Description

After the new IOS 16, Safari changed the behavior of document.adoptNode when called on a template. It's not changing the ownerDocument any more. It leaves this on an empty document (about:blank).

This causing an error at the function contains at this line, because the documentElement property is null on an empty document (about:blank).

If you change this line from
var adown = a.nodeType === 9 ? a.documentElement : a, bup = b && b.parentNode;
to
var adown = a.nodeType === 9 && a.documentElement ? a.documentElement : a, bup = b && b.parentNode;
it's working again.

More details can be found here and aurelia/framework#1003.

Link to test case

You can see the problem in this fiddler if you try it with Safari 16+.
If you press "add" and then "remove" you get the error.