A major release of Bundler is finally happening, consolidating unreleased major changes that had been pending for a decade. It will be named Bundler 4 (skipping Bundler 3), so that we can release it in lockstep with RubyGems 4, making the version number of Bundler & RubyGems in sync from now on.

Final Bundler 4 release will happen at the end of 2025, but for now we’re presenting Bundler 2.7 as the last big step towards this major release.

Bundler 2.7 features a simulate_version configuration that will allow users to configure Bundler to behave exactly as Bundler 4 will behave, with all major breaking changes enabled by default. We encourage all users to enable this setting, experiment with Bundler 4, and leave us feedback. Community feedback is super important to us, and we’re still open to revisiting the changes that the final version will include.

You can find more about future Bundler 4 changes and how to enable Bundler 4 mode in our upgrade guide

In addition to changes to get ready for Bundler 4, Bundler 2.7 also features some additional improvements such as:

• Our gem generator is now more customizable than ever, displays more informative output, and provides a skeleton with better defaults.
• Network errors are better handled to print more actionable errors and avoid unnecessary retries that will never succeed.
• Bundler is now more resilient in presence of incorrect lockfiles, or locally installed gemspecs with incorrect dependencies.
• Several issues have been fixed to make Bundler play nicer with default gems like rdoc or irb.
• Auto-switch and auto-restart mechanism based on locked version of Bundler has been improved.
• bundle install can now properly unlock rails (or any other gem including its own dependencies as a monorepo) when changing its Gemfile git source to pin it to a specific ref.

Happy bundling!