Implements a new provider that uses Google's Antigravity unified gateway API to access Claude, Gemini, and other models through a single OAuth2-authenticated endpoint.
Features:
- OAuth2 token management with automatic refresh
- Multi-account rotation for rate limit distribution
- Support for Claude Opus/Sonnet 4.5 (with/without thinking)
- Support for Gemini 2.5/3 models (Pro/Flash variants)
- Thinking mode support with configurable tokens
- Image processing support
- Dual quota pool tracking (antigravity vs gemini-cli)
- Gemini-style API request format
Authentication:
- Reads from ANTIGRAVITY_REFRESH_TOKEN env var (priority)
- Falls back to ~/.config/opencode/antigravity-accounts.json
- Automatic token refresh with retry logic
- Rate limit tracking per account and quota pool
Files added:
- providers/antigravity.py - Main provider implementation
- providers/antigravity_auth.py - OAuth token manager
- providers/registries/antigravity.py - Model registry
- conf/antigravity_models.json - Model definitions (11 models)
- docs/antigravity_provider.md - Setup and usage docs
- tests/test_antigravity_provider.py - Unit tests (14 pass)
Integration:
- Added to provider priority order after ZEN
- Registered in server.py with auto-detection
- ToS warning logged on first use
