Rack middleware for deleting 'Set-Cookie' headers.

application.rb

module MyApp
  class Application < Rails::Application
    config.autoload_paths += %W(#{config.root}/lib)
    config.middleware.insert_before ActionDispatch::Cookies, "CookieFilter"
  end
end

cookie_filter.rb

class CookieFilter
  def initialize(app)
    @app = app
  end

  def call(env)
    status, headers, body = @app.call(env)
    headers.delete 'Set-Cookie'
    [status, headers, body]
  end
end