Worked on the facebook/pyrefly repository to deliver a targeted safety enhancement focused on enum management and type safety. Developed and implemented Enum Finalization for Safe Inheritance, a feature that prevents extending Enum classes with new members, thereby reducing the risk of inheritance-related bugs and ensuring safer downstream code. The approach involved marking Enum class instances as final, leveraging Python’s enum capabilities and disciplined type-safety practices. Emphasized unit testing to validate the new logic and maintain code reliability. This work contributed to easier maintenance and refactoring, providing stronger guarantees around Enum usage without introducing new bugs during the development period.