Andreas Klebinger focused on enhancing the reliability and maintainability of the haskell/cabal build system by addressing incomplete selector warnings and improving error messaging. Working primarily in Haskell, Andreas introduced total getters and added invariant checks at usage sites, which strengthened data handling and reduced the risk of runtime errors. The refactoring efforts targeted build-related code, making it easier for developers to diagnose and resolve failures. By reducing warning noise and clarifying error output, Andreas’s work improved the debuggability of the Cabal build system. This contribution demonstrated depth in build system development and compiler internals, delivering clear value to downstream users.