During March 2025, Zwei focused on enhancing the reliability of the Buck2 prelude module by addressing test brittleness across Kotlin compiler versions. Working primarily in Java and Kotlin, Zwei implemented dynamic handling of Kotlin metadata within Stub JAR generation tests, allowing the test suite to adapt to differences between Kotlin 2.0.x and 2.1.x. This approach reduced flaky outcomes and improved cross-version compatibility for downstream users of facebook/buck2-prelude. By delivering a targeted fix to the Kotlin ABI test for version 2.1, Zwei strengthened build stability, improved CI reliability, and laid the groundwork for smoother future Kotlin upgrades within the build system.