diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/integration_test.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/integration_test.go
index 506d92b..16f7e01 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/integration_test.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/integration_test.go
@@ -168,6 +168,27 @@ func (b *bed) putJSON(t *testing.T, bucket, key string, value []byte) {
 	}
 }
 
+// compose says the controller composed module for node at fp, with the digest d (a letter repeated) and the judgement of the
+// move to it, in mesh-controller_composed.
+func (b *bed) compose(t *testing.T, node, module, fp string, d byte, judgement delivery.Judgement) string {
+	t.Helper()
+	key, err := delivery.ComposedKey(node, module, fp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	digest := "sha256:" + strings.Repeat(string(d), 64)
+	cd := delivery.ComposedDigest{Digest: digest, Judgement: judgement}
+	if judgement != delivery.JudgedNeither {
+		cd.Against, cd.Words = "sha256:"+strings.Repeat("0", 64), "cannot be told"
+	}
+	v, err := delivery.EncodeComposedDigest(cd)
+	if err != nil {
+		t.Fatal(err)
+	}
+	b.putJSON(t, delivery.ControllerComposedBucket, key, v)
+	return digest
+}
+
 // manifest keeps a manifest in the indexer's bucket by its digest and answers the digest.
 func (b *bed) manifest(t *testing.T, module, body string) string {
 	t.Helper()
@@ -260,6 +281,8 @@ func TestWantsAreWrittenAndNoDifferenceIs(t *testing.T) {
 	gkey, _ := delivery.ControllerGrantKey("web", fNew)
 	grant, _ := delivery.EncodeControllerGrant(delivery.ControllerGrant{})
 	b.putJSON(t, delivery.ControllerGrantsBucket, gkey, grant)
+	b.compose(t, "ace", "web", fNew, 'c', delivery.JudgedNeither)
+	b.compose(t, "g14", "web", fNew, 'c', delivery.JudgedNeither)
 	for _, node := range []string{"ace", "g14"} {
 		on, _ := delivery.EncodePresence(delivery.Presence{Online: true})
 		b.putJSON(t, delivery.PresenceBucket, node, on)
@@ -356,7 +379,7 @@ func TestAFailedDataModuleIsAskedToRestore(t *testing.T) {
 	failed, _ := delivery.EncodeHave(delivery.Have{FP: fNew, Phase: delivery.PhaseRunning, Health: delivery.HealthFailed, Detail: "connection refused"})
 	b.putJSON(t, delivery.HaveBucket, "ace.mail", failed)
 	wantKey, _ := delivery.WantKey("ace", "mail")
-	want, _ := delivery.EncodeWant(delivery.Want{FP: fNew})
+	want, _ := delivery.EncodeWant(delivery.Want{FP: fNew, Composed: "sha256:" + strings.Repeat("c", 64)})
 	b.putJSON(t, delivery.AssignerWantsBucket, wantKey, want)
 	b.putJSON(t, provider.AssignmentsBucket, "ace.mail", []byte(`{"node":"ace","module":"mail","build":"b-1"}`))
 	b.start(t)
@@ -410,6 +433,7 @@ func TestTheAssignerReplacedResumesWithNothingLostOrRepeated(t *testing.T) {
 		gkey, _ := delivery.ControllerGrantKey(name, fp)
 		grant, _ := delivery.EncodeControllerGrant(delivery.ControllerGrant{})
 		b.putJSON(t, delivery.ControllerGrantsBucket, gkey, grant)
+		b.compose(t, "ace", name, fp, 'c', delivery.JudgedNeither)
 		b.putJSON(t, provider.AssignmentsBucket, "ace."+name, []byte(fmt.Sprintf(`{"node":"ace","module":%q,"build":"b-%d"}`, name, i)))
 	}
 	count := func() int {
@@ -439,3 +463,55 @@ func TestTheAssignerReplacedResumesWithNothingLostOrRepeated(t *testing.T) {
 		}
 	}
 }
+
+// 1906/D2 (ADR 0539 §6), whole on the bus: a want waits for the composition of its module for the node, names its digest once it
+// appears, and a new revision of the composition at the same fingerprint is written as a new want; the node's own want
+// `want.<node>.node` is written once the node's composition exists, and again when its digest changes.
+func TestAWantWaitsForItsComposition(t *testing.T) {
+	b := startBed(t, "")
+	fNew := delivery.SourcePrefix2 + strings.Repeat("e", 64)
+	digest := b.manifest(t, "web", `{"module":"web","version":"1"}`)
+	mod, _ := delivery.EncodeModule(delivery.Module{FP2: fNew, Manifest: digest, Repository: "novox/web", Commit: strings.Repeat("1", 40), Path: delivery.RootPath})
+	b.putJSON(t, delivery.ModulesBucket, "web", mod)
+	built, _ := delivery.EncodeBuilderBuild(delivery.BuilderBuild{State: delivery.BuildDone, By: "builder.novox.1", Step: "pushed", Manifest: digest})
+	bkey, _ := delivery.BuilderBuildKey("web", fNew)
+	b.putJSON(t, delivery.BuilderBuildsBucket, bkey, built)
+	gkey, _ := delivery.ControllerGrantKey("web", fNew)
+	grant, _ := delivery.EncodeControllerGrant(delivery.ControllerGrant{})
+	b.putJSON(t, delivery.ControllerGrantsBucket, gkey, grant)
+	on, _ := delivery.EncodePresence(delivery.Presence{Online: true})
+	b.putJSON(t, delivery.PresenceBucket, "ace", on)
+	b.putJSON(t, provider.AssignmentsBucket, "ace.web", []byte(`{"node":"ace","module":"web","build":"b-1"}`))
+	b.start(t)
+	wkey, _ := delivery.WantKey("ace", "web")
+	time.Sleep(time.Second)
+	if e, err := b.buckets[delivery.AssignerWantsBucket].Get(b.ctx, wkey); err == nil {
+		t.Fatalf("a want was written before the composition existed: %s", e.Value())
+	}
+	first := b.compose(t, "ace", "web", fNew, 'c', delivery.JudgedNeither)
+	if w, err := delivery.DecodeWant(b.get(t, delivery.AssignerWantsBucket, wkey)); err != nil || w.FP != fNew || w.Composed != first {
+		t.Fatalf("the want = %+v, %v; want F naming %s", w, err, first)
+	}
+	second := b.compose(t, "ace", "web", fNew, 'd', delivery.JudgedNeither)
+	for deadline := time.Now().Add(10 * time.Second); time.Now().Before(deadline); time.Sleep(50 * time.Millisecond) {
+		if e, err := b.buckets[delivery.AssignerWantsBucket].Get(b.ctx, wkey); err == nil {
+			if w, err := delivery.DecodeWant(e.Value()); err == nil && w.Composed == second {
+				break
+			}
+		}
+	}
+	if w, err := delivery.DecodeWant(b.get(t, delivery.AssignerWantsBucket, wkey)); err != nil || w.Composed != second {
+		t.Fatalf("after a new revision at the same fingerprint the want = %+v, %v; want it naming %s", w, err, second)
+	}
+	// the node's own want
+	nkey, _ := delivery.WantNodeKey("ace")
+	if e, err := b.buckets[delivery.AssignerWantsBucket].Get(b.ctx, nkey); err == nil {
+		t.Fatalf("the node's own want was written before its composition: %s", e.Value())
+	}
+	ownKey, _ := delivery.ComposedNodeKey("ace")
+	own, _ := delivery.EncodeComposedDigest(delivery.ComposedDigest{Digest: "sha256:" + strings.Repeat("a", 64), Judgement: delivery.JudgedNeither})
+	b.putJSON(t, delivery.ControllerComposedBucket, ownKey, own)
+	if w, err := delivery.DecodeNodeWant(b.get(t, delivery.AssignerWantsBucket, nkey)); err != nil || w.Composed != "sha256:"+strings.Repeat("a", 64) {
+		t.Fatalf("the node's own want = %+v, %v", w, err)
+	}
+}
diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go
index 7fdea8b..980abe2 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go
@@ -41,6 +41,7 @@ func main() {
 var readBuckets = []string{
 	provider.AssignmentsBucket,
 	delivery.ControllerGrantsBucket,
+	delivery.ControllerComposedBucket,
 	delivery.BuilderBuildsBucket,
 	delivery.CandidatesBucket,
 	delivery.ManifestsBucket,
@@ -132,6 +133,7 @@ func run(ctx context.Context, getenv func(string) string, logOut io.Writer) erro
 var watched = []string{
 	provider.AssignmentsBucket,
 	delivery.ControllerGrantsBucket,
+	delivery.ControllerComposedBucket,
 	delivery.BuilderBuildsBucket,
 	delivery.CandidatesBucket,
 	delivery.ModulesBucket,
diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/pass.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/pass.go
index ea1a1b4..ceb7223 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/pass.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/pass.go
@@ -29,6 +29,24 @@ type passer struct {
 func (p *passer) pass(ctx context.Context) {
 	p.compositions(ctx)
 	p.wants(ctx)
+	p.nodeWants(ctx)
+}
+
+// nodeWants writes each node's own want, `want.<node>.node`, naming the digest of the node's own composition, once the
+// 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)
+	for node, d := range p.w.nodeComposed() {
+		key, err := delivery.WantNodeKey(node)
+		if err != nil {
+			continue
+		}
+		if before, err := delivery.DecodeNodeWant(written[key]); err == nil && before.Composed == d.Digest {
+			continue
+		}
+		want := delivery.NodeWant{Composed: d.Digest, Words: "the node's own composition"}
+		p.put(ctx, delivery.AssignerWantsBucket, key, func() ([]byte, error) { return delivery.EncodeNodeWant(want) })
+	}
 }
 
 // wants writes, for every module the trunk holds a fingerprint of, each node's want by the six rules (ADR 0429 §6), and
@@ -64,7 +82,9 @@ func (p *passer) wants(ctx context.Context) {
 	}
 	for name := range names {
 		fp := trunk[name].FP2
-		m := assign.Module{Name: name, FP: fp, Manifest: manifests[name], Nodes: nodesOf[name]}
+		name := name
+		m := assign.Module{Name: name, FP: fp, Manifest: manifests[name], Nodes: nodesOf[name],
+			Composed: func(node, fp string) (delivery.ComposedDigest, bool) { return p.w.composed(node, name, fp) }}
 		if fp != "" {
 			held, _ := delivery.HeldKey(name, fp)
 			grant, _ := delivery.ControllerGrantKey(name, fp)
diff --git a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/world.go b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/world.go
index 1c185eb..48bcbea 100644
--- a/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/world.go
+++ b/modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/world.go
@@ -342,3 +342,35 @@ func (w *world) built(module, fp string) bool {
 	b, err := delivery.DecodeBuilderBuild(value)
 	return err == nil && b.State == delivery.BuildDone
 }
+
+// composed is the controller's composition of module for node at fp: its digest and the judgement of the move to it
+// (mesh-controller_composed `<node>.<module>.<hex>`), and whether it exists and can be read.
+func (w *world) composed(node, module, fp string) (delivery.ComposedDigest, bool) {
+	key, err := delivery.ComposedKey(node, module, fp)
+	if err != nil {
+		return delivery.ComposedDigest{}, false
+	}
+	w.mu.Lock()
+	value, ok := w.values[delivery.ControllerComposedBucket][key]
+	w.mu.Unlock()
+	if !ok {
+		return delivery.ComposedDigest{}, false
+	}
+	d, err := delivery.DecodeComposedDigest(value)
+	return d, err == nil
+}
+
+// nodeComposed is, by node, the digest of the node's own composition (mesh-controller_composed `<node>.node`).
+func (w *world) nodeComposed() map[string]delivery.ComposedDigest {
+	out := map[string]delivery.ComposedDigest{}
+	for key, value := range w.read(delivery.ControllerComposedBucket) {
+		node, _, _, isNode, err := delivery.ParseComposedKey(key)
+		if err != nil || !isNode {
+			continue
+		}
+		if d, err := delivery.DecodeComposedDigest(value); err == nil {
+			out[node] = d
+		}
+	}
+	return out
+}
diff --git a/modules/mesh-delivery-assigner/internal/assign/wants.go b/modules/mesh-delivery-assigner/internal/assign/wants.go
index 8615a3a..d10e2a4 100644
--- a/modules/mesh-delivery-assigner/internal/assign/wants.go
+++ b/modules/mesh-delivery-assigner/internal/assign/wants.go
@@ -20,6 +20,16 @@ type Module struct {
 	Granted  bool
 	Manifest catalogue.Manifest
 	Nodes    []string
+	// Composed answers the controller's composition of the module for a node at a fingerprint (mesh-controller_composed): its
+	// digest and the judgement of the move to it, and whether it exists. Nil: none exists (ADR 0539 §1, §6).
+	Composed func(node, fp string) (delivery.ComposedDigest, bool)
+}
+
+func (m Module) composition(node, fp string) (delivery.ComposedDigest, bool) {
+	if m.Composed == nil {
+		return delivery.ComposedDigest{}, false
+	}
+	return m.Composed(node, fp)
 }
 
 // Node is what the rules read of the nodes: whether each is online (the watchman's presence) and each module's have.
@@ -72,6 +82,9 @@ func Holds(m Module, node string, n Nodes) (bool, int, string) {
 	if !m.Granted {
 		return false, delivery.RuleGrant, fmt.Sprintf("the controller has not issued the credential of %s for %s", m.Name, short(m.FP))
 	}
+	if _, ok := m.composition(node, m.FP); !ok {
+		return false, delivery.RuleComposed, fmt.Sprintf("the controller has not composed %s for %s at %s", m.Name, node, short(m.FP))
+	}
 	return true, 0, ""
 }
 
@@ -157,7 +170,8 @@ func Wants(m Module, n Nodes, wants map[string]delivery.Want, lastHealthy map[st
 		var next delivery.Want
 		switch ok, rule, words := Holds(mm, node, n); {
 		case ok:
-			next = delivery.Want{FP: m.FP}
+			d, _ := m.composition(node, m.FP)
+			next = delivery.Want{FP: m.FP, Composed: d.Digest}
 		case held && had && before.FP == m.FP:
 			out.Rules[node] = Holding{Rule: rule, Words: words}
 			last := lastHealthy[node]
@@ -170,16 +184,22 @@ func Wants(m Module, n Nodes, wants map[string]delivery.Want, lastHealthy map[st
 				next = before
 				next.Words = fmt.Sprintf("%s is held at %s and %s ran no other fingerprint healthy to set it back to", m.Name, short(m.FP), node)
 			default:
-				next = delivery.Want{FP: last, Newest: m.FP, Rule: rule, Words: words}
+				d, there := m.composition(node, last)
+				if !there {
+					next = before
+					next.Words = fmt.Sprintf("%s is held at %s, and the composition of %s at %s is gone, so %s is not set back", m.Name, short(m.FP), m.Name, short(last), node)
+					break
+				}
+				next = delivery.Want{FP: last, Composed: d.Digest, Newest: m.FP, Rule: rule, Words: words}
 			}
 		default:
 			out.Rules[node] = Holding{Rule: rule, Words: words}
 			if !had || before.Removed {
 				continue
 			}
-			next = delivery.Want{FP: before.FP, Newest: m.FP, Rule: rule, Words: words}
+			next = delivery.Want{FP: before.FP, Composed: before.Composed, Newest: m.FP, Rule: rule, Words: words}
 			if before.FP == m.FP {
-				next = delivery.Want{FP: m.FP}
+				next = delivery.Want{FP: m.FP, Composed: before.Composed}
 			}
 		}
 		if !had || !delivery.SameWant(normal(before), normal(next)) {
diff --git a/modules/mesh-delivery-assigner/internal/assign/wants_test.go b/modules/mesh-delivery-assigner/internal/assign/wants_test.go
index cdae3cd..d29ceb5 100644
--- a/modules/mesh-delivery-assigner/internal/assign/wants_test.go
+++ b/modules/mesh-delivery-assigner/internal/assign/wants_test.go
@@ -19,7 +19,7 @@ var (
 // ready is a module mail at fNew on ace and g14 for which every rule holds: built, not held, granted, its provider
 // store healthy on ace and the canary ace running fNew healthy.
 func ready() (Module, Nodes) {
-	m := Module{Name: "mail", FP: fNew, Built: true, Granted: true, Nodes: []string{"g14", "ace"},
+	m := Module{Name: "mail", FP: fNew, Built: true, Granted: true, Composed: composedEverywhere, Nodes: []string{"g14", "ace"},
 		Manifest: catalogue.Manifest{Module: "mail", Requires: []string{"database"}}}
 	n := Nodes{
 		Online: map[string]bool{"ace": true, "g14": true},
@@ -32,8 +32,16 @@ func ready() (Module, Nodes) {
 	return m, n
 }
 
+// dig is the digest of the composition at a fingerprint in these tests: the fingerprint's last character repeated.
+func dig(fp string) string { return "sha256:" + strings.Repeat(fp[len(fp)-1:], 64) }
+
+// composedEverywhere is a Module.Composed with a composition for every node at every fingerprint, judged neither.
+func composedEverywhere(_, fp string) (delivery.ComposedDigest, bool) {
+	return delivery.ComposedDigest{Digest: dig(fp), Judgement: delivery.JudgedNeither}, true
+}
+
 func wantedOld() map[string]delivery.Want {
-	return map[string]delivery.Want{"ace": {FP: fOld}, "g14": {FP: fOld}}
+	return map[string]delivery.Want{"ace": {FP: fOld, Composed: dig(fOld)}, "g14": {FP: fOld, Composed: dig(fOld)}}
 }
 
 // 1297/B4: with every rule holding, both nodes' wants move to the new fingerprint (the canary ace runs it healthy, so
@@ -42,7 +50,7 @@ func TestEveryRuleHoldsSoTheWantsMove(t *testing.T) {
 	m, n := ready()
 	out := Wants(m, n, wantedOld(), nil)
 	for _, node := range []string{"ace", "g14"} {
-		if out.Wants[node].FP != fNew || out.Wants[node].Rule != 0 {
+		if out.Wants[node].FP != fNew || out.Wants[node].Rule != 0 || out.Wants[node].Composed != dig(fNew) {
 			t.Errorf("%s's want = %+v, want %s", node, out.Wants[node], fNew)
 		}
 	}
@@ -60,6 +68,9 @@ func TestEachRuleHoldsTheWantBack(t *testing.T) {
 			n.Haves["ace"]["store"] = delivery.Have{FP: fpOf('s'), Phase: delivery.PhaseRunning, Health: delivery.HealthWaits}
 		},
 		delivery.RuleGrant: func(m *Module, _ *Nodes) { m.Granted = false },
+		delivery.RuleComposed: func(m *Module, _ *Nodes) {
+			m.Composed = func(string, string) (delivery.ComposedDigest, bool) { return delivery.ComposedDigest{}, false }
+		},
 	} {
 		m, n := ready()
 		breakIt(&m, &n)
@@ -99,11 +110,11 @@ func TestAnOfflineCanaryIsPassedOver(t *testing.T) {
 func TestAFailedHealthHoldsAndSetsBack(t *testing.T) {
 	m, n := ready()
 	n.Haves["ace"]["mail"] = delivery.Have{FP: fNew, Phase: delivery.PhaseRunning, Health: delivery.HealthFailed, Detail: "connection refused"}
-	out := Wants(m, n, map[string]delivery.Want{"ace": {FP: fNew}, "g14": {FP: fOld}}, map[string]string{"ace": fOld})
+	out := Wants(m, n, map[string]delivery.Want{"ace": {FP: fNew, Composed: dig(fNew)}, "g14": {FP: fOld, Composed: dig(fOld)}}, map[string]string{"ace": fOld})
 	if out.Held == nil || out.Held.Node != "ace" || out.Held.Words != "connection refused" {
 		t.Fatalf("held = %+v", out.Held)
 	}
-	if w := out.Wants["ace"]; w.FP != fOld || w.Newest != fNew || w.Rule != delivery.RuleNotHeld {
+	if w := out.Wants["ace"]; w.FP != fOld || w.Composed != dig(fOld) || w.Newest != fNew || w.Rule != delivery.RuleNotHeld {
 		t.Errorf("ace's want = %+v, want set back to the last healthy fingerprint", w)
 	}
 	if w, ok := out.Wants["g14"]; ok && w.FP == fNew {
@@ -144,7 +155,7 @@ func TestAModuleWithoutDataIsNotAskedToRestore(t *testing.T) {
 func TestALeavingNodeIsRemovedAndNothingIsWrittenTwice(t *testing.T) {
 	m, n := ready()
 	m.Nodes = []string{"ace"}
-	out := Wants(m, n, map[string]delivery.Want{"ace": {V: 1, FP: fNew}, "g14": {FP: fOld}}, nil)
+	out := Wants(m, n, map[string]delivery.Want{"ace": {V: 1, FP: fNew, Composed: dig(fNew)}, "g14": {FP: fOld, Composed: dig(fOld)}}, nil)
 	if w := out.Wants["g14"]; !w.Removed {
 		t.Errorf("g14's want = %+v, want removed", w)
 	}
@@ -152,3 +163,81 @@ func TestALeavingNodeIsRemovedAndNothingIsWrittenTwice(t *testing.T) {
 		t.Errorf("ace's want, unchanged, was written again: %+v", out.Wants["ace"])
 	}
 }
+
+// 1906/D2 (ADR 0539 §6): the seventh rule. A want waits for the composition of the module for that node at F, and names its
+// digest once it exists; a node with no want before still gets none until then.
+func TestAWantWaitsForItsCompositionAndNamesItsDigest(t *testing.T) {
+	m, n := ready()
+	have := map[string]bool{}
+	m.Composed = func(node, fp string) (delivery.ComposedDigest, bool) {
+		if !have[node+"|"+fp] {
+			return delivery.ComposedDigest{}, false
+		}
+		return composedEverywhere(node, fp)
+	}
+	out := Wants(m, n, wantedOld(), nil)
+	for node, w := range out.Wants {
+		if w.FP == fNew {
+			t.Errorf("%s's want moved to F before its composition exists: %+v", node, w)
+		}
+	}
+	if r := out.Rules["ace"]; r.Rule != delivery.RuleComposed || !strings.Contains(r.Words, "ace") {
+		t.Errorf("ace is held back by %+v, want rule 7 naming the node", r)
+	}
+	// and a node that never had a want gets none
+	if out := Wants(m, n, nil, nil); len(out.Wants) != 0 {
+		t.Errorf("wants without a composition: %+v", out.Wants)
+	}
+	have["ace|"+fNew] = true
+	out = Wants(m, n, wantedOld(), nil)
+	if w := out.Wants["ace"]; w.FP != fNew || w.Composed != dig(fNew) {
+		t.Errorf("ace's want = %+v, want F naming the composition's digest", w)
+	}
+	if w, ok := out.Wants["g14"]; ok && w.FP == fNew {
+		t.Errorf("g14, whose composition does not exist, moved: %+v", w)
+	}
+}
+
+// 1906/D2 (ADR 0539 §5): a new revision of the composition at the same fingerprint reaches the node only through a new want,
+// by the same rules: written when they hold, and not while one does not.
+func TestARevisionAtTheSameFingerprintIsAWantByTheSameRules(t *testing.T) {
+	m, n := ready()
+	revised := "sha256:" + strings.Repeat("9", 64)
+	m.Composed = func(node, fp string) (delivery.ComposedDigest, bool) {
+		return delivery.ComposedDigest{Digest: revised, Judgement: delivery.JudgedNeither}, true
+	}
+	running := map[string]delivery.Want{"ace": {FP: fNew, Composed: dig(fNew)}, "g14": {FP: fNew, Composed: dig(fNew)}}
+	out := Wants(m, n, running, nil)
+	for _, node := range []string{"ace", "g14"} {
+		if w := out.Wants[node]; w.FP != fNew || w.Composed != revised {
+			t.Errorf("%s's want = %+v, want F naming the revised digest", node, w)
+		}
+	}
+	m.Granted = false
+	out = Wants(m, n, running, nil)
+	if w, ok := out.Wants["ace"]; ok && w.Composed == revised {
+		t.Errorf("a revision was written while a rule holds: %+v", w)
+	}
+}
+
+// 1906/D2: a set-back names the composition of the fingerprint it sets back to, and when that is gone the want stays and says so.
+func TestASetBackNamesTheOlderCompositionOrStays(t *testing.T) {
+	m, n := ready()
+	n.Haves["ace"]["mail"] = delivery.Have{FP: fNew, Phase: delivery.PhaseRunning, Health: delivery.HealthFailed, Detail: "x"}
+	running := map[string]delivery.Want{"ace": {FP: fNew, Composed: dig(fNew)}}
+	m.Composed = func(node, fp string) (delivery.ComposedDigest, bool) {
+		if fp == fOld {
+			return delivery.ComposedDigest{}, false
+		}
+		return composedEverywhere(node, fp)
+	}
+	out := Wants(m, n, running, map[string]string{"ace": fOld})
+	if w := out.Wants["ace"]; w.FP == fOld {
+		t.Errorf("set back to a fingerprint whose composition is gone: %+v", w)
+	}
+	m.Composed = composedEverywhere
+	out = Wants(m, n, running, map[string]string{"ace": fOld})
+	if w := out.Wants["ace"]; w.FP != fOld || w.Composed != dig(fOld) {
+		t.Errorf("set-back want = %+v", w)
+	}
+}
diff --git a/modules/mesh-delivery-assigner/manifest_test.go b/modules/mesh-delivery-assigner/manifest_test.go
index 13508e5..31f2192 100644
--- a/modules/mesh-delivery-assigner/manifest_test.go
+++ b/modules/mesh-delivery-assigner/manifest_test.go
@@ -32,7 +32,7 @@ func TestManifest(t *testing.T) {
 	}
 	reads := slices.Clone(m.Reads)
 	slices.Sort(reads)
-	want := []string{"mesh-controller.assignments", "mesh-controller.grants",
+	want := []string{"mesh-controller.assignments", "mesh-controller.composed", "mesh-controller.grants",
 		"mesh-delivery-builder.builds", "mesh-delivery-indexer.candidates", "mesh-delivery-indexer.manifests",
 		"mesh-delivery-indexer.modules", "mesh-delivery-watchman.presence", "node-engine.have"}
 	if !reflect.DeepEqual(reads, want) {
diff --git a/modules/mesh-delivery-assigner/module.json b/modules/mesh-delivery-assigner/module.json
index 2d8b303..38541cc 100644
--- a/modules/mesh-delivery-assigner/module.json
+++ b/modules/mesh-delivery-assigner/module.json
@@ -4,6 +4,7 @@
   "slug": "assigner",
   "reads": [
     "mesh-controller.assignments",
+    "mesh-controller.composed",
     "mesh-controller.grants",
     "mesh-delivery-builder.builds",
     "mesh-delivery-indexer.candidates",