How to specify JVM maximum heap size "-Xmx" for running an application with "run" action in SBT?

For forked processes you should look at Build.scala To modify the java options for forked processes you need to specify them in the Build.scala (or whatever you've named your build) like this: val buildSettings = Defaults.defaultSettings ++ Seq( //… javaOptions += "-Xmx1G", //… ) This will give you the proper options without modifying JAVA_OPTS globally, and it will put custom JAVA_OPTS in an sbt