Claude Code Free

Use Claude Code CLI for free through Google's Antigravity (Cloud Code Assist) subscription.

A lightweight local proxy that bridges Claude Code CLI ↔ Google Cloud Code Assist API, giving you access to Claude Opus 4.6 and Claude Sonnet 4.5 — no Anthropic API key needed.

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How It Works

┌──────────────┐     ┌─────────────────┐     ┌──────────────────────────┐
│  Claude Code  │────▶│  Local Proxy     │────▶│  Google Cloud Code Assist│
│  CLI          │◀────│  (localhost:51200)│◀────│  (Antigravity API)       │
└──────────────┘     └─────────────────┘     └──────────────────────────┘
   Anthropic API         Translates             Has Claude models via
   format                formats                Google subscription

The proxy intercepts Claude Code CLI requests, translates them from Anthropic's format to Google's Cloud Code Assist API, and returns the responses in the format Claude Code expects. This works because Google's Antigravity/Code Assist subscription includes access to Claude models.

Prerequisites

• Node.js 18+ — Download
• Claude Code CLI — npm install -g @anthropic-ai/claude-code
• Google Account with Antigravity IDE Ultra or Google One AI Premium subscription

Quick Start

1. Clone the repo

git clone https://github.com/SovranAMR/claude-code-via-antigravity.git
cd claude-code-via-antigravity

2. Authenticate with Google

node setup.mjs login

This opens your browser for Google OAuth. Sign in with the account that has the Antigravity/AI Premium subscription.

3. Launch Claude Code

Linux / macOS:

./start.sh

Windows (PowerShell):

.\start.ps1

Windows (double-click): Just double-click start.bat

That's it! Claude Code CLI opens with full access to Claude models. 🚀

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Available Models

Model	Description
claude-opus-4-6-thinking	Most capable, with extended thinking
claude-sonnet-4-5	Fast and capable
claude-sonnet-4-5-thinking	Sonnet with thinking

All Claude Code model requests are automatically mapped to the best available model.

Platform Support

✅ Linux

Fully supported. Desktop shortcut included:

# Copy desktop shortcut
cp claude-free.desktop ~/.local/share/applications/
# Edit the Exec line to point to your start.sh path:
sed -i "s|%SCRIPT_DIR%|$(pwd)|g" ~/.local/share/applications/claude-free.desktop

✅ macOS

Fully supported via start.sh. You can also create an Automator app for dock access.

✅ Windows

Fully supported via PowerShell (start.ps1) or batch file (start.bat).

Requirements:

• Node.js for Windows
• Claude Code CLI (npm install -g @anthropic-ai/claude-code)
• Windows Terminal recommended

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Configuration

Environment Variables

Variable	Default	Description
PROXY_PORT	51200	Port for the local proxy
ANTHROPIC_BASE_URL	http://localhost:51200	Set automatically by launcher
ANTHROPIC_API_KEY	claude-code-via-antigravity	Set automatically (any value works)

Proxy Log

The proxy writes logs to a file instead of the terminal to keep Claude Code's UI clean:

• Linux/macOS: ~/.claude-code-via-antigravity-proxy.log
• Windows: %USERPROFILE%\.claude-code-via-antigravity-proxy.log

Watch logs in real-time:

tail -f ~/.claude-code-via-antigravity-proxy.log

Token Refresh

Tokens are automatically refreshed by the proxy. If you encounter auth errors:

node setup.mjs refresh

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Project Structure

claude-code-via-antigravity/
├── proxy.mjs          # Local proxy server (Anthropic ↔ Google translation)
├── setup.mjs          # OAuth authentication & credential setup
├── start.sh           # Linux/macOS launcher
├── start.ps1          # Windows PowerShell launcher
├── start.bat          # Windows batch launcher
├── claude-free.desktop # Linux desktop shortcut
├── LICENSE            # MIT
└── README.md

How the Proxy Works (Technical)

1. Message Conversion: Translates Anthropic's Messages API format to Google's streamGenerateContent format
2. Tool Schema Sanitization: Strips unsupported JSON Schema fields (anyOf, oneOf, $schema), flattens complex types, and ensures all schemas have a type field
3. Streaming: Converts Google's SSE stream to Anthropic's SSE stream format in real-time
4. Role Alternation: Enforces Google's user→model→user→model turn structure by merging consecutive same-role messages
5. Thinking Blocks: Drops internal thinking blocks that would confuse the API
6. Dynamic Thinking Budget: Scales thinking budget based on request size (25% of max_tokens, clamped 1024–10240)
7. Parallel Endpoints: Races both production and sandbox endpoints simultaneously for lower latency
8. Auto Token Refresh: Refreshes OAuth tokens automatically when they expire

Troubleshooting

Issue	Solution
Cannot read credentials	Run node setup.mjs login first
429 Rate Limited	Wait a few seconds and retry
503 Service Unavailable	Google's API is temporarily down, retry
tools.*.input_schema.type: Field required	Update to the latest version
Proxy logs mixed with Claude output	Update to latest version (logs now go to file)
EADDRINUSE	Kill existing proxy: kill -9 $(lsof -t -i :51200)

Contributing

Pull requests welcome! Some areas that could use improvement:

• macOS Automator app template
• Prompt caching support (if Google API adds it)
• Streaming thinking blocks back to Claude Code
• Auto-update mechanism

Disclaimer

This project is not affiliated with Anthropic or Google. It uses publicly available APIs. Use responsibly and in accordance with Google's and Anthropic's terms of service.

License

Personal & Non-Commercial Use Only — see LICENSE

You may use, modify, and share this freely for personal/hobby purposes. Commercial use, resale, or bundling with paid products is not permitted.