ChatKit.js provides TypeScript type definitions and React bindings for the ChatKit web component, which is served from a CDN. The repository does not contain the actual web component implementation but offers ergonomic React integration via the `useChatKit` hook and `ChatKit` component, along with comprehensive type safety. Key functionality includes synchronizing React state with the web component, mapping custom events to React handler props, and providing imperative methods to control the chat UI (e.g., sending messages, managing threads). The library emphasizes stable references for options and event handlers to prevent stale closures in React, ensuring reliable integration with the external web component.