Aceto

A local dev server with a browser overlay and MCP interface for building HTML mockups together with an AI agent.

Not a drawing tool, not a visual editor. Instead, a feedback loop between you and an agent:

1. Tell the agent what you want
2. The agent generates/modifies real HTML + Tailwind
3. See the result live in your browser
4. Point at an element and say "change this"
5. The agent understands which element you mean and modifies it

Why Aceto

• Token-efficient: The agent doesn't need to read and parse the full HTML to understand what you mean. You point at an element in the browser, the agent gets a precise selector. Write tools use the current selection by default — one tool call, no roundtrip.
• Real HTML: No abstraction layer, no component model. The output is a plain HTML file you can read with cat and send by email.
• Live feedback loop: DOM morphing keeps scroll position and selection state. You see changes instantly without page reload flicker.

Features

Hover Highlighting

User moves the mouse over any element — a blue outline appears with the element's tag and classes.

Element Selection

User clicks an element to select it (pink outline). The breadcrumb bar at the bottom shows the full DOM path. Scroll wheel navigates up/down the tree (parent/child).

Agent Highlight

The agent highlights elements in cyan to communicate visually — e.g. to ask "Do you mean this one?":

highlight_element("section#pricing > div:nth-of-type(2)", {
  label: "Make this card wider?",
  style: "pulse"
})

Both selections (pink = user, cyan = agent) can be visible simultaneously.

Inline Editing

User double-clicks any editable element to modify it directly in the browser:

• Text elements (headings, paragraphs, links, etc.) — edit the text content. Enter to save, Escape to cancel.
• Inputs — edit the value attribute. Enter to save, Escape to cancel.
• Textareas — edit the value. Ctrl+Enter to save, Escape to cancel, Enter adds a newline.
• Checkboxes / Radio buttons — double-click to enter edit mode, Space to toggle, Enter to save, Escape to cancel.

CSS Class Editor

User presses c on a selected element to edit its Tailwind classes inline. Enter to apply, Escape to cancel.

Table Controls

User selects a table cell — a floating toolbar appears with +Row, −Row, +Col, −Col controls.

DaisyUI Support

Add component libraries via the CLI — DaisyUI components work out of the box with Tailwind v4:

aceto add daisyui

More Features

• Content shortcuts — type [] or [x] in a cell to insert a checkbox
• Slash commands — type /list in an empty element to open a modal for creating <ul>/<ol> lists. Edit badges appear on existing lists for quick re-editing via double-click.
• Element defaults — define default classes for generated elements via aceto.defaults.json
• Paste images — Ctrl+V with selection inserts instantly; without selection, stages the image for agent-driven placement
• Asset picker — press a to browse and reuse previously pasted images from the assets folder
• Yank/Paste — press y to copy a selected element, p to paste it after another selection
• Screenshots — the agent captures full-page or element-level screenshots via get_screenshot()
• Live reload — DOM morphing keeps scroll position and selection state, no flickering

What Aceto Does Not Do

• No editor — you don't edit anything yourself, you steer the agent
• No build system — an HTML file you can read with cat
• No framework — Tailwind v4 via CDN, optionally DaisyUI/Flowbite

Keyboard Shortcuts (Select Mode)

Installation

bun install -g github:alexzeitler/aceto

Requires Bun runtime.

MCP Setup

Once aceto dev is running, add it as an MCP server to Claude Code:

claude mcp add aceto -s user --transport http http://localhost:3000/mcp

Getting Started

# Create a new project
mkdir my-mockup && cd my-mockup
aceto init

# Start the dev server
aceto dev

# Export for production
aceto export --production

CLI

aceto init                    # Create index.html + CLAUDE.md + aceto.md
aceto init --eject            # Write default instructions into aceto.md
aceto init --preset daisyui   # Create project with DaisyUI v5 pre-installed
aceto dev                     # Start dev server + MCP server
aceto dev about.html          # Start with a specific page
aceto dev --port 3001         # Custom port
aceto new about               # Create a new HTML page
aceto new dashboard/settings -l daisyui  # New page with DaisyUI
aceto add daisyui             # Add DaisyUI v5 to an existing project
aceto export                  # Export HTML with cleanup to dist/
aceto export --production     # Export with Tailwind CSS build

Agent Instructions

On aceto init, a minimal CLAUDE.md is created that tells the agent to call get_instructions() via MCP. This tool returns the project's aceto.md if it has content, or the built-in default instructions.

To customize the instructions, run aceto init --eject to write the defaults into aceto.md, then edit to your needs.

Element Defaults

Create an aceto.defaults.json in your project root to define default classes for generated elements:

{
  "checkbox": "h-4 w-4",
  "img": "max-w-full h-auto rounded"
}

• checkbox — applied to checkboxes created via []/[x] shortcuts
• img — applied to images inserted via paste (Ctrl+V)

The file is hot-reloaded — changes take effect immediately without restarting the server.

Tech Stack

Bun runtime, parse5 for HTML parsing, css-select for selectors, idiomorph for DOM morphing, MCP SDK for the agent interface. No Express, no React, no build step.