[BUG] CronCreate: session-only cron silently misses scheduled fires during idle sessions

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Bug — Critical

Feature: CronCreate scheduled jobs (session-only)

I set up a recurring hourly cron to run a command at :40 every hour.
The session was confirmed idle for 47 minutes (verified via session log
timestamps) covering the scheduled fire time. The cron silently did not
fire — no execution, no error, no log entry. This happened repeatedly.

The only successful fire was when the session had just transitioned from
active to idle (warm event loop). All subsequent fires during cold-idle
sessions were missed with zero feedback.

Steps to reproduce:

1. CronCreate(cron="40 ", prompt="...", recurring=True)
2. Confirm listed via CronList
3. Let session go fully idle for 30+ minutes
4. Observe: scheduled time passes, nothing fires, no indication of failure

Expected: cron fires reliably during idle sessions, OR user is notified
of a missed fire, OR docs clearly state it only works for warm sessions.

Actual: silent miss. No retry, no notification, no log.

Impact: multiple health checks missed in a production monitoring workflow.
Significant time wasted debugging — the feature appeared to work on first
fire then silently stopped. This feature should not be presented as
reliable scheduling until it actually is. Do not advertise untested features. (Apple Claude Code v1.3.0)

What Should Happen?

cron should trigger reliably

Error Messages/Logs

Steps to Reproduce

Is in the body

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Apple Claude 1.3.0

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_