🚀 Open source Claude Code CLI source code. Advanced AI Agent for developers. Includes TypeScript codebase for LLM tool-calling, agentic workflows, and terminal UI. Remember this is just the skeleton not the brain itself. Found by Chaofan Shou.
Claude Code's Entire Source Code Got Leaked via a Sourcemap in npm, Let's Talk About It
PS: This breakdown is also available on this blog with a better reading experience and UX :)
Note: There's a non-zero chance this repo might be taken down. If you want to play around with it later or archive it yourself, feel free to fork it and bookmark the external blog link!
⚠️ Important Disclaimer
I did not leak these files. I have simply provided an easy, documented way to access and study this codebase for research purposes. All files and information originate from public findings shared on Twitter/X. All credit for the discovery goes to the original source.
Earlier today (March 31st, 2026) - Chaofan Shou (@Fried_rice) discovered something that Anthropic probably didn't want the world to see: the entire source code of Claude Code, Anthropic's official AI coding CLI, was sitting in plain sight on the npm registry via a sourcemap file bundled into the published package.
This repository is a backup of that leaked source, providing a full breakdown of what's in it, how the leak happened, and the internal systems that were never meant to be public.
🧐 How Did This Even Happen?
When you publish a JavaScript/TypeScript package to npm, the build toolchain often generates source map files (.map files). These files bridge minified production code and the original source for debugging.
The agent harness performance optimization system. Skills, instincts, memory, security, and research-first development for Claude Code, Codex, Opencode, Cursor and beyond.
First-time install walkthrough for Claude Code, Codex CLI, and ChatGPT.
The catch? Source maps contain the original source code embedded as strings inside a JSON file under the sourcesContent key.
{
"version": 3,
"sources": ["../src/main.tsx", "../src/tools/BashTool.ts", "..."],
"sourcesContent": ["// The ENTIRE original source code of each file", "..."],
"mappings": "AAAA,SAAS,OAAO..."
}
By forgetting to add *.map to .npmignore or failing to disable source maps in production builds (Bun's default behavior), the entire raw source was shipped to the npm registry.
🛠 What's Under the Hood?
Claude Code is not just a simple CLI. It's a massive 785KB main.tsx entry point featuring a custom React terminal renderer (Ink), 40+ tools, and complex multi-agent orchestration.
🐣 BUDDY - The Terminal Tamagotchi
Inside src/buddy/, there is a full Tamagotchi-style companion system.
Deterministic Gacha: Uses a Mulberry32 PRNG seeded from your userId.
18 Species: Ranging from Common (Pebblecrab) to Legendary (Nebulynx).
Stats & Souls: Every buddy has stats like DEBUGGING, CHAOS, and SNARK, with a "soul" description written by Claude.
🕵️♂️ Undercover Mode - "Do Not Blow Your Cover"
Anthropic employees use Claude Code to contribute to public repos. Undercover Mode (src/utils/undercover.ts) prevents the AI from leaking internal info:
Blocks internal model codenames (e.g., Capybara, Tengu).
Hides the fact that the user is an AI.
Confirms that "Tengu" is likely the internal codename for Claude Code.
🌙 The "Dream" System
Claude Code "dreams" to consolidate memory. The autoDream service (src/services/autoDream/) runs as a background subagent to:
Orient: Read MEMORY.md.
Gather: Find new signals from daily logs.
Consolidate: Update durable memory files.
Prune: Keep context efficient.
🚀 KAIROS & ULTRAPLAN
KAIROS: An "always-on" proactive assistant that watches logs and acts without waiting for input.
ULTRAPLAN: Offloads complex tasks to a remote Opus 4.6 session for up to 30 minutes of deep planning.
Disclaimer: All original source code is the proprietary property of Anthropic PBC. This repository is for educational and archival purposes only. This is not an official Anthropic product.
The agent harness performance optimization system. Skills, instincts, memory, security, and research-first development for Claude Code, Codex, Opencode, Cursor and beyond.
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.
