John Mortlock developed a privacy-focused feature for the withastro/astro repository, introducing support for partitioned cookies with top-level site scoping to address cross-site tracking concerns while maintaining legitimate third-party usage. He extended the existing cookie API in JavaScript and Node.js, enabling developers to create partitioned cookies and update cookie settings with greater control. John authored comprehensive end-to-end and unit tests to validate privacy boundaries and ensure robust functionality. He also prepared detailed documentation and changelog updates to facilitate adoption. Throughout the project, John collaborated with cross-functional partners, demonstrating depth in full stack development and a methodical approach to privacy compliance.