is there something like

BehaviorSubject

but where the value is not optional?

You mean a default value?

BehaviorSubject.createDefault(1)

I mean, that I can call

value

on it and it returns the value, not an optional @kioba

ahh, I don’t know any Subject that a non optional value. Behaviour subject can extended with a property which throws exceptions or returns a default value in case of missing

null

. Altho it works, Wouldn’t suggest the value usage. Sometimes i comes handy but on a longer terms it is a bad decision. Try to subscribe to the stream instead