diff --git a/src/Models/SimulateConfigModel.cs b/src/Models/SimulateConfigModel.cs
index beb9539..64832c4 100644
--- a/src/Models/SimulateConfigModel.cs
+++ b/src/Models/SimulateConfigModel.cs
@@ -5,38 +5,16 @@ namespace GeneralUpdate.Tools.Models;
 public record PlatformItem(int Value, string DisplayName) { public override string ToString() => DisplayName; }
 public record AppTypeItem(int Value, string DisplayName) { public override string ToString() => DisplayName; }
 
-/// <summary>
-/// Configuration for the simulate-update module.
-/// </summary>
 public partial class SimulateConfigModel : ObservableObject
 {
-    /// <summary>User-provided old-version app directory to test against.</summary>
     [ObservableProperty] private string _appDirectory = string.Empty;
-
-    /// <summary>Path to a patch .zip generated by the Patch module.</summary>
     [ObservableProperty] private string _patchFilePath = string.Empty;
-
-    /// <summary>The current version of the app being tested.</summary>
     [ObservableProperty] private string _currentVersion = "1.0.0.0";
-
-    /// <summary>The target version the patch upgrades to.</summary>
     [ObservableProperty] private string _targetVersion = "2.0.0.0";
-
-    /// <summary>Platform selector.</summary>
-    [ObservableProperty] private PlatformItem _platform = new(1, "Windows");
-
-    /// <summary>AppType selector.</summary>
-    [ObservableProperty] private AppTypeItem _appType = new(1, "ClientApp");
-
-    /// <summary>Application secret key for the update API.</summary>
+    [ObservableProperty] private int _platform = 1;
+    [ObservableProperty] private int _appType = 1;
     [ObservableProperty] private string _appSecretKey = "dfeb5833-975e-4afb-88f1-6278ee9aeff6";
-
-    /// <summary>Product identifier.</summary>
     [ObservableProperty] private string _productId = "2d974e2a-31e6-4887-9bb1-b4689e98c77a";
-
-    /// <summary>Directory where client.cs / upgrade.cs and server are generated.</summary>
     [ObservableProperty] private string _outputDirectory = string.Empty;
-
-    /// <summary>Server port assigned at runtime (set by SimulationService).</summary>
     public int ServerPort { get; set; } = 5000;
 }
diff --git a/src/Services/ReportGeneratorService.cs b/src/Services/ReportGeneratorService.cs
index 45dba05..899cb92 100644
--- a/src/Services/ReportGeneratorService.cs
+++ b/src/Services/ReportGeneratorService.cs
@@ -26,8 +26,8 @@ public async Task<string> GenerateAsync(
         sb.AppendLine("|-------|-------|");
         sb.AppendLine($"| Patch | {EscapeMd(config.PatchFilePath)} |");
         sb.AppendLine($"| App Directory | {EscapeMd(config.AppDirectory)} |");
-        sb.AppendLine($"| Platform | {config.Platform.DisplayName} |");
-        sb.AppendLine($"| AppType | {config.AppType.DisplayName} |");
+        sb.AppendLine($"| Platform | {config.Platform} |");
+        sb.AppendLine($"| AppType | {config.AppType} |");
         sb.AppendLine($"| Version | {config.CurrentVersion} → {config.TargetVersion} |");
         sb.AppendLine($"| Server Port | {config.ServerPort} |");
         sb.AppendLine($"| Simulation Time | {DateTime.Now:yyyy-MM-dd HH:mm:ss} |");
diff --git a/src/Services/SimulationService.cs b/src/Services/SimulationService.cs
index 9e7d6c0..0e828d9 100644
--- a/src/Services/SimulationService.cs
+++ b/src/Services/SimulationService.cs
@@ -50,7 +50,7 @@ public async Task<SimulationResult> RunAsync(
 
             var hash = ComputeQuickHash(patchDest);
             LocalUpdateServerFiles.Register(patchName, patchDest);
-            _server.Updates.Add((config.CurrentVersion, config.TargetVersion, hash, patchDest, config.AppType.Value));
+            _server.Updates.Add((config.CurrentVersion, config.TargetVersion, hash, patchDest, config.AppType));
 
             await _server.StartAsync(config.ServerPort);
             Log($"  Server running on {_server.BaseUrl}", progress);
diff --git a/src/ViewModels/SimulateViewModel.cs b/src/ViewModels/SimulateViewModel.cs
index c419a1b..0bc67c0 100644
--- a/src/ViewModels/SimulateViewModel.cs
+++ b/src/ViewModels/SimulateViewModel.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.ObjectModel;
 using System.IO;
+using System.Linq;
 using System.Threading.Tasks;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
@@ -36,8 +37,26 @@ public partial class SimulateViewModel : ViewModelBase
     public SimulateViewModel()
     {
         _status = _loc["Patch.Ready"];
-        Config.Platform = Platforms[0];
-        Config.AppType = AppTypes[0];
+    }
+
+    /// <summary>
+    /// Maps Config.Platform (int) to Platforms collection index.
+    /// 1 (Windows) → 0, 2 (Linux) → 1.
+    /// </summary>
+    public int PlatformIndex
+    {
+        get => Config.Platform == 2 ? 1 : 0;
+        set => Config.Platform = value == 1 ? 2 : 1;
+    }
+
+    /// <summary>
+    /// Maps Config.AppType (int) to AppTypes collection index.
+    /// 1 (ClientApp) → 0, 2 (UpgradeApp) → 1.
+    /// </summary>
+    public int AppTypeIndex
+    {
+        get => Config.AppType == 2 ? 1 : 0;
+        set => Config.AppType = value == 1 ? 2 : 1;
     }
 
     async Task<string?> PickFolder(string title)
@@ -87,7 +106,6 @@ async Task StartSimulation()
                 foreach (var note in result.Notes)
                     L($"  Note: {note}");
 
-                // Generate report
                 var reportPath = await _report.GenerateAsync(Config, result, Config.OutputDirectory);
                 L($"Report: {reportPath}");
             }
diff --git a/src/Views/SimulateView.axaml b/src/Views/SimulateView.axaml
index 4c27b84..e09b162 100644
--- a/src/Views/SimulateView.axaml
+++ b/src/Views/SimulateView.axaml
@@ -38,10 +38,10 @@
                     <Grid ColumnDefinitions="Auto,*,Auto,*">
                         <TextBlock Grid.Column="0" Text="Platform" VerticalAlignment="Center"/>
                         <ComboBox Grid.Column="1" ItemsSource="{Binding Platforms}"
-                                  SelectedItem="{Binding Config.Platform}" Margin="8,0,16,0"/>
+                                  SelectedIndex="{Binding PlatformIndex}" Margin="8,0,16,0"/>
                         <TextBlock Grid.Column="2" Text="AppType" VerticalAlignment="Center"/>
                         <ComboBox Grid.Column="3" ItemsSource="{Binding AppTypes}"
-                                  SelectedItem="{Binding Config.AppType}" Margin="8,0"/>
+                                  SelectedIndex="{Binding AppTypeIndex}" Margin="8,0"/>
                     </Grid>
                     <Grid ColumnDefinitions="Auto,*,Auto,*">
                         <TextBlock Grid.Column="0" Text="AppSecret" VerticalAlignment="Center"/>