multi page view transitions and speculative prefetching my have a transformative impact on how we architect web applications.

I'd certainly be investing some energy in understanding them

https://developer.mozilla.org/en-US/docs/Web/API/Speculation_Rules_API

https://developer.mozilla.org/en-US/docs/Web/API/View_Transitions_API

Speculation Rules API - Web APIs | MDN

The Speculation Rules API is designed to improve performance for future navigations. It targets document URLs rather than specific resource files, and so makes sense for multi-page applications (MPAs) rather than single-page applications (SPAs).

MDN Web Docs
@johnallsopp I'd add Declarative Shadow DOM and #PHOOOS out-of-order HTML streaming to the list: https://github.com/niutech/phooos
It enables islands architecture without JS, just pure HTML & CSS!
GitHub - niutech/phooos: Pure HTML Out-Of-Order Streaming (PHOOOS) without JavaScript

Pure HTML Out-Of-Order Streaming (PHOOOS) without JavaScript - niutech/phooos

GitHub