Worked on the symfony/symfony repository to enhance the reliability of static analysis and dependency injection configuration validation. Addressed a bug by refining the Psalm typing for the _instanceof configuration in Symfony Dependency Injection, updating the type from a generic InstanceofType to an array keyed by class-string. This adjustment reduced false positives in static analysis and improved the accuracy of service configuration validation, aligning with FrameworkBundle requirements. The work demonstrated expertise in PHP, Dependency Injection, and Psalm, and contributed to a smoother developer experience by ensuring that instanceof definitions in DI configurations are validated more precisely during continuous integration.