The integration of ENSIME with sbt is provided by sbt-ensime, whose primary function is generating the .ensime file by inspecting the sbt build setup. In addition sbt-ensime provides various convenience commands for interacting with the ENSIME server.


sbt-ensime is an editor integration plugin and isn’t a strict requirement of the build.

Therefore it is recommended to install it as a global plugin so that it’s always available.

To do so, add it to ~/.sbt/1.0/plugins/plugins.sbt (create if necessary) as such:

addSbtPlugin("org.ensime" % "sbt-ensime" % "2.5.1")

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

Common Mistakes

  1. If you accidentally use ~/.sbt/1.0/plugins.sbt instead of ~/.sbt/1.0/plugins/plugins.sbt you’ll get an sbt resolution error - make sure you’re defining the plugin in the right place.

  2. Use ~/.sbt/0.13/plugins/plugins.sbt if you are using the older sbt 0.13

Unstable Server

The latest stable release of the server is downloaded by default. If you wish to follow the unstable (continuously released) server, add the following to ~/.sbt/0.13/global.sbt

import org.ensime.EnsimeCoursierKeys._
import org.ensime.EnsimeKeys._

ensimeRepositoryUrls in ThisBuild += ""
ensimeServerVersion in ThisBuild := "3.0.0-SNAPSHOT"
ensimeProjectServerVersion in ThisBuild := "3.0.0-SNAPSHOT"

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.
ensimeTestOnlyDebug ...debug extension to testOnly. Has the same logic as ensimeRunDebug in regard of ensimeRunMain. See debugging example below.

The following are tasks can be used to create an optimal workflow (the server must not be running when using these tasks):

ensimeServerIndex Starts the server to create / update the index and then exits.
ensimeClearCache Deletes the current server cache.
ensimeSnapshot Creates a snapshot of the ensime-server’s index that can be restored at a later date.
ensimeRestore Recover a previous snapshot of the server’s index.

For example, the following is a good “start the day” workflow hack while you go and get tea or coffee:

alias ensime="ctags -Re . & sbt clean ensimeConfig test:compile ensimeServerIndex"

sprinkling in an ensimeRestore if you regularly run ensimeSnapshot.

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

Ensime plugin has two helpful comands for debugging: ensimeRunDebug for applications and ensimeTestOnlyDebug for tests.

> ensimeRunDebug foo.Bar
> ensimeTestOnlyDebug foo.BarTest


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._

The “Find Usages” server feature is disabled by default due to the performance cost. If you would like to enable it, use

ensimeServerFindUsages in ThisBuild := true

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-M2" // or "1.0.1"
ensimeProjectServerVersion in ThisBuild := "2.0.0-M2" // or "1.0.1"

to not download javadocs (who writes them anyway?)

transitiveClassifiers := Seq("sources")


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

Tickets are hard to reproduce unless you create an 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. Pull requests with tests and fixes are living the dream.

Starting the Server

  1. Update this plugin and re-run the .ensime generator
  2. If that doesn’t work: exit sbt, clear out the sbt caches and recreate .ensime (change 0.13 by 1.0 if you are using sbt 1.0):
sbt> exit

rm -rf ~/.coursier/cache/v1/https/ \
       ~/.ivy2/cache/org.ensime \
       ~/.ivy2/local \
       project/target \
       ~/.sbt/0.13/target \

$ sbt
sbt> ensimeConfig

If that doesn’t work, move your ivy and coursier folders aside, the caches have probably become corrupted:

mv ~/.ivy2 ~/.ivy2.bak
mv ~/.coursier ~/.coursier.bak

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, at least, a recent version of 0.13.x





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.