alt Hacker NewsIt's documented behavior for the low-level API (e.g. asyncio.call_soon https://docs.python.org/3/library/asyncio-eventloop.html#asy...). More broadly, this has been a stable behavior of the Python standard library for almost a decade now. If it does change, that would be a huge behavioral change that would come with plenty of warning and time for adjustment.
In my experience, developers who rely on precise and relatively obscure corner cases, tend to assume that they are more stable than they later prove to be. I've been that developer, and I've been burned because of it.
Even more painfully, I've been the maintenance programmer who was burned because some OTHER programmer trusted such a feature. And then it was my job to figure out the hidden assumption after it broke, long after the original programmer was gone. You know the old saying that you have to be twice as clever to debug code, as you need to be to write it? Debugging another person's clever and poorly commented tricks is no fun!
I'd therefore trust this feature a lot less than you appear to. I'd be tempted to instead wrap the existing loop with a new loop to which I can add instrumentation etc. It's more work. But if it breaks, it will be clear why it broke.