This sbt plugin generates a .ensime file and provides various convenience commands for interacting with ENSIME.


Add these lines to ~/.sbt/0.13/plugins/plugins.sbt as opposed to project/plugins.sbt (the decision to use ENSIME is per-user, rather than per-project):

addSbtPlugin("org.ensime" % "sbt-ensime" % "1.12.13")

Check that again, if you incorrectly used ~/.sbt/0.13/plugins.sbt you’ll get an sbt resolution error, it really has to be in the plugins folder.

In order to create the .ensime file for you project, start sbt (in the terminal or your editor’s sbt mode) and run the ensimeConfig command.

Learn to Use sbt

If you’ve come from an IDE you might not be aware of the power of sbt. Please take the time to read the sbt Getting Started Guide before proceeding and appreciate that sbt is responsible for building your project, not ENSIME.

Core Commands

The core sbt-ensime plugin allows you to generate .ensime files:

Note that downloading and resolving the sources and javadocs can take some time on first use, so we recommend that you use coursier.

Extra Tasks and Commands

Also bundled are extra workflow tasks, which are used by ENSIME clients:

ensimeRunMain Alternative to runMain allowing environment variables and jvm arguments to be used, e.g. a/ensimeRunMain FOO=BAR -Xmx2g foo.Bar baz.
c/ensimeLaunch MyApp A launch manager that lets you define canned ensimeRunMain applications (analogous to IntelliJ’s “Run Configurations”—see below).
b/ensimeCompileOnly Compile a single fully-qualified .scala file using b’s classpath. Very useful to avoid triggering a full compile or to see the AST during a phase of the compile. e.g. a/ensimeCompileOnly -Xprint:type /path/to/Foo.scala
b/ensimeScalariformOnly Format a single fully-qualified .scala file using b’s Scalariform settings (compatible with, but does not require, sbt-scalariform).
ensimeRunDebug Like ensimeRunMain but adds debugging flags automatically.
debugging / debuggingOff Mutates the default javaOptions to include debugging flags (see below).

Launch Configurations

To define presets for the ensimeLaunch command, use the LaunchConfig and JavaArgs case classes provided by sbt-ensime, assigning a sequence to the ensimeLaunchConfigurations setting for a project:

ensimeLaunchConfigurations := Seq(
      mainClass = "mypackage.Server",
      classArgs = Seq("start", "--foreground"),
      envArgs   = Map("MYSERVER_PORT" -> "8080"),
      jvmArgs   = Seq("-Xmx2g")

Invoking ensimeLaunch server will then execute the given class with the specified arguments and environment.

An untracked ensime.sbt file is advised for this, assuming you have installed sbt-ensime as a global plugin as recommended.

Debugging Example

Debugging an application is the easiest:

> ensimeRunDebug foo.Bar

but debugging tests are trickier.

If you do not fork your tests from sbt you may be able to attach a remote debugger to the entire session by starting like sbt -jvm-debug 1337 (check the docs of your sbt script). However, if you have fork in Test := true then you can use our debugging task to mutate the java options to include the necessary flags:

crossbuild ~/Projects/ensime-server sbt
> debugging
[warn] Enabling debugging for all forked processes
[info] Only one JVM can use the port and it will await a connection before proceeding.
> jerk/test-only *JerkFormatsSpec
Listening for transport dt_socket at address: 5005

at which point, the test will hang until you connect a remote debugger to port 5005. When you are finished debugging, cancel the test or let it run to completion, and then type debuggingOff.


For project-specific tailorings, you do not need to commit anything to your project. Simply create an ensime.sbt in your project’s base directory (beside build.sbt). Don’t forget to add it to your ~/.gitignore.

Think long and hard before adding any of these settings to your global ~/.sbt/0.13/global.sbt. For example, if you were to set a global ensimeScalaVersion, it will break if you are working on sbt plugins, old projects or upgrade to the latest scala. When putting settings in your global configuration, you must import org.ensime.EnsimeKeys._

Here is an example that sets a specific memory size for the ensime server:

ensimeJavaFlags in ThisBuild := Seq("-Xss2m", "-Xmx2g", "-XX:MaxMetaspaceSize=512m")

another, to use ENSIME on a Java 6 or 7 project (the server needs JDK 8). This is reasonably safe in your ~/.sbt/0.13/global.sbt:

ensimeJavaHome in ThisBuild := file("/usr/lib/jvm/java-8-openjdk")

another, to add a custom compiler plugin to your entire build (this is just an example, it’s not available yet. You can write your own simpler compiler plugins to replace larger, slower, and buggy corporate plugins should the need arise)

addEnsimeScalaPlugin("org.ensime" %% "ensime-plugin-implicits" % "1.0.0")

another, to use the assembly jar which you build locally:

ensimeServerJars in ThisBuild := List(file("../ensime_2.11-2.0.0-SNAPSHOT-assembly.jar"))
ensimeServerProjectJars in ThisBuild := List(file("../ensime_2.10-2.0.0-SNAPSHOT-assembly.jar"))

another, for Android projects:

ensimeJavacOptions ++= (javacOptions in (core, Compile)).value,
ensimeScalacOptions ++= (scalacOptions in (core, Compile)).value

another, to revert to a previous stable or milestone of the server:

ensimeServerVersion in ThisBuild := "2.0.0-M1" // or "1.0.1"
ensimeProjectServerVersion in ThisBuild := "2.0.0-M1" // or "1.0.1"


Always check the tickets flagged as FAQ before reporting a new issue.

Tickets are extremely hard to reproduce unless you create a minimal example project and share with us the steps to reproduce the problem.

Bug reports in the form of a pull request into the src/sbt-test/ensime-sbt directory are well received, which is our suite of integration tests using the sbt scripted framework (its very simple to use). Pull requests with tests and fixes are living the dream.

You can follow snapshot releases by using the following instead of the stable release

// or clone this repo and type `sbt publishLocal`
resolvers += Resolver.sonatypeRepo("snapshots")

// update to the latest development version, see project/EnsimeSbtBuild.scala
addSbtPlugin("org.ensime" % "sbt-ensime" % "<WHATEVER IS LATEST>")

Cancel Processes

By default, sbt will not cancel a running subprocess if you type C-c. You are recommended to add the following to your ~/.sbt/0.13/global.sbt so that it will do so:

cancelable in Global := true

Emacs users should recall that in order to send a control sequence to the sbt-mode subprocess, first run sbt-clear (bound to C-c C-v by default) then C-c. i.e. to send C-c to sbt, type C-c C-v C-c C-c (you probably want to bind this to something easier).

sbt Version

Your project/ needs to use a version newer than 0.13.5 of sbt due to a breaking AutoPlugin change, e.g.



You can check what runs in the CI by investigating the .drone.yml, appveyor.yml and .travis.yml files. These should give you a good feel for what to run locally.

When submitting a PR, we expect an accompanying test in the sbt-test folder. These use the sbt scripted plugin and you can start by copying one of the existing tests (use symbolic links instead of copying files).

To try your build locally, use sbt publishLocal (which will also happen as part of running sbt scripted) and make your required sbt-ensime version match that of the snapshot you are building. Remember to nuke your ~/.ivy2/local once the fix is merged and published upstream.

Feel free to ask support questions in the gitter room for the editor that you use (there is no dedicated chat room for sbt-ensime). Also feel free to post reproducible bugs on the GitHub issue tracker.