Yechen worked on the element-plus/element-plus repository, focusing on stabilizing the tree-v2 component’s expansion state. Using Vue.js and TypeScript, Yechen addressed a bug where the expanded state could become inconsistent with defaultExpandedKeys, especially when defaults changed. The solution involved refactoring component logic, removing legacy code paths, and simplifying reactivity by moving key logic to a data watcher. This approach reduced complexity and improved correctness, making the component more predictable and easier to maintain. Yechen also improved test clarity and collaborated with teammates to resolve related issues, demonstrating a thoughtful approach to front end component design and code quality.