> ## Documentation Index
> Fetch the complete documentation index at: https://usefused.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Cron schedules

> Declare fixed UTC task schedules in the cron folder.

Put fixed schedules in `cron/`. Harnest discovers them automatically in both ADK and LangGraph projects.

## Folder layout

```text theme={null}
my-agent/
├── tasks/build_report.py
├── cron/daily_report.py
└── lifecycle/storage.py
```

Use one schedule per Python file, with a matching export: `daily_report.py` defines `daily_report`. Nested folders are unsupported; names beginning with `_` or `.` are ignored. No import in `agent.py` is needed.

## Declare an application-owned schedule

This example queues a report at **09:00 UTC, Monday–Friday**:

<CodeGroup>
  ```python tasks/build_report.py theme={null}
  from harnest.task import task


  @task(queue="reports", max_retries=3)
  async def build_report(account_id: str) -> dict:
      """Build one account report on the reports queue."""

      return {"account_id": account_id, "status": "ready"}
  ```

  ```python cron/daily_report.py theme={null}
  from harnest import cron
  from tasks.build_report import build_report


  daily_report = cron.Cron(
      "0 9 * * 1-5",
      task=build_report,
      arguments={"account_id": "acct_123"},
  )
  ```
</CodeGroup>

Target a root `@task` and pass JSON-safe arguments matching its signature.

## Start the scheduler

Register the **same storage instance** with `@lifecycle.storage.tasks` and `@lifecycle.storage.cron` ([setup](/docs/harnest/runtime/task-storage)), then run:

```bash theme={null}
harnest serve .
```

Keep this process running. `harnest run` does not activate schedules.

## Schedule contract

| Rule     | Supported value                                              |
| -------- | ------------------------------------------------------------ |
| Fields   | Minute, hour, day of month, month, day of week               |
| Timezone | `UTC` only                                                   |
| Syntax   | `*`, ASCII numbers, comma lists, ascending ranges, `/step`   |
| Replicas | Shared task/cron provider atomically commits each occurrence |

Tasks may retry; make their side effects idempotent. See [task execution](/docs/harnest/build/queued-tasks). Scheduled tasks that invoke an agent need an explicit [service principal](/docs/harnest/runtime/agent-runtime-principals) to access governed tools and MCP operations.

For schedules created by tools at runtime, see [Dynamic schedules](/docs/harnest/build/dynamic-schedules).