At Layouts and Rendering in Rails — Ruby on Rails Guides (also in version 3.2.13)
“By default, the file is rendered without using the current layout. If you want Rails to put the file into the current layout, you need to add the layout: true
option.”
I think it’s not true, at least in Rails 3.2.18. I tried yesterday (render file: … without layout option and I needed fix it today by adding layout: nil)