I remember chunked transfer encoding shipped in 1997. It's been possible since then to readily and easily stream bytes of text or chunks of html the way everyone sees LLMs do today.

I used this to write a web based telnet client in 1997, and later a text moo / chat for the web. In both cases used a frameset so your line to send was at bottom of screen, the incoming lines were server-sent as things happened server side, and scrolled the client as new lines came in.

There were other things you could abuse before that, but less reliable.

But yeah, talk about things nobody used....