SKETCHMASON

Most AI design tools start with a text box. Describing a layout in a paragraph is slow, and what comes back rarely matches the picture in your head. A rough sketch says more about structure than a long prompt ever will.

I wanted a tool where you draw the boxes and get a real design back, built on a style you chose.

SketchMason is a canvas. You draw a frame, block out rectangles, add a label or two and press generate. The screen streams in beside your sketch, so you know within seconds if the layout is going the wrong way.

It starts with a mood board. The app reads your images for palette and type and turns them into a style guide every screen follows. From there you revise by asking, grow one screen into a flow, and export the design as HTML.

It runs on Next.js and Convex. Generation goes through the Vercel AI SDK to Anthropic models, and Polar handles billing. One credit pays for one generation.

The model sees your frame as an image, and on its own that image loses a lot. Two boxes at 40% and 55% of the width are an exact split in the shape data. In a picture they are just two columns. A box inside a box turns into one solid block.

So the browser writes the sketch out as text first. Every shape becomes a line of whole-number percentages of the frame, sent ahead of the image. It needs no extra model call. The model reads the geometry from numbers, and the picture only has to show what numbers can't.

Streaming made billing its own problem. The credit is taken before the first byte arrives. If the stream drops on the model's side, the credit goes back. If most of the design already arrived, it is kept and marked as cut off, so you press Continue instead of starting over.

SketchMason is live at sketchmason.com. A new account gets two free generations, then there are two monthly plans and one-off credit top-ups.

Model output is never trusted as it is. Every design is checked against an allow-list of tags and attributes before it reaches the page, and its styles are scoped so one bad rule can't blank the editor. It's what I'm building right now.