.NET: Fix RunStreamingAsync not including chat history in messages sent to chat client

[Copilot]

Motivation and Context

SessionMaintainsHistoryAsync streaming tests fail consistently because RunCoreStreamingAsync passes inputMessagesForProviders (current input only) to GetStreamingResponseAsync instead of inputMessagesForChatClient (chat history + current input). The non-streaming path already uses the correct collection. Without chat history, follow-up questions like "And Austria?" after "What is the capital of France?" lack context and the model can't infer intent.

Description

One-line fix in ChatClientAgent.RunCoreStreamingAsync: swap inputMessagesForProviders → inputMessagesForChatClient in the GetStreamingResponseAsync call, matching the non-streaming path.

- responseUpdatesEnumerator = chatClient.GetStreamingResponseAsync(inputMessagesForProviders, chatOptions, cancellationToken)
+ responseUpdatesEnumerator = chatClient.GetStreamingResponseAsync(inputMessagesForChatClient, chatOptions, cancellationToken)

Added a unit test that makes two streaming calls on the same session and asserts the second call's messages include prior chat history (3 messages: original user message, assistant response, follow-up).

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

• Fixes .NET: [Bug]: AgentSession ignored by agent.RunStreamingAsync after upgrade from 1.0.0-preview.260205.1 to 1.0.0-preview.260209.1 #3848
• Fixes .NET: [Bug]: FunctionCall regressions in 1.0.0-preview.260209.1 #3849

Original prompt

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This section details on the original issue you should resolve

<issue_title>.NET: [Bug]: OpenAIChatCompletion.IntegrationTests fail in merge queue</issue_title>
<issue_description>Failing test: OpenAIChatCompletion.IntegrationTests.OpenAIChatCompletionReasoningRunStreamingTests.SessionMaintainsHistoryAsync

Error:

[xUnit.net 00:00:43.37] OpenAIChatCompletion.IntegrationTests.OpenAIChatCompletionReasoningRunStreamingTests.SessionMaintainsHistoryAsync [FAIL]
[xUnit.net 00:00:43.37] Assert.Contains() Failure: Sub-string not found
[xUnit.net 00:00:43.37] String: "Could you clarify what you’d like to know"···
[xUnit.net 00:00:43.37] Not found: "Vienna"
[xUnit.net 00:00:43.37] Stack Trace:
[xUnit.net 00:00:43.37] /home/runner/work/agent-framework/agent-framework/dotnet/tests/AgentConformance.IntegrationTests/RunStreamingTests.cs(107,0): at AgentConformance.IntegrationTests.RunStreamingTests1.SessionMaintainsHistoryAsync() [xUnit.net 00:00:43.37] /home/runner/work/agent-framework/agent-framework/dotnet/tests/AgentConformance.IntegrationTests/RunStreamingTests.cs(116,0): at AgentConformance.IntegrationTests.RunStreamingTests1.SessionMaintainsHistoryAsync()
[xUnit.net 00:00:43.37] --- End of stack trace from previous location ---
Failed OpenAIChatCompletion.IntegrationTests.OpenAIChatCompletionReasoningRunStreamingTests.SessionMaintainsHistoryAsync [6 s]
Error Message:
Assert.Contains() Failure: Sub-string not found
String: "Could you clarify what you’d like to know"···
Not found: "Vienna"
Stack Trace:
at AgentConformance.IntegrationTests.RunStreamingTests1.SessionMaintainsHistoryAsync() in /home/runner/work/agent-framework/agent-framework/dotnet/tests/AgentConformance.IntegrationTests/RunStreamingTests.cs:line 107 at AgentConformance.IntegrationTests.RunStreamingTests1.SessionMaintainsHistoryAsync() in /home/runner/work/agent-framework/agent-framework/dotnet/tests/AgentConformance.IntegrationTests/RunStreamingTests.cs:line 116</issue_description>

<agent_instructions>This test fails consistently with the same error message each time.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes .NET: [Bug]: OpenAIChatCompletion.IntegrationTests fail in merge queue #3797

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[Copilot]

Pull request overview

Fixes a streaming conversation-history bug in ChatClientAgent where the streaming path was sending only the current input to the chat client, instead of chat history + current input (matching the non-streaming path). This restores multi-turn context for streaming runs and addresses the failing SessionMaintainsHistoryAsync streaming scenario.

Changes:

• Update ChatClientAgent.RunCoreStreamingAsync to pass inputMessagesForChatClient into GetStreamingResponseAsync.
• Add a unit test validating that a second streaming call on the same session includes prior turn history in the messages sent to the chat client.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs	Fix streaming invocation to send chat-history-inclusive message list to the underlying IChatClient.
dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs	Add regression test ensuring streaming calls include prior session history on subsequent turns.