OpenCode Chrome Annotation

Annotate any page in Chrome and send the screenshot, selected element metadata, and your instruction directly into OpenCode.

https://github.com/user-attachments/assets/bdee8a15-6720-4e57-b28d-ee6440722b71

Install

Add the plugin to your OpenCode config:

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["opencode-chrome-annotation@latest"]
}

Install the Chrome extension from the Chrome Web Store:

https://chromewebstore.google.com/detail/abeihanpaeioklkhioiigklonbomhjfd

How It Works

1. Start OpenCode in your project.
2. Click the extension button in Chrome.
3. Connect the current tab to your OpenCode session from the in-page picker.
4. Click Annotate in the in-page pill.
5. Select an element, write your instruction, and submit.

What Gets Sent

• Your written instruction.
• The current page URL and title.
• Selected element metadata such as selector, tag, text, role, aria label, and bounds.
• A screenshot saved locally by the plugin and referenced in the OpenCode prompt.

Troubleshooting

The plugin runs a local HTTP server bound to 127.0.0.1 on ports 39240-39260. The extension discovers the active OpenCode plugin instance over localhost.

• The extension can't start a new session, you need to be in an active OpenCode session to connect.
• If the extension can't find any session, ask your agent to run chrome_status that should give a detailed report.
• Make sure OpenCode and your Chromium browser exist in the same localhost network (not in seperate containers).

Development

Plugin

The OpenCode plugin source lives in src/plugin.ts. The published package entrypoint is generated at dist/plugin.js.

Install dependencies:

bun install

Build the plugin:

bun run build

Extension

The Chrome extension source lives in extension-src/. The loadable extension output is generated into extension/ and is not tracked by git.

bun run build:extension

Then load the generated extension/ directory from chrome://extensions.

To create the Chrome Web Store upload zip:

bun run build:zip