It looks like the issue comes down to the fact that babel can't properly extend native classes.

In Babel 7, they introduced a wrapper that can be applied to built-in classes.

TypeScript has a proposal to introduce a helper to improve interop with ES5/ES6.

To work around this issue, the users have to either use native classes or babel classes. Which means that if we transpile classes in our library then app classes have to be transpiled. On the flip side, if native ES6 classes are used, then our library has to provide native ES6 classes.

To do this, we can distribute cjs files for Node without transpiling classes. We would only transpile the ES6 modules classes with the assumption that web apps would be transpiled with babel.

There is another alternative which is to remove class from the mechanism that stabilizes classes but I don't know how to achieve the same stable instances without the mechanism that we have.

Is this still open?

closing unless it's still a problem /cc @taras