I tried copying this regex "\A[^{@\s]+@[@\s]+\z"} to https://rubular.com/ but it aren't working until I remove the \A and \z making this [^@\s]+@[@\s]+ before it could work, any reason for that?

An alternative to using the Regex can be using a built-in Ruby constant

validates :email, format: { with: URI::MailTo::EMAIL_REGEXP, message: 'invalid email address provided' }