We introduced breaking changes in RubyGems/Bundler 4 in order to improve usability, security, and maintainability of the tool.

I’ve upgraded a few projects and not noticed any issues so far. Restoring the default command to be install is nice for my muscle memory locally, but elsewhere, like in a Dockerfile, I already use bundle install explicitly.

And while new lockfiles include checksums by default, you have to manually add them to existing lockfiles via bundle lock --add-checksums.