diff --git a/dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/CopyConversationMessagesExecutor.cs b/dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/CopyConversationMessagesExecutor.cs
index 6a51ce5805..bf5be5310f 100644
--- a/dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/CopyConversationMessagesExecutor.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/ObjectModel/CopyConversationMessagesExecutor.cs
@@ -42,14 +42,11 @@ internal sealed class CopyConversationMessagesExecutor(CopyConversationMessages
 
     private IEnumerable<ChatMessage>? GetInputMessages()
     {
-        DataValue? messages = null;
+        Throw.IfNull(this.Model.Messages, $"{nameof(this.Model)}.{nameof(this.Model.Messages)}");
 
-        if (this.Model.Messages is not null)
-        {
-            EvaluationResult<DataValue> expressionResult = this.Evaluator.GetValue(this.Model.Messages);
-            messages = expressionResult.Value;
-        }
+        EvaluationResult<DataValue> expressionResult = this.Evaluator.GetValue(this.Model.Messages);
+        DataValue messages = expressionResult.Value;
 
-        return messages?.ToChatMessages();
+        return messages.ToChatMessages();
     }
 }
diff --git a/dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.UnitTests/ObjectModel/CopyConversationMessagesExecutorTest.cs b/dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.UnitTests/ObjectModel/CopyConversationMessagesExecutorTest.cs
new file mode 100644
index 0000000000..cb818fec15
--- /dev/null
+++ b/dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.UnitTests/ObjectModel/CopyConversationMessagesExecutorTest.cs
@@ -0,0 +1,202 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.Agents.AI.Workflows.Declarative.Extensions;
+using Microsoft.Agents.AI.Workflows.Declarative.ObjectModel;
+using Microsoft.Agents.AI.Workflows.Declarative.PowerFx;
+using Microsoft.Agents.ObjectModel;
+using Microsoft.Extensions.AI;
+using Microsoft.PowerFx.Types;
+using Xunit.Abstractions;
+
+namespace Microsoft.Agents.AI.Workflows.Declarative.UnitTests.ObjectModel;
+
+/// <summary>
+/// Tests for <see cref="CopyConversationMessagesExecutor"/>.
+/// </summary>
+public sealed class CopyConversationMessagesExecutorTest(ITestOutputHelper output) : WorkflowActionExecutorTest(output)
+{
+    [Fact]
+    public async Task CopyMessagesWithSingleStringMessageAsync()
+    {
+        // Arrange, Act, Assert
+        await this.ExecuteTestAsync(
+            displayName: nameof(CopyMessagesWithSingleStringMessageAsync),
+            conversationId: "TestConversationId",
+            messages: ValueExpression.Literal(StringDataValue.Create("Hello, how can I help you?")),
+            expectedMessageCount: 1);
+    }
+
+    [Fact]
+    public async Task CopyMessagesWithSingleRecordMessageAsync()
+    {
+        // Arrange
+        ChatMessage testMessage = new(ChatRole.User, "Test message content");
+        DataValue messageDataValue = testMessage.ToRecord().ToDataValue();
+        Assert.IsType<RecordDataValue>(messageDataValue);
+        RecordDataValue messageRecord = (RecordDataValue)messageDataValue;
+
+        // Act, Assert
+        await this.ExecuteTestAsync(
+            displayName: nameof(CopyMessagesWithSingleRecordMessageAsync),
+            conversationId: "TestConversationId",
+            messages: ValueExpression.Literal(messageRecord),
+            expectedMessageCount: 1);
+    }
+
+    [Fact]
+    public async Task CopyMessagesWithMultipleMessagesAsync()
+    {
+        // Arrange
+        List<ChatMessage> testMessages =
+        [
+            new ChatMessage(ChatRole.User, "First message"),
+            new ChatMessage(ChatRole.Assistant, "Second message"),
+            new ChatMessage(ChatRole.User, "Third message")
+        ];
+        DataValue messagesDataValue = testMessages.ToTable().ToDataValue();
+        Assert.IsType<TableDataValue>(messagesDataValue);
+        TableDataValue messagesTable = (TableDataValue)messagesDataValue;
+
+        // Act, Assert
+        await this.ExecuteTestAsync(
+            displayName: nameof(CopyMessagesWithMultipleMessagesAsync),
+            conversationId: "TestConversationId",
+            messages: ValueExpression.Literal(messagesTable),
+            expectedMessageCount: 3);
+    }
+
+    [Fact]
+    public async Task CopyMessagesWithVariableExpressionAsync()
+    {
+        // Arrange
+        List<ChatMessage> testMessages =
+        [
+            new ChatMessage(ChatRole.User, "Message from variable")
+        ];
+        TableValue messagesTable = testMessages.ToTable();
+        this.State.Set("SourceMessages", messagesTable);
+
+        // Act, Assert
+        await this.ExecuteTestAsync(
+            displayName: nameof(CopyMessagesWithVariableExpressionAsync),
+            conversationId: "TestConversationId",
+            messages: ValueExpression.Variable(PropertyPath.TopicVariable("SourceMessages")),
+            expectedMessageCount: 1);
+    }
+
+    [Fact]
+    public async Task CopyMessagesToWorkflowConversationAsync()
+    {
+        // Arrange
+        this.State.Set(SystemScope.Names.ConversationId, FormulaValue.New("WorkflowConversationId"), VariableScopeNames.System);
+
+        List<ChatMessage> testMessages =
+        [
+            new ChatMessage(ChatRole.User, "Message to workflow conversation")
+        ];
+        DataValue messagesDataValue = testMessages.ToTable().ToDataValue();
+        Assert.IsType<TableDataValue>(messagesDataValue);
+        TableDataValue messagesTable = (TableDataValue)messagesDataValue;
+
+        // Act, Assert
+        await this.ExecuteTestAsync(
+            displayName: nameof(CopyMessagesToWorkflowConversationAsync),
+            conversationId: "WorkflowConversationId",
+            messages: ValueExpression.Literal(messagesTable),
+            expectedMessageCount: 1,
+            expectWorkflowEvent: true);
+    }
+
+    [Fact]
+    public async Task CopyMessagesToNonWorkflowConversationAsync()
+    {
+        // Arrange
+        this.State.Set(SystemScope.Names.ConversationId, FormulaValue.New("WorkflowConversationId"), VariableScopeNames.System);
+
+        List<ChatMessage> testMessages =
+        [
+            new ChatMessage(ChatRole.User, "Message to non-workflow conversation")
+        ];
+        DataValue messagesDataValue = testMessages.ToTable().ToDataValue();
+        Assert.IsType<TableDataValue>(messagesDataValue);
+        TableDataValue messagesTable = (TableDataValue)messagesDataValue;
+
+        // Act, Assert
+        await this.ExecuteTestAsync(
+            displayName: nameof(CopyMessagesToNonWorkflowConversationAsync),
+            conversationId: "DifferentConversationId",
+            messages: ValueExpression.Literal(messagesTable),
+            expectedMessageCount: 1,
+            expectWorkflowEvent: false);
+    }
+
+    [Fact]
+    public async Task CopyMessagesWithBlankDataValueAsync()
+    {
+        // Arrange, Act, Assert
+        await this.ExecuteTestAsync(
+            displayName: nameof(CopyMessagesWithBlankDataValueAsync),
+            conversationId: "TestConversationId",
+            messages: ValueExpression.Literal(DataValue.Blank()),
+            expectedMessageCount: 0);
+    }
+
+    private async Task ExecuteTestAsync(
+        string displayName,
+        string conversationId,
+        ValueExpression messages,
+        int expectedMessageCount,
+        bool expectWorkflowEvent = false)
+    {
+        // Arrange
+        MockAgentProvider mockAgentProvider = new();
+        mockAgentProvider.TestMessages.Clear();
+
+        CopyConversationMessages model = this.CreateModel(
+            this.FormatDisplayName(displayName),
+            conversationId,
+            messages);
+
+        CopyConversationMessagesExecutor action = new(model, mockAgentProvider.Object, this.State);
+
+        // Act
+        WorkflowEvent[] events = await this.ExecuteAsync(action);
+
+        // Assert
+        Assert.Equal(expectedMessageCount, mockAgentProvider.TestMessages.Count);
+        VerifyModel(model, action);
+
+        AgentResponseEvent[] responseEvents = events.OfType<AgentResponseEvent>().ToArray();
+        if (expectWorkflowEvent && expectedMessageCount > 0)
+        {
+            Assert.NotEmpty(responseEvents);
+            AgentResponseEvent responseEvent = responseEvents.First();
+            Assert.Equal(action.Id, responseEvent.ExecutorId);
+            Assert.NotNull(responseEvent.Response);
+            Assert.Equal(expectedMessageCount, responseEvent.Response.Messages.Count);
+        }
+        else
+        {
+            Assert.Empty(responseEvents);
+        }
+    }
+
+    private CopyConversationMessages CreateModel(
+        string displayName,
+        string conversationId,
+        ValueExpression messages)
+    {
+        CopyConversationMessages.Builder actionBuilder = new()
+        {
+            Id = this.CreateActionId(),
+            DisplayName = this.FormatDisplayName(displayName),
+            ConversationId = StringExpression.Literal(conversationId),
+            Messages = messages
+        };
+
+        return AssignParent<CopyConversationMessages>(actionBuilder);
+    }
+}