The concern is how frequently that recovery becomes necessary. In our tests, an ordinary external folder rename reproduces the problem on FAT32/exFAT, while the same workflow appears to work on APFS.
If it was me, then I wouldn't worry about it. Foreign file systems are always problematic.
While the app remains running, its existing file descriptor still tracks the renamed folder. On exFAT, we traced creation of the replacement security-scoped bookmark to an open() failure with EPERM. Reselecting that same folder through the system picker allows bookmark creation and subsequent access after relaunch.
Two questions:
What are you doing with this folder? It sounds like you're keeping a file descriptor open on it for a long time. That's risky.
Ideally, you're going to wrap each access in a file coordination block. In theory, that should guard against some level of external manipulation. Are you doing that?
(Note: my own file coordination experience is strictly theoretical. I've never seen it do anything really.)
At a fundamental level, if you're app is saving a folder URL and the user trashes, renames, or moves the folder, that's a user problem. Your app should have no expectation of recovery. I realize end users may have different expectations. They do tend towards cognitive dissonance.
Saving the last known URL could help guide the user through recovery, but would not itself restore authorization or establish that a folder subsequently found at that path is the original resource.
No. It wouldn't. It's more for developer and user convenience.
Also, it's important to note that you're specifically talking about folders here, correct? Folders aren't completely supported by security-scoped bookmarks, even on APFS. Perhaps you just haven't found the gaps yet. 😄
The remaining question is whether repeated reselection after ordinary renames is unavoidable under these constraints: a sandboxed app, public APIs, and authorization limited to the selected folder.
Have you encountered this specific FAT32/exFAT rename scenario, and do you know an approach that avoids repeated reselection?
Usually the best solution is an app design that steers the user towards manual selection as part of a normal app flow. Security-scoped bookmarks are fundamentally about accessing files outside of your sandbox. Avoid that at all costs.
There's another important plot point here with respect to "support", public APIs, and authorization. None of these are designed to facilitate access. They're specifically designed to block access. The barriers they introduce aren't side effects, they're design goals.
If you haven't already heard, Full Disk Access is next on the chopping block. Even if you don't use or access this feature, the changes that Apple is going to implement will likely require some coding changes. So my advice is not to put much effort into any feature that depends on security-scoped bookmarks as that it likely to be a source of user annoyance. Try to structure your app around documents and/or data in your sandbox.