Windows 11 an error occurs when copying files with excessively long path names

Success in a shorter destination means the filename alone is not decisive. Windows evaluates the complete absolute path, and Microsoft notes that the shell and file system can have different limits. Long-path support also requires both the Windows setting and an application that declares itself long-path aware; enabling the policy does not remove every Explorer limitation. Copy the file to a short local path such as C:\Temp and compare. Then measure the full source and destination paths, including the drive, OneDrive organization folder, every separator, and filename. Check each folder name for trailing spaces, reserved names, or unsupported characters, and review OneDrive’s sync status. Shorten the destination root or one parent folder instead of renaming a project file that other software references. If local copying works but the synced location fails, capture the exact path and OneDrive error and apply the documented OneDrive or SharePoint naming and path restrictions.