During September 2025, Caifan Zhang focused on improving build stability and portability for the FFmpeg/FFmpeg repository, specifically targeting embedded systems. He addressed a macro redefinition issue in C by implementing a preprocessor guard for USEC_PER_SEC within libavcodec/v4l2_buffers.c, ensuring the macro was only defined if not already present in system headers. This change reduced compiler warnings and prevented build conflicts, particularly on platforms like NuttX. Leveraging his expertise in C programming, build systems, and embedded environments, Caifan’s work enhanced cross-platform compatibility and contributed to smoother enterprise deployments, demonstrating careful attention to source-level robustness and maintainability.