.NET: Fix bug with per-service-call persistence and approvals (#4933)

* Fix bug with per-service-call persistence and approvals

* Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs

@@ -788,6 +788,13 @@ public sealed partial class ChatClientAgent : AIAgent
             chatOptions.ConversationId = typedSession.ConversationId;
         }
 
+        // When per-service-call persistence is active, set a sentinel conversation ID so that
+        // FunctionInvokingChatClient treats locally-persisted history the same as service-managed
+        // history. This prevents it from adding duplicate FunctionCallContent messages into the
+        // request when processing approval responses — the loaded history already contains them.
+        // ChatHistoryPersistingChatClient strips the sentinel before forwarding to the inner client.
+        chatOptions = this.SetLocalHistoryConversationIdIfNeeded(chatOptions);
+
         // Materialize the accumulated messages once at the end of the provider pipeline, reusing the existing list if possible.
         List<ChatMessage> messagesList = inputMessagesForChatClient as List<ChatMessage> ?? inputMessagesForChatClient.ToList();
 
@@ -929,6 +936,26 @@ public sealed partial class ChatClientAgent : AIAgent
         }
     }
 
+    /// <summary>
+    /// Sets the <see cref="ChatHistoryPersistingChatClient.LocalHistoryConversationId"/> sentinel on
+    /// <paramref name="chatOptions"/> when per-service-call persistence is active and no real
+    /// conversation ID is present.
+    /// </summary>
+    /// <returns>
+    /// The (possibly new) <see cref="ChatOptions"/> with the sentinel set, or the original
+    /// <paramref name="chatOptions"/> if no sentinel is needed.
+    /// </returns>
+    private ChatOptions? SetLocalHistoryConversationIdIfNeeded(ChatOptions? chatOptions)
+    {
+        if (this.PersistsChatHistoryPerServiceCall && string.IsNullOrWhiteSpace(chatOptions?.ConversationId))
+        {
+            chatOptions ??= new ChatOptions();
+            chatOptions.ConversationId = ChatHistoryPersistingChatClient.LocalHistoryConversationId;
+        }
+
+        return chatOptions;
+    }
+
     /// <summary>
     /// Gets a value indicating whether the agent has a <see cref="ChatHistoryPersistingChatClient"/>
     /// decorator in mark-only mode, which marks messages for later persistence at the end of the run.

dotnet/src/Microsoft.Agents.AI/ChatClient/ChatHistoryPersistingChatClient.cs

@@ -50,6 +50,26 @@ internal sealed class ChatHistoryPersistingChatClient : DelegatingChatClient
     /// </summary>
     internal const string PersistedMarkerKey = "_chatHistoryPersisted";
 
+    /// <summary>
+    /// A sentinel value set on <see cref="ChatOptions.ConversationId"/> by <see cref="ChatClientAgent"/>
+    /// when per-service-call persistence is active and no real conversation ID exists.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This signals to <see cref="FunctionInvokingChatClient"/> that the chat history is being managed
+    /// externally (by this decorator), which prevents it from adding duplicate <see cref="FunctionCallContent"/>
+    /// messages into the request during approval-response processing. Without this sentinel,
+    /// <see cref="FunctionInvokingChatClient"/> would reconstruct function-call messages from approval
+    /// responses and append them to the original messages — but the loaded history already contains
+    /// those same function calls, causing duplicate tool-call entries that the model rejects.
+    /// </para>
+    /// <para>
+    /// This decorator strips the sentinel before forwarding requests to the inner client, so the
+    /// underlying model never sees it.
+    /// </para>
+    /// </remarks>
+    internal const string LocalHistoryConversationId = "_agent_local_history";
+
     /// <summary>
     /// Initializes a new instance of the <see cref="ChatHistoryPersistingChatClient"/> class.
     /// </summary>
@@ -87,6 +107,7 @@ internal sealed class ChatHistoryPersistingChatClient : DelegatingChatClient
         CancellationToken cancellationToken = default)
     {
         var (agent, session) = GetRequiredAgentAndSession();
+        options = StripLocalHistoryConversationId(options);
 
         ChatResponse response;
         try
@@ -130,6 +151,7 @@ internal sealed class ChatHistoryPersistingChatClient : DelegatingChatClient
         [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
         var (agent, session) = GetRequiredAgentAndSession();
+        options = StripLocalHistoryConversationId(options);
 
         List<ChatResponseUpdate> responseUpdates = [];
 
@@ -310,4 +332,20 @@ internal sealed class ChatHistoryPersistingChatClient : DelegatingChatClient
             }
         }
     }
+
+    /// <summary>
+    /// If the <paramref name="options"/> carry the <see cref="LocalHistoryConversationId"/> sentinel,
+    /// returns a clone with the conversation ID cleared so the inner client never sees it.
+    /// Otherwise returns the original <paramref name="options"/> unchanged.
+    /// </summary>
+    private static ChatOptions? StripLocalHistoryConversationId(ChatOptions? options)
+    {
+        if (options?.ConversationId == LocalHistoryConversationId)
+        {
+            options = options.Clone();
+            options.ConversationId = null;
+        }
+
+        return options;
+    }
 }