During August 2025, Mathieu Olivari enhanced build reliability and developer experience across the bazelbuild/rules_swift and bazelbuild/rules_apple repositories. He introduced an environment-variable-driven override for Xcode Swift toolchain target triples, allowing custom toolchains and maintaining compatibility with Swift rules by leveraging Starlark and Python for toolchain configuration. In rules_apple, Mathieu resolved failures in SDK environment handling by normalizing platform strings to lowercase, preventing errors with xcrun when SDK versions included letters. His work demonstrated technical depth in build systems and platform configuration, delivering targeted solutions that improved predictability and reduced runtime failures in complex, rules-based Bazel environments.