Read Frog is a browser extension for AI-assisted language learning. It provides in-page translation, video subtitle translation, text-to-speech, and a selection toolbar with custom AI actions. The extension supports over 30 language model and translation providers, configurable via a unified provider interface, with features like automatic page translation, hover translation, and AI-powered note suggestions. The architecture is built on the WXT framework (MV3) for cross-browser compatibility, with a background service worker orchestrating translation queues, caching, and state management. The frontend uses React 19, Jotai for state, TanStack Query for data fetching, and a custom Base UI component library. The codebase is highly modular with extensive test coverage, a versioned configuration migration system (100+ schema versions), and sophisticated DOM manipulation for in-place translation.