diff --git a/.drone.yml b/.drone.yml
index 839cbb9a1aae..35a4b6177b49 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -27,7 +27,7 @@ steps:
 
 - name: test
   pull: default
-  image: lampepfl/dotty:2019-10-17
+  image: lampepfl/dotty:2020-01-09
   depends_on: [ clone ]
   commands:
   - cp -R . /tmp/1/ && cd /tmp/1/
@@ -36,16 +36,16 @@ steps:
 
 - name: test_bootstrapped
   pull: default
-  image: lampepfl/dotty:2019-10-17
+  image: lampepfl/dotty:2020-01-09
   depends_on: [ clone ]
   commands:
   - cp -R . /tmp/2/ && cd /tmp/2/
-  - ./project/scripts/sbt ";dotty-bootstrapped/compile ;dotty-bootstrapped/test ;dotty-staging/test ;sjsSandbox/run;sjsSandbox/test;sjsJUnitTests/test"
+  - ./project/scripts/sbt ";dotty-bootstrapped/compile ;dotty-bootstrapped/test ;dotty-staging/test ;sjsSandbox/run;sjsSandbox/test;sjsJUnitTests/test ;configureIDE"
   - ./project/scripts/bootstrapCmdTests
 
 - name: community_build
   pull: default
-  image: lampepfl/dotty:2019-10-17
+  image: lampepfl/dotty:2020-01-09
   depends_on: [ clone ]
   commands:
   - cp -R . /tmp/3/ && cd /tmp/3/
@@ -55,7 +55,7 @@ steps:
 
 - name: test_sbt
   pull: default
-  image: lampepfl/dotty:2019-10-17
+  image: lampepfl/dotty:2020-01-09
   depends_on: [ clone ]
   commands:
   - cp -R . /tmp/4/ && cd /tmp/4/
@@ -67,7 +67,7 @@ steps:
 
 - name: test_java11
   pull: default
-  image: lampepfl/dotty:2019-10-17
+  image: lampepfl/dotty:2020-01-09
   depends_on: [ clone ]
   commands:
   - export PATH="/usr/lib/jvm/java-11-openjdk-amd64/bin:$PATH"
@@ -80,7 +80,7 @@ steps:
 
 - name: documentation
   pull: default
-  image: lampepfl/dotty:2019-10-17
+  image: lampepfl/dotty:2020-01-09
   depends_on:
   - test
   - test_bootstrapped
@@ -99,7 +99,7 @@ steps:
 
 - name: publish_nightly
   pull: default
-  image: lampepfl/dotty:2019-10-17
+  image: lampepfl/dotty:2020-01-09
   depends_on:
   - test
   - test_bootstrapped
@@ -126,7 +126,7 @@ steps:
 
 - name: publish_release
   pull: default
-  image: lampepfl/dotty:2019-10-17
+  image: lampepfl/dotty:2020-01-09
   depends_on:
   - test
   - test_bootstrapped
@@ -169,7 +169,7 @@ steps:
 
 - name: publish_sbt_release
   pull: default
-  image: lampepfl/dotty:2019-10-17
+  image: lampepfl/dotty:2020-01-09
   depends_on:
   - test
   - test_bootstrapped
diff --git a/community-build/community-projects/scalap b/community-build/community-projects/scalap
index fe6239e99c07..a20c669b8f26 160000
--- a/community-build/community-projects/scalap
+++ b/community-build/community-projects/scalap
@@ -1 +1 @@
-Subproject commit fe6239e99c07bf838e57fe0dc9930208a5486ad3
+Subproject commit a20c669b8f264a7b08cfccd875049420007deada
diff --git a/community-build/community-projects/semanticdb b/community-build/community-projects/semanticdb
index 05b8001beade..168b1f6881dd 160000
--- a/community-build/community-projects/semanticdb
+++ b/community-build/community-projects/semanticdb
@@ -1 +1 @@
-Subproject commit 05b8001beade3492f7eb8ab9425dd7454f66fe4b
+Subproject commit 168b1f6881dd2f79025ae3db61bf7f56120c369b
diff --git a/community-build/community-projects/stdLib213 b/community-build/community-projects/stdLib213
index ec4624b48262..1886950613d8 160000
--- a/community-build/community-projects/stdLib213
+++ b/community-build/community-projects/stdLib213
@@ -1 +1 @@
-Subproject commit ec4624b482626020e154d2e6161ef5f5f38f166c
+Subproject commit 1886950613d85af824435b2c072e9eedb12d6851
diff --git a/community-build/project/build.properties b/community-build/project/build.properties
deleted file mode 100644
index 72f902892a13..000000000000
--- a/community-build/project/build.properties
+++ /dev/null
@@ -1 +0,0 @@
-sbt.version=1.2.7
diff --git a/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala b/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala
index 1c2c8aba7321..d03ebc905e15 100644
--- a/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala
+++ b/community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala
@@ -100,7 +100,7 @@ final case class SbtCommunityProject(project: String, sbtTestCommand: String,
       case Some(ivyHome) => List(s"-Dsbt.ivy.home=$ivyHome")
       case _ => Nil
     extraSbtArgs ++ sbtProps ++ List(
-      "-sbt-version", "1.2.7",
+      "-sbt-version", "1.3.6",
       s"--addPluginSbtFile=$sbtPluginFilePath")
 
 object projects
diff --git a/compiler/test/dotty/tools/dotc/CompilationTests.scala b/compiler/test/dotty/tools/dotc/CompilationTests.scala
index 8e5cf657a624..246a7331106b 100644
--- a/compiler/test/dotty/tools/dotc/CompilationTests.scala
+++ b/compiler/test/dotty/tools/dotc/CompilationTests.scala
@@ -7,6 +7,7 @@ import org.junit.Assert._
 import org.junit.Assume._
 import org.junit.experimental.categories.Category
 
+import java.io.File
 import java.nio.file._
 import java.util.stream.{ Stream => JStream }
 import scala.collection.JavaConverters._
@@ -197,24 +198,26 @@ class CompilationTests extends ParallelTesting {
    */
   @Test def tastyBootstrap: Unit = {
     implicit val testGroup: TestGroup = TestGroup("tastyBootstrap/tests")
+    val libGroup = TestGroup("tastyBootstrap/lib")
+    val tastyCoreGroup = TestGroup("tastyBootstrap/tastyCore")
     val dotty1Group = TestGroup("tastyBootstrap/dotty1")
     val dotty2Group = TestGroup("tastyBootstrap/dotty2")
-    val libGroup = TestGroup("tastyBootstrap/lib")
 
     // Make sure that the directory is clean
     dotty.tools.io.Directory(defaultOutputDir + "tastyBootstrap").deleteRecursively()
 
-    val sep = java.io.File.pathSeparator
-
     val opt = TestFlags(
-      // compile with bootstrapped library on cp:
-      defaultOutputDir + libGroup + "/src/" + sep +
-      // as well as bootstrapped compiler:
-      defaultOutputDir + dotty1Group + "/dotty/" + sep +
-      // and the other compiler dependenies:
-      Properties.compilerInterface + sep + Properties.scalaLibrary + sep + Properties.scalaAsm + sep +
-      Properties.dottyInterfaces + sep + Properties.tastyCore + sep + Properties.jlineTerminal + sep +
-      Properties.jlineReader,
+      List(
+        // compile with bootstrapped library on cp:
+        defaultOutputDir + libGroup + "/lib/",
+        // and bootstrapped tasty-core:
+        defaultOutputDir + tastyCoreGroup + "/tastyCore/",
+        // as well as bootstrapped compiler:
+        defaultOutputDir + dotty1Group + "/dotty1/",
+        // and the other compiler dependencies:
+        Properties.compilerInterface, Properties.scalaLibrary, Properties.scalaAsm,
+        Properties.dottyInterfaces, Properties.jlineTerminal, Properties.jlineReader,
+      ).mkString(File.pathSeparator),
       Array("-Ycheck-reentrant", "-Yemit-tasty-in-class")
     )
 
@@ -222,20 +225,23 @@ class CompilationTests extends ParallelTesting {
     val librarySources = libraryDirs.flatMap(sources(_))
 
     val lib =
-      compileList("src", librarySources,
+      compileList("lib", librarySources,
         defaultOptions.and("-Ycheck-reentrant",
           "-Yerased-terms", // support declaration of scala.compiletime.erasedValue
           //  "-strict",  // TODO: re-enable once we allow : @unchecked in pattern definitions. Right now, lots of narrowing pattern definitions fail.
           "-priorityclasspath", defaultOutputDir))(libGroup)
 
+    val tastyCoreSources = sources(Paths.get("tasty/src"))
+    val tastyCore = compileList("tastyCore", tastyCoreSources, opt)(tastyCoreGroup)
+
     val compilerSources = sources(Paths.get("compiler/src"))
     val compilerManagedSources = sources(Properties.dottyCompilerManagedSources)
 
-    val dotty1 = compileList("dotty", compilerSources ++ compilerManagedSources, opt)(dotty1Group)
-    val dotty2 = compileList("dotty", compilerSources ++ compilerManagedSources, opt)(dotty2Group)
+    val dotty1 = compileList("dotty1", compilerSources ++ compilerManagedSources, opt)(dotty1Group)
+    val dotty2 = compileList("dotty2", compilerSources ++ compilerManagedSources, opt)(dotty2Group)
 
     val tests = {
-      lib.keepOutput :: dotty1.keepOutput :: aggregateTests(
+      lib.keepOutput :: tastyCore.keepOutput :: dotty1.keepOutput :: aggregateTests(
         dotty2,
         compileShallowFilesInDir("compiler/src/dotty/tools", opt),
         compileShallowFilesInDir("compiler/src/dotty/tools/dotc", opt),
@@ -255,9 +261,10 @@ class CompilationTests extends ParallelTesting {
     }.map(_.checkCompile())
 
     def assertExists(path: String) = assertTrue(Files.exists(Paths.get(path)))
-    assertExists(s"out/$dotty1Group/dotty/")
-    assertExists(s"out/$dotty2Group/dotty/")
-    assertExists(s"out/$libGroup/src/")
+    assertExists(s"out/$libGroup/lib/")
+    assertExists(s"out/$tastyCoreGroup/tastyCore/")
+    assertExists(s"out/$dotty1Group/dotty1/")
+    assertExists(s"out/$dotty2Group/dotty2/")
     compileList("idempotency", List("tests/idempotency/BootstrapChecker.scala", "tests/idempotency/IdempotencyCheck.scala"), defaultOptions).checkRuns()
 
     tests.foreach(_.delete())
diff --git a/project/Build.scala b/project/Build.scala
index 43c8ea9b47c1..f73866848728 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -54,14 +54,18 @@ object MyScalaJSPlugin extends AutoPlugin {
 
     // Typecheck the Scala.js IR found on the classpath
     scalaJSLinkerConfig ~= (_.withCheckIR(true)),
+
+    // Exclude all these projects from `configureIDE/launchIDE` since they
+    // take time to compile, print a bunch of warnings, and are rarely edited.
+    excludeFromIDE := true
   )
 }
 
 object Build {
-  val referenceVersion = "0.21.0-RC1"
+  val referenceVersion = "0.22.0-bin-20200114-193f7de-NIGHTLY"
 
   val baseVersion = "0.22.0"
-  val baseSbtDottyVersion = "0.3.5"
+  val baseSbtDottyVersion = "0.4.0"
 
   // Versions used by the vscode extension to create a new project
   // This should be the latest published releases.
@@ -192,6 +196,11 @@ object Build {
       state
     },
 
+    // Turn off the sbt supershell because it can mangle the output of some tasks
+    // (see https://github.com/sbt/sbt/issues/5122, https://github.com/sbt/sbt/issues/5352)
+    // and in general I find it more distracting than helpful anyway.
+    useSuperShell := false,
+
     // Credentials to release to Sonatype
     credentials ++= (
       for {
@@ -730,16 +739,18 @@ object Build {
     case Bootstrapped => `dotty-compiler-bootstrapped`
   }
 
-  // Settings shared between dotty-library and dotty-library-bootstrapped
+  // Settings shared between dotty-library, dotty-library-bootstrapped and dotty-library-bootstrappedJS
   lazy val dottyLibrarySettings = Seq(
-    // Needed so that the library sources are visible when `dotty.tools.dotc.core.Definitions#init` is called
-    scalacOptions in Compile ++= Seq("-sourcepath", (sourceDirectories in Compile).value.map(_.getAbsolutePath).distinct.mkString(File.pathSeparator)),
+    scalacOptions in Compile ++= Seq(
+      // Needed so that the library sources are visible when `dotty.tools.dotc.core.Definitions#init` is called
+      "-sourcepath", (sourceDirectories in Compile).value.map(_.getAbsolutePath).distinct.mkString(File.pathSeparator),
+     // support declaration of scala.compiletime.erasedValue
+      "-Yerased-terms"
+    ),
   )
 
   lazy val `dotty-library` = project.in(file("library")).asDottyLibrary(NonBootstrapped)
   lazy val `dotty-library-bootstrapped`: Project = project.in(file("library")).asDottyLibrary(Bootstrapped)
-    // TODO: move -Yerased-terms to dottyLibrarySettings on reference compiler update
-    .settings(scalacOptions in Compile += "-Yerased-terms") // support declaration of scala.compiletime.erasedValue
 
   def dottyLibrary(implicit mode: Mode): Project = mode match {
     case NonBootstrapped => `dotty-library`
@@ -761,7 +772,6 @@ object Build {
     settings(
       unmanagedSourceDirectories in Compile :=
         (unmanagedSourceDirectories in (`dotty-library-bootstrapped`, Compile)).value,
-      scalacOptions += "-Yerased-terms", // support declaration of scala.compiletime.erasedValue
     )
 
   lazy val tastyCoreSettings = Seq(
@@ -1109,8 +1119,6 @@ object Build {
       version := "0.1.17-snapshot", // Keep in sync with package.json
       autoScalaLibrary := false,
       publishArtifact := false,
-      includeFilter in unmanagedSources := NothingFilter | "*.ts" | "**.json",
-      watchSources in Global ++= (unmanagedSources in Compile).value,
       resourceGenerators in Compile += Def.task {
         // Resources that will be copied when bootstrapping a new project
         val buildSbtFile = baseDirectory.value / "out" / "build.sbt"
diff --git a/project/build.properties b/project/build.properties
index 72f902892a13..00b48d978b25 100644
--- a/project/build.properties
+++ b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.2.7
+sbt.version=1.3.6
diff --git a/sbt-dotty/sbt-test/sbt-dotty/i7897/build.sbt b/sbt-dotty/sbt-test/sbt-dotty/i7897/build.sbt
new file mode 100644
index 000000000000..0f1833c230ab
--- /dev/null
+++ b/sbt-dotty/sbt-test/sbt-dotty/i7897/build.sbt
@@ -0,0 +1,5 @@
+scalaVersion := sys.props("plugin.scalaVersion")
+
+libraryDependencies += "ch.epfl.lamp" %% "dotty-staging" % scalaVersion.value
+
+fork := true
diff --git a/sbt-dotty/sbt-test/sbt-dotty/i7897/changes/build-no-fork.sbt b/sbt-dotty/sbt-test/sbt-dotty/i7897/changes/build-no-fork.sbt
new file mode 100644
index 000000000000..802dff0748fe
--- /dev/null
+++ b/sbt-dotty/sbt-test/sbt-dotty/i7897/changes/build-no-fork.sbt
@@ -0,0 +1,5 @@
+scalaVersion := sys.props("plugin.scalaVersion")
+
+libraryDependencies += "ch.epfl.lamp" %% "dotty-staging" % scalaVersion.value
+
+fork := false
diff --git a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/project/plugins.sbt b/sbt-dotty/sbt-test/sbt-dotty/i7897/project/plugins.sbt
similarity index 100%
rename from sbt-dotty/sbt-test/source-dependencies/relative-source-error/project/plugins.sbt
rename to sbt-dotty/sbt-test/sbt-dotty/i7897/project/plugins.sbt
diff --git a/sbt-dotty/sbt-test/sbt-dotty/i7897/src/main/scala/hello/i7897.scala b/sbt-dotty/sbt-test/sbt-dotty/i7897/src/main/scala/hello/i7897.scala
new file mode 100644
index 000000000000..eb4b5ac08be4
--- /dev/null
+++ b/sbt-dotty/sbt-test/sbt-dotty/i7897/src/main/scala/hello/i7897.scala
@@ -0,0 +1,14 @@
+import scala.quoted._, staging._
+
+given Toolbox = Toolbox.make(getClass.getClassLoader)
+
+val f: Array[Int] => Int = run {
+  val stagedSum: Expr[Array[Int] => Int] = '{ (arr: Array[Int]) => 6 }
+  println(stagedSum.show)
+  stagedSum
+}
+
+object Main {
+  def main(args: Array[String]): Unit =
+    f.apply(Array(1, 2, 3)) // Returns 6
+}
diff --git a/sbt-dotty/sbt-test/sbt-dotty/i7897/test b/sbt-dotty/sbt-test/sbt-dotty/i7897/test
new file mode 100644
index 000000000000..42d5b04677a8
--- /dev/null
+++ b/sbt-dotty/sbt-test/sbt-dotty/i7897/test
@@ -0,0 +1,4 @@
+> run
+$ copy-file changes/build-no-fork.sbt build.sbt
+> reload
+> run
diff --git a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/changes/absolute.sbt b/sbt-dotty/sbt-test/source-dependencies/relative-source-error/changes/absolute.sbt
deleted file mode 100644
index a5f2d007a58c..000000000000
--- a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/changes/absolute.sbt
+++ /dev/null
@@ -1 +0,0 @@
-scalaSource in Compile := baseDirectory.value / "src"
\ No newline at end of file
diff --git a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/changes/relative.sbt b/sbt-dotty/sbt-test/source-dependencies/relative-source-error/changes/relative.sbt
deleted file mode 100644
index 8e898fe02829..000000000000
--- a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/changes/relative.sbt
+++ /dev/null
@@ -1 +0,0 @@
-scalaSource in Compile := file("src")
\ No newline at end of file
diff --git a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/project/DottyInjectedPlugin.scala b/sbt-dotty/sbt-test/source-dependencies/relative-source-error/project/DottyInjectedPlugin.scala
deleted file mode 100644
index 6a77cb33121e..000000000000
--- a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/project/DottyInjectedPlugin.scala
+++ /dev/null
@@ -1,12 +0,0 @@
-import sbt._
-import Keys._
-
-object DottyInjectedPlugin extends AutoPlugin {
-  override def requires = plugins.JvmPlugin
-  override def trigger = allRequirements
-
-  override val projectSettings = Seq(
-    scalaVersion := sys.props("plugin.scalaVersion"),
-    scalacOptions += "-language:Scala2Compat"
-  )
-}
diff --git a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/src/A.scala b/sbt-dotty/sbt-test/source-dependencies/relative-source-error/src/A.scala
deleted file mode 100644
index 528ffce71c5f..000000000000
--- a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/src/A.scala
+++ /dev/null
@@ -1 +0,0 @@
-object A
\ No newline at end of file
diff --git a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/test b/sbt-dotty/sbt-test/source-dependencies/relative-source-error/test
deleted file mode 100644
index fb8e9dce835f..000000000000
--- a/sbt-dotty/sbt-test/source-dependencies/relative-source-error/test
+++ /dev/null
@@ -1,7 +0,0 @@
-$ copy-file changes/relative.sbt build.sbt
-> reload
--> compile
-
-$ copy-file changes/absolute.sbt build.sbt
-> reload
-> compile
diff --git a/sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala b/sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala
index 2b12150520a2..3af93b4d6bd2 100644
--- a/sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala
+++ b/sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala
@@ -154,7 +154,7 @@ object DottyPlugin extends AutoPlugin {
   override val globalSettings: Seq[Def.Setting[_]] = Seq(
     onLoad in Global := onLoad.in(Global).value.andThen { state =>
 
-      val requiredVersion = ">=1.2.7"
+      val requiredVersion = ">=1.3.6"
 
       val sbtV = sbtVersion.value
       if (!VersionNumber(sbtV).matchesSemVer(SemanticSelector(requiredVersion)))
@@ -210,41 +210,42 @@ object DottyPlugin extends AutoPlugin {
           scalaBinaryVersion.value
       },
 
-      // Ideally, we should have:
+      // We want:
       //
       // 1. Nothing but the Java standard library on the _JVM_ bootclasspath
       //    (starting with Java 9 we cannot inspect it so we don't have a choice)
       //
-      // 2. scala-library, dotty-library, dotty-compiler, dotty-doc on the _JVM_
-      //    classpath, because we need all of those to actually run the compiler
-      //    and the doc tool.
+      // 2. scala-library, dotty-library, dotty-compiler and its dependencies on the _JVM_
+      //    classpath, because we need all of those to actually run the compiler.
       //    NOTE: All of those should have the *same version* (equal to scalaVersion
       //    for everything but scala-library).
+      //    (Complication: because dottydoc is a separate artifact with its own dependencies,
+      //     running it requires putting extra dependencies on the _JVM_ classpath)
       //
-      // 3. scala-library, dotty-library on the _compiler_ bootclasspath because
-      //    user code should always have access to the symbols from these jars but
-      //    should not be able to shadow them (the compiler bootclasspath has
-      //    higher priority than the compiler classpath).
+      // 3. scala-library, dotty-library on the _compiler_ bootclasspath or
+      //    classpath (the only difference between them is that the compiler
+      //    bootclasspath has higher priority, but that should never
+      //    make a difference in a sane environment).
       //    NOTE: the versions of {scala,dotty}-library used here do not necessarily
       //    match the one used in 2. because a dependency of the current project might
-      //    require more recent versions, this is OK.
+      //    require a more recent standard library version, this is OK
+      //    TODO: ... but if macros are used we might be forced to use the same
+      //    versions in the JVM and compiler classpaths to avoid problems, this
+      //    needs to be investigated.
       //
       // 4. every other dependency of the user project on the _compiler_
       //    classpath.
       //
-      // Unfortunately, zinc assumes that the compiler bootclasspath is only
-      // made of one jar (scala-library), so to make this work we'll need to
-      // either change sbt's bootclasspath handling or wait until the
-      // dotty-library jar and scala-library jars are merged into one jar.
-      // Furthermore, zinc will put on the compiler bootclasspath the
+      // By default, zinc will put on the compiler bootclasspath the
       // scala-library used on the JVM classpath, even if the current project
       // transitively depends on a newer scala-library (this works because Scala
       // 2 guarantees forward- and backward- binary compatibility, but we don't
       // necessarily want to keep doing that in Scala 3).
       // So for the moment, let's just put nothing at all on the compiler
-      // bootclasspath, and instead have scala-library and dotty-library on the
-      // compiler classpath. This means that user code could shadow symbols
-      // from these jars but we can live with that for now.
+      // bootclasspath, and instead let sbt dependency management choose which
+      // scala-library and dotty-library to put on the compiler classpath.
+      // Maybe eventually we should just remove the compiler bootclasspath since
+      // it's a source of complication with only dubious benefits.
 
       // sbt crazy scoping rules mean that when we override `classpathOptions`
       // below we also override `classpathOptions in console` which is normally
@@ -404,7 +405,7 @@ object DottyPlugin extends AutoPlugin {
 
   /** Create a scalaInstance task that uses Dotty based on `moduleName`. */
   def dottyScalaInstanceTask(moduleName: String): Initialize[Task[ScalaInstance]] = Def.task {
-    val ivyConfig0 = mkIvyConfiguration.value
+    val ivyConfig0 = Classpaths.mkIvyConfiguration.value
     // When compiling non-bootstrapped projects in the build of Dotty itself,
     // dependency resolution might pick a local project which is not what we
     // want. We avoid this by dropping the inter-project resolver.
@@ -436,37 +437,22 @@ object DottyPlugin extends AutoPlugin {
     )
   }
 
-  // Copy-pasted from sbt until we upgrade to a version of sbt
-  // with https://github.com/sbt/sbt/pull/5271 in.
-  def mkIvyConfiguration: Initialize[Task[InlineIvyConfiguration]] =
-    Def.task {
-      val (rs, other) = (fullResolvers.value.toVector, otherResolvers.value.toVector)
-      val s = streams.value
-      Classpaths.warnResolversConflict(rs ++: other, s.log)
-      InlineIvyConfiguration()
-        .withPaths(ivyPaths.value)
-        .withResolvers(rs)
-        .withOtherResolvers(other)
-        .withModuleConfigurations(moduleConfigurations.value.toVector)
-        .withLock(Defaults.lock(appConfiguration.value))
-        .withChecksums((checksums in update).value.toVector)
-        .withResolutionCacheDir(crossTarget.value / "resolution-cache")
-        .withUpdateOptions(updateOptions.value)
-        .withLog(s.log)
-    }
-
+  // Adapted from private mkScalaInstance in sbt
   def makeScalaInstance(
     state: State, dottyVersion: String, scalaLibrary: File, dottyLibrary: File, compiler: File, all: Seq[File]
   ): ScalaInstance = {
-    val loader = state.classLoaderCache(all.toList)
-    val loaderLibraryOnly = state.classLoaderCache(List(dottyLibrary, scalaLibrary))
+    val libraryLoader = state.classLoaderCache(List(dottyLibrary, scalaLibrary))
+    class DottyLoader
+        extends URLClassLoader(all.map(_.toURI.toURL).toArray, libraryLoader)
+    val fullLoader = state.classLoaderCache.cachedCustomClassloader(
+      all.toList,
+      () => new DottyLoader
+    )
     new ScalaInstance(
       dottyVersion,
-      loader,
-      loaderLibraryOnly,
-      scalaLibrary, // Should be a Seq also containing dottyLibrary but zinc
-                    // doesn't support this, see comment above our redefinition
-                    // of `classpathOption`
+      fullLoader,
+      libraryLoader,
+      Array(dottyLibrary, scalaLibrary),
       compiler,
       all.toArray,
       None)
diff --git a/staging/src/scala/quoted/staging/QuoteDriver.scala b/staging/src/scala/quoted/staging/QuoteDriver.scala
index 68441e61cf84..fe4410bafeb6 100644
--- a/staging/src/scala/quoted/staging/QuoteDriver.scala
+++ b/staging/src/scala/quoted/staging/QuoteDriver.scala
@@ -11,6 +11,9 @@ import dotty.tools.dotc.reporting._
 import scala.quoted._
 import scala.quoted.staging.Toolbox
 import java.net.URLClassLoader
+import java.nio.file.Paths
+import java.io.File
+import scala.annotation.tailrec
 
 /** Driver to compile quoted code
  *
@@ -53,7 +56,7 @@ private class QuoteDriver(appClassloader: ClassLoader) extends Driver {
 
   override def initCtx: Context = {
     val ictx = contextBase.initialCtx
-    ictx.settings.classpath.update(getCurrentClasspath(appClassloader))(ictx)
+    ictx.settings.classpath.update(classpathFromClassloader(appClassloader))(ictx)
     ictx
   }
 
@@ -64,17 +67,42 @@ private class QuoteDriver(appClassloader: ClassLoader) extends Driver {
     ctx.setReporter(new ThrowingReporter(ctx.reporter))
   }
 
-  private def getCurrentClasspath(cl: ClassLoader): String = {
-    val classpath0 = System.getProperty("java.class.path")
-    cl match {
-      case cl: URLClassLoader =>
-        // Loads the classes loaded by this class loader
-        // When executing `run` or `test` in sbt the classpath is not in the property java.class.path
-        import java.nio.file.Paths
-        val newClasspath = cl.getURLs.map(url => Paths.get(url.toURI).toString)
-        newClasspath.mkString("", java.io.File.pathSeparator, if (classpath0 == "") "" else java.io.File.pathSeparator + classpath0)
-      case _ => classpath0
+  /** Attempt to recreate a classpath from a classloader.
+   *
+   *  BEWARE: with exotic enough classloaders, this may not work at all or do
+   *  the wrong thing.
+   */
+  private def classpathFromClassloader(cl: ClassLoader): String = {
+    val classpathBuff = List.newBuilder[String]
+    def collectClassLoaderPaths(cl: ClassLoader): Unit = {
+      if (cl != null) {
+        cl match {
+          case cl: URLClassLoader =>
+            // This is wrong if we're in a subclass of URLClassLoader
+            // that filters loading classes from its parent ¯\_(ツ)_/¯
+            collectClassLoaderPaths(cl.getParent)
+            // Parent classloaders are searched before their child, so the part of
+            // the classpath coming from the child is added at the _end_ of the
+            // classpath.
+            classpathBuff ++=
+              cl.getURLs.iterator.map(url => Paths.get(url.toURI).toAbsolutePath.toString)
+          case _ =>
+            // HACK: We can't just collect the classpath from arbitrary parent
+            // classloaders since the current classloader might intentionally
+            // filter loading classes from its parent (for example
+            // BootFilteredLoader in the sbt launcher does this and we really
+            // don't want to include the scala-library that sbt depends on
+            // here), but we do need to look at the parent of the REPL
+            // classloader, so we special case it. We can't do this using a type
+            // test since the REPL classloader class itself is normally loaded
+            // with a different classloader.
+            if (cl.getClass.getName == classOf[AbstractFileClassLoader].getName)
+              collectClassLoaderPaths(cl.getParent)
+        }
+      }
     }
+    collectClassLoaderPaths(cl)
+    classpathBuff.result().mkString(java.io.File.pathSeparator)
   }
 }
 
diff --git a/tests/idempotency/BootstrapChecker.scala b/tests/idempotency/BootstrapChecker.scala
index 7c88ed597298..cfd868060409 100644
--- a/tests/idempotency/BootstrapChecker.scala
+++ b/tests/idempotency/BootstrapChecker.scala
@@ -1,5 +1,5 @@
 
 object Test {
   def main(args: Array[String]): Unit =
-    IdempotencyCheck.checkIdempotency("out/tastyBootstrap/dotty1", "out/tastyBootstrap/dotty2")
+    IdempotencyCheck.checkIdempotency("out/tastyBootstrap/dotty1/dotty1", "out/tastyBootstrap/dotty2/dotty2")
 }