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