When i write following class:

@Model
Test(var test: String)

the Compose framework will observe it and recompose the UI when it changes. Can i also observe this class in my custom code outside of a @Composable function?

Yes, though the API is pretty raw right now. Take a look at

Frames.kt

for some of the low-level details

We just made public the class we use for such observations in our non-composable code: https://cs.android.com/androidx/platform/frameworks/support/+/androidx-master-dev:ui/ui-platform/src/main/java/androidx/ui/core/ModelObserver.kt

Ok thx Andrey that looks good. Unfortunately i currently working with the 0.1.0-dev03 version. Maybe i will change to the dev branch because i also see other things working better on dev (e.g. animation)