My ex introduced her new partner to the kids and didn't tell me

Found out from my 10yo that he met his mom's "boyfriend" last weekend. Didn't get a heads up, no discussion about whether it was appropriate yet, nothing. I'm trying not to lose my mind but also like... shouldn't we have talked about this?

Our agreement doesn't explicitly say we need to notify each other about this stuff but it feels like basic respect? Is this a hill to die on or am I being controlling?