Developed deprecation-aware error handling for the ndmitchell/pyrefly repository, focusing on improving stability and user feedback when deprecated functions are called. The solution detects usage of functions marked with the @deprecated annotation and raises clear, actionable errors, preventing silent failures and guiding developers toward correct API usage. This approach enhanced the reliability and maintainability of the backend by enforcing explicit handling of deprecated interfaces. Leveraging Python and Rust programming skills, the work prioritized robust error handling and upgrade safety, simplifying troubleshooting for users and developers. The feature contributed to a more transparent development process and improved overall codebase quality.