Josh Arnold focused on improving the build reliability of the swiftlang/sourcekit-lsp repository by addressing a complex bug in the BuildSystemManager’s dependency analysis. He identified and fixed an algorithmic issue where the depth check failed to use the dependency’s recorded depth, which previously caused exponential blowup in large dependency graphs. By optimizing the dependency resolution process, Josh enhanced both performance and correctness for Swift-based builds. His work demonstrated strong skills in algorithm optimization, build systems, and dependency analysis, and involved careful debugging and collaboration through Git. The solution reflects a deep understanding of build infrastructure and efficient dependency management.