Worked on the marimo-team/marimo repository to enhance the file browser’s user experience by introducing a loading spinner that appears when file listings exceed 200 milliseconds. This feature was implemented in React using both JavaScript and TypeScript, with careful attention to threshold logic to prevent unnecessary spinner flicker during fast directory loads. The solution targeted slow listings, particularly those involving S3 storage, and included thorough validation through automated tests and local verification. Documentation was updated to reflect the changes, and all work adhered to established contributor guidelines, demonstrating a methodical approach to front end development and user interface feedback.