Antigravity OAuth Proxy for Claude Code

---

Install (No Repo Clone)

One-line install that adds the gclaude helper to your shell and sets up the proxy runner:

curl -fsSL https://raw.githubusercontent.com/ankurkakroo2/claudecode-antigravity-auth/main/scripts/install.sh | bash

After install:

• Initialize OAuth + model mappings: gclaude init
• Run Claude Code with auto-starting proxy: gclaude "your prompt"

You can also install the helper manually with:

gclaude install-shell

The shell helper is named gclaude. It routes gclaude start|stop|status|... to the server CLI, and treats everything else as a Claude Code invocation. For explicit CLI help, use gclaude cli --help.

Quick Start (OAuth / Google AI Pro)

This proxy is Antigravity-only (Google OAuth). No Gemini API key is supported or required.

1. Clone and enter the repo

   git clone <your-repo-url>
   cd <repo-directory>

2. Create a virtual environment and install dependencies

   python3 -m venv .venv
   source .venv/bin/activate
   pip install -r requirements.txt
   pip install -e .

3. Run OAuth setup + model detection

   python -m gclaude init

4. Install the shell helper (auto-starts proxy)

   gclaude install-shell
   source ~/.zshrc   # or ~/.bashrc

5. Run Claude Code via the helper

   gclaude "ping"

6. Verify

   opencode run -m google/antigravity-claude-sonnet-4-5-thinking "ping"
   opencode run -m google/antigravity-claude-opus-4-5-thinking "ping"
   gclaude -p --model sonnet "ping"
   gclaude -p --model opus "ping"

Docs

Project docs live in docs/:

• docs/LLD.md (low-level design / architecture)
• docs/IMPLEMENTATION_PLAN.md (current plan)
• docs/RUNNING_NOTES.md (live progress + fixes + remaining issues)

Older notes were moved to .archived/.

gclaude at a glance

gclaude provides:

• OAuth authentication (PKCE) for Antigravity
• Model detection and interactive mapping
• Start/stop/status/logs for the proxy

See the gclaude CLI section for full commands and config paths.

---

This server bridges Claude Code with Antigravity (Google OAuth). It translates requests from Anthropic's Messages API format into the Antigravity API and converts responses back so Claude Code can work seamlessly.

Features

• Antigravity OAuth (Google AI Pro): Use Claude Sonnet/Opus via Google OAuth.
• Claude Code Compatibility: Works with Claude Code CLI and its tool-call format.
• Model Mapping: Maps Claude Code aliases (haiku, sonnet, opus) to Antigravity model IDs.
• Streaming Support: Handles streaming responses with retries for malformed chunks.
• Tool Use Translation: Converts Claude tool calls to Antigravity function schemas.
• Token Counting: /v1/messages/count_tokens endpoint compatible with Claude Code.
• Diagnostics: /health and /antigravity-status for troubleshooting.

Prerequisites

• Python 3.8+.
• Claude Code CLI installed (e.g., npm install -g @anthropic-ai/claude-code).
• Google AI Pro subscription (OAuth / Antigravity).
• Optional: OpenCode CLI (opencode) for quick verification.

Usage with Claude Code

1. Use the shell helper (recommended): gclaude auto-starts the proxy, writes ~/.claude/antigravity-settings.json, and uses ~/.claude/mcp_config.json if present.

   gclaude "summarize my repo"

   If Claude Code asks for a token, set ANTHROPIC_AUTH_TOKEN to any dummy value.

2. Manual mode (optional):

   claude --settings ~/.claude/antigravity-settings.json

   gclaude init generates ~/.claude/antigravity-settings.json automatically.

3. Quick non-interactive test

   gclaude -p --model sonnet "ping"
   gclaude -p --model opus "ping"

How It Works

1. Claude Code sends Anthropic-format requests to the proxy (http://localhost:8082).
2. The proxy maps Claude model aliases to Antigravity model IDs.
3. Requests are translated to the Antigravity API format and sent with OAuth.
4. Responses are converted back to Anthropic format and returned to Claude Code.

Model Mapping for Claude Code

Model aliases map to Antigravity models:

• ANTIGRAVITY_HAIKU_MODEL (default: antigravity-gemini-3-flash)
• ANTIGRAVITY_SONNET_MODEL (default: antigravity-claude-sonnet-4-5-thinking)
• ANTIGRAVITY_OPUS_MODEL (default: antigravity-claude-opus-4-5-thinking)

If Claude Code requests a full antigravity-* model ID, the proxy will use it directly.

Endpoints

• POST /v1/messages: Claude Code messages endpoint.
• POST /v1/messages/count_tokens: Token count estimation using local model metadata.
• GET /health: Health status, streaming settings, and Antigravity status.
• GET /antigravity-status: OAuth account + quota status.
• GET /: Root endpoint with configuration summary.

Error Handling & Troubleshooting

Streaming Errors (malformed chunks):

• The proxy retries malformed chunk parsing automatically.
• Set FORCE_DISABLE_STREAMING=true if you need a temporary fallback.

Connection Timeouts:

• Increase REQUEST_TIMEOUT if you see frequent timeouts.
• Check network connectivity and firewall settings.

Rate Limiting:

• Check python -m gclaude status or /antigravity-status for quota info.

Antigravity OAuth Issues:

• Re-run python -m gclaude init if you see auth or token errors.

Logging

Logs show request routing, retries, and conversion details. Adjust verbosity with LOG_LEVEL:

• DEBUG: Detailed request/response logging
• INFO: General operation logging
• WARNING: Error recovery notifications (recommended)
• ERROR: Only errors and failures

Performance Tips

• Use ANTIGRAVITY_* model IDs that match your access.
• Keep streaming enabled for interactive output; the proxy handles retries.
• Increase REQUEST_TIMEOUT for large requests.
• Adjust MAX_STREAMING_RETRIES for unstable networks.

Contributing

Contributions, issues, and feature requests are welcome.

Areas where contributions are especially valuable:

• Antigravity model routing improvements
• Error recovery strategies
• Documentation improvements

---

gclaude CLI

Installation

pip install -e .

Usage

# Initialize with guided setup
python -m gclaude init

# Start the proxy
python -m gclaude start

# Check status
python -m gclaude status

# View logs
python -m gclaude logs

# Follow logs live
python -m gclaude logs -f

Features

Model Detection: Automatically detects which Antigravity models are available to your account.

Interactive Mapping: Select which models to use for haiku/sonnet/opus requests based on your access.

OAuth Management: Add, remove, and list Antigravity OAuth accounts.

Status Dashboard: Terminal UI showing proxy status, auth state, and model routes.

Configuration Files

File	Location
Config	~/.gclaude/config.json
OAuth Tokens	~/.config/gclaude/antigravity-accounts.json
Logs	~/.gclaude/logs/proxy.log

Model Routes

Claude Code Pattern	Antigravity Model	Description
*haiku*	antigravity-gemini-3-flash	Fast & efficient - Best for haiku requests
*sonnet*	antigravity-claude-sonnet-4-5-thinking	Extended reasoning - For complex tasks
*opus*	antigravity-claude-opus-4-5-thinking	Advanced reasoning - Best for opus requests

Full list of available Antigravity models:

Model ID	Name	Description
antigravity-gemini-3-flash	Gemini 3 Flash	Fast & efficient - Best for haiku requests
antigravity-gemini-3-pro-low	Gemini 3 Pro Low	Faster responses with less thinking
antigravity-gemini-3-pro-high	Gemini 3 Pro High	Deeper reasoning with more thinking
antigravity-claude-sonnet-4-5	Claude Sonnet 4.5	Balanced capability - Good for general coding
antigravity-claude-sonnet-4-5-thinking	Claude Sonnet 4.5 (Thinking)	Extended reasoning - For complex tasks
antigravity-claude-opus-4-5-thinking	Claude Opus 4.5 (Thinking)	Advanced reasoning - Best for opus requests
antigravity-gpt-oss-120b-medium	GPT-OSS 120B Medium	Open source alternative - Medium capability

Architecture Overview

┌─────────────────┐     ┌──────────────────┐     ┌─────────────────────────┐
│  Claude Code    │────▶│  gclaude Proxy   │────▶│  Antigravity API        │
│  (claude cli)   │     │  (localhost:8082)│     │  (Google OAuth)         │
└─────────────────┘     └──────────────────┘     └─────────────────────────┘

Request Flow:

1. Claude Code sends Anthropic-format requests to http://localhost:8082
2. Proxy translates to Antigravity format and routes via OAuth
3. Responses are translated back to Anthropic format for Claude Code