diff --git a/dotnet/src/Microsoft.Agents.AI.DurableTask/DurableWorkflowRunner.cs b/dotnet/src/Microsoft.Agents.AI.DurableTask/DurableWorkflowRunner.cs
index 3f59aaea86..247b87c27b 100644
--- a/dotnet/src/Microsoft.Agents.AI.DurableTask/DurableWorkflowRunner.cs
+++ b/dotnet/src/Microsoft.Agents.AI.DurableTask/DurableWorkflowRunner.cs
@@ -29,7 +29,7 @@ namespace Microsoft.Agents.AI.DurableTask;
 /// <item><description>Understand the expected request and response types for proper serialization</description></item>
 /// </list>
 /// </remarks>
-public sealed record PendingExternalEventStatus(
+internal sealed record PendingExternalEventStatus(
     string EventName,
     string Input,
     string RequestType,
@@ -57,7 +57,7 @@ public sealed record PendingExternalEventStatus(
 /// </description></item>
 /// </list>
 /// </remarks>
-public sealed class DurableWorkflowCustomStatus
+internal sealed class DurableWorkflowCustomStatus
 {
     /// <summary>
     /// Gets or sets the pending external event status when waiting for HITL input.
@@ -184,7 +184,7 @@ public sealed class DurableWorkflowCustomStatus
 /// └─────────────────────────────────────────────────────────────────────────────────┘
 /// </code>
 /// </remarks>
-public class DurableWorkflowRunner
+internal class DurableWorkflowRunner
 {
     /// <summary>
     /// Initializes a new instance of the <see cref="DurableWorkflowRunner"/> class.
diff --git a/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowExecutionPlan.cs b/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowExecutionPlan.cs
index 66647fcd95..1312ba7a06 100644
--- a/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowExecutionPlan.cs
+++ b/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowExecutionPlan.cs
@@ -5,7 +5,7 @@ namespace Microsoft.Agents.AI.DurableTask;
 /// <summary>
 /// Represents the complete execution plan for a workflow, including parallel execution levels.
 /// </summary>
-public sealed class WorkflowExecutionPlan
+internal sealed class WorkflowExecutionPlan
 {
     /// <summary>
     /// The execution levels in order. Each level contains executors that can run in parallel.
diff --git a/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowHelper.cs b/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowHelper.cs
index 231cd34d23..35db3052c3 100644
--- a/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowHelper.cs
+++ b/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowHelper.cs
@@ -10,7 +10,7 @@ namespace Microsoft.Agents.AI.DurableTask;
 /// <param name="ExecutorId">The unique identifier of the executor.</param>
 /// <param name="IsAgenticExecutor">Indicates whether this executor is an agentic executor.</param>
 /// <param name="RequestPort">The request port if this executor is a request port executor; otherwise, null.</param>
-public sealed record WorkflowExecutorInfo(string ExecutorId, bool IsAgenticExecutor, RequestPort? RequestPort = null)
+internal sealed record WorkflowExecutorInfo(string ExecutorId, bool IsAgenticExecutor, RequestPort? RequestPort = null)
 {
     /// <summary>
     /// Gets a value indicating whether this executor is a request port executor (human-in-the-loop).
@@ -25,12 +25,12 @@ public sealed record WorkflowExecutorInfo(string ExecutorId, bool IsAgenticExecu
 /// <param name="Level">The level number (0-based, starting from the root executor).</param>
 /// <param name="Executors">The executors that can run in parallel at this level.</param>
 /// <param name="IsFanIn">Indicates if this level is a Fan-In point (has executors with multiple predecessors).</param>
-public sealed record WorkflowExecutionLevel(int Level, List<WorkflowExecutorInfo> Executors, bool IsFanIn);
+internal sealed record WorkflowExecutionLevel(int Level, List<WorkflowExecutorInfo> Executors, bool IsFanIn);
 
 /// <summary>
 /// Provides helper methods for analyzing and executing workflows.
 /// </summary>
-public static class WorkflowHelper
+internal static class WorkflowHelper
 {
     /// <summary>
     /// Accepts a workflow instance and returns a list of executors with metadata in the order they should be executed.
diff --git a/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowNamingHelper.cs b/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowNamingHelper.cs
index 6c53fd5b36..feabe90ee6 100644
--- a/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowNamingHelper.cs
+++ b/dotnet/src/Microsoft.Agents.AI.DurableTask/WorkflowNamingHelper.cs
@@ -5,7 +5,7 @@ namespace Microsoft.Agents.AI.DurableTask;
 /// <summary>
 /// Provides helper methods for workflow naming conventions used in durable orchestrations.
 /// </summary>
-public static class WorkflowNamingHelper
+internal static class WorkflowNamingHelper
 {
     /// <summary>
     /// The prefix used for durable workflow orchestration function names.