opencode-antigravity-auth

OpenCode plugin for Google Antigravity OAuth authentication.

Features

• 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
• Plugin Compatible - Works alongside other OpenCode plugins (opencodesync, etc.)
• Extended Thinking - Native support for Claude thinking budgets and Gemini 3 thinking levels
• Auto Recovery - Automatic session recovery from Claude tool_result_missing errors

Installation

npm install opencode-antigravity-auth

Add to your OpenCode config (~/.config/opencode/opencode.json):

{
  "plugins": ["opencode-antigravity-auth@latest"],
  "provider": "google",
  "model": "google/antigravity-gemini-3-flash"
}

On first run, a browser window opens for Google OAuth. Tokens are stored securely and refresh automatically.

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/antigravity.json

{
  // JSON Schema for IDE autocompletion
  "$schema": "https://raw.githubusercontent.com/anthropics/opencode-antigravity-auth/main/assets/antigravity.schema.json",

  // === General ===
  "quiet_mode": false,           // Suppress toast notifications (except recovery)
  "debug": false,                // Enable debug logging to file
  "log_dir": "/custom/log/path", // Custom debug log directory (optional)
  "auto_update": true,           // Auto-update plugin

  // === Thinking Blocks ===
  "keep_thinking": false,        // Preserve thinking blocks (may cause signature errors)

  // === Session Recovery ===
  "session_recovery": true,      // Auto-recover from tool_result_missing errors
  "auto_resume": true,           // Auto-send "continue" after recovery
  "resume_text": "continue",     // Custom resume prompt text

  // === Empty Response Handling ===
  "empty_response_max_attempts": 4,      // Max retries for empty responses
  "empty_response_retry_delay_ms": 2000, // Delay between retries (ms)

  // === Tool Handling ===
  "tool_id_recovery": true,       // Fix mismatched tool IDs from context compaction
  "claude_tool_hardening": true,  // Prevent Claude tool hallucinations

  // === Token Refresh ===
  "proactive_token_refresh": true,              // Background token refresh
  "proactive_refresh_buffer_seconds": 1800,     // Refresh 30min before expiry
  "proactive_refresh_check_interval_seconds": 300, // Check every 5min

  // === Rate Limiting ===
  "max_rate_limit_wait_seconds": 300, // Max wait time when rate limited (0=unlimited)
  "quota_fallback": false,            // Try alternate quota when rate limited

  // === Signature Cache (for keep_thinking=true) ===
  "signature_cache": {
    "enabled": true,
    "memory_ttl_seconds": 3600,      // 1 hour in-memory
    "disk_ttl_seconds": 172800,      // 48 hours on disk
    "write_interval_seconds": 60     // Background write interval
  }
}

Create ~/.config/opencode/opencode.json

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": [
    "opencode-antigravity-auth@latest"
  ],
  "provider": {
    "google": {
      "models": {
        "antigravity-gemini-3-pro-low": {
          "name": "Gemini 3 Pro Low (Antigravity)",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-gemini-3-pro-high": {
          "name": "Gemini 3 Pro High (Antigravity)",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-gemini-3-flash": {
          "name": "Gemini 3 Flash (Antigravity)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "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-low": {
          "name": "Claude Sonnet 4.5 Think Low (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-sonnet-4-5-thinking-medium": {
          "name": "Claude Sonnet 4.5 Think Medium (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-sonnet-4-5-thinking-high": {
          "name": "Claude Sonnet 4.5 Think High (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-opus-4-5-thinking-low": {
          "name": "Claude Opus 4.5 Think Low (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-opus-4-5-thinking-medium": {
          "name": "Claude Opus 4.5 Think Medium (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-opus-4-5-thinking-high": {
          "name": "Claude Opus 4.5 Think High (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        }
      }
    }
  }
}

Beta Versions

For the latest development features, check the dev branch README for beta installation instructions.

Available Models

Antigravity Quota

Models with antigravity- prefix use Antigravity quota:

Model	Description
google/antigravity-gemini-3-flash	Gemini 3 Flash (minimal thinking)
google/antigravity-gemini-3-pro-low	Gemini 3 Pro with low thinking
google/antigravity-gemini-3-pro-high	Gemini 3 Pro with high thinking
google/antigravity-claude-sonnet-4-5	Claude Sonnet 4.5 (no thinking)
google/antigravity-claude-sonnet-4-5-thinking-low	Sonnet with 8K thinking budget
google/antigravity-claude-sonnet-4-5-thinking-medium	Sonnet with 16K thinking budget
google/antigravity-claude-sonnet-4-5-thinking-high	Sonnet with 32K thinking budget
google/antigravity-claude-opus-4-5-thinking-low	Opus with 8K thinking budget
google/antigravity-claude-opus-4-5-thinking-medium	Opus with 16K thinking budget
google/antigravity-claude-opus-4-5-thinking-high	Opus with 32K thinking budget

Gemini CLI Quota

Models without antigravity- prefix 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	Gemini 3 Flash
google/gemini-3-pro-low	Gemini 3 Pro with low thinking
google/gemini-3-pro-high	Gemini 3 Pro with high thinking

Full models configuration

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": [
    "opencode-antigravity-auth@latest"
  ],
  "provider": {
    "google": {
      "models": {
        "antigravity-gemini-3-pro-low": {
          "name": "Gemini 3 Pro Low (Antigravity)",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-gemini-3-pro-high": {
          "name": "Gemini 3 Pro High (Antigravity)",
          "limit": { "context": 1048576, "output": 65535 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-gemini-3-flash": {
          "name": "Gemini 3 Flash (Antigravity)",
          "limit": { "context": 1048576, "output": 65536 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "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-low": {
          "name": "Claude Sonnet 4.5 Think Low (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-sonnet-4-5-thinking-medium": {
          "name": "Claude Sonnet 4.5 Think Medium (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-sonnet-4-5-thinking-high": {
          "name": "Claude Sonnet 4.5 Think High (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-opus-4-5-thinking-low": {
          "name": "Claude Opus 4.5 Think Low (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-opus-4-5-thinking-medium": {
          "name": "Claude Opus 4.5 Think Medium (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        },
        "antigravity-claude-opus-4-5-thinking-high": {
          "name": "Claude Opus 4.5 Think High (Antigravity)",
          "limit": { "context": 200000, "output": 64000 },
          "modalities": { "input": ["text", "image", "pdf"], "output": ["text"] }
        }
      }
    }
  }
}

Configuration

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

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

{
  // JSON Schema for IDE autocompletion
  "$schema": "https://raw.githubusercontent.com/anthropics/opencode-antigravity-auth/main/assets/antigravity.schema.json",

  // === General ===
  "quiet_mode": false,           // Suppress toast notifications (except recovery)
  "debug": false,                // Enable debug logging to file
  "log_dir": "/custom/log/path", // Custom debug log directory (optional)
  "auto_update": true,           // Auto-update plugin

  // === Thinking Blocks ===
  "keep_thinking": false,        // Preserve thinking blocks (may cause signature errors)

  // === Session Recovery ===
  "session_recovery": true,      // Auto-recover from tool_result_missing errors
  "auto_resume": true,           // Auto-send "continue" after recovery
  "resume_text": "continue",     // Custom resume prompt text

  // === Empty Response Handling ===
  "empty_response_max_attempts": 4,      // Max retries for empty responses
  "empty_response_retry_delay_ms": 2000, // Delay between retries (ms)

  // === Tool Handling ===
  "tool_id_recovery": true,       // Fix mismatched tool IDs from context compaction
  "claude_tool_hardening": true,  // Prevent Claude tool hallucinations

  // === Token Refresh ===
  "proactive_token_refresh": true,              // Background token refresh
  "proactive_refresh_buffer_seconds": 1800,     // Refresh 30min before expiry
  "proactive_refresh_check_interval_seconds": 300, // Check every 5min

  // === Rate Limiting ===
  "max_rate_limit_wait_seconds": 300, // Max wait time when rate limited (0=unlimited)
  "quota_fallback": false,            // Try alternate quota when rate limited

  // === Signature Cache (for keep_thinking=true) ===
  "signature_cache": {
    "enabled": true,
    "memory_ttl_seconds": 3600,      // 1 hour in-memory
    "disk_ttl_seconds": 172800,      // 48 hours on disk
    "write_interval_seconds": 60     // Background write interval
  }
}

Multi-Account Setup

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

# Add accounts
opencode auth login

Compatible Plugins

This plugin works alongside other OpenCode plugins. Some important notes:

Plugin Ordering

If using @tarquinen/opencode-dcp (Dynamic Context Protocol), our plugin must be listed first:

{
  "plugins": [
    "opencode-antigravity-auth@latest",
    "@tarquinen/opencode-dcp@1.1.2"
  ]
}

Plugins You Don't Need

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

Rate Limit Considerations

• oh-my-opencode - This plugin may make background API calls that consume your quota. If you're hitting rate limits unexpectedly, check if oh-my-opencode is making requests.

Migration Guide (v1.2.7+)

If upgrading from v1.2.6 or earlier, follow these steps:

Step 1: Clear Old Tokens

rm -rf ~/.config/opencode/antigravity-tokens/

Step 2: Update opencode.json

Replace your old config with:

{
  "plugins": ["opencode-antigravity-auth@latest"],
  "provider": "google",
  "model": "google/antigravity-gemini-3-flash"
}

Step 3: Create antigravity.json (Optional)

If you had custom settings, migrate them to ~/.config/opencode/antigravity.json:

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

Step 4: Re-authenticate

Run OpenCode once. A browser window will open for Google OAuth:

opencode

Breaking Changes

Old (v1.2.6)	New (v1.2.7+)
OPENCODE_ANTIGRAVITY_* env vars	~/.config/opencode/antigravity.json
gemini-3-pro	google/antigravity-gemini-3-pro-low
claude-sonnet-4-5	google/antigravity-claude-sonnet-4-5

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) - stress testing with 8-50 turn conversations
npx tsx script/test-regression.ts --heavy

# Concurrent tests (3 tests) - rate limit handling with 5-10 parallel requests
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

Enable debug logging:

# Via environment
OPENCODE_ANTIGRAVITY_DEBUG=1 opencode

# Via config
echo '{"debug": true}' > ~/.config/opencode/antigravity.json

Logs are written to ~/.config/opencode/antigravity-logs/ (or log_dir if configured).

Documentation

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

License

MIT