> My response was to not take care of that in the first time, but provide the building blocks for alternative REPL, in a second time provide an async-input, and a way to register runner for alternative async libraries.

Yeah, I think this is pretty simple: the runtime/stdlib should provide the primitives to compile top-level async code, get coroutines, etc., and then a REPL like ipython can take care of handing that off to asyncio or whatever library they want.

Maybe in the long run the builtin REPL should get async support "out of the box", but that's much less clear, and anyway we should split that off into a separate issue if we want to discuss it.

async-input isn't even useful for ipython, is it? you use prompt-toolkit :-)