diff --git a/dotnet/samples/04-hosting/DurableWorkflows/ConsoleApps/06_WorkflowSharedState/Executors.cs b/dotnet/samples/04-hosting/DurableWorkflows/ConsoleApps/06_WorkflowSharedState/Executors.cs
index 57d2964c0c..5dd6d11526 100644
--- a/dotnet/samples/04-hosting/DurableWorkflows/ConsoleApps/06_WorkflowSharedState/Executors.cs
+++ b/dotnet/samples/04-hosting/DurableWorkflows/ConsoleApps/06_WorkflowSharedState/Executors.cs
@@ -38,6 +38,23 @@ internal sealed class ValidateOrder() : Executor<string, OrderDetails>("Validate
         string message,
         IWorkflowContext context,
         CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            return await HandleAsyncCore(message, context, cancellationToken);
+        }
+        catch (Exception ex)
+        {
+            Console.Error.WriteLine($"[DIAG] ValidateOrder.HandleAsync failed: {ex.GetType().FullName}: {ex.Message}");
+            Console.Error.WriteLine($"[DIAG]   StackTrace: {ex.StackTrace}");
+            throw;
+        }
+    }
+
+    private async ValueTask<OrderDetails> HandleAsyncCore(
+        string message,
+        IWorkflowContext context,
+        CancellationToken cancellationToken = default)
     {
         await Task.Delay(TimeSpan.FromMilliseconds(200), cancellationToken);
 
diff --git a/dotnet/src/Microsoft.Agents.AI.DurableTask/Workflows/DurableActivityExecutor.cs b/dotnet/src/Microsoft.Agents.AI.DurableTask/Workflows/DurableActivityExecutor.cs
index c9e9a1b125..d7497036cc 100644
--- a/dotnet/src/Microsoft.Agents.AI.DurableTask/Workflows/DurableActivityExecutor.cs
+++ b/dotnet/src/Microsoft.Agents.AI.DurableTask/Workflows/DurableActivityExecutor.cs
@@ -46,14 +46,46 @@ internal static class DurableActivityExecutor
         object typedInput = DeserializeInput(executorInput, inputType);
 
         DurableWorkflowContext workflowContext = new(sharedState, executor);
-        object? result = await executor.ExecuteCoreAsync(
-            typedInput,
-            new TypeId(inputType),
-            workflowContext,
-            WorkflowTelemetryContext.Disabled,
-            cancellationToken).ConfigureAwait(false);
 
-        return SerializeActivityOutput(result, workflowContext);
+        object? result;
+        try
+        {
+            result = await executor.ExecuteCoreAsync(
+                typedInput,
+                new TypeId(inputType),
+                workflowContext,
+                WorkflowTelemetryContext.Disabled,
+                cancellationToken).ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            // Diagnostic logging to surface inner exception details in CI
+            Console.Error.WriteLine($"[DIAG] DurableActivityExecutor: ExecuteCoreAsync failed for '{binding.Id}' (inputType={inputType.FullName})");
+            Console.Error.WriteLine($"[DIAG]   Exception: {ex.GetType().FullName}: {ex.Message}");
+            for (Exception? inner = ex.InnerException; inner is not null; inner = inner.InnerException)
+            {
+                Console.Error.WriteLine($"[DIAG]   Inner: {inner.GetType().FullName}: {inner.Message}");
+                Console.Error.WriteLine($"[DIAG]   StackTrace: {inner.StackTrace}");
+            }
+
+            throw;
+        }
+
+        string serialized;
+        try
+        {
+            serialized = SerializeActivityOutput(result, workflowContext);
+        }
+        catch (Exception ex)
+        {
+            Console.Error.WriteLine($"[DIAG] DurableActivityExecutor: SerializeActivityOutput failed for '{binding.Id}'");
+            Console.Error.WriteLine($"[DIAG]   Result type: {result?.GetType().FullName ?? "null"}");
+            Console.Error.WriteLine($"[DIAG]   Exception: {ex.GetType().FullName}: {ex.Message}");
+            Console.Error.WriteLine($"[DIAG]   StackTrace: {ex.StackTrace}");
+            throw;
+        }
+
+        return serialized;
     }
 
     private static string SerializeActivityOutput(object? result, DurableWorkflowContext context)
diff --git a/dotnet/src/Microsoft.Agents.AI.Workflows/Executor.cs b/dotnet/src/Microsoft.Agents.AI.Workflows/Executor.cs
index d865b990c4..7f25e8021e 100644
--- a/dotnet/src/Microsoft.Agents.AI.Workflows/Executor.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Workflows/Executor.cs
@@ -284,7 +284,11 @@ public abstract class Executor : IIdentified
 
         if (!result.IsSuccess)
         {
-            throw new TargetInvocationException($"Error invoking handler for {message.GetType()}", result.Exception);
+            // Include inner exception details for diagnostics (otherwise hidden by DTS FailureDetails)
+            string innerDetails = result.Exception is not null
+                ? $" --> {result.Exception.GetType().Name}: {result.Exception.Message}"
+                : string.Empty;
+            throw new TargetInvocationException($"Error invoking handler for {message.GetType()}{innerDetails}", result.Exception);
         }
 
         if (result.IsVoid)