> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/badrisnarayanan/antigravity-claude-proxy/llms.txt
> Use this file to discover all available pages before exploring further.

# API Overview

> Anthropic-compatible API for Claude and Gemini models

## Base URL

```
http://localhost:8080
```

The default port is 8080. You can configure this via the `PORT` environment variable or in `config.json`.

## API Compatibility

Antigravity Claude Proxy provides an **Anthropic Messages API-compatible** interface. This means you can use the proxy as a drop-in replacement for the official Anthropic API by:

1. Setting `ANTHROPIC_BASE_URL=http://localhost:8080`
2. Setting `ANTHROPIC_AUTH_TOKEN=test` (or any value if API key auth is disabled)

The proxy translates requests from Anthropic format → Google Generative AI format → Antigravity Cloud Code API, then converts responses back to Anthropic format.

## Request/Response Format

All API requests use **JSON** payloads with `Content-Type: application/json`.

Responses follow the Anthropic Messages API format:

```json theme={null}
{
  "id": "msg_01...",
  "type": "message",
  "role": "assistant",
  "content": [...],
  "model": "claude-sonnet-4-5-thinking",
  "stop_reason": "end_turn",
  "usage": {
    "input_tokens": 150,
    "output_tokens": 250
  }
}
```

## Available Endpoints

<CardGroup cols={2}>
  <Card title="Messages" icon="message" href="/api-reference/messages">
    Send messages to Claude or Gemini models
  </Card>

  <Card title="Models" icon="brain" href="/api-reference/models">
    List available models
  </Card>

  <Card title="Health" icon="heart-pulse" href="/api-reference/health">
    Check server and account health
  </Card>

  <Card title="Authentication" icon="key" href="/api-reference/authentication">
    Configure API authentication
  </Card>
</CardGroup>

## Streaming Support

The proxy supports **Server-Sent Events (SSE)** for streaming responses. Set `stream: true` in your request to receive incremental updates as the model generates its response.

See the [Messages endpoint](/api-reference/messages#streaming) for details.

## Model Support

### Claude Models

* `claude-opus-4-6-thinking` - Extended reasoning, highest capability
* `claude-sonnet-4-5-thinking` - Balanced reasoning and speed
* `claude-sonnet-4-5` - Fast, production-ready

### Gemini Models

* `gemini-3.1-pro-high` - Highest quality Gemini
* `gemini-3.1-pro-low` - Cost-optimized Gemini
* `gemini-3-flash` - Fastest Gemini model

Use `GET /v1/models` to see all available models in your accounts.

## Error Handling

Errors follow the Anthropic API format:

```json theme={null}
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "messages is required and must be an array"
  }
}
```

### Error Types

* `authentication_error` - Invalid or missing API key (if auth is enabled)
* `invalid_request_error` - Malformed request or invalid parameters
* `api_error` - Upstream API error or network issue
* `not_found_error` - Endpoint not found

## Rate Limiting

The proxy automatically handles rate limits across multiple accounts:

* When an account is rate-limited, the proxy switches to another available account
* Rate limit state is tracked per model
* Accounts are automatically re-enabled when their quota resets

You can monitor account status via the [Health endpoint](/api-reference/health) or the Web UI.