Worked on the streamlit/streamlit repository to deliver a feature supporting modern ES module workflows by adding MIME type handling for .mjs and worker scripts. Implemented backend changes in Python to register the .mjs extension as application/javascript, updated web server configuration, and introduced targeted tests to ensure correct MIME handling for worker scripts, particularly on Windows platforms. This work enhanced cross-platform compatibility and reduced runtime MIME errors in Streamlit applications. Focused on backend development, testing, and web server configuration, the changes improved reliability for developers using ES modules and worker scripts, while strengthening test coverage for these scenarios within the codebase.