4.2 made a change in Ext.data.proxy.Rest to include id 0 in buildUrl (see isValidId). Why was this change made? As a phantom record has id 0, then a record.save() will post with a url ending in '/0'. I don't think that is the normal REST convention, but rather the id should no go on the end. Does someone have more info on why this was changed in such a way?