The UI cluster had ballooned to 24 slices, 11 of them the os-vps app family. New `os` category across the taxonomy (SliceCategory union, slice-schema enum, sidebar order + "OS Apps" label, /build picker groups automatically): appshell, file-explorer, image-editor, reel-editor, code-editor, media-viewer, system-monitor, os-terminal, assistant (moved from AI — it is the OS assistant app; ai tag stays), browser, app-store. Category is metadata-only — no version bumps, `npx rr add <slug>` unchanged. Sidebar now: UI 13, OS Apps 11.

Site-simplify follow-up: variant previews were only reachable inside the Bundle Builder, so the catalog detail pages still read as static docs. Every /slices/<slug> page whose slug is in the preview registry now gets a "Live" tab next to Preview/Code/Details — the same auto-knob VariantPreview widget the builder mounts, fed by the same rr-demo localStorage data. 37 slices become interactive where people actually evaluate them.

gen-preview-registry now scans template-base/frontend/slices too — with a twist the smoke gate caught before production: template-base ships its OWN node_modules (a second react), so any .tsx living there crashes hooks when bundled. Render files for template-base slices therefore live SITE-SIDE at components/templates/_shared/previews/<slug>.preview.tsx (importing only site-compiled code) while the previews declaration stays in the slice's slice.json. dashboard-shell previews the real _shared DashboardShell all 8 OS templates mount (flat-nav / grouped-nav scenarios); admin-panel previews the 17-block operational overview grid. Registry: 37 slugs. Honest boundary documented in the spec: motion-primitives, responsive-dialog, three-column and workspace-shell are facades over @/frontend/shared/* — their implementations exist only in consumer projects, so rr cannot preview them truthfully; contact-form-resend is convex-bound.

Investigating a "previews are missing" report: every one of the 35 registered previews renders clean (verified live on production via headless Chromium + a new happy-dom smoke test). The real gap was silence — selected slices WITHOUT a preview (headless/server slices, opt-outs, template-base slices outside the registry) rendered nothing at all in /build, which reads as broken. The SlicePreviews panel now shows coverage (n/total) and an explicit "No live preview — headless / server-side, or preview not yet authored" card listing those slugs. New permanent gate: lib/preview/preview-smoke.test.tsx mounts EVERY registered preview with default variants in happy-dom on `npm test` (pre-push) — catches mount crashes and declared-component drift that tsc + the generator can't. vitest aliases now mirror tsconfig paths (@/features, @/shared dual-mapping) so tests can import through the registry.

M2c+M3+M4 land in one wave, closing the port that started 2026-06-03. M2c composes the working editor: BlockEditor + PageEditor orchestrators (dnd-kit drag with column layouts, slash menu, markdown triggers, per-block undo, paste-markdown import via a synthesized insertBlocksAfter over the seam's block CRUD), PageActionsMenu (font/width/lock/copy/duplicate/move/trash + md/html/txt export through the vendored export libs), SelectionToolbar (inline formatting), MentionTypeahead (async adapter search), DatabasePicker (delegates to adapter.database.pickDatabase), TocBlock, PageRefBlock, the page-editor chrome (title, breadcrumbs, actions, subpages, cover strip, skeleton/not-found) and a props-driven RowPropertiesPanel. M3 ports the pure convex block helpers (_blocks/_blockOps, 31 unit tests) into convex/features/notion. M4 flips the slice off WIP: version 1.0.0, public catalog entry (npx rr add notion), and a live variant preview — the full PageEditor running on a localStorage-backed in-memory EditorDataAdapter (two scenarios, every edit persists). Mount with adapter `{}` for a plain markdown block editor; wire data/selection/comments/ai/database/mention/page adapters to light up host capabilities. Source app peers that don't cross the seam (sharing, snapshots, wiki, analytics, notifications, presence) stay host-side by design.

validate:manifests had 23 long-standing (warn-only) errors: 7 slices still shipped the legacy {name, deps, notes} manifest shape and user-management used a stability value outside the enum. All 7 are converted to Schema A (slug/version/tier/distribution/files/imports — file lists from git, imports scanned from source; preview.tsx excluded), user-management moves alpha → experimental, and the validator now reports 0 errors. The two os-vps editors lifted this morning also join the variant-preview registry (33 slugs total): code-editor with three mock-fs scenarios and media-viewer with the offline sample gallery + a data-URI remote payload.

VP-6 closes the VP wave. 28 new preview.tsx files land across the catalog (31 total in the generated registry): every marketing section, UI utility, content/data surface and previewable subsystem now renders live in the Bundle Builder with auto-generated knobs. Headless / embed / no-seam slices (ai-router, audit-log, cal-com-booking, resend-newsletter, reel-editor, seo, vector-search) explicitly opt out with `"previews": []` — a new audit:slices rule warns when a component-bearing slice neither declares nor opts out, and gen-preview-registry errors on an opt-out that still ships a preview.tsx. layouts.ts gains demoUrl: all 8 OS templates now link their own Vercel deployments (the dev-lab repos, always ahead of rr's snapshot) from the detail page, overriding the demo-subdomain rewrite.

The shell framework grows a shell REGISTRY: chrome is now pluggable while the window store stays single. registry/shells.tsx holds ShellDescriptor (id/surface/group/windowed/wallpaper/render) + per-surface user prefs (a desktop shell AND a mobile shell, resolved by live form factor; sv:shell). Built-ins register on import: macOS (existing DesktopChrome), Windows 11 (centered taskbar + Start menu + Snap-Assist + caption-button windows via Window variant=windows), Android Material-You (status-bar shade w/ quick tiles, at-a-glance home, swipe-up App Drawer, gesture nav, Recents deck) and iOS (existing MobileShell, now with a left-half pull-down Notification Center + app long-press quick-actions). Consumers register their own (os-vps adds a single-pane Dashboard cockpit). Geometry became chrome-aware: WindowState.snapZone persists the snapped zone and applyChromeInsets() re-tiles snapped/maximized windows when a shell with different chrome mounts. Desktop fidelity pass rides along: dock magnification (gaussian, width-conserving) + dock right-click menus, macOS Notification Center backed by a persistent toast log (lib/toast), Cmd+Tab app switcher, Window Overview (Mission Control), desktop context menus, menu-bar Window/Help system menus, and wallpaper=auto resolving to the active shell's native backdrop (wp-win11/material/ios presets). Lifted from os-vps (Topside) after a two-way merge with app-rahmanef's fork — close guards + winId, dock Link deep-links and the shadcn Button sweep all kept. Every file under the 200-LOC gate (dock/menu-bar/mobile-home/store/android split into *-parts).

The big lift wave — every remaining os-vps app that could stand alone now does. Each follows the established host-seam recipe: lib/host.ts is the ONLY coupling point, with an injectable adapter and an honest offline default, so all five render alive with zero backend. system-monitor runs on a wavy telemetry mock until configureSysmon points at a real host; os-terminal's 17 built-ins run on its in-memory FsModel, with configureTerminal flipping ls/cat live and passing unknown commands to one-shot exec; assistant answers with a typing demo stream until configureAssistantStream brings any async text-delta generator; browser fakes its viewport with a canvas demo renderer until configureBrowser drives a real headless Chromium; app-store (with the Create-App flow bundled in — rr forbids cross-slice imports) manages a localStorage app registry whose useInstalledApps() feeds any appshell-style launcher. Skipped on purpose: os-settings (host-specific devices/server panels). The catalog now carries 9 of the 10 os-vps user apps.