that does seem right either. turning on new inference in the compiler is still letting it through as a warning rather than error. Perhaps because the android Nullable is @hide so not in the byte code handed to the compiler? doesn't explain why the bundle api's work as expected. how does the kotlin compiler know about the annotations? is there an external mapping that it is fed? would the ordering of annotation and visibility modifier impact whatever toolchain is operating on this?

reworded the question in the OP

in API N+1 it will be properly non-null