0-RTT session resumption

One click measures three connections from your browser: a cold HTTP/2 handshake, a cold HTTP/3 handshake, and an HTTP/3 reconnect that resumes the earlier session — capable of carrying the request 0 round-trips in.

"Resumed" is measured as a genuine reconnect (connection reuse is detected via Resource Timing and discarded). The label upgrades to "0-RTT confirmed ✓" only when the server reports the request actually arrived in TLS early data (RFC 8470). Browsers decide for themselves whether to send early data — an unconfirmed run still shows the resumption win honestly. DNS lookup time is excluded from all bars — cold legs pay DNS, a resumed connection doesn't, and that difference isn't 0-RTT's doing.