Disclaimer, I've not used A/Bingo, so there might be a caveat I'm missing. But: It sounds like you're talking about prepend_view_path, which doesn't require mon

Disclaimer, I've not used A/Bingo, so there might be a caveat I'm missing. But: It sounds like you're talking about prepend_view_path, which doesn't require monkey patching. class ApplicationController < ActionController::Base before_filter ->() { prepend_view_path "app/views/YOU_CALCULATE_THIS_PART" } end With that, Rails should look for e.g. "products/index.html.erb" first in "app/views/YOU_CALCULATE_THIS_PART/products/index.html.erb", and only if it doesn't find it there, it looks in "app/views/products/index.html.erb" It seems like you could do something like this: class ApplicationController < ActionController::Base before_filter ->() { if cookies[:test_a] prepend_view_path "app/views/test_a" elsif cookies[:test_b] prepend_view_path "app/views/test_b" end } end The neat thing about prepend_view_path is that if it doesn't find a matching file in the prepended path, it falls back to the default rails paths. This makes piecemeal upgrades or redesigns much easier.