Anthropic's Claude Code CLI Source Code Leaked via npm

A security researcher discovered that the entire source code of Anthropic's Claude Code CLI tool was exposed through a source map file published on npm. The leaked codebase reveals a highly sophisticated AI-powered coding assistant with a modular architecture and advanced features.

Details

The leaked source code of Anthropic's Claude Code CLI tool reveals a highly sophisticated AI-powered coding assistant. With ~1,900 TypeScript files and over 512,000 lines of code, it is a production-grade system, not a toy project. Claude Code is built on the Bun JavaScript runtime, leveraging its performance features, and uses React with Ink for its terminal user interface. The tool has a modular, plugin-like architecture, with around 40 discrete capabilities (file read, bash execution, web fetch, LSP integration, etc.) each gated by permissions. The core of the system is the 46,000-line query engine, which handles all the LLM API calls, streaming, caching, and orchestration. Claude Code can also spawn sub-agents, or 'swarms', to handle complex, parallelizable tasks. Additionally, it has an IDE bridge system for bidirectional communication with extensions in tools like VS Code and JetBrains IDEs. The leaked codebase provides a fascinating look into the technical architecture and design decisions behind this advanced AI coding assistant, including the use of Bun, React with Ink, Zod for validation, and a rich system of slash commands.