diff --git a/public/index.html b/public/index.html
index 4fcb28d..68dca8d 100644
--- a/public/index.html
+++ b/public/index.html
@@ -56,5 +56,6 @@
 <script src="/links.js"></script>
 <script src="/palette.js"></script>
 <script src="/app.js"></script>
+<script src="/shell.js"></script>
 </body>
 </html>
diff --git a/public/shell.js b/public/shell.js
new file mode 100644
index 0000000..813d3bc
--- /dev/null
+++ b/public/shell.js
@@ -0,0 +1,56 @@
+// App-shell niceties that do not belong to any one tab: offline notice and an accessibility layer
+// (names for icon-only buttons, a skip link, keyboard handling and focus for sheets).
+(function () {
+  // ---- Offline notice
+  const bar = document.createElement('div');
+  bar.id = 'offline'; bar.setAttribute('role', 'status'); bar.hidden = true;
+  bar.textContent = 'You are offline. Showing what was saved on this device; changes will not sync until you are back online.';
+  document.body.appendChild(bar);
+  const sync = () => { bar.hidden = navigator.onLine; };
+  addEventListener('online', sync); addEventListener('offline', sync); sync();
+
+  // ---- Skip link and landmarks
+  const skip = document.createElement('a');
+  skip.href = '#view'; skip.className = 'skip'; skip.textContent = 'Skip to content';
+  skip.addEventListener('click', e => { e.preventDefault(); const v = document.getElementById('view'); if (v) { v.setAttribute('tabindex', '-1'); v.focus(); } });
+  document.body.insertBefore(skip, document.body.firstChild);
+  const nav = document.getElementById('nav'); if (nav && !nav.getAttribute('aria-label')) nav.setAttribute('aria-label', 'Main');
+
+  // ---- Give every button or link that has only an icon a name (from its title, tooltip, id or class)
+  const NAMES = { more: 'More', navcol: 'Collapse the menu', sx: 'Cancel', x: 'Close', close: 'Close', back: 'Back', fwd: 'Forward', menu: 'Menu', play: 'Play', pause: 'Pause', next: 'Next', prev: 'Previous', shuffle: 'Shuffle', repeat: 'Repeat', send: 'Send', clip: 'Attach a file', lyrics: 'Lyrics', full: 'Full screen', refresh: 'Refresh', ext: 'Open in a new tab' };
+  const named = el => (el.getAttribute('aria-label') || el.getAttribute('aria-labelledby') || el.textContent.trim() || el.getAttribute('title') || '');
+  function label(root) {
+    root.querySelectorAll('button, a[href], [role="button"]').forEach(el => {
+      if (named(el)) { if (!el.getAttribute('aria-label') && !el.textContent.trim()) el.setAttribute('aria-label', el.getAttribute('title')); return; }
+      const key = (el.id || '').replace(/^(btn|b)-?/, '') || [...el.classList].find(c => NAMES[c]) || '';
+      const l = NAMES[key] || NAMES[el.id] || (el.querySelector('img[alt]') || {}).alt;
+      if (l) el.setAttribute('aria-label', l);
+    });
+    root.querySelectorAll('input:not([type=hidden]):not([type=checkbox]):not([type=radio]), select, textarea').forEach(el => {
+      if (el.getAttribute('aria-label') || el.getAttribute('aria-labelledby') || (el.id && document.querySelector(`label[for="${CSS.escape(el.id)}"]`)) || el.closest('label')) return;
+      const l = el.getAttribute('placeholder') || el.getAttribute('title'); if (l) el.setAttribute('aria-label', l);
+    });
+  }
+  let pending = false;
+  new MutationObserver(() => { if (pending) return; pending = true; requestAnimationFrame(() => { pending = false; label(document.body); }); })
+    .observe(document.body, { childList: true, subtree: true });
+  label(document.body);
+
+  // ---- Sheets (bottom sheets and dialogs): Escape closes, focus moves in and returns, Tab stays inside
+  let lastFocus = null;
+  new MutationObserver(() => {
+    const s = document.getElementById('sheet');
+    if (s && !s._a11y) { s._a11y = true; lastFocus = document.activeElement; setTimeout(() => { if (!s.contains(document.activeElement)) { const f = s.querySelector('input:not([type=hidden]), textarea, select, button'); if (f) f.focus(); } }, 50); }
+    if (!s && lastFocus) { try { lastFocus.focus(); } catch {} lastFocus = null; }
+  }).observe(document.body, { childList: true });
+  addEventListener('keydown', e => {
+    const s = document.getElementById('sheet'); if (!s) return;
+    if (e.key === 'Escape' && typeof closeSheet === 'function') { e.preventDefault(); closeSheet(); return; }
+    if (e.key !== 'Tab') return;
+    const f = [...s.querySelectorAll('a[href], button:not([disabled]), input:not([type=hidden]):not([disabled]), select, textarea, [tabindex]:not([tabindex="-1"])')].filter(x => x.offsetParent !== null);
+    if (!f.length) return;
+    const first = f[0], last = f[f.length - 1];
+    if (e.shiftKey && document.activeElement === first) { e.preventDefault(); last.focus(); }
+    else if (!e.shiftKey && (document.activeElement === last || !s.contains(document.activeElement))) { e.preventDefault(); first.focus(); }
+  });
+})();
diff --git a/public/style.css b/public/style.css
index bc43da8..36c0076 100644
--- a/public/style.css
+++ b/public/style.css
@@ -495,3 +495,9 @@ body.lyropen { overflow: hidden; }
 .palrow.on { background: var(--panel2); }
 .palrow svg { width: 20px; height: 20px; color: var(--muted); }
 @media (prefers-reduced-motion: reduce) { * { animation-duration: .01ms !important; transition-duration: .01ms !important; } }
+
+/* Offline notice, skip link, keyboard focus */
+#offline { position: fixed; left: 0; right: 0; top: 0; z-index: 70; padding: calc(var(--sat) + 6px) 16px 6px; text-align: center; font-size: 13px; background: #b26a00; color: #fff; }
+.skip { position: fixed; left: 8px; top: -60px; z-index: 80; padding: 10px 14px; border-radius: 10px; background: var(--accent); color: var(--accent-t); }
+.skip:focus { top: calc(var(--sat) + 8px); }
+:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
diff --git a/public/sw.js b/public/sw.js
index ede84f2..452a2ec 100644
--- a/public/sw.js
+++ b/public/sw.js
@@ -1,11 +1,22 @@
 // App-shell cache only; Seafile/API traffic always goes to the network.
-const CACHE = 'hub-v6';
+const CACHE = 'hub-v7';
 const SHELL = ['/icon.svg', '/manifest.webmanifest', '/icons/icon-192.png', '/icons/apple-touch-icon.png'];
 
-self.addEventListener('install', e => {
-  e.waitUntil(caches.open(CACHE).then(c => c.addAll(SHELL)));
-  self.skipWaiting();
-});
+// Install: keep the icons, and (when signed in) the page itself with the scripts and styles it names, so the app opens offline.
+async function precache() {
+  const c = await caches.open(CACHE);
+  await c.addAll(SHELL);
+  try {
+    const r = await fetch('/', { credentials: 'same-origin', redirect: 'manual' });
+    if (r.ok) {
+      const html = await r.clone().text();
+      await c.put('/', r);
+      const urls = [...html.matchAll(/(?:src|href)="(\/[^"]+\.(?:js|css)(?:\?[^"]*)?)"/g)].map(m => m[1]);
+      await Promise.all(urls.map(u => c.add(u).catch(() => {})));
+    }
+  } catch { /* signed out or offline: it is cached the first time it is used */ }
+}
+self.addEventListener('install', e => { e.waitUntil(precache()); self.skipWaiting(); });
 self.addEventListener('activate', e => {
   e.waitUntil(caches.keys().then(ks => Promise.all(ks.filter(k => k !== CACHE).map(k => caches.delete(k)))));
   self.clients.claim();
diff --git a/server.js b/server.js
index 1941db2..5362f88 100644
--- a/server.js
+++ b/server.js
@@ -99,7 +99,7 @@ function serveStatic(req, res) {
     if (err) { res.writeHead(404); return res.end('Not found'); }
     // The pages link to /app.js?v=<build> etc. A new release changes the address, so no proxy cache ("Cache Assets" in
     // Nginx Proxy Manager, a CDN, the browser) can hand out an old copy.
-    if (p === '/index.html' || p === '/login.html') data = Buffer.from(String(data).replace(/(src|href)="(\/(?:app|webauthn|login|links|palette)\.js|\/style\.css)"/g, `$1="$2?v=${BUILD}"`));
+    if (p === '/index.html' || p === '/login.html') data = Buffer.from(String(data).replace(/(src|href)="(\/(?:app|webauthn|login|links|palette|shell)\.js|\/style\.css)"/g, `$1="$2?v=${BUILD}"`));
     const headers = { 'content-type': TYPES[path.extname(file)] || 'application/octet-stream' };
     if (p.startsWith('/icons/')) headers['cache-control'] = 'public, max-age=604800'; // icons and splash screens rarely change
     else { // everything else: the browser may keep a copy but must check with us first, so a new version is never missed
@@ -113,7 +113,7 @@ function serveStatic(req, res) {
 }
 
 // Changes whenever the app's files change, so an open page can tell that a newer version is available.
-const BUILD = (() => { try { return crypto.createHash('sha1').update(['app.js', 'links.js', 'palette.js', 'index.html', 'style.css', 'webauthn.js', 'login.js', 'login.html', 'sw.js'].map(f => fs.readFileSync(path.join(PUBLIC, f))).join('')).digest('hex').slice(0, 12); } catch { return String(Date.now()); } })();
+const BUILD = (() => { try { return crypto.createHash('sha1').update(['app.js', 'links.js', 'palette.js', 'shell.js', 'index.html', 'style.css', 'webauthn.js', 'login.js', 'login.html', 'sw.js'].map(f => fs.readFileSync(path.join(PUBLIC, f))).join('')).digest('hex').slice(0, 12); } catch { return String(Date.now()); } })();
 
 // ---- OnlyOffice in-app editing (JWT-signed editor config + save-back callback to Seafile)
 const JWT_SECRET = process.env.ONLYOFFICE_JWT_SECRET || '';