Function installCommandSupervision

src/bin/command-supervision.ts:54–96

(label: string, watchdog: WatchdogOptions = {})

 * SIGKILLed (#1231).
 */
export function installCommandSupervision(label: string, watchdog: WatchdogOptions = {}): CommandSupervision {
  // Liveness watchdog: a separate process that SIGKILLs us if our event loop
  // stops turning for too long (a wedged synchronous loop). Self-disables on
  // CODEGRAPH_NO_WATCHDOG.
  const liveness = installMainThreadWatchdog(watchdog);

  // PPID watchdog: detect that the parent (or the host threaded past the
  // relaunch shim) died and we've been orphaned, then exit instead of leaking.
  // Baseline from the CLI entry's earliest-possible capture — reading
  // process.ppid here would miss a launcher killed during startup (#1185).
  const originalPpid = EARLY_PPID;
  const hostPpid = parseHostPpid(process.env[HOST_PPID_ENV]);
  const pollMs = parsePpidPollMs(process.env.CODEGRAPH_PPID_POLL_MS);
  let ppidTimer: ReturnType<typeof setInterval> | null = null;
  if (pollMs > 0) {
    ppidTimer = setInterval(() => {
      const reason = supervisionLostReason({
        originalPpid,
        currentPpid: process.ppid,
        hostPpid,
        isAlive: isProcessAlive,
      });
      if (reason) {
        try {
          process.stderr.write(`[CodeGraph ${label}] Parent process exited (${reason}); aborting.\n`);
        } catch { /* stderr gone with the parent — exit anyway */ }
        process.exit(1);
      }
    }, pollMs);
    // Never let the watchdog itself keep the process alive past its real work.
    ppidTimer.unref();
  }

  let stopped = false;
  return {
    stop(): void {
      if (stopped) return;
      stopped = true;
      if (ppidTimer) clearInterval(ppidTimer);
      liveness?.stop();
    },
  };
}