Worked on the spring-projects/spring-framework repository to resolve a regression affecting Kotlin value class interoperability, specifically addressing issues with nullable value class parameter handling. Focused on backend development using Java and Kotlin, the work involved updating logic to ensure correct processing of nullable types and expanding unit test coverage to prevent future regressions. By closing the regression and adding targeted tests, the changes reinforced API compatibility and improved runtime correctness for Kotlin users across Spring components. Demonstrated a methodical approach to regression testing, cross-language interoperability, and Git-based workflows, contributing to the stability and maintainability of the framework’s Kotlin integration.