ProcessWire 3.0.219 on the dev branch focuses primarily on a major overhaul to the core $modules system. The Modules class had grown into more than 5000 lines of code — all related to modules, but with lots of different areas of focus within that. It had become a little bit messy, fragile and hard to maintain at that size. I've had @todo notes in the class to "clean it up" for quite awhile, but this week I finally got to it.
The approach is similar to that of our $pages API (Pages class), which is split into separate classes for page finding, loading, editing, caching, etc. The Modules class has been split into several much more focused classes for module information, installers, loaders, files, flags, duplicates, and configurations. This leaves the main Modules class as the gatekeeper, making it less fragile and easier to maintain.
If this overhaul was perfect, you shouldn't notice any difference, and the public $modules API remains as before. But with such significant overhaul that took a full week to complete, there's also an increased potential for temporary errors, so please let me know if you encounter any. Thanks for reading and have a great weekend!