Doing a MR and will arrive from DEN on UA at 9:15 p, leaving at 6:00a the following day to SFO on UA as well. All on one ticket.

Would prefer not to shell out money for a hotel for just a couple of hours, plus at that time of the year it will be very cold outside. Can I stay airside at YVR?
How does that work with the trans border situation?

Any insight will be very much appreciated.