opencode-agy-bridge

OpenCode plugin + provider that routes LLM prompts to agy (Google Antigravity CLI).

How it works

opencode TUI
  └─ /model → select agy/antigravity
      └─ you type a prompt
          └─ provider spawns: agy --add-dir <cwd> [--conversation <id>] -p -
              └─ agy → Google Antigravity backend → Gemini
                  └─ stdout (buffered, full response)
              └─ provider extracts delta vs previous turn
          └─ text-delta + finish → opencode renders the response

Prerequisites

1. agy installed and authenticated — run agy standalone at least once to complete OAuth.
2. Node.js ≥ 18 or Bun ≥ 1.0.
3. OpenCode >= 1.15.x (uses Vercel AI SDK v3).

Installation

Automatic (hands-free)

Add the package with its version to ~/.config/opencode/opencode.json. OpenCode will download and resolve it from npm automatically — no terminal commands needed.

Manual global install

npm install -g opencode-agy-bridge
# or: bun install -g opencode-agy-bridge
# or: pnpm add -g opencode-agy-bridge

Build from source

git clone https://github.com/raultov/opencode-agy-bridge.git
cd opencode-agy-bridge
bun install && bun run build && bun test

Configuration

Add the plugin and provider to ~/.config/opencode/opencode.json.

The node.js path represents a package (directory or npm package name), not a .js file. Pointing "npm" at a .js file will cause a ProviderInitError because opencode internally appends /provider to resolve the exports map.

Recommended: automatic from npm

{
  "plugin": [
    "[email protected]"
  ],
  "provider": {
    "agy": {
      "npm": "opencode-agy-bridge",
      "name": "Google Antigravity (via agy CLI)",
      "options": { "binary": "agy", "timeoutMs": 300000 },
      "models": { "antigravity": { "name": "Antigravity (server-selected Gemini)" } }
    }
  }
}

Using npm global install path

{
  "plugin": [
    "opencode-agy-bridge"
  ],
  "provider": {
    "agy": {
      "npm": "opencode-agy-bridge",
      "name": "Google Antigravity (via agy CLI)",
      "options": { "binary": "agy", "timeoutMs": 300000 },
      "models": { "antigravity": { "name": "Antigravity (server-selected Gemini)" } }
    }
  }
}

Local development (absolute paths)

{
  "plugin": [
    "/home/USER/workspace/opencode-agy-bridge/dist/plugin.js"
  ],
  "provider": {
    "agy": {
      "npm": "/home/USER/workspace/opencode-agy-bridge",
      "name": "Google Antigravity (via agy CLI)",
      "options": { "binary": "agy", "timeoutMs": 300000 },
      "models": { "antigravity": { "name": "Antigravity (server-selected Gemini)" } }
    }
  }
}

Then restart OpenCode and run /model → select agy/antigravity.

Features

• Robust Delta Extraction: Automatically normalizes \r\n (CRLF) and \n (LF) line endings, tolerates trailing whitespace/newline differences, and implements suffix-based alignment to support seamless recovery during context window truncation.

Known limitations

| Limitation | Detail | |---|---| | No real streaming | agy --print buffers the full response and emits it on completion. Tokens appear in one batch, not one-by-one. PTY allocation (script -q) was tested and does not destrabilize the buffering — agy holds output until the response is complete regardless of whether stdout is a TTY. The provider therefore emits a single text-delta per turn instead of faking progressive chunks. | | Single cosmetic model | agy does not accept --model. The model is chosen server-side by Antigravity. Declaring extra models in config has no effect. | | Requires authenticated agy | You must run agy standalone at least once to authenticate via OAuth. | | No tool-call passthrough | agy CLI does not return structured tool calls to the caller. Tool use happens inside agy's own process. | | Per-turn subprocess | Each prompt spawns a fresh agy process. Context is preserved via --conversation <id>. | | Images/file parts omitted | OpenCode messages with image/file content parts are skipped with a warning — agy CLI does not support them. | | Conversation binding heuristic | The bridge infers conversation_id by diffing ~/.gemini/antigravity-cli/conversations/*.pb before/after each turn. If multiple .pb files appear simultaneously, binding is refused and each turn runs in single-turn mode. |

Project structure

src/
├── agy-runner.ts           # spawn agy, capture stdout/stderr
├── conversation-tracker.ts # snapshot .pb files, infer conversation_id
├── session-store.ts        # persist session→conversation_id mapping
├── prompt-mapper.ts        # Vercel AI SDK prompt → plain text
├── provider.ts             # LanguageModelV2 implementation (core)
└── plugin.ts               # OpenCode plugin entrypoint (hooks)

Development

bun run build   # compile TypeScript
bun test        # run test suite

CI/CD (GitHub Actions)

• CI (ci.yml): Runs on push and pull requests to main — compiles and runs all tests.
• Release (release.yml): Runs on v* tags — builds, tests, and publishes to npm.

Setup

1. Generate a Granular Access Token on npmjs.com with Bypass 2FA enabled.
2. Add it as repository secret NPM_TOKEN in GitHub Settings → Secrets and variables → Actions.