feat(companion): add heartbeat loop getState snapshot

README.md

@@ -1200,7 +1200,7 @@ Companion runtime helper:
   - `createHeartbeatLoop()` convenience helper that returns a bound `CompanionHeartbeatLoop`
   - optional `defaultSessionId` for canvas helper calls so `sessionId` can be omitted per call
   - `dispose()` lifecycle helper for unified runtime teardown
-- `src/companion/heartbeatLoop.ts` provides `CompanionHeartbeatLoop` for periodic heartbeat scheduling (`publishHeartbeat`) with start/stop safety, optional interval jitter (`jitterRatio`) to spread load, `tickNow()` for manual sends, success/error hooks, failure observability (`failureCount`, `lastFailure`), and optional auto-stop after repeated failures.
+- `src/companion/heartbeatLoop.ts` provides `CompanionHeartbeatLoop` for periodic heartbeat scheduling (`publishHeartbeat`) with start/stop safety, optional interval jitter (`jitterRatio`) to spread load, `tickNow()` for manual sends, success/error hooks, failure observability (`failureCount`, `lastFailure`, `getState()`), and optional auto-stop after repeated failures.
 
 ## Canvas / A2UI Foundation
 

docs/plans/state.json

@@ -540,6 +540,20 @@
       ],
       "test_status": "pnpm test:run src/companion/runtimeClient.test.ts src/companion/platformClients.test.ts src/companion/heartbeatLoop.test.ts src/companion/platformClients.integration.test.ts + pnpm typecheck passing"
     },
+    "companion-heartbeat-loop-state-snapshot": {
+      "status": "completed",
+      "date": "2026-02-17",
+      "updated": "2026-02-17",
+      "summary": "Added `getState()` snapshot helper on `CompanionHeartbeatLoop` to expose consolidated runtime state (`running`, `failureCount`, `lastFailure`) for companion observability surfaces.",
+      "files_modified": [
+        "src/companion/heartbeatLoop.ts",
+        "src/companion/heartbeatLoop.test.ts",
+        "src/companion/index.ts",
+        "README.md",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/companion/heartbeatLoop.test.ts src/companion/runtimeClient.test.ts src/companion/platformClients.test.ts src/companion/platformClients.integration.test.ts + pnpm typecheck passing"
+    },
     "browser-tools-activation-clarity": {
       "status": "completed",
       "date": "2026-02-17",

src/companion/heartbeatLoop.test.ts

@@ -191,5 +191,10 @@ describe('CompanionHeartbeatLoop', () => {
     await loop.tickNow();
     expect(publishHeartbeat).toHaveBeenCalledTimes(1);
     expect(loop.running).toBe(false);
+    expect(loop.getState()).toEqual({
+      running: false,
+      failureCount: 0,
+      lastFailure: null,
+    });
   });
 });

src/companion/heartbeatLoop.ts

@@ -16,6 +16,12 @@ export interface CompanionHeartbeatLoopOptions {
   randomFn?: () => number;
 }
 
+export interface CompanionHeartbeatLoopState {
+  running: boolean;
+  failureCount: number;
+  lastFailure: Error | null;
+}
+
 /**
  * Lightweight periodic heartbeat loop for companion runtimes.
  * Calls `publishHeartbeat` on a fixed interval with optional dynamic payload generation.
@@ -77,6 +83,14 @@ export class CompanionHeartbeatLoop {
     return this.lastError;
   }
 
+  getState(): CompanionHeartbeatLoopState {
+    return {
+      running: this.running,
+      failureCount: this.failureCount,
+      lastFailure: this.lastFailure,
+    };
+  }
+
   start(runImmediately = true): void {
     if (this.started) {
       return;

src/companion/index.ts

@@ -57,4 +57,5 @@ export type {
 export type {
   HeartbeatPublisher,
   CompanionHeartbeatLoopOptions,
+  CompanionHeartbeatLoopState,
 } from './heartbeatLoop.js';