Ruby 4.0 Upgrade Preparation

Analyze your Ruby on Rails application for Ruby 4.0 compatibility using actual breaking changes from the Ruby 4.0.0 release.

Ruby 4.0.3 is now released - Latest stable: 4.0.3

Use this skill when

• Planning Ruby 4.0 upgrade from Ruby 3.x
• Analyzing compatibility before upgrade
• Identifying breaking changes in codebase
• Checking gem compatibility with Ruby 4.0
• Preparing migration strategy

Do not use this skill when

• Upgrading Ruby 2.x to 3.x (use Ruby 3 upgrade guides)
• Fixing current Ruby bugs (use ruby-help)
• General code refactoring (use rails-refactoring-guide)