diff --git a/invokeai/frontend/web/src/features/controlLayers/components/MaskOpacity.tsx b/invokeai/frontend/web/src/features/controlLayers/components/MaskOpacity.tsx
index 58c659c65b..d3372f4fae 100644
--- a/invokeai/frontend/web/src/features/controlLayers/components/MaskOpacity.tsx
+++ b/invokeai/frontend/web/src/features/controlLayers/components/MaskOpacity.tsx
@@ -13,7 +13,7 @@ export const MaskOpacity = memo(() => {
   const opacity = useAppSelector((s) => Math.round(s.canvasV2.settings.maskOpacity * 100));
   const onChange = useCallback(
     (v: number) => {
-      dispatch(maskOpacityChanged(v / 100));
+      dispatch(maskOpacityChanged(Math.max(v / 100, 0.25)));
     },
     [dispatch]
   );
@@ -22,7 +22,7 @@ export const MaskOpacity = memo(() => {
       <FormLabel m={0}>{t('controlLayers.globalMaskOpacity')}</FormLabel>
       <Flex gap={4}>
         <CompositeSlider
-          min={0}
+          min={25}
           max={100}
           step={1}
           value={opacity}
@@ -32,7 +32,7 @@ export const MaskOpacity = memo(() => {
           minW={48}
         />
         <CompositeNumberInput
-          min={0}
+          min={25}
           max={100}
           step={1}
           value={opacity}
diff --git a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasInpaintMask.ts b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasInpaintMask.ts
index d2ce4518df..8861e45fe9 100644
--- a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasInpaintMask.ts
+++ b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasInpaintMask.ts
@@ -20,6 +20,7 @@ export class CanvasInpaintMask {
   getLoggingContext: GetLoggingContext;
 
   state: CanvasInpaintMaskState;
+  maskOpacity: number;
 
   transformer: CanvasTransformer;
   renderer: CanvasObjectRenderer;
@@ -47,7 +48,7 @@ export class CanvasInpaintMask {
     };
 
     this.transformer = new CanvasTransformer(this);
-    this.renderer = new CanvasObjectRenderer(this, true);
+    this.renderer = new CanvasObjectRenderer(this);
     assert(this.renderer.konva.compositingRect, 'Compositing rect must be set');
 
     this.konva.layer.add(this.konva.objectGroup);
@@ -55,6 +56,7 @@ export class CanvasInpaintMask {
     this.konva.layer.add(...this.transformer.getNodes());
 
     this.state = state;
+    this.maskOpacity = this.manager.stateApi.getMaskOpacity();
   }
 
   destroy = (): void => {
@@ -67,14 +69,18 @@ export class CanvasInpaintMask {
 
   update = async (arg?: { state: CanvasInpaintMaskState; toolState: CanvasV2State['tool']; isSelected: boolean }) => {
     const state = get(arg, 'state', this.state);
+    const maskOpacity = this.manager.stateApi.getMaskOpacity();
 
-    if (!this.isFirstRender && state === this.state) {
+    if (
+      !this.isFirstRender &&
+      state === this.state &&
+      state.fill === this.state.fill &&
+      maskOpacity === this.maskOpacity
+    ) {
       this.log.trace('State unchanged, skipping update');
       return;
     }
 
-    // const maskOpacity = this.manager.stateApi.getMaskOpacity()
-
     this.log.debug('Updating');
     const { position, objects, isEnabled } = state;
 
@@ -82,18 +88,23 @@ export class CanvasInpaintMask {
       await this.updateObjects({ objects });
     }
     if (this.isFirstRender || position !== this.state.position) {
-      await this.transformer.updatePosition({ position });
+      this.transformer.updatePosition({ position });
     }
     // if (this.isFirstRender || opacity !== this.state.opacity) {
     //   await this.updateOpacity({ opacity });
     // }
     if (this.isFirstRender || isEnabled !== this.state.isEnabled) {
-      await this.updateVisibility({ isEnabled });
+      this.updateVisibility({ isEnabled });
+    }
+
+    if (this.isFirstRender || state.fill !== this.state.fill || maskOpacity !== this.maskOpacity) {
+      this.renderer.updateCompositingRect(state.fill, maskOpacity);
+      this.maskOpacity = maskOpacity;
     }
     // this.transformer.syncInteractionState();
 
     if (this.isFirstRender) {
-      await this.transformer.updateBbox();
+      this.transformer.updateBbox();
     }
 
     this.state = state;
@@ -110,8 +121,6 @@ export class CanvasInpaintMask {
     if (didUpdate) {
       this.transformer.requestRectCalculation();
     }
-
-    this.isFirstRender = false;
   };
 
   // updateOpacity = (arg?: { opacity: number }) => {
diff --git a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasManager.ts b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasManager.ts
index 6d80a45540..571eac133b 100644
--- a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasManager.ts
+++ b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasManager.ts
@@ -366,6 +366,7 @@ export class CanvasManager {
     let currentFill: RgbaColor = state.tool.fill;
     const selectedEntity = this.getSelectedEntity();
     if (selectedEntity) {
+      // These two entity types use a compositing rect for opacity. Their alpha is always 1.
       if (selectedEntity.state.type === 'regional_guidance') {
         currentFill = { ...selectedEntity.state.fill, a: 1 };
       } else if (selectedEntity.state.type === 'inpaint_mask') {
@@ -470,6 +471,7 @@ export class CanvasManager {
 
     if (
       this._isFirstRender ||
+      state.inpaintMask !== this._prevState.inpaintMask ||
       state.settings.maskOpacity !== this._prevState.settings.maskOpacity ||
       state.tool.selected !== this._prevState.tool.selected ||
       state.selectedEntityIdentifier?.id !== this._prevState.selectedEntityIdentifier?.id
diff --git a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasObjectRenderer.ts b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasObjectRenderer.ts
index 35ae6209d5..c62d2a3d68 100644
--- a/invokeai/frontend/web/src/features/controlLayers/konva/CanvasObjectRenderer.ts
+++ b/invokeai/frontend/web/src/features/controlLayers/konva/CanvasObjectRenderer.ts
@@ -14,6 +14,7 @@ import type {
   CanvasEraserLineState,
   CanvasImageState,
   CanvasRectState,
+  RgbColor,
 } from 'features/controlLayers/store/types';
 import Konva from 'konva';
 import type { Logger } from 'roarr';
@@ -58,11 +59,26 @@ export class CanvasObjectRenderer {
    */
   renderers: Map<string, AnyObjectRenderer> = new Map();
 
+  /**
+   * A object containing singleton Konva nodes.
+   */
   konva: {
+    /**
+     * The compositing rect is used to draw the inpaint mask as a single shape with a given opacity.
+     *
+     * When drawing multiple transparent shapes on a canvas, overlapping regions will be more opaque. This doesn't
+     * match the expectation for a mask, where all shapes should have the same opacity, even if they overlap.
+     *
+     * To prevent this, we use a trick. Instead of drawing all shapes at the desired opacity, we draw them at opacity of 1.
+     * Then we draw a single rect that covers the entire canvas at the desired opacity, with a globalCompositeOperation
+     * of 'source-in'. The shapes effectively become a mask for the "compositing rect".
+     *
+     * This node is only added when the parent of the renderer is an inpaint mask or region, which require this behavior.
+     */
     compositingRect: Konva.Rect | null;
   };
 
-  constructor(parent: CanvasLayer | CanvasInpaintMask, withCompositingRect: boolean = false) {
+  constructor(parent: CanvasLayer | CanvasInpaintMask) {
     this.id = getPrefixedId(CanvasObjectRenderer.TYPE);
     this.parent = parent;
     this.manager = parent.manager;
@@ -74,10 +90,11 @@ export class CanvasObjectRenderer {
       compositingRect: null,
     };
 
-    if (withCompositingRect) {
+    if (this.parent.type === 'inpaint_mask') {
       this.konva.compositingRect = new Konva.Rect({
         name: CanvasObjectRenderer.KONVA_COMPOSITING_RECT_NAME,
         listening: false,
+        globalCompositeOperation: 'source-in',
       });
       this.parent.konva.objectGroup.add(this.konva.compositingRect);
     }
@@ -131,27 +148,20 @@ export class CanvasObjectRenderer {
       didRender = (await this.renderObject(this.buffer)) || didRender;
     }
 
-    if (didRender && this.parent.type === 'inpaint_mask') {
-      assert(this.konva.compositingRect, 'Compositing rect must exist for inpaint mask');
-
-      // Convert the color to a string, stripping the alpha - the object group will handle opacity.
-      const rgbColor = rgbColorToString(this.parent.state.fill);
-      const maskOpacity = this.manager.stateApi.getMaskOpacity();
-
-      this.konva.compositingRect.setAttrs({
-        fill: rgbColor,
-        opacity: maskOpacity,
-        // Draw this rect only where there are non-transparent pixels under it (e.g. the mask shapes)
-        globalCompositeOperation: 'source-in',
-        visible: true,
-        // This rect must always be on top of all other shapes
-        // zIndex: this.renderers.size + 1,
-      });
-    }
-
     return didRender;
   };
 
+  updateCompositingRect = (fill: RgbColor, opacity: number) => {
+    this.log.trace('Updating compositing rect');
+    assert(this.konva.compositingRect, 'Missing compositing rect');
+
+    const rgbColor = rgbColorToString(fill);
+    this.konva.compositingRect.setAttrs({
+      fill: rgbColor,
+      opacity,
+    });
+  };
+
   /**
    * Renders the given object. If the object renderer does not exist, it will be created and its Konva group added to the
    * parent entity's object group.
@@ -230,12 +240,6 @@ export class CanvasObjectRenderer {
 
     this.buffer = objectState;
     return await this.renderObject(this.buffer, true);
-
-    // const didDraw = await this.renderObject(this.buffer, true);
-    // if (didDraw && this.konva.compositingRect) {
-    //   this.konva.compositingRect.zIndex(this.renderers.size + 1);
-    // }
-    // return didDraw;
   };
 
   /**