# Engine Errors

## `Engine.AsyncScopeError`

Thrown when [`Engine.with`](/api/Engine/with) is given an asynchronous function.

**Source:** [src/core/Engine.ts](https://github.com/wevm/ox/blob/main/src/core/Engine.ts#L237)

## `Engine.UnknownPrimitiveError`

Thrown when a slot is given an unrecognized primitive name.

**Source:** [src/core/Engine.ts](https://github.com/wevm/ox/blob/main/src/core/Engine.ts#L237)

## `Engine.UnknownSlotError`

Thrown when an unrecognized engine slot is supplied.

**Source:** [src/core/Engine.ts](https://github.com/wevm/ox/blob/main/src/core/Engine.ts#L237)