diff --git a/app/static/js/vault.js b/app/static/js/vault.js
index a32c657..dafb05c 100644
--- a/app/static/js/vault.js
+++ b/app/static/js/vault.js
@@ -1867,10 +1867,10 @@ const Vault = (() => {
     // Tabs
     document.querySelectorAll('.panel-tabs').forEach(c => initTabs(c));
 
-    // Sidebar collapse toggle — desktop only (mobile uses hamburger instead)
+    // Sidebar collapse toggle (desktop) and mobile hamburger
     const sidebar = document.getElementById('sidebar');
     const toggleBtn = document.getElementById('btn-sidebar-toggle');
-    if (sidebar && toggleBtn && document.documentElement.classList.contains('is-desktop')) {
+    if (sidebar && toggleBtn) {
       const STORAGE_KEY = 'sidebar_collapsed';
       if (localStorage.getItem(STORAGE_KEY) === '1') {
         sidebar.classList.add('collapsed');
@@ -1905,9 +1905,10 @@ const Vault = (() => {
     backdrop?.addEventListener('touchstart', closeMobileSidebar, { passive: true });
 
     // Close mobile sidebar when a nav item is tapped (mobile only)
+    const mobileQuery = window.matchMedia('(max-width: 768px)');
     document.querySelectorAll('.sidebar-item').forEach(item => {
       item.addEventListener('click', () => {
-        if (document.documentElement.classList.contains('is-mobile')) closeMobileSidebar();
+        if (mobileQuery.matches) closeMobileSidebar();
       });
     });