Is there a way to change the model to Opus it's using sonnet. I have a claude code max x2 subscription.

I'm trying to submit a new version of my app. I get an Invalid binary notification but no email and no details on what is wrong. I've been fighting this for two days now. Appreciate any ideas or help. My app passes validation fine. I'm using xcode 8. I'm on OS X El Capitan 10.11.6