diff --git a/dotnet/src/Microsoft.Agents.AI.Workflows/InProc/InProcessRunnerContext.cs b/dotnet/src/Microsoft.Agents.AI.Workflows/InProc/InProcessRunnerContext.cs
index dec2b31bb8..8201f8d8fe 100644
--- a/dotnet/src/Microsoft.Agents.AI.Workflows/InProc/InProcessRunnerContext.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Workflows/InProc/InProcessRunnerContext.cs
@@ -271,7 +271,7 @@ internal sealed class InProcessRunnerContext : IRunnerContext
 
         if (!this._outputFilter.TryGetTags(sourceId, out HashSet<OutputTag>? tags))
         {
-            // Not designated as an output source — drop silently (matches Python semantics).
+            // Not designated as an output source — drop silently.
             return;
         }
 
diff --git a/dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowOutputEvent.cs b/dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowOutputEvent.cs
index 73b60f9643..fab2d4d30a 100644
--- a/dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowOutputEvent.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowOutputEvent.cs
@@ -14,6 +14,8 @@ namespace Microsoft.Agents.AI.Workflows;
 [JsonDerivedType(typeof(AgentResponseUpdateEvent))]
 public class WorkflowOutputEvent : WorkflowEvent
 {
+    private HashSet<OutputTag> _tags;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="WorkflowOutputEvent"/> class with no tags.
     /// </summary>
@@ -44,7 +46,7 @@ public class WorkflowOutputEvent : WorkflowEvent
     public WorkflowOutputEvent(object data, string executorId, IEnumerable<OutputTag>? tags) : base(data)
     {
         this.ExecutorId = executorId;
-        this.Tags = tags is null ? new HashSet<OutputTag>() : new HashSet<OutputTag>(tags);
+        this._tags = tags is null ? new HashSet<OutputTag>() : new HashSet<OutputTag>(tags);
     }
 
     /// <summary>
@@ -64,12 +66,12 @@ public class WorkflowOutputEvent : WorkflowEvent
     /// empty for terminal/regular outputs. The presence of <see cref="OutputTag.Intermediate"/>
     /// marks this event as an intermediate output.
     /// </summary>
-    public HashSet<OutputTag> Tags { get; }
+    public IEnumerable<OutputTag> Tags => this._tags;
 
     /// <summary>
     /// Returns <see langword="true"/> if this event carries the given tag.
     /// </summary>
-    public bool HasTag(OutputTag tag) => this.Tags.Contains(tag);
+    public bool HasTag(OutputTag tag) => this._tags.Contains(tag);
 
     /// <summary>
     /// Determines whether the underlying data is of the specified type or a derived type.