Sandbox container does not sleep with SANDBOX_SLEEP_AFTER=10m due to recurring Sandbox DO alarms

[Shefcoding]

Summary

My moltworker container doesnt sleep after long idle periods even
with SANDBOX_SLEEP_AFTER=10m.
No persistent UI/WebSocket clients are intentionally open, and cron has been
reduced to every 6 hours.

Environment

• Project: cloudflare/moltworker (official codebase)
• Worker name: moltbot-sandbox
• Date observed: 2026-02-12
• SANDBOX_SLEEP_AFTER secret set to: 10m
• Cron trigger set to: 0 */6 * * *

Expected behavior

After ~10 minutes with no user traffic, container should sleep.
Next request should trigger a cold start.

Actual behavior

Container appears to stay warm; no cold start observed after idle periods.
wrangler tail shows recurring Alarm events from Sandbox Durable Object
roughly every ~3 minutes.

Evidence (tail excerpts)

• Alarm @ 12-2-2026, 11:16:44 - Ok
• Alarm @ 12-2-2026, 11:19:44 - Ok
• Alarm @ 12-2-2026, 11:22:44 - Ok
• Alarm @ 12-2-2026, 11:25:44 - Ok

Related logs around same window:

• Sandbox.listProcesses - Canceled @ 12-2-2026, 11:16:46
• Sandbox.startProcess - Canceled @ 12-2-2026, 11:16:46
• details":"mount | grep \"s3fs on /data/moltbot\" ...
• Sandbox.containerFetch - Canceled @ 12-2-2026, 11:16:49

Notes

• External request example appears later:
  • GET https://xxx.workers.dev/ - Ok @ 12-2-2026, 11:26:34
• The recurring alarms occur even when traffic is expected to be idle.
• This suggests internal Sandbox DO alarms may be preventing inactivity-based
  sleep.

Request

Please confirm:

1. Whether recurring Sandbox DO alarms reset/extend inactivity timers for
   sleepAfter.
2. Whether this is expected behavior or a bug.
3. Recommended mitigation to allow reliable sleeping with
   SANDBOX_SLEEP_AFTER.