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

# Errors

> Errors the Stateful Actor runtime can surface — BlockConcurrencyTimeoutError, ActorOutputGateError, ActorMethodTimeoutError, ActorFetchTimeoutError, and CodecError.

| Error                          | Meaning                                                                                                                                                                                                                                     |
| ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `BlockConcurrencyTimeoutError` | `ctx.blockConcurrencyWhile`'s callback exceeded the 30s budget                                                                                                                                                                              |
| `ActorOutputGateError`         | A storage write initiated during a method rejected after the method returned; surfaces in place of the successful return value, with the underlying failure appended to the error message. Also raised when a `transaction` callback throws |
| `ActorMethodTimeoutError`      | An RPC method exceeded its wall-clock budget (30s by default). The invocation fails; the instance is not torn down                                                                                                                          |
| `ActorFetchTimeoutError`       | The actor's `fetch(req)` handler exceeded its wall-clock budget (30s)                                                                                                                                                                       |
| `CodecError`                   | A method argument, return value, or storage value could not be serialized (e.g. a function, a circular structure)                                                                                                                           |

On the **caller** side, a failed stub call rejects with an `Error` whose `name` identifies
the cause — for example `ActorMethodError` (your method threw; message preserved),
`ActorPrivateMethodError` (`_`-prefixed method), or `ActorUnknownMethodError`. Branch on
`err.name` if you need to distinguish them.

## Related

* [Actor Context](/docs/edge-compute/stateful-actors/api-reference/context) — `blockConcurrencyWhile`
* [Execution Model](/docs/edge-compute/stateful-actors/concepts/execution-model) — the output-gate guarantee behind `ActorOutputGateError`