diff --git a/src/frontend/src/components/NotificationCenter.tsx b/src/frontend/src/components/NotificationCenter.tsx
index c43d9ab..3ccc4b2 100644
--- a/src/frontend/src/components/NotificationCenter.tsx
+++ b/src/frontend/src/components/NotificationCenter.tsx
@@ -68,7 +68,7 @@ export default function NotificationCenter({ onClose }: { onClose: () => void })
         if (importantTypes.includes(e.type || data.event_type)) {
           setSseEvents(prev => [{
             id: data.id || `sse-${Date.now()}`,
-            type: (e.type === 'task_failed' ? 'error' : e.type === 'task_completed' ? 'success' : 'info'),
+            type: (e.type === 'task_failed' ? 'error' : e.type === 'task_completed' ? 'success' : 'info') as NotifItem['type'],
             title: data.title || data.event_type || e.type,
             message: data.detail || JSON.stringify(data).slice(0, 100),
             time: data.timestamp || new Date().toISOString(),