client – Long paths in synced Sharepoint folders

I’m seeing inconsistent behavior with Sharepoint folders synced via the OneDrive client on Windows 10 computers. Specifically, files with path length longer than 260 characters. On each of the systems I’ve tested, I have enabled long file path support via registry.

On my computer, files with paths longer than 260 characters open fine. If you get the Properties on such a file, they show the 8.3 short pathname (e.g. FILENA~1.TXT) for each component of the path after the root of the Sharepoint root folder (i.e. C:UsersusernameTenantName).

On other systems I’ve tested, the Properties shows the UNC prefix (i.e. \?C:) plus the full, unabbreviated path. On these systems, files with long paths will not open. Instead, Explorer gives an error message The data area passed to a system call is too small.

I can’t find any documentation to determine whether this is expected behavior. All clients tested appear to be identically patched and are on the same build of the OneDrive client. Has anyone else experienced this behavior? If so, do you know how to force the 8.3 file path behavior? Or some other resolution to allow these files to be opened?

We are in the process of migrating project data from SMB shares to Sharepoint, and we’ve used file system integration via the OneDrive client as a selling point, but if we can’t predict how long paths will be handled, we may have to rethink our approach.