> For the complete documentation index, see [llms.txt](https://docs.layerlens.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.layerlens.ai/more-in-this-section-9/authentication-1.md).

# Authentication Problems

Authentication troubleshooting — 401 errors, invalid keys, missing configuration.

This guide covers common authentication-related issues when using the LayerLens Python SDK.

## Common Authentication Errors

### Invalid or Missing API Key

**Error**: `AuthenticationError: Invalid API key`

**Symptoms**:

* 401 Unauthorized responses
* "Invalid API key" error messages
* Authentication fails immediately

### Missing Required Configuration

**Error**: `StratixError: The api_key client option must be set either by passing api_key to the client or by setting the LAYERLENS_STRATIX_API_KEY environment variable`

Set the environment variable or pass the key explicitly:

```bash
export LAYERLENS_STRATIX_API_KEY="your-api-key"
```

```python
from layerlens import Stratix

client = Stratix(api_key="your-api-key")
```

## See Also

* [API Key Management](/more-in-this-section-9/api-key-management.md)
* [Environment Variables](/more-in-this-section-9/environment-variables.md)
* [Error Codes Reference](/more-in-this-section-9/error-codes.md)