# `ALLM.Error.EngineError`
[🔗](https://github.com/cykod/ALLM/blob/v0.3.0/lib/allm/error/engine_error.ex#L1)

Errors raised by engine-level operations before any adapter call.

Layer A — serializable (no PIDs, refs, funs, or raw API keys). Refines spec
§20's atom taxonomy into a first-class struct so every Layer B/C/D public
function can return `{:error, %ALLM.Error.EngineError{}}` uniformly.

See Phase 1 design §Sub-phase 1.1 for the closed reason enum.

# `reason`

```elixir
@type reason() ::
  :missing_adapter
  | :missing_stream_adapter
  | :missing_model
  | :missing_key
  | :unknown_tool
  | :invalid_engine
  | :unsupported_response_format
  | :no_image_adapter
```

Closed set of engine-level error reasons (spec §20, §35.4).

# `t`

```elixir
@type t() :: %ALLM.Error.EngineError{
  __exception__: true,
  cause: term() | nil,
  message: String.t(),
  metadata: map(),
  provider: atom() | nil,
  reason: reason()
}
```

# `new`

```elixir
@spec new(
  reason(),
  keyword()
) :: t()
```

Build an `%EngineError{}` from a `reason` atom and optional keyword fields.

`opts` may include `:message`, `:provider`, `:cause`, and `:metadata`. When
`:message` is omitted, it defaults to `"engine error: #{reason}"` so
`Exception.message/1` always returns a non-empty binary.

Raises `ArgumentError` if `reason` is not one of the atoms in the closed
`t:reason/0` enum.

## Examples

    iex> err = ALLM.Error.EngineError.new(:missing_adapter)
    iex> err.reason
    :missing_adapter
    iex> Exception.message(err)
    "engine error: missing_adapter"

    iex> err = ALLM.Error.EngineError.new(:missing_key, provider: :openai, message: "OPENAI_API_KEY unset")
    iex> err.provider
    :openai
    iex> Exception.message(err)
    "OPENAI_API_KEY unset"

---

*Consult [api-reference.md](api-reference.md) for complete listing*