UI workspace

426 preset packages, organized by role in the page — UI/<category>/<preset>/ (package names unchanged; import by name). The engine sidebar shows 427 presets (426 + home); all 426 ship to the shadcn registry (see Install below).

Category	Count	Role / "when do I use it"
chrome/	38	The page chassis & system surfaces: header variants, footer, drawer, sticky action bar, announcement, search, consent, notifications, status, error, empty-state
hero/	75	Opening statements: classic/scroll/ink/manifesto/product/ticker heroes, curtain intros, type animators + the zigzag scroll tunnel
content/	159	Proof and narrative sections: features, bento, stats, steps, team & expert spotlights, timeline, gallery, blog, events, careers, changelog/roadmap, testimonials, FAQ, tables, newsletter & letter… plus the device stage family (desktop / laptop / tablet / mobile / responsive mockups) and the composable stack-proof
commerce/	50	Offers and conversion: cta, pricing, offer (flip-clock countdown), gift (flip card), vault (value receipt), menu, download, waitlist, poll, review ask, aftercare recap — plus the layer-stack family (burger builder / pricing card / receipt)
engage/	35	Do-the-thing & trust: contact, auth, upload, choice, stepper, visit-us, schedule (hours+slots), place, facts, ritual, ambiance, promise
dnd/	24	Drag & drop systems: kanban, sortable lists/grids/trees, form & page builders (dnd-kit)
sidebar/	1	Sidebar systems: solid rail — a complete [sidebar | content] app shell: workspace switcher, primary nav, presence select, account menu, collapsible rail; built-in mobile (off-canvas below md), mobile={false} pins the desktop rail so hosts can mount it in their own sheet
branding/	25	Brand & identity surfaces: logo systems, palette tools, tone/voice strips
insight/	19	Analytics & observation decks

Authoritative map: CATEGORIES.json (read by the engine sidebar grouping and scripts/create-preset.py --cat).

Install any preset (shadcn registry — one command, own the source)

In any shadcn-initialized project (aliases + cn() + theme tokens):

npx shadcn@latest add https://ui-engine.pages.dev/r/footer-cta.json

The CLI writes the raw .tsx into your repo (@components/, @ui/), installs the npm deps from the item manifest (motion, lucide-react, …), and asks before overwriting files you already have. The code is yours after that: editable, no runtime registry, no npm package. Every preset also carries a companion CSS file when it needs more than theme tokens (@import it — the manifest description says so).

Regenerate after editing any package's sources (single source of truth: UI/*/src — never hand-edit generated JSON):

bun run --cwd engine generate:distribution

This writes UI/registry/r/*.json (+ registry.json index) and mirrors the same bytes to engine/public/r/ (dev-server DRY RUN + engine deploy). Details: UI/registry/README.md.

Path invariants (do not regress)

• Engine Tailwind scans ../UI/*/*/src/**/*.{ts,tsx} — one wildcard, survives any future regrouping.
• Package names (npm identifiers) are the stable key; workspace scripts address them by name (--workspace=<name>), never by path.
• New presets: python3 scripts/create-preset.py NAME --cat content … then add to CATEGORIES.json, root workspaces is already glob-based. Then wire into engine/package.json (file:../UI/<cat>/<name>), build its dist/, and regenerate sources + registry so sidebar, source panel, and shadcn all see it.

Embedding fixed chrome in constrained shells

Standalone sites want cookie/consent bars, headers and action bars pinned to the viewport — that is the default (--fixed-inset-left/right fall back to 0px). Hosts with their own chrome (app shells, dashboards, the UI Engine's sidebar) can re-anchor any fixed preset to their content column by setting two custom properties on any ancestor:

--fixed-inset-left: 300px;  /* width of your own rail, if any */
--fixed-inset-right: 0px;

Presets honoring this contract: header (fixed mode), header-pill, header-minimal, sticky-cookie, consent, action-bar. Position stays fixed — pinning, hide-on-scroll and portal behavior are untouched.

Vendored primitives — tokenization contract

components/primitives/{text-shimmer,glow-effect,border-trail}.tsx are vendored from motion-primitives (MIT) with ONE deliberate local craft change everywhere: hardcoded demo/zinc hexes are replaced by the shadcn token set, per HANDCRAFT-CHECKLIST.md ("never hardcode hex for anything token-able"). Copies are kept byte-identical across all presets — sync from the canonical copy when adopting upstream changes, don't hand-edit one.