Worked on cross-repository enhancements to mdspan header emulation in the spack and spack-packages repositories, focusing on build system configuration and package management using Python and CMake. Developed a new build variant that enables installation of emulated standard library headers for stable mdspan releases, improving compatibility and simplifying downstream adoption. Updated packaging logic to pass this variant through CMake, introducing conditional definitions to ensure headers are installed only for stable versions. These changes aligned both repositories to provide a consistent stdheaders capability, reducing maintenance overhead and streamlining workflows for users deploying environments that rely on standard library header emulation.