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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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.