Dobby

Dobby is a free elf!

A Chrome extension that drops a small chat assistant into the side panel. Dobby runs entirely on your machine using Chrome's built-in Gemini Nano model — no servers, no API keys, no network round-trips for the chat itself.

What it is

Dobby is a single-purpose side-panel app. Click the toolbar icon, a panel slides in, you talk to a local LLM. That's it. The point of the project is to show how slim a useful on-device assistant can be when you lean on Chrome's Prompt API (the LanguageModel global).

Highlights:

• Runs offline once the model is downloaded.
• English and Traditional Chinese (台灣正體) UI and system prompts.
• Memory-pressure indicator so you know when to start a fresh chat.
• Markdown rendering via marked (vendored locally — extensions can't pull from CDNs at runtime).

Requirements

Dobby is only as available as the underlying Prompt API, which means:

• Chrome 138 or newer
• One of: Windows 10/11, macOS 13+, Linux, or a Chromebook Plus
• 22 GB of free disk for the model (first-run download)
• A GPU with more than 4 GB VRAM, or 16 GB RAM and a 4-core CPU

If the API isn't available, Dobby will tell you why and point you at chrome://on-device-internals.

Install (load unpacked)

1. Clone this repo.
2. Open chrome://extensions.
3. Turn on Developer mode (top right).
4. Click Load unpacked and select this folder.
5. Pin Dobby to the toolbar and click the icon — the side panel opens.

The first conversation will trigger a one-time model download. Subsequent runs are instant.

File layout

manifest.json     Manifest V3 declaration
background.js     Service worker — opens the side panel on icon click
sidepanel.html    Panel markup
sidepanel.css     Panel styles
sidepanel.js      App logic: i18n, session, streaming, usage meter
marked.min.js     Vendored Markdown renderer
icons/            Toolbar and store icons (dobby-16/32/48/128, .svg)

marked.min.js is vendored on purpose — Chrome extensions can't fetch scripts from a CDN at runtime, and pulling it in via a build step would be overkill for a project this size. The file is unmodified upstream; see its header for the original license.

Development notes

There is no build step. Edit the source, reload the extension from chrome://extensions, and reopen the side panel.

To package a release for the Chrome Web Store, zip everything except the items listed in .gitignore — the .zip files in the repo root are previous release artifacts (also gitignored). A minimal one-liner:

zip -r dobby-v0.X.zip . -x '*.git*' '*.zip' 'icons/Screenshot*' 'README.md'

What's intentionally not committed

The .gitignore keeps a few things out of source control:

• Release .zip artifacts (regenerated per release)
• icons/Screenshot* — Chrome Web Store listing screenshots, not runtime assets
• OS junk (.DS_Store, Thumbs.db, desktop.ini)
• Editor folders (.vscode/, .idea/) and swap files
• .env / .env.local (Dobby doesn't use these today, but it's a guard for later)

Privacy

Dobby never sends your messages anywhere. The only storage it touches is localStorage (inside the extension's own sandbox) to remember your language choice. There is no telemetry.

License

CC0 1.0 Universal

Acknowledgements

The "free elf" framing is a Harry Potter reference. The actual model work is all Chrome and Google's Gemini Nano team; Dobby is just a small UI on top.