I notice that when sitting on a Blue Ocean page for pipeline A, I'm also seeing SSE even traffic coming to the browser for pipelines B, C etc.

Would be good to analyse how we're subscribing to these SSE events and maybe see if we can optimise things a bit. Obviously there are tradeoffs wrt complexity of the client-side code etc, but we should at least analyse it a bit.

Tip: Turn on client-side logging via the org.jenkinsci.sse log category.