cron-mastery – OpenClaw Skill

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name: cron-mastery description: Master OpenClaw's timing systems. Use for scheduling reliable reminders, setting up periodic maintenance (janitor jobs), and understanding when to use Cron vs Heartbeat for time-sensitive tasks.

Cron Mastery

Rule #1: Heartbeats drift. Cron is precise.

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

The Core Principle

System	Behavior	Best For	Risk
Heartbeat	"I'll check in when I can" (e.g., every 30-60m)	Email checks, casual news summaries, low-priority polling.	Drift: A "remind me in 10m" task will fail if the heartbeat is 30m.
Cron	"I will run at exactly X time"	Reminders ("in 5 mins"), daily reports, system maintenance.	Clutter: Creates one-off jobs that need cleanup.

1. Setting Reliable Reminders

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

Standard Reminder Pattern (JSON)

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

{
  "name": "Remind: Drink Water",
  "schedule": {
    "kind": "at",
    "atMs": <CURRENT_MS + DELAY_MS>
  },
  "payload": {
    "kind": "agentTurn",
    "message": "⏰ Reminder: Drink water!",
    "deliver": true
  },

Note: Even with wakeMode: "next-heartbeat", the cron system forces an event injection at atMs. Use mode: "now" in the cron:wake tool if you need to force an immediate wake outside of a job payload.

⚠️ The Delivery Rule (CRITICAL)

When scheduling an agentTurn via Cron that is meant to provide an update to the user:

• ALWAYS set "deliver": true in the payload.
• Without "deliver": true, the sub-agent will run the task but the output will NEVER be seen by the human. It will be "talking in a dark room."

2. The Janitor (Auto-Cleanup)

One-shot cron jobs (kind: at) disable themselves after running but stay in the list as "ghosts" (enabled: false, lastStatus: ok). To prevent clutter, install the Daily Janitor.

Setup Instructions

1. Check current jobs: cron:list (includeDisabled: true)
2. Create the Janitor:
   • Name: Daily Cron Cleanup
   • Schedule: Every 24 hours (everyMs: 86400000)
   • Payload: An agent turn that runs a specific prompt.

The Janitor Prompt (Agent Turn)

"Time for the 24-hour cron sweep. List all cron jobs including disabled ones. If you find any jobs that are enabled: false and have lastStatus: ok (finished one-shots), delete them to keep the list clean. Do not delete active recurring jobs. Log what you deleted."

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".

Example Payload for "Checking back in 30s":

{
  "schedule": { "kind": "at", "atMs": <NOW + 30000> },
  "payload": { "kind": "agentTurn", "message": "⏱️ 30s check-in. Report status." },
  "wakeMode": "now"
}

Troubleshooting

• "My reminder didn't fire": Check cron:list. If the job exists but didn't fire, check the system clock vs atMs.
• "I have 50 old jobs": Run the Janitor manually immediately.