diff --git a/app/templates/snapshots.html b/app/templates/snapshots.html
index 5fcf759..830c920 100644
--- a/app/templates/snapshots.html
+++ b/app/templates/snapshots.html
@@ -18,8 +18,32 @@
     .badge-age-warn  { background: rgba(245,158,11,.20); color: #f59e0b; border: 1px solid #f59e0b; }
     .badge-age-fresh { background: rgba(34,197,94,.20); color: #22c55e; border: 1px solid #22c55e; }
     .filters-card label { display: flex; align-items: center; gap: 0.5rem; }
+    /* Overlay plein page pendant les actions async */
+    #busy-overlay {
+        position: fixed; inset: 0; z-index: 9999;
+        background: rgba(10,14,23,0.75); backdrop-filter: blur(2px);
+        display: none; align-items: center; justify-content: center;
+        flex-direction: column; gap: 1rem;
+    }
+    #busy-overlay.active { display: flex; }
+    .spinner {
+        width: 64px; height: 64px;
+        border: 4px solid rgba(245,158,11,0.2);
+        border-top-color: #f59e0b;
+        border-radius: 50%;
+        animation: spin 0.9s linear infinite;
+    }
+    @keyframes spin { to { transform: rotate(360deg); } }
+    #busy-text { color: #f59e0b; font-size: 1.05rem; font-weight: 600; text-shadow: 0 0 12px rgba(245,158,11,0.6); }
+    #busy-sub  { color: #9ca3af; font-size: 0.85rem; }
 </style>
 
+<div id="busy-overlay">
+    <div class="spinner"></div>
+    <div id="busy-text">Action en cours…</div>
+    <div id="busy-sub">Ne ferme pas la page, ne navigue pas ailleurs.</div>
+</div>
+
 <div class="card p-4 mb-4 filters-card">
     <div class="grid grid-cols-12 gap-3 items-end">
         <div class="col-span-3">
@@ -199,8 +223,19 @@
         btnDelete.textContent = n > 0 ? `✕ SUPPRIMER ${n} SNAPSHOT${n>1?'S':''}` : '✕ SUPPRIMER LA SÉLECTION';
     }
 
-    function setBusy(msg, btn) {
+    // Overlay plein page : bloque toute interaction pendant les actions async.
+    // Empêche aussi la navigation accidentelle via beforeunload.
+    const overlay = document.getElementById('busy-overlay');
+    const busyText = document.getElementById('busy-text');
+    const busySub = document.getElementById('busy-sub');
+    let busyActive = false;
+
+    function setBusy(msg, btn, sub) {
         status.innerHTML = '<span class="text-cyber-yellow">⏳ ' + escapeHTML(msg) + '</span>';
+        busyText.textContent = '⏳ ' + msg;
+        busySub.textContent = sub || 'Ne ferme pas la page, ne navigue pas ailleurs.';
+        overlay.classList.add('active');
+        busyActive = true;
         if (btn) {
             btn.disabled = true;
             btn._origText = btn._origText || btn.textContent;
@@ -208,11 +243,21 @@
         }
     }
     function clearBusy(btn) {
+        overlay.classList.remove('active');
+        busyActive = false;
         if (btn && btn._origText) {
             btn.disabled = false;
             btn.textContent = btn._origText;
         }
     }
+    // Avertit si l'utilisateur tente de quitter la page pendant une action
+    window.addEventListener('beforeunload', (e) => {
+        if (busyActive) {
+            e.preventDefault();
+            e.returnValue = 'Une action est en cours. Quitter maintenant peut interrompre la requête.';
+            return e.returnValue;
+        }
+    });
 
     btnRefresh.addEventListener('click', async () => {
         setBusy('Recherche en cours… (peut prendre 10-30 s selon les vCenters)', btnRefresh);