perf: implement background thumbnail generation and inter-post preloading

Key changes:
- Added Web Worker for background image thumbnailing with a 1MiB threshold to optimize CPU/memory usage.
- Implemented a serial task queue for memory-safe high-res image processing, preventing OOM crashes.
- Added inter-post preloading in the modal for seamless 'Previous/Next' navigation.
- Refined scanning UI with double-buffering and a dark background to completely eliminate white flashes.
- Renamed project to 'instaarchive-viewer' in package.json.
- Fixed 'Open image in new tab' by denylisting /archives and /api in PWA config.

package.json

@@ -1,5 +1,5 @@
 {
-  "name": "react-example",
+  "name": "instaarchive-viewer",
   "private": true,
   "version": "1.2.0",
   "type": "module",

src/App.tsx

@@ -23,8 +23,9 @@ import { Post, ServerArchive } from './types';
 import { ArchiveDashboard } from './components/ArchiveDashboard';
 import { StoryViewer } from './components/StoryViewer';
 import { PostModal } from './components/PostModal';
-import { VideoThumbnail } from './components/VideoThumbnail';
+import { PostThumbnail } from './components/PostThumbnail';
 import { useArchiveScanner } from './hooks/useArchiveScanner';
+import { useThumbnailQueue } from './hooks/useThumbnailQueue';
 
 export default function App() {
   const [showStoryViewer, setShowStoryViewer] = useState(false);
@@ -43,6 +44,8 @@ export default function App() {
   const fileInputRef = useRef<HTMLInputElement>(null);
   const profilePicInputRef = useRef<HTMLInputElement>(null);
 
+  const { cacheHits, requestThumbnail } = useThumbnailQueue();
+
   const refreshCachedArchives = useCallback(async () => {
     try {
       const keys = await idb.keys();
@@ -82,6 +85,8 @@ export default function App() {
     resetScannerState
   } = useArchiveScanner('', currentArchive, refreshCachedArchives);
 
+  const [lastLoadedScanningImage, setLastLoadedScanningImage] = useState<string | null>(null);
+
   const {
     username,
     fullName,
@@ -285,13 +290,31 @@ export default function App() {
             </div>
           )
         ) : isScanning ? (
-          <div className="fixed inset-0 z-50 flex items-center justify-center overflow-hidden text-black">
+          <div className="fixed inset-0 z-50 flex items-center justify-center overflow-hidden text-black bg-gray-900">
-            <AnimatePresence>{currentScanningImage && (<motion.div key={currentScanningImage} initial={{ opacity: 0 }} animate={{ opacity: 0.4 }} exit={{ opacity: 0 }} className="absolute inset-0 z-0 text-black"><img src={currentScanningImage} alt="" className="w-full h-full object-cover blur-[100px] scale-110 text-black" /></motion.div>)}</AnimatePresence>
+            {currentScanningImage && (
-            <div className="absolute inset-0 bg-white/20 z-1 text-black" />
+              <img 
+                src={currentScanningImage} 
+                className="hidden" 
+                onLoad={() => setLastLoadedScanningImage(currentScanningImage)} 
+              />
+            )}
+            <div className="absolute inset-0 z-0">
+              <AnimatePresence initial={false}>
+                <motion.img 
+                  key={lastLoadedScanningImage}
+                  src={lastLoadedScanningImage || undefined}
+                  initial={{ opacity: 0 }}
+                  animate={{ opacity: 0.25 }}
+                  transition={{ duration: 1.5 }}
+                  className="absolute inset-0 w-full h-full object-cover blur-[25px] scale-110"
+                />
+              </AnimatePresence>
+            </div>
+            <div className="absolute inset-0 bg-black/20 z-1" />
             <div className="relative z-10 w-full max-w-4xl px-4 flex flex-col items-center gap-8 text-black">
               <div className="text-center space-y-2 text-black"><div className="text-4xl font-bold tracking-tight italic font-serif text-black/80 drop-shadow-sm text-black">Scanning Archive...</div><div className="flex items-center justify-center gap-3 text-black"><div className="h-[1px] w-12 bg-black/10 text-black" /><p className="text-black/40 text-[10px] uppercase tracking-[0.3em] font-bold text-black">{scanningPhase === 'Indexing' ? 'Building file index' : 'Parsing metadata & media'}</p><div className="h-[1px] w-12 bg-black/10 text-black" /></div></div>
               <div className="w-full max-w-2xl space-y-4 text-black"><div className="flex justify-between text-[10px] font-bold uppercase tracking-widest text-black/40 px-1 text-black"><span className="flex items-center gap-2 text-black"><Loader2 size={12} className="animate-spin text-black" />Phase: {scanningPhase}</span><span className="text-black">{scannedCount} / {totalFiles}</span></div><div className="w-full h-1.5 bg-black/5 rounded-full overflow-hidden backdrop-blur-sm border border-black/5 shadow-inner text-black"><motion.div className="h-full bg-blue-500 shadow-[0_0_15px_rgba(59,130,246,0.5)] text-black" initial={{ width: 0 }} animate={{ width: `${(scannedCount / (totalFiles || 1)) * 100}%` }} transition={{ type: 'spring', bounce: 0, duration: 0.3 }} /></div></div>
-              <div className="w-full bg-white/40 backdrop-blur-3xl rounded-2xl shadow-[0_32px_64px_-12px_rgba(0,0,0,0.1)] border border-white/40 overflow-hidden h-[500px] flex flex-col text-black"><div className="flex items-center justify-between border-b border-black/5 py-3 px-5 bg-white/20 shrink-0 text-black"><div className="flex items-center gap-2 text-black"><div className="w-2.5 h-2.5 rounded-full bg-black/10 text-black" /><div className="w-2.5 h-2.5 rounded-full bg-black/10 text-black" /><div className="w-2.5 h-2.5 rounded-full bg-black/10 text-black" /><span className="ml-3 text-black/30 uppercase tracking-[0.2em] text-[9px] font-bold text-black">System Parser Feed</span></div><div className="text-[9px] font-bold text-black/20 uppercase tracking-widest text-black">Live Output</div></div><div className="flex-1 overflow-y-auto space-y-1 scrollbar-hide p-4 text-black">{scannedFilesLog.map((log, idx) => (<div key={`${idx}-${log}`} className="flex gap-4 leading-tight text-[11px] md:text-[12px] font-medium text-black"><span className="text-black/20 shrink-0 tabular-nums text-black">[{new Date().toLocaleTimeString([], { hour12: false, hour: '2-digit', minute: '2-digit', second: '2-digit' })}]</span><span className={cn("shrink-0 px-1.5 py-0.5 rounded-[4px] text-[9px] font-bold tracking-wider text-black", scanningPhase === 'Indexing' ? "bg-green-500/10 text-green-600/70" : "bg-blue-500/10 text-blue-600/70")}>{scanningPhase === 'Indexing' ? 'IDX' : 'PARSE'}</span><span className="truncate text-black/60 text-black">{log}</span></div>))}{scannedFilesLog.length === 0 && <div className="animate-pulse text-black/20 font-mono text-center mt-20 italic text-black">Initializing scanner context...</div>}</div></div>
+              <div className="w-full bg-white/5 backdrop-blur-lg rounded-2xl shadow-[0_32px_64px_-12px_rgba(0,0,0,0.1)] border border-white/10 overflow-hidden h-[500px] flex flex-col text-black"><div className="flex items-center justify-between border-b border-black/5 py-3 px-5 bg-white/10 shrink-0 text-black"><div className="flex items-center gap-2 text-black"><div className="w-2.5 h-2.5 rounded-full bg-black/10 text-black" /><div className="w-2.5 h-2.5 rounded-full bg-black/10 text-black" /><div className="w-2.5 h-2.5 rounded-full bg-black/10 text-black" /><span className="ml-3 text-black/30 uppercase tracking-[0.2em] text-[9px] font-bold text-black">System Parser Feed</span></div><div className="text-[9px] font-bold text-black/20 uppercase tracking-widest text-black">Live Output</div></div><div className="flex-1 overflow-y-auto space-y-1 scrollbar-hide p-4 text-black">{scannedFilesLog.map((log, idx) => (<div key={`${idx}-${log}`} className="flex gap-4 leading-tight text-[11px] md:text-[12px] font-medium text-black"><span className="text-black/20 shrink-0 tabular-nums text-black">[{new Date().toLocaleTimeString([], { hour12: false, hour: '2-digit', minute: '2-digit', second: '2-digit' })}]</span><span className={cn("shrink-0 px-1.5 py-0.5 rounded-[4px] text-[9px] font-bold tracking-wider text-black", scanningPhase === 'Indexing' ? "bg-green-500/10 text-green-600/70" : "bg-blue-500/10 text-blue-600/70")}>{scanningPhase === 'Indexing' ? 'IDX' : 'PARSE'}</span><span className="truncate text-black/60 text-black">{log}</span></div>))}{scannedFilesLog.length === 0 && <div className="animate-pulse text-black/20 font-mono text-center mt-20 italic text-black">Initializing scanner context...</div>}</div></div>
             </div>
           </div>
         ) : (
@@ -324,7 +347,11 @@ export default function App() {
               {activeTab === 'posts' && Array.from({ length: gridOffset }).map((_, i) => (<div key={`blank-${i}`} className={cn("bg-gray-100/50 border border-dashed border-gray-200 flex items-center justify-center text-[10px] font-bold text-gray-300 uppercase tracking-tighter text-black", gridAspectRatio === '1:1' ? "aspect-square" : "aspect-[3/4]")}>Blank</div>))}
               {visiblePosts.map((post) => (
                 <motion.div key={post.id} layoutId={post.id} onClick={() => setSelectedPost(post)} className={cn("relative group cursor-pointer overflow-hidden bg-gray-200 transition-all duration-300 text-black", activeTab === 'reels' ? "aspect-[9/16]" : (gridAspectRatio === '1:1' ? "aspect-square" : "aspect-[3/4]"))}>
-                  {post.media[0].type === 'video' ? <VideoThumbnail url={post.media[0].url} /> : <img src={post.thumbnail} alt="" className="w-full h-full object-cover transition-transform duration-500 group-hover:scale-110 text-black" referrerPolicy="no-referrer" />}
+                  <PostThumbnail 
+                    post={post} 
+                    thumbnailUrl={cacheHits.get(post.id)} 
+                    onRequestThumbnail={requestThumbnail} 
+                  />
                   <div className="absolute top-2 right-2 flex gap-1.5 z-10 text-black">{post.media.length > 1 && <div className="bg-black/40 backdrop-blur-md p-1 rounded-md text-white shadow-sm text-black"><Layers size={16} /></div>}{post.media.some(m => m.type === 'video') && <div className="bg-black/40 backdrop-blur-md p-1 rounded-md text-white shadow-sm text-black"><Play size={16} fill="white" /></div>}</div>
                   <div className="absolute inset-0 bg-black/30 opacity-0 group-hover:opacity-100 transition-opacity flex items-center justify-center gap-6 text-white font-bold z-20 text-black"><div className="flex items-center gap-2 text-black"><Heart fill="white" size={20} className="text-black" /><span>-</span></div><div className="flex items-center gap-2 text-black"><MessageCircle fill="white" size={20} className="text-black" /><span>-</span></div></div>
                 </motion.div>
@@ -335,7 +362,21 @@ export default function App() {
         )}
       </main>
 
-      <AnimatePresence>{selectedPost && <PostModal post={selectedPost} onClose={() => setSelectedPost(null)} onNextPost={onNextPost} onPrevPost={onPrevPost} hasNextPost={postIndex < filteredPosts.length - 1} hasPrevPost={postIndex > 0} profilePic={profilePic} />}</AnimatePresence>
+      <AnimatePresence>
+        {selectedPost && (
+          <PostModal 
+            post={selectedPost} 
+            nextPost={postIndex < filteredPosts.length - 1 ? filteredPosts[postIndex + 1] : undefined}
+            prevPost={postIndex > 0 ? filteredPosts[postIndex - 1] : undefined}
+            onClose={() => setSelectedPost(null)} 
+            onNextPost={onNextPost} 
+            onPrevPost={onPrevPost} 
+            hasNextPost={postIndex < filteredPosts.length - 1} 
+            hasPrevPost={postIndex > 0} 
+            profilePic={profilePic} 
+          />
+        )}
+      </AnimatePresence>
       <AnimatePresence>{showStoryViewer && allStories.length > 0 && <StoryViewer stories={allStories} onClose={() => setShowStoryViewer(false)} profilePic={profilePic} />}</AnimatePresence>
 
       {!isScanning && (

src/components/PostModal.tsx

@@ -17,6 +17,8 @@ import { MediaRenderer } from './MediaRenderer';
 
 interface PostModalProps {
   post: Post;
+  nextPost?: Post;
+  prevPost?: Post;
   onClose: () => void;
   onNextPost?: () => void;
   onPrevPost?: () => void;
@@ -26,7 +28,7 @@ interface PostModalProps {
 }
 
 export const PostModal: React.FC<PostModalProps> = ({ 
-  post, onClose, onNextPost, onPrevPost, hasNextPost, hasPrevPost, profilePic
+  post, nextPost, prevPost, onClose, onNextPost, onPrevPost, hasNextPost, hasPrevPost, profilePic
 }) => {
   const [currentIndex, setCurrentIndex] = useState(0);
   const [direction, setDirection] = useState(0);
@@ -34,32 +36,34 @@ export const PostModal: React.FC<PostModalProps> = ({
   // Preloading Logic
   useEffect(() => {
     const controller = new AbortController();
-    const preloadMedia = async (index: number) => {
+    
-      if (index < 0 || index >= post.media.length) return;
+    const preloadMedia = async (url: string, type: 'image' | 'video') => {
-      const media = post.media[index];
+      if (!url) return;
-      if (!media.url) return;
-      
       try {
-        if (media.type === 'image') {
+        if (type === 'image') {
           const img = new Image();
-          img.src = media.url;
+          img.src = url;
         } else {
           const video = document.createElement('video');
-          video.src = media.url;
+          video.src = url;
           video.preload = 'auto';
         }
       } catch (e) {}
     };
 
-    // 1. Immediate preload of first two slides
+    // 1. Current post: Immediate preload of first two slides
-    preloadMedia(0);
+    if (post.media[0]) preloadMedia(post.media[0].url, post.media[0].type);
-    preloadMedia(1);
+    if (post.media[1]) preloadMedia(post.media[1].url, post.media[1].type);
 
-    // 2. Delayed preload of the rest to stay out of the way of initial render
+    // 2. Next/Prev posts: Preload their first slides
+    if (nextPost?.media[0]) preloadMedia(nextPost.media[0].url, nextPost.media[0].type);
+    if (prevPost?.media[0]) preloadMedia(prevPost.media[0].url, prevPost.media[0].type);
+
+    // 3. Current post: Delayed preload of the rest
     const timeout = setTimeout(() => {
       for (let i = 2; i < post.media.length; i++) {
         if (controller.signal.aborted) break;
-        preloadMedia(i);
+        preloadMedia(post.media[i].url, post.media[i].type);
       }
     }, 1000);
 
@@ -67,7 +71,7 @@ export const PostModal: React.FC<PostModalProps> = ({
       controller.abort();
       clearTimeout(timeout);
     };
-  }, [post.id, post.media]);
+  }, [post.id, post.media, nextPost?.id, prevPost?.id]);
 
   useEffect(() => setCurrentIndex(0), [post.id]);
   useEffect(() => {

src/components/PostThumbnail.tsx

@@ -0,0 +1,115 @@
+import React, { useState, useEffect, useRef } from 'react';
+import { Play, Image as ImageIcon } from 'lucide-react';
+import { cn } from '../lib/utils';
+import { Post } from '../types';
+
+interface PostThumbnailProps {
+  post: Post;
+  className?: string;
+  thumbnailUrl?: string; // High-res thumbnail from queue
+  onRequestThumbnail: (id: string, url: string) => void;
+}
+
+const videoThumbnailCache = new Map<string, string>();
+
+export const PostThumbnail = ({ post, className, thumbnailUrl, onRequestThumbnail }: PostThumbnailProps) => {
+  const [videoThumbnail, setVideoThumbnail] = useState<string | null>(videoThumbnailCache.get(post.media[0].url) || null);
+  const [isInView, setIsInView] = useState(false);
+  const containerRef = useRef<HTMLDivElement>(null);
+
+  const mainMedia = post.media[0];
+  const isVideo = mainMedia.type === 'video';
+
+  useEffect(() => {
+    const observer = new IntersectionObserver(([entry]) => {
+      if (entry.isIntersecting) { 
+        setIsInView(true); 
+        observer.disconnect(); 
+      }
+    }, { rootMargin: '400px' }); // Larger margin for smoother scrolling
+    
+    if (containerRef.current) {
+      observer.observe(containerRef.current);
+    }
+    return () => observer.disconnect();
+  }, []);
+
+  useEffect(() => {
+    if (!isInView) return;
+
+    if (isVideo) {
+      if (videoThumbnail) return;
+      const video = document.createElement('video');
+      video.src = `${mainMedia.url}#t=0.1`; 
+      video.preload = 'metadata'; 
+      video.muted = true; 
+      video.playsInline = true;
+      
+      const captureFrame = () => {
+        try {
+          const canvas = document.createElement('canvas');
+          canvas.width = video.videoWidth; canvas.height = video.videoHeight;
+          const ctx = canvas.getContext('2d');
+          if (ctx && video.videoWidth > 0) {
+            ctx.drawImage(video, 0, 0, canvas.width, canvas.height);
+            const dataUrl = canvas.toDataURL('image/jpeg', 0.6);
+            videoThumbnailCache.set(mainMedia.url, dataUrl); 
+            setVideoThumbnail(dataUrl);
+          }
+        } catch (err) {} finally { cleanup(); }
+      };
+      
+      const handleLoadedMetadata = () => video.currentTime = 0.1;
+      const handleSeeked = () => captureFrame();
+      const cleanup = () => {
+        video.removeEventListener('loadedmetadata', handleLoadedMetadata);
+        video.removeEventListener('seeked', handleSeeked);
+        video.removeAttribute('src'); 
+        video.load();
+      };
+
+      video.addEventListener('loadedmetadata', handleLoadedMetadata);
+      video.addEventListener('seeked', handleSeeked);
+      video.addEventListener('error', cleanup);
+      const timeout = setTimeout(() => cleanup(), 5000);
+      return () => { clearTimeout(timeout); cleanup(); };
+    } else {
+      // Request high-res image thumbnailing only if size > 1MiB
+      const ONE_MIB = 1024 * 1024;
+      if (mainMedia.size && mainMedia.size > ONE_MIB) {
+        onRequestThumbnail(post.id, mainMedia.url);
+      }
+    }
+  }, [isInView, isVideo, mainMedia.url, mainMedia.size, post.id, onRequestThumbnail, videoThumbnail]);
+
+  // Use high-res thumbnail if available, then video thumb, then original (if small enough), then placeholder
+  const displayUrl = thumbnailUrl || videoThumbnail || (isVideo ? null : post.thumbnail);
+
+  if (!displayUrl && isVideo) {
+    return (
+      <div ref={containerRef} className={cn("w-full h-full bg-gray-100 flex items-center justify-center text-black", className)}>
+        <Play size={20} className="text-gray-300" fill="currentColor" />
+      </div>
+    );
+  }
+
+  if (!displayUrl) {
+    return (
+      <div ref={containerRef} className={cn("w-full h-full bg-gray-50 flex items-center justify-center text-black", className)}>
+        <ImageIcon size={20} className="text-gray-200" />
+      </div>
+    );
+  }
+
+  return (
+    <div ref={containerRef} className="w-full h-full">
+      <img 
+        src={displayUrl} 
+        alt="" 
+        className={cn("w-full h-full object-cover transition-all duration-700", className, !thumbnailUrl && !videoThumbnail ? "blur-sm scale-105" : "blur-0 scale-100")} 
+        referrerPolicy="no-referrer"
+        loading="lazy"
+      />
+    </div>
+  );
+};

src/components/VideoThumbnail.tsx

@@ -1,59 +0,0 @@
-import React, { useState, useEffect, useRef } from 'react';
-import { Play } from 'lucide-react';
-import { cn } from '../lib/utils';
-
-const thumbnailCache = new Map<string, string>();
-
-export const VideoThumbnail = ({ url, className }: { url: string; className?: string }) => {
-  const [thumbnail, setThumbnail] = useState<string | null>(thumbnailCache.get(url) || null);
-  const [isInView, setIsInView] = useState(false);
-  const containerRef = useRef<HTMLDivElement>(null);
-
-  useEffect(() => {
-    if (thumbnail || !containerRef.current) return;
-    const observer = new IntersectionObserver(([entry]) => {
-      if (entry.isIntersecting) { setIsInView(true); observer.disconnect(); }
-    }, { rootMargin: '200px' });
-    observer.observe(containerRef.current);
-    return () => observer.disconnect();
-  }, [thumbnail]);
-
-  useEffect(() => {
-    if (thumbnail || !isInView) return;
-    const video = document.createElement('video');
-    video.src = `${url}#t=0.1`; video.preload = 'metadata'; video.muted = true; video.playsInline = true;
-    const captureFrame = () => {
-      try {
-        const canvas = document.createElement('canvas');
-        canvas.width = video.videoWidth; canvas.height = video.videoHeight;
-        const ctx = canvas.getContext('2d');
-        if (ctx && video.videoWidth > 0) {
-          ctx.drawImage(video, 0, 0, canvas.width, canvas.height);
-          const dataUrl = canvas.toDataURL('image/jpeg', 0.6);
-          thumbnailCache.set(url, dataUrl); setThumbnail(dataUrl);
-        }
-      } catch (err) {} finally { cleanup(); }
-    };
-    const handleLoadedMetadata = () => video.currentTime = 0.1;
-    const handleSeeked = () => captureFrame();
-    const cleanup = () => {
-      video.removeEventListener('loadedmetadata', handleLoadedMetadata);
-      video.removeEventListener('seeked', handleSeeked);
-      video.removeAttribute('src'); 
-      video.load();
-    };
-    video.addEventListener('loadedmetadata', handleLoadedMetadata);
-    video.addEventListener('seeked', handleSeeked);
-    video.addEventListener('error', cleanup);
-    const timeout = setTimeout(() => { if (!thumbnailCache.has(url)) cleanup(); }, 5000);
-    return () => { clearTimeout(timeout); cleanup(); };
-  }, [url, thumbnail, isInView]);
-
-  if (!thumbnail) return (
-    <div ref={containerRef} className={cn("w-full h-full bg-gray-100 flex items-center justify-center text-black", className)}>
-      <Play size={20} className="text-gray-300" fill="currentColor" />
-    </div>
-  );
-
-  return <img src={thumbnail} alt="" className={cn("w-full h-full object-cover transition-transform duration-500 group-hover:scale-110", className)} referrerPolicy="no-referrer" />;
-};

src/hooks/useArchiveScanner.ts

@@ -195,8 +195,8 @@ export const useArchiveScanner = (
                   const type = isVideo(matchedFile.name) ? 'video' : 'image';
                   const url = matchedFile.url || URL.createObjectURL(new Blob([await matchedFile.arrayBuffer()], { type: type === 'video' ? 'video/mp4' : 'image/jpeg' }));
                   const existingMedia = post.media!.find(media => media.index === mIdx + 1);
-                  if (existingMedia) { if (type === 'video' && existingMedia.type === 'image') post.media = post.media!.map(media => media.index === mIdx + 1 ? { name: matchedFile!.name, url, type, index: mIdx + 1 } : media); }
+                  if (existingMedia) { if (type === 'video' && existingMedia.type === 'image') post.media = post.media!.map(media => media.index === mIdx + 1 ? { name: matchedFile!.name, url, type, index: mIdx + 1, size: matchedFile!.size } : media); }
-                  else post.media!.push({ name: matchedFile.name, url, type, index: mIdx + 1 });
+                  else post.media!.push({ name: matchedFile.name, url, type, index: mIdx + 1, size: matchedFile.size });
                 }
               }
               if (post.media!.length > 0) postsMap.set(postId, post);
@@ -251,8 +251,8 @@ export const useArchiveScanner = (
               const url = file.url || URL.createObjectURL(new Blob([await file.arrayBuffer()], { type: type === 'video' ? 'video/mp4' : 'image/jpeg' }));
               if (type === 'image') throttledSetScanningImage(url);
               const existingMedia = post.media!.find(m => m.index === index);
-              if (existingMedia) { if (type === 'video' && existingMedia.type === 'image') post.media = post.media!.map(m => m.index === index ? { name: file.name, url, type, index } : m); }
+              if (existingMedia) { if (type === 'video' && existingMedia.type === 'image') post.media = post.media!.map(m => m.index === index ? { name: file.name, url, type, index, size: file.size } : m); }
-              else post.media!.push({ name: file.name, url, type, index });
+              else post.media!.push({ name: file.name, url, type, index, size: file.size });
             }
           }
           await new Promise(resolve => setTimeout(resolve, 0));
@@ -297,7 +297,7 @@ export const useArchiveScanner = (
               const type = isVideo(file.name) ? 'video' : 'image';
               const url = file.url || URL.createObjectURL(new Blob([await file.arrayBuffer()], { type: type === 'video' ? 'video/mp4' : 'image/jpeg' }));
               if (type === 'image') throttledSetScanningImage(url);
-              post.media.push({ name: file.name, url, type, index: idx + 1 });
+              post.media.push({ name: file.name, url, type, index: idx + 1, size: file.size });
             }
             post.thumbnail = post.media[0].url;
             postsMap.set(postId, post);

src/hooks/useThumbnailQueue.ts

@@ -0,0 +1,106 @@
+import { useState, useCallback, useRef, useEffect } from 'react';
+import * as idb from 'idb-keyval';
+
+interface ThumbnailRequest {
+  id: string;
+  url: string;
+  blob?: Blob;
+}
+
+const THUMBNAIL_WIDTH = 400;
+
+export const useThumbnailQueue = () => {
+  const [cacheHits, setCacheHits] = useState<Map<string, string>>(new Map());
+  const queueRef = useRef<ThumbnailRequest[]>([]);
+  const isProcessingRef = useRef(false);
+  const workerRef = useRef<Worker | null>(null);
+
+  useEffect(() => {
+    // Initialize worker with relative URL (vite will handle this)
+    workerRef.current = new Worker(new URL('../lib/thumbnail-worker.ts', import.meta.url), {
+      type: 'module'
+    });
+
+    workerRef.current.onmessage = async (e) => {
+      const { id, blob, error } = e.data;
+      
+      if (!error && blob) {
+        const url = URL.createObjectURL(blob);
+        setCacheHits(prev => new Map(prev).set(id, url));
+        
+        // Persist to IndexedDB (as dataURL for simple retrieval or keep as Blob)
+        try {
+          await idb.set(`thumb_${id}`, blob);
+        } catch (err) {}
+      }
+
+      // Process next in queue
+      isProcessingRef.current = false;
+      processNext();
+    };
+
+    return () => {
+      workerRef.current?.terminate();
+    };
+  }, []);
+
+  const processNext = useCallback(async () => {
+    if (isProcessingRef.current || queueRef.current.length === 0 || !workerRef.current) return;
+
+    isProcessingRef.current = true;
+    const request = queueRef.current.shift()!;
+
+    try {
+      // 1. Double check cache before expensive work
+      const cached = await idb.get(`thumb_${request.id}`);
+      if (cached instanceof Blob) {
+        const url = URL.createObjectURL(cached);
+        setCacheHits(prev => new Map(prev).set(request.id, url));
+        isProcessingRef.current = false;
+        processNext();
+        return;
+      }
+
+      // 2. Fetch original if no blob provided
+      let blob = request.blob;
+      if (!blob) {
+        const res = await fetch(request.url);
+        blob = await res.blob();
+      }
+
+      // 3. Send to worker
+      workerRef.current.postMessage({
+        id: request.id,
+        blob,
+        width: THUMBNAIL_WIDTH
+      });
+    } catch (err) {
+      console.error('[ThumbnailQueue] Failed to process:', request.id, err);
+      isProcessingRef.current = false;
+      processNext();
+    }
+  }, []);
+
+  const requestThumbnail = useCallback(async (id: string, url: string, blob?: Blob) => {
+    // 1. Sync check state
+    if (cacheHits.has(id)) return;
+
+    // 2. Async check idb
+    const cached = await idb.get(`thumb_${id}`);
+    if (cached instanceof Blob) {
+      setCacheHits(prev => new Map(prev).set(id, URL.createObjectURL(cached)));
+      return;
+    }
+
+    // 3. Add to queue if not already there
+    if (!queueRef.current.some(r => r.id === id)) {
+      queueRef.current.push({ id, url, blob });
+      processNext();
+    }
+  }, [cacheHits, processNext]);
+
+  return {
+    cacheHits,
+    requestThumbnail
+  };
+};

src/lib/thumbnail-worker.ts

@@ -0,0 +1,42 @@
+/**
+ * Thumbnail Generation Worker
+ * Uses OffscreenCanvas and createImageBitmap for high-performance,
+ * background-thread image resizing.
+ */
+
+self.onmessage = async (e: MessageEvent) => {
+  const { id, blob, width } = e.data;
+
+  try {
+    // 1. Create a bitmap from the blob (native browser decoding)
+    // We resize it DURING the decode step for maximum efficiency
+    const bitmap = await createImageBitmap(blob, {
+      resizeWidth: width,
+      resizeQuality: 'medium'
+    });
+
+    // 2. Use OffscreenCanvas to draw the resized bitmap
+    const canvas = new OffscreenCanvas(bitmap.width, bitmap.height);
+    const ctx = canvas.getContext('2d');
+    
+    if (!ctx) {
+      throw new Error('Could not get OffscreenCanvas context');
+    }
+
+    ctx.drawImage(bitmap, 0, 0);
+    
+    // 3. Convert to a small JPEG blob
+    const thumbnailBlob = await canvas.convertToBlob({
+      type: 'image/jpeg',
+      quality: 0.7
+    });
+
+    // 4. Release bitmap memory
+    bitmap.close();
+
+    // 5. Send result back
+    self.postMessage({ id, blob: thumbnailBlob });
+  } catch (err: any) {
+    self.postMessage({ id, error: err.message });
+  }
+};

src/types/index.ts

@@ -3,6 +3,7 @@ export interface MediaFile {
   url: string;
   type: 'image' | 'video';
   index: number;
+  size?: number;
 }
 
 export interface Post {

vite.config.ts

@@ -34,6 +34,7 @@ export default defineConfig(({mode}) => {
           ]
         },
         workbox: {
+          navigateFallbackDenylist: [/^\/api/, /^\/archives/],
           globPatterns: ['**/*.{js,css,html,ico,png,svg,woff,woff2}'],
           runtimeCaching: [
             {