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

• Google OAuth sign-in with automatic token refresh via opencode auth login
• Dual Quota System - Access both Antigravity quota (Claude, Gemini 3) and Gemini CLI quota from a single plugin
• Multi-Account Rotation - Add multiple Google accounts; automatically rotates when one is rate-limited
• Real-time SSE streaming including thinking blocks and incremental output
• Model Variants - Configure thinking budget dynamically via OpenCode's variant system
• Extended Thinking - Native support for Claude thinking budgets and Gemini 3 thinking levels
• Auto Recovery - Automatic session recovery from Claude tool_result_missing errors
• Plugin Compatible - Works alongside other OpenCode plugins (opencodesync, 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

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

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

2. Authenticate:

   opencode auth login
   

3. Add models (see Available Models for full list):

   {
     "plugin": ["opencode-antigravity-auth@beta"],
     "provider": {
       "google": {
         "models": {
           "antigravity-claude-sonnet-4-5-thinking": {
             "name": "Claude Sonnet 4.5 Thinking",
             "limit": { "context": 200000, "output": 64000 },
             "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
             "variants": {
               "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
               "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
               "high": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
             }
           }
         }
       }
     }
   }
   

4. Use it:

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

Installation Guide for LLM Agents

Step-by-Step Instructions

1. Edit the OpenCode configuration file:

   • Linux/Mac: ~/.config/opencode/opencode.json
   • Windows: %APPDATA%\opencode\opencode.json

2. Add the plugin to the plugins array

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

Complete Configuration Example

Create ~/.config/opencode/opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["opencode-antigravity-auth@beta"],
  "provider": {
    "google": {
      "models": {
        "antigravity-gemini-3-pro": {
          "name": "Gemini 3 Pro",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
            "high": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
          }
        },
        "antigravity-gemini-3-flash": {
          "name": "Gemini 3 Flash",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
            "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
            "high": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
          }
        },
        "antigravity-claude-sonnet-4-5": {
          "name": "Claude Sonnet 4.5 (no thinking)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-sonnet-4-5-thinking": {
          "name": "Claude Sonnet 4.5 Thinking",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
            "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
            "max": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
          }
        },
        "antigravity-claude-opus-4-5-thinking": {
          "name": "Claude Opus 4.5 Thinking",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
            "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
            "max": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
          }
        },
        "gemini-2.5-flash": {
          "name": "Gemini 2.5 Flash (CLI)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "gemini-2.5-pro": {
          "name": "Gemini 2.5 Pro (CLI)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "gemini-3-flash-preview": {
          "name": "Gemini 3 Flash Preview (CLI)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "gemini-3-pro-preview": {
          "name": "Gemini 3 Pro Preview (CLI)",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        }
      }
    }
  }
}

Verification

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

Available Models

Antigravity Quota (with Variants)

Models with antigravity- prefix use Antigravity quota. Thinking models support variants for dynamic thinking budget configuration:

Model	Variants	Description
google/antigravity-gemini-3-pro	low, high	Gemini 3 Pro with configurable thinking
google/antigravity-gemini-3-flash	low, medium, high	Gemini 3 Flash with configurable thinking
google/antigravity-claude-sonnet-4-5	-	Claude Sonnet 4.5 (no thinking)
google/antigravity-claude-sonnet-4-5-thinking	low, medium, max	Claude Sonnet with configurable thinking
google/antigravity-claude-opus-4-5-thinking	low, medium, max	Claude Opus with configurable thinking

Variant thinking budgets:

• low: 8,192 tokens
• medium: 16,384 tokens
• high: 32,768 tokens

Usage:

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

Gemini CLI Quota

Models with -preview suffix use Gemini CLI quota:

Model	Description
google/gemini-2.5-flash	Gemini 2.5 Flash
google/gemini-2.5-pro	Gemini 2.5 Pro
google/gemini-3-flash-preview	Gemini 3 Flash (preview)
google/gemini-3-pro-preview	Gemini 3 Pro (preview)

Full models configuration (copy-paste ready)

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["opencode-antigravity-auth@beta"],
  "provider": {
    "google": {
      "models": {
        "antigravity-gemini-3-pro": {
          "name": "Gemini 3 Pro",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
            "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
            "high": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
          }
        },
        "antigravity-gemini-3-flash": {
          "name": "Gemini 3 Flash",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
            "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
            "high": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
          }
        },
        "antigravity-claude-sonnet-4-5": {
          "name": "Claude Sonnet 4.5 (no thinking)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-sonnet-4-5-thinking": {
          "name": "Claude Sonnet 4.5 Thinking",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
            "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
            "max": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
          }
        },
        "antigravity-claude-opus-4-5-thinking": {
          "name": "Claude Opus 4.5 Thinking",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
          "variants": {
            "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
            "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
            "max": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
          }
        },
        "gemini-2.5-flash": {
          "name": "Gemini 2.5 Flash (CLI)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "gemini-2.5-pro": {
          "name": "Gemini 2.5 Pro (CLI)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "gemini-3-flash-preview": {
          "name": "Gemini 3 Flash Preview (CLI)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "gemini-3-pro-preview": {
          "name": "Gemini 3 Pro Preview (CLI)",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        }
      }
    }
  }
}

Model Variants

OpenCode's variant system allows you to configure thinking budget dynamically instead of defining separate models for each thinking level.

How Variants Work

When you define a model with variants, OpenCode will show variant options in the model picker. Selecting a variant passes the providerOptions to the plugin, which extracts the thinking configuration.

Variant Configuration

{
  "antigravity-claude-sonnet-4-5-thinking": {
    "name": "Claude Sonnet 4.5 Thinking",
    "limit": { "context": 200000, "output": 64000 },
    "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
    "variants": {
      "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
      "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
      "max": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
    }
  }
}

Supported Provider Formats

The plugin accepts thinking configuration in multiple AI SDK formats:

Format	Structure
Google	{ google: { thinkingConfig: { thinkingBudget: N } } }
Anthropic	{ anthropic: { thinking: { type: "enabled", budgetTokens: N } } }

Gemini 3 Budget Mapping

For Gemini 3 models, thinking budget is automatically mapped to thinking level:

Budget Range	Thinking Level
≤ 8192	low
≤ 16384	medium
> 16384	high

Backward Compatibility

Legacy tier-suffixed models still work:

• antigravity-claude-sonnet-4-5-thinking-low
• antigravity-claude-sonnet-4-5-thinking-medium
• antigravity-claude-sonnet-4-5-thinking-high
• antigravity-gemini-3-pro-low
• antigravity-gemini-3-pro-high

However, we recommend using variants for a cleaner model picker and more flexibility.

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

How multi-account works

Load Balancing Behavior

• Sticky account selection - Sticks to the same account until rate-limited (preserves Anthropic's prompt cache)
• Per-model-family limits - Rate limits tracked separately for Claude and Gemini models
• Dual quota pools for Gemini - Automatic fallback between Antigravity quota and Gemini CLI quota before switching accounts
• Smart retry threshold - Short rate limits (≤5s) are retried on same account
• Exponential backoff - Increasing delays for consecutive rate limits

Dual Quota Pools (Gemini only)

For Gemini models, the plugin accesses two independent quota pools per account:

Quota Pool	When Used
Antigravity	Primary (tried first)
Gemini CLI	Fallback when Antigravity is rate-limited

This effectively doubles your Gemini quota per account.

Adding Accounts

When running opencode auth login with existing accounts:

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

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

Account Storage

• Stored in ~/.config/opencode/antigravity-accounts.json
• Contains OAuth refresh tokens - treat like a password
• If Google revokes a token (invalid_grant), that account is automatically removed

Configuration

Create ~/.config/opencode/antigravity.json (or .opencode/antigravity.json in project root):

General Settings

Option	Default	Description
quiet_mode	false	Suppress toast notifications (except recovery)
debug	false	Enable debug logging to file
log_dir	OS default	Custom directory for debug logs
auto_update	true	Enable automatic plugin updates

Session Recovery

Option	Default	Description
session_recovery	true	Auto-recover from tool_result_missing errors
auto_resume	true	Auto-send resume prompt after recovery
resume_text	"continue"	Text to send when auto-resuming

Error Recovery

Option	Default	Description
empty_response_max_attempts	4	Retries for empty API responses
empty_response_retry_delay_ms	2000	Delay between retries
tool_id_recovery	true	Fix mismatched tool IDs from context compaction
claude_tool_hardening	true	Prevent tool parameter hallucination

Token Management

Option	Default	Description
proactive_token_refresh	true	Refresh tokens before expiry
proactive_refresh_buffer_seconds	1800	Refresh 30min before expiry
max_rate_limit_wait_seconds	300	Max wait time when rate limited (0=unlimited)
quota_fallback	false	Try alternate quota when rate limited

Account Selection

Option	Default	Description
account_selection_strategy	"sticky"	Strategy for distributing requests across accounts
pid_offset_enabled	false	Use PID-based offset for multi-session distribution

Available strategies:

Strategy	Behavior	Best For
sticky	Same account until rate-limited	Prompt cache preservation
round-robin	Rotate to next account on every request	Maximum throughput
hybrid	Touch all fresh accounts first, then sticky	Sync reset timers + cache

Error handling:

Error Type	Behavior
MODEL_CAPACITY_EXHAUSTED	Wait (escalating 5s→60s) and retry same account
QUOTA_EXCEEDED	Switch to next available account immediately

This prevents unnecessary account switching when server-side capacity issues affect all accounts equally.

Environment Overrides

OPENCODE_ANTIGRAVITY_QUIET=1                              # quiet_mode
OPENCODE_ANTIGRAVITY_DEBUG=1                              # debug
OPENCODE_ANTIGRAVITY_LOG_DIR=/path                        # log_dir
OPENCODE_ANTIGRAVITY_KEEP_THINKING=1                      # keep_thinking
OPENCODE_ANTIGRAVITY_ACCOUNT_SELECTION_STRATEGY=round-robin  # account_selection_strategy
OPENCODE_ANTIGRAVITY_PID_OFFSET_ENABLED=1                 # pid_offset_enabled

Full configuration example

{
  "$schema": "https://raw.githubusercontent.com/NoeFabris/opencode-antigravity-auth/main/assets/antigravity.schema.json",
  "quiet_mode": false,
  "debug": false,
  "log_dir": "/custom/log/path",
  "auto_update": true,
  "keep_thinking": false,
  "session_recovery": true,
  "auto_resume": true,
  "resume_text": "continue",
  "empty_response_max_attempts": 4,
  "empty_response_retry_delay_ms": 2000,
  "tool_id_recovery": true,
  "claude_tool_hardening": true,
  "proactive_token_refresh": true,
  "proactive_refresh_buffer_seconds": 1800,
  "proactive_refresh_check_interval_seconds": 300,
  "max_rate_limit_wait_seconds": 300,
  "quota_fallback": false,
  "account_selection_strategy": "sticky",
  "pid_offset_enabled": false,
  "signature_cache": {
    "enabled": true,
    "memory_ttl_seconds": 3600,
    "disk_ttl_seconds": 172800,
    "write_interval_seconds": 60
  }
}

Known Plugin Interactions

@tarquinen/opencode-dcp

DCP creates synthetic assistant messages that lack thinking blocks. Our plugin must be listed BEFORE DCP:

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

oh-my-opencode

When spawning parallel subagents, multiple processes may select the same account causing rate limit errors. Workaround: Enable pid_offset_enabled: true to distribute sessions across accounts, or add more accounts via opencode auth login.

Plugins You Don't Need

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

Migration Guide (v1.2.8+ - Variants)

What Changed

v1.2.8+ introduces model variants for dynamic thinking configuration. Instead of separate models for each thinking level, you now define one model with variants.

Before (v1.2.7)

{
  "antigravity-claude-sonnet-4-5-thinking-low": { ... },
  "antigravity-claude-sonnet-4-5-thinking-medium": { ... },
  "antigravity-claude-sonnet-4-5-thinking-high": { ... }
}

After (v1.2.8+)

{
  "antigravity-claude-sonnet-4-5-thinking": {
    "name": "Claude Sonnet 4.5 Thinking",
    "limit": { "context": 200000, "output": 64000 },
    "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] },
    "variants": {
      "low": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 8192 } } } },
      "medium": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 16384 } } } },
      "max": { "providerOptions": { "google": { "thinkingConfig": { "thinkingBudget": 32768 } } } }
    }
  }
}

Benefits

• Cleaner model picker - 4 models instead of 12+
• Flexible budgets - Define any budget, not just low/medium/high
• Future-proof - Works with OpenCode's native variant system

Backward Compatibility

Old tier-suffixed models (antigravity-claude-sonnet-4-5-thinking-low, etc.) still work. No action required if you prefer the old style.

Migration Guide (v1.2.7 - Prefix)

If upgrading from v1.2.6 or earlier:

What Changed

v1.2.7+ uses explicit prefixes to distinguish quota sources:

Model Type	New Name (Recommended)	Old Name (Still Works)
Gemini 3 (Antigravity)	antigravity-gemini-3-pro	gemini-3-pro-low
Gemini 3 (CLI)	gemini-3-pro-preview	N/A
Claude	antigravity-claude-sonnet-4-5	claude-sonnet-4-5

Action Required

Update your config to use antigravity- prefix:

- "gemini-3-pro-low": { ... }
+ "antigravity-gemini-3-pro": { ... }

Why update? Old names work now as a fallback, but this depends on Gemini CLI using -preview suffix. If Google removes -preview in the future, old names may route to the wrong quota. The antigravity- prefix is explicit and stable.

Step 1: Clear Old Tokens (Optional - do this if you have issues calling models)

rm -rf ~/.config/opencode/antigravity-account.json
opencode auth login

Step 2: Update opencode.json

Models now use antigravity- prefix for Antigravity quota. See Available Models.

Step 3: Create antigravity.json (Optional)

{
  "$schema": "https://raw.githubusercontent.com/NoeFabris/opencode-antigravity-auth/main/assets/antigravity.schema.json",
  "quiet_mode": false,
  "debug": false
}

E2E Testing

The plugin includes regression tests for stability verification. Tests consume API quota.

# Sanity tests (7 tests, ~5 min)
npx tsx script/test-regression.ts --sanity

# Heavy tests (4 tests, ~30 min)
npx tsx script/test-regression.ts --heavy

# Concurrent tests (3 tests)
npx tsx script/test-regression.ts --category concurrency

# Run specific test
npx tsx script/test-regression.ts --test thinking-tool-use

# List tests without running
npx tsx script/test-regression.ts --dry-run

Debugging

OPENCODE_ANTIGRAVITY_DEBUG=1 opencode   # Basic logging
OPENCODE_ANTIGRAVITY_DEBUG=2 opencode   # Verbose (full request/response bodies)

Logs are written to ~/.config/opencode/antigravity-logs/.

Documentation

• Architecture - Plugin internals and request flow
• API Spec - Antigravity API reference

Safety, Usage & Legal

Intended Use

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

Warning (Assumption of Risk)

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

Legal

• Not affiliated with Google. This is an independent open-source project.
• "Antigravity", "Gemini", "Google Cloud", and "Google" are trademarks of Google LLC.
• Software is provided "as is", without warranty.

Credits

Built with help from:

• opencode-gemini-auth - Gemini OAuth groundwork by @jenslys
• CLIProxyAPI - Antigravity API reference

Support

If this plugin helps you, consider supporting its continued maintenance:

License

MIT