Hold a node's want until the grant names its account (issue 1945, rule 6 per node)

Rule 6 read only whether a grant of the module's fingerprint existed. A grant
written for the module's other nodes then let a node whose account was never
issued or sealed be wanted: on 2026-10-25 at 20:04 ace's mesh-build-go was
wanted with no ace.mesh-build-go on the bus, and crash-looped 20 times for
its missing credential. A grant that names accounts now grants a node only
when it names that node's own or a process's account; one that names none
grants every node, as before.
Research 072: the grants piece (memberships and credentials heard from placement).

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

@@ -129,6 +129,11 @@ func (p *passer) wants(ctx context.Context) {
 			m.Released = p.answeredWith(hold, "release")
 			m.Kept = p.answeredWith(hold, "keep")
 			m.Built, m.Held, m.Granted = p.w.built(name, fp), p.w.has(delivery.AssignerWantsBucket, held) && !m.Released, p.w.has(delivery.ControllerGrantsBucket, grant)
+			if raw := p.w.value(delivery.ControllerGrantsBucket, grant); raw != nil {
+				if g, err := delivery.DecodeControllerGrant(raw); err == nil {
+					m.GrantedOn = func(node string) bool { return assign.GrantNamesNode(g, node, name) }
+				}
+			}
 			if m.Released {
 				p.clearHeld(name, fp)
 			}

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

@@ -23,6 +23,10 @@ type Module struct {
 	// GrantedAt says whether the controller issued the module's credential for another fingerprint than FP: the first want of a node
 	// that runs an older one names it (issue 1945). Nil: none.
 	GrantedAt func(fp string) bool
+	// GrantedOn says whether the controller's grant of FP names the module's accounts on a node, when the grant names any:
+	// a grant written for the module's other nodes says nothing of a node whose account is not issued and sealed (issue
+	// 1945, live on 2026-10-25 at 20:04: ace's mesh-build-go was wanted with no account on the bus). Nil: the grant alone.
+	GrantedOn func(node string) 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
@@ -108,6 +112,10 @@ func holds(m Module, node string, n Nodes, ordering bool) (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 m.GrantedOn != nil && !m.GrantedOn(node) {
+		return false, delivery.RuleGrant, fmt.Sprintf("the controller has not issued the credential of %s on %s for %s", m.Name, node,
+			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))
 	}
@@ -466,3 +474,18 @@ func (m Module) userListRevision(node string, before delivery.Want, had bool, n
 	}
 	return w, true
 }
+
+// GrantNamesNode says whether a grant of module names its accounts on node: its own `<node>.<module>` or a process's
+// `<node>.<module>.<process>`. A grant that names no account (a module that does not speak on the bus) names every node.
+func GrantNamesNode(g delivery.ControllerGrant, node, module string) bool {
+	if len(g.Accounts) == 0 {
+		return true
+	}
+	own := node + "." + module
+	for _, a := range g.Accounts {
+		if a == own || strings.HasPrefix(a, own+".") {
+			return true
+		}
+	}
+	return false
+}

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

@@ -86,6 +86,33 @@ func TestEachRuleHoldsTheWantBack(t *testing.T) {
 			t.Errorf("rule %d broken: g14's want is %+v", rule, w)
 		}
 	}
+
+	// Rule 6 per node: a grant written for the module's other nodes does not grant a node whose account it does not name
+	// (issue 1945, live on 2026-10-25 at 20:04: ace's mesh-build-go was wanted with no account on the bus).
+	m, n := ready()
+	grant := delivery.ControllerGrant{Accounts: []string{"ace.mail", "ace.mail.send"}}
+	m.GrantedOn = func(node string) bool { return GrantNamesNode(grant, node, "mail") }
+	out := Wants(m, n, wantedOld(), nil)
+	if w := out.Wants["ace"]; w.FP != fNew {
+		t.Errorf("ace, whose account the grant names, wants %+v", w)
+	}
+	if got := out.Rules["g14"]; got.Rule != delivery.RuleGrant || !strings.Contains(got.Words, "on g14") {
+		t.Errorf("g14, whose account the grant does not name, is held by %+v", got)
+	}
+	for _, c := range []struct {
+		accounts     []string
+		node, module string
+		named        bool
+	}{
+		{nil, "g14", "mail", true},
+		{[]string{"g14.mail.send"}, "g14", "mail", true},
+		{[]string{"g14.mailer"}, "g14", "mail", false},
+		{[]string{"ace.mail"}, "g14", "mail", false},
+	} {
+		if got := GrantNamesNode(delivery.ControllerGrant{Accounts: c.accounts}, c.node, c.module); got != c.named {
+			t.Errorf("%v names %s of %s: %v, want %v", c.accounts, c.module, c.node, got, c.named)
+		}
+	}
 }
 
 // 1297/B4, ADR 0435 §3: a canary that is offline is passed over: the next node by name is the canary, and moves first.