diff --git a/src/app/components/url-preview/UrlPreviewCard.tsx b/src/app/components/url-preview/UrlPreviewCard.tsx
index c408bf3e9..d5e1ddf6b 100644
--- a/src/app/components/url-preview/UrlPreviewCard.tsx
+++ b/src/app/components/url-preview/UrlPreviewCard.tsx
@@ -1965,16 +1965,29 @@ function GenericCard({
   const description = prev['og:description'] ?? '';
   const siteName = typeof prev['og:site_name'] === 'string' ? prev['og:site_name'] : undefined;
 
+  // Synapse returns 400 from the thumbnail endpoint when it can't thumbnail a
+  // cached preview image (e.g. SVG/animated). Fall back to the full image, then
+  // hide entirely if that also fails — otherwise the card shows a broken image
+  // and the browser keeps re-requesting the failing thumbnail (console spam).
+  const [useFullImg, setUseFullImg] = useState(false);
+  const [imgFailed, setImgFailed] = useState(false);
+  const displayThumb = useFullImg ? imgUrl : thumbUrl;
+  const handleImgError = () => {
+    if (!useFullImg && imgUrl && imgUrl !== thumbUrl) setUseFullImg(true);
+    else setImgFailed(true);
+  };
+
   return (
     <>
-      {thumbUrl && (
+      {!imgFailed && displayThumb && (
         <UrlPreviewImg
-          src={thumbUrl}
+          src={displayThumb}
           alt={prev['og:title']}
           title={prev['og:title']}
           tabIndex={0}
           onKeyDown={(evt) => onEnterOrSpace(() => onOpenViewer())(evt)}
           onClick={onOpenViewer}
+          onError={handleImgError}
         />
       )}
       {imgUrl && (
@@ -1997,7 +2010,7 @@ function GenericCard({
           size="T200"
           priority="300"
         >
-          {!thumbUrl && (
+          {(!displayThumb || imgFailed) && (
             <Icon
               src={Icons.Link}
               size="50"
diff --git a/src/index.tsx b/src/index.tsx
index 25e6f5da0..0ebabbf03 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -68,13 +68,25 @@ window.addEventListener('vite:preloadError', () => {
 // Clear the reload flag after a successful load so future deploys can still trigger a reload
 window.addEventListener('load', () => sessionStorage.removeItem('chunk-reload-attempted'));
 
-// Synapse does not yet ship MSC3786/MSC3914 as server-default push rules.
-// matrix-js-sdk patches them client-side on every login and logs a warn for each.
-// Suppress the noise until Synapse implements these MSCs upstream.
+// Filter out known-benign, high-volume matrix-js-sdk console warnings that we
+// can't fix client-side and that would otherwise flood the console:
+//   - "Adding default global …": the SDK patches MSC3786/MSC3914 push rules on
+//     every login (one warn each) until Synapse ships them as server defaults.
+//   - "EventTimelineSet…": the SDK loudly warns whenever a decrypted event
+//     references a thread/room the current timeline set doesn't hold, then
+//     discards it harmlessly. This fires constantly in E2EE rooms with threads.
+//   - "Decrypted event … is not in room …": same family — a late decryption for
+//     an event the room's timeline no longer tracks; ignored by the SDK.
+// These are informational SDK bookkeeping, not errors; real warnings still log.
 {
+  const suppressedPrefixes = ['Adding default global ', 'EventTimelineSet'];
   const _warn = console.warn.bind(console);
   console.warn = (...args: unknown[]) => {
-    if (typeof args[0] === 'string' && args[0].startsWith('Adding default global ')) return;
+    const first = args[0];
+    if (typeof first === 'string') {
+      if (suppressedPrefixes.some((p) => first.startsWith(p))) return;
+      if (first.startsWith('Decrypted event ') && first.includes('is not in room')) return;
+    }
     _warn(...args);
   };
 }