Gemma Gem Browser AI

Skill by ara.so — Daily 2026 Skills collection.

Gemma Gem is a Chrome extension that runs Google's Gemma 4 model entirely on-device via WebGPU. It injects a chat overlay into every page and exposes a tool-calling agent loop that can read pages, click elements, fill forms, execute JavaScript, and take screenshots — all without sending data to any server.

Architecture Overview

Offscreen Document          Service Worker           Content Script
(Gemma 4 + Agent Loop)  <-> (Message Router)    <-> (Chat UI + DOM Tools)
       |                         |
  WebGPU inference          Screenshot capture
  Token streaming           JS execution

• Offscreen document (offscreen/): Loads the ONNX model via @huggingface/transformers, runs the agent loop, streams tokens.
• Service worker (background/): Routes messages, handles take_screenshot and run_javascript.
• Content script (content/): Injects shadow DOM chat UI, executes DOM tools.