OpenBSD 7.3 found a process with PID 0

[Alessandro Baggi]

Hi list,
running this python3 script:

#!/usr/bin/env python3
import psutil

pids = psutil.pids()
for i in pids:
    p = psutil.Process(i)
    with p.oneshot():
        print(str(i) + " " + p.name())

The result start with:

0 swapper
1 init
536 smtpd
868 ksh
...

This process does not appear in ps, top and htop.

How could be that there is a process with PID 0 before init?
Probably I'm missing something about OpenBSD core.

Can someone point me in the right direction?

Thank you in advance.

Alessandro.