Marc worked on enhancing PII detection capabilities for the vllm-project/semantic-router repository, focusing on configurable privacy controls and improved testability. He implemented new options to reveal original text and filter by entity types, wiring up PIIOptions fields such as EntityTypes, ConfidenceThreshold, ReturnPositions, and MaskEntities. Using Go for back end development, Marc created a buildPIIResponse helper to streamline testing and wrote comprehensive table-driven unit tests to cover all configuration scenarios. His work emphasized test-driven development and clear documentation, resulting in more reliable and maintainable code that enables safer data handling within semantic routing pipelines.