External Drives not recognised in Tahoe

[Skoobunny]

This is precisely bug no. FB13749402, reported to Apple in July 2025 and confirmed by MacBook M2/M3 users after upgrading from Sequoia to Tahoe.

Tahoe has a broken USB Mass Storage support — affecting not only FAT/exFAT, but occasionally APFS as well.
The diskarbitrationd daemon (responsible for mounting new volumes) hangs after upgrading from Sequoia to Tahoe.
Some USB devices are visible in diskutil, but lack virtual access permissions assigned by kernel_task.

Apple plans to fix this issue in a future build, where diskarbitrationd regains the correct entitlements after upgrading from Sequoia.

In Darwin 26.x, Apple introduced a new access management layer for block devices with enforced kernel-level sandboxing.
This is precisely why mount_msdos and mount_apfs return “Operation not permitted” errors despite successful formatting.


ChatGPT said so

 

[Ifti]

Strange - I have tons of external SSD drives - both RAID (using SoftRAID) and single drives, exFAT, HFS+ and APFS, across USB4, Thunderbolt 3, 4 and 5 interfaces. All work perfectly fine on a Mac Studio M4 Max.
Upgraded to Tahoe from Sonoma a few weeks back and been using them as normal.
Wonder if it is more isolated to Intel based machines.....
Is your MacBook an Apple Silicon machine? If so you could always try upgrading that to Tahoe and see if they work.....although downgrade the iMAC first so you can still access the drives somewhere at least!

 

[Skoobunny]

Strange - I have tons of external SSD drives - both RAID (using SoftRAID) and single drives, exFAT, HFS+ and APFS, across USB4, Thunderbolt 3, 4 and 5 interfaces. All work perfectly fine on a Mac Studio M4 Max.
Upgraded to Tahoe from Sonoma a few weeks back and been using them as normal.
Wonder if it is more isolated to Intel based machines.....
Is your MacBook an Apple Silicon machine? If so you could always try upgrading that to Tahoe and see if they work.....although downgrade the iMAC first so you can still access the drives somewhere at least!

The situation is even more interesting. My wife's MacBook Air M3 has no problems after switching from Mac OS Sequoia to Mac OS Tahoe. My MacBook Pro M3 (Pro) cannot work with external drives after upgrade.