Open Claude Code

Open Source Claude Code CLI — Reverse Engineered & Rebuilt

A fully functional open source implementation of Anthropic's Claude Code CLI,
built from decompiled source intelligence using ruDevolution.

Automated Nightly Releases — Open Claude Code automatically detects new Claude Code releases, runs 903+ tests to verify zero regressions, and publishes verified builds with AI-powered discovery analysis. See Releases | ADR-001 | pi.ruv.io

⚡ Quick Start

# Run instantly (no install)
npx @ruvnet/open-claude-code "explain this codebase"

# Or install globally
npm install -g @ruvnet/open-claude-code
occ "hello"

# Interactive mode
occ

Requires: ANTHROPIC_API_KEY environment variable set.

export ANTHROPIC_API_KEY=sk-ant-...
npx @ruvnet/open-claude-code "what files are in this directory?"

🖥️ VSCode Extension

A Cursor-style AI coding assistant built directly into VSCode — no terminal required.

Quick install (pre-built VSIX)

The extension package is included in the repo and ready to install:

code --install-extension vscode-extension/open-claude-code-1.4.0.vsix

Or use Extensions → … → Install from VSIX… and pick the file from the vscode-extension/ folder.

Build from source

cd vscode-extension
npm install
npm run package          # prepackage → package → postpackage
code --install-extension open-claude-code-1.4.0.vsix

Highlights

Dedicated activity bar icon — opens a full Cursor-style chat panel in the sidebar
@claude chat participant — access Claude directly from VS Code's built-in Chat panel
Full tool access — all 25+ agent tools (Read, Write, Edit, Bash, Glob, Grep, WebFetch, …)
Rich markdown + syntax highlighting — code blocks with copy & Apply-to-file buttons
Copy whole answer — ⎘ Copy button on every assistant reply copies the full response to the clipboard
Session memory — the model remembers the full conversation from the beginning across VS Code restarts (Claude Premium-style); auto-saves after every response and restores on reopen
Chat history — History button shows all past conversations (Cursor-style panel); "New" auto-saves the current session; sessions persist across VS Code restarts; up to 30 sessions are retained
▶ Resume — any past session can be fully resumed: all messages are restored in the chat panel and the model's context is re-injected into the agent bridge
⚙ Settings shortcut — gear button in the header opens the extension settings directly — no need to navigate through the marketplace
Streaming responses — tokens arrive in real time with an animated cursor
Tool visualization — collapsible cards showing each tool execution and result
@file context injection — type @filename or click 📄 to add a file to the prompt
@git context chip — type @git or click the git button to inject current branch, changed files, and diff summary into the conversation
@errors context chip — type @errors or click the ⚠ button to inject all workspace errors and warnings (VSCode diagnostics) into the conversation
@openfiles autocomplete — type @openfiles to pick from your currently open editor tabs
Auto-attach active file — toggle the 🔗 button (or openClaudeCode.autoAttachActiveFile setting) to automatically include the active editor with every message
Context-full warning — a banner appears when the context window exceeds 85%, with a quick "New chat" shortcut
Per-message response time — each assistant reply shows how long it took to generate (visible on hover)
Ctrl/Cmd+Enter — additional keyboard shortcut for sending a message
Multi-provider — Anthropic Claude, OpenAI GPT, Google Gemini, NVIDIA NIM
Model & permission-mode selector — switch model and mode directly from the UI
Session stats — token count, cost estimate, and elapsed time always visible
Proactive workspace analysis — the agent explores your project automatically before answering; never asks you to paste code

See vscode-extension/README.md for the full setup and configuration guide.

🧠 What Is This?

Open Claude Code is a ground-up open source rebuild of Anthropic's Claude Code CLI, informed by ruDevolution's AI-powered decompilation of the published npm package.

It's not a copy — it's a clean-room implementation that mirrors the actual Claude Code architecture: async generator agent loop, 25 tools, 4 MCP transports, 6 permission modes, hooks, settings chain, sessions, and more.

1,581 tests. 61 files. 8,314 lines. 100% functional.

📦 Installation

npx (no install needed)

npx @ruvnet/open-claude-code "your prompt here"

Global install

npm install -g @ruvnet/open-claude-code
occ "your prompt here"

From source

git clone https://github.com/ruvnet/open-claude-code.git
cd open-claude-code/v2
export ANTHROPIC_API_KEY=sk-ant-...
node src/index.mjs "hello"

🖥️ Usage

One-shot mode

occ "explain the auth module"
occ "fix the bug in server.js"
occ "create a REST API for user management"
occ "find all TODO comments in this project"

Interactive REPL

occ
# > explain this codebase
# > /help
# > /tools
# > /model claude-opus-4-6
# > refactor the database layer
# > /cost
# > /exit

CLI Options

occ [options] [prompt]

Options:
  -m, --model <model>          Model to use (default: claude-sonnet-4-6)
  -p, --print                  Print mode (non-interactive, output only)
  --permission-mode <mode>     Permission mode: default, auto, plan, acceptEdits, 
                               bypassPermissions, dontAsk
  --system-prompt <text>       Override system prompt
  --add-dir <path>             Additional CLAUDE.md directory
  --max-turns <n>              Maximum conversation turns
  --allowedTools <tools>       Comma-separated allowed tools
  --disallowedTools <tools>    Comma-separated denied tools
  --output-format <fmt>        Output: text, json, stream-json
  -v, --verbose                Verbose output
  -d, --debug                  Debug mode
  --version                    Show version
  -h, --help                   Show help

Examples

# Use a different model
occ -m claude-opus-4-6 "design a database schema for a blog"

# Print mode (for piping)
occ -p "list all functions in src/" > functions.txt

# Plan mode (read-only, no edits)
occ --permission-mode plan "review the security of auth.js"

# Restrict tools
occ --allowedTools "Read,Glob,Grep" "find all API endpoints"

# With custom system prompt
occ --system-prompt "You are a senior Go developer" "review main.go"

🔧 Interactive Commands

40 slash commands available in REPL mode:

Command	Description
`/help`	Show all commands
`/model <name>`	Switch model mid-conversation
`/tools`	List available tools
`/tokens`	Show current token usage
`/cost`	Show session cost estimate
`/compact`	Compact context window
`/undo`	Undo last file edit
`/clear`	Clear conversation history
`/doctor`	Check API connectivity + health
`/fast`	Toggle fast mode (Haiku)
`/effort <level>`	Set effort: low, medium, high, max
`/resume [id]`	Resume a previous session
`/sessions`	List saved sessions
`/agents`	List custom agents
`/skills`	List available skills
`/hooks`	Show active hooks
`/config`	Show current settings
`/permissions`	Show permission mode
`/mcp`	Show MCP server status
`/memory`	Show memory usage
`/exit`	Exit

🔨 Tools

25 built-in tools matching Claude Code's tool system:

Tool	Description
Bash	Execute shell commands (sandboxed)
Read	Read files with line numbers
Edit	Replace strings in files
Write	Create/overwrite files
Glob	Find files by pattern
Grep	Search file contents (regex)
LS	List directory contents
Agent	Spawn sub-agents
WebFetch	Fetch URL content
WebSearch	Web search
TodoWrite	Task management
NotebookEdit	Edit Jupyter notebooks
MultiEdit	Atomic multi-file edits
ToolSearch	Discover deferred tools
AskUser	Prompt user for input
Skill	Invoke a skill
SendMessage	Agent team messaging
CronCreate/Delete/List	Scheduled tasks
EnterWorktree/ExitWorktree	Git worktree isolation
RemoteTrigger	Remote execution
LSP	Language server protocol
ReadMcpResource	Read MCP resources

⚙️ Configuration

Settings

Create .claude/settings.json in your project or ~/.claude/settings.json globally:

{
  "model": "claude-sonnet-4-6",
  "permissions": {
    "defaultMode": "auto"
  },
  "hooks": {
    "PreToolUse": [{
      "matcher": "Bash",
      "hooks": [{ "type": "command", "command": "echo 'Running bash...'" }]
    }]
  },
  "autoCompactEnabled": true,
  "alwaysThinkingEnabled": true
}

Settings are loaded from 4 sources (in priority order):

.claude/settings.local.json (local, gitignored)
.claude/settings.json (project, shared)
~/.claude/settings.json (user global)
Managed policy (enterprise)

CLAUDE.md

Create a CLAUDE.md in your project root to customize behavior:

# Project Rules
- Always use TypeScript
- Follow TDD
- Keep files under 500 lines

CLAUDE.md files are loaded from: ~/.claude/CLAUDE.md → parent directories → project root → .claude/CLAUDE.md.

Custom Agents

Create .claude/agents/reviewer.md:

---
name: reviewer
description: Code review specialist
model: claude-sonnet-4-6
tools: [Read, Glob, Grep]
---

You are a thorough code reviewer. Check for bugs, security issues, and style.

Skills

Create .claude/skills/deploy/SKILL.md:

---
name: deploy
description: Deploy to production
---

1. Run tests: npm test
2. Build: npm run build
3. Deploy: ./scripts/deploy.sh

Invoke with /deploy in the REPL.

🔐 Multi-Provider Support

Works with 5 AI providers:

# Anthropic (default)
ANTHROPIC_API_KEY=... occ "hello"

# OpenAI
OPENAI_API_KEY=... occ -m gpt-4o "hello"

# Google
GOOGLE_AI_API_KEY=... occ -m gemini-2.5-flash "hello"

# AWS Bedrock
AWS_ACCESS_KEY_ID=... AWS_SECRET_ACCESS_KEY=... occ -m bedrock/claude-sonnet "hello"

# Google Vertex
GOOGLE_APPLICATION_CREDENTIALS=... occ -m vertex/claude-sonnet "hello"

# NVIDIA NIM (kimi-k2.5, deepseek-r1, and other thinking models supported)
NVIDIA_API_KEY=nvapi-... occ -m kimi-k2.5 "hello"

Note — NVIDIA models (Kimi K2.5, DeepSeek R1): These models support full tool-calling by default — they can Read, Write, Bash, Grep, and run all 25+ agent tools exactly like Cursor or opencode. Set NVIDIA_THINKING_MODE=true (or toggle the openClaudeCode.nvidiaThinkingMode setting in the VSCode extension) to opt into extended reasoning mode; in that mode tools are replaced with a rich workspace snapshot injected into the system prompt (file tree + key file contents), since NVIDIA NIM does not allow tools and thinking simultaneously.

🔗 MCP Integration

Connect to MCP servers for additional tools:

// .mcp.json
{
  "mcpServers": {
    "my-server": {
      "command": "npx",
      "args": ["-y", "my-mcp-server"],
      "env": { "API_KEY": "..." }
    }
  }
}

Supports 4 transports: stdio, SSE, Streamable HTTP, WebSocket.

🔍 Background: The Claude Code Source Leak

On March 31, 2026, Anthropic accidentally shipped source maps in the Claude Code npm package, exposing the full TypeScript source. This project takes a different approach — we use ruDevolution to analyze the published npm package legally and rebuild from that intelligence.

What ruDevolution Found

Discovery	Evidence
🤖 Agent Teams	`CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS`
🌙 Auto Dream Mode	`tengu_auto_dream_completed`
🔮 claude-opus-4-6	Unreleased model ID
🔐 6 "amber" codenames	Internal feature gates
☁️ Cloud Code Runner	BYOC compute
📡 MCP Streamable HTTP	New transport

Download decompiled releases →

⚖️ Legal

This is a clean-room implementation — no leaked source used. Architecture informed by analysis of the published npm package, legal under US DMCA §1201(f), EU Software Directive Art. 6, UK CDPA §50B.

🆕 What's New

v1.4.0 — Context Injection, Auto-Attach & UX Improvements

Richer context injection

@git chip — type @git in the chat input (or click the new git toolbar button) to instantly inject the current branch name, git status, and git diff --stat as a context chip. The content is appended inline to your message so the model has full awareness of your working-tree state
@errors chip — type @errors (or click the ⚠ toolbar button) to pull all workspace errors and warnings from the VSCode diagnostics API into the conversation, grouped by severity
@openfiles autocomplete — type @openfiles to populate the @ autocomplete dropdown with every file currently open in the editor, making it easy to add multiple files without typing paths
Auto-attach active file — click the new 🔗 toolbar button (or set openClaudeCode.autoAttachActiveFile: true in settings) to automatically include the currently active editor file with every message you send — no need to type @ every time

UX improvements

Context-full warning banner — a visible warning appears above the input when context usage exceeds 85%, with a one-click "New chat" shortcut to start fresh before responses degrade
Per-message response time — each assistant reply now shows how long it took to generate (e.g. 3.2s) in the message header, visible on hover
Ctrl/Cmd+Enter — added as a second keyboard shortcut for sending messages (in addition to plain Enter)
Consistent keyboard hint — the input area now shows Enter / Ctrl+Enter send to surface the new shortcut

v1.3.1 — Bridge Stability & Session Memory Fixes

Session memory loss fix — agent bridge now auto-injects the full session history whenever a new bridge process is created (covers crashes, settings changes, and VS Code restarts)
Bridge queue stability — message queue is drained reliably on bridge restart so in-flight requests are not lost
Max-turns UX hint — when the agent loop hits its turn limit a visible ⚙ Max turns reached notice is shown with instructions to continue

v1.3.0 — Session Memory (Claude Premium-style)

Session Memory algorithm — the model now remembers the full conversation from the very beginning, just like Claude premium sessions:

Auto-persist active session — the current conversation is automatically saved to VS Code globalState after every response. If you close and reopen VS Code, your conversation is fully restored — messages in the chat panel and the model's context in the bridge subprocess
Session resume from history — every past conversation in the History panel now has a ▶ Resume button. Clicking it:
1. Saves your current in-progress chat to history
2. Restores all messages of the selected session in the main chat panel
3. Re-injects the full conversation into the agent loop (resume command in agent-bridge.mjs) so the model has complete memory of everything said — no context lost
New resume bridge protocol — agent-bridge.mjs accepts {"type":"resume","messages":[…]} which converts the stored UI message format back to the Anthropic/OpenAI API message format and sets it directly on the agent loop's state
Auto-clear on new chat — starting a new conversation clears the persisted active session so the next restart begins fresh

v1.2.0 — Chat History, Settings Button & Copy Answer

New UI features (this PR)

⚙ Settings button — a gear icon added to the chat header opens openClaudeCode settings directly; no more navigating through the Extensions marketplace
⎘ Copy whole answer — each finalized assistant reply now has a ⎘ Copy button in the message header; one click copies the full raw markdown response to the clipboard
Chat history panel (Cursor-style) — clicking the new History header button opens a full-overlay panel listing all past sessions. Pressing New auto-saves the current conversation to history first. Sessions are persisted in VS Code globalState and survive restarts; up to 30 sessions are retained
Cursor-style session navigation — click any session in the history list to view its messages read-only (with Copy buttons intact); a Back button returns to the session list

Fix: Proactive workspace analysis for all models

All models now receive a strong agentic system prompt declaring the workspace cwd and instructing them to explore files with LS / Glob / Read / Grep / Bash before answering — never asking the user to paste code
New buildWorkspaceSnapshot helper recursively walks the workspace (skipping node_modules, .git, dist, etc.) and returns a compact indented file tree capped at 200 entries
New buildWorkspaceContent helper reads key project files (README, package.json, entry points, etc.) and returns their contents for inline injection — capped at 64 KB total
Kimi K2.5 and DeepSeek R1 now use full tool-calling by default — Read, Write, Bash, Grep, and all 25+ tools work exactly like Cursor or opencode; thinking/reasoning mode is an opt-in setting (NVIDIA_THINKING_MODE=true or openClaudeCode.nvidiaThinkingMode in VSCode settings)
When thinking mode IS enabled a rich workspace snapshot (file tree + key file contents) is injected into the system prompt with a purpose-built thinking-model system prompt
Extension model descriptions updated; version bumped to 1.2.0

v1.1.0 — VSCode Extension & Bug Fixes

VSCode Extension — Cursor-style sidebar panel (PR #2)

New dedicated activity bar icon with a full-screen Cursor-style chat panel
Rich markdown rendering, syntax-highlighted code blocks, copy & Apply-to-file buttons
Streaming responses with animated cursor, tool visualization cards, extended thinking blocks
@file context injection, file picker, model/mode selector, session stats, and stop button
Pre-built VSIX committed to vscode-extension/open-claude-code-1.1.0.vsix — install with one command

VSCode Extension — @claude Chat Participant (PR #1)

New vscode-extension/ package exposing the v2/src agent loop as a native VSCode Chat participant
Long-lived agent-bridge.mjs subprocess keeps conversation history across turns
API key stored in VSCode SecretStorage — never written to disk in plaintext
/clear and /model slash commands; configurable permission mode, max turns, and tool visibility

Fix: NVIDIA NIM thinking models (PR #3)

kimi-k2.5, deepseek-r1, and other NVIDIA thinking models no longer crash with HTTP 400
Tool array is now omitted for thinking models (the two parameters are mutually exclusive)
Clean system prompt (without tool descriptions) is used for thinking-model calls

VSCode extension package now tracked in git (PR #4)

*.vsix removed from .gitignore — the built package lives at vscode-extension/open-claude-code-1.1.0.vsix

📚 Related

ruDevolution — AI-Powered JavaScript Decompiler
Decompiled Releases — Every Claude Code version
v2 Architecture (ADR-001)
Path to 100% (ADR-002)

Nightly Release Pipeline

Automated Nightly Verified Releases (ADR-001)

Open Claude Code includes an automated nightly CI/CD pipeline that:

Detects new Claude Code releases from npm registry (03:00 UTC daily)
Verifies compatibility with 903+ tests, npm audit, and smoke tests
Analyzes changes using Claude Sonnet 4.6 AI-powered discovery
Publishes verified releases with detailed notes — only if ALL gates pass

Cron 03:00 UTC → npm check → 903+ tests → npm audit → AI analysis → verified release

Manual trigger:

gh workflow run nightly.yml -f force_release=true

Required secrets:

GITHUB_TOKEN — automatic
ANTHROPIC_API_KEY — optional, for AI discovery analysis

See ADR-001 for full architecture.

rudevolution Integration

The rudevolution submodule provides AI-powered decompilation analysis of Claude Code releases, tracking 34,759+ functions with 95.7% name accuracy. Used by the nightly pipeline for change discovery.

📄 License

MIT

Name		Name	Last commit message	Last commit date
Latest commit History 100 Commits
.github/workflows		.github/workflows
archive/open_claude_code		archive/open_claude_code
assets		assets
docs/adr		docs/adr
rudevolution @ 53af4c0		rudevolution @ 53af4c0
scripts		scripts
v2		v2
vscode-extension		vscode-extension
.gitignore		.gitignore
.gitmodules		.gitmodules
LICENSE		LICENSE
README.md		README.md

Folders and files

Latest commit

History

Repository files navigation

Open Claude Code

Open Source Claude Code CLI — Reverse Engineered & Rebuilt

⚡ Quick Start

🖥️ VSCode Extension

Quick install (pre-built VSIX)

Build from source

Highlights

🧠 What Is This?

📦 Installation

npx (no install needed)

Global install

From source

🖥️ Usage

One-shot mode

Interactive REPL

CLI Options

Examples

🔧 Interactive Commands

🔨 Tools

⚙️ Configuration

Settings

CLAUDE.md

Custom Agents

Skills

🔐 Multi-Provider Support

🔗 MCP Integration

🔍 Background: The Claude Code Source Leak

What ruDevolution Found

⚖️ Legal

🆕 What's New

v1.4.0 — Context Injection, Auto-Attach & UX Improvements

v1.3.1 — Bridge Stability & Session Memory Fixes

v1.3.0 — Session Memory (Claude Premium-style)

v1.2.0 — Chat History, Settings Button & Copy Answer

v1.1.0 — VSCode Extension & Bug Fixes

📚 Related

Automated Nightly Verified Releases (ADR-001)

rudevolution Integration

📄 License

About

Resources

License

Uh oh!

Stars

Watchers

Forks

Releases

Packages 0

Uh oh!

Contributors

Uh oh!

Languages

Packages