Worked on stability improvements for the replit/upm repository by addressing a critical backend reliability issue. Focused on the package guessing path, the developer implemented a defensive nil-check in Go to ensure that calls to the language backend’s Guess function are only made when the backend is available. This approach prevented potential nil dereference crashes during backend downtime, thereby maintaining uninterrupted user workflows. The work demonstrated backend development skills and robust error handling, with clear commit traceability. By hardening the system against backend unavailability, the developer improved runtime reliability and contributed to a more resilient integration within the Go codebase.