Formwise: a form builder with AI drafts, designed and built

A simple intake form often means a heavy form tool or hand-written code. Formwise lets you drag questions onto a page, add show-if rules and publish a link, with no account. Or describe the form and edit Claude's draft. Slotwise uses these forms for the questions students answer when they book.

The idea is a printed form. Every question is a numbered box on green-bar paper, so the builder looks like the thing it makes, and the preview on the right is the real renderer, not a mock-up. Conditions get one colour, yellow, everywhere they appear, so you can see at a glance which questions only show up for some people.

Edits that can't break the form. Moving or deleting a question can break a show-if rule that points at it. Every edit is a command run through one pure function. When an edit breaks a rule, the rule is removed and the builder says which question lost it. A test applies 300 random edits and checks the form is still valid after each.

One set of rules everywhere. The builder preview, the public form, the API and Slotwise all check answers with the same code from one shared package. Each answer records the form version it was given against, so publishing a change never rejects someone halfway through.

AI output treated as untrusted input. Claude fills a small draft format through structured outputs. The server turns the draft into a real form and validates it like any import. If that fails, the exact errors go back to the model once. Descriptions are length-limited and rate-limited.

8 of 8 test descriptions gave a valid form on Claude Opus 5.5, median 4.45 s end to end (15 Oct 2026). 98 Lighthouse mobile performance and 100 accessibility on the builder (median of 3 runs, 14 Oct 2026). 140 unit and API tests, plus 16 browser test runs, green in CI.

Built with Vite and React, Zustand, dnd-kit, a Hono API on Vercel Functions, Postgres on Neon with Drizzle, Zod, Claude Opus 5.5, Vitest with PGlite and Playwright.

Open the builder: formwise-builder.vercel.app (no account needed). Code: github.com/krishnanbhupathi/formwise-builder