How do I set the parameters so that changes in camera raw in adobe bridge are automatically saved on the disc?
You can't. I brought this up as a feature request several months ago but no joy. Try posting in the Camera RAW forum.
To both of you: are you referring to the changes in the image via the XML or something else? If so, what is that else?
In my case, it was changes via preset. Those appear in ACR but aren't actually written to XMP automatically.