Apple is likely preparing to remove it for a secure alternative and all it takes is someone to find a single or a bunch of multiple vulnerabilities in sandbox-exec to give a wake up call to everyone why were they using it in the first place.
I predict that there is a CVE lurking in sandbox-exec waiting to be discovered.
The security researchers will leverage every part of the OS stack to bypass the sandbox in XNU which they have done multiple times.
Now, there is a good reason for them to break the sandbox thanks to the hype of 'agents'. It could even take a single file to break it. [0]
> My guess is sandbox-exec is deprecated more because it never was adequately documented rather than because it’s flawed in some way.
You do not know that. I am saying that it has been bypassed before and having it being used all over the OS doesn't mean anything. It actually makes it worse.
[0] https://the-sequence.com/crashone-cve-2025-24277-macos-sandb...
Apple can still decide to change it for any reason, regardless of who uses it, since it is undocumented for their use anyway.
> I’m not sure Apple could remove it even if they were sufficiently motivated to.
It can take multiple security issues for them to remove it.