I only use frontier models to vibe code iOS apps, as I'm not an iOS developer. I haven't tried the local models post qwen coder 3.5 release for all the reasons.

AFAIK, a limiter for iOS engineers (and AI agents) for concurrent feature development is the xcode environment and hardware limits. BE engineers can easily have 3 agents working on 3 different microservices (or gitwork trees), but iOS devs can basically only manage one version of the code at a time, due to externalized state (like derived data and bundle ids).