Win32Window::Create calls Destroy() before it makes the window, which ran FlutterWindow::OnDestroy and armed the 3 s exit timer at launch: the window showed, then the process ended with code 0, no crash, no close lines. The timer is only armed with an engine to tear down. Found and fixed by Fun Maker's agent on Windows (a debugger caught the exit on the timer's thread). The smoke runs missed it (they closed at ~4 s anyway): the app now stays up 10 s, and the scripts require 'closing' and 'quitting' from its own close. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>