As it is the case with almost every update 2025.4 brought a lot of great improvements to Home Assistant. However, since I started using Home Assistant about 4 years ago, I never was more excited after reading the release notes than with this update.
I’d like to say thank you to @arturpragacz for making variables not restricted to local scopes. It took me way too long getting used to namespaces and even now this update will save me a lot of time wondering why some template isn’t working as expected because I forgot about local scopes… again. 
Thank you @frenck for adding typeof. This will be sooooo useful for debugging templates!
Thanks again @frenck for adding list/dict manipulation functions!! I know you wrote the release notes and probably didn’t want to give yourself credit for that but these things are huge! Every time I searched the web for some list or dict related solution I got the impression that even outside the context of Home Assistant people are desperately seeking those kind of functions when using jinja.
Thank you @petro for making template sensors less buggy and creating them in yaml much better!