v2.1.0-rc1has been out. For 2.2.x, it is better to keep sbt up-to-date, and upgrade it from 0.13.11 to 0.13.13. The release notes since the last version we used are: https://github.com/sbt/sbt/releases/tag/v0.13.12 and https://github.com/sbt/sbt/releases/tag/v0.13.13. Both releases include some regression fixes. This jira will also update Zinc and Maven plugins.