Claude Code — Rebuilt from Leaked Source

Disclaimer: This repository contains proprietary source code belonging to Anthropic that was unintentionally exposed via a source map file (.js.map) included in the official @anthropic-ai/claude-code npm package. This repository is provided strictly for educational and research purposes — to study the architecture, design patterns, and engineering of a production-grade AI coding agent. This project is not affiliated with, endorsed by, or authorized by Anthropic. If you are a representative of Anthropic and wish to have this repository removed, please open an issue or contact the repository owner. Use at your own risk. The authors assume no liability for any use or misuse of this code.

On March 31, 2026, the full source code of Anthropic's Claude Code CLI was leaked via a .map file exposed in their npm registry. This repo contains that source rebuilt into a runnable CLI.

Quick Start

Prerequisites: Bun v1.1+

git clone https://github.com/fazxes/claude-code.git
cd claude-code
bun install
bun run build
bun dist/cli.js

That's it. The CLI will launch and prompt you to authenticate via OAuth (same flow as the official Claude Code).

Commands

bun dist/cli.js                    # Launch interactive REPL
bun dist/cli.js --help             # Show all options
bun dist/cli.js --version          # Show version
bun dist/cli.js -p "your prompt"   # Non-interactive mode (pipe-friendly)
bun dist/cli.js auth login         # Authenticate

How It Was Leaked

Chaofan Shou (@Fried_rice) discovered the leak:

"Claude code source code has been leaked via a map file in their npm registry!"

— @Fried_rice, March 31, 2026

The source map in the published npm package contained a reference to the full, unobfuscated TypeScript source, downloadable as a zip from Anthropic's R2 storage bucket.

What's Inside

~1,900 source files, 512,000+ lines of TypeScript
Runtime: Bun
Terminal UI: React + custom forked Ink
CLI parser: Commander.js
Layout engine: Pure TypeScript port of Yoga (Meta's flexbox engine)

Architecture

src/
├── main.tsx                 # Entrypoint (Commander.js CLI parser)
├── commands.ts              # Command registry
├── tools.ts                 # Tool registry (~40 tools)
├── QueryEngine.ts           # LLM query engine (Anthropic API)
├── context.ts               # System/user context collection
├── ink/                     # Custom Ink fork (terminal React renderer)
├── commands/                # Slash command implementations
├── tools/                   # Agent tool implementations
├── components/              # React UI components
├── services/                # API, MCP, OAuth, telemetry
├── screens/                 # Full-screen UIs (REPL, Doctor)
├── native-ts/               # Pure TS ports of native modules
│   ├── yoga-layout/         # Flexbox layout engine
│   ├── color-diff/          # Syntax-highlighted diffs
│   └── file-index/          # Fuzzy file search
└── vim/                     # Vim mode implementation

What's Stubbed Out

Some internal Anthropic features weren't included in the leak or are behind private packages. These are stubbed with no-ops:

Computer Use (@ant/computer-use-*) — screen control tools
Chrome Integration (@ant/claude-for-chrome-mcp) — browser automation
Sandbox Runtime (@anthropic-ai/sandbox-runtime) — sandboxed execution
TungstenTool, REPLTool — internal-only tools
Context Collapse — internal compaction feature

The core CLI, all standard tools (Bash, Edit, Read, Write, Grep, Glob, etc.), MCP support, and the full terminal UI work.

Build Details

The build script (build.ts) uses Bun's bundler to:

Bundle 4,500+ modules into a single dist/cli.js (~21 MB)
Define MACRO.* build-time constants (version, feedback channel)
Externalize optional native deps (sharp, react-devtools-core)

Feature flags from bun:bundle's feature() all return false — internal Anthropic features (voice mode, coordinator mode, etc.) are disabled.

Telemetry

By default, Claude Code sends telemetry to Anthropic (event logging, Datadog, GrowthBook). To disable all telemetry:

DISABLE_TELEMETRY=1 bun dist/cli.js

Or for maximum privacy:

DISABLE_TELEMETRY=1 CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1 bun dist/cli.js

Disclaimer

This repository contains proprietary source code that was unintentionally made public by Anthropic through their npm package distribution. It is provided here for educational and research purposes only.

This project is not affiliated with Anthropic
No warranty is provided, express or implied
Users are responsible for their own compliance with applicable laws
This repository may be subject to takedown at Anthropic's request
Do not use this for commercial purposes

Claude-code