# Phase 4 — Local Design Studio Date: 2026-10-19. Delivered: non-AI authoring, isolated previews, local history, import/export, review and local application revisions on the existing engine and 104 component contracts. ## What shipped A new private workspace package, `@wrnexus/design-studio`, separates its browser-safe state model from the filesystem/compiler/SSR server entry. Run `bun run design:studio`; optionally pass `--app-root ` to enable application bundles. The default URL is `http://127.0.0.1:4320/`. The editor supports blank creation, presets, duplication, system identity, searchable foundation tokens and semantic bindings, base/mode/density layers, token aliases, additional tokens/layers, contract inspection for all 104 components, allowed part defaults, complete per-component recipe JSON, and canonical source editing. Variants, sizes, states and compound rules use the same engine schema; no second styling schema was introduced. The Swiss authoring shell uses white surfaces, Helvetica typography, hairline grid divisions and blue actions. Its draft remains visually separate from the design being authored. The paired editor/source model is the main interaction: structured controls edit the canonical document, and invalid source remains recoverable while previews use its last valid revision. Previews compile trusted shipped `.wrn` components and use the normal SSR document renderer, theme adapter and browser behavior runtime. They include a composed form/dialog page and seven catalog pages covering all 104 default component states. Controls select mode, density, width, direction, comparison and catalog page. Comparison uses identical authored content and can show a preset or last applied design. No AI provider is involved. ## Drafts, history and imports Autosave stores the raw canonical draft, last valid preview, applied baseline and up to 25 revisions in local browser storage. Undo/redo preserves invalid revisions and supports branching. Reload recovery is tested with realistic full-preset histories. Corrupt storage and quota failures are reported; raw draft export remains available. Import inspection reports preserved, ambiguous and unsupported values before accepting a document. Canonical JSON round-trips losslessly. Legacy import maps known literal theme suffixes and reports unmapped fields. Exchange import supports a documented scalar/alias subset with group type inheritance and descriptions; composite/structured values are reported as unsupported, and missing WrNexus semantic bindings are marked ambiguous. Imports never execute configuration files, fetch assets or infer missing inheritance parents. Exports include canonical JSON, standalone compiled CSS, existing-adapter theme configuration, resolved flat exchange tokens, compatibility reports and raw invalid drafts. Canonical JSON is the editable source of truth; exchange export is intentionally resolved and lossy. See the [package guide](../../packages/design-studio/README.md) for exact fidelity limits. ## Review, application and rollback Review shows affected paths and before/after values. Foundation changes are described as potentially affecting all contracted components; component recipe changes identify their component names. Local apply writes immutable version directories containing system JSON, CSS, theme configuration, exchange tokens, compatibility report and integration guidance. A single atomic `CURRENT.json` pointer selects the active local revision. Base revisions detect conflicts. Rollback swaps the current and previous pointers, including undoing a first apply to `none`. Existing app configuration is preserved. Applications explicitly import a reviewed generated `theme.json` into their existing configuration. Explicit app theme overrides and instance props retain their established precedence. Changing a Studio pointer alone does not rebuild an app pinned to an earlier import, publish a package or deploy anything. `/application-preview` verifies the selected on-disk system through the existing adapter. Browser verification used only `output/design-system-phase-4/application-demo`, not an existing user application. ## Verification - Combined regression: **358 pass, 0 fail**, 33 files, 6,965 assertions across Studio, engine, CLI, styles, UI, SSR and theme runtime. - Focused TypeScript check includes all Studio sources, tests and launcher and passes. Targeted lint passes. - Model tests cover invalid drafts, reload recovery, undo/redo/branching/history bounds, storage failure, canonical round trips, legacy/exchange fidelity, malicious/oversized/missing/cyclic imports and applied snapshot detachment. - Application/server tests cover immutable bundles, existing config preservation, adapter consumption, conflicts, rollback including initial application, same-origin/local-host restrictions, request bounds, read-only startup and browser-safe bundling. - Preview tests cover three presets × two modes, RTL, SSR control registries, real component hooks and all 104 catalog defaults. Preview scripts do not try to load external controller bundles. - Native browser verified six composed preset/mode combinations with expected fonts and radii: Square 0px/mono, Soft 16px/serif, Angular 0px/sans. Those tested desktop pages had no horizontal overflow. - Native browser verified token editing, recipe editing (8px Button override), invalid source/reload/undo recovery, import diagnostics, comparisons, dark mode, RTL and width selection; switch, InputNumber and dialog interactions worked. Fresh composed previews had no console errors after the SSR registry repair. - Native browser applied two revisions to the demonstration folder, rolled back to the earlier 12px-radius revision, and displayed a precise 12px → 16px remaining draft diff. Application files and existing config preservation are also checked by tests. Evidence: `output/design-system-phase-4/` contains browser results and screenshots. Existing Phase 3 catalog verification remains applicable to the component sources, which this phase does not modify. ## Boundaries and follow-on work The shell has responsive CSS, and preview frames support narrow widths. The current native browser viewport override did not change the shell's measured 1280px width; full mobile-shell certification is not claimed. External provider pixels, native popups, user-owned content and all populated interaction states retain their contract limitations. During exploratory DatePicker interaction, its existing client expression parser emitted a diagnostic; its source/API is unchanged and it remains in the default-state gallery. The composed preview focuses on core form controls, InputNumber and dialogs. Preview frames allow scripts without same-origin privileges, use bounded server-generated documents, and block network, forms and remote fonts. The loopback server rejects foreign hosts/origins and only writes to its configured root. The draft store is local and single-user; multiple tabs do not merge concurrent drafts. Local history is not collaborative storage or a backup. Guided generation, natural-language edits, decision locks, MCP mutation tools, collaborative storage and package publication remain later phases. The Studio is private and repository-local in this phase. Existing public API and visual-hash drift outside this delivery is preserved; only the new Studio package is added to the API baseline. No existing component source, runtime or theme API was changed for this phase.