Worked on the remix-run/react-router repository to address a routing reliability issue by normalizing basename handling within the createRouter function. The solution involved updating the logic to automatically prefix a missing leading slash to basename props, ensuring consistent routing behavior even when non-standard basenames are used. This change reduced the risk of runtime errors and improved compatibility for downstream applications. A regression test was added to the test suite to verify the fix and prevent future issues. The work was carried out using TypeScript and JavaScript, with a focus on front-end development and robust routing configuration for React applications.