.NET: Add Message Delivery Callback Overloads to Executor (#5081)

* feat: Implement Executor Message Delivery Event callbacks

* fix: ResumeAsync does not run pending steps

* fix: address review comments

dotnet/src/Microsoft.Agents.AI.Workflows/Executor.cs

@@ -310,22 +310,40 @@ public abstract class Executor : IIdentified
         return result.Result;
     }
 
+    /// <summary>
+    /// Invoked once per superstep before any messages are delivered to the Executor.
+    /// </summary>
+    /// <param name="context">The workflow context.</param>
+    /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests.
+    /// The default is <see cref="CancellationToken.None"/>.</param>
+    /// <returns>A ValueTask representing the asynchronous operation.</returns>
+    protected internal virtual ValueTask OnMessageDeliveryStartingAsync(IWorkflowContext context, CancellationToken cancellationToken = default) => default;
+
+    /// <summary>
+    /// Invoked once per superstep after all messages have been delivered to the Executor.
+    /// </summary>
+    /// <param name="context">The workflow context.</param>
+    /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests.
+    /// The default is <see cref="CancellationToken.None"/>.</param>
+    /// <returns>A ValueTask representing the asynchronous operation.</returns>
+    protected internal virtual ValueTask OnMessageDeliveryFinishedAsync(IWorkflowContext context, CancellationToken cancellationToken = default) => default;
+
     /// <summary>
     /// Invoked before a checkpoint is saved, allowing custom pre-save logic in derived classes.
     /// </summary>
     /// <param name="context">The workflow context.</param>
-    /// <returns>A ValueTask representing the asynchronous operation.</returns>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests.
     /// The default is <see cref="CancellationToken.None"/>.</param>
+    /// <returns>A ValueTask representing the asynchronous operation.</returns>
     protected internal virtual ValueTask OnCheckpointingAsync(IWorkflowContext context, CancellationToken cancellationToken = default) => default;
 
     /// <summary>
     /// Invoked after a checkpoint is loaded, allowing custom post-load logic in derived classes.
     /// </summary>
     /// <param name="context">The workflow context.</param>
-    /// <returns>A ValueTask representing the asynchronous operation.</returns>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests.
     /// The default is <see cref="CancellationToken.None"/>.</param>
+    /// <returns>A ValueTask representing the asynchronous operation.</returns>
     protected internal virtual ValueTask OnCheckpointRestoredAsync(IWorkflowContext context, CancellationToken cancellationToken = default) => default;
 
     /// <summary>

dotnet/src/Microsoft.Agents.AI.Workflows/InProc/InProcessExecutionEnvironment.cs

@@ -182,6 +182,9 @@ public sealed class InProcessExecutionEnvironment : IWorkflowExecutionEnvironmen
         AsyncRunHandle runHandle = await this.ResumeRunAsync(workflow, fromCheckpoint, [], cancellationToken)
                                              .ConfigureAwait(false);
 
-        return new(runHandle);
+        Run run = new(runHandle);
+        await run.RunToNextHaltAsync(cancellationToken).ConfigureAwait(false);
+
+        return run;
     }
 }

dotnet/src/Microsoft.Agents.AI.Workflows/InProc/InProcessRunner.cs

@@ -249,17 +249,33 @@ internal sealed class InProcessRunner : ISuperStepRunner, ICheckpointingHandle
         Executor executor = await this.RunContext.EnsureExecutorAsync(receiverId, this.StepTracer, cancellationToken).ConfigureAwait(false);
 
         this.StepTracer.TraceActivated(receiverId);
-        while (envelopes.TryDequeue(out var envelope))
-        {
-            (object message, TypeId messageType) = await TranslateMessageAsync(envelope).ConfigureAwait(false);
 
-            await executor.ExecuteCoreAsync(
-                message,
-                messageType,
-                this.RunContext.BindWorkflowContext(receiverId, envelope.TraceContext),
-                this.TelemetryContext,
-                cancellationToken
-            ).ConfigureAwait(false);
+        // TODO: #5084 - Add delivery-level activity (max one per step per executor) to capture non-message
+        // specific invocations of executor logic.
+        IWorkflowContext tracelessContext = this.RunContext.BindWorkflowContext(receiverId);
+
+        try
+        {
+            await executor.OnMessageDeliveryStartingAsync(tracelessContext, cancellationToken)
+                          .ConfigureAwait(false);
+
+            while (envelopes.TryDequeue(out var envelope))
+            {
+                (object message, TypeId messageType) = await TranslateMessageAsync(envelope).ConfigureAwait(false);
+
+                await executor.ExecuteCoreAsync(
+                    message,
+                    messageType,
+                    this.RunContext.BindWorkflowContext(receiverId, envelope.TraceContext),
+                    this.TelemetryContext,
+                    cancellationToken
+                ).ConfigureAwait(false);
+            }
+        }
+        finally
+        {
+            await executor.OnMessageDeliveryFinishedAsync(tracelessContext, cancellationToken)
+                          .ConfigureAwait(false);
         }
 
         async ValueTask<(object, TypeId)> TranslateMessageAsync(MessageEnvelope envelope)