Worked on the stryker-mutator/stryker-net repository to refine the default behavior of nullable compilation options, shifting the default from enabled to disabled to reduce unintended nullable behavior for users. The approach involved updating build tool configurations and expanding unit tests in C# to cover invalid and empty nullable option values, thereby improving the robustness and reliability of the configuration management process. By increasing test coverage and ensuring clearer traceability of changes, the work enhanced the safety and predictability of nullable handling for adopters. The focus on configuration management and unit testing contributed to more reliable default behaviors in the project.