Worked on stabilizing artifact handling in the swiftlang/swift-package-manager repository by addressing concurrency issues in Swift. Developed and implemented a locking mechanism to serialize concurrent downloads of the same binary artifact, resolving a race condition that occurred when multiple targets referenced the same artifact. This approach ensured that only one download occurred at a time, improving artifact caching reliability and making build processes more deterministic. Added regression tests using unit testing techniques to validate correct behavior under concurrent download scenarios. The work focused on concurrency control, file system management, and robust testing, ultimately reducing CI flakiness and unnecessary network I/O.