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.

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.)

Installation

For Humans

Option A: Let an LLM do it

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

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

Option B: Manual setup

Add the plugin to ~/.config/opencode/opencode.json:
```
{
  "plugin": ["opencode-antigravity-auth@latest"]
}
```
Want bleeding-edge features? Use opencode-antigravity-auth@beta instead.
Login with your Google account:
```
opencode auth login
```
Add models — copy the full configuration below

Use it:

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

For LLM Agents

Step-by-Step Instructions

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).
Add the plugin to the plugin array
Add the model definitions from the Full models configuration section
Set provider to "google" and choose a model

Verification

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

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

Full models configuration (copy-paste ready)

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

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["opencode-antigravity-auth@latest"],
  "provider": {
    "google": {
      "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:

Delete the accounts file:

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

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:

Go to Google Cloud Console
Create or select a project
Enable the Gemini for Google Cloud API (cloudaicompanion.googleapis.com)

Add projectId to your accounts file:

{
  "accounts": [
    {
      "email": "your@email.com",
      "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:

Update to latest beta:

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

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

Add npm override:

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

MCP Servers Causing Errors

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

Diagnosis:

Disable all MCP servers in your config
Enable one-by-one until error reappears
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:

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

Session Recovery

If you encounter errors during a session:

Type continue to trigger the recovery mechanism
If blocked, use /undo to revert to pre-error state
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": "google/antigravity-gemini-3-pro" },
    "document-writer": { "model": "google/antigravity-gemini-3-flash" }
  }
}

Infinite `.tmp` Files Created

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

Workaround:

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

OAuth Callback Issues

Safari OAuth Callback Fails (macOS)

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:

Use Chrome or Firefox (easiest): Copy the OAuth URL and paste into a different browser.
Disable HTTPS-Only Mode temporarily:
- Safari > Settings (⌘,) > Privacy
- Uncheck "Enable HTTPS-Only Mode"
- Run opencode auth login
- Re-enable after authentication

Port Conflict (Address Already in Use)

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

Docker / WSL2 / Remote Development

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": ["opencode-antigravity-auth@beta"]
}

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

Migrating Accounts Between Machines

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

Ensure the plugin is installed: "plugin": ["opencode-antigravity-auth@beta"]
Copy ~/.config/opencode/antigravity-accounts.json
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": [
    "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": "google/antigravity-gemini-3-pro" },
    "document-writer": { "model": "google/antigravity-gemini-3-flash" },
    "multimodal-looker": { "model": "google/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/NoeFabris/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`

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

License

MIT License. See LICENSE for details.

Legal

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.

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Antigravity + Gemini CLI OAuth Plugin for Opencode

What You Get

Installation

Step-by-Step Instructions

Verification

Models

Model Reference

Multi-Account Setup

Troubleshoot

Configuration Path (All Platforms)

Multi-Account Auth Issues

403 Permission Denied (rising-fact-p41fc)

Gemini Model Not Found

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

MCP Servers Causing Errors

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

Session Recovery

Using with Oh-My-OpenCode

Infinite .tmp Files Created

OAuth Callback Issues

Configuration Key Typo: plugin not plugins

Migrating Accounts Between Machines

Known Plugin Interactions

Plugin Compatibility

@tarquinen/opencode-dcp

oh-my-opencode

Plugins you don't need

Configuration

Model Behavior

Account Rotation

App Behavior

Troubleshooting

Documentation

Support

Credits

License

Intended Use

Warning

Disclaimer

403 Permission Denied (`rising-fact-p41fc`)

Infinite `.tmp` Files Created

Configuration Key Typo: `plugin` not `plugins`