diff --git a/frontend/src/components/ChatHeader.tsx b/frontend/src/components/ChatHeader.tsx
index 113c04d..76546fc 100644
--- a/frontend/src/components/ChatHeader.tsx
+++ b/frontend/src/components/ChatHeader.tsx
@@ -19,7 +19,7 @@ export default function ChatHeader({ chat, onBack, onRefresh, onShowInfo }: Prop
 
   const typing = typingUsers[chat.id] || [];
   const isPrivate = chat.type === 'private';
-  const isOnline = isPrivate && chat.privateUserId && onlineUsers.has(chat.privateUserId);
+  const isOnline = !!(isPrivate && chat.privateUserId && onlineUsers.has(chat.privateUserId));
 
   let subtitle = '';
   if (typing.length > 0) {
diff --git a/frontend/src/vite-env.d.ts b/frontend/src/vite-env.d.ts
new file mode 100644
index 0000000..11f02fe
--- /dev/null
+++ b/frontend/src/vite-env.d.ts
@@ -0,0 +1 @@
+/// <reference types="vite/client" />