diff --git a/src/Infrastructure/BotSharp.Abstraction/Conversations/Models/ConversationState.cs b/src/Infrastructure/BotSharp.Abstraction/Conversations/Models/ConversationState.cs
index b56187b5..8382cdf2 100644
--- a/src/Infrastructure/BotSharp.Abstraction/Conversations/Models/ConversationState.cs
+++ b/src/Infrastructure/BotSharp.Abstraction/Conversations/Models/ConversationState.cs
@@ -1,6 +1,8 @@
+using System.Collections.Concurrent;
+
 namespace BotSharp.Abstraction.Conversations.Models;
 
-public class ConversationState : Dictionary<string, StateKeyValue>
+public class ConversationState : ConcurrentDictionary<string, StateKeyValue>
 {
     public ConversationState()
     {
diff --git a/src/Plugins/BotSharp.Plugin.KnowledgeBase/Services/KnowledgeService.Vector.cs b/src/Plugins/BotSharp.Plugin.KnowledgeBase/Services/KnowledgeService.Vector.cs
index 498e8c99..908fdc23 100644
--- a/src/Plugins/BotSharp.Plugin.KnowledgeBase/Services/KnowledgeService.Vector.cs
+++ b/src/Plugins/BotSharp.Plugin.KnowledgeBase/Services/KnowledgeService.Vector.cs
@@ -80,6 +80,7 @@ public partial class KnowledgeService
             }).ToList();
 
             var vectorDb = GetVectorDb();
+            if (vectorDb == null) return [];
             var dbCollections = await vectorDb.GetCollections();
             return configs.Where(x => dbCollections.Contains(x.Name));
         }
diff --git a/tests/BotSharp.LLM.Tests/Core/NullConversationStateService.cs b/tests/BotSharp.LLM.Tests/Core/NullConversationStateService.cs
index befc6c06..bed47b24 100644
--- a/tests/BotSharp.LLM.Tests/Core/NullConversationStateService.cs
+++ b/tests/BotSharp.LLM.Tests/Core/NullConversationStateService.cs
@@ -1,4 +1,4 @@
-using System.Text.Json;
+using System.Text.Json;
 using BotSharp.Abstraction.Conversations;
 using BotSharp.Abstraction.Conversations.Enums;
 using BotSharp.Abstraction.Conversations.Models;
@@ -68,8 +68,8 @@ namespace BotSharp.Plugin.Google.Core
 
         public ConversationState GetCurrentState()
         {
-           
-            return new ConversationState { { "StateKey", new StateKeyValue { Key = "Key", Values = new List<StateValue>()} } };
+
+            return new ConversationState();
         }
 
         public void SetCurrentState(ConversationState state)
diff --git a/tests/BotSharp.Plugin.PizzaBot/data/agents/8970b1e5-d260-4e2c-90b1-f1415a257c18/agent.json b/tests/BotSharp.Plugin.PizzaBot/data/agents/8970b1e5-d260-4e2c-90b1-f1415a257c18/agent.json
index 99f1f2fd..3826234e 100644
--- a/tests/BotSharp.Plugin.PizzaBot/data/agents/8970b1e5-d260-4e2c-90b1-f1415a257c18/agent.json
+++ b/tests/BotSharp.Plugin.PizzaBot/data/agents/8970b1e5-d260-4e2c-90b1-f1415a257c18/agent.json
@@ -13,7 +13,7 @@
   "labels": [ "experiment" ],
   "llmConfig": {
     "provider": "openai",
-    "model": "gpt-4.1-nano"
+    "model": "gpt-5-nano"
   },
   "routingRules": [
     {