> For the complete documentation index, see [llms.txt](https://docs.unitlab.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.unitlab.ai/api-sdk-cli/sdks/pattern-workflow-worker.md).

# Pattern: Workflow worker

{% hint style="info" %}
**Outcome:** Claim available tasks, perform bounded work, and submit through the configured stage edge.
{% endhint %}

```python
annotate = project.workflow.get_stage(name="Annotate")

for task in annotate.get_tasks():
    task.claim()
    try:
        # Perform the approved external operation here.
        task.submit()
    except Exception:
        task.release()
        raise
```

A real worker should bound concurrency, record task IDs, handle already-claimed work, respect role permissions, and separate retriable execution from irreversible stage actions. Do not submit merely because an external process returned successfully; validate the expected annotation or artifact first.

### Operating contract

| Concern           | Required behavior                                                                |
| ----------------- | -------------------------------------------------------------------------------- |
| Execution surface | Pinned `unitlab==3.0.0` application environment on Python 3.10+.                 |
| Identity          | Least-privilege API key supplied through approved configuration.                 |
| Target resolution | Stable resource IDs and an explicitly bounded target set.                        |
| Success evidence  | Typed return fields, server-side state, and downstream acceptance of the result. |

### Failure and recovery boundary

| Condition                                       | Response                                                                                                     |
| ----------------------------------------------- | ------------------------------------------------------------------------------------------------------------ |
| Authentication or authorization fails           | Stop, correct the service identity or access model, rotate exposed credentials, and rerun a read-only check. |
| Validation or entitlement rejects the operation | Correct the input or entitlement; do not retry an unchanged request.                                         |
| A request times out                             | Inspect remote state before repeating a mutation because the server may have accepted it.                    |
| Asynchronous processing exceeds its deadline    | Preserve the Batch Queue or release ID, continue bounded monitoring, and inspect item-level failures.        |
| Only part of a batch succeeds                   | Keep successful identifiers, isolate failed rows, and retry only the corrected subset.                       |

{% hint style="warning" %}
Pin and test the production SDK version. Use stable IDs, keep secrets out of logs and command history, and record the correlation ID, target IDs, counts, final state, and redacted error details for material state changes.
{% endhint %}