diff --git a/packages/coding-agent/src/core/subagent-runner.ts b/packages/coding-agent/src/core/subagent-runner.ts
index 1aa2b24df..8ce6da0db 100644
--- a/packages/coding-agent/src/core/subagent-runner.ts
+++ b/packages/coding-agent/src/core/subagent-runner.ts
@@ -282,12 +282,11 @@ export async function runSubagent(
 	const promptTask = `Task: ${task}`;
 
 	try {
-		const promptPromise = session.prompt(promptTask, {
-			runExtensionHooks: false,
-		});
-
-		if (timeoutMs === 0 && !options?.signal) {
+		if (timeoutMs === 0 && noOutputTimeoutMs === 0 && !options?.signal) {
 			// Fast path: no watchdog, no cancellation.
+			const promptPromise = session.prompt(promptTask, {
+				runExtensionHooks: false,
+			});
 			await promptPromise;
 			cleanup();
 			return { ok: true, output: extractFinalOutput(), exitCode: 0 };
@@ -300,9 +299,7 @@ export async function runSubagent(
 			cancelled?: true;
 			error?: unknown;
 		};
-		const competitors: Promise<RaceResult>[] = [
-			promptPromise.then(() => ({}) as RaceResult),
-		];
+		const competitors: Promise<RaceResult>[] = [];
 
 		if (timeoutMs > 0) {
 			competitors.push(
@@ -364,6 +361,11 @@ export async function runSubagent(
 			);
 		}
 
+		const promptPromise = session.prompt(promptTask, {
+			runExtensionHooks: false,
+		});
+		competitors.unshift(promptPromise.then(() => ({}) as RaceResult));
+
 		const result = await Promise.race(competitors);
 
 		cleanup();
diff --git a/src/resources/extensions/sf/auto/loop.js b/src/resources/extensions/sf/auto/loop.js
index 8f5524df8..ed9197bf9 100644
--- a/src/resources/extensions/sf/auto/loop.js
+++ b/src/resources/extensions/sf/auto/loop.js
@@ -117,7 +117,12 @@ const DEFAULT_HALT_THRESHOLD_MS = 10_000;
 function haltStatePath(basePath) {
 	return join(sfRoot(basePath), "runtime", HALT_STATE_FILE);
 }
-class HaltWatchdog {
+/**
+ * Check whether elapsed time since last heartbeat exceeds the threshold.
+ * On first detection, emit a BLOCKING_NOTICE, file high-severity self-feedback,
+ * and log the transition. Returns { stuck, elapsedMs }.
+ */
+export class HaltWatchdog {
 	constructor(basePath, thresholdMs = DEFAULT_HALT_THRESHOLD_MS) {
 		this.basePath = basePath;
 		this.thresholdMs = thresholdMs;
@@ -368,7 +373,7 @@ async function drainSleeptimeQueue(basePath) {
  * @param {object} deps
  * @param {object} ctx
  */
-async function autoTriageTodo(basePath, iteration, deps, ctx) {
+async function autoTriageTodo(basePath, iteration, _deps, ctx) {
 	const todoPath = join(basePath, "TODO.md");
 	if (!existsSync(todoPath)) return;
 	const raw = readFileSync(todoPath, "utf-8");
diff --git a/src/resources/extensions/sf/tests/auto-halt-watchdog-notify.test.mjs b/src/resources/extensions/sf/tests/auto-halt-watchdog-notify.test.mjs
new file mode 100644
index 000000000..d22e0798c
--- /dev/null
+++ b/src/resources/extensions/sf/tests/auto-halt-watchdog-notify.test.mjs
@@ -0,0 +1,99 @@
+import assert from "node:assert/strict";
+import { existsSync, mkdirSync, readFileSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, beforeEach, test, vi } from "vitest";
+import { HaltWatchdog } from "../auto/loop.js";
+import { installNotifyInterceptor } from "../bootstrap/notify-interceptor.js";
+import {
+	_resetNotificationStore,
+	appendNotification,
+	getAppendFailureCount,
+	initNotificationStore,
+	NOTICE_KIND,
+} from "../notification-store.js";
+
+let testDir;
+
+beforeEach(() => {
+	_resetNotificationStore();
+	testDir = join(tmpdir(), `sf-watchdog-test-${Date.now()}`);
+	mkdirSync(testDir, { recursive: true });
+	initNotificationStore(testDir);
+});
+
+afterEach(() => {
+	rmSync(testDir, { recursive: true, force: true });
+	_resetNotificationStore();
+	vi.useRealTimers();
+});
+
+function readNotifications() {
+	const notificationFile = join(testDir, ".sf", "notifications.jsonl");
+	if (!existsSync(notificationFile)) return [];
+	const content = readFileSync(notificationFile, "utf-8").trim();
+	if (!content) return [];
+	return content.split("\n").map((line) => JSON.parse(line));
+}
+
+test("HaltWatchdog.check_when_idle_exceeds_threshold_emits_blocking_notice", () => {
+	vi.useFakeTimers();
+	const thresholdMs = 10;
+	const watchdog = new HaltWatchdog(testDir, thresholdMs);
+	const originalNotify = vi.fn();
+	const mockCtx = { ui: { notify: originalNotify }, basePath: testDir };
+	installNotifyInterceptor(mockCtx);
+
+	watchdog.heartbeat();
+	vi.advanceTimersByTime(thresholdMs + 5);
+	const result = watchdog.check(mockCtx, 1);
+
+	assert.equal(result.stuck, true);
+	assert.equal(originalNotify.mock.calls.length, 1);
+	const entries = readNotifications();
+	assert.equal(entries.length, 1);
+	assert.equal(entries[0].noticeKind, NOTICE_KIND.BLOCKING_NOTICE);
+	assert.equal(entries[0].metadata.dedupe_key, "halt-watchdog-stuck");
+	assert.match(entries[0].message, /idle for/);
+});
+
+test("HaltWatchdog.check_when_within_threshold_emits_no_notification", () => {
+	vi.useFakeTimers();
+	const thresholdMs = 10_000;
+	const watchdog = new HaltWatchdog(testDir, thresholdMs);
+	const originalNotify = vi.fn();
+	const mockCtx = { ui: { notify: originalNotify } };
+	installNotifyInterceptor(mockCtx);
+
+	watchdog.heartbeat();
+	vi.advanceTimersByTime(100);
+	const result = watchdog.check(mockCtx, 1);
+
+	assert.equal(result.stuck, false);
+	assert.equal(originalNotify.mock.calls.length, 0);
+	assert.deepEqual(readNotifications(), []);
+});
+
+test("HaltWatchdog.check_reports_only_once_per_idle_period", () => {
+	vi.useFakeTimers();
+	const thresholdMs = 10;
+	const watchdog = new HaltWatchdog(testDir, thresholdMs);
+	const originalNotify = vi.fn();
+	const mockCtx = { ui: { notify: originalNotify }, basePath: testDir };
+	installNotifyInterceptor(mockCtx);
+
+	watchdog.heartbeat();
+	vi.advanceTimersByTime(thresholdMs + 5);
+	watchdog.check(mockCtx, 1);
+	watchdog.check(mockCtx, 2);
+
+	assert.equal(readNotifications().length, 1);
+});
+
+test("appendNotification_when_store_not_initialized_fails_open", () => {
+	_resetNotificationStore();
+
+	appendNotification("test", "info", "test");
+
+	assert.equal(getAppendFailureCount(), 0);
+});