diff --git a/.appveyor.yml b/.appveyor.yml
index 0c3f595a1..bad54a126 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -155,4 +155,6 @@ for:
     - '%USERPROFILE%\.sbt'
 
   test_script:
-    - sbt "scripted actions/* classloader-cache/* nio/* watch/*" "serverTestProj/test"
+    # The server tests often fail in CI when run together so just run a single test to ensure
+    # that the thin client works on windows
+    - sbt "scripted actions/* classloader-cache/* nio/* watch/*" "serverTestProj/testOnly testpkg.ClientTest"
diff --git a/.travis.yml b/.travis.yml
index 31d026e20..dcf88b527 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,7 +11,7 @@ env:
     # WHITESOURCE_PASSWORD=
     - secure: d3bu2KNwsVHwfhbGgO+gmRfDKBJhfICdCJFGWKf2w3Gv86AJZX9nuTYRxz0KtdvEHO5Xw8WTBZLPb2thSJqhw9OCm4J8TBAVqCP0ruUj4+aqBUFy4bVexQ6WKE6nWHs4JPzPk8c6uC1LG3hMuzlC8RGETXtL/n81Ef1u7NjyXjs=
   matrix:
-    - SBT_CMD="mimaReportBinaryIssues ; javafmtCheck ; Test / javafmtCheck; scalafmtCheckAll ; scalafmtSbtCheck; headerCheck ;test:headerCheck ;whitesourceOnPush ;test:compile; publishLocal; test; serverTestProj/test; doc; $UTIL_TESTS; ++$SCALA_213; $UTIL_TESTS"
+    - SBT_CMD="mimaReportBinaryIssues ; javafmtCheck ; Test / javafmtCheck; scalafmtCheckAll ; scalafmtSbtCheck; serverTestProj/scalafmtCheckAll; headerCheck ;test:headerCheck ;whitesourceOnPush ;test:compile; publishLocal; test; serverTestProj/test; doc; $UTIL_TESTS; ++$SCALA_213; $UTIL_TESTS"
     - SBT_CMD="scripted actions/* apiinfo/* compiler-project/* ivy-deps-management/* reporter/* tests/* watch/* classloader-cache/* package/*"
     - SBT_CMD="scripted dependency-management/* plugins/* project-load/* java/* run/* nio/*"
     - SBT_CMD="repoOverrideTest:scripted dependency-management/*; scripted source-dependencies/* project/*"
diff --git a/build.sbt b/build.sbt
index 511f7a153..5572d44ab 100644
--- a/build.sbt
+++ b/build.sbt
@@ -973,7 +973,18 @@ lazy val mainProj = (project in file("main"))
       // the binary compatible version.
       exclude[IncompatibleMethTypeProblem]("sbt.internal.server.NetworkChannel.this"),
       exclude[IncompatibleSignatureProblem]("sbt.internal.DeprecatedContinuous.taskDefinitions"),
-      exclude[MissingClassProblem]("sbt.internal.SettingsGraph*")
+      exclude[MissingClassProblem]("sbt.internal.SettingsGraph*"),
+      // Tasks include non-Files, but it's ok
+      exclude[IncompatibleSignatureProblem]("sbt.Defaults.outputConfigPaths"),
+      // private[sbt]
+      exclude[DirectMissingMethodProblem]("sbt.Classpaths.trackedExportedProducts"),
+      exclude[DirectMissingMethodProblem]("sbt.Classpaths.trackedExportedJarProducts"),
+      exclude[DirectMissingMethodProblem]("sbt.Classpaths.unmanagedDependencies0"),
+      exclude[DirectMissingMethodProblem]("sbt.Classpaths.internalDependenciesImplTask"),
+      exclude[DirectMissingMethodProblem]("sbt.Classpaths.internalDependencyJarsImplTask"),
+      exclude[DirectMissingMethodProblem]("sbt.Classpaths.interDependencies"),
+      exclude[DirectMissingMethodProblem]("sbt.Classpaths.productsTask"),
+      exclude[DirectMissingMethodProblem]("sbt.Classpaths.jarProductsTask"),
     )
   )
   .configure(
diff --git a/internal/util-complete/src/main/scala/sbt/internal/util/LineReader.scala b/internal/util-complete/src/main/scala/sbt/internal/util/LineReader.scala
index 34526a948..52a36ca8d 100644
--- a/internal/util-complete/src/main/scala/sbt/internal/util/LineReader.scala
+++ b/internal/util-complete/src/main/scala/sbt/internal/util/LineReader.scala
@@ -57,11 +57,14 @@ object LineReader {
          * `testOnly testOnly\ com.foo.FooSpec` instead of `testOnly com.foo.FooSpec`.
          */
         if (c.append.nonEmpty) {
-          if (!pl.line().endsWith(" ")) {
-            candidates.add(new Candidate(pl.line().split(" ").last + c.append))
-          } else {
-            candidates.add(new Candidate(c.append))
-          }
+          val comp =
+            if (!pl.line().endsWith(" ")) pl.line().split(" ").last + c.append else c.append
+          // tell jline to append a " " if the completion would be valid with a " " appended
+          // which can be the case for input tasks and some commands. We need to exclude
+          // the empty string and ";" which always seem to be present.
+          val complete = (Parser.completions(parser, comp + " ", 10).get.map(_.display) --
+            Set(";", "")).nonEmpty
+          candidates.add(new Candidate(comp, comp, null, null, null, null, complete))
         }
       }
     }
diff --git a/internal/util-logging/src/main/scala/sbt/internal/util/Terminal.scala b/internal/util-logging/src/main/scala/sbt/internal/util/Terminal.scala
index 019e0bb46..e44573930 100644
--- a/internal/util-logging/src/main/scala/sbt/internal/util/Terminal.scala
+++ b/internal/util-logging/src/main/scala/sbt/internal/util/Terminal.scala
@@ -7,7 +7,7 @@
 
 package sbt.internal.util
 
-import java.io.{ InputStream, InterruptedIOException, OutputStream, PrintStream }
+import java.io.{ InputStream, InterruptedIOException, IOException, OutputStream, PrintStream }
 import java.nio.channels.ClosedChannelException
 import java.util.{ Arrays, Locale }
 import java.util.concurrent.atomic.{ AtomicBoolean, AtomicReference }
@@ -163,7 +163,7 @@ trait Terminal extends AutoCloseable {
     if (lines.nonEmpty) lines.tail.foldLeft(lines.headOption.fold(0)(count))(_ + count(_))
     else 0
   }
-
+  private[sbt] def flush(): Unit = printStream.flush()
 }
 
 object Terminal {
@@ -171,7 +171,8 @@ object Terminal {
   if (System.getProperty("sbt.jline.verbose", "false") != "true")
     jline.internal.Log.setOutput(new PrintStream(_ => {}, false))
   def consoleLog(string: String): Unit = {
-    Terminal.console.printStream.println(s"[info] $string")
+    try Terminal.console.printStream.println(s"[info] $string")
+    catch { case _: IOException => }
   }
   private[sbt] def set(terminal: Terminal) = {
     activeTerminal.set(terminal)
diff --git a/main-actions/src/main/scala/sbt/RawCompileLike.scala b/main-actions/src/main/scala/sbt/RawCompileLike.scala
index b2cf1fb27..7ac1a12cc 100644
--- a/main-actions/src/main/scala/sbt/RawCompileLike.scala
+++ b/main-actions/src/main/scala/sbt/RawCompileLike.scala
@@ -11,7 +11,7 @@ import scala.annotation.tailrec
 import java.io.File
 import sbt.io.syntax._
 import sbt.io.IO
-import sbt.internal.inc.{ PlainVirtualFile, RawCompiler, ScalaInstance }
+import sbt.internal.inc.{ RawCompiler, ScalaInstance }
 import sbt.internal.util.Types.:+:
 import sbt.internal.util.HListFormats._
 import sbt.internal.util.HNil
@@ -88,11 +88,7 @@ object RawCompileLike {
   def rawCompile(instance: ScalaInstance, cpOptions: ClasspathOptions): Gen =
     (sources, classpath, outputDirectory, options, _, log) => {
       val compiler = new RawCompiler(instance, cpOptions, log)
-      compiler(sources map { x =>
-        PlainVirtualFile(x.toPath)
-      }, classpath map { x =>
-        PlainVirtualFile(x.toPath)
-      }, outputDirectory.toPath, options)
+      compiler(sources.map(_.toPath), classpath.map(_.toPath), outputDirectory.toPath, options)
     }
 
   def compile(
diff --git a/main-settings/src/main/scala/sbt/Def.scala b/main-settings/src/main/scala/sbt/Def.scala
index 2f6833fb8..2467f6b6c 100644
--- a/main-settings/src/main/scala/sbt/Def.scala
+++ b/main-settings/src/main/scala/sbt/Def.scala
@@ -18,10 +18,12 @@ import sbt.internal.util.complete.Parser
 import sbt.internal.util._
 import Util._
 import sbt.util.Show
+import xsbti.VirtualFile
 
 /** A concrete settings system that uses `sbt.Scope` for the scope type. */
 object Def extends Init[Scope] with TaskMacroExtra with InitializeImplicits {
   type Classpath = Seq[Attributed[File]]
+  type VirtualClasspath = Seq[Attributed[VirtualFile]]
 
   def settings(ss: SettingsDefinition*): Seq[Setting[_]] = ss.flatMap(_.settings)
 
diff --git a/main-settings/src/main/scala/sbt/PromiseWrap.scala b/main-settings/src/main/scala/sbt/PromiseWrap.scala
index 2706ac5bc..ec9a50817 100644
--- a/main-settings/src/main/scala/sbt/PromiseWrap.scala
+++ b/main-settings/src/main/scala/sbt/PromiseWrap.scala
@@ -18,4 +18,5 @@ final class PromiseWrap[A] {
     }
   def success(value: A): Unit = underlying.success(value)
   def failure(cause: Throwable): Unit = underlying.failure(cause)
+  def isCompleted: Boolean = underlying.isCompleted
 }
diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 1f046a7e5..360564cfb 100644
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -26,7 +26,8 @@ import sbt.Project.{
   inTask,
   richInitialize,
   richInitializeTask,
-  richTaskSessionVar
+  richTaskSessionVar,
+  sbtRichTaskPromise,
 }
 import sbt.Scope.{ GlobalScope, ThisScope, fillTaskAxis }
 import sbt.coursierint._
@@ -35,7 +36,14 @@ import sbt.internal._
 import sbt.internal.classpath.AlternativeZincUtil
 import sbt.internal.inc.JavaInterfaceUtil._
 import sbt.internal.inc.classpath.{ ClassLoaderCache, ClasspathFilter, ClasspathUtil }
-import sbt.internal.inc.{ MappedFileConverter, PlainVirtualFile, Stamps, ZincLmUtil, ZincUtil }
+import sbt.internal.inc.{
+  CompileOutput,
+  MappedFileConverter,
+  PlainVirtualFile,
+  Stamps,
+  ZincLmUtil,
+  ZincUtil
+}
 import sbt.internal.io.{ Source, WatchState }
 import sbt.internal.librarymanagement.mavenint.{
   PomExtraDependencyAttributes,
@@ -68,7 +76,6 @@ import sbt.librarymanagement.Configurations.{
   Provided,
   Runtime,
   Test,
-  names
 }
 import sbt.librarymanagement.CrossVersion.{ binarySbtVersion, binaryScalaVersion, partialVersion }
 import sbt.librarymanagement._
@@ -82,7 +89,7 @@ import sbt.nio.Watch
 import sbt.std.TaskExtra._
 import sbt.testing.{ AnnotatedFingerprint, Framework, Runner, SubclassFingerprint }
 import sbt.util.CacheImplicits._
-import sbt.util.InterfaceUtil.{ toJavaFunction => f1 }
+import sbt.util.InterfaceUtil.{ toJavaFunction => f1, t2 }
 import sbt.util._
 import sjsonnew._
 import sjsonnew.support.scalajson.unsafe.Converter
@@ -97,7 +104,6 @@ import sbt.SlashSyntax0._
 import sbt.internal.inc.{
   Analysis,
   AnalyzingCompiler,
-  FileValueCache,
   Locate,
   ManagedLoggedReporter,
   MixedAnalyzingCompiler,
@@ -112,6 +118,7 @@ import xsbti.compile.{
   CompileOptions,
   CompileOrder,
   CompileResult,
+  CompileProgress,
   CompilerCache,
   Compilers,
   DefinesClass,
@@ -180,16 +187,10 @@ object Defaults extends BuildCommon {
       apiMappings := Map.empty,
       autoScalaLibrary :== true,
       managedScalaInstance :== true,
-      classpathEntryDefinesClass := {
-        val converter = fileConverter.value
-        val f = FileValueCache({ x: NioPath =>
-          if (x.getFileName.toString != "rt.jar") Locate.definesClass(converter.toVirtualFile(x))
-          else ((_: String) => false): DefinesClass
-        }).get;
-        { (x: File) =>
-          f(x.toPath)
-        }
+      classpathEntryDefinesClass := { (file: File) =>
+        sys.error("use classpathEntryDefinesClassVF instead")
       },
+      extraIncOptions :== Seq("JAVA_CLASS_VERSION" -> sys.props("java.class.version")),
       allowMachinePath :== true,
       rootPaths := {
         val app = appConfiguration.value
@@ -374,6 +375,7 @@ object Defaults extends BuildCommon {
         () => Clean.deleteContents(tempDirectory, _ => false)
       },
       turbo :== SysProp.turbo,
+      usePipelining :== SysProp.pipelining,
       useSuperShell := { if (insideCI.value) false else Terminal.console.isSupershellEnabled },
       progressReports := {
         val rs = EvaluateTask.taskTimingProgress.toVector ++ EvaluateTask.taskTraceEvent.toVector
@@ -544,10 +546,16 @@ object Defaults extends BuildCommon {
   )
   // This exists for binary compatibility and probably never should have been public.
   def addBaseSources: Seq[Def.Setting[Task[Seq[File]]]] = Nil
-  lazy val outputConfigPaths = Seq(
+  lazy val outputConfigPaths: Seq[Setting[_]] = Seq(
     classDirectory := crossTarget.value / (prefix(configuration.value.name) + "classes"),
+    // TODO: Use FileConverter once Zinc can handle non-Path
+    backendOutput := PlainVirtualFile(classDirectory.value.toPath),
+    earlyOutput / artifactPath := earlyArtifactPathSetting(artifact).value,
+    // TODO: Use FileConverter once Zinc can handle non-Path
+    earlyOutput := PlainVirtualFile((earlyOutput / artifactPath).value.toPath),
     semanticdbTargetRoot := crossTarget.value / (prefix(configuration.value.name) + "meta"),
     compileAnalysisTargetRoot := crossTarget.value / (prefix(configuration.value.name) + "zinc"),
+    earlyCompileAnalysisTargetRoot := crossTarget.value / (prefix(configuration.value.name) + "early-zinc"),
     target in doc := crossTarget.value / (prefix(configuration.value.name) + "api")
   )
 
@@ -671,9 +679,10 @@ object Defaults extends BuildCommon {
   def defaultCompileSettings: Seq[Setting[_]] =
     globalDefaults(enableBinaryCompileAnalysis := true)
 
-  lazy val configTasks: Seq[Setting[_]] = docTaskSettings(doc) ++ inTask(compile)(
-    compileInputsSettings
-  ) ++ configGlobal ++ defaultCompileSettings ++ compileAnalysisSettings ++ Seq(
+  lazy val configTasks: Seq[Setting[_]] = docTaskSettings(doc) ++
+    inTask(compile)(compileInputsSettings) ++
+    inTask(compileJava)(compileInputsSettings(dependencyVirtualClasspath)) ++
+    configGlobal ++ defaultCompileSettings ++ compileAnalysisSettings ++ Seq(
     compileOutputs := {
       import scala.collection.JavaConverters._
       val c = fileConverter.value
@@ -685,9 +694,31 @@ object Defaults extends BuildCommon {
     },
     compileOutputs := compileOutputs.triggeredBy(compile).value,
     clean := (compileOutputs / clean).value,
+    earlyOutputPing := Def.promise[Boolean],
+    compileProgress := {
+      val s = streams.value
+      val promise = earlyOutputPing.value
+      val mn = moduleName.value
+      val c = configuration.value
+      new CompileProgress {
+        override def afterEarlyOutput(isSuccess: Boolean): Unit = {
+          if (isSuccess) s.log.debug(s"[$mn / $c] early output is success")
+          else s.log.debug(s"[$mn / $c] early output can't be made because of macros")
+          promise.complete(Value(isSuccess))
+        }
+      }
+    },
+    compileEarly := compileEarlyTask.value,
     compile := compileTask.value,
+    compileScalaBackend := compileScalaBackendTask.value,
+    compileJava := compileJavaTask.value,
+    compileSplit := {
+      // conditional task
+      if (incOptions.value.pipelining) compileJava.value
+      else compileScalaBackend.value
+    },
     internalDependencyConfigurations := InternalDependencies.configurations.value,
-    manipulateBytecode := compileIncremental.value,
+    manipulateBytecode := compileSplit.value,
     compileIncremental := compileIncrementalTask.tag(Tags.Compile, Tags.CPU).value,
     printWarnings := printWarningsTask.value,
     compileAnalysisFilename := {
@@ -699,6 +730,9 @@ object Defaults extends BuildCommon {
         else ""
       s"inc_compile$extra.zip"
     },
+    earlyCompileAnalysisFile := {
+      earlyCompileAnalysisTargetRoot.value / compileAnalysisFilename.value
+    },
     compileAnalysisFile := {
       compileAnalysisTargetRoot.value / compileAnalysisFilename.value
     },
@@ -716,6 +750,22 @@ object Defaults extends BuildCommon {
               ): ClassFileManagerType
           ).toOptional
         )
+        .withPipelining(usePipelining.value)
+    },
+    scalacOptions := {
+      val old = scalacOptions.value
+      val converter = fileConverter.value
+      if (usePipelining.value)
+        Vector("-Ypickle-java", "-Ypickle-write", converter.toPath(earlyOutput.value).toString) ++ old
+      else old
+    },
+    classpathEntryDefinesClassVF := {
+      val converter = fileConverter.value
+      val f = VirtualFileValueCache(converter)({ x: VirtualFile =>
+        if (x.name.toString != "rt.jar") Locate.definesClass(x)
+        else ((_: String) => false): DefinesClass
+      }).get
+      f
     },
     compileIncSetup := compileIncSetupTask.value,
     console := consoleTask.value,
@@ -1430,6 +1480,19 @@ object Defaults extends BuildCommon {
       excludes: ScopedTaskable[FileFilter]
   ): Initialize[Task[Seq[File]]] = collectFiles(dirs: Taskable[Seq[File]], filter, excludes)
 
+  private[sbt] def earlyArtifactPathSetting(art: SettingKey[Artifact]): Initialize[File] =
+    Def.setting {
+      val f = artifactName.value
+      crossTarget.value / "early" / f(
+        ScalaVersion(
+          (scalaVersion in artifactName).value,
+          (scalaBinaryVersion in artifactName).value
+        ),
+        projectID.value,
+        art.value
+      )
+    }
+
   def artifactPathSetting(art: SettingKey[Artifact]): Initialize[File] =
     Def.setting {
       val f = artifactName.value
@@ -1837,6 +1900,43 @@ object Defaults extends BuildCommon {
     finally w.close() // workaround for #937
   }
 
+  /** Handles traditional Scalac compilation. For non-pipelined compilation,
+   *  this also handles Java compilation.
+   */
+  private[sbt] def compileScalaBackendTask: Initialize[Task[CompileResult]] = Def.task {
+    val setup: Setup = compileIncSetup.value
+    val useBinary: Boolean = enableBinaryCompileAnalysis.value
+    val analysisResult: CompileResult = compileIncremental.value
+    // Save analysis midway if pipelining is enabled
+    if (analysisResult.hasModified && setup.incrementalCompilerOptions.pipelining) {
+      val store =
+        MixedAnalyzingCompiler.staticCachedStore(setup.cacheFile.toPath, !useBinary)
+      val contents = AnalysisContents.create(analysisResult.analysis(), analysisResult.setup())
+      store.set(contents)
+    }
+    analysisResult
+  }
+
+  /** Block on earlyOutputPing promise, which will be completed by `compile` midway
+   * via `compileProgress` implementation.
+   */
+  private[sbt] def compileEarlyTask: Initialize[Task[CompileAnalysis]] = Def.task {
+    if ({
+      streams.value.log
+        .debug(s"${name.value}: compileEarly: blocking on earlyOutputPing")
+      earlyOutputPing.await.value
+    }) {
+      val useBinary: Boolean = enableBinaryCompileAnalysis.value
+      val store =
+        MixedAnalyzingCompiler.staticCachedStore(earlyCompileAnalysisFile.value.toPath, !useBinary)
+      store.get.toOption match {
+        case Some(contents) => contents.getAnalysis
+        case _              => Analysis.empty
+      }
+    } else {
+      compile.value
+    }
+  }
   def compileTask: Initialize[Task[CompileAnalysis]] = Def.task {
     val setup: Setup = compileIncSetup.value
     val useBinary: Boolean = enableBinaryCompileAnalysis.value
@@ -1861,11 +1961,31 @@ object Defaults extends BuildCommon {
   def compileIncrementalTask = Def.task {
     BspCompileTask.compute(bspTargetIdentifier.value, thisProjectRef.value, configuration.value) {
       // TODO - Should readAnalysis + saveAnalysis be scoped by the compile task too?
-      compileIncrementalTaskImpl(streams.value, (compileInputs in compile).value)
+      compileIncrementalTaskImpl(
+        streams.value,
+        (compile / compileInputs).value,
+        earlyOutputPing.value
+      )
     }
   }
   private val incCompiler = ZincUtil.defaultIncrementalCompiler
-  private[this] def compileIncrementalTaskImpl(s: TaskStreams, ci: Inputs): CompileResult = {
+  private[sbt] def compileJavaTask: Initialize[Task[CompileResult]] = Def.task {
+    val s = streams.value
+    val in = (compileJava / compileInputs).value
+    val _ = compileScalaBackend.value
+    try {
+      incCompiler.asInstanceOf[sbt.internal.inc.IncrementalCompilerImpl].compileAllJava(in, s.log)
+    } finally {
+      in.setup.reporter match {
+        case r: BuildServerReporter => r.sendFinalReport()
+      }
+    }
+  }
+  private[this] def compileIncrementalTaskImpl(
+      s: TaskStreams,
+      ci: Inputs,
+      promise: PromiseWrap[Boolean]
+  ): CompileResult = {
     lazy val x = s.text(ExportStream)
     def onArgs(cs: Compilers) = {
       cs.withScalac(
@@ -1875,13 +1995,14 @@ object Defaults extends BuildCommon {
         }
       )
     }
-    // .withJavac(
-    //  cs.javac.onArgs(exported(x, "javac"))
-    //)
     val compilers: Compilers = ci.compilers
     val i = ci.withCompilers(onArgs(compilers))
     try {
       incCompiler.compile(i, s.log)
+    } catch {
+      case e: Throwable if !promise.isCompleted =>
+        promise.failure(e)
+        throw e
     } finally {
       i.setup.reporter match {
         case r: BuildServerReporter => r.sendFinalReport()
@@ -1890,47 +2011,44 @@ object Defaults extends BuildCommon {
     }
   }
   def compileIncSetupTask = Def.task {
-    val converter = fileConverter.value
+    val cp = dependencyPicklePath.value
     val lookup = new PerClasspathEntryLookup {
-      private val cachedAnalysisMap: File => Option[CompileAnalysis] =
-        analysisMap(dependencyClasspath.value)
-      private val cachedPerEntryDefinesClassLookup: File => DefinesClass =
-        Keys.classpathEntryDefinesClass.value
-
+      private val cachedAnalysisMap: VirtualFile => Option[CompileAnalysis] =
+        analysisMap(cp)
+      private val cachedPerEntryDefinesClassLookup: VirtualFile => DefinesClass =
+        Keys.classpathEntryDefinesClassVF.value
       override def analysis(classpathEntry: VirtualFile): Optional[CompileAnalysis] =
-        cachedAnalysisMap(converter.toPath(classpathEntry).toFile).toOptional
+        cachedAnalysisMap(classpathEntry).toOptional
       override def definesClass(classpathEntry: VirtualFile): DefinesClass =
-        cachedPerEntryDefinesClassLookup(converter.toPath(classpathEntry).toFile)
+        cachedPerEntryDefinesClassLookup(classpathEntry)
     }
+    val extra = extraIncOptions.value.map(t2)
     Setup.of(
       lookup,
       (skip in compile).value,
-      // TODO - this is kind of a bad way to grab the cache directory for streams...
       compileAnalysisFile.value.toPath,
       compilerCache.value,
       incOptions.value,
       (compilerReporter in compile).value,
-      // TODO - task / setting for compile progress
-      None.toOptional: Optional[xsbti.compile.CompileProgress],
-      // TODO - task / setting for extra,
-      Array.empty: Array[xsbti.T2[String, String]],
+      Some((compile / compileProgress).value).toOptional,
+      extra.toArray,
     )
   }
-  def compileInputsSettings: Seq[Setting[_]] = {
+  def compileInputsSettings: Seq[Setting[_]] =
+    compileInputsSettings(dependencyPicklePath)
+  def compileInputsSettings(classpathTask: TaskKey[VirtualClasspath]): Seq[Setting[_]] = {
     Seq(
       compileOptions := {
         val c = fileConverter.value
-        val cp0 = classDirectory.value +: data(dependencyClasspath.value)
-        val cp = cp0 map { x =>
-          PlainVirtualFile(x.toPath)
-        }
+        val cp0 = classpathTask.value
+        val cp = backendOutput.value +: data(cp0)
         val vs = sources.value.toVector map { x =>
           c.toVirtualFile(x.toPath)
         }
         CompileOptions.of(
-          cp.toArray: Array[VirtualFile],
+          cp.toArray,
           vs.toArray,
-          classDirectory.value.toPath,
+          c.toPath(backendOutput.value),
           scalacOptions.value.toArray,
           javacOptions.value.toArray,
           maxErrors.value,
@@ -1939,7 +2057,7 @@ object Defaults extends BuildCommon {
           None.toOptional: Optional[NioPath],
           Some(fileConverter.value).toOptional,
           Some(reusableStamper.value).toOptional,
-          None.toOptional: Optional[xsbti.compile.Output],
+          Some(CompileOutput(c.toPath(earlyOutput.value))).toOptional,
         )
       },
       compilerReporter := {
@@ -2167,8 +2285,10 @@ object Classpaths {
   def concatSettings[T](a: SettingKey[Seq[T]], b: SettingKey[Seq[T]]): Initialize[Seq[T]] =
     concatSettings(a: Initialize[Seq[T]], b) // forward to widened variant
 
+  // Included as part of JvmPlugin#projectSettings.
   lazy val configSettings: Seq[Setting[_]] = classpaths ++ Seq(
     products := makeProducts.value,
+    pickleProducts := makePickleProducts.value,
     productDirectories := classDirectory.value :: Nil,
     classpathConfiguration := findClasspathConfig(
       internalConfigurationMap.value,
@@ -2182,7 +2302,7 @@ object Classpaths {
       externalDependencyClasspath := concat(unmanagedClasspath, managedClasspath).value,
       dependencyClasspath := concat(internalDependencyClasspath, externalDependencyClasspath).value,
       fullClasspath := concatDistinct(exportedProducts, dependencyClasspath).value,
-      internalDependencyClasspath := internalDependencies.value,
+      internalDependencyClasspath := ClasspathImpl.internalDependencyClasspathTask.value,
       unmanagedClasspath := unmanagedDependencies.value,
       managedClasspath := {
         val isMeta = isMetaBuild.value
@@ -2199,12 +2319,20 @@ object Classpaths {
         if (isMeta && !force && !csr) mjars ++ sbtCp
         else mjars
       },
-      exportedProducts := trackedExportedProducts(TrackLevel.TrackAlways).value,
-      exportedProductsIfMissing := trackedExportedProducts(TrackLevel.TrackIfMissing).value,
-      exportedProductsNoTracking := trackedExportedProducts(TrackLevel.NoTracking).value,
-      exportedProductJars := trackedExportedJarProducts(TrackLevel.TrackAlways).value,
-      exportedProductJarsIfMissing := trackedExportedJarProducts(TrackLevel.TrackIfMissing).value,
-      exportedProductJarsNoTracking := trackedExportedJarProducts(TrackLevel.NoTracking).value,
+      exportedProducts := ClasspathImpl.trackedExportedProducts(TrackLevel.TrackAlways).value,
+      exportedProductsIfMissing := ClasspathImpl
+        .trackedExportedProducts(TrackLevel.TrackIfMissing)
+        .value,
+      exportedProductsNoTracking := ClasspathImpl
+        .trackedExportedProducts(TrackLevel.NoTracking)
+        .value,
+      exportedProductJars := ClasspathImpl.trackedExportedJarProducts(TrackLevel.TrackAlways).value,
+      exportedProductJarsIfMissing := ClasspathImpl
+        .trackedExportedJarProducts(TrackLevel.TrackIfMissing)
+        .value,
+      exportedProductJarsNoTracking := ClasspathImpl
+        .trackedExportedJarProducts(TrackLevel.NoTracking)
+        .value,
       internalDependencyAsJars := internalDependencyJarsTask.value,
       dependencyClasspathAsJars := concat(internalDependencyAsJars, externalDependencyClasspath).value,
       fullClasspathAsJars := concatDistinct(exportedProductJars, dependencyClasspathAsJars).value,
@@ -2222,7 +2350,38 @@ object Classpaths {
         dependencyClasspathFiles.value.flatMap(
           p => FileStamp(stamper.library(converter.toVirtualFile(p))).map(p -> _)
         )
-      }
+      },
+      dependencyVirtualClasspath := {
+        // TODO: Use converter
+        val cp0 = dependencyClasspath.value
+        cp0 map {
+          _ map { file =>
+            PlainVirtualFile(file.toPath): VirtualFile
+          }
+        }
+      },
+      // Note: invoking this task from shell would block indefinately because it will
+      // wait for the upstream compilation to start.
+      dependencyPicklePath := {
+        // This is a conditional task. Do not refactor.
+        if (incOptions.value.pipelining) {
+          concat(
+            internalDependencyPicklePath,
+            Def.task {
+              // TODO: Use converter
+              externalDependencyClasspath.value map {
+                _ map { file =>
+                  PlainVirtualFile(file.toPath): VirtualFile
+                }
+              }
+            }
+          ).value
+        } else {
+          dependencyVirtualClasspath.value
+        }
+      },
+      internalDependencyPicklePath := ClasspathImpl.internalDependencyPicklePathTask.value,
+      exportedPickles := ClasspathImpl.exportedPicklesTask.value,
     )
 
   private[this] def exportClasspath(s: Setting[Task[Classpath]]): Setting[Task[Classpath]] =
@@ -3190,15 +3349,15 @@ object Classpaths {
     }
 
   /*
-	// can't cache deliver/publish easily since files involved are hidden behind patterns.  publish will be difficult to verify target-side anyway
-	def cachedPublish(cacheFile: File)(g: (IvySbt#Module, PublishConfiguration) => Unit, module: IvySbt#Module, config: PublishConfiguration) => Unit =
-	{ case module :+: config :+: HNil =>
-	/*	implicit val publishCache = publishIC
-		val f = cached(cacheFile) { (conf: IvyConfiguration, settings: ModuleSettings, config: PublishConfiguration) =>*/
-		    g(module, config)
-		/*}
-		f(module.owner.configuration :+: module.moduleSettings :+: config :+: HNil)*/
-	}*/
+    // can't cache deliver/publish easily since files involved are hidden behind patterns.  publish will be difficult to verify target-side anyway
+    def cachedPublish(cacheFile: File)(g: (IvySbt#Module, PublishConfiguration) => Unit, module: IvySbt#Module, config: PublishConfiguration) => Unit =
+    { case module :+: config :+: HNil =>
+    /*	implicit val publishCache = publishIC
+      val f = cached(cacheFile) { (conf: IvyConfiguration, settings: ModuleSettings, config: PublishConfiguration) =>*/
+          g(module, config)
+      /*}
+      f(module.owner.configuration :+: module.moduleSettings :+: config :+: HNil)*/
+    }*/
 
   def defaultRepositoryFilter: MavenRepository => Boolean = repo => !repo.root.startsWith("file:")
 
@@ -3291,140 +3450,37 @@ object Classpaths {
       new RawRepository(resolver, resolver.getName)
     }
 
-  def analyzed[T](data: T, analysis: CompileAnalysis) =
-    Attributed.blank(data).put(Keys.analysis, analysis)
+  def analyzed[T](data: T, analysis: CompileAnalysis) = ClasspathImpl.analyzed[T](data, analysis)
   def makeProducts: Initialize[Task[Seq[File]]] = Def.task {
+    val c = fileConverter.value
     compile.value
     copyResources.value
-    classDirectory.value :: Nil
+    c.toPath(backendOutput.value).toFile :: Nil
   }
-  private[sbt] def trackedExportedProducts(track: TrackLevel): Initialize[Task[Classpath]] =
-    Def.task {
-      val _ = (packageBin / dynamicDependency).value
-      val art = (artifact in packageBin).value
-      val module = projectID.value
-      val config = configuration.value
-      for { (f, analysis) <- trackedExportedProductsImplTask(track).value } yield APIMappings
-        .store(analyzed(f, analysis), apiURL.value)
-        .put(artifact.key, art)
-        .put(moduleID.key, module)
-        .put(configuration.key, config)
-    }
-  private[sbt] def trackedExportedJarProducts(track: TrackLevel): Initialize[Task[Classpath]] =
-    Def.task {
-      val _ = (packageBin / dynamicDependency).value
-      val art = (artifact in packageBin).value
-      val module = projectID.value
-      val config = configuration.value
-      for { (f, analysis) <- trackedJarProductsImplTask(track).value } yield APIMappings
-        .store(analyzed(f, analysis), apiURL.value)
-        .put(artifact.key, art)
-        .put(moduleID.key, module)
-        .put(configuration.key, config)
-    }
-  private[this] def trackedExportedProductsImplTask(
-      track: TrackLevel
-  ): Initialize[Task[Seq[(File, CompileAnalysis)]]] =
-    Def.taskDyn {
-      val _ = (packageBin / dynamicDependency).value
-      val useJars = exportJars.value
-      if (useJars) trackedJarProductsImplTask(track)
-      else trackedNonJarProductsImplTask(track)
-    }
-  private[this] def trackedNonJarProductsImplTask(
-      track: TrackLevel
-  ): Initialize[Task[Seq[(File, CompileAnalysis)]]] =
-    Def.taskDyn {
-      val dirs = productDirectories.value
-      val view = fileTreeView.value
-      def containsClassFile(): Boolean =
-        view.list(dirs.map(Glob(_, RecursiveGlob / "*.class"))).nonEmpty
-      TrackLevel.intersection(track, exportToInternal.value) match {
-        case TrackLevel.TrackAlways =>
-          Def.task {
-            products.value map { (_, compile.value) }
-          }
-        case TrackLevel.TrackIfMissing if !containsClassFile() =>
-          Def.task {
-            products.value map { (_, compile.value) }
-          }
-        case _ =>
-          Def.task {
-            val analysis = previousCompile.value.analysis.toOption.getOrElse(Analysis.empty)
-            dirs.map(_ -> analysis)
-          }
-      }
-    }
-  private[this] def trackedJarProductsImplTask(
-      track: TrackLevel
-  ): Initialize[Task[Seq[(File, CompileAnalysis)]]] =
-    Def.taskDyn {
-      val jar = (artifactPath in packageBin).value
-      TrackLevel.intersection(track, exportToInternal.value) match {
-        case TrackLevel.TrackAlways =>
-          Def.task {
-            Seq((packageBin.value, compile.value))
-          }
-        case TrackLevel.TrackIfMissing if !jar.exists =>
-          Def.task {
-            Seq((packageBin.value, compile.value))
-          }
-        case _ =>
-          Def.task {
-            val analysisOpt = previousCompile.value.analysis.toOption
-            Seq(jar) map { x =>
-              (
-                x,
-                if (analysisOpt.isDefined) analysisOpt.get
-                else Analysis.empty
-              )
-            }
-          }
+
+  private[sbt] def makePickleProducts: Initialize[Task[Seq[VirtualFile]]] = Def.task {
+    // This is a conditional task.
+    if (earlyOutputPing.await.value) {
+      // TODO: copyResources.value
+      earlyOutput.value :: Nil
+    } else {
+      val c = fileConverter.value
+      products.value map { x: File =>
+        c.toVirtualFile(x.toPath)
       }
     }
+  }
 
   def constructBuildDependencies: Initialize[BuildDependencies] =
     loadedBuild(lb => BuildUtil.dependencies(lb.units))
 
+  @deprecated("not used", "1.4.0")
   def internalDependencies: Initialize[Task[Classpath]] =
-    Def.taskDyn {
-      val _ = (
-        (exportedProductsNoTracking / transitiveClasspathDependency).value,
-        (exportedProductsIfMissing / transitiveClasspathDependency).value,
-        (exportedProducts / transitiveClasspathDependency).value,
-        (exportedProductJarsNoTracking / transitiveClasspathDependency).value,
-        (exportedProductJarsIfMissing / transitiveClasspathDependency).value,
-        (exportedProductJars / transitiveClasspathDependency).value
-      )
-      internalDependenciesImplTask(
-        thisProjectRef.value,
-        classpathConfiguration.value,
-        configuration.value,
-        settingsData.value,
-        buildDependencies.value,
-        trackInternalDependencies.value
-      )
-    }
+    ClasspathImpl.internalDependencyClasspathTask
+
   def internalDependencyJarsTask: Initialize[Task[Classpath]] =
-    Def.taskDyn {
-      internalDependencyJarsImplTask(
-        thisProjectRef.value,
-        classpathConfiguration.value,
-        configuration.value,
-        settingsData.value,
-        buildDependencies.value,
-        trackInternalDependencies.value
-      )
-    }
-  def unmanagedDependencies: Initialize[Task[Classpath]] =
-    Def.taskDyn {
-      unmanagedDependencies0(
-        thisProjectRef.value,
-        configuration.value,
-        settingsData.value,
-        buildDependencies.value
-      )
-    }
+    ClasspathImpl.internalDependencyJarsTask
+  def unmanagedDependencies: Initialize[Task[Classpath]] = ClasspathImpl.unmanagedDependenciesTask
   def mkIvyConfiguration: Initialize[Task[InlineIvyConfiguration]] =
     Def.task {
       val (rs, other) = (fullResolvers.value.toVector, otherResolvers.value.toVector)
@@ -3443,37 +3499,12 @@ object Classpaths {
         .withLog(s.log)
     }
 
-  import java.util.LinkedHashSet
-
-  import collection.JavaConverters._
   def interSort(
       projectRef: ProjectRef,
       conf: Configuration,
       data: Settings[Scope],
       deps: BuildDependencies
-  ): Seq[(ProjectRef, String)] = {
-    val visited = (new LinkedHashSet[(ProjectRef, String)]).asScala
-    def visit(p: ProjectRef, c: Configuration): Unit = {
-      val applicableConfigs = allConfigs(c)
-      for (ac <- applicableConfigs) // add all configurations in this project
-        visited add (p -> ac.name)
-      val masterConfs = names(getConfigurations(projectRef, data).toVector)
-
-      for (ResolvedClasspathDependency(dep, confMapping) <- deps.classpath(p)) {
-        val configurations = getConfigurations(dep, data)
-        val mapping =
-          mapped(confMapping, masterConfs, names(configurations.toVector), "compile", "*->compile")
-        // map master configuration 'c' and all extended configurations to the appropriate dependency configuration
-        for (ac <- applicableConfigs; depConfName <- mapping(ac.name)) {
-          for (depConf <- confOpt(configurations, depConfName))
-            if (!visited((dep, depConfName)))
-              visit(dep, depConf)
-        }
-      }
-    }
-    visit(projectRef, conf)
-    visited.toSeq
-  }
+  ): Seq[(ProjectRef, String)] = ClasspathImpl.interSort(projectRef, conf, data, deps)
 
   def interSortConfigurations(
       projectRef: ProjectRef,
@@ -3485,143 +3516,50 @@ object Classpaths {
       case (projectRef, configName) => (projectRef, ConfigRef(configName))
     }
 
-  private[sbt] def unmanagedDependencies0(
-      projectRef: ProjectRef,
-      conf: Configuration,
-      data: Settings[Scope],
-      deps: BuildDependencies
-  ): Initialize[Task[Classpath]] =
-    Def.value {
-      interDependencies(
-        projectRef,
-        deps,
-        conf,
-        conf,
-        data,
-        TrackLevel.TrackAlways,
-        true,
-        (dep, conf, data, _) => unmanagedLibs(dep, conf, data),
-      )
-    }
-  private[sbt] def internalDependenciesImplTask(
-      projectRef: ProjectRef,
-      conf: Configuration,
-      self: Configuration,
-      data: Settings[Scope],
-      deps: BuildDependencies,
-      track: TrackLevel
-  ): Initialize[Task[Classpath]] =
-    Def.value { interDependencies(projectRef, deps, conf, self, data, track, false, productsTask) }
-  private[sbt] def internalDependencyJarsImplTask(
-      projectRef: ProjectRef,
-      conf: Configuration,
-      self: Configuration,
-      data: Settings[Scope],
-      deps: BuildDependencies,
-      track: TrackLevel
-  ): Initialize[Task[Classpath]] =
-    Def.value {
-      interDependencies(projectRef, deps, conf, self, data, track, false, jarProductsTask)
-    }
-  private[sbt] def interDependencies(
-      projectRef: ProjectRef,
-      deps: BuildDependencies,
-      conf: Configuration,
-      self: Configuration,
-      data: Settings[Scope],
-      track: TrackLevel,
-      includeSelf: Boolean,
-      f: (ProjectRef, String, Settings[Scope], TrackLevel) => Task[Classpath]
-  ): Task[Classpath] = {
-    val visited = interSort(projectRef, conf, data, deps)
-    val tasks = (new LinkedHashSet[Task[Classpath]]).asScala
-    for ((dep, c) <- visited)
-      if (includeSelf || (dep != projectRef) || (conf.name != c && self.name != c))
-        tasks += f(dep, c, data, track)
-
-    (tasks.toSeq.join).map(_.flatten.distinct)
-  }
-
   def mapped(
       confString: Option[String],
       masterConfs: Seq[String],
       depConfs: Seq[String],
       default: String,
       defaultMapping: String
-  ): String => Seq[String] = {
-    lazy val defaultMap = parseMapping(defaultMapping, masterConfs, depConfs, _ :: Nil)
-    parseMapping(confString getOrElse default, masterConfs, depConfs, defaultMap)
-  }
+  ): String => Seq[String] =
+    ClasspathImpl.mapped(confString, masterConfs, depConfs, default, defaultMapping)
+
   def parseMapping(
       confString: String,
       masterConfs: Seq[String],
       depConfs: Seq[String],
       default: String => Seq[String]
   ): String => Seq[String] =
-    union(confString.split(";") map parseSingleMapping(masterConfs, depConfs, default))
+    ClasspathImpl.parseMapping(confString, masterConfs, depConfs, default)
+
   def parseSingleMapping(
       masterConfs: Seq[String],
       depConfs: Seq[String],
       default: String => Seq[String]
-  )(confString: String): String => Seq[String] = {
-    val ms: Seq[(String, Seq[String])] =
-      trim(confString.split("->", 2)) match {
-        case x :: Nil => for (a <- parseList(x, masterConfs)) yield (a, default(a))
-        case x :: y :: Nil =>
-          val target = parseList(y, depConfs);
-          for (a <- parseList(x, masterConfs)) yield (a, target)
-        case _ => sys.error("Invalid configuration '" + confString + "'") // shouldn't get here
-      }
-    val m = ms.toMap
-    s => m.getOrElse(s, Nil)
-  }
+  )(confString: String): String => Seq[String] =
+    ClasspathImpl.parseSingleMapping(masterConfs, depConfs, default)(confString)
 
   def union[A, B](maps: Seq[A => Seq[B]]): A => Seq[B] =
-    a => maps.foldLeft(Seq[B]()) { _ ++ _(a) } distinct;
+    ClasspathImpl.union[A, B](maps)
 
   def parseList(s: String, allConfs: Seq[String]): Seq[String] =
-    (trim(s split ",") flatMap replaceWildcard(allConfs)).distinct
-  def replaceWildcard(allConfs: Seq[String])(conf: String): Seq[String] = conf match {
-    case ""  => Nil
-    case "*" => allConfs
-    case _   => conf :: Nil
-  }
+    ClasspathImpl.parseList(s, allConfs)
+
+  def replaceWildcard(allConfs: Seq[String])(conf: String): Seq[String] =
+    ClasspathImpl.replaceWildcard(allConfs)(conf)
 
-  private def trim(a: Array[String]): List[String] = a.toList.map(_.trim)
   def missingConfiguration(in: String, conf: String) =
     sys.error("Configuration '" + conf + "' not defined in '" + in + "'")
-  def allConfigs(conf: Configuration): Seq[Configuration] =
-    Dag.topologicalSort(conf)(_.extendsConfigs)
+  def allConfigs(conf: Configuration): Seq[Configuration] = ClasspathImpl.allConfigs(conf)
 
   def getConfigurations(p: ResolvedReference, data: Settings[Scope]): Seq[Configuration] =
-    ivyConfigurations in p get data getOrElse Nil
+    ClasspathImpl.getConfigurations(p, data)
   def confOpt(configurations: Seq[Configuration], conf: String): Option[Configuration] =
-    configurations.find(_.name == conf)
-  private[sbt] def productsTask(
-      dep: ResolvedReference,
-      conf: String,
-      data: Settings[Scope],
-      track: TrackLevel
-  ): Task[Classpath] =
-    track match {
-      case TrackLevel.NoTracking     => getClasspath(exportedProductsNoTracking, dep, conf, data)
-      case TrackLevel.TrackIfMissing => getClasspath(exportedProductsIfMissing, dep, conf, data)
-      case TrackLevel.TrackAlways    => getClasspath(exportedProducts, dep, conf, data)
-    }
-  private[sbt] def jarProductsTask(
-      dep: ResolvedReference,
-      conf: String,
-      data: Settings[Scope],
-      track: TrackLevel
-  ): Task[Classpath] =
-    track match {
-      case TrackLevel.NoTracking     => getClasspath(exportedProductJarsNoTracking, dep, conf, data)
-      case TrackLevel.TrackIfMissing => getClasspath(exportedProductJarsIfMissing, dep, conf, data)
-      case TrackLevel.TrackAlways    => getClasspath(exportedProductJars, dep, conf, data)
-    }
+    ClasspathImpl.confOpt(configurations, conf)
 
   def unmanagedLibs(dep: ResolvedReference, conf: String, data: Settings[Scope]): Task[Classpath] =
-    getClasspath(unmanagedJars, dep, conf, data)
+    ClasspathImpl.unmanagedLibs(dep, conf, data)
 
   def getClasspath(
       key: TaskKey[Classpath],
@@ -3629,7 +3567,7 @@ object Classpaths {
       conf: String,
       data: Settings[Scope]
   ): Task[Classpath] =
-    (key in (dep, ConfigKey(conf))) get data getOrElse constant(Nil)
+    ClasspathImpl.getClasspath(key, dep, conf, data)
 
   def defaultConfigurationTask(p: ResolvedReference, data: Settings[Scope]): Configuration =
     flatten(defaultConfiguration in p get data) getOrElse Configurations.Default
@@ -3712,13 +3650,14 @@ object Classpaths {
       val ref = thisProjectRef.value
       val data = settingsData.value
       val deps = buildDependencies.value
-      internalDependenciesImplTask(
+      ClasspathImpl.internalDependenciesImplTask(
         ref,
         CompilerPlugin,
         CompilerPlugin,
         data,
         deps,
-        TrackLevel.TrackAlways
+        TrackLevel.TrackAlways,
+        streams.value.log
       )
     }
 
diff --git a/main/src/main/scala/sbt/Keys.scala b/main/src/main/scala/sbt/Keys.scala
index 7333ac8a1..504b69a74 100644
--- a/main/src/main/scala/sbt/Keys.scala
+++ b/main/src/main/scala/sbt/Keys.scala
@@ -36,7 +36,7 @@ import sbt.librarymanagement.ivy.{ Credentials, IvyConfiguration, IvyPaths, Upda
 import sbt.nio.file.Glob
 import sbt.testing.Framework
 import sbt.util.{ Level, Logger }
-import xsbti.FileConverter
+import xsbti.{ FileConverter, VirtualFile }
 import xsbti.compile._
 import xsbti.compile.analysis.ReadStamps
 
@@ -151,6 +151,8 @@ object Keys {
 
   // Output paths
   val classDirectory = settingKey[File]("Directory for compiled classes and copied resources.").withRank(AMinusSetting)
+  val earlyOutput = settingKey[VirtualFile]("JAR file for pickles used for build pipelining")
+  val backendOutput = settingKey[VirtualFile]("Directory or JAR file for compiled classes and copied resources")
   val cleanFiles = taskKey[Seq[File]]("The files to recursively delete during a clean.").withRank(BSetting)
   val cleanKeepFiles = settingKey[Seq[File]]("Files or directories to keep during a clean. Must be direct children of target.").withRank(CSetting)
   val cleanKeepGlobs = settingKey[Seq[Glob]]("Globs to keep during a clean. Must be direct children of target.").withRank(CSetting)
@@ -167,6 +169,7 @@ object Keys {
   val scalacOptions = taskKey[Seq[String]]("Options for the Scala compiler.").withRank(BPlusTask)
   val javacOptions = taskKey[Seq[String]]("Options for the Java compiler.").withRank(BPlusTask)
   val incOptions = taskKey[IncOptions]("Options for the incremental compiler.").withRank(BTask)
+  val extraIncOptions = taskKey[Seq[(String, String)]]("Extra options for the incremental compiler").withRank(CTask)
   val compileOrder = settingKey[CompileOrder]("Configures the order in which Java and sources within a single compilation are compiled.  Valid values are: JavaThenScala, ScalaThenJava, or Mixed.").withRank(BPlusSetting)
   val initialCommands = settingKey[String]("Initial commands to execute when starting up the Scala interpreter.").withRank(AMinusSetting)
   val cleanupCommands = settingKey[String]("Commands to execute before the Scala interpreter exits.").withRank(BMinusSetting)
@@ -211,14 +214,24 @@ object Keys {
   val manipulateBytecode = taskKey[CompileResult]("Manipulates generated bytecode").withRank(BTask)
   val compileIncremental = taskKey[CompileResult]("Actually runs the incremental compilation").withRank(DTask)
   val previousCompile = taskKey[PreviousResult]("Read the incremental compiler analysis from disk").withRank(DTask)
+  private[sbt] val compileScalaBackend = taskKey[CompileResult]("Compiles only Scala sources if pipelining is enabled. Compiles both Scala and Java sources otherwise").withRank(Invisible)
+  private[sbt] val compileEarly = taskKey[CompileAnalysis]("Compiles only Scala sources if pipelining is enabled, and produce an early output (pickle JAR)").withRank(Invisible)
+  private[sbt] val earlyOutputPing = taskKey[PromiseWrap[Boolean]]("When pipelining is enabled, this returns true when early output (pickle JAR) is created; false otherwise").withRank(Invisible)
+  private[sbt] val compileJava = taskKey[CompileResult]("Compiles only Java sources (called only for pipelining)").withRank(Invisible)
+  private[sbt] val compileSplit = taskKey[CompileResult]("When pipelining is enabled, compile Scala then Java; otherwise compile both").withRank(Invisible)
+
+  val compileProgress = taskKey[CompileProgress]("Callback used by the compiler to report phase progress")
   val compilers = taskKey[Compilers]("Defines the Scala and Java compilers to use for compilation.").withRank(DTask)
   val compileAnalysisFilename = taskKey[String]("Defines the filename used for compileAnalysisFile.").withRank(DTask)
   val compileAnalysisTargetRoot = settingKey[File]("The output directory to produce Zinc Analysis files").withRank(DSetting)
+  val earlyCompileAnalysisTargetRoot = settingKey[File]("The output directory to produce Zinc Analysis files").withRank(DSetting)
   val compileAnalysisFile = taskKey[File]("Zinc analysis storage.").withRank(DSetting)
+  val earlyCompileAnalysisFile = taskKey[File]("Zinc analysis storage for early compilation").withRank(DSetting)
   val compileIncSetup = taskKey[Setup]("Configures aspects of incremental compilation.").withRank(DTask)
   val compilerCache = taskKey[GlobalsCache]("Cache of scala.tools.nsc.Global instances.  This should typically be cached so that it isn't recreated every task run.").withRank(DTask)
   val stateCompilerCache = AttributeKey[GlobalsCache]("stateCompilerCache", "Internal use: Global cache.")
   val classpathEntryDefinesClass = taskKey[File => DefinesClass]("Internal use: provides a function that determines whether the provided file contains a given class.").withRank(Invisible)
+  val classpathEntryDefinesClassVF = taskKey[VirtualFile => DefinesClass]("Internal use: provides a function that determines whether the provided file contains a given class.").withRank(Invisible)
   val doc = taskKey[File]("Generates API documentation.").withRank(AMinusTask)
   val copyResources = taskKey[Seq[(File, File)]]("Copies resources to the output directory.").withRank(AMinusTask)
   val aggregate = settingKey[Boolean]("Configures task aggregation.").withRank(BMinusSetting)
@@ -302,6 +315,7 @@ object Keys {
 
   // Classpath/Dependency Management Keys
   type Classpath = Def.Classpath
+  type VirtualClasspath = Def.VirtualClasspath
 
   val name = settingKey[String]("Project name.").withRank(APlusSetting)
   val normalizedName = settingKey[String]("Project name transformed from mixed case and spaces to lowercase and dash-separated.").withRank(BSetting)
@@ -333,12 +347,17 @@ object Keys {
   val internalDependencyClasspath = taskKey[Classpath]("The internal (inter-project) classpath.").withRank(CTask)
   val externalDependencyClasspath = taskKey[Classpath]("The classpath consisting of library dependencies, both managed and unmanaged.").withRank(BMinusTask)
   val dependencyClasspath = taskKey[Classpath]("The classpath consisting of internal and external, managed and unmanaged dependencies.").withRank(BPlusTask)
+  val dependencyVirtualClasspath = taskKey[VirtualClasspath]("The classpath consisting of internal and external, managed and unmanaged dependencies.").withRank(CTask)
+  val dependencyPicklePath = taskKey[VirtualClasspath]("The classpath consisting of internal pickles and external, managed and unmanaged dependencies. This task is promise-blocked.")
+  val internalDependencyPicklePath = taskKey[VirtualClasspath]("The internal (inter-project) pickles. This task is promise-blocked.")
   val fullClasspath = taskKey[Classpath]("The exported classpath, consisting of build products and unmanaged and managed, internal and external dependencies.").withRank(BPlusTask)
   val trackInternalDependencies = settingKey[TrackLevel]("The level of tracking for the internal (inter-project) dependency.").withRank(BSetting)
   val exportToInternal = settingKey[TrackLevel]("The level of tracking for this project by the internal callers.").withRank(BSetting)
   val exportedProductJars = taskKey[Classpath]("Build products that go on the exported classpath as JARs.")
   val exportedProductJarsIfMissing = taskKey[Classpath]("Build products that go on the exported classpath as JARs if missing.")
   val exportedProductJarsNoTracking = taskKey[Classpath]("Just the exported classpath as JARs without triggering the compilation.")
+  val exportedPickles = taskKey[VirtualClasspath]("Build products that go on the exported compilation classpath as JARs. Note this is promise-blocked.").withRank(DTask)
+  val pickleProducts = taskKey[Seq[VirtualFile]]("Pickle JARs").withRank(DTask)
   val internalDependencyAsJars = taskKey[Classpath]("The internal (inter-project) classpath as JARs.")
   val dependencyClasspathAsJars = taskKey[Classpath]("The classpath consisting of internal and external, managed and unmanaged dependencies, all as JARs.")
   val fullClasspathAsJars = taskKey[Classpath]("The exported classpath, consisting of build products and unmanaged and managed, internal and external dependencies, all as JARs.")
@@ -357,6 +376,7 @@ object Keys {
   val pushRemoteCacheConfiguration = taskKey[PublishConfiguration]("")
   val pushRemoteCacheTo = settingKey[Option[Resolver]]("The resolver to publish remote cache to.")
   val remoteCachePom = taskKey[File]("Generates a pom for publishing when publishing Maven-style.")
+  val usePipelining = settingKey[Boolean]("Use subproject pipelining for compilation.").withRank(BSetting)
 
   val bspTargetIdentifier = settingKey[BuildTargetIdentifier]("Id for BSP build target.").withRank(DSetting)
   val bspWorkspace = settingKey[Map[BuildTargetIdentifier, Scope]]("Mapping of BSP build targets to sbt scopes").withRank(DSetting)
@@ -387,7 +407,7 @@ object Keys {
   val csrExtraCredentials = taskKey[Seq[lmcoursier.credentials.Credentials]]("")
   val csrPublications = taskKey[Seq[(lmcoursier.definitions.Configuration, lmcoursier.definitions.Publication)]]("")
   val csrReconciliations = settingKey[Seq[(ModuleMatchers, Reconciliation)]]("Strategy to reconcile version conflicts.")
-  
+
   val internalConfigurationMap = settingKey[Configuration => Configuration]("Maps configurations to the actual configuration used to define the classpath.").withRank(CSetting)
   val classpathConfiguration = taskKey[Configuration]("The configuration used to define the classpath.").withRank(CTask)
   val ivyConfiguration = taskKey[IvyConfiguration]("General dependency management (Ivy) settings, such as the resolvers and paths to use.").withRank(DTask)
@@ -457,7 +477,7 @@ object Keys {
   val fullResolvers = taskKey[Seq[Resolver]]("Combines the project resolver, default resolvers, and user-defined resolvers.").withRank(CTask)
   val otherResolvers = taskKey[Seq[Resolver]]("Resolvers not included in the main resolver chain, such as those in module configurations.").withRank(CSetting)
   val scalaCompilerBridgeResolvers = taskKey[Seq[Resolver]]("Resolvers used to resolve compiler bridges.").withRank(CSetting)
-  val includePluginResolvers = settingKey[Boolean]("Include the resolvers from the metabuild.").withRank(CSetting)  
+  val includePluginResolvers = settingKey[Boolean]("Include the resolvers from the metabuild.").withRank(CSetting)
   val useJCenter = settingKey[Boolean]("Use JCenter as the default repository.").withRank(CSetting)
   val moduleConfigurations = settingKey[Seq[ModuleConfiguration]]("Defines module configurations, which override resolvers on a per-module basis.").withRank(BMinusSetting)
   val retrievePattern = settingKey[String]("Pattern used to retrieve managed dependencies to the current build.").withRank(DSetting)
diff --git a/main/src/main/scala/sbt/Main.scala b/main/src/main/scala/sbt/Main.scala
index 763d6cef6..9184670bf 100644
--- a/main/src/main/scala/sbt/Main.scala
+++ b/main/src/main/scala/sbt/Main.scala
@@ -971,22 +971,23 @@ object BuiltinCommands {
   }
 
   private[sbt] def waitCmd: Command =
-    Command.arb(_ => (ContinuousCommands.waitWatch: Parser[String]).examples()) { (s0, _) =>
+    Command.arb(
+      _ => ContinuousCommands.waitWatch.examples() ~> " ".examples() ~> matched(any.*).examples()
+    ) { (s0, channel) =>
       val exchange = StandardMain.exchange
-      if (exchange.channels.exists(ContinuousCommands.isInWatch)) {
-        val s1 = exchange.run(s0)
-        exchange.channels.foreach {
-          case c if ContinuousCommands.isPending(c) =>
-          case c                                    => c.prompt(ConsolePromptEvent(s1))
-        }
-        val exec: Exec = getExec(s1, Duration.Inf)
-        val remaining: List[Exec] =
-          Exec(ContinuousCommands.waitWatch, None) ::
-            Exec(FailureWall, None) :: s1.remainingCommands
-        val newState = s1.copy(remainingCommands = exec +: remaining)
-        if (exec.commandLine.trim.isEmpty) newState
-        else newState.clearGlobalLog
-      } else s0
+      exchange.channelForName(channel) match {
+        case Some(c) if ContinuousCommands.isInWatch(s0, c) =>
+          c.prompt(ConsolePromptEvent(s0))
+          val s1 = exchange.run(s0)
+          val exec: Exec = getExec(s1, Duration.Inf)
+          val remaining: List[Exec] =
+            Exec(s"${ContinuousCommands.waitWatch} $channel", None) ::
+              Exec(FailureWall, None) :: s1.remainingCommands
+          val newState = s1.copy(remainingCommands = exec +: remaining)
+          if (exec.commandLine.trim.isEmpty) newState
+          else newState.clearGlobalLog
+        case _ => s0
+      }
     }
 
   private[sbt] def promptChannel = Command.arb(_ => reportParser(PromptChannel)) {
diff --git a/main/src/main/scala/sbt/MainLoop.scala b/main/src/main/scala/sbt/MainLoop.scala
index 09f26e96e..99256ed79 100644
--- a/main/src/main/scala/sbt/MainLoop.scala
+++ b/main/src/main/scala/sbt/MainLoop.scala
@@ -23,6 +23,7 @@ import sbt.util.Logger
 
 import scala.annotation.tailrec
 import scala.util.control.NonFatal
+import sbt.internal.FastTrackCommands
 
 object MainLoop {
 
@@ -201,7 +202,18 @@ object MainLoop {
         StandardMain.exchange.setState(progressState)
         StandardMain.exchange.setExec(Some(exec))
         StandardMain.exchange.unprompt(ConsoleUnpromptEvent(exec.source))
-        val newState = Command.process(exec.commandLine, progressState)
+        /*
+         * FastTrackCommands.evaluate can be significantly faster than Command.process because
+         * it avoids an expensive parsing step for internal commands that are easy to parse.
+         * Dropping (FastTrackCommands.evaluate ... getOrElse) should be functionally identical
+         * but slower.
+         */
+        val newState = FastTrackCommands.evaluate(progressState, exec.commandLine) getOrElse
+          Command.process(exec.commandLine, progressState)
+        // Flush the terminal output after command evaluation to ensure that all output
+        // is displayed in the thin client before we report the command status.
+        val terminal = channelName.flatMap(exchange.channelForName(_).map(_.terminal))
+        terminal.foreach(_.flush())
         if (exec.execId.fold(true)(!_.startsWith(networkExecPrefix)) &&
             !exec.commandLine.startsWith(networkExecPrefix)) {
           val doneEvent = ExecStatusEvent(
diff --git a/main/src/main/scala/sbt/internal/Aggregation.scala b/main/src/main/scala/sbt/internal/Aggregation.scala
index df7e43ee3..62b6fa7d9 100644
--- a/main/src/main/scala/sbt/internal/Aggregation.scala
+++ b/main/src/main/scala/sbt/internal/Aggregation.scala
@@ -131,7 +131,7 @@ object Aggregation {
     if (get(showSuccess)) {
       if (get(showTiming)) {
         val msg = timingString(start, stop, structure.data, currentRef)
-        if (success) log.success(msg) else log.error(msg)
+        if (success) log.success(msg) else if (Terminal.get.isSuccessEnabled) log.error(msg)
       } else if (success)
         log.success("")
     }
diff --git a/main/src/main/scala/sbt/internal/ClasspathImpl.scala b/main/src/main/scala/sbt/internal/ClasspathImpl.scala
new file mode 100644
index 000000000..d9f36cb88
--- /dev/null
+++ b/main/src/main/scala/sbt/internal/ClasspathImpl.scala
@@ -0,0 +1,427 @@
+/*
+ * sbt
+ * Copyright 2011 - 2018, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt
+package internal
+
+import java.io.File
+import java.util.LinkedHashSet
+import sbt.SlashSyntax0._
+import sbt.Keys._
+import sbt.nio.Keys._
+import sbt.nio.file.{ Glob, RecursiveGlob }
+import sbt.Def.Initialize
+import sbt.internal.inc.Analysis
+import sbt.internal.inc.JavaInterfaceUtil._
+import sbt.internal.util.{ Attributed, Dag, Settings }
+import sbt.librarymanagement.{ Configuration, TrackLevel }
+import sbt.librarymanagement.Configurations.names
+import sbt.std.TaskExtra._
+import sbt.util._
+import scala.collection.JavaConverters._
+import xsbti.compile.CompileAnalysis
+
+private[sbt] object ClasspathImpl {
+
+  // Since we can't predict the path for pickleProduct,
+  // we can't reduce the track level.
+  def exportedPicklesTask: Initialize[Task[VirtualClasspath]] =
+    Def.task {
+      val module = projectID.value
+      val config = configuration.value
+      val products = pickleProducts.value
+      val analysis = compileEarly.value
+      val xs = products map { _ -> analysis }
+      for { (f, analysis) <- xs } yield APIMappings
+        .store(analyzed(f, analysis), apiURL.value)
+        .put(moduleID.key, module)
+        .put(configuration.key, config)
+    }
+
+  def trackedExportedProducts(track: TrackLevel): Initialize[Task[Classpath]] =
+    Def.task {
+      val _ = (packageBin / dynamicDependency).value
+      val art = (artifact in packageBin).value
+      val module = projectID.value
+      val config = configuration.value
+      for { (f, analysis) <- trackedExportedProductsImplTask(track).value } yield APIMappings
+        .store(analyzed(f, analysis), apiURL.value)
+        .put(artifact.key, art)
+        .put(moduleID.key, module)
+        .put(configuration.key, config)
+    }
+
+  def trackedExportedJarProducts(track: TrackLevel): Initialize[Task[Classpath]] =
+    Def.task {
+      val _ = (packageBin / dynamicDependency).value
+      val art = (artifact in packageBin).value
+      val module = projectID.value
+      val config = configuration.value
+      for { (f, analysis) <- trackedJarProductsImplTask(track).value } yield APIMappings
+        .store(analyzed(f, analysis), apiURL.value)
+        .put(artifact.key, art)
+        .put(moduleID.key, module)
+        .put(configuration.key, config)
+    }
+
+  private[this] def trackedExportedProductsImplTask(
+      track: TrackLevel
+  ): Initialize[Task[Seq[(File, CompileAnalysis)]]] =
+    Def.taskDyn {
+      val _ = (packageBin / dynamicDependency).value
+      val useJars = exportJars.value
+      if (useJars) trackedJarProductsImplTask(track)
+      else trackedNonJarProductsImplTask(track)
+    }
+
+  private[this] def trackedNonJarProductsImplTask(
+      track: TrackLevel
+  ): Initialize[Task[Seq[(File, CompileAnalysis)]]] =
+    Def.taskDyn {
+      val dirs = productDirectories.value
+      val view = fileTreeView.value
+      def containsClassFile(): Boolean =
+        view.list(dirs.map(Glob(_, RecursiveGlob / "*.class"))).nonEmpty
+      TrackLevel.intersection(track, exportToInternal.value) match {
+        case TrackLevel.TrackAlways =>
+          Def.task {
+            products.value map { (_, compile.value) }
+          }
+        case TrackLevel.TrackIfMissing if !containsClassFile() =>
+          Def.task {
+            products.value map { (_, compile.value) }
+          }
+        case _ =>
+          Def.task {
+            val analysis = previousCompile.value.analysis.toOption.getOrElse(Analysis.empty)
+            dirs.map(_ -> analysis)
+          }
+      }
+    }
+
+  private[this] def trackedJarProductsImplTask(
+      track: TrackLevel
+  ): Initialize[Task[Seq[(File, CompileAnalysis)]]] =
+    Def.taskDyn {
+      val jar = (artifactPath in packageBin).value
+      TrackLevel.intersection(track, exportToInternal.value) match {
+        case TrackLevel.TrackAlways =>
+          Def.task {
+            Seq((packageBin.value, compile.value))
+          }
+        case TrackLevel.TrackIfMissing if !jar.exists =>
+          Def.task {
+            Seq((packageBin.value, compile.value))
+          }
+        case _ =>
+          Def.task {
+            val analysisOpt = previousCompile.value.analysis.toOption
+            Seq(jar) map { x =>
+              (
+                x,
+                if (analysisOpt.isDefined) analysisOpt.get
+                else Analysis.empty
+              )
+            }
+          }
+      }
+    }
+
+  def internalDependencyClasspathTask: Initialize[Task[Classpath]] = {
+    Def.taskDyn {
+      val _ = (
+        (exportedProductsNoTracking / transitiveClasspathDependency).value,
+        (exportedProductsIfMissing / transitiveClasspathDependency).value,
+        (exportedProducts / transitiveClasspathDependency).value,
+        (exportedProductJarsNoTracking / transitiveClasspathDependency).value,
+        (exportedProductJarsIfMissing / transitiveClasspathDependency).value,
+        (exportedProductJars / transitiveClasspathDependency).value
+      )
+      internalDependenciesImplTask(
+        thisProjectRef.value,
+        classpathConfiguration.value,
+        configuration.value,
+        settingsData.value,
+        buildDependencies.value,
+        trackInternalDependencies.value,
+        streams.value.log,
+      )
+    }
+  }
+
+  def internalDependenciesImplTask(
+      projectRef: ProjectRef,
+      conf: Configuration,
+      self: Configuration,
+      data: Settings[Scope],
+      deps: BuildDependencies,
+      track: TrackLevel,
+      log: Logger
+  ): Initialize[Task[Classpath]] =
+    Def.value {
+      interDependencies(projectRef, deps, conf, self, data, track, false, log)(
+        exportedProductsNoTracking,
+        exportedProductsIfMissing,
+        exportedProducts
+      )
+    }
+
+  def internalDependencyPicklePathTask: Initialize[Task[VirtualClasspath]] = {
+    def implTask(
+        projectRef: ProjectRef,
+        conf: Configuration,
+        self: Configuration,
+        data: Settings[Scope],
+        deps: BuildDependencies,
+        track: TrackLevel,
+        log: Logger
+    ): Initialize[Task[VirtualClasspath]] =
+      Def.value {
+        interDependencies(projectRef, deps, conf, self, data, track, false, log)(
+          exportedPickles,
+          exportedPickles,
+          exportedPickles
+        )
+      }
+    Def.taskDyn {
+      implTask(
+        thisProjectRef.value,
+        classpathConfiguration.value,
+        configuration.value,
+        settingsData.value,
+        buildDependencies.value,
+        TrackLevel.TrackAlways,
+        streams.value.log,
+      )
+    }
+  }
+
+  def internalDependencyJarsTask: Initialize[Task[Classpath]] =
+    Def.taskDyn {
+      internalDependencyJarsImplTask(
+        thisProjectRef.value,
+        classpathConfiguration.value,
+        configuration.value,
+        settingsData.value,
+        buildDependencies.value,
+        trackInternalDependencies.value,
+        streams.value.log,
+      )
+    }
+
+  private def internalDependencyJarsImplTask(
+      projectRef: ProjectRef,
+      conf: Configuration,
+      self: Configuration,
+      data: Settings[Scope],
+      deps: BuildDependencies,
+      track: TrackLevel,
+      log: Logger
+  ): Initialize[Task[Classpath]] =
+    Def.value {
+      interDependencies(projectRef, deps, conf, self, data, track, false, log)(
+        exportedProductJarsNoTracking,
+        exportedProductJarsIfMissing,
+        exportedProductJars
+      )
+    }
+
+  def unmanagedDependenciesTask: Initialize[Task[Classpath]] =
+    Def.taskDyn {
+      unmanagedDependencies0(
+        thisProjectRef.value,
+        configuration.value,
+        settingsData.value,
+        buildDependencies.value,
+        streams.value.log
+      )
+    }
+
+  def unmanagedDependencies0(
+      projectRef: ProjectRef,
+      conf: Configuration,
+      data: Settings[Scope],
+      deps: BuildDependencies,
+      log: Logger
+  ): Initialize[Task[Classpath]] =
+    Def.value {
+      interDependencies(
+        projectRef,
+        deps,
+        conf,
+        conf,
+        data,
+        TrackLevel.TrackAlways,
+        true,
+        log
+      )(
+        unmanagedJars,
+        unmanagedJars,
+        unmanagedJars
+      )
+    }
+
+  def unmanagedLibs(
+      dep: ResolvedReference,
+      conf: String,
+      data: Settings[Scope]
+  ): Task[Classpath] =
+    getClasspath(unmanagedJars, dep, conf, data)
+
+  def interDependencies[A](
+      projectRef: ProjectRef,
+      deps: BuildDependencies,
+      conf: Configuration,
+      self: Configuration,
+      data: Settings[Scope],
+      track: TrackLevel,
+      includeSelf: Boolean,
+      log: Logger
+  )(
+      noTracking: TaskKey[Seq[A]],
+      trackIfMissing: TaskKey[Seq[A]],
+      trackAlways: TaskKey[Seq[A]]
+  ): Task[Seq[A]] = {
+    val interDepConfigs = interSort(projectRef, conf, data, deps) filter {
+      case (dep, c) =>
+        includeSelf || (dep != projectRef) || (conf.name != c && self.name != c)
+    }
+    val tasks = (new LinkedHashSet[Task[Seq[A]]]).asScala
+    for {
+      (dep, c) <- interDepConfigs
+    } {
+      tasks += (track match {
+        case TrackLevel.NoTracking =>
+          getClasspath(noTracking, dep, c, data)
+        case TrackLevel.TrackIfMissing =>
+          getClasspath(trackIfMissing, dep, c, data)
+        case TrackLevel.TrackAlways =>
+          getClasspath(trackAlways, dep, c, data)
+      })
+    }
+    (tasks.toSeq.join).map(_.flatten.distinct)
+  }
+
+  def analyzed[A](data: A, analysis: CompileAnalysis) =
+    Attributed.blank(data).put(Keys.analysis, analysis)
+
+  def interSort(
+      projectRef: ProjectRef,
+      conf: Configuration,
+      data: Settings[Scope],
+      deps: BuildDependencies
+  ): Seq[(ProjectRef, String)] = {
+    val visited = (new LinkedHashSet[(ProjectRef, String)]).asScala
+    def visit(p: ProjectRef, c: Configuration): Unit = {
+      val applicableConfigs = allConfigs(c)
+      for {
+        ac <- applicableConfigs
+      } // add all configurations in this project
+      visited add (p -> ac.name)
+      val masterConfs = names(getConfigurations(projectRef, data).toVector)
+
+      for {
+        ResolvedClasspathDependency(dep, confMapping) <- deps.classpath(p)
+      } {
+        val configurations = getConfigurations(dep, data)
+        val mapping =
+          mapped(confMapping, masterConfs, names(configurations.toVector), "compile", "*->compile")
+        // map master configuration 'c' and all extended configurations to the appropriate dependency configuration
+        for {
+          ac <- applicableConfigs
+          depConfName <- mapping(ac.name)
+        } {
+          for {
+            depConf <- confOpt(configurations, depConfName)
+          } if (!visited((dep, depConfName))) {
+            visit(dep, depConf)
+          }
+        }
+      }
+    }
+    visit(projectRef, conf)
+    visited.toSeq
+  }
+
+  def mapped(
+      confString: Option[String],
+      masterConfs: Seq[String],
+      depConfs: Seq[String],
+      default: String,
+      defaultMapping: String
+  ): String => Seq[String] = {
+    lazy val defaultMap = parseMapping(defaultMapping, masterConfs, depConfs, _ :: Nil)
+    parseMapping(confString getOrElse default, masterConfs, depConfs, defaultMap)
+  }
+
+  def parseMapping(
+      confString: String,
+      masterConfs: Seq[String],
+      depConfs: Seq[String],
+      default: String => Seq[String]
+  ): String => Seq[String] =
+    union(confString.split(";") map parseSingleMapping(masterConfs, depConfs, default))
+
+  def parseSingleMapping(
+      masterConfs: Seq[String],
+      depConfs: Seq[String],
+      default: String => Seq[String]
+  )(confString: String): String => Seq[String] = {
+    val ms: Seq[(String, Seq[String])] =
+      trim(confString.split("->", 2)) match {
+        case x :: Nil => for (a <- parseList(x, masterConfs)) yield (a, default(a))
+        case x :: y :: Nil =>
+          val target = parseList(y, depConfs);
+          for (a <- parseList(x, masterConfs)) yield (a, target)
+        case _ => sys.error("Invalid configuration '" + confString + "'") // shouldn't get here
+      }
+    val m = ms.toMap
+    s => m.getOrElse(s, Nil)
+  }
+
+  def union[A, B](maps: Seq[A => Seq[B]]): A => Seq[B] =
+    a => maps.foldLeft(Seq[B]()) { _ ++ _(a) } distinct;
+
+  def parseList(s: String, allConfs: Seq[String]): Seq[String] =
+    (trim(s split ",") flatMap replaceWildcard(allConfs)).distinct
+
+  def replaceWildcard(allConfs: Seq[String])(conf: String): Seq[String] = conf match {
+    case ""  => Nil
+    case "*" => allConfs
+    case _   => conf :: Nil
+  }
+
+  private def trim(a: Array[String]): List[String] = a.toList.map(_.trim)
+
+  def allConfigs(conf: Configuration): Seq[Configuration] =
+    Dag.topologicalSort(conf)(_.extendsConfigs)
+
+  def getConfigurations(p: ResolvedReference, data: Settings[Scope]): Seq[Configuration] =
+    (p / ivyConfigurations).get(data).getOrElse(Nil)
+
+  def confOpt(configurations: Seq[Configuration], conf: String): Option[Configuration] =
+    configurations.find(_.name == conf)
+
+  def getClasspath[A](
+      key: TaskKey[Seq[A]],
+      dep: ResolvedReference,
+      conf: Configuration,
+      data: Settings[Scope]
+  ): Task[Seq[A]] = getClasspath(key, dep, conf.name, data)
+
+  def getClasspath[A](
+      key: TaskKey[Seq[A]],
+      dep: ResolvedReference,
+      conf: String,
+      data: Settings[Scope]
+  ): Task[Seq[A]] =
+    (dep / ConfigKey(conf) / key).get(data) match {
+      case Some(x) => x
+      case _       => constant(Nil)
+    }
+
+}
diff --git a/main/src/main/scala/sbt/internal/CommandExchange.scala b/main/src/main/scala/sbt/internal/CommandExchange.scala
index d4c6bbf27..3a5eaea79 100644
--- a/main/src/main/scala/sbt/internal/CommandExchange.scala
+++ b/main/src/main/scala/sbt/internal/CommandExchange.scala
@@ -170,17 +170,15 @@ private[sbt] final class CommandExchange {
     currentExec.filter(_.source.map(_.channelName) == Some(c.name)).foreach { e =>
       Util.ignoreResult(NetworkChannel.cancel(e.execId, e.execId.getOrElse("0")))
     }
-    if (ContinuousCommands.isInWatch(c)) {
-      try commandQueue.put(Exec(s"${ContinuousCommands.stopWatch} ${c.name}", None))
-      catch { case _: InterruptedException => }
-    }
+    try commandQueue.put(Exec(s"${ContinuousCommands.stopWatch} ${c.name}", None))
+    catch { case _: InterruptedException => }
   }
 
   private[this] def mkAskUser(
       name: String,
   ): (State, CommandChannel) => UITask = { (state, channel) =>
     ContinuousCommands
-      .watchUITaskFor(channel)
+      .watchUITaskFor(state, channel)
       .getOrElse(new UITask.AskUserTask(state, channel))
   }
 
@@ -353,8 +351,8 @@ private[sbt] final class CommandExchange {
   def prompt(event: ConsolePromptEvent): Unit = {
     currentExecRef.set(null)
     channels.foreach {
-      case c if ContinuousCommands.isInWatch(c) =>
-      case c                                    => c.prompt(event)
+      case c if ContinuousCommands.isInWatch(lastState.get, c) =>
+      case c                                                   => c.prompt(event)
     }
   }
   def unprompt(event: ConsoleUnpromptEvent): Unit = channels.foreach(_.unprompt(event))
@@ -459,10 +457,9 @@ private[sbt] final class CommandExchange {
                 Option(currentExecRef.get).foreach(cancel)
                 mt.channel.prompt(ConsolePromptEvent(lastState.get))
               case t if t.startsWith(ContinuousCommands.stopWatch) =>
-                ContinuousCommands.stopWatchImpl(mt.channel.name)
                 mt.channel match {
                   case c: NetworkChannel if !c.isInteractive => exit(mt)
-                  case _                                     => mt.channel.prompt(ConsolePromptEvent(lastState.get))
+                  case _                                     =>
                 }
                 commandQueue.add(Exec(t, None, None))
               case `TerminateAction` => exit(mt)
diff --git a/main/src/main/scala/sbt/internal/Continuous.scala b/main/src/main/scala/sbt/internal/Continuous.scala
index 86618ceb2..cd6682433 100644
--- a/main/src/main/scala/sbt/internal/Continuous.scala
+++ b/main/src/main/scala/sbt/internal/Continuous.scala
@@ -108,8 +108,8 @@ private[sbt] object Continuous extends DeprecatedContinuous {
           case Some(c) => s -> c
           case None    => StandardMain.exchange.run(s) -> ConsoleChannel.defaultName
         }
-        ContinuousCommands.setupWatchState(channel, initialCount, commands, s1)
-        s"${ContinuousCommands.runWatch} $channel" :: s1
+        val ws = ContinuousCommands.setupWatchState(channel, initialCount, commands, s1)
+        s"${ContinuousCommands.runWatch} $channel" :: ws
     }
 
   @deprecated("The input task version of watch is no longer available", "1.4.0")
@@ -1056,7 +1056,7 @@ private[sbt] object Continuous extends DeprecatedContinuous {
       val commands: Seq[String],
       beforeCommandImpl: (State, mutable.Set[DynamicInput]) => State,
       val afterCommand: State => State,
-      val afterWatch: () => Unit,
+      val afterWatch: State => State,
       val callbacks: Callbacks,
       val dynamicInputs: mutable.Set[DynamicInput],
       val pending: Boolean,
@@ -1102,7 +1102,8 @@ private[sbt] object ContinuousCommands {
       "",
       Int.MaxValue
     )
-  private[this] val watchStates = new ConcurrentHashMap[String, ContinuousState]
+  private[this] val watchStates =
+    AttributeKey[Map[String, ContinuousState]]("sbt-watch-states", Int.MaxValue)
   private[sbt] val runWatch = networkExecPrefix + "runWatch"
   private[sbt] val preWatch = networkExecPrefix + "preWatch"
   private[sbt] val postWatch = networkExecPrefix + "postWatch"
@@ -1120,10 +1121,10 @@ private[sbt] object ContinuousCommands {
     "",
     Int.MaxValue
   )
-  private[sbt] val setupWatchState: (String, Int, Seq[String], State) => Unit =
+  private[sbt] val setupWatchState: (String, Int, Seq[String], State) => State =
     (channelName, count, commands, state) => {
-      watchStates.get(channelName) match {
-        case null =>
+      state.get(watchStates).flatMap(_.get(channelName)) match {
+        case None =>
           val extracted = Project.extract(state)
           val repo = state.get(globalFileTreeRepository) match {
             case Some(r) => localRepo(r)
@@ -1161,27 +1162,37 @@ private[sbt] object ContinuousCommands {
               stateWithCache.put(Continuous.DynamicInputs, dynamicInputs)
             },
             afterCommand = state => {
-              watchStates.get(channelName) match {
-                case null =>
-                case ws   => watchStates.put(channelName, ws.incremented)
+              val newWatchState = state.get(watchStates) match {
+                case None => state
+                case Some(ws) =>
+                  ws.get(channelName) match {
+                    case None     => state
+                    case Some(cs) => state.put(watchStates, ws + (channelName -> cs.incremented))
+                  }
               }
-              val restoredState = state.get(stashedRepo) match {
+              val restoredState = newWatchState.get(stashedRepo) match {
                 case None    => throw new IllegalStateException(s"No stashed repository for $state")
-                case Some(r) => state.put(globalFileTreeRepository, r)
+                case Some(r) => newWatchState.put(globalFileTreeRepository, r)
               }
               restoredState.remove(persistentFileStampCache).remove(Continuous.DynamicInputs)
             },
-            afterWatch = () => {
-              watchStates.remove(channelName)
+            afterWatch = state => {
               LogExchange.unbindLoggerAppenders(channelName + "-watch")
               repo.close()
+              state.get(watchStates) match {
+                case None     => state
+                case Some(ws) => state.put(watchStates, ws - channelName)
+              }
             },
             callbacks = cb,
             dynamicInputs = dynamicInputs,
             pending = false,
           )
-          Util.ignoreResult(watchStates.put(channelName, s))
-        case cs =>
+          state.get(watchStates) match {
+            case None     => state.put(watchStates, Map(channelName -> s))
+            case Some(ws) => state.put(watchStates, ws + (channelName -> s))
+          }
+        case Some(cs) =>
           val cmd = cs.commands.mkString("; ")
           val msg =
             s"Tried to start new watch while channel, '$channelName', was already watching '$cmd'"
@@ -1194,28 +1205,26 @@ private[sbt] object ContinuousCommands {
     Command.arb { state =>
       (cmdParser(name) ~> channelParser).map(channel => () => updateState(channel, state))
     } { case (_, newState) => newState() }
-  private[this] val runWatchCommand = watchCommand(runWatch) { (channel, state) =>
-    watchStates.get(channel) match {
-      case null => state
-      case cs =>
+  private[sbt] val runWatchCommand = watchCommand(runWatch) { (channel, state) =>
+    state.get(watchStates).flatMap(_.get(channel)) match {
+      case None => state
+      case Some(cs) =>
         val pre = StashOnFailure :: s"$SetTerminal $channel" :: s"$preWatch $channel" :: Nil
         val post = FailureWall :: PopOnFailure :: s"$SetTerminal ${ConsoleChannel.defaultName}" ::
-          s"$postWatch $channel" :: waitWatch :: Nil
+          s"$postWatch $channel" :: s"$waitWatch $channel" :: Nil
         pre ::: cs.commands.toList ::: post ::: state
     }
   }
-  private[sbt] def watchUITaskFor(channel: CommandChannel): Option[UITask] =
-    watchStates.get(channel.name) match {
-      case null => None
-      case cs   => Some(new WatchUITask(channel, cs))
-    }
-  private[sbt] def isInWatch(channel: CommandChannel): Boolean =
-    watchStates.get(channel.name) != null
-  private[sbt] def isPending(channel: CommandChannel): Boolean =
-    Option(watchStates.get(channel.name)).fold(false)(_.pending)
+  private[sbt] def watchUITaskFor(state: State, channel: CommandChannel): Option[UITask] =
+    state.get(watchStates).flatMap(_.get(channel.name)).map(new WatchUITask(channel, _, state))
+  private[sbt] def isInWatch(state: State, channel: CommandChannel): Boolean =
+    state.get(watchStates).exists(_.contains(channel.name))
+  private[sbt] def isPending(state: State, channel: CommandChannel): Boolean =
+    state.get(watchStates).exists(_.get(channel.name).exists(_.pending))
   private[this] class WatchUITask(
       override private[sbt] val channel: CommandChannel,
       cs: ContinuousState,
+      state: State
   ) extends Thread(s"sbt-${channel.name}-watch-ui-thread")
       with UITask {
     override private[sbt] def reader: UITask.Reader = () => {
@@ -1229,8 +1238,12 @@ private[sbt] object ContinuousCommands {
           recursive = false
         )
       }
-      val ws = watchState(channel.name)
-      watchStates.put(channel.name, ws.withPending(true))
+      val ws = state.get(watchStates) match {
+        case None => throw new IllegalStateException("no watch states")
+        case Some(ws) =>
+          ws.get(channel.name)
+            .getOrElse(throw new IllegalStateException(s"no watch state for ${channel.name}"))
+      }
       exitAction match {
         // Use a Left so that the client can immediately exit watch via <enter>
         case Watch.CancelWatch => Left(s"$stopWatch ${channel.name}")
@@ -1248,33 +1261,43 @@ private[sbt] object ContinuousCommands {
     }
   }
   @inline
-  private[this] def watchState(channel: String): ContinuousState = watchStates.get(channel) match {
-    case null => throw new IllegalStateException(s"No watch state for $channel")
-    case s    => s
-  }
+  private[this] def watchState(state: State, channel: String): ContinuousState =
+    state.get(watchStates).flatMap(_.get(channel)) match {
+      case None    => throw new IllegalStateException(s"no watch state for $channel")
+      case Some(s) => s
+    }
 
-  private[this] val preWatchCommand = watchCommand(preWatch) { (channel, state) =>
-    StandardMain.exchange.channelForName(channel).foreach(_.terminal.setPrompt(Prompt.Watch))
-    watchState(channel).beforeCommand(state)
+  private[sbt] val preWatchCommand = watchCommand(preWatch) { (channel, state) =>
+    watchState(state, channel).beforeCommand(state)
   }
-  private[this] val postWatchCommand = watchCommand(postWatch) { (channel, state) =>
-    StandardMain.exchange.unprompt(ConsoleUnpromptEvent(Some(CommandSource(channel))))
-    val ws = watchState(channel)
-    watchStates.put(channel, ws.withPending(false))
-    ws.afterCommand(state)
+  private[sbt] val postWatchCommand = watchCommand(postWatch) { (channel, state) =>
+    val cs = watchState(state, channel)
+    StandardMain.exchange.channelForName(channel).foreach { c =>
+      c.terminal.setPrompt(Prompt.Watch)
+      c.unprompt(ConsoleUnpromptEvent(Some(CommandSource(channel))))
+    }
+    val postState = state.get(watchStates) match {
+      case None     => state
+      case Some(ws) => state.put(watchStates, ws + (channel -> cs.withPending(false)))
+    }
+    cs.afterCommand(postState)
   }
-  private[this] val stopWatchCommand = watchCommand(stopWatch) { (channel, state) =>
-    stopWatchImpl(channel)
-    state
-  }
-  private[sbt] def stopWatchImpl(channelName: String): Unit = {
-    StandardMain.exchange.unprompt(ConsoleUnpromptEvent(Some(CommandSource(channelName))))
-    Option(watchStates.get(channelName)).foreach { ws =>
-      ws.afterWatch()
-      ws.callbacks.onExit()
+  private[sbt] val stopWatchCommand = watchCommand(stopWatch) { (channel, state) =>
+    state.get(watchStates).flatMap(_.get(channel)) match {
+      case Some(cs) =>
+        val afterWatchState = cs.afterWatch(state)
+        cs.callbacks.onExit()
+        StandardMain.exchange
+          .channelForName(channel)
+          .foreach(_.unprompt(ConsoleUnpromptEvent(Some(CommandSource(channel)))))
+        afterWatchState.get(watchStates) match {
+          case None    => afterWatchState
+          case Some(w) => afterWatchState.put(watchStates, w - channel)
+        }
+      case _ => state
     }
   }
-  private[this] val failWatchCommand = watchCommand(failWatch) { (channel, state) =>
+  private[sbt] val failWatchCommand = watchCommand(failWatch) { (channel, state) =>
     state.fail
   }
   /*
diff --git a/main/src/main/scala/sbt/internal/FastTrackCommands.scala b/main/src/main/scala/sbt/internal/FastTrackCommands.scala
new file mode 100644
index 000000000..8c53f81de
--- /dev/null
+++ b/main/src/main/scala/sbt/internal/FastTrackCommands.scala
@@ -0,0 +1,53 @@
+/*
+ * sbt
+ * Copyright 2011 - 2018, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt
+package internal
+
+import BasicCommandStrings._
+import BasicCommands._
+import BuiltinCommands.{ setTerminalCommand, shell, waitCmd }
+import ContinuousCommands._
+
+import sbt.internal.util.complete.Parser
+
+/** This is used to speed up command parsing. */
+private[sbt] object FastTrackCommands {
+  private def fromCommand(
+      cmd: String,
+      command: Command,
+      arguments: Boolean = true,
+  ): (State, String) => Option[State] =
+    (s, c) =>
+      Parser.parse(if (arguments) c else "", command.parser(s)) match {
+        case Right(newState) => Some(newState())
+        case l               => None
+      }
+  private val commands = Map[String, (State, String) => Option[State]](
+    FailureWall -> { case (s, c) => if (c == FailureWall) Some(s) else None },
+    StashOnFailure -> fromCommand(StashOnFailure, stashOnFailure, arguments = false),
+    PopOnFailure -> fromCommand(PopOnFailure, popOnFailure, arguments = false),
+    Shell -> fromCommand(Shell, shell),
+    SetTerminal -> fromCommand(SetTerminal, setTerminalCommand),
+    failWatch -> fromCommand(failWatch, failWatchCommand),
+    preWatch -> fromCommand(preWatch, preWatchCommand),
+    postWatch -> fromCommand(postWatch, postWatchCommand),
+    runWatch -> fromCommand(runWatch, runWatchCommand),
+    stopWatch -> fromCommand(stopWatch, stopWatchCommand),
+    waitWatch -> fromCommand(waitWatch, waitCmd),
+  )
+  private[sbt] def evaluate(state: State, cmd: String): Option[State] = {
+    cmd.trim.split(" ") match {
+      case Array(h, _*) =>
+        commands.get(h) match {
+          case Some(command) => command(state, cmd)
+          case _             => None
+        }
+      case _ => None
+    }
+  }
+}
diff --git a/main/src/main/scala/sbt/internal/SysProp.scala b/main/src/main/scala/sbt/internal/SysProp.scala
index 43ef5ec00..15c971af4 100644
--- a/main/src/main/scala/sbt/internal/SysProp.scala
+++ b/main/src/main/scala/sbt/internal/SysProp.scala
@@ -116,6 +116,7 @@ object SysProp {
   def banner: Boolean = getOrTrue("sbt.banner")
 
   def turbo: Boolean = getOrFalse("sbt.turbo")
+  def pipelining: Boolean = getOrFalse("sbt.pipelining")
 
   def taskTimings: Boolean = getOrFalse("sbt.task.timings")
   def taskTimingsOnShutdown: Boolean = getOrFalse("sbt.task.timings.on.shutdown")
diff --git a/main/src/main/scala/sbt/internal/VirtualFileValueCache.scala b/main/src/main/scala/sbt/internal/VirtualFileValueCache.scala
new file mode 100644
index 000000000..56ca6ad78
--- /dev/null
+++ b/main/src/main/scala/sbt/internal/VirtualFileValueCache.scala
@@ -0,0 +1,69 @@
+/*
+ * sbt
+ * Copyright 2011 - 2018, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt
+package internal
+
+import java.util.concurrent.ConcurrentHashMap
+import sbt.internal.inc.Stamper
+import xsbti.{ FileConverter, VirtualFile, VirtualFileRef }
+import xsbti.compile.analysis.{ Stamp => XStamp }
+
+/**
+ * Cache based on path and its stamp.
+ */
+sealed trait VirtualFileValueCache[A] {
+  def clear(): Unit
+  def get: VirtualFile => A
+}
+
+object VirtualFileValueCache {
+  def apply[A](converter: FileConverter)(f: VirtualFile => A): VirtualFileValueCache[A] = {
+    import collection.mutable.{ HashMap, Map }
+    val stampCache: Map[VirtualFileRef, (Long, XStamp)] = new HashMap
+    make(
+      Stamper.timeWrap(stampCache, converter, {
+        case (vf: VirtualFile) => Stamper.forContentHash(vf)
+      })
+    )(f)
+  }
+  def make[A](stamp: VirtualFile => XStamp)(f: VirtualFile => A): VirtualFileValueCache[A] =
+    new VirtualFileValueCache0[A](stamp, f)
+}
+
+private[this] final class VirtualFileValueCache0[A](
+    getStamp: VirtualFile => XStamp,
+    make: VirtualFile => A
+)(
+    implicit equiv: Equiv[XStamp]
+) extends VirtualFileValueCache[A] {
+  private[this] val backing = new ConcurrentHashMap[VirtualFile, VirtualFileCache]
+
+  def clear(): Unit = backing.clear()
+  def get = file => {
+    val ifAbsent = new VirtualFileCache(file)
+    val cache = backing.putIfAbsent(file, ifAbsent)
+    (if (cache eq null) ifAbsent else cache).get()
+  }
+
+  private[this] final class VirtualFileCache(file: VirtualFile) {
+    private[this] var stampedValue: Option[(XStamp, A)] = None
+    def get(): A = synchronized {
+      val latest = getStamp(file)
+      stampedValue match {
+        case Some((stamp, value)) if (equiv.equiv(latest, stamp)) => value
+        case _                                                    => update(latest)
+      }
+    }
+
+    private[this] def update(stamp: XStamp): A = {
+      val value = make(file)
+      stampedValue = Some((stamp, value))
+      value
+    }
+  }
+}
diff --git a/main/src/main/scala/sbt/internal/server/NetworkChannel.scala b/main/src/main/scala/sbt/internal/server/NetworkChannel.scala
index 4aa3c1f81..f7583f9e1 100644
--- a/main/src/main/scala/sbt/internal/server/NetworkChannel.scala
+++ b/main/src/main/scala/sbt/internal/server/NetworkChannel.scala
@@ -149,7 +149,7 @@ final class NetworkChannel(
   protected def authOptions: Set[ServerAuthentication] = auth
 
   override def mkUIThread: (State, CommandChannel) => UITask = (state, command) => {
-    if (interactive.get || ContinuousCommands.isInWatch(this)) mkUIThreadImpl(state, command)
+    if (interactive.get || ContinuousCommands.isInWatch(state, this)) mkUIThreadImpl(state, command)
     else
       new UITask {
         override private[sbt] def channel = NetworkChannel.this
@@ -653,6 +653,13 @@ final class NetworkChannel(
   import sjsonnew.BasicJsonProtocol._
 
   import scala.collection.JavaConverters._
+  private[this] val outputBuffer = new LinkedBlockingQueue[Byte]
+  private[this] val flushFuture = new AtomicReference[java.util.concurrent.Future[_]]
+  private[this] def doFlush()() = {
+    val list = new java.util.ArrayList[Byte]
+    outputBuffer.synchronized(outputBuffer.drainTo(list))
+    if (!list.isEmpty) jsonRpcNotify(Serialization.systemOut, list.asScala.toSeq)
+  }
   private[this] lazy val outputStream: OutputStream with AutoCloseable = new OutputStream
     with AutoCloseable {
     /*
@@ -670,28 +677,21 @@ final class NetworkChannel(
       Executors.newSingleThreadScheduledExecutor(
         r => new Thread(r, s"$name-output-buffer-timer-thread")
       )
-    private[this] val buffer = new LinkedBlockingQueue[Byte]
-    private[this] val future = new AtomicReference[java.util.concurrent.Future[_]]
-    private[this] def doFlush()() = {
-      val list = new java.util.ArrayList[Byte]
-      buffer.synchronized(buffer.drainTo(list))
-      if (!list.isEmpty) jsonRpcNotify(Serialization.systemOut, list.asScala.toSeq)
-    }
     override def close(): Unit = {
       Util.ignoreResult(executor.shutdownNow())
       doFlush()
     }
-    override def write(b: Int): Unit = buffer.synchronized {
-      buffer.put(b.toByte)
+    override def write(b: Int): Unit = outputBuffer.synchronized {
+      outputBuffer.put(b.toByte)
     }
     override def flush(): Unit = {
-      future.get match {
+      flushFuture.get match {
         case null =>
           try {
-            future.set(
+            flushFuture.set(
               executor.schedule(
                 (() => {
-                  future.set(null)
+                  flushFuture.set(null)
                   doFlush()
                 }): Runnable,
                 20,
@@ -702,8 +702,8 @@ final class NetworkChannel(
         case f =>
       }
     }
-    override def write(b: Array[Byte]): Unit = buffer.synchronized {
-      b.foreach(buffer.put)
+    override def write(b: Array[Byte]): Unit = outputBuffer.synchronized {
+      b.foreach(outputBuffer.put)
     }
     override def write(b: Array[Byte], off: Int, len: Int): Unit = {
       write(java.util.Arrays.copyOfRange(b, off, off + len))
@@ -789,7 +789,8 @@ final class NetworkChannel(
     override def isAnsiSupported: Boolean = getProperty(_.isAnsiSupported, false).getOrElse(false)
     override def isEchoEnabled: Boolean = waitForPending(_.isEchoEnabled)
     override def isSuccessEnabled: Boolean =
-      prompt != Prompt.Batch || ContinuousCommands.isInWatch(NetworkChannel.this)
+      prompt != Prompt.Batch ||
+        StandardMain.exchange.withState(ContinuousCommands.isInWatch(_, NetworkChannel.this))
     override lazy val isColorEnabled: Boolean = waitForPending(_.isColorEnabled)
     override lazy val isSupershellEnabled: Boolean = waitForPending(_.isSupershellEnabled)
     getProperties(false)
@@ -880,6 +881,7 @@ final class NetworkChannel(
         catch { case _: InterruptedException => }
       }
 
+    override def flush(): Unit = doFlush()
     override def toString: String = s"NetworkTerminal($name)"
     override def close(): Unit = if (closed.compareAndSet(false, true)) {
       val threads = blockedThreads.synchronized {
diff --git a/project/Dependencies.scala b/project/Dependencies.scala
index 2df70417c..2b5a340f9 100644
--- a/project/Dependencies.scala
+++ b/project/Dependencies.scala
@@ -14,7 +14,7 @@ object Dependencies {
   private val ioVersion = nightlyVersion.getOrElse("1.4.0-M6")
   private val lmVersion =
     sys.props.get("sbt.build.lm.version").orElse(nightlyVersion).getOrElse("1.4.0-M2")
-  val zincVersion = nightlyVersion.getOrElse("1.4.0-M7")
+  val zincVersion = nightlyVersion.getOrElse("1.4.0-M8")
 
   private val sbtIO = "org.scala-sbt" %% "io" % ioVersion
 
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining-java/build.sbt b/sbt/src/sbt-test/source-dependencies/pipelining-java/build.sbt
new file mode 100644
index 000000000..a5b9eef0d
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining-java/build.sbt
@@ -0,0 +1,13 @@
+ThisBuild / scalaVersion := "2.13.3"
+ThisBuild / usePipelining := true
+
+lazy val root = (project in file("."))
+  .aggregate(dep, use)
+  .settings(
+    name := "pipelining Java",
+  )
+
+lazy val dep = project
+
+lazy val use = project
+  .dependsOn(dep)
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining-java/changes/Break.java b/sbt/src/sbt-test/source-dependencies/pipelining-java/changes/Break.java
new file mode 100644
index 000000000..014567f98
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining-java/changes/Break.java
@@ -0,0 +1,2 @@
+public class Break {
+}
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining-java/dep/A.java b/sbt/src/sbt-test/source-dependencies/pipelining-java/dep/A.java
new file mode 100644
index 000000000..56fa6cd06
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining-java/dep/A.java
@@ -0,0 +1,3 @@
+public class A {
+  public static int x = 3;
+}
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining-java/test b/sbt/src/sbt-test/source-dependencies/pipelining-java/test
new file mode 100644
index 000000000..78b6178ee
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining-java/test
@@ -0,0 +1,5 @@
+> use/compile
+
+$ delete dep/A.java
+$ copy-file changes/Break.java dep/Break.java
+-> use/compile
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining-java/use/B.java b/sbt/src/sbt-test/source-dependencies/pipelining-java/use/B.java
new file mode 100644
index 000000000..60121dd8e
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining-java/use/B.java
@@ -0,0 +1,3 @@
+public class B {
+  public static int y = A.x;
+}
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining/build.sbt b/sbt/src/sbt-test/source-dependencies/pipelining/build.sbt
new file mode 100644
index 000000000..36db86700
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining/build.sbt
@@ -0,0 +1,22 @@
+ThisBuild / scalaVersion := "2.13.3"
+ThisBuild / usePipelining := true
+
+lazy val root = (project in file("."))
+  .aggregate(dep, use)
+  .settings(
+    name := "pipelining basics",
+  )
+
+lazy val dep = project
+
+lazy val use = project
+  .dependsOn(dep)
+  .settings(
+    TaskKey[Unit]("checkPickle") := {
+      val s = streams.value
+      val x = (dep / Compile / compile).value
+      val picklePath = (Compile / internalDependencyPicklePath).value
+      assert(picklePath.size == 1 &&
+        picklePath.head.data.name == "dep_2.13-0.1.0-SNAPSHOT.jar", s"picklePath = ${picklePath}")
+    },
+  )
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining/changes/Break.scala b/sbt/src/sbt-test/source-dependencies/pipelining/changes/Break.scala
new file mode 100644
index 000000000..b2dfe50e1
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining/changes/Break.scala
@@ -0,0 +1,3 @@
+package example
+
+object Break
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining/dep/A.scala b/sbt/src/sbt-test/source-dependencies/pipelining/dep/A.scala
new file mode 100644
index 000000000..2221c2ebc
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining/dep/A.scala
@@ -0,0 +1,5 @@
+package example
+
+object A {
+  val x = 3
+}
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining/test b/sbt/src/sbt-test/source-dependencies/pipelining/test
new file mode 100644
index 000000000..6b3baa1c6
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining/test
@@ -0,0 +1,9 @@
+> dep/compile
+
+> use/checkPickle
+
+> compile
+
+# making subproject dep should trigger failure
+$ copy-file changes/Break.scala dep/A.scala
+-> compile
diff --git a/sbt/src/sbt-test/source-dependencies/pipelining/use/B.scala b/sbt/src/sbt-test/source-dependencies/pipelining/use/B.scala
new file mode 100644
index 000000000..f8ec39178
--- /dev/null
+++ b/sbt/src/sbt-test/source-dependencies/pipelining/use/B.scala
@@ -0,0 +1,5 @@
+package example
+
+object B {
+  val y = A.x
+}
diff --git a/sbt/src/sbt-test/watch/legacy-sources/build.sbt b/sbt/src/sbt-test/watch/legacy-sources/build.sbt
index 3ee3097d9..9c20c4496 100644
--- a/sbt/src/sbt-test/watch/legacy-sources/build.sbt
+++ b/sbt/src/sbt-test/watch/legacy-sources/build.sbt
@@ -1,7 +1,17 @@
-import sbt.legacy.sources.Build._
-
 Global / watchSources += new sbt.internal.io.Source(baseDirectory.value, "global.txt", NothingFilter, false)
 
+val setStringValue = inputKey[Unit]("set a global string to a value")
+val checkStringValue = inputKey[Unit]("check the value of a global")
+
+def setStringValueImpl: Def.Initialize[InputTask[Unit]] = Def.inputTask {
+  val Seq(stringFile, string) = Def.spaceDelimited().parsed.map(_.trim)
+  IO.write(file(stringFile), string)
+}
+def checkStringValueImpl: Def.Initialize[InputTask[Unit]] = Def.inputTask {
+  val Seq(stringFile, string) = Def.spaceDelimited().parsed
+  assert(IO.read(file(stringFile)) == string)
+}
+
 watchSources in setStringValue += new sbt.internal.io.Source(baseDirectory.value, "foo.txt", NothingFilter, false)
 
 setStringValue := setStringValueImpl.evaluated
diff --git a/sbt/src/sbt-test/watch/legacy-sources/project/Build.scala b/sbt/src/sbt-test/watch/legacy-sources/project/Build.scala
deleted file mode 100644
index 17643092a..000000000
--- a/sbt/src/sbt-test/watch/legacy-sources/project/Build.scala
+++ /dev/null
@@ -1,17 +0,0 @@
-package sbt.legacy.sources
-
-import sbt._
-import Keys._
-
-object Build {
-  val setStringValue = inputKey[Unit]("set a global string to a value")
-  val checkStringValue = inputKey[Unit]("check the value of a global")
-  def setStringValueImpl: Def.Initialize[InputTask[Unit]] = Def.inputTask {
-    val Seq(stringFile, string) = Def.spaceDelimited().parsed.map(_.trim)
-    IO.write(file(stringFile), string)
-  }
-  def checkStringValueImpl: Def.Initialize[InputTask[Unit]] = Def.inputTask {
-    val Seq(stringFile, string) = Def.spaceDelimited().parsed
-    assert(IO.read(file(stringFile)) == string)
-  }
-}
\ No newline at end of file
diff --git a/server-test/src/test/scala/testpkg/ClientTest.scala b/server-test/src/test/scala/testpkg/ClientTest.scala
index 145f12e0f..bdb71b513 100644
--- a/server-test/src/test/scala/testpkg/ClientTest.scala
+++ b/server-test/src/test/scala/testpkg/ClientTest.scala
@@ -93,11 +93,17 @@ object ClientTest extends AbstractServerTest {
       "compileAnalysisFile",
       "compileAnalysisFilename",
       "compileAnalysisTargetRoot",
+      "compileEarly",
       "compileIncSetup",
       "compileIncremental",
+      "compileJava",
       "compileOutputs",
+      "compileProgress",
+      "compileScalaBackend",
+      "compileSplit",
       "compilers",
     )
+
     assert(complete("compi") == expected)
   }
   test("testOnly completions") { _ =>
diff --git a/server-test/src/test/scala/testpkg/EventsTest.scala b/server-test/src/test/scala/testpkg/EventsTest.scala
index 9e5f30424..e3ae360b4 100644
--- a/server-test/src/test/scala/testpkg/EventsTest.scala
+++ b/server-test/src/test/scala/testpkg/EventsTest.scala
@@ -66,7 +66,7 @@ object EventsTest extends AbstractServerTest {
     })
   }
 
-/* This test is timing out.
+  /* This test is timing out.
   test("cancel on-going task with string id") { _ =>
     import sbt.Exec
     val id = Exec.newExecId
@@ -84,5 +84,5 @@ object EventsTest extends AbstractServerTest {
       s contains """"result":{"status":"Task cancelled""""
     })
   }
-*/
+ */
 }