diff --git a/extensions/diffs/src/browser.test.ts b/extensions/diffs/src/browser.test.ts
index 48ff91b40..e23dec9e7 100644
--- a/extensions/diffs/src/browser.test.ts
+++ b/extensions/diffs/src/browser.test.ts
@@ -58,6 +58,12 @@ describe("PlaywrightDiffScreenshotter", () => {
 
     expect(launchMock).toHaveBeenCalledTimes(1);
     expect(browser.newPage).toHaveBeenCalledTimes(2);
+    expect(browser.newPage).toHaveBeenNthCalledWith(
+      1,
+      expect.objectContaining({
+        deviceScaleFactor: 2,
+      }),
+    );
     expect(pages).toHaveLength(2);
     expect(pages[0]?.close).toHaveBeenCalledTimes(1);
     expect(pages[1]?.close).toHaveBeenCalledTimes(1);
diff --git a/extensions/diffs/src/browser.ts b/extensions/diffs/src/browser.ts
index 0ca661d7e..c5a8b38c1 100644
--- a/extensions/diffs/src/browser.ts
+++ b/extensions/diffs/src/browser.ts
@@ -122,15 +122,29 @@ export class PlaywrightDiffScreenshotter implements DiffScreenshotter {
         throw new Error("Diff frame was lost after resizing.");
       }
 
+      const dpr = await page.evaluate(() => window.devicePixelRatio || 1);
+
+      // Raw clip in CSS px
+      const rawX = Math.max(box.x - padding, 0);
+      const rawY = Math.max(box.y - padding, 0);
+      const rawRight = rawX + clipWidth;
+      const rawBottom = rawY + clipHeight;
+
+      // Snap to device-pixel grid to avoid soft text from sub-pixel crop
+      const x = Math.floor(rawX * dpr) / dpr;
+      const y = Math.floor(rawY * dpr) / dpr;
+      const right = Math.ceil(rawRight * dpr) / dpr;
+      const bottom = Math.ceil(rawBottom * dpr) / dpr;
+
       await page.screenshot({
         path: params.outputPath,
         type: "png",
         scale: "device",
         clip: {
-          x: Math.max(box.x - padding, 0),
-          y: Math.max(box.y - padding, 0),
-          width: clipWidth,
-          height: clipHeight,
+          x,
+          y,
+          width: right - x,
+          height: bottom - y,
         },
       });
       return params.outputPath;
@@ -233,7 +247,7 @@ async function acquireSharedBrowser(params: {
       .launch({
         headless: true,
         ...(executablePath ? { executablePath } : {}),
-        args: ["--disable-dev-shm-usage", "--disable-gpu"],
+        args: ["--disable-dev-shm-usage"],
       })
       .then((browser) => {
         if (sharedBrowserState?.browserPromise === browserPromise) {
diff --git a/extensions/diffs/src/render.test.ts b/extensions/diffs/src/render.test.ts
index e9b7f764a..b0ce38cc8 100644
--- a/extensions/diffs/src/render.test.ts
+++ b/extensions/diffs/src/render.test.ts
@@ -24,6 +24,9 @@ describe("renderDiffDocument", () => {
     expect(rendered.html).toContain("/plugins/diffs/assets/viewer.js");
     expect(rendered.imageHtml).not.toContain("/plugins/diffs/assets/viewer.js");
     expect(rendered.imageHtml).toContain('data-openclaw-diffs-ready="true"');
+    expect(rendered.imageHtml).toContain("max-width: 960px;");
+    expect(rendered.imageHtml).toContain("--diffs-font-size: 16px;");
+    expect(rendered.html).toContain("--diffs-font-size: 15px;");
     expect(rendered.html).not.toContain("fonts.googleapis.com");
   });
 
diff --git a/extensions/diffs/src/render.ts b/extensions/diffs/src/render.ts
index a6ebd29d9..53de0c0a8 100644
--- a/extensions/diffs/src/render.ts
+++ b/extensions/diffs/src/render.ts
@@ -136,6 +136,16 @@ function buildDiffOptions(options: DiffRenderOptions): DiffViewerOptions {
   };
 }
 
+function buildImageRenderOptions(options: DiffRenderOptions): DiffRenderOptions {
+  return {
+    ...options,
+    presentation: {
+      ...options.presentation,
+      fontSize: Math.max(16, options.presentation.fontSize),
+    },
+  };
+}
+
 function normalizeSupportedLanguage(value?: string): SupportedLanguages | undefined {
   const normalized = value?.trim();
   return normalized ? (normalized as SupportedLanguages) : undefined;
@@ -225,7 +235,7 @@ function buildHtmlDocument(params: {
       }
 
       .oc-frame[data-render-mode="image"] {
-        max-width: 1120px;
+        max-width: 960px;
       }
 
       [data-openclaw-diff-root] {
@@ -293,22 +303,33 @@ async function renderBeforeAfterDiff(
     contents: input.after,
     ...(lang ? { lang } : {}),
   };
-  const payloadOptions = buildDiffOptions(options);
-  const result = await preloadMultiFileDiff({
-    oldFile,
-    newFile,
-    options: payloadOptions,
-  });
+  const viewerPayloadOptions = buildDiffOptions(options);
+  const imagePayloadOptions = buildDiffOptions(buildImageRenderOptions(options));
+  const [viewerResult, imageResult] = await Promise.all([
+    preloadMultiFileDiff({
+      oldFile,
+      newFile,
+      options: viewerPayloadOptions,
+    }),
+    preloadMultiFileDiff({
+      oldFile,
+      newFile,
+      options: imagePayloadOptions,
+    }),
+  ]);
 
   return {
     viewerBodyHtml: renderDiffCard({
-      prerenderedHTML: result.prerenderedHTML,
-      oldFile: result.oldFile,
-      newFile: result.newFile,
-      options: payloadOptions,
-      langs: buildPayloadLanguages({ oldFile: result.oldFile, newFile: result.newFile }),
+      prerenderedHTML: viewerResult.prerenderedHTML,
+      oldFile: viewerResult.oldFile,
+      newFile: viewerResult.newFile,
+      options: viewerPayloadOptions,
+      langs: buildPayloadLanguages({
+        oldFile: viewerResult.oldFile,
+        newFile: viewerResult.newFile,
+      }),
     }),
-    imageBodyHtml: renderStaticDiffCard(result.prerenderedHTML),
+    imageBodyHtml: renderStaticDiffCard(imageResult.prerenderedHTML),
     fileCount: 1,
   };
 }
@@ -322,22 +343,29 @@ async function renderPatchDiff(
     throw new Error("Patch input did not contain any file diffs.");
   }
 
-  const payloadOptions = buildDiffOptions(options);
+  const viewerPayloadOptions = buildDiffOptions(options);
+  const imagePayloadOptions = buildDiffOptions(buildImageRenderOptions(options));
   const sections = await Promise.all(
     files.map(async (fileDiff) => {
-      const result = await preloadFileDiff({
-        fileDiff,
-        options: payloadOptions,
-      });
+      const [viewerResult, imageResult] = await Promise.all([
+        preloadFileDiff({
+          fileDiff,
+          options: viewerPayloadOptions,
+        }),
+        preloadFileDiff({
+          fileDiff,
+          options: imagePayloadOptions,
+        }),
+      ]);
 
       return {
         viewer: renderDiffCard({
-          prerenderedHTML: result.prerenderedHTML,
-          fileDiff: result.fileDiff,
-          options: payloadOptions,
-          langs: buildPayloadLanguages({ fileDiff: result.fileDiff }),
+          prerenderedHTML: viewerResult.prerenderedHTML,
+          fileDiff: viewerResult.fileDiff,
+          options: viewerPayloadOptions,
+          langs: buildPayloadLanguages({ fileDiff: viewerResult.fileDiff }),
         }),
-        image: renderStaticDiffCard(result.prerenderedHTML),
+        image: renderStaticDiffCard(imageResult.prerenderedHTML),
       };
     }),
   );