Worked on stabilizing Kotlin argument construction in the facebook/buck2-prelude repository by addressing a regression in how the language version was handled during compilation. Using Kotlin and Starlark, restructured the build system configuration to ensure the get_language_version function directly contributed the correct arguments to kotlinc, removing the need for a separate argument function. This change restored the expected construction of compiler arguments, preventing build and configuration errors that could disrupt developer workflows. The approach demonstrated careful rollback and refactoring practices, improving build reliability and maintaining downstream compatibility for Kotlin projects relying on Buck2’s build infrastructure and argument management.