Carry a module on the tool runner only when the runner has something of it to serve, so a part on its own credential has one writer (issue 1329)

internal/broker/delivery_gate_grant_test.go

@@ -67,8 +67,8 @@ func TestTheGatesBucketsAreWritableByItsMachinesToolRunner(t *testing.T) {
 		if !canRead(runner, read, "k") {
 			t.Errorf("novox's tool runner may not read %s, which the gate declares reading", read)
 		}
-		// (The runner may write the teller's answers: the teller declares no runs-as, so the runner carries it too. See the report of issue 1326.)
+		// 1329/AC3: the runner no longer carries the teller, so it may not write the teller's answers either.
-		if canWrite(runner, read, "k") && read != "mesh-delivery-teller_answers" {
+		if canWrite(runner, read, "k") {
 			t.Errorf("novox's tool runner may write %s, which the gate only reads", read)
 		}
 	}

internal/broker/delivery_parts_grant_test.go

@@ -13,8 +13,9 @@ import (
 // and streams, `reads` watching another module's bucket and never writing it, `consumes` hearing the named events,
 // `invokes` calling the named tools, `uses` the seat operator-channel's by-caller subjects under the module's own name.
 //
-// The three manifests are copied from mesh-delivery's main at 6a23627426c6 (modules/<module>/module.json, read
+// The four manifests (the watchman's is the fourth, issue 1329) are copied from mesh-delivery's main at 9c15112d935a
-// 2026-10-19), whole, so a change to one of them there that changes its grant is a change to read here.
+// (modules/<module>/module.json, read 2026-10-20; the first three are unchanged since 6a23627426c6), whole, so a change
+// to one of them there that changes its grant is a change to read here.
 const bridgeManifest = `{
   "module": "mesh-delivery-forge-bridge",
   "version": "1",
@@ -160,6 +161,69 @@ const indexerManifest = `{
   }
 }`
 
+const watchmanManifest = `{
+  "module": "mesh-delivery-watchman",
+  "version": "1",
+  "slug": "watchman",
+  "reads": [
+    "mesh-controller.checks-running"
+  ],
+  "state": [
+    { "name": "presence", "history": 20 },
+    { "name": "pulse", "key-ttl": true },
+    { "name": "stuck", "history": 20 }
+  ],
+  "own-secrets": {
+    "broker": "${dir:state}/broker"
+  },
+  "secrets-owner": "mesh-delivery-watchman",
+  "resources": [
+    {
+      "id": "account",
+      "type": "user",
+      "name": "mesh-delivery-watchman",
+      "shell": "/usr/bin/nologin",
+      "home": "/var/lib/mesh-delivery-watchman"
+    },
+    {
+      "id": "state",
+      "type": "directory",
+      "mode": "0700",
+      "owner": "mesh-delivery-watchman",
+      "place": ".",
+      "unknown": "program"
+    },
+    {
+      "id": "watchman",
+      "type": "process",
+      "name": "mesh-delivery-watchman",
+      "artifact": "program",
+      "run": [
+        "./mesh-delivery-watchman"
+      ],
+      "env": {
+        "MESH_BROKER_FILE": "${dir:state}/broker"
+      },
+      "user": "mesh-delivery-watchman",
+      "health": {
+        "kind": "unit"
+      }
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "program",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/mesh-delivery-watchman",
+        "binary": "mesh-delivery-watchman"
+      }
+    ]
+  }
+}`
+
 const tellerManifest = `{
   "module": "mesh-delivery-teller",
   "version": "1",
@@ -488,3 +552,87 @@ func TestNoPartsCredentialReachesBeyondItsDeclaration(t *testing.T) {
 		}
 	}
 }
+
+// toolServer is a module that serves a tool on its own broker credential: the runner carries it (ADR 0175).
+func toolServer() Declared {
+	return Declared{Module: "some-tools", Serves: []string{"some_tool"},
+		State: []Bucket{{Module: "some-tools", Name: "kept", History: 1}}}
+}
+
+// 1329/AC1: composed from the manifests of mesh-delivery's main, the machine's tool runner may write no bucket of the
+// forge bridge, the indexer, the teller or the watchman, publish none of their stream events nor the teller's
+// operator-channel accept subjects, and pull none of their consumers; each part's own credential still may.
+func TestTheToolRunnerCarriesNoneOfTheDeliverysParts(t *testing.T) {
+	streams := map[string]ModuleStream{"mesh-delivery-forge-bridge": {Module: "mesh-delivery-forge-bridge", Name: "FORGE"}}
+	all := composed(t, Records{Nodes: []string{"novox"}, Assigned: map[string][]Declared{"novox": {
+		{Module: RuntimeModule}, declaredOf(t, bridgeManifest, streams), declaredOf(t, indexerManifest, streams),
+		declaredOf(t, tellerManifest, streams), declaredOf(t, watchmanManifest, streams),
+	}}})
+	runner := all["runner@novox"]
+	buckets := map[string][]string{
+		"mesh-delivery-forge-bridge": {"heads"}, "mesh-delivery-indexer": {"candidates", "modules"},
+		"mesh-delivery-teller": {"answers"}, "mesh-delivery-watchman": {"presence", "pulse", "stuck"},
+	}
+	for part, names := range buckets {
+		own, there := all[part+"@novox"]
+		if !there {
+			t.Errorf("%s has no credential of its own", part)
+			continue
+		}
+		for _, name := range names {
+			if canWrite(runner, part+"_"+name, "some.key") {
+				t.Errorf("novox's tool runner may write %s_%s", part, name)
+			}
+			if !canWrite(own, part+"_"+name, "some.key") {
+				t.Errorf("%s may not write its own bucket %s", part, name)
+			}
+		}
+	}
+	for _, subject := range []string{
+		"mesh.stream.mesh-delivery-forge-bridge.event.forge.merged",
+		"mesh.seat.operator-channel.accept.ask.mesh-delivery-teller",
+		"mesh.seat.operator-channel.accept.cancel.mesh-delivery-teller",
+		"mesh.seat.operator-channel.accept.condition.mesh-delivery-teller",
+		"$JS.API.CONSUMER.MSG.NEXT.FORGE.novox_mesh-delivery-indexer",
+	} {
+		if allowed(runner.Publish, subject) {
+			t.Errorf("novox's tool runner may publish %s", subject)
+		}
+	}
+	if !allowed(all["mesh-delivery-forge-bridge@novox"].Publish, "mesh.stream.mesh-delivery-forge-bridge.event.forge.merged") ||
+		!allowed(all["mesh-delivery-teller@novox"].Publish, "mesh.seat.operator-channel.accept.ask.mesh-delivery-teller") ||
+		!allowed(all["mesh-delivery-indexer@novox"].Publish, "$JS.API.CONSUMER.MSG.NEXT.FORGE.novox_mesh-delivery-indexer") {
+		t.Error("a part's own credential lost what its manifest grants")
+	}
+}
+
+// 1329/AC2: a module with tools and a broker secret of its own stays carried by the tool runner, beside its own
+// credential (ADR 0175); a module with neither tools, a seat, waits nor a check is not.
+func TestTheToolRunnerStillCarriesAModuleWithToolsAndItsOwnCredential(t *testing.T) {
+	process := Declared{Module: "only-process", State: []Bucket{{Module: "only-process", Name: "mine", History: 1}}}
+	all := composed(t, Records{Nodes: []string{"novox"}, Assigned: map[string][]Declared{"novox": {
+		{Module: RuntimeModule}, toolServer(), process,
+	}}})
+	runner := all["runner@novox"]
+	if !canWrite(runner, "some-tools_kept", "k") {
+		t.Error("novox's tool runner does not carry a module with tools")
+	}
+	if !canWrite(all["some-tools@novox"], "some-tools_kept", "k") {
+		t.Error("the module with tools lost its own credential")
+	}
+	if canWrite(runner, "only-process_mine", "k") {
+		t.Error("novox's tool runner carries a module that has nothing to serve")
+	}
+	if !canWrite(all["only-process@novox"], "only-process_mine", "k") {
+		t.Error("the process module lost its own credential")
+	}
+	for name, d := range map[string]Declared{
+		"a held seat": {Module: "m", Holds: []Seat{{Name: "some-seat"}}},
+		"a wait":      {Module: "m", Waits: []Wait{{}}},
+		"a check":     {Module: "m", Checks: []string{"m.check"}},
+	} {
+		if !runnerServes(d) {
+			t.Errorf("the tool runner does not serve a module with %s", name)
+		}
+	}
+}

internal/broker/modstreams_test.go

@@ -154,7 +154,7 @@ func TestTheToolRunnerNeverHearsARestrictedStream(t *testing.T) {
 	records := Records{Nodes: []string{"ace", "novox"}, Assigned: map[string][]Declared{
 		"novox": {{Module: "mesh-mail", Streams: []ModuleStream{mailStream}}, {Module: "news", Streams: []ModuleStream{newsStream}}},
 		"ace": {{Module: RuntimeModule},
-			{Module: "carried", Hears: []Heard{mailHeard, newsHeard}, HearsAStream: true},
+			{Module: "carried", NoAccount: true, Hears: []Heard{mailHeard, newsHeard}, HearsAStream: true},
 			{Module: "mailer", RunsAs: "mailer", Hears: []Heard{mailHeard}, HearsAStream: true}},
 	}}
 	users, err := Users(records)

internal/broker/users.go

@@ -206,7 +206,7 @@ func Users(r Records) ([]Principal, error) {
 		if runtimeHere {
 			var carried []Declared
 			for _, d := range r.Assigned[node] {
-				if d.RunsAs == "" {
+				if d.RunsAs == "" && runnerServes(d) {
 					// Never a restricted stream for what the tool runner carries (novox/hq ADR 0376 §1).
 					d.Hears = ComposedHears(d)
 					carried = append(carried, d)
@@ -391,3 +391,14 @@ func boundBucketsOf(r Records) []string {
 	sort.Strings(out)
 	return out
 }
+
+// runnerServes says the machine's tool runner has something of this module to serve (novox/hq ADR 0436 §1,
+// ADR 0437 §4, issue 1329): tools or loads it answers, a seat it holds, event families a session waits on,
+// or a check its health asks. A module with none of these is a process of its own on its own credential, and
+// carrying it would hand every session on the machine the runner's account with that module's state, seat
+// traffic and streams. A module with no account of its own (NoAccount) is spoken for by the runner, so it
+// stays carried, and so does the runtime module itself. Whether the module has its own broker secret is not
+// the test: a module with tools and its own credential is still carried (ADR 0175).
+func runnerServes(d Declared) bool {
+	return d.Module == RuntimeModule || d.NoAccount || len(d.Serves) > 0 || len(d.Holds) > 0 || len(d.Waits) > 0 || len(d.Checks) > 0
+}