diff --git a/extensions/cornerstone/src/commandsModule.ts b/extensions/cornerstone/src/commandsModule.ts
index d702d7b7b2e..0c5c3e523dc 100644
--- a/extensions/cornerstone/src/commandsModule.ts
+++ b/extensions/cornerstone/src/commandsModule.ts
@@ -40,6 +40,7 @@ import { updateSegmentBidirectionalStats } from './utils/updateSegmentationStats
 import { generateSegmentationCSVReport } from './utils/generateSegmentationCSVReport';
 import { getUpdatedViewportsForSegmentation } from './utils/hydrationUtils';
 import { SegmentationRepresentations } from '@cornerstonejs/tools/enums';
+import { DisplaySet } from 'platform/core/src/types';
 
 const { DefaultHistoryMemo } = csUtils.HistoryMemo;
 const toggleSyncFunctions = {
@@ -117,9 +118,13 @@ function commandsModule({
     hangingProtocolService,
     syncGroupService,
     segmentationService,
+    userAuthenticationService,
     displaySetService,
   } = servicesManager.services as AppTypes.Services;
 
+  let _protocolViewportDataInitSubscription: { unsubscribe: () => void } | null = null;
+  let _protocolViewportDataChangedSubscription: { unsubscribe: () => void } | null = null;
+
   function _getActiveViewportEnabledElement() {
     return getActiveViewportEnabledElement(viewportGridService);
   }
@@ -145,7 +150,99 @@ function commandsModule({
     };
   }
 
+  /**
+   * Retrieves derived segmentations (SEG/RTSTRUCT) that are not yet hydrated
+   * for the given display set UID.
+   */
+  function getDerivedData(modalities: string[], displaySetUID: string): DisplaySet[] {
+    const currentDisplaySet = displaySetService.getDisplaySetByUID(displaySetUID);
+    if (!currentDisplaySet) {
+      return [];
+    }
+
+    const displaySetCache = displaySetService.getDisplaySetCache();
+    const allDisplaySets = Array.from(displaySetCache.values());
+
+    return allDisplaySets.filter((ds): ds is DisplaySet => {
+      const isValidModality = modalities.includes(ds.Modality);
+      if (!isValidModality) {
+        return false;
+      }
+
+      /** Check if this derived display set references the current display set */
+      const referencesDisplaySet =
+        ds.referencedDisplaySetInstanceUID === displaySetUID ||
+        ds.SeriesInstanceUID === currentDisplaySet.SeriesInstanceUID;
+
+      return referencesDisplaySet;
+    });
+  }
+
+  const loadDerivedDisplaySetsForActiveViewport = async (
+    modalities: string[],
+    onLoadComplete: (displaySet: any, activeViewportId: string) => Promise<void> | void
+  ): Promise<boolean> => {
+    const activeViewportId = viewportGridService.getActiveViewportId();
+    if (!activeViewportId) {
+      console.warn('No active viewport found');
+      return false;
+    }
+
+    const displaySetInstanceUIDs =
+      viewportGridService.getDisplaySetsUIDsForViewport(activeViewportId);
+    if (!displaySetInstanceUIDs?.length) {
+      console.warn('No display sets found for active viewport');
+      return false;
+    }
+
+    const primaryDisplaySetUID = displaySetInstanceUIDs[0];
+    const derivedDisplaySets = getDerivedData(modalities, primaryDisplaySetUID);
+    if (!derivedDisplaySets.length) {
+      console.warn('No derived data found for active viewport!');
+      return false;
+    }
+
+    const headers = userAuthenticationService.getAuthorizationHeader();
+
+    const loadPromises = derivedDisplaySets.map(async displaySet => {
+      try {
+        await displaySet.load({ headers });
+        await onLoadComplete(displaySet, activeViewportId);
+      } catch (error) {
+        console.error(`Failed to load segmentation ${displaySet.displaySetInstanceUID}:`, error);
+      }
+    });
+
+    await Promise.all(loadPromises);
+    return true;
+  };
+
   const actions = {
+    loadSegmentationsForActiveViewport: async () => {
+      console.info('Loading segmentations for active viewport...');
+
+      const loaded = await loadDerivedDisplaySetsForActiveViewport(
+        ['SEG', 'RTSTRUCT'],
+        async (displaySet, activeViewportId) => {
+          const representationType =
+            displaySet.Modality === 'SEG'
+              ? Enums.SegmentationRepresentations.Labelmap
+              : Enums.SegmentationRepresentations.Contour;
+
+          segmentationService.addSegmentationRepresentation(activeViewportId, {
+            segmentationId: displaySet.displaySetInstanceUID,
+            type: representationType,
+          });
+        }
+      );
+
+      if (!loaded) {
+        console.warn('No derived segmentations found for active viewport');
+        return;
+      }
+
+      console.info('Segmentations loaded for active viewport.');
+    },
     jumpToMeasurementViewport: ({ annotationUID, measurement }) => {
       cornerstoneTools.annotation.selection.setAnnotationSelected(annotationUID, true);
       const { metadata } = measurement;
@@ -1306,16 +1403,62 @@ function commandsModule({
       const command = protocol.callbacks.onViewportDataInitialized;
       const numPanes = protocol.stages?.[stageIndex]?.viewports.length ?? 1;
       let numPanesWithData = 0;
-      const { unsubscribe } = cornerstoneViewportService.subscribe(EVENT, evt => {
+
+      actions.detachProtocolViewportDataListener?.();
+
+      const subscription = cornerstoneViewportService.subscribe(EVENT, () => {
         numPanesWithData++;
 
         if (numPanesWithData === numPanes) {
-          commandsManager.run(...command);
+          commandsManager.run(command);
 
           // Unsubscribe from the event
-          unsubscribe(EVENT);
+          subscription.unsubscribe();
+          _protocolViewportDataInitSubscription = null;
         }
       });
+
+      _protocolViewportDataInitSubscription = subscription;
+    },
+
+    detachProtocolViewportDataListener: () => {
+      if (_protocolViewportDataInitSubscription) {
+        _protocolViewportDataInitSubscription.unsubscribe();
+        _protocolViewportDataInitSubscription = null;
+      }
+    },
+
+    attachProtocolViewportDataChangedListener: ({ protocol, stageIndex }) => {
+      const EVENT = cornerstoneViewportService.EVENTS.VIEWPORT_DATA_CHANGED;
+      const command = protocol.callbacks.onViewportDataChanged;
+
+      actions.detachProtocolViewportDataChangedListener?.();
+
+      const subscription = cornerstoneViewportService.subscribe(
+        EVENT,
+        (evt: { viewportId?: string; viewportData?: unknown }) => {
+          const viewportId = evt?.viewportId;
+          if (!viewportId) {
+            return;
+          }
+
+          commandsManager.run(command, {
+            viewportId,
+            viewportData: evt.viewportData,
+            protocol,
+            stageIndex,
+          });
+        }
+      );
+
+      _protocolViewportDataChangedSubscription = subscription;
+    },
+
+    detachProtocolViewportDataChangedListener: () => {
+      if (_protocolViewportDataChangedSubscription) {
+        _protocolViewportDataChangedSubscription.unsubscribe();
+        _protocolViewportDataChangedSubscription = null;
+      }
     },
 
     setViewportPreset: ({ viewportId, preset }) => {
@@ -2211,6 +2354,9 @@ function commandsModule({
   };
 
   const definitions = {
+    loadSegmentationsForActiveViewport: {
+      commandFn: actions.loadSegmentationsForActiveViewport,
+    },
     // The command here is to show the viewer context menu, as being the
     // context menu
     showCornerstoneContextMenu: {
@@ -2370,6 +2516,15 @@ function commandsModule({
     attachProtocolViewportDataListener: {
       commandFn: actions.attachProtocolViewportDataListener,
     },
+    detachProtocolViewportDataListener: {
+      commandFn: actions.detachProtocolViewportDataListener,
+    },
+    attachProtocolViewportDataChangedListener: {
+      commandFn: actions.attachProtocolViewportDataChangedListener,
+    },
+    detachProtocolViewportDataChangedListener: {
+      commandFn: actions.detachProtocolViewportDataChangedListener,
+    },
     setViewportPreset: {
       commandFn: actions.setViewportPreset,
     },
diff --git a/extensions/default/src/getHangingProtocolModule.js b/extensions/default/src/getHangingProtocolModule.js
index 4ccd6e271a3..132eb18833f 100644
--- a/extensions/default/src/getHangingProtocolModule.js
+++ b/extensions/default/src/getHangingProtocolModule.js
@@ -14,6 +14,9 @@ const defaultProtocol = {
   modifiedDate: '2023-04-01',
   availableTo: {},
   editableBy: {},
+  callbacks: {
+    onViewportDataChanged: ['loadSegmentationsForActiveViewport'],
+  },
   protocolMatchingRules: [],
   toolGroupIds: ['default'],
   // -1 would be used to indicate active only, whereas other values are
diff --git a/platform/core/src/services/HangingProtocolService/HangingProtocolService.ts b/platform/core/src/services/HangingProtocolService/HangingProtocolService.ts
index fd85749acf1..474ee9f51ba 100644
--- a/platform/core/src/services/HangingProtocolService/HangingProtocolService.ts
+++ b/platform/core/src/services/HangingProtocolService/HangingProtocolService.ts
@@ -430,7 +430,10 @@ export default class HangingProtocolService extends PubSubService {
       this.customAttributeRetrievalCallbacks
     );
 
-    // Resets the full protocol status here.
+    this._commandsManager.run('detachProtocolViewportDataListener');
+    this._commandsManager.run('detachProtocolViewportDataChangedListener');
+
+    // Resets the full protocol status here
     this.protocol = null;
 
     if (protocolId && typeof protocolId === 'string') {
@@ -1032,6 +1035,10 @@ export default class HangingProtocolService extends PubSubService {
 
     try {
       if (!this.protocol || this.protocol.id !== protocol.id) {
+
+        this._commandsManager.run('detachProtocolViewportDataListener');
+        this._commandsManager.run('detachProtocolViewportDataChangedListener');
+
         this.stageIndex = options?.stageIndex || 0;
         //Reset load performed to false to re-fire loading strategy at new study opening
         this.customImageLoadPerformed = false;
@@ -1212,8 +1219,18 @@ export default class HangingProtocolService extends PubSubService {
 
     const { columns: numCols, rows: numRows, layoutOptions = [] } = layoutProps;
 
+    this._commandsManager.run('detachProtocolViewportDataListener');
+    this._commandsManager.run('detachProtocolViewportDataChangedListener');
+
     if (this.protocol?.callbacks?.onViewportDataInitialized) {
-      this._commandsManager.runCommand('attachProtocolViewportDataListener', {
+      this._commandsManager.run('attachProtocolViewportDataListener', {
+        protocol: this.protocol,
+        stageIndex: this.stageIndex,
+      });
+    }
+
+    if (this.protocol?.callbacks?.onViewportDataChanged) {
+      this._commandsManager.run('attachProtocolViewportDataChangedListener', {
         protocol: this.protocol,
         stageIndex: this.stageIndex,
       });
diff --git a/platform/core/src/types/DisplaySet.ts b/platform/core/src/types/DisplaySet.ts
index 7eee952ec94..c5ec90038a7 100644
--- a/platform/core/src/types/DisplaySet.ts
+++ b/platform/core/src/types/DisplaySet.ts
@@ -51,6 +51,13 @@ export type DisplaySet = {
 
   isHydrated?: boolean;
   isRehydratable?: boolean;
+
+  /**
+   * Loads the display set.
+   * @param headers - The headers to use for the request.
+   * @returns A promise that resolves when the display set is loaded.
+   */
+  load: ({ headers }: { headers?: unknown }) => Promise<void>;
 };
 
 export type DisplaySetSeriesMetadataInvalidatedEvent = {
diff --git a/platform/core/src/types/HangingProtocol.ts b/platform/core/src/types/HangingProtocol.ts
index 189fe0dcc08..c3e825e0bf9 100644
--- a/platform/core/src/types/HangingProtocol.ts
+++ b/platform/core/src/types/HangingProtocol.ts
@@ -293,6 +293,15 @@ export type ProtocolNotifications = {
   // and all viewport data includes a designated display set. This command
   // will run on every stage's initial layout.
   onViewportDataInitialized?: Command[];
+  // This set of commands is executed whenever viewport data has changed for a
+  // given viewport.
+  //
+  // Commands will receive an options object containing:
+  // - viewportId
+  // - viewportData
+  // - protocol
+  // - stageIndex
+  onViewportDataChanged?: Command[];
   // This set of commands is executed before the stage change is applied
   onStageChange?: Command[];
 };
diff --git a/platform/docs/docs/platform/extensions/modules/hpModule.md b/platform/docs/docs/platform/extensions/modules/hpModule.md
index 1fb26c3a6cb..3fb3f8a9ab1 100644
--- a/platform/docs/docs/platform/extensions/modules/hpModule.md
+++ b/platform/docs/docs/platform/extensions/modules/hpModule.md
@@ -600,6 +600,17 @@ The `onLayoutChange` callback is executed before the layout change is started. Y
 
 The `onViewportDataInitialized` callback is executed after the initial viewport grid data is set and all viewport data includes a designated display set. This callback runs during the initial layout setup for each stage. You can use it to perform actions or apply settings to the viewports at the start.
 
+### `onViewportDataChanged`
+
+The `onViewportDataChanged` callback is executed whenever a viewport's data changes (for example, when a different display set is assigned to a viewport). This is useful for reacting to runtime changes like drag/drop swaps, layout tools that reassign data, etc.
+
+Commands in `onViewportDataChanged` will receive an options object including:
+
+- `viewportId`
+- `viewportData`
+- `protocol`
+- `stageIndex`
+
 Here is an example of how you can add these callbacks to your hanging protocol configuration:
 
 ```javascript
@@ -620,7 +631,11 @@ const protocol = {
     onViewportDataInitialized: [
       // Array of commands or actions to execute on viewport data initialization
     ],
+    onViewportDataChanged: [
+      // Array of commands or actions to execute when viewport data changes
+    ],
   },
   // protocolMatchingRules
   // the rest
 };
+```
diff --git a/platform/docs/versioned_docs/version-3.10/platform/extensions/modules/hpModule.md b/platform/docs/versioned_docs/version-3.10/platform/extensions/modules/hpModule.md
index 8920ccc255a..99dbe1f0c34 100644
--- a/platform/docs/versioned_docs/version-3.10/platform/extensions/modules/hpModule.md
+++ b/platform/docs/versioned_docs/version-3.10/platform/extensions/modules/hpModule.md
@@ -622,3 +622,4 @@ const protocol = {
   // protocolMatchingRules
   // the rest
 };
+```