Worked on the ndmitchell/pyre-check repository to restore compatibility between Buck and Buck2 build systems by reinstating the use_buck2 flag in the Pyre client. Addressed a regression by updating command-line argument parsing, configuration management, and backend argument serialization, ensuring seamless interoperability across different build configurations. Focused on backend development and build systems, the work involved careful coordination to revert previous changes while maintaining backward compatibility and minimizing user disruption. Utilized Python to implement these updates, validating downstream components and preserving consistent behavior for environments relying on either Buck1 or Buck2, thereby supporting multi-build-system workflows with minimal impact.