diff --git a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasEntity/CanvasEntityAdapterBase.ts b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasEntity/CanvasEntityAdapterBase.ts
index 2b45f61b291..c733334ed09 100644
--- a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasEntity/CanvasEntityAdapterBase.ts
+++ b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasEntity/CanvasEntityAdapterBase.ts
@@ -546,6 +546,14 @@ export abstract class CanvasEntityAdapterBase<T extends CanvasEntityState, U ext
     this.renderer.syncKonvaCache();
   };
 
+  /**
+   * Invalidates the raster cache for this entity by delegating to the renderer's
+   * `invalidateRasterCache` method.
+   */
+  invalidateRasterCache = () => {
+    this.renderer.invalidateRasterCache();
+  };
+
   /**
    * Synchronizes the entity's locked state with the canvas.
    */
diff --git a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasEntity/CanvasEntityObjectRenderer.ts b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasEntity/CanvasEntityObjectRenderer.ts
index 8bb8ec25319..57aea0630cd 100644
--- a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasEntity/CanvasEntityObjectRenderer.ts
+++ b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasEntity/CanvasEntityObjectRenderer.ts
@@ -65,6 +65,11 @@ export class CanvasEntityObjectRenderer extends CanvasModuleBase {
    */
   renderers = new SyncableMap<string, AnyObjectRenderer>();
 
+  /**
+   * Tracks the cache keys used when rasterizing this entity so they can be invalidated on demand.
+   */
+  rasterCacheKeys = new Set<string>();
+
   /**
    * A object containing singleton Konva nodes.
    */
@@ -476,7 +481,7 @@ export class CanvasEntityObjectRenderer extends CanvasModuleBase {
   }): Promise<ImageDTO> => {
     const rasterizingAdapter = this.manager.stateApi.$rasterizingAdapter.get();
     if (rasterizingAdapter) {
-      assert(false, `Already rasterizing an entity: ${rasterizingAdapter.id}`);
+      await this.manager.stateApi.waitForRasterizationToFinish();
     }
 
     const { rect, replaceObjects, attrs, bg, ignoreCache } = {
@@ -493,6 +498,7 @@ export class CanvasEntityObjectRenderer extends CanvasModuleBase {
     if (cachedImageName && !ignoreCache) {
       imageDTO = await getImageDTOSafe(cachedImageName);
       if (imageDTO) {
+        this.rasterCacheKeys.add(hash);
         this.log.trace({ rect, cachedImageName, imageDTO }, 'Using cached rasterized image');
         return imageDTO;
       }
@@ -524,6 +530,7 @@ export class CanvasEntityObjectRenderer extends CanvasModuleBase {
         replaceObjects,
       });
       this.manager.cache.imageNameCache.set(hash, imageDTO.image_name);
+      this.rasterCacheKeys.add(hash);
       return imageDTO;
     } catch (error) {
       this.log.error({ rasterizeArgs, error: serializeError(error as Error) }, 'Failed to rasterize entity');
@@ -533,6 +540,22 @@ export class CanvasEntityObjectRenderer extends CanvasModuleBase {
     }
   };
 
+  /**
+   * Invalidates all cached rasterizations for this entity by removing the cached image
+   * names from the image cache and clearing the tracked raster cache keys. This forces
+   * future rasterizations to regenerate images instead of using potentially stale
+   * cached versions.
+   */
+  invalidateRasterCache = () => {
+    if (this.rasterCacheKeys.size === 0) {
+      return;
+    }
+    for (const key of this.rasterCacheKeys) {
+      this.manager.cache.imageNameCache.delete(key);
+    }
+    this.rasterCacheKeys.clear();
+  };
+
   cloneObjectGroup = (arg: { attrs?: GroupConfig } = {}): Konva.Group => {
     const { attrs } = arg;
     const clone = this.konva.objectGroup.clone();
diff --git a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasManager.ts b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasManager.ts
index 38248136625..4b210cf327a 100644
--- a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasManager.ts
+++ b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasManager.ts
@@ -199,6 +199,17 @@ export class CanvasManager extends CanvasModuleBase {
     ];
   };
 
+  /**
+   * Invalidates the raster cache for all regional guidance adapters.
+   * This should be called when bbox or related regional guidance settings change
+   * to ensure that cached masks are regenerated with the new settings.
+   */
+  invalidateRegionalGuidanceRasterCache = () => {
+    for (const adapter of this.adapters.regionMasks.values()) {
+      adapter.invalidateRasterCache();
+    }
+  };
+
   createAdapter = (entityIdentifier: CanvasEntityIdentifier): CanvasEntityAdapter => {
     if (isRasterLayerEntityIdentifier(entityIdentifier)) {
       const adapter = new CanvasEntityAdapterRasterLayer(entityIdentifier, this);
diff --git a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasStateApiModule.ts b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasStateApiModule.ts
index 57027aaa8f9..dc2c0b15043 100644
--- a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasStateApiModule.ts
+++ b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasStateApiModule.ts
@@ -213,6 +213,52 @@ export class CanvasStateApiModule extends CanvasModuleBase {
    */
   setGenerationBbox = (rect: Rect) => {
     this.store.dispatch(bboxChangedFromCanvas(rect));
+    this.manager.invalidateRegionalGuidanceRasterCache();
+  };
+
+  /**
+   * Waits for the current rasterization operation to complete.
+   *
+   * If no rasterization is in progress, this returns immediately. Use this
+   * before starting a new rasterization to avoid multiple simultaneous
+   * rasterization operations acting on the same canvas state.
+   *
+   * @returns A promise that resolves once rasterization has finished or
+   *          immediately if no rasterization is in progress.
+   */
+  waitForRasterizationToFinish = async () => {
+    if (!this.$rasterizingAdapter.get()) {
+      return;
+    }
+
+    await new Promise<void>((resolve) => {
+      // Ensure we only resolve once, even if multiple events fire.
+      let resolved = false;
+
+      // Re-check before subscribing to avoid a race where rasterization completes
+      // between the outer check and listener registration.
+      if (!this.$rasterizingAdapter.get()) {
+        resolved = true;
+        resolve();
+        return;
+      }
+
+      const unsubscribe = this.$rasterizingAdapter.listen((adapter) => {
+        if (!adapter && !resolved) {
+          resolved = true;
+          unsubscribe();
+          resolve();
+        }
+      });
+
+      // Re-check immediately after subscribing to close the race where
+      // rasterization completes between the check above and `listen()`.
+      if (!this.$rasterizingAdapter.get() && !resolved) {
+        resolved = true;
+        unsubscribe();
+        resolve();
+      }
+    });
   };
 
   /**