Worked on the Unity-Technologies/InputSystem repository to address a stability issue in the Input System UI module. Focused on resolving a nullability edge case in the InputSystemUIInputModule, specifically ensuring that navigation and submission continued to function correctly when localMultiPlayerRoot was set to null. Utilized C# and Unity, applying skills in UI development and testing to implement targeted unit tests that validated navigation and submit flows under null conditions. Updated the changelog to document the fix and prevent future regressions. This work improved the reliability of multi-player UI input handling and reduced the risk of user-facing navigation issues.