Curious the direction of Webkit as there was a nebulous mention of select portions being rewritten from C++ to Swift. And yet, the new ECMAScript module (ESM) loader for Safari 27 is implemented in C++ (https://webkit.org/blog/17967/news-from-wwdc26-webkit-in-saf...).
No idea, maybe the private parts of the code, Safari isn't open source, or is coming later.
In any case I would have liked to have more info during the deep dive sessions.
As it is, Meet with Apple on security (a 5h long event) had much more information.