Worked on enhancing build reliability and configurability across the bazelbuild/rules_swift and bazelbuild/rules_apple repositories. Delivered a feature enabling Xcode Swift toolchain target triple overrides via the CC_TARGET_TRIPLE environment variable, allowing custom toolchains and maintaining compatibility with evolving Swift rules. Addressed a bug in rules_apple by normalizing SDK environment strings to lowercase, preventing failures in xcrun when SDK versions include letters. Applied expertise in build systems, platform configuration, and toolchain configuration, leveraging Python and Starlark to implement environment-driven configuration and robust string handling. These contributions improved developer experience and reduced runtime failures in complex build environments.