One of these is ignoring peace treaties, never getting stability hits
The player can also ignore a truce to answer a defensive call to arms.
They don't get stability hits from calling a war on you directly after signing peace, without CB. Good try, though.
I've never seen this happen.
..... You must not have played much. The AI breaks truces all the time, I'd call it near-constant but in reality its mostly directed towards the player due to the AI not knowing how to play the game and therefore suicide attacking the PC.
I've had multiple cases of bordering countries breaking truces a year after a peace agreement, even declaring wars outright without a CB and still getting full support from allies, because the AI
literally gets no penalty from doing so. Why? It doesn't know how to deal with the simple mechanic of stability hits.
With all this chess talk, I'll give a comparison: If chess were a Paradox game, the AI would know how to move the pieces [the simple basic premise of running the game -although the economic and stability functions are turned off for the most part-] but not how to utilize the back row of units [the diplomacy, war nuances aside from outright suicide wars/steamrolls, trading mechanics], the complexities are lost entirely on the computer and it gets curb-stomped because it only knows how to utilize the pawns on the gameboard in a limited scope.
Some people enjoy this.
Some people look at the board and say there's a complete game. I agree, EU4 is a complete game with neat mechanics.
Yet, it doesn't matter if what you're competing against doesn't know how to use half the pieces.
[This analogy leaves out the fact that Paradox AIs blatantly ignore the maluses and penalties incurred on the player for making basic gameplay decisions. Modding cannot fix this entirely, unfortunately.]