Just ran into it not working with WebSockets either, which are classes, though not sure you can move a WebSocket anyway...

As discussed, it's expected (and documented) that class instances are only supported if they extend RpcTarget or are instances of one of the specific API types that are documented to work. WebSocket is not currently supported.

That said, it sounds like there is arguably a bug in the TypeScript types. It sounds like the types treat interface as strictly referring to class instances, but actually an interface can be satisfied by a plain object too.

@mrbbot Is there any way for us to more specifically filter out class instances using the TypeScript type system?

Err, apparently @mrbbot recently left the company. Sorry for the spurious ping @mrbbot, hope things go well at whatever's next for you.

I'm not sure who that leaves as the typescript wizard now. @GregBrimble any thoughts?

Recursively mapping the return type to a type alias helped me work around this issue with some 3rd party types

type InterfaceToType<T> = T extends object ? { [P in keyof T]: InterfaceToType<T[P]> } : T

class Foo extends RpcTarget {
	async bar(): Promise<InterfaceToType<InterfaceOfThirdParty>> {
            // ...
        }
}

@penalosa would be my next go-to!