diff --git a/NEW/src/Utils/JdeScoping.ConfigManager/ViewModels/TreeNodeViewModel.cs b/NEW/src/Utils/JdeScoping.ConfigManager/ViewModels/TreeNodeViewModel.cs
index 1b6f332..f8db87b 100644
--- a/NEW/src/Utils/JdeScoping.ConfigManager/ViewModels/TreeNodeViewModel.cs
+++ b/NEW/src/Utils/JdeScoping.ConfigManager/ViewModels/TreeNodeViewModel.cs
@@ -2,17 +2,35 @@ using System.Collections.ObjectModel;
 
 namespace JdeScoping.ConfigManager.ViewModels;
 
+public enum TreeNodeType
+{
+    Folder,
+    SettingsSection,
+    Pipeline
+}
+
+public enum ValidationState
+{
+    Valid,
+    Warning,
+    Error,
+    Unknown
+}
+
 /// <summary>
 /// ViewModel for a tree node in the configuration tree.
-/// This is a stub implementation for Task 11 - full implementation in Task 12.
 /// </summary>
 public class TreeNodeViewModel : ViewModelBase
 {
     private bool _isModified;
+    private bool _isExpanded;
+    private bool _isSelected;
+    private ValidationState _validationState = ValidationState.Unknown;
 
-    public string Name { get; set; } = string.Empty;
-    public string Icon { get; set; } = string.Empty;
-    public string StatusIcon { get; set; } = string.Empty;
+    public string Name { get; }
+    public string Icon { get; }
+    public TreeNodeType NodeType { get; }
+    public string? SectionKey { get; init; }
     public ObservableCollection<TreeNodeViewModel> Children { get; } = [];
 
     public bool IsModified
@@ -20,4 +38,41 @@ public class TreeNodeViewModel : ViewModelBase
         get => _isModified;
         set => SetProperty(ref _isModified, value);
     }
+
+    public bool IsExpanded
+    {
+        get => _isExpanded;
+        set => SetProperty(ref _isExpanded, value);
+    }
+
+    public bool IsSelected
+    {
+        get => _isSelected;
+        set => SetProperty(ref _isSelected, value);
+    }
+
+    public ValidationState ValidationState
+    {
+        get => _validationState;
+        set
+        {
+            if (SetProperty(ref _validationState, value))
+                OnPropertyChanged(nameof(StatusIcon));
+        }
+    }
+
+    public string StatusIcon => ValidationState switch
+    {
+        ValidationState.Valid => "✓",
+        ValidationState.Warning => "⚠",
+        ValidationState.Error => "✗",
+        _ => ""
+    };
+
+    public TreeNodeViewModel(string name, string icon, TreeNodeType nodeType)
+    {
+        Name = name;
+        Icon = icon;
+        NodeType = nodeType;
+    }
 }
diff --git a/NEW/tests/JdeScoping.ConfigManager.Tests/ViewModels/TreeNodeViewModelTests.cs b/NEW/tests/JdeScoping.ConfigManager.Tests/ViewModels/TreeNodeViewModelTests.cs
new file mode 100644
index 0000000..2a071df
--- /dev/null
+++ b/NEW/tests/JdeScoping.ConfigManager.Tests/ViewModels/TreeNodeViewModelTests.cs
@@ -0,0 +1,221 @@
+using JdeScoping.ConfigManager.ViewModels;
+
+namespace JdeScoping.ConfigManager.Tests.ViewModels;
+
+public class TreeNodeViewModelTests
+{
+    [Fact]
+    public void Constructor_SetsProperties()
+    {
+        // Arrange & Act
+        var node = new TreeNodeViewModel("DataSync", "⟳", TreeNodeType.SettingsSection);
+
+        // Assert
+        node.Name.ShouldBe("DataSync");
+        node.Icon.ShouldBe("⟳");
+        node.NodeType.ShouldBe(TreeNodeType.SettingsSection);
+    }
+
+    [Fact]
+    public void IsModified_WhenSet_RaisesPropertyChanged()
+    {
+        // Arrange
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+        var propertyChangedRaised = false;
+        node.PropertyChanged += (s, e) =>
+        {
+            if (e.PropertyName == nameof(TreeNodeViewModel.IsModified))
+                propertyChangedRaised = true;
+        };
+
+        // Act
+        node.IsModified = true;
+
+        // Assert
+        propertyChangedRaised.ShouldBeTrue();
+    }
+
+    [Fact]
+    public void IsExpanded_WhenSet_RaisesPropertyChanged()
+    {
+        // Arrange
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+        var propertyChangedRaised = false;
+        node.PropertyChanged += (s, e) =>
+        {
+            if (e.PropertyName == nameof(TreeNodeViewModel.IsExpanded))
+                propertyChangedRaised = true;
+        };
+
+        // Act
+        node.IsExpanded = true;
+
+        // Assert
+        propertyChangedRaised.ShouldBeTrue();
+        node.IsExpanded.ShouldBeTrue();
+    }
+
+    [Fact]
+    public void IsSelected_WhenSet_RaisesPropertyChanged()
+    {
+        // Arrange
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+        var propertyChangedRaised = false;
+        node.PropertyChanged += (s, e) =>
+        {
+            if (e.PropertyName == nameof(TreeNodeViewModel.IsSelected))
+                propertyChangedRaised = true;
+        };
+
+        // Act
+        node.IsSelected = true;
+
+        // Assert
+        propertyChangedRaised.ShouldBeTrue();
+        node.IsSelected.ShouldBeTrue();
+    }
+
+    [Fact]
+    public void ValidationState_WhenSetToValid_StatusIconIsCheckmark()
+    {
+        // Arrange
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+
+        // Act
+        node.ValidationState = ValidationState.Valid;
+
+        // Assert
+        node.StatusIcon.ShouldBe("✓");
+    }
+
+    [Fact]
+    public void ValidationState_WhenSetToWarning_StatusIconIsWarning()
+    {
+        // Arrange
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+
+        // Act
+        node.ValidationState = ValidationState.Warning;
+
+        // Assert
+        node.StatusIcon.ShouldBe("⚠");
+    }
+
+    [Fact]
+    public void ValidationState_WhenSetToError_StatusIconIsX()
+    {
+        // Arrange
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+
+        // Act
+        node.ValidationState = ValidationState.Error;
+
+        // Assert
+        node.StatusIcon.ShouldBe("✗");
+    }
+
+    [Fact]
+    public void ValidationState_WhenSetToUnknown_StatusIconIsEmpty()
+    {
+        // Arrange
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+
+        // Act
+        node.ValidationState = ValidationState.Unknown;
+
+        // Assert
+        node.StatusIcon.ShouldBe("");
+    }
+
+    [Fact]
+    public void ValidationState_WhenChanged_RaisesPropertyChangedForStatusIcon()
+    {
+        // Arrange
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+        var statusIconPropertyChanged = false;
+        node.PropertyChanged += (s, e) =>
+        {
+            if (e.PropertyName == nameof(TreeNodeViewModel.StatusIcon))
+                statusIconPropertyChanged = true;
+        };
+
+        // Act
+        node.ValidationState = ValidationState.Valid;
+
+        // Assert
+        statusIconPropertyChanged.ShouldBeTrue();
+    }
+
+    [Fact]
+    public void SectionKey_CanBeSetViaInitializer()
+    {
+        // Arrange & Act
+        var node = new TreeNodeViewModel("DataSync", "⟳", TreeNodeType.SettingsSection)
+        {
+            SectionKey = "DataSync"
+        };
+
+        // Assert
+        node.SectionKey.ShouldBe("DataSync");
+    }
+
+    [Fact]
+    public void Children_IsInitialized()
+    {
+        // Arrange & Act
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+
+        // Assert
+        node.Children.ShouldNotBeNull();
+        node.Children.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public void Children_CanAddChildNodes()
+    {
+        // Arrange
+        var parent = new TreeNodeViewModel("Settings", "📁", TreeNodeType.Folder);
+        var child = new TreeNodeViewModel("DataSync", "⟳", TreeNodeType.SettingsSection);
+
+        // Act
+        parent.Children.Add(child);
+
+        // Assert
+        parent.Children.Count.ShouldBe(1);
+        parent.Children[0].ShouldBe(child);
+    }
+
+    [Theory]
+    [InlineData(TreeNodeType.Folder)]
+    [InlineData(TreeNodeType.SettingsSection)]
+    [InlineData(TreeNodeType.Pipeline)]
+    public void NodeType_CanBeSetForAllTypes(TreeNodeType nodeType)
+    {
+        // Arrange & Act
+        var node = new TreeNodeViewModel("Test", "📁", nodeType);
+
+        // Assert
+        node.NodeType.ShouldBe(nodeType);
+    }
+
+    [Fact]
+    public void IsModified_WhenSetToSameValue_DoesNotRaisePropertyChanged()
+    {
+        // Arrange
+        var node = new TreeNodeViewModel("Test", "📁", TreeNodeType.Folder);
+        node.IsModified = true;
+
+        var propertyChangedRaised = false;
+        node.PropertyChanged += (s, e) =>
+        {
+            if (e.PropertyName == nameof(TreeNodeViewModel.IsModified))
+                propertyChangedRaised = true;
+        };
+
+        // Act
+        node.IsModified = true; // Same value
+
+        // Assert
+        propertyChangedRaised.ShouldBeFalse();
+    }
+}