# tinker_cookbook.rl.RolloutError

## *class* [**tinker_cookbook.rl.RolloutError**](https://github.com/thinking-machines-lab/tinker-cookbook/blob/main/tinker_cookbook/rl/types.py#L285)()

A captured error from a failed trajectory rollout.

Stored on [`TrajectoryGroup`](https://tinker-docs.thinkingmachines.ai/cookbook/api-reference/rl/trajectorygroup/index.md) so error information flows through return values (including across process boundaries via pickle) without requiring shared mutable state.

**Fields:**

- [**error_type**](https://github.com/thinking-machines-lab/tinker-cookbook/blob/main/tinker_cookbook/rl/types.py#L299) (*str*) – The exception class name, e.g. `'BadRequestError'`.
- [**error_message**](https://github.com/thinking-machines-lab/tinker-cookbook/blob/main/tinker_cookbook/rl/types.py#L301) (*str*) – `str(exception)` — the human-readable error description.

## Referenced by

- [tinker_cookbook.rl.TrajectoryGroup](https://tinker-docs.thinkingmachines.ai/cookbook/api-reference/rl/trajectorygroup/index.md)