Summer Schedule Disagreement

Location: New Mexico

I am located in NM and dealing with a summer schedule issue with my son’s dad who is in Phx, AZ.

Our parenting plan doesn’t set a fixed summer schedule. It says we’re supposed to agree each year and that decisions should consider the child’s needs and involve flexibility.
Last summer my son (12) spent 5 weeks straight with his dad in Phoenix. This year he’s been very clear he doesn’t want to do that again and only wants to go for 3 weeks.
Part of it is his experience there. His dad lives in a small one-bedroom apartment with his grandmother, so my son shares a room with him. He’s also told me he feels bored and lonely a lot of the time. Last summer and even over spring break, he was spending a large portion of the day on his phone (like ~8 hours/day).
I brought this up back in April and suggested 3 weeks at the beginning of summer, then he has a soccer camp, then comes home. I’ve said I’m open to working out other time that fits around his schedule.
His dad is insisting on 5 total weeks. He has offered to split it up, but my son still doesn’t want to be there that long overall. He keeps saying he’s “entitled” to half the summer, won’t ask our son what he wants, and is now talking about filing an emergency hearing.
I’m not trying to keep my son from him. I’m just not agreeing to 5 weeks total when my son has been clear about what he’s comfortable with.
If we can’t agree, what actually happens in a situation like this?
And is this even something that would qualify as an emergency hearing (a threat on his end, not mine)