Thanks! Do you also know if there's a certain trust threshold where the AI will break an alliance (like, usually they will break it if you go from 50 to 30 by breaking land promise)? Reason I'm asking:
trust has nothing to do with allies breaking alliances. that is a misunderstanding many people have. Only thing trust does, is preventing ally to RIVAL you when you got 80 trust. it will give them more positive reasons to join defensive and offensive CTA, and that is about it.
If you play as Savoy and ally France, and if you have 100 trust France can STILL break Alliance if they get a militaristic ruler who claims all your land.
Why? Because the 'wants your land' opinion modifier will put their opinion below 0, even with maxed out +100 relations. If you can avoid this somehow, and keep France at +5 positive relations, they might not go hostile.
but all in all, high trust will not protect you versus neighbouring militarist flagging your land as vital interest, claiming it all, and then getting -200 wants your provinces opinion malus that breaks alliance because they go below 0 opinion.
you get 1 month warning, but its usually too late. i they flip hostile due to going below 0 opinion, you need to go +100 again to solve situation. and that is impossible within month, unless the militarist miraculously dies same month.
badly designed mechanic, and they should make all this more clear ingame, as so many other things.