diff --git a/mods/features/adblock.js b/mods/features/adblock.js
index d9959264..06720011 100644
--- a/mods/features/adblock.js
+++ b/mods/features/adblock.js
@@ -341,24 +341,27 @@ function deArrowify(items) {
   }
 }
 
-
 function hqify(items) {
   for (const item of items) {
     if (!item.tileRenderer) continue;
     if (item.tileRenderer.style !== 'TILE_STYLE_YTLR_DEFAULT') continue;
-    if (configRead('enableHqThumbnails')) {
-      if (!item.tileRenderer.onSelectCommand?.watchEndpoint?.videoId) continue;
-      if (!item.tileRenderer.header?.tileHeaderRenderer?.thumbnail?.thumbnails?.[0]?.url) continue;
-      const videoID = item.tileRenderer.onSelectCommand.watchEndpoint.videoId;
-      const queryArgs = item.tileRenderer.header.tileHeaderRenderer.thumbnail.thumbnails[0].url.split('?')[1];
-      item.tileRenderer.header.tileHeaderRenderer.thumbnail.thumbnails = [
-        {
-          url: `https://i.ytimg.com/vi/${videoID}/sddefault.jpg${queryArgs ? `?${queryArgs}` : ''}`,
-          width: 640,
-          height: 480
-        }
-      ];
-    }
+    if (!configRead('enableHqThumbnails')) continue;
+    const videoID = item.tileRenderer.onSelectCommand?.watchEndpoint?.videoId;
+    if (!videoID) continue;
+    // Guard: some home page tiles have no thumbnail yet (lazy-loaded) — skip rather than crash.
+    const existingUrl = item.tileRenderer.header?.tileHeaderRenderer?.thumbnail?.thumbnails?.[0]?.url;
+    if (!existingUrl) continue;
+    // Do NOT carry over query args: the original `sqp` param is a signed token tied to the
+    // original filename — reusing it on a different filename causes a CDN signature mismatch
+    // and YouTube returns the grey "not available" placeholder instead of the real thumbnail.
+    // Start with hqdefault (guaranteed for every video), then async-upgrade to
+    // sddefault (640x480) if it exists on the CDN. On a TV the JSON parse →
+    // layout pipeline is slow enough that the HEAD usually resolves in time.
+    const thumbs = item.tileRenderer.header.tileHeaderRenderer.thumbnail.thumbnails;
+    thumbs[0] = { url: `https://i.ytimg.com/vi/${videoID}/hqdefault.jpg`, width: 480, height: 360 };
+    fetch(`https://i.ytimg.com/vi/${videoID}/sddefault.jpg`, { method: 'HEAD' })
+      .then(res => { if (res.ok) thumbs[0] = { url: `https://i.ytimg.com/vi/${videoID}/sddefault.jpg`, width: 640, height: 480 }; })
+      .catch(() => {});
   }
 }