Steer it. Iterate. Then build.

Defaults keep you on-scheme; prompts set the direction. Every chat message rides with an explicit contract — preserve: palette, type, spacing · vary: layout, hierarchy, density · steer: your words — so iteration changes the design without ever drifting off-system. When a round wins, the agent ships it.

Silent by design — 0:34. Every beat is legible with the sound off.

What happens

Round 1 — steer (0:07). "make it a horizontal strip — label left, number right." The alternatives arrive as strips: structure changed, palette and type untouched.

Round 2 — iterate (0:17). "tighter — smaller number, drop the arrow." Same contract, new direction: a compact strip lands.

Build (0:26). The winner ships. Design mode is deliberately preview-only — it never writes into the target subtree — so the ship step is the agent's normal path: a source edit and an HMR reload, shown here as the direct DOM change it produces.

How it's made

Recorded by the scripted demo engine against the real stack; every chat message is a real design_chat event with the full constraints block. make demo NAME=design-steer re-records it.