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Scala sbt 1.2.6 patch notes

Eugene Yokota Scala Team, Lightbend, Inc.

Hi everyone. sbt 1.2.6 patch release is available.

How to upgrade

Change project/build.properties as follows:


The sbt launcher will automatically resolve the sbt JARs based on what’s in project/build.properties.

However, if you want to resolve them faster, you should use the installers. zip, tgz, and msi installers contain all the JAR files so the resolution completes from the preloaded-local repository.

Note: Please run clean after updating since sbt 1.2.6 includes a fix in the incremental compiler.

Fix for “Different extra API hashes” problem

People who have upgraded to sbt 1.2.4 noticed a weird error complaining about “Different extra API hashes”:

[error] java.lang.RuntimeException: A fatal error happened in `SameAPI`: different extra api hashes for no traits!
[error]   `akka.util.OptionVal`: 0
[error]   `akka.util.OptionVal`: 2116911007

sbt 1.2.5 fixes the issue by defaulting the extra hash to 0. This issue had been fixed in develop branch, but it did not get backported when the private trait detection patch got backported by me. Thanks Guillaume Martres for fixing it twice! zinc#606 by @smarter

Fix for cached resolution

Cached resolution feature has not been working in sbt 1.x for multiple reasons. Over time, Peter Vlugter and Kenji Yoshida have come up with enough hints that Eugene was able to get cached resolution going again. #4425/lm#269 by @eed3si9n

Other fix(es)


sbt 1.2.6 was brought to you by 5 contributors. Eugene Yokota, Olli Helenius, Dale Wijnand, Guillaume Martres, and Jason Zaugg. Thank you!

Thanks to everyone who’s helped improve sbt and Zinc 1 by using them, reporting bugs, improving our documentation, porting builds, porting plugins, and submitting and reviewing pull requests.

For anyone interested in helping sbt, there are many avenues for you to help, depending on your interest.

If you’re interested, Contributing, “help wanted”, “good first issue” are good starting points. If you have ideas, come talk to us on sbt-contrib or on Lightbend Discuss.


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Of Lightbend Akka

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  • 50% to 75% faster time-to-market
  • 20x increase in developer throughput
  • <6 months Akka pays for itself