That's interesting, I've always thought the WebSocket spec is too complicated with all those frame types and message fragmentation, and I completely ignored contunation frames when I had to implement the protocol myself. But it seems more versatile than I imagined. Though the workaround you mentioned sounds a bit hacky.

And yeah, I now remember that masking was also a problem at the time. So even if web browsers adopt a new API to send fragmented messages, it would still not be possible to directly plug in them to legacy servers. Sad.

Edit: It would also be possible to send a single giant message, which contains a single giant continuation frame sent for the lifetime of the session, which is followed by a FIN frame. Am I correct?