Also, it’s in the baby’s best interest for adoptive mother to have custody rights.

Can you clarify what you mean here? Obviously the adoptive mother would have rights to custody if, y'know.. the child is adopted by her. But it reads to me like you're saying it's in the baby's best interest for the adoptive mother to have custody over the paternal parent because she's a female parental figure? Or because she's the primary?

I just want clarification, I hope you're not suggesting what I'm thinking. This is a trigger for me in a sense, because my ex was my son's primary care giver for the first year while I was the bread winner. I've had sole custody for going on 6 years now. I don't like the thought of this mother-child bond trumps all vibe I'm getting.

The op makes it sound like should they divorce, his plan is to take the child and leave. Mother-child bonds don’t work like that.

I don't think it reads like that. He wants himself and his child to be protected for a while in case any issues do arise. They're not even married yet! He said he's willing to do this after they are married. Seems reasonable to me. Why would someone even think of doing this before marriage?

At best, he’s hoping to burden her with all the emotional responsibility of a child, but give her none of the legal benefits as a parent.

That is not the "at best" here and if you say that vile information is the 'at best' then you truly must think of OP as the second coming of Hitler.

You can’t ask someone to take all the responsibility and enjoy none of the benefits. It’s also unfair to the child that their primary care giver has no legal say in their lives.

I do agree with this in a sense, but again.. they're not even married yet.

Or mom can’t pick the kid up from school without a note from dad?

School's are very easy to deal with in this regard. Add person to the pickup list/emergency contact info. Not an issue.

Or when the kid’s a teenager and mom has to discipline? “You’re not my real mom! You’re not even my legal mom!”

Again again, he said he's willing to when they're married.

Also, the 'not my real mom' thing can come up anyway.

And 'not even my legal mom' ...? What about step parents, is it common for them to seek adoption of their partners child? Genuine question

Maybe he's going about this the wrong way, I don't know. I think dealing with this after marriage is the most reasonable thing, and that's what he suggested. I don't even think I want to continue reading the comments here, OP is being painted as this disgustingly evil, villainous, despicable human being for this situation in other comments.

I do think the fact that this happened with an already well-established partner is an important variable and carries weight compared to say.. a woman he started seeing a few months after the baby was born or something. But I just think it's insane for people to want to consider adoption prior to marriage.

I lost the quote about the hospital thing you mentioned while replying to this but it was a helluva good point, what can OP do to allow his SO to visit the child in the hospital in the event of an emergency prior to marriage? It's my understanding that that would change once they're married, regardless of the state of adoption, right? This is actually really important and I'm glad you brought it up!