Refined GitHub is a browser extension (Chrome, Firefox, Safari) that enhances the GitHub web interface with over 200 modular features. The system is a content script injected into GitHub pages, managed by a feature lifecycle system (feature-manager.tsx) that uses AbortSignal for cleanup. Features are self-contained .tsx files that observe DOM changes, add event listeners, or inject UI elements via Svelte components or dom-chef JSX. The background script handles messaging, hotfixes, and context menus. The options page allows per-domain feature toggles, token management, and custom CSS. The architecture is highly modular and well-organized, with a strong emphasis on performance and cleanup. While the core functionality is UI enhancement, it also makes extensive use of GitHub's GraphQL API for data fetching, with caching via webext-storage-cache. The codebase demonstrates high craftsmanship with patterns like selector-observer, batched functions, and a unidirectional feature registration pattern. Maintenance is active with daily releases, and technical drift is low due to modern tooling (TypeScript, Svelte 5, Rollup, Vitest).