config/initializers/action_cable.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+# Ensure ActionCable has a logger in all environments.
+# In apps upgraded from older Rails versions, the logger chain
+# may not propagate to ActionCable out of the box, causing:
+#   NoMethodError (undefined method 'info' for nil)
+#   in ActionCable::Connection::TaggedLoggerProxy#log
+#
+Rails.application.config.after_initialize do
+  ActionCable.server.config.logger ||= Rails.logger || ActiveSupport::Logger.new($stdout)
+  ActionCable.server.config.logger.level = Rails.logger&.level || Logger::INFO
+end