We were told in marriage prep that entering into a prenuptial agreement is potential grounds for annulment, because it signals a lack of commitment by leaving an exit agreement.
Discussion
It may signal that, as I wrote in the other thread, but only so long as it isn't the de facto standard marriage contract (because everyone has one) and/or it contains clauses to make divorce easier or more-likely. If it contains additional divorce penalties and clarifies inheritence rules for property brought into a marriage, for example, it shows no lack of commitment.
Also, it's not grounds for annulment, but can be used as evidence in an annulment (which usually takes place after a civil divorce).
https://catholicreview.org/question-corner-does-a-prenuptial-agreement-invalidate-a-marriage/
Just read that some diocese require you to send them a copy of a prenup for evaluation, before the wedding, to make sure it would not be evidence of invalidity.
I was wrong about divorce penalties. It cannot mention divorce, at all, as that would be assuming a future condition and go against CIC 1102.
What you bring up is what I referred to here. If a prenup is obviously designed as an exit strategy and they exit, then it is an open and shut case, in front of the annulment tribunal.