The bus node follows the grants part's sealed user list, and only the grants part reads the vault's hashes (ADR 0547 clauses 7, 9; issue 1945)

The grants part writes its list as an object of its own bucket, sealed to the bus node's key, and names it in
user-list.sealed; the node-engine of the node holding mesh-broker is granted that one key and an object by name, the
grants part its bucket (the controller's copy carries the same grants, byte for byte, golden regenerated there).
A state may name its readers (announce, NamedReaders): mesh-vault.bus-accounts is read by mesh-grants alone.

go/buscompose/users.go

@@ -147,14 +147,19 @@ func Users(r Records) ([]Principal, error) {
 	for _, node := range sortedCopy(r.Nodes) {
 		witness := false
 		var checks []string
+		bus := false
 		for _, d := range r.Assigned[node] {
 			if d.Module == controllerModule {
 				witness = true
 			}
+			if d.SnapshotsTheBus {
+				bus = true
+			}
 			checks = append(checks, d.Checks...)
 		}
 		out = append(out, Principal{Kind: KindNode, Node: node, WitnessesController: witness, Checks: checks,
-			MovesIntoTheVault: servesMoveIn(r), StatesItsKeyToTheVault: servesVerb(r, VaultNodeKey)})
+			MovesIntoTheVault: servesMoveIn(r), StatesItsKeyToTheVault: servesVerb(r, VaultNodeKey),
+			FollowsGrantsUserList: bus})
 		// **And the machine's provisioner client, on an account of its own** (novox/hq ADR 0349 clause 11): one
 		// per machine that runs it, delivered to the module running it.
 		for _, d := range r.Assigned[node] {
@@ -176,6 +181,9 @@ func Users(r Records) ([]Principal, error) {
 			}
 		}
 		for _, d := range r.Assigned[node] {
+			// A state with named readers is read by them alone (ADR 0547 clause 9): a read named for another module is
+			// granted nothing, here and in the runtime carrying the module.
+			d = withNamedReaders(d)
 			// **A process account is its own, delivered in its own secret** (broker-<process id>, novox/hq
 			// ADR 0436 §1, §2), never the module's `broker` — so it is composed whether or not the module
 			// itself has an account, and is never carried by the machine's runtime, which runs as the
@@ -223,6 +231,7 @@ func Users(r Records) ([]Principal, error) {
 			var carried []Declared
 			for _, d := range r.Assigned[node] {
 				if d.RunsAs == "" && runnerServes(d) {
+					d = withNamedReaders(d)
 					// Never a restricted stream for what the tool runner carries (novox/hq ADR 0376 §1).
 					d.Hears = ComposedHears(d)
 					carried = append(carried, d)