This returns the name (including path) of your current layout:

response.layout
=> "layouts/admin" # inside views that are using the 'admin' layout

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

• Prevents you from data breaches and liability risks
• Upgrade at your own pace
• Works with modern Rubies

Read more Show archive.org snapshot

You most likely do not need the full path, so go ahead and do this:

File.basename(response.layout)
=> "admin"