fix: avoid object head precheck for watermarked media

scripts/test-media-watermark-policy.mjs

@@ -116,6 +116,11 @@ await runTest('local storage route uses watermark access instead of exposing raw
 
   assert.match(source, /shouldWatermarkStorageResponse\(/);
   assert.match(source, /serveWatermarkedStorageFile\(/);
+  assert.doesNotMatch(
+    source,
+    /shouldWatermarkStorageResponse[\s\S]+?fileExistsAsync\(/,
+    'storage display route should not require a slow object HEAD before watermark rendering',
+  );
 });
 
 await runTest('download route applies watermark and checks authenticated no-watermark entitlement', () => {

src/app/api/download/route.ts

@@ -122,20 +122,21 @@ async function downloadLocalStorageFile(
   const mayAccessOriginal = canAccessOriginalMedia(watermarkAccess);
 
   if (shouldWatermark) {
-    if (!await localStorage.fileExistsAsync(key)) {
+    try {
+      const watermarked = await serveWatermarkedDownloadFile(key, contentType);
+      return buildDownloadResponse(
+        watermarked.buffer.buffer.slice(
+          watermarked.buffer.byteOffset,
+          watermarked.buffer.byteOffset + watermarked.buffer.byteLength,
+        ) as ArrayBuffer,
+        watermarked.contentType,
+        filename,
+        watermarked.buffer.byteLength,
+        disposition,
+      );
+    } catch {
       return NextResponse.json({ error: '文件不存在' }, { status: 404 });
     }
-    const watermarked = await serveWatermarkedDownloadFile(key, contentType);
-    return buildDownloadResponse(
-      watermarked.buffer.buffer.slice(
-        watermarked.buffer.byteOffset,
-        watermarked.buffer.byteOffset + watermarked.buffer.byteLength,
-      ) as ArrayBuffer,
-      watermarked.contentType,
-      filename,
-      watermarked.buffer.byteLength,
-      disposition,
-    );
   }
 
   const shouldTryObjectRedirect = contentType.startsWith('video/') || !localStorage.fileExists(key);

src/app/api/local-storage/[...path]/route.ts

@@ -18,11 +18,12 @@ export async function GET(request: NextRequest, { params }: { params: Promise<{
 
     const contentType = getContentType(filePath);
     if (shouldWatermarkStorageResponse(filePath, contentType, null)) {
-      if (!await localStorage.fileExistsAsync(filePath)) {
+      try {
+        const watermarked = await serveWatermarkedStorageFile(filePath, contentType);
+        return serveLocalBuffer(watermarked.key, watermarked.buffer, WATERMARK_CACHE_CONTROL, watermarked.contentType);
+      } catch {
         return NextResponse.json({ error: 'File not found' }, { status: 404 });
       }
-      const watermarked = await serveWatermarkedStorageFile(filePath, contentType);
-      return serveLocalBuffer(watermarked.key, watermarked.buffer, WATERMARK_CACHE_CONTROL, watermarked.contentType);
     }
 
     if (filePath.startsWith('thumbnails/')) {