Fabien Fleureau developed an API-first PREVIEW mode enforcement feature for the Qovery/console repository, focusing on aligning the front end with backend state to reduce configuration errors. Using React and TypeScript, he implemented UI safeguards that disable manual mode selection when PREVIEW is active, ensuring this mode can only be set via the API. His approach included adding a watch hook to monitor mode changes and filtering PREVIEW from dropdowns unless it matches the API-provided value. This work improved reliability for operators and automation by preventing manual misconfigurations, demonstrating a thoughtful application of React hooks and robust input validation patterns.