Marius contributed to the httpwg/http-extensions repository by enhancing the resiliency and security of resumable upload features. He addressed Time-of-Check to Time-of-Use vulnerabilities, implementing safeguards against race conditions and abuse, and refined upload limit policies to prevent disruption of ongoing transfers. His work clarified edge-case behaviors, such as handling upload length and offsets, ensuring robust server-side validation and failure handling for invalid states. Marius updated Markdown documentation alongside code changes, improving clarity and interoperability for developers. His efforts combined API design, security best practices, and technical writing, resulting in deeper reliability and clearer guidance for HTTP extension implementers.