OpenCode Gemini CLI OAuth Plugin

Use Gemini models in OpenCode with your Google account quota - no API keys needed!

This plugin integrates Gemini CLI's OAuth authentication with OpenCode, allowing you to use Google's free Gemini quota without generating API keys.

✨ Features

- 🔐 OAuth Authentication - Reuses Gemini CLI credentials from ~/.gemini/oauth_creds.json
- 👥 Multi-Account Support - Automatic rotation across multiple Google accounts
- 🔄 Auto Token Refresh - Handles expired tokens seamlessly
- 🚦 Rate Limit Handling - Auto-switches to next account when rate limited
- 🤝 Antigravity Compatible - Works alongside opencode-antigravity-auth plugin
- 🆓 Free Quota - Use Google's free tier quota (1,500 requests/day per account)

📦 Installation

$3

1. Gemini CLI must be installed and authenticated:
``bash
npm install -g @google/gemini-cli
gemini auth login # Authenticate with your Google account
`

2. OpenCode v1.0.0 or higher

$3

`bash


Install globally from NPM


npm install -g opencode-gemini-cli-oauth
`

$3

Run the setup wizard to automatically configure OpenCode with Gemini models:

`bash
opencode-gemini-setup
`

This will:
1. Check your Gemini CLI authentication
2. Login if needed
3. Configure opencode.json with the latest models (Gemini 2.0, 1.5, etc.)

$3

If you prefer to configure manually, add to ~/.config/opencode/opencode.json:

`json
{
"plugin": [
"opencode-antigravity-auth@beta",
"opencode-gemini-cli-oauth"
],
"provider": {
"gemini-cli-oauth": {
"npm": "@ai-sdk/google",
"models": {
"gemini-2.5-flash-exp": {
"name": "Gemini 2.5 Flash (Google Account)",
"limit": { "context": 1048576, "output": 65536 },
"modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
}
}
}
}
}
`

🚀 Usage

$3

`bash


Login with your Google account

gemini auth login

Verify authentication

gemini "hello"
`

$3

`bash
opencode
`

$3

In OpenCode:
- Press Ctrl+P → "Switch Model"
- Choose "Gemini 2.5 Flash (Google Account)" or any model with "(Google Account)"
- Start chatting!

🔀 3-Way Authentication Options

After installing this plugin, you have 3 authentication methods for Google models:

| Method | Provider | Models | Source | Quota |
|--------|----------|--------|--------|-------|
| 1. Google Account (OAuth) | gemini-cli-oauth | Gemini 2.5 Flash/Pro, Gemini 2.0 Flash | This plugin | Google account free tier |
| 2. API Key | google-api-key | Gemini 1.5/2.5 models | Generated from AI Studio | API key quota |
| 3. Antigravity | google | Gemini 3 Pro/Flash, Claude Sonnet/Opus | opencode-antigravity-auth | Antigravity quota |

All three can coexist without conflicts!

👥 Multi-Account Setup

To rotate across multiple Google accounts:

1. Authenticate each account with Gemini CLI:
`bash
gemini auth login # Login with account 1
# Complete OAuth flow

# Repeat for more accounts (Gemini CLI will store them)
`

2. Plugin automatically rotates between accounts when:
- An account hits rate limit (429 error)
- Distributing requests evenly

3. Check account pool:
`bash
cat ~/.gemini/opencode-plugin/account_pool.json
`

🔧 How It Works

1. OAuth Token Injection
- Plugin reads credentials from ~/.gemini/oauth_creds.json (created by Gemini CLI)
- Injects Authorization: Bearer header to Gemini API requests
- Removes ?key= parameter from URLs (OAuth doesn't need it)

2. Request Interception
- Only intercepts requests to generativelanguage.googleapis.com
- Other providers (Antigravity, standard Google) are unaffected

3. Token Refresh
- Monitors token expiry (expiry_date field)
- Auto-refreshes 5 minutes before expiration
- Uses refresh_token to get new access_token

4. Rate Limit Handling
- Detects 429 responses
- Marks account as rate-limited with retry-after timestamp
- Switches to next available account
- Retries request automatically

📊 Quota Management

Free Tier Limits (per Google account):
- Requests: 1,500 requests/day
- Tokens: 1,000,000 tokens/day
- RPM: 15 requests/minute (Gemini 2.5 Flash)

With 5 accounts, you get:
- 7,500 requests/day
- 5,000,000 tokens/day
- Automatic rotation on rate limits

🐛 Troubleshooting

$3

`bash


Re-authenticate with Gemini CLI


gemini auth login
`

$3

`bash


Clear cached credentials and re-auth


rm ~/.gemini/oauth_creds.json
gemini auth login
`

$3

`bash


Check plugin is installed

npm list -g opencode-gemini-cli-oauth

Re-link if needed

cd ~/projects/opencode-gemini-cli-oauth
npm link
`

$3

`bash


Check account pool status

cat ~/.gemini/opencode-plugin/account_pool.json

Clear rate limit timestamps

echo '{"accounts":[],"currentIndex":0}' > ~/.gemini/opencode-plugin/account_pool.json

Or wait for retry-after period to expire

`

🔒 Security Notes

1. OAuth credentials are stored locally in ~/.gemini/oauth_creds.json
2. Client ID/Secret are public (safe for "installed applications" per Google OAuth guidelines)
3. Tokens auto-refresh - no manual intervention needed
4. No credentials sent to third parties - direct Google API communication only

📚 API Reference

$3

`typescript
import {
OAuthManager, // OAuth token management
AccountManager, // Multi-account rotation
StorageManager, // Credentials storage
} from 'opencode-gemini-cli-oauth';

// Example: Get current access token
const oauthManager = new OAuthManager();
const token = await oauthManager.getAccessToken();

// Example: Check account pool stats
const accountManager = new AccountManager();
const stats = await accountManager.getPoolStats();
console.log(stats); // { totalAccounts: 5, availableAccounts: 4, rateLimitedAccounts: 1 }
``

🤝 Contributing

Contributions welcome! Please:

1. Fork the repository
2. Create a feature branch
3. Submit a pull request

📄 License

MIT License - see LICENSE file for details

🙏 Credits

- Built by @yusuf
- Inspired by opencode-antigravity-auth
- Uses Google Auth Library

🔗 Related Projects

- Gemini CLI - Official Google Gemini CLI
- OpenCode - AI-powered code editor
- OpenCode Antigravity Auth - Antigravity integration

---

Made with ❤️ for the OpenCode community