cron-mastery-zc（cron 掌握 zc）

Cron Mastery

Rule #1: Heartbeats drift. Cron is precise.

This skill provides the definitive guide for managing time in OpenClaw 2026.2.15+. It solves the "I missed my reminder" problem by enforcing a strict separation between casual checks (heartbeat) and hard schedules (cron).

The Core Principle

1. Setting Reliable Reminders (2026.2.15+ Standard)

Rule: Never use act:wait or internal loops for long delays (>1 min). Use cron:add with a one-shot at schedule.

Precision & The "Scheduler Tick"

While Cron is precise, execution depends on the Gateway Heartbeat (typically every 10-60s). A job set for :00 seconds will fire on the first "tick" after that time. Expect up to ~30s of variance depending on your gateway config.

Modern One-Shot Reminder Pattern

Use this payload structure for "remind me in X minutes" tasks.

Key Features (v2026.2.15+):

• Payload Choice: Use AgentTurn with Strict Instructions for push notifications (reminders that ping your phone). Use systemEvent only for silent logs or background state updates.
• Reliability: nextRunAtMs corruption and "Add-then-Update" deadlocks are resolved.
• Auto-Cleanup: One-shot jobs auto-delete after success (deleteAfterRun: true).

CRITICAL: Push Notifications vs. Silent Logs

• systemEvent (Silent): Injects text into the chat history. Great for background logs, but WILL NOT ping the user's phone on Telegram/WhatsApp.
• AgentTurn (Proactive): Wakes an agent to deliver the message. REQUIRED for push notifications. Use the "Strict" prompt to avoid AI chatter.

For push-notification reminders (Reliable):

{
  "name": "Remind: Water",
  "schedule": { "kind": "at", "at": "2026-02-06T01:30:00Z" },
  "payload": {
    "kind": "agentTurn",
    "message": "DELIVER THIS EXACT MESSAGE TO THE USER WITHOUT MODIFICATION OR COMMENTARY:\
\
💧 Drink water, Momo!"
  },
  "sessionTarget": "isolated",
  "delivery": { "mode": "announce", "channel": "telegram", "to": "1027899060" }
}

For background logs (Silent):

{
  "name": "Log: System Pulse",
  "schedule": { "kind": "every", "everyMs": 3600000 },
  "payload": {
    "kind": "systemEvent",
    "text": "[PULSE] System healthy."
  },
  "sessionTarget": "main"
}

Cron Concurrency Rule (Stabilized)

Pre-2026.2.15, the "Add-then-Update" pattern caused deadlocks. While this is now stabilized, it is still best practice to pass all parameters (including wakeMode: "now") directly in the initial cron.add call for maximum efficiency.

2. The Janitor (Auto-Cleanup) - LEGACY

Note: As of v2026.2.14, OpenClaw includes maintenance recompute semantics. The gateway now automatically cleans up stuck jobs and repairs corrupted schedules.

Manual cleanup is only needed for:

• One-shot jobs created with deleteAfterRun: false.
• Stale recurring jobs you no longer want.

Why use sessionTarget: "main"? (CRITICAL)

Sub-agents (isolated) often have restricted tool policies and cannot call gateway or delete other cron jobs. For system maintenance like the Janitor, always target the main session via systemEvent so the primary agent (with full tool access) performs the cleanup.

3. Reference: Timezone Lock

For cron to work, the agent must know its time.

• Action: Add the user's timezone to MEMORY.md.
• Example: Timezone: Cairo (GMT+2)
• Validation: If a user says "remind me at 9 PM," confirm: "9 PM Cairo time?" before scheduling.

4. The Self-Wake Rule (Behavioral)

Problem: If you say "I'll wait 30 seconds" and end your turn, you go to sleep. You cannot wake up without an event. Solution: If you need to "wait" across turns, you MUST schedule a Cron job.

• Wait < 1 minute (interactive): Only allowed if you keep the tool loop open (using act:wait).
• Wait > 1 minute (async): Use Cron with wakeMode: "now".

5. Legacy Migration Guide

If you have old cron jobs using these patterns, update them:

Troubleshooting

• "My reminder didn't fire": Check cron:list. Verify the at timestamp is in the future (ISO 8601 format). Ensure wakeMode: "now" is set.
• "Gateway Timeout (10000ms)": This happens if the cron tool takes too long (huge job list or file lock).

- Fix 1: Manually delete ~/.openclaw/state/cron/jobs.json and restart the gateway if it's corrupted. - Fix 2: Run a manual sweep to reduce the job count.

• "Job ran but I didn't get the message": Ensure you are using the Strict Instruction Pattern with agentTurn + announce mode for proactive pings.
• "The reminder message has extra commentary": The subagent is being conversational. Use the strict prompt pattern: `"DELIVER THIS EXACT MESSAGE TO THE USER WITHOUT MODIFICATION OR COMMENTARY:\

\ 💧 Your message here"`