Free & Open Source Powered by onLLM

Beta - currently in active development

Ship cleaner UI products by annotating any UI directly in the browser.

onUI adds a visual annotation layer to any web app, then exports structured context your agents can use immediately. With onui-local MCP connected, your agent can continuously read fresh annotations and keep applying fixes - like UI pair programming. No app code changes. No backend.

Get Started View on GitHub

Quick start

git clone https://github.com/onllm-dev/onUI.git && cd onUI && pnpm install && pnpm build
Load packages/extension/dist in chrome://extensions -> Developer mode -> Load unpacked. Optional local MCP setup: pnpm build:mcp && pnpm setup:mcp && pnpm doctor:mcp.

AI Pair Programming

You annotate once. Your agent keeps fixing in a loop.

01

Mark UI issues with intent and severity.

02

Agent reads fresh annotations from local MCP tools.

03

Fix, verify, and iterate until the UI is production-clean.

Works with Claude Code and Codex as a continuous, annotation-driven UI workflow.

Demo

See onUI in real usage

Features

Built for annotation-first agent workflows

No integration work

Run on any supported webpage where content scripts can execute. No app instrumentation required.

Precision context

Capture intent and severity directly on UI elements so agents understand what to fix and how urgent it is.

Multiple output formats

Export compact, standard, detailed, or forensic reports depending on your debugging depth.

Shadow DOM isolation

Stable styling that avoids clashes with host app CSS while keeping overlays visually consistent.

Local MCP server

Your agent can keep checking annotations via onui_get_report and onui_search_annotations, apply fixes, and repeat in a pair-programming loop.

Private by design

Your data stays local through native messaging plus a local store. No SaaS dependency required.

Install

Get up and running in minutes

1. Clone repository

git clone https://github.com/onllm-dev/onUI.git && cd onUI

2. Install deps + build extension

pnpm install && pnpm build

3. Load extension in Chrome

  1. Open chrome://extensions
  2. Enable Developer mode
  3. Click Load unpacked
  4. Select packages/extension/dist

4. Optional local MCP setup

pnpm build:mcp && pnpm setup:mcp && pnpm doctor:mcp

Builds and registers local onui-local MCP for Claude Code and Codex when available.

Repository Issues MCP Setup Docs

FAQ

Quick answers

Which browsers are supported in this release?

Chrome stable only.

Can I enable onUI globally?

onUI is tab-scoped by design. New tabs start with onUI off.

Does onUI require a cloud backend?

No. The extension, native host, and MCP server run locally.