pfSense 25.11 - you added leases logs and kea won't start : read on :
kea 4 and 6 won't start if the file output folder is /var/log/.
It has to be /var/log/kea/
[25.11-RELEASE][root@pfSense.bhf.tld]/var/log: 2025-12-15 10:40:05.854 FATAL [kea-dhcp-ddns.dctl/81131.0x1437a5275010] DCTL_CONFIG_FILE_LOAD_FAIL DhcpDdns reason: Configuration parsing failed: invalid path in `output`: invalid path specified: '/var/log', supported path is '/var/log/kea' (/usr/local/etc/kea/kea-dhcp-ddns.conf:39:13)
Service failed: Could Not load configuration file: Configuration parsing failed: invalid path in `output`: invalid path specified: '/var/log', supported path is '/var/log/kea' (/usr/local/etc/kea/kea-dhcp-ddns.conf:39:13)
So, again, this is only valid for suckers like me that use the JSON mod 'leases log' as proposed above.
Solution :
mkdir /var/log/kea
Change
"output": "/var/log/kea-dhcp-leases.log",
for
"output": "/var/log/kea/kea-dhcp-leases.log",
Save, Apply, and back to the coffee dispenser.