---
summary: "Guidance for choosing between heartbeat and cron jobs for automation"
read_when:
  - Deciding how to schedule recurring tasks
  - Setting up background monitoring or notifications
  - Optimizing token usage for periodic checks
title: "Cron vs Heartbeat"
---

# Cron vs Heartbeat: When to Use Each

Both heartbeats and cron jobs let you run tasks on a schedule. This guide helps you choose the right mechanism for your use case.

## Quick Decision Guide

| Use Case                             | Recommended         | Why                                      |
| ------------------------------------ | ------------------- | ---------------------------------------- |
| Check inbox every 30 min             | Heartbeat           | Batches with other checks, context-aware |
| Send daily report at 9am sharp       | Cron (isolated)     | Exact timing needed                      |
| Monitor calendar for upcoming events | Heartbeat           | Natural fit for periodic awareness       |
| Run weekly deep analysis             | Cron (isolated)     | Standalone task, can use different model |
| Remind me in 20 minutes              | Cron (main, `--at`) | One-shot with precise timing             |
| Background project health check      | Heartbeat           | Piggybacks on existing cycle             |

## Heartbeat: Periodic Awareness

Heartbeats run in the **main session** at a regular interval (default: 30 min). They're designed for the koi to check on things and surface anything important.

### When to use heartbeat

- **Multiple periodic checks**: Instead of 5 separate cron jobs checking inbox, calendar, weather, notifications, and project status, a single heartbeat can batch all of these.
- **Context-aware decisions**: The koi has full main-session context, so it can make smart decisions about what's urgent vs. what can wait.
- **Conversational continuity**: Heartbeat runs share the same session, so the koi remembers recent conversations and can follow up naturally.
- **Low-overhead monitoring**: One heartbeat replaces many small polling tasks.

### Heartbeat advantages

- **Batches multiple checks**: One koi turn can review inbox, calendar, and notifications together.
- **Reduces API calls**: A single heartbeat is cheaper than 5 isolated cron jobs.
- **Context-aware**: The koi knows what you've been working on and can prioritize accordingly.
- **Smart suppression**: If nothing needs attention, the koi replies `HEARTBEAT_OK` and no message is delivered.
- **Natural timing**: Drifts slightly based on queue load, which is fine for most monitoring.

### Heartbeat example: HEARTBEAT.md checklist

```md
# Heartbeat checklist

- Check email for urgent messages
- Review calendar for events in next 2 hours
- If a background task finished, summarize results
- If idle for 8+ hours, send a brief check-in
```

The koi reads this on each heartbeat and handles all items in one turn.

### Configuring heartbeat

```json5
{
  kois: {
    defaults: {
      heartbeat: {
        every: "30m", // interval
        target: "last", // where to deliver alerts
        activeHours: { start: "08:00", end: "22:00" }, // optional
      },
    },
  },
}
```

See [Heartbeat](/gateway/heartbeat) for full configuration.

## Cron: Precise Scheduling

Cron jobs run at **exact times** and can run in isolated sessions without affecting main context.

### When to use cron

- **Exact timing required**: "Send this at 9:00 AM every Monday" (not "sometime around 9").
- **Standalone tasks**: Tasks that don't need conversational context.
- **Different model/thinking**: Heavy analysis that warrants a more powerful model.
- **One-shot reminders**: "Remind me in 20 minutes" with `--at`.
- **Noisy/frequent tasks**: Tasks that would clutter main session history.
- **External triggers**: Tasks that should run independently of whether the koi is otherwise active.

### Cron advantages

- **Exact timing**: 5-field cron expressions with timezone support.
- **Session isolation**: Runs in `cron:<jobId>` without polluting main history.
- **Model overrides**: Use a cheaper or more powerful model per job.
- **Delivery control**: Isolated jobs default to `announce` (summary); choose `none` as needed.
- **Immediate delivery**: Announce mode posts directly without waiting for heartbeat.
- **No koi context needed**: Runs even if main session is idle or compacted.
- **One-shot support**: `--at` for precise future timestamps.

### Cron example: Daily morning briefing

```bash
SKYKOI cron add \
  --name "Morning briefing" \
  --cron "0 7 * * *" \
  --tz "America/New_York" \
  --session isolated \
  --message "Generate today's briefing: weather, calendar, top emails, news summary." \
  --model opus \
  --announce \
  --channel whatsapp \
  --to "+15551234567"
```

This runs at exactly 7:00 AM New York time, uses Opus for quality, and announces a summary directly to WhatsApp.

### Cron example: One-shot reminder

```bash
SKYKOI cron add \
  --name "Meeting reminder" \
  --at "20m" \
  --session main \
  --system-event "Reminder: standup meeting starts in 10 minutes." \
  --wake now \
  --delete-after-run
```

See [Cron jobs](/automation/cron-jobs) for full CLI reference.

## Decision Flowchart

```
Does the task need to run at an EXACT time?
  YES -> Use cron
  NO  -> Continue...

Does the task need isolation from main session?
  YES -> Use cron (isolated)
  NO  -> Continue...

Can this task be batched with other periodic checks?
  YES -> Use heartbeat (add to HEARTBEAT.md)
  NO  -> Use cron

Is this a one-shot reminder?
  YES -> Use cron with --at
  NO  -> Continue...

Does it need a different model or thinking level?
  YES -> Use cron (isolated) with --model/--thinking
  NO  -> Use heartbeat
```

## Combining Both

The most efficient setup uses **both**:

1. **Heartbeat** handles routine monitoring (inbox, calendar, notifications) in one batched turn every 30 minutes.
2. **Cron** handles precise schedules (daily reports, weekly reviews) and one-shot reminders.

### Example: Efficient automation setup

**HEARTBEAT.md** (checked every 30 min):

```md
# Heartbeat checklist

- Scan inbox for urgent emails
- Check calendar for events in next 2h
- Review any pending tasks
- Light check-in if quiet for 8+ hours
```

**Cron jobs** (precise timing):

```bash
# Daily morning briefing at 7am
SKYKOI cron add --name "Morning brief" --cron "0 7 * * *" --session isolated --message "..." --announce

# Weekly project review on Mondays at 9am
SKYKOI cron add --name "Weekly review" --cron "0 9 * * 1" --session isolated --message "..." --model opus

# One-shot reminder
SKYKOI cron add --name "Call back" --at "2h" --session main --system-event "Call back the client" --wake now
```

## Lobster: Deterministic workflows with approvals

Lobster is the workflow runtime for **multi-step tool pipelines** that need deterministic execution and explicit approvals.
Use it when the task is more than a single koi turn, and you want a resumable workflow with human checkpoints.

### When Lobster fits

- **Multi-step automation**: You need a fixed pipeline of tool calls, not a one-off prompt.
- **Approval gates**: Side effects should pause until you approve, then resume.
- **Resumable runs**: Continue a paused workflow without re-running earlier steps.

### How it pairs with heartbeat and cron

- **Heartbeat/cron** decide _when_ a run happens.
- **Lobster** defines _what steps_ happen once the run starts.

For scheduled workflows, use cron or heartbeat to trigger an koi turn that calls Lobster.
For ad-hoc workflows, call Lobster directly.

### Operational notes (from the code)

- Lobster runs as a **local subprocess** (`lobster` CLI) in tool mode and returns a **JSON envelope**.
- If the tool returns `needs_approval`, you resume with a `resumeToken` and `approve` flag.
- The tool is an **optional plugin**; enable it additively via `tools.alsoAllow: ["lobster"]` (recommended).
- If you pass `lobsterPath`, it must be an **absolute path**.

See [Lobster](/tools/lobster) for full usage and examples.

## Main Session vs Isolated Session

Both heartbeat and cron can interact with the main session, but differently:

|         | Heartbeat                       | Cron (main)              | Cron (isolated)            |
| ------- | ------------------------------- | ------------------------ | -------------------------- |
| Session | Main                            | Main (via system event)  | `cron:<jobId>`             |
| History | Shared                          | Shared                   | Fresh each run             |
| Context | Full                            | Full                     | None (starts clean)        |
| Model   | Main session model              | Main session model       | Can override               |
| Output  | Delivered if not `HEARTBEAT_OK` | Heartbeat prompt + event | Announce summary (default) |

### When to use main session cron

Use `--session main` with `--system-event` when you want:

- The reminder/event to appear in main session context
- The koi to handle it during the next heartbeat with full context
- No separate isolated run

```bash
SKYKOI cron add \
  --name "Check project" \
  --every "4h" \
  --session main \
  --system-event "Time for a project health check" \
  --wake now
```

### When to use isolated cron

Use `--session isolated` when you want:

- A clean slate without prior context
- Different model or thinking settings
- Announce summaries directly to a channel
- History that doesn't clutter main session

```bash
SKYKOI cron add \
  --name "Deep analysis" \
  --cron "0 6 * * 0" \
  --session isolated \
  --message "Weekly codebase analysis..." \
  --model opus \
  --thinking high \
  --announce
```

## Cost Considerations

| Mechanism       | Cost Profile                                            |
| --------------- | ------------------------------------------------------- |
| Heartbeat       | One turn every N minutes; scales with HEARTBEAT.md size |
| Cron (main)     | Adds event to next heartbeat (no isolated turn)         |
| Cron (isolated) | Full koi turn per job; can use cheaper model            |

**Tips**:

- Keep `HEARTBEAT.md` small to minimize token overhead.
- Batch similar checks into heartbeat instead of multiple cron jobs.
- Use `target: "none"` on heartbeat if you only want internal processing.
- Use isolated cron with a cheaper model for routine tasks.

## Related

- [Heartbeat](/gateway/heartbeat) - full heartbeat configuration
- [Cron jobs](/automation/cron-jobs) - full cron CLI and API reference
- [System](/cli/system) - system events + heartbeat controls
