diff --git a/dev-docs/BACKLOG.md b/dev-docs/BACKLOG.md
index 0c24878d..c1795912 100644
--- a/dev-docs/BACKLOG.md
+++ b/dev-docs/BACKLOG.md
@@ -2299,7 +2299,7 @@ positives from `useForm` colliding with Crewli's own `useFormDraft` /
 `useFormSteps` / `useFormSchemas` / `useFormFailures` composables.
 
 Removed both packages from `apps/app/package.json`, regenerated
-`pnpm-lock.yaml`. Canonical form pattern formalized in `CLAUDE.md`
+`pnpm-lock.yaml`. Canonical form pattern formalised in `CLAUDE.md`
 "Forms" + `dev-docs/VUEXY_COMPONENTS.md` "Form validation" row.
 
 **Refs:** Session 4 follow-up Step 1; `apps/app/src/components/timetable/AddPerformanceDialog.vue` and `apps/app/src/components/sections/CreateShiftDialog.vue` as canonical references.
@@ -2333,10 +2333,13 @@ assertions are necessary but not sufficient.
 - CI strategy: Playwright CT runs on every PR (slow lane); Vitest unit
   on pre-commit (fast lane).
 
-**Trigger:** **Before opening the Sessie 5 prompt.** Sessie 5 builds
-Engagement Detail (6 tabs, complex form state) and Portal pages
-(drag-to-reorder, file uploads). Adding more jsdom-based component
-tests for those surfaces compounds the migration cost.
+**Trigger:** Eerstvolgende sprint na merge van
+`fix/timetable-stabilization`. ART-S4-UX-PARITY en alle Sessie 5+ werk
+gates op merge van TEST-INFRA-001. Reden: drie incidenten in dit
+sprint-blok hebben aangetoond dat jsdom-tests structureel niet
+beschermen tegen schema drift, filter drift, of UX divergence. Verder
+bouwen zonder Playwright + visual regression infrastructure herhaalt het
+patroon.
 
 **Refs:** Session 4 follow-up commits `5f135ec`..`985a5ab`,
 RFC-TIMETABLE D14/D20/D21, the new `apps/app/tests/utils/mountWithVuexy.ts`
@@ -2387,23 +2390,98 @@ padding, or animation timing would not trigger a test failure even
 though the visual contract is broken.
 
 **Wat:**
-- After TEST-INFRA-001 lands, add `apps/app/tests-pw/visual/PerformanceBlock.spec.ts`.
-- Render PerformanceBlock in each documented state: option, confirmed,
-  contracted, cancelled; with/without capacity warn; with/without B2B
-  dots; with/without conflict ring; mid-cascade-pulse.
-- Use Playwright's `toHaveScreenshot()` with locked viewport size and
-  font rendering.
-- Commit baseline PNGs to `apps/app/tests-pw/visual/__screenshots__/`.
-- CI fails on diff > 0.1% pixel delta. Diffs trigger a manual review and
-  baseline update if the change was intentional.
+- Visual regression baselines for PerformanceBlock states, generated from
+  `./resources/Crewli - Artist  Timetable Management/Crewli Timetable.html`
+  rendered states (the canonical prototype is the baseline source — not
+  hand-curated screenshots).
+- Compare implementation Playwright renders against prototype renders
+  pixel-for-pixel (with reasonable tolerance for font rendering).
+- Failures block PR merge unless a baseline update is intentional and
+  reviewed.
+- Apply to:
+  - **PerformanceBlock** — 8 states minimum: option / requested /
+    confirmed / contracted / cancelled × with-warning / without-warning;
+    plus B2B dots and cascade-pulse at the millisecond keyframe peak.
+  - **PerformancePopover** — open state with full detail (avatar +
+    time/duration + multi-select status + advancing detail breakdown).
+  - **AddPerformanceDialog** — drag-mode (pre-fill from drop target)
+    and button-mode (name/genre/status/duration → land in Wachtrij).
+  - **Wachtrij** — filtered / unfiltered / grouped / ungrouped.
 - Pin font hinting and OS rendering: run visual tests only on Linux CI
   runners (consistent rendering across Mac/Windows is expensive — Linux
   baseline is sufficient).
+- Commit baseline PNGs to `apps/app/tests-pw/visual/__screenshots__/`.
+- CI fails on diff > 0.1% pixel delta.
 
-**Trigger:** Second addition to the TEST-INFRA-001 sprint. After
-TEST-CONTRACT-001 (contract-first, visual-regression-second).
+**Trigger:** Onderdeel van TEST-INFRA-001 sprint. Tweede toevoeging na
+TEST-CONTRACT-001.
 
-**Refs:** RFC-TIMETABLE D21, D22, D25, D26.
+**Refs:** RFC-TIMETABLE D21, D22, D25, D26;
+`./resources/Crewli - Artist  Timetable Management/` prototype.
+
+---
+
+### ART-S4-UX-PARITY — Timetable UX parity with prototype
+
+**Aanleiding:** Manual browser testing after `fix/timetable-stabilization`
+merge surfaced substantial UX divergence between implementation and the
+canonical prototype at `./resources/Crewli - Artist  Timetable Management/Crewli Timetable.html`.
+Mechanical layer (backend, schema, layout, scroll, sticky panes) is
+correct; visual and interaction layer diverge significantly.
+
+**Categories of divergence (seed list — full gap analysis is sprint Phase A):**
+
+- **A. Component-shape drift**
+  - PerformanceBlock missing: genre tag, advancing progress bar,
+    capacity-warning visibility
+  - PerformancePopover missing: avatar, time+duration display,
+    multi-select status, advancing detail breakdown
+  - Wachtrij missing: multi-select status filter pills, status grouping
+    with counts, grouping toggle, status/genre per item
+
+- **B. Interaction drift**
+  - Drag within timetable: not working
+  - Drag between Wachtrij and timetable: not working
+  - Click handling: inconsistent across blocks (some open popover, some
+    don't)
+  - Resize handles: missing entirely
+
+- **C. Logic drift / rendering**
+  - Conflict detection: not visually surfacing (red border + warning
+    icon)
+  - Lane stacking on overlap: behavior unverified against prototype
+  - Capacity warnings: rendering unverified
+  - Block rendered outside timetable bounds (Bert's screenshot 3)
+
+- **D. AddPerformanceDialog two-mode behavior**
+  - "Add via timetable click-drag" mode: should pre-fill
+    stage/start/end/duration from drop target — currently always shows
+    full form
+  - "Add via +Optreden button" mode: should only ask
+    name/genre/status/duration and land in Wachtrij — currently asks
+    stage/time/lane
+
+For the complete 20-item itemization with severity ratings, see the Phase
+A report in `feat/timetable-stabilization` finalization commit.
+
+**Wat:**
+- Sprint Phase A: line-by-line gap analysis of prototype HTML vs. current
+  implementation, produces an exhaustive table (this seed list above is
+  incomplete on purpose — full audit belongs in the sprint, not in this
+  BACKLOG entry)
+- Sprint Phase B: implement parity, prioritised by category and severity
+  from Phase A
+- Sprint Phase C: visual regression baselines locked in via TEST-VISUAL-001
+- Sprint Phase D: manual prototype-side-by-side walkthrough by Bert before
+  merge
+
+**Trigger:** Direct na merge van TEST-INFRA-001 sprint. Sessie 5
+(Engagement Detail) en alle volgende Artist-domain frontend sprints
+gates op merge van ART-S4-UX-PARITY.
+
+**Refs:** Bert's screenshot report (chat thread on stabilization merge
+readiness), `dev-docs/audits/PROTOTYPE-AUDIT-ARTIST-TIMETABLE.md`,
+RFC-TIMETABLE D8/D17/D18/D19/D20/D21/D22/D25/D26.
 
 ---