Rustaceans at the border

Rustaceans at the border

That's fine. Programs are supposed to assume that the filesystem may change under them. That's the cost of a shared resource which doesn't use Microsoft Visual SourceSafe-style locking overkill.

What's important is that, if the OS APIs give you a string identifier, your internal string processing can round-trip what you were given without altering it.

For comparison, I imagine that using the Windows version of Python's os.path.normcase for purposes other than in-process equality comparisons would cause i18n issues since it uses Python's internal .lower() method and thus the Unicode case-conversion tables baked into that version of Python while NTFS lookups use a case-folding table baked into the NTFS partition at the time it was formatted to ensure that Unicode updates can't introduce case-equivalence collisions for already-existing paths.