Worked on enhancing security and data isolation in the LibreChat repository by strengthening per-user authentication and secure model fetching. Addressed a critical bug involving user authentication headers, ensuring that Authorization headers are correctly forwarded and template variables are resolved for model fetch requests. Implemented robust caching strategies in TypeScript to prevent token leakage, including header-aware fetch coalescing and cache scoping based on user-specific headers. Expanded automated testing coverage to validate header forwarding, cache behavior, and token-key scoping, while also improving code quality through import order alignment. Focused on API development, authentication, and testing to deliver measurable improvements in reliability and performance.