diff --git a/.scalafmt.conf b/.scalafmt.conf
index 6767c084ca..5401d30296 100644
--- a/.scalafmt.conf
+++ b/.scalafmt.conf
@@ -1,5 +1,5 @@
 version = 3.8.3
-runner.dialect = scala213
+runner.dialect = scala3
 
 project.git = true
 project.excludeFilters = [ /sbt-test/, /input_sources/, /contraband-scala/ ]
@@ -27,12 +27,13 @@ danglingParentheses.defnSite = true
 rewrite.trailingCommas.style = keep
 
 rewrite.scala3.convertToNewSyntax = true
+rewrite.scala3.newSyntax.control = false
 fileOverride {
   "glob:**/internal/compiler-bridge/**" {
     rewrite.scala3.convertToNewSyntax = false
+    runner.dialect = scala213
   }
 }
 runner.dialectOverride.allowSignificantIndentation = false
 runner.dialectOverride.allowAsForImportRename = false
 runner.dialectOverride.allowStarWildcardImport = false
-runner.dialectOverride.allowPostfixStarVarargSplices = false
diff --git a/internal/zinc-apiinfo/src/test/scala/xsbt/api/ClassLikeHelpers.scala b/internal/zinc-apiinfo/src/test/scala/xsbt/api/ClassLikeHelpers.scala
index cfd3a2f588..8f66e28d59 100644
--- a/internal/zinc-apiinfo/src/test/scala/xsbt/api/ClassLikeHelpers.scala
+++ b/internal/zinc-apiinfo/src/test/scala/xsbt/api/ClassLikeHelpers.scala
@@ -20,17 +20,17 @@ object ClassLikeHelpers {
     Structure.of(lzy(Array.empty[Type]), lzy(defs.toArray), emptyMembers)
 
   def simpleTrait(name: String, defs: List[ClassDefinition]): ClassLike = {
-    val structure = simpleStructure(defs: _*)
+    val structure = simpleStructure(defs*)
     simpleClassLike(name, structure, dt = DefinitionType.Trait)
   }
 
   def simpleClass(name: String, defs: ClassDefinition*): ClassLike = {
-    val structure = simpleStructure(defs: _*)
+    val structure = simpleStructure(defs*)
     simpleClassLike(name, structure)
   }
 
   def simpleObject(name: String, defs: ClassDefinition*): ClassLike = {
-    val structure = simpleStructure(defs: _*)
+    val structure = simpleStructure(defs*)
     simpleClassLike(name, structure, dt = DefinitionType.Module)
   }
 
diff --git a/internal/zinc-classfile/src/main/scala/sbt/internal/inc/classfile/JavaAnalyze.scala b/internal/zinc-classfile/src/main/scala/sbt/internal/inc/classfile/JavaAnalyze.scala
index 28eb16f4b4..892d7b1721 100644
--- a/internal/zinc-classfile/src/main/scala/sbt/internal/inc/classfile/JavaAnalyze.scala
+++ b/internal/zinc-classfile/src/main/scala/sbt/internal/inc/classfile/JavaAnalyze.scala
@@ -71,7 +71,7 @@ private[sbt] object JavaAnalyze {
         classFile
 
     val sourceToClassFiles = mutable.HashMap[VirtualFile, Buffer[ClassFile]](
-      sources.map(vf => vf -> new ArrayBuffer[ClassFile]): _*
+      sources.map(vf => vf -> new ArrayBuffer[ClassFile])*
     )
 
     val binaryClassNameToLoadedClass = new mutable.HashMap[String, Class[?]]
diff --git a/internal/zinc-classfile/src/test/scala/sbt/internal/inc/classfile/JavaCompilerForUnitTesting.scala b/internal/zinc-classfile/src/test/scala/sbt/internal/inc/classfile/JavaCompilerForUnitTesting.scala
index 1f61717d1d..779613d4ab 100644
--- a/internal/zinc-classfile/src/test/scala/sbt/internal/inc/classfile/JavaCompilerForUnitTesting.scala
+++ b/internal/zinc-classfile/src/test/scala/sbt/internal/inc/classfile/JavaCompilerForUnitTesting.scala
@@ -37,7 +37,7 @@ object JavaCompilerForUnitTesting {
   }
 
   def extractDependenciesFromSrcs(srcs: (String, String)*): ExtractedClassDependencies = {
-    val (_, testCallback) = compileJavaSrcs(srcs: _*)((_, _, classes) => extractParents(classes))
+    val (_, testCallback) = compileJavaSrcs(srcs*)((_, _, classes) => extractParents(classes))
 
     val memberRefDeps = testCallback.classDependencies
       .collect({
diff --git a/internal/zinc-classpath/src/main/scala/sbt/internal/inc/ReflectUtilities.scala b/internal/zinc-classpath/src/main/scala/sbt/internal/inc/ReflectUtilities.scala
index 61f376182d..c98e040960 100644
--- a/internal/zinc-classpath/src/main/scala/sbt/internal/inc/ReflectUtilities.scala
+++ b/internal/zinc-classpath/src/main/scala/sbt/internal/inc/ReflectUtilities.scala
@@ -36,7 +36,7 @@ object ReflectUtilities {
     else clazz :: ancestry(clazz.getSuperclass);
 
   def fields(clazz: Class[?]) =
-    mutable.OpenHashMap(ancestry(clazz).flatMap(_.getDeclaredFields).map(f => (f.getName, f)): _*)
+    mutable.OpenHashMap(ancestry(clazz).flatMap(_.getDeclaredFields).map(f => (f.getName, f))*)
 
   /**
    * Collects all `val`s of type `T` defined on value `self`.
diff --git a/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/AnalyzingCompiler.scala b/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/AnalyzingCompiler.scala
index 735bc65ab2..2bc26682de 100644
--- a/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/AnalyzingCompiler.scala
+++ b/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/AnalyzingCompiler.scala
@@ -325,8 +325,8 @@ final class AnalyzingCompiler(
   private def invoke(bridge: AnyRef, bridgeClass: Class[?], methodName: String, log: Logger)(
       argTypes: Class[?]*
   )(args: AnyRef*): AnyRef = {
-    val method = bridgeClass.getMethod(methodName, argTypes: _*)
-    try method.invoke(bridge, args: _*)
+    val method = bridgeClass.getMethod(methodName, argTypes*)
+    try method.invoke(bridge, args*)
     catch {
       case e: InvocationTargetException =>
         e.getCause match {
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 bfdc68c21b..8773d3b5a8 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
@@ -88,9 +88,9 @@ final class CompilerArguments(
    */
   def finishClasspath(classpath: Seq[Path]): Seq[Path] = {
     val filteredClasspath = filterLibrary(classpath)
-    val extraCompiler = include(cpOptions.compiler, scalaInstance.compilerJars.map(_.toPath): _*)
+    val extraCompiler = include(cpOptions.compiler, scalaInstance.compilerJars.map(_.toPath)*)
     val otherJars = scalaInstance.otherJars.toList.map(_.toPath)
-    val extraClasspath = include(cpOptions.extra, otherJars: _*)
+    val extraClasspath = include(cpOptions.extra, otherJars*)
     filteredClasspath ++ extraCompiler ++ extraClasspath
   }
 
diff --git a/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/javac/LocalJava.scala b/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/javac/LocalJava.scala
index ff3f9f6594..f0dd3f8e06 100644
--- a/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/javac/LocalJava.scala
+++ b/internal/zinc-compile-core/src/main/scala/sbt/internal/inc/javac/LocalJava.scala
@@ -129,7 +129,7 @@ object LocalJava {
   ): Int =
     javadocTool match {
       case Some(m) =>
-        m.run(in, out, err, args: _*)
+        m.run(in, out, err, args*)
       case _ =>
         System.err.println(JavadocFailure)
         -1
diff --git a/internal/zinc-core/src/main/scala/sbt/internal/inc/Stamp.scala b/internal/zinc-core/src/main/scala/sbt/internal/inc/Stamp.scala
index 3efd1a2d0c..609c31b372 100644
--- a/internal/zinc-core/src/main/scala/sbt/internal/inc/Stamp.scala
+++ b/internal/zinc-core/src/main/scala/sbt/internal/inc/Stamp.scala
@@ -356,7 +356,7 @@ private class MStamps(
         val rs = removeSources.toSet
         Map(sources.toSeq.filter {
           case (file, stamp) => !rs(file)
-        }: _*)
+        }*)
       },
       libraries.view.filterKeys(lib).toMap
     )
diff --git a/internal/zinc-persist/src/main/scala/sbt/internal/inc/text/TextAnalysisFormat.scala b/internal/zinc-persist/src/main/scala/sbt/internal/inc/text/TextAnalysisFormat.scala
index 09ec21071d..2bb72a63bc 100644
--- a/internal/zinc-persist/src/main/scala/sbt/internal/inc/text/TextAnalysisFormat.scala
+++ b/internal/zinc-persist/src/main/scala/sbt/internal/inc/text/TextAnalysisFormat.scala
@@ -287,7 +287,7 @@ class TextAnalysisFormat(val mappers: ReadWriteMappers)
           keyMapper: Mapper[File],
           valueMapper: ContextAwareMapper[File, Stamp]
       ): TreeMap[File, Stamp] = {
-        TreeMap(readMappedPairs(in)(expectedHeader, keyMapper.read, valueMapper.read).toSeq: _*)
+        TreeMap(readMappedPairs(in)(expectedHeader, keyMapper.read, valueMapper.read).toSeq*)
       }
       def doReadMapV(
           expectedHeader: String,
@@ -295,7 +295,7 @@ class TextAnalysisFormat(val mappers: ReadWriteMappers)
           valueMapper: ContextAwareMapper[VirtualFileRef, Stamp]
       ): TreeMap[VirtualFileRef, Stamp] = {
         import VirtualFileUtil._
-        TreeMap(readMappedPairs(in)(expectedHeader, keyMapper.read, valueMapper.read).toSeq: _*)
+        TreeMap(readMappedPairs(in)(expectedHeader, keyMapper.read, valueMapper.read).toSeq*)
       }
 
       val products = doReadMapV(Headers.products, productsMapper, productsStampsMapper)
diff --git a/internal/zinc-persist/src/test/scala/sbt/inc/AnalysisGenerators.scala b/internal/zinc-persist/src/test/scala/sbt/inc/AnalysisGenerators.scala
index b47bc24c30..0fb6cdbc4e 100644
--- a/internal/zinc-persist/src/test/scala/sbt/inc/AnalysisGenerators.scala
+++ b/internal/zinc-persist/src/test/scala/sbt/inc/AnalysisGenerators.scala
@@ -79,7 +79,7 @@ object AnalysisGenerators {
     import VirtualFileUtil._
 
     def stamp(xs: Iterable[VirtualFileRef]) =
-      for (stamps <- listOfN(xs.size, genStamp)) yield TreeMap(xs.toList.zip(stamps): _*)
+      for (stamps <- listOfN(xs.size, genStamp)) yield TreeMap(xs.toList.zip(stamps)*)
 
     for {
       prods <- stamp(rel.allProducts)
diff --git a/zinc/src/main/scala/sbt/internal/inc/javac/AnalyzingJavaCompiler.scala b/zinc/src/main/scala/sbt/internal/inc/javac/AnalyzingJavaCompiler.scala
index 6d0f3630f8..da62d88aca 100644
--- a/zinc/src/main/scala/sbt/internal/inc/javac/AnalyzingJavaCompiler.scala
+++ b/zinc/src/main/scala/sbt/internal/inc/javac/AnalyzingJavaCompiler.scala
@@ -208,7 +208,7 @@ final class AnalyzingJavaCompiler private[sbt] (
         } {
           val classes = classFinder.classes
           try {
-            val newClasses = Set(classes.paths: _*) -- oldClasses
+            val newClasses = Set(classes.paths*) -- oldClasses
             JavaAnalyze(newClasses.toSeq, srcs, log, output, finalJarOutput)(
               callback,
               loader,
diff --git a/zinc/src/test/scala/sbt/inc/IncrementalCompilerSpec.scala b/zinc/src/test/scala/sbt/inc/IncrementalCompilerSpec.scala
index c812e68980..aeca3ee54f 100644
--- a/zinc/src/test/scala/sbt/inc/IncrementalCompilerSpec.scala
+++ b/zinc/src/test/scala/sbt/inc/IncrementalCompilerSpec.scala
@@ -194,7 +194,7 @@ class IncrementalCompilerSpec extends BaseCompilerSpec {
               )
           )
         }
-        comp.doCompileWithStore(newInputs = incrementalJavaInputs(sources: _*))
+        comp.doCompileWithStore(newInputs = incrementalJavaInputs(sources*))
       }
 
       val res1 = compileJava(f1, f2, f3)
diff --git a/zinc/src/test/scala/sbt/inc/TestProjectSetup.scala b/zinc/src/test/scala/sbt/inc/TestProjectSetup.scala
index 6710af83c2..ebe2f46052 100644
--- a/zinc/src/test/scala/sbt/inc/TestProjectSetup.scala
+++ b/zinc/src/test/scala/sbt/inc/TestProjectSetup.scala
@@ -126,8 +126,8 @@ case class CompilerSetup(
   }
 
   def compileBoth(sources: VirtualFile*) = {
-    val res = compile(sources: _*)
-    if (res.hasModified) compileAllJava(sources: _*) else res
+    val res = compile(sources*)
+    if (res.hasModified) compileAllJava(sources*) else res
   }
 
   def withSrcs(vs: Array[VirtualFile]) = (in: Inputs) => in.withOptions(in.options.withSources(vs))