Claude Code Source Code Leak

Complete Guide & Documentation

What Happened?

On March 31, 2026, Anthropic accidentally leaked the entire source code of their popular AI coding assistant Claude Code through their npm registry. The leak occurred when a 59.8 MB source map file (.map) was inadvertently included in version 2.1.88 of the @anthropic/claude-code npm package.

BREAKING: The entire proprietary source code of one of the most popular AI coding assistants has been exposed to the public.

Table of Contents

• What Happened?
• The Technical Details
• Repository Contents
• Leaked Source Code
• Clean Room Rust Implementation
• Key Discoveries
• Timeline of Events
• Security Implications
• Frequently Asked Questions
• Resources & References

What Happened?

On March 31, 2026, Anthropic accidentally leaked the entire source code of their popular AI coding assistant Claude Code through their npm registry. The leak occurred when a 59.8 MB source map file (.map) was inadvertently included in version 2.1.88 of the @anthropic/claude-code npm package.

This incident exposed approximately 512,000+ lines of TypeScript source code, revealing internal architectures, secret features, system prompts, and development tools that Anthropic had never intended to make public.

BREAKING: The entire proprietary source code of one of the most popular AI coding assistants has been exposed to the public.

The Technical Details

How Source Maps Work

Source maps are debugging artifacts generated during the build process. They create a mapping between:

Minified Production Code <-> Original Source Code

Why This Leak Happened

The source map file contained a critical field called sourcesContent - an array that embeds the entire original source code of each file as plain text strings within a JSON structure:

{
  "version": 3,
  "file": "bundle.js",
  "sources": ["../src/main.ts", "../src/tools/..."],
  "sourcesContent": [
    "// All your original TypeScript code here",
    "// Every file, comment, and constant",
    "// Exposed in plain text"
  ],
  "mappings": "AAAA,SAAS,OAAO,CAAC,..."
}

What Anthropic Missed

1. No .npmignore file to exclude source maps
2. No files field in package.json to whitelist allowed files
3. Source maps in production builds (should only be in development)

Repository Contents

This repository contains 248 files of source code and documentation:

Leaked Source Code

Directory Structure

leaked-source/
├── assistant/
│   └── sessionHistory.ts          # Session management
├── bridge/
│   ├── bridgeApi.ts               # IDE Bridge API
│   ├── bridgeConfig.ts            # Bridge configuration
│   ├── bridgeDebug.ts             # Debug utilities
│   ├── bridgeEnabled.ts           # Enable/disable bridge
│   ├── bridgeMain.ts              # Main bridge logic
│   ├── bridgeMessaging.ts         # Message handling
│   ├── bridgePermissionCallbacks.ts
│   ├── bridgePointer.ts
│   ├── bridgeStatusUtil.ts        # Status utilities
│   ├── bridgeUI.ts               # UI components
│   ├── capacityWake.ts
│   ├── codeSessionApi.ts          # Code session API
│   ├── createSession.ts          # Session creation
│   ├── debugUtils.ts             # Debug utilities
│   ├── envLessBridgeConfig.ts
│   ├── flushGate.ts
│   ├── inboundAttachments.ts
│   ├── inboundMessages.ts
│   ├── initReplBridge.ts          # REPL bridge initialization
│   ├── jwtUtils.ts               # JWT utilities
│   ├── pollConfig.ts
│   ├── pollConfigDefaults.ts
│   ├── remoteBridgeCore.ts        # Remote bridge core
│   ├── replBridge.ts             # REPL bridge
│   ├── replBridgeHandle.ts
│   ├── replBridgeTransport.ts
│   ├── sessionIdCompat.ts
│   ├── sessionRunner.ts
│   ├── trustedDevice.ts
│   ├── types.ts                  # Type definitions
│   └── workSecret.ts
├── buddy/                        # Pet/Companion System
│   ├── CompanionSprite.tsx        # Sprite component
│   ├── companion.ts              # Companion logic
│   ├── prompt.ts                 # Companion prompts
│   ├── sprites.ts                # Sprite definitions
│   ├── types.ts                  # Companion types
│   └── useBuddyNotification.tsx
├── cli/
│   ├── exit.ts                   # Exit handling
│   ├── handlers/
│   │   ├── agents.ts             # Agent handlers
│   │   ├── auth.ts              # Authentication
│   │   ├── autoMode.ts          # Auto mode
│   │   ├── mcp.tsx              # MCP handlers
│   │   ├── plugins.ts           # Plugin system
│   │   └── util.tsx             # Utilities
│   ├── ndjsonSafeStringify.ts
│   ├── print.ts                  # Print utilities
│   ├── remoteIO.ts              # Remote I/O
│   ├── structuredIO.ts          # Structured I/O
│   └── transports/
│       └── HybridTransport.ts    # Hybrid transport
└── [More files in cli/ directory]

Key Files Overview

assistant/sessionHistory.ts

• Session history management
• Stores conversation context

bridge/ - IDE Bridge System

• Purpose: Bidirectional communication between IDE and CLI
• Features: VS Code extension, JetBrains plugin support
• Security: JWT-authenticated channels

buddy/ - The Pet System

• Virtual companion with mood tracking
• Hunger, happiness, energy metrics
• ASCII sprite-based UI

cli/ - Command Line Interface

• Main CLI entry points
• Handler system for different commands
• Transport layer for communication

Clean Room Rust Implementation

Overview

A Rust-based clean-room rewrite based on behavioral analysis of the leaked code.

Directory Structure

clean-room-rust/
├── spec/                         # Behavioral Specifications
│   ├── 00_overview.md           # System overview
│   ├── 01_core_entry_query.md   # Core query handling
│   ├── 02_commands.md           # Command system
│   ├── 03_tools.md              # Tool definitions
│   ├── 04_components_core_messages.md
│   ├── 05_components_agents_permissions_design.md
│   ├── 06_services_context_state.md
│   ├── 07_hooks.md              # Hook system
│   ├── 08_ink_terminal.md       # Terminal UI
│   ├── 09_bridge_cli_remote.md  # Bridge system
│   ├── 10_utils.md              # Utilities
│   ├── 11_special_systems.md    # Special features
│   ├── 12_constants_types.md    # Constants & types
│   ├── 13_rust_codebase.md      # Rust implementation
│   └── INDEX.md                 # Specification index
│
└── src-rust/
    └── crates/
        ├── api/                 # API definitions
        ├── bridge/              # Bridge implementation
        ├── buddy/               # Pet system
        ├── cli/                 # CLI entry point
        ├── commands/            # Command handlers
        ├── core/                # Core functionality
        │   ├── analytics.rs
        │   ├── attachments.rs
        │   ├── auto_mode.rs
        │   ├── bash_classifier.rs
        │   ├── claudemd.rs
        │   ├── cloud_session.rs
        │   └── crypto_utils.rs
        └── [More modules]

Key Discoveries

The "Pet" System (Tamagotchi-Style)

One of the most surprising discoveries was a complete virtual pet system:

interface PetState {
  name: string;
  species: 'cat' | 'dog' | 'custom';
  hunger: number;      // 0-100
  happiness: number;  // 0-100
  energy: number;     // 0-100
  mood: 'happy' | 'neutral' | 'sad' | 'excited';
}

IDE Bridge System

Real-time bidirectional communication system:

• VS Code extension integration
• JetBrains plugin support
• JWT authentication

Multi-Agent Architecture

Revealed a multi-agent orchestration system that had been quietly developing since August 2024.

Timeline of Events

Security Implications

What's NOT Affected

What's Affected

Frequently Asked Questions

Q: Is the source code still available?

A: Yes! This repository contains the original leaked TypeScript source code.

Q: Can I use this code commercially?

A: No. The code is copyrighted by Anthropic. Using it commercially would likely constitute copyright infringement.

Q: What's in the Rust implementation?

A: A clean-room rewrite inspired by the behavioral analysis of the leaked code.

Q: What makes this significant?

A: One of the most significant tech leaks in AI history, giving unprecedented access to how a leading AI company builds products.

Resources & References

News Coverage

• The Verge
• Ars Technica
• VentureBeat
• BleepingComputer

Contributing

Contributions welcome! Help document this historic leak.

1. Fork the repository
2. Create your feature branch
3. Commit your changes
4. Push to the branch
5. Open a Pull Request

License

This documentation is for educational purposes. The original Claude Code source code is property of Anthropic, PBC.

Last updated: April 2, 2026 | Maintained by the community