> all OS code recompiled for Apple Silicon / ARM? Yes, of course. > two binaries Yes and no. Technically, they are single binaries. The Mach-O binary for

> all OS code recompiled for Apple Silicon / ARM? Yes, of course. > two binaries Yes and no. Technically, they are single binaries. The Mach-O binary format has supported the concept of a "fat binary" at least since NeXTStep was ported to Intel. So it's a single file, a single "binary", but with different sections for different architectures. Kernel selects the right bits of the binary to executer when loading. > flag at boot-time Nope. On an ARM Mac, ARM code will run natively, Intel code will run via Rosetta. On an Intel code, Intel code runs natively and ARM code does not run. This is done transparently for each binary.