What I often do, and completely works, is telling Claude Code to git-clone the library in question. Then I /add-dir it, so I can tell it to understand the code factually and as of the exact version I'm using.

You often don't even need cloning, for instance in the Ruby ecosystem, for the Pundit gem `bundle show pundit` tells you `/Users/vemv/.rbenv/versions/3.4.5/lib/ruby/gems/3.4.0/gems/pundit-2.3.2` which is a vanilla dir (non-zipped), ready to be added to the Claude context.