I leave the browser waiting for a fetch-response from the server. The server responds only later when the page that is open in the browser was updated on server. Seems to work much of the time, but sometimes it seems Chrome closes the connection after a timeout and shows a network error in the dev-tools. FireFox not.

I assume web-sockets could make it work more robustly.

my solution to version changes in a rest api is to sent a version header with every response, the app checks it and if it does not match reloads the page, thus loading the new js.

I would not accept your wager. That being said if this was a “really big problem” I’d bet you that most developers on HN would have an idea how to address it.