Upgrade OpenBSD via syspatch

https://man.openbsd.org/syspatch.8

syspatch (Binary updates)

If you are on a more recent OpenBSD (6.1 or newer) you can use syspatch.

ushellnotpass# syspatch
Get/Verify syspatch65-001_rip6cks... 100% |******************************************************|   196 KB    00:01
Installing patch 001_rip6cksum
Relinking to create unique kernel... done; reboot to load the new kernel

Then just reboot: your kernel, each time ;)