Antigravity Claude Proxy

A proxy server that exposes an Anthropic-compatible API backed by Antigravity's Cloud Code, letting you use Claude and Gemini models with Claude Code CLI.

How It Works

┌──────────────────┐     ┌─────────────────────┐     ┌────────────────────────────┐
│   Claude Code    │────▶│  This Proxy Server  │────▶│  Antigravity Cloud Code    │
│   (Anthropic     │     │  (Anthropic → Google│     │  (daily-cloudcode-pa.      │
│    API format)   │     │   Generative AI)    │     │   sandbox.googleapis.com)  │
└──────────────────┘     └─────────────────────┘     └────────────────────────────┘

1. Receives requests in Anthropic Messages API format
2. Uses OAuth tokens from added Google accounts (or Antigravity's local database)
3. Transforms to Google Generative AI format with Cloud Code wrapping
4. Sends to Antigravity's Cloud Code API
5. Converts responses back to Anthropic format with full thinking/streaming support

Prerequisites

• Node.js 18 or later
• Antigravity installed (for single-account mode) OR Google account(s) for multi-account mode

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Installation

Option 1: npm (Recommended)

# Run directly with npx (no install needed)
npx antigravity-claude-proxy@latest start

# Or install globally
npm install -g antigravity-claude-proxy@latest
antigravity-claude-proxy start

Option 2: Clone Repository

git clone https://github.com/badri-s2001/antigravity-claude-proxy.git
cd antigravity-claude-proxy
npm install
npm start

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Quick Start

1. Start the Proxy Server

# If installed via npm
antigravity-claude-proxy start

# If using npx
npx antigravity-claude-proxy@latest start

# If cloned locally
npm start

The server runs on http://localhost:8080 by default.

2. Link Account(s)

Choose one of the following methods to authorize the proxy:

Method A: Web Dashboard (Recommended)

1. With the proxy running, open http://localhost:8080 in your browser.
2. Navigate to the Accounts tab and click Add Account.
3. Complete the Google OAuth authorization in the popup window.

Method B: CLI (Desktop or Headless)

If you prefer the terminal or are on a remote server:

# Desktop (opens browser)
antigravity-claude-proxy accounts add

# Headless (Docker/SSH)
antigravity-claude-proxy accounts add --no-browser

For full CLI account management options, run antigravity-claude-proxy accounts --help.

Method C: Automatic (Antigravity Users)

If you have the Antigravity app installed and logged in, the proxy will automatically detect your local session. No additional setup is required.

To use a custom port:

PORT=3001 antigravity-claude-proxy start

3. Verify It's Working

# Health check
curl http://localhost:8080/health

# Check account status and quota limits
curl "http://localhost:8080/account-limits?format=table"

---

Using with Claude Code CLI

Configure Claude Code

You can configure these settings in two ways:

Via Web Console (Recommended)

1. Open the WebUI at http://localhost:8080.
2. Go to Settings → Claude CLI.
3. Select your preferred models and click Apply to Claude CLI.

[!TIP] > Configuration Precedence: System environment variables (set in shell profile like .zshrc) take precedence over the settings.json file. If you use the Web Console to manage settings, ensure you haven't manually exported conflicting variables in your terminal.

Manual Configuration

Create or edit the Claude Code settings file:

macOS: ~/.claude/settings.json Linux: ~/.claude/settings.json Windows: %USERPROFILE%\.claude\settings.json

Add this configuration:

{
  "env": {
    "ANTHROPIC_AUTH_TOKEN": "test",
    "ANTHROPIC_BASE_URL": "http://localhost:8080",
    "ANTHROPIC_MODEL": "claude-opus-4-5-thinking",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "claude-opus-4-5-thinking",
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-sonnet-4-5-thinking",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "gemini-2.5-flash-lite[1m]",
    "CLAUDE_CODE_SUBAGENT_MODEL": "claude-sonnet-4-5-thinking",
    "ENABLE_EXPERIMENTAL_MCP_CLI": "true"
  }
}

(Please use gemini-2.5-flash-lite as the default haiku model, even if others are claude, as claude code makes several calls via the haiku model for background tasks. If you use claude model for it, you may use you claude usage sooner)

Or to use Gemini models:

{
  "env": {
    "ANTHROPIC_AUTH_TOKEN": "test",
    "ANTHROPIC_BASE_URL": "http://localhost:8080",
    "ANTHROPIC_MODEL": "gemini-3-pro-high[1m]",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "gemini-3-pro-high[1m]",
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "gemini-3-flash[1m]",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "gemini-2.5-flash-lite[1m]",
    "CLAUDE_CODE_SUBAGENT_MODEL": "gemini-3-flash[1m]",
    "ENABLE_EXPERIMENTAL_MCP_CLI": "true"
  }
}

Load Environment Variables

Add the proxy settings to your shell profile:

macOS / Linux:

echo 'export ANTHROPIC_BASE_URL="http://localhost:8080"' >> ~/.zshrc
echo 'export ANTHROPIC_AUTH_TOKEN="test"' >> ~/.zshrc
source ~/.zshrc

For Bash users, replace ~/.zshrc with ~/.bashrc

Windows (PowerShell):

Add-Content $PROFILE "`n`$env:ANTHROPIC_BASE_URL = 'http://localhost:8080'"
Add-Content $PROFILE "`$env:ANTHROPIC_AUTH_TOKEN = 'test'"
. $PROFILE

Windows (Command Prompt):

setx ANTHROPIC_BASE_URL "http://localhost:8080"
setx ANTHROPIC_AUTH_TOKEN "test"

Restart your terminal for changes to take effect.

Run Claude Code

# Make sure the proxy is running first
antigravity-claude-proxy start

# In another terminal, run Claude Code
claude

Note: If Claude Code asks you to select a login method, add "hasCompletedOnboarding": true to ~/.claude.json (macOS/Linux) or %USERPROFILE%\.claude.json (Windows), then restart your terminal and try again.

Multiple Claude Code Instances (Optional)

To run both the official Claude Code and Antigravity version simultaneously, add this alias:

macOS / Linux:

# Add to ~/.zshrc or ~/.bashrc
alias claude-antigravity='CLAUDE_CONFIG_DIR=~/.claude-account-antigravity ANTHROPIC_BASE_URL="http://localhost:8080" ANTHROPIC_AUTH_TOKEN="test" command claude'

Windows (PowerShell):

# Add to $PROFILE
function claude-antigravity {
    $env:CLAUDE_CONFIG_DIR = "$env:USERPROFILE\.claude-account-antigravity"
    $env:ANTHROPIC_BASE_URL = "http://localhost:8080"
    $env:ANTHROPIC_AUTH_TOKEN = "test"
    claude
}

Then run claude for official API or claude-antigravity for this proxy.

---

Available Models

Claude Models

Model ID	Description
claude-sonnet-4-5-thinking	Claude Sonnet 4.5 with extended thinking
claude-opus-4-5-thinking	Claude Opus 4.5 with extended thinking
claude-sonnet-4-5	Claude Sonnet 4.5 without thinking

Gemini Models

Model ID	Description
gemini-3-flash	Gemini 3 Flash with thinking
gemini-3-pro-low	Gemini 3 Pro Low with thinking
gemini-3-pro-high	Gemini 3 Pro High with thinking

Gemini models include full thinking support with thoughtSignature handling for multi-turn conversations.

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Multi-Account Load Balancing

When you add multiple accounts, the proxy automatically:

• Sticky account selection: Stays on the same account to maximize prompt cache hits
• Smart rate limit handling: Waits for short rate limits (≤2 min), switches accounts for longer ones
• Automatic cooldown: Rate-limited accounts become available after reset time expires
• Invalid account detection: Accounts needing re-authentication are marked and skipped
• Prompt caching support: Stable session IDs enable cache hits across conversation turns

Check account status, subscription tiers, and quota anytime:

# Web UI: http://localhost:8080/ (Accounts tab - shows tier badges and quota progress)
# CLI Table:
curl "http://localhost:8080/account-limits?format=table"

CLI Management Reference

If you prefer using the terminal for management:

# List all accounts
antigravity-claude-proxy accounts list

# Verify account health
antigravity-claude-proxy accounts verify

# Interactive CLI menu
antigravity-claude-proxy accounts

---

Web Management Console

The proxy includes a built-in, modern web interface for real-time monitoring and configuration. Access the console at: http://localhost:8080 (default port).

Key Features

• Real-time Dashboard: Monitor request volume, active accounts, model health, and subscription tier distribution.
• Visual Model Quota: Track per-model usage and next reset times with color-coded progress indicators.
• Account Management: Add/remove Google accounts via OAuth, view subscription tiers (Free/Pro/Ultra) and quota status at a glance.
• Claude CLI Configuration: Edit your ~/.claude/settings.json directly from the browser.
• Persistent History: Tracks request volume by model family for 30 days, persisting across server restarts.
• Time Range Filtering: Analyze usage trends over 1H, 6H, 24H, 7D, or All Time periods.
• Smart Analysis: Auto-select top 5 most used models or toggle between Family/Model views.
• Live Logs: Stream server logs with level-based filtering and search.
• Advanced Tuning: Configure retries, timeouts, and debug mode on the fly.
• Bilingual Interface: Full support for English and Chinese (switch via Settings).

---

Advanced Configuration

While most users can use the default settings, you can tune the proxy behavior via the Settings → Server tab in the WebUI or by creating a config.json file.

Configurable Options

• API Key Authentication: Protect /v1/* API endpoints with API_KEY env var or apiKey in config.
• WebUI Password: Secure your dashboard with WEBUI_PASSWORD env var or in config.
• Custom Port: Change the default 8080 port.
• Retry Logic: Configure maxRetries, retryBaseMs, and retryMaxMs.
• Load Balancing: Adjust defaultCooldownMs and maxWaitBeforeErrorMs.
• Persistence: Enable persistTokenCache to save OAuth sessions across restarts.

Refer to config.example.json for a complete list of fields and documentation.

---

API Endpoints

Endpoint	Method	Description
/health	GET	Health check
/account-limits	GET	Account status and quota limits (add ?format=table for ASCII table)
/v1/messages	POST	Anthropic Messages API
/v1/models	GET	List available models
/refresh-token	POST	Force token refresh

---

Testing

Run the test suite (requires server running):

# Start server in one terminal
npm start

# Run tests in another terminal
npm test

Individual tests:

npm run test:signatures    # Thinking signatures
npm run test:multiturn     # Multi-turn with tools
npm run test:streaming     # Streaming SSE events
npm run test:interleaved   # Interleaved thinking
npm run test:images        # Image processing
npm run test:caching       # Prompt caching

---

Troubleshooting

"Could not extract token from Antigravity"

If using single-account mode with Antigravity:

1. Make sure Antigravity app is installed and running
2. Ensure you're logged in to Antigravity

Or add accounts via OAuth instead: antigravity-claude-proxy accounts add

401 Authentication Errors

The token might have expired. Try:

curl -X POST http://localhost:8080/refresh-token

Or re-authenticate the account:

antigravity-claude-proxy accounts

Rate Limiting (429)

With multiple accounts, the proxy automatically switches to the next available account. With a single account, you'll need to wait for the rate limit to reset.

Account Shows as "Invalid"

Re-authenticate the account:

antigravity-claude-proxy accounts
# Choose "Re-authenticate" for the invalid account

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Safety, Usage, and Risk Notices

Intended Use

• Personal / internal development only
• Respect internal quotas and data handling policies
• Not for production services or bypassing intended limits

Not Suitable For

• Production application traffic
• High-volume automated extraction
• Any use that violates Acceptable Use Policies

Warning (Assumption of Risk)

By using this software, you acknowledge and accept the following:

• Terms of Service risk: This approach may violate the Terms of Service of AI model providers (Anthropic, Google, etc.). You are solely responsible for ensuring compliance with all applicable terms and policies.

• Account risk: Providers may detect this usage pattern and take punitive action, including suspension, permanent ban, or loss of access to paid subscriptions.

• No guarantees: Providers may change APIs, authentication, or policies at any time, which can break this method without notice.

• Assumption of risk: You assume all legal, financial, and technical risks. The authors and contributors of this project bear no responsibility for any consequences arising from your use.

Use at your own risk. Proceed only if you understand and accept these risks.

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Legal

• Not affiliated with Google or Anthropic. This is an independent open-source project and is not endorsed by, sponsored by, or affiliated with Google LLC or Anthropic PBC.

• "Antigravity", "Gemini", "Google Cloud", and "Google" are trademarks of Google LLC.

• "Claude" and "Anthropic" are trademarks of Anthropic PBC.

• Software is provided "as is", without warranty. You are responsible for complying with all applicable Terms of Service and Acceptable Use Policies.

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Development

For Developers & Contributors

This project uses a local Tailwind CSS build system. CSS is pre-compiled and included in the repository, so you can run the project immediately after cloning.

Quick Start

git clone https://github.com/badri-s2001/antigravity-claude-proxy.git
cd antigravity-claude-proxy
npm install  # Automatically builds CSS via prepare hook
npm start    # Start server (no rebuild needed)

Frontend Development

If you need to modify styles in public/css/src/input.css:

# Option 1: Build once
npm run build:css

# Option 2: Watch for changes (auto-rebuild)
npm run watch:css

# Option 3: Watch both CSS and server (recommended)
npm run dev:full

File Structure:

• public/css/src/input.css - Source CSS with Tailwind @apply directives (edit this)
• public/css/style.css - Compiled & minified CSS (auto-generated, don't edit)
• tailwind.config.js - Tailwind configuration
• postcss.config.js - PostCSS configuration

Backend-Only Development

If you're only working on backend code and don't need frontend dev tools:

npm install --production  # Skip devDependencies (saves ~20MB)
npm start

Note: Pre-compiled CSS is committed to the repository, so you don't need to rebuild unless modifying styles.

Project Structure

See CLAUDE.md for detailed architecture documentation, including:

• Request flow and module organization
• Frontend architecture (Alpine.js + Tailwind)
• Service layer patterns (ErrorHandler.withLoading, AccountActions)
• Dashboard module documentation

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Credits

This project is based on insights and code from:

• opencode-antigravity-auth - Antigravity OAuth plugin for OpenCode
• claude-code-proxy - Anthropic API proxy using LiteLLM

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License

MIT

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