Rubygems introduced a file option to specify Ruby version in Gemfile | Saeloun Blog

We add ruby version in the Gemfile or in the .ruby-version files. This ensures that the application runs on the correct version of Ruby.In case of version mismatch bundler throws an error.Your Ruby version is 3.1.0, but your Gemfile specified 3.2.2BeforeWe needed to add the ruby version in the Gemfile so the bundler uses correct ruby version or warns if incorrect ruby version is in use..ruby-version file is used by tools like rvm or rbenv to switch the ruby version.Gemfile.