Steve Chen contributed to the kookouri/ECSE-428-05 repository by developing two core features over two months, focusing on both backend reliability and frontend consistency. He built a comprehensive LoginService Authentication Testing Suite using Java, Mockito, and Spring Boot, which validated critical login scenarios and improved regression detection through robust unit tests. In addition, Steve standardized the item card layout in the frontend using Vue and CSS, ensuring consistent visuals and maintainable code for the item list. His work addressed authentication reliability and UI uniformity, demonstrating depth in both test-driven backend development and thoughtful frontend design within a collaborative codebase.