The sidescroll configuration option was removed, it is alway

Error message

The sidescroll configuration option was removed, it is always enabled now.

What it means

RailsAdmin 3.x made horizontal scrolling of the list view permanently enabled (sticky columns), so the global sidescroll= setter (lib/rails_admin/config.rb:291) only emits an ActiveSupport::Deprecation warning and ignores the value. It exists purely so 2.x initializers keep booting.

Source

Thrown at lib/rails_admin/config.rb:291

      def parent_controller=(name)
        @parent_controller = name

        if defined?(RailsAdmin::ApplicationController) || defined?(RailsAdmin::MainController)
          RailsAdmin::Config::ConstLoadSuppressor.allowing do
            RailsAdmin.send(:remove_const, :ApplicationController)
            RailsAdmin.send(:remove_const, :MainController)
            load RailsAdmin::Engine.root.join('app/controllers/rails_admin/application_controller.rb')
            load RailsAdmin::Engine.root.join('app/controllers/rails_admin/main_controller.rb')
          end
        end
      end

      def total_columns_width=(_)
        ActiveSupport::Deprecation.warn('The total_columns_width configuration option is deprecated and has no effect.')
      end

      def sidescroll=(_)
        ActiveSupport::Deprecation.warn('The sidescroll configuration option was removed, it is always enabled now.')
      end

      # Setup actions to be used.
      def actions(&block)
        return unless block

        RailsAdmin::Config::Actions.reset
        RailsAdmin::Config::Actions.instance_eval(&block)
      end

      # Returns all model configurations
      #
      # @see RailsAdmin::Config.registry
      def models
        RailsAdmin::AbstractModel.all.collect { |m| model(m) }
      end

      # Reset all configurations to defaults.

View on GitHub (pinned to 0690a5e62f)

Solutions

Delete the `config.sidescroll = ...` line from the initializer — sidescroll is always on and there is no replacement switch.
If you wanted to reduce horizontal scrolling, cut the number of visible columns instead: `list { field :description { visible false } }` or configure only the fields you need.
Remove the per-model variant too if present (`list { sidescroll false }` warns separately via sections/list.rb).

Example fix

# before: config/initializers/rails_admin.rb
RailsAdmin.config do |config|
  config.sidescroll = false
end

# after: sidescroll is always enabled; remove the line
RailsAdmin.config do |config|
end

Defensive patterns

Strategy: validation

Validate before calling

# Fail fast in test env if removed options are still configured
ActiveSupport::Deprecation.behavior = :raise
# plus: grep config/ for `config.sidescroll =` and delete every occurrence

Prevention

Read the rails_admin upgrading notes (CHANGELOG 'Breaking changes' sections) when bumping major versions.
Grep for both spellings once: global `config.sidescroll` and per-model `list { sidescroll ... }`.
Keep a smoke spec that loads every configured model's index page; deprecated options only fire when the config block evaluates.

When it happens

Trigger: An initializer containing `config.sidescroll = false` (or true). The warning appears at boot when the initializer is evaluated; the list view keeps sidescrolling regardless of the value passed.

Common situations: Upgrading rails_admin 2.x → 3.x where sidescroll = false was a common way to force the old table layout; initializers shared between apps of different rails_admin versions; CI configured to raise on deprecation warnings.

Related errors

AI-assisted analysis of railsadminteam/rails_admin@0690a5e62f (2026-08-21). Data as JSON: /api/errors/0cab91e632bdcd26. Report an issue: GitHub.