Worked on stabilizing the Streamable HTTP Client within the modelcontextprotocol/rust-sdk repository, focusing on backend development using Rust. Addressed stale-session error handling by mapping HTTP 401 responses to status-aware error messages, ensuring that client integrations receive accurate feedback aligned with API semantics. Expanded test coverage to include scenarios where a stale session ID returns a 404 status, verifying correct behavior when sessions are not found. This approach improved the reliability and debuggability of session lifecycle management. The work emphasized robust error signaling and comprehensive testing, contributing to a more stable backend service without introducing new features during the period.