Antigravity + Gemini CLI OAuth Plugin for Opencode

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 and claude-opus-4-5-thinking with your Google credentials.

Fork notice: This project is based on https://github.com/NoeFabris/opencode-antigravity-auth and modified by @shaywong. License: MIT (see LICENSE).

What You Get

• Claude Opus 4.5, Sonnet 4.5 and Gemini 3 Pro/Flash via Google OAuth
• Multi-account support — add multiple Google accounts, auto-rotates when rate-limited
• Dual quota system — access both Antigravity and Gemini CLI quotas from one plugin
• Thinking models — extended thinking for Claude and Gemini 3 with configurable budgets
• Google Search grounding — enable web search for Gemini models (auto or always-on)
• Auto-recovery — handles session errors and tool failures automatically
• Plugin compatible — works alongside other OpenCode plugins (oh-my-opencode, dcp, etc.)

[!CAUTION] Using this plugin may violate Google's Terms of Service. A small number of users have reported their Google accounts being banned or shadow-banned (restricted access without explicit notification).

High-risk scenarios:

• 🚨 Fresh Google accounts have a very high chance of getting banned
• 🚨 New accounts with Pro/Ultra subscriptions are frequently flagged and banned

By using this plugin, you acknowledge:

• This is an unofficial tool not endorsed by Google
• Your account may be suspended or permanently banned
• You assume all risks associated with using this plugin

Recommendation: Use an established Google account that you don't rely on for critical services. Avoid creating new accounts specifically for this plugin.

Installation

Option A: Let an LLM do it

Paste this into any LLM agent (Claude Code, OpenCode, Cursor, etc.):

Install the @shaywong/opencode-antigravity-auth plugin and add the Antigravity model definitions to ~/.config/opencode/opencode.json by following: https://raw.githubusercontent.com/shay-wong/opencode-antigravity-auth/dev/README.md

Option B: Manual setup

1. Add the plugin to ~/.config/opencode/opencode.json:

   {
     "plugin": ["@shaywong/opencode-antigravity-auth@latest"]
   }

   Want bleeding-edge features? Use @shaywong/opencode-antigravity-auth@beta instead.

2. Login with your Google account:

   opencode auth login

3. Add models — copy the full configuration below

4. Use it:

   opencode run "Hello" --model=antigravity/antigravity-claude-sonnet-4-5-thinking --variant=max

Step-by-Step Instructions

1. Edit the OpenCode configuration file at ~/.config/opencode/opencode.json

   Note: This path works on all platforms. On Windows, ~ resolves to your user home directory (e.g., C:\Users\YourName).

2. Add the plugin to the plugin array

3. Add the model definitions from the Full models configuration section

4. Set provider to "google" and choose a model

Verification

   opencode run "Hello" --model=antigravity/antigravity-claude-sonnet-4-5-thinking --variant=max

Models

Model Reference

Antigravity quota (Claude + Gemini 3):

| Model | Variants | Notes | |-------|----------|-------| | antigravity-gemini-3-pro | low, high | Gemini 3 Pro with thinking | | antigravity-gemini-3-flash | minimal, low, medium, high | Gemini 3 Flash with thinking | | antigravity-claude-sonnet-4-5 | — | Claude Sonnet 4.5 | | antigravity-claude-sonnet-4-5-thinking | low, max | Claude Sonnet with extended thinking | | antigravity-claude-opus-4-5-thinking | low, max | Claude Opus with extended thinking |

Gemini CLI quota (separate from Antigravity):

| Model | Notes | |-------|-------| | gemini-2.5-flash | Gemini 2.5 Flash | | gemini-2.5-pro | Gemini 2.5 Pro | | gemini-3-flash-preview | Gemini 3 Flash (preview) | | gemini-3-pro-preview | Gemini 3 Pro (preview) |

Using variants:

   opencode run "Hello" --model=antigravity/antigravity-claude-sonnet-4-5-thinking --variant=max

For details on variant configuration and thinking levels, see docs/MODEL-VARIANTS.md.

Add this to your ~/.config/opencode/opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["@shaywong/opencode-antigravity-auth@latest"],
  "provider": {
    "antigravity": {
      "models": {
        "antigravity-gemini-3-pro": {
          "name": "Gemini 3 Pro (Antigravity)",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "thinkingLevel": "low" },
            "high": { "thinkingLevel": "high" }
          }
        },
        "antigravity-gemini-3-flash": {
          "name": "Gemini 3 Flash (Antigravity)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "minimal": { "thinkingLevel": "minimal" },
            "low": { "thinkingLevel": "low" },
            "medium": { "thinkingLevel": "medium" },
            "high": { "thinkingLevel": "high" }
          }
        },
        "antigravity-claude-sonnet-4-5": {
          "name": "Claude Sonnet 4.5 (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-sonnet-4-5-thinking": {
          "name": "Claude Sonnet 4.5 Thinking (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "thinkingConfig": { "thinkingBudget": 8192 } },
            "max": { "thinkingConfig": { "thinkingBudget": 32768 } }
          }
        },
        "antigravity-claude-opus-4-5-thinking": {
          "name": "Claude Opus 4.5 Thinking (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "thinkingConfig": { "thinkingBudget": 8192 } },
            "max": { "thinkingConfig": { "thinkingBudget": 32768 } }
          }
        },
        "gemini-2.5-flash": {
          "name": "Gemini 2.5 Flash (Gemini CLI)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "gemini-2.5-pro": {
          "name": "Gemini 2.5 Pro (Gemini CLI)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "gemini-3-flash-preview": {
          "name": "Gemini 3 Flash Preview (Gemini CLI)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "gemini-3-pro-preview": {
          "name": "Gemini 3 Pro Preview (Gemini CLI)",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        }
      }
    }
  }
}

Multi-Account Setup

Add multiple Google accounts for higher combined quotas. The plugin automatically rotates between accounts when one is rate-limited.

opencode auth login  # Run again to add more accounts

For details on load balancing, dual quota pools, and account storage, see docs/MULTI-ACCOUNT.md.

Troubleshoot

Quick Reset: Most issues can be resolved by deleting ~/.config/opencode/antigravity-accounts.json and running opencode auth login again.

Configuration Path (All Platforms)

OpenCode uses ~/.config/opencode/ on all platforms including Windows.

| File | Path | |------|------| | Main config | ~/.config/opencode/opencode.json | | Accounts | ~/.config/opencode/antigravity-accounts.json | | Plugin config | ~/.config/opencode/antigravity.json | | Debug logs | ~/.config/opencode/antigravity-logs/ |

Windows users: ~ resolves to your user home directory (e.g., C:\Users\YourName). Do NOT use %APPDATA%.

Multi-Account Auth Issues

If you encounter authentication issues with multiple accounts:

1. Delete the accounts file:

   rm ~/.config/opencode/antigravity-accounts.json

2. Re-authenticate:

   opencode auth login

403 Permission Denied (rising-fact-p41fc)

Error:

Permission 'cloudaicompanion.companions.generateChat' denied on resource
'//cloudaicompanion.googleapis.com/projects/rising-fact-p41fc/locations/global'

Cause: Plugin falls back to a default project ID when no valid project is found. This works for Antigravity but fails for Gemini CLI models.

Solution:

1. Go to Google Cloud Console
2. Create or select a project
3. Enable the Gemini for Google Cloud API (cloudaicompanion.googleapis.com)
4. Add projectId to your accounts file:

   {
     "accounts": [
       {
         "email": "[email protected]",
         "refreshToken": "...",
         "projectId": "your-project-id"
       }
     ]
   }

Note: Do this for each account in a multi-account setup.

Gemini Model Not Found

Add this to your google provider config:

{
  "provider": {
    "google": {
      "npm": "@ai-sdk/google",
      "models": { ... }
    }
  }
}

Gemini 3 Models 400 Error ("Unknown name 'parameters'")

Error:

Invalid JSON payload received. Unknown name "parameters" at 'request.tools[0]'

Causes:

• Tool schema incompatibility with Gemini's strict protobuf validation
• MCP servers with malformed schemas
• Plugin version regression

Solutions:

1. Update to latest beta:

   { "plugin": ["@shaywong/opencode-antigravity-auth@beta"] }

2. Disable MCP servers one-by-one to find the problematic one

3. Add npm override:

   { "provider": { "antigravity": { "npm": "@ai-sdk/google" } } }

MCP Servers Causing Errors

Some MCP servers have schemas incompatible with Antigravity's strict JSON format.

Diagnosis:

1. Disable all MCP servers in your config
2. Enable one-by-one until error reappears
3. Report the specific MCP in a GitHub issue

"All Accounts Rate-Limited" (But Quota Available)

Cause: Cascade bug in clearExpiredRateLimits() in hybrid mode (fixed in recent beta).

Solutions:

1. Update to latest beta version
2. If persists, delete accounts file and re-authenticate
3. Try switching account_selection_strategy to "sticky" in antigravity.json

Session Recovery

If you encounter errors during a session:

1. Type continue to trigger the recovery mechanism
2. If blocked, use /undo to revert to pre-error state
3. Retry the operation

Using with Oh-My-OpenCode

Important: Disable the built-in Google auth to prevent conflicts:

// ~/.config/opencode/oh-my-opencode.json
{
  "google_auth": false,
  "agents": {
  "frontend-ui-ux-engineer": { "model": "antigravity/antigravity-gemini-3-pro" },
  "document-writer": { "model": "antigravity/antigravity-gemini-3-flash" }
  }
}

Infinite .tmp Files Created

Cause: When account is rate-limited and plugin retries infinitely, it creates many temp files.

Workaround:

1. Stop OpenCode
2. Clean up: rm ~/.config/opencode/*.tmp
3. Add more accounts or wait for rate limit to expire

OAuth Callback Issues

Symptoms:

• "fail to authorize" after successful Google login
• Safari shows "Safari can't open the page"

Cause: Safari's "HTTPS-Only Mode" blocks http://localhost callback.

Solutions:

1. Use Chrome or Firefox (easiest): Copy the OAuth URL and paste into a different browser.

2. Disable HTTPS-Only Mode temporarily:

   • Safari > Settings (⌘,) > Privacy
   • Uncheck "Enable HTTPS-Only Mode"
   • Run opencode auth login
   • Re-enable after authentication

macOS / Linux:

# Find process using the port
lsof -i :51121

# Kill if stale
kill -9 <PID>

# Retry
opencode auth login

Windows (PowerShell):

netstat -ano | findstr :51121
taskkill /PID <PID> /F
opencode auth login

OAuth callback requires browser to reach localhost on the machine running OpenCode.

WSL2:

• Use VS Code's port forwarding, or
• Configure Windows → WSL port forwarding

SSH / Remote:

ssh -L 51121:localhost:51121 user@remote

Docker / Containers:

• OAuth with localhost redirect doesn't work in containers
• Wait 30s for manual URL flow, or use SSH port forwarding

Configuration Key Typo: plugin not plugins

The correct key is plugin (singular):

{
  "plugin": ["@shaywong/opencode-antigravity-auth@beta"]
}

Not "plugins" (will cause "Unrecognized key" error).

Migrating Accounts Between Machines

When copying antigravity-accounts.json to a new machine:

1. Ensure the plugin is installed: "plugin": ["@shaywong/opencode-antigravity-auth@beta"]
2. Copy ~/.config/opencode/antigravity-accounts.json
3. If you get "API key missing" error, the refresh token may be invalid — re-authenticate

Known Plugin Interactions

For details on load balancing, dual quota pools, and account storage, see docs/MULTI-ACCOUNT.md.

Plugin Compatibility

@tarquinen/opencode-dcp

DCP creates synthetic assistant messages that lack thinking blocks. List this plugin BEFORE DCP:

{
  "plugin": [
    "@shaywong/opencode-antigravity-auth@latest",
    "@tarquinen/opencode-dcp@latest"
  ]
}

oh-my-opencode

Disable built-in auth and override agent models in oh-my-opencode.json:

{
  "google_auth": false,
  "agents": {
  "frontend-ui-ux-engineer": { "model": "antigravity/antigravity-gemini-3-pro" },
  "document-writer": { "model": "antigravity/antigravity-gemini-3-flash" },
  "multimodal-looker": { "model": "antigravity/antigravity-gemini-3-flash" }
  }
}

Tip: When spawning parallel subagents, enable pid_offset_enabled: true in antigravity.json to distribute sessions across accounts.

Plugins you don't need

• gemini-auth plugins — Not needed. This plugin handles all Google OAuth.

Configuration

Create ~/.config/opencode/antigravity.json for optional settings:

{
  "$schema": "https://raw.githubusercontent.com/shay-wong/opencode-antigravity-auth/main/assets/antigravity.schema.json"
}

Most users don't need to configure anything — defaults work well.

Model Behavior

| Option | Default | What it does | |--------|---------|-------------- | keep_thinking | false | Preserve Claude's thinking across turns. Warning: enabling may degrade model stability. | | session_recovery | true | Auto-recover from tool errors | | web_search.default_mode | "off" | Gemini Google Search: "auto" or "off" |

Account Rotation

| Your Setup | Recommended Config | |------------|-------------------| | 1 account | "account_selection_strategy": "sticky" | | 2-5 accounts | Default ("hybrid") works great | | 5+ accounts | "account_selection_strategy": "round-robin" | | Parallel agents | Add "pid_offset_enabled": true |

Rate Limit Scheduling

Control how the plugin handles rate limits:

| Option | Default | What it does | |--------|---------|--------------| | scheduling_mode | "cache_first" | "cache_first" = wait for same account (preserves prompt cache), "balance" = switch immediately, "performance_first" = round-robin | | max_cache_first_wait_seconds | 60 | Max seconds to wait in cache_first mode before switching accounts | | failure_ttl_seconds | 3600 | Reset failure count after this many seconds (prevents old failures from permanently penalizing accounts) |

When to use each mode:

• cache_first (default): Best for long conversations. Waits for the same account to recover, preserving your prompt cache.
• balance: Best for quick tasks. Switches accounts immediately when rate-limited for maximum availability.
• performance_first: Best for many short requests. Distributes load evenly across all accounts.

App Behavior

| Option | Default | What it does | |--------|---------|--------------| | quiet_mode | false | Hide toast notifications | | debug | false | Enable debug logging | | auto_update | true | Auto-update plugin |

For all options, see docs/CONFIGURATION.md.

Environment variables:

OPENCODE_ANTIGRAVITY_DEBUG=1 opencode   # Enable debug logging
OPENCODE_ANTIGRAVITY_DEBUG=2 opencode   # Verbose logging

Troubleshooting

See the full Troubleshooting Guide for solutions to common issues including:

• Auth problems and token refresh
• "Model not found" errors
• Session recovery
• Gemini CLI permission errors
• Safari OAuth issues
• Plugin compatibility
• Migration guides

Documentation

• Configuration — All configuration options
• Multi-Account — Load balancing, dual quota pools, account storage
• Model Variants — Thinking budgets and variant system
• Troubleshooting — Common issues and fixes
• Architecture — How the plugin works
• API Spec — Antigravity API reference

Support

If this plugin helps you, consider supporting its maintenance:

Credits

• opencode-gemini-auth by @jenslys
• CLIProxyAPI

License

MIT License. See LICENSE for details.

Intended Use

• Personal / internal development only
• Respect internal quotas and data handling policies
• Not for production services or bypassing intended limits

Warning

By using this plugin, you acknowledge:

• Terms of Service risk — This approach may violate ToS of AI model providers
• Account risk — Providers may suspend or ban accounts
• No guarantees — APIs may change without notice
• Assumption of risk — You assume all legal, financial, and technical risks

Disclaimer

• Not affiliated with Google. This is an independent open-source project.
• "Antigravity", "Gemini", "Google Cloud", and "Google" are trademarks of Google LLC.