Function startStallWatchdog

src/tasks/LocalShellTask/LocalShellTask.tsx:46–104

(taskId: string, description: string, kind: BashTaskKind | undefined, toolUseId?: string, agentId?: AgentId)

// Output-side analog of peekForStdinData (utils/process.ts): fire a one-shot
// notification if output stops growing and the tail looks like a prompt.
function startStallWatchdog(taskId: string, description: string, kind: BashTaskKind | undefined, toolUseId?: string, agentId?: AgentId): () => void {
  if (kind === 'monitor') return () => {};
  const outputPath = getTaskOutputPath(taskId);
  let lastSize = 0;
  let lastGrowth = Date.now();
  let cancelled = false;
  const timer = setInterval(() => {
    void stat(outputPath).then(s => {
      if (s.size > lastSize) {
        lastSize = s.size;
        lastGrowth = Date.now();
        return;
      }
      if (Date.now() - lastGrowth < STALL_THRESHOLD_MS) return;
      void tailFile(outputPath, STALL_TAIL_BYTES).then(({
        content
      }) => {
        if (cancelled) return;
        if (!looksLikePrompt(content)) {
          // Not a prompt — keep watching. Reset so the next check is
          // 45s out instead of re-reading the tail on every tick.
          lastGrowth = Date.now();
          return;
        }
        // Latch before the async-boundary-visible side effects so an
        // overlapping tick's callback sees cancelled=true and bails.
        cancelled = true;
        clearInterval(timer);
        const toolUseIdLine = toolUseId ? `\n<${TOOL_USE_ID_TAG}>${toolUseId}</${TOOL_USE_ID_TAG}>` : '';
        const summary = `${BACKGROUND_BASH_SUMMARY_PREFIX}"${description}" appears to be waiting for interactive input`;
        // No <status> tag — print.ts treats <status> as a terminal
        // signal and an unknown value falls through to 'completed',
        // falsely closing the task for SDK consumers. Statusless
        // notifications are skipped by the SDK emitter (progress ping).
        const message = `<${TASK_NOTIFICATION_TAG}>
<${TASK_ID_TAG}>${taskId}</${TASK_ID_TAG}>${toolUseIdLine}
<${OUTPUT_FILE_TAG}>${outputPath}</${OUTPUT_FILE_TAG}>
<${SUMMARY_TAG}>${escapeXml(summary)}</${SUMMARY_TAG}>
</${TASK_NOTIFICATION_TAG}>
Last output:
${content.trimEnd()}

The command is likely blocked on an interactive prompt. Kill this task and re-run with piped input (e.g., \`echo y | command\`) or a non-interactive flag if one exists.`;
        enqueuePendingNotification({
          value: message,
          mode: 'task-notification',
          priority: 'next',
          agentId
        });
      }, () => {});
    }, () => {} // File may not exist yet
    );
  }, STALL_CHECK_INTERVAL_MS);
  timer.unref();
  return () => {
    cancelled = true;
    clearInterval(timer);
  };