"Do not create agreements for expectations of behavior you are not willing/able to keep. And if over time an agreement no longer fits, ask to renegotiate it FIRST. "
That seems the easiest and most polite.
The details of how people want to be together in whatever open relationship model they are practicing is going to vary.
has some sheets if you need something to look at to help "calibrate" and get on the same page so misunderstandings are minimized.
If you and your partner choose to participate in polyship with X agreements in place and once of you breaks them? And conflict resolution doesn't work out? The simplest consequence is you both stop
participating in polyship.
Whether than means you "close" or "break up" is on both to discern. Either party can withdraw their willingness to participate. Nobody is going to make them participate against their will!
People could have second chances, and some skills take longer to learn and I'm willing to support them while they are trying. But there's a point where it becomes "no effort being made" here and gets ridiculous. You don't get 5 million "second chances" just to coast. YKWIM?
For myself? I like (3 strikes you are out.) Lying to me is a 1 strike because if I can't trust your word, all communication about all else is broken. If there's a problem that's becoming chronic and there is NO reasonable effort being made at all? It's just lip service?
On the clock then -- for 3 strikes you are out. If I have to bring it to your attention 3 times you are not serious. That (3 strikes) limit helps prevent me from allowing soft feelings for the person tempt me to put up with shenanigans longer than needed.
It's good you are talking this out. What the dealbreakers are and how you want to be together and how you want to be as exes if that ever comes to pass. Then there too you know what behavior to expect from YOURSELF as well as the other person, and can come to agreement on that. Then you can hold each other accountable to your agreements and play ball -- hopefully well!