Eunwoo focused on stabilizing build instrumentation and improving bundle analysis for the toss/frontend-fundamentals repository, addressing a configuration issue in Vite by correctly integrating the rollup-plugin-visualizer within build.rollupOptions.plugins. This adjustment enabled Rollup to process the plugin as intended, providing accurate bundle insights and supporting data-driven performance optimizations. In the TanStack/query repository, Eunwoo enhanced code maintainability by refining documentation, specifically clarifying a duplicated word in a core comment to reduce future contributor confusion. Throughout both projects, Eunwoo applied skills in TypeScript, JavaScript, and bundler configuration, demonstrating careful attention to build tooling and code clarity over the two-month period.