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

Step 1: Create your config file

If this is your first time using Opencode, create the config directory first:

mkdir -p ~/.config/opencode

Then create or edit the config file at ~/.config/opencode/opencode.json:

{
  "plugin": ["opencode-antigravity-auth@1.1.1"]
}

Note: You can also use a project-local .opencode.json file in your project root instead. The global config at ~/.config/opencode/opencode.json applies to all projects.

Step 2: Authenticate

Run the authentication command:

opencode auth login

Select Google as the provider
Select OAuth with Google (Antigravity)
Project ID prompt: You'll see this prompt:
```
Project ID (leave blank to use your default project):
```
Just press Enter to skip this — it's optional and only needed if you want to use a specific Google Cloud project. Most users can leave it blank.
Sign in via the browser and return to Opencode. If the browser doesn't open, copy the displayed URL manually.
After signing in, you can add more Google accounts (up to 10) for load balancing, or press Enter to finish.

Alternative: For a quick single-account setup without project ID options, open opencode and use the /connect command instead.

Step 3: Add the models you want to use

Open the same config file you created in Step 1 (~/.config/opencode/opencode.json) and add the models under provider.google.models:

{
  "plugin": ["opencode-antigravity-auth@1.1.1"],
  "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
          }
        }
      }
    }
  }
}

Tip: You only need to add the models you plan to use. The example above includes all available models, but you can remove any you don't need.

Step 4: Use a model

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

Or start the interactive TUI and select a model from the model picker:

opencode

Multi-account load balancing

The plugin supports multiple Google accounts to maximize rate limits and provide automatic failover.

How it works

Round-robin selection: Each request uses the next account in the pool
Automatic failover: On HTTP 429 (rate limit), the plugin automatically switches to the next available account
Smart cooldown: Rate-limited accounts are temporarily cooled down and automatically become available again after the cooldown expires
Single-account retry: If you only have one account, the plugin waits for the rate limit to reset and retries automatically
Toast notifications: The TUI shows which account is being used and when switching occurs

Adding accounts

CLI flow (opencode auth login):

When you run opencode auth login and already have accounts saved, you'll be prompted:

2 account(s) saved:
  1. user1@gmail.com
  2. user2@gmail.com

(a)dd new account(s) or (f)resh start? [a/f]:

Press a to add more accounts to your existing pool
Press f to clear all existing accounts and start fresh

TUI flow (/connect):

The /connect command in the TUI adds accounts non-destructively — it will never clear your existing accounts. To start fresh via TUI, run opencode auth logout first, then /connect.

Account storage

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 or commit it
The plugin automatically syncs with OpenCode's auth state — if you log out via OpenCode, stale account storage is cleared automatically

Automatic account recovery

If Google revokes a refresh token (invalid_grant), that account is automatically removed from the pool
Rerun opencode auth login to re-add the account

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: