I don't understand -- does AA routinely remove codeshares for no apparent reason? or at some point if their own flights aren't full enough on certain days?

My experiences with codeshares recently is pretty limited. Just HA in the islands which is a unique situation I don't see them messing with extensively.

But I have several other codeshares coming up over next 3-4 months and will start planning contingencies if this is a 'thing'.