feat(FN-5425): add coordination notice system for multi-agent room task fil

Adds a `room-coordination.ts` helper module for multi-agent coordination messaging, wires coordination notices into the agent heartbeat path, and ships tests plus documentation for the feature. A changeset prepares the `@runfusion/fusion` package for release.

Fusion-Task-Id: FN-5425

packages/engine/src/__tests__/__snapshots__/agent-heartbeat-procedures.test.ts.snap

@@ -109,7 +109,11 @@ exports[`agent-heartbeat procedure templates > keeps strict no-task procedure st
    reply_to_message_id when answering. If Pending Room Messages are present,
    review them in the prompt and use fn_post_room_message only when relevant.
    When Room Ambiguity Notices appear, follow the resolve/clarify branch and do
-   not create tasks under clarification notices.
+   not create tasks under clarification notices. If a Room Coordination Notices
+   section is present, follow its claim/defer branch exactly: under "claim" post
+   a one-line claim before calling fn_task_create; under "defer-suggested" do
+   NOT call fn_task_create and instead acknowledge the prior claim via
+   fn_post_room_message.
 3. **Wake delta** — read the Wake Delta block above. The wake reason is the
    highest-priority change for this heartbeat. If you were woken by a comment
    or a message, acknowledge it before doing anything else.
@@ -147,7 +151,11 @@ exports[`agent-heartbeat procedure templates > keeps strict task procedure stabl
    reply_to_message_id when answering. If Pending Room Messages are present,
    review them in the prompt and use fn_post_room_message only when relevant.
    When Room Ambiguity Notices appear, follow the resolve/clarify branch and do
-   not create tasks under clarification notices.
+   not create tasks under clarification notices. If a Room Coordination Notices
+   section is present, follow its claim/defer branch exactly: under "claim" post
+   a one-line claim before calling fn_task_create; under "defer-suggested" do
+   NOT call fn_task_create and instead acknowledge the prior claim via
+   fn_post_room_message.
 3. **Wake delta** — read the Wake Delta block above. The wake reason is the
    highest-priority change for this heartbeat. If you were woken by a comment
    or a message, acknowledge it before doing anything else.

packages/engine/src/__tests__/heartbeat-room-messages.test.ts

@@ -4,6 +4,7 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { AgentStore, ChatStore, TaskStore } from "@fusion/core";
 import { HeartbeatMonitor } from "../agent-heartbeat.js";
+import * as roomCoordination from "../room-coordination.js";
 
 const sessionCapture = vi.hoisted(() => ({
   prompt: "",
@@ -283,6 +284,176 @@ describe("heartbeat room messages", () => {
     expect(sessionCapture.prompt).not.toContain("Resolved Referent:");
   });
 
+  describe("multi-agent room coordination (FN-5425)", () => {
+    async function seedMultiAgentRoom(
+      localHarness: Harness,
+      { peerAgentId = "agent-peer", roomName }: { peerAgentId?: string; roomName: string },
+    ): Promise<{ room: ReturnType<ChatStore["createRoom"]>; peerAgentId: string }> {
+      const peerAgent = await localHarness.agentStore.createAgent({
+        name: peerAgentId,
+        role: "executor",
+        soul: "Peer room member",
+        runtimeConfig: { enabled: true },
+      });
+      const room = localHarness.chatStore.createRoom({ name: roomName, memberAgentIds: [localHarness.agentId] });
+      localHarness.chatStore.addRoomMember(room.id, peerAgent.id);
+      return { room, peerAgentId: peerAgent.id };
+    }
+
+    it("renders claim branch and emits coordination audit in multi-agent room", async () => {
+      harness = await createHarness();
+      const { room } = await seedMultiAgentRoom(harness, { roomName: "coord-claim" });
+      const userMessage = harness.chatStore.addRoomMessage(room.id, {
+        role: "user",
+        content: "please file a task for the secrets-sync regression",
+      });
+
+      const monitor = new HeartbeatMonitor({
+        store: harness.agentStore,
+        taskStore: harness.taskStore,
+        rootDir: harness.rootDir,
+        chatStore: harness.chatStore,
+      });
+
+      const run = await monitor.executeHeartbeat({ agentId: harness.agentId, source: "timer" as any });
+
+      expect(sessionCapture.prompt).toContain("Room Coordination Notices:");
+      expect(sessionCapture.prompt).toContain("branch: claim");
+      expect(sessionCapture.prompt).toContain("Claiming:");
+      expect(sessionCapture.prompt).toContain("fn_task_create");
+      expect(sessionCapture.prompt).toContain("fn_post_room_message");
+      expect(sessionCapture.prompt).toContain("FN-4918");
+
+      const event = harness.taskStore
+        .getRunAuditEvents({ runId: run!.id })
+        .find((auditEvent) => auditEvent.mutationType === "room:coordination:branch" && auditEvent.target === userMessage.id);
+      expect(event?.metadata).toMatchObject({ branch: "claim" });
+    });
+
+    it("renders defer branch when peer already claimed", async () => {
+      harness = await createHarness();
+      const { room, peerAgentId } = await seedMultiAgentRoom(harness, { roomName: "coord-defer-claim" });
+      const priorClaim = harness.chatStore.addRoomMessage(room.id, {
+        role: "assistant",
+        senderAgentId: peerAgentId,
+        content: "Claiming: filing task for the secrets-sync regression",
+      });
+      harness.chatStore.addRoomMessage(room.id, {
+        role: "user",
+        content: "please file a task for the secrets-sync regression",
+      });
+
+      const monitor = new HeartbeatMonitor({
+        store: harness.agentStore,
+        taskStore: harness.taskStore,
+        rootDir: harness.rootDir,
+        chatStore: harness.chatStore,
+      });
+
+      const run = await monitor.executeHeartbeat({ agentId: harness.agentId, source: "timer" as any });
+      expect(sessionCapture.prompt).toContain("branch: defer-suggested");
+      expect(sessionCapture.prompt).toContain(peerAgentId);
+      expect(sessionCapture.prompt).toContain("Do NOT call fn_task_create");
+
+      const event = harness.taskStore
+        .getRunAuditEvents({ runId: run!.id })
+        .find((auditEvent) => auditEvent.mutationType === "room:coordination:branch");
+      expect(event?.metadata).toMatchObject({ branch: "defer-suggested", priorClaimMessageId: priorClaim.id });
+    });
+
+    it("captures prior task id from peer announcement", async () => {
+      harness = await createHarness();
+      const { room, peerAgentId } = await seedMultiAgentRoom(harness, { roomName: "coord-defer-task" });
+      harness.chatStore.addRoomMessage(room.id, {
+        role: "assistant",
+        senderAgentId: peerAgentId,
+        content: "Filed FN-9042 for the secrets-sync regression",
+      });
+      harness.chatStore.addRoomMessage(room.id, { role: "user", content: "please file a task for the secrets-sync regression" });
+
+      const monitor = new HeartbeatMonitor({
+        store: harness.agentStore,
+        taskStore: harness.taskStore,
+        rootDir: harness.rootDir,
+        chatStore: harness.chatStore,
+      });
+
+      const run = await monitor.executeHeartbeat({ agentId: harness.agentId, source: "timer" as any });
+      expect(sessionCapture.prompt).toContain("FN-9042");
+      const event = harness.taskStore.getRunAuditEvents({ runId: run!.id }).find((auditEvent) => auditEvent.mutationType === "room:coordination:branch");
+      expect(event?.metadata).toMatchObject({ priorTaskId: "FN-9042" });
+    });
+
+    it("does not render coordination notices for single-agent room", async () => {
+      harness = await createHarness();
+      const room = harness.chatStore.createRoom({ name: "single-agent", memberAgentIds: [harness.agentId] });
+      harness.chatStore.addRoomMessage(room.id, { role: "user", content: "file a task for X" });
+
+      const monitor = new HeartbeatMonitor({ store: harness.agentStore, taskStore: harness.taskStore, rootDir: harness.rootDir, chatStore: harness.chatStore });
+      const run = await monitor.executeHeartbeat({ agentId: harness.agentId, source: "timer" as any });
+
+      expect(sessionCapture.prompt).not.toContain("Room Coordination Notices:");
+      expect(harness.taskStore.getRunAuditEvents({ runId: run!.id }).some((event) => event.mutationType === "room:coordination:branch")).toBe(false);
+    });
+
+    it("does not render coordination notices for non-task-filing content", async () => {
+      harness = await createHarness();
+      const { room } = await seedMultiAgentRoom(harness, { roomName: "coord-non-intent" });
+      harness.chatStore.addRoomMessage(room.id, { role: "user", content: "what do you think about the secrets-sync regression?" });
+
+      const monitor = new HeartbeatMonitor({ store: harness.agentStore, taskStore: harness.taskStore, rootDir: harness.rootDir, chatStore: harness.chatStore });
+      const run = await monitor.executeHeartbeat({ agentId: harness.agentId, source: "timer" as any });
+
+      expect(sessionCapture.prompt).not.toContain("Room Coordination Notices:");
+      expect(harness.taskStore.getRunAuditEvents({ runId: run!.id }).some((event) => event.mutationType === "room:coordination:branch")).toBe(false);
+    });
+
+    it("keeps deictic-only messages in ambiguity layer only", async () => {
+      harness = await createHarness();
+      const { room } = await seedMultiAgentRoom(harness, { roomName: "coord-deictic-only" });
+      harness.chatStore.addRoomMessage(room.id, { role: "user", content: "we should investigate the secrets-sync regression" });
+      harness.chatStore.addRoomMessage(room.id, { role: "user", content: "yeah, create it" });
+
+      const monitor = new HeartbeatMonitor({ store: harness.agentStore, taskStore: harness.taskStore, rootDir: harness.rootDir, chatStore: harness.chatStore });
+      await monitor.executeHeartbeat({ agentId: harness.agentId, source: "timer" as any });
+
+      expect(sessionCapture.prompt).toContain("Room Ambiguity Notices:");
+      expect(sessionCapture.prompt).not.toContain("Room Coordination Notices:");
+    });
+
+    it("does not defer to a self-authored prior claim", async () => {
+      harness = await createHarness();
+      const { room } = await seedMultiAgentRoom(harness, { roomName: "coord-self-claim" });
+      harness.chatStore.addRoomMessage(room.id, {
+        role: "assistant",
+        senderAgentId: harness.agentId,
+        content: "Claiming: filing task for the secrets-sync regression",
+      });
+      harness.chatStore.addRoomMessage(room.id, { role: "user", content: "please file a task for the secrets-sync regression" });
+
+      const monitor = new HeartbeatMonitor({ store: harness.agentStore, taskStore: harness.taskStore, rootDir: harness.rootDir, chatStore: harness.chatStore });
+      await monitor.executeHeartbeat({ agentId: harness.agentId, source: "timer" as any });
+
+      expect(sessionCapture.prompt).toContain("branch: claim");
+      expect(sessionCapture.prompt).not.toContain("branch: defer-suggested");
+    });
+
+    it("fails open when coordination helper throws", async () => {
+      harness = await createHarness();
+      const { room } = await seedMultiAgentRoom(harness, { roomName: "coord-throw" });
+      harness.chatStore.addRoomMessage(room.id, { role: "user", content: "please file a task for the secrets-sync regression" });
+      const spy = vi.spyOn(roomCoordination, "decideRoomCoordination").mockImplementation(() => {
+        throw new Error("boom");
+      });
+
+      const monitor = new HeartbeatMonitor({ store: harness.agentStore, taskStore: harness.taskStore, rootDir: harness.rootDir, chatStore: harness.chatStore });
+      await expect(monitor.executeHeartbeat({ agentId: harness.agentId, source: "timer" as any })).resolves.toBeTruthy();
+      expect(sessionCapture.prompt).not.toContain("Room Coordination Notices:");
+
+      spy.mockRestore();
+    });
+  });
+
   it("registers fn_post_room_message and posts through the real ChatStore under restrictive policy", async () => {
     harness = await createHarness({
       presetId: "approval-required",

packages/engine/src/__tests__/room-coordination.test.ts

@@ -0,0 +1,217 @@
+import type { ChatRoomMember, ChatRoomMessage } from "@fusion/core";
+import { describe, expect, it } from "vitest";
+import {
+  countActiveAgentMembers,
+  decideRoomCoordination,
+  detectTaskFilingIntent,
+  renderRoomCoordinationPromptBlock,
+} from "../room-coordination.js";
+
+function roomMember(agentId: string | null): ChatRoomMember {
+  return {
+    roomId: "room-1",
+    // cast for test-only simulation of nullable rows from external callers
+    agentId: agentId as unknown as string,
+    role: "member",
+    addedAt: new Date().toISOString(),
+  };
+}
+
+function roomMessage(id: string, content: string, senderAgentId: string | null = "agent-peer"): ChatRoomMessage {
+  return {
+    id,
+    roomId: "room-1",
+    role: senderAgentId ? "assistant" : "user",
+    content,
+    thinkingOutput: null,
+    metadata: null,
+    senderAgentId,
+    mentions: [],
+    createdAt: new Date().toISOString(),
+  };
+}
+
+describe("room-coordination", () => {
+  describe("detectTaskFilingIntent", () => {
+    it("detects explicit task-filing intent with extracted subject", () => {
+      const result = detectTaskFilingIntent("please file a task for the secrets-sync regression");
+      expect(result.isTaskFilingIntent).toBe(true);
+      expect(result.subject).toBe("the secrets-sync regression");
+      expect(result.cues.length).toBeGreaterThan(0);
+    });
+
+    it.each([
+      ["Can you create a task to fix the broken merge?", "fix the broken merge"],
+      ["open a task about the new typecheck failure", "the new typecheck failure"],
+      ["track this as a task", null],
+      ["FILE A TASK: dashboard FAB regression.", "dashboard FAB regression"],
+      ["create a task for it", "it"],
+      ["create a task for FN-1234", "FN-1234"],
+    ])("handles positive variants: %s", (content, expectedSubject) => {
+      const result = detectTaskFilingIntent(content);
+      expect(result.isTaskFilingIntent).toBe(true);
+      if (expectedSubject === null) {
+        expect([null, "this"]).toContain(result.subject);
+      } else {
+        expect(result.subject).toContain(expectedSubject);
+      }
+    });
+
+    it.each([
+      "file it",
+      "create it now",
+      "do that as a task",
+      "this is a task list",
+      "I filed the task report yesterday",
+      "",
+      "   ",
+    ])("rejects non-intent content: %s", (content) => {
+      const result = detectTaskFilingIntent(content);
+      expect(result).toEqual({ isTaskFilingIntent: false, cues: [], subject: null });
+    });
+
+    it("returns true for past-tense phrasing trade-off", () => {
+      const result = detectTaskFilingIntent("I filed a task earlier");
+      expect(result.isTaskFilingIntent).toBe(true);
+    });
+
+    it("rejects oversized content", () => {
+      const result = detectTaskFilingIntent(`create a task for ${"x".repeat(1000)}`);
+      expect(result).toEqual({ isTaskFilingIntent: false, cues: [], subject: null });
+    });
+  });
+
+  describe("countActiveAgentMembers", () => {
+    it("counts unique active agent members", () => {
+      expect(countActiveAgentMembers([roomMember("a1"), roomMember("a2"), roomMember("a3")])).toBe(3);
+    });
+
+    it("deduplicates duplicate agent ids", () => {
+      expect(countActiveAgentMembers([roomMember("a1"), roomMember("a1"), roomMember("a2")])).toBe(2);
+    });
+
+    it("ignores non-agent members", () => {
+      expect(countActiveAgentMembers([roomMember(null), roomMember("a1")])).toBe(1);
+    });
+  });
+
+  describe("decideRoomCoordination", () => {
+    const detection = detectTaskFilingIntent("please file a task for secrets sync");
+
+    it("returns null for non-intent detection", () => {
+      const result = decideRoomCoordination({
+        detection: { isTaskFilingIntent: false, cues: [], subject: null },
+        members: [roomMember("a1"), roomMember("a2")],
+        recentMessages: [],
+        pendingSenderAgentId: null,
+      });
+      expect(result).toBeNull();
+    });
+
+    it("returns null for single-agent rooms", () => {
+      const result = decideRoomCoordination({
+        detection,
+        members: [roomMember("a1")],
+        recentMessages: [],
+        pendingSenderAgentId: null,
+      });
+      expect(result).toBeNull();
+    });
+
+    it("returns claim when no prior peer claim exists", () => {
+      const result = decideRoomCoordination({
+        detection,
+        members: [roomMember("a1"), roomMember("a2")],
+        recentMessages: [roomMessage("m1", "hello", null)],
+        pendingSenderAgentId: null,
+      });
+      expect(result?.branch).toBe("claim");
+      expect(result?.priorClaimMessageId).toBeUndefined();
+    });
+
+    it("returns defer-suggested with prior peer claim", () => {
+      const result = decideRoomCoordination({
+        detection,
+        members: [roomMember("a1"), roomMember("a2")],
+        recentMessages: [roomMessage("m1", "Claiming: filing task for secrets sync", "agent-peer")],
+        pendingSenderAgentId: "agent-main",
+      });
+      expect(result?.branch).toBe("defer-suggested");
+      expect(result?.priorClaimMessageId).toBe("m1");
+      expect(result?.priorClaimSenderId).toBe("agent-peer");
+    });
+
+    it("returns defer-suggested with prior task announcement", () => {
+      const result = decideRoomCoordination({
+        detection,
+        members: [roomMember("a1"), roomMember("a2")],
+        recentMessages: [roomMessage("m2", "Filed FN-9001 for the secrets-sync regression", "agent-peer")],
+        pendingSenderAgentId: "agent-main",
+      });
+      expect(result?.branch).toBe("defer-suggested");
+      expect(result?.priorTaskId).toBe("FN-9001");
+    });
+
+    it("does not defer to self-authored claim", () => {
+      const result = decideRoomCoordination({
+        detection,
+        members: [roomMember("a1"), roomMember("a2")],
+        recentMessages: [roomMessage("m3", "Claiming: filing task for secrets sync", "agent-main")],
+        pendingSenderAgentId: "agent-main",
+      });
+      expect(result?.branch).toBe("claim");
+    });
+
+    it("skips pending message itself from prior lookup", () => {
+      const result = decideRoomCoordination({
+        detection,
+        members: [roomMember("a1"), roomMember("a2")],
+        recentMessages: [roomMessage("pending", "Claiming: filing task for secrets sync", "agent-main")],
+        pendingSenderAgentId: "agent-main",
+      });
+      expect(result?.branch).toBe("claim");
+    });
+  });
+
+  describe("renderRoomCoordinationPromptBlock", () => {
+    it("renders claim branch instructions with explicit guard references", () => {
+      const lines = renderRoomCoordinationPromptBlock(
+        {
+          branch: "claim",
+          memberCount: 3,
+          detection: { isTaskFilingIntent: true, cues: ["file a task"], subject: "secrets-sync regression" },
+        },
+        { id: "m5" },
+      );
+
+      const block = lines.join("\n");
+      expect(block).toContain("fn_post_room_message");
+      expect(block).toContain("fn_task_create");
+      expect(block).toContain("FN-4918");
+      expect(block).toContain("FN-4829");
+      expect(block).toContain("FN-5152");
+      expect(block).toContain("FN-5220");
+      expect(block).toContain("reply_to_message_id = m5");
+    });
+
+    it("renders defer branch with peer, message, and prior task id", () => {
+      const lines = renderRoomCoordinationPromptBlock(
+        {
+          branch: "defer-suggested",
+          memberCount: 2,
+          detection: { isTaskFilingIntent: true, cues: ["create a task"], subject: "secrets-sync regression" },
+          priorClaimMessageId: "m4",
+          priorClaimSenderId: "agent-peer",
+          priorTaskId: "FN-9042",
+        },
+        { id: "m6" },
+      );
+
+      const block = lines.join("\n");
+      expect(block).toContain("agent-peer");
+      expect(block).toContain("message m4");
+      expect(block).toContain("FN-9042");
+      expect(block).toContain("reply_to_message_id = m6");
+    });
+  });
+});

packages/engine/src/agent-heartbeat.ts

@@ -42,6 +42,7 @@ import { buildSessionSkillContextSync } from "./session-skill-context.js";
 import type { AgentReflectionService } from "./agent-reflection.js";
 import { trimPromptMd, trimTaskDescription, trimTriggeringComments } from "./heartbeat-prompt-trim.js";
 import { detectDeicticReference, extractAntecedentCandidates, renderAmbiguityPromptBlock, scoreReferentConfidence } from "./room-ambiguity.js";
+import { countActiveAgentMembers, decideRoomCoordination, detectTaskFilingIntent, renderRoomCoordinationPromptBlock } from "./room-coordination.js";
 
 const promptSizeLog = createLogger("prompt-size");
 
@@ -400,6 +401,7 @@ When you are woken by an incoming message (source includes "wake-on-message"), y
 4. If a Pending Room Messages section is present, review it too:
    - Use fn_post_room_message only when the room content is relevant to your role, soul, or identity.
    - If a Room Ambiguity Notices section is present, follow it exactly: echo resolved referents before acting, and under clarification notices do not create tasks.
+   - If a Room Coordination Notices section is present, follow its claim/defer branch exactly: under "claim" post a one-line claim before calling fn_task_create; under "defer-suggested" do NOT call fn_task_create and instead acknowledge the prior claim via fn_post_room_message.
    - Reference room message IDs when replying so humans can trace context.
 5. After processing messages, continue with your normal heartbeat duties.
 
@@ -486,7 +488,7 @@ When you are woken by an incoming message (source includes "wake-on-message"), y
    - If the message is informational, acknowledge it and respond via fn_send_message when appropriate.
    - If the message requests work, create a follow-up task with fn_task_create.
    - If the request has a clear owner and fn_delegate_task is available, delegate it directly.
-3. If a Pending Room Messages section is present, review it too and use fn_post_room_message only when the room content is relevant to your role or identity; if Room Ambiguity Notices are present, follow their resolve/clarify branch instructions exactly.
+3. If a Pending Room Messages section is present, review it too and use fn_post_room_message only when the room content is relevant to your role or identity; if Room Ambiguity Notices are present, follow their resolve/clarify branch instructions exactly. If a Room Coordination Notices section is present, follow its claim/defer branch exactly: under "claim" post a one-line claim before calling fn_task_create; under "defer-suggested" do NOT call fn_task_create and instead acknowledge the prior claim via fn_post_room_message.
 4. After processing messages, continue with your ambient work.
 
 Example flow:
@@ -518,7 +520,11 @@ export const HEARTBEAT_PROCEDURE_STRICT = `## Heartbeat Procedure (run every tic
    reply_to_message_id when answering. If Pending Room Messages are present,
    review them in the prompt and use fn_post_room_message only when relevant.
    When Room Ambiguity Notices appear, follow the resolve/clarify branch and do
-   not create tasks under clarification notices.
+   not create tasks under clarification notices. If a Room Coordination Notices
+   section is present, follow its claim/defer branch exactly: under "claim" post
+   a one-line claim before calling fn_task_create; under "defer-suggested" do
+   NOT call fn_task_create and instead acknowledge the prior claim via
+   fn_post_room_message.
 3. **Wake delta** — read the Wake Delta block above. The wake reason is the
    highest-priority change for this heartbeat. If you were woken by a comment
    or a message, acknowledge it before doing anything else.
@@ -618,7 +624,11 @@ export const HEARTBEAT_NO_TASK_PROCEDURE_STRICT = `## Heartbeat Procedure (run e
    reply_to_message_id when answering. If Pending Room Messages are present,
    review them in the prompt and use fn_post_room_message only when relevant.
    When Room Ambiguity Notices appear, follow the resolve/clarify branch and do
-   not create tasks under clarification notices.
+   not create tasks under clarification notices. If a Room Coordination Notices
+   section is present, follow its claim/defer branch exactly: under "claim" post
+   a one-line claim before calling fn_task_create; under "defer-suggested" do
+   NOT call fn_task_create and instead acknowledge the prior claim via
+   fn_post_room_message.
 3. **Wake delta** — read the Wake Delta block above. The wake reason is the
    highest-priority change for this heartbeat. If you were woken by a comment
    or a message, acknowledge it before doing anything else.
@@ -954,6 +964,86 @@ export class HeartbeatMonitor {
     return lines;
   }
 
+  private async getRoomCoordinationNoticesSection(
+    agent: Agent,
+    runId: string,
+    entries: Array<{ room: ChatRoom; messages: ChatRoomMessage[] }>,
+    audit: ReturnType<typeof createRunAuditor>,
+  ): Promise<string[]> {
+    if (!this.chatStore || entries.length === 0) {
+      return [];
+    }
+
+    const lines: string[] = [];
+
+    for (const entry of entries) {
+      for (const message of entry.messages) {
+        try {
+          const detection = detectTaskFilingIntent(message.content);
+          if (!detection.isTaskFilingIntent) {
+            continue;
+          }
+
+          const members = this.chatStore.listRoomMembers(entry.room.id);
+          if (countActiveAgentMembers(members) < 2) {
+            continue;
+          }
+
+          const roomTimeline = this.chatStore.getRoomMessages(entry.room.id, { limit: 100 });
+          const messageIndex = roomTimeline.findIndex((roomMessage) => roomMessage.id === message.id);
+          if (messageIndex < 0) {
+            continue;
+          }
+          // messageIndex === 0 means no prior messages; coordination correctly defaults to claim.
+          const recentMessages = messageIndex === 0
+            ? []
+            : roomTimeline.slice(Math.max(0, messageIndex - 15), messageIndex);
+
+          const decision = decideRoomCoordination({
+            detection,
+            members,
+            recentMessages,
+            pendingSenderAgentId: message.senderAgentId ?? agent.id,
+          });
+          if (!decision) {
+            continue;
+          }
+
+          if (lines.length === 0) {
+            lines.push("", "Room Coordination Notices:");
+          }
+
+          lines.push(
+            `- [room: ${entry.room.name} (${entry.room.id})] [message: ${message.id}] [branch: ${decision.branch}]`,
+            ...renderRoomCoordinationPromptBlock(decision, message).map((line) => `  - ${line}`),
+          );
+
+          await audit.database({
+            type: "room:coordination:branch",
+            target: message.id,
+            metadata: {
+              roomId: entry.room.id,
+              agentId: agent.id,
+              branch: decision.branch,
+              memberCount: decision.memberCount,
+              intentCue: detection.cues[0] ?? null,
+              priorClaimMessageId: decision.priorClaimMessageId ?? null,
+              priorTaskId: decision.priorTaskId ?? null,
+            },
+          });
+
+          heartbeatLog.log(
+            `[room-coordination] agent=${agent.id} run=${runId} room=${entry.room.id} messageId=${message.id} branch=${decision.branch} members=${decision.memberCount}`,
+          );
+        } catch (err) {
+          heartbeatLog.warn(`Room coordination notice failed for ${message.id}: ${err instanceof Error ? err.message : String(err)}`);
+        }
+      }
+    }
+
+    return lines;
+  }
+
   private async getPendingRoomMessages(agent: Agent, sinceIso: string): Promise<{
     entries: Array<{ room: ChatRoom; messages: ChatRoomMessage[] }>;
     total: number;
@@ -2493,6 +2583,12 @@ export class HeartbeatMonitor {
             pendingRoomMessages.entries,
             audit,
           );
+          const roomCoordinationNoticesLines = await this.getRoomCoordinationNoticesSection(
+            agent,
+            run.id,
+            pendingRoomMessages.entries,
+            audit,
+          );
 
           // Fetch unread messages when messageStore is available (for all trigger types)
           if (this.messageStore) {
@@ -2679,6 +2775,7 @@ export class HeartbeatMonitor {
               ...pendingMessagesLines,
               ...pendingRoomMessagesLines,
               ...roomAmbiguityNoticesLines,
+              ...roomCoordinationNoticesLines,
               "",
               "Your soul, instructions, and memory are already loaded in the system prompt.",
               "Focus on work that benefits the project without requiring a specific task context.",
@@ -2767,6 +2864,7 @@ export class HeartbeatMonitor {
               ...pendingMessagesLines,
               ...pendingRoomMessagesLines,
               ...roomAmbiguityNoticesLines,
+              ...roomCoordinationNoticesLines,
               ...(reportsHealthSection ? ["", reportsHealthSection] : []),
               "",
               "Run the Heartbeat Procedure above. Call fn_heartbeat_done when finished.",

packages/engine/src/room-coordination.ts

@@ -0,0 +1,205 @@
+import type { ChatRoomMember, ChatRoomMessage } from "@fusion/core";
+
+/**
+ * FN-5425: prompt-layer multi-agent coordination advisory for explicit task-filing room messages.
+ * This module stays deterministic and fail-open: it only detects intent + suggests claim/defer
+ * prompt branches, while authoritative duplicate prevention remains in intake safeguards.
+ */
+export interface TaskFilingIntentDetection {
+  isTaskFilingIntent: boolean;
+  cues: string[];
+  subject: string | null;
+}
+
+export interface RoomCoordinationDecision {
+  branch: "claim" | "defer-suggested";
+  memberCount: number;
+  detection: TaskFilingIntentDetection;
+  priorClaimMessageId?: string;
+  priorClaimSenderId?: string | null;
+  priorTaskId?: string;
+}
+
+export interface RenderCoordinationOptions {
+  deicticMessageId?: never;
+  pendingMessageId: string;
+}
+
+const MAX_INTENT_CONTENT_LENGTH = 800;
+const MAX_SUBJECT_LENGTH = 140;
+const DEICTIC_NOUN_FOLLOWUP_PATTERN = /\b(?:it|that|this)\s+(?:as|for|to)\b/i;
+const TASK_ID_PATTERN = /\b(FN-\d{1,6})\b/i;
+const PRIOR_CLAIM_RE = /^\s*claiming[:-]/i;
+const TASK_ANNOUNCED_RE = /\b(?:filed|created|opened|tracked|added)\b[\s\S]{0,60}?\b(FN-\d{1,6})\b|\b(FN-\d{1,6})\b[\s\S]{0,60}?\b(?:filed|created|opened|tracked|added)\b/i;
+
+const TASK_CONTEXT_SUFFIX = "(?=$|[.?!,:;-]|\\s+(?:for|about|to|on|regarding)\\b)";
+
+const TASK_FILING_CUES: ReadonlyArray<[string, RegExp]> = [
+  ["file a task", new RegExp(`\\bfile\\w*\\s+(?:a\\s+|the\\s+)?task${TASK_CONTEXT_SUFFIX}`, "i")],
+  ["filed a task", /\bfiled\s+(?:a\s+|the\s+)?task\b/i],
+  ["create a task", new RegExp(`\\bcreate\\s+(?:a\\s+|the\\s+)?task${TASK_CONTEXT_SUFFIX}`, "i")],
+  ["open a task", new RegExp(`\\bopen\\s+(?:a\\s+|the\\s+)?task${TASK_CONTEXT_SUFFIX}`, "i")],
+  ["add a task", new RegExp(`\\badd\\s+(?:a\\s+|the\\s+)?task${TASK_CONTEXT_SUFFIX}`, "i")],
+  ["track this/that as a task", new RegExp(`\\btrack\\s+(?:this|that)\\s+(?:as\\s+)?(?:a\\s+)?task${TASK_CONTEXT_SUFFIX}`, "i")],
+  ["start a task", new RegExp(`\\bstart\\s+(?:a\\s+|the\\s+)?task${TASK_CONTEXT_SUFFIX}`, "i")],
+  ["make a task", new RegExp(`\\bmake\\s+(?:a\\s+|the\\s+)?task${TASK_CONTEXT_SUFFIX}`, "i")],
+];
+
+function normalizeMessageContent(content: string): string {
+  return content.replace(/\s+/g, " ").trim();
+}
+
+function truncateWithEllipsis(value: string, maxLength = MAX_SUBJECT_LENGTH): string {
+  if (value.length <= maxLength) {
+    return value;
+  }
+  return `${value.slice(0, maxLength - 1).trimEnd()}…`;
+}
+
+function cleanExtractedSubject(subject: string): string {
+  return truncateWithEllipsis(
+    subject
+      .replace(/^\s*["'`]+|["'`]+\s*$/g, "")
+      .replace(/\s+/g, " ")
+      .trim(),
+  );
+}
+
+function extractSubject(normalized: string): string | null {
+  const preferred = normalized.match(
+    /(?:file\w*|create|open|add|track|start|make)\s+(?:a\s+|the\s+)?task\s+(?:for|about|to|on|regarding)\s+(.+?)(?:[.?!]|$)/i,
+  );
+  if (preferred?.[1]) {
+    const cleaned = cleanExtractedSubject(preferred[1]);
+    return cleaned || null;
+  }
+
+  const fallback = normalized.match(
+    /(?:file\w*|create|open|add|track|start|make)\s+(?:a\s+|the\s+)?task(?:\s+|\s*[:-]\s*)(.+?)(?:[.?!]|$)/i,
+  );
+  if (fallback?.[1]) {
+    const cleaned = cleanExtractedSubject(fallback[1]);
+    return cleaned || null;
+  }
+
+  return null;
+}
+
+export function detectTaskFilingIntent(content: string): TaskFilingIntentDetection {
+  const normalized = normalizeMessageContent(content);
+  if (!normalized || normalized.length > MAX_INTENT_CONTENT_LENGTH) {
+    return { isTaskFilingIntent: false, cues: [], subject: null };
+  }
+
+  const cueMatches: Array<{ cue: string; index: number }> = [];
+  for (const [cue, pattern] of TASK_FILING_CUES) {
+    const match = pattern.exec(normalized);
+    if (match?.index != null) {
+      cueMatches.push({ cue, index: match.index });
+    }
+  }
+
+  if (cueMatches.length === 0) {
+    return { isTaskFilingIntent: false, cues: [], subject: null };
+  }
+
+  if (/\bfiled\s+(?:a\s+|the\s+)?task\s+report\b/i.test(normalized)) {
+    return { isTaskFilingIntent: false, cues: [], subject: null };
+  }
+
+  const earliestCueIndex = cueMatches.reduce((min, current) => Math.min(min, current.index), Number.POSITIVE_INFINITY);
+  const deicticMatch = DEICTIC_NOUN_FOLLOWUP_PATTERN.exec(normalized);
+  const deicticIndex = deicticMatch?.index ?? -1;
+  if (deicticIndex >= 0 && deicticIndex < earliestCueIndex) {
+    return { isTaskFilingIntent: false, cues: [], subject: null };
+  }
+
+  const subject = extractSubject(normalized);
+
+  // Intentional trade-off: the advisory is harmless under occasional tense false positives,
+  // and FN-5152/FN-5220 intake dedup remains the deterministic backstop.
+  return {
+    isTaskFilingIntent: true,
+    cues: cueMatches.sort((a, b) => a.index - b.index).map((entry) => entry.cue),
+    subject,
+  };
+}
+
+export function countActiveAgentMembers(members: ChatRoomMember[]): number {
+  // ChatStore.removeRoomMember hard-deletes rows, so listRoomMembers is already active-only.
+  const uniqueAgentIds = new Set(members.map((member) => member.agentId).filter((agentId): agentId is string => Boolean(agentId)));
+  return uniqueAgentIds.size;
+}
+
+export function decideRoomCoordination(args: {
+  detection: TaskFilingIntentDetection;
+  members: ChatRoomMember[];
+  recentMessages: ChatRoomMessage[];
+  pendingSenderAgentId: string | null;
+}): RoomCoordinationDecision | null {
+  const { detection, members, recentMessages, pendingSenderAgentId } = args;
+  if (!detection.isTaskFilingIntent) {
+    return null;
+  }
+
+  const memberCount = countActiveAgentMembers(members);
+  if (memberCount < 2) {
+    return null;
+  }
+
+  const lookback = recentMessages.slice(-15);
+  let priorClaimMessageId: string | undefined;
+  let priorClaimSenderId: string | null | undefined;
+  let priorTaskId: string | undefined;
+
+  for (const message of lookback) {
+    if (!message.senderAgentId) {
+      continue;
+    }
+    if (pendingSenderAgentId && message.senderAgentId === pendingSenderAgentId) {
+      continue;
+    }
+
+    const claimMatch = PRIOR_CLAIM_RE.test(message.content);
+    const announcedMatch = TASK_ANNOUNCED_RE.exec(message.content);
+    if (!claimMatch && !announcedMatch) {
+      continue;
+    }
+
+    priorClaimMessageId = message.id;
+    priorClaimSenderId = message.senderAgentId;
+    const captured = announcedMatch?.[1] ?? announcedMatch?.[2] ?? message.content.match(TASK_ID_PATTERN)?.[1];
+    priorTaskId = captured?.toUpperCase();
+    break;
+  }
+
+  return {
+    branch: priorClaimMessageId ? "defer-suggested" : "claim",
+    memberCount,
+    detection,
+    priorClaimMessageId,
+    priorClaimSenderId,
+    priorTaskId,
+  };
+}
+
+export function renderRoomCoordinationPromptBlock(
+  decision: RoomCoordinationDecision,
+  pendingMessage: Pick<ChatRoomMessage, "id">,
+): string[] {
+  if (decision.branch === "claim") {
+    return [
+      `Multi-agent room (${decision.memberCount} agents). Before calling fn_task_create for this request, coordinate:`,
+      `1. Post a ONE-LINE claim to the room first via fn_post_room_message: "Claiming: filing task for <subject>" (reply_to_message_id = ${pendingMessage.id}).`,
+      "2. Then call fn_task_create. The deterministic / near-duplicate / explicit-marker intake guards (FN-4918 / FN-4829 / FN-5152 / FN-5220) are your authoritative backstop — do NOT pass acknowledgedDuplicates or bypassDuplicateCheck to silence a duplicate match for a room request.",
+      `3. After fn_task_create returns, post the resulting FN-NNNN id back to the room via fn_post_room_message (reply_to_message_id = ${pendingMessage.id}).`,
+      `Detected subject: ${decision.detection.subject ?? "(none extracted — restate the user's request in your claim)"}.`,
+    ];
+  }
+
+  return [
+    `Multi-agent room (${decision.memberCount} agents). A peer agent (${decision.priorClaimSenderId ?? "unknown"}) already posted a claim or task announcement in this room (message ${decision.priorClaimMessageId}${decision.priorTaskId ? `, task ${decision.priorTaskId}` : ""}).`,
+    `Do NOT call fn_task_create for this request. Reply once via fn_post_room_message (reply_to_message_id = ${pendingMessage.id}) acknowledging the existing claim${decision.priorTaskId ? ` and echoing ${decision.priorTaskId}` : ""}.`,
+    "If you believe the peer's task does NOT cover this request, say so explicitly in your reply and wait for human disambiguation rather than filing in parallel.",
+  ];
+}

packages/engine/src/run-audit.ts

@@ -307,7 +307,8 @@ export type DatabaseMutationType =
    * ```
    */
   | "worktree:pool-double-lease-detected"
-  | "room:ambiguity:branch";
+  | "room:ambiguity:branch"
+  | "room:coordination:branch";
 
 // ── Filesystem mutation types ─────────────────────────────────────────────────