Is there an official stance on whether ntdll is stable? Obviously they're not going to change things arbitrarily since applications depend on it, but I'm wondering if there is a guarantee like the linux syscall interface or how you can run a win32 application compiled in 2004 on Win11.
It's partially stable.
Basically any thing documented on msdn in the API docs is considered stable.
Such as: https://learn.microsoft.com/en-us/windows/win32/api/winternl...