Current behavior 🐛

A certain combination of Uno features (Hosting, Navigation, ThemeService, Toolkit) causes the system theme to be incorrectly saved into app settings, which makes the app unfollow the system theme.

Expected behavior 🎯

Uno app follows the system theme when no theme is explicitly requested, which it does if any(?) of these features is removed.

How to reproduce it (as minimally and precisely as possible) 🔬

1. create project

   $ dotnet new unoapp -platforms desktop -di -nav regions -theme-service -toolkit -o UnoThemeApp

2. run app

   $ dotnet run -f net9.0-desktop --project UnoThemeApp/UnoThemeApp/UnoThemeApp.csproj

3. toggle system theme

   Screencast.From.2025-10-17.15-06-08.mp4

4. observe settings

   $ cat ~/.local/share/UnoThemeApp/com.companyname.unothemeapp/Settings/Local.dat
   CurrentTheme�System.String:Dark/...

Workaround 🛠️

No response

Renderer 🎨

• Skia
• Native

Affected platforms 📱💻🖥️

Desktop (Windows), Desktop (macOS), Desktop (X11)

Uno.Sdk version (and other relevant versions) 📦

6.3.28

IDE version 🧑‍💻

JetBrains Rider 2025.2.3

Anything else we need to know? 💬

No response