# Antigravity Claude Proxy

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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**.

![Antigravity Claude Proxy Banner](images/banner.png)

## 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

---

## Installation

### Option 1: npm (Recommended)

```bash
# 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

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

---

## Quick Start

### 1. Start the Proxy Server

```bash
# 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.

> **Headless/Remote Servers**: If running on a server without a browser, the WebUI supports a "Manual Authorization" mode. After clicking "Add Account", you can copy the OAuth URL, complete authorization on your local machine, and paste the authorization code back.

#### **Method B: CLI (Desktop or Headless)**

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

```bash
# 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:

```bash
PORT=3001 antigravity-claude-proxy start
```

### 3. Verify It's Working

```bash
# 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. Use the **Connection Mode** toggle to switch between:
   - **Proxy Mode**: Uses the local proxy server (Antigravity Cloud Code). Configure models, base URL, and presets here.
   - **Paid Mode**: Uses the official Anthropic Credits directly (requires your own subscription). This hides proxy settings to prevent accidental misconfiguration.
4. Click **Apply to Claude CLI** to save your changes.

> [!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:

```json
{
  "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": "claude-sonnet-4-5",
    "CLAUDE_CODE_SUBAGENT_MODEL": "claude-sonnet-4-5-thinking",
    "ENABLE_EXPERIMENTAL_MCP_CLI": "true"
  }
}
```

Or to use Gemini models:

```json
{
  "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-3-flash[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:**

```bash
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):**

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

**Windows (Command Prompt):**

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

Restart your terminal for changes to take effect.

### Run Claude Code

```bash
# 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.

### Proxy Mode vs. Paid Mode

Toggle in **Settings** → **Claude CLI**:

| Feature | 🔌 Proxy Mode | 💳 Paid Mode |
| :--- | :--- | :--- |
| **Backend** | Local Server (Antigravity) | Official Anthropic Credits |
| **Cost** | Free (Google Cloud) | Paid (Anthropic Credits) |
| **Models** | Claude + Gemini | Claude Only |

**Paid Mode** automatically clears proxy settings so you can use your official Anthropic account directly.

### Multiple Claude Code Instances (Optional)

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

**macOS / Linux:**

```bash
# 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):**

```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.

---

## Multi-Account Load Balancing

When you add multiple accounts, the proxy intelligently distributes requests across them using configurable selection strategies.

### Account Selection Strategies

Choose a strategy based on your needs:

| Strategy | Best For | Description |
| --- | --- | --- |
| **Hybrid** (Default) | Most users | Smart selection combining health score, token bucket rate limiting, quota awareness, and LRU freshness |
| **Sticky** | Prompt caching | Stays on the same account to maximize cache hits, switches only when rate-limited |
| **Round-Robin** | Even distribution | Cycles through accounts sequentially for balanced load |

**Configure via CLI:**

```bash
antigravity-claude-proxy start --strategy=hybrid    # Default: smart distribution
antigravity-claude-proxy start --strategy=sticky    # Cache-optimized
antigravity-claude-proxy start --strategy=round-robin  # Load-balanced
```

**Or via WebUI:** Settings → Server → Account Selection Strategy

### How It Works

- **Health Score Tracking**: Accounts earn points for successful requests and lose points for failures/rate-limits
- **Token Bucket Rate Limiting**: Client-side throttling with regenerating tokens (50 max, 6/minute)
- **Quota Awareness**: Accounts below configurable quota thresholds are deprioritized; exhausted accounts trigger emergency fallback
- **Quota Protection**: Set minimum quota levels globally, per-account, or per-model to switch accounts before quota runs out
- **Emergency Fallback**: When all accounts appear exhausted, bypasses checks with throttle delays (250-500ms)
- **Automatic Cooldown**: Rate-limited accounts recover automatically after reset time expires
- **Invalid Account Detection**: Accounts needing re-authentication are marked and skipped
- **Prompt Caching Support**: Session IDs derived from conversation enable cache hits across turns

### Monitoring

Check account status, subscription tiers, and quota anytime:

```bash
# 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:

```bash
# 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).

![Antigravity Console](images/webui-dashboard.png)

### 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 and draggable per-account threshold markers.
- **Account Management**: Add/remove Google accounts via OAuth, view subscription tiers (Free/Pro/Ultra), quota status, and per-account threshold settings.
- **Manual OAuth Mode**: Add accounts on headless servers by copying the OAuth URL and pasting the authorization code.
- **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.
- **Quota Protection**: Set global or per-account minimum quota thresholds to proactively switch accounts before quota runs out.
- **Advanced Tuning**: Configure retries, timeouts, and debug mode on the fly.
- **Multi-language Interface**: Full support for English, Chinese (中文), Indonesian (Bahasa), Portuguese (PT-BR), and Turkish (Türkçe).

---

## 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`.
- **Rate Limit Handling**: Comprehensive rate limit detection from headers and error messages with intelligent retry-after parsing.
- **Load Balancing**: Adjust `defaultCooldownMs` and `maxWaitBeforeErrorMs`.
- **Persistence**: Enable `persistTokenCache` to save OAuth sessions across restarts.
- **Max Accounts**: Set `maxAccounts` (1-100) to limit the number of Google accounts. Default: 10.
- **Quota Threshold**: Set `globalQuotaThreshold` (0-0.99) to switch accounts before quota drops below a minimum level. Supports per-account and per-model overrides.
- **Endpoint Fallback**: Automatic 403/404 endpoint fallback for API compatibility.

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

---

## macOS Menu Bar App

For macOS users who prefer a native experience, there's a companion menu bar app that provides quick access to server controls without touching the terminal. Get it from: [antigravity-claude-proxy-bar](https://github.com/IrvanFza/antigravity-claude-proxy-bar)

> **Note:** This is a GUI wrapper only. You still need to install and setup the proxy server first using one of the [installation methods](#installation) above.

![AntiGravity Claude Proxy Bar](https://github.com/IrvanFza/antigravity-claude-proxy-bar/blob/main/images/application.png?raw=true)

### Key Features

- **Server Control**: Start/stop the proxy server with a single click or ⌘S shortcut.
- **Status Indicator**: Menu bar icon shows server running state at a glance.
- **WebUI Access**: Open the web management console directly from the menu.
- **Port Configuration**: Customize the proxy server port (default: 8080).
- **Account Selection Strategy**: Choose between Hybrid, Sticky, or Round-Robin load balancing strategies.
- **Auto-Start Options**: Launch server on app start and launch app at login.
- **Native Experience**: Clean, native SwiftUI interface designed for macOS.

---

## 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):

```bash
# Start server in one terminal
npm start

# Run tests in another terminal
npm test
```

Individual tests:

```bash
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
npm run test:strategies    # Account selection strategies
npm run test:cache-control # Cache control field stripping
```

---

## Troubleshooting

### Windows: OAuth Port Error (EACCES)

On Windows, the default OAuth callback port (51121) may be reserved by Hyper-V, WSL2, or Docker. If you see:

```
Error: listen EACCES: permission denied 0.0.0.0:51121
```

The proxy will automatically try fallback ports (51122-51126). If all ports fail, try these solutions:

#### Option 1: Use a Custom Port (Recommended)

Set a custom port outside the reserved range:

```bash
# Windows PowerShell
$env:OAUTH_CALLBACK_PORT = "3456"
antigravity-claude-proxy start

# Windows CMD
set OAUTH_CALLBACK_PORT=3456
antigravity-claude-proxy start

# Or add to your .env file
OAUTH_CALLBACK_PORT=3456
```

#### Option 2: Reset Windows NAT

Run as Administrator:

```powershell
net stop winnat
net start winnat
```

#### Option 3: Check Reserved Ports

See which ports are reserved:

```powershell
netsh interface ipv4 show excludedportrange protocol=tcp
```

If 51121 is in a reserved range, use Option 1 with a port outside those ranges.

#### Option 4: Permanently Exclude Port (Admin)

Reserve the port before Hyper-V claims it (run as Administrator):

```powershell
netsh int ipv4 add excludedportrange protocol=tcp startport=51121 numberofports=1
```

> **Note:** The server automatically tries fallback ports (51122-51126) if the primary port fails.

---

### "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:

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

Or re-authenticate the account:

```bash
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:

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

---

## 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.**

---

## 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.

---

## 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

```bash
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`:

```bash
# 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:

```bash
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](./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

---

## Credits

This project is based on insights and code from:

- [opencode-antigravity-auth](https://github.com/NoeFabris/opencode-antigravity-auth) - Antigravity OAuth plugin for OpenCode
- [claude-code-proxy](https://github.com/1rgs/claude-code-proxy) - Anthropic API proxy using LiteLLM

---

## License

MIT

---

## Star History

[![Star History Chart](https://api.star-history.com/svg?repos=badrisnarayanan/antigravity-claude-proxy&type=date&legend=top-left&cache-control=no-cache)](https://www.star-history.com/#badrisnarayanan/antigravity-claude-proxy&type=date&legend=top-left)
