Enable Opencode to authenticate against Antigravity (Google's IDE) via OAuth so you can use Antigravity rate limits and access models like gemini-3-pro-high and claude-opus-4-5-thinking with your Google credentials.

What you get

Google OAuth sign-in (multi-account via opencode auth login) with automatic token refresh
Multi-account load balancing Automatically cycle through multiple Google accounts to maximize rate limits
Automatic endpoint fallback between Antigravity API endpoints (daily → autopush → prod)
Antigravity API compatibility for OpenAI-style requests
Debug logging for requests and responses
Drop-in setup Opencode auto-installs the plugin from config

Quick start

Add the plugin to config (~/.config/opencode/opencode.json or project .opencode.json):

{
  "plugin": ["opencode-antigravity-auth@1.1.0"]
}

Authenticate

For multi-account + per-account project IDs (recommended): run opencode auth login.
For a quick single-account connect: open opencode and run /connect.
Choose Google → OAuth with Google (Antigravity).
Sign in via the browser and return to Opencode. If the browser doesn’t open, use the displayed link.
opencode auth login will ask for a project ID for each account, and after each sign-in you can add another account (up to 10).

Declare the models you want

Add Antigravity models under the provider.google.models section of your config:

{
  "plugin": ["opencode-antigravity-auth"],
  "provider": {
    "google": {
      "models": {
        "gemini-3-pro-high": {
          "name": "Gemini 3 Pro High (Antigravity)",
          "limit": {
            "context": 1048576,
            "output": 65535
          }
        },
        "gemini-3-pro-low": {
          "name": "Gemini 3 Pro Low (Antigravity)",
          "limit": {
            "context": 1048576,
            "output": 65535
          }
        },
        "claude-sonnet-4-5": {
          "name": "Claude Sonnet 4.5 (Antigravity)",
          "limit": {
            "context": 200000,
            "output": 64000
          }
        },
        "claude-sonnet-4-5-thinking": {
          "name": "Claude Sonnet 4.5 Thinking (Antigravity)",
          "limit": {
            "context": 200000,
            "output": 64000
          }
        },
        "claude-opus-4-5-thinking": {
          "name": "Claude Opus 4.5 Thinking (Antigravity)",
          "limit": {
            "context": 200000,
            "output": 64000
          }
        },
        "gpt-oss-120b-medium": {
          "name": "GPT-OSS 120B Medium (Antigravity)",
          "limit": {
            "context": 131072,
            "output": 32768
          }
        }
      }
    }
  }
}

Use a model

opencode run "Hello world" --model=google/gemini-3-pro-high

Multi-account load balancing

Account pool is stored in ~/.config/opencode/antigravity-accounts.json (or %APPDATA%/opencode/antigravity-accounts.json on Windows).
This file contains OAuth refresh tokens; treat it like a password and don’t share/commit it.
TUI /connect only supports single-account sign-in (no per-account project ID prompts). Use opencode auth login to add multiple accounts or set per-account project IDs.
Each request picks the next account round-robin; on HTTP 429 the account is cooled down and the request retries with the next account.
If Google revokes a refresh token (invalid_grant), that account is removed from the pool; rerun opencode auth login to add it back.

Debugging

Enable verbose logging:

export OPENCODE_ANTIGRAVITY_DEBUG=1

Logs are written to the current directory (e.g., antigravity-debug-<timestamp>.log).

Development

npm install

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 plugin, you acknowledge and accept the following:

Terms of Service risk: This approach may violate the Terms of Service of AI model providers (Anthropic, OpenAI, 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. This is an independent open-source project and is not endorsed by, sponsored by, or affiliated with Google LLC.
"Antigravity", "Gemini", "Google Cloud", and "Google" are trademarks of Google LLC.
Software is provided "as is", without warranty. You are responsible for complying with Google's Terms of Service and Acceptable Use Policy.

Credits

Built with help and inspiration from:

opencode-gemini-auth — Gemini OAuth groundwork by @jenslys
CLIProxyAPI — Helpful reference for Antigravity API

Support

If this plugin helps you, consider supporting its continued maintenance:

README.md Unescape Escape

Antigravity OAuth Plugin for Opencode