Close but htmx with SSE and dom swaps and morphing gets you there without reinventing any wheels.

Pretty much every web app I build has this pattern in it from day 1, as they all quickly expand to have a realtime inbox and notifications subsystem to support workflows and agents.

now check out datastar for a smaller, faster, more extensible, more powerful version of that

HTMX only does GET, doesn't to expo backoff, etc. Let alone the fact you need more extensions. Try it before claiming victory maybe?