pf2e.fyi
From Pathfinder Impossible Magic, which isn't enabled.

Resilient Chassis

FEAT 5
AUTOMATONCONCENTRATE
Activity reaction
Prerequisites defensive automaton heritage
Frequency once per day
Trigger You would take damage.

You are tough enough to draw on your own internal stores of energy when you get injured. You gain 4 temporary Hit Points that last for 1 round. At 8th level and every 4 levels thereafter, the temporary Hit Points increase by 4.

Enhancement Resilient Chassis's frequency becomes once per 10 minutes.

Pathfinder Impossible MagicORC