❌ Switch from Window to ReactiveWindow: CS0534

MainWindow.xaml

@@ -1,8 +1,12 @@
-<Window x:Class="WPFRxUISTJSourceGenerationMinimalReproduction.MainWindow"
-        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
-        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
-        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
-        mc:Ignorable="d"
-        Title="MainWindow" Height="450" Width="800">
-</Window>
+<reactiveui:ReactiveWindow
+    x:Class="WPFRxUISTJSourceGenerationMinimalReproduction.MainWindow"
+    x:TypeArguments="local:MainWindowViewModel"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:local="clr-namespace:WPFRxUISTJSourceGenerationMinimalReproduction"
+    xmlns:reactiveui="http://reactiveui.net"
+    mc:Ignorable="d"
+    Title="MainWindow" Height="450" Width="800">
+</reactiveui:ReactiveWindow>

MainWindow.xaml.cs

@@ -10,7 +10,7 @@ public partial class MainWindow
     public MainWindow()
     {
         InitializeComponent();
-        DataContext = new MainWindowViewModel();
+        ViewModel = new();
         _ = JsonSerializer.Serialize(new Settings(), SettingsJsonSerializerContext.Default.Settings);
     }
 }