Simplify test comment.

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

dotnet/src/Microsoft.Agents.AI.Workflows.Declarative.Foundry/AzureAgentProvider.cs

@@ -4,7 +4,6 @@ using System;
 using System.ClientModel.Primitives;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
-using System.Linq;
 using System.Net.Http;
 using System.Runtime.CompilerServices;
 using System.Text.Json.Nodes;
@@ -70,7 +69,14 @@ public sealed class AzureAgentProvider(Uri projectEndpoint, TokenCredential proj
                 include: null,
                 cancellationToken).ConfigureAwait(false);
 
-        return newItems.AsChatMessages().Single();
+        ChatMessage[] createdMessages = [.. newItems.AsChatMessages()];
+        if (createdMessages.Length != 1)
+        {
+            throw new InvalidOperationException(
+                $"Expected exactly one chat message from created conversation item in conversation '{conversationId}', but got {createdMessages.Length}.");
+        }
+
+        return createdMessages[0];
 
         IEnumerable<ResponseItem> GetResponseItems()
         {
@@ -208,7 +214,14 @@ public sealed class AzureAgentProvider(Uri projectEndpoint, TokenCredential proj
     {
         AgentResponseItem responseItem = await this.GetConversationClient().GetProjectConversationItemAsync(conversationId, messageId, include: null, cancellationToken).ConfigureAwait(false);
         ResponseItem[] items = [responseItem.AsResponseResultItem()];
-        return items.AsChatMessages().Single();
+        ChatMessage[] messages = [.. items.AsChatMessages()];
+        if (messages.Length != 1)
+        {
+            throw new InvalidOperationException(
+                $"Expected exactly one chat message for message '{messageId}' in conversation '{conversationId}', but got {messages.Length}.");
+        }
+
+        return messages[0];
     }
 
     /// <inheritdoc/>

dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/InvokeAzureAgentExecutor.cs

@@ -49,7 +49,11 @@ internal sealed class InvokeAzureAgentExecutor(InvokeAzureAgent model, ResponseA
 
     public async ValueTask ResumeAsync(IWorkflowContext context, ExternalInputResponse response, CancellationToken cancellationToken)
     {
-        await context.SetLastMessageAsync(response.Messages.Last()).ConfigureAwait(false);
+        ChatMessage? lastMessage = response.Messages.LastOrDefault();
+        if (lastMessage is not null)
+        {
+            await context.SetLastMessageAsync(lastMessage).ConfigureAwait(false);
+        }
         await this.InvokeAgentAsync(context, response.Messages, cancellationToken).ConfigureAwait(false);
     }
 
@@ -85,15 +89,19 @@ internal sealed class InvokeAzureAgentExecutor(InvokeAzureAgent model, ResponseA
         await this.AssignAsync(this.AgentOutput?.Messages?.Path, agentResponse.Messages.ToTable(), context).ConfigureAwait(false);
 
         // Attempt to parse the last message as JSON and assign to the response object variable.
-        try
+        string? lastMessageText = agentResponse.Messages.LastOrDefault()?.Text;
+        if (!string.IsNullOrEmpty(lastMessageText))
         {
-            JsonDocument jsonDocument = JsonDocument.Parse(agentResponse.Messages.Last().Text);
-            Dictionary<string, object?> objectProperties = jsonDocument.ParseRecord(VariableType.RecordType);
-            await this.AssignAsync(this.AgentOutput?.ResponseObject?.Path, objectProperties.ToFormula(), context).ConfigureAwait(false);
-        }
-        catch
-        {
-            // Not valid json, skip assignment.
+            try
+            {
+                using JsonDocument jsonDocument = JsonDocument.Parse(lastMessageText);
+                Dictionary<string, object?> objectProperties = jsonDocument.ParseRecord(VariableType.RecordType);
+                await this.AssignAsync(this.AgentOutput?.ResponseObject?.Path, objectProperties.ToFormula(), context).ConfigureAwait(false);
+            }
+            catch (JsonException)
+            {
+                // Not valid json, skip assignment.
+            }
         }
 
         if (this.Model.Input?.ExternalLoop?.When is not null)

dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/QuestionExecutor.cs

@@ -122,10 +122,13 @@ internal sealed class QuestionExecutor(Question model, ResponseAgentProvider age
                 string? workflowConversationId = context.GetWorkflowConversation();
                 if (workflowConversationId is not null)
                 {
-                    // Input message always defined if values has been extracted.
-                    ChatMessage input = response.Messages.Last();
-                    await agentProvider.CreateMessageAsync(workflowConversationId, input, cancellationToken).ConfigureAwait(false);
-                    await context.SetLastMessageAsync(input).ConfigureAwait(false);
+                    // Input message expected to be defined when values have been extracted, but guard defensively.
+                    ChatMessage? input = response.Messages.LastOrDefault();
+                    if (input is not null)
+                    {
+                        await agentProvider.CreateMessageAsync(workflowConversationId, input, cancellationToken).ConfigureAwait(false);
+                        await context.SetLastMessageAsync(input).ConfigureAwait(false);
+                    }
                 }
             }
 

dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/RequestExternalInputExecutor.cs

@@ -45,7 +45,11 @@ internal sealed class RequestExternalInputExecutor(RequestExternalInput model, R
                 await agentProvider.CreateMessageAsync(workflowConversationId, inputMessage, cancellationToken).ConfigureAwait(false);
             }
         }
-        await context.SetLastMessageAsync(response.Messages.Last()).ConfigureAwait(false);
+        ChatMessage? lastMessage = response.Messages.LastOrDefault();
+        if (lastMessage is not null)
+        {
+            await context.SetLastMessageAsync(lastMessage).ConfigureAwait(false);
+        }
         await this.AssignAsync(this.Model.Variable?.Path, response.Messages.ToFormula(), context).ConfigureAwait(false);
 
         await context.RaiseCompletionEventAsync(this.Model, cancellationToken).ConfigureAwait(false);

dotnet/src/Microsoft.Agents.AI.Workflows/Execution/StreamingRunEventStream.cs

@@ -77,12 +77,13 @@ internal sealed class StreamingRunEventStream : IRunEventStream
 
         try
         {
-            // Wait for the first input before starting
-            // The consumer will call EnqueueMessageAsync which signals the run loop
+            // Wait for the first input before starting.
+            // The consumer will call EnqueueMessageAsync which signals the run loop.
+            // Note: AsyncRunHandle also signals here on checkpoint resume when there are
+            // already pending requests, so the first iteration can emit a PendingRequests
+            // halt signal even without unprocessed messages.
             await this._inputWaiter.WaitForInputAsync(cancellationToken: linkedSource.Token).ConfigureAwait(false);
 
-            this._runStatus = RunStatus.Running;
-
             while (!linkedSource.Token.IsCancellationRequested)
             {
                 // Start a new run-stage activity for this input→processing→halt cycle
@@ -95,6 +96,13 @@ internal sealed class StreamingRunEventStream : IRunEventStream
                 // Events are streamed out in real-time as they happen via the event handler
                 if (this._stepRunner.HasUnprocessedMessages)
                 {
+                    // Flip to Running only when there's actual work to process.
+                    // This is intentionally inside the HasUnprocessedMessages branch so
+                    // that stale input signals cannot transiently flip status back to
+                    // Running after a prior halt has already been observed by callers
+                    // (e.g. Run.ResumeAsync returning after reading an Idle halt signal).
+                    this._runStatus = RunStatus.Running;
+
                     // Emit WorkflowStartedEvent only when there's actual work to process
                     // This avoids spurious events on timeout-only loop iterations
                     await this._eventChannel.Writer.WriteAsync(new WorkflowStartedEvent(), linkedSource.Token).ConfigureAwait(false);
@@ -129,9 +137,6 @@ internal sealed class StreamingRunEventStream : IRunEventStream
                 // Wait for next input from the consumer
                 // Works for both Idle (no work) and PendingRequests (waiting for responses)
                 await this._inputWaiter.WaitForInputAsync(linkedSource.Token).ConfigureAwait(false);
-
-                // When signaled, resume running
-                this._runStatus = RunStatus.Running;
             }
         }
         catch (OperationCanceledException)

dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.UnitTests/ObjectModel/RequestExternalInputExecutorTest.cs

@@ -85,6 +85,29 @@ public sealed class RequestExternalInputExecutorTest(ITestOutputHelper output) :
             expectMessagesCreated: true);
     }
 
+    [Fact]
+    public async Task CaptureResponseWithEmptyMessagesAsync()
+    {
+        await this.CaptureResponseTestAsync(
+            displayName: nameof(CaptureResponseWithEmptyMessagesAsync),
+            variableName: "TestVariable",
+            messageCount: 0);
+    }
+
+    [Fact]
+    public async Task CaptureResponseWithEmptyMessagesAndWorkflowConversationAsync()
+    {
+        // Arrange
+        this.State.Set(SystemScope.Names.ConversationId, FormulaValue.New("WorkflowConversationId"), VariableScopeNames.System);
+
+        // Act & Assert
+        await this.CaptureResponseTestAsync(
+            displayName: nameof(CaptureResponseWithEmptyMessagesAndWorkflowConversationAsync),
+            variableName: "TestVariable",
+            messageCount: 0,
+            expectMessagesCreated: false);
+    }
+
     private async Task ExecuteTestAsync(
         string displayName,
         string variableName)

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/SampleSmokeTest.cs

@@ -269,6 +269,29 @@ public class SampleSmokeTest
         _ = await Step9EntryPoint.RunAsync(writer, environment.ToWorkflowExecutionEnvironment());
     }
 
+    /// <summary>
+    /// Stress regression for the off-thread run-status race: after
+    /// <c>Run.ResumeAsync</c> returns at a halt boundary,
+    /// callers must observe a stable terminal status and never a transient
+    /// <see cref="RunStatus.Running"/>. Step9 is the canonical multi-response resume
+    /// sample; prior to the fix in <see cref="Execution.StreamingRunEventStream"/>,
+    /// its `runStatus.Should().Be(RunStatus.Idle)` assertion failed intermittently
+    /// on roughly 1-in-10 iterations under InProcess_OffThread.
+    /// </summary>
+    [Fact]
+    internal async Task Test_RunSample_Step9_OffThread_MultiResponseResume_StatusIsStableAsync()
+    {
+        const int Iterations = 50;
+
+        for (int i = 0; i < Iterations; i++)
+        {
+            using StringWriter writer = new();
+            _ = await Step9EntryPoint.RunAsync(
+                writer,
+                ExecutionEnvironment.InProcess_OffThread.ToWorkflowExecutionEnvironment());
+        }
+    }
+
     [Theory]
     [InlineData(ExecutionEnvironment.InProcess_Lockstep)]
     [InlineData(ExecutionEnvironment.InProcess_OffThread)]