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

# MODEL_AUTHENTICATION

<Note>
  Currently only used in `langchainjs` (JavaScript/TypeScript).
</Note>

Your model provider is denying you access to their service.

This error typically occurs when there's an issue with your authentication credentials or API keys.

## Troubleshooting

* Confirm that your API key or authentication credentials are accurate and valid.
* If using environment-based authentication, verify:
  * The variable name is spelled correctly
  * The variable contains an assigned value
  * Third-party packages like `dotenv` haven't interfered with loading
* If using a proxy or non-standard endpoint, make sure that your custom provider does not expect an alternative authentication scheme.
* Bypass environment variable issues by passing credentials explicitly:

```python theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
from langchain_openai import ChatOpenAI

model = ChatOpenAI(api_key="YOUR_KEY_HERE")
```

***

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