diff --git a/app/layout.tsx b/app/layout.tsx
index 117443a..6159151 100644
--- a/app/layout.tsx
+++ b/app/layout.tsx
@@ -147,7 +147,7 @@ export default function RootLayout({
       <body className="antialiased">
         <ThemeProvider
           attribute="class"
-          defaultTheme="system"
+          defaultTheme="dark"
           disableTransitionOnChange
           enableSystem
         >
diff --git a/components/image-annotator.tsx b/components/image-annotator.tsx
index 6e14a9d..5aa747d 100644
--- a/components/image-annotator.tsx
+++ b/components/image-annotator.tsx
@@ -564,8 +564,11 @@ export function ImageAnnotator({ imageUrl, onConfirm, onCancel }: ImageAnnotator
   };
 
   return (
-    <div className="fixed inset-0 z-[9999] flex items-center justify-center bg-black/70 backdrop-blur-md p-4" onClick={onCancel}>
-      {/* 弹窗容器 - 固定在屏幕中央，固定大小 */}
+    <div 
+      className="fixed inset-0 z-[9999] flex items-center justify-center bg-black/70 backdrop-blur-md p-4"
+      onClick={onCancel}
+    >
+      {/* 弹窗容器 - 使用与preview-attachment相同的居中方式 */}
       <div 
         className="flex flex-col overflow-hidden rounded-xl border border-border bg-background shadow-2xl"
         style={{