macOS 27 Golden Gate hides working bootable backups from Startup Disk (September 14, 2026)

What the backup developers said on release day

Dave Nanian published his note ahead of the release, which he said would likely arrive "a few hours after this posts". The warning in it is one sentence. "The big but ... in Golden Gate 27.0 is a SuperDuper issue (that is actually an Apple issue): backups, even though a bootable backup is properly configured to boot, they aren't showing up as choices in either the startup disk preference pane or the startup picker." The Feedback number follows in the next breath: "(FB24210103, reported quite a while ago, Apple friends.)"

Nothing announces the problem while the copy is being made. "Fortunately, unlike when this happened before, there's no error during copy. But, even though the end result is bootable, it just doesn't appear." The volume is a working startup disk. The list you pick it from no longer lists it.

Later the same day Shirt Pocket published a screen shot of a Mac Studio booted from a SuperDuper copy written to a JBOD PRO-BLADE Station, and said a MacBook Neo and a MacBook Pro were tested the same way. That post describes the defect as "a bug in Golden Gate that is not showing proper external copies as bootable, even though they're made correctly, with Apple's own replicator".

Michael Tsai collected the day's developer reports on macOS 27 Golden Gate on September 14, 2026, and quoted that same sentence from Nanian.

Bombich points at Apple's copying tool

Mike Bombich published on the same day and gave the failure a history. "I remember seeing this one way back in Big Sur; you'd create a perfectly functional bootable copy of the system, but it wouldn't show up in the Startup Disk Preference Pane." He says Apple resolved that one in macOS Monterey, and that it is back, "unfixed in the Golden Gate release candidate".

This time the escape hatch is gone as well. "This time it's a little bit worse, because the workaround to choose the volume via the Startup Manager wasn't working (e.g. boot while holding the Power button)." Holding the Power button is the usual fallback when the Startup Disk pane will not cooperate.

He also says where the gap is, without saying what it is. "With a lot of in-depth research, I finally figured out what Apple's ASR utility wasn't doing, and now CCC handles that last little detail too." Two developers working separately both end up at Apple's copying tool rather than at their own code: Shirt Pocket says its copies are made "with Apple's own replicator", and Bombich names "Apple's ASR utility".

The result he promises is specific. "So once again, bootable copies made with CCC 7.2 will appear in both the Startup Disk app, and in the Startup Manager, no Terminal commands or reduced boot security required". Both are what Nanian's footnote workaround requires. The post gives no release date for CCC 7.2.

The build this lands in

The Eclectic Light Company put the release details in one place on September 14, 2026. "The build number of 27.0 is 26A428 (the same as the release candidate)". It needs an Apple silicon Mac and the download was advertised at 30.8 GB.

The same post counts the security work: "Security release notes for Golden Gate list around 206 items, none of them suspected of being exploited in the wild". That count is The Eclectic Light Company's, not Apple's. Apple's own list, About the security content of macOS Golden Gate 27, carries the line "Released September 14, 2026" and gives no total of its own.

Build 26A428 is the number to hold on to, because it is the release candidate build from earlier this month. The press-and-drag selection failure of September 11 and the Font Book crash of September 12 were both seen in 26A428. Nothing published today says either of them changed, and no Apple note says either was repaired.

If the Mac you are moving from runs macOS Tahoe 26.4 or later, the login keychain problem in yesterday's post still applies, and Migration Assistant is the route that carries the contents across.

What Apple has not said

I have seen nothing from Apple about the startup disk behaviour. FB24210103 was filed, in Nanian's words, "quite a while ago", and the release shipped with the behaviour in it.

Three things are unknown today. Whether Apple treats this as a defect or as a deliberate change in the way the startup picker filters volumes. What ASR stopped doing, because Bombich found it and did not describe it. And when a repair might arrive: the only thing said about timing is Nanian's "I'm hoping Apple will fix this soon".

Nanian's verdict on the release as a whole is warm. "Golden Gate, in my view, looks to be one of the more reliable releases we've had in years, even in its 27.0 release." He says he would not hesitate to encourage people to install it without waiting for 27.1, and he shipped SuperDuper 4.0.6 the same day.

What to do today

1. Check the clone before you need it. Make a copy, open the Startup Disk pane in System Settings, and look for the volume. If it is missing on Golden Gate 27.0, that is the behaviour both developers described on September 14, 2026, and not a damaged backup.

2. Do not erase or remake a copy because it vanished from the list. Nanian's line is the one to keep: "a drive doesn't have to boot to be fully restored". A restore reads the files. It does not need the startup entry.

3. If you use Carbon Copy Cloner, take the update. Bombich says copies made with CCC 7.2 appear in the Startup Disk app and in the Startup Manager again, with no Terminal commands and no reduced boot security. His post names no release date, so look in the application's own updater.

4. If you use SuperDuper, the workaround is in a footnote of Nanian's post: boot into Recovery, reduce security with the Startup Security utility, then run bless --mount /Volumes/Backup-Volume --setBoot in Recovery's Terminal. He says not to do it unless you really have to, and the cost is that the Mac is left on reduced boot security until you put it back. Shirt Pocket's second post of the day adds that you should also be able to install Golden Gate over the backup from Recovery, which costs a full operating system install onto that drive and the time it takes.

5. Keep a copy of the data that does not depend on booting at all, and if you look after Macs for other people, tell them what a missing entry means before they ring.

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