Claude Code — Leaked Source

The full source code of Anthropic's Claude Code CLI, leaked on March 31, 2026

The original unmodified leaked source is preserved here .

---

Table of Contents

• How It Leaked
• What Is Claude Code?
• Documentation
• Explore with MCP Server
• Directory Structure
• Architecture
  • Tool System
  • Command System
  • Service Layer
  • Bridge System
  • Permission System
  • Feature Flags
• Key Files
• Tech Stack
• Design Patterns
• GitPretty Setup
• Contributing
• Disclaimer

---

How It Leaked

Chaofan Shou (@Fried_rice) discovered that the published npm package for Claude Code included a .map file referencing the full, unobfuscated TypeScript source — downloadable as a zip from Anthropic's R2 storage bucket.

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

— @Fried_rice, March 31, 2026

---

What Is Claude Code?

Claude Code is Anthropic's official CLI tool for interacting with Claude directly from the terminal — editing files, running commands, searching codebases, managing git workflows, and more. This repository contains the leaked src/ directory.

Leaked	2026-03-31
Language	TypeScript (strict)
Runtime	Bun
Terminal UI	React + Ink
Scale	~1,900 files · 512,000+ lines of code

---

� Documentation

For in-depth guides, see the docs/ directory:

Guide	Description
Architecture	Core pipeline, startup sequence, state management, rendering, data flow
Tools Reference	Complete catalog of all ~40 agent tools with categories and permission model
Commands Reference	All ~85 slash commands organized by category
Subsystems Guide	Deep dives into Bridge, MCP, Permissions, Plugins, Skills, Tasks, Memory, Voice
Exploration Guide	How to navigate the codebase — study paths, grep patterns, key files

Also see: CONTRIBUTING.md · MCP Server README

---

�🔍 Explore with MCP Server

This repo ships an MCP server that lets any MCP-compatible client (Claude Code, Claude Desktop, VS Code Copilot, Cursor) explore the full source interactively.

Step-by-step setup

# 1. Clone the repo
git clone https://github.com/utkarshcse2026/claude-code.git
cd claude-code/mcp-server

# 2. Install & build
npm install && npm run build

# 3. Register with Claude Code
claude mcp add claude-code-explorer -- node /absolute/path/to/claude-code/mcp-server/dist/index.js

Replace /absolute/path/to/claude-code with your actual clone path.

VS Code / Cursor / Claude Desktop config

VS Code — add to .vscode/mcp.json:

{
  "servers": {
    "claude-code-explorer": {
      "type": "stdio",
      "command": "node",
      "args": ["${workspaceFolder}/mcp-server/dist/index.js"],
      "env": { "CLAUDE_CODE_SRC_ROOT": "${workspaceFolder}/src" }
    }
  }
}

Claude Desktop — add to your config file:

{
  "mcpServers": {
    "claude-code-explorer": {
      "command": "node",
      "args": ["/absolute/path/to/claude-code/mcp-server/dist/index.js"],
      "env": { "CLAUDE_CODE_SRC_ROOT": "/absolute/path/to/claude-code/src" }
    }
  }
}

Cursor — add to ~/.cursor/mcp.json (same format as Claude Desktop).

Available tools & prompts

Tool	Description
list_tools	List all ~40 agent tools with source files
list_commands	List all ~50 slash commands with source files
get_tool_source	Read full source of any tool (e.g. BashTool, FileEditTool)
get_command_source	Read source of any slash command (e.g. review, mcp)
read_source_file	Read any file from src/ by path
search_source	Grep across the entire source tree
list_directory	Browse src/ directories
get_architecture	High-level architecture overview

Prompt	Description
explain_tool	Deep-dive into how a specific tool works
explain_command	Understand a slash command's implementation
architecture_overview	Guided tour of the full architecture
how_does_it_work	Explain any subsystem (permissions, MCP, bridge, etc.)
compare_tools	Side-by-side comparison of two tools

Try asking: "How does the BashTool work?" · "Search for where permissions are checked" · "Show me the /review command source"

Custom source path / Remove

# Custom source location
claude mcp add claude-code-explorer -e CLAUDE_CODE_SRC_ROOT=/path/to/src -- node /path/to/mcp-server/dist/index.js

# Remove
claude mcp remove claude-code-explorer

---

Directory Structure

src/
├── main.tsx                 # Entrypoint — Commander.js CLI parser + React/Ink renderer
├── QueryEngine.ts           # Core LLM API caller (~46K lines)
├── Tool.ts                  # Tool type definitions (~29K lines)
├── commands.ts              # Command registry (~25K lines)
├── tools.ts                 # Tool registry
├── context.ts               # System/user context collection
├── cost-tracker.ts          # Token cost tracking
│
├── tools/                   # Agent tool implementations (~40)
├── commands/                # Slash command implementations (~50)
├── components/              # Ink UI components (~140)
├── services/                # External service integrations
├── hooks/                   # React hooks (incl. permission checks)
├── types/                   # TypeScript type definitions
├── utils/                   # Utility functions
├── screens/                 # Full-screen UIs (Doctor, REPL, Resume)
│
├── bridge/                  # IDE integration (VS Code, JetBrains)
├── coordinator/             # Multi-agent orchestration
├── plugins/                 # Plugin system
├── skills/                  # Skill system
├── server/                  # Server mode
├── remote/                  # Remote sessions
├── memdir/                  # Persistent memory directory
├── tasks/                   # Task management
├── state/                   # State management
│
├── voice/                   # Voice input
├── vim/                     # Vim mode
├── keybindings/             # Keybinding configuration
├── schemas/                 # Config schemas (Zod)
├── migrations/              # Config migrations
├── entrypoints/             # Initialization logic
├── query/                   # Query pipeline
├── ink/                     # Ink renderer wrapper
├── buddy/                   # Companion sprite (Easter egg 🐣)
├── native-ts/               # Native TypeScript utils
├── outputStyles/            # Output styling
└── upstreamproxy/           # Proxy configuration

---

Architecture

1. Tool System

src/tools/ — Every tool Claude can invoke is a self-contained module with its own input schema, permission model, and execution logic.

Tool	Description
File I/O
FileReadTool	Read files (images, PDFs, notebooks)
FileWriteTool	Create / overwrite files
FileEditTool	Partial modification (string replacement)
NotebookEditTool	Jupyter notebook editing
Search
GlobTool	File pattern matching
GrepTool	ripgrep-based content search
WebSearchTool	Web search
WebFetchTool	Fetch URL content
Execution
BashTool	Shell command execution
SkillTool	Skill execution
MCPTool	MCP server tool invocation
LSPTool	Language Server Protocol integration
Agents & Teams
AgentTool	Sub-agent spawning
SendMessageTool	Inter-agent messaging
TeamCreateTool / TeamDeleteTool	Team management
TaskCreateTool / TaskUpdateTool	Task management
Mode & State
EnterPlanModeTool / ExitPlanModeTool	Plan mode toggle
EnterWorktreeTool / ExitWorktreeTool	Git worktree isolation
ToolSearchTool	Deferred tool discovery
SleepTool	Proactive mode wait
CronCreateTool	Scheduled triggers
RemoteTriggerTool	Remote trigger
SyntheticOutputTool	Structured output generation

2. Command System

src/commands/ — User-facing slash commands invoked with / in the REPL.

Command	Description		Command	Description
/commit	Git commit		/memory	Persistent memory
/review	Code review		/skills	Skill management
/compact	Context compression		/tasks	Task management
/mcp	MCP server management		/vim	Vim mode toggle
/config	Settings		/diff	View changes
/doctor	Environment diagnostics		/cost	Check usage cost
/login / /logout	Auth		/theme	Change theme
/context	Context visualization		/share	Share session
/pr_comments	PR comments		/resume	Restore session
/desktop	Desktop handoff		/mobile	Mobile handoff

3. Service Layer

src/services/ — External integrations and core infrastructure.

Service	Description
api/	Anthropic API client, file API, bootstrap
mcp/	Model Context Protocol connection & management
oauth/	OAuth 2.0 authentication
lsp/	Language Server Protocol manager
analytics/	GrowthBook feature flags & analytics
plugins/	Plugin loader
compact/	Conversation context compression
extractMemories/	Automatic memory extraction
teamMemorySync/	Team memory synchronization
tokenEstimation.ts	Token count estimation
policyLimits/	Organization policy limits
remoteManagedSettings/	Remote managed settings

4. Bridge System

src/bridge/ — Bidirectional communication layer connecting IDE extensions (VS Code, JetBrains) with the CLI.

Key files: bridgeMain.ts (main loop) · bridgeMessaging.ts (protocol) · bridgePermissionCallbacks.ts (permission callbacks) · replBridge.ts (REPL session) · jwtUtils.ts (JWT auth) · sessionRunner.ts (session execution)

5. Permission System

src/hooks/toolPermission/ — Checks permissions on every tool invocation.

Prompts the user for approval/denial or auto-resolves based on the configured permission mode: default, plan, bypassPermissions, auto, etc.

6. Feature Flags

Dead code elimination at build time via Bun's bun:bundle:

import { feature } from 'bun:bundle'

const voiceCommand = feature('VOICE_MODE')
  ? require('./commands/voice/index.js').default
  : null

Notable flags: PROACTIVE · KAIROS · BRIDGE_MODE · DAEMON · VOICE_MODE · AGENT_TRIGGERS · MONITOR_TOOL

---

Key Files

File	Lines	Purpose
QueryEngine.ts	~46K	Core LLM API engine — streaming, tool loops, thinking mode, retries, token counting
Tool.ts	~29K	Base types/interfaces for all tools — input schemas, permissions, progress state
commands.ts	~25K	Command registration & execution with conditional per-environment imports
main.tsx	—	CLI parser + React/Ink renderer; parallelizes MDM, keychain, and GrowthBook on startup

---

Tech Stack

Category	Technology
Runtime	Bun
Language	TypeScript (strict)
Terminal UI	React + Ink
CLI Parsing	Commander.js (extra-typings)
Schema Validation	Zod v4
Code Search	ripgrep (via GrepTool)
Protocols	MCP SDK · LSP
API	Anthropic SDK
Telemetry	OpenTelemetry + gRPC
Feature Flags	GrowthBook
Auth	OAuth 2.0 · JWT · macOS Keychain

---

Design Patterns

Parallel Prefetch — Startup optimization

MDM settings, keychain reads, and API preconnect fire in parallel as side-effects before heavy module evaluation:

// main.tsx
startMdmRawRead()
startKeychainPrefetch()

Lazy Loading — Deferred heavy modules

OpenTelemetry (~400KB) and gRPC (~700KB) are loaded via dynamic import() only when needed.

Agent Swarms — Multi-agent orchestration

Sub-agents spawn via AgentTool, with coordinator/ handling orchestration. TeamCreateTool enables team-level parallel work.

Skill System — Reusable workflows

Defined in skills/ and executed through SkillTool. Users can add custom skills.

Plugin Architecture — Extensibility

Built-in and third-party plugins loaded through the plugins/ subsystem.

---

GitPretty Setup

Show per-file emoji commit messages in GitHub's file UI

# Apply emoji commits
bash ./gitpretty-apply.sh .

# Optional: install hooks for future commits
bash ./gitpretty-apply.sh . --hooks

# Push as usual
git push origin main

---

Contributing

Contributions to documentation, the MCP server, and exploration tooling are welcome. See CONTRIBUTING.md for guidelines.

Note: The src/ directory is the original leaked source and should not be modified.

---

Disclaimer

This repository archives source code leaked from Anthropic's npm registry on 2026-03-31. All original source code is the property of Anthropic. This is not an official release and is not licensed for redistribution. Contact Utkarsh Aggarwal✦ for any comments.

---