Aleivag worked on restoring build system compatibility in the ndmitchell/pyre-check repository by reinstating the use_buck2 flag, which had previously been removed. This change addressed a regression affecting workflows that rely on both Buck and Buck2 build systems. Aleivag updated Python-based CLI argument parsing, configuration management, and backend argument serialization to ensure seamless interoperability across different build environments. The work focused on minimizing user disruption and maintaining backward compatibility, allowing existing pipelines to function without modification. By carefully reverting the prior change and validating downstream components, Aleivag demonstrated depth in backend development and configuration management within complex build systems.