Worked on the jlowin/fastmcp repository to enhance backend reliability and identity propagation in API workflows. Addressed a session lifecycle issue by ensuring the StreamableHTTPSessionManager was properly re-initialized across FastAPI TestClient lifespans, preventing resource leaks and enabling repeated client use. Developed regression tests to validate session management and maintain runtime stability. Introduced upstream claims propagation in the OAuthProxy, allowing verified FastMCP JWT claims to be included in downstream AccessTokens without mutating cached references. Leveraged Python, FastAPI, and OAuth token handling, applying test-driven development practices to improve test reliability and ensure consistent identity data flow for API clients.