From 6c37ce845060551479c84d5a048d0152fbf656ca Mon Sep 17 00:00:00 2001
From: Copilot <198982749+Copilot@users.noreply.github.com>
Date: Tue, 10 Feb 2026 10:50:41 -0500
Subject: [PATCH] Fix streaming path to include chat history in messages sent
 to chat client (#3798)

RunCoreStreamingAsync was passing inputMessagesForProviders (which lacks
chat history) to GetStreamingResponseAsync instead of
inputMessagesForChatClient (which includes chat history). This caused
streaming runs to lose conversation context on subsequent calls.

The non-streaming path (RunCoreAsync) already correctly used
inputMessagesForChatClient. This aligns the streaming path to match.

Also adds a unit test that validates chat history is included in
messages sent to the chat client during streaming on subsequent calls.

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: lokitoth <6936551+lokitoth@users.noreply.github.com>
---
 .../ChatClient/ChatClientAgent.cs             |  2 +-
 .../ChatClient/ChatClientAgentTests.cs        | 39 +++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
index 5878d877b2..37e673f710 100644
--- a/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
+++ b/dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs
@@ -226,7 +226,7 @@ public sealed partial class ChatClientAgent : AIAgent
         try
         {
             // Using the enumerator to ensure we consider the case where no updates are returned for notification.
-            responseUpdatesEnumerator = chatClient.GetStreamingResponseAsync(inputMessagesForProviders, chatOptions, cancellationToken).GetAsyncEnumerator(cancellationToken);
+            responseUpdatesEnumerator = chatClient.GetStreamingResponseAsync(inputMessagesForChatClient, chatOptions, cancellationToken).GetAsyncEnumerator(cancellationToken);
         }
         catch (Exception ex)
         {
diff --git a/dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs b/dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs
index 41fb29bfed..c23e8cffaf 100644
--- a/dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs
+++ b/dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs
@@ -1320,6 +1320,45 @@ public partial class ChatClientAgentTests
         mockFactory.Verify(f => f(It.IsAny<ChatClientAgentOptions.ChatHistoryProviderFactoryContext>(), It.IsAny<CancellationToken>()), Times.Once);
     }
 
+    /// <summary>
+    /// Verify that RunStreamingAsync includes chat history in messages sent to the chat client on subsequent calls.
+    /// </summary>
+    [Fact]
+    public async Task RunStreamingAsyncIncludesChatHistoryInMessagesToChatClientAsync()
+    {
+        // Arrange
+        List<IEnumerable<ChatMessage>> capturedMessages = [];
+        Mock<IChatClient> mockService = new();
+        ChatResponseUpdate[] returnUpdates =
+            [
+                new ChatResponseUpdate(role: ChatRole.Assistant, content: "response"),
+            ];
+        mockService.Setup(
+            s => s.GetStreamingResponseAsync(
+                It.IsAny<IEnumerable<ChatMessage>>(),
+                It.IsAny<ChatOptions>(),
+                It.IsAny<CancellationToken>()))
+            .Returns(ToAsyncEnumerableAsync(returnUpdates))
+            .Callback<IEnumerable<ChatMessage>, ChatOptions?, CancellationToken>((msgs, _, _) => capturedMessages.Add(msgs.ToList()));
+        ChatClientAgent agent = new(mockService.Object, options: new()
+        {
+            ChatOptions = new() { Instructions = "test instructions" },
+        });
+
+        // Act
+        ChatClientAgentSession? session = await agent.CreateSessionAsync() as ChatClientAgentSession;
+        await agent.RunStreamingAsync([new(ChatRole.User, "first")], session).ToListAsync();
+        await agent.RunStreamingAsync([new(ChatRole.User, "second")], session).ToListAsync();
+
+        // Assert - the second call should include chat history (first user message + first response) plus the new message
+        Assert.Equal(2, capturedMessages.Count);
+        var secondCallMessages = capturedMessages[1].ToList();
+        Assert.Equal(3, secondCallMessages.Count);
+        Assert.Equal("first", secondCallMessages[0].Text);
+        Assert.Equal("response", secondCallMessages[1].Text);
+        Assert.Equal("second", secondCallMessages[2].Text);
+    }
+
     /// <summary>
     /// Verify that RunStreamingAsync throws when a <see cref="ChatHistoryProvider"/> factory is provided and the chat client returns a conversation id.
     /// </summary>