This is a leaked internal source of 'Claude Code', a terminal-based AI coding assistant CLI built by Anthropic. The application is a monolith written in TypeScript with React/Ink for terminal UIs, running on the Bun runtime. In production, it provides an interactive REPL that connects to Claude LLMs to perform software engineering tasks: reading/writing files, executing bash/PowerShell commands, searching code with grep/glob, managing git operations, spawning sub-agents, running MCP servers, and more. It features a sophisticated permission engine, plugin ecosystem, skill system, IDE bridge (VS Code/JetBrains), and remote session support. The architecture is centered around a QueryEngine that orchestrates LLM API calls with streaming, tool loops, and retries. There are ~40+ tools (BashTool, FileEditTool, MCPTool, etc.) and ~50+ slash commands (/commit, /review, /config, /doctor). The codebase is extremely large (~1900 files, 512K+ lines) with significant internal complexity. However, it contains many stubs for removed internal packages (@ant/*, @anthropic-ai/mcpb, etc.), heavy use of bun:bundle feature flags, and countless ant-only conditionals (process.env.USER_TYPE === 'ant') that gate internal-only features. This means the source cannot be run as-is without Anthropic's infrastructure. While the engineering quality is high in places (clean TypeScript with Zod schemas, well-structured tool pipelines, a custom Ink renderer with Yoga layout), the codebase is not designed for external reuse or portability. It requires Bun, has many hardcoded internal service URLs, and the stubbed packages would need real implementations. For learning and inspiration, however, it offers excellent examples of: terminal UI architecture, permission engines, plugin systems, and AI agent tool frameworks.