diff --git a/docs/preview/winui3-mainwindow-dark.png b/docs/preview/winui3-mainwindow-dark.png
new file mode 100644
index 0000000..0d401c6
Binary files /dev/null and b/docs/preview/winui3-mainwindow-dark.png differ
diff --git a/docs/preview/winui3-mainwindow-light.png b/docs/preview/winui3-mainwindow-light.png
new file mode 100644
index 0000000..b9c2023
Binary files /dev/null and b/docs/preview/winui3-mainwindow-light.png differ
diff --git a/src/TeamsISO.App.WinUI/Services/ThemeManager.cs b/src/TeamsISO.App.WinUI/Services/ThemeManager.cs
index 7cc683a..1553263 100644
--- a/src/TeamsISO.App.WinUI/Services/ThemeManager.cs
+++ b/src/TeamsISO.App.WinUI/Services/ThemeManager.cs
@@ -29,6 +29,8 @@ public sealed class ThemeManager
     }
 
     private readonly UISettings _uiSettings;
+    // Default: System (follow OS app-mode). Override at runtime via Set();
+    // persistence to UIPreferences.Theme lands in the view-model commit.
     private string _preference = "System";
 
     public string Preference => _preference;