ func TestMergeIntoAHeadAlreadyInTheTrunkChangesNothing(t *testing.T) {
 		t.Errorf("result = %+v, %v", res, err)
 	}
 }
+
+// 1921/S6: with a mirror brought to the head and to the trunk commit, the merge asks the forge for nothing: it succeeds
+// with the forge gone.
+func TestMergeIntoWithAMirrorAtTheTrunkNeedsNoForge(t *testing.T) {
+	r := newMergeRig(t)
+	head := r.head(map[string]string{"b.txt": "head\n"})
+	base := r.advance(map[string]string{"a.txt": "one\ntwo\nthree\nfour\n"})
+	mirror := filepath.Join(t.TempDir(), "mirror.git")
+	if err := os.MkdirAll(mirror, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	for _, c := range []string{head, base} {
+		if err := UpdateMirror(context.Background(), forgekey.ExecRunner, mirror, r.remote, c, "", AllowFileRemote()); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := FetchCommit(context.Background(), forgekey.ExecRunner, r.ws, r.remote, head, "", AllowFileRemote(), WithMirror(mirror)); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.RemoveAll(r.bare); err != nil { // the forge is gone
+		t.Fatal(err)
+	}
+	res, err := MergeInto(context.Background(), forgekey.ExecRunner, r.ws, r.remote, base, head, AllowFileRemote(), WithMirror(mirror))
+	if err != nil {
+		t.Fatalf("the merge asked the forge: %v", err)
+	}
+	if len(res.Merge) != 40 || !reflect.DeepEqual(res.Changed, []string{"b.txt"}) {
+		t.Errorf("result = %+v", res)
+	}
+}

go/buildstep/merge_test.go

@@ -72,3 +72,39 @@ func TestMergeIntoRunsTheCheckMergesCommands(t *testing.T) {
 		}
 	}
 }
+
+// 1921/S6: with a mirror that holds the trunk commit, the merge deepens the workspace from the mirror, a local fetch,
+// and asks the forge nothing; a mirror that cannot answer falls back to the forge.
+func TestMergeIntoWithAMirrorFetchesTheTrunkFromTheMirror(t *testing.T) {
+	base := strings.Repeat("b", 40)
+	mirror := t.TempDir()
+	answer := func(failMirror bool) *fakeGit {
+		return &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"}
+			case failMirror && strings.Contains(l, " fetch ") && strings.Contains(l, mirror):
+				return forgekey.Ran{Status: 128, Stderr: "fatal: not our ref"}
+			}
+			return forgekey.Ran{}
+		}}
+	}
+	f := answer(false)
+	dir := t.TempDir()
+	if _, err := MergeInto(context.Background(), f.run, dir, "ssh://mesh-forge/o/r.git", base, sha, WithMirror(mirror)); err != nil {
+		t.Fatal(err)
+	}
+	all := strings.Join(f.calls, "\n")
+	if !strings.Contains(all, "fetch --no-tags --unshallow "+mirror+" "+base) || strings.Contains(all, "--unshallow origin") {
+		t.Errorf("the trunk was not fetched from the mirror alone:\n%s", all)
+	}
+	g := answer(true)
+	if _, err := MergeInto(context.Background(), g.run, t.TempDir(), "ssh://mesh-forge/o/r.git", base, sha, WithMirror(mirror)); err != nil {
+		t.Fatal(err)
+	}
+	if all := strings.Join(g.calls, "\n"); !strings.Contains(all, "fetch --no-tags --unshallow origin "+base) {
+		t.Errorf("a mirror that could not answer did not fall back to the forge:\n%s", all)
+	}
+}

go/catalogue/delivery_seat.go

@@ -9,7 +9,26 @@ package catalogue
 // DeliverySeat is the seat mesh-delivery holds.
 const DeliverySeat = "mesh-delivery"
 
-// deliveryVerbs are the delivery seat's tools: six that read, and the acts of a person, a reviewer and healer H2.
+// RemovedDeliveryVerbs are the delivery seat's verbs release 6 removed (novox/hq ADR 0539 clause 17): with no plan the
+// gate keeps the merge's states and derives nothing after the merge. Each stays in deliveryVerbs as an optional row
+// with no input, so the holder of before and the holder of release 6 both hold the seat and a caller is answered by
+// name with its replacement, given here.
+var RemovedDeliveryVerbs = map[string]string{
+	"times":          "the delivery view (nox-delivery): each machine's want and have, and since when",
+	"what-if":        "the merge check's composition, which composes every machine a change touches",
+	"release":        "the assigner's asks (hold, restore, backup, record), answered on the phone or in the delivery view",
+	"stop":           "a bad fingerprint is held and its canary set back by the assigner (ADR 0429 §6, ADR 0539 clause 18)",
+	"retire-history": "nothing to retire: the gate keeps no delivery after its merge",
+}
+
+// deliveryRemovedInR6 is the row of a verb release 6 removed from the delivery seat.
+func deliveryRemovedInR6(name string) Verb {
+	return Verb{Name: name, Description: "Removed in R6 (ADR 0539): refused by name, naming its replacement: " +
+		RemovedDeliveryVerbs[name], Input: schema(nil, nil), Optional: true}
+}
+
+// deliveryVerbs are the delivery seat's tools: what reads the merges and checks, and the acts of a person and healer H2
+// on a merge (ADR 0539 clause 17).
 func deliveryVerbs() []Verb {
 	return []Verb{
 		{Name: "deliveries", Description: "Every delivery not final, and those that ended in the last day, one line " +
@@ -18,15 +37,7 @@ func deliveryVerbs() []Verb {
 			Input: schema(map[string]string{"state": "one state, e.g. delivering or held",
 				"repository": "owner/repository", "group": "a group's id (its branch name)",
 				"all": "\"true\": the final ones of the last thirty days too"}, nil, "all")},
-		// Delivery time against the delivery budgets (novox/hq ADR 0282): what probe D16 reads, optional until its
+		deliveryRemovedInR6("times"),
-		// holder serves it.
-		{Name: "times", Description: "Delivery time: from a merge to every machine of its walk running the build. " +
-			"Each class's delivery budget (a leaf module three minutes, a core module ten), the last days' median and " +
-			"worst, how many within and over, the newest delivery of each class, every delivery over its budget with its " +
-			"longest phase, and the delivered ones whose time is not known. Given a delivery's id, its time phase by phase.",
-			Input: schema(map[string]string{"days": "how many days back (default 7)", "id": "one delivery's id: its phases"}, nil),
-			// Optional until mesh-delivery serves it: its holder lives in the catalogue (design 33 §7).
-			Optional: true},
 		{Name: "show", Description: "One delivery or group whole: its delivery plan (what it builds, what each " +
 			"machine receives, what is not an ordinary send), every transition with when and why, the machine " +
 			"steps of its walk, its group and its order.",
@@ -35,12 +46,7 @@ func deliveryVerbs() []Verb {
 			"(declared, built by, version skew, engine before controller, by name), its composed check and its " +
 			"state, derived from its members.",
 			Input: schema(map[string]string{"all": "\"true\": the groups that ended too"}, nil, "all")},
-		{Name: "what-if", Description: "The delivery plan a change would have, asked of the controller's planner " +
+		deliveryRemovedInR6("what-if"),
-			"and kept nowhere: the modules it moves and their dependents in tiers, what each machine would receive, " +
-			"the steps that are not an ordinary send.",
-			Input: schema(map[string]string{"repository": "owner/repository",
-				"paths": "the files it changes, comma-separated, from the repository's root",
-				"base":  "the branch it merges into (default main)"}, []string{"repository", "paths"})},
 		{Name: "checks", Description: "What the mesh's checks said of a pull request's head or of one commit: each " +
 			"of the commit's mesh statuses (mesh/check, the one a main requires from R4e, hq's mesh/repo-check, " +
 			"mesh/delivery, …) with its state, " +
@@ -62,40 +68,13 @@ func deliveryVerbs() []Verb {
 			"controller is asked for its check. With why.",
 			Input: schema(map[string]string{"id": "the delivery's id", "why": "why, kept with the transition"},
 				[]string{"id", "why"})},
-		{Name: "release", Description: "A person's word that a held delivery goes on: it starts delivering. With why.",
+		deliveryRemovedInR6("release"),
-			Input: schema(map[string]string{"id": "the delivery's id", "why": "why, kept with the transition"},
+		deliveryRemovedInR6("stop"),
-				[]string{"id", "why"})},
-		{Name: "stop", Description: "Stop a delivery that is not final, with why; its walk is ended through the " +
-			"controller, and in a group every member after it is stopped too, naming it.",
-			Input: schema(map[string]string{"id": "the delivery's id", "why": "why, kept with the transition"},
-				[]string{"id", "why"})},
 		{Name: "close", Description: "Healer H2's verb: take the one transition the table names for a delivery held " +
 			"past its bound. Refused for any other.",
 			Input: schema(map[string]string{"id": "the delivery's id", "why": "the condition it answers"},
 				[]string{"id", "why"})},
-		{Name: "retire-history", Description: "Retire held deliveries that are history, on a person's word, with " +
+		deliveryRemovedInR6("retire-history"),
-			"why: each made from the forge's word for a merge on the trunk heard long after it happened — replayed " +
-			"when the holder first held the seat — with no walk of it open. Never released, delivered or put back: " +
-			"retired, final. One by id, refused when the rule does not take it; or every held one, of one " +
-			"repository when named, answering how many it retired and naming those it left held. dry \"true\" " +
-			"answers what it would do and changes nothing.",
-			Input: schema(map[string]string{"why": "why, kept with every transition",
-				"id":         "one delivery's id; every held one when empty",
-				"repository": "owner/repository: only its held deliveries",
-				"dry":        "\"true\": what it would retire, changing nothing"}, []string{"why"}, "dry"),
-			// Added after the seat's holder shipped (novox/hq issue 313): optional until mesh-delivery serves it.
-			Optional: true},
-		{Name: "mark-ready", Description: "A reviewer's word that a delivery's head is approved: the holder puts the " +
-			"label mesh/ready on its pull request and then writes \"ready at <head>\", the order the forge counts, " +
-			"as the mesh's own forge account, naming who reviewed it and why. Refused when the delivery's commit is " +
-			"no longer its pull request's head. mesh-delivery then merges it once its checks pass (novox/hq ADR 0364).",
-			Input: schema(map[string]string{"id": "the delivery's id (owner/repository@commit): the head reviewed",
-				"reviewed-by": "who reviewed it, as who@node", "why": "the review's verdict in a line"},
-				[]string{"id", "reviewed-by", "why"}),
-			// Kept one more release, optional (novox/hq issue 1022): mesh-delivery no longer serves it, but the manifest
-			// it still has on the mesh does until its catalogue member merges, and a seat refuses a holder that serves
-			// a verb it does not promise. The next release removes this entry.
-			Optional: true},
 	}
 }
 

go/catalogue/delivery_seat_test.go

@@ -58,107 +58,3 @@ func TestTheDeliverySeatPromisesChecks(t *testing.T) {
 		t.Fatalf("a holder without %s: %v", before[0], err)
 	}
 }
-
-// The seat retires history on a person's word (novox/hq issue 313): `retire-history`, with why, one delivery by
-// id or every held one, dry to see first. Added after the holder shipped, it is optional, so the holder that
-// does not serve it yet still holds the seat, and one that does is not refused for a verb the seat lacks.
-func TestTheDeliverySeatPromisesRetireHistoryOptionally(t *testing.T) {
-	seat, _ := SeatNamed(DeliverySeat)
-	var retire *Verb
-	for i := range seat.Serves {
-		if seat.Serves[i].Name == "retire-history" {
-			retire = &seat.Serves[i]
-		}
-	}
-	if retire == nil || !retire.Optional {
-		t.Fatalf("the delivery seat promises %v, retire-history optionally", VerbNames(seat.Serves))
-	}
-	props, _ := retire.Input["properties"].(map[string]any)
-	for _, arg := range []string{"why", "id", "repository", "dry"} {
-		if _, has := props[arg]; !has {
-			t.Errorf("retire-history takes no %q", arg)
-		}
-	}
-	if req, _ := retire.Input["required"].([]string); !reflect.DeepEqual(req, []string{"why"}) {
-		t.Errorf("retire-history requires %v, wanted only why", req)
-	}
-	var without []string
-	for _, v := range VerbNames(seat.Serves) {
-		if v != "retire-history" {
-			without = append(without, v)
-		}
-	}
-	m := Manifest{Module: "mesh-delivery", Claims: []Claim{{Name: DeliverySeat, Scope: ScopeMesh, Serves: without}}}
-	if err := CanHold(m, seat); err != nil {
-		t.Fatalf("a holder without retire-history yet: %v", err)
-	}
-	m.Claims[0].Serves = VerbNames(seat.Serves)
-	if err := CanHold(m, seat); err != nil {
-		t.Fatalf("a holder serving retire-history: %v", err)
-	}
-}
-
-// The seat says delivery times (novox/hq ADR 0282, issue 382): `times`, over some days or for one delivery. Added
-// after the holder shipped, it is optional, so the holder that does not serve it yet still holds the seat, and one
-// that does is not refused for a verb the seat lacks.
-func TestTheDeliverySeatPromisesTimesOptionally(t *testing.T) {
-	seat, _ := SeatNamed(DeliverySeat)
-	var times *Verb
-	for i := range seat.Serves {
-		if seat.Serves[i].Name == "times" {
-			times = &seat.Serves[i]
-		}
-	}
-	if times == nil || !times.Optional {
-		t.Fatalf("the delivery seat promises %v, times optionally", VerbNames(seat.Serves))
-	}
-	props, _ := times.Input["properties"].(map[string]any)
-	for _, arg := range []string{"days", "id"} {
-		if _, has := props[arg]; !has {
-			t.Errorf("times takes no %q", arg)
-		}
-	}
-	var without []string
-	for _, v := range VerbNames(seat.Serves) {
-		if v != "times" {
-			without = append(without, v)
-		}
-	}
-	m := Manifest{Module: "mesh-delivery", Claims: []Claim{{Name: DeliverySeat, Scope: ScopeMesh, Serves: without}}}
-	if err := CanHold(m, seat); err != nil {
-		t.Fatalf("a holder without times yet: %v", err)
-	}
-	m.Claims[0].Serves = VerbNames(seat.Serves)
-	if err := CanHold(m, seat); err != nil {
-		t.Fatalf("a holder serving times: %v", err)
-	}
-}
-
-// The seat still promises `mark-ready`, optionally, for one more release (issue 1022); it was added by novox/hq issue 913: `mark-ready`, with the delivery's id, who reviewed it
-// and why, so a reviewer marks a pull request through one audited verb, label and comment in the order the forge
-// counts, instead of two raw forge calls. Added after the holder shipped, it is optional.
-func TestTheDeliverySeatPromisesMarkReadyOptionally(t *testing.T) {
-	seat, _ := SeatNamed(DeliverySeat)
-	var mark *Verb
-	for i := range seat.Serves {
-		if seat.Serves[i].Name == "mark-ready" {
-			mark = &seat.Serves[i]
-		}
-	}
-	if mark == nil || !mark.Optional {
-		t.Fatalf("the delivery seat promises %v, mark-ready optionally", VerbNames(seat.Serves))
-	}
-	if req, _ := mark.Input["required"].([]string); !reflect.DeepEqual(req, []string{"id", "reviewed-by", "why"}) {
-		t.Errorf("mark-ready requires %v, wanted id, reviewed-by and why", req)
-	}
-	var without []string
-	for _, v := range VerbNames(seat.Serves) {
-		if v != "mark-ready" {
-			without = append(without, v)
-		}
-	}
-	m := Manifest{Module: "mesh-delivery", Claims: []Claim{{Name: DeliverySeat, Scope: ScopeMesh, Serves: without}}}
-	if err := CanHold(m, seat); err != nil {
-		t.Fatalf("a holder without mark-ready yet: %v", err)
-	}
-}

go/catalogue/seats.go

@@ -110,15 +110,18 @@ var defaultSeats = append([]Seat{
 			"rolled-back",
 			// A pull request's merge check, judged (novox/hq to-be 45 §9).
 			"checked",
-			// A walk kept in a new state, for the delivery it walks (novox/hq ADR 0239).
+			// A walk kept in a new state, and a tier sent to a machine: kept until the catalogue's main consumes them no
+			// more; nothing emits them (ADR 0539).
 			"plan-moved",
-			// A tier sent to a machine, once the send is kept (novox/hq ADR 0406 §5, issue 974).
 			"sent",
 			// A key of a record mirror written or removed (novox/hq ADR 0289, design 54 §3; design 57 F3).
 			"assignment-changed", "declared-config-changed", "predefined-changed",
 			// A builder's key not taken in because the artifact store does not hold an artifact it names (novox/hq
 			// issue 1937): the builder builds it again.
-			"artifacts-gone"},
+			"artifacts-gone",
+			// A bucket of a state this release deleted, deleted at the controller's first start (novox/hq ADR 0539
+			// clause 13): the merge window's, the silent sends' and the building plans' hold, each said once.
+			"bucket-deleted"},
 		Serves: ControllerVerbs},
 	// The store's first verbs (novox/hq ADR 0159): the smallest set that makes the store askable,
 	// served by whichever module holds the seat with tools of these names.

go/catalogue/verbs.go

@@ -74,6 +74,29 @@ func VerbNames(verbs []Verb) []string {
 	return out
 }
 
+// RemovedControllerVerbs are the controller seat's verbs release 6 removed (novox/hq ADR 0539, ADR 0429 §8): no
+// delivery plan, batch, tier or push exists, so nothing starts, stops, retries, follows or reads one. Each stays in
+// ControllerVerbs as a row with no input, so a caller is answered by name with its replacement, given here.
+var RemovedControllerVerbs = map[string]string{
+	"plans": "the delivery view (nox-delivery): each machine's want and have, read from the assigner's wants and the " +
+		"node-engine's haves",
+	"plan": "the node's compositions: mesh-controller_composed holds each module's digest and judgement per node, and " +
+		"mesh-hand-compose prints one module's composition for one node",
+	"push": "a want: the assigner writes want.<node>.<module> by its rules, and by hand the operator's credential writes " +
+		"it, naming a kept composition (ADR 0539 clause 10)",
+	"deliver":                "nothing to start: a merged change reaches each machine by its want",
+	"delivery-stop":          "a bad fingerprint is held and its canary set back by the assigner (ADR 0429 §6, ADR 0539 clause 18)",
+	"delivery-backups-again": "the assigner's backup ask, answered on the phone or in the delivery view (ADR 0539 clause 16)",
+	"delivery-walks":         "the delivery view (nox-delivery) and the wants, haves and compositions on the bus",
+	"delivery-order":         "no order to keep: each module reaches its machines by its own want, its providers first by rule 5",
+}
+
+// removedInR6 is the row of a verb release 6 removed from the controller's seat: no input, refused by name.
+func removedInR6(name string) Verb {
+	return Verb{Name: name, Description: "Removed in R6 (ADR 0539): refused by name, naming its replacement: " +
+		RemovedControllerVerbs[name], Input: schema(nil, nil)}
+}
+
 // ControllerSeatName is the seat the control plane holds, whose tools are the mesh's own verbs.
 const ControllerSeatName = "mesh-controller"
 
@@ -115,87 +138,23 @@ var ControllerVerbs = []Verb{
 			"log":    "a build's id (as `builds` lists it): print what the build machine said, line by line",
 			"limit":  "how many builds to list (default 20); not with log",
 		}, nil)},
-	{Name: "plans", Description: "What the last merges produced and where each stands (novox/hq ADR 0162): " +
+	removedInR6("plans"),
-		"the tiers, the tier a plan is at, what it waits for and since when; one plan whole, given its id; " +
-		"or, given wait, one plan followed until it moves.",
-		Input: schema(map[string]string{
-			"id": "a plan's id (as `plans` lists them): that plan, tier by tier",
-			"wait": "a plan's id: wait until it moves, then answer it as data — the plan, and what ended the wait " +
-				"(moved, tier, done, or bound); ask again to follow it further (novox/hq issue 229)",
-			"until": "with wait: moved (any change, the default), tier (it reaches another tier) or done (it ends)",
-			"bound": "with wait: how long to wait at most, as 15s or seconds — 20s, the default, is the longest, " +
-				"inside what a call is answered within",
-			"stop":  "a plan's id: stop it — what was asked still builds, nothing further is asked",
-			"close": "a plan's id: close a plan that will not move again, as failed by hand (novox/hq issue 254)",
-			"retry": "a failed plan's id: ask its failed builds again under new ids, and carry the plan on from that tier (novox/hq ADR 0219)",
-			"go": "a walk's id that waits for its delivery's word: start it by hand, in place of mesh-delivery — with why, " +
-				"recorded in the hand-act log (novox/hq ADR 0239)",
-			"repository": "owner/repository: the plan a merge there would produce, saving nothing (what-if); with paths or modules",
-			"paths":      "with repository: the files the merge would change, comma-separated, from the repository's root",
-			"modules":    "with repository: or the modules it would change, comma-separated",
-			"module-dirs": "with repository and paths: the directories holding a module.json at the commit, comma-separated, " +
-				"as the forge's announcer says them (novox/hq issue 278); without it, a directory is a module only when the paths hold its manifest",
-			"data": "with repository and paths: true answers the change plan as data, the document delivery-plan answers " +
-				"(moved, dependents, new, tiers, machines with what each receives and waits for, steps, summary, class, head, base); " +
-				"without it the answer is text (novox/hq ADR 0450 §2)",
-			"head":    "with data: the commit at hand",
-			"base":    "with data: the branch it merges into (default main)",
-			"removed": "with data: the files among paths the change deletes, comma-separated",
-			"limit":   "how many plans to list (default 10); only when listing",
-			"why":     "with stop, close or go: why it is done by hand — required, and recorded in the hand-act log (novox/hq to-be 45 §7)",
-			"cause":   "with stop, close or go: the cause in a word, or a condition's kind (optional)",
-		}, nil, "data")},
 	// The verbs the delivery's owner asks with (novox/hq ADR 0239): the planner's answer, a group's order and
 	// composed check, and the start and end of a walk. Callable by a person too; mesh-delivery is who needs them.
 	{Name: "delivery-plan", Description: "Removed in R4e (ADR 0501 §5 / ADR 0503 §3): refused by name, naming its replacement",
 		Input: schema(nil, nil)},
-	{Name: "delivery-order", Description: "A delivery group's order (novox/hq ADR 0419): its members in the order " +
+	removedInR6("delivery-order"),
-		"they are delivered, every pair and why — built by, verb before caller, version skew, engine before " +
-		"controller — read from the module graph and the manifests' change alone; no `after:` line is read. The " +
-		"cycle, with every module and edge of it, is the one refusal.",
-		Input: schema(map[string]string{"members": "the members, as JSON: [{id, repository, base, head, number, paths, " +
-			"module_dirs, module_dirs_said, removed}]"}, []string{"members"})},
 	{Name: "delivery-check", Description: "Answers that the checker (mesh-delivery-checker) judges a group (novox/hq " +
 		"ADR 0503 §3); asks nothing. Its inputs stay, since hq's repository check still names it (ADR 0513 §4).",
 		Input: schema(map[string]string{"group": "the group's id (none for one head checked again)",
 			"members": "the members, as JSON, as delivery-order takes them",
 			"ready":   "\"true\" when the pull request is marked ready: its check is queued before every other check (novox/hq ADR 0406 §3)"},
 			[]string{"members"})},
-	{Name: "deliver", Description: "The delivery's word that a walk waiting for it may start (novox/hq ADR 0239): its " +
+	removedInR6("deliver"),
-		"first tier is asked at the controller's next pass. Refused for a walk that waits for nobody.",
+	removedInR6("delivery-stop"),
-		Input: schema(map[string]string{"plan": "the walk's id", "why": "what lets it go: its turn, a person's release"},
+	removedInR6("delivery-backups-again"),
-			[]string{"plan"})},
+	removedInR6("delivery-walks"),
-	{Name: "delivery-stop", Description: "End a walk on its delivery's word (novox/hq ADR 0239): failed, said as stopped " +
+	removedInR6("plan"),
-		"by whom and why; what it asked still builds and registers, nothing further is asked or sent. Given merges to " +
-		"leave out, every other merge the walk answered is walked again — in the open batch of its kind, or a new one — " +
-		"without them, without each later merge of their repository, which contains one, and without each merge moving " +
-		"a module one moves, each left out too and named (novox/hq ADR 0299); a batch not yet cut drops the merges. The " +
-		"answer names the batch, the merges walked again, the merges left out, the modules the stopped walk sent that " +
-		"stay on their machines, and the merges elsewhere that will still deliver a stopped change.",
-		Input: schema(map[string]string{"plan": "the walk's id", "why": "why", "by": "who stopped the delivery",
-			"without": "merges to leave out, <repository>@<commit>, comma-separated"},
-			[]string{"plan", "why"})},
-	{Name: "delivery-backups-again", Description: "Ask again the backups a walk was held for (novox/hq ADR 0404 " +
-		"decision 4): a walk whose backup before its send failed or did not answer is held, nothing asked or sent; this " +
-		"clears those failed backups and the next look at the plans asks them again, and only them. Refused for a walk " +
-		"with no failed backup. The delivery's release calls it. The answer names the walk and the backups asked again.",
-		Input: schema(map[string]string{"plan": "the held walk's id", "why": "a person's reason, as release passes it",
-			"by": "who released the delivery"}, []string{"plan", "why"})},
-	{Name: "delivery-walks", Description: "The walks the controller keeps (novox/hq ADR 0239): every open one and the " +
-		"last ended ones, each whole — its tiers, each module's state, first machines and first-node gate with its readings, and its " +
-		"phases from its merge to every machine running it (novox/hq ADR 0282) — and whether the delivery seat has a " +
-		"holder on record. Given a plan, that one.",
-		Input: schema(map[string]string{"plan": "one walk's id", "limit": "how many ended walks beside the open ones (default 50)"},
-			nil)},
-	{Name: "plan", Description: "What one machine would run, and why: the declaration the mesh would send it — " +
-		"or, with files, the files it would be given; or, with diff, what a push would change there against what " +
-		"it was last sent: resources added, removed and changed, a container's changed fields (it is recreated), " +
-		"and any mount whose directory on the machine would move (novox/hq ADR 0217).",
-		Input: schema(map[string]string{
-			"node":  "the machine's name",
-			"files": "\"true\": the files this machine would be given, instead of the declaration as JSON",
-			"diff":  "\"true\": what a push would change on this machine, against what it was last sent; not with files",
-		}, []string{"node"}, "files", "diff")},
 	{Name: "assign", Description: "Put a module on a machine. Refused with the mesh's own words when it cannot resolve there, " +
 		"or when a seat its resources are applied through is held by nothing on the machine (novox/hq ADR 0207). " +
 		"A module not registered yet is looked for (novox/hq issue 325, ADR 0261): while its build runs — a merge " +
@@ -221,22 +180,7 @@ var ControllerVerbs = []Verb{
 		}, []string{"node", "provision", "from", "module"})},
 	{Name: "unpin", Description: "Take that choice back, putting the question to the mesh again.",
 		Input: schema(map[string]string{"node": "the machine's name", "provision": "the provision"}, []string{"node", "provision"})},
-	{Name: "push", Description: "Send one machine everything it should be. With no machine named it is a push of the " +
+	removedInR6("push"),
-		"WHOLE mesh — every machine that is behind — and the answer says so first; behind says that outright. " +
-		"Answers at once that it is running, with a call id: `calls` with that id says what it sent and, for a " +
-		"machine named, how that machine applied it — applied, refused with its reason, or each failed resource — " +
-		"once it reports within wait (a push can reload the bus, which then refuses any answer still to come). A push by hand is a repair, " +
-		"and says why: recorded in the hand-act log (novox/hq to-be 45 §7). A machine whose push would give a " +
-		"running module's data another directory is held and named, the others sent (novox/hq ADR 0217): read " +
-		"`plan` with diff, and name the machine with move to send it.",
-		Input: schema(map[string]string{
-			"node":   "the machine's name; without it, every machine that is behind",
-			"move":   "with node: the modules whose data may move with this push, comma-separated (optional)",
-			"wait":   "with node: how long the call waits for the machine to report how it applied what it was sent, as \"90s\" or \"2m\"; \"0\" waits for nothing; without it, the controller's setting push-wait (optional)",
-			"behind": "\"true\": every machine that is behind, the whole mesh — the same as naming none, said outright; not with node",
-			"why":    "why this is pushed by hand: recorded in the hand-act log",
-			"cause":  "the cause in a word, or a condition's kind — the word a second push for the same reason uses (optional)",
-		}, []string{"why"}, "behind")},
 	{Name: "rotate", Description: "Replace a credential. A pair credential, by provision (and a consuming machine and module, " +
 		"else every holder): both ends are re-sent together. Or a module's own secret, by machine, module and " +
 		"name: made anew and the machine sent, so the module starts again on it — for a secret its definition " +
@@ -457,26 +401,22 @@ var ControllerVerbs = []Verb{
 			"probe":   "one probe's id (D14): its verdict alone, with every finding — the verdict shows at most twenty a probe",
 		}, nil, "run", "probes", "signals")},
 	// How a module's new builds reach its machines, and the bus's planned step (novox/hq ADR 0236).
-	{Name: "upgrade", Description: "How each module's new builds reach its machines (novox/hq ADR 0236): rolled " +
+	{Name: "upgrade", Description: "Whether each module's new builds wait for a person (novox/hq ADR 0236, ADR 0539 clause 14): " +
-		"out one machine first and judged there at the gate, then the rest — or recorded, waiting for a person's " +
+		"for a module of policy record, the assigner writes no want naming a composition judged to recreate a container or move " +
-		"push — with where that comes from (a person, the module, the bus, its irreplaceable data, the default) and " +
+		"data until the operator answers its ask; with where the policy comes from (a person, the module, the bus, its " +
-		"why. With module, that one; with policy, a person's choice for it — roll-out, record (with why) or default " +
+		"irreplaceable data, the default) and why. With module, that one; with policy, a person's choice for it — roll-out, " +
-		"to take the choice back. The bus is never rolled out.",
+		"record (with why) or default to take the choice back. The bus is never moved by the assigner (ADR 0539 clause 15).",
 		Input: schema(map[string]string{
-			"module":   "one module",
+			"module": "one module",
-			"policy":   "with module: roll-out, record or default",
+			"policy": "with module: roll-out, record or default",
-			"together": "\"true\": with roll-out, every machine at once instead of one machine first",
+			"why":    "with policy: why — required for record, kept",
-			"why":      "with policy or release-backlog: why — required for record and for a release, kept",
+		}, nil)},
-			"backlog":  "\"true\": every build waiting for a gate, per machine — what a release plan would send",
+	{Name: "bus", Description: "The bus as a person's step (novox/hq to-be 45 §8, ADR 0236, ADR 0539 clause 15): what a bus " +
-			"release-backlog": "\"true\": release what waits now, one machine at a time, each judged — after a release " +
+		"upgrade would do — the bus's build on each machine against the one the mesh holds — and how the last step went. " +
-				"plan failed, the mesh waits for this; with why",
+		"With upgrade, check one: a person's act with why, after the streams are snapshotted (snapshot-taken says where, " +
-			"cause": "with release-backlog: the cause in a word (optional)",
+		"while the mesh takes none itself), saying first whether it can be reverted; then it answers the want the operator " +
-		}, nil, "together", "backlog", "release-backlog")},
+		"writes with the operator's credential, want.<node>.<bus module>, recorded — nothing is sent, and the assigner never " +
-	{Name: "bus", Description: "The bus as a planned step (novox/hq to-be 45 §8, ADR 0236): what a bus upgrade " +
+		"moves the bus.",
-		"would do — the bus's build on each machine against the one the mesh holds — and how the last step went. " +
-		"With upgrade, start one: a person's act with why, after the streams are snapshotted (snapshot-taken says " +
-		"where, while the mesh takes none itself), saying first whether it can be reverted; bus-maintenance is open " +
-		"while it runs and every stream, consumer and a round trip are checked after.",
 		Input: schema(map[string]string{
 			"upgrade":        "\"true\": start the bus's upgrade",
 			"why":            "with upgrade: why — required, recorded in the hand-act log",

go/catalogue/verbs_r6_test.go

@@ -0,0 +1,115 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// 1943/AC4: the controller's seat no longer offers a verb that starts, stops, retries, follows or reads a delivery
+// plan, nor a push: each is a row with no input whose description refuses it by name and names its replacement, and
+// each is in the removed list the holder answers from. upgrade keeps its policy and drops the plan's backlog.
+func TestTheControllerSeatHasNoPlanVerbs(t *testing.T) {
+	rows := map[string]Verb{}
+	for _, v := range ControllerVerbs {
+		rows[v.Name] = v
+	}
+	gone := []string{"plans", "plan", "push", "deliver", "delivery-stop", "delivery-backups-again", "delivery-walks", "delivery-order"}
+	for _, name := range gone {
+		v, ok := rows[name]
+		if !ok {
+			t.Errorf("%s is not in the table, so a caller is not answered by name", name)
+			continue
+		}
+		replacement, removed := RemovedControllerVerbs[name]
+		if !removed || replacement == "" {
+			t.Errorf("%s is not in the removed list with its replacement", name)
+		}
+		if !strings.HasPrefix(v.Description, "Removed in R6 (ADR 0539): refused by name") || !strings.Contains(v.Description, replacement) {
+			t.Errorf("%s = %q, want refused by name, naming %q", name, v.Description, replacement)
+		}
+		if props, _ := v.Input["properties"].(map[string]any); len(props) > 0 {
+			t.Errorf("%s still takes %v", name, props)
+		}
+	}
+	props, _ := rows["upgrade"].Input["properties"].(map[string]any)
+	for _, arg := range []string{"together", "backlog", "release-backlog", "cause"} {
+		if _, has := props[arg]; has {
+			t.Errorf("upgrade still takes %s, a plan's", arg)
+		}
+	}
+	for _, arg := range []string{"module", "policy", "why"} {
+		if _, has := props[arg]; !has {
+			t.Errorf("upgrade no longer takes %s", arg)
+		}
+	}
+	for _, word := range []string{"rolled", "gate", "backlog", "push"} {
+		if strings.Contains(rows["upgrade"].Description, word) {
+			t.Errorf("upgrade's description still speaks of %q: %q", word, rows["upgrade"].Description)
+		}
+	}
+	if !strings.Contains(rows["bus"].Description, "want") {
+		t.Errorf("bus does not say the operator writes the bus's want: %q", rows["bus"].Description)
+	}
+	for name := range RemovedControllerVerbs {
+		if v := rows[name]; !strings.HasPrefix(v.Description, "Removed in R6") {
+			t.Errorf("%s is in the removed list and its row says %q", name, v.Description)
+		}
+	}
+}
+
+// 1943/AC4: the delivery seat keeps the merge's verbs and no longer offers times, what-if, release, stop or
+// retire-history: each is a row with no input, optional so the holder of before and the holder of release 6 both hold
+// the seat, refusing it by name; mark-ready, served by nobody since issue 1022, is gone.
+func TestTheDeliverySeatHasNoPlanVerbs(t *testing.T) {
+	seat, ok := SeatNamed(DeliverySeat)
+	if !ok {
+		t.Fatal("the delivery seat is not in the set")
+	}
+	rows := map[string]Verb{}
+	for _, v := range seat.Serves {
+		rows[v.Name] = v
+	}
+	for _, name := range []string{"times", "what-if", "release", "stop", "retire-history"} {
+		v, ok := rows[name]
+		replacement, removed := RemovedDeliveryVerbs[name]
+		if !ok || !removed || replacement == "" {
+			t.Errorf("%s: in the table %v, in the removed list %v", name, ok, removed)
+			continue
+		}
+		if !strings.HasPrefix(v.Description, "Removed in R6 (ADR 0539): refused by name") || !strings.Contains(v.Description, replacement) || !v.Optional {
+			t.Errorf("%s = %q (optional %v), want an optional row refusing it by name", name, v.Description, v.Optional)
+		}
+		if props, _ := v.Input["properties"].(map[string]any); len(props) > 0 {
+			t.Errorf("%s still takes %v", name, props)
+		}
+	}
+	if _, ok := rows["mark-ready"]; ok {
+		t.Errorf("mark-ready is still promised")
+	}
+	for _, kept := range []string{"deliveries", "show", "groups", "checks", "table", "recheck", "close", "stalled"} {
+		if v, ok := rows[kept]; !ok || strings.HasPrefix(v.Description, "Removed") {
+			t.Errorf("%s is not kept (ADR 0539 clause 17)", kept)
+		}
+	}
+	gate := Manifest{Module: "mesh-delivery", Claims: []Claim{{Name: DeliverySeat, Scope: ScopeMesh,
+		Serves: []string{"deliveries", "show", "groups", "checks", "table", "stalled", "recheck", "close"}}}}
+	if err := CanHold(gate, seat); err != nil {
+		t.Errorf("the gate of release 6 cannot hold the seat: %v", err)
+	}
+	gate.Claims[0].Serves = append(gate.Claims[0].Serves, "times", "what-if", "release", "stop", "retire-history")
+	if err := CanHold(gate, seat); err != nil {
+		t.Errorf("the gate of release 5 cannot hold the seat: %v", err)
+	}
+}
+
+// 1943 (for 1945/AC14): the controller's seat says a bucket it deleted at its first start as its event, bucket-deleted
+// (ADR 0539 clause 13).
+func TestTheControllerSaysABucketItDeleted(t *testing.T) {
+	seat, ok := SeatNamed(ControllerSeatName)
+	if !ok {
+		t.Fatal("no controller seat")
+	}
+	if !SeatSays(seat.Emits, "bucket-deleted") {
+		t.Errorf("the controller's seat does not emit bucket-deleted: %v", seat.Emits)
+	}
+}

go/cmd/mesh-hand-compose/main.go

@@ -0,0 +1,209 @@
+// mesh-hand-compose composes one module for one node by hand, from the inputs the controller keeps, and signs it with the
+// operator's key, for the hand path of novox/hq ADR 0539 clause 10: a fingerprint the controller never composed (a
+// hand build), while the controller cannot compose its own fix. It composes with mesh-sdk's composition, the one the
+// controller writes with (compose.Compositions), and prints the composition, its key and its digest; only with -write
+// does it write them, with the operator's credential: the composition into the node's bucket composed-<node>, each
+// file over 64 KiB into the node's object bucket, and the digest into mesh-controller_composed. The want is the
+// operator's next act, naming that digest; each act is recorded in the hand-act log.
+//
+//	mesh-hand-compose -input <inputs.json> -node <node> -module <module> -fp <src2:...> -key <operator key>
+//	             [-write -nats <url> -creds <operator credential>]
+//
+// The inputs are a compose.Input as JSON. The key is the operator's ed25519 private key, PKCS#8 in PEM; the
+// node-engine trusts it beside the controller's (ADR 0539 clause 3).
+package main
+
+import (
+	"context"
+	"crypto/ed25519"
+	"crypto/x509"
+	"encoding/json"
+	"encoding/pem"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"git.novox.be/novox/mesh-sdk/go/compose"
+	"git.novox.be/novox/mesh-sdk/go/declaration"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+func main() {
+	if err := run(os.Args[1:], os.Stdout); err != nil {
+		fmt.Fprintln(os.Stderr, "mesh-hand-compose:", err)
+		os.Exit(1)
+	}
+}
+
+// printed is what mesh-hand-compose prints: where the composition goes, its digest, the composition, and whether it was
+// written.
+type printed struct {
+	Bucket      string          `json:"bucket"`
+	Key         string          `json:"key"`
+	Digest      string          `json:"digest"`
+	Composition json.RawMessage `json:"composition"`
+	Objects     []string        `json:"objects,omitempty"`
+	Written     bool            `json:"written"`
+	Next        string          `json:"next"`
+}
+
+func run(args []string, stdout io.Writer) error {
+	fs := flag.NewFlagSet("mesh-hand-compose", flag.ContinueOnError)
+	input := fs.String("input", "", "the controller's kept inputs, a compose.Input as JSON")
+	node := fs.String("node", "", "the node to compose for")
+	module := fs.String("module", "", "the module to compose")
+	fp := fs.String("fp", "", "the module's fingerprint, src2: and 64 hex digits")
+	keyFile := fs.String("key", "", "the operator's ed25519 private key, PKCS#8 in PEM")
+	write := fs.Bool("write", false, "write the composition, its files and its digest, with the operator's credential")
+	url := fs.String("nats", nats.DefaultURL, "with -write: the bus")
+	creds := fs.String("creds", "", "with -write: the operator's credential file")
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+	switch {
+	case *input == "" || *node == "" || *module == "" || *fp == "":
+		return errors.New("-input, -node, -module and -fp are each required")
+	case *keyFile == "":
+		return errors.New("-key is required: a composition made by hand is signed by the operator's key, and the node-engine applies no other")
+	case *write && *creds == "":
+		return errors.New("-write needs -creds: the operator's credential is the only hand writer of a composition")
+	}
+	key, err := readKey(*keyFile)
+	if err != nil {
+		return err
+	}
+	key2, err := delivery.ComposedKey(*node, *module, *fp)
+	if err != nil {
+		return err
+	}
+	bucket, err := delivery.ComposedBucketFor(*node)
+	if err != nil {
+		return err
+	}
+	raw, err := os.ReadFile(*input)
+	if err != nil {
+		return err
+	}
+	var in compose.Input
+	if err := json.Unmarshal(raw, &in); err != nil {
+		return fmt.Errorf("the inputs in %s are not a compose.Input: %w", *input, err)
+	}
+	all, _, err := compose.Compositions(in, *node, map[string]string{*module: *fp}, compose.Reading)
+	if err != nil {
+		return err
+	}
+	c, ok := all[key2]
+	if !ok {
+		return fmt.Errorf("%s does not run %s: its composition holds none of it", *node, *module)
+	}
+	c, objects, err := c.ByDigest()
+	if err != nil {
+		return err
+	}
+	if c, err = delivery.SignComposed(c, key); err != nil {
+		return err
+	}
+	encoded, err := delivery.EncodeComposed(c)
+	if err != nil {
+		return err
+	}
+	digest, err := delivery.ComposedDigestOf(c)
+	if err != nil {
+		return err
+	}
+	out := printed{Bucket: bucket, Key: key2, Digest: digest, Composition: encoded,
+		Next: fmt.Sprintf("write want.%s.%s naming fp %s and composed %s with the operator's credential, and record each act in the hand-act log", *node, *module, *fp, digest)}
+	for d := range objects {
+		out.Objects = append(out.Objects, d)
+	}
+	if *write {
+		if err := writeIt(*url, *creds, *node, bucket, key2, encoded, digest, objects); err != nil {
+			return err
+		}
+		out.Written = true
+	}
+	enc := json.NewEncoder(stdout)
+	enc.SetIndent("", "  ")
+	return enc.Encode(out)
+}
+
+func readKey(path string) (ed25519.PrivateKey, error) {
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	block, _ := pem.Decode(raw)
+	if block == nil {
+		return nil, fmt.Errorf("%s holds no PEM block", path)
+	}
+	parsed, err := x509.ParsePKCS8PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", path, err)
+	}
+	key, ok := parsed.(ed25519.PrivateKey)
+	if !ok {
+		return nil, fmt.Errorf("%s is not an ed25519 key", path)
+	}
+	return key, nil
+}
+
+// writeIt writes the files by digest, then the composition, then its digest: a reader that finds the digest finds the
+// composition and its files already there.
+func writeIt(url, creds, node, bucket, key string, encoded []byte, digest string, objects map[string][]byte) error {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+	defer cancel()
+	nc, err := nats.Connect(url, nats.UserCredentials(creds), nats.Name("mesh-hand-compose"))
+	if err != nil {
+		return err
+	}
+	defer nc.Close()
+	js, err := jetstream.New(nc)
+	if err != nil {
+		return err
+	}
+	if len(objects) > 0 {
+		filesBucket, err := declaration.FileBucketFor(node)
+		if err != nil {
+			return err
+		}
+		store, err := js.ObjectStore(ctx, filesBucket)
+		if err != nil {
+			return fmt.Errorf("the node's object bucket %s: %w", filesBucket, err)
+		}
+		for d, body := range objects {
+			name, err := declaration.ObjectName(d)
+			if err != nil {
+				return err
+			}
+			if _, err := store.PutBytes(ctx, name, body); err != nil {
+				return fmt.Errorf("the file %s: %w", d, err)
+			}
+		}
+	}
+	composed, err := js.KeyValue(ctx, bucket)
+	if err != nil {
+		return fmt.Errorf("the bucket %s: %w", bucket, err)
+	}
+	if _, err := composed.Put(ctx, key, encoded); err != nil {
+		return fmt.Errorf("%s in %s: %w", key, bucket, err)
+	}
+	value, err := delivery.EncodeComposedDigest(delivery.ComposedDigest{Digest: digest, Judgement: delivery.JudgedCannot,
+		Words: "composed by hand with mesh-hand-compose (ADR 0539 clause 10): the operator writes the want"})
+	if err != nil {
+		return err
+	}
+	digests, err := js.KeyValue(ctx, delivery.ControllerComposedBucket)
+	if err != nil {
+		return fmt.Errorf("the bucket %s: %w", delivery.ControllerComposedBucket, err)
+	}
+	if _, err := digests.Put(ctx, key, value); err != nil {
+		return fmt.Errorf("%s in %s: %w", key, delivery.ControllerComposedBucket, err)
+	}
+	return nil
+}

go/cmd/mesh-hand-compose/main_test.go

@@ -0,0 +1,145 @@
+package main
+
+import (
+	"bytes"
+	"crypto/ed25519"
+	"crypto/rand"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"encoding/pem"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/compose"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/overlay"
+)
+
+// aMesh is the Input of mesh-controller's aMesh, as mesh-sdk's compose tests make it (compose/fixture_test.go): two
+// machines on the private network, the module the mesh provides for itself assigned to both. The manifest is the one
+// the controller provides (overlay.Manifest), read back as the catalogue reads it.
+func aMesh(t *testing.T) compose.Input {
+	t.Helper()
+	var m catalogue.Manifest
+	b, _ := json.Marshal(overlay.Manifest())
+	if err := json.Unmarshal(b, &m); err != nil {
+		t.Fatal(err)
+	}
+	in := compose.Input{Catalogue: map[string]catalogue.Manifest{overlay.Name: m}}
+	for i, name := range []string{"anchor", "laptop"} {
+		pub, _, _ := ed25519.GenerateKey(rand.Reader)
+		in.Nodes = append(in.Nodes, compose.Node{Name: name,
+			Place:    compose.Place{Key: base64.StdEncoding.EncodeToString(pub), Endpoint: name + ".example:51820", Site: "here", Hub: name == "anchor", Address: []string{"10.77.0.1", "10.77.0.2"}[i]},
+			Assigned: []string{overlay.Name}, Capabilities: map[string]bool{"container-runtime": true, "wireguard": true, "systemd": true}})
+	}
+	return in
+}
+
+func writeKey(t *testing.T, dir string) ed25519.PublicKey {
+	t.Helper()
+	pub, priv, _ := ed25519.GenerateKey(rand.Reader)
+	der, err := x509.MarshalPKCS8PrivateKey(priv)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "operator.key"), pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: der}), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	return pub
+}
+
+// 1943/AC5: mesh-hand-compose, given the kept inputs, a node, a module and its fingerprint, prints that module's
+// composition for that node signed by the operator's key and its digest: its resources are the controller's for that
+// module on that node (compose.Compose), and it verifies against the operator's key. Without --write it writes nothing.
+func TestMeshComposeGivesTheControllersResourcesSignedByTheOperator(t *testing.T) {
+	dir := t.TempDir()
+	in := aMesh(t)
+	raw, err := json.Marshal(in)
+	if err != nil {
+		t.Fatal(err)
+	}
+	input := filepath.Join(dir, "input.json")
+	if err := os.WriteFile(input, raw, 0o600); err != nil {
+		t.Fatal(err)
+	}
+	operator := writeKey(t, dir)
+	fp := delivery.SourcePrefix2 + strings.Repeat("a", 64)
+
+	var out bytes.Buffer
+	if err := run([]string{"-input", input, "-node", "laptop", "-module", overlay.Name, "-fp", fp,
+		"-key", filepath.Join(dir, "operator.key")}, &out); err != nil {
+		t.Fatal(err)
+	}
+	var printed struct {
+		Key         string          `json:"key"`
+		Bucket      string          `json:"bucket"`
+		Digest      string          `json:"digest"`
+		Composition json.RawMessage `json:"composition"`
+		Written     bool            `json:"written"`
+	}
+	if err := json.Unmarshal(out.Bytes(), &printed); err != nil {
+		t.Fatalf("%s: %v", out.String(), err)
+	}
+	c, err := delivery.DecodeComposed(printed.Composition)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if digest, err := delivery.VerifyComposed(c, []ed25519.PublicKey{operator}); err != nil || digest != printed.Digest {
+		t.Errorf("the composition verifies %q, %v against the operator's key; printed %s", digest, err, printed.Digest)
+	}
+	wantKey, _ := delivery.ComposedKey("laptop", overlay.Name, fp)
+	if printed.Key != wantKey || printed.Bucket != "composed-laptop" || printed.Written {
+		t.Errorf("printed key %s in %s, written %v", printed.Key, printed.Bucket, printed.Written)
+	}
+
+	d, _, err := compose.Compose(in, "laptop")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var want, got []string
+	for _, r := range d.Resources {
+		want = append(want, r["id"].(string))
+	}
+	for _, r := range c.Resources {
+		var head struct{ ID string }
+		_ = json.Unmarshal(r, &head)
+		got = append(got, head.ID)
+	}
+	sort.Strings(want)
+	sort.Strings(got)
+	if len(got) == 0 || strings.Join(got, " ") != strings.Join(want, " ") {
+		t.Errorf("mesh-hand-compose gives %v, the controller's composition %v", got, want)
+	}
+}
+
+// 1943/AC5: mesh-hand-compose refuses what it cannot compose, naming why: no key, a fingerprint not of the new form, a
+// module the node does not run, a node the mesh does not have.
+func TestMeshComposeRefuses(t *testing.T) {
+	dir := t.TempDir()
+	raw, _ := json.Marshal(aMesh(t))
+	input := filepath.Join(dir, "input.json")
+	_ = os.WriteFile(input, raw, 0o600)
+	writeKey(t, dir)
+	key := filepath.Join(dir, "operator.key")
+	fp := delivery.SourcePrefix2 + strings.Repeat("a", 64)
+	for _, c := range []struct {
+		args []string
+		why  string
+	}{
+		{[]string{"-input", input, "-node", "laptop", "-module", overlay.Name, "-fp", fp}, "-key"},
+		{[]string{"-input", input, "-node", "laptop", "-module", overlay.Name, "-fp", "src2:1", "-key", key}, "fingerprint"},
+		{[]string{"-input", input, "-node", "laptop", "-module", "mesh-mail", "-fp", fp, "-key", key}, "does not run mesh-mail"},
+		{[]string{"-input", input, "-node", "nowhere", "-module", overlay.Name, "-fp", fp, "-key", key}, "nowhere"},
+		{[]string{"-input", input, "-node", "laptop", "-module", overlay.Name, "-fp", fp, "-key", key, "-write"}, "-creds"},
+	} {
+		var out bytes.Buffer
+		if err := run(c.args, &out); err == nil || !strings.Contains(err.Error(), c.why) {
+			t.Errorf("mesh-hand-compose %v = %v, want a refusal saying %q", c.args, err, c.why)
+		}
+	}
+}

go/compose/composed.go

@@ -0,0 +1,94 @@
+package compose
+
+import (
+	"encoding/json"
+	"fmt"
+	"sort"
+
+	"git.novox.be/novox/mesh-sdk/go/declaration"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// Compositions is one node's compositions (novox/hq ADR 0539 clauses 1 and 2): its declaration composed over in, as
+// the controller composes it, split into each module's composition at the fingerprint fps gives it and the node's own
+// (`<node>.node`), by key (delivery.ComposedKey). Each resource says its module, whatever the node reported it reads.
+// A module fps gives no fingerprint for is not composed and is named in skipped, so a caller composing one module
+// (mesh-hand-compose) gets that one. Each module's Data says whether its manifest declares data. The compositions are not
+// signed and not yet by digest: the writer does both (delivery.SignComposed, Composed.ByDigest).
+func Compositions(in Input, node string, fps map[string]string, mode Mode) (out map[string]delivery.Composed, skipped []string, err error) {
+	reading := in
+	reading.Nodes = append([]Node(nil), in.Nodes...)
+	found := false
+	for i := range reading.Nodes {
+		if reading.Nodes[i].Name == node {
+			reading.Nodes[i].ReadsModules = true
+			found = true
+		}
+	}
+	if !found {
+		return nil, nil, fmt.Errorf("compose: the mesh has no node %q", node)
+	}
+	d, problems, err := ComposeIn(reading, node, mode)
+	if err != nil {
+		return nil, nil, err
+	}
+	if len(problems) > 0 {
+		return nil, nil, fmt.Errorf("compose: %s's declaration is refused by the node-engine's validator: %v", node, problems)
+	}
+	body, err := d.Body()
+	if err != nil {
+		return nil, nil, err
+	}
+	var envelope struct {
+		Resources   []json.RawMessage     `json:"resources"`
+		Adoption    *declaration.Adoption `json:"adoption"`
+		Filled      []string              `json:"filled_files"`
+		Provisioner string                `json:"provisioner_account"`
+	}
+	if err := json.Unmarshal(body, &envelope); err != nil {
+		return nil, nil, err
+	}
+	var kept []json.RawMessage
+	keptPaths := map[string]bool{}
+	left := map[string]bool{}
+	for _, raw := range envelope.Resources {
+		var head struct {
+			Module string `json:"module"`
+			Type   string `json:"type"`
+			Path   string `json:"path"`
+		}
+		if err := json.Unmarshal(raw, &head); err != nil {
+			return nil, nil, err
+		}
+		if _, ok := fps[head.Module]; head.Module != "" && !ok {
+			left[head.Module] = true
+			continue
+		}
+		if head.Type == string(declaration.TypeFile) {
+			keptPaths[head.Path] = true
+		}
+		kept = append(kept, raw)
+	}
+	var filled []string
+	for _, p := range envelope.Filled {
+		if keptPaths[p] {
+			filled = append(filled, p)
+		}
+	}
+	out, err = delivery.SplitComposed(node, kept, fps, filled,
+		delivery.NodeOwn{Adoption: envelope.Adoption, Provisioner: envelope.Provisioner})
+	if err != nil {
+		return nil, nil, err
+	}
+	for key, c := range out {
+		if m, ok := in.Catalogue[c.Module]; ok && c.Module != "" {
+			c.Data = len(m.DataItems()) > 0
+			out[key] = c
+		}
+	}
+	for m := range left {
+		skipped = append(skipped, m)
+	}
+	sort.Strings(skipped)
+	return out, skipped, nil
+}

go/compose/composed_test.go

@@ -0,0 +1,88 @@
+package compose
+
+import (
+	"encoding/json"
+	"sort"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+func fpFor(c byte) string { return delivery.SourcePrefix2 + strings.Repeat(string(c), 64) }
+
+// 1943/AC5: a node's compositions are its declaration as Compose gives it, split by the module each resource belongs
+// to: every resource once, each in its module's composition at the fingerprint given, the module's ownership said on
+// it; a module given no fingerprint is named as skipped and composed nowhere.
+func TestCompositionsAreTheDeclarationSplitByModule(t *testing.T) {
+	in := aSmallMesh(t)
+	d, _, err := Compose(in, "laptop")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var want []string
+	for _, r := range d.Resources {
+		want = append(want, r["type"].(string)+":"+r["id"].(string))
+	}
+	sort.Strings(want)
+
+	fps := map[string]string{"mesh-wireguard": fpFor('a'), "files": fpFor('b')}
+	out, skipped, err := Compositions(in, "laptop", fps, Foreseeing)
+	if err != nil || len(skipped) != 0 {
+		t.Fatalf("Compositions = %v, skipped %v", err, skipped)
+	}
+	var got []string
+	for key, c := range out {
+		node, module, fp, isNode, err := delivery.ParseComposedKey(key)
+		if err != nil || node != "laptop" || module != c.Module || fp != c.FP || (isNode != (module == "")) {
+			t.Errorf("key %s holds %s at %s (%v)", key, c.Module, c.FP, err)
+		}
+		if !isNode && fp != fps[module] {
+			t.Errorf("%s is composed at %s, given %s", module, fp, fps[module])
+		}
+		if _, err := delivery.EncodeComposed(c); err != nil {
+			t.Errorf("%s: %v", key, err)
+		}
+		for _, raw := range c.Resources {
+			var r struct{ ID, Type, Module string }
+			_ = json.Unmarshal(raw, &r)
+			if r.Module != module {
+				t.Errorf("%s holds %s of %q", key, r.ID, r.Module)
+			}
+			got = append(got, r.Type+":"+r.ID)
+		}
+	}
+	sort.Strings(got)
+	if strings.Join(got, " ") != strings.Join(want, " ") {
+		t.Errorf("the compositions hold %v, the declaration %v", got, want)
+	}
+
+	one, skipped, err := Compositions(in, "laptop", map[string]string{"files": fpFor('b')}, Foreseeing)
+	if err != nil || strings.Join(skipped, ",") != "mesh-wireguard" {
+		t.Fatalf("one module: %v, skipped %v", err, skipped)
+	}
+	for _, c := range one {
+		if c.Module == "mesh-wireguard" {
+			t.Errorf("a module given no fingerprint was composed")
+		}
+	}
+	if _, _, err := Compositions(in, "nowhere", fps, Foreseeing); err == nil {
+		t.Errorf("a node the mesh does not have was composed")
+	}
+}
+
+// 1943/AC1: the upgrade policies and sources a composition's value may name are the catalogue's own words.
+func TestTheComposedPoliciesAreTheCatalogues(t *testing.T) {
+	for _, p := range []string{catalogue.PolicyRoll, catalogue.PolicyTogether, catalogue.PolicyRecord} {
+		for _, from := range []string{catalogue.FromPerson, catalogue.FromModule, catalogue.FromBus, catalogue.FromData, catalogue.FromDefault} {
+			v := delivery.ComposedDigest{Digest: "sha256:" + strings.Repeat("a", 64), Judgement: delivery.JudgedNeither, Policy: p, PolicyFrom: from}
+			if _, err := delivery.EncodeComposedDigest(v); err != nil {
+				t.Errorf("%s from %s: %v", p, from, err)
+			}
+		}
+	}
+	if delivery.PolicyRecord != catalogue.PolicyRecord {
+		t.Errorf("delivery.PolicyRecord = %q, the catalogue's %q", delivery.PolicyRecord, catalogue.PolicyRecord)
+	}
+}

go/declaration/resource.go

@@ -0,0 +1,47 @@
+package declaration
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// ParseResource reads one resource as Parse reads each of a declaration's resources: by its type, strictly, refusing
+// a field its kind does not use and anything its kind refuses, and never an action (the link may not carry one, ADR
+// 0005). It judges the resource alone: what Parse judges across resources (an opening on a node not adopted, the
+// files the provisioner fills, what replaces what) is for the whole a node applies (novox/hq ADR 0539 clause 1: a
+// composition is one module's resources, and a node applies its compositions together with its own key).
+func ParseResource(raw json.RawMessage) (Resource, error) {
+	var head struct {
+		ID   string `json:"id"`
+		Type Type   `json:"type"`
+	}
+	if err := json.Unmarshal(raw, &head); err != nil {
+		return nil, &RefusalError{Problems: []string{"not a resource: " + err.Error()}}
+	}
+	where := "resource"
+	if head.ID == "" {
+		return nil, &RefusalError{Problems: []string{where + ": no id. Identity is what lets the host know this is " +
+			"the same resource it applied last time"}}
+	}
+	where = fmt.Sprintf("resource %q", head.ID)
+	resource := newOf(head.Type)
+	if resource == nil {
+		return nil, &RefusalError{Problems: []string{fmt.Sprintf("%s: unknown type %q. This host understands %s",
+			where, head.Type, vocabulary())}}
+	}
+	if unknown := unknownFields(raw, resource); len(unknown) > 0 {
+		var problems []string
+		for _, field := range unknown {
+			problems = append(problems, fmt.Sprintf("%s: a %s does not use %q, and it is set. Refused rather "+
+				"than ignored", where, head.Type, field))
+		}
+		return nil, &RefusalError{Problems: problems}
+	}
+	if err := json.Unmarshal(raw, resource); err != nil {
+		return nil, &RefusalError{Problems: []string{fmt.Sprintf("%s: %s", where, err)}}
+	}
+	if problems := resource.validate(where, false); len(problems) > 0 {
+		return nil, &RefusalError{Problems: problems}
+	}
+	return resource, nil
+}

go/delivery/assigner.go

@@ -1,6 +1,7 @@
 package delivery
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"reflect"
@@ -16,6 +17,10 @@ import (
 // only compared; the node agent applying them is release 6 (ADR 0429 §7). Only the assigner's credential writes these
 // buckets; the watchman, the view and the controller read them.
 //
+// **Release 6** (ADR 0539 clauses 1, 6 and 16): a want also names the digest of the one composition it allows, written
+// only once that composition exists (the seventh rule, RuleComposed), and carries the answer to a failed backup; the
+// node's own want `want.<node>.node` names the digest of the node's own composition (NodeWant).
+//
 // **The bucket is the first word, the key the rest** (as the builder's `builds.<module>.<fp>` is the key
 // `<module>.<fp>` in its builds bucket): the differences bucket's keys are `<node>.<module>`. The wants bucket holds
 // two kinds of key, so each keeps its word: `want.<node>.<module>` and `held.<module>.<fingerprint hex>`.
@@ -50,7 +55,33 @@ func WantKey(node, module string) (string, error) {
 	return wantWord + "." + have, nil
 }
 
-// ParseWantKey is the inverse of WantKey; it refuses a held key, a have key and any key of another bucket, naming it.
+// WantNodeKey is the key, in AssignerWantsBucket, of a node's own want: `want.<node>.node`, naming the digest of the
+// node's own composition (ADR 0539 clause 6; ADR 0429 §4's node key). The assigner writes it once the node's own
+// composition exists.
+func WantNodeKey(node string) (string, error) {
+	own, err := HaveNodeKey(node)
+	if err != nil {
+		return "", err
+	}
+	return wantWord + "." + own, nil
+}
+
+// ParseWantNodeKey is the inverse of WantNodeKey; it refuses a module's want key and any key of another bucket,
+// naming it.
+func ParseWantNodeKey(key string) (node string, err error) {
+	rest, ok := strings.CutPrefix(key, wantWord+".")
+	if !ok {
+		return "", fmt.Errorf("delivery: %q is not a node's own want key, want.<node>.node", key)
+	}
+	node, _, isNode, err := ParseHaveKey(rest)
+	if err != nil || !isNode {
+		return "", fmt.Errorf("delivery: %q is not a node's own want key, want.<node>.node", key)
+	}
+	return node, nil
+}
+
+// ParseWantKey is the inverse of WantKey; it refuses a held key, a have key, the node's own want key and any key of
+// another bucket, naming it.
 func ParseWantKey(key string) (node, module string, err error) {
 	rest, ok := strings.CutPrefix(key, wantWord+".")
 	if !ok {
@@ -100,7 +131,8 @@ func ParseDifferenceKey(key string) (node, module string, err error) {
 	return node, module, nil
 }
 
-// The six rules of ADR 0429 §6, by number, as a want or a difference names the one that holds a node back.
+// The rules of ADR 0429 §6 and ADR 0539 clause 6, by number, as a want or a difference names the one that holds a node
+// back.
 const (
 	RuleBuildDone = 1 // the build of F is done
 	RuleNotHeld   = 2 // F is not held
@@ -108,15 +140,25 @@ const (
 	RuleStep      = 4 // at most step other nodes are ahead (step 0: no limit, ADR 0528 §3)
 	RuleProviders = 5 // every provider the module requires runs healthy on that node, or at its canary
 	RuleGrant     = 6 // the module's credential for F exists (grants.<module>.<fp>)
+	RuleComposed  = 7 // the module's composition for that node at F exists (mesh-controller_composed, ADR 0539 §6)
 )
 
 func checkRule(rule int, of string) error {
-	if rule < RuleBuildDone || rule > RuleGrant {
+	if rule < RuleBuildDone || rule > RuleComposed {
-		return fmt.Errorf("delivery: %s names the rule %d, which is not one of the six (1 to 6)", of, rule)
+		return fmt.Errorf("delivery: %s names the rule %d, which is not one of the seven (1 to 7)", of, rule)
 	}
 	return nil
 }
 
+// The answers a want carries to a failed backup before an apply (ADR 0539 clause 16): the node agent reads them from
+// its own want and from nothing else.
+const (
+	// BackupAgain is the answer to back the module up again before the apply.
+	BackupAgain = "again"
+	// BackupSkip is the answer to go on without a backup.
+	BackupSkip = "skip"
+)
+
 func checkFingerprint(fp, of string) error {
 	if _, err := FingerprintKeyPart(fp); err != nil {
 		return fmt.Errorf("delivery: %s: %w", of, err)
@@ -124,29 +166,44 @@ func checkFingerprint(fp, of string) error {
 	return nil
 }
 
-// Want is a node's want for a module: the fingerprint FP the node should run, or Removed for a module that left the
+// Want is a node's want for a module: the fingerprint FP the node should run and the digest Composed of the one
-// node's modules (then FP is empty). When the module's newest fingerprint is not yet allowed on this node, Newest names
+// composition of it the node may apply (ADR 0539 clause 1), or Removed for a module that left the node's modules (then
-// it and Rule the rule that holds the node back; both are empty when FP is the newest. Words say why in a sentence.
+// both are empty). When the module's newest fingerprint is not yet allowed on this node, Newest names it and Rule the
-// The entry's own time says since when.
+// rule that holds the node back; both are empty when FP is the newest. Backup is the answer to a failed backup before
+// the apply, BackupAgain or BackupSkip (clause 16), empty when none was asked. Words say why in a sentence. The
+// entry's own time says since when.
 type Want struct {
-	V       int    `json:"v"`
+	V        int    `json:"v"`
-	FP      string `json:"fp,omitempty"`
+	FP       string `json:"fp,omitempty"`
-	Removed bool   `json:"removed,omitempty"`
+	Composed string `json:"composed,omitempty"`
-	Newest  string `json:"newest,omitempty"`
+	Removed  bool   `json:"removed,omitempty"`
-	Rule    int    `json:"rule,omitempty"`
+	Newest   string `json:"newest,omitempty"`
-	Words   string `json:"words,omitempty"`
+	Rule     int    `json:"rule,omitempty"`
+	Backup   string `json:"backup,omitempty"`
+	Words    string `json:"words,omitempty"`
 }
 
 func (w Want) check() error {
 	if w.Removed {
-		if w.FP != "" || w.Newest != "" || w.Rule != 0 {
+		if w.FP != "" || w.Composed != "" || w.Newest != "" || w.Rule != 0 || w.Backup != "" {
-			return fmt.Errorf("delivery: a removed want names no fingerprint and no rule")
+			return fmt.Errorf("delivery: a removed want names no fingerprint, composition, rule or backup answer")
 		}
 		return nil
 	}
 	if err := checkFingerprint(w.FP, "a want's fingerprint"); err != nil {
 		return err
 	}
+	if w.Composed == "" {
+		return fmt.Errorf("delivery: the want of %s names no composition: a want names the digest of the one composition it allows (ADR 0539 clause 1)", w.FP)
+	}
+	if err := checkDigest(w.Composed, "a want's composition digest"); err != nil {
+		return err
+	}
+	switch w.Backup {
+	case "", BackupAgain, BackupSkip:
+	default:
+		return fmt.Errorf("delivery: the backup answer %q is not %s or %s", w.Backup, BackupAgain, BackupSkip)
+	}
 	if w.Newest == "" && w.Rule == 0 {
 		return nil
 	}
@@ -236,6 +293,41 @@ func DecodeWant(data []byte) (Want, error) {
 // SameWant says whether two wants are the same value, so the assigner writes only when they differ.
 func SameWant(a, b Want) bool { return a == b }
 
+// NodeWant is a node's own want (WantNodeKey): the digest Composed of the node's own composition it may apply. Words
+// say why in a sentence.
+type NodeWant struct {
+	V        int    `json:"v"`
+	Composed string `json:"composed"`
+	Words    string `json:"words,omitempty"`
+}
+
+// EncodeNodeWant is w as JSON at Version; it refuses a digest not of the sha256 form.
+func EncodeNodeWant(w NodeWant) ([]byte, error) {
+	if err := checkDigest(w.Composed, "the node's own want's composition digest"); err != nil {
+		return nil, err
+	}
+	w.V = Version
+	return json.Marshal(w)
+}
+
+// DecodeNodeWant reads a node's own want; it refuses an unknown version (ErrUnknownVersion), a field a node's own want
+// does not have (a fingerprint among them), and what EncodeNodeWant refuses.
+func DecodeNodeWant(data []byte) (NodeWant, error) {
+	if err := checkVersion(data); err != nil {
+		return NodeWant{}, err
+	}
+	var w NodeWant
+	d := json.NewDecoder(bytes.NewReader(data))
+	d.DisallowUnknownFields()
+	if err := d.Decode(&w); err != nil {
+		return NodeWant{}, fmt.Errorf("delivery: a node's own want does not fit its shape: %w", err)
+	}
+	if err := checkDigest(w.Composed, "the node's own want's composition digest"); err != nil {
+		return NodeWant{}, err
+	}
+	return w, nil
+}
+
 // EncodeHeld is h as JSON at Version; it refuses a node name a key refuses.
 func EncodeHeld(h Held) ([]byte, error) {
 	if err := h.check(); err != nil {

go/delivery/assigner_test.go

@@ -74,8 +74,8 @@ func TestDifferenceKey(t *testing.T) {
 // 1297/B1a: wants, holds and differences round-trip through their encoders unchanged, at Version.
 func TestAssignerValuesRoundTrip(t *testing.T) {
 	wants := []Want{
-		{FP: fp2of('a')},
+		{FP: fp2of('a'), Composed: hashOf('1')},
-		{FP: fp2of('a'), Newest: fp2of('b'), Rule: RuleCanary, Words: "the canary ace does not run it healthy yet"},
+		{FP: fp2of('a'), Composed: hashOf('1'), Newest: fp2of('b'), Rule: RuleCanary, Words: "the canary ace does not run it healthy yet"},
 		{Removed: true, Words: "the module left g14"},
 	}
 	for _, w := range wants {
@@ -127,7 +127,7 @@ func TestAssignerValuesRefused(t *testing.T) {
 		{Removed: true, FP: fp2of('a')},
 		{FP: fp2of('a'), Newest: fp2of('b')},
 		{FP: fp2of('a'), Newest: fp2of('a'), Rule: 3},
-		{FP: fp2of('a'), Newest: fp2of('b'), Rule: 7},
+		{FP: fp2of('a'), Composed: hashOf('1'), Newest: fp2of('b'), Rule: 8},
 	} {
 		if _, err := EncodeWant(w); err == nil {
 			t.Errorf("EncodeWant(%+v) accepted", w)

go/delivery/candidate_merged_test.go

@@ -0,0 +1,27 @@
+package delivery
+
+import (
+	"strings"
+	"testing"
+)
+
+// 1791/1921 S9: a member of a group that merged stays in the candidate, marked merged, with its head, so the heads hash
+// the Approve covers holds until every member merged; a candidate whose every member merged is refused.
+func TestACandidateKeepsAMergedMemberAndRefusesOneWhoseEveryMemberMerged(t *testing.T) {
+	a := Head{Repository: "novox/a", Number: 1, Head: strings.Repeat("1", 40)}
+	b := Head{Repository: "novox/b", Number: 2, Head: strings.Repeat("2", 40)}
+	hash, _ := HeadsHash([]Head{a, b})
+	c := Candidate{Group: "feat/x", HeadsHash: hash, Pulls: []CandidatePull{{Head: a, Modules: []string{}, Merged: true}, {Head: b, Modules: []string{}}}}
+	raw, err := EncodeCandidate(c)
+	if err != nil {
+		t.Fatal(err)
+	}
+	back, err := DecodeCandidate(raw)
+	if err != nil || !back.Pulls[0].Merged || back.Pulls[1].Merged || back.HeadsHash != hash {
+		t.Fatalf("read back %+v, %v", back, err)
+	}
+	c.Pulls[1].Merged = true
+	if _, err := EncodeCandidate(c); err == nil {
+		t.Error("a candidate whose every member merged was written")
+	}
+}

go/delivery/composed.go

@@ -0,0 +1,241 @@
+package delivery
+
+import (
+	"encoding/json"
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// The controller's compositions (novox/hq ADR 0539 clauses 1 to 4). A **composition** is one module's resources
+// composed for one node at one fingerprint, written by the controller, which keeps the inputs. It lives in a bucket of
+// each node, `composed-<node>`, which only that node's node-engine reads (a composition can carry a sealed value), under
+// `<node>.<module>.<fingerprint hex>`, and the node's own resources (adoption, firewall openings, accounts, the
+// resolver, identities and groups) under `<node>.node`. Beside it, under the same key in `mesh-controller_composed`,
+// which the assigner reads, the controller writes the composition's digest and its judgement of the move from the
+// composition the node runs now (ComposedDigest). The controller writes both by compare-and-set while it holds the
+// lease; the operator's credential is a second writer on the hand path alone (clause 10, mesh-hand-compose).
+//
+// A composition is derived state (clause 4): its key and its digest are deleted by the controller when its fingerprint
+// is no longer among the module's five newest and no want names it, and each bucket keeps five revisions of a key.
+const (
+	// ComposedBucketPrefix starts the name of a node's bucket of compositions, ComposedBucketFor(node).
+	ComposedBucketPrefix = "composed-"
+	// ComposedHistory is the revisions a node's composition bucket keeps per key (ADR 0539 clause 4).
+	ComposedHistory = 5
+	// ControllerModule is the module of the controller, the writer of the compositions.
+	ControllerModule = "mesh-controller"
+	// ControllerComposedBucket is the controller's bucket of each composition's digest and judgement, `<owner
+	// module>_<name>`, read by the assigner (ADR 0539 clauses 2 and 6).
+	ControllerComposedBucket = ControllerModule + "_composed"
+	// ControllerComposedHistory is the revisions that bucket keeps per key.
+	ControllerComposedHistory = 5
+	// ComposedKeep is how many of a module's newest fingerprints keep their compositions though no want names them
+	// (ADR 0539 clause 4).
+	ComposedKeep = 5
+)
+
+// nodeWord is the last part of a node's own key, in the have bucket and in a node's composition bucket alike.
+const nodeWord = "node"
+
+var bucketNode = regexp.MustCompile(`^[A-Za-z0-9_-]+$`)
+
+// ComposedBucketFor is the name of a node's bucket of compositions, "composed-<node>", as declaration.FileBucketFor
+// names a node's object bucket (ADR 0488 §4). The node name must be one a bucket and a subject token accept: letters,
+// digits, '_' and '-'.
+func ComposedBucketFor(node string) (string, error) {
+	if node == "" {
+		return "", fmt.Errorf("delivery: the node name is empty; a node's composition bucket is named for its node")
+	}
+	if !bucketNode.MatchString(node) {
+		return "", fmt.Errorf("delivery: the node name %q is not one a bucket accepts: letters, digits, '_' and '-' only", node)
+	}
+	return ComposedBucketPrefix + node, nil
+}
+
+// ComposedKey is the key, in ComposedBucketFor(node) and in ControllerComposedBucket, of a module's composition for a
+// node at a fingerprint: `<node>.<module>.<hex>`, the hex being the fingerprint's key part (FingerprintKeyPart). A
+// module named `node` is refused, since `<node>.node` is the node's own key.
+func ComposedKey(node, module, fingerprint string) (string, error) {
+	have, err := HaveKey(node, module)
+	if err != nil {
+		return "", err
+	}
+	part, err := FingerprintKeyPart(fingerprint)
+	if err != nil {
+		return "", err
+	}
+	return have + "." + part, nil
+}
+
+// ComposedNodeKey is the key of a node's own composition: `<node>.node`.
+func ComposedNodeKey(node string) (string, error) {
+	return HaveNodeKey(node)
+}
+
+// ParseComposedKey is the inverse of ComposedKey and ComposedNodeKey: isNode is true for `<node>.node`, with module
+// and fingerprint empty. It refuses any other shape, naming the key.
+func ParseComposedKey(key string) (node, module, fingerprint string, isNode bool, err error) {
+	refused := func(why error) (string, string, string, bool, error) {
+		return "", "", "", false, fmt.Errorf("delivery: %q is not a composition key, <node>.<module>.<fingerprint hex> or <node>.node: %w", key, why)
+	}
+	parts := strings.Split(key, ".")
+	switch len(parts) {
+	case 2:
+		if parts[1] != nodeWord {
+			return refused(fmt.Errorf("a module's composition names its fingerprint"))
+		}
+		if err := checkName("node", parts[0]); err != nil {
+			return refused(err)
+		}
+		return parts[0], "", "", true, nil
+	case 3:
+		node, module, isNode, err := ParseHaveKey(parts[0] + "." + parts[1])
+		if err != nil {
+			return refused(err)
+		}
+		if isNode {
+			return refused(fmt.Errorf("the node's own key names no fingerprint"))
+		}
+		fp, err := ParseFingerprintKeyPart(parts[2])
+		if err != nil {
+			return refused(err)
+		}
+		return node, module, fp, false, nil
+	}
+	return refused(fmt.Errorf("it has %d parts", len(parts)))
+}
+
+// Judgement is the controller's judgement of a move from the composition a node runs, as its have names it, to a new
+// one (ADR 0539 clauses 2 and 14, by ADR 0377 §3's tests).
+type Judgement string
+
+// The judgements of a move.
+const (
+	// JudgedRecreates is a move that recreates a container.
+	JudgedRecreates Judgement = "recreates"
+	// JudgedMovesData is a move that gives the module's data another place.
+	JudgedMovesData Judgement = "moves-data"
+	// JudgedNeither is a move that does neither, and the judgement of a composition the node never ran.
+	JudgedNeither Judgement = "neither"
+	// JudgedCannot is a move that cannot be judged, because the composition the node runs is gone or cannot be read.
+	JudgedCannot Judgement = "cannot-judge"
+	// JudgedUnchanged is a composition equal to the module's slice of the declaration the node last applied, for a node
+	// whose have names no composition yet (the first want at the switch, novox/hq ADR 0540 clause 9): applying it
+	// changes nothing on the node, so it needs no person's yes.
+	JudgedUnchanged Judgement = "unchanged"
+)
+
+var digestForm = regexp.MustCompile(`^sha256:[0-9a-f]{64}$`)
+
+func checkDigest(digest, of string) error {
+	if !digestForm.MatchString(digest) {
+		return fmt.Errorf("delivery: %s %q is not sha256:<64 lowercase hex digits>", of, digest)
+	}
+	return nil
+}
+
+// ComposedDigest is the value, in ControllerComposedBucket, beside a composition: its Digest (ComposedDigestOf), and
+// the Judgement of the move to it from the composition the node runs now, whose digest is Against (empty when the node
+// runs no composition of the module). Words say why, and are required for a move that cannot be judged. Rewritten when
+// the node's have changes.
+//
+// Policy is the module's upgrade policy as the controller holds it (ADR 0236, ADR 0539 clause 14), with PolicyFrom
+// where it comes from and PolicyWhy why: the assigner holds a move of a module of policy record from it, the operator's
+// own choice (`upgrade` with policy) included. Rewritten when the policy changes. Empty on a composition made by hand
+// (mesh-hand-compose), whose want the operator writes.
+type ComposedDigest struct {
+	V         int       `json:"v"`
+	Digest    string    `json:"digest"`
+	Judgement Judgement `json:"judgement"`
+	Against   string    `json:"against,omitempty"`
+	Words     string    `json:"words,omitempty"`
+	// UserListOnly says the composition differs from the one the node's have names only in the bus's user list (the
+	// bus module's file `<module>.bus-users`), whatever the judgement says of its mount: the assigner writes such a
+	// revision into the bus node's want at once, outside the record hold, at the fingerprint the node runs (ADR 0539
+	// clause 7).
+	UserListOnly bool   `json:"user-list-only,omitempty"`
+	Policy       string `json:"policy,omitempty"`
+	PolicyFrom   string `json:"policy-from,omitempty"`
+	PolicyWhy    string `json:"policy-why,omitempty"`
+}
+
+// The upgrade policies and their sources a composition's value names: catalogue.PolicyRoll, PolicyTogether and
+// PolicyRecord, and catalogue.FromPerson, FromModule, FromBus, FromData and FromDefault, the same words (the compose
+// package's test holds them equal; this package does not import the catalogue).
+var (
+	composedPolicies    = []string{"roll", "together", "record"}
+	composedPolicyFroms = []string{"person", "module", "the bus", "irreplaceable data", "default"}
+)
+
+func oneOf(v string, of []string) bool {
+	for _, o := range of {
+		if v == o {
+			return true
+		}
+	}
+	return false
+}
+
+func (c ComposedDigest) check() error {
+	if err := checkDigest(c.Digest, "the composition's digest"); err != nil {
+		return err
+	}
+	if c.Against != "" {
+		if err := checkDigest(c.Against, "the digest a move is judged against"); err != nil {
+			return err
+		}
+	}
+	switch c.Judgement {
+	case JudgedRecreates, JudgedMovesData:
+		if c.Against == "" {
+			return fmt.Errorf("delivery: a move judged %s names the composition it is judged against", c.Judgement)
+		}
+	case JudgedNeither, JudgedUnchanged:
+	case JudgedCannot:
+		if c.Words == "" {
+			return fmt.Errorf("delivery: a move that cannot be judged says why")
+		}
+	default:
+		return fmt.Errorf("delivery: the judgement %q is not %s, %s, %s, %s or %s", c.Judgement, JudgedRecreates,
+			JudgedMovesData, JudgedNeither, JudgedCannot, JudgedUnchanged)
+	}
+	if c.Policy != "" || c.PolicyFrom != "" {
+		if !oneOf(c.Policy, composedPolicies) {
+			return fmt.Errorf("delivery: the upgrade policy %q is not one of %v", c.Policy, composedPolicies)
+		}
+		if !oneOf(c.PolicyFrom, composedPolicyFroms) {
+			return fmt.Errorf("delivery: the upgrade policy's source %q is not one of %v", c.PolicyFrom, composedPolicyFroms)
+		}
+	}
+	return nil
+}
+
+// PolicyRecord is the policy whose moves the assigner holds for a person's yes (ADR 0539 clause 14).
+const PolicyRecord = "record"
+
+// EncodeComposedDigest is c as JSON at Version; it refuses an unknown judgement, a digest not of the sha256 form, a
+// move judged to recreate or move data against nothing, and a move that cannot be judged without its reason.
+func EncodeComposedDigest(c ComposedDigest) ([]byte, error) {
+	if err := c.check(); err != nil {
+		return nil, err
+	}
+	c.V = Version
+	return json.Marshal(c)
+}
+
+// DecodeComposedDigest reads the value beside a composition; it refuses an unknown version (ErrUnknownVersion) and
+// what EncodeComposedDigest refuses.
+func DecodeComposedDigest(data []byte) (ComposedDigest, error) {
+	var c ComposedDigest
+	if err := decode(data, &c); err != nil {
+		return ComposedDigest{}, err
+	}
+	if err := c.check(); err != nil {
+		return ComposedDigest{}, err
+	}
+	return c, nil
+}
+
+// SameComposedDigest says whether two values are the same, so the controller writes only when they differ.
+func SameComposedDigest(a, b ComposedDigest) bool { return a == b }

go/delivery/composed_keys_test.go

@@ -0,0 +1,125 @@
+package delivery
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+// 1943/AC1: a node's composition bucket is named for the node, and a node with no name, or one a bucket refuses,
+// is refused, naming why.
+func TestComposedBucketFor(t *testing.T) {
+	b, err := ComposedBucketFor("ace")
+	if err != nil || b != "composed-ace" {
+		t.Fatalf("ComposedBucketFor(ace) = %q, %v", b, err)
+	}
+	for _, bad := range []string{"", "a.b", "a*", "a b", "a>"} {
+		if _, err := ComposedBucketFor(bad); err == nil || !strings.Contains(err.Error(), "node") {
+			t.Errorf("ComposedBucketFor(%q) = %v, want a refusal naming the node", bad, err)
+		}
+	}
+}
+
+// 1943/AC1: a module's composition key and the node's own key round-trip through one parser; an empty node, a
+// module named node, a bad fingerprint and a key of another shape are refused, naming why.
+func TestComposedKeys(t *testing.T) {
+	fp := fp2of('c')
+	key, err := ComposedKey("ace", "mesh-mail", fp)
+	if err != nil || key != "ace.mesh-mail."+strings.Repeat("c", 64) {
+		t.Fatalf("ComposedKey = %q, %v", key, err)
+	}
+	node, module, back, isNode, err := ParseComposedKey(key)
+	if err != nil || node != "ace" || module != "mesh-mail" || back != fp || isNode {
+		t.Errorf("ParseComposedKey(%q) = %q, %q, %q, %v, %v", key, node, module, back, isNode, err)
+	}
+	own, err := ComposedNodeKey("ace")
+	if err != nil || own != "ace.node" {
+		t.Fatalf("ComposedNodeKey = %q, %v", own, err)
+	}
+	node, module, back, isNode, err = ParseComposedKey(own)
+	if err != nil || node != "ace" || module != "" || back != "" || !isNode {
+		t.Errorf("ParseComposedKey(%q) = %q, %q, %q, %v, %v", own, node, module, back, isNode, err)
+	}
+
+	refusals := []struct {
+		node, module, fp, why string
+	}{
+		{"", "mesh-mail", fp, "node name is empty"},
+		{"ace", "node", fp, `"node" is refused`},
+		{"ace", "", fp, "module name is empty"},
+		{"ace", "mesh-mail", "src2:abc", "not a fingerprint of the new form"},
+		{"ace", "mesh-mail", "src1:" + strings.Repeat("c", 64), "not a fingerprint of the new form"},
+		{"a.b", "mesh-mail", fp, "node name"},
+	}
+	for _, r := range refusals {
+		if _, err := ComposedKey(r.node, r.module, r.fp); err == nil || !strings.Contains(err.Error(), r.why) {
+			t.Errorf("ComposedKey(%q, %q, %q) = %v, want a refusal saying %q", r.node, r.module, r.fp, err, r.why)
+		}
+	}
+	if _, err := ComposedNodeKey(""); err == nil {
+		t.Errorf("ComposedNodeKey(\"\") accepted")
+	}
+	for _, bad := range []string{"", "ace", "ace.mesh-mail", "ace.node.x", "ace.mesh-mail.abc", ".mesh-mail." + strings.Repeat("c", 64),
+		"ace.node." + strings.Repeat("c", 64), "ace.mesh-mail." + strings.Repeat("c", 64) + ".x", "want.ace.mesh-mail"} {
+		if _, _, _, _, err := ParseComposedKey(bad); err == nil || !strings.Contains(err.Error(), "\""+bad+"\"") {
+			t.Errorf("ParseComposedKey(%q) = %v, want a refusal naming it", bad, err)
+		}
+	}
+}
+
+// 1943/AC1: the controller's value beside a composition, its digest and the judgement of the move, round-trips; an
+// unknown judgement, a digest not of the sha256 form, a move judged against nothing, a cannot-judge without its
+// reason, and an upgrade policy or source outside the catalogue's words are refused, naming why; an unknown version is
+// refused as one. The module's upgrade policy and its source ride beside the judgement, for the assigner's hold.
+func TestComposedDigestValue(t *testing.T) {
+	digest := "sha256:" + strings.Repeat("d", 64)
+	against := "sha256:" + strings.Repeat("e", 64)
+	for _, v := range []ComposedDigest{
+		{Digest: digest, Judgement: JudgedNeither},
+		{Digest: digest, Judgement: JudgedNeither, Against: against},
+		{Digest: digest, Judgement: JudgedRecreates, Against: against, Words: "the container's image changes"},
+		{Digest: digest, Judgement: JudgedMovesData, Against: against},
+		{Digest: digest, Judgement: JudgedCannot, Words: "the composition the node runs is gone"},
+		{Digest: digest, Judgement: JudgedUnchanged, Words: "equal to the declaration the node last applied"},
+		{Digest: digest, Judgement: JudgedNeither, Policy: "record", PolicyFrom: "person", PolicyWhy: "the operator: its data"},
+		{Digest: digest, Judgement: JudgedNeither, Policy: "roll", PolicyFrom: "default"},
+		{Digest: digest, Judgement: JudgedNeither, Against: against, UserListOnly: true, Words: "only the bus's user list changes"},
+	} {
+		raw, err := EncodeComposedDigest(v)
+		if err != nil {
+			t.Fatalf("EncodeComposedDigest(%+v): %v", v, err)
+		}
+		back, err := DecodeComposedDigest(raw)
+		v.V = Version
+		if err != nil || !SameComposedDigest(back, v) {
+			t.Errorf("round trip of %+v = %+v, %v", v, back, err)
+		}
+	}
+	refusals := []struct {
+		v   ComposedDigest
+		why string
+	}{
+		{ComposedDigest{Digest: digest, Judgement: "maybe"}, `judgement "maybe"`},
+		{ComposedDigest{Digest: digest}, `judgement ""`},
+		{ComposedDigest{Digest: "sha256:abc", Judgement: JudgedNeither}, "not sha256"},
+		{ComposedDigest{Judgement: JudgedNeither}, "not sha256"},
+		{ComposedDigest{Digest: digest, Judgement: JudgedRecreates}, "against"},
+		{ComposedDigest{Digest: digest, Judgement: JudgedMovesData}, "against"},
+		{ComposedDigest{Digest: digest, Judgement: JudgedCannot}, "why"},
+		{ComposedDigest{Digest: digest, Judgement: JudgedNeither, Against: "sha256:zz"}, "not sha256"},
+		{ComposedDigest{Digest: digest, Judgement: JudgedNeither, Policy: "sometimes", PolicyFrom: "person"}, `policy "sometimes"`},
+		{ComposedDigest{Digest: digest, Judgement: JudgedNeither, Policy: "record"}, `source ""`},
+		{ComposedDigest{Digest: digest, Judgement: JudgedNeither, PolicyFrom: "person"}, `policy ""`},
+	}
+	for _, r := range refusals {
+		if _, err := EncodeComposedDigest(r.v); err == nil || !strings.Contains(err.Error(), r.why) {
+			t.Errorf("EncodeComposedDigest(%+v) = %v, want a refusal saying %q", r.v, err, r.why)
+		}
+	}
+	if _, err := DecodeComposedDigest([]byte(`{"v":2,"digest":"` + digest + `","judgement":"neither"}`)); !errors.Is(err, ErrUnknownVersion) {
+		t.Errorf("version 2 = %v, want ErrUnknownVersion", err)
+	}
+	if _, err := DecodeComposedDigest([]byte(`{"v":1,"digest":"` + digest + `","judgement":"perhaps"}`)); err == nil {
+		t.Errorf("an unknown judgement was read")
+	}
+}

go/delivery/composed_signature.go

@@ -0,0 +1,100 @@
+package delivery
+
+import (
+	"crypto/ed25519"
+	"encoding/base64"
+	"fmt"
+)
+
+// A composition's signature (novox/hq ADR 0539 clause 3): the controller signs each composition it writes with its
+// key, and the operator signs one made by hand with mesh-hand-compose with theirs. The node-engine trusts exactly these two
+// signers and applies nothing of a composition whose signature fails or whose signer is neither. The signature is an
+// ed25519 signature, as a declaration's is, of the composition's digest (ComposedDigestOf) after a context line, so a
+// signature made for anything else never verifies here.
+const composedSigningContext = "novox composition v1\n"
+
+// Signature is who signed a composition and the signature: Signer the signer's ed25519 public key and Sig the
+// signature, both in standard base64.
+type Signature struct {
+	Signer string `json:"signer"`
+	Sig    string `json:"sig"`
+}
+
+func (s Signature) check() error {
+	if key, err := base64.StdEncoding.DecodeString(s.Signer); err != nil || len(key) != ed25519.PublicKeySize {
+		return fmt.Errorf("delivery: a composition's signer %q is not an ed25519 public key in base64", s.Signer)
+	}
+	if sig, err := base64.StdEncoding.DecodeString(s.Sig); err != nil || len(sig) != ed25519.SignatureSize {
+		return fmt.Errorf("delivery: a composition's signature is not an ed25519 signature in base64")
+	}
+	return nil
+}
+
+// SignComposed is c signed with key: its digest signed, and the key's public half named as the signer. A signature c
+// already carries is replaced.
+func SignComposed(c Composed, key ed25519.PrivateKey) (Composed, error) {
+	if len(key) != ed25519.PrivateKeySize {
+		return Composed{}, fmt.Errorf("delivery: the key to sign a composition with is not an ed25519 private key")
+	}
+	return SignComposedBy(c, key.Public().(ed25519.PublicKey), func(message []byte) ([]byte, error) {
+		return ed25519.Sign(key, message), nil
+	})
+}
+
+// SignComposedBy is SignComposed for a signer that keeps its private half to itself (the controller's identity store
+// signs a message and hands back the signature): sign signs the message it is given with the key whose public half is
+// signer. A signature that does not verify against signer is refused, so a composition is never written signed by a
+// key other than the one it names.
+func SignComposedBy(c Composed, signer ed25519.PublicKey, sign func(message []byte) ([]byte, error)) (Composed, error) {
+	if len(signer) != ed25519.PublicKeySize {
+		return Composed{}, fmt.Errorf("delivery: the signer of a composition is not an ed25519 public key")
+	}
+	c.Signature = nil
+	digest, err := ComposedDigestOf(c)
+	if err != nil {
+		return Composed{}, err
+	}
+	message := []byte(composedSigningContext + digest)
+	sig, err := sign(message)
+	if err != nil {
+		return Composed{}, err
+	}
+	if !ed25519.Verify(signer, message, sig) {
+		return Composed{}, fmt.Errorf("delivery: the signature made for the composition of %q on %s does not verify against its signer", c.Module, c.Node)
+	}
+	c.Signature = &Signature{Signer: base64.StdEncoding.EncodeToString(signer), Sig: base64.StdEncoding.EncodeToString(sig)}
+	return c, nil
+}
+
+// VerifyComposed is c's digest when c is signed by one of the trusted keys and its signature verifies against its
+// digest; otherwise it refuses, saying why, and nothing of c is to be applied: an unsigned composition, one whose
+// signer is not a trusted key, and one changed after it was signed.
+func VerifyComposed(c Composed, trusted []ed25519.PublicKey) (string, error) {
+	if c.Signature == nil {
+		return "", fmt.Errorf("delivery: the composition of %q on %s is unsigned, and only a signed one is applied", c.Module, c.Node)
+	}
+	if err := c.Signature.check(); err != nil {
+		return "", err
+	}
+	signer, _ := base64.StdEncoding.DecodeString(c.Signature.Signer)
+	var key ed25519.PublicKey
+	for _, t := range trusted {
+		if t.Equal(ed25519.PublicKey(signer)) {
+			key = t
+		}
+	}
+	if key == nil {
+		return "", fmt.Errorf("delivery: the composition of %q on %s is signed by %s, which is not a trusted signer (the controller's key or the operator's)",
+			c.Module, c.Node, c.Signature.Signer)
+	}
+	digest, err := ComposedDigestOf(c)
+	if err != nil {
+		return "", err
+	}
+	sig, _ := base64.StdEncoding.DecodeString(c.Signature.Sig)
+	if !ed25519.Verify(key, []byte(composedSigningContext+digest), sig) {
+		return "", fmt.Errorf("delivery: the composition of %q on %s does not match its signature: it was changed after it was signed, or signed for another",
+			c.Module, c.Node)
+	}
+	return digest, nil
+}

go/delivery/composed_signature_test.go

@@ -0,0 +1,103 @@
+package delivery
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func aSigningKey(t *testing.T) (ed25519.PublicKey, ed25519.PrivateKey) {
+	t.Helper()
+	pub, priv, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return pub, priv
+}
+
+func aComposition() Composed {
+	return Composed{Node: "ace", Module: "m", FP: fp2of('a'), Resources: []json.RawMessage{
+		json.RawMessage(`{"id":"m.f","type":"file","module":"m","path":"/etc/m","content":"x"}`)}}
+}
+
+// 1943/AC5: a composition signed by the controller's key or by the operator's verifies against the two trusted keys,
+// keeps its digest, and survives its encoding; one signed by another key, unsigned, or changed by one byte after it was
+// signed does not verify, and nothing of it is to be applied.
+func TestACompositionIsSignedByATrustedKey(t *testing.T) {
+	controllerPub, controller := aSigningKey(t)
+	operatorPub, operator := aSigningKey(t)
+	_, stranger := aSigningKey(t)
+	trusted := []ed25519.PublicKey{controllerPub, operatorPub}
+	c := aComposition()
+	want, _ := ComposedDigestOf(c)
+
+	for name, key := range map[string]ed25519.PrivateKey{"controller": controller, "operator": operator} {
+		signed, err := SignComposed(c, key)
+		if err != nil {
+			t.Fatalf("%s: %v", name, err)
+		}
+		raw, err := EncodeComposed(signed)
+		if err != nil {
+			t.Fatal(err)
+		}
+		back, err := DecodeComposed(raw)
+		if err != nil {
+			t.Fatal(err)
+		}
+		digest, err := VerifyComposed(back, trusted)
+		if err != nil || digest != want {
+			t.Errorf("%s's signature: %q, %v; want the digest %s", name, digest, err, want)
+		}
+		if d, _ := ComposedDigestOf(back); d != want {
+			t.Errorf("%s's signature changed the digest: %s", name, d)
+		}
+
+		changed := strings.Replace(string(raw), `"content":"x"`, `"content":"y"`, 1)
+		if changed == string(raw) {
+			t.Fatal("the test changed nothing")
+		}
+		if tampered, err := DecodeComposed([]byte(changed)); err != nil {
+			t.Fatal(err)
+		} else if _, err := VerifyComposed(tampered, trusted); err == nil || !strings.Contains(err.Error(), "signature") {
+			t.Errorf("%s: a composition changed by one byte verified: %v", name, err)
+		}
+	}
+
+	byStranger, _ := SignComposed(c, stranger)
+	if _, err := VerifyComposed(byStranger, trusted); err == nil || !strings.Contains(err.Error(), "not a trusted") {
+		t.Errorf("a stranger's signature = %v, want refused as no trusted signer", err)
+	}
+	if _, err := VerifyComposed(c, trusted); err == nil || !strings.Contains(err.Error(), "unsigned") {
+		t.Errorf("an unsigned composition = %v, want refused", err)
+	}
+	signed, _ := SignComposed(c, controller)
+	forged := signed
+	forged.Signature = &Signature{Signer: signed.Signature.Signer, Sig: byStranger.Signature.Sig}
+	if _, err := VerifyComposed(forged, trusted); err == nil {
+		t.Errorf("a stranger's signature under the controller's name verified")
+	}
+	if _, err := EncodeComposed(Composed{Node: "ace", Module: "m", FP: fp2of('a'), Resources: c.Resources,
+		Signature: &Signature{Signer: "not base64!", Sig: "x"}}); err == nil {
+		t.Errorf("a signature naming no key was encoded")
+	}
+}
+
+// 1943/AC5: a signer that keeps its private half signs through a function, and the composition verifies as one signed
+// with the key; a function that signs with another key than the one named is refused.
+func TestACompositionIsSignedByAKeptKey(t *testing.T) {
+	pub, priv := aSigningKey(t)
+	_, other := aSigningKey(t)
+	c := aComposition()
+	signed, err := SignComposedBy(c, pub, func(m []byte) ([]byte, error) { return ed25519.Sign(priv, m), nil })
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := VerifyComposed(signed, []ed25519.PublicKey{pub}); err != nil {
+		t.Errorf("a composition signed through the function does not verify: %v", err)
+	}
+	if _, err := SignComposedBy(c, pub, func(m []byte) ([]byte, error) { return ed25519.Sign(other, m), nil }); err == nil {
+		t.Errorf("a signature by another key than the one named was accepted")
+	}
+}

go/delivery/composed_value.go

@@ -0,0 +1,330 @@
+package delivery
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+
+	"git.novox.be/novox/mesh-sdk/go/declaration"
+)
+
+// NodeOwn is what a node's own composition (`<node>.node`) carries beside its resources: what the declaration says of
+// the node as a whole (novox/hq ADR 0539 clause 2: adoption, accounts, identities and groups). A module's composition
+// carries none of it.
+type NodeOwn struct {
+	// Adoption says the node is adopted and which of its modules are taken (ADR 0100, ADR 0103); nil for a converged node.
+	Adoption *declaration.Adoption `json:"adoption,omitempty"`
+	// Identities is the identity of every module assigned to the node (ADR 0328 §4), Groups and Libraries every library
+	// it is reached by (ADR 0328 §3).
+	Identities []declaration.Identity `json:"identities,omitempty"`
+	Groups     []declaration.Group    `json:"groups,omitempty"`
+	Libraries  []declaration.Library  `json:"libraries,omitempty"`
+	// Provisioner is the account the provisioner's client runs as on the node (ADR 0349 §4).
+	Provisioner string `json:"provisioner_account,omitempty"`
+}
+
+func (o NodeOwn) empty() bool {
+	return o.Adoption == nil && len(o.Identities) == 0 && len(o.Groups) == 0 && len(o.Libraries) == 0 && o.Provisioner == ""
+}
+
+// Composed is a composition (ADR 0539 clause 1): one module's resources composed for one node at one fingerprint, or,
+// with Module and FP empty, the node's own resources and parts (Own). Each resource is a declaration resource as the
+// node-engine reads it, saying its module; it is kept as JSON and written canonically (its keys sorted, its spacing
+// dropped), so its digest (ComposedDigestOf) is a function of its content alone. Data says the module declares data,
+// so the node agent backs it up before it moves (ADR 0429 §14). Filled names the files of the module the provisioner
+// fills (ADR 0349 §5). A file over 64 KiB travels by digest and size (ByDigest), its content in the node's object
+// bucket (ADR 0539 clause 4).
+type Composed struct {
+	V         int
+	Node      string
+	Module    string
+	FP        string
+	Data      bool
+	Resources []json.RawMessage
+	Filled    []string
+	Own       NodeOwn
+	// Signature is the controller's or, made by hand, the operator's (ADR 0539 clause 3, SignComposed); it signs the
+	// digest and is never part of it.
+	Signature *Signature
+}
+
+// composedWire is a composition as it is written.
+type composedWire struct {
+	V         int               `json:"v"`
+	Node      string            `json:"node"`
+	Module    string            `json:"module,omitempty"`
+	FP        string            `json:"fp,omitempty"`
+	Data      bool              `json:"data,omitempty"`
+	Resources []json.RawMessage `json:"resources"`
+	Filled    []string          `json:"filled_files,omitempty"`
+	Own       *NodeOwn          `json:"own,omitempty"`
+	Signature *Signature        `json:"signature,omitempty"`
+}
+
+// canonicalJSON is raw with its object keys sorted and its spacing dropped, its numbers kept as written.
+func canonicalJSON(raw json.RawMessage) (json.RawMessage, error) {
+	var v any
+	d := json.NewDecoder(bytes.NewReader(raw))
+	d.UseNumber()
+	if err := d.Decode(&v); err != nil {
+		return nil, err
+	}
+	if _, err := d.Token(); err != io.EOF {
+		return nil, fmt.Errorf("more after the value")
+	}
+	return json.Marshal(v)
+}
+
+func (c Composed) check() error {
+	if _, err := HaveNodeKey(c.Node); err != nil {
+		return err
+	}
+	if c.Module == "" {
+		if c.FP != "" {
+			return fmt.Errorf("delivery: the node's own composition names no fingerprint, and this one names %s", c.FP)
+		}
+		// It carries the filled paths of its own files, those of a module with no fingerprint of the new form moved
+		// into it (issue 1945), and never a module's data.
+		if c.Data {
+			return fmt.Errorf("delivery: the node's own composition holds no module's data")
+		}
+	} else {
+		if _, err := ComposedKey(c.Node, c.Module, c.FP); err != nil {
+			return err
+		}
+		if !c.Own.empty() {
+			return fmt.Errorf("delivery: the composition of %s carries the node's own parts, which only <node>.node carries", c.Module)
+		}
+	}
+	seen := map[string]bool{}
+	files := map[string][]*declaration.File{}
+	for _, raw := range c.Resources {
+		r, err := declaration.ParseResource(raw)
+		if err != nil {
+			return fmt.Errorf("delivery: the composition of %q on %s: %w", c.Module, c.Node, err)
+		}
+		if seen[r.Identity()] {
+			return fmt.Errorf("delivery: the composition of %q on %s holds the resource %q twice", c.Module, c.Node, r.Identity())
+		}
+		seen[r.Identity()] = true
+		if r.DeclaredModule() != c.Module {
+			return fmt.Errorf("delivery: the resource %q is of %q, and this is the composition of %q on %s",
+				r.Identity(), r.DeclaredModule(), c.Module, c.Node)
+		}
+		if f, ok := r.(*declaration.File); ok {
+			if f.TravelsByDigest() {
+				return fmt.Errorf("delivery: the file %q is over %d bytes and travels by digest (ByDigest), not whole",
+					f.ID, declaration.FileReferenceThreshold)
+			}
+			files[f.Path] = append(files[f.Path], f)
+		}
+	}
+	// A file the provisioner fills says no content, so a composition that does not say it is filled would have the
+	// node-engine write it empty (issue 1945, live on 2026-10-25): refused, naming it.
+	filledHere := make(map[string]bool, len(c.Filled))
+	for _, path := range c.Filled {
+		filledHere[path] = true
+	}
+	for path, fs := range files {
+		for _, f := range fs {
+			if f.OwnerAtRuntime == declaration.RuntimeOwned && !filledHere[path] && !saysContent(f) {
+				return fmt.Errorf("delivery: the file %q says no content and the composition of %q on %s does not say "+
+					"the provisioner fills %s: the node-engine would write it empty", f.ID, c.Module, c.Node, path)
+			}
+		}
+	}
+	for _, path := range c.Filled {
+		if len(files[path]) == 0 {
+			return fmt.Errorf("delivery: the composition of %q fills %q, and declares no file there", c.Module, path)
+		}
+		for _, f := range files[path] {
+			if f.OwnerAtRuntime == "" {
+				return fmt.Errorf("delivery: the file %q is filled by the provisioner and says no owner-at-runtime", f.ID)
+			}
+		}
+	}
+	if c.Signature != nil {
+		if err := c.Signature.check(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// saysContent says a file names what to write: content, bytes, a digest or a sealed value. A file the provisioner fills
+// names none of them.
+func saysContent(f *declaration.File) bool {
+	return f.Content != "" || f.Bytes != "" || f.Digest != "" || f.Sealed != "" || f.VaultSealed != nil
+}
+
+// wire is c checked and made canonical, ready to marshal.
+func (c Composed) wire() (composedWire, error) {
+	if err := c.check(); err != nil {
+		return composedWire{}, err
+	}
+	w := composedWire{V: Version, Node: c.Node, Module: c.Module, FP: c.FP, Data: c.Data, Filled: c.Filled,
+		Signature: c.Signature, Resources: make([]json.RawMessage, len(c.Resources))}
+	for i, r := range c.Resources {
+		canon, err := canonicalJSON(r)
+		if err != nil {
+			return composedWire{}, fmt.Errorf("delivery: a resource of %q is not JSON: %w", c.Module, err)
+		}
+		w.Resources[i] = canon
+	}
+	if !c.Own.empty() {
+		own := c.Own
+		w.Own = &own
+	}
+	return w, nil
+}
+
+// EncodeComposed is c as JSON at Version, each resource canonical. It refuses a composition whose node or fingerprint
+// a key refuses, a resource its kind refuses (an action among them), a resource of another module, a module's
+// composition carrying the node's own parts, a file over 64 KiB carried whole, and a filled path no file declares.
+func EncodeComposed(c Composed) ([]byte, error) {
+	w, err := c.wire()
+	if err != nil {
+		return nil, err
+	}
+	return json.Marshal(w)
+}
+
+// DecodeComposed reads a composition; it refuses an unknown version (ErrUnknownVersion), a field it does not know, and
+// what EncodeComposed refuses.
+func DecodeComposed(data []byte) (Composed, error) {
+	if err := checkVersion(data); err != nil {
+		return Composed{}, err
+	}
+	var w composedWire
+	d := json.NewDecoder(bytes.NewReader(data))
+	d.DisallowUnknownFields()
+	if err := d.Decode(&w); err != nil {
+		return Composed{}, fmt.Errorf("delivery: a composition does not fit its shape: %w", err)
+	}
+	c := Composed{V: w.V, Node: w.Node, Module: w.Module, FP: w.FP, Data: w.Data, Resources: w.Resources,
+		Filled: w.Filled, Signature: w.Signature}
+	if w.Own != nil {
+		c.Own = *w.Own
+	}
+	if err := c.check(); err != nil {
+		return Composed{}, err
+	}
+	return c, nil
+}
+
+// ComposedDigestOf is a composition's digest, "sha256:<hex>", of its encoding without its signature. A want names it
+// (ADR 0539 clause 1), the controller writes it beside the composition, and the signature signs it.
+func ComposedDigestOf(c Composed) (string, error) {
+	c.Signature = nil
+	raw, err := EncodeComposed(c)
+	if err != nil {
+		return "", err
+	}
+	sum := sha256.Sum256(raw)
+	return "sha256:" + hex.EncodeToString(sum[:]), nil
+}
+
+// SameComposed says whether two compositions are the same value, their signatures included, so the controller writes
+// only when they differ.
+func SameComposed(a, b Composed) bool {
+	ra, errA := EncodeComposed(a)
+	rb, errB := EncodeComposed(b)
+	return errA == nil && errB == nil && bytes.Equal(ra, rb)
+}
+
+// ByDigest is c with every file over 64 KiB given by its digest and size, and the content of each by digest, for the
+// writer to put in the node's object bucket (declaration.FileBucketFor) under declaration.ObjectName before it writes
+// the composition (ADR 0539 clause 4, ADR 0488 §3). A file that is sealed, filled with secrets or written into another
+// stays as it is (declaration.File.TravelsByDigest).
+func (c Composed) ByDigest() (Composed, map[string][]byte, error) {
+	out := c
+	out.Resources = make([]json.RawMessage, len(c.Resources))
+	objects := map[string][]byte{}
+	for i, raw := range c.Resources {
+		out.Resources[i] = raw
+		r, err := declaration.ParseResource(raw)
+		if err != nil {
+			return Composed{}, nil, err
+		}
+		f, ok := r.(*declaration.File)
+		if !ok || !f.TravelsByDigest() {
+			continue
+		}
+		ref, body, err := f.AsReference()
+		if err != nil {
+			return Composed{}, nil, err
+		}
+		var fields map[string]json.RawMessage
+		if err := json.Unmarshal(raw, &fields); err != nil {
+			return Composed{}, nil, err
+		}
+		delete(fields, "content")
+		delete(fields, "bytes")
+		fields["digest"], _ = json.Marshal(ref.Digest)
+		fields["size"], _ = json.Marshal(ref.Size)
+		rewritten, err := json.Marshal(fields)
+		if err != nil {
+			return Composed{}, nil, err
+		}
+		out.Resources[i] = rewritten
+		objects[ref.Digest] = body
+	}
+	return out, objects, nil
+}
+
+// SplitComposed splits a node's composed resources into its compositions, by key (ComposedKey, ComposedNodeKey): each
+// resource into the composition of the module it says, under that module's fingerprint in fps, and a resource that
+// says no module into the node's own, with own. Each filled path goes with the module whose file declares it. The order
+// of the resources is kept within each composition. A resource of a module fps names no fingerprint for is refused,
+// naming it. Data is the caller's to set, from the module's manifest.
+func SplitComposed(node string, resources []json.RawMessage, fps map[string]string, filled []string, own NodeOwn) (map[string]Composed, error) {
+	nodeKey, err := ComposedNodeKey(node)
+	if err != nil {
+		return nil, err
+	}
+	out := map[string]Composed{nodeKey: {Node: node, Own: own, Resources: []json.RawMessage{}}}
+	pathOf := map[string]string{}
+	for _, raw := range resources {
+		var head struct {
+			ID     string `json:"id"`
+			Type   string `json:"type"`
+			Module string `json:"module"`
+			Path   string `json:"path"`
+		}
+		if err := json.Unmarshal(raw, &head); err != nil {
+			return nil, fmt.Errorf("delivery: a resource of %s is not JSON: %w", node, err)
+		}
+		key := nodeKey
+		if head.Module != "" {
+			fp, ok := fps[head.Module]
+			if !ok {
+				return nil, fmt.Errorf("delivery: the resource %q is of %q, whose fingerprint on %s is not given", head.ID, head.Module, node)
+			}
+			if key, err = ComposedKey(node, head.Module, fp); err != nil {
+				return nil, err
+			}
+			if _, ok := out[key]; !ok {
+				out[key] = Composed{Node: node, Module: head.Module, FP: fp}
+			}
+		}
+		if head.Type == string(declaration.TypeFile) && head.Module != "" {
+			pathOf[head.Path] = key
+		}
+		c := out[key]
+		c.Resources = append(c.Resources, raw)
+		out[key] = c
+	}
+	for _, path := range filled {
+		key, ok := pathOf[path]
+		if !ok {
+			return nil, fmt.Errorf("delivery: the provisioner fills %q on %s, and no module's file declares it", path, node)
+		}
+		c := out[key]
+		c.Filled = append(c.Filled, path)
+		out[key] = c
+	}
+	return out, nil
+}

go/delivery/composed_value_test.go

@@ -0,0 +1,364 @@
+package delivery
+
+import (
+	"bytes"
+	"compress/gzip"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"sort"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/declaration"
+)
+
+// capturedDeclaration is a node's declaration as the controller's `plan` verb answered it on 2026-10-24 at 16:19
+// (testdata/declaration-<node>.json.gz; the resources carrying a sealed value or a secret taken out, and the filled
+// files that named them), never typed by hand.
+type capturedDeclaration struct {
+	Builds      map[string]string `json:"builds"`
+	Resources   []json.RawMessage `json:"resources"`
+	Filled      []string          `json:"filled_files"`
+	Provisioner string            `json:"provisioner_account"`
+}
+
+func readCaptured(t *testing.T, node string) capturedDeclaration {
+	t.Helper()
+	f, err := os.Open("testdata/declaration-" + node + ".json.gz")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	z, err := gzip.NewReader(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	raw, err := io.ReadAll(z)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var c capturedDeclaration
+	if err := json.Unmarshal(raw, &c); err != nil {
+		t.Fatal(err)
+	}
+	return c
+}
+
+// fpOfBuild stands for each module's fingerprint in a captured declaration, which names builds, not fingerprints.
+func fpOfBuild(build string) string {
+	var b strings.Builder
+	for b.Len() < 64 {
+		b.WriteString(fmt.Sprintf("%x", []byte(build)))
+	}
+	return SourcePrefix2 + b.String()[:64]
+}
+
+func splitCaptured(t *testing.T, node string, c capturedDeclaration) map[string]Composed {
+	t.Helper()
+	fps := map[string]string{}
+	for m, b := range c.Builds {
+		fps[m] = fpOfBuild(b)
+	}
+	// mesh-wireguard's resources are composed with no build of it named; its fingerprint is the indexer's, as every
+	// module's is, and stood in for here by its name.
+	for _, r := range c.Resources {
+		var head struct {
+			Module string `json:"module"`
+		}
+		_ = json.Unmarshal(r, &head)
+		if _, ok := fps[head.Module]; head.Module != "" && !ok {
+			fps[head.Module] = fpOfBuild(head.Module)
+		}
+	}
+	split, err := SplitComposed(node, c.Resources, fps, c.Filled, NodeOwn{Provisioner: c.Provisioner})
+	if err != nil {
+		t.Fatalf("SplitComposed(%s): %v", node, err)
+	}
+	return split
+}
+
+func canonical(t *testing.T, raw json.RawMessage) string {
+	t.Helper()
+	var v any
+	d := json.NewDecoder(bytes.NewReader(raw))
+	d.UseNumber()
+	if err := d.Decode(&v); err != nil {
+		t.Fatal(err)
+	}
+	out, _ := json.Marshal(v)
+	return string(out)
+}
+
+// 1943/AC2: each module's slice of a captured declaration of each node, and the node's own resources, round-trip
+// through the composition's encoding with the same digest; together they are the declaration's resources, each once,
+// each in the composition of the module it says.
+func TestCompositionsOfACapturedDeclaration(t *testing.T) {
+	t.Parallel()
+	for _, node := range []string{"ace", "g14"} {
+		t.Run(node, func(t *testing.T) {
+			t.Parallel()
+			oneCapturedDeclaration(t, node)
+		})
+	}
+}
+
+func oneCapturedDeclaration(t *testing.T, node string) {
+	{
+		c := readCaptured(t, node)
+		split := splitCaptured(t, node, c)
+		modules := map[string]bool{}
+		for m := range c.Builds {
+			modules[m] = true
+		}
+		var union []string
+		for key, comp := range split {
+			n, module, fp, isNode, err := ParseComposedKey(key)
+			if err != nil || n != node || comp.Node != node || comp.Module != module || comp.FP != fp {
+				t.Fatalf("%s: key %q holds %s/%s/%s (%v)", node, key, comp.Node, comp.Module, comp.FP, err)
+			}
+			if !isNode && !modules[module] && module != "mesh-wireguard" {
+				t.Errorf("%s: a composition of %s, which the declaration names no build of", node, module)
+			}
+			raw, err := EncodeComposed(comp)
+			if err != nil {
+				t.Fatalf("%s: EncodeComposed(%s): %v", node, key, err)
+			}
+			back, err := DecodeComposed(raw)
+			if err != nil {
+				t.Fatalf("%s: DecodeComposed(%s): %v", node, key, err)
+			}
+			if !SameComposed(back, comp) {
+				t.Errorf("%s: %s did not round-trip", node, key)
+			}
+			// SameComposed encodes both, so the digest of what was read back, a hash of its encoding, is the one written.
+			if d, err := ComposedDigestOf(back); err != nil || !digestForm.MatchString(d) {
+				t.Errorf("%s: %s digests %q (%v)", node, key, d, err)
+			}
+			for _, r := range back.Resources {
+				var head struct {
+					Module string `json:"module"`
+				}
+				_ = json.Unmarshal(r, &head)
+				if head.Module != module {
+					t.Errorf("%s: %s holds a resource of %q", node, key, head.Module)
+				}
+				union = append(union, canonical(t, r))
+			}
+		}
+		var want []string
+		for _, r := range c.Resources {
+			want = append(want, canonical(t, r))
+		}
+		sort.Strings(union)
+		sort.Strings(want)
+		if strings.Join(union, "\n") != strings.Join(want, "\n") {
+			t.Errorf("%s: the compositions hold %d resources, the declaration %d, or they differ", node, len(union), len(want))
+		}
+	}
+}
+
+// 1943/AC2: one changed byte of a resource is another digest; the same composition written with its keys in another
+// order is the same digest.
+func TestComposedDigestFollowsTheContent(t *testing.T) {
+	c := readCaptured(t, "g14")
+	split := splitCaptured(t, "g14", c)
+	var comp Composed
+	for _, v := range split {
+		if v.Module != "" && len(v.Resources) > 1 {
+			comp = v
+			break
+		}
+	}
+	d1, _ := ComposedDigestOf(comp)
+	var m map[string]json.RawMessage
+	_ = json.Unmarshal(comp.Resources[0], &m)
+	var keys []string
+	for k := range m {
+		keys = append(keys, k)
+	}
+	sort.Sort(sort.Reverse(sort.StringSlice(keys)))
+	var parts []string
+	for _, k := range keys {
+		parts = append(parts, fmt.Sprintf("%q :  %s", k, m[k]))
+	}
+	reordered := json.RawMessage("{ " + strings.Join(parts, ",\n ") + " }")
+	shuffled := comp
+	shuffled.Resources = append([]json.RawMessage{reordered}, comp.Resources[1:]...)
+	if d2, _ := ComposedDigestOf(shuffled); d2 != d1 {
+		t.Errorf("the same resources in another order and spacing digest %s and %s", d1, d2)
+	}
+	changed := comp
+	changed.Resources = append([]json.RawMessage{json.RawMessage(strings.Replace(canonical(t, comp.Resources[0]), `"id":"`, `"id":"x`, 1))}, comp.Resources[1:]...)
+	if d3, _ := ComposedDigestOf(changed); d3 == d1 {
+		t.Errorf("a changed resource kept its digest")
+	}
+	revised := comp
+	revised.Data = !comp.Data
+	if d4, _ := ComposedDigestOf(revised); d4 == d1 {
+		t.Errorf("a changed data flag kept its digest")
+	}
+}
+
+// 1943/AC2: a file over 64 KiB is carried by digest and size, its content handed back to be put in the node's object
+// bucket; a composition that carries such a file whole is refused.
+func TestAComposedFileOver64KiBIsCarriedByDigest(t *testing.T) {
+	c := readCaptured(t, "g14")
+	split := splitCaptured(t, "g14", c)
+	var comp Composed
+	var at int
+	for _, v := range split {
+		for i, r := range v.Resources {
+			var f map[string]any
+			_ = json.Unmarshal(r, &f)
+			if f["type"] == "file" && v.Module != "" && f["bytes"] == nil && f["into"] == nil {
+				comp, at = v, i
+				break
+			}
+		}
+		if comp.Module != "" {
+			break
+		}
+	}
+	var f map[string]any
+	_ = json.Unmarshal(comp.Resources[at], &f)
+	// Grown past the threshold from a captured file: no captured file of this node is over 64 KiB.
+	body := strings.Repeat("x", declaration.FileReferenceThreshold+1)
+	f["content"] = body
+	big, _ := json.Marshal(f)
+	comp.Resources = append([]json.RawMessage{}, comp.Resources...)
+	comp.Resources[at] = big
+	if _, err := EncodeComposed(comp); err == nil || !strings.Contains(err.Error(), "by digest") {
+		t.Fatalf("a file over 64 KiB carried whole = %v, want refused", err)
+	}
+	byDigest, objects, err := comp.ByDigest()
+	if err != nil {
+		t.Fatal(err)
+	}
+	var ref map[string]any
+	_ = json.Unmarshal(byDigest.Resources[at], &ref)
+	digest := declaration.DigestOf([]byte(body))
+	if ref["digest"] != digest || ref["size"] != float64(len(body)) || ref["content"] != nil {
+		t.Errorf("the file became %v, want digest %s and size %d", ref, digest, len(body))
+	}
+	if string(objects[digest]) != body || len(objects) != 1 {
+		t.Errorf("the objects handed back are %d, want the file's content under its digest", len(objects))
+	}
+	if _, err := EncodeComposed(byDigest); err != nil {
+		t.Errorf("the composition by digest is refused: %v", err)
+	}
+}
+
+// 1943/AC2: an unknown version is refused as one; a module's composition carrying the node's own parts, a resource of
+// another module, a resource its kind refuses, or no fingerprint, is refused, naming why.
+func TestComposedRefusals(t *testing.T) {
+	fp := fp2of('a')
+	file := json.RawMessage(`{"id":"m.f","type":"file","module":"m","path":"/etc/m","content":"x"}`)
+	ok := Composed{Node: "ace", Module: "m", FP: fp, Resources: []json.RawMessage{file}}
+	raw, err := EncodeComposed(ok)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := DecodeComposed(bytes.Replace(raw, []byte(`"v":1`), []byte(`"v":2`), 1)); !errors.Is(err, ErrUnknownVersion) {
+		t.Errorf("version 2 = %v, want ErrUnknownVersion", err)
+	}
+	refusals := []struct {
+		c   Composed
+		why string
+	}{
+		{Composed{Node: "ace", Module: "m", Resources: []json.RawMessage{file}}, "fingerprint"},
+		{Composed{Node: "", Module: "m", FP: fp, Resources: []json.RawMessage{file}}, "node name is empty"},
+		{Composed{Node: "ace", Module: "other", FP: fp, Resources: []json.RawMessage{file}}, `of "m"`},
+		{Composed{Node: "ace", Module: "m", FP: fp, Resources: []json.RawMessage{file}, Own: NodeOwn{Provisioner: "p"}}, "node's own"},
+		{Composed{Node: "ace", FP: fp, Resources: []json.RawMessage{}}, "names no fingerprint"},
+		{Composed{Node: "ace", Resources: []json.RawMessage{file}}, `of "m"`},
+		{Composed{Node: "ace", Module: "m", FP: fp, Resources: []json.RawMessage{json.RawMessage(`{"id":"m.f","type":"file","module":"m","path":"/etc/m","content":"x","image":"y"}`)}}, `"image"`},
+		{Composed{Node: "ace", Module: "m", FP: fp, Resources: []json.RawMessage{json.RawMessage(`{"id":"m.a","type":"action","module":"m"}`)}}, "action"},
+	}
+	for _, r := range refusals {
+		if _, err := EncodeComposed(r.c); err == nil || !strings.Contains(err.Error(), r.why) {
+			t.Errorf("EncodeComposed(%s/%s) = %v, want a refusal saying %q", r.c.Node, r.c.Module, err, r.why)
+		}
+	}
+}
+
+// 1943/AC2 (issue 1150): a module whose name holds a dot keys its have, its want and its composition escaped, and the
+// parsers give its name back; a name with a wildcard, whitespace or an escape of its own is still refused.
+func TestADottedModuleKeysEscaped(t *testing.T) {
+	fp := fp2of('f')
+	have, err := HaveKey("ace", "novox.be")
+	if err != nil || have != "ace.novox=2ebe" {
+		t.Fatalf("HaveKey = %q, %v", have, err)
+	}
+	if n, m, isNode, err := ParseHaveKey(have); err != nil || n != "ace" || m != "novox.be" || isNode {
+		t.Errorf("ParseHaveKey(%q) = %q, %q, %v, %v", have, n, m, isNode, err)
+	}
+	want, err := WantKey("ace", "novox.be")
+	if err != nil || want != "want.ace.novox=2ebe" {
+		t.Fatalf("WantKey = %q, %v", want, err)
+	}
+	if n, m, err := ParseWantKey(want); err != nil || n != "ace" || m != "novox.be" {
+		t.Errorf("ParseWantKey(%q) = %q, %q, %v", want, n, m, err)
+	}
+	comp, err := ComposedKey("ace", "novox.be", fp)
+	if err != nil || comp != "ace.novox=2ebe."+strings.Repeat("f", 64) {
+		t.Fatalf("ComposedKey = %q, %v", comp, err)
+	}
+	if n, m, back, _, err := ParseComposedKey(comp); err != nil || n != "ace" || m != "novox.be" || back != fp {
+		t.Errorf("ParseComposedKey(%q) = %q, %q, %q, %v", comp, n, m, back, err)
+	}
+	for _, bad := range []string{"m*", "m x", "m=2e", "m>", ".m", "m.", "a..b"} {
+		if _, err := HaveKey("ace", bad); err == nil {
+			t.Errorf("HaveKey(ace, %q) accepted", bad)
+		}
+	}
+	for _, bad := range []string{"ace.m=2", "ace.m=2E", "ace.m=41", "ace.=6eode"} {
+		if _, _, _, err := ParseHaveKey(bad); err == nil {
+			t.Errorf("ParseHaveKey(%q) accepted", bad)
+		}
+	}
+}
+
+// The node's own composition carries the filled paths of the files moved into it, the files of a module with no
+// fingerprint of the new form: the provisioner fills them all the same (issue 1945, live on 2026-10-25: the paths were
+// dropped and the node-engine wrote those files empty). It still holds no module's data.
+func TestTheNodesOwnCompositionCarriesTheFilledPathsOfItsFiles(t *testing.T) {
+	filled := json.RawMessage(`{"id":"power.unit","type":"file","path":"/etc/systemd/system/p.service","mode":"0644","owner-at-runtime":"owned"}`)
+	own := Composed{Node: "ace", Resources: []json.RawMessage{filled}, Filled: []string{"/etc/systemd/system/p.service"},
+		Own: NodeOwn{Provisioner: "mesh-provisioner-client"}}
+	raw, err := EncodeComposed(own)
+	if err != nil {
+		t.Fatalf("the node's own composition with a filled file: %v", err)
+	}
+	back, err := DecodeComposed(raw)
+	if err != nil || len(back.Filled) != 1 {
+		t.Fatalf("read back: %v %v", back.Filled, err)
+	}
+	if _, err := EncodeComposed(Composed{Node: "ace", Data: true, Resources: []json.RawMessage{filled},
+		Filled: own.Filled}); err == nil {
+		t.Error("the node's own composition was let hold a module's data")
+	}
+}
+
+// A file the provisioner fills says no content: in a composition that does not say it is filled, the node-engine would
+// write it empty. Such a composition is refused, in the node's own as in a module's (issue 1945).
+func TestAFileWithNoContentThatIsNotFilledIsRefused(t *testing.T) {
+	fp := fp2of('a')
+	for _, c := range []Composed{
+		{Node: "ace", Resources: []json.RawMessage{json.RawMessage(
+			`{"id":"power.unit","type":"file","path":"/etc/p","mode":"0644","owner-at-runtime":"owned"}`)}},
+		{Node: "ace", Module: "m", FP: fp, Resources: []json.RawMessage{json.RawMessage(
+			`{"id":"m.f","type":"file","module":"m","path":"/etc/m","mode":"0644","owner-at-runtime":"owned"}`)}},
+	} {
+		if _, err := EncodeComposed(c); err == nil || !strings.Contains(err.Error(), "empty") {
+			t.Errorf("%s/%s: %v, want a refusal saying it would be written empty", c.Node, c.Module, err)
+		}
+	}
+	// A file that says its content, even an empty one, is written as it says.
+	if _, err := EncodeComposed(Composed{Node: "ace", Resources: []json.RawMessage{json.RawMessage(
+		`{"id":"x.f","type":"file","path":"/etc/x","mode":"0644","content":""}`)}}); err != nil {
+		t.Errorf("a file that says it is empty: %v", err)
+	}
+}

go/delivery/delivery.go

@@ -11,7 +11,8 @@
 // `node`. A presence key is `<node>` for a node and `part.<part>.<instance>` for a part's instance, so a node may
 // not be named `part`. A pulse key is `<bucket>.<key>`: the full name of the bucket watched, then that bucket's key,
 // which may hold dots, so it splits at the first dot. A name is refused when it is empty or holds a dot, a wildcard,
-// whitespace or a character a bus key refuses, and the error names it.
+// whitespace or a character a bus key refuses, and the error names it; but a module's name may hold dots between its
+// parts (`novox.be`), and keys with each dot escaped as EscapeName writes it (`novox=2ebe`, issue 1150).
 //
 // **Values** are JSON of under about 500 bytes, each carrying its version in `v`. A reader refuses a value whose
 // version is missing or one it does not know, with an error that is ErrUnknownVersion (research 063 section 05
@@ -35,7 +36,7 @@
 // builder's build keys (builder.go) and the checker's verdicts and kept verdicts (checker.go). A manifests value is the
 // one exception to the size above: a manifest is up to about 21 KB, whole, byte for byte.
 //
-// Standard library only, and this module's own asks package.
+// Standard library only, and this module's own asks and declaration packages (a composition holds declaration resources).
 package delivery
 
 import (
@@ -89,6 +90,10 @@ const (
 	// for which it had written a have key; the key is never deleted (issue 1369, ADR 0408 §4), so a reader can tell
 	// that the module stopped.
 	PhaseRemoved Phase = "removed"
+	// PhaseHeld is a module whose backup before an apply failed: it keeps running what it has, nothing of the new
+	// composition is applied, and the node waits for the answer in its want (novox/hq ADR 0539 clause 16). Detail
+	// carries the backup's own words.
+	PhaseHeld Phase = "held"
 )
 
 // Health is what the module's own check says.
@@ -164,13 +169,45 @@ func HaveKey(node, module string) (string, error) {
 	if err := checkName("node", node); err != nil {
 		return "", err
 	}
-	if err := checkName("module", module); err != nil {
+	part, err := moduleKeyPart(module)
+	if err != nil {
 		return "", err
 	}
 	if module == "node" {
 		return "", fmt.Errorf(`delivery: the module name "node" is refused: %s.node is the node's own key`, node)
 	}
-	return node + "." + module, nil
+	return node + "." + part, nil
+}
+
+var moduleNameOK = regexp.MustCompile(`^[-/_a-zA-Z0-9]+(\.[-/_a-zA-Z0-9]+)*$`)
+
+// moduleKeyPart is a module's name as a key part (issue 1150): a name may hold a dot (`novox.be`), which a key part
+// may not, so a dot is escaped as EscapeName writes it (`novox=2ebe`); a name of letters, digits, `-`, `/` and `_` keys
+// as it is. A name that is empty, or holds a wildcard, whitespace, `=`, or an empty part between dots, is refused.
+func moduleKeyPart(module string) (string, error) {
+	if module == "" {
+		return "", fmt.Errorf("delivery: the module name is empty")
+	}
+	if !moduleNameOK.MatchString(module) {
+		return "", fmt.Errorf("delivery: the module name %q holds a wildcard, whitespace, '=', an empty part between dots or a character a key refuses", module)
+	}
+	return EscapeName(module), nil
+}
+
+// parseModuleKeyPart is the inverse of moduleKeyPart; it refuses a part that is not the one moduleKeyPart writes for
+// its name (an escape of a character that keys as it is, an upper-case escape, an escape of a refused character).
+func parseModuleKeyPart(part string) (string, error) {
+	if err := checkName("module", part); err != nil {
+		return "", err
+	}
+	module, err := UnescapeName(part)
+	if err != nil {
+		return "", err
+	}
+	if back, err := moduleKeyPart(module); err != nil || back != part {
+		return "", fmt.Errorf("delivery: the module part %q is not a module name as a key writes it", part)
+	}
+	return module, nil
 }
 
 // HaveNodeKey is the key, in HaveBucket, of a node's own facts: `<node>.node`.
@@ -190,12 +227,13 @@ func ParseHaveKey(key string) (node, module string, isNode bool, err error) {
 	if err := checkName("node", node); err != nil {
 		return "", "", false, fmt.Errorf("delivery: %q is not a have key: %w", key, err)
 	}
-	if err := checkName("module", module); err != nil {
-		return "", "", false, fmt.Errorf("delivery: %q is not a have key: %w", key, err)
-	}
 	if module == "node" {
 		return node, "", true, nil
 	}
+	module, err = parseModuleKeyPart(module)
+	if err != nil {
+		return "", "", false, fmt.Errorf("delivery: %q is not a have key: %w", key, err)
+	}
 	return node, module, false, nil
 }
 
@@ -282,24 +320,31 @@ func PulseTTL(moveAge time.Duration) (ttl time.Duration, stalled bool) {
 // Have is a module's state on a node, written by that node's node-engine under HaveKey. FP is the module's
 // fingerprint once the indexer exists (design 47 release 3); until then Build is the build the node was sent, and
 // the view compares by build.
+//
+// Composed is the digest of the composition the node runs for the module (novox/hq ADR 0539 clause 9): the
+// controller judges a move against it (clause 14), and the assigner reads it to know a want was applied.
 type Have struct {
-	V      int    `json:"v"`
+	V        int    `json:"v"`
-	FP     string `json:"fp,omitempty"`
+	FP       string `json:"fp,omitempty"`
-	Build  string `json:"build,omitempty"`
+	Composed string `json:"composed,omitempty"`
-	Phase  Phase  `json:"phase"`
+	Build    string `json:"build,omitempty"`
-	Health Health `json:"health"`
+	Phase    Phase  `json:"phase"`
-	Detail string `json:"detail,omitempty"`
+	Health   Health `json:"health"`
+	Detail   string `json:"detail,omitempty"`
 }
 
 // HaveNode is a node's own facts, written under HaveNodeKey. Each field is the node-engine's own JSON, carried whole:
 // this package names the facts and does not type them.
+//
+// Composed is the digest of the node's own composition it runs (ADR 0539 clause 9).
 type HaveNode struct {
-	V       int             `json:"v"`
+	V        int             `json:"v"`
-	Windows json.RawMessage `json:"windows,omitempty"`
+	Composed string          `json:"composed,omitempty"`
-	Busy    json.RawMessage `json:"busy,omitempty"`
+	Windows  json.RawMessage `json:"windows,omitempty"`
-	Strays  json.RawMessage `json:"strays,omitempty"`
+	Busy     json.RawMessage `json:"busy,omitempty"`
-	Filters json.RawMessage `json:"filters,omitempty"`
+	Strays   json.RawMessage `json:"strays,omitempty"`
-	Profile json.RawMessage `json:"profile,omitempty"`
+	Filters  json.RawMessage `json:"filters,omitempty"`
+	Profile  json.RawMessage `json:"profile,omitempty"`
 }
 
 // Presence is whether a node or a part's instance is online; the entry's own time says since when. The watchman
@@ -347,9 +392,14 @@ func decode(data []byte, into any) error {
 
 func (h Have) check() error {
 	switch h.Phase {
-	case PhaseBackingUp, PhaseApplying, PhaseChecking, PhaseRunning, PhaseFailed, PhaseRemoved:
+	case PhaseBackingUp, PhaseApplying, PhaseChecking, PhaseRunning, PhaseFailed, PhaseRemoved, PhaseHeld:
 	default:
-		return fmt.Errorf("delivery: phase %q is not backing-up, applying, checking, running, failed or removed", h.Phase)
+		return fmt.Errorf("delivery: phase %q is not backing-up, applying, checking, running, failed, removed or held", h.Phase)
+	}
+	if h.Composed != "" {
+		if err := checkDigest(h.Composed, "the have's composition digest"); err != nil {
+			return err
+		}
 	}
 	switch h.Health {
 	case HealthOK, HealthFailed, HealthWaits, HealthUnknown:
@@ -424,7 +474,7 @@ func SameHave(a, b Have) bool { return a == b }
 
 // SameHaveNode says whether two node facts are the same value, comparing each carried JSON without its spacing.
 func SameHaveNode(a, b HaveNode) bool {
-	return a.V == b.V && sameJSON(a.Windows, b.Windows) && sameJSON(a.Busy, b.Busy) &&
+	return a.V == b.V && a.Composed == b.Composed && sameJSON(a.Windows, b.Windows) && sameJSON(a.Busy, b.Busy) &&
 		sameJSON(a.Strays, b.Strays) && sameJSON(a.Filters, b.Filters) && sameJSON(a.Profile, b.Profile)
 }
 

go/delivery/source.go

@@ -269,6 +269,10 @@ type CandidatePull struct {
 	Head
 	Modules []string                   `json:"modules"`
 	Fps     map[string]CandidateModule `json:"fps,omitempty"`
+	// Merged says the pull request merged while another member of its group is still open: it stays in the candidate
+	// with the head it merged at, so the heads hash an Approve covers holds until every member merged, and the checker
+	// judges the members still open by the verdict the group had (issue 1791). A reader of the older shape ignores it.
+	Merged bool `json:"merged,omitempty"`
 }
 
 // CandidateNoneNoModule is the None2 of a candidate's module whose directory the merge preview names no manifest for:
@@ -346,6 +350,13 @@ func (c Candidate) check() error {
 	if len(c.Pulls) == 0 {
 		return fmt.Errorf("delivery: a candidate names no pull request")
 	}
+	open := false
+	for _, p := range c.Pulls {
+		open = open || !p.Merged
+	}
+	if !open {
+		return fmt.Errorf("delivery: every pull request of the candidate merged: the group is no candidate any more")
+	}
 	heads := make([]Head, len(c.Pulls))
 	for i, p := range c.Pulls {
 		heads[i] = p.Head

go/delivery/view_answers.go

@@ -32,19 +32,27 @@ const (
 	AskKindHold = "hold"
 	// AskKindRestore is the kind of the assigner's ask about a data module set back.
 	AskKindRestore = "restore"
+	// AskKindBackup is the kind of the assigner's ask about a backup before an apply that failed: back up again, or go
+	// on without one (novox/hq ADR 0539 clause 16).
+	AskKindBackup = "backup"
+	// AskKindRecord is the kind of the assigner's ask about a move a person must allow, for a module of policy record:
+	// a composition judged to recreate a container or move data, or one that cannot be judged (ADR 0539 clause 14).
+	AskKindRecord = "record"
 
 	viewWord = "view"
 )
 
 // AskKey is an ask's key read whole: its Kind, and the parts its kind has: a merge's Group and heads Hash, a hold's
-// Module and fingerprint FP, a restore's Node, Module and FP.
+// Module and fingerprint FP, a restore's and a backup's Node, Module and FP, a record's Node, Module and the digest
+// Composed of the composition it would allow.
 type AskKey struct {
-	Kind   string
+	Kind     string
-	Group  string
+	Group    string
-	Hash   string
+	Hash     string
-	Node   string
+	Node     string
-	Module string
+	Module   string
-	FP     string
+	FP       string
+	Composed string
 }
 
 // AskNeedsProof says whether an ask of this kind must prove who answered it, so the view may not answer it: the
@@ -53,10 +61,11 @@ func AskNeedsProof(kind string) (bool, error) {
 	switch kind {
 	case AskKindMerge:
 		return true, nil
-	case AskKindHold, AskKindRestore:
+	case AskKindHold, AskKindRestore, AskKindBackup, AskKindRecord:
 		return false, nil
 	}
-	return false, fmt.Errorf("delivery: %q is not a kind of ask, %s, %s or %s", kind, AskKindMerge, AskKindHold, AskKindRestore)
+	return false, fmt.Errorf("delivery: %q is not a kind of ask, %s, %s, %s, %s or %s", kind, AskKindMerge, AskKindHold,
+		AskKindRestore, AskKindBackup, AskKindRecord)
 }
 
 // HoldAskKey is the key, in AssignerAsksBucket, of the ask about a module's held fingerprint: `hold.<module>.<hex>`.
@@ -81,7 +90,32 @@ func RestoreAskKey(node, module, fingerprint string) (string, error) {
 	return AskKindRestore + "." + node + "." + key, nil
 }
 
-// ParseAnyAskKey reads an ask key of any kind (MergeAskKey, HoldAskKey, RestoreAskKey); it refuses an unknown kind
+// BackupAskKey is the key, in AssignerAsksBucket, of the ask about a module's failed backup on a node before it applies
+// a fingerprint: `backup.<node>.<module>.<hex>`.
+func BackupAskKey(node, module, fingerprint string) (string, error) {
+	key, err := ComposedKey(node, module, fingerprint)
+	if err != nil {
+		return "", err
+	}
+	return AskKindBackup + "." + key, nil
+}
+
+// RecordAskKey is the key, in AssignerAsksBucket, of the ask about a move of a module on a node to the composition
+// whose digest it names: `record.<node>.<module>.<digest hex>`, so a new revision at the same fingerprint is asked
+// again (ADR 0539 clause 14).
+func RecordAskKey(node, module, composed string) (string, error) {
+	have, err := HaveKey(node, module)
+	if err != nil {
+		return "", err
+	}
+	if err := checkDigest(composed, "a record ask's composition digest"); err != nil {
+		return "", err
+	}
+	return AskKindRecord + "." + have + "." + strings.TrimPrefix(composed, "sha256:"), nil
+}
+
+// ParseAnyAskKey reads an ask key of any kind (MergeAskKey, HoldAskKey, RestoreAskKey, BackupAskKey, RecordAskKey); it
+// refuses an unknown kind
 // and a key whose parts do not fit its kind, naming the key.
 func ParseAnyAskKey(key string) (AskKey, error) {
 	kind, rest, _ := strings.Cut(key, ".")
@@ -114,6 +148,26 @@ func ParseAnyAskKey(key string) (AskKey, error) {
 			return refused(err)
 		}
 		return AskKey{Kind: kind, Node: node, Module: module, FP: fp}, nil
+	case AskKindBackup:
+		node, module, fp, isNode, err := ParseComposedKey(rest)
+		if err != nil || isNode {
+			return refused(fmt.Errorf("a backup ask is backup.<node>.<module>.<fingerprint hex>"))
+		}
+		return AskKey{Kind: kind, Node: node, Module: module, FP: fp}, nil
+	case AskKindRecord:
+		parts := strings.Split(rest, ".")
+		if len(parts) != 3 {
+			return refused(fmt.Errorf("a record ask is record.<node>.<module>.<digest hex>"))
+		}
+		node, module, isNode, err := ParseHaveKey(parts[0] + "." + parts[1])
+		if err != nil || isNode {
+			return refused(fmt.Errorf("a record ask is record.<node>.<module>.<digest hex>"))
+		}
+		composed := "sha256:" + parts[2]
+		if err := checkDigest(composed, "a record ask's composition digest"); err != nil {
+			return refused(err)
+		}
+		return AskKey{Kind: kind, Node: node, Module: module, Composed: composed}, nil
 	}
 	_, err := AskNeedsProof(kind)
 	return refused(err)

go/delivery/want_composed_test.go

@@ -0,0 +1,176 @@
+package delivery
+
+import (
+	"strings"
+	"testing"
+)
+
+func hashOf(c byte) string { return "sha256:" + digestOf(c) }
+
+// 1943/AC3: a want naming its fingerprint and the digest of the composition it allows round-trips, and so does one
+// carrying the answer to a failed backup; a want naming a fingerprint without a digest, a digest not of the sha256
+// form, a removed want naming a digest, an unknown backup answer and a rule past the seventh are refused.
+func TestAWantNamesItsComposition(t *testing.T) {
+	for _, w := range []Want{
+		{FP: fp2of('a'), Composed: hashOf('1')},
+		{FP: fp2of('a'), Composed: hashOf('1'), Backup: BackupAgain},
+		{FP: fp2of('a'), Composed: hashOf('1'), Backup: BackupSkip, Words: "the operator: go on without a backup"},
+		{FP: fp2of('a'), Composed: hashOf('1'), Newest: fp2of('b'), Rule: RuleComposed, Words: "no composition of b for ace yet"},
+		{Removed: true},
+	} {
+		raw, err := EncodeWant(w)
+		if err != nil {
+			t.Fatalf("EncodeWant(%+v): %v", w, err)
+		}
+		back, err := DecodeWant(raw)
+		w.V = Version
+		if err != nil || !SameWant(back, w) {
+			t.Errorf("want %+v came back %+v, %v", w, back, err)
+		}
+	}
+	refusals := []struct {
+		w   Want
+		why string
+	}{
+		{Want{FP: fp2of('a')}, "names no composition"},
+		{Want{FP: fp2of('a'), Composed: "sha256:12"}, "not sha256"},
+		{Want{Removed: true, Composed: hashOf('1')}, "removed want names no"},
+		{Want{FP: fp2of('a'), Composed: hashOf('1'), Backup: "later"}, `backup answer "later"`},
+		{Want{Removed: true, Backup: BackupAgain}, "removed want names no"},
+		{Want{FP: fp2of('a'), Composed: hashOf('1'), Newest: fp2of('b'), Rule: 8}, "rule 8"},
+	}
+	for _, r := range refusals {
+		if _, err := EncodeWant(r.w); err == nil || !strings.Contains(err.Error(), r.why) {
+			t.Errorf("EncodeWant(%+v) = %v, want a refusal saying %q", r.w, err, r.why)
+		}
+	}
+	if _, err := DecodeWant([]byte(`{"v":1,"fp":"` + fp2of('a') + `"}`)); err == nil || !strings.Contains(err.Error(), "names no composition") {
+		t.Errorf("a want of release 5, naming no composition, was read: %v", err)
+	}
+	if RuleComposed != 7 {
+		t.Errorf("RuleComposed = %d, want the seventh rule", RuleComposed)
+	}
+}
+
+// 1943/AC3: the node's own want is `want.<node>.node` and round-trips through its parser, while a module named node is
+// still refused a want key; its value names the digest of the node's own composition and no fingerprint.
+func TestTheNodesOwnWant(t *testing.T) {
+	key, err := WantNodeKey("ace")
+	if err != nil || key != "want.ace.node" {
+		t.Fatalf("WantNodeKey = %q, %v", key, err)
+	}
+	if node, err := ParseWantNodeKey(key); err != nil || node != "ace" {
+		t.Errorf("ParseWantNodeKey(%q) = %q, %v", key, node, err)
+	}
+	if _, err := WantKey("ace", "node"); err == nil {
+		t.Errorf(`WantKey(ace, "node") accepted`)
+	}
+	if _, _, err := ParseWantKey(key); err == nil {
+		t.Errorf("ParseWantKey read the node's own want as a module's")
+	}
+	for _, bad := range []string{"want.ace.mesh-mail", "want.node", "ace.node", "want.a.b.node", ""} {
+		if _, err := ParseWantNodeKey(bad); err == nil || !strings.Contains(err.Error(), "\""+bad+"\"") {
+			t.Errorf("ParseWantNodeKey(%q) = %v, want a refusal naming it", bad, err)
+		}
+	}
+	if _, err := WantNodeKey(""); err == nil {
+		t.Errorf("WantNodeKey(\"\") accepted")
+	}
+	w := NodeWant{Composed: hashOf('2'), Words: "the node's own composition"}
+	raw, err := EncodeNodeWant(w)
+	if err != nil {
+		t.Fatal(err)
+	}
+	back, err := DecodeNodeWant(raw)
+	w.V = Version
+	if err != nil || back != w {
+		t.Errorf("node want came back %+v, %v", back, err)
+	}
+	for _, bad := range []NodeWant{{}, {Composed: "sha256:1"}} {
+		if _, err := EncodeNodeWant(bad); err == nil {
+			t.Errorf("EncodeNodeWant(%+v) accepted", bad)
+		}
+	}
+	if _, err := DecodeNodeWant([]byte(`{"v":1,"composed":"` + hashOf('2') + `","fp":"` + fp2of('a') + `"}`)); err == nil {
+		t.Errorf("a node want naming a fingerprint was read")
+	}
+}
+
+// 1943/AC3: a have held after a failed backup, naming the composition it runs, round-trips; so does the node's own have
+// naming its composition; a have's digest not of the sha256 form is refused.
+func TestAHaveNamesItsComposition(t *testing.T) {
+	for _, h := range []Have{
+		{FP: fp2of('a'), Composed: hashOf('3'), Phase: PhaseHeld, Health: HealthOK, Detail: "the backup failed: no space left"},
+		{FP: fp2of('a'), Composed: hashOf('3'), Phase: PhaseRunning, Health: HealthOK},
+	} {
+		raw, err := EncodeHave(h)
+		if err != nil {
+			t.Fatalf("EncodeHave(%+v): %v", h, err)
+		}
+		back, err := DecodeHave(raw)
+		h.V = Version
+		if err != nil || !SameHave(back, h) {
+			t.Errorf("have %+v came back %+v, %v", h, back, err)
+		}
+	}
+	if _, err := EncodeHave(Have{Composed: "sha256:x", Phase: PhaseRunning, Health: HealthOK}); err == nil || !strings.Contains(err.Error(), "not sha256") {
+		t.Errorf("a have naming a bad digest = %v", err)
+	}
+	n := HaveNode{Composed: hashOf('4')}
+	raw, err := EncodeHaveNode(n)
+	if err != nil {
+		t.Fatal(err)
+	}
+	back, err := DecodeHaveNode(raw)
+	n.V = Version
+	if err != nil || !SameHaveNode(back, n) {
+		t.Errorf("node have came back %+v, %v", back, err)
+	}
+	if SameHaveNode(n, HaveNode{V: Version, Composed: hashOf('5')}) {
+		t.Errorf("node haves naming two compositions are the same")
+	}
+}
+
+// 1943/AC3: the assigner's backup ask (back up again, or go on without one, ADR 0539 clause 16) and its record ask (a
+// move a person must allow, clause 14) key by node, module and fingerprint or composition, round-trip through
+// ParseAnyAskKey, and the view may answer both.
+func TestTheBackupAndRecordAsks(t *testing.T) {
+	fp, digest := fp2of('a'), hashOf('6')
+	backup, err := BackupAskKey("ace", "mesh-mail", fp)
+	if err != nil || backup != "backup.ace.mesh-mail."+strings.Repeat("a", 64) {
+		t.Fatalf("BackupAskKey = %q, %v", backup, err)
+	}
+	record, err := RecordAskKey("ace", "mesh-mail", digest)
+	if err != nil || record != "record.ace.mesh-mail."+strings.Repeat("6", 64) {
+		t.Fatalf("RecordAskKey = %q, %v", record, err)
+	}
+	if got, err := ParseAnyAskKey(backup); err != nil || got != (AskKey{Kind: AskKindBackup, Node: "ace", Module: "mesh-mail", FP: fp}) {
+		t.Errorf("ParseAnyAskKey(%q) = %+v, %v", backup, got, err)
+	}
+	if got, err := ParseAnyAskKey(record); err != nil || got != (AskKey{Kind: AskKindRecord, Node: "ace", Module: "mesh-mail", Composed: digest}) {
+		t.Errorf("ParseAnyAskKey(%q) = %+v, %v", record, got, err)
+	}
+	for _, kind := range []string{AskKindBackup, AskKindRecord} {
+		if proof, err := AskNeedsProof(kind); err != nil || proof {
+			t.Errorf("AskNeedsProof(%s) = %v, %v; the view may answer it", kind, proof, err)
+		}
+	}
+	for _, k := range []string{backup, record} {
+		if _, err := ViewAnswerKey(k); err != nil {
+			t.Errorf("the view may not answer %s: %v", k, err)
+		}
+	}
+	for _, bad := range [][3]string{{"", "mesh-mail", fp}, {"ace", "node", fp}, {"ace", "mesh-mail", "src2:1"}} {
+		if _, err := BackupAskKey(bad[0], bad[1], bad[2]); err == nil {
+			t.Errorf("BackupAskKey(%v) accepted", bad)
+		}
+	}
+	if _, err := RecordAskKey("ace", "mesh-mail", "sha256:1"); err == nil {
+		t.Errorf("a record ask naming a bad digest was keyed")
+	}
+	for _, bad := range []string{"backup.ace.mesh-mail", "record.ace.mesh-mail.12", "record.ace." + strings.Repeat("6", 64)} {
+		if _, err := ParseAnyAskKey(bad); err == nil {
+			t.Errorf("ParseAnyAskKey(%q) accepted", bad)
+		}
+	}
+}