During October 2025, Andres Dos Santos worked on the stryker-mutator/stryker-net repository, focusing on improving configuration management and unit testing for C# build tools. He changed the default nullable compilation options from enabled to disabled, addressing unintended nullable behavior for users and enhancing the reliability of the tool’s default settings. To ensure robustness, Andres expanded unit test coverage to include invalid and empty nullable option values, preventing regressions and increasing configuration safety. His technical approach emphasized traceability and clarity in commit history, resulting in more predictable behavior for adopters and a more maintainable codebase within the Stryker.NET project.