Ruby's Bundler 4.0.18 Extends Cooldown to bundle lock and bundle cache
Brief
Bundler 4.
- 18 adds the opt-in --cooldown flag to bundle lock and bundle cache, closing gaps where the setting could not be applied. Bundler 4.
- 18, released August 5, 2026 alongside RubyGems 4.
- 18, extends the cooldown feature to two more commands. The opt-in --cooldown flag now works with bundle lock and bundle cache, which previously resolved dependencies without accepting the flag.
RubyGems lists the change under Bundler security in the release notes. The cooldown feature is not new. It shipped in Bundler 4.
- 13 in June as a time-based filter that refuses to resolve to a gem version until it has been public for a set number of days. The 4.
- 18 change does not alter how cooldown works. It makes the flag available on commands that were left out of the first release.
What cooldown does #
Cooldown delays resolution to gem versions that are too new under a configured policy.