diff --git a/src/components/LibraryApp.tsx b/src/components/LibraryApp.tsx
index 3fdf788..6412511 100644
--- a/src/components/LibraryApp.tsx
+++ b/src/components/LibraryApp.tsx
@@ -66,7 +66,7 @@ export default function LibraryApp() {
           {items.map((v) => (
             <article key={v.id} className={`kachel ${sel.has(v.id) ? 'gewaehlt' : ''}`}>
               <div className="kachel-bild" onClick={() => toggle(v.id)}>
-                <img src={`/api/items/${v.id}/file`} alt="" loading="lazy" />
+                <img src={`/api/items/${v.id}/file?thumb=1`} alt="" loading="lazy" />
                 <span className="haken">{sel.has(v.id) ? '✓' : ''}</span>
               </div>
               <input className="name" defaultValue={v.filename || ''} onBlur={(e) => rename(v.id, e.target.value)} />
diff --git a/src/pages/api/items/[id]/file.ts b/src/pages/api/items/[id]/file.ts
index 13515e9..2ada5e3 100644
--- a/src/pages/api/items/[id]/file.ts
+++ b/src/pages/api/items/[id]/file.ts
@@ -7,15 +7,23 @@ export const prerender = false;
 // Streamt das Ergebnis- (oder Quell-)Bild aus dem Objektspeicher.
 export const GET: APIRoute = async ({ params, url, locals }) => {
   if (!locals.user) return new Response('Unauthorized', { status: 401 });
-  const which = url.searchParams.get('src') === '1' ? 'source_path' : 'result_path';
-  const item = await one<any>(`SELECT ${which} AS path, filename, has_alpha FROM items WHERE id=$1`, [params.id]);
-  if (!item?.path) return new Response('Nicht gefunden', { status: 404 });
+  const q = url.searchParams;
+  const wantThumb = q.get('thumb') === '1';
+  const wantSrc = q.get('src') === '1';
+  const item = await one<any>(
+    `SELECT source_path, result_path, thumb_path, filename, has_alpha FROM items WHERE id=$1`, [params.id]);
+  // Vorschau: Thumbnail bevorzugen, sonst Ergebnis. Quelle nur explizit.
+  const path = wantSrc ? item?.source_path
+    : wantThumb ? (item?.thumb_path || item?.result_path)
+    : item?.result_path;
+  if (!path) return new Response('Nicht gefunden', { status: 404 });
   try {
-    const buf = await getObject(item.path);
-    const download = url.searchParams.get('download') === '1';
+    const buf = await getObject(path);
+    const download = q.get('download') === '1';
+    const isWebp = path.endsWith('.webp');
     return new Response(buf, {
       headers: {
-        'Content-Type': item.has_alpha ? 'image/png' : 'image/png',
+        'Content-Type': isWebp ? 'image/webp' : 'image/png',
         'Cache-Control': 'private, max-age=300',
         ...(download ? { 'Content-Disposition': `attachment; filename="${item.filename || 'klarbild.png'}"` } : {}),
       },