MacBook Air Tahoe 26.0.1 cannot mount vault.sparseimage

I have seen a couple of reports of .sparseimage files failing to mount on Tahoe. In one case, the user created a new disk image in Tahoe, opened the old one on a Mac running Sequoia and copied over the data.

Part of the issue may be that with Tahoe, Apple replaced the prior sparse image format with a new one, ASIF. If you need immediate access, perhaps you can borrow a Mac with an older macOS. Else, hopefully it's sorted in a point update.

Bugs can be reported to Apple here:

Feedback - macOS - Apple

wadefrommountain wrote:

I found a neighbour with a MacBook and he had not yet upgraded to Tahoe. I copied the vault sparse.image to a USB stick and read it with his computer, and put the unencrypted files back on the stick - and brought it back to my computer. I now have access to those files!

That's the way to do it.

If there's anything I don't understand, it's the "trade in" program. Why would someone give up an older system for a couple hundred dollar discount? I may not use the old 2014 computer very often, but sometimes, I do need it for things that the new ones simply can't do. And yet, the old one can do everything the new one can, it's just slower.

etresoft wrote:

Never use any of these experimental file systems for important data. They're fine to play around with. But always have a backup on some more stable, supported format. For macOS, that means an AFPS SSD or hard drive, or perhaps a network volume.

I presume* the file 'vault.sparseimage' is a sparse disk image named 'vault'. How is a .sparseimage file experimental or unsupported? You can make one in Disk Utility, and have been able to do so for a very long time.

Perhaps the argument could be made that Tahoe's new ASIF format that replaced the UDSP format that's been used for many years is 'experimental' but clearly it's not unsupported if you can choose if from the dropdown menu in a native Apple application.

*My presumption may be incorrect, since the default name from DU would be vault.dmg.sparseimage, but the 'dmg' part can certainly be deleted without issue.

neuroanatomist wrote:

How is a .sparseimage file experimental or unsupported?

I don't know. Ask the OP. 😄

Yeah, that's one a list of a few words that just freaks people out for some reason. They assume that words like "supported", "all", "always", and "never" are numeric, mathematic absolutes. I'll tell someone that some technique "never" works and they'll quit their job, spend the next six years researching the issue full time, find a case where it worked once, then come back and say, "Ha! You were wrong!".

"Supported" is very similar. There's a button for it. It's mentioned in an Apple web page. It's The Gospel!

No, it's not. It's just an easy way to corrupt your data.

You can make one in Disk Utility, and have been able to do so for a very long time.

That reminds me. I thought of that gospel joke and remembered that I need to fix my Sacred Texts Archive dmg. It's not even a sparse image. Just a regular dmg from 2010. If I try to mount it, it locks up the Finder, which can't then be relaunched. I have to restart the whole machine. Maybe I should submit it as a DOS attack and try to collect a bug bounty! Nah. I'll AirDrop it to the 2014 machine running BigSur and copy the contents to a new image.

Perhaps the argument could be made that Tahoe's new ASIF format that replaced the UDSP format that's been used for many years is 'experimental' but clearly it's not unsupported if you can choose if from the dropdown menu in a native Apple application.

That is a good question though. Why use "unsupported" vs. "unreliable" or "LOL! That doesn't work!"?

I think the word "unsupported" is better because it encourages acceptance, without judgement. Apple's constant firehose of software updates gives people this erroneous assumption that Apple is going to fix something that is "unreliable" or "doesn't work". But that's simply not true.

(Dang it! There I go again!) Somebody pulls up some Apple note where it mentions how an update fixes some problem reported by 12 people. For example, macOS 26.0.1 fixes "an issue that prevented some users from upgrading to macOS Tahoe on Mac Studio (M3 Ultra, 2025)". Yeah, if you can't update to Tahoe, Apple's going to fix that! Good luck getting any of the other things in Tahoe fixed.

My interest is in helping people have a better overall experience. That means not submitting a bug report that will just be ignored, closed as "unreproducible" or "working as designed", or with some nonsensical response. It also means not joining the hip crowd raging at Apple for ruining their lives. There's more than one way to get things done. If you want to be on the update rollercoaster, you're gonna have to roll with the punches. If not, you gotta learn somehow.

Never use any of these experimental file systems for important data. They're fine to play around with. But always have a backup on some more stable, supported format. For macOS, that means an AFPS SSD or hard drive, or perhaps a network volume.

Thanks for the deets!

neuroanatomist wrote:

Thanks for the deets!

And my DMG is now fixed. Alas, AirDrop didn't work. I had to use file sharing. Strange. AirDrop is definitely supported on that computer. 😄