diff --git a/.agents/skills/ohif-test-agent/SKILL.md b/.agents/skills/ohif-test-agent/SKILL.md
index dea38c445..650e82764 100644
--- a/.agents/skills/ohif-test-agent/SKILL.md
+++ b/.agents/skills/ohif-test-agent/SKILL.md
@@ -17,7 +17,7 @@ This package follows the agentskills.io SKILL.md convention. `SKILL.md` is the e
 2. **Read the seed spec.** Consult [references/patterns-by-feature.md](references/patterns-by-feature.md) to find the canonical existing spec for that area. Read it end-to-end before writing. This is the single most important step — OHIF specs follow consistent idioms that are easier to mimic than to reconstruct from first principles. (This mirrors Playwright's own agent guidance: use seed tests as the example for generated tests.)
 3. **Scaffold from the template.** Start from [assets/spec-template.ts](assets/spec-template.ts) — or copy the seed spec and adapt.
 4. **Look up specifics in the source, not from memory.** The reference files [page-objects.md](references/page-objects.md) and [utilities.md](references/utilities.md) capture the **stable rules** — fixture keys, import conventions, access idioms, the reasons certain things trip people up. They deliberately do not enumerate methods. For the current method surface or a utility's exact signature, open the relevant file under `tests/pages/` or `tests/utils/` — the source evolves, and the source is always right. The seed spec you picked in step 2 is usually the fastest second source, because it co-evolves with the API.
-5. **Run the test when execution is available.** `yarn test:e2e:ci` runs the whole suite, but for iteration use `yarn playwright test tests/YourNew.spec.ts` (or via the Playwright VS Code extension).
+5. **Run the test when execution is available.** `pnpm run test:e2e:ci` runs the whole suite, but for iteration use `TEST_ENV=true pnpm exec playwright test tests/YourNew.spec.ts` (or the Playwright VS Code extension). Invoke Playwright directly for targeted flags; `pnpm run test:e2e -- ...` inserts a `--` separator that can prevent Playwright from parsing options such as `--update-snapshots` and `--reporter`.
 6. **If runtime execution is unavailable, do static validation.** Validate import source, fixture keys, normalized viewport usage, UID/mode pairing, and hydration/tracking prompt handling. Then report clearly that execution was not performed.
 7. **If it fails, triage before debugging.** Use [references/failure-triage.md](references/failure-triage.md) — most OHIF test failures are timing / hydration, not real regressions.
 
diff --git a/.agents/skills/ohif-test-agent/references/failure-triage.md b/.agents/skills/ohif-test-agent/references/failure-triage.md
index b11b90dc5..419f18d7c 100644
--- a/.agents/skills/ohif-test-agent/references/failure-triage.md
+++ b/.agents/skills/ohif-test-agent/references/failure-triage.md
@@ -6,9 +6,9 @@ Before debugging, classify. Most OHIF test failures are timing or hydration —
 |----------|---------|-----|
 | Timing | Element not visible, action timeout | Add / increase the `delay` param of `visitStudy`; for actions that re-render viewports, use `waitForViewportRenderCycle(page)` (started before the action) instead of `waitForTimeout`; wrap the assertion in `expect.toPass({ timeout })` |
 | Selector | Element not found | Verify `data-cy` on the target; confirm the panel is open (`toggle()` / `select()` before interacting); check for capital `D` in `DOMOverlayPageObject` when destructuring |
-| Hydration | Segmentation/RT not interactive | Ensure the `segmentationHydration.yes.click()` fired; add `waitForTimeout(3000)` after `loadSeriesByModality('SEG'\|'RTSTRUCT'\|'SR')` |
+| Hydration | Segmentation/RT/SR not interactive | Ensure the `segmentationHydration.yes.click()` fired; wait for an observable hydrated state such as measurement/segment rows or the target series overlay, then wait for the resulting viewport render |
 | Data | Study not found, empty viewport | Confirm the UID is in the canonical list (see [patterns-by-feature.md](patterns-by-feature.md)); confirm the mode supports the feature (segmentation tools aren't in `viewer` mode) |
-| Visual drift | Screenshot mismatch but feature works | Have a human review the diff, then regenerate the baseline with `yarn playwright test --update-snapshots`. Do not adjust `maxDiffPixelRatio` or `threshold` to make a failing screenshot pass. |
+| Visual drift | Screenshot mismatch but feature works | Have a human review the diff, then regenerate the baseline with `TEST_ENV=true pnpm exec playwright test --update-snapshots`. Do not adjust `maxDiffPixelRatio` or `threshold` to make a failing screenshot pass. |
 | Real regression | Feature is actually broken | Report as a bug — this is the test doing its job |
 
 ## Prefer render-cycle waits over sleeps
@@ -33,6 +33,8 @@ Symptom: the test fails inside `waitForAnyViewportNeedsRender` after 5s, with th
 
 Don't react by raising the cycle's timeout — the transition isn't coming. Replace the cycle wrapper with an auto-retrying DOM/SVG assertion, or `expect.toPass({ timeout })` around the assertion block.
 
+An immediate `waitForViewportsRendered(page)` can also return too early when a click dispatches work through an asynchronous state machine: the old viewport is already `rendered` before the new series or annotations are applied. In that case, first wait for the target state (for example, hydrated measurement rows or the expected series overlay), then call `waitForViewportsRendered(page)` to settle that state's render.
+
 ## The `toPass` pattern
 
 When an assertion needs to wait for async render / propagation:
@@ -64,7 +66,7 @@ await press({ page, key: 'ArrowDown', nTimes: 50 }); // object param, not (page,
 Screenshots live under `tests/screenshots/chromium/<testFilePath>/`. To accept new output as the baseline:
 
 ```sh
-yarn playwright test tests/YourSpec.spec.ts --update-snapshots
+TEST_ENV=true pnpm exec playwright test tests/YourSpec.spec.ts --update-snapshots
 ```
 
 Review the resulting PNGs carefully — an agent-accepted baseline that's subtly wrong is worse than a failing test.
diff --git a/extensions/cornerstone-dicom-pmap/package.json b/extensions/cornerstone-dicom-pmap/package.json
index 8a8ba8671..559eef5bb 100644
--- a/extensions/cornerstone-dicom-pmap/package.json
+++ b/extensions/cornerstone-dicom-pmap/package.json
@@ -41,8 +41,8 @@
   },
   "dependencies": {
     "@babel/runtime": "7.29.7",
-    "@cornerstonejs/adapters": "5.4.13",
-    "@cornerstonejs/core": "5.4.13",
+    "@cornerstonejs/adapters": "5.4.17",
+    "@cornerstonejs/core": "5.4.17",
     "@kitware/vtk.js": "35.5.3"
   },
   "devDependencies": {
diff --git a/extensions/cornerstone-dicom-seg/package.json b/extensions/cornerstone-dicom-seg/package.json
index daa8add22..beb970127 100644
--- a/extensions/cornerstone-dicom-seg/package.json
+++ b/extensions/cornerstone-dicom-seg/package.json
@@ -41,8 +41,8 @@
   },
   "dependencies": {
     "@babel/runtime": "7.29.7",
-    "@cornerstonejs/adapters": "5.4.13",
-    "@cornerstonejs/core": "5.4.13",
+    "@cornerstonejs/adapters": "5.4.17",
+    "@cornerstonejs/core": "5.4.17",
     "@kitware/vtk.js": "35.5.3"
   },
   "devDependencies": {
diff --git a/extensions/cornerstone-dicom-seg/src/commandsModule.ts b/extensions/cornerstone-dicom-seg/src/commandsModule.ts
index 43ed2dff8..b70f60071 100644
--- a/extensions/cornerstone-dicom-seg/src/commandsModule.ts
+++ b/extensions/cornerstone-dicom-seg/src/commandsModule.ts
@@ -6,7 +6,11 @@ import { adaptersRT, adaptersSEG } from '@cornerstonejs/adapters';
 import { createReportDialogPrompt, useUIStateStore } from '@ohif/extension-default';
 
 import PROMPT_RESPONSES from '../../default/src/utils/_shared/PROMPT_RESPONSES';
-import { getSegmentationSaveOptions } from './utils/segmentationConfig';
+import {
+  getSegmentationSaveOptions,
+  LABELMAP_SEG_SOP_CLASS_UID,
+  BITMAP_SEG_SOP_CLASS_UID,
+} from './utils/segmentationConfig';
 
 const getTargetViewport = ({ viewportId, viewportGridService }) => {
   const { viewports, activeViewportId } = viewportGridService.getState();
@@ -29,7 +33,6 @@ const {
   },
 } = adaptersRT;
 
-
 const commandsModule = ({
   servicesManager,
   extensionManager,
@@ -105,57 +108,69 @@ const commandsModule = ({
         : extensionManager.getActiveDataSourceDefinition();
       const dataSourceStoreOverride = dataSourceDefinition?.configuration?.segmentation?.store;
 
-      const { imageIds } = segmentation.representationData.Labelmap;
+      const labelmapData = segmentation.representationData.Labelmap;
 
-      const segImages = imageIds.map(imageId => cache.getImage(imageId));
-      const referencedImages = segImages.map((segImage, sliceIndex) => {
-        const referencedImage = cache.getImage(segImage.referencedImageId);
+      // Build a labelmap3D (one labelmaps2D entry per source slice) from a list of
+      // derived labelmap image ids. When `referencedImageIds` is supplied (the
+      // multi-layer/overlap path) each frame is indexed by its source slice so the
+      // layers align to the same frames; otherwise frames are sequential (the legacy
+      // single-layer behavior, kept byte-identical).
+      const buildLabelmap3D = (segImageIds: string[], metadata, referencedImageIds?: string[]) => {
+        const segImages = segImageIds.map(imageId => cache.getImage(imageId));
+        const labelmaps2D = [];
 
-        if (!referencedImage) {
-          throw new Error(
-            `Referenced source image not in cache for segmentation slice ${sliceIndex} ` +
-              `(referencedImageId: ${segImage.referencedImageId}). Ensure the referenced series is fully loaded before storing.`
-          );
-        }
+        // Map each source imageId to its frame index once (O(n)) so the per-slice lookup
+        // below is O(1) — avoids the O(slices^2) indexOf scan on the multi-layer path.
+        const referencedFrameIndexById = referencedImageIds
+          ? new Map(referencedImageIds.map((imageId, index) => [imageId, index]))
+          : undefined;
 
-        return referencedImage;
-      });
+        let z = 0;
 
-      const labelmaps2D = [];
+        for (const segImage of segImages) {
+          const segmentsOnLabelmap = new Set();
+          const pixelData = segImage.getPixelData();
+          const { rows, columns } = segImage;
 
-      let z = 0;
-
-      for (const segImage of segImages) {
-        const segmentsOnLabelmap = new Set();
-        const pixelData = segImage.getPixelData();
-        const { rows, columns } = segImage;
-
-        // Use a single pass through the pixel data
-        for (let i = 0; i < pixelData.length; i++) {
-          const segment = pixelData[i];
-          if (segment !== 0) {
-            segmentsOnLabelmap.add(segment);
+          // Use a single pass through the pixel data
+          for (let i = 0; i < pixelData.length; i++) {
+            const segment = pixelData[i];
+            if (segment !== 0) {
+              segmentsOnLabelmap.add(segment);
+            }
           }
+
+          const frameIndex = referencedFrameIndexById
+            ? referencedFrameIndexById.get(segImage.referencedImageId) ?? -1
+            : z++;
+
+          if (frameIndex < 0) {
+            continue;
+          }
+
+          labelmaps2D[frameIndex] = {
+            segmentsOnLabelmap: Array.from(segmentsOnLabelmap),
+            pixelData,
+            rows,
+            columns,
+          };
         }
 
-        labelmaps2D[z++] = {
-          segmentsOnLabelmap: Array.from(segmentsOnLabelmap),
-          pixelData,
-          rows,
-          columns,
+        const allSegmentsOnLabelmap = labelmaps2D
+          .filter(Boolean)
+          .map(labelmap => labelmap.segmentsOnLabelmap);
+
+        return {
+          segmentsOnLabelmap: Array.from(new Set(allSegmentsOnLabelmap.flat())),
+          metadata,
+          labelmaps2D,
         };
-      }
-
-      const allSegmentsOnLabelmap = labelmaps2D.map(labelmap => labelmap.segmentsOnLabelmap);
-
-      const labelmap3D = {
-        segmentsOnLabelmap: Array.from(new Set(allSegmentsOnLabelmap.flat())),
-        metadata: [],
-        labelmaps2D,
       };
 
+      // Segment metadata (shared across all layers).
       const segmentationInOHIF = segmentationService.getSegmentation(segmentationId);
       const representations = segmentationService.getRepresentationsForSegmentation(segmentationId);
+      const metadata = [];
 
       Object.entries(segmentationInOHIF.segments).forEach(([segmentIndex, segment]) => {
         // segmentation service already has a color for each segment
@@ -176,7 +191,7 @@ const commandsModule = ({
           color.slice(0, 3).map(value => value / 255)
         ).map(value => Math.round(value));
 
-        const segmentMetadata = {
+        metadata[segmentIndex] = {
           SegmentNumber: segmentIndex.toString(),
           SegmentLabel: label,
           SegmentAlgorithmType: segment?.algorithmType || 'MANUAL',
@@ -193,14 +208,76 @@ const commandsModule = ({
             CodeMeaning: 'Tissue',
           },
         };
-        labelmap3D.metadata[segmentIndex] = segmentMetadata;
       });
 
-      const generatedSegmentation = generateSegmentation(referencedImages, labelmap3D, metaData, {
+      // Multi-layer (overlapping) SEGs register one labelmap layer per conflict-free
+      // group. Export each layer as its own labelmap3D against the UNIQUE referenced
+      // source series, so cornerstone writes overlapping segments as separate frames
+      // that reference the same source slice (the DICOM SEG overlap encoding). The
+      // cs3D adapter's fillSegmentation accepts an array of labelmap3D for exactly
+      // this. Single-layer SEGs keep the original single-labelmap3D path unchanged.
+      const layers = labelmapData.labelmaps ? Object.values(labelmapData.labelmaps) : undefined;
+
+      // The referenced source images must be fully loaded (in cache) before we can
+      // build the SEG dataset against them; fail loudly rather than passing undefined
+      // frames to the adapter.
+      const resolveReferencedImage = (referencedImageId: string, sliceIndex: number) => {
+        const referencedImage = cache.getImage(referencedImageId);
+        if (!referencedImage) {
+          throw new Error(
+            `Referenced source image not in cache for segmentation slice ${sliceIndex} ` +
+              `(referencedImageId: ${referencedImageId}). Ensure the referenced series is fully loaded before storing.`
+          );
+        }
+        return referencedImage;
+      };
+
+      let referencedImages;
+      let labelmaps3D;
+
+      if (layers && layers.length > 1) {
+        const referencedImageIds =
+          layers[0].referencedImageIds ?? labelmapData.referencedImageIds ?? [];
+        referencedImages = referencedImageIds.map(resolveReferencedImage);
+        labelmaps3D = layers.map(layer =>
+          buildLabelmap3D(layer.imageIds ?? [], metadata, referencedImageIds)
+        );
+      } else {
+        const { imageIds } = labelmapData;
+        const segImages = imageIds.map(imageId => cache.getImage(imageId));
+        referencedImages = segImages.map((image, sliceIndex) =>
+          resolveReferencedImage(image.referencedImageId, sliceIndex)
+        );
+        labelmaps3D = buildLabelmap3D(imageIds, metadata);
+      }
+
+      const saveOptions = {
         predecessorImageId,
         ...getSegmentationSaveOptions(customizationService, dataSourceStoreOverride),
         ...generateOptions,
-      });
+      };
+
+      // A LABELMAP SEG frame stores a single label per voxel, so the labelmap
+      // encoder cannot represent overlapping segments — it keeps only the last
+      // layer written to each voxel. Overlapping segmentations arrive here as
+      // multiple layers, so switch those to the binary SEG encoding, which
+      // writes overlapping segments as separate frames referencing the same
+      // source slice.
+      const hasOverlappingLayers = Boolean(layers && layers.length > 1);
+      if (hasOverlappingLayers && saveOptions.sopClassUID === LABELMAP_SEG_SOP_CLASS_UID) {
+        console.warn(
+          'generateSegmentation: overlapping segments cannot be stored as a LABELMAP SEG; ' +
+            'switching to the binary SEG encoding for this store.'
+        );
+        saveOptions.sopClassUID = BITMAP_SEG_SOP_CLASS_UID;
+      }
+
+      const generatedSegmentation = generateSegmentation(
+        referencedImages,
+        labelmaps3D,
+        metaData,
+        saveOptions
+      );
 
       return generatedSegmentation;
     },
@@ -266,9 +343,7 @@ const commandsModule = ({
       }
 
       const defaultFileName =
-        modality === 'RTSTRUCT'
-          ? `rtss-${segmentationId}.dcm`
-          : `${label || 'segmentation'}.dcm`;
+        modality === 'RTSTRUCT' ? `rtss-${segmentationId}.dcm` : `${label || 'segmentation'}.dcm`;
 
       const storeFn = commandsManager.runCommand('createStoreFunction', {
         dataSource: dataSourceName,
diff --git a/extensions/cornerstone-dicom-sr/package.json b/extensions/cornerstone-dicom-sr/package.json
index e408d9ae3..d10b8f7ee 100644
--- a/extensions/cornerstone-dicom-sr/package.json
+++ b/extensions/cornerstone-dicom-sr/package.json
@@ -40,9 +40,9 @@
   },
   "dependencies": {
     "@babel/runtime": "7.29.7",
-    "@cornerstonejs/adapters": "5.4.13",
-    "@cornerstonejs/core": "5.4.13",
-    "@cornerstonejs/tools": "5.4.13",
+    "@cornerstonejs/adapters": "5.4.17",
+    "@cornerstonejs/core": "5.4.17",
+    "@cornerstonejs/tools": "5.4.17",
     "classnames": "2.5.1"
   },
   "devDependencies": {
diff --git a/extensions/cornerstone-dicom-sr/src/utils/hydrateStructuredReport.ts b/extensions/cornerstone-dicom-sr/src/utils/hydrateStructuredReport.ts
index b934f6562..4d6a8a1a8 100644
--- a/extensions/cornerstone-dicom-sr/src/utils/hydrateStructuredReport.ts
+++ b/extensions/cornerstone-dicom-sr/src/utils/hydrateStructuredReport.ts
@@ -142,15 +142,22 @@ export default function hydrateStructuredReport(
     hydratableMeasurementsInSR,
     sopInstanceUIDToImageId
   );
+  const displaySetsByFrameOfReferenceUID = new Map();
 
   for (const FrameOfReferenceUID of frameOfReferenceUIDs) {
     const displaySetsFOR = displaySetService.getDisplaySetsBy(
       ds => ds.FrameOfReferenceUID === FrameOfReferenceUID && !ds.isDerivedDisplaySet
     );
-    const ds = chooseDisplaySet(displaySetsFOR, FrameOfReferenceUID);
+    const ds = getReferencedDisplaySet(
+      displaySet,
+      displaySetsFOR,
+      FrameOfReferenceUID,
+      displaySetService
+    );
     if (!ds) {
       continue;
     }
+    displaySetsByFrameOfReferenceUID.set(FrameOfReferenceUID, ds);
     if (!SeriesInstanceUIDs.includes(ds.SeriesInstanceUID)) {
       SeriesInstanceUIDs.push(ds.SeriesInstanceUID);
     }
@@ -174,7 +181,7 @@ export default function hydrateStructuredReport(
     const imageId = sopInstanceUIDToImageId[`${toolData.sopInstanceUid}:${frameNumber}`];
 
     if (!imageId) {
-      return getReferenceData3D(toolData, servicesManager);
+      return getReferenceData3D(toolData, servicesManager, displaySetsByFrameOfReferenceUID);
     }
 
     const instance = metaData.get('instance', imageId);
@@ -316,21 +323,60 @@ function chooseDisplaySet(displaySets, reference) {
     console.warn('No display set found for', reference);
     return;
   }
-  if (displaySets.length === 1) {
-    return displaySets[0];
+  const sortedDisplaySets = OHIF.utils.sortDisplaySetsCopy(displaySets);
+  if (sortedDisplaySets.length === 1) {
+    return sortedDisplaySets[0];
   }
-  const volumeDs = displaySets.find(ds => ds.isReconstructable);
+  const volumeDs = sortedDisplaySets.find(ds => ds.isReconstructable);
   if (volumeDs) {
     return volumeDs;
   }
-  return displaySets[0];
+  return sortedDisplaySets[0];
+}
+
+/**
+ * SCOORD3D only identifies a frame of reference, so many series can be valid
+ * candidates. The SR loader has already selected and recorded a stable display
+ * set for each measurement. Reuse that selection during hydration so the
+ * viewport series and annotation volume cannot depend on display-set load order.
+ */
+function getReferencedDisplaySet(
+  srDisplaySet,
+  displaySets,
+  FrameOfReferenceUID,
+  displaySetService
+) {
+  const referencedDisplaySetInstanceUID = srDisplaySet.measurements?.find(measurement =>
+    measurement.coords?.some(
+      coord =>
+        coord.ValueType === 'SCOORD3D' &&
+        coord.ReferencedFrameOfReferenceSequence === FrameOfReferenceUID
+    )
+  )?.displaySetInstanceUID;
+
+  const referencedDisplaySet = referencedDisplaySetInstanceUID
+    ? displaySetService.getDisplaySetByUID(referencedDisplaySetInstanceUID)
+    : undefined;
+
+  if (
+    referencedDisplaySet?.FrameOfReferenceUID === FrameOfReferenceUID &&
+    !referencedDisplaySet.isDerivedDisplaySet
+  ) {
+    return referencedDisplaySet;
+  }
+
+  return chooseDisplaySet(displaySets, FrameOfReferenceUID);
 }
 
 /**
  * Gets the additional reference data appropriate for a 3d reference.
  * This will choose a volume id, frame of reference and a plane restriction.
  */
-function getReferenceData3D(toolData, servicesManager: Types.ServicesManager) {
+function getReferenceData3D(
+  toolData,
+  servicesManager: Types.ServicesManager,
+  displaySetsByFrameOfReferenceUID = new Map()
+) {
   const { FrameOfReferenceUID } = toolData.annotation.metadata;
   const { points } = toolData.annotation.data.handles;
   const { displaySetService } = servicesManager.services;
@@ -342,7 +388,9 @@ function getReferenceData3D(toolData, servicesManager: Types.ServicesManager) {
       FrameOfReferenceUID,
     };
   }
-  const ds = chooseDisplaySet(displaySetsFOR, toolData.annotation);
+  const ds =
+    displaySetsByFrameOfReferenceUID.get(FrameOfReferenceUID) ||
+    chooseDisplaySet(displaySetsFOR, toolData.annotation);
   const cameraView = chooseCameraView(ds, points);
 
   const viewReference = {
diff --git a/extensions/cornerstone-dynamic-volume/package.json b/extensions/cornerstone-dynamic-volume/package.json
index bee6c9568..953135e06 100644
--- a/extensions/cornerstone-dynamic-volume/package.json
+++ b/extensions/cornerstone-dynamic-volume/package.json
@@ -45,8 +45,8 @@
   },
   "dependencies": {
     "@babel/runtime": "7.29.7",
-    "@cornerstonejs/core": "5.4.13",
-    "@cornerstonejs/tools": "5.4.13",
+    "@cornerstonejs/core": "5.4.17",
+    "@cornerstonejs/tools": "5.4.17",
     "classnames": "2.5.1"
   },
   "devDependencies": {
diff --git a/extensions/cornerstone/package.json b/extensions/cornerstone/package.json
index e6a5bfa56..3b74f7f42 100644
--- a/extensions/cornerstone/package.json
+++ b/extensions/cornerstone/package.json
@@ -38,7 +38,7 @@
     "@cornerstonejs/codec-libjpeg-turbo-8bit": "1.2.2",
     "@cornerstonejs/codec-openjpeg": "1.3.0",
     "@cornerstonejs/codec-openjph": "2.4.7",
-    "@cornerstonejs/dicom-image-loader": "5.4.13",
+    "@cornerstonejs/dicom-image-loader": "5.4.17",
     "@ohif/core": "workspace:*",
     "@ohif/extension-default": "workspace:*",
     "@ohif/ui": "workspace:*",
@@ -52,13 +52,13 @@
   },
   "dependencies": {
     "@babel/runtime": "7.29.7",
-    "@cornerstonejs/adapters": "5.4.13",
-    "@cornerstonejs/ai": "5.4.13",
-    "@cornerstonejs/core": "5.4.13",
-    "@cornerstonejs/labelmap-interpolation": "5.4.13",
-    "@cornerstonejs/metadata": "5.4.13",
-    "@cornerstonejs/polymorphic-segmentation": "5.4.13",
-    "@cornerstonejs/tools": "5.4.13",
+    "@cornerstonejs/adapters": "5.4.17",
+    "@cornerstonejs/ai": "5.4.17",
+    "@cornerstonejs/core": "5.4.17",
+    "@cornerstonejs/labelmap-interpolation": "5.4.17",
+    "@cornerstonejs/metadata": "5.4.17",
+    "@cornerstonejs/polymorphic-segmentation": "5.4.17",
+    "@cornerstonejs/tools": "5.4.17",
     "@icr/polyseg-wasm": "0.4.0",
     "@itk-wasm/morphological-contour-interpolation": "1.1.0",
     "@kitware/vtk.js": "35.5.3",
diff --git a/extensions/cornerstone/src/Viewport/Overlays/CustomizableViewportOverlay.tsx b/extensions/cornerstone/src/Viewport/Overlays/CustomizableViewportOverlay.tsx
index e9a91a920..557ba77ee 100644
--- a/extensions/cornerstone/src/Viewport/Overlays/CustomizableViewportOverlay.tsx
+++ b/extensions/cornerstone/src/Viewport/Overlays/CustomizableViewportOverlay.tsx
@@ -1,7 +1,7 @@
 import React, { useCallback, useEffect, useMemo, useState } from 'react';
 import { vec3 } from 'gl-matrix';
 import PropTypes from 'prop-types';
-import { metaData, Enums, utilities, eventTarget } from '@cornerstonejs/core';
+import { metaData, Enums, eventTarget } from '@cornerstonejs/core';
 import { Enums as csToolsEnums, UltrasoundPleuraBLineTool } from '@cornerstonejs/tools';
 import type { ImageSliceData } from '@cornerstonejs/core/types';
 import { ViewportOverlay, formatDICOMDate } from '@ohif/ui-next';
@@ -9,6 +9,8 @@ import type { InstanceMetadata } from '@ohif/core/src/types';
 import { formatDICOMTime, formatNumberPrecision } from './utils';
 import { utils } from '@ohif/core';
 import { StackViewportData, VolumeViewportData } from '../../types/CornerstoneCacheService';
+import { getViewportAdapter } from '../../services/ViewportService/adapter';
+import { getViewportDataShapeType } from '../../utils/viewportDataShape';
 
 import './CustomizableViewportOverlay.css';
 import { useViewportRendering } from '../../hooks';
@@ -269,7 +271,7 @@ function getDisplaySets(viewportData, displaySetService) {
 const getInstanceNumber = (viewportData, viewportId, imageIndex, cornerstoneViewportService) => {
   let instanceNumber;
 
-  switch (viewportData.viewportType) {
+  switch (getViewportDataShapeType(viewportData)) {
     case Enums.ViewportType.STACK:
       instanceNumber = _getInstanceNumberFromStack(viewportData, imageIndex);
       break;
@@ -336,8 +338,11 @@ function _getInstanceNumberFromVolume(
     return;
   }
 
-  const camera = cornerstoneViewport.getCamera();
-  const { viewPlaneNormal } = camera;
+  const viewPlaneNormal = getViewportAdapter(cornerstoneViewport).getViewPlaneNormal();
+
+  if (!viewPlaneNormal) {
+    return;
+  }
   // checking if camera is looking at the acquisition plane (defined by the direction on the volume)
 
   const scanAxisNormal = direction.slice(6, 9);
diff --git a/extensions/cornerstone/src/Viewport/Overlays/ViewportImageScrollbar.tsx b/extensions/cornerstone/src/Viewport/Overlays/ViewportImageScrollbar.tsx
index b7d3f004a..11b4d4009 100644
--- a/extensions/cornerstone/src/Viewport/Overlays/ViewportImageScrollbar.tsx
+++ b/extensions/cornerstone/src/Viewport/Overlays/ViewportImageScrollbar.tsx
@@ -1,8 +1,9 @@
 import React, { useEffect } from 'react';
 import PropTypes from 'prop-types';
-import { Enums, utilities as csUtils } from '@cornerstonejs/core';
+import { utilities as csUtils } from '@cornerstonejs/core';
 import { ImageScrollbar } from '@ohif/ui-next';
 import { isVolume3DViewportType } from '../../utils/getLegacyViewportType';
+import { getSliceEventName, getViewportSliceCount } from '../../utils/viewportDataShape';
 
 function CornerstoneImageScrollbar({
   viewportData,
@@ -47,10 +48,10 @@ function CornerstoneImageScrollbar({
 
     try {
       const imageIndex = viewport.getCurrentImageIdIndex();
-      const numberOfSlices = viewport.getNumberOfSlices();
+      const numberOfSlices = getViewportSliceCount(viewportData, viewport);
 
       setImageSliceData({
-        imageIndex: imageIndex,
+        imageIndex,
         numberOfSlices,
       });
     } catch (error) {
@@ -62,11 +63,7 @@ function CornerstoneImageScrollbar({
     if (!viewportData) {
       return;
     }
-    const { viewportType } = viewportData;
-    const eventId =
-      (viewportType === Enums.ViewportType.STACK && Enums.Events.STACK_NEW_IMAGE) ||
-      (viewportType === Enums.ViewportType.ORTHOGRAPHIC && Enums.Events.VOLUME_NEW_IMAGE) ||
-      Enums.Events.IMAGE_RENDERED;
+    const eventId = getSliceEventName(viewportData);
 
     const updateIndex = event => {
       const viewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
diff --git a/extensions/cornerstone/src/Viewport/Overlays/ViewportOrientationMarkers.tsx b/extensions/cornerstone/src/Viewport/Overlays/ViewportOrientationMarkers.tsx
index c390308b8..19eb04ac1 100644
--- a/extensions/cornerstone/src/Viewport/Overlays/ViewportOrientationMarkers.tsx
+++ b/extensions/cornerstone/src/Viewport/Overlays/ViewportOrientationMarkers.tsx
@@ -6,6 +6,7 @@ import { vec3 } from 'gl-matrix';
 
 import './ViewportOrientationMarkers.css';
 import { useViewportRendering } from '../../hooks';
+import { getViewportDataShapeType } from '../../utils/viewportDataShape';
 const { getOrientationStringLPS, invertOrientationStringLPS } = utilities.orientation;
 
 function ViewportOrientationMarkers({
@@ -46,7 +47,9 @@ function ViewportOrientationMarkers({
       return '';
     }
 
-    if (viewportData.viewportType === 'stack') {
+    // Use the persisted data shape, not viewportType: a native stack reports
+    // PLANAR_NEXT, which would skip this synthetic-IOP default-cosine guard.
+    if (getViewportDataShapeType(viewportData) === Enums.ViewportType.STACK) {
       const imageIndex = imageSliceData.imageIndex;
       const imageId = viewportData.data[0].imageIds?.[imageIndex];
 
diff --git a/extensions/cornerstone/src/Viewport/Overlays/ViewportSliceProgressScrollbar/helpers.ts b/extensions/cornerstone/src/Viewport/Overlays/ViewportSliceProgressScrollbar/helpers.ts
index 0022ba277..783668ed8 100644
--- a/extensions/cornerstone/src/Viewport/Overlays/ViewportSliceProgressScrollbar/helpers.ts
+++ b/extensions/cornerstone/src/Viewport/Overlays/ViewportSliceProgressScrollbar/helpers.ts
@@ -1,6 +1,6 @@
-import { Enums } from '@cornerstonejs/core';
 import { ViewportData } from './types';
 import { isVolume3DViewportType } from '../../../utils/getLegacyViewportType';
+import { getViewportAdapter } from '../../../services/ViewportService/adapter';
 
 export function getImageIndexFromEvent(event): number | undefined {
   const { imageIndex, newImageIdIndex = imageIndex, imageIdIndex } = event.detail;
@@ -24,12 +24,17 @@ export function isProgressFullMode(viewportData: ViewportData, viewport): boolea
     return false;
   }
 
-  if (viewportData.viewportType === Enums.ViewportType.STACK) {
+  // A stack renders the full progress UI; an acquisition-plane volume is the
+  // volume-mode equivalent. The adapter classifies both lanes (legacy by
+  // viewport type / isInAcquisitionPlane; native by content mode + view-state
+  // orientation, since PLANAR_NEXT collapses the runtime type).
+  const adapter = getViewportAdapter(viewport);
+  const shape = adapter.getShape();
+  if (shape === 'stack') {
     return true;
   }
-
-  if (viewportData.viewportType === Enums.ViewportType.ORTHOGRAPHIC) {
-    return !!viewport.isInAcquisitionPlane?.();
+  if (shape === 'volume') {
+    return adapter.isInAcquisitionPlane();
   }
 
   return false;
diff --git a/extensions/cornerstone/src/Viewport/Overlays/ViewportSliceProgressScrollbar/hooks.ts b/extensions/cornerstone/src/Viewport/Overlays/ViewportSliceProgressScrollbar/hooks.ts
index a0ca18448..6943d96da 100644
--- a/extensions/cornerstone/src/Viewport/Overlays/ViewportSliceProgressScrollbar/hooks.ts
+++ b/extensions/cornerstone/src/Viewport/Overlays/ViewportSliceProgressScrollbar/hooks.ts
@@ -1,12 +1,8 @@
 import { useEffect, useRef, useState } from 'react';
-import {
-  cache as cornerstoneCache,
-  Enums,
-  eventTarget,
-  utilities,
-} from '@cornerstonejs/core';
+import { cache as cornerstoneCache, Enums, eventTarget, utilities } from '@cornerstonejs/core';
 import { useByteArray } from '@ohif/ui-next';
 import { isVolume3DViewportType } from '../../../utils/getLegacyViewportType';
+import { getSliceEventName, getViewportSliceCount } from '../../../utils/viewportDataShape';
 import { getImageIdFromCacheEvent, getImageIndexFromEvent, isProgressFullMode } from './helpers';
 import { ImageSliceData, ViewportData } from './types';
 
@@ -97,26 +93,48 @@ export function useViewportSliceSync({
       return;
     }
 
-    const viewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
-    if (viewport && !isVolume3DViewportType(viewport)) {
+    // Last values we pushed, so re-seeding on camera changes does not churn React
+    // state on pure pan/zoom (which keep the slice geometry unchanged).
+    const lastSlice = { imageIndex: -1, numberOfSlices: -1 };
+
+    const pushSliceData = (imageIndex: number, numberOfSlices: number) => {
+      if (imageIndex === lastSlice.imageIndex && numberOfSlices === lastSlice.numberOfSlices) {
+        return;
+      }
+      lastSlice.imageIndex = imageIndex;
+      lastSlice.numberOfSlices = numberOfSlices;
+      setImageSliceData({ imageIndex, numberOfSlices });
+    };
+
+    // Seeds the shared slice state from the live viewport. Re-run on the initial
+    // effect and on camera/orientation changes (below).
+    const syncFromViewport = () => {
+      const viewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
+      if (!viewport || isVolume3DViewportType(viewport)) {
+        return;
+      }
       try {
         const currentImageIndex = viewport.getCurrentImageIdIndex();
-        const currentNumberOfSlices = viewport.getNumberOfSlices();
+        const currentNumberOfSlices = getViewportSliceCount(viewportData, viewport);
 
-        setImageSliceData({
-          imageIndex: currentImageIndex,
-          numberOfSlices: currentNumberOfSlices,
-        });
+        pushSliceData(currentImageIndex, currentNumberOfSlices);
       } catch (error) {
         console.warn(error);
       }
-    }
+    };
 
-    const { viewportType } = viewportData;
-    const eventId =
-      (viewportType === Enums.ViewportType.STACK && Enums.Events.STACK_NEW_IMAGE) ||
-      (viewportType === Enums.ViewportType.ORTHOGRAPHIC && Enums.Events.VOLUME_NEW_IMAGE) ||
-      Enums.Events.IMAGE_RENDERED;
+    syncFromViewport();
+
+    // A post-mount camera carry (e.g. the layout-selector MPR protocol restoring
+    // the prior stack slice onto the freshly-mounted volume viewport) moves the
+    // camera and fires its slice events synchronously during the mount — before
+    // these listeners attach and around the initial seed above — so the scrollbar
+    // can latch the mount-time index instead of the carried slice. Re-seed once on
+    // the next frame, after the mount+carry settles; pushSliceData makes it a
+    // no-op when nothing changed (no churn/flicker).
+    const reseedRaf = requestAnimationFrame(syncFromViewport);
+
+    const eventId = getSliceEventName(viewportData);
 
     const updateIndex = event => {
       const viewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
@@ -130,16 +148,22 @@ export function useViewportSliceSync({
       }
       const nextNumberOfSlices = viewport.getNumberOfSlices();
 
-      setImageSliceData({
-        imageIndex: nextImageIndex,
-        numberOfSlices: nextNumberOfSlices,
-      });
+      pushSliceData(nextImageIndex, nextNumberOfSlices);
     };
 
     element.addEventListener(eventId, updateIndex);
+    // Native ("next") viewports keep the same viewportData across a stack->volume
+    // transition or an orientation change, so this effect does not re-run and the
+    // slice-navigation event above may not fire until the first scroll, leaving the
+    // scrollbar unseeded (or stale, with a now-wrong slice count). CAMERA_MODIFIED
+    // fires on those orientation/geometry changes, so re-seed from the viewport
+    // then; the pushSliceData guard makes pan/zoom (same geometry) a no-op.
+    element.addEventListener(Enums.Events.CAMERA_MODIFIED, syncFromViewport);
 
     return () => {
+      cancelAnimationFrame(reseedRaf);
       element.removeEventListener(eventId, updateIndex);
+      element.removeEventListener(Enums.Events.CAMERA_MODIFIED, syncFromViewport);
     };
   }, [viewportData, element, viewportId, cornerstoneViewportService, setImageSliceData]);
 }
diff --git a/extensions/cornerstone/src/commandsModule.ts b/extensions/cornerstone/src/commandsModule.ts
index ad77a0aba..cd71c3386 100644
--- a/extensions/cornerstone/src/commandsModule.ts
+++ b/extensions/cornerstone/src/commandsModule.ts
@@ -29,8 +29,10 @@ import {
   colorPickerDialog,
   callInputDialog,
 } from '@ohif/extension-default';
-import { vec3, mat4 } from 'gl-matrix';
 import toggleImageSliceSync from './utils/imageSliceSync/toggleImageSliceSync';
+// Sanctioned flag read: RTSTRUCT contour hydration pins the referenced image to
+// stack mode on the native ("next") path, a decision made before a target viewport exists.
+import { getHydrationViewportTypeForModality } from './utils/nextViewportPolicies';
 import { getFirstAnnotationSelected } from './utils/measurementServiceMappings/utils/selection';
 import { getViewportEnabledElement } from './utils/getViewportEnabledElement';
 import getActiveViewportEnabledElement from './utils/getActiveViewportEnabledElement';
@@ -41,6 +43,8 @@ import {
   isVolume3DViewportType,
   isVolumeViewportType,
 } from './utils/getLegacyViewportType';
+import { viewportOperations as ops } from './services/ViewportService/backends/viewportOperations';
+import { getViewportAdapter } from './services/ViewportService/adapter';
 import {
   usePositionPresentationStore,
   useSegmentationPresentationStore,
@@ -52,8 +56,6 @@ import { updateSegmentBidirectionalStats } from './utils/updateSegmentationStats
 import { generateSegmentationCSVReport } from './utils/generateSegmentationCSVReport';
 import { getUpdatedViewportsForSegmentation } from './utils/hydrationUtils';
 import { SegmentationRepresentations } from '@cornerstonejs/tools/enums';
-import { isMeasurementWithinViewport } from './utils/isMeasurementWithinViewport';
-import { getCenterExtent } from './utils/getCenterExtent';
 import { EasingFunctionEnum } from './utils/transitions';
 import { createSegmentationForViewport } from './utils/createSegmentationForViewport';
 import { utilities as segmentationUtilities } from '@cornerstonejs/tools/segmentation';
@@ -146,6 +148,15 @@ function commandsModule({
     return getViewportEnabledElement(viewportId);
   }
 
+  // Resolves the cornerstone viewport for a command: the given viewport id, else the
+  // active one. Returns undefined when nothing is enabled.
+  function _resolveViewport(viewportId?: string) {
+    const enabledElement = viewportId
+      ? _getViewportEnabledElement(viewportId)
+      : _getActiveViewportEnabledElement();
+    return enabledElement?.viewport;
+  }
+
   function _getActiveViewportToolGroupId() {
     const viewport = _getActiveViewportEnabledElement();
     const toolGroup = viewport && toolGroupService.getToolGroupForViewport(viewport.id);
@@ -238,23 +249,11 @@ function commandsModule({
         viewport.setViewReference(metadata);
         viewport.render();
 
-        /**
-         * If the measurement is not visible inside the current viewport,
-         * we need to move the camera to the measurement.
-         */
-        if (!isMeasurementWithinViewport(viewport, measurement)) {
-          const camera = viewport.getCamera();
-          const { focalPoint: cameraFocalPoint, position: cameraPosition } = camera;
-          const { center, extent } = getCenterExtent(measurement);
-          const position = vec3.sub(vec3.create(), cameraPosition, cameraFocalPoint);
-          vec3.add(position, position, center);
-          viewport.setCamera({ focalPoint: center, position: position as any });
-          /** Zoom out if the measurement is too large */
-          const measurementSize = vec3.dist(extent.min, extent.max);
-          if (measurementSize > camera.parallelScale) {
-            const scaleFactor = measurementSize / camera.parallelScale;
-            viewport.setZoom(viewport.getZoom() / scaleFactor);
-          }
+        // If the measurement is not visible inside the current viewport, move the
+        // camera to it. The operations backend handles the lane: legacy re-centers
+        // in-plane (getCamera/setCamera), native skips it (no in-plane pan yet, CS-14)
+        // since setViewReference above already navigated to the measurement's slice.
+        if (ops.centerOnMeasurement(viewport, measurement)) {
           viewport.render();
         }
 
@@ -372,6 +371,9 @@ function commandsModule({
         const results = commandsManager.runCommand('loadSegmentationDisplaySetsForViewport', {
           viewportId,
           displaySetInstanceUIDs: [referencedDisplaySet.displaySetInstanceUID],
+          // RTSTRUCT-on-next pins the referenced image to stack mode on hydrate;
+          // see the policy's rationale in utils/nextViewportPolicies.
+          viewportType: getHydrationViewportTypeForModality(displaySet.Modality),
         });
 
         const disableEditing = customizationService.getCustomization(
@@ -921,34 +923,28 @@ function commandsModule({
       const windowWidthNum = Number(windowWidth);
       const windowCenterNum = Number(windowCenter);
 
-      // get actor from the viewport
       const renderingEngine = cornerstoneViewportService.getRenderingEngine();
       const viewport = renderingEngine.getViewport(viewportId);
 
-      const { lower, upper } = csUtils.windowLevel.toLowHighRange(windowWidthNum, windowCenterNum);
-
-      if (isVolumeViewportType(viewport)) {
-        const volumeId = actions.getVolumeIdForDisplaySet({
-          viewportId,
-          displaySetInstanceUID,
-        });
-        viewport.setProperties(
-          {
-            voiRange: {
-              upper,
-              lower,
-            },
-          },
-          volumeId
-        );
-      } else {
-        viewport.setProperties({
-          voiRange: {
-            upper,
-            lower,
-          },
-        });
+      // Stale/invalid viewport ids resolve to undefined; bail out before the VOI
+      // apply + render below would throw.
+      if (!viewport) {
+        return;
       }
+
+      // Legacy volume viewports target a specific volume; the command owns that
+      // resolution (it needs the service). The operations backend applies the VOI
+      // (legacy setProperties vs native setDisplaySetPresentation on the active binding).
+      const volumeId = isVolumeViewportType(viewport)
+        ? actions.getVolumeIdForDisplaySet({ viewportId, displaySetInstanceUID })
+        : undefined;
+
+      ops.setWindowLevel(viewport, {
+        windowWidth: windowWidthNum,
+        windowCenter: windowCenterNum,
+        volumeId,
+        displaySetInstanceUID,
+      });
       viewport.render();
     },
     toggleViewportColorbar: ({ viewportId, displaySetInstanceUIDs, options = {} }) => {
@@ -1187,25 +1183,11 @@ function commandsModule({
       viewportId?: string;
       newValue?: 'toggle' | boolean;
     }) => {
-      const enabledElement = viewportId
-        ? _getViewportEnabledElement(viewportId)
-        : _getActiveViewportEnabledElement();
-
-      if (!enabledElement) {
+      const viewport = _resolveViewport(viewportId);
+      if (!viewport) {
         return;
       }
-
-      const { viewport } = enabledElement;
-
-      let flipHorizontal: boolean;
-      if (newValue === 'toggle') {
-        const { flipHorizontal: currentHorizontalFlip } = viewport.getCamera();
-        flipHorizontal = !currentHorizontalFlip;
-      } else {
-        flipHorizontal = newValue;
-      }
-
-      viewport.setCamera({ flipHorizontal });
+      ops.flipHorizontal(viewport, newValue);
       viewport.render();
     },
     flipViewportVertical: ({
@@ -1215,78 +1197,36 @@ function commandsModule({
       viewportId?: string;
       newValue?: 'toggle' | boolean;
     }) => {
-      const enabledElement = viewportId
-        ? _getViewportEnabledElement(viewportId)
-        : _getActiveViewportEnabledElement();
-
-      if (!enabledElement) {
+      const viewport = _resolveViewport(viewportId);
+      if (!viewport) {
         return;
       }
-
-      const { viewport } = enabledElement;
-
-      let flipVertical: boolean;
-      if (newValue === 'toggle') {
-        const { flipVertical: currentVerticalFlip } = viewport.getCamera();
-        flipVertical = !currentVerticalFlip;
-      } else {
-        flipVertical = newValue;
-      }
-      viewport.setCamera({ flipVertical });
+      ops.flipVertical(viewport, newValue);
       viewport.render();
     },
     invertViewport: ({ element }) => {
-      let enabledElement;
-
-      if (element === undefined) {
-        enabledElement = _getActiveViewportEnabledElement();
-      } else {
-        enabledElement = element;
-      }
-
-      if (!enabledElement) {
+      const viewport = element === undefined ? _resolveViewport() : element.viewport;
+      if (!viewport) {
         return;
       }
-
-      const { viewport } = enabledElement;
-
-      const { invert } = viewport.getProperties();
-      viewport.setProperties({ invert: !invert });
+      ops.invert(viewport);
       viewport.render();
     },
     resetViewport: () => {
-      const enabledElement = _getActiveViewportEnabledElement();
-
-      if (!enabledElement) {
+      const viewport = _resolveViewport();
+      if (!viewport) {
         return;
       }
-
-      const { viewport } = enabledElement;
-
-      viewport.resetProperties?.();
-      viewport.resetCamera();
-
+      ops.reset(viewport);
       viewport.render();
     },
     scaleViewport: ({ direction }) => {
-      const enabledElement = _getActiveViewportEnabledElement();
-      const scaleFactor = direction > 0 ? 0.9 : 1.1;
-
-      if (!enabledElement) {
+      const viewport = _resolveViewport();
+      if (!viewport) {
         return;
       }
-      const { viewport } = enabledElement;
-
-      if (isStackViewportType(viewport)) {
-        if (direction) {
-          const { parallelScale } = viewport.getCamera();
-          viewport.setCamera({ parallelScale: parallelScale * scaleFactor });
-          viewport.render();
-        } else {
-          viewport.resetCamera();
-          viewport.render();
-        }
-      }
+      ops.scaleBy(viewport, direction);
+      viewport.render();
     },
 
     /** Jumps the active viewport or the specified one to the given slice index */
@@ -1365,24 +1305,15 @@ function commandsModule({
       // HP takes priority over the default opacity
       colormap = { ...colormap, opacity: hpOpacity || opacity };
 
-      if (isStackViewportType(viewport)) {
-        viewport.setProperties({ colormap });
+      // The legacy orthographic branch resolves the volumeId from the display set;
+      // fall back to the viewport's first display set (needs viewportGridService, so
+      // it is resolved here in the command rather than in the operations backend).
+      if (isOrthographicViewportType(viewport) && !displaySetInstanceUID) {
+        const { viewports } = viewportGridService.getState();
+        displaySetInstanceUID = viewports.get(viewportId)?.displaySetInstanceUIDs[0];
       }
 
-      if (isOrthographicViewportType(viewport)) {
-        if (!displaySetInstanceUID) {
-          const { viewports } = viewportGridService.getState();
-          displaySetInstanceUID = viewports.get(viewportId)?.displaySetInstanceUIDs[0];
-        }
-
-        // ToDo: Find a better way of obtaining the volumeId that corresponds to the displaySetInstanceUID
-        const volumeId =
-          viewport
-            .getAllVolumeIds()
-            .find((_volumeId: string) => _volumeId.includes(displaySetInstanceUID)) ??
-          viewport.getVolumeId();
-        viewport.setProperties({ colormap }, volumeId);
-      }
+      ops.setColormap(viewport, { colormap, displaySetInstanceUID });
 
       if (immediate) {
         viewport.render();
@@ -1488,9 +1419,7 @@ function commandsModule({
       if (!viewport) {
         return;
       }
-      viewport.setProperties({
-        preset,
-      });
+      ops.setPreset(viewport, preset);
       viewport.render();
     },
 
@@ -1502,20 +1431,10 @@ function commandsModule({
 
     setVolumeRenderingQulaity: ({ viewportId, volumeQuality }) => {
       const viewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
-      const { actor } = viewport.getActors()[0];
-      const mapper = actor.getMapper();
-      const image = mapper.getInputData();
-      const dims = image.getDimensions();
-      const spacing = image.getSpacing();
-      const spatialDiagonal = vec3.length(
-        vec3.fromValues(dims[0] * spacing[0], dims[1] * spacing[1], dims[2] * spacing[2])
-      );
-
-      let sampleDistance = spacing.reduce((a, b) => a + b) / 3.0;
-      sampleDistance /= volumeQuality > 1 ? 0.5 * volumeQuality ** 2 : 1.0;
-      const samplesPerRay = spatialDiagonal / sampleDistance + 1;
-      mapper.setMaximumSamplesPerRay(samplesPerRay);
-      mapper.setSampleDistance(sampleDistance);
+      if (!viewport) {
+        return;
+      }
+      ops.setVolumeRenderingQuality(viewport, volumeQuality);
       viewport.render();
     },
 
@@ -1526,27 +1445,10 @@ function commandsModule({
      */
     shiftVolumeOpacityPoints: ({ viewportId, shift }) => {
       const viewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
-      const { actor } = viewport.getActors()[0];
-      const ofun = actor.getProperty().getScalarOpacity(0);
-
-      const opacityPointValues = []; // Array to hold values
-      // Gather Existing Values
-      const size = ofun.getSize();
-      for (let pointIdx = 0; pointIdx < size; pointIdx++) {
-        const opacityPointValue = [0, 0, 0, 0];
-        ofun.getNodeValue(pointIdx, opacityPointValue);
-        // opacityPointValue now holds [xLocation, opacity, midpoint, sharpness]
-        opacityPointValues.push(opacityPointValue);
+      if (!viewport) {
+        return;
       }
-      // Add offset
-      opacityPointValues.forEach(opacityPointValue => {
-        opacityPointValue[0] += shift; // Change the location value
-      });
-      // Set new values
-      ofun.removeAllPoints();
-      opacityPointValues.forEach(opacityPointValue => {
-        ofun.addPoint(...opacityPointValue);
-      });
+      ops.shiftVolumeOpacityPoints(viewport, shift);
       viewport.render();
     },
 
@@ -1562,25 +1464,10 @@ function commandsModule({
 
     setVolumeLighting: ({ viewportId, options }) => {
       const viewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
-      const { actor } = viewport.getActors()[0];
-      const property = actor.getProperty();
-
-      if (options.shade !== undefined) {
-        property.setShade(options.shade);
+      if (!viewport) {
+        return;
       }
-
-      if (options.ambient !== undefined) {
-        property.setAmbient(options.ambient);
-      }
-
-      if (options.diffuse !== undefined) {
-        property.setDiffuse(options.diffuse);
-      }
-
-      if (options.specular !== undefined) {
-        property.setSpecular(options.specular);
-      }
-
+      ops.setVolumeLighting(viewport, options);
       viewport.render();
     },
     resetCrosshairs: ({ viewportId }) => {
@@ -1588,7 +1475,13 @@ function commandsModule({
 
       const getCrosshairInstances = toolGroupId => {
         const toolGroup = toolGroupService.getToolGroup(toolGroupId);
-        crosshairInstances.push(toolGroup.getToolInstance('Crosshairs'));
+        // Only fetch the instance when Crosshairs is registered in this tool
+        // group. getToolInstance logs a warning for an unregistered tool, and a
+        // viewport's default tool group does not always include Crosshairs (e.g.
+        // next viewports), which made Reset Viewport log a spurious warning.
+        if (toolGroup?.hasTool('Crosshairs')) {
+          crosshairInstances.push(toolGroup.getToolInstance('Crosshairs'));
+        }
       };
 
       if (!viewportId) {
@@ -1596,7 +1489,9 @@ function commandsModule({
         toolGroupIds.forEach(getCrosshairInstances);
       } else {
         const toolGroup = toolGroupService.getToolGroupForViewport(viewportId);
-        getCrosshairInstances(toolGroup.id);
+        if (toolGroup) {
+          getCrosshairInstances(toolGroup.id);
+        }
       }
 
       crosshairInstances.forEach(ins => {
@@ -2165,7 +2060,11 @@ function commandsModule({
       }
       segmentationService.addSegment(activeSegmentation.segmentationId);
     },
-    loadSegmentationDisplaySetsForViewport: ({ viewportId, displaySetInstanceUIDs }) => {
+    loadSegmentationDisplaySetsForViewport: ({
+      viewportId,
+      displaySetInstanceUIDs,
+      viewportType,
+    }) => {
       const updatedViewports = getUpdatedViewportsForSegmentation({
         viewportId,
         servicesManager,
@@ -2185,13 +2084,21 @@ function commandsModule({
         viewportsToUpdate: updatedViewports.map(viewport => ({
           viewportId: viewport.viewportId,
           displaySetInstanceUIDs: viewport.displaySetInstanceUIDs,
+          // When the caller pins a viewportType (RTSTRUCT contour hydration on a
+          // native "next" viewport requests 'stack'), force it so the referenced
+          // image stays in that render mode instead of resolving to a volume slice.
+          ...(viewportType
+            ? { viewportOptions: { ...viewport.viewportOptions, viewportType } }
+            : {}),
         })),
       });
     },
     setViewportOrientation: ({ viewportId, orientation }) => {
       const viewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
 
-      if (!viewport || !isOrthographicViewportType(viewport)) {
+      // Accept any viewport already rendering volume content (legacy ORTHOGRAPHIC
+      // or a native viewport in volume mode) — both expose setOrientation().
+      if (!viewport || !getViewportAdapter(viewport).canReorientInPlace()) {
         console.warn('Orientation can only be set on volume viewports');
         return;
       }
@@ -2263,50 +2170,12 @@ function commandsModule({
       viewportId?: string;
       rotationMode?: 'apply' | 'set';
     }) => {
-      const enabledElement = viewportId
-        ? _getViewportEnabledElement(viewportId)
-        : _getActiveViewportEnabledElement();
-
-      if (!enabledElement) {
+      const viewport = _resolveViewport(viewportId);
+      if (!viewport) {
         return;
       }
-
-      const { viewport } = enabledElement;
-
-      if (isVolumeViewportType(viewport)) {
-        const camera = viewport.getCamera();
-        const rotAngle = (rotation * Math.PI) / 180;
-        const rotMat = mat4.identity(new Float32Array(16));
-        mat4.rotate(rotMat, rotMat, rotAngle, camera.viewPlaneNormal);
-        const rotatedViewUp = vec3.transformMat4(vec3.create(), camera.viewUp, rotMat);
-        viewport.setCamera({ viewUp: rotatedViewUp as CoreTypes.Point3 });
-        viewport.render();
-        return;
-      }
-
-      if (viewport.getRotation !== undefined) {
-        const { rotation: currentRotation } = viewport.getViewPresentation();
-        const newRotation =
-          rotationMode === 'apply'
-            ? (currentRotation + rotation + 360) % 360
-            : (() => {
-                // In 'set' mode, account for the effect horizontal/vertical flips
-                // have on the perceived rotation direction. A single flip mirrors
-                // the image and inverses rotation direction, while two flips
-                // restore the original parity. We therefore invert the rotation
-                // angle when an odd number of flips are applied so that the
-                // requested absolute rotation matches the user expectation.
-                const { flipHorizontal = false, flipVertical = false } =
-                  viewport.getViewPresentation();
-
-                const flipsParity = (flipHorizontal ? 1 : 0) + (flipVertical ? 1 : 0);
-                const effectiveRotation = flipsParity % 2 === 1 ? -rotation : rotation;
-
-                return (effectiveRotation + 360) % 360;
-              })();
-        viewport.setViewPresentation({ rotation: newRotation });
-        viewport.render();
-      }
+      ops.rotate(viewport, rotation, rotationMode);
+      viewport.render();
     },
     startRecordingForAnnotationGroup: () => {
       cornerstoneTools.AnnotationTool.startGroupRecording();
diff --git a/extensions/cornerstone/src/components/ViewportColorbar/ViewportColorbarsContainer.tsx b/extensions/cornerstone/src/components/ViewportColorbar/ViewportColorbarsContainer.tsx
index b4f0fc08b..3864f8885 100644
--- a/extensions/cornerstone/src/components/ViewportColorbar/ViewportColorbarsContainer.tsx
+++ b/extensions/cornerstone/src/components/ViewportColorbar/ViewportColorbarsContainer.tsx
@@ -83,10 +83,16 @@ const ViewportColorbarsContainer = memo(function ViewportColorbarsContainer({
         const { displaySetInstanceUID: dsUID } =
           displaySetService.getDisplaySetByUID(displaySetInstanceUID) ?? {};
 
+        // Default the fused (horizontal) colorbar to the foreground (e.g. the PT
+        // in a PET/CT fusion), which is the meaningful layer. Only fall back to
+        // the background (CT) colorbar when the foreground has been explicitly
+        // faded to zero opacity. Previously a null/undefined opacity (e.g. before
+        // the hook resolved it) also fell through to the background, so the
+        // colorbar would flicker between CT and PT depending on timing.
         const targetUID =
-          opacity === 0 || opacity == null
+          opacity === 0
             ? backgroundDisplaySet?.displaySetInstanceUID
-            : foregroundDisplaySets[0].displaySetInstanceUID;
+            : foregroundDisplaySets[0]?.displaySetInstanceUID;
 
         return dsUID === targetUID;
       });
diff --git a/extensions/cornerstone/src/components/ViewportOrientationMenu/ViewportOrientationMenu.tsx b/extensions/cornerstone/src/components/ViewportOrientationMenu/ViewportOrientationMenu.tsx
index 8452b7841..508d5a974 100644
--- a/extensions/cornerstone/src/components/ViewportOrientationMenu/ViewportOrientationMenu.tsx
+++ b/extensions/cornerstone/src/components/ViewportOrientationMenu/ViewportOrientationMenu.tsx
@@ -2,6 +2,7 @@ import React from 'react';
 import { cn, Icons, useIconPresentation } from '@ohif/ui-next';
 import { useSystem } from '@ohif/core';
 import { Enums } from '@cornerstonejs/core';
+import { getViewportAdapter } from '../../services/ViewportService/adapter';
 import { Popover, PopoverTrigger, PopoverContent, Button, useViewportGrid } from '@ohif/ui-next';
 
 function ViewportOrientationMenu({
@@ -36,8 +37,6 @@ function ViewportOrientationMenu({
 
   const handleOrientationChange = (orientation: string) => {
     setCurrentOrientation(orientation);
-    const viewportInfo = cornerstoneViewportService.getViewportInfo(viewportIdToUse);
-    const currentViewportType = viewportInfo?.getViewportType();
 
     if (!displaySets.length) {
       return;
@@ -72,8 +71,17 @@ function ViewportOrientationMenu({
 
     const displaySetUIDs = displaySets.map(ds => ds.displaySetInstanceUID);
 
-    // If viewport is not already a volume type, we need to convert it
-    if (currentViewportType !== Enums.ViewportType.ORTHOGRAPHIC) {
+    // A viewport already rendering in volume mode (legacy ORTHOGRAPHIC OR a next
+    // viewport that reports planarNext but renders volume actors, e.g. a CT+PET
+    // fusion) can be reoriented in place. Recreating it via setDisplaySetsForViewports
+    // would pass empty displaySetOptions and drop per-display-set presentation such
+    // as the PET overlay colormap/opacity. Only the genuine stack -> volume (MPR)
+    // case needs recreation.
+    const csViewport = cornerstoneViewportService.getCornerstoneViewport(viewportIdToUse);
+    const isVolumeMode = !!csViewport && getViewportAdapter(csViewport).canReorientInPlace();
+
+    // If viewport is not already in volume mode, we need to convert it
+    if (!isVolumeMode) {
       // Configure the viewport to be a volume viewport with current display sets
       const updatedViewport = {
         viewportId: viewportIdToUse,
diff --git a/extensions/cornerstone/src/components/ViewportWindowLevel/utils.ts b/extensions/cornerstone/src/components/ViewportWindowLevel/utils.ts
index a68728aab..ea7ff017e 100644
--- a/extensions/cornerstone/src/components/ViewportWindowLevel/utils.ts
+++ b/extensions/cornerstone/src/components/ViewportWindowLevel/utils.ts
@@ -2,6 +2,7 @@ import { cache as cs3DCache, Types } from '@cornerstonejs/core';
 import vtkColorMaps from '@kitware/vtk.js/Rendering/Core/ColorTransferFunction/ColorMaps';
 import { utilities as csUtils } from '@cornerstonejs/core';
 import { getViewportVolumeHistogram } from './getViewportVolumeHistogram';
+import { getViewportAdapter } from '../../services/ViewportService/adapter';
 
 /**
  * Gets node opacity from volume actor
@@ -101,8 +102,18 @@ export const getWindowLevelsData = async (
     return [];
   }
 
-  const volumeIds = (viewport as Types.IBaseVolumeViewport).getAllVolumeIds();
-  const viewportProperties = viewport.getProperties();
+  // The per-volume histogram WL panel is a legacy volume-viewport feature; the
+  // adapter reports no volumeIds for native viewports (and legacy stacks), so
+  // those degrade gracefully to no histogram rows rather than erroring; the
+  // native WL path is driven by setViewportWindowLevel.
+  // TODO(next): port per-volume histograms to the native volume API.
+  const adapter = getViewportAdapter(viewport);
+  const volumeIds = adapter.getVolumeIds();
+  if (!volumeIds.length) {
+    return [];
+  }
+
+  const viewportProperties = adapter.getPresentation();
   const { voiRange } = viewportProperties || {};
   const viewportVoi = voiRange
     ? {
diff --git a/extensions/cornerstone/src/components/WindowLevelActionMenu/WindowLevel.tsx b/extensions/cornerstone/src/components/WindowLevelActionMenu/WindowLevel.tsx
index 623cdaedc..7f0b264e3 100644
--- a/extensions/cornerstone/src/components/WindowLevelActionMenu/WindowLevel.tsx
+++ b/extensions/cornerstone/src/components/WindowLevelActionMenu/WindowLevel.tsx
@@ -1,15 +1,54 @@
 import React, { ReactElement, useEffect, useRef, useState } from 'react';
 import { AllInOneMenu, ScrollArea, Switch, Tabs, TabsList, TabsTrigger } from '@ohif/ui-next';
 import { useViewportRendering } from '../../hooks/useViewportRendering';
+import { useViewportDisplaySets } from '../../hooks/useViewportDisplaySets';
 import { WindowLevelPreset } from '../../types/WindowLevel';
 import { useTranslation } from 'react-i18next';
 
 export function WindowLevel({ viewportId }: { viewportId?: string } = {}): ReactElement {
   const { t } = useTranslation('WindowLevelActionMenu');
-  const { viewportDisplaySets } = useViewportRendering(viewportId);
+  const { viewportDisplaySets, foregroundDisplaySets } = useViewportDisplaySets(viewportId);
+  // Default the active tab to the foreground layer (e.g. the PT in a PET/CT
+  // fusion), matching the other window-level controls, instead of the grayscale
+  // background (CT) at index 0. The CT/PT tabs still let the user switch.
+  const defaultDisplaySetUID =
+    foregroundDisplaySets?.length > 0
+      ? foregroundDisplaySets[foregroundDisplaySets.length - 1].displaySetInstanceUID
+      : viewportDisplaySets?.[0]?.displaySetInstanceUID;
   const [activeDisplaySetUID, setActiveDisplaySetUID] = useState<string | undefined>(
-    viewportDisplaySets?.[0]?.displaySetInstanceUID
+    defaultDisplaySetUID
   );
+  // Tracks whether the user has explicitly picked a tab, so the foreground-default
+  // sync below stops overriding their choice.
+  const userSelectedRef = useRef(false);
+
+  // Adopt the foreground default if the display sets resolve after first render
+  // (and the user has not picked a tab yet). This must re-sync even when the
+  // initial render already seeded `activeDisplaySetUID` with the CT fallback
+  // (because `foregroundDisplaySets` was still empty at mount) — otherwise the
+  // tab stays pinned to CT once the foreground (PT) layer resolves.
+  useEffect(() => {
+    // If the active tab's display set is no longer in the viewport (e.g. the
+    // viewport switched to a different study/series), drop the now-stale
+    // selection — including a user pick — so it re-defaults instead of leaving an
+    // invalid UID that later fails validateActiveDisplaySet.
+    const activeStillPresent = viewportDisplaySets?.some(
+      ds => ds.displaySetInstanceUID === activeDisplaySetUID
+    );
+    if (activeDisplaySetUID && viewportDisplaySets?.length && !activeStillPresent) {
+      userSelectedRef.current = false;
+      setActiveDisplaySetUID(defaultDisplaySetUID);
+      return;
+    }
+
+    if (
+      !userSelectedRef.current &&
+      defaultDisplaySetUID &&
+      activeDisplaySetUID !== defaultDisplaySetUID
+    ) {
+      setActiveDisplaySetUID(defaultDisplaySetUID);
+    }
+  }, [activeDisplaySetUID, defaultDisplaySetUID, viewportDisplaySets]);
 
   // Use the hook with the active display set
   const { windowLevelPresets, setWindowLevel } = useViewportRendering(viewportId, {
@@ -49,6 +88,7 @@ export function WindowLevel({ viewportId }: { viewportId?: string } = {}): React
           <Tabs
             value={activeDisplaySetUID}
             onValueChange={displaySetUID => {
+              userSelectedRef.current = true;
               setActiveDisplaySetUID(displaySetUID);
             }}
           >
diff --git a/extensions/cornerstone/src/getSopClassHandlerModule.js b/extensions/cornerstone/src/getSopClassHandlerModule.js
index 157b7aef2..071083d5a 100644
--- a/extensions/cornerstone/src/getSopClassHandlerModule.js
+++ b/extensions/cornerstone/src/getSopClassHandlerModule.js
@@ -8,7 +8,11 @@ import { buildEcgModule } from './utils/ecgMetadata';
 const { MetadataModules } = csEnums;
 const { utils } = OHIF;
 const { denaturalizeDataset } = dcmjs.data.DicomMetaDictionary;
-const { transferDenaturalizedDataset, fixMultiValueKeys } = dicomWebUtils;
+// NOTE: access transferDenaturalizedDataset / fixMultiValueKeys lazily (at call
+// time) rather than destructuring here. This module and @ohif/extension-default
+// form a circular import, so dicomWebUtils can be undefined at module-eval time
+// depending on bundler eval order; a top-level destructure then throws and
+// crashes app boot.
 
 const SOP_CLASS_UIDS = {
   VL_WHOLE_SLIDE_MICROSCOPY_IMAGE_STORAGE: '1.2.840.10008.5.1.4.1.1.77.1.6',
@@ -139,8 +143,8 @@ function getDICOMwebMetadata(instanceMap, imageId) {
     console.warn('Metadata not already found for', imageId, 'in', instanceMap);
     return this.super.getDICOMwebMetadata(imageId);
   }
-  return transferDenaturalizedDataset(
-    denaturalizeDataset(fixMultiValueKeys(instanceMap.get(imageId)))
+  return dicomWebUtils.transferDenaturalizedDataset(
+    denaturalizeDataset(dicomWebUtils.fixMultiValueKeys(instanceMap.get(imageId)))
   );
 }
 
diff --git a/extensions/cornerstone/src/getToolbarModule.tsx b/extensions/cornerstone/src/getToolbarModule.tsx
index 5f96730a1..80fa83c4f 100644
--- a/extensions/cornerstone/src/getToolbarModule.tsx
+++ b/extensions/cornerstone/src/getToolbarModule.tsx
@@ -1,5 +1,6 @@
 import { Enums } from '@cornerstonejs/tools';
 import i18n from '@ohif/i18n';
+import { getViewportAdapter, isVolumeRenderingViewport } from './services/ViewportService/adapter';
 import { utils } from '@ohif/ui-next';
 import { ViewportDataOverlayMenuWrapper } from './components/ViewportDataOverlaySettingMenu/ViewportDataOverlayMenuWrapper';
 import { ViewportOrientationMenuWrapper } from './components/ViewportOrientationMenu/ViewportOrientationMenuWrapper';
@@ -309,7 +310,11 @@ export default function getToolbarModule({ servicesManager, extensionManager }:
           };
         }
 
-        if (viewport.type !== 'orthographic') {
+        // Recognize native "next" volume viewports too. A next MPR/volume viewport
+        // runs as PLANAR_NEXT (requestedType PLANAR_NEXT, not ORTHOGRAPHIC), so this
+        // checks volume content via getCurrentMode(). Without it the PT threshold
+        // control stayed disabled on the next backend (e.g. TMTV fusion/PT).
+        if (!isVolumeRenderingViewport(viewport)) {
           return {
             disabled: true,
           };
@@ -332,7 +337,7 @@ export default function getToolbarModule({ servicesManager, extensionManager }:
       evaluate: ({ viewportId }) => {
         const viewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
 
-        if (!viewport || viewport.type !== 'orthographic') {
+        if (!viewport || !isVolumeRenderingViewport(viewport)) {
           return {
             disabled: true,
           };
@@ -449,8 +454,7 @@ export default function getToolbarModule({ servicesManager, extensionManager }:
           mode === Enums.ToolModes.Enabled;
 
         const toolBindings = toolGroupService.getToolBindings(toolGroup.id, toolName);
-        const hasModifierKey =
-          toolBindings?.some(binding => binding.modifierKey != null) ?? false;
+        const hasModifierKey = toolBindings?.some(binding => binding.modifierKey != null) ?? false;
 
         return {
           disabled: false,
@@ -459,7 +463,7 @@ export default function getToolbarModule({ servicesManager, extensionManager }:
           icon:
             isToggled && hasModifierKey && toggledOnIcon
               ? toggledOnIcon
-              : defaultIcon ?? button.props.icon,
+              : (defaultIcon ?? button.props.icon),
         };
       },
     },
@@ -543,8 +547,9 @@ export default function getToolbarModule({ servicesManager, extensionManager }:
 
         const propId = button.id;
 
-        const properties = viewport.getProperties();
-        const camera = viewport.getCamera();
+        const adapter = getViewportAdapter(viewport);
+        const properties = adapter.getPresentation();
+        const camera = adapter.getViewState();
 
         const prop = camera?.[propId] || properties?.[propId];
 
diff --git a/extensions/cornerstone/src/hooks/useViewportRendering.tsx b/extensions/cornerstone/src/hooks/useViewportRendering.tsx
index c134657f9..19d43dbbe 100644
--- a/extensions/cornerstone/src/hooks/useViewportRendering.tsx
+++ b/extensions/cornerstone/src/hooks/useViewportRendering.tsx
@@ -1,13 +1,9 @@
 import React, { useCallback, useState, useEffect, useMemo } from 'react';
 import { useSystem } from '@ohif/core';
 import { useViewportDisplaySets } from './useViewportDisplaySets';
-import { Types, utilities, Enums, cache } from '@cornerstonejs/core';
-import { getDataIdForViewport } from '../utils/getDataIdForViewport';
-import {
-  isStackViewportType,
-  isVolumeViewportType,
-  isVolume3DViewportType,
-} from '../utils/getLegacyViewportType';
+import { Types, utilities, Enums } from '@cornerstonejs/core';
+import { isVolume3DViewportType } from '../utils/getLegacyViewportType';
+import { getViewportAdapter, LEGACY_OPACITY_GAMMA } from '../services/ViewportService/adapter';
 import { WindowLevelPreset } from '../types/WindowLevel';
 import { ColorbarPositionType, ColorbarOptions, ColorbarProperties } from '../types/Colorbar';
 import { VolumeRenderingConfig } from '../types/VolumeRenderingConfig';
@@ -92,14 +88,26 @@ const getPosition = (location: number): ColorbarPositionType => {
   }
 };
 
-const GAMMA = 1 / 5;
+/**
+ * Normalizes a colormap opacity value to a single 0..1 scalar for the opacity
+ * slider. `colormap.opacity` may be a plain number or an array of
+ * `{ value, opacity }` points (e.g. the HP fusion opacity ramp); for the array
+ * case we represent it by its maximum opacity. (A prior reduce ran over the point
+ * objects directly, producing NaN and a mispositioned slider.)
+ */
+const resolveOpacityScalar = (opacityVal: unknown): number | undefined => {
+  if (opacityVal === undefined || opacityVal === null) {
+    return undefined;
+  }
 
-const linearToOpacity = (linearValue: number): number => {
-  return Math.pow(linearValue, GAMMA);
-};
+  if (Array.isArray(opacityVal)) {
+    return opacityVal.reduce((max: number, point) => {
+      const value = typeof point === 'number' ? point : (point?.opacity ?? 0);
+      return Math.max(max, value);
+    }, 0);
+  }
 
-const opacityToLinear = (opacityValue: number): number => {
-  return Math.pow(opacityValue, 1.0 / GAMMA);
+  return opacityVal as number;
 };
 
 /**
@@ -128,12 +136,28 @@ export function useViewportRendering(
     viewportId ? (cornerstoneViewportService.getCornerstoneViewport(viewportId) ?? null) : null
   );
   const [is3DVolume, setIs3DVolume] = useState(isVolume3DViewportType(viewport));
+
+  // The opacity slider gamma follows the rendering path (linear on native,
+  // the historical 1/5 curve on legacy), so the slider feel and its initial
+  // position match what is rendered.
+  const opacityGamma = viewport
+    ? getViewportAdapter(viewport).getOpacityGamma()
+    : LEGACY_OPACITY_GAMMA;
+  const linearToOpacity = useCallback(
+    (linearValue: number): number => Math.pow(linearValue, opacityGamma),
+    [opacityGamma]
+  );
+  const opacityToLinear = useCallback(
+    (opacityValue: number): number => Math.pow(opacityValue, 1.0 / opacityGamma),
+    [opacityGamma]
+  );
+
   const [opacity, setOpacityState] = useState<number | undefined>();
   const [opacityLinear, setOpacityLinearState] = useState<number | undefined>();
   const [threshold, setThresholdState] = useState<number | undefined>();
   const [pixelValueRange, setPixelValueRange] = useState<PixelValueRange>({ min: 0, max: 255 });
 
-  const { viewportDisplaySets } = useViewportDisplaySets(viewportId);
+  const { viewportDisplaySets, foregroundDisplaySets } = useViewportDisplaySets(viewportId);
   const { displaySetService } = servicesManager.services;
 
   // Determine the active display set instance UID (internal only, not exposed)
@@ -142,12 +166,21 @@ export function useViewportRendering(
       return options.displaySetInstanceUID;
     }
 
+    // Window-level / colormap / threshold controls operate on the foreground
+    // layer (e.g. the PT in a PET/CT fusion), not the grayscale background (CT).
+    // Use the topmost foreground display set when present; otherwise fall back to
+    // the (single) primary display set. SEG/derived overlays are already excluded
+    // from foregroundDisplaySets.
+    if (foregroundDisplaySets && foregroundDisplaySets.length > 0) {
+      return foregroundDisplaySets[foregroundDisplaySets.length - 1].displaySetInstanceUID;
+    }
+
     if (viewportDisplaySets && viewportDisplaySets.length > 0) {
       return viewportDisplaySets[0].displaySetInstanceUID;
     }
 
     return undefined;
-  }, [options?.displaySetInstanceUID, viewportDisplaySets]);
+  }, [options?.displaySetInstanceUID, viewportDisplaySets, foregroundDisplaySets]);
 
   const viewportInfo = viewportId ? cornerstoneViewportService.getViewportInfo(viewportId) : null;
 
@@ -216,28 +249,14 @@ export function useViewportRendering(
       return;
     }
 
-    if (!isVolumeViewportType(viewport)) {
+    const voxelManager = getViewportAdapter(viewport).getVoxelManagerForDisplaySet(
+      activeDisplaySetInstanceUID
+    );
+
+    if (!voxelManager?.getRange) {
       return;
     }
 
-    const volumeIds = viewport.getAllVolumeIds();
-    const volumeId = volumeIds.find(id => id.includes(activeDisplaySetInstanceUID));
-
-    if (!volumeId) {
-      return;
-    }
-
-    // only handle volume viewports for now
-    const imageData = viewport.getImageData(volumeId);
-
-    if (!imageData) {
-      return;
-    }
-
-    const imageDataVtk = imageData.imageData;
-
-    const { voxelManager } = imageDataVtk.get('voxelManager');
-
     const range = voxelManager.getRange();
 
     setPixelValueRange({ min: range[0], max: range[1] });
@@ -267,12 +286,9 @@ export function useViewportRendering(
       return;
     }
     try {
-      const dataId = getDataIdForViewport(viewport as unknown, activeDisplaySetInstanceUID);
-
-      const properties =
-        dataId != null
-          ? (viewport as Types.IBaseVolumeViewport).getProperties(dataId)
-          : viewport.getProperties();
+      const adapter = getViewportAdapter(viewport);
+      const dataId = adapter.getDataIdForDisplaySet(activeDisplaySetInstanceUID);
+      const properties = adapter.getPresentation(dataId ?? activeDisplaySetInstanceUID);
 
       if (!properties) {
         return;
@@ -281,18 +297,26 @@ export function useViewportRendering(
       if (properties.voiRange) {
         setVoiRange(properties.voiRange);
         voiRangeRef.current = properties.voiRange;
+      } else {
+        // Native ("next") viewports store only explicit VOI overrides in the
+        // per-display-set presentation; a freshly shown series has none, so fall
+        // back to its computed default VOI (undefined on legacy, whose
+        // getProperties always returns the applied VOI). Without this, changing
+        // the series left the overlay showing the previous series' window level.
+        const defaultVOIRange = adapter.getDefaultVOIRange(dataId ?? activeDisplaySetInstanceUID);
+
+        if (defaultVOIRange) {
+          setVoiRange(defaultVOIRange);
+          voiRangeRef.current = defaultVOIRange;
+        }
       }
 
       if (properties.colormap?.opacity !== undefined) {
-        const opacityVal = properties.colormap.opacity;
-        const opacity = Array.isArray(opacityVal)
-          ? (opacityVal as unknown as number[]).reduce(
-              (max, current) => Math.max(max, current),
-              0
-            )
-          : opacityVal;
-        setOpacityState(opacity);
-        setOpacityLinearState(opacityToLinear(opacity));
+        const opacity = resolveOpacityScalar(properties.colormap.opacity);
+        if (opacity !== undefined) {
+          setOpacityState(opacity);
+          setOpacityLinearState(opacityToLinear(opacity));
+        }
       }
 
       if (properties.colormap?.threshold !== undefined) {
@@ -362,8 +386,11 @@ export function useViewportRendering(
       }
 
       if (colormap.opacity !== undefined) {
-        setOpacityState(colormap.opacity);
-        setOpacityLinearState(opacityToLinear(colormap.opacity));
+        const opacity = resolveOpacityScalar(colormap.opacity);
+        if (opacity !== undefined) {
+          setOpacityState(opacity);
+          setOpacityLinearState(opacityToLinear(opacity));
+        }
       }
     };
 
@@ -570,7 +597,7 @@ export function useViewportRendering(
 
   const setOpacity = useCallback(
     (opacityValue: number) => {
-      if (!viewport || !isVolumeViewportType(viewport)) {
+      if (!viewport) {
         return;
       }
 
@@ -580,32 +607,10 @@ export function useViewportRendering(
       setOpacityLinearState(opacityToLinear(opacityValue));
 
       const displaySetInstanceUID = validateActiveDisplaySet();
-      const volumeIds = viewport.getAllVolumeIds();
-      const volumeId = volumeIds.find(id => id.includes(displaySetInstanceUID));
 
-      if (!volumeId) {
-        return;
+      if (getViewportAdapter(viewport).setLayerOpacity(displaySetInstanceUID, opacityValue)) {
+        viewport.render();
       }
-
-      // Get current properties including colormap
-      const properties = viewport.getProperties(volumeId);
-      const currentColormap = properties.colormap || {};
-
-      // Update colormap with new opacity
-      const updatedColormap = {
-        ...currentColormap,
-        opacity: opacityValue,
-      };
-
-      // Apply updated colormap
-      viewport.setProperties(
-        {
-          colormap: updatedColormap,
-        },
-        volumeId
-      );
-
-      viewport.render();
     },
     [validateActiveDisplaySet, opacityToLinear, viewport]
   );
@@ -621,32 +626,16 @@ export function useViewportRendering(
 
   const setThreshold = useCallback(
     (thresholdValue: number) => {
-      if (!viewport || !isVolumeViewportType(viewport)) {
+      if (!viewport) {
         return;
       }
 
-      setThresholdState(thresholdValue);
-
       const displaySetInstanceUID = validateActiveDisplaySet();
-      const volumeIds = viewport.getAllVolumeIds();
-      const volumeId = volumeIds.find(id => id.includes(displaySetInstanceUID));
+      setThresholdState(thresholdValue);
 
-      if (!volumeId) {
-        return;
+      if (getViewportAdapter(viewport).setLayerThreshold(displaySetInstanceUID, thresholdValue)) {
+        viewport.render();
       }
-
-      console.debug('🚀 ~ thresholdValue:', thresholdValue);
-
-      viewport.setProperties(
-        {
-          colormap: {
-            threshold: thresholdValue,
-          },
-        },
-        volumeId
-      );
-
-      viewport.render();
     },
     [validateActiveDisplaySet, viewport]
   );
@@ -662,41 +651,13 @@ export function useViewportRendering(
         return null;
       }
 
-      if (isStackViewportType(viewport)) {
-        const { colormap } = viewport.getProperties();
-        if (!colormap) {
-          return (
-            colorbarProperties?.colormaps?.find(c => c.Name === 'Grayscale') ||
-            colorbarProperties?.colormaps?.[0]
-          );
-        }
-        return colormap;
-      }
+      const colormap = getViewportAdapter(viewport).getColormap(activeDisplaySetInstanceUID);
 
-      const actorEntries = viewport.getActors();
-      const actorEntry = actorEntries?.find(entry =>
-        entry.referencedId?.includes(activeDisplaySetInstanceUID)
+      return (
+        colormap ||
+        colorbarProperties?.colormaps?.find(c => c.Name === 'Grayscale') ||
+        colorbarProperties?.colormaps?.[0]
       );
-
-      if (!actorEntry) {
-        return (
-          colorbarProperties?.colormaps?.find(c => c.Name === 'Grayscale') ||
-          colorbarProperties?.colormaps?.[0]
-        );
-      }
-
-      const { colormap } = (viewport as Types.IVolumeViewport).getProperties(
-        actorEntry.referencedId
-      );
-
-      if (!colormap) {
-        return (
-          colorbarProperties?.colormaps?.find(c => c.Name === 'Grayscale') ||
-          colorbarProperties?.colormaps?.[0]
-        );
-      }
-
-      return colormap;
     } catch (error) {
       console.error('Error getting viewport colormap:', error);
       return (
diff --git a/extensions/cornerstone/src/index.tsx b/extensions/cornerstone/src/index.tsx
index 730ee4aad..5e5fe954d 100644
--- a/extensions/cornerstone/src/index.tsx
+++ b/extensions/cornerstone/src/index.tsx
@@ -37,6 +37,18 @@ import RectangleROI from './utils/measurementServiceMappings/RectangleROI';
 import type { PublicViewportOptions } from './services/ViewportService/Viewport';
 import ImageOverlayViewerTool from './tools/ImageOverlayViewerTool';
 import getSOPInstanceAttributes from './utils/measurementServiceMappings/utils/getSOPInstanceAttributes';
+import {
+  getViewportAdapter,
+  getViewportFocalPoint,
+  isNextViewport,
+  isVolumeRenderingViewport,
+} from './services/ViewportService/adapter';
+import { isNextViewportsEnabled } from './utils/nextViewports';
+import {
+  NEXT_FUSION_PT_OPACITY,
+  NEXT_OVERLAY_OPACITY,
+  getHydrationViewportTypeForModality,
+} from './utils/nextViewportPolicies';
 import { findNearbyToolData } from './utils/findNearbyToolData';
 import { createFrameViewSynchronizer } from './synchronizers/frameViewSynchronizer';
 import { getSopClassHandlerModule } from './getSopClassHandlerModule';
@@ -103,11 +115,7 @@ const cornerstoneExtension: Types.Extensions.Extension = {
    */
   id,
 
-  onModeEnter: ({
-    servicesManager,
-    commandsManager,
-    extensionManager,
-  }: withAppTypes): void => {
+  onModeEnter: ({ servicesManager, commandsManager, extensionManager }: withAppTypes): void => {
     const { cornerstoneViewportService, toolbarService, segmentationService } =
       servicesManager.services;
 
@@ -153,7 +161,10 @@ const cornerstoneExtension: Types.Extensions.Extension = {
      */
     const sourceConfig = extensionManager?.getActiveDataSource?.()?.[0]?.getConfig?.() ?? {};
     const config = sourceConfig.stackRetrieveOptions ?? {};
-    const stackOptions = update(DEFAULT_STACK_RETRIEVE_OPTIONS, toUpdateSpec(config)) as typeof DEFAULT_STACK_RETRIEVE_OPTIONS;
+    const stackOptions = update(
+      DEFAULT_STACK_RETRIEVE_OPTIONS,
+      toUpdateSpec(config)
+    ) as typeof DEFAULT_STACK_RETRIEVE_OPTIONS;
     imageRetrieveMetadataProvider.add('stack', stackOptions);
   },
   getPanelModule,
@@ -286,6 +297,14 @@ export {
   getEnabledElement,
   ImageOverlayViewerTool,
   getSOPInstanceAttributes,
+  getViewportAdapter,
+  getViewportFocalPoint,
+  isNextViewport,
+  isVolumeRenderingViewport,
+  isNextViewportsEnabled,
+  NEXT_FUSION_PT_OPACITY,
+  NEXT_OVERLAY_OPACITY,
+  getHydrationViewportTypeForModality,
   dicomLoaderService,
   // Export all stores
   useLutPresentationStore,
diff --git a/extensions/cornerstone/src/init.tsx b/extensions/cornerstone/src/init.tsx
index cc870af9a..3f0f9e02b 100644
--- a/extensions/cornerstone/src/init.tsx
+++ b/extensions/cornerstone/src/init.tsx
@@ -27,6 +27,12 @@ import initCornerstoneTools from './initCornerstoneTools';
 import { connectToolsToMeasurementService } from './initMeasurementService';
 import initCineService from './initCineService';
 import initStudyPrefetcherService from './initStudyPrefetcherService';
+import {
+  setNextViewportsEnabled,
+  resolveNextViewportsEnabled,
+  resolveViewportRendering,
+  setViewportRenderingOverrides,
+} from './utils/nextViewports';
 import interleaveCenterLoader from './utils/interleaveCenterLoader';
 import nthLoader from './utils/nthLoader';
 import interleaveTopToBottom from './utils/interleaveTopToBottom';
@@ -62,13 +68,52 @@ export default async function init({
   // Note: this should run first before initializing the cornerstone
   // DO NOT CHANGE THE ORDER
 
+  // Enable cornerstone's stats/debug overlay when `?debug=true` is in the URL.
+  // Mirrors the cornerstone demo trigger so the same overlay is available inside
+  // OHIF: FPS / MS / MB panels plus the per-viewport actor & mapper bindings.
+  const statsOverlay =
+    new URLSearchParams(window.location.search).get('debug') === 'true';
+
   await cs3DInit({
     peerImport: appConfig.peerImport,
+    debug: { statsOverlay },
   });
 
-  // For debugging e2e tests that are failing on CI
   cornerstone.setUseCPURendering(Boolean(appConfig.useCPURendering));
 
+  // All native ("next") Generic Viewport settings live under one config object:
+  // appConfig.genericViewports = { enabled, viewportRendering }.
+  const genericViewportsConfig = appConfig.genericViewports ?? {};
+
+  // viewportRendering selects the render backend per-session:
+  // `?viewportRendering=cpu|webgl|webgpu|auto` for all viewports, plus
+  // `?<viewportType>.viewportRendering=<backend>` (e.g.
+  // `?orthographic.viewportRendering=cpu`) to override a single viewport type
+  // via the per-mount renderBackend option. The global value maps to
+  // cornerstone's setRenderBackend; 'cpu'/'gpu' additionally drive the legacy
+  // useCPURendering flag so pre-generic viewports follow the same selection
+  // (letting a session force GPU when the deployed config defaults to CPU).
+  const { renderBackend, renderBackendByViewportType } = resolveViewportRendering(
+    genericViewportsConfig.viewportRendering
+  );
+  if (renderBackend) {
+    if (renderBackend === 'cpu') {
+      cornerstone.setUseCPURendering(true);
+    } else if (renderBackend === 'gpu') {
+      cornerstone.setUseCPURendering(false);
+    }
+    try {
+      cornerstone.setRenderBackend(renderBackend as cornerstone.RenderBackendValue);
+    } catch (error) {
+      console.warn(
+        `viewportRendering: "${renderBackend}" is not a registered render backend; ` +
+          `keeping "${cornerstone.getRenderBackend()}".`,
+        error
+      );
+    }
+  }
+  setViewportRenderingOverrides(renderBackendByViewportType);
+
   cornerstone.setConfiguration({
     ...cornerstone.getConfiguration(),
     rendering: {
@@ -81,6 +126,14 @@ export default async function init({
     },
   });
 
+  // Opt-in: drive viewports through the DIRECT native GenericViewport ("next")
+  // API (PLANAR_NEXT, setDisplaySets, ...). Read by getCornerstoneViewportType
+  // and the CornerstoneViewportService backend split. Distinct from
+  // useGenericViewport above (which only enables cornerstone's compat remap).
+  // resolveNextViewportsEnabled lets a `?useNextViewports=true` URL param opt in
+  // per-session; when the param is absent, appConfig.genericViewports.enabled wins.
+  setNextViewportsEnabled(resolveNextViewportsEnabled(genericViewportsConfig.enabled));
+
   // For debugging large datasets, otherwise prefer the defaults
   const { maxCacheSize } = appConfig;
   if (maxCacheSize) {
diff --git a/extensions/cornerstone/src/services/ColorbarService/ColorbarService.ts b/extensions/cornerstone/src/services/ColorbarService/ColorbarService.ts
index 7e1705631..9601ed9c7 100644
--- a/extensions/cornerstone/src/services/ColorbarService/ColorbarService.ts
+++ b/extensions/cornerstone/src/services/ColorbarService/ColorbarService.ts
@@ -1,7 +1,7 @@
 import { PubSubService, Types as OhifTypes } from '@ohif/core';
 import { RENDERING_ENGINE_ID } from '../ViewportService/constants';
 import { getRenderingEngine } from '@cornerstonejs/core';
-import { getDataIdForViewport } from '../../utils/getDataIdForViewport';
+import { getViewportAdapter } from '../ViewportService/adapter';
 import { ColorbarOptions, ChangeTypes } from '../../types/Colorbar';
 
 export default class ColorbarService extends PubSubService {
@@ -60,8 +60,8 @@ export default class ColorbarService extends PubSubService {
       return;
     }
 
-    const actorEntries = viewport.getActors();
-    if (!actorEntries || actorEntries.length === 0) {
+    const adapter = getViewportAdapter(viewport);
+    if (!adapter.hasContent()) {
       return;
     }
 
@@ -74,8 +74,8 @@ export default class ColorbarService extends PubSubService {
         return;
       }
 
-      const dataId = getDataIdForViewport(viewport, displaySetInstanceUID);
-      const properties = dataId ? viewport.getProperties(dataId) : viewport.getProperties();
+      const dataId = adapter.getDataIdForDisplaySet(displaySetInstanceUID);
+      const properties = adapter.getPresentation(dataId);
       const colormap = properties?.colormap;
 
       if (activeColormapName && !colormap) {
@@ -222,16 +222,18 @@ export default class ColorbarService extends PubSubService {
   private setViewportColormap(viewportId, displaySetInstanceUID, colormap, immediate = false) {
     const renderingEngine = getRenderingEngine(RENDERING_ENGINE_ID);
     const viewport = renderingEngine.getViewport(viewportId);
-    const actorEntries = viewport?.getActors();
-    if (!viewport || !actorEntries || actorEntries.length === 0) {
+    if (!viewport) {
+      return;
+    }
+    const adapter = getViewportAdapter(viewport);
+    if (!adapter.hasContent()) {
       return;
     }
 
-    // Get the appropriate dataId for this viewport/displaySet combination
-    const dataId = getDataIdForViewport(viewport, displaySetInstanceUID);
-
-    // Set properties with or without dataId based on what the viewport supports
-    viewport.setProperties({ colormap }, dataId);
+    // Address the display set's binding (volumeId on legacy multi-volume, bare
+    // UID on native, active binding otherwise)
+    const dataId = adapter.getDataIdForDisplaySet(displaySetInstanceUID);
+    adapter.setPresentation({ colormap }, dataId);
 
     if (immediate) {
       viewport.render();
diff --git a/extensions/cornerstone/src/services/CornerstoneCacheService/CornerstoneCacheService.ts b/extensions/cornerstone/src/services/CornerstoneCacheService/CornerstoneCacheService.ts
index 8940a17cd..73096bab6 100644
--- a/extensions/cornerstone/src/services/CornerstoneCacheService/CornerstoneCacheService.ts
+++ b/extensions/cornerstone/src/services/CornerstoneCacheService/CornerstoneCacheService.ts
@@ -41,12 +41,39 @@ class CornerstoneCacheService {
     const cs3DViewportType = getCornerstoneViewportType(viewportType, displaySets);
     let viewportData: StackViewportData | VolumeViewportData;
 
+    // Native Generic ("next") viewport types (e.g. PLANAR_NEXT) intentionally
+    // collapse the stack/volume distinction into a single type, so they cannot
+    // drive the stack-vs-volume data-builder decision below. Resolve the data
+    // shape from the legacy mapping (which preserves that distinction) and keep
+    // the resolved native type as the produced viewportData's viewportType.
+    let dataShapeType = getCornerstoneViewportType(viewportType, displaySets, false);
+
+    // A data overlay (fusion) of two or more reconstructable image display sets
+    // must render as a volume viewport so the source and overlay share one
+    // representation (volume slice). Without this, a next (PLANAR_NEXT) viewport
+    // keeps the source in vtkImage (stack) mode while the added overlay is a
+    // vtkVolumeSlice, producing the broken/unstable fusion. SEG/RT overlays are
+    // non-reconstructable, so they are not affected.
+    //
+    // Scoped to the native (PLANAR_NEXT) path via cs3DViewportType — NOT the flag, and
+    // NOT the legacy lane: a legacy stack-shaped reconstructable overlay must keep its
+    // existing stack build so the flag-off path stays byte-identical.
+    const isReconstructableFusion =
+      displaySets.length > 1 && displaySets.every(ds => ds.isReconstructable);
     if (
-      cs3DViewportType === Enums.ViewportType.ORTHOGRAPHIC ||
-      cs3DViewportType === Enums.ViewportType.VOLUME_3D
+      isReconstructableFusion &&
+      dataShapeType === Enums.ViewportType.STACK &&
+      cs3DViewportType === Enums.ViewportType.PLANAR_NEXT
+    ) {
+      dataShapeType = Enums.ViewportType.ORTHOGRAPHIC;
+    }
+
+    if (
+      dataShapeType === Enums.ViewportType.ORTHOGRAPHIC ||
+      dataShapeType === Enums.ViewportType.VOLUME_3D
     ) {
       viewportData = await this._getVolumeViewportData(dataSource, displaySets, cs3DViewportType);
-    } else if (cs3DViewportType === Enums.ViewportType.STACK) {
+    } else if (dataShapeType === Enums.ViewportType.STACK) {
       // Everything else looks like a stack
       viewportData = await this._getStackViewportData(
         dataSource,
@@ -64,6 +91,9 @@ class CornerstoneCacheService {
     }
 
     viewportData.viewportType = cs3DViewportType;
+    // Persist the legacy stack/volume shape so consumers can distinguish stack from
+    // volume content even when viewportType is a native Generic type (PLANAR_NEXT).
+    viewportData.dataShapeType = dataShapeType;
 
     return viewportData;
   }
@@ -74,7 +104,13 @@ class CornerstoneCacheService {
     dataSource,
     displaySetService
   ): Promise<VolumeViewportData | StackViewportData> {
-    if (viewportData.viewportType === Enums.ViewportType.STACK) {
+    // Decide stack-vs-volume rebuild from the persisted data shape, NOT viewportType:
+    // native viewports collapse both onto PLANAR_NEXT, so a native stack would
+    // otherwise fall through to the volume rebuild and re-mount as volume data.
+    // Falls back to viewportType for legacy/older viewportData (byte-identical off-path).
+    const dataShapeType = viewportData.dataShapeType ?? viewportData.viewportType;
+
+    if (dataShapeType === Enums.ViewportType.STACK) {
       const displaySet = displaySetService.getDisplaySetByUID(invalidatedDisplaySetInstanceUID);
       const imageIds = this._getCornerstoneStackImageIds(displaySet, dataSource);
 
@@ -86,7 +122,10 @@ class CornerstoneCacheService {
       });
 
       return {
-        viewportType: Enums.ViewportType.STACK,
+        // Preserve the original viewportType (legacy STACK or native PLANAR_NEXT);
+        // the rebuilt data shape, not this field, drives the native re-mount dispatch.
+        viewportType: viewportData.viewportType,
+        dataShapeType: Enums.ViewportType.STACK,
         data: {
           StudyInstanceUID: displaySet.StudyInstanceUID,
           displaySetInstanceUID: invalidatedDisplaySetInstanceUID,
@@ -128,6 +167,7 @@ class CornerstoneCacheService {
       displaySets,
       viewportData.viewportType
     );
+    newViewportData.dataShapeType = dataShapeType;
 
     return newViewportData;
   }
diff --git a/extensions/cornerstone/src/services/SegmentationService/SegmentationService.test.ts b/extensions/cornerstone/src/services/SegmentationService/SegmentationService.test.ts
index 8ad9bd959..754c4aaf0 100644
--- a/extensions/cornerstone/src/services/SegmentationService/SegmentationService.test.ts
+++ b/extensions/cornerstone/src/services/SegmentationService/SegmentationService.test.ts
@@ -19,6 +19,7 @@ import {
 import { EasingFunctionEnum, EasingFunctionMap } from '../../utils/transitions';
 import * as MapROIContoursToRTStructData from './RTSTRUCT/mapROIContoursToRTStructData';
 import SegmentationServiceClass, { SegmentationRepresentation } from './SegmentationService';
+import { setNextViewportsEnabled } from '../../utils/nextViewports';
 
 jest.mock('@cornerstonejs/core', () => ({
   ...jest.requireActual('@cornerstonejs/core'),
@@ -914,6 +915,101 @@ describe('SegmentationService', () => {
       });
     });
 
+    describe('next (generic) viewport', () => {
+      // A native GenericViewport (raw PlanarViewport) exposes setDisplaySets /
+      // setDisplaySetPresentation / setViewState, so csUtils.isGenericViewport is
+      // true and addSegmentationRepresentation routes to NextSegmentationBackend.
+      // It deliberately has NO getViewPresentation: the native path must never reach
+      // convertStackToVolumeViewport (the source of the observed
+      // "getViewPresentation is not a function" / silent ORTHOGRAPHIC flip).
+      const makeNextViewport = () => ({
+        element: { addEventListener: jest.fn(), removeEventListener: jest.fn() },
+        id: viewportId,
+        type: ViewportType.PLANAR_NEXT,
+        setDisplaySets: jest.fn(),
+        setDisplaySetPresentation: jest.fn(),
+        setViewState: jest.fn(),
+      });
+
+      it('renders the labelmap in place and never promotes the viewport (resolver maps in place)', async () => {
+        jest
+          .spyOn(cstSegmentation.state, 'getSegmentation')
+          .mockReturnValue(mockCornerstoneSegmentation as cstTypes.Segmentation);
+        jest
+          .spyOn(serviceManagerMock.services.cornerstoneViewportService, 'getCornerstoneViewport')
+          .mockReturnValue(makeNextViewport() as unknown as csTypes.IStackViewport);
+        jest
+          .spyOn(cstSegmentation.state, 'updateLabelmapSegmentationImageReferences')
+          .mockReturnValue('labelmapImageId');
+        jest
+          .spyOn(cstSegmentation, 'addSegmentationRepresentations')
+          .mockReturnValueOnce(undefined);
+        const convertSpy = jest.spyOn(service, 'convertStackToVolumeViewport');
+
+        const callback = jest.fn();
+        service.subscribe(service.EVENTS.SEGMENTATION_REPRESENTATION_MODIFIED, callback);
+
+        await service.addSegmentationRepresentation(viewportId, {
+          segmentationId: mockCornerstoneSegmentation.segmentationId,
+          type: csToolsEnums.SegmentationRepresentations.Labelmap,
+        });
+
+        // the native in-place resolver is consulted...
+        expect(
+          cstSegmentation.state.updateLabelmapSegmentationImageReferences
+        ).toHaveBeenCalledWith(viewportId, mockCornerstoneSegmentation.segmentationId);
+
+        // ...but the viewport is NEVER promoted to an ORTHOGRAPHIC volume viewport
+        expect(convertSpy).not.toHaveBeenCalled();
+        expect(
+          serviceManagerMock.services.viewportGridService.setDisplaySetsForViewport
+        ).not.toHaveBeenCalled();
+
+        // the representation is added in place, synchronously (isConverted === false)
+        expect(cstSegmentation.addSegmentationRepresentations).toHaveBeenCalledTimes(1);
+        expect(cstSegmentation.addSegmentationRepresentations).toHaveBeenCalledWith(viewportId, [
+          {
+            type: csToolsEnums.SegmentationRepresentations.Labelmap,
+            segmentationId: mockCornerstoneSegmentation.segmentationId,
+            config: { colorLUTOrIndex: undefined },
+          },
+        ]);
+
+        expect(callback).toHaveBeenCalledWith({
+          segmentationId: mockCornerstoneSegmentation.segmentationId,
+        });
+      });
+
+      it('never promotes on native even when the in-place resolver cannot map (returns isConverted:false unconditionally)', async () => {
+        jest
+          .spyOn(cstSegmentation.state, 'getSegmentation')
+          .mockReturnValue(mockCornerstoneSegmentation as cstTypes.Segmentation);
+        jest
+          .spyOn(serviceManagerMock.services.cornerstoneViewportService, 'getCornerstoneViewport')
+          .mockReturnValue(makeNextViewport() as unknown as csTypes.IStackViewport);
+        // resolver fails (FrameOfReference mismatch / mount-timing race): on legacy this
+        // would fall through to convertStackToVolumeViewport; on native it must not.
+        jest
+          .spyOn(cstSegmentation.state, 'updateLabelmapSegmentationImageReferences')
+          .mockReturnValue(undefined);
+        jest
+          .spyOn(cstSegmentation, 'addSegmentationRepresentations')
+          .mockReturnValueOnce(undefined);
+        const convertSpy = jest.spyOn(service, 'convertStackToVolumeViewport');
+
+        await service.addSegmentationRepresentation(viewportId, {
+          segmentationId: mockCornerstoneSegmentation.segmentationId,
+          type: csToolsEnums.SegmentationRepresentations.Labelmap,
+        });
+
+        expect(convertSpy).not.toHaveBeenCalled();
+        expect(
+          serviceManagerMock.services.viewportGridService.setDisplaySetsForViewport
+        ).not.toHaveBeenCalled();
+        expect(cstSegmentation.addSegmentationRepresentations).toHaveBeenCalledTimes(1);
+      });
+    });
+
     describe('volume viewport', () => {
       it('should add a segmentation representation to volume viewport without need for handling', async () => {
         jest
@@ -1471,6 +1567,136 @@ describe('SegmentationService', () => {
 
       expect(retrievedSegmentationId).toEqual(segmentationId);
     });
+
+    describe('overlap / useSliceRendering (next backend)', () => {
+      const segmentationId = 'segmentationId';
+
+      // The session flag selects the seg-backend lane at SEG-load; reset it so it
+      // never leaks into the legacy-path tests that follow.
+      afterEach(() => {
+        setNextViewportsEnabled(false);
+      });
+
+      const segMetadata = {
+        data: [
+          {},
+          { SegmentNumber: '1', SegmentLabel: 'Segment 1', rgba: [255, 0, 0, 255] },
+          { SegmentNumber: '2', SegmentLabel: 'Segment 2', rgba: [0, 255, 0, 255] },
+        ],
+      };
+      const centroids = new Map([
+        [1, { image: { x: 0, y: 0, z: 0 }, world: { x: 0, y: 0, z: 0 } }],
+        [2, { image: { x: 1, y: 1, z: 1 }, world: { x: 1, y: 1, z: 1 } }],
+      ]);
+
+      // labelMapImages is the adapter's array-of-GROUPS (one conflict-free group per
+      // overlap layer). Two groups whose voxels carry values {1} and {2} respectively.
+      const makeOverlapGroups = () => {
+        const vm0 = { getScalarData: jest.fn().mockReturnValue([1, 0]), setScalarData: jest.fn() };
+        const vm1 = { getScalarData: jest.fn().mockReturnValue([0, 2]), setScalarData: jest.fn() };
+        return [
+          [
+            { imageId: 'g0i1', referencedImageId: 'r1', voxelManager: vm0 },
+            { imageId: 'g0i2', referencedImageId: 'r2', voxelManager: vm0 },
+          ],
+          [
+            { imageId: 'g1i1', referencedImageId: 'r1', voxelManager: vm1 },
+            { imageId: 'g1i2', referencedImageId: 'r2', voxelManager: vm1 },
+          ],
+        ];
+      };
+
+      const makeSegDisplaySet = (labelMapImages, overlappingSegments) => ({
+        centroids,
+        displaySetInstanceUID: 'display-set-uid',
+        referencedDisplaySetInstanceUID: 'existent-display-set-uid',
+        labelMapImages,
+        overlappingSegments,
+        segMetadata,
+        SeriesDate: '2025-01-01',
+        SeriesDescription: 'Series Description',
+        Modality: 'SEG',
+        SeriesNumber: 1,
+      });
+
+      const primeMocks = () => {
+        jest
+          .spyOn(serviceManagerMock.services.displaySetService, 'getDisplaySetByUID')
+          .mockReturnValue({ instances: [{ imageId: 'r1' }, { imageId: 'r2' }] });
+        jest.spyOn(metaData, 'get').mockReturnValue({});
+        jest.spyOn(service, 'addOrUpdateSegmentation').mockReturnValue(undefined);
+      };
+
+      it('flag ON + overlapping SEG builds one labelmap layer per group + segmentBindings', async () => {
+        setNextViewportsEnabled(true);
+        primeMocks();
+
+        await service.createSegmentationForSEGDisplaySet(
+          makeSegDisplaySet(makeOverlapGroups(), true),
+          { type: csToolsEnums.SegmentationRepresentations.Labelmap, segmentationId }
+        );
+
+        const seg = jest.mocked(service.addOrUpdateSegmentation).mock.calls[0][0];
+        const data = seg.representation.data as Record<string, any>;
+
+        // one labelmap layer per conflict-free group, under ONE segmentationId
+        expect(Object.keys(data.labelmaps)).toEqual([
+          'segmentationId-storage-0',
+          'segmentationId-storage-1',
+        ]);
+        expect(data.labelmaps['segmentationId-storage-0'].imageIds).toEqual(['g0i1', 'g0i2']);
+        expect(data.labelmaps['segmentationId-storage-1'].imageIds).toEqual(['g1i1', 'g1i2']);
+        expect(data.labelmaps['segmentationId-storage-0'].storageKind).toBe('stack');
+
+        // segment->layer bindings recovered from the distinct non-zero voxel values
+        expect(data.segmentBindings).toEqual({
+          1: { labelmapId: 'segmentationId-storage-0', labelValue: 1 },
+          2: { labelmapId: 'segmentationId-storage-1', labelValue: 2 },
+        });
+        expect(data.primaryLabelmapId).toBe('segmentationId-storage-0');
+        // flattened list retained for legacy singular readers
+        expect(data.imageIds).toEqual(['g0i1', 'g0i2', 'g1i1', 'g1i2']);
+      });
+
+      it('flag ON + non-overlapping SEG stays a single layer (no multi-layer map)', async () => {
+        setNextViewportsEnabled(true);
+        primeMocks();
+
+        const vm = { getScalarData: jest.fn().mockReturnValue([1, 0]), setScalarData: jest.fn() };
+        const singleGroup = [
+          [
+            { imageId: 'i1', referencedImageId: 'r1', voxelManager: vm },
+            { imageId: 'i2', referencedImageId: 'r2', voxelManager: vm },
+          ],
+        ];
+
+        await service.createSegmentationForSEGDisplaySet(makeSegDisplaySet(singleGroup, false), {
+          type: csToolsEnums.SegmentationRepresentations.Labelmap,
+          segmentationId,
+        });
+
+        const seg = jest.mocked(service.addOrUpdateSegmentation).mock.calls[0][0];
+        const data = seg.representation.data as Record<string, any>;
+        expect(data.labelmaps).toBeUndefined();
+        expect(data.segmentBindings).toBeUndefined();
+        expect(data.imageIds).toEqual(['i1', 'i2']);
+      });
+
+      it('flag OFF + overlapping SEG collapses to a single flattened layer (legacy byte-identical)', async () => {
+        // flag stays off (default)
+        primeMocks();
+
+        await service.createSegmentationForSEGDisplaySet(
+          makeSegDisplaySet(makeOverlapGroups(), true),
+          { type: csToolsEnums.SegmentationRepresentations.Labelmap, segmentationId }
+        );
+
+        const seg = jest.mocked(service.addOrUpdateSegmentation).mock.calls[0][0];
+        const data = seg.representation.data as Record<string, any>;
+        expect(data.labelmaps).toBeUndefined();
+        expect(data.imageIds).toEqual(['g0i1', 'g0i2', 'g1i1', 'g1i2']);
+      });
+    });
   });
 
   describe('createSegmentationForRTDisplaySet', () => {
@@ -2698,6 +2924,47 @@ describe('SegmentationService', () => {
       );
     });
 
+    it('navigates a native viewport via setViewReference (no jumpToWorld) and still highlights', () => {
+      const segmentationId = 'segmentationId';
+      const segmentIndex = 1;
+      const viewportId = 'viewportId';
+      // A native PlanarViewport: csUtils.isGenericViewport is true (setDisplaySets +
+      // setDisplaySetPresentation + setViewState) and it has setViewReference but NO
+      // jumpToWorld, so jumpToSegmentCenter routes to the next twin.
+      const viewport = {
+        setDisplaySets: jest.fn(),
+        setDisplaySetPresentation: jest.fn(),
+        setViewState: jest.fn(),
+        setViewReference: jest.fn(),
+        render: jest.fn(),
+      };
+
+      const segmentationWithCenter = {
+        ...mockCornerstoneSegmentation,
+        segments: {
+          ...mockCornerstoneSegmentation.segments,
+          [segmentIndex]: {
+            ...mockCornerstoneSegmentation.segments[segmentIndex],
+            cachedStats: { center: { image: [1, 1, 1], world: [10, 10, 10] } },
+          },
+        },
+      };
+
+      jest.spyOn(cstSegmentation.state, 'getSegmentation').mockReturnValue(segmentationWithCenter);
+      // @ts-expect-error - mock only needed properties
+      getEnabledElementByViewportId.mockReturnValue({ viewport });
+      jest.spyOn(service, 'highlightSegment').mockReturnValue(undefined);
+
+      service.jumpToSegmentCenter(segmentationId, segmentIndex, viewportId);
+
+      // native jump: a view reference centered on the segment world point, then render
+      expect(viewport.setViewReference).toHaveBeenCalledTimes(1);
+      expect(viewport.setViewReference).toHaveBeenCalledWith({ cameraFocalPoint: [10, 10, 10] });
+      expect(viewport.render).toHaveBeenCalledTimes(1);
+      // the recenter happened, so the highlight still runs
+      expect(service.highlightSegment).toHaveBeenCalledTimes(1);
+    });
+
     it('should correctly handle custom animation parameters', () => {
       const segmentationId = 'segmentationId';
       const segmentIndex = 1;
diff --git a/extensions/cornerstone/src/services/SegmentationService/SegmentationService.ts b/extensions/cornerstone/src/services/SegmentationService/SegmentationService.ts
index 7c75978a4..a1dd32264 100644
--- a/extensions/cornerstone/src/services/SegmentationService/SegmentationService.ts
+++ b/extensions/cornerstone/src/services/SegmentationService/SegmentationService.ts
@@ -10,10 +10,7 @@ import {
   metaData,
 } from '@cornerstonejs/core';
 import { ViewportType } from '@cornerstonejs/core/enums';
-import {
-  isVolume3DViewportType,
-  isVolumeViewportType,
-} from '../../utils/getLegacyViewportType';
+import { isVolume3DViewportType } from '../../utils/getLegacyViewportType';
 
 import {
   Enums as csToolsEnums,
@@ -30,6 +27,17 @@ import { mapROIContoursToRTStructData } from './RTSTRUCT/mapROIContoursToRTStruc
 import { SegmentationPresentation, SegmentationPresentationItem } from '../../types/Presentation';
 import { EasingFunctionEnum, EasingFunctionMap } from '../../utils/transitions';
 import { ViewReference } from '@cornerstonejs/core/types';
+import {
+  LegacySegmentationBackend,
+  NextSegmentationBackend,
+  type ISegmentationBackend,
+  type ISegmentationServiceInternals,
+} from './backends';
+// Sanctioned flag read: the SEG data shape (single- vs multi-layer) is fixed at
+// load time, before any target viewport exists, so this one seg-backend dispatch
+// cannot use a per-viewport capability check and reads the session flag instead.
+import { isNextViewportsEnabled } from '../../utils/nextViewports';
+import { isNextViewport } from '../ViewportService/adapter';
 
 const { DefaultHistoryMemo } = csUtils.HistoryMemo;
 
@@ -42,7 +50,7 @@ const {
 const {
   getLabelmapImageIds,
   helpers: { convertStackToVolumeLabelmap },
-  state: { addColorLUT, updateLabelmapSegmentationImageReferences },
+  state: { addColorLUT },
   triggerSegmentationEvents: { triggerSegmentationRepresentationModified },
 } = cstSegmentation;
 
@@ -98,7 +106,7 @@ const EVENTS = {
 
 const VALUE_TYPES = {};
 
-class SegmentationService extends PubSubService {
+class SegmentationService extends PubSubService implements ISegmentationServiceInternals {
   static REGISTRATION = {
     name: 'segmentationService',
     altName: 'SegmentationService',
@@ -109,6 +117,8 @@ class SegmentationService extends PubSubService {
 
   private _segmentationIdToColorLUTIndexMap: Map<string, number>;
   private _segmentationGroupStatsMap: Map<string, any>;
+  private readonly _legacySegBackend: ISegmentationBackend;
+  private readonly _nextSegBackend: ISegmentationBackend;
   readonly servicesManager: AppTypes.ServicesManager;
   highlightIntervalId = null;
   readonly EVENTS = EVENTS;
@@ -121,6 +131,24 @@ class SegmentationService extends PubSubService {
     this.servicesManager = servicesManager;
 
     this._segmentationGroupStatsMap = new Map();
+
+    // Segmentation backend twins (mirror the viewport backend family). Routed PER
+    // VIEWPORT via _segBackend() using the adapter's isNextViewport predicate,
+    // because a flag-on session can mix native and legacy viewports. Both are
+    // constructed eagerly:
+    // per-viewport dispatch has no per-session flag to defer on, and the twins read
+    // state at call time (post-init), not at construction.
+    this._legacySegBackend = new LegacySegmentationBackend(this);
+    this._nextSegBackend = new NextSegmentationBackend();
+  }
+
+  /**
+   * Picks the segmentation backend lane for a specific viewport: the native
+   * ("next") twin for a raw GenericViewport (PlanarViewport), the legacy twin
+   * otherwise. Mirrors viewportOperations' per-viewport dispatch.
+   */
+  private _segBackend(viewport: csTypes.IViewport): ISegmentationBackend {
+    return isNextViewport(viewport) ? this._nextSegBackend : this._legacySegBackend;
   }
 
   public onModeEnter(): void {
@@ -297,6 +325,7 @@ class SegmentationService extends PubSubService {
       type?: csToolsEnums.SegmentationRepresentations;
       config?: {
         blendMode?: csEnums.BlendModes;
+        useSliceRendering?: boolean;
       };
       suppressEvents?: boolean;
     }
@@ -319,6 +348,15 @@ class SegmentationService extends PubSubService {
       return;
     }
 
+    // A stale/invalid segmentationId yields no segmentation; fail fast with a clear
+    // message instead of dereferencing representationData deep inside the backend
+    // classification below.
+    if (!segmentation) {
+      throw new Error(
+        `SegmentationService: cannot add representation - segmentation "${segmentationId}" not found.`
+      );
+    }
+
     const colorLUTIndex = this._segmentationIdToColorLUTIndexMap.get(segmentationId);
 
     let isConverted = false;
@@ -328,20 +366,35 @@ class SegmentationService extends PubSubService {
     let representationTypeToUse = type || defaultRepresentationType;
 
     if (representationTypeToUse === LABELMAP) {
-      const { isVolumeViewport, isVolumeSegmentation } = this.determineViewportAndSegmentationType(
-        csViewport,
-        segmentation
-      ) || { isVolumeViewport: false, isVolumeSegmentation: false };
-
-      ({ representationTypeToUse, isConverted } = await this.handleViewportConversion(
-        isVolumeViewport,
-        isVolumeSegmentation,
+      ({ representationTypeToUse, isConverted } = await this._segBackend(
+        csViewport
+      ).classifyAndPrepareLabelmapAdd(
         csViewport,
         segmentation,
         viewportId,
         segmentationId,
         representationTypeToUse
       ));
+
+      // Overlap precondition: an overlapping SEG is registered as multiple labelmap
+      // layers, but cornerstone only stacks them (slice rendering) when the viewport
+      // renders as a volume slice (VTK_VOLUME_SLICE) — i.e. an MPR/volume viewport. On
+      // a stack/acquisition viewport the render plan falls back to a single layer, so
+      // only the primary group is visible. Warn rather than fail silently.
+      const labelmapLayers = segmentation?.representationData?.[LABELMAP]?.labelmaps;
+      const isOverlapping = labelmapLayers && Object.keys(labelmapLayers).length > 1;
+      if (
+        isOverlapping &&
+        isNextViewport(csViewport) &&
+        !csUtils.viewportIsInVolumeMode(csViewport)
+      ) {
+        console.warn(
+          `Overlapping segmentation ${segmentationId} has multiple labelmap layers, but ` +
+            `viewport ${viewportId} does not render as a volume slice (VTK_VOLUME_SLICE); ` +
+            `only the primary layer will be visible. Display the segmentation in an ` +
+            `MPR/volume layout to see all overlapping segments.`
+        );
+      }
     }
 
     await this._addSegmentationRepresentation(
@@ -592,22 +645,21 @@ class SegmentationService extends PubSubService {
     const colorLUTIndex = addColorLUT(colorLUT);
     this._segmentationIdToColorLUTIndexMap.set(segmentationId, colorLUTIndex);
 
-    const seg: cstTypes.SegmentationPublicInput = {
+    // Build the segmentation input via the backend twin. At SEG-load there is no
+    // target viewport yet, so the lane is chosen by the session flag (the one
+    // viewport-less seg-backend dispatch): the next twin registers overlapping SEGs
+    // as multiple labelmap layers (slice rendering); the legacy twin keeps the single
+    // flattened layer (byte-identical).
+    const segBackend = isNextViewportsEnabled() ? this._nextSegBackend : this._legacySegBackend;
+    const seg = segBackend.assembleSegmentationDataForSEG({
       segmentationId,
-      representation: {
-        type: LABELMAP,
-        data: {
-          imageIds: derivedImageIds,
-          // referencedVolumeId: this._getVolumeIdForDisplaySet(referencedDisplaySet),
-          referencedImageIds: imageIds as string[],
-        },
-      },
-      config: {
-        label: segDisplaySet.SeriesDescription,
-        fallbackLabel: `S:${segDisplaySet.SeriesNumber} ${segDisplaySet.Modality}`,
-        segments,
-      },
-    };
+      segDisplaySet,
+      derivedImageIds,
+      referencedImageIds: imageIds as string[],
+      label: segDisplaySet.SeriesDescription,
+      fallbackLabel: `S:${segDisplaySet.SeriesNumber} ${segDisplaySet.Modality}`,
+      segments,
+    });
 
     segDisplaySet.isLoaded = true;
 
@@ -1515,13 +1567,17 @@ class SegmentationService extends PubSubService {
 
     viewportIds.forEach(viewportId => {
       const { viewport } = getEnabledElementByViewportId(viewportId);
-      if (!viewport?.jumpToWorld) {
+      if (!viewport) {
         return;
       }
 
-      viewport.jumpToWorld(world);
+      // Recenter via the backend twin: legacy jumpToWorld, or native setViewReference
+      // (a native PlanarViewport has no jumpToWorld). Skip the highlight when the
+      // recenter did not happen, matching the previous guarded behavior.
+      const didJump = this._segBackend(viewport).jumpToSegmentCenter(viewport, world);
 
-      highlightSegment &&
+      didJump &&
+        highlightSegment &&
         this.highlightSegment(
           segmentationId,
           segmentIndex,
@@ -1626,87 +1682,11 @@ class SegmentationService extends PubSubService {
     );
   }
 
-  private determineViewportAndSegmentationType(csViewport, segmentation) {
-    const isVolumeViewport = isVolumeViewportType(csViewport);
-    const labelmapData = segmentation?.representationData?.[LABELMAP];
-
-    if (!labelmapData) {
-      return { isVolumeViewport, isVolumeSegmentation: false };
-    }
-
-    const isVolumeSegmentation = 'volumeId' in labelmapData;
-    return { isVolumeViewport, isVolumeSegmentation };
-  }
-
-  private async handleViewportConversion(
-    isVolumeViewport: boolean,
-    isVolumeSegmentation: boolean,
-    csViewport: csTypes.IViewport,
-    segmentation: cstTypes.Segmentation,
-    viewportId: string,
-    segmentationId: string,
-    representationType: csToolsEnums.SegmentationRepresentations
-  ) {
-    let representationTypeToUse = representationType;
-    let isConverted = false;
-
-    const handler = isVolumeViewport ? this.handleVolumeViewportCase : this.handleStackViewportCase;
-
-    ({ representationTypeToUse, isConverted } = await handler.apply(this, [
-      csViewport,
-      segmentation,
-      isVolumeSegmentation,
-      viewportId,
-      segmentationId,
-    ]));
-
-    return { representationTypeToUse, isConverted };
-  }
-
-  private async handleVolumeViewportCase(csViewport, segmentation, isVolumeSegmentation) {
-    if (isVolume3DViewportType(csViewport)) {
-      return {
-        representationTypeToUse: SURFACE,
-        isConverted: false,
-      };
-    } else {
-      await this.handleVolumeViewport(
-        csViewport as csTypes.IVolumeViewport,
-        segmentation,
-        isVolumeSegmentation
-      );
-      return { representationTypeToUse: LABELMAP, isConverted: false };
-    }
-  }
-
-  private async handleStackViewportCase(
-    csViewport: csTypes.IViewport,
-    segmentation: cstTypes.Segmentation,
-    isVolumeSegmentation: boolean,
-    viewportId: string,
-    segmentationId: string
-  ): Promise<{
-    representationTypeToUse: csToolsEnums.SegmentationRepresentations;
-    isConverted: boolean;
-  }> {
-    if (isVolumeSegmentation) {
-      const isConverted = await this.convertStackToVolumeViewport(csViewport);
-      return { representationTypeToUse: LABELMAP, isConverted };
-    }
-
-    if (updateLabelmapSegmentationImageReferences(viewportId, segmentationId)) {
-      return { representationTypeToUse: LABELMAP, isConverted: false };
-    }
-
-    const isConverted = await this.attemptStackToVolumeConversion(
-      csViewport as csTypes.IStackViewport,
-      segmentation,
-      viewportId,
-      segmentationId
-    );
-
-    return { representationTypeToUse: LABELMAP, isConverted };
-  }
+  // Labelmap-add classification (determineViewportAndSegmentationType +
+  // handleViewportConversion + the stack/volume case handlers) now lives in the
+  // segmentation backend twins (backends/{Legacy,Next}SegmentationBackend), routed
+  // per viewport via _segBackend(). The legacy twin reaches the viewport-recreation
+  // and data-volume-conversion helpers below through ISegmentationServiceInternals.
 
   private async _addSegmentationRepresentation(
     viewportId: string,
@@ -1716,6 +1696,7 @@ class SegmentationService extends PubSubService {
     isConverted: boolean,
     config?: {
       blendMode?: csEnums.BlendModes;
+      useSliceRendering?: boolean;
     }
   ): Promise<void> {
     const representation = {
@@ -1743,7 +1724,7 @@ class SegmentationService extends PubSubService {
       addRepresentation();
     }
   }
-  private async handleVolumeViewport(
+  public async handleVolumeViewport(
     viewport: csTypes.IVolumeViewport,
     segmentation: SegmentationData,
     isVolumeSegmentation: boolean
@@ -1761,7 +1742,7 @@ class SegmentationService extends PubSubService {
     }
   }
 
-  private async convertStackToVolumeViewport(viewport: csTypes.IViewport): Promise<boolean> {
+  public async convertStackToVolumeViewport(viewport: csTypes.IViewport): Promise<boolean> {
     const { viewportGridService, cornerstoneViewportService } = this.servicesManager.services;
     const state = viewportGridService.getState();
     const gridViewport = state.viewports.get(viewport.id);
@@ -1800,7 +1781,7 @@ class SegmentationService extends PubSubService {
     return true;
   }
 
-  private async attemptStackToVolumeConversion(
+  public async attemptStackToVolumeConversion(
     viewport: csTypes.IStackViewport,
     segmentation: SegmentationData,
     viewportId: string,
@@ -1820,6 +1801,10 @@ class SegmentationService extends PubSubService {
 
       return isConverted;
     }
+
+    // Frame-of-reference mismatch (or missing): no conversion happened. Return an
+    // explicit boolean so the Promise<boolean> contract holds for callers.
+    return false;
   }
 
   private addSegmentationToSource(segmentationPublicInput: cstTypes.SegmentationPublicInput) {
diff --git a/extensions/cornerstone/src/services/SegmentationService/backends/ISegmentationBackend.ts b/extensions/cornerstone/src/services/SegmentationService/backends/ISegmentationBackend.ts
new file mode 100644
index 000000000..71d98fbda
--- /dev/null
+++ b/extensions/cornerstone/src/services/SegmentationService/backends/ISegmentationBackend.ts
@@ -0,0 +1,102 @@
+import type { Types as csTypes } from '@cornerstonejs/core';
+import type { Enums as csToolsEnums, Types as cstTypes } from '@cornerstonejs/tools';
+
+/** A derived labelmap image produced by the SEG adapter (one per referenced image,
+ *  per overlap group). `voxelManager.getScalarData()` yields the slice's label values. */
+export interface SegLabelmapImage {
+  imageId: string;
+  voxelManager?: { getScalarData: () => ArrayLike<number> };
+}
+
+/** Inputs for assembling the cornerstone SegmentationPublicInput from a loaded SEG
+ *  display set. `segDisplaySet.labelMapImages` is the adapter's array-of-groups (one
+ *  conflict-free group per overlap layer); `overlappingSegments` flags whether the
+ *  SEG actually has overlap. `derivedImageIds` is the flattened image-id list. */
+export interface AssembleSegmentationForSEGParams {
+  segmentationId: string;
+  segDisplaySet: {
+    labelMapImages?: SegLabelmapImage[][];
+    overlappingSegments?: boolean;
+    [key: string]: unknown;
+  };
+  derivedImageIds: string[];
+  referencedImageIds: string[];
+  label: string;
+  fallbackLabel: string;
+  segments: { [segmentIndex: string]: cstTypes.Segment };
+}
+
+/**
+ * Result of classifying a labelmap add: the representation type to actually use
+ * (LABELMAP, or SURFACE for a 3D viewport) and whether the viewport was promoted
+ * stack -> volume (ORTHOGRAPHIC). When `isConverted` is true the caller defers the
+ * representation add until the grid re-mounts the recreated viewport.
+ */
+export interface LabelmapAddClassification {
+  representationTypeToUse: csToolsEnums.SegmentationRepresentations;
+  isConverted: boolean;
+}
+
+/**
+ * Segmentation backend twin (mirrors the viewport backend family at
+ * `ViewportService/backends/`). One implementation per lane:
+ *   - LegacySegmentationBackend: today's behavior (may promote a stack viewport to
+ *     an ORTHOGRAPHIC volume viewport via the host's convertStackToVolumeViewport).
+ *   - NextSegmentationBackend: the native GenericViewport ("next") path — renders
+ *     the labelmap IN PLACE on the raw PlanarViewport and never promotes.
+ *
+ * DISPATCH (deliberately diverges from IViewportBackend): unlike the viewport
+ * lifecycle backend, which is selected ONCE by the appConfig flag, the segmentation
+ * twin is routed PER VIEWPORT via `isNextViewport(viewport)` (the same
+ * runtime predicate used by `viewportOperations`). A flag-on session can hold both
+ * legacy and native viewports, and every viewport-bearing method already has an
+ * already-resolved, self-describing viewport in hand, so per-viewport routing is the
+ * runtime truth. `isNextViewport` is true for the native raw PlanarViewport and
+ * false for legacy StackViewport/VolumeViewport.
+ *
+ * BOUNDARY: viewport (re)creation is NOT a segmentation concern. The Next twin never
+ * calls `convertStackToVolumeViewport` (that recreates the viewport as ORTHOGRAPHIC
+ * and is owned by CornerstoneViewportService); the Legacy twin reaches it through
+ * `ISegmentationServiceInternals`, so the off path stays byte-identical.
+ */
+export interface ISegmentationBackend {
+  /**
+   * Decide how a LABELMAP representation is added for `csViewport`, performing any
+   * stack->volume promotion the lane requires. Called only inside the LABELMAP gate
+   * of `addSegmentationRepresentation` (CONTOUR/SURFACE never reach here).
+   */
+  classifyAndPrepareLabelmapAdd(
+    csViewport: csTypes.IViewport,
+    segmentation: cstTypes.Segmentation,
+    viewportId: string,
+    segmentationId: string,
+    representationType: csToolsEnums.SegmentationRepresentations
+  ): Promise<LabelmapAddClassification>;
+
+  /**
+   * Build the cornerstone SegmentationPublicInput for a loaded DICOM SEG display set.
+   *
+   * Dispatched by the session flag at SEG-load (NOT per viewport): no target viewport
+   * exists yet, and the data shape (single- vs multi-layer) is fixed at creation.
+   *
+   * Legacy: a single flattened labelmap layer (today's behavior, byte-identical).
+   * Next: when the SEG has overlapping segments, register each conflict-free group as
+   * its own labelmap layer under one segmentationId (+ segmentBindings) so cornerstone
+   * renders all overlapping segments via the slice path; otherwise identical to Legacy.
+   */
+  assembleSegmentationDataForSEG(
+    params: AssembleSegmentationForSEGParams
+  ): cstTypes.SegmentationPublicInput;
+
+  /**
+   * Recenter a viewport on a segment's world-space center point. Returns whether it
+   * actually recentered, so the caller can skip the segment highlight when it did not
+   * (preserving today's "no jump -> no highlight" behavior).
+   *
+   * Legacy: `viewport.jumpToWorld(world)` (guarded; absent -> false no-op, as today).
+   * Next: a native PlanarViewport has no jumpToWorld -> navigate via a view reference
+   * centered on `world` (setViewReference), turning today's silent native no-op into a
+   * working jump-to-slice. (In-plane pan-to-center is a separate, deferred refinement.)
+   */
+  jumpToSegmentCenter(viewport: csTypes.IViewport, world: csTypes.Point3): boolean;
+}
diff --git a/extensions/cornerstone/src/services/SegmentationService/backends/ISegmentationServiceInternals.ts b/extensions/cornerstone/src/services/SegmentationService/backends/ISegmentationServiceInternals.ts
new file mode 100644
index 000000000..13be732d1
--- /dev/null
+++ b/extensions/cornerstone/src/services/SegmentationService/backends/ISegmentationServiceInternals.ts
@@ -0,0 +1,44 @@
+import type { Types as csTypes } from '@cornerstonejs/core';
+import type { Types as cstTypes } from '@cornerstonejs/tools';
+
+/**
+ * The narrow slice of SegmentationService that a segmentation backend is allowed to
+ * reach (mirrors `IViewportServiceInternals`). The service `implements` this and
+ * passes `this` to each backend, so the legacy twin can delegate the viewport
+ * (re)creation / data-volume conversion work back to the shared service methods
+ * (which touch servicesManager-owned services) without the backends reaching into
+ * unrelated internals. Keeping this surface narrow is what stops the legacy path
+ * from drifting as the next backend grows.
+ *
+ * Only the LEGACY twin uses these; the NEXT twin renders in place and needs none of
+ * them (it never converts).
+ */
+export interface ISegmentationServiceInternals {
+  /**
+   * Recreate the stack viewport as an ORTHOGRAPHIC volume viewport (legacy
+   * promotion). Owned by the service because it drives viewportGridService /
+   * cornerstoneViewportService. Returns true (converted).
+   */
+  convertStackToVolumeViewport(viewport: csTypes.IViewport): Promise<boolean>;
+
+  /**
+   * Promote a stack viewport to volume only when the segmentation's
+   * FrameOfReference matches the viewport's. Returns whether it converted.
+   */
+  attemptStackToVolumeConversion(
+    viewport: csTypes.IStackViewport,
+    segmentation: cstTypes.Segmentation,
+    viewportId: string,
+    segmentationId: string
+  ): Promise<boolean>;
+
+  /**
+   * Convert the segmentation DATA to a volume labelmap when its FrameOfReference
+   * matches a volume viewport (pure data; no viewport recreation).
+   */
+  handleVolumeViewport(
+    viewport: csTypes.IVolumeViewport,
+    segmentation: cstTypes.Segmentation,
+    isVolumeSegmentation: boolean
+  ): Promise<void>;
+}
diff --git a/extensions/cornerstone/src/services/SegmentationService/backends/LegacySegmentationBackend.ts b/extensions/cornerstone/src/services/SegmentationService/backends/LegacySegmentationBackend.ts
new file mode 100644
index 000000000..e382e92d3
--- /dev/null
+++ b/extensions/cornerstone/src/services/SegmentationService/backends/LegacySegmentationBackend.ts
@@ -0,0 +1,139 @@
+import type { Types as csTypes } from '@cornerstonejs/core';
+import {
+  Enums as csToolsEnums,
+  segmentation as cstSegmentation,
+  type Types as cstTypes,
+} from '@cornerstonejs/tools';
+import { isVolume3DViewportType, isVolumeViewportType } from '../../../utils/getLegacyViewportType';
+import type {
+  AssembleSegmentationForSEGParams,
+  ISegmentationBackend,
+  LabelmapAddClassification,
+} from './ISegmentationBackend';
+import type { ISegmentationServiceInternals } from './ISegmentationServiceInternals';
+
+const { Labelmap: LABELMAP, Surface: SURFACE } = csToolsEnums.SegmentationRepresentations;
+const {
+  state: { updateLabelmapSegmentationImageReferences },
+} = cstSegmentation;
+
+/**
+ * Legacy (default) segmentation backend. Selected when the target viewport is NOT a
+ * native GenericViewport (the off path / legacy StackViewport / VolumeViewport).
+ * Holds the labelmap-add decision tree verbatim (determine + handleViewportConversion
+ * + the stack/volume case handlers) and delegates the servicesManager-coupled work
+ * (convertStackToVolumeViewport / attemptStackToVolumeConversion / handleVolumeViewport)
+ * back to the service via ISegmentationServiceInternals, so behavior is byte-identical
+ * to before the backend split.
+ */
+export class LegacySegmentationBackend implements ISegmentationBackend {
+  constructor(private readonly service: ISegmentationServiceInternals) {}
+
+  async classifyAndPrepareLabelmapAdd(
+    csViewport: csTypes.IViewport,
+    segmentation: cstTypes.Segmentation,
+    viewportId: string,
+    segmentationId: string,
+    // The case handlers return LABELMAP/SURFACE directly (byte-identical to the
+    // pre-split handleViewportConversion), so the incoming type is unused here.
+    _representationType: csToolsEnums.SegmentationRepresentations
+  ): Promise<LabelmapAddClassification> {
+    const isVolumeViewport = isVolumeViewportType(csViewport);
+    // A missing labelmap representation (stale/partial segmentation state) must not
+    // throw on the `'volumeId' in ...` probe; treat it as a non-volume segmentation.
+    const labelmapData = segmentation?.representationData?.[LABELMAP];
+    const isVolumeSegmentation = !!labelmapData && 'volumeId' in labelmapData;
+
+    return isVolumeViewport
+      ? this.handleVolumeViewportCase(csViewport, segmentation, isVolumeSegmentation)
+      : this.handleStackViewportCase(
+          csViewport,
+          segmentation,
+          isVolumeSegmentation,
+          viewportId,
+          segmentationId
+        );
+  }
+
+  private async handleVolumeViewportCase(
+    csViewport: csTypes.IViewport,
+    segmentation: cstTypes.Segmentation,
+    isVolumeSegmentation: boolean
+  ): Promise<LabelmapAddClassification> {
+    if (isVolume3DViewportType(csViewport)) {
+      return { representationTypeToUse: SURFACE, isConverted: false };
+    }
+
+    await this.service.handleVolumeViewport(
+      csViewport as csTypes.IVolumeViewport,
+      segmentation,
+      isVolumeSegmentation
+    );
+    return { representationTypeToUse: LABELMAP, isConverted: false };
+  }
+
+  private async handleStackViewportCase(
+    csViewport: csTypes.IViewport,
+    segmentation: cstTypes.Segmentation,
+    isVolumeSegmentation: boolean,
+    viewportId: string,
+    segmentationId: string
+  ): Promise<LabelmapAddClassification> {
+    if (isVolumeSegmentation) {
+      const isConverted = await this.service.convertStackToVolumeViewport(csViewport);
+      return { representationTypeToUse: LABELMAP, isConverted };
+    }
+
+    if (updateLabelmapSegmentationImageReferences(viewportId, segmentationId)) {
+      return { representationTypeToUse: LABELMAP, isConverted: false };
+    }
+
+    const isConverted = await this.service.attemptStackToVolumeConversion(
+      csViewport as csTypes.IStackViewport,
+      segmentation,
+      viewportId,
+      segmentationId
+    );
+
+    return { representationTypeToUse: LABELMAP, isConverted };
+  }
+
+  assembleSegmentationDataForSEG(
+    params: AssembleSegmentationForSEGParams
+  ): cstTypes.SegmentationPublicInput {
+    const { segmentationId, derivedImageIds, referencedImageIds, label, fallbackLabel, segments } =
+      params;
+
+    // Single flattened labelmap layer — byte-identical to the pre-split builder in
+    // createSegmentationForSEGDisplaySet. Overlap is collapsed (one voxel = one id).
+    return {
+      segmentationId,
+      representation: {
+        type: LABELMAP,
+        data: {
+          imageIds: derivedImageIds,
+          referencedImageIds,
+        },
+      },
+      config: {
+        label,
+        fallbackLabel,
+        segments,
+      },
+    };
+  }
+
+  jumpToSegmentCenter(viewport: csTypes.IViewport, world: csTypes.Point3): boolean {
+    // Byte-identical to the pre-split guarded recenter: legacy stack/volume viewports
+    // have jumpToWorld; if absent (e.g. a native viewport reaching the legacy twin),
+    // no-op and report it so the caller skips the highlight, exactly as before.
+    const legacyViewport = viewport as csTypes.IViewport & {
+      jumpToWorld?: (world: csTypes.Point3) => void;
+    };
+    if (!legacyViewport?.jumpToWorld) {
+      return false;
+    }
+    legacyViewport.jumpToWorld(world);
+    return true;
+  }
+}
diff --git a/extensions/cornerstone/src/services/SegmentationService/backends/NextSegmentationBackend.ts b/extensions/cornerstone/src/services/SegmentationService/backends/NextSegmentationBackend.ts
new file mode 100644
index 000000000..49c3036ca
--- /dev/null
+++ b/extensions/cornerstone/src/services/SegmentationService/backends/NextSegmentationBackend.ts
@@ -0,0 +1,159 @@
+import type { Types as csTypes } from '@cornerstonejs/core';
+import {
+  Enums as csToolsEnums,
+  segmentation as cstSegmentation,
+  type Types as cstTypes,
+} from '@cornerstonejs/tools';
+import type {
+  AssembleSegmentationForSEGParams,
+  ISegmentationBackend,
+  LabelmapAddClassification,
+} from './ISegmentationBackend';
+
+const { Labelmap: LABELMAP } = csToolsEnums.SegmentationRepresentations;
+const {
+  state: { updateLabelmapSegmentationImageReferences },
+} = cstSegmentation;
+
+/**
+ * Native GenericViewport ("next") segmentation backend. Selected when the target
+ * viewport is a native generic viewport (raw PlanarViewport;
+ * `isNextViewport(viewport)` is true).
+ *
+ * The keystone of the native migration: a native PlanarViewport renders a labelmap
+ * IN PLACE — cornerstone's `resolveLabelmapRenderPlan` picks `legacy-stack-image`
+ * for a stack labelmap (no volumeId, no VTK_VOLUME_SLICE precondition) and the
+ * duck-typed image-reference resolver maps it onto the viewport's current image. So
+ * this twin NEVER promotes the viewport to an ORTHOGRAPHIC volume viewport: the
+ * legacy `convertStackToVolumeViewport` calls `getViewPresentation` /
+ * `setViewPresentation`, which the raw PlanarViewport does not implement — it throws
+ * (the observed `getViewPresentation is not a function`) and would recreate the
+ * viewport, defeating `useNextViewports`.
+ *
+ * Needs nothing from the host service (it never converts / never touches
+ * servicesManager), so unlike the legacy twin it takes no internals handle.
+ */
+export class NextSegmentationBackend implements ISegmentationBackend {
+  async classifyAndPrepareLabelmapAdd(
+    _csViewport: csTypes.IViewport,
+    _segmentation: cstTypes.Segmentation,
+    viewportId: string,
+    segmentationId: string,
+    representationType: csToolsEnums.SegmentationRepresentations
+  ): Promise<LabelmapAddClassification> {
+    // Try the duck-typed in-place resolver so the labelmap's images map onto the
+    // viewport's current image when the FrameOfReference matches. Its return value
+    // is intentionally ignored: we return isConverted:false UNCONDITIONALLY so we
+    // never promote, even on a mount-timing race where the resolver cannot map yet.
+    updateLabelmapSegmentationImageReferences(viewportId, segmentationId);
+
+    return { representationTypeToUse: representationType, isConverted: false };
+  }
+
+  assembleSegmentationDataForSEG(
+    params: AssembleSegmentationForSEGParams
+  ): cstTypes.SegmentationPublicInput {
+    const {
+      segmentationId,
+      segDisplaySet,
+      derivedImageIds,
+      referencedImageIds,
+      label,
+      fallbackLabel,
+      segments,
+    } = params;
+
+    const groups = segDisplaySet.labelMapImages ?? [];
+    const config = { label, fallbackLabel, segments };
+
+    // Non-overlapping (or a single group): identical to the legacy single-layer build.
+    if (!segDisplaySet.overlappingSegments || groups.length <= 1) {
+      return {
+        segmentationId,
+        representation: {
+          type: LABELMAP,
+          data: { imageIds: derivedImageIds, referencedImageIds },
+        },
+        config,
+      };
+    }
+
+    // Overlapping SEG: register each conflict-free group as its OWN labelmap layer
+    // under one segmentationId. cornerstone's slice path auto-fires for >1 stack layer
+    // (shouldUseSliceRendering) and stacks one depth-offset vtkImageSlice actor per
+    // layer, so all overlapping segments stay simultaneously visible.
+    // ensureLabelmapState preserves a supplied labelmaps/segmentBindings/
+    // primaryLabelmapId map via its `||=` guards, so this needs NO cornerstone change.
+    const labelmaps: Record<
+      string,
+      { labelmapId: string; storageKind: 'stack'; imageIds: string[]; referencedImageIds: string[] }
+    > = {};
+    const segmentBindings: Record<number, { labelmapId: string; labelValue: number }> = {};
+
+    groups.forEach((group, index) => {
+      const labelmapId = `${segmentationId}-storage-${index}`;
+      labelmaps[labelmapId] = {
+        labelmapId,
+        storageKind: 'stack',
+        imageIds: group.map(image => image.imageId),
+        referencedImageIds,
+      };
+
+      // The adapter bin-packs non-overlapping segments into each group and writes each
+      // segment's index as its label value (the colorLUT is segment-indexed, so
+      // labelValue === segmentIndex). Group membership is implicit in the pixel data,
+      // so recover it by collecting the distinct non-zero values present in the group;
+      // those segment indices bind to this layer (so ensureLabelmapState does not
+      // default them all onto the primary layer, which would hide layers 1..N-1).
+      const valuesInGroup = new Set<number>();
+      for (const image of group) {
+        const scalarData = image.voxelManager?.getScalarData();
+        if (!scalarData) {
+          continue;
+        }
+        for (let i = 0; i < scalarData.length; i++) {
+          const value = scalarData[i];
+          if (value !== 0) {
+            valuesInGroup.add(value);
+          }
+        }
+      }
+      valuesInGroup.forEach(value => {
+        segmentBindings[value] = { labelmapId, labelValue: value };
+      });
+    });
+
+    return {
+      segmentationId,
+      representation: {
+        type: LABELMAP,
+        data: {
+          // Keep the flattened list for legacy singular readers (getLabelmapImageIds,
+          // SEG export); the per-layer truth lives in `labelmaps`.
+          imageIds: derivedImageIds,
+          referencedImageIds,
+          labelmaps,
+          segmentBindings,
+          primaryLabelmapId: `${segmentationId}-storage-0`,
+        },
+      },
+      config,
+    } as cstTypes.SegmentationPublicInput;
+  }
+
+  jumpToSegmentCenter(viewport: csTypes.IViewport, world: csTypes.Point3): boolean {
+    // A native PlanarViewport has no jumpToWorld; navigate via a view reference
+    // centered on the segment's world point. This snaps to the slice containing
+    // `world` along the viewport's current view normal (the core of jump-to-segment).
+    // In-plane pan-to-center is a separate, deferred refinement.
+    const nativeViewport = viewport as csTypes.IViewport & {
+      setViewReference?: (ref: csTypes.ViewReference) => void;
+    };
+    if (typeof nativeViewport.setViewReference !== 'function') {
+      return false;
+    }
+    nativeViewport.setViewReference({ cameraFocalPoint: world } as csTypes.ViewReference);
+    viewport.render();
+    return true;
+  }
+}
diff --git a/extensions/cornerstone/src/services/SegmentationService/backends/index.ts b/extensions/cornerstone/src/services/SegmentationService/backends/index.ts
new file mode 100644
index 000000000..caff62183
--- /dev/null
+++ b/extensions/cornerstone/src/services/SegmentationService/backends/index.ts
@@ -0,0 +1,4 @@
+export type { ISegmentationBackend, LabelmapAddClassification } from './ISegmentationBackend';
+export type { ISegmentationServiceInternals } from './ISegmentationServiceInternals';
+export { LegacySegmentationBackend } from './LegacySegmentationBackend';
+export { NextSegmentationBackend } from './NextSegmentationBackend';
diff --git a/extensions/cornerstone/src/services/ViewportService/CornerstoneViewportService.ts b/extensions/cornerstone/src/services/ViewportService/CornerstoneViewportService.ts
index 7d9734d05..8e35219f7 100644
--- a/extensions/cornerstone/src/services/ViewportService/CornerstoneViewportService.ts
+++ b/extensions/cornerstone/src/services/ViewportService/CornerstoneViewportService.ts
@@ -35,13 +35,19 @@ import { usePositionPresentationStore } from '../../stores/usePositionPresentati
 import { useSynchronizersStore } from '../../stores/useSynchronizersStore';
 import { useSegmentationPresentationStore } from '../../stores/useSegmentationPresentationStore';
 import getClosestOrientationFromIOP from '../../utils/isReferenceViewable';
+import { getViewportAdapter } from './adapter';
+import { viewportOperations } from './backends/viewportOperations';
 import {
   getLegacyViewportType,
-  isStackViewportType,
   isVolume3DViewportType,
   isVolumeViewportType,
 } from '../../utils/getLegacyViewportType';
 import { BlendModes } from '@cornerstonejs/core/enums';
+import { isNextViewportsEnabled } from '../../utils/nextViewports';
+import type { IViewportBackend } from './backends/IViewportBackend';
+import type { IViewportServiceInternals } from './backends/IViewportServiceInternals';
+import { LegacyViewportBackend } from './backends/LegacyViewportBackend';
+import { NextViewportBackend } from './backends/NextViewportBackend';
 
 const EVENTS = {
   VIEWPORT_DATA_CHANGED: 'event::cornerstoneViewportService:viewportDataChanged',
@@ -108,7 +114,10 @@ export const WITH_ORIENTATION = { withNavigation: true, withOrientation: true };
  * Handles cornerstone viewport logic including enabling, disabling, and
  * updating the viewport.
  */
-class CornerstoneViewportService extends PubSubService implements IViewportService {
+class CornerstoneViewportService
+  extends PubSubService
+  implements IViewportService, IViewportServiceInternals
+{
   static REGISTRATION = {
     name: 'cornerstoneViewportService',
     altName: 'CornerstoneViewportService',
@@ -133,12 +142,32 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
   gridResizeDelay = 50;
   gridResizeTimeOut = null;
 
+  // Resolved once, lazily, on first use. Forked viewport concerns (mount dispatch +
+  // native dataId lifecycle) route through it.
+  private _backend: IViewportBackend | null = null;
+
   constructor(servicesManager: AppTypes.ServicesManager) {
     super(EVENTS);
     this.renderingEngine = null;
     this.viewportGridResizeObserver = null;
     this.servicesManager = servicesManager;
   }
+
+  /**
+   * Sanctioned flag read (the exhaustive list lives in backends/README.md): pick
+   * the viewport backend once, on first use. Resolved lazily (not in the
+   * constructor) because the service singleton is constructed during extension
+   * registration, BEFORE init.tsx runs setNextViewportsEnabled — the first mount
+   * (when this is first read) always happens after init, so the flag is settled.
+   */
+  private get backend(): IViewportBackend {
+    if (!this._backend) {
+      this._backend = isNextViewportsEnabled()
+        ? new NextViewportBackend(this)
+        : new LegacyViewportBackend(this);
+    }
+    return this._backend;
+  }
   hangingProtocolService: unknown;
   viewportsInfo: unknown;
   sceneVolumeInputs: unknown;
@@ -236,6 +265,8 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
   public destroy() {
     this._removeResizeObserver();
     this.viewportGridResizeObserver = null;
+    // Flush any native dataId registrations the backend owns (§4.7); no-op for legacy.
+    this.backend.destroy();
     try {
       this.renderingEngine?.destroy?.();
     } catch (e) {
@@ -257,6 +288,10 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
    * @param viewportId - The viewportId to disable
    */
   public disableElement(viewportId: string): void {
+    // Release native dataId registrations BEFORE the viewport bookkeeping is
+    // deleted (§4.7 ref-counted GC); no-op for the legacy backend.
+    this.backend.onViewportDisabled(viewportId);
+
     this.renderingEngine?.disableElement(viewportId);
 
     // clean up
@@ -272,6 +307,12 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
    * @param presentations - The presentations to apply to the viewport.
    * @param viewportInfo - Contains a view reference for immediate application
    */
+  // Public so the viewport backends (IViewportServiceInternals) can record which
+  // display sets a viewport shows from their mount bodies.
+  _trackViewportDisplaySets(viewportId: string, displaySetInstanceUIDs: string[]): void {
+    this.viewportsDisplaySets.set(viewportId, displaySetInstanceUIDs);
+  }
+
   public setPresentations(viewportId: string, presentations: Presentations): void {
     const viewport = this.getCornerstoneViewport(viewportId) as
       | Types.IStackViewport
@@ -379,12 +420,9 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
 
     const viewportInfo = this.viewportsById.get(viewportId);
 
-    return {
-      viewportType: viewportInfo.getViewportType(),
-      viewReference: isVolume3DViewportType(csViewport) ? null : csViewport.getViewReference(),
-      viewPresentation: csViewport.getViewPresentation({ pan: true, zoom: true }),
-      viewportId,
-    };
+    // Forked per backend (§4.3 presentation read): legacy reads getViewPresentation
+    // (pan/zoom); native omits it (a PLANAR_NEXT viewport has no getViewPresentation).
+    return this.backend.getPositionPresentation(csViewport, viewportInfo, viewportId);
   }
 
   private _getLutPresentation(viewportId: string): LutPresentation {
@@ -411,7 +449,7 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
 
     const properties = isVolumeViewportType(csViewport)
       ? new Map()
-      : cleanProperties(csViewport.getProperties());
+      : cleanProperties(getViewportAdapter(csViewport).getPresentation());
 
     if (properties instanceof Map) {
       const volumeIds = (csViewport as Types.IBaseVolumeViewport).getAllVolumeIds();
@@ -661,7 +699,8 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
 
     for (const id of this.viewportsById.keys()) {
       const viewport = this.getCornerstoneViewport(id);
-      const { viewPlaneNormal } = viewport.getCamera();
+      // Lane-appropriate view-plane normal (legacy getCamera vs native getViewReference).
+      const viewPlaneNormal = viewportOperations.getViewPlaneNormal(viewport);
 
       if (!viewPlaneNormal) {
         continue;
@@ -830,7 +869,8 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
   /**
    * Sets the image data for the given viewport.
    */
-  private async _setEcgViewport(
+  // Public so the viewport backends (IViewportServiceInternals) can dispatch to it.
+  async _setEcgViewport(
     viewport: Types.IECGViewport,
     viewportData: StackViewportData
   ): Promise<void> {
@@ -840,38 +880,29 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
       console.error('[CornerstoneViewportService] ECG display set has no imageId');
       return;
     }
-    return viewport.setEcg(imageId);
+
+    return this.backend.mountEcg(viewport, displaySet, imageId);
   }
 
-  private async _setOtherViewport(
+  // Public so the viewport backends (IViewportServiceInternals) can dispatch to it.
+  async _setOtherViewport(
     viewport: Types.IStackViewport,
     viewportData: StackViewportData,
     viewportInfo: ViewportInfo,
     _presentations: Presentations = {}
   ): Promise<void> {
     const [displaySet] = viewportData.data;
-    const displaySetId = displaySet.imageIds[0];
-    // Register the WSI dataset so the viewport can resolve its imageIds +
-    // webClient by display-set id, then mount via setDisplaySets. The webClient
-    // was registered under the WADO_WEB_CLIENT module (keyed by imageIds[0]) by
-    // the SM SOP class handler. CS3D's "redo viewports" reads this same registry
-    // (genericViewportDisplaySetMetadataProvider) from its WSI data provider;
-    // without this entry setDisplaySets throws "No registered WSI dataset" and
-    // the viewport renders gray.
-    const webClient = metaData.get(csEnums.MetadataModules.WADO_WEB_CLIENT, displaySetId);
-    csUtils.genericViewportDisplaySetMetadataProvider.add(displaySetId, {
-      imageIds: displaySet.imageIds,
-      kind: 'wsi',
-      options: { webClient },
-    });
-    await viewport.setDisplaySets({ displaySetId });
+
+    await this.backend.mountOther(viewport, displaySet);
+
     const viewReference = viewportInfo.getViewReference();
     if (viewReference) {
       viewport.setViewReference(viewReference);
     }
   }
 
-  private async _setStackViewport(
+  // Public so the viewport backends (IViewportServiceInternals) can dispatch to it.
+  async _setStackViewport(
     viewport: Types.IStackViewport,
     viewportData: StackViewportData,
     viewportInfo: ViewportInfo,
@@ -924,7 +955,7 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
     const overlayProcessingResults = this._processExtraDisplaySetsForViewport(viewport);
 
     const referencedImageId = presentations?.positionPresentation?.viewReference?.referencedImageId;
-    if (referencedImageId) {
+    if (referencedImageId && imageIds) {
       initialImageIndexToUse = imageIds.indexOf(referencedImageId);
     }
 
@@ -936,21 +967,20 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
       initialImageIndexToUse = this._getInitialImageIndexForViewport(viewportInfo, imageIds) || 0;
     }
 
-    await viewport.setStack(imageIds, initialImageIndexToUse);
-    viewport.setProperties({ ...properties });
-    this.setPresentations(viewport.id, presentations, viewportInfo);
-
-    await this._addOverlayRepresentations(overlayProcessingResults);
-
-    if (displayArea) {
-      viewport.setDisplayArea(displayArea);
-    }
-    if (rotation) {
-      viewport.setProperties({ rotation });
-    }
-    if (flipHorizontal) {
-      viewport.setCamera({ flipHorizontal: true });
-    }
+    // The lane-specific mount (legacy setStack/setProperties vs native
+    // setDisplaySets/setDisplaySetPresentation/setViewState) lives in the backend.
+    return this.backend.mountStack(viewport, {
+      displaySetInstanceUIDs,
+      imageIds,
+      initialImageIndex: initialImageIndexToUse,
+      properties,
+      displayArea,
+      rotation,
+      flipHorizontal,
+      presentations,
+      viewportInfo,
+      overlayProcessingResults,
+    });
   }
 
   private _getInitialImageIndexForViewport(
@@ -1149,6 +1179,24 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
 
     // For SEG and RT viewports
     const overlayProcessingResults = this._processExtraDisplaySetsForViewport(viewport) || [];
+
+    // Lane-specific volume mount: the native backend mounts registered dataIds via
+    // setDisplaySets + per-binding presentations and reports the mount handled;
+    // legacy reports unhandled and runs the shared setVolumes tail below (which a
+    // native overlay-only mount also traverses — its legacy-surface steps are
+    // lane-guarded via mountOverlayOnlyVolumes).
+    const handledByBackend = await this.backend.mountVolumes(viewport, {
+      filteredVolumeInputArray,
+      volumesProperties,
+      viewportInfo,
+      overlayProcessingResults,
+      presentations,
+    });
+    if (handledByBackend) {
+      this._broadcastEvent(this.EVENTS.VIEWPORT_VOLUMES_CHANGED, { viewportInfo });
+      return;
+    }
+
     if (!filteredVolumeInputArray.length && overlayProcessingResults?.length) {
       overlayProcessingResults.forEach(({ imageIds, addOverlayFn }) => {
         if (addOverlayFn) {
@@ -1213,7 +1261,10 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
         await viewport.setVolumes(baseVolumeInputs);
       }
     } else if (volumeInputArray.length) {
-      await viewport.setVolumes(volumeInputArray);
+      // Every volume input is an overlay display set. Legacy still mounts them via
+      // setVolumes; the native backend no-ops (its overlays are added via
+      // _addOverlayRepresentations below).
+      await this.backend.mountOverlayOnlyVolumes(viewport, volumeInputArray);
     }
 
     await this._addOverlayRepresentations(overlayProcessingResults);
@@ -1412,7 +1463,9 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
     return applyRepresentation();
   }
 
-  private async _addOverlayRepresentations(
+  // Public so the viewport backends (IViewportServiceInternals) can run the
+  // pending overlay adds from their mount bodies.
+  async _addOverlayRepresentations(
     overlayProcessingResults?: Array<{ addOverlayFn?: () => Promise<void> }>
   ): Promise<void> {
     if (!overlayProcessingResults?.length) {
@@ -1430,21 +1483,20 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
   public updateViewport(viewportId: string, viewportData, keepCamera = false) {
     const viewportInfo = this.getViewportInfo(viewportId);
     const viewport = this.getCornerstoneViewport(viewportId);
-    const viewportCamera = viewport.getCamera();
 
-    let displaySetPromise;
+    // The camera snapshot/restore surface is forked per lane (legacy
+    // getCamera/setCamera vs native view state), so the backend owns the re-mount.
+    const displaySetPromise = this.backend.remount(
+      viewport,
+      viewportData,
+      viewportInfo,
+      keepCamera
+    );
 
-    if (isVolumeViewportType(viewport)) {
-      displaySetPromise = this._setVolumeViewport(viewport, viewportData, viewportInfo).then(() => {
-        if (keepCamera) {
-          viewport.setCamera(viewportCamera);
-          viewport.render();
-        }
-      });
-    }
-
-    if (isStackViewportType(viewport)) {
-      displaySetPromise = this._setStackViewport(viewport, viewportData, viewportInfo);
+    // remount() returns undefined for viewport families with no re-mount path
+    // (matching legacy behavior); nothing changed, so skip the event broadcast.
+    if (!displaySetPromise) {
+      return;
     }
 
     displaySetPromise.then(() => {
@@ -1461,37 +1513,11 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
     viewportInfo: ViewportInfo,
     presentations: Presentations = {}
   ): Promise<void> {
-    if (isStackViewportType(viewport)) {
-      return this._setStackViewport(
-        viewport,
-        viewportData as StackViewportData,
-        viewportInfo,
-        presentations
-      );
-    }
-
-    if (isVolumeViewportType(viewport)) {
-      return this._setVolumeViewport(
-        viewport as Types.IVolumeViewport,
-        viewportData as VolumeViewportData,
-        viewportInfo,
-        presentations
-      );
-    }
-
-    if (getLegacyViewportType(viewport) === csEnums.ViewportType.ECG) {
-      return this._setEcgViewport(
-        viewport as unknown as Types.IECGViewport,
-        viewportData as StackViewportData
-      );
-    }
-
-    return this._setOtherViewport(
-      viewport,
-      viewportData as StackViewportData,
-      viewportInfo,
-      presentations
-    );
+    // The backend (legacy vs native, selected once in the constructor) owns the
+    // per-family routing: legacy dispatches by the runtime cornerstone viewport
+    // type; native dispatches by the bound data shape, because native stack and
+    // volume content both report a single PLANAR_NEXT type (§4.4).
+    return this.backend.dispatchMount(viewport, viewportData, viewportInfo, presentations);
   }
 
   /**
@@ -1626,44 +1652,20 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
     viewport: Types.IStackViewport | Types.IVolumeViewport,
     lutPresentation: LutPresentation
   ): void {
-    if (!lutPresentation) {
-      return;
-    }
-
-    const { properties } = lutPresentation;
-    if (isVolumeViewportType(viewport)) {
-      if (properties instanceof Map) {
-        properties.forEach((propertiesEntry, volumeId) => {
-          viewport.setProperties(propertiesEntry, volumeId);
-        });
-      } else {
-        viewport.setProperties(properties);
-      }
-    } else {
-      viewport.setProperties(properties);
-    }
+    // Forked per backend (§4.3 presentation write): legacy applies via setProperties;
+    // native via setDisplaySetPresentation (a PLANAR_NEXT viewport has no setProperties),
+    // so setPresentations no longer throws on the native path.
+    this.backend.setLutPresentation(viewport, lutPresentation);
   }
 
   private _setPositionPresentation(
     viewport: Types.IStackViewport | Types.IVolumeViewport,
     positionPresentation: PositionPresentation
   ): void {
-    const viewRef = positionPresentation?.viewReference;
-    if (viewRef) {
-      // The orientation can be updated here to navigate to the specified
-      // measurement or previous item, but this will not switch to volume
-      // or to stack from the other type
-      if (viewport.isReferenceViewable(viewRef, WITH_ORIENTATION)) {
-        viewport.setViewReference(viewRef);
-      } else {
-        console.warn('Unable to apply reference viewable', viewRef);
-      }
-    }
-
-    const viewPresentation = positionPresentation?.viewPresentation;
-    if (viewPresentation) {
-      viewport.setViewPresentation(viewPresentation);
-    }
+    // Forked per backend (§4.3 presentation write): both apply the view reference;
+    // legacy then applies getViewPresentation pan/zoom via setViewPresentation, native
+    // omits it for now (a PLANAR_NEXT viewport has no setViewPresentation).
+    this.backend.setPositionPresentation(viewport, positionPresentation);
   }
 
   private _setSegmentationPresentation(
diff --git a/extensions/cornerstone/src/services/ViewportService/Viewport.ts b/extensions/cornerstone/src/services/ViewportService/Viewport.ts
index dadae5878..e45340529 100644
--- a/extensions/cornerstone/src/services/ViewportService/Viewport.ts
+++ b/extensions/cornerstone/src/services/ViewportService/Viewport.ts
@@ -227,9 +227,16 @@ class ViewportInfo {
     // via cornerstoneViewportService
     let viewportData = this.getViewportData();
 
+    // Branch on the persisted data shape, not viewportType: native ("next") volume
+    // viewports carry viewportType === PLANAR_NEXT while their data is still a volume
+    // array, so keying off viewportType alone would treat them as a stack object and
+    // miss the display set — skipping invalidateViewportData() on metadata invalidation.
+    // Falls back to viewportType for legacy viewportData with no dataShapeType.
+    const dataShapeType = viewportData.dataShapeType ?? viewportData.viewportType;
+
     if (
-      viewportData.viewportType === Enums.ViewportType.ORTHOGRAPHIC ||
-      viewportData.viewportType === Enums.ViewportType.VOLUME_3D
+      dataShapeType === Enums.ViewportType.ORTHOGRAPHIC ||
+      dataShapeType === Enums.ViewportType.VOLUME_3D
     ) {
       viewportData = viewportData as VolumeViewportData;
       return viewportData.data.some(
diff --git a/extensions/cornerstone/src/services/ViewportService/adapter/IViewportAdapter.contract.test.ts b/extensions/cornerstone/src/services/ViewportService/adapter/IViewportAdapter.contract.test.ts
new file mode 100644
index 000000000..b7fe5be43
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/adapter/IViewportAdapter.contract.test.ts
@@ -0,0 +1,443 @@
+import { Enums, cache } from '@cornerstonejs/core';
+import {
+  getViewportAdapter,
+  isNextViewport,
+  isVolumeRenderingViewport,
+} from './getViewportAdapter';
+import { LegacyViewportAdapter, LEGACY_OPACITY_GAMMA } from './LegacyViewportAdapter';
+import { NextViewportAdapter } from './NextViewportAdapter';
+
+/**
+ * Contract tests for IViewportAdapter: every behavioral guarantee the UI layer
+ * relies on is asserted against BOTH lane implementations over mock viewports.
+ * If a legacy/native divergence is intentional (e.g. opacity gamma), the
+ * divergent expectations are asserted side by side so the difference is
+ * documented here rather than rediscovered in a viewer session.
+ */
+
+const { ViewportType, OrientationAxis } = Enums;
+
+/** Minimal native ("next") viewport: satisfies csUtils.isGenericViewport. */
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function makeNextViewport(overrides: Record<string, unknown> = {}): any {
+  return {
+    id: 'next-viewport',
+    setDisplaySets: jest.fn().mockResolvedValue(undefined),
+    setDisplaySetPresentation: jest.fn(),
+    setViewState: jest.fn(),
+    getViewState: jest.fn().mockReturnValue({ rotation: 90, flipHorizontal: true }),
+    getCurrentMode: jest.fn().mockReturnValue('stack'),
+    getSourceDataId: jest.fn().mockReturnValue('source-uid'),
+    getDisplaySetPresentation: jest.fn().mockReturnValue({}),
+    getDefaultVOIRange: jest.fn().mockReturnValue(undefined),
+    getViewReference: jest.fn().mockReturnValue({
+      viewPlaneNormal: [0, 0, 1],
+      cameraFocalPoint: [1, 2, 3],
+    }),
+    ...overrides,
+  };
+}
+
+/** Minimal legacy stack viewport: no setDisplaySets/setViewState surface. */
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function makeLegacyStackViewport(overrides: Record<string, unknown> = {}): any {
+  return {
+    id: 'legacy-stack',
+    type: ViewportType.STACK,
+    getProperties: jest.fn().mockReturnValue({ voiRange: { lower: 0, upper: 100 } }),
+    setProperties: jest.fn(),
+    getCamera: jest.fn().mockReturnValue({
+      viewPlaneNormal: [0, 0, 1],
+      focalPoint: [1, 2, 3],
+      rotation: 90,
+    }),
+    setCamera: jest.fn(),
+    getActors: jest.fn().mockReturnValue([{ referencedId: 'imageId:abc' }]),
+    ...overrides,
+  };
+}
+
+/** Minimal legacy orthographic (volume) viewport. */
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function makeLegacyVolumeViewport(overrides: Record<string, unknown> = {}): any {
+  const propertiesByVolumeId = {
+    'volumeId-ds-1': { colormap: { name: 'hsv', opacity: 0.9 } },
+  };
+  return {
+    id: 'legacy-volume',
+    type: ViewportType.ORTHOGRAPHIC,
+    getAllVolumeIds: jest.fn().mockReturnValue(['volumeId-ds-1', 'volumeId-ds-2']),
+    getProperties: jest.fn((volumeId?: string) =>
+      volumeId ? (propertiesByVolumeId[volumeId] ?? {}) : { voiRange: { lower: 5, upper: 50 } }
+    ),
+    setProperties: jest.fn(),
+    getCamera: jest.fn().mockReturnValue({ viewPlaneNormal: [1, 0, 0], focalPoint: [4, 5, 6] }),
+    setCamera: jest.fn(),
+    getActors: jest.fn().mockReturnValue([{ referencedId: 'volumeId-ds-1' }]),
+    isInAcquisitionPlane: jest.fn().mockReturnValue(true),
+    getImageData: jest.fn(),
+    ...overrides,
+  };
+}
+
+describe('getViewportAdapter dispatch', () => {
+  it('routes native viewports to NextViewportAdapter and legacy to LegacyViewportAdapter', () => {
+    expect(getViewportAdapter(makeNextViewport())).toBeInstanceOf(NextViewportAdapter);
+    expect(getViewportAdapter(makeLegacyStackViewport())).toBeInstanceOf(LegacyViewportAdapter);
+    expect(getViewportAdapter(makeLegacyVolumeViewport())).toBeInstanceOf(LegacyViewportAdapter);
+  });
+
+  it('caches one adapter per viewport instance', () => {
+    const viewport = makeNextViewport();
+    expect(getViewportAdapter(viewport)).toBe(getViewportAdapter(viewport));
+  });
+
+  it('throws on a missing viewport', () => {
+    expect(() => getViewportAdapter(null)).toThrow();
+    expect(() => getViewportAdapter(undefined)).toThrow();
+  });
+
+  it('isNextViewport matches the dispatch decision', () => {
+    expect(isNextViewport(makeNextViewport())).toBe(true);
+    expect(isNextViewport(makeLegacyStackViewport())).toBe(false);
+  });
+});
+
+describe('classification', () => {
+  it('getShape resolves the content shape on both lanes', () => {
+    expect(getViewportAdapter(makeLegacyStackViewport()).getShape()).toBe('stack');
+    expect(getViewportAdapter(makeLegacyVolumeViewport()).getShape()).toBe('volume');
+    expect(
+      getViewportAdapter(makeLegacyVolumeViewport({ type: ViewportType.VOLUME_3D })).getShape()
+    ).toBe('volume3d');
+
+    expect(
+      getViewportAdapter(
+        makeNextViewport({ getCurrentMode: jest.fn().mockReturnValue('stack') })
+      ).getShape()
+    ).toBe('stack');
+    expect(
+      getViewportAdapter(
+        makeNextViewport({ getCurrentMode: jest.fn().mockReturnValue('volume') })
+      ).getShape()
+    ).toBe('volume');
+  });
+
+  it('isVolumeRendering: legacy ORTHOGRAPHIC / native volume mode only', () => {
+    expect(isVolumeRenderingViewport(makeLegacyVolumeViewport())).toBe(true);
+    expect(isVolumeRenderingViewport(makeLegacyStackViewport())).toBe(false);
+    expect(
+      isVolumeRenderingViewport(
+        makeNextViewport({ getCurrentMode: jest.fn().mockReturnValue('volume') })
+      )
+    ).toBe(true);
+    expect(
+      isVolumeRenderingViewport(
+        makeNextViewport({ getCurrentMode: jest.fn().mockReturnValue('stack') })
+      )
+    ).toBe(false);
+    // Native 3D reorients in place but does NOT support planar volume controls.
+    const next3d = makeNextViewport({ getCurrentMode: jest.fn().mockReturnValue('volume3d') });
+    expect(isVolumeRenderingViewport(next3d)).toBe(false);
+    expect(getViewportAdapter(next3d).canReorientInPlace()).toBe(true);
+  });
+
+  it('isInAcquisitionPlane: legacy asks the viewport; native reads view-state orientation', () => {
+    expect(getViewportAdapter(makeLegacyVolumeViewport()).isInAcquisitionPlane()).toBe(true);
+    expect(
+      getViewportAdapter(
+        makeLegacyVolumeViewport({ isInAcquisitionPlane: jest.fn().mockReturnValue(false) })
+      ).isInAcquisitionPlane()
+    ).toBe(false);
+
+    // Native default (unset orientation) counts as acquisition.
+    expect(
+      getViewportAdapter(
+        makeNextViewport({ getViewState: jest.fn().mockReturnValue({}) })
+      ).isInAcquisitionPlane()
+    ).toBe(true);
+    expect(
+      getViewportAdapter(
+        makeNextViewport({
+          getViewState: jest.fn().mockReturnValue({ orientation: OrientationAxis.SAGITTAL }),
+        })
+      ).isInAcquisitionPlane()
+    ).toBe(false);
+  });
+
+  it('hasContent: legacy via actors, native via content mode', () => {
+    expect(getViewportAdapter(makeLegacyStackViewport()).hasContent()).toBe(true);
+    expect(
+      getViewportAdapter(
+        makeLegacyStackViewport({ getActors: jest.fn().mockReturnValue([]) })
+      ).hasContent()
+    ).toBe(false);
+
+    expect(getViewportAdapter(makeNextViewport()).hasContent()).toBe(true);
+    expect(
+      getViewportAdapter(
+        makeNextViewport({ getCurrentMode: jest.fn().mockReturnValue('empty') })
+      ).hasContent()
+    ).toBe(false);
+  });
+});
+
+describe('view geometry', () => {
+  it('getViewState/setViewState map to getCamera/setCamera on legacy', () => {
+    const viewport = makeLegacyStackViewport();
+    const adapter = getViewportAdapter(viewport);
+    expect(adapter.getViewState().rotation).toBe(90);
+    adapter.setViewState({ flipHorizontal: true });
+    expect(viewport.setCamera).toHaveBeenCalledWith({ flipHorizontal: true });
+  });
+
+  it('getViewState/setViewState pass through natively', () => {
+    const viewport = makeNextViewport();
+    const adapter = getViewportAdapter(viewport);
+    expect(adapter.getViewState().rotation).toBe(90);
+    adapter.setViewState({ rotation: 180 });
+    expect(viewport.setViewState).toHaveBeenCalledWith({ rotation: 180 });
+  });
+
+  it('getViewPlaneNormal and getFocalPoint resolve on both lanes', () => {
+    expect(getViewportAdapter(makeLegacyStackViewport()).getViewPlaneNormal()).toEqual([0, 0, 1]);
+    expect(getViewportAdapter(makeLegacyStackViewport()).getFocalPoint()).toEqual([1, 2, 3]);
+    expect(getViewportAdapter(makeNextViewport()).getViewPlaneNormal()).toEqual([0, 0, 1]);
+    expect(getViewportAdapter(makeNextViewport()).getFocalPoint()).toEqual([1, 2, 3]);
+  });
+});
+
+describe('per-display-set appearance', () => {
+  it('getPresentation: legacy getProperties with/without dataId', () => {
+    const viewport = makeLegacyVolumeViewport();
+    const adapter = getViewportAdapter(viewport);
+    expect(adapter.getPresentation()).toEqual({ voiRange: { lower: 5, upper: 50 } });
+    expect(adapter.getPresentation('volumeId-ds-1').colormap).toEqual({
+      name: 'hsv',
+      opacity: 0.9,
+    });
+  });
+
+  it('getPresentation: native per-binding read, defaulting to the source dataId', () => {
+    const viewport = makeNextViewport({
+      getDisplaySetPresentation: jest.fn().mockReturnValue({ invert: true }),
+    });
+    const adapter = getViewportAdapter(viewport);
+    expect(adapter.getPresentation()).toEqual({ invert: true });
+    expect(viewport.getDisplaySetPresentation).toHaveBeenCalledWith('source-uid');
+    adapter.getPresentation('ds-2');
+    expect(viewport.getDisplaySetPresentation).toHaveBeenCalledWith('ds-2');
+  });
+
+  it('getPresentation: native stamps isComputedVOI when the VOI matches the binding default', () => {
+    const voiRange = { lower: 0, upper: 80 };
+    const stamped = getViewportAdapter(
+      makeNextViewport({
+        getDisplaySetPresentation: jest.fn().mockReturnValue({ voiRange }),
+        getDefaultVOIRange: jest.fn().mockReturnValue({ lower: 0, upper: 80 }),
+      })
+    ).getPresentation();
+    expect(stamped.isComputedVOI).toBe(true);
+
+    const notStamped = getViewportAdapter(
+      makeNextViewport({
+        getDisplaySetPresentation: jest.fn().mockReturnValue({ voiRange }),
+        getDefaultVOIRange: jest.fn().mockReturnValue({ lower: 10, upper: 90 }),
+      })
+    ).getPresentation();
+    expect(notStamped.isComputedVOI).toBeUndefined();
+  });
+
+  it('setPresentation targets setProperties (legacy) / setDisplaySetPresentation (native)', () => {
+    const legacy = makeLegacyVolumeViewport();
+    getViewportAdapter(legacy).setPresentation({ invert: true }, 'volumeId-ds-1');
+    expect(legacy.setProperties).toHaveBeenCalledWith({ invert: true }, 'volumeId-ds-1');
+
+    const next = makeNextViewport();
+    getViewportAdapter(next).setPresentation({ invert: true }, 'ds-1');
+    expect(next.setDisplaySetPresentation).toHaveBeenCalledWith('ds-1', { invert: true });
+
+    // No dataId: native falls back to the source binding.
+    getViewportAdapter(next).setPresentation({ invert: false });
+    expect(next.setDisplaySetPresentation).toHaveBeenCalledWith('source-uid', { invert: false });
+  });
+
+  it('getDefaultVOIRange: native binding default; legacy has none', () => {
+    expect(getViewportAdapter(makeLegacyStackViewport()).getDefaultVOIRange()).toBeUndefined();
+    expect(
+      getViewportAdapter(
+        makeNextViewport({ getDefaultVOIRange: jest.fn().mockReturnValue({ lower: 1, upper: 2 }) })
+      ).getDefaultVOIRange('ds-1')
+    ).toEqual({ lower: 1, upper: 2 });
+  });
+
+  it('getColormap: legacy stack properties / legacy volume actor lookup / native presentation', () => {
+    const stack = makeLegacyStackViewport({
+      getProperties: jest.fn().mockReturnValue({ colormap: { name: 'gray' } }),
+    });
+    expect(getViewportAdapter(stack).getColormap('anything')).toEqual({ name: 'gray' });
+
+    const volume = makeLegacyVolumeViewport();
+    expect(getViewportAdapter(volume).getColormap('ds-1')).toEqual({ name: 'hsv', opacity: 0.9 });
+    expect(getViewportAdapter(volume).getColormap('ds-unknown')).toBeUndefined();
+
+    const next = makeNextViewport({
+      getDisplaySetPresentation: jest.fn().mockReturnValue({ colormap: { name: 'jet' } }),
+    });
+    expect(getViewportAdapter(next).getColormap('ds-1')).toEqual({ name: 'jet' });
+  });
+
+  it('setLayerOpacity merges into the existing colormap on both lanes', () => {
+    const volume = makeLegacyVolumeViewport();
+    expect(getViewportAdapter(volume).setLayerOpacity('ds-1', 0.5)).toBe(true);
+    expect(volume.setProperties).toHaveBeenCalledWith(
+      { colormap: { name: 'hsv', opacity: 0.5 } },
+      'volumeId-ds-1'
+    );
+
+    const next = makeNextViewport({
+      getDisplaySetPresentation: jest.fn().mockReturnValue({ colormap: { name: 'jet' } }),
+    });
+    expect(getViewportAdapter(next).setLayerOpacity('ds-1', 0.5)).toBe(true);
+    expect(next.setDisplaySetPresentation).toHaveBeenCalledWith('ds-1', {
+      colormap: { name: 'jet', opacity: 0.5 },
+    });
+  });
+
+  it('setLayerOpacity is unsupported on a legacy stack (caller must not render)', () => {
+    const stack = makeLegacyStackViewport();
+    expect(getViewportAdapter(stack).setLayerOpacity('ds-1', 0.5)).toBe(false);
+    expect(stack.setProperties).not.toHaveBeenCalled();
+  });
+
+  it('setLayerThreshold: legacy historically does NOT merge; native merges', () => {
+    const volume = makeLegacyVolumeViewport();
+    expect(getViewportAdapter(volume).setLayerThreshold('ds-1', 42)).toBe(true);
+    expect(volume.setProperties).toHaveBeenCalledWith(
+      { colormap: { threshold: 42 } },
+      'volumeId-ds-1'
+    );
+
+    const next = makeNextViewport({
+      getDisplaySetPresentation: jest.fn().mockReturnValue({ colormap: { name: 'jet' } }),
+    });
+    expect(getViewportAdapter(next).setLayerThreshold('ds-1', 42)).toBe(true);
+    expect(next.setDisplaySetPresentation).toHaveBeenCalledWith('ds-1', {
+      colormap: { name: 'jet', threshold: 42 },
+    });
+  });
+
+  it('getOpacityGamma: linear on native, historical 1/5 curve on legacy', () => {
+    expect(getViewportAdapter(makeNextViewport()).getOpacityGamma()).toBe(1);
+    expect(getViewportAdapter(makeLegacyVolumeViewport()).getOpacityGamma()).toBe(
+      LEGACY_OPACITY_GAMMA
+    );
+  });
+});
+
+describe('data addressing', () => {
+  it('getDataIdForDisplaySet: bare UID on native; matching volumeId on legacy volume; undefined on legacy stack', () => {
+    expect(getViewportAdapter(makeNextViewport()).getDataIdForDisplaySet('ds-1')).toBe('ds-1');
+    expect(getViewportAdapter(makeLegacyVolumeViewport()).getDataIdForDisplaySet('ds-1')).toBe(
+      'volumeId-ds-1'
+    );
+    expect(
+      getViewportAdapter(makeLegacyVolumeViewport()).getDataIdForDisplaySet('nope')
+    ).toBeUndefined();
+    expect(
+      getViewportAdapter(makeLegacyStackViewport()).getDataIdForDisplaySet('ds-1')
+    ).toBeUndefined();
+  });
+
+  it('getVolumeIds: legacy volume list; empty on native and legacy stack', () => {
+    expect(getViewportAdapter(makeLegacyVolumeViewport()).getVolumeIds()).toEqual([
+      'volumeId-ds-1',
+      'volumeId-ds-2',
+    ]);
+    expect(getViewportAdapter(makeLegacyStackViewport()).getVolumeIds()).toEqual([]);
+    expect(getViewportAdapter(makeNextViewport()).getVolumeIds()).toEqual([]);
+  });
+
+  it('getVoxelManagerForDisplaySet: native resolves from the cornerstone cache', () => {
+    const voxelManager = { getRange: () => [0, 100] as [number, number] };
+    const derivedVoxelManager = { getRange: () => [0, 1] as [number, number] };
+    const spy = jest.spyOn(cache, 'getVolumes').mockReturnValue([
+      // A derived id that merely EMBEDS the UID must not match (anchored lookup);
+      // real volumeIds are `${volumeLoaderSchema}:${displaySetInstanceUID}`.
+      { volumeId: 'derived-ds-1-labelmap', voxelManager: derivedVoxelManager },
+      { volumeId: 'cornerstoneStreamingImageVolume:ds-1', voxelManager },
+    ] as never);
+    try {
+      expect(getViewportAdapter(makeNextViewport()).getVoxelManagerForDisplaySet('ds-1')).toBe(
+        voxelManager
+      );
+      expect(
+        getViewportAdapter(makeNextViewport()).getVoxelManagerForDisplaySet('missing')
+      ).toBeUndefined();
+    } finally {
+      spy.mockRestore();
+    }
+  });
+
+  it('getVoxelManagerForDisplaySet: legacy volume reads getImageData(volumeId)', () => {
+    const voxelManager = { getRange: () => [0, 50] as [number, number] };
+    const viewport = makeLegacyVolumeViewport({
+      getImageData: jest.fn().mockReturnValue({
+        imageData: {
+          get: (key: string) => (key === 'voxelManager' ? { voxelManager } : undefined),
+        },
+      }),
+    });
+    expect(getViewportAdapter(viewport).getVoxelManagerForDisplaySet('ds-1')).toBe(voxelManager);
+    expect(viewport.getImageData).toHaveBeenCalledWith('volumeId-ds-1');
+    expect(
+      getViewportAdapter(makeLegacyStackViewport()).getVoxelManagerForDisplaySet('ds-1')
+    ).toBeUndefined();
+  });
+});
+
+describe('capture (copyDisplayedContentTo)', () => {
+  it('legacy: setStack + properties + view presentation + view reference onto the target', async () => {
+    const source = makeLegacyStackViewport({
+      getCurrentImageId: jest.fn().mockReturnValue('imageId:abc'),
+      getViewReference: jest.fn().mockReturnValue({ viewPlaneNormal: [0, 0, 1] }),
+      getViewPresentation: jest.fn().mockReturnValue({ zoom: 2 }),
+    });
+    const target = makeLegacyStackViewport({
+      setStack: jest.fn().mockResolvedValue(undefined),
+      setViewPresentation: jest.fn(),
+      setViewReference: jest.fn(),
+    });
+
+    await getViewportAdapter(source).copyDisplayedContentTo(target as never);
+
+    expect(target.setStack).toHaveBeenCalledWith(['imageId:abc']);
+    expect(target.setViewPresentation).toHaveBeenCalledWith({ zoom: 2 });
+    expect(target.setProperties).toHaveBeenCalledWith({ voiRange: { lower: 0, upper: 100 } });
+    expect(target.setViewReference).toHaveBeenCalledWith({ viewPlaneNormal: [0, 0, 1] });
+  });
+
+  it('native: remounts the source dataId and copies presentation + view state', async () => {
+    const source = makeNextViewport({
+      getDisplaySetPresentation: jest.fn().mockReturnValue({ invert: true }),
+      getViewState: jest.fn().mockReturnValue({ orientation: 'axial', rotation: 45 }),
+    });
+    const target = makeNextViewport({
+      getSourceDataId: jest.fn().mockReturnValue('capture-uid'),
+      setViewReference: jest.fn(),
+    });
+
+    await getViewportAdapter(source).copyDisplayedContentTo(target as never);
+
+    expect(target.setDisplaySets).toHaveBeenCalledWith({
+      displaySetId: 'source-uid',
+      options: { orientation: 'axial', role: 'source' },
+    });
+    expect(target.setDisplaySetPresentation).toHaveBeenCalledWith('capture-uid', { invert: true });
+    expect(target.setViewReference).toHaveBeenCalledWith({
+      viewPlaneNormal: [0, 0, 1],
+      cameraFocalPoint: [1, 2, 3],
+    });
+    expect(target.setViewState).toHaveBeenCalledWith({ orientation: 'axial', rotation: 45 });
+  });
+});
diff --git a/extensions/cornerstone/src/services/ViewportService/adapter/IViewportAdapter.ts b/extensions/cornerstone/src/services/ViewportService/adapter/IViewportAdapter.ts
new file mode 100644
index 000000000..0eaad651f
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/adapter/IViewportAdapter.ts
@@ -0,0 +1,179 @@
+import type { Types as CoreTypes } from '@cornerstonejs/core';
+
+/**
+ * Content shape of a viewport, independent of the runtime cornerstone viewport
+ * type. Native ("next") viewports collapse stack/volume/MPR onto a single
+ * PLANAR_NEXT runtime type, so `viewport.type` checks cannot classify them;
+ * this is the lane-agnostic answer to "what is this viewport showing".
+ */
+export type ViewportShape = 'stack' | 'volume' | 'volume3d' | 'unknown';
+
+export type VOIRange = { lower: number; upper: number };
+
+export interface ViewportColormap {
+  name?: string;
+  opacity?: number | Array<{ value: number; opacity: number }> | number[];
+  threshold?: number;
+  [key: string]: unknown;
+}
+
+/**
+ * Per-display-set appearance (VOI/colormap/invert). On legacy this is the
+ * getProperties()/setProperties() surface; on native it is the per-binding
+ * display-set presentation keyed by dataId.
+ */
+export interface ViewportPresentation {
+  voiRange?: VOIRange;
+  colormap?: ViewportColormap;
+  invert?: boolean;
+  isComputedVOI?: boolean;
+  [key: string]: unknown;
+}
+
+/**
+ * View-level state (rotation, flip, orientation, pan/zoom). On legacy this is
+ * the getCamera()/setCamera() surface; on native it is the semantic
+ * getViewState()/setViewState() surface. Field names follow the native shape
+ * where the two overlap (rotation, flipHorizontal, flipVertical).
+ */
+export type ViewportViewState = Record<string, unknown>;
+
+/**
+ * The single OHIF-facing per-viewport contract over the legacy and native
+ * ("next") cornerstone viewport APIs.
+ *
+ * The contract is NEXT-SHAPED: method names and semantics follow the native
+ * API (view state, per-display-set presentation keyed by dataId, view
+ * reference). `NextViewportAdapter` is a thin pass-through;
+ * `LegacyViewportAdapter` is the side doing the adapting
+ * (getCamera -> view state, volumeId -> dataId). When the legacy path is
+ * eventually removed, the migration ends by deleting the legacy adapter — not
+ * by unwinding call-site ternaries.
+ *
+ * Obtain an instance ONLY via `getViewportAdapter(viewport)` — the one place
+ * allowed to call `csUtils.isGenericViewport`. UI code (hooks, overlays,
+ * components, toolbar evaluators) must consume this interface instead of
+ * probing the raw viewport surface.
+ */
+export interface IViewportAdapter {
+  // ---- classification ----
+
+  /** Lane-agnostic content shape (see ViewportShape). */
+  getShape(): ViewportShape;
+
+  /**
+   * True when the viewport renders volume content and supports volume-only
+   * appearance controls (threshold, per-layer opacity): legacy ORTHOGRAPHIC,
+   * or a native viewport whose active binding is a volume.
+   */
+  isVolumeRendering(): boolean;
+
+  /**
+   * True when the viewport can be reoriented in place via setOrientation()
+   * without being recreated: legacy ORTHOGRAPHIC, or a native viewport already
+   * rendering volume content (volume slice or 3D). Differs from
+   * isVolumeRendering() on native 3D viewports, which reorient in place but do
+   * not support the planar volume appearance controls.
+   */
+  canReorientInPlace(): boolean;
+
+  /**
+   * True when a volume-mode viewport is looking down the acquisition axis
+   * (legacy isInAcquisitionPlane(); native view-state orientation ACQUISITION,
+   * which is also the native default when unset).
+   */
+  isInAcquisitionPlane(): boolean;
+
+  /**
+   * True when the viewport has renderable content bound. Legacy reports this
+   * via actors; native (which has no getActors on planar viewports) via its
+   * content mode.
+   */
+  hasContent(): boolean;
+
+  // ---- view geometry ----
+
+  /** Read view-level state (rotation/flip/orientation/...). Empty object when unavailable. */
+  getViewState(): ViewportViewState;
+
+  /** Apply a partial view-state patch; unspecified fields are preserved. */
+  setViewState(patch: ViewportViewState): void;
+
+  /** Current view-plane normal (legacy camera; native view reference). */
+  getViewPlaneNormal(): CoreTypes.Point3 | undefined;
+
+  /** World-space focal point / slice center (legacy camera; native view reference). */
+  getFocalPoint(): CoreTypes.Point3 | undefined;
+
+  // ---- per-display-set appearance ----
+
+  /**
+   * Read appearance (voiRange/colormap/invert/...) for a display set binding.
+   * Defaults to the active source binding when no dataId is given. On native,
+   * a VOI matching the binding's computed default is stamped
+   * `isComputedVOI: true` so LUT-presentation capture strips it (matching
+   * legacy StackViewport behavior).
+   */
+  getPresentation(dataId?: string): ViewportPresentation;
+
+  /** Write appearance for a display set binding (active source binding when no dataId). */
+  setPresentation(props: ViewportPresentation, dataId?: string): void;
+
+  /** The binding's computed default VOI (native only; legacy returns undefined). */
+  getDefaultVOIRange(dataId?: string): VOIRange | undefined;
+
+  /**
+   * The colormap currently applied to a display set's layer, or undefined when
+   * none (callers supply their own fallback, e.g. Grayscale).
+   */
+  getColormap(displaySetInstanceUID: string): ViewportColormap | undefined;
+
+  /**
+   * Merge an opacity into the display set layer's colormap. Returns true when
+   * applied (caller renders); false when the viewport/layer does not support it.
+   */
+  setLayerOpacity(displaySetInstanceUID: string, opacity: number): boolean;
+
+  /**
+   * Apply a threshold to the display set layer's colormap. Returns true when
+   * applied (caller renders); false when unsupported.
+   */
+  setLayerThreshold(displaySetInstanceUID: string, threshold: number): boolean;
+
+  /**
+   * Gamma applied between the fusion opacity slider position and the rendered
+   * opacity. Native renders a linear blend (gamma 1); legacy rendering expects
+   * its historical 1/5 curve.
+   */
+  getOpacityGamma(): number;
+
+  // ---- data addressing ----
+
+  /**
+   * Resolve the dataId to address a display set's binding on this viewport:
+   * the bare display set UID on native; the matching volumeId on legacy volume
+   * viewports; undefined on legacy single-actor viewports (callers fall back
+   * to the active binding).
+   */
+  getDataIdForDisplaySet(displaySetInstanceUID: string): string | undefined;
+
+  /**
+   * The legacy volumeIds bound to this viewport ([] on native and on legacy
+   * stack viewports). For legacy-only features such as per-volume histograms.
+   */
+  getVolumeIds(): string[];
+
+  /** Voxel data access (getRange etc.) for a display set's volume, when available. */
+  getVoxelManagerForDisplaySet(
+    displaySetInstanceUID: string
+  ): { getRange?: () => [number, number]; [key: string]: unknown } | undefined;
+
+  // ---- capture ----
+
+  /**
+   * Mount this viewport's currently-displayed data onto another (same-lane)
+   * viewport and copy its appearance + view state. Used by the download/
+   * capture form; the caller renders the target afterwards.
+   */
+  copyDisplayedContentTo(target: CoreTypes.IViewport): Promise<void>;
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/adapter/LegacyViewportAdapter.ts b/extensions/cornerstone/src/services/ViewportService/adapter/LegacyViewportAdapter.ts
new file mode 100644
index 000000000..08ca81275
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/adapter/LegacyViewportAdapter.ts
@@ -0,0 +1,240 @@
+import { Enums, Types as CoreTypes } from '@cornerstonejs/core';
+import {
+  getLegacyViewportType,
+  isOrthographicViewportType,
+  isStackViewportType,
+  isVolumeViewportType,
+} from '../../../utils/getLegacyViewportType';
+import type {
+  IViewportAdapter,
+  ViewportColormap,
+  ViewportPresentation,
+  ViewportShape,
+  ViewportViewState,
+  VOIRange,
+} from './IViewportAdapter';
+
+/**
+ * Structural view of the legacy StackViewport/VolumeViewport surface used by
+ * the adapter. Optional-chained because different legacy families expose
+ * different subsets (e.g. only volume viewports have getAllVolumeIds).
+ * Deliberately NOT an intersection with CoreTypes.IViewport: the adapter
+ * contract types these members with the next-shaped signatures (e.g. getCamera
+ * as a plain record), and IViewport's own declarations would win otherwise.
+ */
+type LegacyViewport = {
+  getProperties?: (dataId?: string) => ViewportPresentation | undefined;
+  setProperties?: (props: ViewportPresentation, dataId?: string) => void;
+  getCamera?: () => Record<string, unknown> | undefined;
+  setCamera?: (patch: Record<string, unknown>) => void;
+  getAllVolumeIds?: () => string[];
+  getImageData?: (volumeId?: string) => {
+    imageData?: { get: (key: string) => { voxelManager?: unknown } | undefined };
+  };
+  getActors?: () => Array<{ referencedId?: string }>;
+  isInAcquisitionPlane?: () => boolean;
+  getViewReference?: () => CoreTypes.ViewReference | undefined;
+  setViewReference?: (ref: CoreTypes.ViewReference) => void;
+  getViewPresentation?: () => unknown;
+  setViewPresentation?: (presentation: unknown) => void;
+  getCurrentImageId?: () => string;
+  setStack?: (imageIds: string[]) => Promise<unknown>;
+  setVolumes?: (volumes: Array<{ volumeId: string }>) => Promise<unknown>;
+};
+
+/**
+ * Opacity slider gamma the legacy fusion rendering expects: the slider value is
+ * applied through a 1/5 curve (native renders a linear blend and uses gamma 1).
+ */
+export const LEGACY_OPACITY_GAMMA = 1 / 5;
+
+/**
+ * Legacy lane of IViewportAdapter — adapts the StackViewport/VolumeViewport
+ * surface (getCamera/getProperties/volumeIds) to the next-shaped contract.
+ * Deleting the legacy path deletes this file. Instantiated only by
+ * `getViewportAdapter`.
+ */
+export class LegacyViewportAdapter implements IViewportAdapter {
+  constructor(private readonly viewport: LegacyViewport) {}
+
+  // ---- classification ----
+
+  getShape(): ViewportShape {
+    switch (getLegacyViewportType(this.viewport)) {
+      case Enums.ViewportType.STACK:
+        return 'stack';
+      case Enums.ViewportType.ORTHOGRAPHIC:
+        return 'volume';
+      case Enums.ViewportType.VOLUME_3D:
+        return 'volume3d';
+      default:
+        return 'unknown';
+    }
+  }
+
+  isVolumeRendering(): boolean {
+    return isOrthographicViewportType(this.viewport);
+  }
+
+  canReorientInPlace(): boolean {
+    return isOrthographicViewportType(this.viewport);
+  }
+
+  isInAcquisitionPlane(): boolean {
+    return !!this.viewport.isInAcquisitionPlane?.();
+  }
+
+  hasContent(): boolean {
+    const actorEntries = this.viewport.getActors?.();
+    return !!actorEntries && actorEntries.length > 0;
+  }
+
+  // ---- view geometry ----
+
+  getViewState(): ViewportViewState {
+    return this.viewport.getCamera?.() ?? {};
+  }
+
+  setViewState(patch: ViewportViewState): void {
+    this.viewport.setCamera?.(patch);
+  }
+
+  getViewPlaneNormal(): CoreTypes.Point3 | undefined {
+    return this.viewport.getCamera?.()?.viewPlaneNormal as CoreTypes.Point3 | undefined;
+  }
+
+  getFocalPoint(): CoreTypes.Point3 | undefined {
+    return this.viewport.getCamera?.()?.focalPoint as CoreTypes.Point3 | undefined;
+  }
+
+  // ---- per-display-set appearance ----
+
+  getPresentation(dataId?: string): ViewportPresentation {
+    return (dataId ? this.viewport.getProperties?.(dataId) : this.viewport.getProperties?.()) ?? {};
+  }
+
+  setPresentation(props: ViewportPresentation, dataId?: string): void {
+    this.viewport.setProperties?.(props, dataId);
+  }
+
+  getDefaultVOIRange(): VOIRange | undefined {
+    // Legacy getProperties always returns the applied VOI; there is no separate
+    // computed-default accessor.
+    return undefined;
+  }
+
+  getColormap(displaySetInstanceUID: string): ViewportColormap | undefined {
+    if (isStackViewportType(this.viewport)) {
+      return this.viewport.getProperties?.()?.colormap;
+    }
+
+    const actorEntries = this.viewport.getActors?.();
+    const actorEntry = actorEntries?.find(entry =>
+      entry.referencedId?.includes(displaySetInstanceUID)
+    );
+    if (!actorEntry) {
+      return undefined;
+    }
+    return this.viewport.getProperties?.(actorEntry.referencedId)?.colormap;
+  }
+
+  setLayerOpacity(displaySetInstanceUID: string, opacity: number): boolean {
+    if (!isVolumeViewportType(this.viewport)) {
+      return false;
+    }
+    const volumeId = this.getDataIdForDisplaySet(displaySetInstanceUID);
+    if (!volumeId) {
+      return false;
+    }
+
+    // Merge the opacity into the current colormap so its name/threshold persist.
+    const currentColormap = this.viewport.getProperties?.(volumeId)?.colormap ?? {};
+    this.viewport.setProperties?.({ colormap: { ...currentColormap, opacity } }, volumeId);
+    return true;
+  }
+
+  setLayerThreshold(displaySetInstanceUID: string, threshold: number): boolean {
+    if (!isVolumeViewportType(this.viewport)) {
+      return false;
+    }
+    const volumeId = this.getDataIdForDisplaySet(displaySetInstanceUID);
+    if (!volumeId) {
+      return false;
+    }
+
+    this.viewport.setProperties?.({ colormap: { threshold } }, volumeId);
+    return true;
+  }
+
+  getOpacityGamma(): number {
+    return LEGACY_OPACITY_GAMMA;
+  }
+
+  // ---- data addressing ----
+
+  getDataIdForDisplaySet(displaySetInstanceUID: string): string | undefined {
+    // Multi-volume viewports address a layer by the volumeId that embeds the
+    // display set UID; single-actor viewports (stack) address the active layer
+    // implicitly (undefined).
+    if (typeof this.viewport.getAllVolumeIds !== 'function') {
+      return undefined;
+    }
+    const volumeIds = this.viewport.getAllVolumeIds() || [];
+    return volumeIds.length > 0
+      ? (volumeIds.find(id => id.includes(displaySetInstanceUID)) ?? undefined)
+      : undefined;
+  }
+
+  getVolumeIds(): string[] {
+    if (typeof this.viewport.getAllVolumeIds !== 'function') {
+      return [];
+    }
+    return this.viewport.getAllVolumeIds() || [];
+  }
+
+  getVoxelManagerForDisplaySet(
+    displaySetInstanceUID: string
+  ): { getRange?: () => [number, number]; [key: string]: unknown } | undefined {
+    if (!isVolumeViewportType(this.viewport)) {
+      return undefined;
+    }
+    const volumeId = this.getDataIdForDisplaySet(displaySetInstanceUID);
+    if (!volumeId) {
+      return undefined;
+    }
+    const imageData = this.viewport.getImageData?.(volumeId);
+    return imageData?.imageData?.get('voxelManager')?.voxelManager as
+      | { getRange?: () => [number, number]; [key: string]: unknown }
+      | undefined;
+  }
+
+  // ---- capture ----
+
+  async copyDisplayedContentTo(target: CoreTypes.IViewport): Promise<void> {
+    const targetViewport = target as unknown as LegacyViewport;
+    const viewRef = this.viewport.getViewReference?.();
+
+    // - properties: VOI, colormap, interpolation, etc.
+    // - viewPresentation: flip/rotate/zoom presentation state (preserves flip/rotate)
+    const properties = this.viewport.getProperties?.();
+    const viewPresentation = this.viewport.getViewPresentation?.();
+
+    if (isStackViewportType(targetViewport)) {
+      const imageId = this.viewport.getCurrentImageId?.();
+      await targetViewport.setStack?.([imageId]);
+    } else if (isVolumeViewportType(targetViewport)) {
+      const volumeIds = this.getVolumeIds();
+      await targetViewport.setVolumes?.([{ volumeId: volumeIds[0] }]);
+    }
+
+    if (viewPresentation && targetViewport.setViewPresentation) {
+      targetViewport.setViewPresentation(viewPresentation);
+    }
+
+    targetViewport.setProperties?.(properties);
+
+    if (viewRef && targetViewport.setViewReference) {
+      targetViewport.setViewReference(viewRef);
+    }
+  }
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/adapter/NextViewportAdapter.ts b/extensions/cornerstone/src/services/ViewportService/adapter/NextViewportAdapter.ts
new file mode 100644
index 000000000..4385a7554
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/adapter/NextViewportAdapter.ts
@@ -0,0 +1,233 @@
+import { Enums, cache, Types as CoreTypes } from '@cornerstonejs/core';
+import { isVolume3DViewportType } from '../../../utils/getLegacyViewportType';
+import type {
+  IViewportAdapter,
+  ViewportColormap,
+  ViewportPresentation,
+  ViewportShape,
+  ViewportViewState,
+  VOIRange,
+} from './IViewportAdapter';
+
+/**
+ * Structural view of the native ("next") viewport surface used by the adapter.
+ * These accessors live on IGenericViewport (not IViewport), so we cast at this
+ * boundary rather than import core-internal PlanarViewport types.
+ */
+type NativeViewport = CoreTypes.IViewport & {
+  getSourceDataId?: () => string | undefined;
+  getDisplaySetPresentation?: (dataId: string) => ViewportPresentation | undefined;
+  getDefaultVOIRange?: (dataId?: string) => VOIRange | undefined;
+  setDisplaySetPresentation?: {
+    (props: ViewportPresentation): void;
+    (dataId: string, props: ViewportPresentation): void;
+  };
+  getViewState?: () => ViewportViewState | undefined;
+  setViewState?: (patch: ViewportViewState) => void;
+  getViewReference?: () => CoreTypes.ViewReference | undefined;
+  setViewReference?: (ref: CoreTypes.ViewReference) => void;
+  getCurrentMode?: () => string;
+  setDisplaySets?: (args: {
+    displaySetId: string;
+    options?: Record<string, unknown>;
+  }) => Promise<void>;
+};
+
+const voiRangesClose = (a: VOIRange, b: VOIRange, eps = 0.001): boolean =>
+  Math.abs(a.lower - b.lower) < eps && Math.abs(a.upper - b.upper) < eps;
+
+/**
+ * Native ("next") lane of IViewportAdapter — a thin pass-through to the native
+ * semantic API (view state, per-binding display-set presentation, view
+ * reference). Instantiated only by `getViewportAdapter`.
+ */
+export class NextViewportAdapter implements IViewportAdapter {
+  constructor(private readonly viewport: NativeViewport) {}
+
+  // ---- classification ----
+
+  getShape(): ViewportShape {
+    if (isVolume3DViewportType(this.viewport)) {
+      return 'volume3d';
+    }
+    const mode = this.viewport.getCurrentMode?.();
+    if (mode === 'stack') {
+      return 'stack';
+    }
+    if (mode === 'volume') {
+      return 'volume';
+    }
+    return 'unknown';
+  }
+
+  isVolumeRendering(): boolean {
+    return this.viewport.getCurrentMode?.() === 'volume';
+  }
+
+  canReorientInPlace(): boolean {
+    const mode = this.viewport.getCurrentMode?.();
+    return mode === 'volume' || mode === 'volume3d';
+  }
+
+  isInAcquisitionPlane(): boolean {
+    // orientation defaults to ACQUISITION when unset on the native view state.
+    const orientation = this.viewport.getViewState?.()?.orientation;
+    return orientation === Enums.OrientationAxis.ACQUISITION || orientation == null;
+  }
+
+  hasContent(): boolean {
+    // Planar native viewports have no getActors (it throws); content presence
+    // is reported by the content mode (empty/unknown means nothing bound).
+    const mode = this.viewport.getCurrentMode?.();
+    return !!mode && mode !== 'empty' && mode !== 'unknown';
+  }
+
+  // ---- view geometry ----
+
+  getViewState(): ViewportViewState {
+    return this.viewport.getViewState?.() ?? {};
+  }
+
+  setViewState(patch: ViewportViewState): void {
+    this.viewport.setViewState?.(patch);
+  }
+
+  getViewPlaneNormal(): CoreTypes.Point3 | undefined {
+    return this.viewport.getViewReference?.()?.viewPlaneNormal as CoreTypes.Point3 | undefined;
+  }
+
+  getFocalPoint(): CoreTypes.Point3 | undefined {
+    // The native view state carries no focalPoint; it comes from the view reference.
+    return this.viewport.getViewReference?.()?.cameraFocalPoint as CoreTypes.Point3 | undefined;
+  }
+
+  // ---- per-display-set appearance ----
+
+  getPresentation(dataId?: string): ViewportPresentation {
+    const id = dataId ?? this.viewport.getSourceDataId?.();
+    const presentation = (id ? this.viewport.getDisplaySetPresentation?.(id) : undefined) ?? {};
+
+    // A native binding's presentation normally holds only EXPLICIT VOI overrides,
+    // but a computed default VOI can transiently land here during intermediate
+    // mounts (e.g. while a SEG hydrates, the base image briefly mounts as a volume
+    // and its min/max default is stored). Flag such a VOI as computed when it
+    // matches the binding's default so the LUT-presentation capture (cleanProperties)
+    // strips it instead of persisting+restoring it over the real default — matching
+    // legacy StackViewport's isComputedVOI. Stamping is harmless even on a genuine
+    // user VOI that happens to equal the default (stripping it falls back to the
+    // same value).
+    const voiRange = presentation.voiRange;
+    if (voiRange && presentation.isComputedVOI === undefined) {
+      const defaultVOIRange = this.viewport.getDefaultVOIRange?.(id);
+      if (defaultVOIRange && voiRangesClose(voiRange, defaultVOIRange)) {
+        return { ...presentation, isComputedVOI: true };
+      }
+    }
+
+    return presentation;
+  }
+
+  setPresentation(props: ViewportPresentation, dataId?: string): void {
+    const id = dataId ?? this.viewport.getSourceDataId?.();
+    if (id) {
+      this.viewport.setDisplaySetPresentation?.(id, props);
+    } else {
+      this.viewport.setDisplaySetPresentation?.(props);
+    }
+  }
+
+  getDefaultVOIRange(dataId?: string): VOIRange | undefined {
+    return this.viewport.getDefaultVOIRange?.(dataId);
+  }
+
+  getColormap(displaySetInstanceUID: string): ViewportColormap | undefined {
+    return this.getPresentation(displaySetInstanceUID).colormap;
+  }
+
+  setLayerOpacity(displaySetInstanceUID: string, opacity: number): boolean {
+    // Merge the opacity into the existing colormap so its name/threshold persist,
+    // targeting the binding by its dataId (the bare display set UID). A uniform
+    // (flat) opacity makes the slider a linear background<->foreground blend,
+    // matching the flat default presentation set by the fusion hanging protocol.
+    const currentColormap = this.getPresentation(displaySetInstanceUID).colormap ?? {};
+    this.setPresentation({ colormap: { ...currentColormap, opacity } }, displaySetInstanceUID);
+    return true;
+  }
+
+  setLayerThreshold(displaySetInstanceUID: string, threshold: number): boolean {
+    // Merge the threshold into the existing colormap so its name/opacity persist.
+    // The threshold is an absolute pixel/SUV value, matching the legacy volume path.
+    const currentColormap = this.getPresentation(displaySetInstanceUID).colormap ?? {};
+    this.setPresentation({ colormap: { ...currentColormap, threshold } }, displaySetInstanceUID);
+    return true;
+  }
+
+  getOpacityGamma(): number {
+    // Native volume viewports render the fusion as a volume slice whose blend is
+    // linear in the opacity scalar, so the slider maps 1:1.
+    return 1;
+  }
+
+  // ---- data addressing ----
+
+  getDataIdForDisplaySet(displaySetInstanceUID: string): string | undefined {
+    // Native viewports key their per-display-set presentation by the bare display
+    // set UID (the dataId used by get/setDisplaySetPresentation). Returning it
+    // directly keeps fusion layer reads on the intended binding instead of falling
+    // back to the active source layer.
+    return displaySetInstanceUID;
+  }
+
+  getVolumeIds(): string[] {
+    // No legacy getAllVolumeIds surface; volume data is addressed by dataId.
+    return [];
+  }
+
+  getVoxelManagerForDisplaySet(
+    displaySetInstanceUID: string
+  ): { getRange?: () => [number, number]; [key: string]: unknown } | undefined {
+    // No getAllVolumeIds/getImageData(volumeId); resolve the display set's volume
+    // from the cornerstone cache instead. Anchored match: volumeIds are built as
+    // `${loaderSchema}:${displaySetInstanceUID}`, and an unanchored includes()
+    // could resolve a different cached volume whose id merely embeds the same
+    // UID (e.g. a derived labelmap id).
+    const volume = cache
+      .getVolumes()
+      .find(
+        v =>
+          v.volumeId === displaySetInstanceUID || v.volumeId?.endsWith(`:${displaySetInstanceUID}`)
+      );
+    return volume?.voxelManager as unknown as
+      | { getRange?: () => [number, number]; [key: string]: unknown }
+      | undefined;
+  }
+
+  // ---- capture ----
+
+  async copyDisplayedContentTo(target: CoreTypes.IViewport): Promise<void> {
+    const targetViewport = target as NativeViewport;
+    const viewRef = this.viewport.getViewReference?.();
+
+    // The source's dataId is already registered in the global GenericViewport
+    // metadata provider, so re-mount it on the capture viewport by id, then copy
+    // per-binding presentation + view state. The native classes have no
+    // setStack/setVolumes/setProperties/setViewPresentation.
+    const sourceDataId = this.viewport.getSourceDataId?.();
+    if (sourceDataId) {
+      const { orientation } = this.getViewState();
+      await targetViewport.setDisplaySets?.({
+        displaySetId: sourceDataId,
+        options: { orientation, role: 'source' },
+      });
+
+      const captureDataId = targetViewport.getSourceDataId?.() ?? sourceDataId;
+      targetViewport.setDisplaySetPresentation?.(captureDataId, this.getPresentation(sourceDataId));
+    }
+
+    // Slice/orientation via the view reference, then pan/zoom/rotate/flip via view state.
+    if (viewRef && targetViewport.setViewReference) {
+      targetViewport.setViewReference(viewRef);
+    }
+    targetViewport.setViewState?.(this.getViewState());
+  }
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/adapter/getViewportAdapter.ts b/extensions/cornerstone/src/services/ViewportService/adapter/getViewportAdapter.ts
new file mode 100644
index 000000000..e1e4c3d2d
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/adapter/getViewportAdapter.ts
@@ -0,0 +1,62 @@
+import { utilities as csUtils, Types as CoreTypes } from '@cornerstonejs/core';
+import type { IViewportAdapter } from './IViewportAdapter';
+import { LegacyViewportAdapter } from './LegacyViewportAdapter';
+import { NextViewportAdapter } from './NextViewportAdapter';
+
+const adapterCache = new WeakMap<object, IViewportAdapter>();
+
+/**
+ * Resolves the IViewportAdapter for a cornerstone viewport. This is THE ONE
+ * place (outside the segmentation backend family) allowed to call
+ * `csUtils.isGenericViewport` — all other code must consume the adapter (or
+ * the `isNextViewport` predicate below) instead of branching on the raw
+ * viewport surface. Enforced by scripts/check-next-viewport-boundaries.sh.
+ *
+ * Adapters are stateless wrappers over the viewport, cached per viewport
+ * instance, so calling this in render paths is cheap.
+ */
+export function getViewportAdapter(viewport: unknown): IViewportAdapter {
+  if (!viewport || typeof viewport !== 'object') {
+    throw new Error('getViewportAdapter: a viewport instance is required');
+  }
+  let adapter = adapterCache.get(viewport);
+  if (!adapter) {
+    adapter = csUtils.isGenericViewport(viewport)
+      ? new NextViewportAdapter(viewport as ConstructorParameters<typeof NextViewportAdapter>[0])
+      : new LegacyViewportAdapter(
+          viewport as ConstructorParameters<typeof LegacyViewportAdapter>[0]
+        );
+    adapterCache.set(viewport, adapter);
+  }
+  return adapter;
+}
+
+/**
+ * The per-viewport lane predicate, for the few dispatchers (viewport
+ * operations, segmentation backend) that hold their own per-lane
+ * implementations. Everyone else should call adapter methods instead of
+ * branching on this.
+ */
+export function isNextViewport(viewport: unknown): boolean {
+  return csUtils.isGenericViewport(viewport);
+}
+
+/**
+ * True for any viewport that renders volume content and therefore supports
+ * volume-only appearance controls (threshold, per-layer opacity): a legacy
+ * ORTHOGRAPHIC viewport, or a native ("next") viewport whose active binding is
+ * a volume. A native MPR/volume viewport runs as PLANAR_NEXT (not
+ * ORTHOGRAPHIC), so legacy type guards alone miss it.
+ */
+export function isVolumeRenderingViewport(viewport: unknown): boolean {
+  return !!viewport && getViewportAdapter(viewport).isVolumeRendering();
+}
+
+/**
+ * World-space focal point (current slice center) for any viewport. Exposed as
+ * a free function because it is part of the extension's public API (consumed
+ * by tmtv).
+ */
+export function getViewportFocalPoint(viewport: unknown): CoreTypes.Point3 | undefined {
+  return viewport ? getViewportAdapter(viewport).getFocalPoint() : undefined;
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/adapter/index.ts b/extensions/cornerstone/src/services/ViewportService/adapter/index.ts
new file mode 100644
index 000000000..8f63817d4
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/adapter/index.ts
@@ -0,0 +1,16 @@
+export type {
+  IViewportAdapter,
+  ViewportColormap,
+  ViewportPresentation,
+  ViewportShape,
+  ViewportViewState,
+  VOIRange,
+} from './IViewportAdapter';
+export {
+  getViewportAdapter,
+  getViewportFocalPoint,
+  isNextViewport,
+  isVolumeRenderingViewport,
+} from './getViewportAdapter';
+export { LegacyViewportAdapter, LEGACY_OPACITY_GAMMA } from './LegacyViewportAdapter';
+export { NextViewportAdapter } from './NextViewportAdapter';
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/IViewportBackend.ts b/extensions/cornerstone/src/services/ViewportService/backends/IViewportBackend.ts
new file mode 100644
index 000000000..23e1e8efc
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/IViewportBackend.ts
@@ -0,0 +1,195 @@
+import type { Types } from '@cornerstonejs/core';
+import type ViewportInfo from '../Viewport';
+import type {
+  Presentations,
+  PositionPresentation,
+  LutPresentation,
+} from '../../../types/Presentation';
+import type { StackViewportData, VolumeViewportData } from '../../../types/CornerstoneCacheService';
+import type { DataIdPayload } from './dataIdRegistry';
+
+/** A pending overlay (SEG/RTSTRUCT) add produced by the service's prelude. */
+export type OverlayMountTask = {
+  imageIds?: string[];
+  addOverlayFn?: () => Promise<void>;
+};
+
+/**
+ * Everything the service's lane-agnostic stack-mount prelude computes: the
+ * backend receives it ready-made and performs only the lane-specific mount.
+ */
+export interface StackMountContext {
+  /** All display set UIDs bound to the viewport (first = the stack source). */
+  displaySetInstanceUIDs: string[];
+  imageIds: string[];
+  /** Resolved initial slice (position presentation / view reference / HP options). */
+  initialImageIndex: number;
+  /** VOI/invert/colormap seeded from the LUT presentation or display set options. */
+  properties: Record<string, unknown>;
+  displayArea?: unknown;
+  rotation?: number;
+  flipHorizontal?: boolean;
+  presentations: Presentations;
+  viewportInfo: ViewportInfo;
+  overlayProcessingResults?: OverlayMountTask[];
+}
+
+/**
+ * Everything the service's lane-agnostic volume-mount prelude computes before
+ * the lane fork in setVolumesForViewport.
+ */
+export interface VolumeMountContext {
+  /** Volume inputs with their display set options, overlays already filtered out. */
+  filteredVolumeInputArray: Array<{
+    volumeInput: {
+      imageIds?: string[];
+      volumeId: string;
+      displaySetInstanceUID: string;
+      blendMode?: unknown;
+      slabThickness?: number;
+      [key: string]: unknown;
+    };
+    displaySetOptions: unknown;
+  }>;
+  /** Per-volume VOI/invert/colormap/preset derived from the display set options. */
+  volumesProperties: Array<{ properties: Record<string, unknown>; volumeId: string }>;
+  viewportInfo: ViewportInfo;
+  overlayProcessingResults?: OverlayMountTask[];
+  presentations: Presentations;
+}
+
+/**
+ * Selects how OHIF drives cornerstone viewports (migration plan §4.3). One
+ * implementation is chosen ONCE, lazily on first use (a `get backend()` getter on
+ * CornerstoneViewportService — NOT the constructor, because the service singleton is
+ * built during extension registration before init.tsx sets the flag), from
+ * `appConfig.useNextViewports`:
+ *   - LegacyViewportBackend: today's behavior, selected when the flag is off (default).
+ *   - NextViewportBackend: the native GenericViewport ("next") path.
+ *
+ * The service holds exactly one backend for its lifetime and routes the forked
+ * concerns through it: mount dispatch, the per-family MOUNT BODIES
+ * (mountStack/mountVolumes/mountEcg/mountOther/remount), presentation
+ * capture/restore, and the native dataId lifecycle. The service keeps only the
+ * lane-agnostic preludes (option/property derivation, bookkeeping, events) and
+ * the genuinely shared volume tail; it contains no per-lane branches itself.
+ */
+export interface IViewportBackend {
+  /**
+   * Routes a viewport's data to the correct per-family mount. Legacy routes by the
+   * runtime cornerstone viewport type; next routes by the bound data shape, because
+   * native stack and volume content both report a single PLANAR_NEXT type (§4.4).
+   */
+  dispatchMount(
+    viewport: Types.IViewport,
+    viewportData: StackViewportData | VolumeViewportData,
+    viewportInfo: ViewportInfo,
+    presentations?: Presentations
+  ): Promise<void>;
+
+  /**
+   * Mounts an image stack. Legacy: setStack/setProperties/setPresentations +
+   * displayArea/rotation/flip via the camera surface. Next: register the dataId,
+   * setDisplaySets, seed VOI from metadata, apply presentation + view state.
+   */
+  mountStack(viewport: Types.IStackViewport, context: StackMountContext): Promise<void>;
+
+  /**
+   * Lane-specific volume mount. Next mounts the volumes natively (registered
+   * dataIds + one setDisplaySets call + per-binding presentations) and returns
+   * true — the service then only broadcasts. Legacy returns false, and the
+   * service runs the shared volume tail (setVolumes/addVolumes optimization,
+   * property application, presentations, jumpToSlice), which a native
+   * overlay-only mount also traverses safely.
+   */
+  mountVolumes(viewport: Types.IViewport, context: VolumeMountContext): Promise<boolean>;
+
+  /**
+   * The shared volume tail's overlay-only fallback: when every volume input is
+   * an overlay display set, legacy still mounts them via setVolumes; next
+   * no-ops (its overlays are added via the segmentation representations).
+   */
+  mountOverlayOnlyVolumes(viewport: Types.IViewport, volumeInputArray: unknown[]): Promise<void>;
+
+  /**
+   * Mounts an ECG waveform. Legacy: viewport.setEcg(imageId). Next: register
+   * the display set's dataId and mount through the generic setDisplaySets API.
+   */
+  mountEcg(
+    viewport: Types.IECGViewport,
+    displaySet: { displaySetInstanceUID: string; imageIds?: string[] },
+    imageId: string
+  ): Promise<void>;
+
+  /**
+   * Mounts video / whole-slide content (the caller applies the view reference
+   * afterwards). Legacy keys the displaySetId off imageIds[0]; next registers
+   * the family-specific dataId first.
+   */
+  mountOther(
+    viewport: Types.IViewport,
+    displaySet: { displaySetInstanceUID: string; imageIds: string[] }
+  ): Promise<void>;
+
+  /**
+   * Re-mounts changed viewport data onto an existing viewport (updateViewport),
+   * optionally restoring the camera afterwards. Legacy snapshots getCamera and
+   * dispatches by runtime type; next snapshots the semantic view state and
+   * routes through dispatchMount. May return undefined when the viewport family
+   * has no re-mount path (matching the historical legacy behavior).
+   */
+  remount(
+    viewport: Types.IViewport,
+    viewportData: StackViewportData | VolumeViewportData,
+    viewportInfo: ViewportInfo,
+    keepCamera: boolean
+  ): Promise<void> | undefined;
+
+  /**
+   * Reads the position presentation (camera/zoom/pan + view reference) to persist
+   * for restore. Legacy uses getViewPresentation (pan/zoom); native stores the
+   * semantic view-state displayArea (pan/zoom) since it has no getViewPresentation.
+   */
+  getPositionPresentation(
+    csViewport: Types.IViewport,
+    viewportInfo: ViewportInfo,
+    viewportId: string
+  ): PositionPresentation;
+
+  /**
+   * Restores a position presentation. Both apply the view reference (slice/
+   * orientation); legacy then applies getViewPresentation via setViewPresentation,
+   * native applies the stored displayArea via setViewState.
+   */
+  setPositionPresentation(
+    viewport: Types.IViewport,
+    positionPresentation: PositionPresentation
+  ): void;
+
+  /**
+   * Restores a LUT presentation (VOI/colormap/invert). Legacy uses setProperties;
+   * native uses setDisplaySetPresentation (a PLANAR_NEXT viewport has no
+   * setProperties), so calling setPresentations on native no longer throws.
+   */
+  setLutPresentation(viewport: Types.IViewport, lutPresentation: LutPresentation): void;
+
+  /**
+   * Registers a native dataset id for a viewport against cornerstone's global
+   * GenericViewport metadata provider (§4.7). Next ref-counts and tracks per
+   * viewport so it can be released on unmount; legacy is a no-op (never registers).
+   */
+  registerDataId(viewportId: string, dataId: string, payload: DataIdPayload): void;
+
+  /**
+   * Releases the dataset registrations a viewport owns. Called from the service's
+   * disableElement BEFORE the viewport bookkeeping is deleted. Next releases (and
+   * removes from the provider when the last reference is gone); legacy is a no-op.
+   */
+  onViewportDisabled(viewportId: string): void;
+
+  /**
+   * Flushes all remaining registrations. Called from the service's destroy().
+   * Next clears its registry; legacy is a no-op.
+   */
+  destroy(): void;
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/IViewportOperations.ts b/extensions/cornerstone/src/services/ViewportService/backends/IViewportOperations.ts
new file mode 100644
index 000000000..04bc9ff97
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/IViewportOperations.ts
@@ -0,0 +1,98 @@
+import type { Types as CoreTypes } from '@cornerstonejs/core';
+
+export type FlipValue = 'toggle' | boolean;
+export type RotationMode = 'apply' | 'set';
+
+export interface VolumeLightingOptions {
+  shade?: boolean;
+  ambient?: number;
+  diffuse?: number;
+  specular?: number;
+}
+
+export interface WindowLevelParams {
+  windowWidth: number;
+  windowCenter: number;
+  /** Legacy volume target; resolved by the caller. Ignored on native (active binding). */
+  volumeId?: string;
+  /** Native per-binding target (e.g. the PT overlay in a fusion); ignored on legacy. */
+  displaySetInstanceUID?: string;
+}
+
+export interface ColormapParams {
+  colormap: Record<string, unknown>;
+  /** Used by the legacy orthographic branch to resolve the volumeId; ignored on native. */
+  displaySetInstanceUID?: string;
+}
+
+/**
+ * Per-viewport interaction/appearance operations, extracted out of commandsModule so
+ * command bodies stay thin (migration plan §4.3). This mirrors the IViewportBackend
+ * family (LegacyViewportBackend / NextViewportBackend): there is one implementation per
+ * lane and each uses its lane's cornerstone APIs DIRECTLY (legacy getCamera/setProperties/
+ * getViewPresentation vs native getViewState/setDisplaySetPresentation/getViewReference).
+ *
+ * DISPATCH: unlike IViewportBackend (selected once by the appConfig flag because it owns
+ * per-session mount lifecycle), operations are routed PER VIEWPORT via the dispatcher in
+ * viewportOperations.ts (isNextViewport(viewport) ? next : legacy). The viewport is
+ * already created and self-describing, and a session can hold a mix of legacy and native
+ * viewports; per-viewport routing is the runtime truth.
+ *
+ * RENDER: no method calls viewport.render(). The caller renders, matching today's
+ * per-command render timing (e.g. setViewportColormap renders only when immediate).
+ *
+ * VIEWPORT RESOLUTION: never done here — the command owns "which viewport".
+ */
+export interface IViewportOperations {
+  // ---- camera / view-state ----
+
+  /** Toggle (default) or set horizontal flip. */
+  flipHorizontal(viewport: CoreTypes.IViewport, newValue?: FlipValue): void;
+
+  /** Toggle (default) or set vertical flip. */
+  flipVertical(viewport: CoreTypes.IViewport, newValue?: FlipValue): void;
+
+  /** Rotate: mode 'apply' = relative, mode 'set' = absolute (with flip-parity correction). */
+  rotate(viewport: CoreTypes.IViewport, rotation: number, mode?: RotationMode): void;
+
+  /** Reset properties + camera/view-state to defaults (slice/navigation preserved on native). */
+  reset(viewport: CoreTypes.IViewport): void;
+
+  /** Zoom by direction: >0 in, <0 out, 0 = fit-to-window (reset). */
+  scaleBy(viewport: CoreTypes.IViewport, direction: number): void;
+
+  /** Read the view-plane normal in a lane-appropriate way. */
+  getViewPlaneNormal(viewport: CoreTypes.IViewport): CoreTypes.Point3 | undefined;
+
+  /**
+   * In-plane re-center (+ zoom-to-fit) of a measurement AFTER the caller's setViewReference
+   * slice jump. Returns true when it re-centered (caller should render), false when the
+   * measurement was already visible or in-plane centering is unsupported on the lane.
+   */
+  centerOnMeasurement(viewport: CoreTypes.IViewport, measurement: Record<string, unknown>): boolean;
+
+  // ---- appearance / properties ----
+
+  /** Toggle invert. */
+  invert(viewport: CoreTypes.IViewport): void;
+
+  /** Apply a VOI window/level. */
+  setWindowLevel(viewport: CoreTypes.IViewport, params: WindowLevelParams): void;
+
+  /** Apply a colormap. */
+  setColormap(viewport: CoreTypes.IViewport, params: ColormapParams): void;
+
+  // ---- 3D volume rendering (CS-14: native unsupported yet) ----
+
+  /** VR preset. */
+  setPreset(viewport: CoreTypes.IViewport, preset: string): void;
+
+  /** VR sample distance / samples-per-ray quality. */
+  setVolumeRenderingQuality(viewport: CoreTypes.IViewport, volumeQuality: number): void;
+
+  /** Shift scalar-opacity transfer-function points. */
+  shiftVolumeOpacityPoints(viewport: CoreTypes.IViewport, shift: number): void;
+
+  /** VR lighting (shade/ambient/diffuse/specular). */
+  setVolumeLighting(viewport: CoreTypes.IViewport, options: VolumeLightingOptions): void;
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/IViewportServiceInternals.ts b/extensions/cornerstone/src/services/ViewportService/backends/IViewportServiceInternals.ts
new file mode 100644
index 000000000..752c31bc2
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/IViewportServiceInternals.ts
@@ -0,0 +1,47 @@
+import type { Types } from '@cornerstonejs/core';
+import type ViewportInfo from '../Viewport';
+import type { Presentations } from '../../../types/Presentation';
+import type { StackViewportData, VolumeViewportData } from '../../../types/CornerstoneCacheService';
+import type { OverlayMountTask } from './IViewportBackend';
+
+/**
+ * The narrow slice of CornerstoneViewportService that a viewport backend is
+ * allowed to reach (migration plan §4.3 access pattern). The service `implements`
+ * this and passes `this` to each backend, so a backend can dispatch the per-family
+ * mount work back to the shared service methods without reaching into unrelated
+ * internals. Keeping this interface narrow is what stops the off (legacy) path
+ * from drifting as the next backend grows.
+ */
+export interface IViewportServiceInternals {
+  _setStackViewport(
+    viewport: Types.IStackViewport,
+    viewportData: StackViewportData,
+    viewportInfo: ViewportInfo,
+    presentations?: Presentations
+  ): Promise<void>;
+
+  _setVolumeViewport(
+    viewport: Types.IVolumeViewport,
+    viewportData: VolumeViewportData,
+    viewportInfo: ViewportInfo,
+    presentations?: Presentations
+  ): Promise<void>;
+
+  _setEcgViewport(viewport: Types.IECGViewport, viewportData: StackViewportData): Promise<void>;
+
+  _setOtherViewport(
+    viewport: Types.IStackViewport,
+    viewportData: StackViewportData,
+    viewportInfo: ViewportInfo,
+    presentations?: Presentations
+  ): Promise<void>;
+
+  /** Applies lut/position/segmentation presentations to a mounted viewport. */
+  setPresentations(viewportId: string, presentations: Presentations): void;
+
+  /** Runs the pending overlay (SEG/RTSTRUCT) adds produced by the mount prelude. */
+  _addOverlayRepresentations(overlayProcessingResults?: OverlayMountTask[]): Promise<void>;
+
+  /** Records which display sets a viewport shows (service bookkeeping). */
+  _trackViewportDisplaySets(viewportId: string, displaySetInstanceUIDs: string[]): void;
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/LegacyViewportBackend.ts b/extensions/cornerstone/src/services/ViewportService/backends/LegacyViewportBackend.ts
new file mode 100644
index 000000000..529e9ff5d
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/LegacyViewportBackend.ts
@@ -0,0 +1,264 @@
+import { Enums as csEnums, Types, metaData } from '@cornerstonejs/core';
+import {
+  getLegacyViewportType,
+  isStackViewportType,
+  isVolume3DViewportType,
+  isVolumeViewportType,
+} from '../../../utils/getLegacyViewportType';
+import type ViewportInfo from '../Viewport';
+import type {
+  Presentations,
+  PositionPresentation,
+  LutPresentation,
+} from '../../../types/Presentation';
+import type { StackViewportData, VolumeViewportData } from '../../../types/CornerstoneCacheService';
+import type { IViewportBackend, StackMountContext, VolumeMountContext } from './IViewportBackend';
+import type { IViewportServiceInternals } from './IViewportServiceInternals';
+import { DataIdRegistry } from './dataIdRegistry';
+
+// Mirrors WITH_ORIENTATION in CornerstoneViewportService (inlined to avoid a
+// value import that would create a backend -> service circular dependency).
+const WITH_ORIENTATION = { withNavigation: true, withOrientation: true };
+
+/**
+ * Legacy (default) viewport backend. Selected when `appConfig.useNextViewports`
+ * is off. Routing mirrors today's CornerstoneViewportService._setDisplaySets legacy
+ * branch exactly (dispatch by runtime cornerstone viewport type) and delegates the
+ * per-family mount to the unchanged service methods, so the off path stays
+ * byte-identical. The one legacy family that touches the GenericViewport metadata
+ * provider is WSI (mountOther); those registrations go through the same
+ * ref-counted registry as the native backend so they are released on viewport
+ * disable/destroy instead of leaking across viewport reuse.
+ */
+export class LegacyViewportBackend implements IViewportBackend {
+  private readonly registry = new DataIdRegistry();
+
+  constructor(private readonly service: IViewportServiceInternals) {}
+
+  dispatchMount(
+    viewport: Types.IViewport,
+    viewportData: StackViewportData | VolumeViewportData,
+    viewportInfo: ViewportInfo,
+    presentations: Presentations = {}
+  ): Promise<void> {
+    if (isStackViewportType(viewport)) {
+      return this.service._setStackViewport(
+        viewport as Types.IStackViewport,
+        viewportData as StackViewportData,
+        viewportInfo,
+        presentations
+      );
+    }
+
+    if (isVolumeViewportType(viewport)) {
+      return this.service._setVolumeViewport(
+        viewport as Types.IVolumeViewport,
+        viewportData as VolumeViewportData,
+        viewportInfo,
+        presentations
+      );
+    }
+
+    if (getLegacyViewportType(viewport) === csEnums.ViewportType.ECG) {
+      return this.service._setEcgViewport(
+        viewport as unknown as Types.IECGViewport,
+        viewportData as StackViewportData
+      );
+    }
+
+    return this.service._setOtherViewport(
+      viewport as Types.IStackViewport,
+      viewportData as StackViewportData,
+      viewportInfo,
+      presentations
+    );
+  }
+
+  async mountStack(viewport: Types.IStackViewport, context: StackMountContext): Promise<void> {
+    const {
+      imageIds,
+      initialImageIndex,
+      properties,
+      displayArea,
+      rotation,
+      flipHorizontal,
+      presentations,
+      overlayProcessingResults,
+    } = context;
+
+    await viewport.setStack(imageIds, initialImageIndex);
+    viewport.setProperties({ ...properties });
+    this.service.setPresentations(viewport.id, presentations);
+
+    await this.service._addOverlayRepresentations(overlayProcessingResults);
+
+    if (displayArea) {
+      viewport.setDisplayArea(displayArea as Types.DisplayArea);
+    }
+    if (rotation) {
+      viewport.setProperties({ rotation } as Parameters<typeof viewport.setProperties>[0]);
+    }
+    if (flipHorizontal) {
+      viewport.setCamera({ flipHorizontal: true });
+    }
+  }
+
+  async mountVolumes(): Promise<boolean> {
+    // Legacy volumes mount through the service's shared volume tail
+    // (setVolumes/addVolumes optimization, property application, presentations).
+    return false;
+  }
+
+  async mountOverlayOnlyVolumes(
+    viewport: Types.IViewport,
+    volumeInputArray: unknown[]
+  ): Promise<void> {
+    await (viewport as Types.IVolumeViewport).setVolumes(volumeInputArray as Types.IVolumeInput[]);
+  }
+
+  async mountEcg(
+    viewport: Types.IECGViewport,
+    _displaySet: { displaySetInstanceUID: string; imageIds?: string[] },
+    imageId: string
+  ): Promise<void> {
+    return viewport.setEcg(imageId);
+  }
+
+  async mountOther(
+    viewport: Types.IViewport,
+    displaySet: { displaySetInstanceUID: string; imageIds: string[] }
+  ): Promise<void> {
+    // CS3D's "redo viewports" replaced setDataIds with the generic
+    // setDisplaySets({ displaySetId }) API; the legacy adapters key off
+    // imageIds[0] as the displaySetId, so do the same here.
+    const displaySetId = displaySet.imageIds[0];
+    // Register the WSI dataset so the viewport can resolve its imageIds +
+    // webClient by display-set id, then mount via setDisplaySets. The webClient
+    // was registered under the WADO_WEB_CLIENT module (keyed by imageIds[0]) by
+    // the SM SOP class handler. CS3D's "redo viewports" reads this same registry
+    // (genericViewportDisplaySetMetadataProvider) from its WSI data provider;
+    // without this entry setDisplaySets throws "No registered WSI dataset" and
+    // the viewport renders gray.
+    const webClient = metaData.get(csEnums.MetadataModules.WADO_WEB_CLIENT, displaySetId);
+    // Ref-counted registration so the provider entry is removed when the last
+    // viewport showing this WSI display set is disabled (or on service destroy).
+    this.registry.register(viewport.id, displaySetId, {
+      kind: 'wsi',
+      imageIds: displaySet.imageIds,
+      options: { webClient },
+    });
+    await (
+      viewport as unknown as {
+        setDisplaySets: (args: { displaySetId: string }) => Promise<void>;
+      }
+    ).setDisplaySets({ displaySetId });
+  }
+
+  remount(
+    viewport: Types.IViewport,
+    viewportData: StackViewportData | VolumeViewportData,
+    viewportInfo: ViewportInfo,
+    keepCamera: boolean
+  ): Promise<void> | undefined {
+    let displaySetPromise: Promise<void> | undefined;
+
+    if (isVolumeViewportType(viewport)) {
+      // Snapshot the camera only for the family that uses it; taking it before
+      // the family checks would throw for families with no re-mount path.
+      const vp = viewport as Types.IVolumeViewport;
+      const viewportCamera = keepCamera ? vp.getCamera() : undefined;
+      displaySetPromise = this.service
+        ._setVolumeViewport(
+          viewport as Types.IVolumeViewport,
+          viewportData as VolumeViewportData,
+          viewportInfo
+        )
+        .then(() => {
+          if (viewportCamera) {
+            vp.setCamera(viewportCamera);
+            vp.render();
+          }
+        });
+    }
+
+    if (isStackViewportType(viewport)) {
+      displaySetPromise = this.service._setStackViewport(
+        viewport as Types.IStackViewport,
+        viewportData as StackViewportData,
+        viewportInfo
+      );
+    }
+
+    return displaySetPromise;
+  }
+
+  getPositionPresentation(
+    csViewport: Types.IViewport,
+    viewportInfo: ViewportInfo,
+    viewportId: string
+  ): PositionPresentation {
+    const vp = csViewport as Types.IStackViewport;
+    return {
+      viewportType: viewportInfo.getViewportType(),
+      viewReference: isVolume3DViewportType(csViewport) ? null : vp.getViewReference(),
+      viewPresentation: vp.getViewPresentation({ pan: true, zoom: true }),
+      viewportId,
+    };
+  }
+
+  setPositionPresentation(
+    viewport: Types.IViewport,
+    positionPresentation: PositionPresentation
+  ): void {
+    const vp = viewport as Types.IStackViewport | Types.IVolumeViewport;
+    const viewRef = positionPresentation?.viewReference;
+    if (viewRef) {
+      // The orientation can be updated here to navigate to the specified
+      // measurement or previous item, but this will not switch to volume
+      // or to stack from the other type
+      if (vp.isReferenceViewable(viewRef, WITH_ORIENTATION)) {
+        vp.setViewReference(viewRef);
+      } else {
+        console.warn('Unable to apply reference viewable', viewRef);
+      }
+    }
+
+    const viewPresentation = positionPresentation?.viewPresentation;
+    if (viewPresentation) {
+      vp.setViewPresentation(viewPresentation);
+    }
+  }
+
+  setLutPresentation(viewport: Types.IViewport, lutPresentation: LutPresentation): void {
+    if (!lutPresentation) {
+      return;
+    }
+
+    const vp = viewport as Types.IStackViewport | Types.IVolumeViewport;
+    const { properties } = lutPresentation;
+    if (isVolumeViewportType(vp)) {
+      if (properties instanceof Map) {
+        properties.forEach((propertiesEntry, volumeId) => {
+          (vp as Types.IVolumeViewport).setProperties(propertiesEntry, volumeId);
+        });
+      } else {
+        vp.setProperties(properties);
+      }
+    } else {
+      vp.setProperties(properties);
+    }
+  }
+
+  registerDataId(): void {
+    // Legacy mounts do not register dataIds through the backend interface; the
+    // one provider-backed family (WSI) registers inline in mountOther.
+  }
+
+  onViewportDisabled(viewportId: string): void {
+    this.registry.releaseViewport(viewportId);
+  }
+
+  destroy(): void {
+    this.registry.destroy();
+  }
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/LegacyViewportOperations.ts b/extensions/cornerstone/src/services/ViewportService/backends/LegacyViewportOperations.ts
new file mode 100644
index 000000000..af3d180d4
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/LegacyViewportOperations.ts
@@ -0,0 +1,272 @@
+import { utilities as csUtils, Types as CoreTypes } from '@cornerstonejs/core';
+import { mat4, vec3 } from 'gl-matrix';
+import {
+  isStackViewportType,
+  isVolumeViewportType,
+  isOrthographicViewportType,
+} from '../../../utils/getLegacyViewportType';
+import { getCenterExtent } from '../../../utils/getCenterExtent';
+import { isMeasurementWithinViewport } from '../../../utils/isMeasurementWithinViewport';
+import type {
+  IViewportOperations,
+  FlipValue,
+  RotationMode,
+  VolumeLightingOptions,
+  WindowLevelParams,
+  ColormapParams,
+} from './IViewportOperations';
+
+// Loose view of the VTK actor/mapper/property chain used by the 3D VR ops. These
+// live on vtk.js objects, not cornerstone types, so they are accessed structurally
+// (mirrors the previously-untyped commandsModule bodies).
+type VtkActorChain = {
+  actor: {
+    getMapper: () => Record<string, (...args: unknown[]) => unknown>;
+    getProperty: () => Record<string, (...args: unknown[]) => unknown>;
+  };
+};
+
+/**
+ * Legacy lane of IViewportOperations: every method is the corresponding
+ * commandsModule body lifted verbatim, using the legacy cornerstone APIs directly
+ * (getCamera/setCamera, getProperties/setProperties, getViewPresentation/
+ * setViewPresentation, resetCamera, getActors). This is the byte-identical flag-off
+ * path; the dispatcher only routes non-generic viewports here.
+ *
+ * No method calls viewport.render() — the command renders (matching per-command
+ * render timing).
+ */
+export const legacyViewportOperations: IViewportOperations = {
+  flipHorizontal(viewport: CoreTypes.IViewport, newValue: FlipValue = 'toggle'): void {
+    const vp = viewport as CoreTypes.IStackViewport;
+    let flipHorizontal: boolean;
+    if (newValue === 'toggle') {
+      flipHorizontal = !vp.getCamera().flipHorizontal;
+    } else {
+      flipHorizontal = newValue;
+    }
+    vp.setCamera({ flipHorizontal });
+  },
+
+  flipVertical(viewport: CoreTypes.IViewport, newValue: FlipValue = 'toggle'): void {
+    const vp = viewport as CoreTypes.IStackViewport;
+    let flipVertical: boolean;
+    if (newValue === 'toggle') {
+      flipVertical = !vp.getCamera().flipVertical;
+    } else {
+      flipVertical = newValue;
+    }
+    vp.setCamera({ flipVertical });
+  },
+
+  invert(viewport: CoreTypes.IViewport): void {
+    const vp = viewport as CoreTypes.IStackViewport;
+    const { invert } = vp.getProperties();
+    vp.setProperties({ invert: !invert });
+  },
+
+  rotate(viewport: CoreTypes.IViewport, rotation: number, mode: RotationMode = 'apply'): void {
+    if (isVolumeViewportType(viewport)) {
+      const vp = viewport as CoreTypes.IVolumeViewport;
+      const camera = vp.getCamera();
+      const rotAngle = (rotation * Math.PI) / 180;
+      const rotMat = mat4.identity(new Float32Array(16));
+      mat4.rotate(rotMat, rotMat, rotAngle, camera.viewPlaneNormal);
+      const rotatedViewUp = vec3.transformMat4(vec3.create(), camera.viewUp, rotMat);
+      vp.setCamera({ viewUp: rotatedViewUp as CoreTypes.Point3 });
+      return;
+    }
+
+    const vp = viewport as CoreTypes.IStackViewport;
+    if (vp.getRotation !== undefined) {
+      const { rotation: currentRotation } = vp.getViewPresentation();
+      const newRotation =
+        mode === 'apply'
+          ? (currentRotation + rotation + 360) % 360
+          : (() => {
+              // In 'set' mode, account for the effect horizontal/vertical flips
+              // have on the perceived rotation direction. A single flip mirrors
+              // the image and inverses rotation direction, while two flips
+              // restore the original parity. We therefore invert the rotation
+              // angle when an odd number of flips are applied so that the
+              // requested absolute rotation matches the user expectation.
+              const { flipHorizontal = false, flipVertical = false } = vp.getViewPresentation();
+
+              const flipsParity = (flipHorizontal ? 1 : 0) + (flipVertical ? 1 : 0);
+              const effectiveRotation = flipsParity % 2 === 1 ? -rotation : rotation;
+
+              return (effectiveRotation + 360) % 360;
+            })();
+      vp.setViewPresentation({ rotation: newRotation });
+    }
+  },
+
+  reset(viewport: CoreTypes.IViewport): void {
+    const vp = viewport as CoreTypes.IStackViewport;
+    vp.resetProperties?.();
+    vp.resetCamera();
+  },
+
+  scaleBy(viewport: CoreTypes.IViewport, direction: number): void {
+    const scaleFactor = direction > 0 ? 0.9 : 1.1;
+    if (isStackViewportType(viewport)) {
+      const vp = viewport as CoreTypes.IStackViewport;
+      if (direction) {
+        const { parallelScale } = vp.getCamera();
+        vp.setCamera({ parallelScale: parallelScale * scaleFactor });
+      } else {
+        vp.resetCamera();
+      }
+    }
+  },
+
+  getViewPlaneNormal(viewport: CoreTypes.IViewport): CoreTypes.Point3 | undefined {
+    return (viewport as CoreTypes.IStackViewport).getCamera().viewPlaneNormal;
+  },
+
+  centerOnMeasurement(
+    viewport: CoreTypes.IViewport,
+    measurement: Record<string, unknown>
+  ): boolean {
+    if (isMeasurementWithinViewport(viewport, measurement)) {
+      return false;
+    }
+
+    const vp = viewport as CoreTypes.IStackViewport;
+    const camera = vp.getCamera();
+    const { focalPoint: cameraFocalPoint, position: cameraPosition } = camera;
+    const { center, extent } = getCenterExtent(measurement);
+    const position = vec3.sub(vec3.create(), cameraPosition, cameraFocalPoint);
+    vec3.add(position, position, center);
+    vp.setCamera({ focalPoint: center, position: position as unknown as CoreTypes.Point3 });
+    // Zoom out if the measurement is too large
+    const measurementSize = vec3.dist(extent.min, extent.max);
+    if (measurementSize > camera.parallelScale) {
+      const scaleFactor = measurementSize / camera.parallelScale;
+      vp.setZoom(vp.getZoom() / scaleFactor);
+    }
+    return true;
+  },
+
+  setWindowLevel(viewport: CoreTypes.IViewport, params: WindowLevelParams): void {
+    const { lower, upper } = csUtils.windowLevel.toLowHighRange(
+      params.windowWidth,
+      params.windowCenter
+    );
+    if (isVolumeViewportType(viewport)) {
+      (viewport as CoreTypes.IVolumeViewport).setProperties(
+        { voiRange: { upper, lower } },
+        params.volumeId
+      );
+    } else {
+      (viewport as CoreTypes.IStackViewport).setProperties({ voiRange: { upper, lower } });
+    }
+  },
+
+  setColormap(viewport: CoreTypes.IViewport, params: ColormapParams): void {
+    const { colormap, displaySetInstanceUID } = params;
+    if (isStackViewportType(viewport)) {
+      (viewport as CoreTypes.IStackViewport).setProperties({ colormap });
+    }
+
+    if (isOrthographicViewportType(viewport)) {
+      const vp = viewport as CoreTypes.IVolumeViewport;
+      // ToDo: Find a better way of obtaining the volumeId that corresponds to the displaySetInstanceUID
+      const volumeId =
+        vp.getAllVolumeIds().find((_volumeId: string) => _volumeId.includes(displaySetInstanceUID)) ??
+        vp.getVolumeId();
+      vp.setProperties({ colormap }, volumeId);
+    }
+  },
+
+  setPreset(viewport: CoreTypes.IViewport, preset: string): void {
+    (viewport as CoreTypes.IVolumeViewport).setProperties({ preset });
+  },
+
+  setVolumeRenderingQuality(viewport: CoreTypes.IViewport, volumeQuality: number): void {
+    const actorEntry = (viewport as unknown as CoreTypes.IVolumeViewport).getActors()[0];
+    if (!actorEntry) {
+      return;
+    }
+    const { actor } = actorEntry;
+    const mapper = (actor as unknown as VtkActorChain['actor']).getMapper();
+    const image = mapper.getInputData() as {
+      getDimensions: () => number[];
+      getSpacing: () => number[];
+    };
+    const dims = image.getDimensions();
+    const spacing = image.getSpacing();
+    const spatialDiagonal = vec3.length(
+      vec3.fromValues(dims[0] * spacing[0], dims[1] * spacing[1], dims[2] * spacing[2])
+    );
+
+    let sampleDistance = spacing.reduce((a, b) => a + b) / 3.0;
+    sampleDistance /= volumeQuality > 1 ? 0.5 * volumeQuality ** 2 : 1.0;
+    const samplesPerRay = spatialDiagonal / sampleDistance + 1;
+    mapper.setMaximumSamplesPerRay(samplesPerRay);
+    mapper.setSampleDistance(sampleDistance);
+  },
+
+  shiftVolumeOpacityPoints(viewport: CoreTypes.IViewport, shift: number): void {
+    const actorEntry = (viewport as unknown as CoreTypes.IVolumeViewport).getActors()[0];
+    if (!actorEntry) {
+      return;
+    }
+    const { actor } = actorEntry;
+    const ofun = (actor as unknown as VtkActorChain['actor']).getProperty().getScalarOpacity(0) as {
+      getSize: () => number;
+      getNodeValue: (i: number, v: number[]) => void;
+      removeAllPoints: () => void;
+      addPoint: (...args: number[]) => void;
+    };
+
+    const opacityPointValues: number[][] = []; // Array to hold values
+    // Gather Existing Values
+    const size = ofun.getSize();
+    for (let pointIdx = 0; pointIdx < size; pointIdx++) {
+      const opacityPointValue = [0, 0, 0, 0];
+      ofun.getNodeValue(pointIdx, opacityPointValue);
+      // opacityPointValue now holds [xLocation, opacity, midpoint, sharpness]
+      opacityPointValues.push(opacityPointValue);
+    }
+    // Add offset
+    opacityPointValues.forEach(opacityPointValue => {
+      opacityPointValue[0] += shift; // Change the location value
+    });
+    // Set new values
+    ofun.removeAllPoints();
+    opacityPointValues.forEach(opacityPointValue => {
+      ofun.addPoint(...opacityPointValue);
+    });
+  },
+
+  setVolumeLighting(viewport: CoreTypes.IViewport, options: VolumeLightingOptions): void {
+    const actorEntry = (viewport as unknown as CoreTypes.IVolumeViewport).getActors()[0];
+    if (!actorEntry) {
+      return;
+    }
+    const { actor } = actorEntry;
+    const property = (actor as unknown as VtkActorChain['actor']).getProperty() as {
+      setShade: (v: boolean) => void;
+      setAmbient: (v: number) => void;
+      setDiffuse: (v: number) => void;
+      setSpecular: (v: number) => void;
+    };
+
+    if (options.shade !== undefined) {
+      property.setShade(options.shade);
+    }
+
+    if (options.ambient !== undefined) {
+      property.setAmbient(options.ambient);
+    }
+
+    if (options.diffuse !== undefined) {
+      property.setDiffuse(options.diffuse);
+    }
+
+    if (options.specular !== undefined) {
+      property.setSpecular(options.specular);
+    }
+  },
+};
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/NextViewportBackend.ts b/extensions/cornerstone/src/services/ViewportService/backends/NextViewportBackend.ts
new file mode 100644
index 000000000..241ca621c
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/NextViewportBackend.ts
@@ -0,0 +1,671 @@
+import {
+  Enums as csEnums,
+  Types,
+  metaData,
+  utilities as csUtils,
+  CONSTANTS as csConstants,
+  isRegisteredRenderBackend,
+} from '@cornerstonejs/core';
+import type { RenderBackendValue } from '@cornerstonejs/core';
+import { utilities as csToolsUtils } from '@cornerstonejs/tools';
+import { isVolume3DViewportType } from '../../../utils/getLegacyViewportType';
+import { getViewportRenderingOverride } from '../../../utils/nextViewports';
+import type ViewportInfo from '../Viewport';
+import type {
+  Presentations,
+  PositionPresentation,
+  LutPresentation,
+} from '../../../types/Presentation';
+import type { StackViewportData, VolumeViewportData } from '../../../types/CornerstoneCacheService';
+import type { IViewportBackend, StackMountContext, VolumeMountContext } from './IViewportBackend';
+import type { IViewportServiceInternals } from './IViewportServiceInternals';
+import { DataIdRegistry, type DataIdPayload } from './dataIdRegistry';
+
+// Mirrors WITH_ORIENTATION in CornerstoneViewportService (inlined to avoid a
+// value import that would create a backend -> service circular dependency).
+const WITH_ORIENTATION = { withNavigation: true, withOrientation: true };
+
+/**
+ * Per-mount render backend override for a planar mount, resolved from the
+ * `<viewportType>.viewportRendering` URL param / appConfig captured at init
+ * (e.g. `?orthographic.viewportRendering=cpu`). Validated at mount time (not
+ * init) because extension backends may call registerRenderBackend after the
+ * cornerstone extension initializes; an unregistered value is dropped with a
+ * warning rather than failing the mount.
+ */
+function getMountRenderBackend(viewportTypeKey: string): RenderBackendValue | undefined {
+  const backend = getViewportRenderingOverride(viewportTypeKey);
+  if (!backend) {
+    return undefined;
+  }
+  if (backend !== 'auto' && !isRegisteredRenderBackend(backend)) {
+    console.warn(
+      `${viewportTypeKey}.viewportRendering: "${backend}" is not a registered render backend; ignoring.`
+    );
+    return undefined;
+  }
+  return backend as RenderBackendValue;
+}
+
+// The PlanarViewState fields that encode pan/zoom/rotation/flip. Slice and
+// orientation are deliberately EXCLUDED — they are restored via the view reference,
+// and a partial setViewState patch that omits them leaves them untouched (the merge
+// at PlanarViewport.setViewState preserves unspecified fields).
+const NATIVE_VIEW_PRESENTATION_KEYS = [
+  'displayArea',
+  'anchorWorld',
+  'anchorCanvas',
+  'scale',
+  'scaleMode',
+  'rotation',
+  'flipHorizontal',
+  'flipVertical',
+] as const;
+
+// Minimal structural view of a native PlanarViewport's semantic accessors. These
+// live on IGenericViewport (not IStackViewport/IViewport), so we cast at the boundary
+// rather than import core-internal PlanarViewport/PlanarViewState types.
+type NativePlanarViewport = Types.IViewport & {
+  getViewState: () => Record<string, unknown>;
+  setViewState: (patch: Record<string, unknown>) => void;
+  getViewReference: () => Types.ViewReference;
+  setViewReference: (ref: Types.ViewReference) => void;
+  isReferenceViewable?: (ref: Types.ViewReference, opts?: unknown) => boolean;
+};
+
+/** Picks the pan/zoom/rotation/flip subset out of a (deep-cloned) getViewState() result. */
+function pickNativeViewPresentation(viewState: Record<string, unknown>): Record<string, unknown> {
+  const out: Record<string, unknown> = {};
+  for (const key of NATIVE_VIEW_PRESENTATION_KEYS) {
+    if (viewState[key] !== undefined) {
+      out[key] = viewState[key];
+    }
+  }
+  return out;
+}
+
+/**
+ * Derives a default VOI window/level range from an image's DICOM voiLutModule
+ * metadata (first WindowCenter/WindowWidth pair). Used to seed native viewport
+ * windowing, which (unlike legacy StackViewport) is not auto-applied from
+ * metadata. Returns undefined when the metadata has no usable window.
+ */
+function getDefaultVoiRangeFromMetadata(
+  imageId: string
+): { lower: number; upper: number } | undefined {
+  if (!imageId) {
+    return;
+  }
+  const voiLutModule = metaData.get('voiLutModule', imageId);
+  const wc = Array.isArray(voiLutModule?.windowCenter)
+    ? voiLutModule.windowCenter[0]
+    : voiLutModule?.windowCenter;
+  const ww = Array.isArray(voiLutModule?.windowWidth)
+    ? voiLutModule.windowWidth[0]
+    : voiLutModule?.windowWidth;
+  if (wc == null || ww == null) {
+    return;
+  }
+  return csUtils.windowLevel.toLowHighRange(ww, wc);
+}
+
+/**
+ * Native GenericViewport ("next") backend. Selected when `appConfig.useNextViewports`
+ * is on. Routes the mount by the bound data shape (native stack and volume content
+ * both report a single PLANAR_NEXT type, so the legacy runtime-type checks cannot
+ * classify them — §4.4), owns the per-family native MOUNT BODIES
+ * (mountStack/mountVolumes/mountEcg/mountOther/remount), and owns the ref-counted
+ * dataId lifecycle (§4.7) over cornerstone's global GenericViewport metadata
+ * provider. The service's shared methods hold no native branches.
+ */
+export class NextViewportBackend implements IViewportBackend {
+  private readonly registry = new DataIdRegistry();
+
+  constructor(private readonly service: IViewportServiceInternals) {}
+
+  dispatchMount(
+    viewport: Types.IViewport,
+    viewportData: StackViewportData | VolumeViewportData,
+    viewportInfo: ViewportInfo,
+    presentations: Presentations = {}
+  ): Promise<void> {
+    // Non-planar native families (video / WSI / ECG) route by viewport TYPE to their
+    // dedicated mounts: the bound data shape cannot distinguish them, and each needs
+    // family-specific dataId registration. Mirrors the legacy backend's type dispatch.
+    const type = (viewport as { type?: string }).type;
+
+    if (type === csEnums.ViewportType.ECG_NEXT) {
+      return this.service._setEcgViewport(
+        viewport as unknown as Types.IECGViewport,
+        viewportData as StackViewportData
+      );
+    }
+
+    if (
+      type === csEnums.ViewportType.VIDEO_NEXT ||
+      type === csEnums.ViewportType.WHOLE_SLIDE_NEXT
+    ) {
+      return this.service._setOtherViewport(
+        viewport as unknown as Types.IStackViewport,
+        viewportData as StackViewportData,
+        viewportInfo,
+        presentations
+      );
+    }
+
+    // Planar stack vs volume content both report PLANAR_NEXT, so infer from the
+    // persisted dataShapeType contract (§4.4) — the canonical discriminator set by
+    // CornerstoneCacheService and used everywhere else. Don't probe `'volume' in
+    // firstData`: that field can be lazily initialized after the data object is built,
+    // so the presence check is unreliable. Fall back to the probe only when an older
+    // viewportData has no dataShapeType.
+    const dataShapeType = (viewportData as { dataShapeType?: csEnums.ViewportType }).dataShapeType;
+    const firstData = (viewportData?.data?.[0] ?? {}) as Record<string, unknown>;
+    const isVolumeContent =
+      dataShapeType === csEnums.ViewportType.ORTHOGRAPHIC ||
+      dataShapeType === csEnums.ViewportType.VOLUME_3D ||
+      (dataShapeType === undefined && 'volume' in firstData);
+
+    if (isVolumeContent) {
+      return this.service._setVolumeViewport(
+        viewport as unknown as Types.IVolumeViewport,
+        viewportData as VolumeViewportData,
+        viewportInfo,
+        presentations
+      );
+    }
+
+    return this.service._setStackViewport(
+      viewport as unknown as Types.IStackViewport,
+      viewportData as StackViewportData,
+      viewportInfo,
+      presentations
+    );
+  }
+
+  /**
+   * Native stack mount: register the display set and mount it with
+   * setDisplaySets (render path inferred from the data), then apply
+   * VOI/colormap via setDisplaySetPresentation and pan/zoom/rotate/flip/
+   * displayArea via setViewState — instead of the legacy setStack/setProperties/
+   * setCamera surface, which a direct PLANAR_NEXT viewport does not expose.
+   */
+  async mountStack(viewport: Types.IStackViewport, context: StackMountContext): Promise<void> {
+    const {
+      displaySetInstanceUIDs,
+      imageIds,
+      initialImageIndex,
+      properties,
+      displayArea,
+      rotation,
+      flipHorizontal,
+      presentations,
+      overlayProcessingResults,
+    } = context;
+
+    // Native stacks arrive as PLANAR_NEXT and bypass the legacy STACK-typed
+    // invalid-stack guard upstream, so guard empty/malformed stack data here
+    // before registering and indexing imageIds below.
+    if (!imageIds?.length) {
+      return;
+    }
+
+    const vp = viewport as unknown as NativePlanarViewport & {
+      setDisplaySets: (args: {
+        displaySetId: string;
+        options: Record<string, unknown>;
+      }) => Promise<void>;
+      setDisplaySetPresentation: (props: Record<string, unknown>) => void;
+      element: HTMLDivElement;
+      id: string;
+    };
+    const dataId = displaySetInstanceUIDs[0];
+
+    // Register through the ref-counted registry (§4.7) instead of the raw
+    // provider.add, so the registration is released on unmount and shared
+    // (MPR) registrations are not double-added or prematurely removed.
+    this.registerDataId(vp.id, dataId, {
+      kind: 'planar',
+      imageIds,
+      initialImageIdIndex: initialImageIndex,
+    });
+
+    const stackRenderBackend = getMountRenderBackend('stack');
+    await vp.setDisplaySets({
+      displaySetId: dataId,
+      options: {
+        orientation: csEnums.OrientationAxis.ACQUISITION,
+        role: 'source',
+        ...(stackRenderBackend ? { renderBackend: stackRenderBackend } : {}),
+      },
+    });
+
+    // Native viewports are presentation-driven and do NOT auto-derive a default
+    // window/level from the image's DICOM VOI metadata the way legacy StackViewport
+    // does, so without this the image renders with a raw/full-range VOI (too dark).
+    // When no explicit VOI is provided, seed it from the voiLutModule metadata.
+    if (!properties.voiRange) {
+      const defaultVoi = getDefaultVoiRangeFromMetadata(imageIds[initialImageIndex] ?? imageIds[0]);
+      if (defaultVoi) {
+        properties.voiRange = defaultVoi;
+      }
+    }
+
+    const presentationProps: Record<string, unknown> = {};
+    if (properties.voiRange) {
+      presentationProps.voiRange = properties.voiRange;
+    }
+    if (properties.invert !== undefined) {
+      presentationProps.invert = properties.invert;
+    }
+    if (properties.colormap) {
+      presentationProps.colormap = properties.colormap;
+    }
+    if (Object.keys(presentationProps).length > 0) {
+      vp.setDisplaySetPresentation(presentationProps);
+    }
+
+    const viewStatePatch: Record<string, unknown> = {};
+    if (displayArea) {
+      viewStatePatch.displayArea = displayArea;
+    }
+    if (rotation) {
+      viewStatePatch.rotation = rotation;
+    }
+    if (flipHorizontal) {
+      viewStatePatch.flipHorizontal = true;
+    }
+    if (Object.keys(viewStatePatch).length > 0) {
+      vp.setViewState(viewStatePatch);
+    }
+
+    // Enable stack-context prefetch for the native path. setDisplaySets above has
+    // already populated imageIds via genericViewportDisplaySetMetadataProvider, so
+    // getStackData returns a valid stack at enable() time. Scroll re-prefetch is
+    // driven by the native STACK_NEW_IMAGE event.
+    csToolsUtils.stackContextPrefetch.enable(vp.element);
+
+    // Restore persisted pan/zoom/rotation/flip (+ view reference) on top of the
+    // HP-derived defaults applied above, so a returning display set recovers its
+    // camera presentation. The LUT was already applied inline above, so restore
+    // position + segmentation only. Replaying segmentationPresentation re-adds
+    // hydrated representations (RTSS contour / SEG labelmap) on this native re-mount;
+    // without it a hydrated overlay silently disappears (the contour-vanishes-on-
+    // hydrate bug), because the overlay display set is no longer in the viewport's
+    // display-set list after hydration. Native-safe: position via setViewReference/
+    // setViewState, and the replayed addSegmentationRepresentation routes through the
+    // native segmentation backend (no convertStackToVolumeViewport / getViewPresentation).
+    if (presentations?.positionPresentation || presentations?.segmentationPresentation) {
+      this.service.setPresentations(vp.id, {
+        positionPresentation: presentations.positionPresentation,
+        segmentationPresentation: presentations.segmentationPresentation,
+      });
+    }
+
+    await this.service._addOverlayRepresentations(overlayProcessingResults);
+  }
+
+  /**
+   * Native volume/MPR mount: a direct PLANAR_NEXT viewport renders a volume by
+   * registering the dataset (with the already-cached volumeId) and calling
+   * setDisplaySets with the requested orientation; cornerstone selects the image
+   * vs reformatted-volume render path from that orientation. Returns true so the
+   * service skips the legacy setVolumes/setProperties tail; an overlay-only mount
+   * (no base volumes) returns false and traverses the shared tail, whose
+   * legacy-surface steps are lane-guarded via mountOverlayOnlyVolumes.
+   */
+  async mountVolumes(viewport: Types.IViewport, context: VolumeMountContext): Promise<boolean> {
+    const {
+      filteredVolumeInputArray,
+      volumesProperties,
+      viewportInfo,
+      overlayProcessingResults,
+      presentations,
+    } = context;
+
+    if (!filteredVolumeInputArray.length) {
+      return false;
+    }
+
+    await this._setNativeVolumeDisplaySets(
+      viewport,
+      filteredVolumeInputArray,
+      volumesProperties,
+      viewportInfo,
+      overlayProcessingResults
+    );
+
+    // Restore persisted pan/zoom/rotation/flip (+ view reference) so a returning
+    // MPR/volume pane recovers its camera. Also replay the stored lutPresentation so
+    // user window/level, colormap, invert, opacity or threshold edits survive the
+    // re-mount instead of resetting to the hanging-protocol defaults applied
+    // per-binding above (applied via setDisplaySetPresentation). And replay
+    // segmentationPresentation so hydrated overlays (SEG labelmap / RTSS contour)
+    // reappear on this native re-mount instead of vanishing. Native-safe: position
+    // via setViewReference/setViewState, segmentation via the native backend.
+    if (
+      presentations?.positionPresentation ||
+      presentations?.lutPresentation ||
+      presentations?.segmentationPresentation
+    ) {
+      this.service.setPresentations(viewport.id, {
+        positionPresentation: presentations.positionPresentation,
+        lutPresentation: presentations.lutPresentation,
+        segmentationPresentation: presentations.segmentationPresentation,
+      });
+    }
+    return true;
+  }
+
+  async mountOverlayOnlyVolumes(): Promise<void> {
+    // Generic ("next") viewports don't expose the legacy setVolumes surface. A
+    // native overlay-only mount adds its overlays via _addOverlayRepresentations
+    // in the shared tail; there is nothing to mount here.
+  }
+
+  /**
+   * Native ECG_NEXT has no setEcg; register the waveform under the display set's
+   * dataId and mount it through the generic setDisplaySets API (the native ECG data
+   * provider reads sourceDataId). Ref-counted via the registry (§4.7).
+   */
+  async mountEcg(
+    viewport: Types.IECGViewport,
+    displaySet: { displaySetInstanceUID: string; imageIds?: string[] },
+    imageId: string
+  ): Promise<void> {
+    const dataId = displaySet.displaySetInstanceUID;
+    this.registerDataId(viewport.id, dataId, { kind: 'ecg', sourceDataId: imageId });
+    this.service._trackViewportDisplaySets(viewport.id, [dataId]);
+    await (
+      viewport as unknown as {
+        setDisplaySets: (args: { displaySetId: string }) => Promise<void>;
+      }
+    ).setDisplaySets({ displaySetId: dataId });
+  }
+
+  /**
+   * Native VIDEO_NEXT / WHOLE_SLIDE_NEXT: register the family-specific dataId, then
+   * mount through the generic setDisplaySets API. The native video data provider
+   * reads sourceDataId; the WSI provider reads imageIds + a DICOMweb client, which
+   * we resolve from the WADO_WEB_CLIENT metadata exactly as the legacy WSI adapter
+   * does. Ref-counted via the registry (§4.7).
+   */
+  async mountOther(
+    viewport: Types.IViewport,
+    displaySet: { displaySetInstanceUID: string; imageIds: string[] }
+  ): Promise<void> {
+    const dataId = displaySet.displaySetInstanceUID;
+    const imageId = displaySet.imageIds[0];
+    const isWsi = (viewport as { type?: string }).type === csEnums.ViewportType.WHOLE_SLIDE_NEXT;
+    const payload = isWsi
+      ? {
+          kind: 'wsi' as const,
+          imageIds: displaySet.imageIds,
+          options: {
+            webClient: metaData.get(csEnums.MetadataModules.WADO_WEB_CLIENT, imageId),
+          },
+        }
+      : { kind: 'video' as const, sourceDataId: imageId };
+    this.registerDataId(viewport.id, dataId, payload);
+    this.service._trackViewportDisplaySets(viewport.id, [dataId]);
+    await (
+      viewport as unknown as {
+        setDisplaySets: (args: { displaySetId: string }) => Promise<void>;
+      }
+    ).setDisplaySets({ displaySetId: dataId });
+  }
+
+  /**
+   * Native re-mount: no getCamera/setCamera. Snapshot/restore the camera via the
+   * semantic view state, and route the mount through dispatchMount (it routes by
+   * data shape, since native stack and volume both report PLANAR_NEXT).
+   */
+  remount(
+    viewport: Types.IViewport,
+    viewportData: StackViewportData | VolumeViewportData,
+    viewportInfo: ViewportInfo,
+    keepCamera: boolean
+  ): Promise<void> {
+    const vp = viewport as NativePlanarViewport;
+    const viewState = keepCamera ? (vp.getViewState?.() ?? {}) : undefined;
+    return this.dispatchMount(viewport, viewportData, viewportInfo).then(() => {
+      if (keepCamera && viewState) {
+        vp.setViewState?.(viewState);
+        viewport.render();
+      }
+    });
+  }
+
+  /**
+   * Mounts one or more volumes on a native viewport for volume/MPR rendering.
+   * Each base volume is registered with its already-cached volumeId and bound via
+   * setDisplaySets at the viewport's requested orientation; the first base volume
+   * is the source binding, any others are overlays (fusion). VOI/colormap/invert
+   * are applied per-binding via setDisplaySetPresentation.
+   */
+  private async _setNativeVolumeDisplaySets(
+    viewport: Types.IViewport,
+    filteredVolumeInputArray: VolumeMountContext['filteredVolumeInputArray'],
+    volumesProperties: VolumeMountContext['volumesProperties'],
+    viewportInfo: ViewportInfo,
+    overlayProcessingResults: VolumeMountContext['overlayProcessingResults']
+  ): Promise<void> {
+    const orientation = viewportInfo.getOrientation();
+    // A native VOLUME_3D_NEXT viewport renders the volume as a 3D VTK volume
+    // (renderMode 'vtkVolume3d'), not a reformatted planar slice; its appearance is
+    // driven by a volume-rendering preset, not orientation/role.
+    const is3D = (viewport as { type?: string }).type === csEnums.ViewportType.VOLUME_3D_NEXT;
+    const nativeViewport = viewport as unknown as {
+      setDisplaySets: (
+        ...entries: Array<{ displaySetId: string; options: Record<string, unknown> }>
+      ) => Promise<void>;
+      setDisplaySetPresentation: (dataId: string, props: Record<string, unknown>) => void;
+      getDefaultActor?: () => { actor?: unknown } | undefined;
+      render: () => void;
+    };
+    const setDisplaySetsEntries: Array<{
+      displaySetId: string;
+      options: Record<string, unknown>;
+    }> = [];
+    const volumeRenderBackend = is3D ? undefined : getMountRenderBackend('orthographic');
+
+    // First pass: register each dataId and build the COMPLETE entry set. The native
+    // PlanarViewport.setDisplaySets has replace semantics (removeReplaceableData), so
+    // it must receive ALL entries in ONE call - the first entry (role 'source')
+    // resolves the source binding and the rest are overlays. Calling it once per
+    // volume instead drops the previously-set source (e.g. the fusion CT): the next
+    // single-entry overlay call (PT) finds no source entry, falls back to entries[0]
+    // (= PT), and removeReplaceableData tears down CT - leaving only the PT colormap.
+    for (const [index, { volumeInput }] of filteredVolumeInputArray.entries()) {
+      const { imageIds, volumeId, displaySetInstanceUID } = volumeInput;
+      const dataId = displaySetInstanceUID;
+
+      // Ref-counted registration (§4.7): the MPR triptych shares one dataId across
+      // panes, so register() adds to the provider once and release() removes only
+      // when the last pane unmounts. (kind is stored but ignored by the volume3d
+      // data provider, which reads imageIds/volumeId.)
+      this.registerDataId(viewport.id, dataId, {
+        kind: 'planar',
+        imageIds,
+        volumeId,
+      });
+
+      setDisplaySetsEntries.push({
+        displaySetId: dataId,
+        options: is3D
+          ? { renderMode: 'vtkVolume3d' }
+          : {
+              orientation,
+              role: index === 0 ? 'source' : 'overlay',
+              // Volume/MPR panes are 'orthographic' viewports at the OHIF level;
+              // renderBackend is a planar mount option, so the 3D branch is exempt.
+              ...(volumeRenderBackend ? { renderBackend: volumeRenderBackend } : {}),
+            },
+      });
+    }
+
+    // Single replace call with the full entry set so the source (CT) is resolved
+    // and preserved instead of being torn down by per-volume calls.
+    await nativeViewport.setDisplaySets(...setDisplaySetsEntries);
+
+    // Second pass: per-dataId presentations and the 3D preset.
+    for (const [index, { volumeInput }] of filteredVolumeInputArray.entries()) {
+      const dataId = volumeInput.displaySetInstanceUID;
+      const props = volumesProperties[index]?.properties;
+      if (props) {
+        const presentationProps: Record<string, unknown> = {};
+        if (props.voiRange) {
+          presentationProps.voiRange = props.voiRange;
+        }
+        if (props.invert !== undefined) {
+          presentationProps.invert = props.invert;
+        }
+        // colormap is a planar (LUT) concept; 3D appearance comes from the preset.
+        if (props.colormap && !is3D) {
+          presentationProps.colormap = props.colormap;
+        }
+        // Slab/blend for projection viewports (e.g. the TMTV MIP pane: blendMode
+        // 'MIP' + slabThickness 'fullVolume'). The native volume-slice render path
+        // maps blendMode -> reslice SlabType (MAX/MIN/MEAN) and applies the slab
+        // thickness on the reslice mapper; without them the mapper renders a single
+        // slice instead of a projection. 3D volume rendering derives its look from
+        // the preset, not a slab, so this is planar-only. blendMode was already
+        // normalized from the HP string ('MIP') to a BlendModes enum by
+        // ViewportInfo.mapDisplaySetOptions, and slabThickness was resolved to a
+        // number by _getSlabThickness ('fullVolume' -> volume diagonal).
+        if (!is3D && volumeInput.blendMode !== undefined) {
+          presentationProps.blendMode = volumeInput.blendMode;
+        }
+        if (!is3D && volumeInput.slabThickness !== undefined) {
+          presentationProps.slabThickness = volumeInput.slabThickness;
+        }
+        if (Object.keys(presentationProps).length > 0) {
+          nativeViewport.setDisplaySetPresentation(dataId, presentationProps);
+        }
+      }
+
+      // 3D volume rendering needs an RGBA transfer function (preset) to be visible;
+      // the bare native VolumeViewport3D has no setProperties, so apply the preset to
+      // the volume actor directly (mirrors the legacy adapter's applyPresetToBinding).
+      if (is3D && index === 0 && props?.preset) {
+        const preset = csConstants.VIEWPORT_PRESETS?.find(p => p.name === props.preset);
+        const actor = nativeViewport.getDefaultActor?.()?.actor;
+        if (preset && actor) {
+          csUtils.applyPreset(actor as Parameters<typeof csUtils.applyPreset>[0], preset);
+        }
+      }
+    }
+
+    // Do NOT overwrite the service's viewport display-set bookkeeping here. The
+    // caller (_setVolumeViewport) already populated it with the COMPLETE set (base
+    // volumes + SEG/RT/fusion overlays) before this native mount; writing back the
+    // base-volume-only ids would drop the overlay UIDs from getViewportDisplaySets()
+    // and the later presentation/hydration flows.
+
+    await this.service._addOverlayRepresentations(overlayProcessingResults);
+    nativeViewport.render();
+  }
+
+  getPositionPresentation(
+    csViewport: Types.IViewport,
+    viewportInfo: ViewportInfo,
+    viewportId: string
+  ): PositionPresentation {
+    const is3D = isVolume3DViewportType(csViewport);
+    const vp = csViewport as NativePlanarViewport;
+
+    // A direct PLANAR_NEXT viewport has no getViewPresentation; pan/zoom/rotation/flip
+    // live in the semantic view state. getViewState() is already deep-cloned, normalized
+    // and JSON-serializable, so snapshot the pan/zoom subset (slice/orientation come back
+    // via the view reference).
+    const viewState =
+      !is3D && typeof vp.getViewState === 'function' ? vp.getViewState() : undefined;
+
+    return {
+      viewportType: viewportInfo.getViewportType(),
+      viewReference: is3D ? null : vp.getViewReference(),
+      // Opaque native pan/zoom blob; cast at the boundary (legacy stores a Types.ViewPresentation).
+      viewPresentation: (viewState
+        ? pickNativeViewPresentation(viewState)
+        : undefined) as unknown as Types.ViewPresentation,
+      viewportId,
+    };
+  }
+
+  setPositionPresentation(
+    viewport: Types.IViewport,
+    positionPresentation: PositionPresentation
+  ): void {
+    const vp = viewport as NativePlanarViewport;
+
+    // 1) Slice + orientation first, via the view reference.
+    const viewRef = positionPresentation?.viewReference;
+    if (viewRef && vp.isReferenceViewable?.(viewRef, WITH_ORIENTATION)) {
+      vp.setViewReference(viewRef);
+    }
+
+    // 2) Pan/zoom/rotation/flip second, as a partial setViewState patch that omits
+    //    slice/orientation so step 1 is preserved (the merge keeps unspecified fields).
+    const vpres = positionPresentation?.viewPresentation as unknown as
+      | Record<string, unknown>
+      | undefined;
+    if (vpres && typeof vp.setViewState === 'function') {
+      const patch: Record<string, unknown> = {};
+      for (const key of NATIVE_VIEW_PRESENTATION_KEYS) {
+        if (vpres[key] !== undefined) {
+          patch[key] = vpres[key];
+        }
+      }
+      if (Object.keys(patch).length > 0) {
+        // When the snapshot held live anchor/scale pan/zoom, displayArea was omitted;
+        // clear any stale displayArea explicitly so anchor/scale take effect (setViewState
+        // only rewrites displayArea when it is an own key of the patch).
+        if (!('displayArea' in patch)) {
+          patch.displayArea = undefined;
+        }
+        vp.setViewState(patch);
+      }
+    }
+  }
+
+  setLutPresentation(viewport: Types.IViewport, lutPresentation: LutPresentation): void {
+    if (!lutPresentation) {
+      return;
+    }
+    const { properties } = lutPresentation;
+    // Native LUT presentation is the getDisplaySetPresentation shape (voiRange/
+    // colormap/invert), not a per-volumeId Map; a PLANAR_NEXT viewport applies it via
+    // setDisplaySetPresentation (it has no legacy setProperties).
+    if (!properties || properties instanceof Map) {
+      return;
+    }
+    const nativeViewport = viewport as unknown as {
+      setDisplaySetPresentation: (props: Record<string, unknown>) => void;
+    };
+    const presentationProps: Record<string, unknown> = {};
+    if (properties.voiRange) {
+      presentationProps.voiRange = properties.voiRange;
+    }
+    if (properties.invert !== undefined) {
+      presentationProps.invert = properties.invert;
+    }
+    if (properties.colormap) {
+      presentationProps.colormap = properties.colormap;
+    }
+    if (Object.keys(presentationProps).length > 0) {
+      nativeViewport.setDisplaySetPresentation(presentationProps);
+    }
+  }
+
+  registerDataId(viewportId: string, dataId: string, payload: DataIdPayload): void {
+    this.registry.register(viewportId, dataId, payload);
+  }
+
+  onViewportDisabled(viewportId: string): void {
+    this.registry.releaseViewport(viewportId);
+  }
+
+  destroy(): void {
+    this.registry.destroy();
+  }
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/NextViewportOperations.ts b/extensions/cornerstone/src/services/ViewportService/backends/NextViewportOperations.ts
new file mode 100644
index 000000000..a37fc9d41
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/NextViewportOperations.ts
@@ -0,0 +1,169 @@
+import {
+  utilities as csUtils,
+  CONSTANTS as csConstants,
+  Types as CoreTypes,
+} from '@cornerstonejs/core';
+import { getViewportAdapter } from '../adapter';
+import { legacyViewportOperations } from './LegacyViewportOperations';
+import type {
+  IViewportOperations,
+  FlipValue,
+  RotationMode,
+  VolumeLightingOptions,
+  WindowLevelParams,
+  ColormapParams,
+} from './IViewportOperations';
+
+// Native PLANAR_NEXT semantic accessors not covered by the viewport adapter.
+// They live on IGenericViewport, so cast structurally at the boundary.
+type NativePlanarViewport = CoreTypes.IViewport & {
+  resetViewState?: () => void;
+  resetDisplaySetPresentation?: (dataId?: string) => void;
+  getZoom?: () => number;
+  setZoom?: (zoom: number) => void;
+};
+
+/**
+ * Native ("next") lane of IViewportOperations for direct PLANAR_NEXT viewports.
+ * Appearance and camera/view-state ops go through the viewport adapter (which
+ * encapsulates the native getViewState/setViewState and
+ * getDisplaySetPresentation/setDisplaySetPresentation primitives, including the
+ * active-binding dataId default); the remaining ops use the native semantic API
+ * directly. The dispatcher only routes generic viewports here.
+ *
+ * No method calls viewport.render() — the command renders.
+ */
+export const nextViewportOperations: IViewportOperations = {
+  flipHorizontal(viewport: CoreTypes.IViewport, newValue: FlipValue = 'toggle'): void {
+    const adapter = getViewportAdapter(viewport);
+    const flipHorizontal =
+      newValue === 'toggle' ? !adapter.getViewState().flipHorizontal : newValue;
+    adapter.setViewState({ flipHorizontal });
+  },
+
+  flipVertical(viewport: CoreTypes.IViewport, newValue: FlipValue = 'toggle'): void {
+    const adapter = getViewportAdapter(viewport);
+    const flipVertical = newValue === 'toggle' ? !adapter.getViewState().flipVertical : newValue;
+    adapter.setViewState({ flipVertical });
+  },
+
+  invert(viewport: CoreTypes.IViewport): void {
+    const adapter = getViewportAdapter(viewport);
+    const { invert } = adapter.getPresentation();
+    adapter.setPresentation({ invert: !invert });
+  },
+
+  rotate(viewport: CoreTypes.IViewport, rotation: number, mode: RotationMode = 'apply'): void {
+    // rotation/flip live in the semantic view state; getViewPresentation is absent.
+    const adapter = getViewportAdapter(viewport);
+    const state = adapter.getViewState();
+    const currentRotation = (state.rotation as number) ?? 0;
+    const newRotation =
+      mode === 'apply'
+        ? (currentRotation + rotation + 360) % 360
+        : (() => {
+            const flipsParity = (state.flipHorizontal ? 1 : 0) + (state.flipVertical ? 1 : 0);
+            const effectiveRotation = flipsParity % 2 === 1 ? -rotation : rotation;
+            return (effectiveRotation + 360) % 360;
+          })();
+    adapter.setViewState({ rotation: newRotation });
+  },
+
+  reset(viewport: CoreTypes.IViewport): void {
+    const vp = viewport as NativePlanarViewport;
+    // Reset the per-display-set presentation (VOI/colormap/invert) to defaults.
+    vp.resetDisplaySetPresentation?.();
+    // No resetCamera on PLANAR_NEXT; resetViewState resets pan/zoom/rotation/orientation/flip.
+    vp.resetViewState?.();
+  },
+
+  scaleBy(viewport: CoreTypes.IViewport, direction: number): void {
+    // parallelScale and zoom are inversely related (smaller parallelScale = more
+    // zoomed in = larger zoom), so divide by scaleFactor to match the legacy direction.
+    const scaleFactor = direction > 0 ? 0.9 : 1.1;
+    const vp = viewport as unknown as {
+      getZoom?: () => number;
+      setZoom?: (zoom: number) => void;
+      resetViewState?: (options?: { resetOrientation?: boolean }) => void;
+    };
+    if (direction) {
+      // Zoom is only meaningful on planar (stack / volume-slice / MPR) native viewports.
+      // VolumeViewport3D is also a generic viewport but exposes no getZoom/setZoom, so
+      // guard before calling — a no-op there matches the legacy lane, which only zoomed
+      // stack viewports (otherwise the zoom hotkey would throw on a native 3D viewport).
+      if (vp.getZoom && vp.setZoom) {
+        vp.setZoom(vp.getZoom() / scaleFactor);
+      }
+    } else {
+      // direction === 0 is the fitViewportToWindow command. Legacy resetCamera()
+      // resets pan/zoom/rotation/flip but never the viewing orientation, while a
+      // full native resetViewState() would also snap an MPR back to its requested
+      // axis — so keep the orientation.
+      vp.resetViewState?.({ resetOrientation: false });
+    }
+  },
+
+  getViewPlaneNormal(viewport: CoreTypes.IViewport): CoreTypes.Point3 | undefined {
+    return getViewportAdapter(viewport).getViewPlaneNormal();
+  },
+
+  centerOnMeasurement(): boolean {
+    // CS-14: native PLANAR_NEXT has no getCamera/setCamera for in-plane pan; the
+    // caller's setViewReference already navigated to the measurement's slice.
+    // TODO(next): port in-plane centering via the camera bridge + setViewState pan.
+    return false;
+  },
+
+  setWindowLevel(viewport: CoreTypes.IViewport, params: WindowLevelParams): void {
+    const { lower, upper } = csUtils.windowLevel.toLowHighRange(
+      params.windowWidth,
+      params.windowCenter
+    );
+    // Target the binding for params.displaySetInstanceUID so a PT/CT *fusion* W/L lands
+    // on the intended layer (e.g. the PT overlay) instead of always the source (CT) —
+    // mirroring setColormap. When no id is given (single stack/volume) the adapter falls
+    // back to the source binding.
+    getViewportAdapter(viewport).setPresentation(
+      { voiRange: { upper, lower } },
+      params.displaySetInstanceUID
+    );
+  },
+
+  setColormap(viewport: CoreTypes.IViewport, params: ColormapParams): void {
+    // Target the binding for params.displaySetInstanceUID. OHIF's dataId scheme maps a
+    // display set 1:1 onto its native dataId (bare UID), so a PT/CT *fusion* colormap lands
+    // on the overlay (PT) binding instead of defaulting to the source (CT). When no id is
+    // given (single-volume / plain stack colormap) the adapter falls back to the source.
+    getViewportAdapter(viewport).setPresentation(
+      { colormap: params.colormap },
+      params.displaySetInstanceUID
+    );
+  },
+
+  setPreset(viewport: CoreTypes.IViewport, preset: string): void {
+    // The native VolumeViewport3D has no setProperties; apply the volume-rendering
+    // preset (RGBA transfer function) to the volume actor directly.
+    const presetObj = csConstants.VIEWPORT_PRESETS?.find(p => p.name === preset);
+    const actor = (
+      viewport as unknown as { getDefaultActor?: () => { actor?: unknown } | undefined }
+    ).getDefaultActor?.()?.actor;
+    if (presetObj && actor) {
+      csUtils.applyPreset(actor as Parameters<typeof csUtils.applyPreset>[0], presetObj);
+    }
+  },
+
+  // VR sample-distance / opacity-points / lighting operate on the vtk volume actor via
+  // getActors, which the native VolumeViewport3D exposes; the work is lane-agnostic, so
+  // reuse the legacy actor-based implementations.
+  setVolumeRenderingQuality(viewport: CoreTypes.IViewport, volumeQuality: number): void {
+    legacyViewportOperations.setVolumeRenderingQuality(viewport, volumeQuality);
+  },
+
+  shiftVolumeOpacityPoints(viewport: CoreTypes.IViewport, shift: number): void {
+    legacyViewportOperations.shiftVolumeOpacityPoints(viewport, shift);
+  },
+
+  setVolumeLighting(viewport: CoreTypes.IViewport, options: VolumeLightingOptions): void {
+    legacyViewportOperations.setVolumeLighting(viewport, options);
+  },
+};
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/README.md b/extensions/cornerstone/src/services/ViewportService/backends/README.md
new file mode 100644
index 000000000..8dde22aef
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/README.md
@@ -0,0 +1,62 @@
+# Next-viewport dispatch: how legacy-vs-native is decided
+
+The `useNextViewports` opt-in routes OHIF onto cornerstone3D's native
+("next" / GenericViewport) API. This document is the single description of
+where and how the two lanes are selected. If you are adding a new legacy/native
+divergence, one of the homes below is the right place — never an inline
+`isGenericViewport` / flag check at the call site (enforced by
+`scripts/check-next-viewport-boundaries.sh`).
+
+## The three homes for divergence
+
+| Home | What belongs there |
+|---|---|
+| `../adapter/` (`IViewportAdapter`) | API-surface bridging on a live viewport: reads/writes that exist on both lanes with different spellings (camera vs view state, properties vs display-set presentation, volumeId vs dataId, classification). The contract is next-shaped; the legacy adapter does the adapting. |
+| `./` (`IViewportBackend`, `IViewportOperations`, and the segmentation twins in `../../SegmentationService/backends/`) | Lifecycle and interaction bodies: mount/re-mount, presentation capture/restore, dataId registration, per-command operations (flip/rotate/W-L/...), labelmap add/assembly. |
+| `../../../utils/nextViewportPolicies.ts` | Behavioral policy: appearance defaults and workflow rules that differ by choice, not by API (fusion opacity flattening, overlay opacity, RTSTRUCT hydrate stack-pin). |
+
+Pre-mount classification of `viewportData` (no live viewport yet) lives in
+`../../../utils/viewportDataShape.ts`; the persisted `dataShapeType` field set
+by `CornerstoneCacheService` is the sanctioned way to survive the native
+type collapse (stack/volume/MPR all report `PLANAR_NEXT` at runtime).
+
+## Two dispatch strategies (deliberately different)
+
+- **Session flag, selected once** — `isNextViewportsEnabled()`. Used where no
+  viewport exists yet, or for per-session lifecycle:
+  `IViewportBackend` (the `get backend()` getter on CornerstoneViewportService),
+  `getCornerstoneViewportType` (viewport-type resolution), the SEG assembly
+  path, and the policies module.
+- **Per-viewport predicate** — `isNextViewport(viewport)` (the adapter module's
+  wrapper around `csUtils.isGenericViewport`). Used where a self-describing
+  viewport is in hand, because a flag-on session can hold BOTH native and
+  legacy viewports: `getViewportAdapter`, `viewportOperations`, and the
+  segmentation backend twins.
+
+Do not "unify" these: lifecycle genuinely is per-session; everything else
+genuinely is per-viewport.
+
+## Sanctioned flag reads (`isNextViewportsEnabled`) — the exhaustive list
+
+1. `utils/getCornerstoneViewportType.ts` — maps requested OHIF viewport types
+   to native types.
+2. `services/ViewportService/CornerstoneViewportService.ts` — the lazy
+   `get backend()` selection.
+3. `services/SegmentationService/SegmentationService.ts` —
+   `assembleSegmentationDataForSEG` (dispatched at SEG-load time, before any
+   target viewport exists).
+4. `utils/nextViewportPolicies.ts` — policy rules that apply before viewports
+   exist (e.g. the RTSTRUCT hydrate stack-pin).
+5. `extensions/tmtv/src/getHangingProtocolModule.ts` — applies the
+   `NEXT_FUSION_PT_OPACITY` policy when the HP module is gathered (the flag is
+   settled by then; the legacy ramp in `hpViewports` stays untouched).
+
+Adding a sixth read requires updating this list AND the whitelist in
+`scripts/check-next-viewport-boundaries.sh` — if you can express the change as
+an adapter capability, a backend method, or a policy entry instead, do that.
+
+## Sanctioned `csUtils.isGenericViewport` calls
+
+Only `../adapter/getViewportAdapter.ts` (which also exports the
+`isNextViewport` predicate for the dispatchers above). Everyone else consumes
+`IViewportAdapter` methods.
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/dataIdRegistry.ts b/extensions/cornerstone/src/services/ViewportService/backends/dataIdRegistry.ts
new file mode 100644
index 000000000..9457cd461
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/dataIdRegistry.ts
@@ -0,0 +1,121 @@
+import { utilities as csUtils } from '@cornerstonejs/core';
+
+/**
+ * Payload registered with cornerstone's global GenericViewport dataset metadata
+ * provider. The shape is family-specific and mirrors what each native viewport's
+ * data provider reads (see the cornerstone genericViewport examples):
+ *   - planar : imageIds (+ optional volumeId) — stack / volume-slice / MPR / 3D
+ *   - video  : sourceDataId (the video imageId)
+ *   - ecg    : sourceDataId (the waveform imageId)
+ *   - wsi    : imageIds + a DICOMweb webClient used to fetch tiles
+ */
+export type DataIdPayload =
+  | { kind: 'planar'; imageIds: string[]; volumeId?: string; initialImageIdIndex?: number }
+  | { kind: 'video' | 'ecg'; sourceDataId: string }
+  | { kind: 'wsi'; imageIds: string[]; options: { webClient: unknown } };
+
+/**
+ * Owns the lifecycle of OHIF's `dataId` registrations against cornerstone's
+ * process-global `genericViewportDisplaySetMetadataProvider` (see migration plan §4.7).
+ *
+ * Why this exists: cornerstone's `removeData`/`setDisplaySets` do NOT garbage-collect
+ * the global registration store (upstream blocker CS-18), so OHIF must own add/remove.
+ * The MPR triptych mounts the SAME `dataId` (the displaySetInstanceUID-derived volume)
+ * from N panes, so a naive add-on-every-mount / never-remove both over-registers and
+ * leaks. This registry ref-counts per `dataId` and keeps a per-viewport ledger so:
+ *   - `provider.add` fires only on the 0 -> 1 transition,
+ *   - `provider.remove` fires only on the 1 -> 0 transition,
+ *   - unmounting one pane of a shared-volume triptych does not unregister data the
+ *     other panes still need.
+ *
+ * Used by the native ("next") backend for all families, and by the legacy
+ * backend for its one provider-backed family (WSI mounts via mountOther).
+ */
+export class DataIdRegistry {
+  // Global ref-count keyed by dataId (the provider store is a single global namespace).
+  private readonly refCounts = new Map<string, number>();
+  // Last payload registered per dataId, so a re-registration that promotes a
+  // stack-only dataId to volume-backed can be detected and forwarded to the provider.
+  private readonly payloads = new Map<string, DataIdPayload>();
+  // Per-viewport ledger of the dataIds it registered, to drive release on unmount.
+  private readonly byViewport = new Map<string, string[]>();
+
+  /**
+   * Builds the registration dataId for a display set. PT/CT *fusion* overlays are
+   * distinct display sets with their own UIDs, so the bare displaySetInstanceUID is
+   * already collision-free and is used for both source and overlay bindings (the LUT
+   * presentation store keys by the same UID, giving a clean 1:1 dataId mapping). The
+   * `'overlay'` suffix is reserved for the case where a source and an overlay share the
+   * SAME displaySetInstanceUID but need distinct registrations — i.e. derived labelmap
+   * overlays (segmentation / M4), which are not yet on the native path.
+   */
+  static dataIdFor(displaySetInstanceUID: string, role?: 'overlay'): string {
+    return role === 'overlay' ? `${displaySetInstanceUID}::overlay` : displaySetInstanceUID;
+  }
+
+  /**
+   * Registers (or ref-bumps) a dataId for a viewport. Adds to the cornerstone
+   * provider only on the first reference. Idempotent payloads across panes that
+   * share a dataId are expected (same imageIds/volumeId), so first-writer wins —
+   * EXCEPT when a later payload promotes a previously stack-only registration to
+   * a volume-backed one (gains a `volumeId`). That happens when a data overlay
+   * (fusion) is added to a viewport whose source was first mounted as a vtkImage
+   * stack: the source is re-registered with its volumeId so it can render as a
+   * volume slice alongside the overlay. Without updating the provider here, the
+   * source would keep its volumeId-less payload and stay vtkImage while the
+   * overlay is a vtkVolumeSlice (broken fusion).
+   */
+  register(viewportId: string, dataId: string, payload: DataIdPayload): void {
+    const prev = this.refCounts.get(dataId) ?? 0;
+    const existing = this.payloads.get(dataId);
+    const promotesToVolume =
+      !!(payload as { volumeId?: string }).volumeId &&
+      !(existing as { volumeId?: string } | undefined)?.volumeId;
+
+    if (prev === 0 || promotesToVolume) {
+      csUtils.genericViewportDisplaySetMetadataProvider.add(dataId, payload);
+      this.payloads.set(dataId, payload);
+    }
+    this.refCounts.set(dataId, prev + 1);
+
+    const list = this.byViewport.get(viewportId) ?? [];
+    list.push(dataId);
+    this.byViewport.set(viewportId, list);
+  }
+
+  /**
+   * Releases every dataId a viewport registered (called on element disable).
+   * Removes from the provider only when the last reference is gone.
+   */
+  releaseViewport(viewportId: string): void {
+    const dataIds = this.byViewport.get(viewportId);
+    if (!dataIds) {
+      return;
+    }
+    for (const dataId of dataIds) {
+      const next = (this.refCounts.get(dataId) ?? 1) - 1;
+      if (next <= 0) {
+        this.refCounts.delete(dataId);
+        this.payloads.delete(dataId);
+        csUtils.genericViewportDisplaySetMetadataProvider.remove(dataId);
+      } else {
+        this.refCounts.set(dataId, next);
+      }
+    }
+    this.byViewport.delete(viewportId);
+  }
+
+  /**
+   * Flushes all remaining registrations (called on service destroy). Removes each
+   * dataId individually rather than `provider.clear()`, which would wipe
+   * registrations owned by other rendering contexts / service instances.
+   */
+  destroy(): void {
+    for (const dataId of this.refCounts.keys()) {
+      csUtils.genericViewportDisplaySetMetadataProvider.remove(dataId);
+    }
+    this.refCounts.clear();
+    this.payloads.clear();
+    this.byViewport.clear();
+  }
+}
diff --git a/extensions/cornerstone/src/services/ViewportService/backends/viewportOperations.ts b/extensions/cornerstone/src/services/ViewportService/backends/viewportOperations.ts
new file mode 100644
index 000000000..f421ffe90
--- /dev/null
+++ b/extensions/cornerstone/src/services/ViewportService/backends/viewportOperations.ts
@@ -0,0 +1,71 @@
+import { Types as CoreTypes } from '@cornerstonejs/core';
+import { isNextViewport } from '../adapter';
+import type {
+  IViewportOperations,
+  FlipValue,
+  RotationMode,
+  VolumeLightingOptions,
+  WindowLevelParams,
+  ColormapParams,
+} from './IViewportOperations';
+import { legacyViewportOperations } from './LegacyViewportOperations';
+import { nextViewportOperations } from './NextViewportOperations';
+
+/**
+ * Picks the operations lane for a SPECIFIC viewport. Unlike the IViewportBackend
+ * lifecycle backend (selected once by the appConfig flag because it owns the
+ * per-session mount), operations route per viewport: the viewport is already created
+ * and self-describing, and a session can hold both legacy and native viewports.
+ */
+function backendFor(viewport: CoreTypes.IViewport): IViewportOperations {
+  return isNextViewport(viewport) ? nextViewportOperations : legacyViewportOperations;
+}
+
+/**
+ * Singleton facade over the legacy/next operations backends. commandsModule (and any
+ * other caller) imports this and calls e.g. `viewportOperations.flipHorizontal(viewport)`,
+ * keeping native-vs-legacy interaction logic out of the command bodies (migration §4.3).
+ * Stateless and dependency-free (each op takes an already-resolved viewport), so it is a
+ * plain singleton rather than a registered service.
+ */
+export const viewportOperations: IViewportOperations = {
+  flipHorizontal: (viewport: CoreTypes.IViewport, newValue?: FlipValue) =>
+    backendFor(viewport).flipHorizontal(viewport, newValue),
+
+  flipVertical: (viewport: CoreTypes.IViewport, newValue?: FlipValue) =>
+    backendFor(viewport).flipVertical(viewport, newValue),
+
+  invert: (viewport: CoreTypes.IViewport) => backendFor(viewport).invert(viewport),
+
+  rotate: (viewport: CoreTypes.IViewport, rotation: number, mode?: RotationMode) =>
+    backendFor(viewport).rotate(viewport, rotation, mode),
+
+  reset: (viewport: CoreTypes.IViewport) => backendFor(viewport).reset(viewport),
+
+  scaleBy: (viewport: CoreTypes.IViewport, direction: number) =>
+    backendFor(viewport).scaleBy(viewport, direction),
+
+  getViewPlaneNormal: (viewport: CoreTypes.IViewport) =>
+    backendFor(viewport).getViewPlaneNormal(viewport),
+
+  centerOnMeasurement: (viewport: CoreTypes.IViewport, measurement: Record<string, unknown>) =>
+    backendFor(viewport).centerOnMeasurement(viewport, measurement),
+
+  setWindowLevel: (viewport: CoreTypes.IViewport, params: WindowLevelParams) =>
+    backendFor(viewport).setWindowLevel(viewport, params),
+
+  setColormap: (viewport: CoreTypes.IViewport, params: ColormapParams) =>
+    backendFor(viewport).setColormap(viewport, params),
+
+  setPreset: (viewport: CoreTypes.IViewport, preset: string) =>
+    backendFor(viewport).setPreset(viewport, preset),
+
+  setVolumeRenderingQuality: (viewport: CoreTypes.IViewport, volumeQuality: number) =>
+    backendFor(viewport).setVolumeRenderingQuality(viewport, volumeQuality),
+
+  shiftVolumeOpacityPoints: (viewport: CoreTypes.IViewport, shift: number) =>
+    backendFor(viewport).shiftVolumeOpacityPoints(viewport, shift),
+
+  setVolumeLighting: (viewport: CoreTypes.IViewport, options: VolumeLightingOptions) =>
+    backendFor(viewport).setVolumeLighting(viewport, options),
+};
diff --git a/extensions/cornerstone/src/tools/ImageOverlayViewerTool.tsx b/extensions/cornerstone/src/tools/ImageOverlayViewerTool.tsx
index 84958713c..f4fbd96b3 100644
--- a/extensions/cornerstone/src/tools/ImageOverlayViewerTool.tsx
+++ b/extensions/cornerstone/src/tools/ImageOverlayViewerTool.tsx
@@ -54,8 +54,17 @@ class ImageOverlayViewerTool extends AnnotationDisplayTool {
       return;
     }
 
+    // A direct Generic ("next") viewport returns a falsy view-reference id until
+    // it has data bound (e.g. while it is being enabled, before setDisplaySets).
+    // getTargetId() would throw in that case and break the whole render pass, so
+    // skip overlay rendering until a reference is resolvable. Legacy viewports
+    // always return a string here, so this leaves their behavior unchanged.
+    if (!viewport.getViewReferenceId?.()) {
+      return;
+    }
+
     const targetId = this.getTargetId(viewport);
-    return targetId.split('imageId:')[1];
+    return targetId?.split('imageId:')[1];
   }
 
   renderAnnotation = (enabledElement, svgDrawingHelper) => {
diff --git a/extensions/cornerstone/src/types/CornerstoneCacheService.ts b/extensions/cornerstone/src/types/CornerstoneCacheService.ts
index 261d1b848..19a5967b5 100644
--- a/extensions/cornerstone/src/types/CornerstoneCacheService.ts
+++ b/extensions/cornerstone/src/types/CornerstoneCacheService.ts
@@ -21,11 +21,19 @@ type VolumeData = {
 
 type StackViewportData = {
   viewportType: Enums.ViewportType;
+  // The legacy stack/volume data-shape decision (STACK vs ORTHOGRAPHIC/VOLUME_3D),
+  // preserved even when `viewportType` is a native Generic type (PLANAR_NEXT) that
+  // collapses both. Consumers that must distinguish stack from volume content
+  // (data re-build on invalidation, orientation markers) read this instead of
+  // `viewportType`, which is ambiguous on the native path. See migration plan §4.7.
+  dataShapeType?: Enums.ViewportType;
   data: StackData[];
 };
 
 type VolumeViewportData = {
   viewportType: Enums.ViewportType;
+  /** See StackViewportData.dataShapeType. */
+  dataShapeType?: Enums.ViewportType;
   data: VolumeData[];
 };
 
diff --git a/extensions/cornerstone/src/utils/CornerstoneViewportDownloadForm.tsx b/extensions/cornerstone/src/utils/CornerstoneViewportDownloadForm.tsx
index 61627f126..f7a977efc 100644
--- a/extensions/cornerstone/src/utils/CornerstoneViewportDownloadForm.tsx
+++ b/extensions/cornerstone/src/utils/CornerstoneViewportDownloadForm.tsx
@@ -4,7 +4,7 @@ import html2canvas from 'html2canvas';
 import { getEnabledElement } from '@cornerstonejs/core';
 import { ToolGroupManager, segmentation, Enums } from '@cornerstonejs/tools';
 import { getEnabledElement as OHIFgetEnabledElement } from '../state';
-import { isStackViewportType, isVolumeViewportType } from './getLegacyViewportType';
+import { getViewportAdapter } from '../services/ViewportService/adapter';
 import { useSystem } from '@ohif/core/src';
 
 const { downloadUrl } = utils;
@@ -119,35 +119,12 @@ const CornerstoneViewportDownloadForm = ({
     const downloadViewport = renderingEngine.getViewport(VIEWPORT_ID);
 
     try {
-      // Capture current viewport state
-      // - properties: VOI, colormap, interpolation, etc.
-      // - viewPresentation: flip/rotate/zoom presentation state added for
-      //   saving flip and rotation for capture
-      // - viewReference: image/volume reference
-      const properties = viewport.getProperties();
-      const viewPresentation = viewport.getViewPresentation?.();
-      const viewRef = viewport.getViewReference?.();
-
-      if (isStackViewportType(downloadViewport)) {
-        const imageId = viewport.getCurrentImageId();
-        await downloadViewport.setStack([imageId]);
-      } else if (isVolumeViewportType(downloadViewport)) {
-        const volumeIds = viewport.getAllVolumeIds();
-        await downloadViewport.setVolumes([{ volumeId: volumeIds[0] }]);
-      }
-
-      // Apply presentation state so captured image preserves flip/rotate
-      if (viewPresentation && downloadViewport.setViewPresentation) {
-        downloadViewport.setViewPresentation(viewPresentation);
-      }
-
-      // Apply viewport display properties
-      downloadViewport.setProperties(properties);
-
-      // Ensure correct image/volume reference
-      if (viewRef && downloadViewport.setViewReference) {
-        downloadViewport.setViewReference(viewRef);
-      }
+      // Capture current viewport state. The download (capture) viewport is created
+      // with the SAME type as the source (see handleEnableViewport), so source and
+      // capture are both legacy or both native, and the source's adapter can mount
+      // its displayed content (data + appearance + view state) onto the capture
+      // viewport directly.
+      await getViewportAdapter(viewport).copyDisplayedContentTo(downloadViewport);
 
       downloadViewport.render();
 
diff --git a/extensions/cornerstone/src/utils/getCornerstoneViewportType.test.ts b/extensions/cornerstone/src/utils/getCornerstoneViewportType.test.ts
index b6d02f02b..f13e03c2e 100644
--- a/extensions/cornerstone/src/utils/getCornerstoneViewportType.test.ts
+++ b/extensions/cornerstone/src/utils/getCornerstoneViewportType.test.ts
@@ -11,6 +11,11 @@ jest.mock('@cornerstonejs/core', () => ({
       ORTHOGRAPHIC: 'orthographic',
       VOLUME_3D: 'volume3d',
       ECG: 'ecg',
+      PLANAR_NEXT: 'planarNext',
+      VOLUME_3D_NEXT: 'volume3dNext',
+      VIDEO_NEXT: 'videoNext',
+      WHOLE_SLIDE_NEXT: 'wholeSlideNext',
+      ECG_NEXT: 'ecgNext',
     },
   },
 }));
@@ -58,7 +63,7 @@ describe('getCornerstoneViewportType', () => {
 
   it('should throw error for invalid viewport type', () => {
     expect(() => getCornerstoneViewportType('invalid')).toThrow(
-      'Invalid viewport type: invalid. Valid types are: stack, volume, video, wholeslide, ecg'
+      'Invalid viewport type: invalid. Valid types are: stack, volume, orthographic, volume3d, video, wholeslide, ecg'
     );
   });
 
@@ -94,4 +99,71 @@ describe('getCornerstoneViewportType', () => {
     const result = getCornerstoneViewportType('wholeslide', undefined);
     expect(result).toBe(Enums.ViewportType.WHOLE_SLIDE);
   });
+
+  describe('useNextViewports (native Generic Viewport types)', () => {
+    it('maps stack to PLANAR_NEXT', () => {
+      expect(getCornerstoneViewportType('stack', undefined, true)).toBe(
+        Enums.ViewportType.PLANAR_NEXT
+      );
+    });
+
+    it('maps volume and orthographic to PLANAR_NEXT', () => {
+      expect(getCornerstoneViewportType('volume', undefined, true)).toBe(
+        Enums.ViewportType.PLANAR_NEXT
+      );
+      expect(getCornerstoneViewportType('orthographic', undefined, true)).toBe(
+        Enums.ViewportType.PLANAR_NEXT
+      );
+    });
+
+    it('maps volume3d / video / wholeslide / ecg to their *_NEXT types', () => {
+      expect(getCornerstoneViewportType('volume3d', undefined, true)).toBe(
+        Enums.ViewportType.VOLUME_3D_NEXT
+      );
+      expect(getCornerstoneViewportType('video', undefined, true)).toBe(
+        Enums.ViewportType.VIDEO_NEXT
+      );
+      expect(getCornerstoneViewportType('wholeslide', undefined, true)).toBe(
+        Enums.ViewportType.WHOLE_SLIDE_NEXT
+      );
+      expect(getCornerstoneViewportType('ecg', undefined, true)).toBe(
+        Enums.ViewportType.ECG_NEXT
+      );
+    });
+
+    it('honors the displaySet viewportType override under the flag', () => {
+      const displaySets = [{ viewportType: 'volume' }] as Types.DisplaySet[];
+      expect(getCornerstoneViewportType('stack', displaySets, true)).toBe(
+        Enums.ViewportType.PLANAR_NEXT
+      );
+    });
+
+    it('throws for an invalid viewport type under the flag', () => {
+      expect(() =>
+        getCornerstoneViewportType('invalid', undefined, true)
+      ).toThrow('Invalid viewport type: invalid');
+    });
+
+    it('leaves the legacy mapping unchanged when the flag is off', () => {
+      expect(getCornerstoneViewportType('stack', undefined, false)).toBe(
+        Enums.ViewportType.STACK
+      );
+      expect(getCornerstoneViewportType('volume', undefined, false)).toBe(
+        Enums.ViewportType.ORTHOGRAPHIC
+      );
+    });
+
+    it('is idempotent for already-native types regardless of the flag', () => {
+      // A viewport's stored cs type can be re-fed into the mapper.
+      expect(getCornerstoneViewportType('planarNext', undefined, false)).toBe(
+        Enums.ViewportType.PLANAR_NEXT
+      );
+      expect(getCornerstoneViewportType('planarNext', undefined, true)).toBe(
+        Enums.ViewportType.PLANAR_NEXT
+      );
+      expect(getCornerstoneViewportType('volume3dNext', undefined, true)).toBe(
+        Enums.ViewportType.VOLUME_3D_NEXT
+      );
+    });
+  });
 });
diff --git a/extensions/cornerstone/src/utils/getCornerstoneViewportType.ts b/extensions/cornerstone/src/utils/getCornerstoneViewportType.ts
index fd89f0193..e04d71ddf 100644
--- a/extensions/cornerstone/src/utils/getCornerstoneViewportType.ts
+++ b/extensions/cornerstone/src/utils/getCornerstoneViewportType.ts
@@ -1,5 +1,6 @@
 import type { Types } from '@ohif/core';
 import { Enums } from '@cornerstonejs/core';
+import { isNextViewportsEnabled } from './nextViewports';
 
 const STACK = 'stack';
 const VOLUME = 'volume';
@@ -11,10 +12,53 @@ const ECG = 'ecg';
 
 export default function getCornerstoneViewportType(
   viewportType: string,
-  displaySets?: Types.DisplaySet[]
+  displaySets?: Types.DisplaySet[],
+  useNextViewports = isNextViewportsEnabled()
 ): Enums.ViewportType {
   const lowerViewportType =
     displaySets?.[0]?.viewportType?.toLowerCase() || viewportType.toLowerCase();
+
+  // Already a native Generic ("next") type — e.g. re-derived from a viewport's
+  // stored cornerstone type (ViewportInfo.viewportType). Pass through
+  // idempotently, exactly as the legacy types below map to themselves; this must
+  // hold regardless of the flag so re-entrant callers don't throw.
+  switch (lowerViewportType) {
+    case 'planarnext':
+      return Enums.ViewportType.PLANAR_NEXT;
+    case 'volume3dnext':
+      return Enums.ViewportType.VOLUME_3D_NEXT;
+    case 'videonext':
+      return Enums.ViewportType.VIDEO_NEXT;
+    case 'wholeslidenext':
+      return Enums.ViewportType.WHOLE_SLIDE_NEXT;
+    case 'ecgnext':
+      return Enums.ViewportType.ECG_NEXT;
+  }
+
+  // Native Generic Viewport ("next") path (appConfig.useNextViewports). Stack and
+  // volume/orthographic both collapse to PLANAR_NEXT — the render path (image vs
+  // volume slice) is inferred from the data shape, not from the viewport type.
+  if (useNextViewports) {
+    switch (lowerViewportType) {
+      case STACK:
+      case VOLUME:
+      case ORTHOGRAPHIC:
+        return Enums.ViewportType.PLANAR_NEXT;
+      case VOLUME_3D:
+        return Enums.ViewportType.VOLUME_3D_NEXT;
+      case VIDEO:
+        return Enums.ViewportType.VIDEO_NEXT;
+      case WHOLESLIDE:
+        return Enums.ViewportType.WHOLE_SLIDE_NEXT;
+      case ECG:
+        return Enums.ViewportType.ECG_NEXT;
+      default:
+        throw new Error(
+          `Invalid viewport type: ${viewportType}. Valid types are: stack, volume, orthographic, volume3d, video, wholeslide, ecg`
+        );
+    }
+  }
+
   if (lowerViewportType === STACK) {
     return Enums.ViewportType.STACK;
   }
@@ -39,6 +83,6 @@ export default function getCornerstoneViewportType(
   }
 
   throw new Error(
-    `Invalid viewport type: ${viewportType}. Valid types are: stack, volume, video, wholeslide, ecg`
+    `Invalid viewport type: ${viewportType}. Valid types are: stack, volume, orthographic, volume3d, video, wholeslide, ecg`
   );
 }
diff --git a/extensions/cornerstone/src/utils/getDataIdForViewport.ts b/extensions/cornerstone/src/utils/getDataIdForViewport.ts
deleted file mode 100644
index 3f9111c14..000000000
--- a/extensions/cornerstone/src/utils/getDataIdForViewport.ts
+++ /dev/null
@@ -1,22 +0,0 @@
-/**
- * Resolves the data ID (e.g. volumeId) for a viewport and display set.
- * For viewports with multiple volumes/actors, returns the id that matches the display set; otherwise undefined.
- * Use this to call viewport.getProperties(dataId) in a viewport-type-agnostic way.
- *
- * @param viewport - Viewport instance (stack, volume, or future types with optional getAllVolumeIds)
- * @param displaySetInstanceUID - Display set instance UID to match
- * @returns volumeId (or equivalent) for multi-actor viewports, undefined for single-actor
- */
-export function getDataIdForViewport(
-  viewport: unknown,
-  displaySetInstanceUID: string
-): string | undefined {
-  const vp = viewport as { getAllVolumeIds?: () => string[] };
-  if (typeof vp.getAllVolumeIds !== 'function') {
-    return undefined;
-  }
-  const volumeIds = vp.getAllVolumeIds() || [];
-  return volumeIds.length > 0
-    ? volumeIds.find(id => id.includes(displaySetInstanceUID)) ?? undefined
-    : undefined;
-}
diff --git a/extensions/cornerstone/src/utils/getLegacyViewportType.ts b/extensions/cornerstone/src/utils/getLegacyViewportType.ts
index c36c32049..3407b1e2b 100644
--- a/extensions/cornerstone/src/utils/getLegacyViewportType.ts
+++ b/extensions/cornerstone/src/utils/getLegacyViewportType.ts
@@ -23,44 +23,42 @@ type ViewportLike = {
  * type. For "does this viewport support operation X" questions, prefer the
  * cornerstone capability guards (`utilities.viewportSupports*`) instead.
  */
-export function getLegacyViewportType(
-  viewport: unknown
-): csEnums.ViewportType | undefined {
+export function getLegacyViewportType(viewport: unknown): csEnums.ViewportType | undefined {
   const vp = viewport as ViewportLike | null | undefined;
   return vp?.requestedType ?? vp?.type;
 }
 
 /** Legacy STACK viewport (image stack). Replaces `instanceof StackViewport`. */
-export function isStackViewportType(
-  viewport: unknown
-): viewport is csTypes.IStackViewport {
+export function isStackViewportType(viewport: unknown): viewport is csTypes.IStackViewport {
   return getLegacyViewportType(viewport) === ViewportType.STACK;
 }
 
 /** Legacy ORTHOGRAPHIC (MPR) viewport. Replaces `instanceof VolumeViewport`. */
-export function isOrthographicViewportType(
-  viewport: unknown
-): viewport is csTypes.IVolumeViewport {
+export function isOrthographicViewportType(viewport: unknown): viewport is csTypes.IVolumeViewport {
   return getLegacyViewportType(viewport) === ViewportType.ORTHOGRAPHIC;
 }
 
-/** Legacy VOLUME_3D viewport. Replaces `instanceof VolumeViewport3D`. */
-export function isVolume3DViewportType(
-  viewport: unknown
-): viewport is csTypes.IVolumeViewport {
-  return getLegacyViewportType(viewport) === ViewportType.VOLUME_3D;
+/**
+ * 3D volume viewport. Replaces `instanceof VolumeViewport3D`.
+ *
+ * Matches both the legacy `VOLUME_3D` type and the native ("next") `VOLUME_3D_NEXT`.
+ * Under `useNextViewports`, OHIF requests `VOLUME_3D_NEXT` directly, so cornerstone
+ * leaves `requestedType` unset and `getLegacyViewportType` returns the native type
+ * (cornerstone only rewrites `requestedType` back to the legacy type for its own
+ * compat remap of a legacy `VOLUME_3D` request). Checking only `VOLUME_3D` would miss
+ * native 3D viewports and misroute them through the planar (getViewReference/getViewState)
+ * branch, and would leave 3D gates such as `is3DVolume` false.
+ */
+export function isVolume3DViewportType(viewport: unknown): viewport is csTypes.IVolumeViewport {
+  const legacyType = getLegacyViewportType(viewport);
+  return legacyType === ViewportType.VOLUME_3D || legacyType === ViewportType.VOLUME_3D_NEXT;
 }
 
 /**
  * Legacy ORTHOGRAPHIC or VOLUME_3D viewport (i.e. a `BaseVolumeViewport`).
  * Replaces `instanceof BaseVolumeViewport`.
  */
-export function isVolumeViewportType(
-  viewport: unknown
-): viewport is csTypes.IVolumeViewport {
+export function isVolumeViewportType(viewport: unknown): viewport is csTypes.IVolumeViewport {
   const legacyType = getLegacyViewportType(viewport);
-  return (
-    legacyType === ViewportType.ORTHOGRAPHIC ||
-    legacyType === ViewportType.VOLUME_3D
-  );
+  return legacyType === ViewportType.ORTHOGRAPHIC || legacyType === ViewportType.VOLUME_3D;
 }
diff --git a/extensions/cornerstone/src/utils/nextViewportPolicies.ts b/extensions/cornerstone/src/utils/nextViewportPolicies.ts
new file mode 100644
index 000000000..7d34dc209
--- /dev/null
+++ b/extensions/cornerstone/src/utils/nextViewportPolicies.ts
@@ -0,0 +1,41 @@
+import { isNextViewportsEnabled } from './nextViewports';
+
+/**
+ * The named home for every BEHAVIORAL POLICY difference between the legacy and
+ * native ("next") viewport paths — appearance defaults and workflow rules that
+ * are not API bridging (that's `services/ViewportService/adapter/`) and not
+ * mount lifecycle (that's `services/ViewportService/backends/`). Keeping them
+ * in one greppable file is the point: a policy divergence that lives inline in
+ * a mode or hanging protocol is invisible to the next reader.
+ */
+
+/**
+ * Initial PT opacity for TMTV fusion viewports on the native path. Legacy (in
+ * tmtv's hpViewports) uses a per-value opacity ramp; native applies a ramp
+ * literally through its flat 2D blend (which would keep the background
+ * transparent), so the native path replaces the ramp with this single flat,
+ * more CT-weighted starting blend.
+ */
+export const NEXT_FUSION_PT_OPACITY = 0.4;
+
+/**
+ * Initial opacity for data overlays (e.g. colormapped foreground layers) on
+ * the native path. Native viewports composite an overlay as a 2D image slice
+ * with a flat alpha blend and no volume ray-cast opacity attenuation: the
+ * legacy nominal 0.9 renders at ~40% effective through the ray-cast path but
+ * reads ~80-90% on native, so native starts at the legacy-equivalent
+ * effective value.
+ */
+export const NEXT_OVERLAY_OPACITY = 0.4;
+
+/**
+ * Viewport type to pin when hydrating a segmentation's referenced display set.
+ * RTSTRUCT contours render correctly on a native stack/vtkImage viewport and
+ * scroll fast, so the referenced image stays in stack mode on hydrate rather
+ * than being promoted to a volume slice (which the perf acceptance criteria
+ * forbid). Scoped to RTSTRUCT + the next path; SEG and legacy keep the default
+ * (undefined = no pin).
+ */
+export function getHydrationViewportTypeForModality(modality: string): 'stack' | undefined {
+  return modality === 'RTSTRUCT' && isNextViewportsEnabled() ? 'stack' : undefined;
+}
diff --git a/extensions/cornerstone/src/utils/nextViewports.ts b/extensions/cornerstone/src/utils/nextViewports.ts
new file mode 100644
index 000000000..c61718ef1
--- /dev/null
+++ b/extensions/cornerstone/src/utils/nextViewports.ts
@@ -0,0 +1,157 @@
+/**
+ * Module-level accessor for the `appConfig.genericViewports.enabled` opt-in flag.
+ *
+ * The flag is captured once at extension init (from the `useNextViewports` URL
+ * query param, else appConfig) and read by the
+ * two viewport-type chokepoints (`getCornerstoneViewportType` and the
+ * `CornerstoneViewportService` backend split) without threading appConfig
+ * through every service/viewport constructor. Defaults to `false` so the legacy
+ * path is unchanged until an app opts in.
+ */
+let nextViewportsEnabled = false;
+
+export function setNextViewportsEnabled(value: boolean): void {
+  nextViewportsEnabled = Boolean(value);
+}
+
+export function isNextViewportsEnabled(): boolean {
+  return nextViewportsEnabled;
+}
+
+/**
+ * Resolves the effective flag at init. A `useNextViewports` URL query parameter
+ * takes precedence over the appConfig value, so the native backend can be opted
+ * into per-session via the URL (e.g. `?useNextViewports=true`) without editing
+ * the deployed config. `?useNextViewports` (no value), `=true`, or `=1` enable
+ * it; any other value disables it. When the param is absent, appConfig wins.
+ */
+export function resolveNextViewportsEnabled(appConfigValue: unknown): boolean {
+  return resolveBooleanUrlOptIn('useNextViewports', appConfigValue);
+}
+
+/**
+ * Aliases accepted by the `viewportRendering` param/config, mapped to
+ * cornerstone render backend wire ids ('gpu' is the VTK/WebGL backend).
+ * Values not listed here pass through untouched so backends registered via
+ * cornerstone's `registerRenderBackend()` (e.g. a webgpu backend) can be
+ * selected by their wire id.
+ */
+const RENDER_BACKEND_ALIASES: Record<string, string> = {
+  webgl: 'gpu',
+  gpu: 'gpu',
+  cpu: 'cpu',
+  auto: 'auto',
+};
+
+function normalizeRenderBackend(value: unknown): string | undefined {
+  if (typeof value !== 'string') {
+    return undefined;
+  }
+  const trimmed = value.trim();
+  if (!trimmed) {
+    return undefined;
+  }
+  return RENDER_BACKEND_ALIASES[trimmed.toLowerCase()] ?? trimmed;
+}
+
+export interface ViewportRenderingSelection {
+  /** Global render backend for all viewports (cornerstone `setRenderBackend`). */
+  renderBackend?: string;
+  /**
+   * Per-viewport-type overrides (per-mount `renderBackend` option), keyed by
+   * the lowercased OHIF viewport type (e.g. 'stack', 'orthographic').
+   */
+  renderBackendByViewportType: Record<string, string>;
+}
+
+/**
+ * Resolves the render backend selection at init.
+ *
+ * `?viewportRendering=cpu|webgl|webgpu|auto` selects the render backend for
+ * all viewports per-session, and `?<viewportType>.viewportRendering=<backend>`
+ * (e.g. `?orthographic.viewportRendering=cpu`) overrides it for a single
+ * viewport type via the per-mount `renderBackend` option. URL params take
+ * precedence over `appConfig.genericViewports.viewportRendering`, which accepts
+ * either a backend string or `{ default?, stack?, orthographic? }`.
+ *
+ * 'webgl' is an alias for cornerstone's 'gpu' (VTK/WebGL) backend; 'cpu' and
+ * 'auto' map to the same-named backends; any other value is passed through as
+ * the wire id of a backend registered with `registerRenderBackend()` (e.g. a
+ * webgpu backend). Unlike a boolean CPU flag, this lets a session force GPU
+ * rendering when the deployed config defaults to CPU, and vice versa.
+ */
+export function resolveViewportRendering(appConfigValue: unknown): ViewportRenderingSelection {
+  const selection: ViewportRenderingSelection = { renderBackendByViewportType: {} };
+
+  if (typeof appConfigValue === 'string') {
+    selection.renderBackend = normalizeRenderBackend(appConfigValue);
+  } else if (appConfigValue && typeof appConfigValue === 'object') {
+    for (const [key, value] of Object.entries(appConfigValue)) {
+      const backend = normalizeRenderBackend(value);
+      if (!backend) {
+        continue;
+      }
+      if (key === 'default') {
+        selection.renderBackend = backend;
+      } else {
+        selection.renderBackendByViewportType[key.toLowerCase()] = backend;
+      }
+    }
+  }
+
+  try {
+    const params = new URLSearchParams(window.location.search);
+    for (const [key, value] of params.entries()) {
+      const backend = normalizeRenderBackend(value);
+      if (!backend) {
+        continue;
+      }
+      if (key === 'viewportRendering') {
+        selection.renderBackend = backend;
+      } else if (key.endsWith('.viewportRendering')) {
+        const viewportType = key.slice(0, -'.viewportRendering'.length).toLowerCase();
+        if (viewportType) {
+          selection.renderBackendByViewportType[viewportType] = backend;
+        }
+      }
+    }
+  } catch {
+    // window/URL unavailable (SSR/non-browser) — keep the config-derived selection.
+  }
+
+  return selection;
+}
+
+/**
+ * Per-viewport-type render backend overrides, captured once at extension init
+ * (like the `useNextViewports` flag above) and read by the native mount paths
+ * in NextViewportBackend, which pass the override as the per-mount
+ * `renderBackend` option on `setDisplaySets`.
+ */
+let renderBackendByViewportType: Record<string, string> = {};
+
+export function setViewportRenderingOverrides(overrides: Record<string, string>): void {
+  renderBackendByViewportType = overrides ?? {};
+}
+
+export function getViewportRenderingOverride(viewportType: string): string | undefined {
+  return renderBackendByViewportType[viewportType?.toLowerCase()];
+}
+
+/**
+ * Reads a boolean opt-in URL query param, falling back to a config value when
+ * the param is absent. `?param` (no value), `=true`, or `=1` enable it; any
+ * other value disables it.
+ */
+function resolveBooleanUrlOptIn(paramName: string, fallbackValue: unknown): boolean {
+  try {
+    const params = new URLSearchParams(window.location.search);
+    if (params.has(paramName)) {
+      const value = params.get(paramName);
+      return value === '' || value === 'true' || value === '1';
+    }
+  } catch {
+    // window/URL unavailable (SSR/non-browser) — fall back to the config value.
+  }
+  return Boolean(fallbackValue);
+}
diff --git a/extensions/cornerstone/src/utils/viewportDataShape.ts b/extensions/cornerstone/src/utils/viewportDataShape.ts
new file mode 100644
index 000000000..d24326436
--- /dev/null
+++ b/extensions/cornerstone/src/utils/viewportDataShape.ts
@@ -0,0 +1,85 @@
+import { Enums } from '@cornerstonejs/core';
+
+/**
+ * Pre-mount classification of a viewport's bound data (viewportData from
+ * CornerstoneCacheService), for code that runs before — or independently of —
+ * a live viewport instance (overlays, scrollbars). Native ("next") viewports
+ * collapse stack/volume onto a single PLANAR_NEXT viewportType, so these
+ * helpers classify by the persisted dataShapeType and the data shape itself
+ * (imageIds = stack, volume/volumeId = volume) instead of the runtime type.
+ *
+ * For classification of a LIVE viewport instance, use
+ * `getViewportAdapter(viewport).getShape()` instead.
+ */
+
+type ViewportDatum = {
+  imageIds?: string[];
+  volume?: unknown;
+  volumeId?: string;
+  [key: string]: unknown;
+};
+
+type ViewportDataLike = {
+  viewportType?: Enums.ViewportType;
+  dataShapeType?: Enums.ViewportType;
+  data?: ViewportDatum | ViewportDatum[];
+};
+
+/** The primary (non-overlay) datum of a viewportData. */
+export function getPrimaryViewportDatum(viewportData: ViewportDataLike): ViewportDatum | undefined {
+  return Array.isArray(viewportData?.data) ? viewportData.data[0] : viewportData?.data;
+}
+
+/** True when the primary datum is volume-shaped (volume/volumeId present). */
+export function isVolumeViewportData(viewportData: ViewportDataLike): boolean {
+  const firstData = getPrimaryViewportDatum(viewportData);
+  return !!(firstData && (firstData.volume || firstData.volumeId));
+}
+
+/**
+ * The stack/volume shape a viewportData was built for, transparent across the
+ * native type collapse: the persisted dataShapeType when present (set by
+ * CornerstoneCacheService on the native path), else the legacy viewportType.
+ */
+export function getViewportDataShapeType(
+  viewportData: ViewportDataLike
+): Enums.ViewportType | undefined {
+  return viewportData?.dataShapeType ?? viewportData?.viewportType;
+}
+
+/**
+ * The slice-navigation event for this viewport's content. Resolved from the
+ * legacy viewportType when it is meaningful, else from the bound data shape —
+ * which is known immediately, unlike a runtime content-mode check that may not
+ * be ready while a native viewport is still binding. Native viewports emit the
+ * same STACK_NEW_IMAGE / VOLUME_NEW_IMAGE events as legacy.
+ */
+export function getSliceEventName(viewportData: ViewportDataLike): string {
+  const { viewportType } = viewportData;
+  const firstData = getPrimaryViewportDatum(viewportData);
+  return (
+    (viewportType === Enums.ViewportType.STACK && Enums.Events.STACK_NEW_IMAGE) ||
+    (viewportType === Enums.ViewportType.ORTHOGRAPHIC && Enums.Events.VOLUME_NEW_IMAGE) ||
+    (isVolumeViewportData(viewportData) && Enums.Events.VOLUME_NEW_IMAGE) ||
+    (firstData?.imageIds && Enums.Events.STACK_NEW_IMAGE) ||
+    Enums.Events.IMAGE_RENDERED
+  );
+}
+
+/**
+ * The slice count for a viewport. `viewport.getNumberOfSlices()` can be
+ * premature while a native viewport is still binding its data (it returns 1
+ * until then). For an image stack the count is known from the bound data, so
+ * prefer that and only fall back to the viewport for volume/MPR (where the
+ * count depends on orientation).
+ */
+export function getViewportSliceCount(
+  viewportData: ViewportDataLike,
+  viewport: { getNumberOfSlices: () => number }
+): number {
+  const firstData = getPrimaryViewportDatum(viewportData);
+  return (
+    (!isVolumeViewportData(viewportData) && firstData?.imageIds?.length) ||
+    viewport.getNumberOfSlices()
+  );
+}
diff --git a/extensions/default/src/utils/layerConfigurationUtils.ts b/extensions/default/src/utils/layerConfigurationUtils.ts
index 4d8dda488..04b5b1c78 100644
--- a/extensions/default/src/utils/layerConfigurationUtils.ts
+++ b/extensions/default/src/utils/layerConfigurationUtils.ts
@@ -1,3 +1,5 @@
+import { isNextViewport, NEXT_OVERLAY_OPACITY } from '@ohif/extension-cornerstone';
+
 export const DERIVED_OVERLAY_MODALITIES = ['SEG', 'RTSTRUCT'];
 export const DEFAULT_COLORMAP = 'hsv';
 export const DEFAULT_OPACITY = 0.9;
@@ -93,6 +95,11 @@ export function configureViewportForLayerAddition(params: {
     }
   }
 
+  // Native ("next") viewports need the legacy-equivalent initial overlay opacity
+  // (see the NEXT_OVERLAY_OPACITY policy in @ohif/extension-cornerstone).
+  const liveCsViewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
+  const isLiveViewportNext = !!liveCsViewport && isNextViewport(liveCsViewport);
+
   // create same amount of display set options as the number of display set UIDs
   const displaySetOptions = allDisplaySetInstanceUIDs.map((uid, index) => {
     // There is already a display set option for this display set, so return it.
@@ -106,7 +113,17 @@ export function configureViewportForLayerAddition(params: {
     }
 
     const displaySet = displaySetService.getDisplaySetByUID(uid);
-    return createColormapOverlayDisplaySetOptions(displaySet, 90, customizationService);
+    const overlayOptions = createColormapOverlayDisplaySetOptions(
+      displaySet,
+      90,
+      customizationService
+    );
+
+    if (isLiveViewportNext && typeof overlayOptions.colormap?.opacity === 'number') {
+      overlayOptions.colormap.opacity = NEXT_OVERLAY_OPACITY;
+    }
+
+    return overlayOptions;
   });
 
   viewport.displaySetOptions = displaySetOptions;
diff --git a/extensions/measurement-tracking/package.json b/extensions/measurement-tracking/package.json
index d5a44d4b0..145f54453 100644
--- a/extensions/measurement-tracking/package.json
+++ b/extensions/measurement-tracking/package.json
@@ -27,8 +27,8 @@
     "start": "pnpm run dev"
   },
   "peerDependencies": {
-    "@cornerstonejs/core": "5.4.13",
-    "@cornerstonejs/tools": "5.4.13",
+    "@cornerstonejs/core": "5.4.17",
+    "@cornerstonejs/tools": "5.4.17",
     "@ohif/core": "workspace:*",
     "@ohif/extension-cornerstone-dicom-sr": "workspace:*",
     "@ohif/extension-default": "workspace:*",
diff --git a/extensions/tmtv/src/commandsModule.ts b/extensions/tmtv/src/commandsModule.ts
index bce7a706f..9d457c2f1 100644
--- a/extensions/tmtv/src/commandsModule.ts
+++ b/extensions/tmtv/src/commandsModule.ts
@@ -10,6 +10,7 @@ import dicomRTAnnotationExport from './utils/dicomRTAnnotationExport/RTStructure
 
 import { Enums } from '@cornerstonejs/tools';
 import { utils } from '@ohif/core';
+import { getViewportFocalPoint } from '@ohif/extension-cornerstone';
 
 const { SegmentationRepresentations } = Enums;
 const { formatPN } = utils;
@@ -261,7 +262,15 @@ const commandsModule = ({ servicesManager, commandsManager, extensionManager }:
 
     setStartSliceForROIThresholdTool: () => {
       const { viewport } = _getActiveViewportsEnabledElement();
-      const { focalPoint } = viewport.getCamera();
+      // Native ("next") viewports have no getCamera; the slice-center focal point
+      // comes from the view reference. Bridged so both lanes work.
+      const focalPoint = getViewportFocalPoint(viewport);
+
+      // Native viewports may not resolve a focal point; writing undefined into the
+      // annotation would invalidate its ROI-threshold coordinates.
+      if (!focalPoint) {
+        return;
+      }
 
       const selectedAnnotationUIDs = _getAnnotationsSelectedByToolNames(
         ROI_THRESHOLD_MANUAL_TOOL_IDS
@@ -289,8 +298,11 @@ const commandsModule = ({ servicesManager, commandsManager, extensionManager }:
 
       const annotation = csTools.annotation.state.getAnnotation(annotationUID);
 
-      // get the current focal point
-      const focalPointToEnd = viewport.getCamera().focalPoint;
+      // get the current focal point (bridged: native viewports use the view reference)
+      const focalPointToEnd = getViewportFocalPoint(viewport);
+      if (!focalPointToEnd) {
+        return;
+      }
       annotation.data.endCoordinate = focalPointToEnd;
 
       // IMPORTANT: invalidate the toolData for the cached stat to get updated
diff --git a/extensions/tmtv/src/getHangingProtocolModule.ts b/extensions/tmtv/src/getHangingProtocolModule.ts
index d4f8d9bf6..81cf18322 100644
--- a/extensions/tmtv/src/getHangingProtocolModule.ts
+++ b/extensions/tmtv/src/getHangingProtocolModule.ts
@@ -1,3 +1,4 @@
+import { isNextViewportsEnabled, NEXT_FUSION_PT_OPACITY } from '@ohif/extension-cornerstone';
 import {
   ctAXIAL,
   ctCORONAL,
@@ -339,6 +340,20 @@ const ptCT: AppTypes.HangingProtocol.Protocol = {
 };
 
 function getHangingProtocolModule() {
+  // Replace the fusion PT opacity ramp with a flat scalar for the native ("next")
+  // path only, leaving the legacy ramp in hpViewports untouched. Done here (not at
+  // module load) because the useNextViewports flag is set during cornerstone
+  // preRegistration, which runs before this module is gathered.
+  if (isNextViewportsEnabled()) {
+    [fusionAXIAL, fusionSAGITTAL, fusionCORONAL].forEach(viewport => {
+      const ptDisplaySet = viewport.displaySets?.find(ds => ds.id === 'ptDisplaySet');
+      const colormap = ptDisplaySet?.options?.colormap as { opacity?: unknown } | undefined;
+      if (colormap) {
+        colormap.opacity = NEXT_FUSION_PT_OPACITY;
+      }
+    });
+  }
+
   return [
     {
       name: ptCT.id,
diff --git a/extensions/tmtv/src/utils/hpViewports.ts b/extensions/tmtv/src/utils/hpViewports.ts
index c206c5c52..ba82d1dfb 100644
--- a/extensions/tmtv/src/utils/hpViewports.ts
+++ b/extensions/tmtv/src/utils/hpViewports.ts
@@ -286,6 +286,13 @@ const fusionAXIAL: AppTypes.HangingProtocol.Viewport = {
       options: {
         colormap: {
           name: 'hsv',
+          // Legacy fusion PT opacity ramp (unchanged): low PT values stay mostly
+          // transparent so the CT shows through. Do NOT flatten this to a scalar —
+          // the legacy viewport renders this ramp and depends on it. The native
+          // ("next") viewport would apply the ramp literally (keeping the
+          // background transparent and preventing the 100% opacity slider from
+          // fully covering the CT), so the next path replaces this ramp with a
+          // flat scalar in getHangingProtocolModule instead of changing it here.
           opacity: [
             { value: 0, opacity: 0 },
             { value: 0.1, opacity: 0.8 },
@@ -349,6 +356,13 @@ const fusionSAGITTAL = {
       options: {
         colormap: {
           name: 'hsv',
+          // Legacy fusion PT opacity ramp (unchanged): low PT values stay mostly
+          // transparent so the CT shows through. Do NOT flatten this to a scalar —
+          // the legacy viewport renders this ramp and depends on it. The native
+          // ("next") viewport would apply the ramp literally (keeping the
+          // background transparent and preventing the 100% opacity slider from
+          // fully covering the CT), so the next path replaces this ramp with a
+          // flat scalar in getHangingProtocolModule instead of changing it here.
           opacity: [
             { value: 0, opacity: 0 },
             { value: 0.1, opacity: 0.8 },
@@ -412,6 +426,13 @@ const fusionCORONAL = {
       options: {
         colormap: {
           name: 'hsv',
+          // Legacy fusion PT opacity ramp (unchanged): low PT values stay mostly
+          // transparent so the CT shows through. Do NOT flatten this to a scalar —
+          // the legacy viewport renders this ramp and depends on it. The native
+          // ("next") viewport would apply the ramp literally (keeping the
+          // background transparent and preventing the 100% opacity slider from
+          // fully covering the CT), so the next path replaces this ramp with a
+          // flat scalar in getHangingProtocolModule instead of changing it here.
           opacity: [
             { value: 0, opacity: 0 },
             { value: 0.1, opacity: 0.8 },
diff --git a/extensions/usAnnotation/package.json b/extensions/usAnnotation/package.json
index b10a01e88..20b0ff208 100644
--- a/extensions/usAnnotation/package.json
+++ b/extensions/usAnnotation/package.json
@@ -36,8 +36,8 @@
   },
   "dependencies": {
     "@babel/runtime": "7.29.7",
-    "@cornerstonejs/core": "5.4.13",
-    "@cornerstonejs/tools": "5.4.13",
+    "@cornerstonejs/core": "5.4.17",
+    "@cornerstonejs/tools": "5.4.17",
     "@ohif/core": "workspace:*",
     "@ohif/extension-cornerstone": "workspace:*",
     "@ohif/extension-default": "workspace:*",
diff --git a/modes/usAnnotation/package.json b/modes/usAnnotation/package.json
index b3ebc1277..1fb909995 100644
--- a/modes/usAnnotation/package.json
+++ b/modes/usAnnotation/package.json
@@ -29,8 +29,8 @@
   },
   "dependencies": {
     "@babel/runtime": "7.29.7",
-    "@cornerstonejs/core": "5.4.13",
-    "@cornerstonejs/tools": "5.4.13",
+    "@cornerstonejs/core": "5.4.17",
+    "@cornerstonejs/tools": "5.4.17",
     "@ohif/core": "workspace:*",
     "@ohif/extension-cornerstone-dicom-sr": "workspace:*",
     "@ohif/extension-ultrasound-pleura-bline": "workspace:*",
diff --git a/platform/app/package.json b/platform/app/package.json
index 8ebf715c5..0220555db 100644
--- a/platform/app/package.json
+++ b/platform/app/package.json
@@ -51,7 +51,7 @@
     "@cornerstonejs/codec-libjpeg-turbo-8bit": "1.2.2",
     "@cornerstonejs/codec-openjpeg": "1.3.0",
     "@cornerstonejs/codec-openjph": "2.4.7",
-    "@cornerstonejs/dicom-image-loader": "5.4.13",
+    "@cornerstonejs/dicom-image-loader": "5.4.17",
     "@emotion/serialize": "1.3.3",
     "@ohif/core": "workspace:*",
     "@ohif/i18n": "workspace:*",
diff --git a/platform/app/public/config/default.js b/platform/app/public/config/default.js
index d8e1a64b2..35307320e 100644
--- a/platform/app/public/config/default.js
+++ b/platform/app/public/config/default.js
@@ -37,6 +37,22 @@ window.config = {
   //   '/remote/': 'https://cdn.example.com/ohif-custom/', // ?customization=/remote/siteA
   // },
   // ----------------------------------------------------------------------------
+
+  // --- Native ("next") Generic Viewport --------------------------------------
+  // OFF by default. Set `enabled: true` (or pass ?useNextViewports=true in the
+  // URL) to drive viewports through cornerstone's native GenericViewport
+  // ("next") API instead of the legacy Stack/Volume viewport classes.
+  genericViewports: {
+    enabled: false,
+    // Render backend selection: 'cpu' | 'webgl' | 'auto' | a backend id
+    // registered via cornerstone's registerRenderBackend (e.g. a webgpu
+    // backend), or a map with per-viewport-type overrides, e.g.
+    // { default: 'webgl', orthographic: 'cpu' }. The matching URL params take
+    // precedence per-session: ?viewportRendering=cpu and
+    // ?orthographic.viewportRendering=cpu.
+    // viewportRendering: 'auto',
+  },
+  // ----------------------------------------------------------------------------
   showStudyList: true,
   // some windows systems have issues with more than 3 web workers
   maxNumberOfWebWorkers: 3,
diff --git a/platform/app/src/utils/preserveQueryParameters.ts b/platform/app/src/utils/preserveQueryParameters.ts
index 47e006a94..1261a4996 100644
--- a/platform/app/src/utils/preserveQueryParameters.ts
+++ b/platform/app/src/utils/preserveQueryParameters.ts
@@ -13,6 +13,8 @@ export const preserveKeys = [
   'hangingProtocolId',
   'customization',
   'theme',
+  'debug',
+  'useNextViewports',
 ];
 
 function preserveKey(query: URLSearchParams, current: URLSearchParams, key: string) {
diff --git a/platform/core/package.json b/platform/core/package.json
index e5d7e5497..84b21fb25 100644
--- a/platform/core/package.json
+++ b/platform/core/package.json
@@ -35,9 +35,9 @@
     "@cornerstonejs/codec-libjpeg-turbo-8bit": "1.2.2",
     "@cornerstonejs/codec-openjpeg": "1.3.0",
     "@cornerstonejs/codec-openjph": "2.4.7",
-    "@cornerstonejs/core": "5.4.13",
-    "@cornerstonejs/dicom-image-loader": "5.4.13",
-    "@cornerstonejs/metadata": "5.4.13",
+    "@cornerstonejs/core": "5.4.17",
+    "@cornerstonejs/dicom-image-loader": "5.4.17",
+    "@cornerstonejs/metadata": "5.4.17",
     "@ohif/ui": "workspace:*",
     "cornerstone-math": "0.1.10",
     "dicom-parser": "1.8.21"
diff --git a/platform/core/src/types/AppTypes.ts b/platform/core/src/types/AppTypes.ts
index 7a5817d04..7aad659b1 100644
--- a/platform/core/src/types/AppTypes.ts
+++ b/platform/core/src/types/AppTypes.ts
@@ -126,6 +126,45 @@ declare global {
        * Requires @cornerstonejs/core >= 5.0.0-beta (GenericViewport architecture).
        */
       useGenericViewport?: boolean;
+      /**
+       * Opt-in: drive viewports through the DIRECT native GenericViewport ("next")
+       * API surface — `PLANAR_NEXT` / `VOLUME_3D_NEXT` / etc. created natively and
+       * driven with `setDisplaySets`, `setDisplaySetPresentation`, `setViewState`
+       * and view references — rather than the legacy `setStack` / `setVolumes` /
+       * `setProperties` / `getCamera` / `setCamera` methods.
+       *
+       * This is distinct from (and overrides) `useGenericViewport`: that flag only
+       * routes legacy viewport types through cornerstone's compatibility adapters
+       * (`rendering.useGenericViewport`), keeping the legacy method surface. This
+       * flag instead selects native viewport types in `getCornerstoneViewportType`
+       * and the native data/presentation/view-state APIs inside
+       * `CornerstoneViewportService` (the `nextBackend`). It does NOT set
+       * cornerstone's `rendering.useGenericViewport`.
+       *
+       * Defaults to false (the legacy path, byte-identical to today). Opt-in only;
+       * the community is not force-migrated.
+       * Requires @cornerstonejs/core >= 5.0.x with the GenericViewport "next" APIs.
+       */
+      genericViewports?: {
+        /**
+         * Opt-in for the native path described above. Equivalent to (and
+         * overridable by) the `?useNextViewports=true` URL param.
+         */
+        enabled?: boolean;
+        /**
+         * Render backend selection for viewports. Either a backend for all
+         * viewports ('cpu' | 'webgl' | 'auto' | a wire id registered via
+         * cornerstone's `registerRenderBackend`, e.g. a webgpu backend) or a map
+         * of per-viewport-type overrides plus an optional 'default', e.g.
+         * `{ default: 'webgl', orthographic: 'cpu' }`. The matching URL params
+         * (`?viewportRendering=cpu`, `?orthographic.viewportRendering=cpu`) take
+         * precedence per-session. 'webgl' aliases cornerstone's 'gpu' backend.
+         * The default/global value also drives the legacy useCPURendering flag
+         * ('cpu' → true, 'webgl' → false) so legacy viewports follow the same
+         * selection.
+         */
+        viewportRendering?: string | Record<string, string>;
+      };
       useCursors?: boolean;
       maxCacheSize?: number;
       max3DTextureSize?: number;
diff --git a/platform/ui-next/src/components/SegmentationTable/SegmentationTableConfig.tsx b/platform/ui-next/src/components/SegmentationTable/SegmentationTableConfig.tsx
index b98fb6b50..43dcf9ae2 100644
--- a/platform/ui-next/src/components/SegmentationTable/SegmentationTableConfig.tsx
+++ b/platform/ui-next/src/components/SegmentationTable/SegmentationTableConfig.tsx
@@ -133,10 +133,13 @@ export const SegmentationTableConfig: React.FC<{ children?: React.ReactNode }> =
               mode="singleRange"
               min={0}
               max={10}
-              step={0.1}
+              step={1}
               value={outlineWidth}
               onChange={value =>
-                setOutlineWidth({ type: segmentationRepresentationTypes?.[0] }, value as number)
+                setOutlineWidth(
+                  { type: segmentationRepresentationTypes?.[0] },
+                  Math.round(value as number)
+                )
               }
             >
               <Numeric.SingleRange
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 9bfb7ecab..35a15703f 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -190,11 +190,11 @@ importers:
         specifier: 7.29.7
         version: 7.29.7
       '@cornerstonejs/adapters':
-        specifier: 5.4.13
-        version: 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))
+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))
       '@cornerstonejs/ai':
-        specifier: 5.4.13
-        version: 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))
+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))
       '@cornerstonejs/codec-charls':
         specifier: 1.2.3
         version: 1.2.3
@@ -208,23 +208,23 @@ importers:
         specifier: 2.4.7
         version: 2.4.7
       '@cornerstonejs/core':
-        specifier: 5.4.13
-        version: 5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
+        specifier: 5.4.17
+        version: 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
       '@cornerstonejs/dicom-image-loader':
-        specifier: 5.4.13
-        version: 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/metadata@5.4.13)(dicom-parser@1.8.21)
+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/metadata@5.4.17)(dicom-parser@1.8.21)
       '@cornerstonejs/labelmap-interpolation':
-        specifier: 5.4.13
-        version: 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))
+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))
       '@cornerstonejs/metadata':
-        specifier: 5.4.13
-        version: 5.4.13
+        specifier: 5.4.17
+        version: 5.4.17
       '@cornerstonejs/polymorphic-segmentation':
-        specifier: 5.4.13
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+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
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         version: 0.4.0
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         version: 7.29.7
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+        specifier: 5.4.17
+        version: 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
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@@ -388,11 +388,11 @@ importers:
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         version: 7.29.7
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       '@cornerstonejs/core':
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+        specifier: 5.4.17
+        version: 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
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@@ -437,14 +437,14 @@ importers:
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         version: 7.29.7
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+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))
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+        specifier: 5.4.17
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+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
       '@ohif/core':
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         version: link:../../platform/core
@@ -483,11 +483,11 @@ importers:
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+        specifier: 5.4.17
+        version: 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
       '@cornerstonejs/tools':
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+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
       '@ohif/core':
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         version: link:../../platform/core
@@ -713,11 +713,11 @@ importers:
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+        specifier: 5.4.17
+        version: 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
       '@cornerstonejs/tools':
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+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
       '@ohif/core':
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@@ -836,11 +836,11 @@ importers:
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+        specifier: 5.4.17
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       '@cornerstonejs/tools':
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       '@ohif/core':
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@@ -1280,11 +1280,11 @@ importers:
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+        specifier: 5.4.17
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-        version: 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
       '@ohif/core':
         specifier: workspace:*
         version: link:../../platform/core
@@ -1368,8 +1368,8 @@ importers:
         specifier: 2.4.7
         version: 2.4.7
       '@cornerstonejs/dicom-image-loader':
-        specifier: 5.4.13
-        version: 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/metadata@5.4.13)(dicom-parser@1.8.21)
+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/metadata@5.4.17)(dicom-parser@1.8.21)
       '@emotion/serialize':
         specifier: 1.3.3
         version: 1.3.3
@@ -1579,14 +1579,14 @@ importers:
         specifier: 2.4.7
         version: 2.4.7
       '@cornerstonejs/core':
-        specifier: 5.4.13
-        version: 5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
+        specifier: 5.4.17
+        version: 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
       '@cornerstonejs/dicom-image-loader':
-        specifier: 5.4.13
-        version: 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/metadata@5.4.13)(dicom-parser@1.8.21)
+        specifier: 5.4.17
+        version: 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/metadata@5.4.17)(dicom-parser@1.8.21)
       '@cornerstonejs/metadata':
-        specifier: 5.4.13
-        version: 5.4.13
+        specifier: 5.4.17
+        version: 5.4.17
       '@ohif/ui':
         specifier: workspace:*
         version: link:../ui
@@ -3398,17 +3398,17 @@ packages:
     resolution: {integrity: sha512-ooWCrlZP11i8GImSjTHYHLkvFDP48nS4+204nGb1RiX/WXYHmJA2III9/e2DWVabCESdW7hBAEzHRqUn9OUVvQ==}
     engines: {node: '>=0.1.90'}
 
-  '@cornerstonejs/adapters@5.4.13':
-    resolution: {integrity: sha512-XZcIt0n7APz135OO4m4aSuf9bzLyxQL6shZM3Y9VzhsQ/NB40iU1OlDe2obva3dBZklUneOjkynt4UL5UfUsYA==}
+  '@cornerstonejs/adapters@5.4.17':
+    resolution: {integrity: sha512-DDQBEKEQSXh9e/e7aWAD/HlE/B0vbQGNBWpjtx9qYSfC1GFxwK2DnXiBDMrcMoHd6tapkrIr+a9MrOVb1i1dHQ==}
     peerDependencies:
-      '@cornerstonejs/core': 5.4.13
-      '@cornerstonejs/tools': 5.4.13
+      '@cornerstonejs/core': 5.4.17
+      '@cornerstonejs/tools': 5.4.17
 
-  '@cornerstonejs/ai@5.4.13':
-    resolution: {integrity: sha512-rt1ZYTM5RctBqP3oPd2QrQjaVtiXklS10jcTb/XnWQU1P+8pW6t6NZ95w35moXjignSPBIA8/gNKgrWQJ8uZfg==}
+  '@cornerstonejs/ai@5.4.17':
+    resolution: {integrity: sha512-yGzFNfEn75NzNqxqVIu77Ndm0h0Ju6ndYoFpoiDRuFhLw1FuOG8RaOQuOdudOnKJ0yvtciAGEbX7d6blFwh+vg==}
     peerDependencies:
-      '@cornerstonejs/core': 5.4.13
-      '@cornerstonejs/tools': 5.4.13
+      '@cornerstonejs/core': 5.4.17
+      '@cornerstonejs/tools': 5.4.17
 
   '@cornerstonejs/calculate-suv@1.0.3':
     resolution: {integrity: sha512-2SwVJKzC1DzyxdxJtCht9dhTND2GFjLwhhkDyyC7vJq5tIgbhxgPk1CSwovO1pxmoybAXzjOxnaubllxLgoT+w==}
@@ -3434,40 +3434,40 @@ packages:
     resolution: {integrity: sha512-qvP4q4JDib7mi9r7LqKOwqz7YZ8gjtDX4ZCezeYf8+eb7MBXCz5uXAMeVF3yz9Axw4XiIMdB/pqXkm8tqCl13w==}
     engines: {node: '>=0.14'}
 
-  '@cornerstonejs/core@5.4.13':
-    resolution: {integrity: sha512-VeBsrUla3xsb01veMDaHqR3Yel3M00Fzk7mvNv6aQj/lgnsySoj+HozvL/mlYmmHEGoFMNnLzt+/tTOfvIHoBw==}
+  '@cornerstonejs/core@5.4.17':
+    resolution: {integrity: sha512-9o346NeccyRMz6eOAESuuY/vV4cm2Iuf3aQVM5aB8IJRZOaWtVf4wWqBtwzb9ytTlTxJQe0NlX6sEr7R8b1Ngw==}
     peerDependencies:
-      '@cornerstonejs/metadata': 5.4.13
-      '@cornerstonejs/utils': 5.4.13
+      '@cornerstonejs/metadata': 5.4.17
+      '@cornerstonejs/utils': 5.4.17
 
-  '@cornerstonejs/dicom-image-loader@5.4.13':
-    resolution: {integrity: sha512-0zJfn77fNhvsTYheV63ZjkKtoz/id9+Sw1Tiz/dzriJsWswC9lPx0uJ+1XPbbmBFTcFVFNmm4RIEak+GY2Kcsw==}
+  '@cornerstonejs/dicom-image-loader@5.4.17':
+    resolution: {integrity: sha512-SoNy4Dj09xxs/9qImeMLfwbb1lIB3WQc6DlR3Cyi6F8gQzCjgmtg1SKgUgeJ6E2yVXWQgMWthG79WVzHBr6pJg==}
     peerDependencies:
-      '@cornerstonejs/core': 5.4.13
-      '@cornerstonejs/metadata': 5.4.13
+      '@cornerstonejs/core': 5.4.17
+      '@cornerstonejs/metadata': 5.4.17
       dicom-parser: 1.8.21
 
-  '@cornerstonejs/labelmap-interpolation@5.4.13':
-    resolution: {integrity: sha512-wRa6qaz5CYeI0Am0QXB0/2OdpEBy9pUBuPr2gW+fUkDng4Ape2arGVTcUoiaFUPLOGMxc22Vv5FY9YlMiLsmig==}
+  '@cornerstonejs/labelmap-interpolation@5.4.17':
+    resolution: {integrity: sha512-U9i3dRlydN0e+ve1/fweSLrKnxoqpFt0CEL91Je4Jb2YYw2Zcb97PFm/yq4byxKVoT4c7mZHnGepQFWAmbPHFA==}
     peerDependencies:
-      '@cornerstonejs/core': 5.4.13
-      '@cornerstonejs/tools': 5.4.13
+      '@cornerstonejs/core': 5.4.17
+      '@cornerstonejs/tools': 5.4.17
       '@kitware/vtk.js': 35.5.3
 
-  '@cornerstonejs/metadata@5.4.13':
-    resolution: {integrity: sha512-4D3lQEfw6xys1nVZd784p2enQ55rslU58MsYRC5WiJak0dpKYjV6h05xa+nB5LUl/tKA7AZNSEPzMrpZhqgopQ==}
+  '@cornerstonejs/metadata@5.4.17':
+    resolution: {integrity: sha512-sDJRghnkGJhpLPa/Qkh7bCFHx0ZNOlxj6AGkLe4iNohlFk7w485Ty5JYRuOBvwS7lwz2EFDJt+Dv70xHWlGQAA==}
 
-  '@cornerstonejs/polymorphic-segmentation@5.4.13':
-    resolution: {integrity: sha512-H6vL+xX7EvcHkv27lyBdOkgEYjmWbMz64tewz5kHVuRpb8i71RBh0qzbjtTGp6g/+X6FBlQdAZ9f4jHMQsM15g==}
+  '@cornerstonejs/polymorphic-segmentation@5.4.17':
+    resolution: {integrity: sha512-icbgS1ULmqr8y0Qg1KVRP3E661ZXzFOVCD5Ufvfaxq7wex34EyxnWoR/lmq4/eLpJZT1brKVSpudh4BefAcgWA==}
     peerDependencies:
-      '@cornerstonejs/core': 5.4.13
-      '@cornerstonejs/tools': 5.4.13
+      '@cornerstonejs/core': 5.4.17
+      '@cornerstonejs/tools': 5.4.17
       '@kitware/vtk.js': 35.5.3
 
-  '@cornerstonejs/tools@5.4.13':
-    resolution: {integrity: sha512-YLzJDwDwpaDYAFA2gFs5KXj1svLvHmk2n3Wc8XUl0tUQCNEjX4i+yDRN33muW/WETyfX5e33vGWfhly37FfWOQ==}
+  '@cornerstonejs/tools@5.4.17':
+    resolution: {integrity: sha512-ebsdaxDcJ0ezLLDqEtl3hIFtCWEDIU6OonqOKb62GuEBAWm+ZbLjQgsixHhRa9+rLWxHAoBhgRwmglcxlc/lOw==}
     peerDependencies:
-      '@cornerstonejs/core': 5.4.13
+      '@cornerstonejs/core': 5.4.17
       '@kitware/vtk.js': 35.5.3
       '@types/d3-array': 3.2.1
       '@types/d3-interpolate': 3.0.4
@@ -3475,8 +3475,8 @@ packages:
       d3-interpolate: 3.0.1
       gl-matrix: 3.4.3
 
-  '@cornerstonejs/utils@5.4.13':
-    resolution: {integrity: sha512-V2GQCeqgJc51132rfQEfUCZCVEm4e8nAaXDSQUjiyverXFZ0T0Y4qik2+VZ2F5RKJ1A3sHKiv53iobB02M0A+w==}
+  '@cornerstonejs/utils@5.4.17':
+    resolution: {integrity: sha512-ER8izPlNNMes6orLQ4Z7vm3fHmDOroukz+pF0A/3dp98Ro8KV0Wj39etkz4rInPhL6AL/gl/moi9/HqlKxXyFQ==}
 
   '@cspotcode/source-map-support@0.8.1':
     resolution: {integrity: sha512-IchNf6dN4tHoMFIn/7OE8LWZ19Y6q/67Bmf6vnGREv8RSbBVb9LPJxEcnwrcwX6ixSvaiGoomAUvu4YSxXrVgw==}
@@ -16298,21 +16298,21 @@ snapshots:
   '@colors/colors@1.5.0':
     optional: true
 
-  '@cornerstonejs/adapters@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))':
+  '@cornerstonejs/adapters@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))':
     dependencies:
       '@babel/runtime-corejs2': 7.26.10
-      '@cornerstonejs/core': 5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
-      '@cornerstonejs/tools': 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
+      '@cornerstonejs/core': 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
+      '@cornerstonejs/tools': 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
       buffer: 6.0.3
       dcmjs: 0.52.0
       gl-matrix: 3.4.3
       ndarray: 1.0.19
 
-  '@cornerstonejs/ai@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))':
+  '@cornerstonejs/ai@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))':
     dependencies:
       '@babel/runtime-corejs2': 7.26.10
-      '@cornerstonejs/core': 5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
-      '@cornerstonejs/tools': 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
+      '@cornerstonejs/core': 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
+      '@cornerstonejs/tools': 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
       buffer: 6.0.3
       dcmjs: 0.52.0
       gl-matrix: 3.4.3
@@ -16333,10 +16333,10 @@ snapshots:
 
   '@cornerstonejs/codec-openjph@2.4.7': {}
 
-  '@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)':
+  '@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)':
     dependencies:
-      '@cornerstonejs/metadata': 5.4.13
-      '@cornerstonejs/utils': 5.4.13
+      '@cornerstonejs/metadata': 5.4.17
+      '@cornerstonejs/utils': 5.4.17
       '@kitware/vtk.js': 35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
       comlink: 4.4.2
       gl-matrix: 3.4.3
@@ -16346,24 +16346,24 @@ snapshots:
       - autoprefixer
       - wslink
 
-  '@cornerstonejs/dicom-image-loader@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/metadata@5.4.13)(dicom-parser@1.8.21)':
+  '@cornerstonejs/dicom-image-loader@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/metadata@5.4.17)(dicom-parser@1.8.21)':
     dependencies:
       '@cornerstonejs/codec-charls': 1.2.3
       '@cornerstonejs/codec-libjpeg-turbo-8bit': 1.2.2
       '@cornerstonejs/codec-openjpeg': 1.3.0
       '@cornerstonejs/codec-openjph': 2.4.7
-      '@cornerstonejs/core': 5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
-      '@cornerstonejs/metadata': 5.4.13
+      '@cornerstonejs/core': 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
+      '@cornerstonejs/metadata': 5.4.17
       comlink: 4.4.2
       dicom-parser: 1.8.21
       jpeg-lossless-decoder-js: 2.1.2
       pako: 2.1.0
       uuid: 9.0.1
 
-  '@cornerstonejs/labelmap-interpolation@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))':
+  '@cornerstonejs/labelmap-interpolation@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))':
     dependencies:
-      '@cornerstonejs/core': 5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
-      '@cornerstonejs/tools': 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
+      '@cornerstonejs/core': 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
+      '@cornerstonejs/tools': 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
       '@itk-wasm/morphological-contour-interpolation': 1.1.0
       '@kitware/vtk.js': 35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
       itk-wasm: 1.0.0-b.165
@@ -16371,23 +16371,23 @@ snapshots:
       - debug
       - supports-color
 
-  '@cornerstonejs/metadata@5.4.13':
+  '@cornerstonejs/metadata@5.4.17':
     dependencies:
       '@cornerstonejs/calculate-suv': 1.0.3
-      '@cornerstonejs/utils': 5.4.13
+      '@cornerstonejs/utils': 5.4.17
       dcmjs: 0.52.0
       gl-matrix: 3.4.3
 
-  '@cornerstonejs/polymorphic-segmentation@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))':
+  '@cornerstonejs/polymorphic-segmentation@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@cornerstonejs/tools@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))':
     dependencies:
-      '@cornerstonejs/core': 5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
-      '@cornerstonejs/tools': 5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
+      '@cornerstonejs/core': 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
+      '@cornerstonejs/tools': 5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)
       '@icr/polyseg-wasm': 0.4.0
       '@kitware/vtk.js': 35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
 
-  '@cornerstonejs/tools@5.4.13(@cornerstonejs/core@5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)':
+  '@cornerstonejs/tools@5.4.17(@cornerstonejs/core@5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@kitware/vtk.js@35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0))(@types/d3-array@3.2.1)(@types/d3-interpolate@3.0.4)(d3-array@3.2.4)(d3-interpolate@3.0.1)(gl-matrix@3.4.3)':
     dependencies:
-      '@cornerstonejs/core': 5.4.13(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.13)(@cornerstonejs/utils@5.4.13)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
+      '@cornerstonejs/core': 5.4.17(@babel/preset-env@7.29.7(@babel/core@7.29.7))(@cornerstonejs/metadata@5.4.17)(@cornerstonejs/utils@5.4.17)(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
       '@kitware/vtk.js': 35.5.3(@babel/preset-env@7.29.7(@babel/core@7.29.7))(autoprefixer@10.4.27(postcss@8.5.14))(wslink@2.5.0)
       '@types/d3-array': 3.2.1
       '@types/d3-interpolate': 3.0.4
@@ -16399,7 +16399,7 @@ snapshots:
       gl-matrix: 3.4.3
       lodash.get: 4.4.2
 
-  '@cornerstonejs/utils@5.4.13':
+  '@cornerstonejs/utils@5.4.17':
     dependencies:
       dcmjs: 0.52.0
 
diff --git a/scripts/check-next-viewport-boundaries.sh b/scripts/check-next-viewport-boundaries.sh
new file mode 100755
index 000000000..fd20f39c2
--- /dev/null
+++ b/scripts/check-next-viewport-boundaries.sh
@@ -0,0 +1,66 @@
+#!/usr/bin/env bash
+# Boundary check for the next-viewport migration seams (see
+# extensions/cornerstone/src/services/ViewportService/backends/README.md).
+#
+# Enforces:
+#   1. csUtils.isGenericViewport is called ONLY from the adapter dispatch module.
+#   2. isNextViewportsEnabled() is called ONLY from the sanctioned flag-read list.
+#   3. CornerstoneViewportService and the UI layer (hooks/, Viewport/, components/)
+#      contain no per-lane branching at all.
+#
+# Run from the repo root: ./scripts/check-next-viewport-boundaries.sh
+set -u
+
+cd "$(dirname "$0")/.."
+
+fail=0
+
+report() {
+  echo "BOUNDARY VIOLATION: $1"
+  echo "$2" | sed 's/^/  /'
+  echo "Add the divergence to the adapter, a backend, or nextViewportPolicies instead;"
+  echo "if a new sanctioned site is genuinely required, update backends/README.md and this script."
+  fail=1
+}
+
+# 1. isGenericViewport calls outside the adapter dispatch module (tests excluded).
+generic_hits=$(grep -rn "isGenericViewport(" \
+  --include='*.ts' --include='*.tsx' \
+  extensions platform modes 2>/dev/null |
+  grep -v '\.test\.' |
+  grep -v 'services/ViewportService/adapter/getViewportAdapter\.ts' || true)
+if [ -n "$generic_hits" ]; then
+  report "isGenericViewport called outside adapter/getViewportAdapter.ts" "$generic_hits"
+fi
+
+# 2. isNextViewportsEnabled() calls outside the sanctioned list.
+flag_hits=$(grep -rn "isNextViewportsEnabled()" \
+  --include='*.ts' --include='*.tsx' \
+  extensions platform modes 2>/dev/null |
+  grep -v '\.test\.' |
+  grep -v 'extensions/cornerstone/src/utils/nextViewports\.ts' |
+  grep -v 'extensions/cornerstone/src/utils/nextViewportPolicies\.ts' |
+  grep -v 'extensions/cornerstone/src/utils/getCornerstoneViewportType\.ts' |
+  grep -v 'extensions/cornerstone/src/services/ViewportService/CornerstoneViewportService\.ts' |
+  grep -v 'extensions/cornerstone/src/services/SegmentationService/SegmentationService\.ts' |
+  grep -v 'extensions/tmtv/src/getHangingProtocolModule\.ts' || true)
+if [ -n "$flag_hits" ]; then
+  report "isNextViewportsEnabled() called outside the sanctioned flag-read list" "$flag_hits"
+fi
+
+# 3. Per-lane predicates in the UI layer and the viewport service (must be zero).
+ui_hits=$(grep -rn "isNextViewport(\|isGenericViewport(" \
+  --include='*.ts' --include='*.tsx' \
+  extensions/cornerstone/src/hooks \
+  extensions/cornerstone/src/Viewport \
+  extensions/cornerstone/src/components \
+  extensions/cornerstone/src/services/ViewportService/CornerstoneViewportService.ts 2>/dev/null |
+  grep -v '\.test\.' || true)
+if [ -n "$ui_hits" ]; then
+  report "per-lane predicate in the UI layer / CornerstoneViewportService" "$ui_hits"
+fi
+
+if [ "$fail" -eq 0 ]; then
+  echo "next-viewport boundaries OK"
+fi
+exit "$fail"
diff --git a/tests/OverlappingSegmentationRendering.spec.ts b/tests/OverlappingSegmentationRendering.spec.ts
new file mode 100644
index 000000000..e92de657b
--- /dev/null
+++ b/tests/OverlappingSegmentationRendering.spec.ts
@@ -0,0 +1,36 @@
+import {
+  checkForScreenshot,
+  expect,
+  screenShotPaths,
+  test,
+  visitStudy,
+  waitForViewportRenderCycle,
+  waitForViewportsRendered,
+} from './utils';
+
+test.beforeEach(async ({ page }) => {
+  const studyInstanceUID = '1.3.6.1.4.1.14519.5.2.1.3671.4754.298665348758363466150039312520';
+  await visitStudy(page, `${studyInstanceUID}&useNextViewports=true`, 'viewer', 2000);
+});
+
+test('should render overlapping segments from SEG series 1004', async ({
+  page,
+  DOMOverlayPageObject,
+  leftPanelPageObject,
+  viewportPageObject,
+}) => {
+  await leftPanelPageObject.loadSeriesBySeriesNumber(1004);
+
+  await expect(DOMOverlayPageObject.viewport.segmentationHydration.locator).toBeVisible();
+
+  const viewportRenderCycle = waitForViewportRenderCycle(page);
+  await DOMOverlayPageObject.viewport.segmentationHydration.yes.click();
+  await viewportRenderCycle;
+  await waitForViewportsRendered(page);
+
+  await checkForScreenshot({
+    page,
+    locator: viewportPageObject.grid,
+    screenshotPath: screenShotPaths.overlappingSegmentationRendering.overlappingSegmentsDisplayed,
+  });
+});
diff --git a/tests/Scoord3dProbe.spec.ts b/tests/Scoord3dProbe.spec.ts
index 7db9670e9..dccaa6c2a 100644
--- a/tests/Scoord3dProbe.spec.ts
+++ b/tests/Scoord3dProbe.spec.ts
@@ -5,7 +5,8 @@ import {
   screenShotPaths,
   test,
   visitStudy,
-  waitForPaintToSettle, waitForViewportRenderCycle,
+  waitForPaintToSettle,
+  waitForViewportRenderCycle,
   waitForViewportsRendered,
 } from './utils';
 
@@ -35,7 +36,7 @@ test.beforeEach(async ({ page }) => {
     }
   });
 });
-test.describe.configure({ retries: 1 });
+
 test('should hydrate SCOORD3D probe measurements correctly', async ({
   page,
   DOMOverlayPageObject,
@@ -43,19 +44,17 @@ test('should hydrate SCOORD3D probe measurements correctly', async ({
   rightPanelPageObject,
   viewportPageObject,
 }) => {
-  // Wait for the side panel to be visible and clickable
-  await page.waitForTimeout(3000);
-
   // Navigate to the tracked measurements panel
   await rightPanelPageObject.toggle();
   await rightPanelPageObject.measurementsPanel.select();
 
   // Double-click on the study browser thumbnail to load the SR
   await leftPanelPageObject.loadSeriesByModality('SR');
-  await page.waitForTimeout(2000);
 
-  // Wait for the SR to load and stabilize before taking screenshot
-  await page.waitForTimeout(1000);
+  await DOMOverlayPageObject.viewport.segmentationHydration.yes.button.waitFor({
+    state: 'visible',
+    timeout: 15000,
+  });
 
   const activeViewport = await viewportPageObject.active;
 
@@ -85,25 +84,22 @@ test('should hydrate SCOORD3D probe measurements correctly', async ({
       viewport.render();
     }
   });
-
-  // Wait for rendering to complete
-  await page.waitForTimeout(1000);
-
-  // Wait for the hydrate button to be visible and clickable
-  await DOMOverlayPageObject.viewport.segmentationHydration.yes.button.waitFor({
-    state: 'visible',
-    timeout: 15000,
-  });
+  await waitForViewportsRendered(page);
 
   // Click the hydrate button to load the SCOORD3D probe measurements
   await DOMOverlayPageObject.viewport.segmentationHydration.yes.click();
 
-  // Wait for hydration to complete and rendering to stabilize. SCOORD3D
-  // hydration can swap the displayed series (referenced vs. current volume),
-  // so we must wait for the new image set to render before screenshotting.
-  await waitForViewportsRendered(page);
-  await page.waitForTimeout(3000);
-  await waitForPaintToSettle(page);
+  // SR hydration runs through the tracking state machine after the button click.
+  // Waiting for "rendered" immediately can resolve on the old viewport before
+  // that async work starts, so first wait for the hydrated measurements and
+  // target series to be observable, then wait for rendering to complete.
+  await expect(rightPanelPageObject.measurementsPanel.panel.rows).not.toHaveCount(0, {
+    timeout: 30000,
+  });
+  await expect(activeViewport.overlayText.topLeft.locator).toContainText('t2_tse_sag', {
+    timeout: 30000,
+  });
+  await waitForViewportsRendered(page, { timeout: 30000 });
 
   // Take screenshot after hydration showing the probe measurements - use viewport locator
   await checkForScreenshot(
@@ -152,7 +148,6 @@ test('should hydrate SCOORD3D probe measurements correctly', async ({
   await jumpRenderCycle;
   await waitForPaintToSettle(page);
 
-  // Take screenshot showing the jump to measurement functionality - use viewport locator
   await checkForScreenshot(
     page,
     activeViewport.pane,
@@ -167,14 +162,10 @@ test('should display SCOORD3D probe measurements correctly', async ({
   rightPanelPageObject,
   viewportPageObject,
 }) => {
-  // Wait for the side panel to be visible and clickable
-  await page.waitForTimeout(3000);
-
   // First hydrate the SR to load the measurements
   await rightPanelPageObject.toggle();
   await rightPanelPageObject.measurementsPanel.select();
   await leftPanelPageObject.loadSeriesByModality('SR');
-  await page.waitForTimeout(2000);
 
   // Wait for the hydrate button to be visible and clickable
   await DOMOverlayPageObject.viewport.segmentationHydration.yes.button.waitFor({
@@ -182,7 +173,15 @@ test('should display SCOORD3D probe measurements correctly', async ({
     timeout: 15000,
   });
   await DOMOverlayPageObject.viewport.segmentationHydration.yes.click();
-  await page.waitForTimeout(2000);
+
+  const activeViewport = await viewportPageObject.active;
+  await expect(rightPanelPageObject.measurementsPanel.panel.rows).not.toHaveCount(0, {
+    timeout: 30000,
+  });
+  await expect(activeViewport.overlayText.topLeft.locator).toContainText('t2_tse_sag', {
+    timeout: 30000,
+  });
+  await waitForViewportsRendered(page, { timeout: 30000 });
 
   // Zoom to show the probe measurements clearly
   await page.evaluate(() => {
@@ -202,15 +201,7 @@ test('should display SCOORD3D probe measurements correctly', async ({
       viewport.render();
     }
   });
-
-  // Wait for the zoom re-render to actually settle before capturing. A fixed
-  // delay can capture a partially rendered viewport on a slow/loaded runner,
-  // which shows up as a near-total screenshot diff.
   await waitForViewportsRendered(page);
-  await waitForPaintToSettle(page);
-  await page.waitForTimeout(3000);
-
-  const activeViewport = await viewportPageObject.active;
 
   // Take screenshot showing the SCOORD3D probe measurements rendered correctly - use viewport locator
   await checkForScreenshot(
diff --git a/tests/pages/LeftPanelPageObject.ts b/tests/pages/LeftPanelPageObject.ts
index b188dcba7..a727e49e0 100644
--- a/tests/pages/LeftPanelPageObject.ts
+++ b/tests/pages/LeftPanelPageObject.ts
@@ -32,4 +32,11 @@ export class LeftPanelPageObject {
       .nth(nth);
     await matchingThumbnail.dblclick();
   }
+
+  async loadSeriesBySeriesNumber(seriesNumber: string | number) {
+    const matchingThumbnail = this.page.locator(
+      `[data-cy^="study-browser-thumbnail"][data-series="${seriesNumber}"]`
+    );
+    await matchingThumbnail.dblclick();
+  }
 }
diff --git a/tests/pages/ViewportPageObject.ts b/tests/pages/ViewportPageObject.ts
index 4e8a2861f..f234edd0e 100644
--- a/tests/pages/ViewportPageObject.ts
+++ b/tests/pages/ViewportPageObject.ts
@@ -24,12 +24,14 @@ type NormalizedPathDragParams = {
 };
 
 export interface IOverlayText {
+  locator: Locator;
   get windowLevel(): Locator;
   get instanceNumber(): Locator;
 }
 function overlayTextFactory(viewport: Locator, id: string): IOverlayText {
   const locator = viewport.getByTestId(id);
   return {
+    locator,
     get windowLevel() {
       return locator.getByTitle('Window Level');
     },
@@ -321,9 +323,7 @@ export class ViewportPageObject {
         return this.getSvg(viewport, innerElement);
       },
       getSvgAnnotationStatTextLines: (uid: string) => {
-        return this.getSvg(viewport)
-          .locator(`g[data-annotation-uid="${uid}"]`)
-          .locator('tspan');
+        return this.getSvg(viewport).locator(`g[data-annotation-uid="${uid}"]`).locator('tspan');
       },
       navigationArrows: this.getNavigationArrows(viewport),
       sliceNavigation: this.getSliceNavigation(viewport),
diff --git a/tests/screenshots/chromium/OverlappingSegmentationRendering.spec.ts/overlappingSegmentsDisplayed.png b/tests/screenshots/chromium/OverlappingSegmentationRendering.spec.ts/overlappingSegmentsDisplayed.png
new file mode 100644
index 000000000..9f28ed588
Binary files /dev/null and b/tests/screenshots/chromium/OverlappingSegmentationRendering.spec.ts/overlappingSegmentsDisplayed.png differ
diff --git a/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbeDisplayedCorrectly.png b/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbeDisplayedCorrectly.png
index 49603cd09..36d74d931 100644
Binary files a/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbeDisplayedCorrectly.png and b/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbeDisplayedCorrectly.png differ
diff --git a/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbeJumpToMeasurement.png b/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbeJumpToMeasurement.png
index 7df0682f2..723d06b91 100644
Binary files a/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbeJumpToMeasurement.png and b/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbeJumpToMeasurement.png differ
diff --git a/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbePostHydration.png b/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbePostHydration.png
index 520a378cd..373ef63dd 100644
Binary files a/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbePostHydration.png and b/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbePostHydration.png differ
diff --git a/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbePreHydration.png b/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbePreHydration.png
index f20703423..08076fed9 100644
Binary files a/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbePreHydration.png and b/tests/screenshots/chromium/Scoord3dProbe.spec.ts/scoord3dProbePreHydration.png differ
diff --git a/tests/utils/screenShotPaths.ts b/tests/utils/screenShotPaths.ts
index e53e36998..9c9b80d0c 100644
--- a/tests/utils/screenShotPaths.ts
+++ b/tests/utils/screenShotPaths.ts
@@ -221,6 +221,9 @@ const screenShotPaths = {
     overlaysDisplayed: 'overlaysDisplayed.png',
     overlaySEGsAndRTDisplayed: 'overlaySEGsAndRTDisplayed.png',
   },
+  overlappingSegmentationRendering: {
+    overlappingSegmentsDisplayed: 'overlappingSegmentsDisplayed.png',
+  },
   contourCombineOperations: {
     subtractBigSphereMinusSmallSphereResult: 'subtractBigSphereMinusSmallSphereResult.png',
     intersectBigSphereSmallSphereResult: 'intersectBigSphereSmallSphereResult.png',