Does virtualizing macOS 27 require a macOS 27 host?

A macOS 27 guest should run on a macOS 26.6 host, but we discovered a late incompatibility between the VZMacOSInstaller API on macOS 26.6 and the macOS 27 IPSW.

Unfortunately the best workaround I can think of at the moment is creating a VM on a macOS 27 host and then moving it back to your macOS 26.6 host. I understand this is not ideal. I'll see if we can find a better workaround for you.

Well, as someone who only has a single Mac, I prefer to use VMs to test my software against new releases.

I know I can create a second boot volume to run the beta but that's really quite inconvenient.

So, count me as very interested in a better workaround.

After I first tried to create a macOS 27 VM on macOS 26, I remembered that for prior major releases you needed to install the Xcode beta in order to install the beta into a VM.

So, I installed the Xcode 27 beta on my host.

Now, I can no longer create Tahoe VMs on my Mac. (I was going to upgrade the VM to Golden Gate through Software Update.)

What do I need to do to revert the state of my Mac to the point where I can create Tahoe VMs again?

I was able to get a macOS 27 VM on a macOS 26 host by creating a macOS 26 VM, signing in to iCloud, and enabling the macOS 27 beta channel for software updates. Initially I got an error saying it was unable to customise the install, but I simply quit System Settings, and tried again, which then worked.

Note: macOS 27 appears to actively prevent SIP disablement, lots of people reporting it refuses to install if SIP is already disabled, and I get errors disabling SIP once installed from the recovery mode, which is troublesome for my dev-workflow.

I noticed this on macOS 26.5.1 as well. I made sure to install XCode Beta as well as additional tools as well.

Same here. On macOS 26.5.1. Installed Xcode 27 beta to test macOS 27 in a VM.

Now I can't install any macOS versions (26.x) in a VM.

Seeing the same here, since installing Xcode beta I can't use any macOS VMs, they are all failing the install process at 78%

Having the same issues as everyone else, and none of the suggestions have worked for me.

I ended up doing the following: found a VirtualBuddy VM with the Tahoe beta from last August on my TimeMachine backup, restored the file, upgraded it to 26.5.1 and then upgraded to the macOS 27 beta. Took a while, but it worked flawlessly! And Golden Gate feels extremely polished.

Same issue here, after installing Xcode 27 beta I can no longer create a macOS VM on macOS 26.5.1

I tried creating a macOS 27 VM as well and it failed. I would try to install it on a separate partition, but the last few years I haven't been able to install macOS on separate partitions anymore, as I pointed out last year (nobody answered): https://developer.apple.com/forums/thread/799898

Virtulization App VirtualBuddy supports installation of macOS 27 on macOS 26 hosts in 2.2 beta 2 of the app: https://github.com/insidegui/VirtualBuddy/releases/tag/2.2-b2

Not when you upgrade an existing VM using Software Update within the VM

VurtualProg also support install macOS 27 from ipsw on host Tahoe please check out https://forums.macrumors.com/threads/virtualprog-macos-virtualization-tool.2456173/post-34641389

Just tested the latest Xcode, 26.6b3, and still can't create 27 VMs.

failed to install macOS: Error Domain=VZErrorDomain Code=10007 "Installation failed." UserInfo={NSLocalizedFailure=An error occurred during installation., NSLocalizedFailureReason=Installation failed., NSUnderlyingError=0x7e001c1e0 {Error Domain=com.apple.MobileDevice.MobileRestore Code=-1 "AMRestorePerformRestoreModeRestoreWithError failed with error: 11" UserInfo={NSLocalizedDescription=AMRestorePerformRestoreModeRestoreWithError failed with error: 11, NSLocalizedFailureReason=An unknown error occurred during installation.}}}

Just tested the latest Xcode, 26.6b3, and still can't create 27 VMs.

I’d like to clarify what you mean by this. I presume “26.6b3” refers to macOS 26.6b3, so build number 25G5052e. Right?

But what does “latest Xcode” mean?

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Host: macOS 26.6 b3, correct. Xcode: I grabbed the latest beta from the site, but have since removed it. I can't remember what it was :( Just to confirm: I launched it, installed whatever it asked me to, accepted the license, etc.

OK. I was hoping to test your specific setup, but it’s hard to do without those details.

Anyway, lemme finish up with something general. The issues here all centre on the MobileDevice package. As mentioned upthread, the version that comes with Xcode 27 beta is having problems on macOS 26. The Xcode 27 Beta 2 Release Notes have some details (search for 179068335).

This is one of those weird interaction issues, so there are two ways it can get fixed:

• By changes to macOS 26 itself (r. 179068335).
• By changes to the MobileDevice package installed by Xcode (r. 179503178).

AFAICT the second change is not in any shipping or seeded Xcode. I’m still working to clarify the release vehicle for the first change.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Earlier I wrote:

I’m still working to clarify the release vehicle for the first change.

Our records indicate that macOS 26.6b3 (25G5052e) contains the OS-level fix required to resolve this issue (r. 179068335). Moreover, one of my colleagues actually tested this. Specifically:

1. They installed macOS 26.5.
2. And then Xcode 27 beta on that.
3. And verified that this reproduced the problem.
4. They then updated it to macOS 26.6b3.
5. And the problem was resolved.

Please double check the build of macOS 26.6 beta that you’re testing this with.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Quinn, thanks for the update on the status of a fix. However, I'd like to suggest one other scenario be tested and that is:

1. Install macOS 26.5
2. Update to macOS 26.6b3
3. Install Xcode 27 beta

This would help to show that the act of installing Xcode 27 beta doesn't break something, like it did when installed on macOS 26.5.

I'll be trying upgrading my broken Xcode 27 beta 2 installed host machine to 26.6b3 today once things calm down and and test it out. But yeah, testing the install 26.5, upgrade, then install Xcode 27 beta (without ever having it on the machine) is also a great idea

Both my dev and I confirmed 26.6b3 host OS with not only a pre-existing broken Xcode 27 beta 2 install upgraded to Xcode 27 beta 3, but also no Xcode beta 27 installed at all being installed after the 26.6b3 install. Both work fine now with Anka.

Both work fine now with Anka.

Cool.

Like I said above, I’m expecting an Xcode change (r. 179503178) that’ll help folks who can’t upgrade to 26.6 for some reason (not least because right now it’s still in beta), but I’ve no info to share about the timeline for that, other than to confirm that it’s not in Xcode 27.0b3.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

I skimmed through this post but I'm not sure there are official steps to install macOS 27 yet for those poor developers who don't have separate machines for macOS betas.

I'm getting pinged by Feedback Assistant to verify bugs apparently fixed on macOS 27, but when asked if there is a way to test them without spending thousands of dollars on new hardware, their reply is that "We're confident that you can figure out steps for yourself". What a forthcoming answer. Not only did I invest my time in creating feedbacks to help Apple fix bugs in their own software, but now I also have to invest time in figuring out workarounds on how to test them.

I already mentioned before: installing new macOS releases on a separate partition hasn't been working for the last few years anymore, as I pointed out last year (nobody answered), and now that the official virtualization framework doesn't work either, it's never been more frustrating to test feedback reports: https://developer.apple.com/forums/thread/799898

Could someone from Apple confirm if there is an official way of installing macOS 27 without having to buy new hardware (and possibly without resorting to time- or money-consuming workarounds), and if there currently is not, to let us know when there will? And pleeease... hold back those Feedback Assistant pings until there is an official way to test the reports.

Let’s discuss your issue on your specific thread.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

I managed to get Tart to build both public beta and dev beta macOS 27 VMs using the .ipsw files on a MacBook Pro M3 that I upgraded to macOS 26.6 beta 5. I've also installed beta 4 of the command line tools for XCode 27 and they are ok allowing me to continue to build the VMs.

Just having issues now pushing config profiles to a VM enrolled to a Fleet MDM server. I can enroll, but I'm unable to get the push notifications in order for the mobileconfigs to be installed. Will raise a ticket for the APNs not working on macOS 27 VM.