Worked on improving the stability and reliability of IMAP connectivity in the mustang-im/mustang repository, focusing on backend development using TypeScript and the IMAP protocol. Addressed a critical issue where expired OAuth2 tokens could cause undefined connection states by refining the reconnect logic. Implemented a non-interactive OAuth2 login attempt before re-establishing IMAP connections, which minimizes user disruption and reduces downtime. Enhanced error handling by introducing explicit propagation of LoginError when login renewal fails, preventing unstable reconnect attempts. This targeted bug fix improved the robustness of the authentication flow and ensured that connection issues are surfaced clearly for easier troubleshooting and maintenance.