Are companion perks in Fallout 4 permanent?
Every companion provides a unique perk. I read that you gain the perk after you reach positive reputation with your follower.
Is the perk permanent after you unlock it with reputation (stays active even after you dismiss the follower)?
Do you loose the perk if reputations drops after maxing it out?
Yes, perks stay with you forever once they are unlocked. Treat them like Pokemon and catch them all.