so basically i need to prune my soldiers to high psi strength, so they can't be taken over in one turn.
i see.
how does bravery come into play there?
To elaborate on what X-Man said: assuming OXCE and XCF still mostly use
vanilla-style psi, successful psi panic attacks deplete morale by 110 minus the target's bravery (e.g. 60 Bravery = Psi Panic does 50 morale damage). The lower your soldier's morale is, the higher their chance of panicking when panic checks are run. So a low psistr, high-bravery soldier is
moderately resistant to psi panic, but still weak to MC.
The linked article goes into deeper detail on all the math and interactions, if you're curious.
But basically as soon as you have PsiStr evaluation (via the basic metapsych tech in XCF IIRC) I believe SOP for a lot of veteran players is to go through new recruits and just fire low-psi personnel, then hire replacements, until all of your soldiers are fairly high psi strength. I think it's actually a lot easier to do this in XCF since you can determine psi strength fairly early on, especially if you're working through the Black Lotus arc first.
The canary/psi-dummy tactic dates back as far as vanilla afaik. OXCE/XCF seem a little more lenient in that most enemies seem to need to have LoS from any one of their units to yours in order to make psi-attacks with psi units, whereas aliens in vanilla would start hitting you with psi attacks the moment your skyranger touched down, more or less.