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 current models like gemini-3.1-pro, gemini-3.5-flash, claude-sonnet-4-6, and gpt-oss-120b-medium with your Google credentials.

What You Get

• Gemini 3.1 Pro, Gemini 3.5 Flash, Claude Opus/Sonnet 4.6 Thinking, and GPT-OSS 120B via Google OAuth
• Multi-account support — add multiple Google accounts, auto-rotates when rate-limited
• Antigravity quota routing — current defaults avoid Gemini CLI models because individual Gemini CLI access sunsets on 2026-06-18
• 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 (and any proxy for Antigravity) violates Google's Terms of Service. A number of users have reported their Google accounts being banned or shadow-banned (restricted access without explicit notification).

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

Installation

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

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

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

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

2. Login with your Google account:

   opencode auth login

3. Add models — choose one:

   • Run opencode auth login → Google → OAuth with Google (Antigravity) → select "Configure models in opencode.json" (auto-configures all models)
   • Or manually copy the full configuration below

4. Use it:

   opencode run "Hello" --model=google/antigravity-claude-opus-4-6-thinking

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=google/antigravity-claude-opus-4-6-thinking

Models

Model Reference

Current Antigravity quota set (from the Antigravity Model Quota view):

| Model ID | Quota row | |----------|-----------| | antigravity-gemini-3.1-pro-low | Gemini 3.1 Pro (Low) | | antigravity-gemini-3.1-pro-high | Gemini 3.1 Pro (High) | | antigravity-claude-sonnet-4-6 | Claude Sonnet 4.6 | | antigravity-claude-opus-4-6-thinking | Claude Opus 4.6 (Thinking) | | antigravity-gpt-oss-120b-medium | GPT-OSS 120B (Medium) | | antigravity-gemini-3.5-flash-low | Gemini 3.5 Flash (Low) | | antigravity-gemini-3.5-flash-high | Gemini 3.5 Flash (High) | | antigravity-gemini-3.5-pro-low | Gemini 3.5 Pro (Low) | | antigravity-gemini-3.5-pro-high | Gemini 3.5 Pro (High) |

Gemini CLI sunset: Gemini CLI quota models are no longer included in the default model list. Google announced Gemini CLI access for individual/free Google AI Pro/Ultra and Gemini Code Assist users stops on 2026-06-18. Legacy Gemini CLI routing remains in the plugin for backward compatibility only.

Use a current model:

opencode run "Hello" --model=google/antigravity-gemini-3.5-flash-low
opencode run "Hello" --model=google/antigravity-claude-sonnet-4-6

For details on compatibility with older variant/tier names, see docs/MODEL-VARIANTS.md.

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

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": [
    "opencode-antigravity-auth@latest"
  ],
  "provider": {
    "google": {
      "models": {
        "antigravity-gemini-3.1-pro-low": {
          "name": "Gemini 3.1 Pro Low (Antigravity)",
          "limit": {
            "context": 1048576,
            "output": 65535
          },
          "modalities": {
            "input": [
              "text",
              "image",
              "pdf"
            ],
            "output": [
              "text"
            ]
          }
        },
        "antigravity-gemini-3.1-pro-high": {
          "name": "Gemini 3.1 Pro High (Antigravity)",
          "limit": {
            "context": 1048576,
            "output": 65535
          },
          "modalities": {
            "input": [
              "text",
              "image",
              "pdf"
            ],
            "output": [
              "text"
            ]
          }
        },
        "antigravity-claude-sonnet-4-6": {
          "name": "Claude Sonnet 4.6 (Antigravity)",
          "limit": {
            "context": 200000,
            "output": 64000
          },
          "modalities": {
            "input": [
              "text",
              "image",
              "pdf"
            ],
            "output": [
              "text"
            ]
          }
        },
        "antigravity-claude-opus-4-6-thinking": {
          "name": "Claude Opus 4.6 Thinking (Antigravity)",
          "limit": {
            "context": 200000,
            "output": 64000
          },
          "modalities": {
            "input": [
              "text",
              "image",
              "pdf"
            ],
            "output": [
              "text"
            ]
          }
        },
        "antigravity-gpt-oss-120b-medium": {
          "name": "GPT-OSS 120B Medium (Antigravity)",
          "limit": {
            "context": 200000,
            "output": 64000
          },
          "modalities": {
            "input": [
              "text",
              "image",
              "pdf"
            ],
            "output": [
              "text"
            ]
          }
        },
        "antigravity-gemini-3.5-flash-low": {
          "name": "Gemini 3.5 Flash Low (Antigravity)",
          "limit": {
            "context": 1048576,
            "output": 65536
          },
          "modalities": {
            "input": [
              "text",
              "image",
              "pdf"
            ],
            "output": [
              "text"
            ]
          }
        },
        "antigravity-gemini-3.5-flash-high": {
          "name": "Gemini 3.5 Flash High (Antigravity)",
          "limit": {
            "context": 1048576,
            "output": 65536
          },
          "modalities": {
            "input": [
              "text",
              "image",
              "pdf"
            ],
            "output": [
              "text"
            ]
          }
        },
        "antigravity-gemini-3.5-pro-low": {
          "name": "Gemini 3.5 Pro Low (Antigravity)",
          "limit": {
            "context": 1048576,
            "output": 65536
          },
          "modalities": {
            "input": [
              "text",
              "image",
              "pdf"
            ],
            "output": [
              "text"
            ]
          }
        },
        "antigravity-gemini-3.5-pro-high": {
          "name": "Gemini 3.5 Pro High (Antigravity)",
          "limit": {
            "context": 1048576,
            "output": 65536
          },
          "modalities": {
            "input": [
              "text",
              "image",
              "pdf"
            ],
            "output": [
              "text"
            ]
          }
        }
      }
    }
  }
}

Backward Compatibility: Legacy model names still resolve in the plugin where possible, but they are no longer listed by default. Prefer the current Antigravity quota model IDs above.

Multi-Account Setup

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

opencode auth login  # Run again to add more accounts

Account management options (via opencode auth login):

• Configure models — Auto-configure all plugin models in opencode.json
• Check quotas — View remaining API quota for each account
• Manage accounts — Enable/disable specific accounts for rotation

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

Troubleshooting

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%.

Custom path: Set OPENCODE_CONFIG_DIR environment variable to use a custom location.

Windows migration: If upgrading from plugin v1.3.x or earlier, the plugin will automatically find your existing config in %APPDATA%\opencode\ and use it. New installations use ~/.config/opencode/.

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

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

3. 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.

Common symptom:

Invalid function name must start with a letter or underscore

Sometimes it shows up as:

GenerateContentRequest.tools[0].function_declarations[12].name: Invalid function name must start with a letter or underscore

This usually means an MCP tool name starts with a number (for example, a 1mcp key like 1mcp_*). Rename the MCP key to start with a letter (e.g., gw) or disable that MCP entry for Antigravity models.

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": "google/antigravity-gemini-3.1-pro-high" },
    "document-writer": { "model": "google/antigravity-gemini-3.5-flash-low" }
  }
}

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": ["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": ["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": [
    "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-3.1-pro-high" },
    "document-writer": { "model": "google/antigravity-gemini-3.5-flash-low" },
    "multimodal-looker": { "model": "google/antigravity-gemini-3.5-flash-low" }
  }
}

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 | | cli_first | false | Legacy option for Gemini CLI quota fallback. Current default model definitions avoid Gemini CLI because individual access sunsets on 2026-06-18. |

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 |

Quota Protection

| Option | Default | What it does | |--------|---------|--------------| | soft_quota_threshold_percent | 90 | Skip account when quota usage exceeds this percentage. Prevents Google from penalizing accounts that fully exhaust quota. Set to 100 to disable. | | quota_refresh_interval_minutes | 15 | Background quota refresh interval. After successful API requests, refreshes quota cache if older than this interval. Set to 0 to disable. | | soft_quota_cache_ttl_minutes | "auto" | How long quota cache is considered fresh. "auto" = max(2 × refresh interval, 10 minutes). Set a number (1-120) for fixed TTL. |

How it works: Quota cache is refreshed automatically after API requests (when older than quota_refresh_interval_minutes) and manually via "Check quotas" in opencode auth login. The threshold check uses soft_quota_cache_ttl_minutes to determine cache freshness - if cache is older, the account is considered "unknown" and allowed (fail-open). When ALL accounts exceed the threshold, the plugin waits for the earliest quota reset time (like rate limit behavior). If wait time exceeds max_rate_limit_wait_seconds, it errors immediately.

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 file logging (~/.config/opencode/antigravity-logs/) | | debug_tui | false | Show debug logs in the TUI log panel (independent from debug) | | auto_update | true | Auto-update plugin |

Transport (Advanced)

The plugin supports three transport modes. The default gateway mode is recommended for all normal use.

| Mode | Default | Description | |------|---------|-------------| | gateway | ✅ | CloudCode gateway shim — full streaming, tool calls, multi-account | | cli | No | Opt-in: runs agy --print as subprocess. Text only, no tool calls. | | managed-agent | No | Opt-in: public Managed Agents API with Gemini API key. Billing applies. |

⚠️ Gemini CLI sunset: 2026-06-18. The gemini-cli quota pool stops serving requests for Google AI Pro/Ultra and free Gemini Code Assist individuals after this date. If requests fail after June 18, disable quota_fallback in your config.

See docs/SUPPORT_MATRIX.md for the full feature/model/credential matrix per transport.

For all options, see docs/CONFIGURATION.md.

Environment variables:

OPENCODE_CONFIG_DIR=/path/to/config opencode  # Custom config directory
OPENCODE_ANTIGRAVITY_DEBUG=1 opencode         # Enable debug file logging
OPENCODE_ANTIGRAVITY_DEBUG=2 opencode         # Verbose debug file logging
OPENCODE_ANTIGRAVITY_DEBUG_TUI=1 opencode     # Enable TUI log panel debug output

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 Matrix — Feature/model/credential matrix per transport

Support

If this plugin saves you time, consider supporting its development:

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.