[tialaramex]

> It might contain something like a date or other data specific only to the context it came from.

In all these modern protocols, including SSHv2 / SecSH (Sean Connery fans at the IETF evidently) both parties deliberately introduce random elements into a signed conversation as a liveness check - precisely to prevent replaying previous communications.

TLS 1.3's zero round-trip (ORT) mode cannot do this, which is why it basically says you'd better be damn sure you've figured out exactly why it's safe to use this, including every weird replay scenario and why it's technically sound in your design or else you must not enable it. We may yet regret the whole thing and just tell everybody to refuse it.