Worked on enhancing cookie handling and file I/O reliability across the python/typeshed and picnixz/cpython repositories using Python and type hinting. Improved the typeshed repository by updating cookie Morsel properties to support None values and correcting the return type of BaseCookie.value_encode, increasing type safety and supporting edge cases. In the cpython repository, strengthened pathlib module tests to ensure write_bytes and write_text methods accurately report the length of data written, improving backend reliability. Focused on software engineering best practices, including comprehensive testing and type correctness, to deliver maintainable solutions that benefit downstream users and improve overall code quality.