Am I being unreasonable wanting stronger co-parenting boundaries?

I've been with my partner for about three years. His daughter is four, and we've recently moved to 50/50 care.

The extra time has actually been wonderful. My relationship with his daughter has grown a lot. But it's also brought some issues in my relationship to the surface that I can't seem to shake.

His co-parent is what I'd describe as fairly high conflict. She always seems to need the last word, doesn't take disagreement well, and there seems to be a constant need for contact. My partner manages it by either agreeing or ignoring things because, in his words, it's not worth the fight.

I understand why he does it. Part of me thinks he's trying to avoid conflict, and part of me wonders if he carries guilt about the separation and I know he worries that pushing back could make co-parenting harder. I don't think he's doing anything inappropriate, and I don't think there's anything romantic going on, I trust him.

What I'm struggling with is the amount of access she seems to have to our household.

They do morning and evening check-ins, but there are also random texts and phone calls throughout the day whenever something comes up. Sometimes if he doesn't reply for an hour or two she'll follow up with a "hello??". A lot of it is child-related, but not always urgent.

She also still comments on things that don't really affect her anymore, like how we manage things in our house or even how he spends his money. It feels like there are very few boundaries between their households.

There have also been a handful of interactions over the last few years that have left me feeling like an outsider. For example, conversations where I felt like a third wheel while they talked, or stories being passed on that felt designed to remind me I'm "just Dad's partner." None of these things are huge on their own, but together they've chipped away at me.

Last week I asked my partner whether they could try limiting communication to one planned check-in a day unless something was genuinely urgent. Not because I want to interfere with co-parenting, but because I feel like there needs to be a clearer separation between their parenting relationship and our household.

To his credit, he did raise it with her. Her response was basically, "You can do what you want, but I'm going to check in as much as I want because it's my child." Since then, he's continued replying on his own terms, but she still messages whenever she wants. It left me feeling like any attempt at setting boundaries was dismissed before it even started.

He was also really unhappy with my suggestion in the first place, which has left me wondering if I'm asking for something unreasonable.

For those of you who co-parent or are step-parents:

Is frequent daily contact just the reality of having a four-year-old?

At what point does "good co-parenting" become poor boundaries?

How do you balance staying connected for your child while also protecting your new relationship?

I'm genuinely looking for perspective because I don't want to become the stereotypical jealous step-parent, but I also don't want to ignore something that's making me feel like I'm sharing my relationship with a third person.