I wonder though, doesn't SSE technically violate a lot of HTTP's assumptions? From the point of view of a HTTP middlebox, a SSE response would basically be a single endless entity, transmitted at a very low bandwidth. I'm no expert at real-world deployment of SSE, but that they sounds to me like it could break a lot of proxies that don't have special handling for SSE. (Or at least cause unnecessary resource consumption for those proxies)

Also I wonder why there are not more websocket-based APIs. WS has the same widespread support and ready-made debug tools as HTTP and seemed to be designed exactly for push or non request/response use cases. So, out of couriosity, why would SSE be prepared over WS?