Is it possible to make a class

open

to its own module only but not to "the public"?

You mean internal? https://kotlinlang.org/docs/reference/visibility-modifiers.html#packages

If you mark it

internal

, it is visible everywhere in the same module

no,

internal

only for the

open

part

Ah, I read "open" and thought "visible", sorry

Perhaps 'internal open' then?

Then the whole class is unusable outside the module 🙂

I guess we're not understanding the use case correctly, then.

A class which is usable outside the module, and subclassable only within the module.

internal

constructor should satisfy that 🙂

Hmm, I think your idea of internal constructor should achieve that.

Wasn't my idea but yes 🙂

you could make a internal open class and a (final) class that extends i without changes so you can use it outside, maybe ? possibly implementating a interface by delegation can trick the compiler here