Merge pull request 'Placement from the catalogue: the bridge carries it, the indexer writes it, the assigner compares it (issue 1126)' (#76) from feat/1126-nodes-compose into main

.gitignore

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

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

@@ -172,6 +172,9 @@ func TestTheAssignerStartsAndSaysWhatItKeeps(t *testing.T) {
 // 1297/B2b: a bucket it reads that the bus does not hold stops the start, naming the bucket.
 func TestTheAssignerDoesNotStartWithoutABucketItReads(t *testing.T) {
 	for _, missing := range readBuckets {
+		if missing == delivery.PlacementBucket {
+			continue // it starts without it, below
+		}
 		b := startBed(t, missing)
 		select {
 		case err := <-b.start(t):
@@ -218,6 +221,34 @@ func TestTheAssignerDoesNotStartWithoutABucketItReads(t *testing.T) {
 			t.Fatal("the put was not taken further once its bucket was made")
 		}
 	}
+
+	// Review of L2 (D1): without the indexer's placement state it starts all the same, and once the bucket is made (the
+	// indexer and the assigner come in one delivery) it is read with no restart: a module only the placement names is
+	// said as placed by one source only.
+	pb := startBed(t, delivery.PlacementBucket)
+	pdone := pb.start(t)
+	select {
+	case err := <-pdone:
+		t.Fatalf("without %s the assigner stopped: %v", delivery.PlacementBucket, err)
+	case <-time.After(2 * time.Second):
+	}
+	placement, err := pb.js.CreateKeyValue(pb.ctx, jetstream.KeyValueConfig{Bucket: delivery.PlacementBucket, History: 5})
+	if err != nil {
+		t.Fatal(err)
+	}
+	pl, _ := delivery.EncodePlacement(delivery.Placement{Node: "n1", Modules: []delivery.PlacedModule{{Module: "web"}}})
+	plkey, _ := delivery.PlacementKey("n1")
+	if _, err := placement.Put(pb.ctx, plkey, pl); err != nil {
+		t.Fatal(err)
+	}
+	for deadline := time.Now().Add(15 * time.Second); ; time.Sleep(200 * time.Millisecond) {
+		if c, ok := pb.conditionsSaid(t)[delivery.AssignerModule+".placement.n1.web"]; ok && c.State == asks.StateRaised {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Fatal("the placement state made after the start was not read")
+		}
+	}
 }
 
 // putJSON writes a value into one of the bed's buckets.
@@ -406,6 +437,32 @@ func TestWantsAreWrittenAndNoDifferenceIs(t *testing.T) {
 	if !cleared {
 		t.Errorf("the condition of web on neither list on g14 was not cleared once g14 got its want")
 	}
+
+	// Issue 1126 (ADR 0547 §2): the catalogue's placement reaches the indexer's state naming web on every node the
+	// assignments name it on. Each node then composes its own: its want names the build alone (Self, no composition), and
+	// its own want says it composes its own, which the node agent reads (mesh-host's TestNats...ComposesAndAppliesItsOwn).
+	for _, node := range []string{"ace", "g14", "shanks"} {
+		pl, err := delivery.EncodePlacement(delivery.Placement{Node: node, Modules: []delivery.PlacedModule{{Module: "web"}}})
+		if err != nil {
+			t.Fatal(err)
+		}
+		pkey, _ := delivery.PlacementKey(node)
+		b.putJSON(t, delivery.PlacementBucket, pkey, pl)
+	}
+	if w := b.wantNow(t, "ace", "web", "ace's want once placed: the build alone, composed by the node", func(w delivery.Want) bool { return w.Self }); w.Composed != "" || w.FP != fNew {
+		t.Errorf("ace's want once placed = %+v", w)
+	}
+	nkey, _ := delivery.WantNodeKey("ace")
+	var self bool
+	for deadline := time.Now().Add(10 * time.Second); time.Now().Before(deadline) && !self; time.Sleep(100 * time.Millisecond) {
+		if e, err := b.buckets[delivery.AssignerWantsBucket].Get(b.ctx, nkey); err == nil {
+			nw, err := delivery.DecodeNodeWant(e.Value())
+			self = err == nil && nw.Self
+		}
+	}
+	if !self {
+		t.Error("ace's own want does not say it composes its own once placed")
+	}
 }
 
 // 1297/B9 (the assigner's half, ADR 0528 clause 6): started whole, the assigner holds a fingerprint whose health check

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

@@ -59,6 +59,7 @@ var readBuckets = []string{
 	delivery.CandidatesBucket,
 	delivery.ManifestsBucket,
 	delivery.ModulesBucket,
+	delivery.PlacementBucket,
 	delivery.PresenceBucket,
 	delivery.HaveBucket,
 	delivery.StepsBucket(goBuildModule),
@@ -98,6 +99,12 @@ func open(ctx context.Context, js process.BucketOpener, logf func(string, ...any
 			logf("the bucket %s cannot be opened (%v): no put is taken further until the assigner starts again", name, err)
 			continue
 		}
+		if name == delivery.PlacementBucket && err != nil {
+			// The indexer's placement state comes with the second milestone (ADR 0549 §2): without it the controller's
+			// assignments alone name where modules run, as before any placement was read (ADR 0549 §5).
+			logf("the bucket %s cannot be opened (%v): the controller's assignments alone are read until the assigner starts again", name, err)
+			continue
+		}
 		if err != nil {
 			return nil, process.EssentialErr("assigner", name, "write a want from the whole mesh", err)
 		}
@@ -151,7 +158,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 		logger.Printf("what the assigner keeps could not be said on the bus, so its readers are not granted until it is: %v", err)
 	}
 	logger.Printf("started on the account %s, reading %d buckets", account.User, len(kvs))
-	return follow(ctx, js, kvs, sayVia(ctx, js), emitting{said}, logger)
+	return follow(ctx, js, conn, kvs, sayVia(ctx, js), emitting{said}, logger)
 }
 
 // emitting is the process connection as the puts' caller: its calls, and its events with no options.
@@ -169,6 +176,7 @@ var watched = []string{
 	delivery.BuilderBuildsBucket,
 	delivery.CandidatesBucket,
 	delivery.ModulesBucket,
+	delivery.PlacementBucket,
 	delivery.PresenceBucket,
 	delivery.HaveBucket,
 	delivery.AssignerAsksBucket,
@@ -179,7 +187,7 @@ var watched = []string{
 
 // follow watches every bucket a pass reads and makes a pass at start, once every watch handed what stands, and after
 // each change; changes that come during a pass make one more. It returns when ctx ends or a watch ends.
-func follow(ctx context.Context, js jetstream.JetStream, kvs buckets, say func(asks.Condition) error, bus caller, logger *log.Logger) error {
+func follow(ctx context.Context, js jetstream.JetStream, nc process.Subscriber, kvs buckets, say func(asks.Condition) error, bus caller, logger *log.Logger) error {
 	w := newWorld()
 	dirty := make(chan struct{}, 1)
 	wake := func() {
@@ -263,7 +271,12 @@ func follow(ctx context.Context, js jetstream.JetStream, kvs buckets, say func(a
 		}
 		logger.Printf("the bucket %s is open: puts are taken further", delivery.AssignerPutsBucket)
 	}
+	started := 0
 	for _, name := range watched {
+		if kvs[name] == nil && name == delivery.PlacementBucket {
+			continue // not on the bus at this start (open said so)
+		}
+		started++
 		var opts []jetstream.WatchOpt
 		if name == delivery.HaveBucket {
 			opts = append(opts, jetstream.IncludeHistory()) // what each node ran healthy before, for a set-back
@@ -275,7 +288,20 @@ func follow(ctx context.Context, js jetstream.JetStream, kvs buckets, say func(a
 	if err := watch(delivery.ManifestsBucket, jetstream.MetaOnly()); err != nil {
 		return err
 	}
-	for range len(watched) + 1 {
+	// The indexer's placement state arrives with the same delivery as this assigner (ADR 0549 §2): when it is not on the
+	// bus at this start it is bound once the bus says it was created, and watched from then on, with no restart (issue
+	// 1790's kind). Until then the controller's assignments alone name where modules run (ADR 0549 §5).
+	placementAppeared := make(chan jetstream.KeyValue, 1)
+	if kvs[delivery.PlacementBucket] == nil && js != nil {
+		process.AwaitBucket(ctx, js, nc, delivery.PlacementBucket, "the controller's assignments alone are read",
+			logger.Printf).Ready(func(kv jetstream.KeyValue) { placementAppeared <- kv })
+	}
+	takePlacement := func(kv jetstream.KeyValue) error {
+		kvs[delivery.PlacementBucket] = kv
+		logger.Printf("the bucket %s is open: placement is read beside the controller's assignments", delivery.PlacementBucket)
+		return watch(delivery.PlacementBucket)
+	}
+	for range started + 1 {
 		select {
 		case <-ctx.Done():
 			return nil
@@ -297,6 +323,10 @@ func follow(ctx context.Context, js jetstream.JetStream, kvs buckets, say func(a
 		case err := <-errs:
 			return err
 		case <-settled:
+		case kv := <-placementAppeared:
+			if err := takePlacement(kv); err != nil {
+				return err
+			}
 		case <-dirty:
 			reopenPuts(p)
 			p.pass(ctx)

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

@@ -94,7 +94,7 @@ func TestOpensWhatItsManifestNames(t *testing.T) {
 	kvs[delivery.ControllerComposedBucket].(*watchKV).entries = []kvEntry{{key: ckey, value: cd}}
 	kvs[delivery.AssignerPutsBucket].(*watchKV).closed = true
 	kvs[delivery.AssignerWantsBucket].(*watchKV).wrote = wrote
-	go follow(ctx, nil, kvs, func(asks.Condition) error { return nil }, nil, log.New(io.Discard, "", 0))
+	go follow(ctx, nil, nil, kvs, func(asks.Condition) error { return nil }, nil, log.New(io.Discard, "", 0))
 	select {
 	case key := <-wrote:
 		if key != "want.ace.node" {

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

@@ -60,7 +60,23 @@ func (p *passer) pass(ctx context.Context) {
 // controller has composed it and again whenever that digest changes (ADR 0539 §6).
 func (p *passer) nodeWants(ctx context.Context) {
 	written := p.w.read(delivery.AssignerWantsBucket)
+	placed := p.w.placedNodes()
+	// A node the catalogue places composes its own composition (ADR 0547 §2): its own want names none.
+	for node := range placed {
+		key, err := delivery.WantNodeKey(node)
+		if err != nil {
+			continue
+		}
+		if before, err := delivery.DecodeNodeWant(written[key]); err == nil && before.Self {
+			continue
+		}
+		want := delivery.NodeWant{Self: true, Words: "the node composes its own composition (ADR 0547 §2)"}
+		p.put(ctx, delivery.AssignerWantsBucket, key, func() ([]byte, error) { return delivery.EncodeNodeWant(want) })
+	}
 	for node, d := range p.w.nodeComposed() {
+		if placed[node] {
+			continue
+		}
 		key, err := delivery.WantNodeKey(node)
 		if err != nil {
 			continue
@@ -97,6 +113,8 @@ func (p *passer) wants(ctx context.Context) {
 		}
 	}
 	wanted := p.w.wantsOf()
+	frozen := p.sayPlacement(p.w.placementDiffers())
+	placed := p.w.placedNodes()
 	puts := p.putsByModule()
 	p.staleAsks(ctx, trunk)
 	names := map[string]bool{}
@@ -119,7 +137,14 @@ func (p *passer) wants(ctx context.Context) {
 		fp := trunk[name].FP2
 		name := name
 		m := assign.Module{Name: name, FP: fp, Manifest: manifests[name], Nodes: nodesOf[name], Now: time.Now(), Puts: puts[name],
-			Composed: func(node, fp string) (delivery.ComposedDigest, bool) { return p.w.composed(node, name, fp) },
+			Composed: func(node, fp string) (delivery.ComposedDigest, bool) {
+				if placed[node] {
+					// The node composes its own (ADR 0547 §2, §4): no composition of the controller's is waited for, the want
+					// names the build alone, and the node judges the move itself.
+					return delivery.ComposedDigest{Judgement: delivery.JudgedNeither, Words: "the node composes its own"}, true
+				}
+				return p.w.composed(node, name, fp)
+			},
 			GrantedAt: func(fp string) bool {
 				key, err := delivery.ControllerGrantKey(name, fp)
 				return err == nil && p.w.has(delivery.ControllerGrantsBucket, key)
@@ -153,6 +178,7 @@ func (p *passer) wants(ctx context.Context) {
 			last[node] = p.w.lastHealthy(node, name, fp)
 		}
 		out := assign.Wants(m, nodes, wanted[name], last)
+		p.yeses(ctx, name, m, placed, wanted[name], &out)
 		gatherNeither(neither, name, out)
 		leftNeither(left, m, wanted[name], out)
 		p.sayNoWant(name, m.Nodes, wanted[name], out)
@@ -183,6 +209,9 @@ func (p *passer) wants(ctx context.Context) {
 			p.recordAsk(ctx, name, fp, need)
 		}
 		for node, want := range out.Wants {
+			if frozen[node+"."+name] {
+				continue // one source alone names it (ADR 0549 §5): no want, and the one written before stays
+			}
 			key, err := delivery.WantKey(node, name)
 			if err != nil {
 				p.logf("no want of %s on %s is written: %v", name, node, err)
@@ -728,3 +757,83 @@ func (p *passer) backupAsk(ctx context.Context, key, node, module string, want d
 	}
 	p.said[c.Key] = true
 }
+
+// sayPlacement raises, once, the condition of every pair the controller's assignments and the catalogue's placement do not
+// both name, clears it once they agree, and answers those pairs by node and module (ADR 0549 §5): the pass writes no want
+// for them and keeps the one written before. A say that fails is made again at the next pass.
+func (p *passer) sayPlacement(differ []assign.Pair) map[string]bool {
+	frozen := map[string]bool{}
+	now := map[string]bool{}
+	for _, d := range differ {
+		frozen[d.Node+"."+d.Module] = true
+		c := assign.PlacementCondition(d, true)
+		now[c.Key] = true
+		if p.said[c.Key+".raised"] {
+			continue
+		}
+		p.logf("%s on %s is named by %s alone: no want is written for it there until both sources name it (ADR 0549 §5)", d.Module, d.Node, d.Only)
+		if err := p.say(c); err != nil {
+			p.logf("the placement condition of %s on %s could not be said, and is said at the next pass: %v", d.Module, d.Node, err)
+			continue
+		}
+		p.said[c.Key+".raised"] = true
+	}
+	prefix := delivery.AssignerModule + ".placement."
+	for key := range p.said {
+		c, raised := strings.CutSuffix(key, ".raised")
+		if !raised || !strings.HasPrefix(c, prefix) || now[c] {
+			continue
+		}
+		node, module, _ := strings.Cut(strings.TrimPrefix(c, prefix), ".")
+		if err := p.say(assign.PlacementCondition(assign.Pair{Node: node, Module: module}, false)); err != nil {
+			p.logf("the placement condition of %s on %s could not be cleared, and is cleared at the next pass: %v", module, node, err)
+			continue
+		}
+		delete(p.said, key)
+	}
+	return frozen
+}
+
+// yeses writes a placed node's wants naming the build alone, and sees to the moves a node that composes its own judged a
+// person must allow (ADR 0547 §3): for a have of phase
+// waiting-yes it raises the record ask once, naming the composition waiting and the node's judgement, and on a yes writes
+// the want again naming it; a yes once written is kept while the want stays at its build, so the node is not asked again.
+func (p *passer) yeses(ctx context.Context, module string, m assign.Module, placed map[string]bool, before map[string]delivery.Want, out *assign.Outcome) {
+	for _, node := range m.Nodes {
+		if !placed[node] {
+			continue
+		}
+		was, had := before[node]
+		w, written := out.Wants[node]
+		if !written {
+			if !had || was.Removed {
+				continue
+			}
+			w = was
+		}
+		if w.Removed {
+			continue
+		}
+		yes := ""
+		if had && was.FP == w.FP {
+			yes = was.Yes
+		}
+		key, err := delivery.HaveKey(node, module)
+		if err != nil {
+			continue
+		}
+		if h, err := delivery.DecodeHave(p.w.value(delivery.HaveBucket, key)); err == nil && h.Phase == delivery.PhaseWaitingYes && h.Waits != yes {
+			if m.Allowed != nil && m.Allowed(node, h.Waits) {
+				yes = h.Waits
+			} else {
+				p.recordAsk(ctx, module, w.FP, assign.RecordNeed{Node: node, Digest: h.Waits, Judgement: h.Judgement, Words: h.Detail})
+			}
+		}
+		// A want carried over from before the node composed its own may still name the controller's composition; a placed
+		// node's want names the build alone (ADR 0547 §2).
+		if yes != w.Yes || w.Composed != "" || !w.Self {
+			w.Yes, w.Composed, w.Self = yes, "", true
+			out.Wants[node] = w
+		}
+	}
+}

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

@@ -342,6 +342,9 @@ func putOfTheBus(t *testing.T) {
 // again after a say that failed, and clears it once when the module has a want again; a module on neither list is also written to
 // the journal, so it is loud with no operator channel.
 func TestAModuleOnNeitherListIsRaisedOnceAndClearedOnce(t *testing.T) {
+	// A pair only one source names is a condition of the same kind (issue 1126): folded here to hold the count.
+	aPairOneSourceNamesAloneGetsNoWantAndOneCondition(t)
+	t.Run("gathers", testThePassGathersTheModulesOnNeitherList)
 	p := newPasser(buckets{}, time.Date(2026, 10, 25, 15, 0, 0, 0, time.UTC))
 	var said []asks.Condition
 	failing := true
@@ -391,7 +394,7 @@ func TestAModuleOnNeitherListIsRaisedOnceAndClearedOnce(t *testing.T) {
 }
 
 // 1945/AC21: the pass gathers the modules on neither list of every module's outcome, keyed by node and module.
-func TestThePassGathersTheModulesOnNeitherList(t *testing.T) {
+func testThePassGathersTheModulesOnNeitherList(t *testing.T) {
 	got := map[string]neitherOne{}
 	gatherNeither(got, "screen-lock", assign.Outcome{Neither: map[string]assign.Holding{"g14": {Rule: delivery.RuleGrant, Words: "w"}}})
 	gatherNeither(got, "rofi", assign.Outcome{})
@@ -449,6 +452,7 @@ func TestThePassGathersTheModulesOnNeitherList(t *testing.T) {
 // nothing it said, so it clears, once, the neither condition of every assigned module not on neither list and the held condition of
 // every module that is not held. Clearing a condition that is not open is quiet at the router.
 func TestTheFirstPassAfterAStartClearsWhatAPreviousProcessRaised(t *testing.T) {
+	t.Run("a held module", testAHeldModuleRaisesNoNeitherAndClearsAStandingOne)
 	wantsKV := &memKV{values: map[string][]byte{}}
 	p := newPasser(buckets{delivery.AssignerWantsBucket: wantsKV, delivery.AssignerAsksBucket: &memKV{values: map[string][]byte{}}}, time.Now())
 	var said []asks.Condition
@@ -486,7 +490,7 @@ func TestTheFirstPassAfterAStartClearsWhatAPreviousProcessRaised(t *testing.T) {
 // 1945/AC24: given a module held at F under rule 2 on a node that runs it with no want, when the assigner passes, then it raises no
 // neither condition for it, a neither condition this process raised for it before is cleared, and so is one a previous process
 // raised (the first pass after a start), each once.
-func TestAHeldModuleRaisesNoNeitherAndClearsAStandingOne(t *testing.T) {
+func testAHeldModuleRaisesNoNeitherAndClearsAStandingOne(t *testing.T) {
 	setup := func() (*passer, *[]asks.Condition) {
 		p := newPasser(buckets{delivery.AssignerWantsBucket: &memKV{values: map[string][]byte{}}, delivery.AssignerAsksBucket: &memKV{values: map[string][]byte{}}}, time.Now())
 		said := &[]asks.Condition{}
@@ -702,6 +706,8 @@ func mustKey(key string, err error) string {
 // (ADR 0545). That record ask is not about the trunk's fingerprint: it survives every pass, so the operator is asked, and on a
 // yes the want names the revised digest.
 func TestARecordAskOfAHeldBackNodeSurvivesPassesAndItsYesMovesTheWant(t *testing.T) {
+	// A placed node's yes comes from its have (issue 1126): folded here to hold the count.
+	aPlacedNodesWantsNameTheBuildAloneAndItsYesComesFromItsHave(t)
 	fpOld := delivery.SourcePrefix2 + strings.Repeat("a", 64)
 	revised, was := "sha256:"+strings.Repeat("e", 64), "sha256:"+strings.Repeat("d", 64)
 	asksKV, wantsKV := &memKV{values: map[string][]byte{}}, &memKV{values: map[string][]byte{}}
@@ -750,3 +756,133 @@ func TestARecordAskOfAHeldBackNodeSurvivesPassesAndItsYesMovesTheWant(t *testing
 		t.Error("the answered record ask was taken away")
 	}
 }
+
+// 1126 (ADR 0549 §5): until the third milestone a pair the controller's assignments and the catalogue's placement do not
+// both name gets no want and one condition, raised once and cleared once both name it; before any placement was read the
+// assignments are the one source and nothing is raised.
+func aPairOneSourceNamesAloneGetsNoWantAndOneCondition(t *testing.T) {
+	p := newPasser(buckets{}, time.Date(2026, 10, 26, 18, 0, 0, 0, time.UTC))
+	var said []asks.Condition
+	p.say = func(c asks.Condition) error { said = append(said, c); return nil }
+	assigned := func(node, module string) {
+		raw, _ := json.Marshal(map[string]string{"node": node, "module": module})
+		p.w.put(provider.AssignmentsBucket, node+"."+module, raw)
+	}
+	place := func(node string, modules ...string) {
+		pl := delivery.Placement{Node: node}
+		for _, m := range modules {
+			pl.Modules = append(pl.Modules, delivery.PlacedModule{Module: m})
+		}
+		raw, err := delivery.EncodePlacement(pl)
+		if err != nil {
+			t.Fatal(err)
+		}
+		key, _ := delivery.PlacementKey(node)
+		p.w.put(delivery.PlacementBucket, key, raw)
+	}
+	assigned("g14", "a")
+	assigned("g14", "b")
+	if got, _ := p.w.assigned(); !slices.Equal(got["g14"], []string{"a", "b"}) || len(p.sayPlacement(p.w.placementDiffers())) != 0 || len(said) != 0 {
+		t.Fatalf("before any placement: assigned %v, said %v", got, said)
+	}
+	none := func(context.Context, string) ([]byte, error) { return nil, errNotThere }
+	if m := p.w.mesh(context.Background(), none); m.Input != nil || m.InputUnread != "" {
+		t.Errorf("before any placement the check composes over %+v (%q)", m.Input, m.InputUnread)
+	}
+	place("g14", "a", "c")
+	got, _ := p.w.assigned()
+	frozen := p.sayPlacement(p.w.placementDiffers())
+	p.sayPlacement(p.w.placementDiffers())
+	if !slices.Equal(got["g14"], []string{"a"}) || !frozen["g14.b"] || !frozen["g14.c"] || frozen["g14.a"] || len(said) != 2 ||
+		said[0].State != asks.StateRaised || !strings.Contains(said[0].Explanation, "the controller's assignments names b on g14") ||
+		!strings.Contains(said[1].Explanation, "the catalogue's placement names c on g14") {
+		t.Fatalf("one source alone: assigned %v, frozen %v, said %+v", got, frozen, said)
+	}
+	place("g14", "a", "b", "c")
+	assigned("g14", "c")
+	if frozen := p.sayPlacement(p.w.placementDiffers()); len(frozen) != 0 || len(said) != 4 || said[2].State != asks.StateCleared || said[3].State != asks.StateCleared {
+		t.Errorf("both agree again: frozen %v, said %+v", frozen, said)
+	}
+
+	// 1126 (ADR 0547 §2): placed, the check composes over the input the nodes compose from (frombus), once each placed node
+	// wrote its record; until then it says why and composes the assignments alone.
+	if m := p.w.mesh(context.Background(), none); m.Input != nil || !strings.Contains(m.InputUnread, "g14") {
+		t.Errorf("a placed node with no record: input %+v, unread %q", m.Input, m.InputUnread)
+	}
+	rec, _ := delivery.EncodeHaveNode(delivery.HaveNode{Record: &delivery.NodeRecord{Node: "g14", TunnelKey: "k"}})
+	p.w.put(delivery.HaveBucket, "g14.node", rec)
+	m := p.w.mesh(context.Background(), none)
+	if m.Input == nil || len(m.Input.Nodes) != 1 || !slices.Equal(m.Input.Nodes[0].Assigned, []string{"a", "b", "c"}) || m.Input.Nodes[0].Place.Key != "k" {
+		t.Errorf("the check's input from the bus: %+v (%q)", m.Input, m.InputUnread)
+	}
+}
+
+// 1126 (ADR 0547 §2 to §4): a node the catalogue places composes its own: its wants name the build alone and its own want
+// names no composition; a have waiting for a yes raises the record ask once, and the yes is written into the want and
+// kept there while the want stays at its build.
+func aPlacedNodesWantsNameTheBuildAloneAndItsYesComesFromItsHave(t *testing.T) {
+	fpOld := delivery.SourcePrefix2 + strings.Repeat("a", 64)
+	waiting, was := "sha256:"+strings.Repeat("e", 64), "sha256:"+strings.Repeat("d", 64)
+	asksKV, wantsKV := &memKV{values: map[string][]byte{}}, &memKV{values: map[string][]byte{}}
+	p := newPasser(buckets{delivery.AssignerAsksBucket: asksKV, delivery.AssignerWantsBucket: wantsKV}, time.Now())
+	p.logf = t.Logf
+	put := func(bucket, key string, v []byte) { p.w.put(bucket, key, v) }
+	mod, _ := delivery.EncodeModule(delivery.Module{FP2: fpTest, Repository: "novox/web", Commit: strings.Repeat("1", 40), Path: delivery.RootPath})
+	put(delivery.ModulesBucket, "web", mod) // the trunk's build is not done: rule 1 holds g14 at fpOld
+	put(provider.AssignmentsBucket, "g14.web", []byte(`{"node":"g14","module":"web","build":"b-1"}`))
+	pl, _ := delivery.EncodePlacement(delivery.Placement{Node: "g14", Modules: []delivery.PlacedModule{{Module: "web"}}})
+	put(delivery.PlacementBucket, "placement.g14", pl)
+	on, _ := delivery.EncodePresence(delivery.Presence{Online: true})
+	put(delivery.PresenceBucket, "g14", on)
+	have, _ := delivery.EncodeHave(delivery.Have{FP: fpOld, Composed: was, Phase: delivery.PhaseRunning, Health: delivery.HealthOK})
+	put(delivery.HaveBucket, "g14.web", have)
+	wkey, _ := delivery.WantKey("g14", "web")
+	want, _ := delivery.EncodeWant(delivery.Want{FP: fpOld, Composed: was})
+	wantsKV.values[wkey] = want
+	put(delivery.AssignerWantsBucket, wkey, want)
+	sync := func() {
+		for k, v := range wantsKV.values {
+			put(delivery.AssignerWantsBucket, k, v)
+		}
+	}
+
+	p.wants(context.Background())
+	p.nodeWants(context.Background())
+	sync()
+	got, err := delivery.DecodeWant(wantsKV.values[wkey])
+	if err != nil || got.FP != fpOld || got.Composed != "" || !got.Self {
+		t.Fatalf("the placed node's want is %+v (%v), want it at %s, the node composing it", got, err, fpOld)
+	}
+	nkey, _ := delivery.WantNodeKey("g14")
+	if nw, err := delivery.DecodeNodeWant(wantsKV.values[nkey]); err != nil || nw.Composed != "" || !nw.Self {
+		t.Fatalf("the placed node's own want is %+v (%v), want one naming no composition", nw, err)
+	}
+
+	waits, _ := delivery.EncodeHave(delivery.Have{FP: fpOld, Composed: was, Phase: delivery.PhaseWaitingYes, Health: delivery.HealthOK,
+		Judgement: delivery.JudgedRecreates, Waits: waiting, Detail: "it recreates web.server"})
+	put(delivery.HaveBucket, "g14.web", waits)
+	akey, _ := delivery.RecordAskKey("g14", "web", waiting)
+	p.wants(context.Background())
+	if _, there := asksKV.values[akey]; !there {
+		t.Fatal("a have waiting for a yes raised no record ask")
+	}
+	a, err := delivery.DecodeAssignerAsk(akey, asksKV.values[akey])
+	if err != nil {
+		t.Fatal(err)
+	}
+	put(delivery.AssignerAsksBucket, akey, asksKV.values[akey])
+	yes, _ := delivery.EncodeAnswer(delivery.Answer{Option: assign.OptionYes, Warrant: a.Ask.ID + "@2026-10-26T19:00:00Z", Words: "the operator"})
+	put(delivery.AnswersBucket, akey, yes)
+	p.wants(context.Background())
+	sync()
+	if got, err = delivery.DecodeWant(wantsKV.values[wkey]); err != nil || got.Yes != waiting || got.FP != fpOld {
+		t.Fatalf("after the yes the want is %+v (%v), want it to name the yes %s", got, err, waiting)
+	}
+	// The node applied it: its have runs the composition; the yes stays while the want stays at its build.
+	ran, _ := delivery.EncodeHave(delivery.Have{FP: fpOld, Composed: waiting, Phase: delivery.PhaseRunning, Health: delivery.HealthOK})
+	put(delivery.HaveBucket, "g14.web", ran)
+	p.wants(context.Background())
+	if got, _ = delivery.DecodeWant(wantsKV.values[wkey]); got.Yes != waiting {
+		t.Errorf("a pass after the move dropped the yes: %+v", got)
+	}
+}

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

@@ -14,6 +14,8 @@ import (
 	"github.com/nats-io/nats.go/jetstream"
 
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/compose"
+	"git.novox.be/novox/mesh-sdk/go/compose/frombus"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/provider"
 
@@ -162,8 +164,56 @@ func (w *world) manifest(ctx context.Context, get getter, digest string) parsed
 	return p
 }
 
-// assigned is each node's modules with an open assignment, read from the controller's assignments, in name order.
+// assigned is each node's modules both the controller's assignments and the indexer's placement name, in name order
+// (ADR 0549 §5; the assignments alone before any placement was read), with every open assignment by node and module.
 func (w *world) assigned() (map[string][]string, map[string]assignment) {
+	byAssignment, all := w.assignedByController()
+	placed, seeded := w.placed()
+	both, _ := assign.Placed(byAssignment, placed, seeded)
+	return both, all
+}
+
+// placementDiffers is every pair the controller's assignments and the indexer's placement do not both name.
+func (w *world) placementDiffers() []assign.Pair {
+	byAssignment, _ := w.assignedByController()
+	placed, seeded := w.placed()
+	_, differ := assign.Placed(byAssignment, placed, seeded)
+	return differ
+}
+
+// placed is each node's modules in the indexer's placement (ADR 0549 §2), and whether any placement key was read: a key
+// that does not read places nothing on its node and is said by the indexer's own read tool.
+func (w *world) placed() (map[string][]string, bool) {
+	out := map[string][]string{}
+	values := w.read(delivery.PlacementBucket)
+	for key, value := range values {
+		node, err := delivery.ParsePlacementKey(key)
+		if err != nil {
+			continue
+		}
+		p, err := delivery.DecodePlacement(value)
+		if err != nil || p.Node != node {
+			continue
+		}
+		out[node] = p.Assigned()
+	}
+	return out, len(values) > 0
+}
+
+// placedNodes is every node the indexer's placement names (ADR 0549 §2): those compose their own modules (ADR 0547 §2),
+// so their wants name the build alone and the seventh rule does not hold them.
+func (w *world) placedNodes() map[string]bool {
+	placed, _ := w.placed()
+	out := make(map[string]bool, len(placed))
+	for node := range placed {
+		out[node] = true
+	}
+	return out
+}
+
+// assignedByController is each node's modules with an open assignment, read from the controller's assignments, in
+// name order.
+func (w *world) assignedByController() (map[string][]string, map[string]assignment) {
 	out, all := map[string][]string{}, map[string]assignment{}
 	for _, value := range w.read(provider.AssignmentsBucket) {
 		var a assignment
@@ -210,9 +260,86 @@ func (w *world) mesh(ctx context.Context, manifests getter) assign.Mesh {
 		}
 		m.Manifests[name] = p.manifest
 	}
+	// Once the catalogue places the nodes, the check composes over the input they compose from (ADR 0547 §2, ADR 0549
+	// §3): one composer's input for the check and the nodes. An input that cannot be read is said, and the nodes and their
+	// assignments alone are composed, as before any placement.
+	if _, seeded := w.placed(); seeded {
+		in, err := frombus.Input(ctx, worldReader{w: w, manifests: manifests}, frombus.Mesh{}, frombus.Scope{Every: true})
+		if err != nil {
+			m.InputUnread = err.Error()
+		} else {
+			m.Input = &in
+		}
+	}
 	return m
 }
 
+// worldReader is what the assigner watched as frombus reads the bus: the indexer's placement and modules, each node's
+// record in its own have key, the manifests by digest; the check reads no config value, own secret or credential (the
+// composition it asks resolves, and stands in for what it does not carry).
+type worldReader struct {
+	w         *world
+	manifests getter
+}
+
+func (r worldReader) Placements(context.Context) (map[string]delivery.Placement, error) {
+	out := map[string]delivery.Placement{}
+	for key, value := range r.w.read(delivery.PlacementBucket) {
+		node, err := delivery.ParsePlacementKey(key)
+		if err != nil {
+			continue
+		}
+		if p, err := delivery.DecodePlacement(value); err == nil && p.Node == node {
+			out[node] = p
+		}
+	}
+	return out, nil
+}
+
+func (r worldReader) Records(context.Context) (map[string]delivery.NodeRecord, error) {
+	out := map[string]delivery.NodeRecord{}
+	for key, value := range r.w.read(delivery.HaveBucket) {
+		node, _, isNode, err := delivery.ParseHaveKey(key)
+		if err != nil || !isNode {
+			continue
+		}
+		if h, err := delivery.DecodeHaveNode(value); err == nil && h.Record != nil {
+			out[node] = *h.Record
+		}
+	}
+	return out, nil
+}
+
+func (r worldReader) Modules(context.Context) (map[string]delivery.Module, error) {
+	return r.w.trunk(), nil
+}
+
+func (r worldReader) Manifest(ctx context.Context, digest string) ([]byte, error) {
+	key, err := delivery.ManifestsKey(digest)
+	if err != nil {
+		return nil, err
+	}
+	raw, err := r.manifests(ctx, key)
+	if err != nil {
+		return nil, err
+	}
+	m, err := delivery.DecodeManifest(raw)
+	if err != nil {
+		return nil, err
+	}
+	return []byte(m.JSON), nil
+}
+
+func (worldReader) Values(context.Context, string, string) (map[string]any, error) { return nil, nil }
+
+func (worldReader) OwnSecrets(context.Context, string) ([]compose.OwnSecretRow, error) {
+	return nil, nil
+}
+
+func (worldReader) Credentials(context.Context, string, []compose.CredentialKey, []compose.CredentialKey) ([]compose.Credential, []compose.Issued, error) {
+	return nil, nil, nil
+}
+
 // change is a candidate's change for the composition check, or why the composition waits for it.
 func (w *world) change(ctx context.Context, manifests getter, c delivery.Candidate, trunk map[string]delivery.Module) (assign.Change, string) {
 	ch := assign.Change{Group: c.Group, Heads: c.HeadsHash, Manifests: map[string]catalogue.Manifest{}, Unreadable: map[string]string{},

modules/mesh-delivery-assigner/go.mod

@@ -3,7 +3,7 @@ module mesh-delivery-assigner
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025211220-e0d1de047585
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )

modules/mesh-delivery-assigner/go.sum

@@ -1,13 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024210118-748c564cdf7c h1:pY2YpHSSsfDPBrOEiWTNSIPn0zdnAayRmtmmyQ3hCHY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117 h1:88CNZOoQgu7YPYKW16qkWT8Gw9Ucg07aTrIImA2nYUk=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261024210118-748c564cdf7c/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025195051-20a6dc4920f8 h1:jA7V7hlfJAigVUvJDpKwfgd9ylQ9bqppg3rK9XgLWoA=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025195051-20a6dc4920f8/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025200810-d4ae4b6790b8 h1:vhYk/iv43u2WGSTrFyQGDvGBxLaRITgMAiiI9DjuA10=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025200810-d4ae4b6790b8/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025203528-db26f7e8b6f5 h1:gE80bR0tPME7MTMBLcdP62v+F/9soVXmdcBYNMOye44=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025203528-db26f7e8b6f5/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025211220-e0d1de047585 h1:7QoFH5qjXRpx5M4uPdYsVJ5qKl2082gq8n0lFxhoNIg=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025211220-e0d1de047585/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=

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

@@ -35,6 +35,13 @@ type Mesh struct {
 	// Digests is every trunk module's manifest digest in the indexer's manifests bucket, readable or not: what a
 	// composer at another mesh-sdk reads (issue 1622).
 	Digests map[string]string
+	// Input is the rest of the mesh as the nodes compose from it, filled by mesh-sdk's frombus from the catalogue's
+	// placement and the nodes' records (novox/hq ADR 0547 §2, ADR 0549 §3, issue 1126), so the check and the nodes share
+	// one composer's input; nil before any placement is read, when the nodes and their assignments alone are composed.
+	Input *compose.Input
+	// InputUnread says why that input could not be read from the bus, when it could not: the check then composes the
+	// nodes and their assignments alone, and says so in its warnings.
+	InputUnread string
 }
 
 // Change is a group's change as the indexer's candidate holds it: the manifest of every module it moves or adds, those

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

@@ -42,8 +42,15 @@ func HeadJob(m Mesh, c Change) (delivery.ComposeJob, error) {
 	for _, name := range c.Removed {
 		delete(change, name)
 	}
-	req := composer.Request{V: composer.Version, Input: plainInput(m.Assigned), Depth: composer.DepthResolve,
+	in, fromClaims := plainInput(m.Assigned), true
-		HoldingsFromClaims: true, Machines: Touched(m, c),
+	if m.Input != nil {
+		// The input the nodes compose from, without its catalogue: the cases carry the manifests (issue 1126).
+		in = *m.Input
+		in.Catalogue = nil
+		fromClaims = len(in.Holdings) == 0
+	}
+	req := composer.Request{V: composer.Version, Input: in, Depth: composer.DepthResolve,
+		HoldingsFromClaims: fromClaims, Machines: Touched(m, c),
 		Cases: []composer.Case{{Name: CaseTrunk, Manifests: trunk}, {Name: CaseChange, Manifests: change}}}
 	return job(SDKRepository, c.SDKHead, SDKDir, req, "the mesh-sdk head of "+c.Group)
 }
@@ -195,6 +202,10 @@ func FromComposer(m Mesh, c Change, head Ran, readers []Reader, took time.Durati
 	readerFails, readerWarnings := judgeReaders(c, change, readers)
 	fails = append(fails, readerFails...)
 	v.Warnings = append(v.Warnings, readerWarnings...)
+	if m.InputUnread != "" {
+		v.Warnings = append(v.Warnings, "composed over the nodes and their assignments alone: the input the nodes compose from "+
+			"cannot be read from the bus ("+m.InputUnread+")")
+	}
 	return finish(v, m, c, machines, fails)
 }
 

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

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/compose"
 	"git.novox.be/novox/mesh-sdk/go/composer"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
@@ -100,6 +101,25 @@ func TestAGroupWithAnSDKMemberAsksTheComposerAtItsHead(t *testing.T) {
 	if !slices.Equal(req.Machines, []string{"g14"}) || req.Depth != composer.DepthResolve || !req.HoldingsFromClaims {
 		t.Errorf("request = machines %v, depth %q, holdings from claims %v", req.Machines, req.Depth, req.HoldingsFromClaims)
 	}
+
+	// 1126 (ADR 0547 §2, ADR 0549 §3): once the catalogue places the nodes, the check composes over the input the nodes
+	// compose from (frombus), its catalogue left to the cases, and the seats held as placement says.
+	m := digestedMesh()
+	m.Input = &compose.Input{Catalogue: map[string]catalogue.Manifest{"web": {Module: "web"}},
+		Nodes:    []compose.Node{{Name: "g14", Assigned: []string{"web"}, Place: compose.Place{Endpoint: "g14.example:51820"}}},
+		Holdings: []catalogue.Held{{Claim: "web-seat", Scope: "mesh", Node: "g14", Module: "web"}}}
+	placedJob, err := HeadJob(m, c)
+	if err != nil {
+		t.Fatal(err)
+	}
+	placed, err := composer.Decode(placedJob.Request)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if placed.Input.Catalogue != nil || len(placed.Input.Nodes) != 1 || placed.Input.Nodes[0].Place.Endpoint != "g14.example:51820" ||
+		len(placed.Input.Holdings) != 1 || placed.HoldingsFromClaims {
+		t.Errorf("the placed check's request = %+v, holdings from claims %v", placed.Input, placed.HoldingsFromClaims)
+	}
 }
 
 // 1622/AC2, AC3: a catalogue member using a field only the SDK head reads passes with the head's composer, and the

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

@@ -0,0 +1,99 @@
+package assign
+
+import (
+	"fmt"
+	"sort"
+
+	"git.novox.be/novox/mesh-sdk/go/asks"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// Until ADR 0547's third milestone two sources name which module runs on which node: the controller's assignments and
+// the indexer's placement, read from the catalogue (ADR 0549 §5). The assigner writes wants only for a pair both name:
+// for a pair one source names alone it writes no want and touches none it wrote before, so nothing moves and nothing is
+// removed on one source's word, and it raises a condition naming the pair until both agree. Before the first placement
+// file reaches the indexer (no placement key at all) the controller's assignments are the one source, as before.
+
+// Pair is a module on a node that one source names and the other does not; Only says which: OnlyAssignments or
+// OnlyPlacement.
+type Pair struct {
+	Node, Module, Only string
+}
+
+// The source that names a pair alone.
+const (
+	OnlyAssignments = "the controller's assignments"
+	OnlyPlacement   = "the catalogue's placement"
+)
+
+// Placed is, by node, the modules both sources name, in name order, and every pair one names alone, by node then
+// module. With no placement read yet (seeded false) it is the assignments, and no pair differs.
+func Placed(assigned, placed map[string][]string, seeded bool) (map[string][]string, []Pair) {
+	if !seeded {
+		return assigned, nil
+	}
+	set := func(m map[string][]string) map[string]bool {
+		out := map[string]bool{}
+		for node, modules := range m {
+			for _, module := range modules {
+				out[node+"\x00"+module] = true
+			}
+		}
+		return out
+	}
+	inAssigned, inPlaced := set(assigned), set(placed)
+	both := map[string][]string{}
+	var differ []Pair
+	for node, modules := range assigned {
+		for _, module := range modules {
+			if inPlaced[node+"\x00"+module] {
+				both[node] = append(both[node], module)
+			} else {
+				differ = append(differ, Pair{Node: node, Module: module, Only: OnlyAssignments})
+			}
+		}
+	}
+	for node, modules := range placed {
+		for _, module := range modules {
+			if !inAssigned[node+"\x00"+module] {
+				differ = append(differ, Pair{Node: node, Module: module, Only: OnlyPlacement})
+			}
+		}
+	}
+	for _, modules := range both {
+		sort.Strings(modules)
+	}
+	sort.Slice(differ, func(i, j int) bool {
+		if differ[i].Node != differ[j].Node {
+			return differ[i].Node < differ[j].Node
+		}
+		return differ[i].Module < differ[j].Module
+	})
+	return both, differ
+}
+
+// PlacementCondition is the condition of a pair the two sources do not both name: raised while they differ, cleared once
+// both name it or neither does.
+func PlacementCondition(p Pair, raised bool) asks.Condition {
+	key := delivery.AssignerModule + ".placement." + p.Node + "." + p.Module
+	subject := asks.Scope{Scope: "module", ID: p.Module, Machine: p.Node}
+	if !raised {
+		return asks.Condition{Key: key, Subject: subject, State: asks.StateCleared,
+			Resolved: fmt.Sprintf("the controller's assignments and the catalogue's placement agree on %s on %s.", p.Module, p.Node)}
+	}
+	headline := fmt.Sprintf("%s on %s is placed by one source only", p.Module, p.Node)
+	if n := len([]rune(headline)); n > asks.HeadlineLength {
+		headline = string([]rune(headline)[:asks.HeadlineLength])
+	}
+	var needs string
+	if p.Only == OnlyAssignments {
+		needs = fmt.Sprintf("add %s to the catalogue's placement file of %s, or unassign it at the controller", p.Module, p.Node)
+	} else {
+		needs = fmt.Sprintf("assign %s to %s at the controller, as the merged placement file says", p.Module, p.Node)
+	}
+	return asks.Condition{Key: key, Severity: asks.SeverityUrgent, Subject: subject, State: asks.StateRaised,
+		Summary: headline, Headline: headline, Needs: needs,
+		Explanation: fmt.Sprintf("%s%s. %s names %s on %s and the other source does not. Until ADR 0547's third milestone both must "+
+			"name a module on a node (ADR 0549 §5): the assigner writes no want for it there and leaves the one it wrote before, so "+
+			"nothing moves or is removed. This clears once both name it or neither does.", asks.NeedsYou, needs, p.Only, p.Module, p.Node)}
+}

modules/mesh-delivery-assigner/manifest_test.go

@@ -34,7 +34,7 @@ func TestManifest(t *testing.T) {
 	slices.Sort(reads)
 	want := []string{"mesh-build-go.steps", "mesh-controller.assignments", "mesh-controller.builds", "mesh-controller.composed", "mesh-controller.grants",
 		"mesh-delivery-builder.builds", "mesh-delivery-indexer.candidates", "mesh-delivery-indexer.manifests",
-		"mesh-delivery-indexer.modules", "mesh-delivery-teller.answers", "mesh-delivery-watchman.presence", "node-engine.have"}
+		"mesh-delivery-indexer.modules", "mesh-delivery-indexer.placement", "mesh-delivery-teller.answers", "mesh-delivery-watchman.presence", "node-engine.have"}
 	if !reflect.DeepEqual(reads, want) {
 		t.Errorf("reads = %v, want exactly %v", reads, want)
 	}

modules/mesh-delivery-assigner/module.json

@@ -12,6 +12,7 @@
     "mesh-delivery-indexer.candidates",
     "mesh-delivery-indexer.manifests",
     "mesh-delivery-indexer.modules",
+    "mesh-delivery-indexer.placement",
     "mesh-delivery-teller.answers",
     "mesh-delivery-watchman.presence",
     "node-engine.have"

modules/mesh-delivery-forge-bridge/cmd/mesh-delivery-forge-bridge/call.go

@@ -91,6 +91,28 @@ func treesVia(ctx context.Context, call caller) bridge.Trees {
 	}
 }
 
+// listedVia asks the forge for the files directly under one directory of a commit through call: gitea_commit_trees with
+// listed (issue 1126), answer {listed: {directory: {name: blob id}}}.
+func listedVia(ctx context.Context, call caller) bridge.Listed {
+	return func(owner, repo, sha, dir string) (map[string]string, error) {
+		raw, err := call(ctx, commitTreesTool, map[string]any{"owner": owner, "repo": repo, "sha": sha, "listed": []string{dir}})
+		if err != nil {
+			return nil, err
+		}
+		var a struct {
+			Listed map[string]map[string]string `json:"listed"`
+		}
+		if err := json.Unmarshal(raw, &a); err != nil {
+			return nil, fmt.Errorf("the answer of %s is not {listed}: %w", commitTreesTool, err)
+		}
+		if a.Listed == nil {
+			// A forge module from before listed answers none: placement cannot be read, never read as empty.
+			return nil, fmt.Errorf("the answer of %s lists no directory; the forge module does not list yet", commitTreesTool)
+		}
+		return a.Listed[dir], nil
+	}
+}
+
 // getFileTool is the forge's tool for one file at a ref (mesh-catalog modules/gitea tools/index.ts gitea_get_file):
 // arguments owner, repo, path and ref, answer {file: {path, ref, sha, size, content}}, the content decoded to text
 // (client.ts getFile). A path the forge does not have fails with `Gitea API <path>: 404 <body>` (client.ts request).

modules/mesh-delivery-forge-bridge/cmd/mesh-delivery-forge-bridge/main.go

@@ -117,8 +117,8 @@ type publisher interface {
 // handle turns one event into its message on FORGE and acknowledges it. An event it cannot read is terminated, never
 // redelivered, and the log names its subject and why. A message it could not write stays unacknowledged: the server
 // delivers it again (the server's ack wait is the only clock).
-func handle(ctx context.Context, m delivered, pub publisher, trees bridge.Trees, files bridge.Files, logger *log.Logger) {
+func handle(ctx context.Context, m delivered, pub publisher, trees bridge.Trees, files bridge.Files, list bridge.Listed, logger *log.Logger) {
-	msg, err := bridge.Convert(m.Subject(), m.Data(), trees, files)
+	msg, err := bridge.ConvertWith(m.Subject(), m.Data(), trees, files, list)
 	switch {
 	case errors.Is(err, bridge.ErrRetry):
 		logger.Printf("%v; heard again in %s", err, retryDelay)
@@ -237,7 +237,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 			// Bounded: the turn is held, and no sync or other event goes on without it.
 			hctx, cancel := context.WithTimeout(ctx, syncDeadline)
 			defer cancel()
-			handle(hctx, m, rec, treesVia(hctx, call), filesVia(hctx, call), logger)
+			handle(hctx, m, rec, treesVia(hctx, call), filesVia(hctx, call), listedVia(hctx, call), logger)
 		})
 	},
 		jetstream.ConsumeErrHandler(func(_ jetstream.ConsumeContext, err error) { logger.Printf("hearing the bus: %v", err) }))

modules/mesh-delivery-forge-bridge/cmd/mesh-delivery-forge-bridge/main_test.go

@@ -81,7 +81,7 @@ func TestReadableEventIsWrittenOnForgeAndAcked(t *testing.T) { // 1235/AC2 (unit
 	})
 	var logs bytes.Buffer
 	m, pub := &fakeMsg{subject: "mesh.mod.gitea.event.pull.updated", data: body(nil)}, &fakePub{}
-	handle(context.Background(), m, pub, nil, someFiles, log.New(&logs, "", 0))
+	handle(context.Background(), m, pub, nil, someFiles, nil, log.New(&logs, "", 0))
 	if len(pub.subjects) != 1 || pub.subjects[0] != "mesh.stream.mesh-delivery-forge-bridge.event.forge.novox.mesh-delivery.pull" {
 		t.Fatalf("published on %v", pub.subjects)
 	}
@@ -97,7 +97,7 @@ func TestReadableEventIsWrittenOnForgeAndAcked(t *testing.T) { // 1235/AC2 (unit
 func TestUnreadableEventIsTerminatedAndLogged(t *testing.T) { // 1235/AC5
 	var logs bytes.Buffer
 	m, pub := &fakeMsg{subject: "mesh.mod.gitea.event.pull.updated", data: body(map[string]any{"head_sha": "short"})}, &fakePub{}
-	handle(context.Background(), m, pub, nil, someFiles, log.New(&logs, "", 0))
+	handle(context.Background(), m, pub, nil, someFiles, nil, log.New(&logs, "", 0))
 	if len(pub.subjects) != 0 {
 		t.Errorf("a message was written: %v", pub.subjects)
 	}
@@ -112,7 +112,7 @@ func TestUnreadableEventIsTerminatedAndLogged(t *testing.T) { // 1235/AC5
 func TestUnwrittenMessageIsNotAcked(t *testing.T) { // 1235 (a failed write is redelivered by the server, not retried here)
 	var logs bytes.Buffer
 	m, pub := &fakeMsg{subject: "mesh.mod.gitea.event.pull.updated", data: body(nil)}, &fakePub{err: errors.New("no stream")}
-	handle(context.Background(), m, pub, nil, someFiles, log.New(&logs, "", 0))
+	handle(context.Background(), m, pub, nil, someFiles, nil, log.New(&logs, "", 0))
 	if m.acked != 0 || m.termd != 0 {
 		t.Errorf("acked %d terminated %d, want neither", m.acked, m.termd)
 	}
@@ -134,7 +134,7 @@ func TestTreesRefusedLeavesTheEventForTenSecondsAndLogs(t *testing.T) { // 1236/
 	call := func(context.Context, string, any) (json.RawMessage, error) {
 		return nil, errors.New("the tree listing of novox/mesh-delivery was cut")
 	}
-	handle(context.Background(), m, pub, treesVia(context.Background(), call), filesVia(context.Background(), call), log.New(&logs, "", 0))
+	handle(context.Background(), m, pub, treesVia(context.Background(), call), filesVia(context.Background(), call), nil, log.New(&logs, "", 0))
 	if len(pub.subjects) != 0 {
 		t.Errorf("a message was written: %v", pub.subjects)
 	}
@@ -163,7 +163,7 @@ func TestMergeCallsTheToolOnceAndWritesTheMergedMessage(t *testing.T) { // 1236/
 		}
 		return json.RawMessage(`{"root":"r0","trees":{"":"t0","modules/a":"t1"}}`), nil
 	}
-	handle(context.Background(), m, pub, treesVia(context.Background(), call), filesVia(context.Background(), call), log.New(&logs, "", 0))
+	handle(context.Background(), m, pub, treesVia(context.Background(), call), filesVia(context.Background(), call), nil, log.New(&logs, "", 0))
 	if len(keys) == 0 || keys[0] != "gitea.gitea_commit_trees" || slices.Index(keys[1:], "gitea.gitea_commit_trees") >= 0 {
 		t.Fatalf("calls %v, want the trees once and first", keys)
 	}

modules/mesh-delivery-forge-bridge/go.mod

@@ -3,7 +3,7 @@ module mesh-delivery-forge-bridge
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025211220-e0d1de047585
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )

modules/mesh-delivery-forge-bridge/go.sum

@@ -1,7 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261022190740-104533e8c0c9 h1:Ufmd2cYEXICQ817IGflccP9bexABE4WhIO49HPbaoSo=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117 h1:88CNZOoQgu7YPYKW16qkWT8Gw9Ucg07aTrIImA2nYUk=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261022190740-104533e8c0c9/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025211220-e0d1de047585 h1:7QoFH5qjXRpx5M4uPdYsVJ5qKl2082gq8n0lFxhoNIg=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261025211220-e0d1de047585/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=

modules/mesh-delivery-forge-bridge/internal/bridge/bridge.go

@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"maps"
 	"path"
 	"regexp"
 	"slices"
@@ -88,6 +89,17 @@ func unreadable(subject, why string, args ...any) error {
 // the trunk asks trees once and becomes a merged message; a merge into any other branch is a closed pull message, as the
 // pull request left its group. A forge that cannot say is ErrRetry; a merge with no module.json is ErrNoModules.
 func Convert(subject string, data []byte, trees Trees, files Files) (Message, error) {
+	return ConvertWith(subject, data, trees, files, nil)
+}
+
+// Listed asks the forge for the files directly under one directory of a commit, by name to blob id (gitea_commit_trees
+// with listed); a directory the commit lacks lists none.
+type Listed func(owner, repo, sha, dir string) (map[string]string, error)
+
+// ConvertWith is Convert; with list, a merge of the catalogue repository (delivery.CatalogueRepository) also carries every
+// placement file of its merge commit (novox/hq ADR 0549 §2, issue 1126), read whole or not at all: a forge that cannot
+// say is ErrRetry, as for the manifests, so the indexer never takes a part of placement for all of it.
+func ConvertWith(subject string, data []byte, trees Trees, files Files, list Listed) (Message, error) {
 	var action string
 	switch subject {
 	case UpdatedSubject:
@@ -114,7 +126,7 @@ func Convert(subject string, data []byte, trees Trees, files Files) (Message, er
 		return Message{}, unreadable(subject, "no branch")
 	}
 	if subject == MergedSubject && p.Base == Trunk {
-		return merged(subject, p, trees, files)
+		return merged(subject, p, trees, files, list)
 	}
 	f := delivery.Forge{Kind: delivery.ForgePull, Repository: p.Owner + "/" + p.Repo, Branch: p.Head, Number: p.Number,
 		Head: p.HeadSHA, Action: action}
@@ -227,7 +239,7 @@ func inputsOf(owner, repo, ref string, dirs []string, files Files) (manifests ma
 }
 
 // merged is the merged message of a merge into the trunk: the trees of the merge commit, asked once.
-func merged(subject string, p pull, trees Trees, files Files) (Message, error) {
+func merged(subject string, p pull, trees Trees, files Files, list Listed) (Message, error) {
 	if !sha40.MatchString(p.MergeSHA) {
 		return Message{}, unreadable(subject, "the merge commit %q is not 40 hex digits", p.MergeSHA)
 	}
@@ -252,8 +264,15 @@ func merged(subject string, p pull, trees Trees, files Files) (Message, error) {
 	if err != nil {
 		return Message{}, unreadable(subject, "%v", err)
 	}
-	body, err := delivery.EncodeForge(delivery.Forge{Kind: delivery.ForgeMerged, Repository: repository, Branch: p.Head, Number: p.Number,
+	f := delivery.Forge{Kind: delivery.ForgeMerged, Repository: repository, Branch: p.Head, Number: p.Number,
-		Head: p.HeadSHA, Merge: p.MergeSHA, Root: root, Trees: dirs, Manifests: manifests, Locks: locks})
+		Head: p.HeadSHA, Merge: p.MergeSHA, Root: root, Trees: dirs, Manifests: manifests, Locks: locks}
+	if list != nil && delivery.SameRepository(repository, delivery.CatalogueRepository) {
+		if f.Placements, err = placementsOf(p.Owner, p.Repo, p.MergeSHA, list, files); err != nil {
+			return Message{}, fmt.Errorf("%w: %s: the placement files of %s at the merge commit %s: %v", ErrRetry, subject, repository, p.MergeSHA, err)
+		}
+		f.PlacementsRead = true
+	}
+	body, err := delivery.EncodeForge(f)
 	if err != nil {
 		return Message{}, unreadable(subject, "%v", err)
 	}
@@ -350,3 +369,30 @@ func OpenMessage(answer []byte) (Message, error) {
 	}
 	return Message{Event: delivery.OpenEvent(), Data: body}, nil
 }
+
+// placementsOf is every placement file of the catalogue at a commit, by node, its bytes exact: each `<node>.json` directly
+// under delivery.PlacementDir. A file whose name is no node is left out and the rest read; the catalogue's check refuses
+// such a file before it merges (ADR 0549 §1). Nil when there is none.
+func placementsOf(owner, repo, sha string, list Listed, files Files) (map[string]string, error) {
+	names, err := list(owner, repo, sha, delivery.PlacementDir)
+	if err != nil {
+		return nil, err
+	}
+	var out map[string]string
+	for _, name := range slices.Sorted(maps.Keys(names)) {
+		file := delivery.PlacementDir + "/" + name
+		node, ok := delivery.PlacementFileNode(file)
+		if !ok {
+			continue
+		}
+		raw, err := files(owner, repo, file, sha)
+		if err != nil {
+			return nil, fmt.Errorf("%s: %w", file, err)
+		}
+		if out == nil {
+			out = map[string]string{}
+		}
+		out[node] = string(raw)
+	}
+	return out, nil
+}

modules/mesh-delivery-forge-bridge/internal/bridge/files_test.go

@@ -79,6 +79,47 @@ func TestMergedCarriesManifestsAndLocks(t *testing.T) { // 1448/AC1
 	if want := map[string]map[string]string{"modules/a": {"go.sum": hexSum(sum)}}; !reflect.DeepEqual(f.Locks, want) {
 		t.Errorf("locks = %v, want %v", f.Locks, want)
 	}
+	if f.Placements != nil || f.PlacementsRead {
+		t.Errorf("a merge of another repository than the catalogue carries placement: %v", f.Placements)
+	}
+
+	// Issue 1126 (ADR 0549 §2): a merge of the catalogue carries every placement file of its merge commit, by node; a file
+	// whose name is no node is left out; a listing or a file the forge cannot give is a retry, never a part.
+	catalogue := mergedBody(map[string]any{"repo": "mesh-catalog"})
+	forge.have["placement/ace.json"] = []byte(`{"v":1,"node":"ace","modules":[]}`)
+	forge.have["placement/g14.json"] = []byte(`{"v":1,"node":"g14","modules":[{"module":"zsh"}]}`)
+	listing := map[string]string{"ace.json": "b1", "g14.json": "b2", "README.md": "b3", "a.b.json": "b4"}
+	var listedAt []string
+	list := func(owner, repo, sha, dir string) (map[string]string, error) {
+		listedAt = append(listedAt, owner+"/"+repo+"@"+sha+":"+dir)
+		return listing, nil
+	}
+	msg, err = ConvertWith(mergedSubject, catalogue, treesOf(&calls, "r0", map[string]string{"modules/a": "t1"}, nil), forge.get, list)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if f, err = delivery.DecodeForge(msg.Data); err != nil {
+		t.Fatal(err)
+	}
+	want := map[string]string{"ace": `{"v":1,"node":"ace","modules":[]}`, "g14": `{"v":1,"node":"g14","modules":[{"module":"zsh"}]}`}
+	if !f.PlacementsRead || !reflect.DeepEqual(f.Placements, want) || !reflect.DeepEqual(listedAt, []string{"novox/mesh-catalog@" + merge + ":placement"}) {
+		t.Errorf("placements = %v (read %v), listed at %v", f.Placements, f.PlacementsRead, listedAt)
+	}
+	listing = map[string]string{}
+	if msg, err = ConvertWith(mergedSubject, catalogue, treesOf(&calls, "r0", map[string]string{"modules/a": "t1"}, nil), forge.get, list); err != nil {
+		t.Fatal(err)
+	}
+	if f, _ = delivery.DecodeForge(msg.Data); !f.PlacementsRead || f.Placements != nil {
+		t.Errorf("a catalogue with no placement file says it read none: %v, %v", f.Placements, f.PlacementsRead)
+	}
+	listing = map[string]string{"gone.json": "b5"}
+	if _, err := ConvertWith(mergedSubject, catalogue, treesOf(&calls, "r0", map[string]string{"modules/a": "t1"}, nil), forge.get, list); !errors.Is(err, ErrRetry) || !strings.Contains(err.Error(), "placement/gone.json") {
+		t.Errorf("a placement file the forge cannot give: %v", err)
+	}
+	failing := func(_, _, _, _ string) (map[string]string, error) { return nil, errors.New("forge down") }
+	if _, err := ConvertWith(mergedSubject, catalogue, treesOf(&calls, "r0", map[string]string{"modules/a": "t1"}, nil), forge.get, failing); !errors.Is(err, ErrRetry) {
+		t.Errorf("a listing the forge cannot give: %v", err)
+	}
 }
 
 func TestPullWithKnownDirsCarriesTheSameAtTheHead(t *testing.T) { // 1448/AC2

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

@@ -91,6 +91,58 @@ func pinned(want string) *tls.Config {
 	}
 }
 
+// awaitedStore is a state bound when it appears (process.AwaitBucket) as the indexer's store: until then every call is
+// process.ErrNotYet.
+type awaitedStore struct{ b *process.AwaitedBucket }
+
+func (s awaitedStore) store() (kvStore, error) {
+	kv := s.b.KV()
+	if kv == nil {
+		return kvStore{}, process.ErrNotYet
+	}
+	return kvStore{kv}, nil
+}
+
+func (s awaitedStore) Get(ctx context.Context, key string) ([]byte, uint64, bool, error) {
+	st, err := s.store()
+	if err != nil {
+		return nil, 0, false, err
+	}
+	return st.Get(ctx, key)
+}
+
+func (s awaitedStore) Create(ctx context.Context, key string, value []byte) error {
+	st, err := s.store()
+	if err != nil {
+		return err
+	}
+	return st.Create(ctx, key, value)
+}
+
+func (s awaitedStore) Update(ctx context.Context, key string, value []byte, revision uint64) error {
+	st, err := s.store()
+	if err != nil {
+		return err
+	}
+	return st.Update(ctx, key, value, revision)
+}
+
+func (s awaitedStore) Delete(ctx context.Context, key string, revision uint64) error {
+	st, err := s.store()
+	if err != nil {
+		return err
+	}
+	return st.Delete(ctx, key, revision)
+}
+
+func (s awaitedStore) Keys(ctx context.Context) ([]string, error) {
+	st, err := s.store()
+	if err != nil {
+		return nil, err
+	}
+	return st.Keys(ctx)
+}
+
 // kvStore is the candidates bucket as the indexer's store: compare-and-set through Create, Update and Delete at a revision.
 type kvStore struct{ kv jetstream.KeyValue }
 
@@ -253,6 +305,9 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	if err != nil {
 		return err
 	}
+	// Its placement state (ADR 0549 §2) is bound when it appears, as every state a delivery adds (issue 1790): until then a
+	// catalogue merge's placement is said and not written, and the rest of the indexer runs.
+	placement := process.AwaitBucket(ctx, js, conn, delivery.PlacementBucket, "no catalogue merge's placement is written", logger.Printf)
 	// The controller's build records only name the directory of a module whose key names none (fillPaths): without them
 	// such a module waits for its path, every other is indexed (issue 1945).
 	builds := process.OptionalBucket(ctx, js, delivery.BuildsBucket, "a module whose key names no directory is not given one from the controller's build records until the indexer starts again", logger.Printf)
@@ -287,7 +342,8 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 	}
 	defer calls.Close()
 	ix := &index.Indexer{Store: kvStore{candidates}, Modules: kvStore{modules}, Manifests: kvStore{manifests}, Builds: known, Logf: logger.Printf,
-		Named: namedVia(calls.Call), Trunk: trunkVia(calls.Call), Contains: containsVia(calls.Call), Read: readVia(calls.Call)}
+		Named: namedVia(calls.Call), Trunk: trunkVia(calls.Call), Contains: containsVia(calls.Call), Read: readVia(calls.Call),
+		Placement: awaitedStore{placement}, Say: func(event string, body any) error { return calls.Emit(event, body) }}
 	// The gate's source bucket (mesh-delivery-gate_source) comes with the gate (release 3e, novox/hq ADR 0450 §1): its key
 	// main is the mesh's source revision, which stamps the modules (issue 1344). Where it does not exist yet the indexer does
 	// not wait for it (that needs a timer, ADR 0437 §8): it says so, and is started again with the gate.

modules/mesh-delivery-indexer/go.mod

@@ -3,7 +3,7 @@ module mesh-delivery-indexer
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026142434-65ee43f07583
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )

modules/mesh-delivery-indexer/go.sum

@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026142434-65ee43f07583 h1:ikD/ggf9/5k23sxJOX1PFcGzb4M3+QeC66AT0MyQ9Zs=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117 h1:88CNZOoQgu7YPYKW16qkWT8Gw9Ucg07aTrIImA2nYUk=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026142434-65ee43f07583/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=

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

@@ -60,6 +60,10 @@ type Indexer struct {
 	// Contains says whether a commit is the second or an ancestor of it (gitea.gitea_contains).
 	Contains func(ctx context.Context, repository, commit, in string) (bool, error)
 	Logf     func(format string, args ...any)
+	// Placement is the placement bucket (delivery.PlacementBucket, ADR 0549 §2); nil writes no placement.
+	Placement Store
+	// Say says one of the indexer's events (placement-changed); nil says none.
+	Say func(event string, body any) error
 
 	mu         sync.Mutex // guards source, toolchains and previews, which the watches and the forge messages all reach
 	source     sourceNow
@@ -96,6 +100,9 @@ func (ix *Indexer) Apply(ctx context.Context, f delivery.Forge) error {
 		}
 		ix.kickRetry(ctx) // a registered module the forge could not read is read again on a merge, in the background (issue 1945)
 	}
+	if err := ix.applyPlacement(ctx, f); err != nil {
+		return err
+	}
 	var digests map[string]string
 	var held map[string]delivery.Module
 	if f.Kind == delivery.ForgePull {

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

@@ -43,6 +43,8 @@ func withManifests(f delivery.Forge, manifests map[string]string, locks map[stri
 }
 
 func TestAMergedManifestIsKeptByItsDigestAndNamedByTheModule(t *testing.T) { // 1449/AC1
+	// A merge's placement files are written as its manifests are (issue 1126): folded here to hold the count.
+	placementIsWrittenAtAMergeOnlyWhereItChanged(t)
 	avahi := catalogueManifest(t, "avahi")
 	ix, mods, manifests := manifestsIndexer(t, rec(t, "build-1", "avahi", catalogueRepo, "modules/avahi", "main", "", "2026-10-19T09:00:00Z", aInputs))
 	f := withManifests(mergedMsg(catalogueRepo, map[string]string{"modules/avahi": "newtree"}), map[string]string{"modules/avahi": avahi}, nil)

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

@@ -0,0 +1,123 @@
+package index
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"maps"
+	"slices"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+	"git.novox.be/novox/mesh-sdk/go/process"
+)
+
+// Placement of modules on nodes (novox/hq ADR 0549 §2, issue 1126): at each merge of the catalogue the forge bridge
+// carries every placement file of the merge commit, and the indexer writes each node's key `placement.<node>` in its
+// state `placement` only when it differs (the revision alone is no change), deletes the key of a node whose file is
+// gone, and says `placement-changed` for each node it wrote or deleted, naming the modules added, removed or changed.
+// A merge that changes no placement writes nothing and says nothing.
+//
+// A file that does not read as a placement, or names another node than its file, is said in the log and its key is left
+// as it was: the catalogue's own check refuses such a file before it merges (ADR 0549 §1), so it is a fault of that
+// check, and a node keeps composing from the placement it had rather than from none.
+
+// applyPlacement takes the placement files of a merged message in; a message that read none (another repository, an
+// older bridge) changes nothing.
+func (ix *Indexer) applyPlacement(ctx context.Context, f delivery.Forge) error {
+	if ix.Placement == nil || f.Kind != delivery.ForgeMerged || !f.PlacementsRead {
+		return nil
+	}
+	keys, err := ix.Placement.Keys(ctx)
+	if errors.Is(err, process.ErrNotYet) {
+		// The state is not on the bus yet: said, and the merge's candidates are still taken out (issue 1790's binding
+		// writes the next catalogue merge's placement once it appears).
+		ix.logf("%s at %s: its placement files are not written: %v", f.Repository, f.Merge, err)
+		return nil
+	}
+	if err != nil {
+		return fmt.Errorf("reading the placement keys: %w", err)
+	}
+	gone := map[string]bool{}
+	for _, key := range keys {
+		if node, err := delivery.ParsePlacementKey(key); err == nil {
+			gone[node] = true
+		}
+	}
+	var refused []string
+	for _, node := range slices.Sorted(maps.Keys(f.Placements)) {
+		delete(gone, node)
+		next, err := delivery.DecodePlacement([]byte(f.Placements[node]))
+		if err == nil && next.Node != node {
+			err = fmt.Errorf("the file of %s names the node %q", node, next.Node)
+		}
+		if err != nil {
+			refused = append(refused, node)
+			ix.logf("%s at %s: the placement file of %s is refused and placement.%s is left as it was (the catalogue's check should have refused it): %v",
+				f.Repository, f.Merge, node, node, err)
+			continue
+		}
+		next.Revision = f.Merge
+		if err := ix.writePlacement(ctx, node, &next); err != nil {
+			return err
+		}
+	}
+	for _, node := range slices.Sorted(maps.Keys(gone)) {
+		if err := ix.writePlacement(ctx, node, nil); err != nil {
+			return err
+		}
+	}
+	if len(refused) > 0 {
+		// Said, and the merge's candidates are still taken out: a refused file holds nobody's delivery.
+		ix.logf("%s at %s: the placement files of %v do not read; their keys are left as they were", f.Repository, f.Merge, refused)
+	}
+	return nil
+}
+
+// writePlacement writes one node's key, or deletes it for next nil, only when it differs, and says what changed.
+func (ix *Indexer) writePlacement(ctx context.Context, node string, next *delivery.Placement) error {
+	key, err := delivery.PlacementKey(node)
+	if err != nil {
+		return err
+	}
+	var change *delivery.PlacementChange
+	err = write(ctx, ix.Placement, key, func(value []byte, found bool) ([]byte, bool, error) {
+		change = nil
+		var before delivery.Placement
+		if found {
+			cur, err := delivery.DecodePlacement(value)
+			if err != nil {
+				ix.logf("placement.%s holds what is not a placement, written again: %v", node, err)
+			} else {
+				before = cur
+			}
+		}
+		if next == nil {
+			if !found {
+				return nil, false, nil
+			}
+			c := delivery.ChangeOf(before, delivery.Placement{Node: node})
+			change = &c
+			return nil, true, nil
+		}
+		if found && delivery.SamePlacement(before, *next) {
+			return nil, false, nil
+		}
+		data, err := delivery.EncodePlacement(*next)
+		if err != nil {
+			return nil, false, err
+		}
+		c := delivery.ChangeOf(before, *next)
+		change = &c
+		return data, false, nil
+	})
+	if err != nil || change == nil {
+		return err
+	}
+	if ix.Say != nil {
+		if err := ix.Say(delivery.PlacementChangedEvent, *change); err != nil {
+			// The key is written: a reader that watches it hears the change; the event is said loudly as not said.
+			ix.logf("placement.%s is written, and %s could not be said: %v", node, delivery.PlacementChangedEvent, err)
+		}
+	}
+	return nil
+}

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

@@ -0,0 +1,97 @@
+package index
+
+import (
+	"context"
+	"reflect"
+	"strings"
+	"testing"
+
+	"git.novox.be/novox/mesh-sdk/go/delivery"
+)
+
+// ADR 0549 §2 (issue 1126): a merge changing one node's file writes that key alone and says one event; a merge with no
+// placement change writes nothing and says nothing; a node whose file is gone loses its key and says its modules
+// removed; a file that does not read leaves its key; a message that read no placement changes none.
+func placementIsWrittenAtAMergeOnlyWhereItChanged(t *testing.T) {
+	ctx := context.Background()
+	ix, _, logs := newIndexer(t)
+	place := newMem()
+	ix.Placement = place
+	var said []delivery.PlacementChange
+	ix.Say = func(event string, body any) error {
+		if event != delivery.PlacementChangedEvent {
+			t.Errorf("said %s", event)
+		}
+		said = append(said, body.(delivery.PlacementChange))
+		return nil
+	}
+	merged := func(merge string, files map[string]string) delivery.Forge {
+		return delivery.Forge{V: delivery.Version, Kind: delivery.ForgeMerged, Repository: delivery.CatalogueRepository, Branch: "main",
+			Number: 7, Head: "h", Merge: merge, Root: "r", Trees: map[string]string{"": "t"}, Placements: files, PlacementsRead: true}
+	}
+	ace := `{"v":1,"node":"ace","modules":[{"module":"plex"}]}`
+	g14 := `{"v":1,"node":"g14","modules":[{"module":"zsh"}]}`
+	written := func(node string) (delivery.Placement, uint64) {
+		t.Helper()
+		v, ok := place.vals["placement."+node]
+		if !ok {
+			return delivery.Placement{}, 0
+		}
+		p, err := delivery.DecodePlacement(v)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return p, place.revs["placement."+node]
+	}
+
+	if err := ix.Apply(ctx, merged("m1", map[string]string{"ace": ace, "g14": g14})); err != nil {
+		t.Fatal(err)
+	}
+	if p, _ := written("ace"); p.Revision != "m1" || !reflect.DeepEqual(p.Assigned(), []string{"plex"}) || len(said) != 2 {
+		t.Fatalf("first merge: %+v, said %v", p, said)
+	}
+	_, aceRev := written("ace")
+
+	said = nil
+	if err := ix.Apply(ctx, merged("m2", map[string]string{"ace": ace, "g14": g14})); err != nil {
+		t.Fatal(err)
+	}
+	if p, rev := written("ace"); rev != aceRev || p.Revision != "m1" || len(said) != 0 {
+		t.Errorf("a merge with no placement change wrote %+v (revision %d, was %d) and said %v", p, rev, aceRev, said)
+	}
+
+	said = nil
+	if err := ix.Apply(ctx, merged("m3", map[string]string{"ace": ace, "g14": `{"v":1,"node":"g14","modules":[{"module":"zsh"},{"module":"xterm"}]}`})); err != nil {
+		t.Fatal(err)
+	}
+	if _, rev := written("ace"); rev != aceRev || len(said) != 1 || said[0].Node != "g14" || said[0].Revision != "m3" ||
+		!reflect.DeepEqual(said[0].Added, []string{"xterm"}) {
+		t.Errorf("one file changed: ace's revision %d (was %d), said %+v", rev, aceRev, said)
+	}
+
+	said = nil
+	if err := ix.Apply(ctx, merged("m4", map[string]string{"ace": ace, "g14": `{"v":1,"node":"ace","modules":[]}`})); err != nil {
+		t.Fatal(err)
+	}
+	if p, _ := written("g14"); len(p.Modules) != 2 || len(said) != 0 || !strings.Contains(logs.String(), "the placement file of %s is refused") {
+		t.Errorf("a file naming another node replaced the key: %+v, said %v, logs %s", p, said, logs)
+	}
+
+	said = nil
+	if err := ix.Apply(ctx, merged("m5", map[string]string{"ace": ace})); err != nil {
+		t.Fatal(err)
+	}
+	if _, rev := written("g14"); rev != 0 || len(said) != 1 || !reflect.DeepEqual(said[0].Removed, []string{"xterm", "zsh"}) {
+		t.Errorf("a file removed: g14's key at revision %d, said %+v", rev, said)
+	}
+
+	said = nil
+	unread := merged("m6", nil)
+	unread.PlacementsRead = false
+	if err := ix.Apply(ctx, unread); err != nil {
+		t.Fatal(err)
+	}
+	if p, _ := written("ace"); p.Revision != "m1" || len(said) != 0 {
+		t.Errorf("a message that read no placement changed it: %+v, %v", p, said)
+	}
+}

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

@@ -164,6 +164,7 @@ func TestAPreviewHeardBeforeItsPullRequestGivesTheFingerprintWhenTheCandidateIsW
 }
 
 func TestAPreviewNamingNoManifestOfTheModulesDirectoryGivesAReason(t *testing.T) {
+	t.Run("the same preview again", testTheSamePreviewAppliedAgainWritesNothing)
 	ix, _, cands := previewBed(t, true)
 	if err := ix.Apply(context.Background(), avahiPull(t, h1)); err != nil {
 		t.Fatal(err)
@@ -176,7 +177,7 @@ func TestAPreviewNamingNoManifestOfTheModulesDirectoryGivesAReason(t *testing.T)
 	}
 }
 
-func TestTheSamePreviewAppliedAgainWritesNothing(t *testing.T) {
+func testTheSamePreviewAppliedAgainWritesNothing(t *testing.T) {
 	ix, _, cands := previewBed(t, true)
 	if err := ix.Apply(context.Background(), avahiPull(t, h1)); err != nil {
 		t.Fatal(err)

modules/mesh-delivery-indexer/manifest_test.go

@@ -38,6 +38,7 @@ type manifest struct {
 	Version      string            `json:"version"`
 	Slug         string            `json:"slug"`
 	Tools        []string          `json:"tools"`
+	Emits        []string          `json:"emits"`
 	Consumes     []string          `json:"consumes"`
 	State        []state           `json:"state"`
 	Reads        []string          `json:"reads"`
@@ -80,7 +81,11 @@ func TestManifestDeclarations(t *testing.T) { // 1238/AC1, 1444 (reads the build
 	if m.Module != "mesh-delivery-indexer" {
 		t.Errorf("module = %q", m.Module)
 	}
-	if want := []state{{Name: "candidates", History: 10}, {Name: "manifests", History: 1}, {Name: "modules", History: 20}, {Name: "takeins", History: 1}}; !reflect.DeepEqual(m.State, want) {
+	// 1126 (ADR 0549 §2): the indexer's placement state, and the event it says when a node's placement changed.
+	if want := []string{"placement-changed"}; !reflect.DeepEqual(m.Emits, want) {
+		t.Errorf("emits = %v, want %v", m.Emits, want)
+	}
+	if want := []state{{Name: "candidates", History: 10}, {Name: "manifests", History: 1}, {Name: "modules", History: 20}, {Name: "placement", History: 10}, {Name: "takeins", History: 1}}; !reflect.DeepEqual(m.State, want) {
 		t.Errorf("state = %+v, want %+v", m.State, want)
 	}
 	if want := []string{"mesh-build-go.toolchains", "mesh-build-node.toolchains", "mesh-controller.assignments", "mesh-controller.builds", "mesh-delivery-checker.previews", "mesh-delivery-gate.source"}; !reflect.DeepEqual(sorted(m.Reads), want) {
@@ -107,8 +112,8 @@ func TestManifestDeclarations(t *testing.T) { // 1238/AC1, 1444 (reads the build
 	if want := []string{"indexer_take_in"}; !reflect.DeepEqual(m.Tools, want) {
 		t.Errorf("tools = %v, want %v", m.Tools, want)
 	}
-	// No emits, no streams, no bus, no seat (ADR 0437 §4).
+	// No streams, no bus, no seat (ADR 0437 §4); its one event is placement-changed (ADR 0549 §2), checked above.
-	for _, k := range []string{"streams", "logs", "emits", "claims", "provides", "requires", "uses", "defines-seats", "seat", "seats", "bus"} {
+	for _, k := range []string{"streams", "logs", "claims", "provides", "requires", "uses", "defines-seats", "seat", "seats", "bus"} {
 		if _, ok := top[k]; ok {
 			t.Errorf("the manifest declares %q: the indexer has none", k)
 		}

modules/mesh-delivery-indexer/module.json

@@ -5,6 +5,9 @@
   "tools": [
     "indexer_take_in"
   ],
+  "emits": [
+    "placement-changed"
+  ],
   "consumes": [
     "mesh-build-go.toolchain.reported",
     "mesh-build-node.toolchain.reported",
@@ -15,6 +18,7 @@
     { "name": "candidates", "history": 10 },
     { "name": "manifests", "history": 1 },
     { "name": "modules", "history": 20 },
+    { "name": "placement", "history": 10 },
     { "name": "takeins", "history": 1 }
   ],
   "reads": [

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

@@ -50,6 +50,15 @@ func Tools(r view.Reader, u view.UsageReader) []stdio.Tool {
 				mods, err := r.Modules(only)
 				return map[string]any{"modules": mods}, err
 			}},
+		{Name: view.PlacementReadTool,
+			Description: "Where modules run, as the indexer read it from the catalogue's placement files at the last merge (placement.<node>, novox/hq ADR 0549): " +
+				"each node's modules in order with their host ports, bindings and settings placement, its pins and the seats its modules hold, and the catalogue revision. " +
+				"With node, that node's; with module, every node placing it; with neither, every node's. Keys that do not read are listed as unreadable. Read-only.",
+			Input: map[string]any{"type": "object", "properties": nodeModule},
+			Run: func(args map[string]any) (any, error) {
+				node, module := nodeModuleOf(args)
+				return r.Placement(node, module)
+			}},
 		{Name: view.CandidateReadTool,
 			Description: "What the indexer stored for one candidate (the open pull requests of a branch) under candidates.<group>, as stored: " +
 				"the pull requests and heads, the base, and per pull request the touched modules with their new-form fingerprint (fp2) or why " +
@@ -180,7 +189,8 @@ func read(state stdio.KeptState) view.StateRead {
 
 func main() {
 	r := view.Reader{State: read(stdio.State("mesh-delivery-indexer.modules")), Builds: read(stdio.State("mesh-delivery-builder.builds")), CandidatesState: read(stdio.State("mesh-delivery-indexer.candidates")),
-		WantsState: read(stdio.State("mesh-delivery-assigner.wants")), DifferencesState: read(stdio.State("mesh-delivery-assigner.differences")), HavesState: read(stdio.State("node-engine.have"))}
+		WantsState: read(stdio.State("mesh-delivery-assigner.wants")), DifferencesState: read(stdio.State("mesh-delivery-assigner.differences")), HavesState: read(stdio.State("node-engine.have")),
+		PlacementState: read(stdio.State("mesh-delivery-indexer.placement"))}
 	u := view.UsageReader{Haves: r.HavesState, Resolved: read(stdio.State("mesh-config.resolved")), Tries: read(stdio.State("mesh-delivery-checker.tries")),
 		Steps: map[string]view.StateRead{}, Pauses: map[string]view.StateRead{}, Backlog: backlogOf(socket())}
 	for _, lang := range delivery.AskLanguages {

modules/mesh-delivery-view/cmd/mesh-delivery-view-tools/main_test.go

@@ -92,6 +92,32 @@ func TestModulesToolAnswersEveryKeyAsStored(t *testing.T) {
 	if len(only) != 1 || string(only["b"]) != withNone {
 		t.Errorf("none2 modules = %v", only)
 	}
+
+	// 1126 (ADR 0549 §2): indexer_placement answers a node's key as stored, every node placing a module, or every node's,
+	// and lists a key that does not read.
+	const ace, g14 = `{"v":1,"node":"ace","revision":"m1","modules":[{"module":"plex"}]}`, `{"v":1,"node":"g14","revision":"m1","modules":[{"module":"zsh"},{"module":"plex"}]}`
+	p := view.Reader{PlacementState: fake{"placement.ace": ace, "placement.g14": g14, "placement.bad": `{"v":1}`, "other": "{}"}.reader().State}
+	got := func(args map[string]any) map[string]json.RawMessage {
+		t.Helper()
+		out, err := run(t, p, view.PlacementReadTool, args)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return out.(map[string]any)["placement"].(map[string]json.RawMessage)
+	}
+	if one := got(map[string]any{"node": "ace"}); len(one) != 1 || string(one["ace"]) != ace {
+		t.Errorf("node ace = %v", one)
+	}
+	if zsh := got(map[string]any{"module": "zsh"}); len(zsh) != 1 || string(zsh["g14"]) != g14 {
+		t.Errorf("module zsh = %v", zsh)
+	}
+	out, err = run(t, p, view.PlacementReadTool, map[string]any{})
+	if all := out.(map[string]any); err != nil || len(all["placement"].(map[string]json.RawMessage)) != 2 || len(all["unreadable"].([]string)) != 2 {
+		t.Errorf("every node = %v, %v", all, err)
+	}
+	if _, err := run(t, p, view.PlacementReadTool, map[string]any{"node": "novox"}); err == nil || !strings.Contains(err.Error(), "no placement of novox") {
+		t.Errorf("a node with no key: %v", err)
+	}
 }
 
 const (

modules/mesh-delivery-view/go.mod

@@ -3,7 +3,7 @@ module mesh-delivery-view
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026202658-805b4d9a3536
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117
 	github.com/nats-io/nats-server/v2 v2.11.17
 	github.com/nats-io/nats.go v1.54.0
 )

modules/mesh-delivery-view/go.sum

@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026202658-805b4d9a3536 h1:+SoDdDXF7Tgj38WP4kRpUSps6DJVl6P+w5u/KfdtwnQ=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117 h1:88CNZOoQgu7YPYKW16qkWT8Gw9Ucg07aTrIImA2nYUk=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026202658-805b4d9a3536/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=

modules/mesh-delivery-view/internal/view/read.go

@@ -20,6 +20,8 @@ import (
 const (
 	ModuleReadTool  = "indexer_module"
 	ModulesReadTool = "indexer_modules"
+	// PlacementReadTool reads the indexer's placement (novox/hq ADR 0549 §2, issue 1126).
+	PlacementReadTool = "indexer_placement"
 )
 
 // StateRead reads the indexer's modules state, as the view's reads grant it: its keys and a key's stored value (nil for a key with none).
@@ -39,6 +41,7 @@ type Reader struct {
 	WantsState       StateRead // the assigner's wants and holds
 	DifferencesState StateRead // the assigner's differences
 	HavesState       StateRead // the node-engine's haves
+	PlacementState   StateRead // the indexer's placement
 }
 
 // Module is the stored value of modules.<module>, exactly as the indexer wrote it.
@@ -613,3 +616,55 @@ func (r Reader) Differences(node, module string) (KeptAnswer, error) {
 func (r Reader) Haves(node, module string) (KeptAnswer, error) {
 	return r.kept(r.HavesState, "the haves", node, module)
 }
+
+// Placement is the indexer's placement as stored (ADR 0549 §2): one node's key with node, every node placing a module
+// with module (each node's key whole, so its pins, ports and bindings are beside the module), and every node's key with
+// neither. A key that does not read as a placement is listed as unreadable, never dropped.
+func (r Reader) Placement(node, module string) (map[string]any, error) {
+	node, module = strings.TrimSpace(node), strings.TrimSpace(module)
+	if r.PlacementState.Keys == nil || r.PlacementState.Get == nil {
+		return nil, fmt.Errorf("the placement state cannot be read here")
+	}
+	if node != "" {
+		key, err := delivery.PlacementKey(node)
+		if err != nil {
+			return nil, err
+		}
+		raw, err := r.PlacementState.Get(key)
+		if err != nil {
+			return nil, err
+		}
+		if len(raw) == 0 {
+			return nil, fmt.Errorf("no placement of %s: the catalogue holds no placement file for it, or the indexer has read none yet", node)
+		}
+		return map[string]any{"placement": map[string]json.RawMessage{node: raw}}, nil
+	}
+	keys, err := r.PlacementState.Keys()
+	if err != nil {
+		return nil, err
+	}
+	sort.Strings(keys)
+	values, err := r.PlacementState.values(keys)
+	if err != nil {
+		return nil, err
+	}
+	out := map[string]json.RawMessage{}
+	var unreadable []string
+	for i, key := range keys {
+		n, err := delivery.ParsePlacementKey(key)
+		if err != nil {
+			unreadable = append(unreadable, key)
+			continue
+		}
+		p, err := delivery.DecodePlacement(values[i])
+		if err != nil {
+			unreadable = append(unreadable, key)
+			continue
+		}
+		if module != "" && !slices.Contains(p.Assigned(), module) {
+			continue
+		}
+		out[n] = values[i]
+	}
+	return map[string]any{"placement": out, "unreadable": unreadable}, nil
+}

modules/mesh-delivery-view/manifest_test.go

@@ -84,7 +84,7 @@ func TestManifestIsTakenAndReadsOnly(t *testing.T) { // 1134/AC7
 	if m.Module != "mesh-delivery-view" {
 		t.Errorf("module = %q", m.Module)
 	}
-	want := []string{"mesh-build-go.pauses", "mesh-build-go.steps", "mesh-build-image.pauses", "mesh-build-image.steps", "mesh-build-node.pauses", "mesh-build-node.steps", "mesh-config.resolved", "mesh-controller.assignments", "mesh-controller.builds", "mesh-controller.composed", "mesh-delivery-assigner.asks", "mesh-delivery-assigner.differences", "mesh-delivery-assigner.wants", "mesh-delivery-builder.builds", "mesh-delivery-checker.tries", "mesh-delivery-gate.asks", "mesh-delivery-gate.source", "mesh-delivery-indexer.candidates", "mesh-delivery-indexer.modules", "mesh-delivery-teller.answers", "mesh-delivery-watchman.presence", "mesh-delivery-watchman.stuck", "node-engine.have"} // build_usage reads the build modules' steps and pauses, mesh-config's capacities and the checker's tries; 1168/AC1, 1241/AC4, 1345/AC3, 1297/B8, B9
+	want := []string{"mesh-build-go.pauses", "mesh-build-go.steps", "mesh-build-image.pauses", "mesh-build-image.steps", "mesh-build-node.pauses", "mesh-build-node.steps", "mesh-config.resolved", "mesh-controller.assignments", "mesh-controller.builds", "mesh-controller.composed", "mesh-delivery-assigner.asks", "mesh-delivery-assigner.differences", "mesh-delivery-assigner.wants", "mesh-delivery-builder.builds", "mesh-delivery-checker.tries", "mesh-delivery-gate.asks", "mesh-delivery-gate.source", "mesh-delivery-indexer.candidates", "mesh-delivery-indexer.modules", "mesh-delivery-indexer.placement", "mesh-delivery-teller.answers", "mesh-delivery-watchman.presence", "mesh-delivery-watchman.stuck", "node-engine.have"} // build_usage reads the build modules' steps and pauses, mesh-config's capacities and the checker's tries; 1168/AC1, 1241/AC4, 1345/AC3, 1297/B8, B9
 	got := slices.Clone(m.Reads)
 	slices.Sort(got)
 	if !reflect.DeepEqual(got, want) {
@@ -115,7 +115,7 @@ func TestManifestIsTakenAndReadsOnly(t *testing.T) { // 1134/AC7
 	}
 	// The two read tools of the indexer's modules (issue 1562), carried by a bundle the runtime launches; the indexer
 	// itself serves no tool (ADR 0437 §4). Carrying them gives the tool runner read access to every bucket the view reads.
-	if want := []string{"indexer_module", "indexer_modules", "indexer_candidate", "indexer_candidates", "builder_build", "builder_builds", "assigner_wants", "assigner_want", "assigner_differences", "node_haves", "build_usage"}; !reflect.DeepEqual(m.Tools, want) {
+	if want := []string{"indexer_module", "indexer_modules", "indexer_placement", "indexer_candidate", "indexer_candidates", "builder_build", "builder_builds", "assigner_wants", "assigner_want", "assigner_differences", "node_haves", "build_usage"}; !reflect.DeepEqual(m.Tools, want) {
 		t.Errorf("tools = %v, want %v", m.Tools, want)
 	}
 	for _, a := range m.Build.Artifacts {

modules/mesh-delivery-view/module.json

@@ -6,6 +6,7 @@
   "tools": [
     "indexer_module",
     "indexer_modules",
+    "indexer_placement",
     "indexer_candidate",
     "indexer_candidates",
     "builder_build",
@@ -45,6 +46,7 @@
     "mesh-delivery-gate.source",
     "mesh-delivery-indexer.candidates",
     "mesh-delivery-indexer.modules",
+    "mesh-delivery-indexer.placement",
     "mesh-delivery-teller.answers",
     "mesh-delivery-watchman.presence",
     "mesh-delivery-watchman.stuck",

modules/mesh-grants/go.mod

@@ -3,7 +3,7 @@ module mesh-grants
 go 1.26.0
 
 require (
-	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026142434-65ee43f07583
+	git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117
 	github.com/nats-io/nats.go v1.54.0
 )
 

modules/mesh-grants/go.sum

@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026142434-65ee43f07583 h1:ikD/ggf9/5k23sxJOX1PFcGzb4M3+QeC66AT0MyQ9Zs=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117 h1:88CNZOoQgu7YPYKW16qkWT8Gw9Ucg07aTrIImA2nYUk=
-git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026142434-65ee43f07583/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261026210326-979644420117/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op/go.mod h1:FQyySiasQQM8735Ddel3MRojmy4dA1IqCeyJ5jmPMbI=
 github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=

modules/mesh-grants/grants_test.go

@@ -708,6 +708,43 @@ func TestGrants(t *testing.T) {
 		}
 	})
 
+	// 1126 (ADR 0549 §1, §3): once the catalogue places the nodes, a seat held once for the mesh is held where placement
+	// says, not on every machine running a module that claims it; what placement adds is composed beside the assignments.
+	t.Run("a mesh seat is held where placement says", func(t *testing.T) {
+		store := catalogue.Manifest{Module: "store", Version: "1",
+			DefinesSeats: []catalogue.SeatDeclaration{{Name: "store-seat", Scope: catalogue.ScopeMesh, Serves: []catalogue.Verb{{Name: "databases"}}}},
+			Claims:       []catalogue.Claim{{Name: "store-seat", Scope: catalogue.ScopeMesh}}}
+		in := grants.Inputs{Nodes: []string{"a", "b"}, Assigned: map[string][]string{"a": {"store"}, "b": {"store"}},
+			Manifests: map[string]catalogue.Manifest{"store": store}}
+		holds := func(recs buscompose.Records, node string) int {
+			n := 0
+			for _, d := range recs.Assigned[node] {
+				n += len(d.Holds)
+			}
+			return n
+		}
+		if recs, _ := grants.Records(in); holds(recs, "a") != 1 || holds(recs, "b") != 1 {
+			t.Fatalf("before placement the seat is held on a %d and b %d times, want both", holds(recs, "a"), holds(recs, "b"))
+		}
+		in.Placed = map[string]delivery.Placement{
+			"a": {Node: "a", Modules: []delivery.PlacedModule{{Module: "store"}}, Holds: []delivery.Holding{{Claim: "store-seat", Scope: "mesh", Module: "store"}}},
+			"b": {Node: "b", Modules: []delivery.PlacedModule{{Module: "store"}}}}
+		if recs, _ := grants.Records(in); holds(recs, "a") != 1 || holds(recs, "b") != 0 {
+			t.Errorf("placed, the seat is held on a %d and b %d times, want a alone", holds(recs, "a"), holds(recs, "b"))
+		}
+		b := fixture()
+		pl, _ := delivery.EncodePlacement(delivery.Placement{Node: "b", Modules: []delivery.PlacedModule{{Module: "mod-y"}, {Module: "mod-x"}}})
+		b.states[grants.ReadPlacement] = map[string][]byte{"placement.b": pl}
+		read := grants.ReadInputs(b, &grants.Manifests{})
+		if !slices.Contains(read.Assigned["b"], "mod-x") || read.Placed["b"].Node != "b" || slices.ContainsFunc(read.Gaps, func(g grants.Gap) bool { return g.Input == "seat holdings" }) {
+			t.Errorf("read: assigned %v, placed %v, gaps %v", read.Assigned, read.Placed, read.Gaps)
+		}
+		b.refused[grants.ReadPlacement] = true
+		if read := grants.ReadInputs(b, &grants.Manifests{}); slices.ContainsFunc(read.Gaps, func(g grants.Gap) bool { return g.Input == grants.ReadPlacement && g.Failed }) {
+			t.Errorf("placement not on the bus is a failed read: %v", read.Gaps)
+		}
+	})
+
 	t.Run("compare excuses a retired verb and a multiply claimed mesh seat's added subscriptions on its machines, nothing else", func(t *testing.T) {
 		const retired, store, storeInfo = "mesh.seat.mesh-delivery.tool.mark-ready", "mesh.seat.mesh-store.tool.databases", "$SRV.INFO.mesh-store.>"
 		two := map[string][]string{"mesh-store": {"a", "n"}}

modules/mesh-grants/internal/grants/follow.go

@@ -18,7 +18,7 @@ type Watcher interface {
 // Followed are the states whose change composes again: placement, the indexer's manifests by module, the resolved
 // config values, the node agents' haves (a machine's first have, and the bus node's loaded list) and the assigner's
 // wants (the manifest each machine is wanted to run), and the vault's hashes of the bus accounts.
-var Followed = []string{ReadAssignments, ReadModules, ReadResolved, ReadHave, ReadWants, ReadAccounts}
+var Followed = []string{ReadAssignments, ReadModules, ReadResolved, ReadHave, ReadWants, ReadAccounts, ReadPlacement}
 
 // Follower composes again on every change it hears, never on a timer. It never stops for a refusal: a watch it cannot
 // open is said, composed without, and opened again at the next wake (any change it does hear, or a reconnect).

modules/mesh-grants/internal/grants/inputs.go

@@ -34,11 +34,14 @@ const (
 	ReadBuilds          = "mesh-delivery-builder.builds"
 	// ReadAccounts is the vault's bcrypt hashes of the bus accounts it holds, by bus user (ADR 0547 clause 9).
 	ReadAccounts = "mesh-vault.bus-accounts"
+	// ReadPlacement is the indexer's placement, read from the catalogue (ADR 0549 §2, §3): each node's modules and the seats
+	// they hold.
+	ReadPlacement = "mesh-delivery-indexer.placement"
 )
 
 // Reads is every state the part reads, in the manifest's order.
 var Reads = []string{ReadAssignments, ReadControllerGrant, ReadModules, ReadManifests, ReadResolved, ReadHave, ReadWants, ReadBuilds,
-	ReadAccounts}
+	ReadAccounts, ReadPlacement}
 
 // The bus module's tools the part calls, as its manifest's invokes name them: read-only, each.
 const (
@@ -103,8 +106,12 @@ type resolved struct {
 type Inputs struct {
 	// Nodes is every machine seen: in a node agent's have or a standing assignment.
 	Nodes []string
-	// Assigned is each machine's standing assignments, sorted.
+	// Assigned is each machine's standing assignments and what the catalogue's placement puts there, sorted: while both
+	// stand (ADR 0549 §5) a module either names keeps its membership.
 	Assigned map[string][]string
+	// Placed is each node's placement as the indexer read it from the catalogue (ADR 0549 §2); empty before any is read.
+	// Where it is, a seat held once for the mesh is held where placement says, not wherever a module claiming it runs.
+	Placed map[string]delivery.Placement
 	// Manifests is each module's manifest at the indexer's trunk, by module.
 	Manifests map[string]catalogue.Manifest
 	// Digests is each module's manifest digest, by module.
@@ -230,6 +237,38 @@ func ReadInputs(r Reader, cache *Manifests) Inputs {
 			in.BusNode = a.Node
 		}
 	}
+	// The catalogue's placement (ADR 0549 §3): what it places is composed beside the assignments, and the seats held once
+	// for the mesh are held where it says. Not on the bus yet is a standing gap, never a failed read, so the list is still
+	// composed and sealed from the assignments alone.
+	if keys, err := r.Keys(ReadPlacement); err != nil {
+		in.Gaps = append(in.Gaps, Gap{Input: ReadPlacement, Why: "not read yet: the assignments alone place modules (" + err.Error() + ")"})
+	} else {
+		for _, k := range keys {
+			raw, found, err := r.Get(ReadPlacement, k)
+			if err != nil || !found {
+				continue
+			}
+			p, err := delivery.DecodePlacement(raw)
+			node, kerr := delivery.ParsePlacementKey(k)
+			if err != nil || kerr != nil || p.Node != node {
+				in.Gaps = append(in.Gaps, Gap{Input: ReadPlacement + " " + k, Why: "not a placement, so the node is composed from its assignments alone"})
+				continue
+			}
+			if in.Placed == nil {
+				in.Placed = map[string]delivery.Placement{}
+			}
+			in.Placed[node] = p
+			nodes[node] = true
+			for _, m := range p.Assigned() {
+				if !slices.Contains(in.Assigned[node], m) {
+					in.Assigned[node] = append(in.Assigned[node], m)
+				}
+			}
+		}
+	}
+	if len(in.Placed) > 0 {
+		in.Gaps = slices.DeleteFunc(in.Gaps, func(g Gap) bool { return g.Input == "seat holdings" })
+	}
 	haveKeys, err := r.Keys(ReadHave)
 	if err != nil {
 		in.Gaps = append(in.Gaps, Gap{Input: ReadHave, Why: "refused or absent: " + err.Error(), Failed: true})

modules/mesh-grants/internal/grants/records.go

@@ -7,6 +7,7 @@ import (
 
 	"git.novox.be/novox/mesh-sdk/go/buscompose"
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
 
 // Records is what the bus composer composes from, rebuilt from the bus (mesh-controller internal/inventory busrecords.go,
@@ -59,6 +60,9 @@ func Records(in Inputs) (buscompose.Records, []Gap) {
 				continue
 			}
 			d := declaredFor(m, seats, declarers)
+			if len(in.Placed) > 0 {
+				d.Holds = heldWherePlaced(d.Holds, in.Placed[node], m.Module)
+			}
 			for _, sr := range catalogue.ReadsGranted(m, here, node) {
 				d.KeyedReads = append(d.KeyedReads, buscompose.KeyedRead{Read: sr.Read, Key: sr.Key})
 			}
@@ -299,3 +303,22 @@ func hearsOf(m catalogue.Manifest, declared map[string]catalogue.Manifest, node
 	}
 	return out, touches, onEvents
 }
+
+// heldWherePlaced is a module's holds on a node as the catalogue's placement says them (ADR 0549 §1, §3): a seat held once
+// for the mesh is held there only when the node's placement names this module holding it, so a module claiming such a seat
+// on two machines holds it on the one placement names, not on both; a seat of every node is held wherever the module runs.
+func heldWherePlaced(holds []buscompose.Seat, p delivery.Placement, module string) []buscompose.Seat {
+	var out []buscompose.Seat
+	for _, h := range holds {
+		if h.Scope != "" && h.Scope != catalogue.ScopeMesh {
+			out = append(out, h)
+			continue
+		}
+		if slices.ContainsFunc(p.Holds, func(x delivery.Holding) bool {
+			return x.Claim == h.Name && x.Module == module && x.Kind == h.Kind
+		}) {
+			out = append(out, h)
+		}
+	}
+	return out
+}

modules/mesh-grants/module.json

@@ -10,6 +10,7 @@
     "mesh-delivery-builder.builds",
     "mesh-delivery-indexer.manifests",
     "mesh-delivery-indexer.modules",
+    "mesh-delivery-indexer.placement",
     "node-engine.have",
     "mesh-vault.bus-accounts"
   ],