What was the USP of their CI service?

Ability to virtualize on Apple devices and linux with GPUs https://github.com/scipy/scipy/issues/24990

Better UX than their competitors and support for many different images.

To create an ephemeral (docker-like) MacOS VM on a Mac with full performance and access (e.g. GPU) you have to use a virtualization API provided by Apple.

For most CI use, you can choose between:

  Anka, a "contact-us for pricing" closed-source projet, where you have to pay expensive license (easy 3000 USD/yr per machine)

  tart, which is a lightweight wrapper around the official Apple API.

https://github.com/cirruslabs/orchard/commit/3cfa2445500f45f...

With https://khronokernel.com/macos/2023/08/08/AS-VM.html

Some people might find it very attractive:

  Instead 25 Mac Mini you might need only 5.
  + No licensing to pay to Anka.