10 - 15 second freezing when switching to and from the VM after upgrading host OS

[sinewave-2097]

Has anyone else been experiencing freezing when switching between their VM and host OS? I experienced this previously and resolved it by updating the VM OS to match the host OS, but when it started again after upgrading my host from 15.5 to 15.6, I was disappointed that upgrading the VM to 15.6 didn't resolve it. It manifests as a 10 -15 second lock with a pinwheel, when switching from VM to host or host to VM.

[insidegui]

If you're able to reproduce this, try grabbing a process sample from Activity Monitor while the UI is frozen. This link includes instructions on how to capture a process sample: https://support.omnigroup.com/mac-take-a-sample/

In this case, you'll capture a process sample of the VirtualBuddy process.

[sinewave-2097]

The sample runs pretty quick, so after activating it, it's pretty much done running before I can switch to VB to trigger the issue. Maybe there is something useful in this, tho.

Sample of VirtualBuddy 582.txt

[insidegui]

You should trigger the bug then capture the sample while the app is in the frozen state. Since you mentioned that it takes 10-15s to unfreeze, that should give you enough time to do it.

[sinewave-2097]

Apologies for the confusion. When I switch back and forth, my entire system freezes. If I activate the sample, it runs in like a second, not giving me enough time to switch to VB and get the pinwheel.

[insidegui]

Ah, I see :(

An entire system freeze sounds like a more serious bug rather than an issue with VirtualBuddy itself. I suggest capturing a sysdiagnose and filing a feedback report with Apple on Feedback Assistant.

[insidegui]

Update: I have now reproduced this here with a host on macOS 15.5 and a guest on macOS 26 beta 6. What's actually happening is that apparently the Dock process is hanging in the guest OS, and the hang seems to be caused by icon rendering, as it seems to occur when a new icon that hasn't been rendered yet is shown for the first time. Icon rendering has become quite complex due to all the Liquid Glass effects and variants, so I think something about its implementation is not working correctly when macOS is running in a VM within an older host.

[insidegui]

I have submitted this as FB19576171. If anyone else is having the same issue, please file feedback to Apple via Feedback Assistant and include a sysdiagnose from both the host and the guest (you can capture a sysdiagnose by running sudo sysdiagnose in Terminal within the VM).

[sinewave-2097]

FYI my freezing issue stopped earlier this week. I’ve seen it in the past after upgrading the host OS but not upgrading the guest, so I was surprised to see it even after upgrading the guest this last time. I never run betas, only the latest or n-1.