Edited sentence: A new tab-switching interface previously intended for 3.5 is due to be included in 3.6.As of December 2, the daily development trunk has begun showcasing pre-release builds of the first Firefox 3.6 Alpha 1 Pre (Preview release).At the 2008 Firefox Summit, it was announced that development would be aimed for a release of Firefox 3.1 (3.5) in December, and Firefox 3.2 (3.6) in the second quarter of 2009, both these development branches branching off the trunk builds.Firefox 3.7, based on the Mozilla 1.9.3 engine, has been named as a possible early 2010 release.Since the change, Mozilla developer Mike Shaver has indicated that the release number will be referred to as 3.6 ad interim.The preliminary releases of upcoming Firefox releases are codenamed "Minefield", as this is the name of the trunk builds.The release following Firefox 3.1 (since changed to Firefox 3.5) was originally referred to as 3.2.Version 3.5 was finally released in June 2009, after extensive pre-release builds and test releases in the preceding year