drawui
Draw a UI on a canvas, and your coding agent builds it in your project.
drawui is a local canvas (Excalidraw) with an MCP server. You sketch screens freeform: rectangles are containers, text inside a shape is its label, and text starting with // is a note to the agent. The agent reads the drawing, writes the frontend with the component library you chose, and draws its changes back onto the canvas, so the drawing and the code stay in step.
It works with any MCP client that speaks streamable HTTP, such as Claude Code and Switchback.
Run it
You need Bun 1.4 or later.
git clone https://github.com/Harville-Labs/drawui
cd drawui
bun install
bun run build
bun start ~/code/my-app
That opens the canvas at http://localhost:4747 for ~/code/my-app. Leave the path off to use the current directory, or point it at an empty folder to start from a blank canvas. Then connect your agent:
claude mcp add --transport http drawui http://localhost:4747/mcp
Or copy .mcp.json into your project's root so everyone working in it gets the server. Change the port there if you start drawui with --port.
Pick a component library in the top bar (Sivir UI, shadcn/ui, and shadcn-svelte are suggested; any name works) and, if you like, the URL of your dev server so the preview sits beside the drawing. Then ask the agent to "build what I drew in drawui", or use the build prompt.
How to draw
| You draw | The agent reads |
|---|---|
| A rectangle, ellipse, or frame around other shapes | A container. Nesting is layout; rows and columns are inferred. |
| A frame | A screen, named by the frame's name |
| Text inside a shape | That component's visible text, used verbatim |
Text starting with // |
A note to the agent, attached to the container it sits in |
| An arrow from a note to an element | A note about that element |
| An arrow between elements | Navigation or data flow; its label says which |
| Dashed strokes, fills, colors | Deliberate hints |
| Freehand lines | A rough sketch; the agent looks at an image of it |
Select text and use Mark as note to turn it into a note without typing //. Select part of the drawing to ask the agent to build only that part.
Things the agent draws are tagged as its own, and elements it implemented link to their source file. When it can't build something or had to guess, it leaves a note with an arrow pointing at the element.
What's saved
Everything stays on your machine. The server listens only on 127.0.0.1 and answers only requests addressed to localhost.
drawui.excalidraw: the drawing, in the project directory. Open it in Excalidraw too.drawui.json: the chosen library and preview URL.
Commit both if you want the drawing to live with the code.
MCP tools
get_project, set_project, get_canvas, get_selection, get_canvas_image, wait_for_change, draw, update, delete, and annotate. See docs/mcp.md.
Develop
bun run check # lint, typecheck, tests, build, file length; what CI runs
bun run dev # build the canvas and start the server on the current directory
See AGENTS.md for the layout and the rules changes must follow.