diff --git a/frontend/src/app/messages/[chatId]/page.tsx b/frontend/src/app/messages/[chatId]/page.tsx
index b4f48e96..0f94c106 100644
--- a/frontend/src/app/messages/[chatId]/page.tsx
+++ b/frontend/src/app/messages/[chatId]/page.tsx
@@ -971,7 +971,7 @@ function MessageDialogPageContent() {
           <p className="text-sm">{cm.error}</p>
         </div>
       ) : (
-        <div className="min-h-0 h-full lg:sticky lg:top-22 lg:h-[calc(100dvh-7.5rem)]">
+        <div className="min-h-0 h-full">
         <section className="flex h-full min-h-0 flex-col overflow-hidden lg:rounded-xl lg:border lg:border-[var(--border-subtle)] lg:bg-[var(--surface-primary)] lg:p-4 lg:shadow-[var(--shadow-card)]">
           {cm.chat ? (
             <>
diff --git a/frontend/src/components/AppShell.tsx b/frontend/src/components/AppShell.tsx
index f21a80ef..98bd70a9 100644
--- a/frontend/src/components/AppShell.tsx
+++ b/frontend/src/components/AppShell.tsx
@@ -112,8 +112,8 @@ function Header({ mobileNavPlacement, suppressMobileChrome = false, onOpenLeftNa
     <header
       className={`app-header z-[40] backdrop-blur ${
         isBottomMobileNav
-          ? "fixed inset-x-0 bottom-0 border-t lg:sticky lg:top-0 lg:bottom-auto lg:border-b lg:border-t-0"
-          : "sticky top-0 border-b"
+          ? "fixed inset-x-0 bottom-0 border-t lg:fixed lg:inset-x-0 lg:top-0 lg:bottom-auto lg:border-b lg:border-t-0"
+          : "fixed inset-x-0 top-0 border-b"
       } ${suppressMobileChrome ? "hidden lg:block" : ""} shrink-0`}
     >
       <div className="mx-auto max-w-6xl px-4 sm:px-8">
@@ -447,7 +447,7 @@ export function AppShell({ children }: AppShellProps) {
   }
 
   return (
-    <div className={`${isMessageDialogPage ? 'h-[100dvh] overflow-hidden' : 'min-h-screen'} app-shell flex flex-col ${mobileNavPlacement === "bottom" && !isMessageDialogPage ? "pb-[calc(env(safe-area-inset-bottom)+3.75rem)] lg:pb-0" : ""}`}>
+    <div className={`${isMessageDialogPage ? 'h-[100dvh] overflow-hidden lg:pt-14' : 'min-h-screen pt-10 lg:pt-14'} app-shell flex flex-col ${mobileNavPlacement === "bottom" && !isMessageDialogPage ? "pb-[calc(env(safe-area-inset-bottom)+3.75rem)] lg:pb-0" : ""}`}>
         <Header
           mobileNavPlacement={mobileNavPlacement}
           suppressMobileChrome={isMessageDialogPage}