Arnaud Sevin focused on improving build stability and data handling reliability for the spacetelescope/catkit2 repository during June 2025. He addressed a compilation-time bug by adding the missing cstdint include to FitsFile.h, ensuring proper definition of fixed-width integer types such as uint64_t. This C++ header file management work resolved cross-platform build failures and enhanced the robustness of Fits I/O operations. Although no new user-facing features were introduced, Arnaud’s contribution improved code portability and reduced potential errors during continuous integration and release processes. His efforts reflected a targeted approach to maintaining code quality and reliability within the project’s core infrastructure.