The blue hero is the LCP element. It is not in this HTML — it arrives over AJAX. Run each option and watch what the request has to do before it can paint. Everything is measured in your own browser.
COLD means the request had to open its own socket and pay for a TCP + TLS handshake. WARM means it reused a connection that was already open.
You get one COLD reading per pool, per browser session. Once a socket exists it gets reused, so a second run of the same option will read WARM and look fast. To test cold again, reopen this page in a private window.
Run option 4 last. It fetches with credentials, which reuses the connection this page is already on — so it can never be cold, and running it first changes nothing for the others.
Why this page can only show you one cold reading. GitHub Pages serves everything from a single origin on port 443. Chrome keys its socket pools on (scheme, host, port), so once a socket exists here it gets reused and every later run reads WARM. There is no way for a static host to hand you a fresh connection on demand.
The full experiment runs locally. Four real page loads, each served on a port that
has never been used before, so every load starts cold and the four variants are directly comparable.
It lives in lab/
— ./start.sh, then open the runner it prints.