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

# Error codes

> The error shapes the API returns and what each status code means.

Every endpoint documents the exact responses it returns. This page covers the error shapes and the status codes you see across the API.

## Error shapes

The shape depends on the surface:

**Speech, LLM, and unified endpoints** return a problem object. `title` and `status` are always present; `detail` adds context when available.

```json theme={null}
{
  "title": "Unauthorized",
  "status": 401,
  "detail": "No Authorization Header"
}
```

**The account API** returns a short envelope:

```json theme={null}
{ "error": "API key id not found" }
```

**WebSocket sessions** send an error frame with a machine-readable code and a message:

```json theme={null}
{ "type": "error", "code": "auth_error", "message": "Invalid or expired API key" }
```

Common WebSocket codes are `auth_error`, `config_error`, `rate_limit`, and `provider_error`.

## Status codes

| Status       | Meaning                                                | What to do                                                                                                                       |
| ------------ | ------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------- |
| `400`        | Bad request. The body or parameters are malformed.     | Fix the request and resend.                                                                                                      |
| `401`        | Missing or invalid API key.                            | Check the `Authorization` header. See [Authentication](/api-reference/authentication).                                           |
| `402`        | Insufficient credit or payment required.               | Top up the account or check billing.                                                                                             |
| `403`        | The key is valid but not allowed to use this resource. | Confirm the project has access.                                                                                                  |
| `404`        | The route or model does not exist.                     | Check the path and model code.                                                                                                   |
| `409`        | Conflict with the current state of the resource.       | Reconcile and retry.                                                                                                             |
| `413`        | Payload too large.                                     | Send a smaller request.                                                                                                          |
| `415`        | Unsupported media type.                                | Set a supported `Content-Type`.                                                                                                  |
| `422`        | Validation failed.                                     | Correct the fields named in the response.                                                                                        |
| `429`        | Rate limited.                                          | Back off and retry. See [Rate limits](/api-reference/rate-limits).                                                               |
| `500`        | Server error.                                          | Retry, and contact support if it persists.                                                                                       |
| `502`, `503` | Upstream or service unavailable.                       | Retry with backoff. On the agents control plane, `503` can mean a dependency is preparing, so wait for the `Retry-After` header. |