Worked on improving authentication reliability in the huggingface/chat-ui repository by addressing a critical issue with external provider integration. Focused on backend development using TypeScript and API integration skills, the work involved resolving 401 errors that occurred when authenticating with external providers. The solution conditionally injected the user's OIDC token into the OpenAI endpoint based on the USE_USER_TOKEN configuration, ensuring that the OPENAI_API_KEY was not unintentionally overwritten. This approach restored compatibility with external OpenAI-compatible backends and updated the MCP flow to prevent unintended token leakage, ultimately enhancing security and reducing support incidents for external-provider authentication workflows.