Fix: Mark both TARC and TAResp FunctionCallContent as InformationalOnly after approval processing

src/Libraries/Microsoft.Extensions.AI/ChatCompletion/FunctionInvokingChatClient.cs

@@ -1349,7 +1349,7 @@ FunctionResultContent CreateFunctionResultContent(FunctionInvocationResult resul
     private (List<ApprovalResultWithRequestMessage>? approvals, List<ApprovalResultWithRequestMessage>? rejections) ExtractAndRemoveApprovalRequestsAndResponses(
         List<ChatMessage> messages)
     {
-        Dictionary<string, ChatMessage>? allApprovalRequestsMessages = null;
+        Dictionary<string, (ChatMessage Message, ToolApprovalRequestContent RequestContent)>? allApprovalRequestsMessages = null;
         List<ToolApprovalResponseContent>? allApprovalResponses = null;
         HashSet<string>? approvalRequestCallIds = null;
         HashSet<string>? functionResultCallIds = null;
@@ -1376,7 +1376,7 @@ FunctionResultContent CreateFunctionResultContent(FunctionInvocationResult resul
                     case ToolApprovalRequestContent tarc when tarc.ToolCall is FunctionCallContent { InformationalOnly: false }:
                         // Validation: Capture each call id for each approval request to ensure later we have a matching response.
                         _ = (approvalRequestCallIds ??= []).Add(tarc.ToolCall.CallId);
-                        (allApprovalRequestsMessages ??= []).Add(tarc.RequestId, message);
+                        (allApprovalRequestsMessages ??= []).Add(tarc.RequestId, (message, tarc));
                         break;
 
                     case ToolApprovalResponseContent tarc when tarc.ToolCall is FunctionCallContent { InformationalOnly: false }:
@@ -1451,9 +1451,14 @@ FunctionResultContent CreateFunctionResultContent(FunctionInvocationResult resul
                 ref List<ApprovalResultWithRequestMessage>? targetList = ref approvalResponse.Approved ? ref approvedFunctionCalls : ref rejectedFunctionCalls;
 
                 ChatMessage? requestMessage = null;
-                _ = allApprovalRequestsMessages?.TryGetValue(approvalResponse.RequestId, out requestMessage);
+                ToolApprovalRequestContent? requestContent = null;
+                if (allApprovalRequestsMessages?.TryGetValue(approvalResponse.RequestId, out var requestInfo) is true)
+                {
+                    requestMessage = requestInfo.Message;
+                    requestContent = requestInfo.RequestContent;
+                }
 
-                (targetList ??= []).Add(new() { Response = approvalResponse, RequestMessage = requestMessage });
+                (targetList ??= []).Add(new() { Response = approvalResponse, Request = requestContent, RequestMessage = requestMessage });
             }
         }
 
@@ -1469,17 +1474,21 @@ FunctionResultContent CreateFunctionResultContent(FunctionInvocationResult resul
         rejections is { Count: > 0 } ?
             rejections.ConvertAll(m =>
             {
-                LogFunctionRejected(m.FunctionCallContent.Name, m.Response.Reason);
+                LogFunctionRejected(m.ResponseFunctionCallContent.Name, m.Response.Reason);
 
                 string result = "Tool call invocation rejected.";
                 if (!string.IsNullOrWhiteSpace(m.Response.Reason))
                 {
                     result = $"{result} {m.Response.Reason}";
                 }
 
-                // Mark the function call as purely informational since we're handling it (by rejecting it)
-                m.FunctionCallContent.InformationalOnly = true;
-                return (AIContent)new FunctionResultContent(m.FunctionCallContent.CallId, result);
+                // Mark the function call as purely informational since we're handling it (by rejecting it).
+                // We mark both the response and request FunctionCallContent to ensure consistency
+                // across serialization boundaries where they may be separate object instances.
+                m.ResponseFunctionCallContent.InformationalOnly = true;
+                _ = m.RequestFunctionCallContent?.InformationalOnly = true;
+
+                return (AIContent)new FunctionResultContent(m.ResponseFunctionCallContent.CallId, result);
             }) :
             null;
 
@@ -1708,6 +1717,13 @@ private IList<ChatMessage> ReplaceFunctionCallsWithApprovalRequests(
                 originalMessages, options, notInvokedApprovals.Select(x => x.Response.ToolCall).OfType<FunctionCallContent>().ToList(), 0, consecutiveErrorCount, isStreaming, cancellationToken);
             consecutiveErrorCount = modeAndMessages.NewConsecutiveErrorCount;
 
+            // Also mark the request's FCC as InformationalOnly to ensure consistency
+            // across serialization boundaries where they may be separate object instances.
+            foreach (var approval in notInvokedApprovals)
+            {
+                _ = approval.RequestFunctionCallContent?.InformationalOnly = true;
+            }
+
             return (modeAndMessages.MessagesAdded, modeAndMessages.ShouldTerminate, consecutiveErrorCount);
         }
 
@@ -1788,7 +1804,9 @@ public enum FunctionInvocationStatus
     private readonly struct ApprovalResultWithRequestMessage
     {
         public ToolApprovalResponseContent Response { get; init; }
+        public ToolApprovalRequestContent? Request { get; init; }
         public ChatMessage? RequestMessage { get; init; }
-        public FunctionCallContent FunctionCallContent => (FunctionCallContent)Response.ToolCall;
+        public FunctionCallContent ResponseFunctionCallContent => (FunctionCallContent)Response.ToolCall;
+        public FunctionCallContent? RequestFunctionCallContent => Request?.ToolCall as FunctionCallContent;
     }
 }

test/Libraries/Microsoft.Extensions.AI.Tests/ChatCompletion/FunctionInvokingChatClientApprovalsTests.cs

@@ -754,6 +754,74 @@ public async Task AlreadyExecutedApprovalsAreIgnoredAsync()
         await InvokeAndAssertStreamingAsync(options, input, downstreamClientOutput, output, expectedDownstreamClientInput);
     }
 
+    /// <summary>
+    /// After serialization/deserialization, the TARC and TAResp may contain separate FCC object instances
+    /// for the same call. When a rejection is processed, GenerateRejectedFunctionResults must set
+    /// InformationalOnly=true on BOTH the TAResp's FCC and the TARC's FCC to ensure consistency
+    /// across serialization boundaries. This test verifies that both FCC instances are correctly
+    /// marked after rejection processing.
+    /// </summary>
+    [Theory]
+    [InlineData(false)]
+    [InlineData(true)]
+    public async Task RejectionSetsInformationalOnlyOnBothRequestAndResponseFccInstancesAsync(bool streaming)
+    {
+        // Create two separate FCC objects for the same call — simulating deserialization
+        // where TARC and TAResp hold different FCC instances with the same CallId.
+        var requestFcc = new FunctionCallContent("callId1", "Func1");
+        var responseFcc = new FunctionCallContent("callId1", "Func1");
+
+        Assert.False(requestFcc.InformationalOnly);
+        Assert.False(responseFcc.InformationalOnly);
+
+        var options = new ChatOptions
+        {
+            Tools =
+            [
+                new ApprovalRequiredAIFunction(AIFunctionFactory.Create(() => "Result 1", "Func1")),
+            ]
+        };
+
+        List<ChatMessage> input =
+        [
+            new ChatMessage(ChatRole.User, "hello"),
+            new ChatMessage(ChatRole.Assistant,
+            [
+                new ToolApprovalRequestContent("ficc_callId1", requestFcc),
+            ]) { MessageId = "resp1" },
+            new ChatMessage(ChatRole.User,
+            [
+                new ToolApprovalResponseContent("ficc_callId1", false, responseFcc),
+            ]),
+        ];
+
+        using var innerClient = new TestChatClient
+        {
+            GetResponseAsyncCallback = (contents, actualOptions, actualCancellationToken) =>
+                Task.FromResult(new ChatResponse([new ChatMessage(ChatRole.Assistant, "world")])),
+            GetStreamingResponseAsyncCallback = (contents, actualOptions, actualCancellationToken) =>
+                YieldAsync(new ChatResponse([new ChatMessage(ChatRole.Assistant, "world")]).ToChatResponseUpdates()),
+        };
+
+        IChatClient service = innerClient.AsBuilder()
+            .Use(s => new FunctionInvokingChatClient(s))
+            .Build();
+
+        if (streaming)
+        {
+            await service.GetStreamingResponseAsync(input, options).ToChatResponseAsync();
+        }
+        else
+        {
+            await service.GetResponseAsync(input, options);
+        }
+
+        // The fix ensures both FCC instances are marked InformationalOnly=true,
+        // even when they are separate objects (as happens after serialization).
+        Assert.True(requestFcc.InformationalOnly);
+        Assert.True(responseFcc.InformationalOnly);
+    }
+
     /// <summary>
     /// This verifies the following scenario:
     /// 1. We are streaming (also including non-streaming in the test for completeness).