How can I run iPhone simulator over full-screen(lion) Xcode 4.1?

There doesn't seem to be any way to do this. I think part of the idea of having a full-screen mode is that you cannot have any other windows open on top of the full-screen window.

Try opening Xcode in full-screen mode, then open the organizer window, and you'll see what I mean. The organizer opens in its own full-screen mode space.

Which makes sense, even though it's inconvenient in this case. I think if Apple were to give the iOS simulator its own full-screen mode, that would be nicer than just throwing it up on a desktop.

It seems like the ideal solution would be for Apple to integrate the iOS simulator into the Xcode debugging environment, similar to what they did with Interface Builder in Xcode 4.

To run simulators in full-screen mode, you need to enable fullscreen mode by executing the following command in your terminal:

defaults write com.apple.iphonesimulator AllowFullscreenMode -bool YES

*You need to restart the simulator in order to reflect the changes.

As others point out, Apple doesn't allow to run two full screen apps one over the other one. However, you could put them next to each other like this which already is an enhancement (at least for me):

I use VS Code instead of Xcode but the logic is the same. All you have to do is just to allow iOS Simulator to run in Full Screen by running the following command in terminal:

defaults write com.apple.iphonesimulator AllowFullscreenMode -bool YES