Schedule a prompt to fire on a recurring cron schedule, or one-shot at the next match. Cron tasks re-run an agent prompt automatically on an interval when every firing is allowed to produce a normal assistant response, such as a reminder or a scheduled status report.

Cron is not a silent polling primitive. Every firing starts an agent turn, and hiding the injected cron message does not hide that turn's assistant response. For ongoing logs, file watching, or PR/CI polling that should report only meaningful state changes, use `monitor` with a script that writes a line only when there is an event to process, and set `persistent: true` so the monitor survives the first emitted event. Do not schedule a cron prompt that asks the agent to suppress routine polls; prompt wording cannot make a cron-triggered assistant turn reliably silent.

Use a single `op` field to select the operation:

- `op: "create"` accepts a standard 5-field `cron_expression` in your local timezone, the `prompt` to run, and `recurring` (whether the job recurs or fires once). It returns an 8-character job id you can pass to `op: "delete"`. Each session can hold up to 50 scheduled tasks. Recurring tasks auto-expire 7 days after creation; one-shot tasks self-delete after firing.
- `op: "list"` enumerates every scheduled task in the session.
- `op: "delete"` cancels a task by `id`.

## Cron expressions

`op: "create"` accepts 5-field cron: `minute hour day-of-month month day-of-week`. All fields support `*`, single values (`5`), steps (`*/15`), ranges (`1-5`), and comma lists (`1,15,30`). Day-of-week uses `0`/`7` for Sunday through `6` for Saturday. Extended syntax like `L`, `W`, `?`, or month/weekday names is not supported.

|Example|Meaning|
|:---|:---|
|`*/5 * * * *`|Every 5 minutes|
|`0 * * * *`|Every hour on the hour|
|`0 9 * * *`|Every day at 9am local|
|`0 9 * * 1-5`|Weekdays at 9am local|

## Lifecycle

- Tasks fire between turns, never mid-response.
- All times are interpreted in the local timezone.
- Recurring tasks fire with up to 30 minutes of deterministic jitter (or up to half their interval for sub-hourly tasks). One-shot tasks scheduled for `:00` or `:30` may fire up to 90 s early. Pick an off-minute if exact timing matters.
- Closing or replacing the session clears every scheduled task.