Worked on the fastapi/fastapi repository to enhance stability and typing reliability for Python 3.14 environments. Addressed a compatibility issue related to TYPE_CHECKING and forward references, implementing a fix aligned with PEP 649 to ensure that type annotations function correctly without requiring future imports. Developed and integrated targeted tests to validate forward-reference behavior, reducing the risk of type-checking and runtime errors in typing-heavy codebases. Utilized Python for backend and API development, with a focus on robust testing practices. This work supports smoother adoption of advanced typing features and helps maintain long-term reliability across FastAPI’s core modules.