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How to move an app component into the headless @jasonyangcis/core-ui library — headless conversion, cross-repo file checklist, treeshake sentinel, changeset, consumer wiring.
How to wire a new Builder.io-rendered route or model — fetch helper, route, registry, config.
Pattern for adding a server Route Handler under app/api/** — origin check, zod body, server-only deps, safe responses.
Builder.io Gen-2 SDK patterns — fetch, render, register, model guard, preview.
Tokens, cn(), focus rings, shadcn/ui (new-york), insert-menu groups.
TS strict, four-file folder pattern, import boundaries, no console.
Secret hygiene, CSP, CSRF, webhook HMAC, session encryption.
| name | core-ui-migration |
| description | How to move an app component into the headless @jasonyangcis/core-ui library — headless conversion, cross-repo file checklist, treeshake sentinel, changeset, consumer wiring. |
Moving a component from this app (components/**) into the sibling @jasonyangcis/core-ui repo (../core-ui) is a two-repo change. core-ui is headless — it ships structure, behavior, ARIA, and data-* attributes, but no CSS, no Tailwind, no tokens. The visuals stay in this app. Read core-ui/CLAUDE.md first; this skill is the migration recipe on top of it.
The source component almost certainly carries visuals (Tailwind classes, a .module.scss, inline styles). Those CANNOT come along. Transform them:
data-* attributes on the rendered element (data-variant, data-size, data-slot="<name>"), never internal class strings. The consumer's CSS targets those attributes.null, so type optional props T | null and resolve with prop ?? default so the data attribute always carries a meaningful value.className and ref straight through so call sites can still style one-offs.The visuals you stripped get recreated in this app (Step 4), keyed off the same data-* attributes. Preserve the original values verbatim — same tokens (var(--border), var(--r-xs)), same radii/colors. The migration is a relocation, not a restyle.
Under core-ui/src/components/<Name>/, mirror the existing Badge/Button folders:
<Name>.types.ts — interfaces + prop unions only, no runtime code. ref?: Ref<HTMLElement>.<Name>.tsx — implementation; import type the props and re-export them at the bottom. Relative imports use the emitted .js extension (from './X.types.js').index.ts — barrel: export { X } + export type { XProps }.<Name>.test.tsx — Vitest + Testing Library (renders, data-* emitted, className passthrough, ref forwarding).<Name>.stories.tsx — always required. See rules below.<Name>.stories.css — always required alongside the stories file. Demo styles keyed off data-slot attributes; imported at the top of <Name>.stories.tsx. Never add component styles to .storybook/preview.css.<Name>.builder.ts — ONLY if Builder-registered (like Button). Omit otherwise (like Badge). It is NOT re-exported from src/index.ts; it's reached via deep import.Then export from core-ui/src/index.ts — named exports only (never export default { ... }, which defeats treeshaking).
@jasonyangcis/core-ui (the aliased barrel), not the relative source file.tags: ['autodocs'] on the meta object.Default story plus stories for each meaningful prop combination (variants, conditional sections, slot overrides).<Name>.stories.css alongside the stories file with demo styles keyed off the component's data-slot attributes, then import './<Name>.stories.css' at the top of <Name>.stories.tsx. The library ships no CSS — without these styles the canvas renders blank. Do not add component styles to .storybook/preview.css; that file is intentionally empty so each component's styles stay scoped to its own story.dist/ — tsconfig.build.json excludes **/*.stories.ts(x) already; don't move or rename stories outside that pattern.core-ui/examples/consumer/scripts/check-bundle.mjs proves unused components are treeshaken from a Button-only consumer bundle. Add a unique runtime string from the new component to EXPECTED_ABSENT. Note: every data-slot component is already covered by the existing 'data-slot' sentinel — pick a value that won't collide with React/react-dom internals (avoid bare common words).core-ui/.changeset/<slug>.md with a minor bump describing the new primitive. Release happens later via changeset version → changeset publish.styles/components/<name>.css, keyed off the data-* attributes (e.g. [data-slot="card"] { ... }). Use the values you stripped in Step 1.@import "../styles/components/<name>.css"; in app/globals.css, with the other component imports right after Tailwind + tokens (@import rules must stay at the very top).import { X } from "@jasonyangcis/core-ui";.components/ui/<Name>/ (or wherever it lived).The dev loop only live-rebuilds core-ui if ../core-ui/node_modules exists. If it doesn't (fresh checkout), the app silently falls back to the published registry version, the new export is missing, and tsc fails against stale node_modules. To verify locally:
cd ../core-ui && npm install (once), then npm test && npm run typecheck && npm run lint && npm run build.dist/ into node_modules/@jasonyangcis/core-ui automatically; if you bypassed it, copy core-ui/dist + package.json into the app's node_modules/@jasonyangcis/core-ui/ manually.cd code && npx tsc --noEmit should be clean. Load the page that uses the component and confirm visuals are unchanged.@jasonyangcis/core-ui version pin in package.json until the new version is actually published — a clean npm install re-resolves from the registry and fails with ETARGET. The dev loop overlays the local build, so the new component works in dev without a publish.design-system-docs/*.mdx are read-only virtual files — you can't edit their import examples even though they reference the old path.data-* attribute names are the silent contract between core-ui and styles/components/*.css. A rename breaks styling with no type error — keep both sides in sync.Canonical reference migration: Card (headless data-slot="card" in core-ui, visuals in styles/components/card.css). Sibling primitives: Badge (no builder config) and Button (with Button.builder.ts).