Worked on improving payload handling reliability in the temporalio/ui repository by addressing a bug affecting external payload downloads when the codec server is configured at the namespace level. Replaced the previous reliance on browser localStorage with a centralized endpoint resolution using getCodecEndpoint from page data settings, ensuring the download button and decode requests function correctly even if localStorage is unavailable. Added regression tests to confirm that codeServerRequest consistently uses the correct namespace-level endpoint for encode, decode, and download operations. Utilized Svelte for front end development and applied JavaScript and TypeScript to enhance robustness and maintainability of the user interface.