Note: The original unmodified leaked source is preserved in the backup branch.

Claude Code — Leaked Source (2026-03-31)

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.

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How It Leaked

Chaofan Shou (@Fried_rice) discovered the leak and posted it publicly:

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

— @Fried_rice, March 31, 2026

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

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Overview

Claude Code is Anthropic's official CLI tool that lets you interact with Claude directly from the terminal to perform software engineering tasks — editing files, running commands, searching codebases, managing git workflows, and more.

This repository contains the leaked src/ directory.

• Leaked on: 2026-03-31
• Language: TypeScript
• Runtime: Bun
• Terminal UI: React + Ink (React for CLI)
• Scale: ~1,900 files, 512,000+ lines of code

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Directory Structure

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

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Core Architecture

1. Tool System (src/tools/)

Every tool Claude Code can invoke is implemented as a self-contained module. Each tool defines its input schema, permission model, and execution logic.

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

2. Command System (src/commands/)

User-facing slash commands invoked with / prefix.

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

3. Service Layer (src/services/)

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

4. Bridge System (src/bridge/)

A bidirectional communication layer connecting IDE extensions (VS Code, JetBrains) with the Claude Code CLI.

• bridgeMain.ts — Bridge main loop
• bridgeMessaging.ts — Message protocol
• bridgePermissionCallbacks.ts — Permission callbacks
• replBridge.ts — REPL session bridge
• jwtUtils.ts — JWT-based authentication
• sessionRunner.ts — Session execution management

5. Permission System (src/hooks/toolPermission/)

Checks permissions on every tool invocation. Either prompts the user for approval/denial or automatically resolves based on the configured permission mode (default, plan, bypassPermissions, auto, etc.).

6. Feature Flags

Dead code elimination via Bun's bun:bundle feature flags:

import { feature } from 'bun:bundle'

// Inactive code is completely stripped at build time
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

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Key Files in Detail

QueryEngine.ts (~46K lines)

The core engine for LLM API calls. Handles streaming responses, tool-call loops, thinking mode, retry logic, and token counting.

Tool.ts (~29K lines)

Defines base types and interfaces for all tools — input schemas, permission models, and progress state types.

commands.ts (~25K lines)

Manages registration and execution of all slash commands. Uses conditional imports to load different command sets per environment.

main.tsx

Commander.js-based CLI parser + React/Ink renderer initialization. At startup, parallelizes MDM settings, keychain prefetch, and GrowthBook initialization for faster boot.

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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

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Notable Design Patterns

Parallel Prefetch

Startup time is optimized by prefetching MDM settings, keychain reads, and API preconnect in parallel — before heavy module evaluation begins.

// main.tsx — fired as side-effects before other imports
startMdmRawRead()
startKeychainPrefetch()

Lazy Loading

Heavy modules (OpenTelemetry ~400KB, gRPC ~700KB) are deferred via dynamic import() until actually needed.

Agent Swarms

Sub-agents are spawned via AgentTool, with coordinator/ handling multi-agent 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

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

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GitPretty Setup (Per-File Pretty Commits)

If you want GitHub's file UI to show visually distinct commit messages per file, use the helper script in this repo:

bash ./gitpretty-apply.sh .

This will:

1. Clone gitpretty into ~/.gitpretty (first run only)
2. Make scripts executable
3. Run emoji-file-commits.sh against this repo

Optional: install auto-emoji hooks for future commits:

bash ./gitpretty-apply.sh . --hooks

After running, push as usual:

git push origin main

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Use It in Claude Code (MCP Server)

This repo includes an MCP server that lets you explore the Claude Code source directly from any Claude session. One command to set it up:

Quick Start

# Clone the repo (if you haven't already)
git clone https://github.com/nirholas/claude-code.git
cd claude-code/mcp-server

# Install dependencies and build
npm install && npm run build

# Add to Claude Code (run from the repo root)
claude mcp add claude-code-explorer -- node /absolute/path/to/claude-code/mcp-server/dist/index.js

Replace /absolute/path/to/claude-code with the actual path where you cloned the repo.

Or as a single copy-paste block (clones, builds, and registers in one go):

git clone https://github.com/nirholas/claude-code.git ~/claude-code \
  && cd ~/claude-code/mcp-server \
  && npm install && npm run build \
  && claude mcp add claude-code-explorer -- node ~/claude-code/mcp-server/dist/index.js

What You Get

Once added, Claude has access to these tools for exploring the codebase:

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

Plus prompts for guided exploration:

• 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

Example Usage

After adding the MCP server, just ask Claude naturally:

"How does the BashTool work?" "Search for where permissions are checked" "Show me the /review command source" "Explain the MCP client integration"

Custom Source Path

If your src/ directory is in a non-standard location, set the environment variable:

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

Remove It

claude mcp remove claude-code-explorer

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Disclaimer

This repository archives source code that was leaked from Anthropic's npm registry on 2026-03-31. All original source code is the property of Anthropic. Contact nichxbt for any comments.