diff --git a/dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs b/dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs
index fd3ff10fc2..f104f12890 100644
--- a/dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs
@@ -142,7 +142,7 @@ public InvokingContext(IEnumerable<ChatMessage> requestMessages)
         /// <value>
         /// A collection of <see cref="ChatMessage"/> instances representing new messages that were provided by the caller.
         /// </value>
-        public IEnumerable<ChatMessage> RequestMessages { get; }
+        public IEnumerable<ChatMessage> RequestMessages { get; set { field = Throw.IfNull(value); } }
     }
 
     /// <summary>
@@ -174,7 +174,7 @@ public InvokedContext(IEnumerable<ChatMessage> requestMessages, IEnumerable<Chat
         /// A collection of <see cref="ChatMessage"/> instances representing new messages that were provided by the caller.
         /// This does not include any <see cref="AIContextProvider"/> supplied messages.
         /// </value>
-        public IEnumerable<ChatMessage> RequestMessages { get; }
+        public IEnumerable<ChatMessage> RequestMessages { get; set { field = Throw.IfNull(value); } }
 
         /// <summary>
         /// Gets the messages provided by the <see cref="AIContextProvider"/> for this invocation, if any.
@@ -183,7 +183,7 @@ public InvokedContext(IEnumerable<ChatMessage> requestMessages, IEnumerable<Chat
         /// A collection of <see cref="ChatMessage"/> instances that were provided by the <see cref="AIContextProvider"/>,
         /// and were used by the agent as part of the invocation.
         /// </value>
-        public IEnumerable<ChatMessage>? AIContextProviderMessages { get; }
+        public IEnumerable<ChatMessage>? AIContextProviderMessages { get; set; }
 
         /// <summary>
         /// Gets the collection of response messages generated during this invocation if the invocation succeeded.
diff --git a/dotnet/src/Microsoft.Agents.AI.Abstractions/ChatMessageStore.cs b/dotnet/src/Microsoft.Agents.AI.Abstractions/ChatMessageStore.cs
index d28cd191b7..54cee063d7 100644
--- a/dotnet/src/Microsoft.Agents.AI.Abstractions/ChatMessageStore.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Abstractions/ChatMessageStore.cs
@@ -152,7 +152,7 @@ public InvokingContext(IEnumerable<ChatMessage> requestMessages)
         /// <value>
         /// A collection of <see cref="ChatMessage"/> instances representing new messages that were provided by the caller.
         /// </value>
-        public IEnumerable<ChatMessage> RequestMessages { get; }
+        public IEnumerable<ChatMessage> RequestMessages { get; set { field = Throw.IfNull(value); } }
     }
 
     /// <summary>
@@ -174,7 +174,7 @@ public sealed class InvokedContext
         public InvokedContext(IEnumerable<ChatMessage> requestMessages, IEnumerable<ChatMessage> chatMessageStoreMessages)
         {
             this.RequestMessages = Throw.IfNull(requestMessages);
-            this.ChatMessageStoreMessages = chatMessageStoreMessages;
+            this.ChatMessageStoreMessages = Throw.IfNull(chatMessageStoreMessages);
         }
 
         /// <summary>
@@ -184,7 +184,7 @@ public InvokedContext(IEnumerable<ChatMessage> requestMessages, IEnumerable<Chat
         /// A collection of <see cref="ChatMessage"/> instances representing new messages that were provided by the caller.
         /// This does not include any <see cref="ChatMessageStore"/> supplied messages.
         /// </value>
-        public IEnumerable<ChatMessage> RequestMessages { get; }
+        public IEnumerable<ChatMessage> RequestMessages { get; set { field = Throw.IfNull(value); } }
 
         /// <summary>
         /// Gets the messages retrieved from the <see cref="ChatMessageStore"/> for this invocation, if any.
@@ -193,7 +193,7 @@ public InvokedContext(IEnumerable<ChatMessage> requestMessages, IEnumerable<Chat
         /// A collection of <see cref="ChatMessage"/> instances that were retrieved from the <see cref="ChatMessageStore"/>,
         /// and were used by the agent as part of the invocation.
         /// </value>
-        public IEnumerable<ChatMessage> ChatMessageStoreMessages { get; }
+        public IEnumerable<ChatMessage> ChatMessageStoreMessages { get; set { field = Throw.IfNull(value); } }
 
         /// <summary>
         /// Gets or sets the messages provided by the <see cref="AIContextProvider"/> for this invocation, if any.
diff --git a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
index 0c02932b0a..8f6d6a5160 100644
--- a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
+++ b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
@@ -692,7 +692,7 @@ private async Task
 
         List<ChatMessage> inputMessagesForChatClient = [];
         IList<ChatMessage>? aiContextProviderMessages = null;
-        IList<ChatMessage>? chatMessageStoreMessages = null;
+        IList<ChatMessage>? chatMessageStoreMessages = [];
 
         // Populate the thread messages only if we are not continuing an existing response as it's not allowed
         if (chatOptions?.ContinuationToken is null)