Builder declares its read of the assigner's placement state, which its toolchain gate follows through meshmoduleassignerclient (ADR 0634 §1; issue 1966)

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

modules/mesh-delivery-builder/manifest_test.go

@@ -102,7 +102,7 @@ func TestManifestDeclarations(t *testing.T) { // 1607/AC1
 	// 1887/A4c: the builder chooses no node, so it reads neither presence nor have, invokes no build module's tool and
 	// holds no capacity; it puts asks on the three build seats and reads their steps (ADR 0525 §1, §4, §5).
 	if want := []string{"mesh-build-go.steps", "mesh-build-go.toolchains", "mesh-build-image.steps", "mesh-build-node.steps", "mesh-build-node.toolchains",
-		"mesh-delivery-gate.source"}; !reflect.DeepEqual(sorted(m.Reads), want) {
+		"mesh-delivery-assigner.placement", "mesh-delivery-gate.source"}; !reflect.DeepEqual(sorted(m.Reads), want) {
 		t.Errorf("reads = %v, want %v", m.Reads, want)
 	}
 	if want := []string{"node-build-go", "node-build-image", "node-build-node"}; !reflect.DeepEqual(sorted(m.Uses), want) {
@@ -115,7 +115,9 @@ func TestManifestDeclarations(t *testing.T) { // 1607/AC1
 	// read tools and followed by their views families, never read; so are the indexer's packages, whose names a package is
 	// numbered under (design 32).
 	for _, r := range m.Reads {
-		if strings.HasPrefix(r, "mesh-delivery-indexer.") || strings.HasPrefix(r, "mesh-delivery-assigner.") {
+		// The toolchain gate follows the assigner's placement through meshmoduleassignerclient (buildrun.PlacementBucket), so
+		// it declares that one read, as the console and route-proxy do; everything else of theirs is asked by tools.
+		if strings.HasPrefix(r, "mesh-delivery-indexer.") || (strings.HasPrefix(r, "mesh-delivery-assigner.") && r != "mesh-delivery-assigner.placement") {
 			t.Errorf("reads %s: the indexer's and the assigner's state is read by their tools and views families alone", r)
 		}
 	}

modules/mesh-delivery-builder/module.json

@@ -103,6 +103,7 @@
     "mesh-build-image.steps",
     "mesh-build-node.steps",
     "mesh-build-node.toolchains",
+    "mesh-delivery-assigner.placement",
     "mesh-delivery-gate.source"
   ],
   "uses": [