From 2101d9d36d113bb5e0ac2ccff14719e54088f5a3 Mon Sep 17 00:00:00 2001
From: westey <164392973+westey-m@users.noreply.github.com>
Date: Fri, 31 Oct 2025 14:12:20 +0000
Subject: [PATCH] Don't stamp unknown author name on output messages. (#1830)

---
 .../Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs  |  8 ++++----
 .../ChatClient/ChatClientAgentTests.cs                 | 10 ++++++----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
index 5ae6e59904..46f893e531 100644
--- a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
+++ b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
@@ -353,9 +353,9 @@ public sealed partial class ChatClientAgent : AIAgent
 
         chatClient = ApplyRunOptionsTransformations(options, chatClient);
 
-        var agentName = this.GetLoggingAgentName();
+        var loggingAgentName = this.GetLoggingAgentName();
 
-        this._logger.LogAgentChatClientInvokingAgent(nameof(RunAsync), this.Id, agentName, this._chatClientType);
+        this._logger.LogAgentChatClientInvokingAgent(nameof(RunAsync), this.Id, loggingAgentName, this._chatClientType);
 
         // Call the IChatClient and notify the AIContextProvider of any failures.
         TChatClientResponse chatResponse;
@@ -369,7 +369,7 @@ public sealed partial class ChatClientAgent : AIAgent
             throw;
         }
 
-        this._logger.LogAgentChatClientInvokedAgent(nameof(RunAsync), this.Id, agentName, this._chatClientType, inputMessages.Count);
+        this._logger.LogAgentChatClientInvokedAgent(nameof(RunAsync), this.Id, loggingAgentName, this._chatClientType, inputMessages.Count);
 
         // We can derive the type of supported thread from whether we have a conversation id,
         // so let's update it and set the conversation id for the service thread case.
@@ -378,7 +378,7 @@ public sealed partial class ChatClientAgent : AIAgent
         // Ensure that the author name is set for each message in the response.
         foreach (ChatMessage chatResponseMessage in chatResponse.Messages)
         {
-            chatResponseMessage.AuthorName ??= agentName;
+            chatResponseMessage.AuthorName ??= this.Name;
         }
 
         // Only notify the thread of new messages if the chatResponse was successful to avoid inconsistent message state in the thread.
diff --git a/dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs b/dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs
index 7c90e1a13e..862b9ef3b4 100644
--- a/dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs
+++ b/dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs
@@ -194,8 +194,10 @@ public partial class ChatClientAgentTests
     /// <summary>
     /// Verify that RunAsync sets AuthorName on all response messages.
     /// </summary>
-    [Fact]
-    public async Task RunAsyncSetsAuthorNameOnAllResponseMessagesAsync()
+    [Theory]
+    [InlineData("TestAgent")]
+    [InlineData(null)]
+    public async Task RunAsyncSetsAuthorNameOnAllResponseMessagesAsync(string? authorName)
     {
         // Arrange
         Mock<IChatClient> mockService = new();
@@ -210,13 +212,13 @@ public partial class ChatClientAgentTests
                 It.IsAny<ChatOptions>(),
                 It.IsAny<CancellationToken>())).ReturnsAsync(new ChatResponse(responseMessages));
 
-        ChatClientAgent agent = new(mockService.Object, options: new() { Instructions = "test instructions", Name = "TestAgent" });
+        ChatClientAgent agent = new(mockService.Object, options: new() { Instructions = "test instructions", Name = authorName });
 
         // Act
         var result = await agent.RunAsync([new(ChatRole.User, "test")]);
 
         // Assert
-        Assert.All(result.Messages, msg => Assert.Equal("TestAgent", msg.AuthorName));
+        Assert.All(result.Messages, msg => Assert.Equal(authorName, msg.AuthorName));
     }
 
     /// <summary>