Bug Description

Cron jobs configured with sessionTarget: "isolated" and payload.kind: "agentTurn" never execute automatically, regardless of wakeMode setting.

Environment

• OpenClaw version: 2026.2.3-1
• OS: macOS Darwin arm64 (Apple Silicon)
• Install method: npm (homebrew prefix)

Steps to Reproduce

1. Create a cron job:

{
  "name": "Test Job",
  "schedule": { "kind": "cron", "expr": "*/30 * * * *", "tz": "America/Costa_Rica" },
  "sessionTarget": "isolated",
  "wakeMode": "now",
  "payload": {
    "kind": "agentTurn",
    "message": "Test task"
  }
}

2. Wait for scheduled time to pass
3. Check openclaw cron runs --id <jobId> - no new entries

Expected Behavior

Job should execute at scheduled time and appear in run history.

Actual Behavior

• Job never executes automatically
• openclaw cron list shows job as idle with nextRunAtMs in the past
• No entries in run history
• No errors in gateway logs
• Heartbeats ARE running (verified via sessions_list)

What I've Tried

1. Changed wakeMode from next-heartbeat to now - no effect
2. Changed schedule from kind: "every" to kind: "cron" - no effect
3. Changed sessionTarget to main with systemEvent - also doesn't fire
4. Restarted gateway - no effect
5. Verified heartbeats are running every 15m - they are

Related Issues

• Cron jobs with wakeMode 'now' incorrectly skipped when HEARTBEAT.md is empty #2217 mentions empty-heartbeat-file skip, but our HEARTBEAT.md has content
• PR Fixes cron jobs #3335 has a fix but isn't merged yet

Additional Context

Jobs that ran successfully days ago (same config) now don't fire. Something changed in scheduler behavior.