diff --git a/AICore/Context/SummaryParser/CsvContextSummaryParser.cs b/AICore/Context/SummaryParser/CsvContextSummaryParser.cs
index 7535c8627..874332c57 100644
--- a/AICore/Context/SummaryParser/CsvContextSummaryParser.cs
+++ b/AICore/Context/SummaryParser/CsvContextSummaryParser.cs
@@ -41,7 +41,7 @@ namespace AICore.Context.SummaryParser
 				sb.AppendLine($"Hilfeplan:{summary.SupportConcept}");
 				sb.AppendLine($"Kostenträger:{summary.CostBearer}");
 				sb.AppendLine("Klient:");
-				sb.AppendLine(ToCsvString(summary.Customer, _Delimiter));
+				sb.Append(ToCsvString(summary.Customer, _Delimiter));
 				sb.AppendLine("Zeiterfassungseinträge:");
 				sb.AppendLine(ToCsvString(summary.DataContext, _Delimiter));
 				return sb.ToString();
diff --git a/AICore/Prompt/Core/AiUtils.cs b/AICore/Prompt/Core/AiUtils.cs
index f4dd262f8..7d371bd84 100644
--- a/AICore/Prompt/Core/AiUtils.cs
+++ b/AICore/Prompt/Core/AiUtils.cs
@@ -1,8 +1,59 @@
-namespace AICore.Prompt.Core
+using BeWo.Data.Entities;
+using BS.Shared.Exceptions;
+using System;
+using System.Collections.Generic;
+
+namespace AICore.Prompt.Core
 {
 	public static class AiUtils
 	{
+		public static string CheckTokenSize(IList<AiConversationMessage> messages, string modelName)
+		{
+			var buffer = 500;
 
+			var max_tokens = GetMaxTokensByModel(modelName);
 
+			var prev_tokens = CalculateTokensByModel(messages, modelName);
+
+			var calc_tokens = prev_tokens + buffer;
+
+			var percentage = calc_tokens * 100 / max_tokens;
+
+			if (calc_tokens > max_tokens)
+				return $"Windowsize exceeded: ({prev_tokens}+{buffer})/{max_tokens} ({percentage}%)";
+
+			return null;
+		}
+
+		private static int GetMaxTokensByModel(string modelName)
+		{
+			switch (modelName)
+			{
+				case "llama3.2:latest": return 128000;
+				case "gemma3:12b": return 128000;
+				case "gemma3:4b": return 128000;
+				case "gemma3_12b-max-context:latest": return 128000;
+				case "gemma3_4b-max-context:latest": return 128000;
+				case "mistral:latest": return 32000;
+				case "phi4:latest": return 16000;
+				default:
+					break;
+			}
+
+			throw BeWoNotImplementedException.CreateFromInvalidObject(modelName);
+		}
+
+		private static int CalculateTokensByModel(IList<AiConversationMessage> messages, string modelName)
+		{
+			var count = 0;
+
+			foreach (var message in messages)
+			{
+				count += 4;
+				count += message.Message.Length / 2;
+			}
+
+			return count;
+		}
 	}
 }
diff --git a/Service/Plugins/AiService2.cs b/Service/Plugins/AiService2.cs
index 55a08a109..522343de0 100644
--- a/Service/Plugins/AiService2.cs
+++ b/Service/Plugins/AiService2.cs
@@ -6,6 +6,7 @@ using System.Linq;
 using System.Net;
 using System.ServiceModel;
 using System.Text;
+using AICore.Prompt.Core;
 using AICore.Prompt.Factories;
 using BeWo.Data.Access;
 using BeWo.Data.Entities;
@@ -20,6 +21,7 @@ using BS.Shared.Core;
 using BS.Shared.DataContracts;
 using BS.Shared.DataContracts.Compact;
 using BS.Shared.DataContracts.Feature.AI;
+using BS.Shared.Exceptions;
 using BS.Shared.Extensions;
 using Newtonsoft.Json;
 
@@ -316,12 +318,6 @@ namespace BeWo.Service.Plugins
 				messages = conv.Messages.Select(m => new { role = m.Role.ToString().ToLower(), content = m.Message })
 			};
 
-			// Check Token Size
-			if (!checkTokenSize(conv.Messages, configModelName))
-			{
-				throw new Exception();
-			}
-
 			// Updated
 			conv.Updated = DateTime.Now;
 
@@ -334,6 +330,12 @@ namespace BeWo.Service.Plugins
 
 			conv.Messages.Add(user_msg);
 
+			// Check Token Size
+			if (AiUtils.CheckTokenSize(conv.Messages, configModelName) is string error)
+			{
+				throw new BeWoNotImplementedException(error);
+			}
+
 			// Update DB Entity
 			// DAOFactory.GenericDAO.Update(conv);
 
@@ -370,31 +372,5 @@ namespace BeWo.Service.Plugins
 
 			return new AiConversationMessageDC[] { user_msg_dc, assi_msg_dc };
 		}
-
-		private bool checkTokenSize(IList<AiConversationMessage> messages, string configModelName)
-		{
-
-			return true;
-			//Tokenizer tokenizer = TiktokenTokenizer.CreateForModel(configModelName);
-
-			//int tokens = countChatTokens(messages, tokenizer);
-		}
-
-		//private int countChatTokens(IList<AiConversationMessage> messages, Tokenizer tokenizer)
-		//{
-		//	int tokensPerMessage = 4;  // OpenAI Overhead
-		//	int tokensPerReply = 2;
-
-		//	int total = 0;
-
-		//	foreach (var msg in messages)
-		//	{
-		//		total += tokensPerMessage;
-		//		total += tokenizer.CountTokens(msg.Role.ToString());
-		//		total += tokenizer.CountTokens(msg.Message);
-		//	}
-
-		//	return total + tokensPerReply;
-		//}
 	}
 }
\ No newline at end of file