fix(rectification): keep adopt narration timeout on a clearable ref timer

AbortSignal.timeout() is unref'd, so a hanging generateText drained the test event loop and cancelled the rest of the file. Clear the timer after the model returns.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/lib/rectification-agentic/v9/adopt-narration-agent.ts

@@ -33,24 +33,63 @@ export type AdoptNarrationDelivery = Readonly<{
   adopt_narration: AdoptNarrationOutcome;
 }>;
 
+type DisposableAbort = Readonly<{
+  signal: AbortSignal;
+  dispose: () => void;
+}>;
+
 function composedAbortSignal(
   signal: AbortSignal | undefined,
   timeoutMs: number,
-): AbortSignal {
-  const timeout = AbortSignal.timeout(timeoutMs);
-  return signal ? AbortSignal.any([signal, timeout]) : timeout;
+): DisposableAbort {
+  const controller = new AbortController();
+  // Must stay ref'd. The platform timeout signal uses an unref timer, so a hanging
+  // generateText lets the event loop drain before abort (BUG-523).
+  const timeoutId = globalThis.setTimeout(() => {
+    if (!controller.signal.aborted) {
+      controller.abort(new DOMException("adopt narration timed out", "TimeoutError"));
+    }
+  }, timeoutMs);
+  const onExternalAbort = () => {
+    if (!controller.signal.aborted) {
+      controller.abort(signal?.reason ?? new DOMException("aborted", "AbortError"));
+    }
+  };
+  if (signal) {
+    if (signal.aborted) onExternalAbort();
+    else signal.addEventListener("abort", onExternalAbort);
+  }
+  return {
+    signal: controller.signal,
+    dispose: () => {
+      globalThis.clearTimeout(timeoutId);
+      signal?.removeEventListener("abort", onExternalAbort);
+    },
+  };
 }
 
-function whenAborted(signal: AbortSignal): Promise<never> {
-  return new Promise((_, reject) => {
-    if (signal.aborted) {
+function whenAborted(signal: AbortSignal): {
+  promise: Promise<never>;
+  dispose: () => void;
+} {
+  let onAbort: (() => void) | undefined;
+  const promise = new Promise<never>((_, reject) => {
+    const fail = () => {
       reject(signal.reason ?? new Error("aborted"));
+    };
+    if (signal.aborted) {
+      fail();
       return;
     }
-    signal.addEventListener("abort", () => {
-      reject(signal.reason ?? new Error("aborted"));
-    }, { once: true });
+    onAbort = fail;
+    signal.addEventListener("abort", fail, { once: true });
   });
+  return {
+    promise,
+    dispose: () => {
+      if (onAbort) signal.removeEventListener("abort", onAbort);
+    },
+  };
 }
 
 export function logAdoptNarrationOutcome(outcome: AdoptNarrationOutcome): void {
@@ -117,14 +156,15 @@ export async function deliverAdoptNarration(input: {
     logAdoptNarrationOutcome(delivery.adopt_narration);
     return delivery;
   }
-  const signal = composedAbortSignal(
+  const composed = composedAbortSignal(
     input.signal,
     input.timeoutMs ?? ADOPT_NARRATION_TIMEOUT_MS,
   );
+  const aborted = whenAborted(composed.signal);
   try {
     const text = await Promise.race([
-      generate(input.facts, signal),
-      whenAborted(signal),
+      generate(input.facts, composed.signal),
+      aborted.promise,
     ]);
     const checked = validateAdoptNarration(text, input.facts);
     if (!checked.ok) {
@@ -145,6 +185,9 @@ export async function deliverAdoptNarration(input: {
     const delivery = { text: input.fallback, adopt_narration: "template:model_error" as const };
     logAdoptNarrationOutcome(delivery.adopt_narration);
     return delivery;
+  } finally {
+    aborted.dispose();
+    composed.dispose();
   }
 }