This is fixed in 1.6beta (current master)
When you go to http://travis-sproutcore.heroku.com/#!/svenfuchs/minimal and then click the "Build History" tab then you see 3 items even though a) the json response only contains 2 items and b) the tab controller's content property (i.e. the record array) also only contains 2 records. My impression is that the following happens: 1. Going to http://travis-sproutcore.heroku.com/#!/svenfuchs/minimal (i.e. the "Current" tab) loads a single Build record using the data source's retrieveRecord() method.
~~2. Clicking on the "Build history" tab renders a template collection view which is bound to a record array which is populated via a query that has conditions that match the record loaded in 1). This query needs to be loaded from remote at this point. ~~