Just to be a bit more precise, ART never goes from working profile to display profile directly, but it always goes through the output profile, precisely to avoid the situation that you described above. So yes, if you bypass the output profile you can get some differences between preview and saved image, but that’s not what ART does.
If you get differences, they are due to one of the possibilities below (in order of likelihood):
- There’s a bug in art
- You are using different colour management settings between art and the image viewer
- The image viewer is using a different colour management engine that does things slightly differently from LCMS
- You have an HDR screen, and are using both a viewer capable of displaying HDR content and a suitable output profile and output format that support HDR content. Since art has no support for previewing HDR (but only for generating it), then in this case this is the expected behaviour
Hope this helps!