Antigravity Proxy

An OpenAI-compatible proxy that bridges any OpenAI-compatible client to Google Antigravity's internal Cloud Code Assist API. Uses the OAuth token from the Antigravity CLI (agy) — no API key, no billing.

Access Gemini 3.5 Flash, Gemini 3.1 Pro, Claude Sonnet 4.6, Claude Opus 4.6, and more through a single local endpoint.

Features

• OpenAI-compatible /v1/chat/completions endpoint (streaming + non-streaming)
• Native Gemini passthrough /v1beta/models/{model}:generateContent endpoint
• Tool/function calling support (OpenAI tools → Gemini functionDeclarations, round-tripped)
• Model auto-mapping — use friendly names (gemini-3.5-flash), the proxy translates to backend names automatically
• Token auto-refresh — OAuth token refreshed automatically when expired
• Zero dependencies — pure Python 3.10+, stdlib only
• systemd integration — run as a background service

Available Models

Friendly Name	Backend Model	Notes
gemini-3.1-pro	gemini-3.1-pro-low	Thinking level: low
gemini-3.1-pro-high	gemini-3.1-pro-low	Thinking level: high
gemini-3-flash	gemini-3-flash
gemini-3.5-flash	gemini-3.5-flash-low
gemini-2.5-pro	gemini-2.5-pro
gemini-2.5-flash	gemini-2.5-flash
claude-sonnet-4.6	claude-sonnet-4-6	Via Antigravity backend
claude-opus-4.6	claude-opus-4-6-thinking	Thinking enabled

Model names are mapped automatically on both endpoints. You always use the friendly name in your client config.

---

Prerequisites

You need the Antigravity CLI (agy) installed and authenticated. The proxy reads the OAuth token that agy stores on disk.

Install Antigravity CLI

macOS / Linux:

curl -fsSL https://storage.googleapis.com/antigravity-releases/install.sh | bash

Windows: Download from antigravity.google or use winget:

winget install Google.Antigravity

Authenticate

Run the CLI once to complete the Google OAuth flow:

agy

This opens a browser, you sign in with your Google account, and the token is saved to ~/.gemini/antigravity-cli/antigravity-oauth-token.

Note: The proxy supports both consumer Google accounts and Google Workspace accounts.

---

Quick Start

Option A: Run directly

git clone https://github.com/usamashehab/antigravity-proxy.git
cd antigravity-proxy
python3 antigravity_proxy.py

The proxy starts on http://127.0.0.1:8877.

Option B: Run as a systemd service (recommended)

# 1. Clone to a permanent location
git clone https://github.com/usamashehab/antigravity-proxy.git ~/antigravity-proxy

# 2. Copy the service file
mkdir -p ~/.config/systemd/user
cp ~/antigravity-proxy/antigravity-proxy.service ~/.config/systemd/user/

# 3. If you use a venv, edit the ExecStart path in the service file to point to your python

# 4. Reload systemd and start
systemctl --user daemon-reload
systemctl --user enable antigravity-proxy
systemctl --user start antigravity-proxy

# 5. Verify
systemctl --user status antigravity-proxy
curl http://127.0.0.1:8877/health

Option C: Run with custom host/port

python3 antigravity_proxy.py --port 9000 --host 0.0.0.0

Warning: Binding to 0.0.0.0 exposes the proxy to your network. The proxy has no authentication layer — anyone who can reach it can use your Antigravity quota. Use 127.0.0.1 unless you know what you're doing.

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Configuration

Point your client at the proxy

Any OpenAI-compatible client works. Set:

Setting	Value
Base URL	http://127.0.0.1:8877/v1
API Key	antigravity (any string)
Model	Any name from the table above

Examples

OpenAI Python SDK:

from openai import OpenAI
client = OpenAI(
    base_url="http://127.0.0.1:8877/v1",
    api_key="antigravity",
)
response = client.chat.completions.create(
    model="gemini-3.5-flash",
    messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)

curl:

curl http://127.0.0.1:8877/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3.5-flash",
    "messages": [{"role": "user", "content": "Hello!"}]
  }'

Hermes Agent:

hermes config set model.provider custom
hermes config set model.base_url http://127.0.0.1:8877/v1
hermes config set model.api_key antigravity
hermes config set model.default gemini-3.5-flash

Claude Code:

export ANTHROPIC_BASE_URL=http://127.0.0.1:8877/v1
claude  # uses claude-sonnet-4.6 through the proxy

Continue / Aider / any OpenAI-compatible tool: Set base URL to http://127.0.0.1:8877/v1 and use any model from the table.

---

Two Endpoints

The proxy serves two distinct API surfaces:

1. OpenAI Chat Completions (default)

POST /v1/chat/completions

Standard OpenAI format. Messages, tools, streaming — all supported. Use this for any OpenAI-compatible client.

2. Native Gemini Passthrough

POST /v1beta/models/{model}:generateContent

Accepts the exact same request format as Google's generativelanguage.googleapis.com API. Supports inline_data (images), responseSchema (structured output), thinkingConfig, and everything else — all passed through untouched.

Use this when you need features that don't map to OpenAI format (image inputs, structured JSON schema output, etc.).

Example — structured output with a response schema:

curl http://127.0.0.1:8877/v1beta/models/gemini-3.5-flash:generateContent \
  -H "Content-Type: application/json" \
  -d '{
    "contents": [{"parts": [{"text": "Extract: Ahmed is 30 years old"}]}],
    "generationConfig": {
      "temperature": 0,
      "responseMimeType": "application/json",
      "responseSchema": {
        "type": "OBJECT",
        "properties": {
          "name": {"type": "STRING"},
          "age": {"type": "NUMBER"}
        },
        "required": ["name", "age"]
      }
    }
  }'

---

Management

Check health

curl http://127.0.0.1:8877/health
# {"status": "ok", "service": "antigravity-proxy"}

List available models

curl http://127.0.0.1:8877/v1/models

View logs (systemd)

journalctl --user -u antigravity-proxy -f

Restart

systemctl --user restart antigravity-proxy

Stop

systemctl --user stop antigravity-proxy

Token expired?

If the proxy logs show authentication errors, re-authenticate with the Antigravity CLI:

agy  # opens browser for re-login
systemctl --user restart antigravity-proxy

---

Adding / Updating Models

Edit MODEL_MAP at the top of antigravity_proxy.py:

MODEL_MAP = {
    "gemini-3.5-flash": ("gemini-3.5-flash-low", None),
    # format: "friendly-name": ("backend-name", thinking_level_or_None)
}

• Friendly name: what clients send (e.g. gemini-3.5-flash)
• Backend name: the model ID Antigravity's API expects (e.g. gemini-3.5-flash-low)
• Thinking level: "low", "high", or None

After editing, restart the proxy.

---

How It Works

Your Client (OpenAI format)
    │
    ▼
Antigravity Proxy (localhost:8877)
    │  ┌─ Translates OpenAI → Gemini format
    │  ├─ Manages OAuth token (auto-refresh)
    │  └─ Wraps in Antigravity envelope
    │
    ▼
cloudcode-pa.googleapis.com (Google's internal Code Assist API)
    │
    ▼
Gemini / Claude models

The proxy:

1. Reads the OAuth token from ~/.gemini/antigravity-cli/antigravity-oauth-token
2. Refreshes it automatically via oauth2.googleapis.com when expired
3. Discovers your Cloud Code Assist project ID via v1internal:loadCodeAssist
4. Wraps each request in the Antigravity envelope ({project, model, request, requestType})
5. Forwards to v1internal:generateContent (or streamGenerateContent)
6. Unwraps the response and converts back to OpenAI format

---

Requirements

• Python 3.10+
• Antigravity CLI (agy) installed and authenticated
• No pip dependencies — stdlib only

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FAQ

Is this legal?

The proxy uses the same OAuth token and API endpoints that the Antigravity CLI itself uses. It does not bypass authentication or payment — you still need a valid Google account with Antigravity access. Multiple similar projects exist on GitHub. That said, Google's terms of service may restrict programmatic API access. Use at your own discretion.

Does it support streaming?

Yes. Both SSE streaming (stream: true) on the OpenAI endpoint and the native Gemini stream endpoint.

Can I use it with images?

Yes, through the native Gemini passthrough endpoint (/v1beta/models/{model}:generateContent). Send inline_data with base64-encoded images, exactly like Google's API. The OpenAI chat endpoint does not currently support image inputs.

Is there a rate limit?

Rate limits are determined by Google's Antigravity quota, not the proxy. The proxy itself is multithreaded and has no concurrency limit.

Does the token expire?

Yes, the OAuth access token expires (~1 hour). The proxy auto-refreshes it using the refresh token. The refresh token itself can expire if unused for extended periods — re-run agy if that happens.

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License

MIT