@@ -142,7 +142,6 @@ When to use which:
 |-----------|--------|
 | Click that triggers a re-render and you want to assert after | `waitForViewportRenderCycle(page)` started before the click |
 | Layout switch / series load — render already in flight | `await waitForViewportsRendered(page)` after the call |
-| Slice navigation (`sliceNavigation.toSlice(...)`, `scrollBy`, …) | `await waitForViewportsRendered(page)` after the call (per the `getSliceNavigation` docstring) |
 | Compose with another await (e.g. screenshot the same time as load) | Save the promise, `await` it later |
 
 Replace patterns like this:
@@ -188,6 +187,8 @@ Two page objects are **not** fixture-injected:
 
 See [references/page-objects.md](references/page-objects.md) for fixture rules and a map of which file covers which concern; read the `.ts` file under `tests/pages/` for the current method surface.
 
+Page objects locate elements and perform actions; keep `expect` assertions in the spec.
+
 ## When the control you need has no page object yet
 
 A spec must not reach for `page.getByTestId(...)` / `getByRole(...)` directly for
 
@@ -96,8 +96,9 @@ Read the one-line signature at the top of the utility's source file before calli
 
 Most utilities are obvious once you read the source; these earn a mention:
 
-- **`waitForViewportRenderCycle(page, options?)`** — preferred replacement for `page.waitForTimeout(...)` after any viewport-mutating action (hydration confirm, layout change, segmentation add, series load, etc.). Start it **before** the action, await it after — it captures the `needsRender → rendered` transition the action triggers. Use `waitForViewportsRendered(page)` (the second-half-only variant) when the render is already in flight before you can attach a watcher, and after `sliceNavigation.to*()` / `scrollBy` (their docstring says so). Source: `tests/utils/waitForViewportsRendered.ts`. Seed: `tests/SEGHydrationFromMPR.spec.ts`. The "Wait for renders, don't sleep" section in [SKILL.md](../SKILL.md) covers the idiom in full.
+- **`waitForViewportRenderCycle(page, options?)`** — preferred replacement for `page.waitForTimeout(...)` after any viewport-mutating action (hydration confirm, layout change, segmentation add, series load, etc.). Start it **before** the action, await it after — it captures the `needsRender → rendered` transition the action triggers. Use `waitForViewportsRendered(page)` (the second-half-only variant) when the render is already in flight before you can attach a watcher. Source: `tests/utils/waitForViewportsRendered.ts`. Seed: `tests/SEGHydrationFromMPR.spec.ts`. The "Wait for renders, don't sleep" section in [SKILL.md](../SKILL.md) covers the idiom in full.
 - **`expectAnnotationStatsText({ page, activeViewport, rightPanelPageObject, toolName, expectedPanelPrimaryLines, expectedSvgLines, assertStats? })`** — asserts a measurement's panel row, its SVG text, and its `cachedStats` in one call. Build the expected lines with `measurementTextFormatters`. Seeds: `tests/Length.spec.ts`, `tests/Probe.spec.ts`. Source: `tests/utils/expectAnnotationText.ts`.
+- **`getSegmentStats({ page, segmentIndex })`** — call it before clicking a painted labelmap segment's row: the jump needs the segment's center, which Cornerstone computes in the background. Seed: `tests/ManuallyDrawnSegmentation.spec.ts`.
 - **`subscribeToMeasurementAdded(page)`** — returns `{ waitFired(timeout?), unsubscribe() }`. Use in freehand/livewire/spline specs to assert the event fired. Always wrap in `try { ... } finally { await sub.unsubscribe() }` so a failing assertion doesn't leak the listener across tests.
 - **`attemptAction(action, attempts?, delay?)`** — retries a flaky async action without masking real failures. Mainly used to stabilize 3D scenes (`attemptAction(() => reduce3DViewportSize(page), 10, 100)`).
 
 
@@ -42,6 +42,7 @@ export const CustomSegmentStatisticsHeader = ({
                 variant="ghost"
                 size="sm"
                 className="text-primary flex items-center gap-2"
+                dataCY="segment-bidirectional-compute"
                 onClick={() => {
                   commandsManager.run('runSegmentBidirectional', {
                     segmentationId,
@@ -76,10 +77,10 @@ export const CustomSegmentStatisticsHeader = ({
     <div className="-mt-2 space-y-2">
       <div className="flex items-center justify-between">
         <div className="text-foreground">
-          <div>
+          <div data-cy="segment-bidirectional-length">
             L: {roundNumber(max)} {unit}
           </div>
-          <div>
+          <div data-cy="segment-bidirectional-width">
             W: {roundNumber(min)} {unit}
           </div>
         </div>
@@ -117,6 +118,7 @@ export const CustomSegmentStatisticsHeader = ({
               <Button
                 variant="ghost"
                 size="icon"
+                dataCY="segment-bidirectional-jump"
                 onClick={() => {
                   if (bidirectional.annotationUID) {
                     commandsManager.run('jumpToMeasurement', {
 
@@ -65,7 +65,6 @@ test('should keep a freehand contour drawn on a slice after navigating away and
 
   //Force navigate to first slice
   await activeViewport.sliceNavigation.toFirstSlice();
-  await waitForViewportsRendered(page);
 
   const sliceIndicator = activeViewport.overlayText.bottomRight.instanceNumber;
   const drawingSliceInfo = await sliceIndicator.innerText();
@@ -86,13 +85,11 @@ test('should keep a freehand contour drawn on a slice after navigating away and
 
   //Navigate to last slice
   await activeViewport.sliceNavigation.toLastSlice();
-  await waitForViewportsRendered(page);
   await expect(sliceIndicator, 'Expected to leave drawing slice').not.toHaveText(drawingSliceInfo);
   await expect(paths, 'Expected no contour on the other slice').toHaveCount(0);
 
   // Come back to first slice
   await activeViewport.sliceNavigation.toFirstSlice();
-  await waitForViewportsRendered(page);
   await expect(sliceIndicator, 'Expected to return to drawing slice').toHaveText(drawingSliceInfo);
   await expect(paths, 'Expected the contour to re-render on the drawing slice').toHaveCount(1);
   await expect(paths.nth(0), 'Expected the persisted contour to be visible').toBeVisible();
 
@@ -6,7 +6,6 @@ import {
   screenShotPaths,
   test,
   visitStudy,
-  waitForViewportsRendered,
   withKeyHeld,
 } from './utils';
 
@@ -108,7 +107,6 @@ test('should keep a completed Livewire contour segmentation after navigating awa
 
   // Navigate away: the contour only renders on the slice it was drawn on.
   await activeViewport.sliceNavigation.toLastSlice();
-  await waitForViewportsRendered(page);
   await expect(paths, 'Expected no contour paths on the last slice').toHaveCount(0);
 
   // Clicking Segment 1 activates it and jumps the viewport back to its contour.