Hey Thanks   David Kimura  
i have that. still not working. it keeps raising the same error with 

Tempfile.new

yeah.

require 'fileutils'

unless Rails.env.development?
  # force the whole app to use its own tmpdir
  FileUtils.mkdir_p(Rails.root.join('tmp'))
  ENV['TMPDIR'] = Rails.root.join('tmp').to_s
end

in initializer fix everything

I agree 100%. What about having monolith app? Please share your experience? I have everything on the same app. APIs, several role base users for the frontend (ERB). It works like a charm. The only issue i experience now is the fact we still don't have any 
turbo:after-stream-render event in turbo. This ias a major issue for me since i use several jquery based libraries.
 

In my case the company needs an app and a website. Does it make sense to have monolith app with hotwire and turbo for the web version and a react app binded on the api namespace of the monolith?

This is why i said we need an app. They app relies on some hardware stuff. That's the reason why i would like to propose monolith with front and back Rails. API for react app. We won't be stuck by React development since Rails developpers velocity is much more higher.

PS: It is a banking app