diff --git a/src/components/ThumbnailStrip.tsx b/src/components/ThumbnailStrip.tsx
index f5094722..e5d6810e 100644
--- a/src/components/ThumbnailStrip.tsx
+++ b/src/components/ThumbnailStrip.tsx
@@ -45,6 +45,10 @@ export default function ThumbnailStrip({
 
   const cancelThumbnailRun = useCallback(() => {
     lastRunIdRef.current += 1;
+    if (offscreenVideoRef.current) {
+      offscreenVideoRef.current.src = "";
+      offscreenVideoRef.current.load();
+    }
   }, []);
 
   const generateThumbnails = useCallback(async () => {
@@ -97,8 +101,15 @@ export default function ThumbnailStrip({
 
         const time = times[i] ?? 0;
         await new Promise<void>((resolve) => {
-          const onSeeked = async () => {
+          let timeoutId: number | undefined;
+
+          const cleanup = () => {
             video.removeEventListener("seeked", onSeeked);
+            if (timeoutId) window.clearTimeout(timeoutId);
+          };
+
+          const onSeeked = async () => {
+            cleanup();
 
             if (lastRunIdRef.current !== runId) {
               resolve();
@@ -127,6 +138,13 @@ export default function ThumbnailStrip({
             setProgress(Math.round(((i + 1) / times.length) * 100));
             resolve();
           };
+
+          // Setup timeout fallback (2 seconds max per seek to prevent hang)
+          timeoutId = window.setTimeout(() => {
+            cleanup();
+            resolve();
+          }, 2000);
+
           video.addEventListener("seeked", onSeeked);
           video.currentTime = time;
         });
diff --git a/src/hooks/useAudioWaveform.ts b/src/hooks/useAudioWaveform.ts
index 25ed57d5..a46520d2 100644
--- a/src/hooks/useAudioWaveform.ts
+++ b/src/hooks/useAudioWaveform.ts
@@ -45,6 +45,13 @@ export function useAudioWaveform(
         return;
       }
 
+      // Skip decoding for files larger than 100MB to prevent browser OOM crash
+      if (file.size > 100 * 1024 * 1024) {
+        setWaveform([]);
+        setIsLoading(false);
+        return;
+      }
+
       const AudioContextCtor =
         window.AudioContext || (window as BrowserWindow).webkitAudioContext;