During December 2024, Mathieu worked on stabilizing multisite routing in the discourse/discourse_docker repository by addressing a bug related to Nginx Host header handling. He implemented a fix using YAML and DevOps skills to ensure the original Host header was preserved in upstream Nginx blocks, which is essential for accurate multisite routing. After identifying compatibility issues with newer Nginx versions, Mathieu reverted the change to maintain system stability. He thoroughly documented the rationale behind the revert and provided guidance for future compatibility checks, demonstrating a careful, systems-oriented approach to balancing routing fidelity with ongoing support and maintainability requirements.