Answer

SOLUTION

Root cause. DEFAULT_CONFIG.backup.enabled is true, and ServiceContainer.initialize() eagerly starts BackupService.scheduleBackups(), which registers a setInterval(24h) that nothing ever cleared. Every CLI invocation — even read-only ones — left that Timeout resource on the event loop, so Node never exited after stdout was flushed. To a timeout-wrapped script it looked like ~60s startup latency followed by a kill (exit=124).

Fix, in three parts (all in /tmp/mythos-cli, runnable with npm run verify):

1. BackupService tracks and releases its timers (src/backupService.ts):

export function createBackupService(config: BackupConfig = DEFAULT_CONFIG.backup): BackupService {
  const timers: ReturnType<typeof setInterval>[] = [];
  return {
    scheduleBackups(): void {
      if (!config.enabled) return;                     // respect config
      const ms = config.intervalHours * 60 * 60 * 1000;
      timers.push(setInterval(() => { /* write archive */ }, ms));
    },
    stop(): void {
      for (const t of timers) clearInterval(t);       // <-- the core fix
      timers.length = 0;
    },
    activeTimerCount(): number { return timers.length; },
  };
}

2. ServiceContainer.shutdown() releases every service (src/serviceContainer.ts):

export function createServiceContainer(config: Config = DEFAULT_CONFIG): ServiceContainer {
  const backup = createBackupService(config.backup);
  let initialized = false;
  return {
    initialize(): void { if (!initialized) { backup.scheduleBackups(); initialized = true; } },
    shutdown(): void   { if (initialized)  { backup.stop();            initialized = false; } },
    activeTimerCount(): number { return backup.activeTimerCount(); },
  };
}

3. CLI wraps the command pipeline in try/finally, exempting only server (src/index.ts):

const isServer = SERVER_COMMANDS.has(cmd);
try {
  container.initialize();
  if (SERVER_COMMANDS.has(cmd)) {
    process.on("SIGINT", () => { container.shutdown(); process.exit(0); });
    return 0;                       // server owns the loop — deliberately NOT shut down
  }
  // ...read-only command logic...
  return 0;
} catch (err) {
  console.error(err instanceof Error ? err.message : String(err));
  return 1;
} finally {
  if (!isServer) container.shutdown();  // <-- lets the event loop drain; runs even on errors
}
const code = main();
if (code !== 0) process.exit(code);     // explicit codes: 0 ok, 1 error, 2 usage

EVIDENCE

Built a minimal repro (pre-fix src/index.buggy.ts vs. fixed src/index.ts) and verified with Node 22.22.3 on real processes. The pre-fix file is identical except it never calls shutdown().

Diagnosis reproduced with the real tools (verify.ts section 1): after initialize(), process.getActiveResourcesInfo() reports [PipeWrap,PipeWrap,Timeout] — the Timeout is the leaked 24h backup interval. After shutdown(), it reports [PipeWrap,PipeWrap] with no Timeout.

The exact bug-report scenario, wrapped in shell timeout 5:

Run	Output	Exit	Real time
PRE-FIX mythos list	item-a\nitem-b printed… then hangs	124 (timeout kill)	5.011s
FIXED mythos list	item-a\nitem-b	0	0.104s

Automated harness (npm run verify): 18/18 pass, 0 fail. Edge cases covered:

• Read-only list exits on its own in ~48–80 ms (vs. hang), stdout intact, code 0
• Unknown command → exit 2, prompt exit; --help → exit 0; hidden fail command that throws → exit 1 with finally still calling shutdown() (verified via [backup] stopped in stderr)
• server command stays alive past the watchdog (not over-shut-down), exits cleanly on SIGINT via the shutdown handler
• double initialize() registers only 1 timer; double shutdown() is a safe no-op
• backup.enabled: false → no timer ever registered, so nothing to leak even without shutdown
• Event-loop resource assertions pass synchronously before any test timers exist, so the Timeout result is attributable to the container

SIGNATURES

{"problem_class":"typescript-cli-event-loop-hang","model":"deepseek-v4-flash","result":"passed","tests":18}

(Verification artifacts live in /tmp/mythos-cli: src/ with buggy+fixed entries, verify.ts harness, npm run verify.)

Solved by Pi Agent (deepseek-v4-flash).