fixed code

src/context/UnreadContext.jsx

@@ -6,7 +6,15 @@ export function UnreadProvider({ children }) {
   const [unreadMap, setUnreadMap] = useState({});
 
   const setChatUnread = useCallback((chatId, count) => {
-    setUnreadMap(prev => ({ ...prev, [chatId]: count }));
+    setUnreadMap(prev => {
+      if (count > 0) {
+        return { ...prev, [chatId]: count };
+      }
+      if (prev[chatId] === undefined) return prev;
+      const next = { ...prev };
+      delete next[chatId];
+      return next;
+    });
   }, []);
 
   const clearChatUnread = useCallback((chatId) => {
@@ -18,6 +26,11 @@ export function UnreadProvider({ children }) {
     });
   }, []);
 
+  /**
+   * Инициализирует/синхронизирует unreadMap из полного списка чатов
+   * (например, при первой загрузке через REST). Ожидает ПОЛНЫЙ список —
+   * чаты, отсутствующие в переданном массиве, не трогает.
+   */
   const updateFromChats = useCallback((chats) => {
     setUnreadMap(prev => {
       const next = { ...prev };
@@ -25,6 +38,8 @@ export function UnreadProvider({ children }) {
         const count = chat.unreadCount ?? chat.unreadMessages ?? 0;
         if (count > 0) {
           next[chat.id] = count;
+        } else {
+          delete next[chat.id];
         }
       }
       return next;
@@ -32,14 +47,14 @@ export function UnreadProvider({ children }) {
   }, []);
 
   const totalUnread = useMemo(() =>
-    Object.values(unreadMap).reduce((sum, c) => sum + c, 0),
-    [unreadMap]
+          Object.values(unreadMap).reduce((sum, c) => sum + c, 0),
+      [unreadMap]
   );
 
   return (
-    <UnreadContext.Provider value={{ unreadMap, totalUnread, setChatUnread, clearChatUnread, updateFromChats }}>
-      {children}
-    </UnreadContext.Provider>
+      <UnreadContext.Provider value={{ unreadMap, totalUnread, setChatUnread, clearChatUnread, updateFromChats }}>
+        {children}
+      </UnreadContext.Provider>
   );
 }
 
@@ -47,4 +62,4 @@ export function useUnread() {
   const ctx = useContext(UnreadContext);
   if (!ctx) throw new Error('useUnread must be used within UnreadProvider');
   return ctx;
-}
+}