Worked on the facebook/buck2-prelude repository to address build toolchain version conflicts during the Pika 17 rollout. Introduced an optional configuration flag within the BXL script, enabling teams to specify Swift index toolchain versions and thereby resolve errors caused by mismatches between Xcode and Pika toolchains. This targeted approach improved build reliability and allowed for more reproducible builds across environments. Leveraged skills in build systems, configuration management, and scripting, primarily using Python, to implement and validate the solution. The work focused on enhancing CI throughput and stability by providing precise control over toolchain selection without introducing new features during the period.