diff --git a/app/api/canvas/local-edit/route.ts b/app/api/canvas/local-edit/route.ts
index 04a54f42f..ae64a4f93 100644
--- a/app/api/canvas/local-edit/route.ts
+++ b/app/api/canvas/local-edit/route.ts
@@ -780,6 +780,16 @@ function buildScaleAdjustCompositeRegions(
   });
 }
 
+function buildScaleAdjustPatchCompositeRegions(
+  regions: NormalizedLocalEditRegion[],
+  scalePercent?: ScaleAdjustPercent | null
+) {
+  return regions.flatMap((region) => [
+    region.rect,
+    getScaleAdjustTargetRect(region, scalePercent),
+  ]);
+}
+
 function getScaleAdjustPatchWorkspaceRect(
   regions: NormalizedLocalEditRegion[],
   scalePercent?: ScaleAdjustPercent | null
@@ -3860,6 +3870,9 @@ export async function POST(request: NextRequest) {
     const scaleAdjustCompositeRegions = isScaleAdjustOperation
       ? buildScaleAdjustCompositeRegions(regions, scalePercent)
       : [];
+    const scaleAdjustPatchCompositeRegions = isScaleAdjustOperation
+      ? buildScaleAdjustPatchCompositeRegions(regions, scalePercent)
+      : [];
     const scaleAdjustProtectedRegions =
       isScaleAdjustOperation && scaleAdjustPatchReference
         ? [...scaleAdjustCompositeRegions, scaleAdjustPatchReference.workspaceRect]
@@ -4060,9 +4073,14 @@ export async function POST(request: NextRequest) {
       referenceImages,
       scaleAdjustPatchComposite: scaleAdjustPatchReference
         ? {
+            diffCompareBlurPx: 0.8,
+            diffHighThreshold: 42,
+            diffLowThreshold: 14,
             featherMaxPx: 42,
             featherMinPx: 10,
             featherRatio: 0.018,
+            maskMode: "diff",
+            regions: scaleAdjustPatchCompositeRegions,
             sourceImageUrl,
             workspaceRegion: scaleAdjustPatchReference.workspaceRect,
           }
diff --git a/lib/canvas/generate-image.ts b/lib/canvas/generate-image.ts
index 28617af9b..1002ef17c 100644
--- a/lib/canvas/generate-image.ts
+++ b/lib/canvas/generate-image.ts
@@ -57,6 +57,10 @@ export interface CanvasScaleAdjustPatchCompositeConfig {
   sourceImageUrl: string;
   workspaceRegion: CanvasLocalEditCompositeRegion;
   regions?: CanvasLocalEditCompositeRegion[];
+  maskMode?: "workspace" | "diff";
+  diffLowThreshold?: number;
+  diffHighThreshold?: number;
+  diffCompareBlurPx?: number;
   featherMinPx?: number;
   featherMaxPx?: number;
   featherRatio?: number;
@@ -397,6 +401,19 @@ function normalizeScaleAdjustPatchCompositeConfig(
     sourceImageUrl,
     workspaceRegion,
     ...(regions.length > 0 ? { regions } : {}),
+    maskMode: value.maskMode === "diff" ? "diff" : "workspace",
+    diffHighThreshold: normalizeOptionalNumber(value.diffHighThreshold, {
+      max: 120,
+      min: 1,
+    }),
+    diffLowThreshold: normalizeOptionalNumber(value.diffLowThreshold, {
+      max: 80,
+      min: 0,
+    }),
+    diffCompareBlurPx: normalizeOptionalNumber(value.diffCompareBlurPx, {
+      max: 12,
+      min: 0,
+    }),
     featherMaxPx: normalizeOptionalNumber(value.featherMaxPx, {
       max: 180,
       min: 0,
@@ -2748,27 +2765,69 @@ async function applyScaleAdjustPatchCompositeToImages(params: {
       };
     })
     .filter((box) => box.width > 0 && box.height > 0);
-  const patchMask = buildScaleAdjustPatchCompositeMaskSvg({
-    featherPx,
-    height: workspaceBox.height,
-    regions: maskRegionBoxes,
-    touchesBottom,
-    touchesLeft,
-    touchesRight,
-    touchesTop,
-    width: workspaceBox.width,
-  });
+  const staticPatchMask =
+    composite.maskMode === "diff"
+      ? null
+      : buildScaleAdjustPatchCompositeMaskSvg({
+          featherPx,
+          height: workspaceBox.height,
+          regions: maskRegionBoxes,
+          touchesBottom,
+          touchesLeft,
+          touchesRight,
+          touchesTop,
+          width: workspaceBox.width,
+        });
+  const sourcePatchBuffer = await sharp(sourceBuffer, { failOn: "none" })
+    .extract(workspaceBox)
+    .png({ compressionLevel: 6 })
+    .toBuffer();
+  const diffRegions = (maskRegionBoxes?.length
+    ? maskRegionBoxes
+    : [{ left: 0, top: 0, width: workspaceBox.width, height: workspaceBox.height }]
+  ).map((box) => ({
+    x: box.left / Math.max(1, workspaceBox.width),
+    y: box.top / Math.max(1, workspaceBox.height),
+    width: box.width / Math.max(1, workspaceBox.width),
+    height: box.height / Math.max(1, workspaceBox.height),
+  }));
 
   const mergedImages: ParsedImage[] = [];
   for (const [index, image] of images.entries()) {
     const generatedUrl = image.originalUrl || image.thumbnailUrl;
     const generatedBuffer = await fetchImageBufferFromUrl(generatedUrl);
-    const patchOverlayBuffer = await sharp(generatedBuffer, { failOn: "none" })
+    const resizedGeneratedBuffer = await sharp(generatedBuffer, { failOn: "none" })
       .rotate()
       .resize(workspaceBox.width, workspaceBox.height, {
         fit: "cover",
         position: "center",
       })
+      .png({ compressionLevel: 6 })
+      .toBuffer();
+    const patchMask =
+      composite.maskMode === "diff"
+        ? await buildLocalEditDiffCompositeMask({
+            composite: {
+              diffCompareBlurPx: composite.diffCompareBlurPx,
+              diffHighThreshold: composite.diffHighThreshold,
+              diffLowThreshold: composite.diffLowThreshold,
+              featherMaxPx: composite.featherMaxPx,
+              featherMinPx: composite.featherMinPx,
+              featherRatio: composite.featherRatio,
+              maskMode: "diff",
+              regions: diffRegions,
+              sourceImageUrl: composite.sourceImageUrl,
+            },
+            generatedBuffer: resizedGeneratedBuffer,
+            height: workspaceBox.height,
+            sourceBuffer: sourcePatchBuffer,
+            width: workspaceBox.width,
+          })
+        : staticPatchMask;
+    if (!patchMask) {
+      throw new Error("比例调整局部结果合成失败：无法生成合成蒙版");
+    }
+    const patchOverlayBuffer = await sharp(resizedGeneratedBuffer, { failOn: "none" })
       .ensureAlpha()
       .composite([{ input: patchMask, blend: "dest-in" }])
       .png({ compressionLevel: 6 })
@@ -2811,6 +2870,7 @@ async function applyScaleAdjustPatchCompositeToImages(params: {
     debugLabel,
     featherPx,
     imageCount: mergedImages.length,
+    maskMode: composite.maskMode || "workspace",
     maskRegionCount: maskRegionBoxes?.length || 0,
     sourceHeight,
     sourceWidth,