diff --git a/app/MindWork AI Studio/Chat/StringExtension.cs b/app/MindWork AI Studio/Chat/StringExtension.cs
index d229a0b4..21d0c399 100644
--- a/app/MindWork AI Studio/Chat/StringExtension.cs	
+++ b/app/MindWork AI Studio/Chat/StringExtension.cs	
@@ -6,7 +6,7 @@ public static class StringExtensions
     {
         const string OPEN_TAG = "<think>";
         const string CLOSE_TAG = "</think>";
-        if (string.IsNullOrEmpty(input) || !input.StartsWith(OPEN_TAG))
+        if (string.IsNullOrWhiteSpace(input) || !input.StartsWith(OPEN_TAG, StringComparison.Ordinal))
             return input;
         
         var endIndex = input.IndexOf(CLOSE_TAG, StringComparison.Ordinal);