If you drive the iOS simulator from scripts, test tools or AI agents, this one can cost you an afternoon: every tap is acknowledged, every command returns ok , and nothing happens on screen.

I hit it while building a tool that lets an agent and me work on the same running React Native app. Here's what's going on, how to tell you're in it, and how to get out.

All of this is on Xcode 27.0 with iOS 26.3 simulators, on one Mac. If you're on a different setup, your mileage may vary, and I'd love to hear if you see it too.

First, the change: no more Simulator.app

Xcode 27 doesn't ship a separate Simulator.app anymore. You look at simulators through Device Hub inside Xcode.

Two side effects worth knowing:

Closing the viewer can shut the device down. If you were relying on "the window is open, so the simulator is running", that's no longer a safe assumption.

You don't need a viewer at all.…