diff --git a/website/public/shell.css b/website/public/shell.css
index 8778123..2098044 100644
--- a/website/public/shell.css
+++ b/website/public/shell.css
@@ -20,11 +20,19 @@ body {
   justify-content: space-between;
   padding: 0 16px;
   z-index: 9999;
+  border-bottom: 1px solid var(--rs-glass-border);
+  color: var(--rs-text-primary);
+}
+/* backdrop-filter on pseudo-element so the header doesn't create a
+   containing block that traps position:fixed children (e.g. app-switcher sidebar) */
+.rstack-header::before {
+  content: '';
+  position: absolute;
+  inset: 0;
+  z-index: -1;
   backdrop-filter: blur(12px);
   -webkit-backdrop-filter: blur(12px);
   background: var(--rs-glass-bg);
-  border-bottom: 1px solid var(--rs-glass-border);
-  color: var(--rs-text-primary);
 }
 
 .rstack-header__left {