During June 2025, Jae Kim focused on improving build reliability for the facebook/buck2-prelude repository by addressing toolchain version conflicts encountered during the Pika 17 rollout. He introduced an optional configuration flag to the BXL script, allowing developers to specify Swift index toolchain versions and thereby resolve build errors caused by mismatches between Xcode and Pika toolchains. This targeted solution, implemented using Python and leveraging skills in build systems and configuration management, enabled more precise and reproducible builds. Jae’s work enhanced CI throughput and stability, demonstrating a thoughtful approach to scripting and toolchain control in a complex build environment.