fix: allow WebAssembly in the CSP so xz sidecars can be decoded

The xz decompressor for Instaloader's .json.xz sidecars is WebAssembly,
embedded as a data: URL that it fetches at startup. The CSP added in 1.3.0
blocked both halves of that:

  fetch('data:application/wasm;...')  -> TypeError: Failed to fetch
  WebAssembly.instantiate(...)        -> CompileError: violates script-src 'self'

The first surfaces through new Response(stream).json() as a bare "Failed to
fetch" with no stack, which reads like a network fault and is why this was
mis-diagnosed twice. Vite's dev server never sends the CSP, so it reproduced
only in production — every Instaloader archive silently lost its captions,
story flags and profile metadata from 1.3.0 onward.

script-src now allows 'wasm-unsafe-eval', which permits WebAssembly compilation
without permitting eval() of JavaScript, and connect-src allows data: for the
embedded module.

Verified against the production bundle: rivvsofficial goes from 188 posts / 0
followers / no stories to 68 posts, 120 stories, 10,337 followers and its real
name, bio and link — with zero decode errors.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011uBWhwV3wFQ5MBCcMHHem7

CLAUDE.md

@@ -15,6 +15,9 @@ InstaArchive Viewer is a React 19 + Vite 6 PWA for browsing archived Instagram d
 - `npm run lint` — type-check only (`tsc --noEmit`)
 - `npm test` / `npm run test:watch` — vitest
 - `npx vitest run src/lib/archive-patterns.test.ts` — a single test file
+- `npm run jd2 -- --archives <dir> --dry-run` — generate JDownloader `.crawljob`
+  files for every profile on disk (see `scripts/jd2-sync.ts` and
+  `docs/jdownloader.md`)
 
 Local development usually needs both `npm run dev` and `npm run server`. Local-folder mode works without the backend; server-mode archives do not.
 
@@ -71,14 +74,21 @@ Restoring an archive **rehydrates URLs from `path`**: server archives rebuild HT
 
 Images over 1MiB are downscaled in a Web Worker via `OffscreenCanvas`. The queue is **serial on purpose** — decoding several 50MP+ images at once OOMs the tab. `requestThumbnail` must keep a stable identity (it reads cache state through a ref), or every completed thumbnail re-runs the effect in all mounted thumbnails.
 
-### URL state (`src/App.tsx`)
+### URL state (`src/App.tsx`, `src/lib/routing.ts`)
 
-App state syncs to `?a=` / `?t=` / `?p=`. Two rules, both learned from real bugs:
+Paths mirror Instagram: `/<archive>/`, `/<archive>/reels/`, `/<archive>/p/<shortcode>/`. The old `?a=&t=&p=` form is still parsed for existing links but never written. Reserved prefixes (`api`, `archives`, `assets`…) can't be mistaken for a profile name.
 
-- The initial query string is captured into a ref on first render; the URL is rewritten from state as soon as anything loads, so reading `window.location` later sees the rewrite, not the user's link.
+A post URL carries no tab, as on Instagram — the tab is re-derived from the post's `source`, so a reel link lands on the Reels tab and pages through reels. Sidecar posts keep directory-scoped ids internally but expose only the shortcode.
+
+Three rules, all learned from real bugs:
+
+- The initial route is captured into a ref on first render; the URL is rewritten from state as soon as anything loads, so reading `window.location` later sees the rewrite, not the user's link.
 - URL writing is gated on `hasInitialLoaded`, otherwise it erases the deep link before the loader consumes it.
+- Deep-link resolution waits on the archive fetch having *settled* (`archivesFetched`), not on `isServerMode`, which is still false while the request is in flight.
 
-Deep-link resolution waits on the archive fetch having *settled*, not on `isServerMode` (which is still false while in flight).
+### Mobile feed (`src/components/PostFeed.tsx`)
+
+Below `md`, opening a post renders a scrolling feed page rather than the modal (`useIsMobile` decides). Only a window of posts is mounted; it grows both ways, and prepending corrects `scrollTop` in a `useLayoutEffect` so content doesn't jump. Only the post crossing the viewport centre plays its video and drives the URL. Desktop keeps `PostModal`; both share `MediaCarousel`.
 
 ### Backend (`server.ts`)
 

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "instaarchive-viewer",
-  "version": "1.4.0",
+  "version": "1.6.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "instaarchive-viewer",
-      "version": "1.4.0",
+      "version": "1.6.1",
       "dependencies": {
         "@tailwindcss/vite": "^4.1.14",
         "@vitejs/plugin-react": "^5.0.4",

package.json

@@ -1,7 +1,7 @@
 {
   "name": "instaarchive-viewer",
   "private": true,
-  "version": "1.4.0",
+  "version": "1.6.1",
   "type": "module",
   "scripts": {
     "dev": "vite --port=3000 --host=0.0.0.0",
@@ -12,7 +12,8 @@
     "clean": "rm -rf dist",
     "lint": "tsc --noEmit",
     "test": "vitest run",
-    "test:watch": "vitest"
+    "test:watch": "vitest",
+    "jd2": "tsx scripts/jd2-sync.ts"
   },
   "dependencies": {
     "@tailwindcss/vite": "^4.1.14",

server.ts

@@ -80,10 +80,16 @@ app.use((req, res, next) => {
     "default-src 'self'",
     "img-src 'self' blob: data:",
     "media-src 'self' blob: data:",
-    "script-src 'self'",
+    // 'wasm-unsafe-eval' permits WebAssembly compilation without allowing
+    // eval() of JavaScript. The xz decompressor used for Instaloader's
+    // .json.xz sidecars is WebAssembly, embedded as a data: URL it fetches at
+    // startup — so connect-src must allow data: too. Without both, decoding
+    // fails with a bare "TypeError: Failed to fetch" and every archive silently
+    // loses its captions, story flags and profile metadata.
+    "script-src 'self' 'wasm-unsafe-eval'",
     "style-src 'self' 'unsafe-inline'",
     "font-src 'self'",
-    "connect-src 'self'",
+    "connect-src 'self' data:",
     "worker-src 'self' blob:",
     "frame-ancestors 'self'",
     "object-src 'none'",

src/App.tsx

@@ -17,7 +17,7 @@ import {
 import { motion, AnimatePresence } from 'motion/react';
 
 import { cn } from './lib/utils';
-import { PRESS } from './lib/motion';
+import { PRESS, prefersReducedMotion } from './lib/motion';
 import { buildPath, findPostBySlug, parseRoute, postSlug, tabForSource } from './lib/routing';
 import { LocalArchiveFile, RemoteArchiveFile } from './lib/archive-files';
 import {
@@ -38,6 +38,8 @@ import { CacheData, Post, ServerArchive, ServerArchiveFile } from './types';
 import { ArchiveDashboard } from './components/ArchiveDashboard';
 import { StoryViewer } from './components/StoryViewer';
 import { PostModal } from './components/PostModal';
+import { PostFeed } from './components/PostFeed';
+import { useIsMobile } from './hooks/useIsMobile';
 import { PostThumbnail } from './components/PostThumbnail';
 import { useArchiveScanner } from './hooks/useArchiveScanner';
 import { useThumbnailQueue } from './hooks/useThumbnailQueue';
@@ -70,6 +72,7 @@ export default function App() {
    */
   const initialRouteRef = useRef(parseRoute(window.location.pathname, window.location.search));
 
+  const isMobile = useIsMobile();
   const fileInputRef = useRef<HTMLInputElement>(null);
   const profilePicInputRef = useRef<HTMLInputElement>(null);
 
@@ -108,6 +111,30 @@ export default function App() {
 
   const [lastLoadedScanningImage, setLastLoadedScanningImage] = useState<string | null>(null);
 
+  /**
+   * Blurred backdrops behind the scanning UI, newest last.
+   *
+   * Each new image is stacked *over* the previous one and fades in; the one
+   * underneath stays fully opaque until it's covered. Cross-fading by swapping
+   * a single element left the pale backdrop showing through mid-transition,
+   * which read as a white flash between every image.
+   */
+  const [scanBackdrops, setScanBackdrops] = useState<string[]>([]);
+
+  useEffect(() => {
+    if (!lastLoadedScanningImage) return;
+    setScanBackdrops(prev =>
+      prev[prev.length - 1] === lastLoadedScanningImage
+        ? prev
+        : [...prev, lastLoadedScanningImage].slice(-3),
+    );
+  }, [lastLoadedScanningImage]);
+
+  // Don't carry one archive's backdrops into the next scan.
+  useEffect(() => {
+    if (!isScanning) { setScanBackdrops([]); setLastLoadedScanningImage(null); }
+  }, [isScanning]);
+
   const {
     username,
     fullName,
@@ -457,17 +484,28 @@ export default function App() {
                 onLoad={() => setLastLoadedScanningImage(currentScanningImage)} 
               />
             )}
-            <div className="absolute inset-0 z-0">
-              <AnimatePresence initial={false}>
-                <motion.img 
-                  key={lastLoadedScanningImage}
-                  src={lastLoadedScanningImage || undefined}
+            {/*
+              The 0.4 lives on the group, not the images: two layers overlap
+              during a cross-fade, and fading them individually would darken the
+              backdrop as they cross. Inside the group each layer goes to full
+              opacity, so the stack is always completely covered.
+            */}
+            <div className="absolute inset-0 z-0 opacity-40">
+              {scanBackdrops.map(src => (
+                <motion.img
+                  key={src}
+                  src={src}
                   initial={{ opacity: 0 }}
-                  animate={{ opacity: 0.4 }}
-                  transition={{ duration: 1.5 }}
+                  animate={{ opacity: 1 }}
+                  transition={prefersReducedMotion() ? { duration: 0 } : { duration: 0.9, ease: 'easeInOut' }}
+                  onAnimationComplete={() => setScanBackdrops(prev => {
+                    // Once this layer is opaque it hides everything below it.
+                    const i = prev.indexOf(src);
+                    return i > 0 ? prev.slice(i) : prev;
+                  })}
                   className="absolute inset-0 w-full h-full object-cover blur-[60px] scale-110"
                 />
-              </AnimatePresence>
+              ))}
             </div>
             <div className="absolute inset-0 bg-white/40 z-1" />
             <div className="relative z-10 w-full max-w-4xl px-4 flex flex-col items-center gap-8 text-black">
@@ -549,21 +587,36 @@ export default function App() {
         )}
       </main>
 
-      <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>
+      {/*
+        Mobile opens a real scrolling feed page, the way Instagram does; desktop
+        keeps the modal, where a centred sheet with side arrows fits the pointer.
+      */}
+      {selectedPost && isMobile ? (
+        <PostFeed
+          posts={filteredPosts}
+          initialPostId={selectedPost.id}
+          profilePic={profilePic}
+          title={activeTab === 'reels' ? 'Reels' : 'Posts'}
+          onClose={() => setSelectedPost(null)}
+          onActivePostChange={setSelectedPost}
+        />
+      ) : (
+        <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>
       <AnimatePresence>
         {activeHighlight && (

src/components/FeedPost.tsx

@@ -0,0 +1,67 @@
+import React from 'react';
+import { Bookmark, Heart, MessageCircle, MoreHorizontal, Send } from 'lucide-react';
+import { Post } from '../types';
+import { formatDateSafe } from '../lib/utils';
+import { MediaCarousel } from './MediaCarousel';
+
+interface FeedPostProps {
+  post: Post;
+  profilePic: string | null;
+  /** Off-screen posts keep their video paused. */
+  paused: boolean;
+}
+
+/**
+ * One post in the mobile feed, laid out like Instagram's: header, media,
+ * action row, then caption.
+ *
+ * Media is capped below full viewport height so the next post always peeks in
+ * at the bottom — that overlap is what tells you the page scrolls rather than
+ * pages.
+ */
+export const FeedPost: React.FC<FeedPostProps> = ({ post, profilePic, paused }) => (
+  <article className="bg-white border-b border-gray-200">
+    <header className="flex items-center justify-between px-3 py-2.5">
+      <div className="flex items-center gap-2.5 min-w-0">
+        <div className="w-8 h-8 rounded-full bg-gradient-to-tr from-yellow-400 to-purple-600 p-0.5 shrink-0">
+          <div className="w-full h-full rounded-full bg-white p-0.5">
+            <div className="w-full h-full rounded-full bg-gray-200 overflow-hidden flex items-center justify-center text-[10px] font-bold uppercase">
+              {profilePic
+                ? <img src={profilePic} alt="" className="w-full h-full object-cover" referrerPolicy="no-referrer" />
+                : <span>{post.username[0]}</span>}
+            </div>
+          </div>
+        </div>
+        <span className="font-semibold text-sm truncate">{post.username}</span>
+      </div>
+      <MoreHorizontal size={20} className="text-gray-500 shrink-0" />
+    </header>
+
+    {/*
+      Taller ceiling than the modal so ordinary portrait media (9:16 reels,
+      4:5 photos) fills the feed width instead of sitting in side bars, while
+      still stopping anything extreme from swallowing the screen.
+    */}
+    <MediaCarousel post={post} paused={paused} heightCap="max-h-[85vh]" fillWidth className="bg-black" />
+
+    <div className="px-3 pt-3 pb-1 flex items-center justify-between">
+      <div className="flex items-center gap-4">
+        <Heart size={24} className="cursor-pointer" />
+        <MessageCircle size={24} className="cursor-pointer" />
+        <Send size={24} className="cursor-pointer" />
+      </div>
+      <Bookmark size={24} className="cursor-pointer" />
+    </div>
+
+    {post.caption && (
+      <div className="px-3 pb-1 text-sm">
+        <span className="font-semibold mr-2">{post.username}</span>
+        <span className="whitespace-pre-wrap">{post.caption}</span>
+      </div>
+    )}
+
+    <div className="px-3 pb-3 pt-1 text-[10px] uppercase tracking-wide text-gray-400">
+      {formatDateSafe(post.date, 'MMMM d, yyyy')}
+    </div>
+  </article>
+);

src/components/MediaCarousel.tsx

@@ -0,0 +1,112 @@
+import React, { useEffect, useState } from 'react';
+import { ChevronLeft, ChevronRight } from 'lucide-react';
+import { motion, AnimatePresence } from 'motion/react';
+import { Post } from '../types';
+import { cn } from '../lib/utils';
+import { NAVIGATE, prefersReducedMotion, withVelocity } from '../lib/motion';
+import { MediaRenderer } from './MediaRenderer';
+
+interface MediaCarouselProps {
+  post: Post;
+  /** Pause video even when this slide is on screen (feed: only one plays). */
+  paused?: boolean;
+  /** Override the media height ceiling (the feed allows taller media). */
+  heightCap?: string;
+  /** Size video to the container width (see MediaRenderer). */
+  fillWidth?: boolean;
+  className?: string;
+}
+
+/**
+ * The horizontal slide strip for one post.
+ *
+ * Shared by the desktop modal and the mobile feed so a carousel behaves the
+ * same in both. Horizontal drag belongs to the carousel and never navigates
+ * between posts — vertical movement is the page's to handle.
+ */
+export const MediaCarousel: React.FC<MediaCarouselProps> = ({ post, paused, heightCap, fillWidth, className }) => {
+  const [index, setIndex] = useState(0);
+  const [slide, setSlide] = useState<{ dir: number; velocity: number }>({ dir: 0, velocity: 0 });
+  const reduceMotion = prefersReducedMotion();
+
+  useEffect(() => setIndex(0), [post.id]);
+
+  const paginate = (dir: number, velocity = 0) => {
+    const next = index + dir;
+    if (next < 0 || next >= post.media.length) return;
+    setSlide({ dir, velocity });
+    setIndex(next);
+  };
+
+  const variants = {
+    enter: (d: number) => ({ x: d > 0 ? '100%' : '-100%', opacity: 1, zIndex: 0 }),
+    center: { x: 0, opacity: 1, zIndex: 1 },
+    exit: (d: number) => ({ x: d < 0 ? '100%' : '-100%', opacity: 1, zIndex: 0 }),
+  };
+  const swipePower = (offset: number, velocity: number) => Math.abs(offset) * velocity;
+  const current = post.media[index];
+
+  return (
+    <div className={cn('relative bg-black flex items-center justify-center group overflow-hidden w-full', className)}>
+      <div className="w-full grid grid-cols-1 grid-rows-1">
+        <AnimatePresence initial={false} custom={slide.dir}>
+          <motion.div
+            key={`${post.id}-${index}`}
+            custom={slide.dir}
+            variants={variants}
+            initial="enter"
+            animate="center"
+            exit="exit"
+            transition={reduceMotion ? { duration: 0 } : withVelocity(slide.velocity, NAVIGATE)}
+            drag={post.media.length > 1 ? 'x' : false}
+            dragDirectionLock
+            dragConstraints={{ left: 0, right: 0 }}
+            dragElastic={0.5}
+            onDragEnd={(e, { offset, velocity }) => {
+              const power = swipePower(offset.x, velocity.x);
+              if (power < -15000) paginate(1, velocity.x);
+              else if (power > 15000) paginate(-1, velocity.x);
+            }}
+            className="col-start-1 row-start-1 w-full flex items-center justify-center relative touch-pan-y"
+          >
+            {current && <MediaRenderer file={current} isFullView paused={paused} heightCap={heightCap} fillWidth={fillWidth} />}
+          </motion.div>
+        </AnimatePresence>
+      </div>
+
+      {post.media.length > 1 && (
+        <>
+          {index > 0 && (
+            <button
+              aria-label="Previous photo"
+              onClick={(e) => { e.stopPropagation(); paginate(-1); }}
+              className="hidden md:block absolute left-4 top-1/2 -translate-y-1/2 bg-white/20 hover:bg-white/40 text-white p-2 rounded-full backdrop-blur-md transition-all opacity-0 group-hover:opacity-100 z-30"
+            >
+              <ChevronLeft size={24} />
+            </button>
+          )}
+          {index < post.media.length - 1 && (
+            <button
+              aria-label="Next photo"
+              onClick={(e) => { e.stopPropagation(); paginate(1); }}
+              className="hidden md:block absolute right-4 top-1/2 -translate-y-1/2 bg-white/20 hover:bg-white/40 text-white p-2 rounded-full backdrop-blur-md transition-all opacity-0 group-hover:opacity-100 z-30"
+            >
+              <ChevronRight size={24} />
+            </button>
+          )}
+          <div className="absolute bottom-4 left-1/2 -translate-x-1/2 flex gap-1.5 z-30">
+            {post.media.map((_, i) => (
+              <div
+                key={i}
+                className={cn(
+                  'w-1.5 h-1.5 rounded-full transition-all',
+                  i === index ? 'bg-blue-500 scale-125' : 'bg-white/40 shadow-sm',
+                )}
+              />
+            ))}
+          </div>
+        </>
+      )}
+    </div>
+  );
+};

src/components/MediaRenderer.tsx

@@ -3,7 +3,25 @@ import { Play, Volume2, VolumeX } from 'lucide-react';
 import { MediaFile } from '../types';
 import { cn } from '../lib/utils';
 
-export const MediaRenderer = ({ file, className, isFullView }: { file: MediaFile; className?: string; isFullView?: boolean }) => {
+interface MediaRendererProps {
+  file: MediaFile;
+  className?: string;
+  isFullView?: boolean;
+  /** Hold playback: the feed keeps every off-screen video paused. */
+  paused?: boolean;
+  /** Cap media height to this instead of the default full-view ceiling. */
+  heightCap?: string;
+  /**
+   * Size video to the container width rather than its own intrinsic size.
+   *
+   * A <video> reports 300x150 until metadata loads, so `w-auto` makes it render
+   * narrow and then jump to full width. The feed needs a stable width more than
+   * it needs a snug fit.
+   */
+  fillWidth?: boolean;
+}
+
+export const MediaRenderer = ({ file, className, isFullView, paused, heightCap, fillWidth }: MediaRendererProps) => {
   // Try to play with sound: opening the modal is a user gesture, so browsers
   // generally allow it. If this particular browser still refuses, the effect
   // below falls back to muted playback rather than leaving a stalled video.
@@ -14,6 +32,11 @@ export const MediaRenderer = ({ file, className, isFullView }: { file: MediaFile
     const video = videoRef.current;
     if (!video || file.type !== 'video') return;
 
+    if (paused) {
+      video.pause();
+      return;
+    }
+
     let cancelled = false;
     video.muted = false;
     video.play().catch(() => {
@@ -24,7 +47,7 @@ export const MediaRenderer = ({ file, className, isFullView }: { file: MediaFile
     });
 
     return () => { cancelled = true; };
-  }, [file.url, file.type]);
+  }, [file.url, file.type, paused]);
   /**
    * In full view the media must never outgrow the viewport.
    *
@@ -36,8 +59,11 @@ export const MediaRenderer = ({ file, className, isFullView }: { file: MediaFile
    * The desktop cap subtracts the modal's own padding (md:p-10 = 2.5rem each
    * side); mobile leaves room for the caption panel stacked underneath.
    */
-  const fullViewCap = "max-h-[70vh] md:max-h-[calc(100vh-5rem)] object-contain";
-  const videoSizing = isFullView ? `block w-auto max-w-full ${fullViewCap}` : "w-full h-full object-cover";
+  const fullViewCap = `${heightCap ?? 'max-h-[70vh] md:max-h-[calc(100vh-5rem)]'} object-contain`;
+  const videoFullView = fillWidth
+    ? `block w-full h-auto ${fullViewCap}`
+    : `block w-auto max-w-full ${fullViewCap}`;
+  const videoSizing = isFullView ? videoFullView : "w-full h-full object-cover";
   const imageSizing = isFullView ? `block w-full h-auto ${fullViewCap}` : "w-full h-full object-cover";
   const sizingClass = file.type === 'video' ? videoSizing : imageSizing;
   const mediaStyle = { transform: 'translateZ(0)' };

src/components/PostFeed.tsx

@@ -0,0 +1,150 @@
+import React, { useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react';
+import { ChevronLeft } from 'lucide-react';
+import { Post } from '../types';
+import { FeedPost } from './FeedPost';
+
+interface PostFeedProps {
+  posts: Post[];
+  /** Post the feed should open at. */
+  initialPostId: string;
+  profilePic: string | null;
+  onClose: () => void;
+  /** Fires as the post crossing the viewport centre changes. */
+  onActivePostChange: (post: Post) => void;
+  title?: string;
+}
+
+/** Posts added each time the feed grows in either direction. */
+const BATCH = 6;
+/** Render this many ahead of the entry point so the first scroll is smooth. */
+const LOOKAHEAD = 3;
+
+/**
+ * The mobile post view: a real scrolling feed, not a modal.
+ *
+ * Only a window of posts around the entry point is mounted — a profile can hold
+ * thousands, and mounting them all would mean thousands of full-size images.
+ * The window grows in both directions as you scroll; growing *upwards* shifts
+ * everything below it, so the scroll position is corrected in the same frame to
+ * keep the content under your thumb still.
+ */
+export const PostFeed: React.FC<PostFeedProps> = ({
+  posts, initialPostId, profilePic, onClose, onActivePostChange, title,
+}) => {
+  const initialIndex = useMemo(() => {
+    const found = posts.findIndex(p => p.id === initialPostId);
+    return found === -1 ? 0 : found;
+  }, [posts, initialPostId]);
+
+  const [range, setRange] = useState(() => ({
+    start: initialIndex,
+    end: Math.min(posts.length, initialIndex + LOOKAHEAD + 1),
+  }));
+  const [activeId, setActiveId] = useState(initialPostId);
+
+  const scrollRef = useRef<HTMLDivElement>(null);
+  const topSentinelRef = useRef<HTMLDivElement>(null);
+  const bottomSentinelRef = useRef<HTMLDivElement>(null);
+  /** Distance from the bottom of the content, captured before a prepend. */
+  const anchorRef = useRef<number | null>(null);
+
+  const visible = posts.slice(range.start, range.end);
+
+  const extendDown = useCallback(() => {
+    setRange(r => (r.end >= posts.length ? r : { ...r, end: Math.min(posts.length, r.end + BATCH) }));
+  }, [posts.length]);
+
+  const extendUp = useCallback(() => {
+    const el = scrollRef.current;
+    if (!el) return;
+    setRange(r => {
+      if (r.start === 0) return r;
+      // Measure from the bottom: prepending changes scrollHeight, but the
+      // distance between our position and the end of the content does not.
+      anchorRef.current = el.scrollHeight - el.scrollTop;
+      return { ...r, start: Math.max(0, r.start - BATCH) };
+    });
+  }, []);
+
+  // Restore the scroll position in the same frame the prepended posts appear,
+  // before the browser paints, so nothing visibly jumps.
+  useLayoutEffect(() => {
+    const el = scrollRef.current;
+    if (el && anchorRef.current !== null) {
+      el.scrollTop = el.scrollHeight - anchorRef.current;
+      anchorRef.current = null;
+    }
+  }, [range.start]);
+
+  // Grow the window when either end comes into view.
+  useEffect(() => {
+    const root = scrollRef.current;
+    if (!root) return;
+    const observer = new IntersectionObserver(entries => {
+      for (const entry of entries) {
+        if (!entry.isIntersecting) continue;
+        if (entry.target === bottomSentinelRef.current) extendDown();
+        if (entry.target === topSentinelRef.current) extendUp();
+      }
+    }, { root, rootMargin: '600px 0px' });
+
+    if (topSentinelRef.current) observer.observe(topSentinelRef.current);
+    if (bottomSentinelRef.current) observer.observe(bottomSentinelRef.current);
+    return () => observer.disconnect();
+  }, [extendDown, extendUp]);
+
+  // Track the post crossing the viewport centre. The negative margins collapse
+  // the root to a thin band, so exactly one post qualifies at a time.
+  useEffect(() => {
+    const root = scrollRef.current;
+    if (!root) return;
+    const observer = new IntersectionObserver(entries => {
+      for (const entry of entries) {
+        if (!entry.isIntersecting) continue;
+        const id = (entry.target as HTMLElement).dataset.postId;
+        if (id) setActiveId(id);
+      }
+    }, { root, rootMargin: '-45% 0px -45% 0px', threshold: 0 });
+
+    root.querySelectorAll('[data-post-id]').forEach(el => observer.observe(el));
+    return () => observer.disconnect();
+  }, [visible.length, range.start]);
+
+  useEffect(() => {
+    const post = posts.find(p => p.id === activeId);
+    if (post) onActivePostChange(post);
+  }, [activeId, posts, onActivePostChange]);
+
+  // Escape closes, matching the modal it replaces.
+  useEffect(() => {
+    const onKey = (e: KeyboardEvent) => { if (e.key === 'Escape') onClose(); };
+    window.addEventListener('keydown', onKey);
+    return () => window.removeEventListener('keydown', onKey);
+  }, [onClose]);
+
+  return (
+    <div className="fixed inset-0 z-50 bg-white flex flex-col">
+      <header className="flex items-center gap-3 px-2 h-12 border-b border-gray-200 bg-white/95 backdrop-blur-md shrink-0">
+        <button onClick={onClose} aria-label="Back" className="p-2 -ml-1 active:opacity-60">
+          <ChevronLeft size={24} />
+        </button>
+        <span className="font-semibold text-base">{title ?? 'Posts'}</span>
+      </header>
+
+      <div ref={scrollRef} className="flex-1 overflow-y-auto overscroll-contain">
+        <div ref={topSentinelRef} aria-hidden />
+        {visible.map(post => (
+          <div key={post.id} data-post-id={post.id}>
+            <FeedPost post={post} profilePic={profilePic} paused={post.id !== activeId} />
+          </div>
+        ))}
+        <div ref={bottomSentinelRef} aria-hidden />
+        {range.end >= posts.length && (
+          <div className="py-10 text-center text-xs uppercase tracking-widest text-gray-400">
+            End of {title?.toLowerCase() ?? 'posts'}
+          </div>
+        )}
+      </div>
+    </div>
+  );
+};

src/components/PostModal.tsx

@@ -82,11 +82,14 @@ export const PostModal: React.FC<PostModalProps> = ({
 
   useEffect(() => setCurrentIndex(0), [post.id]);
   useEffect(() => {
+    // Arrows page within the carousel — the thing the arrows visually point at.
+    // Moving between posts stays on the side buttons, with , and . as keyboard
+    // equivalents.
     const handleKeyDown = (e: KeyboardEvent) => {
-      if (e.key === 'ArrowRight') goToPost(1, 'x');
-      else if (e.key === 'ArrowLeft') goToPost(-1, 'x');
-      else if (e.key === '.') paginate(1);
-      else if (e.key === ',') paginate(-1);
+      if (e.key === 'ArrowRight') paginate(1);
+      else if (e.key === 'ArrowLeft') paginate(-1);
+      else if (e.key === '.') goToPost(1, 'x');
+      else if (e.key === ',') goToPost(-1, 'x');
       else if (e.key === 'Escape') onClose();
     };
     window.addEventListener('keydown', handleKeyDown);
@@ -126,44 +129,12 @@ export const PostModal: React.FC<PostModalProps> = ({
   };
   const swipePower = (offset: number, velocity: number) => Math.abs(offset) * velocity;
 
-  /** Gesture navigation is touch-shaped below md; above it the arrows do the job. */
-  const [isMobile, setIsMobile] = useState(
-    () => typeof window !== 'undefined' && window.matchMedia('(max-width: 767px)').matches,
-  );
-  useEffect(() => {
-    const query = window.matchMedia('(max-width: 767px)');
-    const onChange = (e: MediaQueryListEvent) => setIsMobile(e.matches);
-    query.addEventListener('change', onChange);
-    return () => query.removeEventListener('change', onChange);
-  }, []);
-
   /**
-   * Vertical swipe moves between posts on touch, matching Instagram: horizontal
-   * belongs to the carousel and only the carousel, so reaching the last slide
-   * no longer flings you into the next post.
-   *
-   * Swiping down on the first post falls back to dismissing, which keeps the
-   * familiar drag-to-close gesture available where it can't mean "previous".
+   * Desktop-only surface: mobile opens PostFeed instead, so the only vertical
+   * gesture left here is drag-to-dismiss.
    */
-  const SWIPE_DISTANCE = 90;
-  const SWIPE_POWER = 8000;
-
   const handleVerticalDragEnd = (offset: { y: number }, velocity: { y: number }) => {
-    const power = swipePower(offset.y, velocity.y);
-
-    if (!isMobile) {
-      if (offset.y > 200 || velocity.y > 800) onClose();
-      return;
-    }
-
-    const swipedUp = offset.y < -SWIPE_DISTANCE || power < -SWIPE_POWER;
-    const swipedDown = offset.y > SWIPE_DISTANCE || power > SWIPE_POWER;
-
-    if (swipedUp && hasNextPost) goToPost(1, 'y', velocity.y);
-    else if (swipedDown) {
-      if (hasPrevPost) goToPost(-1, 'y', velocity.y);
-      else onClose();
-    }
+    if (offset.y > 200 || velocity.y > 800) onClose();
   };
 
   /*

src/hooks/useArchiveScanner.ts

@@ -107,11 +107,23 @@ export const useArchiveScanner = (
     /** Stable identity for a media file, used to rehydrate URLs after a reload. */
     const mediaPath = (file: ArchiveFile) => file.webkitRelativePath || file.name;
 
+    /**
+     * Decompress an `.xz` metadata sidecar.
+     *
+     * Read fully into memory first rather than handing the live HTTP body to
+     * the decompressor. These sidecars are a few KB, so buffering costs
+     * nothing, and streaming was actively harmful: the decompressor stops
+     * reading at the end of the xz member, leaving the response body neither
+     * drained nor cancelled. Across a couple of hundred sidecars that exhausts
+     * the connection pool and every later fetch fails with "Failed to fetch" —
+     * which silently cost Instaloader archives their captions, story flags and
+     * profile metadata, since all of it lives in these files.
+     */
     const parseXZFile = async (file: ArchiveFile) => {
       try {
-        const stream = new XzReadableStream(file.stream());
-        const response = new Response(stream);
-        return await response.json();
+        const compressed = await file.arrayBuffer();
+        const stream = new XzReadableStream(new Blob([compressed]).stream());
+        return await new Response(stream).json();
       } catch (e) { console.error(`[Scanner] XZ Parse Error:`, file.name, e); return null; }
     };
 

src/hooks/useIsMobile.ts

@@ -0,0 +1,27 @@
+import { useEffect, useState } from 'react';
+
+/** Matches Tailwind's `md` breakpoint, the point where the layout splits. */
+const MOBILE_QUERY = '(max-width: 767px)';
+
+/**
+ * True on phone-sized viewports.
+ *
+ * Drives more than styling: mobile opens posts as a scrollable feed page while
+ * desktop uses the modal, so this needs to be real state rather than a CSS
+ * media query.
+ */
+export const useIsMobile = () => {
+  const [isMobile, setIsMobile] = useState(
+    () => typeof window !== 'undefined' && window.matchMedia(MOBILE_QUERY).matches,
+  );
+
+  useEffect(() => {
+    const query = window.matchMedia(MOBILE_QUERY);
+    const onChange = (e: MediaQueryListEvent) => setIsMobile(e.matches);
+    query.addEventListener('change', onChange);
+    setIsMobile(query.matches);
+    return () => query.removeEventListener('change', onChange);
+  }, []);
+
+  return isMobile;
+};

src/lib/archive-files.ts

@@ -14,7 +14,6 @@ export class LocalArchiveFile implements ArchiveFile {
   get size() { return this.file.size; }
   text() { return this.file.text(); }
   arrayBuffer() { return this.file.arrayBuffer(); }
-  stream() { return this.file.stream(); }
 
   /**
    * A blob: URL backed directly by the on-disk File.
@@ -55,15 +54,6 @@ export class RemoteArchiveFile implements ArchiveFile {
     const res = await fetch(this.url);
     return res.arrayBuffer();
   }
-  stream() {
-    const transform = new TransformStream();
-    fetch(this.url).then(res => {
-      if (res.body) res.body.pipeTo(transform.writable);
-      else transform.writable.getWriter().close();
-    });
-    return transform.readable;
-  }
-
   createObjectUrl() {
     return this.url;
   }

src/lib/archive-index.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from 'vitest';
+import { isSystemDirectory } from './archive-index';
+
+describe('isSystemDirectory', () => {
+  it.each([
+    ['@eaDir', 'Synology thumbnail/index metadata, written inside every folder'],
+    ['@tmp', 'Synology scratch'],
+    ['.sync', 'Resilio state'],
+    ['.DS_Store', 'macOS'],
+    ['#recycle', 'Synology deletions'],
+    ['#snapshot', 'Synology snapshots'],
+  ])('skips %s (%s)', name => {
+    expect(isSystemDirectory(name)).toBe(true);
+  });
+
+  it.each([
+    '4utumn07',
+    '4utumn07 - reels',
+    'story - dawn_petal',
+    'story highlights - official_band - A.B.C',
+    'story highlights - theoldlyricmuseinsta - 💙1999-2005 era',
+    'Heejin_Bubble heejinmedia',
+    'gallery-dl',
+    'posts',
+  ])('keeps %s', name => {
+    expect(isSystemDirectory(name)).toBe(false);
+  });
+
+  it('does not treat a leading underscore as a system directory', () => {
+    // `_gemini-plans` is filtered separately at the archive root only; nothing
+    // below the root should be excluded just for starting with an underscore.
+    expect(isSystemDirectory('_gemini-plans')).toBe(false);
+  });
+});

src/lib/archive-index.ts

@@ -33,6 +33,21 @@ interface DirIndex {
 const MEDIA_RE = /\.(jpg|jpeg|png|webp|gif|bmp|tiff|mp4|webm|ogv|mov)$/i;
 const STAT_CONCURRENCY = 16;
 
+/**
+ * Directories the walk must never descend into.
+ *
+ * NAS filesystems scatter sidecar metadata *inside* every folder, not just at
+ * the share root: Synology writes `@eaDir` (thumbnails and indexing data),
+ * `#recycle` holds deletions, and `.sync` is Resilio's state. Indexing those
+ * would count NAS thumbnails as archive media and spend a stat on each one —
+ * measured on a real share, `@eaDir` accounted for 12,516 of 123,023 files.
+ *
+ * The archive root is already filtered by prefix; this is the same rule applied
+ * at every level below it.
+ */
+export const isSystemDirectory = (name: string): boolean =>
+  name.startsWith('@') || name.startsWith('.') || name === '#recycle' || name === '#snapshot';
+
 export class ArchiveIndex {
   private dirs = new Map<string, DirIndex>();
   private inFlight = new Map<string, Promise<DirIndex>>();
@@ -43,7 +58,7 @@ export class ArchiveIndex {
   /** Visible (non-system) directories at the archive root. */
   private listRootDirs(): string[] {
     return fs.readdirSync(this.archivesDir, { withFileTypes: true })
-      .filter(e => e.isDirectory() && !/^[.@_]/.test(e.name))
+      .filter(e => e.isDirectory() && !isSystemDirectory(e.name) && !e.name.startsWith('_'))
       .map(e => e.name);
   }
 
@@ -69,6 +84,7 @@ export class ArchiveIndex {
       return out;
     }
     for (const entry of entries) {
+      if (isSystemDirectory(entry.name)) continue;
       const rel = base ? `${base}/${entry.name}` : entry.name;
       if (entry.isDirectory()) out = out.concat(this.walk(path.join(absDir, entry.name), rel));
       else if (entry.isFile()) out.push(rel);

src/types/index.ts

@@ -50,7 +50,6 @@ export interface ArchiveFile {
   size: number;
   text(): Promise<string>;
   arrayBuffer(): Promise<ArrayBuffer>;
-  stream(): ReadableStream<Uint8Array>;
   url?: string;
   /**
    * A URL pointing at this file's contents. Local files mint a disk-backed