diff --git a/Service/Plugins/AiFunctionService.cs b/Service/Plugins/AiFunctionService.cs
index 3f69cbb48..3d55c670c 100644
--- a/Service/Plugins/AiFunctionService.cs
+++ b/Service/Plugins/AiFunctionService.cs
@@ -21,6 +21,7 @@ using BS.Shared.Interface;
 using System.Text.Json;
 using BS.Shared.Core;
 using BeWo.Data.Security;
+using BS.Shared.Exceptions;
 
 namespace BeWo.Service.Plugins
 {
@@ -85,7 +86,10 @@ namespace BeWo.Service.Plugins
 
 			if(model.Value > -1)
 			{
-				AiUtils.CheckTokenSize(messages, model.ModelName, model.Value);
+				if(!AiUtils.CheckUserAllMessageContextSize(messages, model.ModelName, model.Value, out var error))
+				{
+					throw new BeWoNotImplementedException(error);
+				}
 			}
 
 			var payload = new
diff --git a/Service/Plugins/AiService2.cs b/Service/Plugins/AiService2.cs
index 88277ae40..a148071dc 100644
--- a/Service/Plugins/AiService2.cs
+++ b/Service/Plugins/AiService2.cs
@@ -231,7 +231,7 @@ namespace BeWo.Service.Plugins
 
 			var conversation = createAiConversation(aiContextType, context, modell_oid.Value, AiDataContextType.csv2);
 
-			return AiUtils.CheckSystemMessageContextSize(conversation.Messages.Select(x => x.Message), modell.ModelName, modell.Value);
+			return AiUtils.CheckSystemMessageContextSize(conversation.Messages.Select(x => x.Message), modell.ModelName, modell.Value, out var error);
 		}
 
 		// ======================[ private ]======================
@@ -349,6 +349,14 @@ namespace BeWo.Service.Plugins
 			// Check Token Size
 			if (-1 < configModel.Value)
 			{
+				if(conv.Messages.Count <= 2)
+				{
+					if(!AiUtils.CheckUserFirstMessageContextSize(conv.Messages.Select(x => x.Message), configModelName, configModel.Value, out var error))
+					{
+						throw new BeWoNotImplementedException(error);
+					}
+				}
+
 				AiUtils.CheckTokenSize(conv.Messages, configModelName, configModel.Value);
 			}
 
diff --git a/Shared/Core/AiUtils.cs b/Shared/Core/AiUtils.cs
index eb08f2564..ad03f0dd9 100644
--- a/Shared/Core/AiUtils.cs
+++ b/Shared/Core/AiUtils.cs
@@ -41,38 +41,25 @@ namespace BS.Shared.Core
 			}
 		}
 
-		public static bool CheckSystemMessageContextSize(IEnumerable<string> messages, string modelName, int max_context_size)
+		public static bool CheckSystemMessageContextSize(IEnumerable<string> messages, string modelName, int max_context_size, out string error)
 		{
-			if (max_context_size < 0)
-				throw new ArgumentOutOfRangeException(nameof(max_context_size));
-
-			if (max_context_size == 0)
-				return false;
-
-			var tokens_count = CalculateTokensByModel(messages, modelName);
-
-			var percentage = (double)tokens_count * 100 / max_context_size;
-
-			return percentage <= MAX_TOKENS_SYSTEM_PERCENTAGE;
+			return CheckContextSize(messages, modelName, max_context_size, MAX_TOKENS_SYSTEM_PERCENTAGE, out error);
 		}
 
-		public static bool CheckUserFirstMessageContextSize(IEnumerable<string> messages, string modelName, int max_context_size)
+		public static bool CheckUserFirstMessageContextSize(IEnumerable<string> messages, string modelName, int max_context_size, out string error)
 		{
-			if (max_context_size < 0)
-				throw new ArgumentOutOfRangeException(nameof(max_context_size));
-
-			if (max_context_size == 0)
-				return false;
-
-			var tokens_count = CalculateTokensByModel(messages, modelName);
-
-			var percentage = (double)tokens_count * 100 / max_context_size;
-
-			return percentage <= MAX_TOKENS_SYSTEM_PERCENTAGE + MAX_TOKENS_USER_PERCENTAGE;
+			return CheckContextSize(messages, modelName, max_context_size, MAX_TOKENS_SYSTEM_PERCENTAGE + MAX_TOKENS_USER_PERCENTAGE, out error);
 		}
 
-		public static bool CheckUserAllMessageContextSize(IEnumerable<string> messages, string modelName, int max_context_size)
+		public static bool CheckUserAllMessageContextSize(IEnumerable<string> messages, string modelName, int max_context_size, out string error)
 		{
+			return CheckContextSize(messages, modelName, max_context_size, MAX_TOKENS_CONVERSATION_PERCENTAGE, out error);
+		}
+
+		private static bool CheckContextSize(IEnumerable<string> messages, string modelName, int max_context_size, double maximum, out string error)
+		{
+			error = null;
+
 			if (max_context_size < 0)
 				throw new ArgumentOutOfRangeException(nameof(max_context_size));
 
@@ -83,7 +70,14 @@ namespace BS.Shared.Core
 
 			var percentage = (double)tokens_count * 100 / max_context_size;
 
-			return percentage <= MAX_TOKENS_CONVERSATION_PERCENTAGE;
+			var success = percentage <= maximum;
+
+			if (!success)
+			{
+				error = $"Windowsize exceeded: {tokens_count}/{max_context_size} ({percentage}%>{maximum}%)";
+			}
+
+			return success;
 		}
 
 		private static int CalculateTokensByModel(IEnumerable<string> messages, string modelName)