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Tahoe Issues
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Topic starter
FYI, at present do not upgrade to macOS Tahoe 26.4 Developer Beta 1 if you also use SoftRAID.
Namely, doing so causes volumes to be Read-Only.
SoftRAID says the volume is fine, no errors, validates, etc.
All indications point to this being an Apple issue, via the fsck_hfs binary being built with a developer runtime that isn't included within the OS Update. As such, I expect this is something Apple will need to fix on their own vs something that SoftRAID can fix in the meantime.
If affected, this is what the user sees:
macOS reports that the drive is corrupted and must be mounted Read-Only and suggests backing up and re-formatting.
DiskUtility First Aid reports:
Running First Aid on “Thunderbay8” (disk18)
Checking file system and repairing if necessary and if possible.
Volume is already unmounted.
Performing fsck_hfs -fy -x /dev/rdisk18
File system check exit code is 6.
Restoring the original state found as unmounted.
File system verify or repair failed. : (-69845)
Operation failed…
Terminal fsck reports:
dyld[1234]: Library not loaded: @rpath/libclang_rt.ubsan_osx_dynamic.dylib
Referenced from: <915F7812-C148-3B7D-8CE9-1A77E6123971> /System/Library/Filesystems/hfs.fs/Contents/Resources/fsck_hfs
Reason: tried: '/System/Library/Filesystems/hfs.fs/Contents/Resources/libclang_rt.ubsan_osx_dynamic.dylib' (no such file, not in dyld cache), '/AppleInternal/Library/BuildRoots/4~CInqugCr-EX0f6D2IRo_C2u-onGfk3sBXON95uA/Applications/Xcode.app/Contents/Developer/Toolchains/OSX26.4.xctoolchain/usr/lib/clang/21/lib/darwin/libclang_rt.ubsan_osx_dynamic.dylib' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/AppleInternal/Library/BuildRoots/4~CInqugCr-EX0f6D2IRo_C2u-onGfk3sBXON95uA/Applications/Xcode.app/Contents/Developer/Toolchains/OSX26.4.xctoolchain/usr/lib/clang/21/lib/darwin/libclang_rt.ubsan_osx_dynamic.dylib' (no such file), '/usr/appleinternal/lib/sanitizers/libclang_rt.ubsan_osx_dynamic.dylib' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/usr/appleinternal/lib/sanitizers/libclang_rt.ubsan_osx_dynamic.dylib' (no such file), '/System/Library/Filesystems/hfs.fs/Contents/Resources/libclang_rt.ubsan_osx_dynamic.dylib' (no such file, not in dyld cache), '/AppleInternal/Library/BuildRoots/4~CInqugCr-EX0f6D2IRo_C2u-onGfk3sBXON95uA/Applications/Xcode.app/Contents/Developer/Toolchains/OSX26.4.xctoolchain/usr/lib/clang/21/lib/darwin/libclang_rt.ubsan_osx_dynamic.dylib' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/AppleInternal/Library/BuildRoots/4~CInqugCr-EX0f6D2IRo_C2u-onGfk3sBXON95uA/Applications/Xcode.app/Contents/Developer/Toolchains/OSX26.4.xctoolchain/usr/lib/clang/21/lib/darwin/libclang_rt.ubsan_osx_dynamic.dylib' (no such file), '/usr/appleinternal/lib/sanitizers/libclang_rt.ubsan_osx_dynamic.dylib' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/usr/appleinternal/lib/sanitizers/libclang_rt.ubsan_osx_dynamic.dylib' (no such file)
Posted : 17/02/2026 12:52 pm
Topic starter
Update that you REALLY shouldn't use!!!
It appears that this is solely an issue if you are using HFS+ rather than APFS.
If you are really content on running macOS 26.4 Developer Beta 1, and you have SIP disabled (which is already a risky endeavor!), you can also download the matching Xcode Beta and then grab
/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/21/lib/darwin/libclang_rt.ubsan_osx_dynamic.dylib
and then place it into the folder:
/System/Library/Filesystems/hfs.fs/Contents/Resources/
This /technically/ fixes the issue and allows for macOS 26.4 DB1 to mount HFS+ volumes.
You could also plug the array into another computer and migrate to APFS, but as there is no defrag capabilities for APFS on HDDs, also not a great solution...
Posted : 17/02/2026 1:37 pm
Topic starter
For the people who will inevitably chime in "this isn't the right place for this conversation... you should really send that to Apple's Feedback app!"
Yes, I know, I have... This was intended as a preemptive warning to others like me who installed the update onto one of my lab systems and were surprised to see their external storage break.
Posted : 17/02/2026 3:06 pm
@kalani
My guess is your speculation is correct. I will research this overnight and see if I can post anything. It does not appear to be a data loss issue at present, but its likely the next beta won't be for 2 weeks.
Note: you cannot "convert" SoftRAID HFS volumes to APFS.
This post was modified 2 months ago by SoftRAID Support
Posted : 17/02/2026 3:31 pm
Topic starter
Worth calling out, I was also able to replicate the same behavior with a USB Thumb Drive formatted as HFS+ and plugged into the 26.4 DB1 system, and that too was fixed after the highly risky and unsafe option I found. Ergo, highly doubt that this is something that you guys can fix since it's bigger than a SoftRaid problem.
Posted : 17/02/2026 3:34 pm
@kalani
We can "complain". ;-)
Once we replicate it, we can pass it on to Apple Engineering, also.
Posted : 17/02/2026 7:23 pm
I did confirm this "Cannot repair the volume " ", affects Apple formatted drives also, so it is a "global" bug.
In doing some research, yes your workaround appears valid, but I do not recommend it.
Its best to back the beta out, go back to 26.3, or do not use SoftRAID on this macOS version until Apple fixes it in a week or two.
It appears that Apple engineers left behind a debugging tool in .4 beta 1, and so will be fixed in beta 2.
Manually working around it as you are requires modifying protected system files - Placing files in /System/Library/ breaks Apple's security system seal, and could cause:
Future OS updates to fail
System instability
Security vulnerabilities
So patience is the best virtue here.
I am sure we will be filing a detailed bug report before end of week.
This post was modified 2 months ago 2 times by SoftRAID Support
Posted : 18/02/2026 2:13 am
@softraid-support facing this... and didn't see the warning before hand.... I may wait it out for the udpate, but is there an easy/smooth way to do this:
Its best to back the beta out, go back to 26.3, or do not use SoftRAID on this macOS version until Apple fixes it in a week or two.
😩
Posted : 18/02/2026 5:10 pm
Topic starter
Developer Beta 2 fixed.
Posted : 23/02/2026 3:45 pm
I am sure we will be filing a detailed bug report before end of week.
Hi, I see that macOS Tahoe 26.4 Developer Beta 2 has been released.
Has there been any news re a fix?
Posted : 23/02/2026 8:48 pm
Topic starter
Yes.
Posted : 25/02/2026 12:56 am
I'm on beta 2 and it's still not fixed for me. Any ideas?
Posted : 27/02/2026 12:34 pm
Do a reinstall. Everyone has confirmed this is fixed in beta 2. One user reported some component was not installed and he had to reinstall beta 2
Posted : 27/02/2026 10:57 pm
