Bedroom etiquette ?

I think you are O.K. to be upset if the agreed lines have been crossed, but all you need to do is sit down and discuss whether those lines are still valid for you, or if new ground rules need to be agreed, or if the relationship should return to closed for the time being. What I mean is, are you upset that the lines were crossed, or that they were crossed without you being asked first. If she had come to you before the encounter and said that she wanted to try something new, would you still be upset at the activity? You are clearly still mad for each other so the marriage is not in jeopardy, and sex is just a pastime, fun while it lasts. Love is stronger than a small inconsequential transgression.

Um, parameters? What does that mean? She can take a lover but she can't go down on said lover? She can fool around with women, but not with men?Or vice versa? we have absolutely no idea what the heck you are talking about. How can we offer opinions? NEED INFO

Okay, we need to know that the "parameters" are. How can we voice opinions if we don't know what they are? And how do you have parameters in bed? "Sorry, can't suck you. It's a parameter and I can't do that," she tells her lover.

that is hilarious! "Rules"?  Since you are ok with your wife servicing strange cock, why not pimp her out downtown by the hour and make yourself some money? May as well get some use out of her, run a "Covid-19 Special". your wife will suck dick for $19.

You haven't told us the parameters you two set, and you haven't told us how she violated them.  We therefore are in no real position to comment intelligently.

And asking us to give to feedback is essentially asking us to judge the situation.  It's is therefore bizarre of you to demand that we "reserve judgment". If what you meant is that you don't want us to make any moral judgements regarding your decision to have an open marriage, then say so.

Be clear about your rules and about what happened, so people can actually comment.  Your question as written is simply too vague and non-specific.

Okay, I commend you two for having such a fluid relationship, I couldn’t do it. I believe that she shouldn’t have violated the 3 parameters, but the fact that she was honest is commendable. In my experience, women do things because they’re  comfortable emotionally and physically. I believe there was more to it than just being ‘caught up in the moment’ and you may have the right to feel offended. As I said, the fact that she was honest means her heart is yours. Let her know you’re upset, stand your ground and I’m sure the ‘offence’ will not be repeated. 

You need to go back and examine your initial parameters.  Maybe only you thought you and she were in agreement.  Or maybe she has changed with time.  Under any circumstances you and she need to redefine your parameters.