This reminds me of something (far, far simpler) that I did long ago. I wrote a small webapp that continually queried various servers and would keep the connection open to push new <div> blocks as the server-side async queries completed. I ran into output-buffering issues (probably from the reverse-proxy server, but I can’t be certain at this point) and ended up appending a 1K block of commented-out non-printing unicode characters to ensure it would get flushed to the browser. I called it the plunger. Probably not the best solution 😅