diff --git a/internal/compiler-bridge-test/src/test/scala/sbt/internal/inc/CompilingSpecification.scala b/internal/compiler-bridge-test/src/test/scala/sbt/internal/inc/CompilingSpecification.scala
index fa420b77a5..6ae5315879 100644
--- a/internal/compiler-bridge-test/src/test/scala/sbt/internal/inc/CompilingSpecification.scala
+++ b/internal/compiler-bridge-test/src/test/scala/sbt/internal/inc/CompilingSpecification.scala
@@ -39,7 +39,7 @@ trait CompilingSpecification extends AbstractBridgeProviderTestkit {
 
   def scalaCompiler(instance: xsbti.compile.ScalaInstance, bridgeJar: Path): AnalyzingCompiler = {
     val bridgeProvider = ZincUtil.constantBridgeProvider(instance, bridgeJar)
-    val classpath = ClasspathOptionsUtil.boot
+    val classpath = ClasspathOptionsUtil.noboot(instance.version)
     val cache = Some(new ClassLoaderCache(new URLClassLoader(Array())))
     new AnalyzingCompiler(instance, bridgeProvider, classpath, _ => (), cache)
   }
diff --git a/internal/compiler-interface/src/main/contraband-java/xsbti/compile/ClasspathOptions.java b/internal/compiler-interface/src/main/contraband-java/xsbti/compile/ClasspathOptions.java
index f7228fd26f..3fac455fc5 100644
--- a/internal/compiler-interface/src/main/contraband-java/xsbti/compile/ClasspathOptions.java
+++ b/internal/compiler-interface/src/main/contraband-java/xsbti/compile/ClasspathOptions.java
@@ -32,7 +32,7 @@ protected ClasspathOptions(boolean _bootLibrary, boolean _compiler, boolean _ext
     }
     /**
      * If true, includes the Scala library on the boot classpath.
-     * This should usually be true.
+     * This should usually be false.
      */
     public boolean bootLibrary() {
         return this.bootLibrary;
@@ -53,14 +53,14 @@ public boolean extra() {
     }
     /**
      * If true, automatically configures the boot classpath.
-     * This should usually be true.
+     * This should usually be false.
      */
     public boolean autoBoot() {
         return this.autoBoot;
     }
     /**
      * If true, the Scala library jar is filtered from the standard classpath.
-     * This should usually be true because the library should be included on the boot
+     * This should usually be false unless the library is included on the boot
      * classpath of the Scala compiler and not the standard classpath.
      */
     public boolean filterLibrary() {
diff --git a/internal/compiler-interface/src/main/contraband/incremental.contra b/internal/compiler-interface/src/main/contraband/incremental.contra
index 09842b2ede..a0617698ce 100644
--- a/internal/compiler-interface/src/main/contraband/incremental.contra
+++ b/internal/compiler-interface/src/main/contraband/incremental.contra
@@ -377,7 +377,7 @@ type Compilers {
 ## compiler-related parameters. Usually, values are all false for Java compilation.
 type ClasspathOptions {
   ## If true, includes the Scala library on the boot classpath.
-  ## This should usually be true.
+  ## This should usually be false.
   bootLibrary: Boolean!
 
   ## If true, includes the Scala compiler on the standard classpath.
@@ -389,11 +389,11 @@ type ClasspathOptions {
   extra: Boolean!
 
   ## If true, automatically configures the boot classpath.
-  ## This should usually be true.
+  ## This should usually be false.
   autoBoot: Boolean!
 
   ## If true, the Scala library jar is filtered from the standard classpath.
-  ## This should usually be true because the library should be included on the boot
+  ## This should usually be false unless the library is included on the boot
   ## classpath of the Scala compiler and not the standard classpath.
   filterLibrary: Boolean!
 }
diff --git a/internal/zinc-compile-core/src/main/java/xsbti/compile/ClasspathOptionsUtil.java b/internal/zinc-compile-core/src/main/java/xsbti/compile/ClasspathOptionsUtil.java
index 1f65c17c5a..2a5e1cf2ef 100644
--- a/internal/zinc-compile-core/src/main/java/xsbti/compile/ClasspathOptionsUtil.java
+++ b/internal/zinc-compile-core/src/main/java/xsbti/compile/ClasspathOptionsUtil.java
@@ -16,7 +16,6 @@
  * that create typical classpath options based on the desired use-case.
  */
 public interface ClasspathOptionsUtil {
-
     /**
      * Define a manual {@link ClasspathOptions} where the client manages everything.
      */
@@ -34,6 +33,16 @@ public static ClasspathOptions boot() {
         return ClasspathOptions.of(true, false, false, true, true);
     }
 
+    /**
+     * Define {@link ClasspathOptions} where the Scala standard library is present in the classpath.
+     */
+    public static ClasspathOptions noboot(String scalaVersion) {
+        if (scalaVersion.startsWith("3.") || scalaVersion.startsWith("2.13."))
+            return ClasspathOptions.of(false, false, false, false, false);
+        else
+            return boot();
+    }
+
     /**
      * Define auto {@link ClasspathOptions} where:
      * 1. the Scala standard library is present in the classpath;
@@ -46,6 +55,19 @@ public static ClasspathOptions auto() {
         return ClasspathOptions.of(true, true, true, true, true);
     }
 
+    /**
+     * Define auto {@link ClasspathOptions} where:
+     * 1. the Scala standard library is present in the classpath;
+     * 2. the Compiler JAR is present in the classpath;
+     * 3. the extra JARs present in the Scala instance are added to the classpath.
+     */
+    public static ClasspathOptions autoNoboot(String scalaVersion) {
+        if (scalaVersion.startsWith("3.") || scalaVersion.startsWith("2.13."))
+            return ClasspathOptions.of(false, true, true, false, false);
+        else
+            return auto();
+    }
+
     /**
      * Define javac {@link ClasspathOptions} where the Compiler JAR may or may not
      * be present in the classpath. Note that the classpath won't be
@@ -69,4 +91,14 @@ public static ClasspathOptions javac(Boolean compilerInClasspath) {
     public static ClasspathOptions repl() {
         return auto();
     }
+
+    /**
+     * Define repl {@link ClasspathOptions} where:
+     * 1. the Scala standard library is present in the classpath;
+     * 2. the Compiler JAR is present in the classpath;
+     * 3. the extra JARs present in the Scala instance are added to the classpath.
+     */
+    public static ClasspathOptions replNoboot(String scalaVersion) {
+        return autoNoboot(scalaVersion);
+    }
 }
diff --git a/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/CompilerArguments.scala b/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/CompilerArguments.scala
index f490e91508..8b3f4c3dc9 100644
--- a/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/CompilerArguments.scala
+++ b/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/CompilerArguments.scala
@@ -76,7 +76,7 @@ final class CompilerArguments(
       if (compilerClasspath.isEmpty) dummy
       else absString(compilerClasspath)
     val classpathOption = Seq("-classpath", stringClasspath)
-    val bootClasspath = bootClasspathOption(hasLibrary(classpath))
+    val bootClasspath = bootClasspathOption(hasLibrary(classpath), classpath)
     options ++ bootClasspath ++ classpathOption ++ abs(sources)
   }
 
@@ -95,13 +95,13 @@ final class CompilerArguments(
   }
 
   def createBootClasspathFor(classpath: Seq[Path]): String =
-    createBootClasspath(hasLibrary(classpath) || cpOptions.compiler || cpOptions.extra)
+    createBootClasspath(hasLibrary(classpath) || cpOptions.compiler || cpOptions.extra, classpath)
 
   /**
    * Return the Scala library to the boot classpath if `addLibrary` is true.
    * @param addLibrary Flag to return the Scala library.
    */
-  def createBootClasspath(addLibrary: Boolean): String = {
+  def createBootClasspath(addLibrary: Boolean, classpath: Seq[Path]): String = {
     def findBoot: String = {
       import scala.collection.JavaConverters._
       System.getProperties.asScala.iterator
@@ -115,7 +115,14 @@ final class CompilerArguments(
       val newBootPrefix =
         if (originalBoot.isEmpty) ""
         else originalBoot + java.io.File.pathSeparator
-      newBootPrefix + absString(scalaInstance.libraryJars.map(_.toPath))
+      val useInstanceLibrary = {
+        val v = scalaInstance.version
+        v.startsWith("3.") || v.startsWith("2.13.")
+      }
+      val library: String =
+        if (useInstanceLibrary) absString(scalaInstance.libraryJars.map(_.toPath))
+        else absString(classpath.filter(isScalaLibrary))
+      newBootPrefix + library
     } else originalBoot
   }
 
@@ -125,16 +132,16 @@ final class CompilerArguments(
 
   def hasLibrary(classpath: Seq[Path]) = classpath.exists(isScalaLibrary)
 
-  def bootClasspathOption(addLibrary: Boolean): Seq[String] =
+  def bootClasspathOption(addLibrary: Boolean, classpath: Seq[Path]): Seq[String] =
     if (!cpOptions.autoBoot) Nil
-    else Seq(BootClasspathOption, createBootClasspath(addLibrary))
+    else Seq(BootClasspathOption, createBootClasspath(addLibrary, classpath))
 
-  def bootClasspath(addLibrary: Boolean): Seq[Path] =
+  def bootClasspath(addLibrary: Boolean, classpath: Seq[Path]): Seq[Path] =
     if (!cpOptions.autoBoot) Nil
-    else IO.parseClasspath(createBootClasspath(addLibrary)).map(_.toPath)
+    else IO.parseClasspath(createBootClasspath(addLibrary, classpath)).map(_.toPath)
 
   def bootClasspathFor(classpath: Seq[Path]) =
-    bootClasspath(hasLibrary(classpath))
+    bootClasspath(hasLibrary(classpath), classpath)
 
   def extClasspath: Seq[Path] =
     List("java.ext.dirs", "scala.ext.dirs").flatMap(k =>
diff --git a/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/javac/JavaCompiler.scala b/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/javac/JavaCompiler.scala
index 610c36354c..2c357a00f2 100644
--- a/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/javac/JavaCompiler.scala
+++ b/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/javac/JavaCompiler.scala
@@ -93,6 +93,7 @@ object JavaCompiler {
       cpOptions: ClasspathOptions
   ): Seq[String] = {
     val cp = classpath.map(converter.toPath)
+    // this seems to duplicate scala-library
     val augmentedClasspath: Seq[Path] =
       if (!cpOptions.autoBoot) cp
       else cp ++ scalaInstance.libraryJars.map(_.toPath)
diff --git a/internal/zinc-scripted/src/test/scala/sbt/internal/inc/IncHandler.scala b/internal/zinc-scripted/src/test/scala/sbt/internal/inc/IncHandler.scala
index 29305fb7cb..b3c22d9691 100644
--- a/internal/zinc-scripted/src/test/scala/sbt/internal/inc/IncHandler.scala
+++ b/internal/zinc-scripted/src/test/scala/sbt/internal/inc/IncHandler.scala
@@ -196,7 +196,7 @@ class IncHandler(directory: Path, cacheDir: Path, scriptedLog: ManagedLogger, co
       toCache
     }
     val analyzingCompiler = scalaCompiler(si, compilerBridge)
-    val cs = incrementalCompiler.compilers(si, ClasspathOptionsUtil.boot, None, analyzingCompiler)
+    val cs = incrementalCompiler.compilers(si, ClasspathOptionsUtil.noboot(si.version), None, analyzingCompiler)
     IncState(si, cs, 0)
   }
 
@@ -204,7 +204,7 @@ class IncHandler(directory: Path, cacheDir: Path, scriptedLog: ManagedLogger, co
 
   def scalaCompiler(instance: XScalaInstance, bridgeJar: Path): AnalyzingCompiler = {
     val bridgeProvider = ZincUtil.constantBridgeProvider(instance, bridgeJar)
-    val classpath = ClasspathOptionsUtil.boot
+    val classpath = ClasspathOptionsUtil.noboot(instance.version)
     new AnalyzingCompiler(instance, bridgeProvider, classpath, unit, IncHandler.classLoaderCache)
   }
 
diff --git a/zinc/src/main/scala/sbt/internal/inc/ZincUtil.scala b/zinc/src/main/scala/sbt/internal/inc/ZincUtil.scala
index d433085e00..4a3ddec802 100644
--- a/zinc/src/main/scala/sbt/internal/inc/ZincUtil.scala
+++ b/zinc/src/main/scala/sbt/internal/inc/ZincUtil.scala
@@ -82,7 +82,11 @@ object ZincUtil {
    * @return A Scala compiler ready to be used.
    */
   def scalaCompiler(scalaInstance: ScalaInstance, compilerBridgeJar: Path): AnalyzingCompiler = {
-    scalaCompiler(scalaInstance, compilerBridgeJar, ClasspathOptionsUtil.boot)
+    scalaCompiler(
+      scalaInstance,
+      compilerBridgeJar,
+      ClasspathOptionsUtil.noboot(scalaInstance.version)
+    )
   }
 
   /**
@@ -98,7 +102,11 @@ object ZincUtil {
    * @return A Scala compiler ready to be used.
    */
   def scalaCompiler(scalaInstance: ScalaInstance, compilerBridgeJar: File): AnalyzingCompiler = {
-    scalaCompiler(scalaInstance, compilerBridgeJar.toPath, ClasspathOptionsUtil.boot)
+    scalaCompiler(
+      scalaInstance,
+      compilerBridgeJar.toPath,
+      ClasspathOptionsUtil.noboot(scalaInstance.version)
+    )
   }
 
   // def compilers(