Worked on the symfony/symfony repository over a two-month period, focusing on backend reliability and state management. Addressed two critical bugs by improving cache integrity and authentication flows using PHP and Symfony, with an emphasis on unit testing. Enhanced the TagAwareAdapter by ensuring its internal state is properly cleared on commit failures, reducing the risk of stale cache data in production environments. Additionally, resolved a state leak in the LogoutUrlGenerator by implementing a reset mechanism and updating service configuration, which stabilized logout URL generation in asynchronous contexts. All changes were validated through targeted tests and code review, contributing to system stability.