claude-code

What it is

Claude Code is an agentic coding tool that lives in your terminal, understands your codebase, and helps you code faster by executing routine tasks, explaining complex code, and handling git workflows - all through natural language commands. This repository contains leaked source code for the Claude Code CLI.

How it works

The project uses a tool system where each tool (e.g., BashTool, FileReadTool, WebFetchTool, LSPTool, etc.) implements its own input schema, permission model, and execution logic. A command system exposes user-facing slash commands (e.g., /commit, /review, /config, /memory). The core architecture includes a QueryEngine for LLM API calls, a bridge system to IDEs, a permission system to gate tool invocations, and feature flags for conditional code paths. It supports parallel prefetch on startup, lazy loading of heavy modules, and an agent swarm pattern for multi-agent coordination. Key files include QueryEngine.ts, Tool.ts, commands.ts, and main.tsx.

Getting started

Prerequisites

• Bun v1.3+ (the project's runtime)
• Node.js v18+ (for npm package installation)
• An Anthropic API key (set as ANTHROPIC_API_KEY environment variable)

Install & Run

# 1. Install Bun (if not already installed)
curl -fsSL https://bun.sh/install | bash
source ~/.bash_profile  # or restart your terminal

# 2. Install dependencies
npm install --legacy-peer-deps

# 3. Run Claude Code
bun run start

# Or with arguments:
bun run start -- --help
bun run start -- --version
bun run start -- -p "Hello Claude"

Available Scripts

| Script | Description | |--------|-------------| | bun run start | Run Claude Code CLI | | bun run dev | Run with hot-reloading (--watch) | | bun run build | Bundle for production | | bun run typecheck | Run TypeScript type checking |

Environment Variables

| Variable | Description | |----------|-------------| | ANTHROPIC_API_KEY | Your Anthropic API key (required to use Claude) | | FEATURE_FLAGS | Comma-separated list of feature flags to enable (e.g., KAIROS,VOICE_MODE) |

Notes

• Some modules from the original source were not included in the leak (Anthropic-internal @ant/* packages, some tools). These have been replaced with stubs that export no-ops.
• The bun:bundle feature flag system is shimmed via a Bun plugin at plugins/bunBundleDev.ts. All flags default to false unless enabled via FEATURE_FLAGS.
• The MACRO.* build-time constants are defined in bunfig.toml and injected by Bun's --define system.

Recent releases

• Releases: none

Traction

• Stars: 2122
• Forks: 2731
• Open issues: 3

Notable design patterns

• Parallel Prefetch to reduce startup time
• Lazy Loading of heavy modules
• Agent Swarms for multi-agent coordination
• Skill System with reusable workflows
• Plugin Architecture for extensibility

Tech stack

• Runtime: Bun
• Language: TypeScript (strict)
• Terminal UI: React + Ink
• CLI Parsing: Commander.js
• Schema Validation: Zod v4
• Code Search: ripgrep via GrepTool
• Protocols: MCP SDK, LSP
• API: Anthropic SDK
• Auth: OAuth 2.0, JWT, macOS Keychain