diff --git a/backend/static/js/app.js b/backend/static/js/app.js
index c863241..738cee6 100644
--- a/backend/static/js/app.js
+++ b/backend/static/js/app.js
@@ -193,7 +193,11 @@ const App = (() => {
   }
 
   function _openSidebar() {
-    document.getElementById('sidebar')?.classList.add('open');
+    const s = document.getElementById('sidebar');
+    if (!s) { UI.toast.error('sidebar: NULL'); return; }
+    s.classList.add('open');
+    const cs = getComputedStyle(s);
+    UI.toast.info(`display:${cs.display} | transform:${cs.transform} | z:${cs.zIndex}`);
     document.getElementById('sidebar-backdrop')?.classList.add('visible');
   }