diff --git a/main-actions/src/main/scala/sbt/Sync.scala b/main-actions/src/main/scala/sbt/Sync.scala
index 7ea32d08b..7760e237c 100644
--- a/main-actions/src/main/scala/sbt/Sync.scala
+++ b/main-actions/src/main/scala/sbt/Sync.scala
@@ -9,14 +9,16 @@
 package sbt
 
 import java.io.{ File, IOException }
+import java.nio.file.Path
 import java.util.zip.ZipException
 
 import sbt.internal.inc.MappedFileConverter
 import sbt.internal.util.Relation
 import sbt.internal.io.TranslatedException
-import sbt.util.CacheImplicits.*
+import sbt.util.CacheImplicits.given
 import sbt.util.{ CacheStore, FileInfo }
 import sbt.io.IO
+import sbt.io.Path.{ flat, rebase }
 import sjsonnew.{
   Builder,
   IsoString,
@@ -27,6 +29,7 @@ import sjsonnew.{
   deserializationError,
 }
 import xsbti.{ FileConverter, VirtualFileRef }
+import xsbti.compile.CompileAnalysis
 
 /**
  * Maintains a set of mappings so that they are uptodate.
@@ -94,6 +97,59 @@ object Sync {
       relation
     }
 
+  private[sbt] def syncClasses(
+      store: CacheStore,
+      fileConverter: FileConverter
+  ): (Option[CompileAnalysis], Path, Path) => Unit =
+    (analysisOpt, backendDir, classesDir) => {
+      val currentStamps = analysisOpt match
+        case Some(a) =>
+          import scala.jdk.CollectionConverters.*
+          a.readStamps
+            .getAllProductStamps()
+            .asScala
+            .map: (k, v) =>
+              (k, v.toString())
+            .toMap
+        case None => Map.empty
+      val currentStampsSeq = currentStamps.toVector.sortBy(_._1.id())
+      val previousStampsSeq = store.read[Vector[(VirtualFileRef, String)]](Vector.empty)
+      val previousStamps = Map(previousStampsSeq*)
+      if currentStampsSeq == previousStampsSeq then ()
+      else
+        val t = classesDir.toFile()
+        val productsVf = currentStamps.map(_._1)
+        val flt: File => Option[File] = flat(t)
+        val transform: VirtualFileRef => Option[File] =
+          (vf: VirtualFileRef) =>
+            val f = fileConverter.toPath(vf).toFile()
+            rebase(backendDir.toFile(), t)(f).orElse(flt(f))
+        val mappings = productsVf.flatMap: x =>
+          transform(x).map(x -> _)
+        val relation = Relation.empty ++ mappings
+        def outofdate(source: VirtualFileRef, target: File): Boolean =
+          !previousStamps.contains(source) ||
+            previousStamps.get(source) != currentStamps.get(source) ||
+            !target.exists
+        val updates = relation.filter(outofdate)
+        val removeTargets = (previousStampsSeq.map(_._1) diff currentStampsSeq.map(_._1)).flatMap:
+          x => transform(x).map(x -> _)
+        val (cleanDirs, cleanFiles) =
+          (updates._2s ++ removeTargets.map(_._2)).partition(_.isDirectory)
+        IO.delete(cleanFiles)
+        IO.deleteIfEmpty(cleanDirs)
+        updates.all.foreach: (k, v) =>
+          val classFile = fileConverter.toPath(k).toFile()
+          copy(classFile, v)
+          if !classFile.getName().contains("$") then
+            val (name, ext) = IO.split(classFile.getName)
+            val tasty = File(classFile.getParentFile(), name + ".tasty")
+            if tasty.exists() then
+              val tastyTarget = File(v.getParentFile(), name + ".tasty")
+              copy(tasty, tastyTarget)
+        store.write(currentStampsSeq)
+    }
+
   def copy(source: File, target: File): Unit =
     if (source.isFile) IO.copyFile(source, target, true)
     else if (!target.exists) { // we don't want to update the last modified time of an existing directory
diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 240461d82..47c821270 100644
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -4069,17 +4069,12 @@ object Classpaths {
     val cacheStore = factory.make("make-product")
     val t = classDirectory.value
     val vfBackendDir = compileIncremental.value._2
+    val setup: Setup = compileIncSetup.value
+    val analysisOut = c.toVirtualFile(setup.cachePath())
+    val analysisOpt = BuildDef.extractAnalysis(analysisOut, c)
     val backendDir = c.toPath(vfBackendDir)
-    val flt: File => Option[File] = flat(t)
-    val transform: File => Option[File] =
-      (f: File) => rebase(backendDir.toFile(), t)(f).orElse(flt(f))
     val resources = copyResources.value.map(_._2).toSet
-    val view = fileTreeView.value
-    val classes = view.list((Glob(backendDir, RecursiveGlob / "*")))
-    val mappings: Seq[(File, File)] = classes.flatMap:
-      case (r, attr) if r != backendDir => transform(r.toFile()).map(r.toFile() -> _)
-      case _                            => None
-    Sync.sync(cacheStore, fileConverter = c)(mappings)
+    Sync.syncClasses(cacheStore, fileConverter = c)(analysisOpt, backendDir, t.toPath())
     t :: Nil
   }
 
diff --git a/main/src/main/scala/sbt/internal/BuildDef.scala b/main/src/main/scala/sbt/internal/BuildDef.scala
index 6ac7b226e..63f1ed890 100644
--- a/main/src/main/scala/sbt/internal/BuildDef.scala
+++ b/main/src/main/scala/sbt/internal/BuildDef.scala
@@ -113,6 +113,15 @@ private[sbt] object BuildDef:
   private[sbt] def extractAnalysis(
       metadata: StringAttributeMap,
       converter: FileConverter
+  ): Option[CompileAnalysis] =
+    for
+      ref <- metadata.get(Keys.analysis)
+      analysis <- extractAnalysis(VirtualFileRef.of(ref), converter)
+    yield analysis
+
+  private[sbt] def extractAnalysis(
+      ref: VirtualFileRef,
+      converter: FileConverter
   ): Option[CompileAnalysis] =
     import sbt.OptionSyntax.*
     def asBinary(file: File) = FileAnalysisStore.binary(file).get.asScala
@@ -129,9 +138,6 @@ private[sbt] object BuildDef:
           val sizeBytes = attrs.size()
           getOrElseUpdate(ref, lastModified, sizeBytes)(fallback(file))
       catch case _: NoSuchFileException => fallback(file)
-    for
-      ref <- metadata.get(Keys.analysis)
-      content <- getContents(VirtualFileRef.of(ref))
-    yield content.getAnalysis
+    getContents(ref).map(_.getAnalysis)
 
 end BuildDef