Confirmed on Xcode 16.4 (16F6). Bug symptoms are the same as previously mentioned: Xcode frequently launches duplicate processes when schema Run action is performed on a macOS command line tool executable that creates UI windows. It is a bug in Xcode due to following: The bug occurs when "Debug executable" is set under the Scheme -> Run -> Info tab. When "Debug executable" is unset, no duplicate processes are launched. No duplicate processes are launched when the executable is launched on terminal. Also confirmed that adding 350 ms delay in program main() is a workaround. For example, using SDL2 add SDL_Delay(350) at the top of the main() function. To Xcode team, let me know if you want a test app for this. Cheers.