This wil be a long post (TLDR at the bottom) but essentially I am looking for advice/literature/podcasts/personal testimonies on non-monogamy and specifically how to deal with repairing trust after it's been broken

I (27f) and my partner (28nb) have been dating for about a year and a half and have always had an open relationship. I personally have never explored outside the relationship, and don't feel called to it right now, but I like the freedom and hope to explore in the future. On the other side, my partner has been exploring a new side of their sexuality, something I cant give them, and I am so pleased that I get to be a support and care system for them while they explore these new feelings. For the most part they have just been engaging in hook-ups and purely sexual endeavors. We agreed that if it it started to become more than sexual then we would have a discussion about it and decide how to proceed with this new information.

Fast forward a year and they went on a trip and spent 3 days with a person we'll call Sam, sleeping over at his house, spending tons of time with him, and generally stepping out of the boundaries that had been the norm for the last year. They told me when they went over to Sam's house but not much else. We had not yet discussed sleepovers, or dates, or hanging out outside of the hook-up. And they engaged in these activities without discussing with me first. I realize that we should have had clearer boundaries, but I'm new to this! and at the time, didn't think we needed to.

Obviously I was very hurt and betrayed and we've talked about this extensively, they have apologized profusely and are empathetic to my pain, and we have been very diligent about keeping good communication surrounding this person, and other hook ups they've had since then.

They have explained that their feelings in regards to Sam are that it is a sexual relationship with feelings of friendship and admiration thrown in the mix. And I believe them. I recognize feelings are not always black and white, and asking for them to have sex with no feelings and only with people they don't have a connection to is unfair and possibly cruel. I don't want that to be our dynamic!

Here is the crux of it, we are going to Sam's hometown together for a visit, and they would like to see him while we're there. And I would like to say yes, but I am struggling with how to say yes AND not suffer unnecessarily for it. I know I will feel anxious and scared and a little jealous, but I need to give our relationship the chance to rebuild trust and I think this is an opportunity to do it. To let them have a connective relationship, and learn that I can still feel loved and cared for and important WHILE they are with someone else. (Mind you, I am not interested in poly-amory, I'm not sure I want to delve into the world of multiple partners, and they know this)

I am really struggling with what sorts of requests I can make of them, what things I could ask of them to help myself feel better, what our conversations should look like before and after they meet with Sam. I'm not looking for permission of what to ask, but just inspiration...literally, what should I be thinking about? I don't have much experience or knowledge about this, so I don't have examples or resources to fall back on. Are there things that you all ask your partners for or about before/after dates, rules you have set? Mantras/affirmations you repeat to yourself? Feelings you know will surface and how you prepare/cope? Feelings that you allow, as in they are not problematic (like small amounts of jealousy or anxiety) vs feelings that you know need to be addressed or are not normal to feel (resentment? I'm really struggling with how much resentment, if any should be felt by either of us!)? Ways you have repaired trust after an episode of broken communication?

Are there articles or books or guides i can read to spark some creativity, so I can have tools at my disposal for the feelings and discussions we'll encounter etc

:) Thank you!

btw im in the middle of polysecure... so, not that one lol

TLDR: partner and I have an open relationship, communication was poor and some boundaries were breached. Looking for resources/advice on how to move forward so both of our needs are taken care of. Mainly their need/want to see this person again, and my need/want to feel safe while they do it