diff --git a/main/Defaults.scala b/main/Defaults.scala
index 4e5e5b902..9f92a6d14 100644
--- a/main/Defaults.scala
+++ b/main/Defaults.scala
@@ -128,7 +128,7 @@ object Defaults
 		compileInputs <<= compileInputsTask,
 		console <<= consoleTask,
 		consoleQuick <<= consoleQuickTask,
-		discoveredMainClasses <<= compile map discoverMainClasses,
+		discoveredMainClasses <<= TaskData.write(compile map discoverMainClasses) triggeredBy compile,
 		definedSbtPlugins <<= discoverPlugins,
 		inTask(run)(runnerSetting :: Nil).head,
 		selectMainClass <<= discoveredMainClasses map selectRunMain,
@@ -190,7 +190,7 @@ object Defaults
 		loadedTestFrameworks <<= (testFrameworks, streams, testLoader) map { (frameworks, s, loader) =>
 			frameworks.flatMap(f => f.create(loader, s.log).map( x => (f,x)).toIterable).toMap
 		},
-		definedTests <<= TaskData.write(detectTests, _.map(_.name).distinct),
+		definedTests <<= TaskData.writeRelated(detectTests)(_.map(_.name).distinct) triggeredBy compile,
 		testListeners :== Nil,
 		testOptions :== Nil,
 		executeTests <<= (streams in test, loadedTestFrameworks, testOptions in test, testLoader, definedTests) flatMap {
@@ -293,8 +293,7 @@ object Defaults
 	def runMainTask(classpath: ScopedTask[Classpath], scalaRun: ScopedSetting[ScalaRun]): Initialize[InputTask[Unit]] =
 	{
 			import DefaultParsers._
-		val mainParser = (Space ~> token(NotSpace, "<main-class>")) ~ complete.Parsers.spaceDelimited("<arg>")
-		InputTask(_ => mainParser) { result =>
+		InputTask( TaskData(discoveredMainClasses)(runMainParser)(Nil) ) { result =>  
 			(classpath, scalaRun, streams, result) map { case (cp, runner, s, (mainClass, args)) =>
 				runner.run(mainClass, data(cp), args, s.log) foreach error
 			}
@@ -381,6 +380,12 @@ object Defaults
 		mappings
 	}
 
+	def runMainParser: (State, Seq[String]) => Parser[(String, Seq[String])] =
+	{
+			import DefaultParsers._
+		(state, mainClasses) => Space ~> token(NotSpace examples mainClasses.toSet) ~ spaceDelimited("<arg>")
+	}
+
 	def testOnlyParser: (State, Seq[String]) => Parser[(Seq[String],Seq[String])] =
 	{ (state, tests) =>
 			import DefaultParsers._
diff --git a/main/Project.scala b/main/Project.scala
index 11123660a..10cdb8b52 100644
--- a/main/Project.scala
+++ b/main/Project.scala
@@ -292,6 +292,8 @@ object Project extends Init[Scope] with ProjectExtra
 		str.open()
 		s.put(logged, str.log).addExitHook { str.close() }
 	}
+	// this is here instead of Scoped so that it is considered without need for import (because of Project.Initialize)
+	implicit def richInitializeTask[T](init: Initialize[Task[T]]): Scoped.RichInitializeTask[T] = new Scoped.RichInitializeTask(init)
 }
 
 trait ProjectExtra
diff --git a/main/Structure.scala b/main/Structure.scala
index a4268cfa0..9ba0a1ef3 100644
--- a/main/Structure.scala
+++ b/main/Structure.scala
@@ -213,8 +213,6 @@ object Scoped
 		def dependOn: Initialize[Task[Unit]]  =  Apply.tasks(KList.fromList(keys)) { kl => nop.dependsOn(kl.toList :_*) }
 	}
 
-
-	implicit def richInitializeTask[T](init: Initialize[Task[T]]): RichInitializeTask[T] = new RichInitializeTask(init)
 	final class RichInitializeTask[T](init: Initialize[Task[T]])
 	{
 		def triggeredBy(tasks: ScopedTask[_]*): Initialize[Task[T]] = nonLocal(tasks, Keys.triggeredBy)
diff --git a/main/TaskData.scala b/main/TaskData.scala
index 810872bee..04667c978 100644
--- a/main/TaskData.scala
+++ b/main/TaskData.scala
@@ -33,7 +33,9 @@ object TaskData
 			val key = ScopedKey(Scope.fillTaskAxis(defined, readFrom), readFrom)
 			structure.streams.use(reader)(ts => f(ts, key))
 		}
-	def write[T, S](i: Initialize[Task[T]], convert: T => S = idFun, id: String = DefaultDataID)(implicit f: Format[S]): Initialize[Task[T]] =
+	def write[T](i: Initialize[Task[T]], id: String = DefaultDataID)(implicit f: Format[T]): Initialize[Task[T]] = writeRelated(i, id)(idFun[T])(f)
+
+	def writeRelated[T, S](i: Initialize[Task[T]], id: String = DefaultDataID)(convert: T => S)(implicit f: Format[S]): Initialize[Task[T]] =
 		(streams.identity zipWith i) { (sTask, iTask) =>
 			(sTask,iTask) map { case s :+: value :+: HNil =>
 				Operations.write( s.binary(id), convert(value) )(f)