[Resolved] – uninitialized constant ActiveSupport::LoggerThreadSafeLevel::Logger (NameError)

When starting Rails server facing the error

uninitialized constant ActiveSupport::LoggerThreadSafeLevel::Logger (NameError) 

This issue started after executing the command “bundle update –bundler”

The following fix will resolve the issue.

  • Open Gemfile
  • Downgrade the gem concurrent-ruby version as 1.3.4
gem 'concurrent-ruby', '1.3.4'

Update bundler by executing the command ‘bundle update’

Now you can start the rails application. Everything should be smooth now.

Happy coding 🙂

Updated: February 25, 2025 — 12:43 pm