at_quick_exit(3) on macOS
The text 1d91586c3b40, as macOS 26.5, macOS 26.4, macOS 26.3, macOS 26.2, macOS 26.1, macOS 26.0, macOS 15.6, macOS 15.5, macOS 15.4, macOS 15.3, macOS 15.2, macOS 15.1, macOS 15.0 shipped it. The page shows this text now.
registers a cleanup function to run on quick exit