Does sbt build against scala 2.11?

We can't break binary compatibility for all the sbt 0.13 plugins until we release the next version sbt 0.14 or potentially sbt 1.0, so no Scala 2.11.x sbt until then.

Update:

One way to work around this is to use Fork API. sbt 0.13 is capable of building Scala 2.11 source using Scala 2.11 compilers. You can mimic the way its done, and run Scala 2.10 or 2.11 code from sbt.

sbt now uses Scala 2.12

The current version of sbt is 1.2.8 (released 30th December 2018) and it supports Scala 2.12 since 1.0.0 (released 10th August 2017)

sbt 1.0 uses Scala 2.12 for build definitions and plugins. This also requires JDK 8.

https://www.scala-sbt.org/1.x/docs/sbt-1.0-Release-Notes.html#sbt+1.0.0

We simply skipped Scala 2.11 and went directly to 2.12.