diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index fea333dde76..477d3e13f7a 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -90,7 +90,7 @@ jobs:
           $CHISEL_FIRTOOL_PATH/firtool -version >> $GITHUB_STEP_SUMMARY
           echo \`\`\` >> $GITHUB_STEP_SUMMARY
       - name: Test
-        run: ./mill -j0 firrtl[].test + svsim[].test + chisel[].test
+        run: ./mill -j0 firrtl.cross[].test + svsim[].test + chisel[].test
       - name: Binary compatibility
         # TODO either make this also check the plugin or decide that we don't
         #      support binary compatibility for the plugin
@@ -183,7 +183,7 @@ jobs:
           dir=$(dirname $(which firtool))
           echo "CHISEL_FIRTOOL_PATH=$dir" >> "$GITHUB_ENV"
       - name: Integration Tests
-        run: ./mill -j0 integrationTests[].test
+        run: ./mill -j0 integration-tests.cross[].test
 
   # Currently just a sanity check that the benchmarking flow works
   benchmark:
@@ -221,7 +221,7 @@ jobs:
           distribution: 'adopt'
           java-version: '11'
       - name: Compile
-        run: ./mill stdlib[_].compile
+        run: ./mill stdlib.cross[_].compile
 
   website:
     name: Build Mdoc & Website
diff --git a/.mill-version b/.mill-version
index 1ee43fc53c1..43c2417ca0c 100644
--- a/.mill-version
+++ b/.mill-version
@@ -1 +1 @@
-0.11.8
+0.12.5
diff --git a/benchmark/package.mill b/benchmark/package.mill
new file mode 100644
index 00000000000..466b729ce3b
--- /dev/null
+++ b/benchmark/package.mill
@@ -0,0 +1,16 @@
+package build.benchmark
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import $ivy.`com.lihaoyi::mill-contrib-jmh:`
+import mill.contrib.jmh.JmhModule
+
+import build._
+
+object `package` extends RootModule with ScalaModule with JmhModule with ScalafmtModule {
+  def scalaVersion = v.scalaVersion
+  def jmhCoreVersion = v.jmhVersion
+
+  override def moduleDeps = Seq(chisel(v.scalaVersion))
+}
diff --git a/build.mill b/build.mill
new file mode 100644
index 00000000000..0e6c8d19b53
--- /dev/null
+++ b/build.mill
@@ -0,0 +1,435 @@
+package build
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.publish._
+import mill.scalalib.scalafmt._
+import mill.api.Result
+import mill.scalalib.api.ZincWorkerUtil.matchingVersions
+import mill.util.Jvm.createJar
+import $ivy.`io.chris-kipp::mill-ci-release::0.1.10`
+import io.kipp.mill.ci.release.{CiReleaseModule, SonatypeHost}
+import de.tobiasroeser.mill.vcs.version.VcsVersion // pulled in by mill-ci-release
+
+import $packages._
+import build._
+
+object v extends Module {
+
+  val javaVersion = {
+    val rawVersion = sys.props("java.specification.version")
+    // Older versions of Java started with 1., e.g. 1.8 == 8
+    rawVersion.stripPrefix("1.").toInt
+  }
+
+  val firtoolVersion = {
+    val j = _root_.upickle.default.read[Map[String, String]](os.read(millSourcePath / os.up / "etc" / "circt.json"))
+    j("version").stripPrefix("firtool-")
+  }
+  // Java 21 only works with 2.13.11+, but Project Panama uses Java 21
+  // Only publish plugin for 2.13.11+ when using Java > 11, but still
+  // publish all versions when Java version <= 11.
+  val pluginScalaCrossVersions = {
+    val latest213 = 15
+    val java21Min213 = 11
+    val minVersion = if (javaVersion > 11) java21Min213 else 0
+    val versions = minVersion to latest213
+    val versionSeq = versions.map(v => s"2.13.$v").toSeq
+    versionSeq ++ Seq("3.3.4")
+  }
+
+  val scalaCrossVersions = Seq(
+    "2.13.15",
+    "3.3.4"
+  )
+
+  def isScala3(ver: String): Boolean = ver.startsWith("3.")
+
+  def buildUnits(): Seq[ScalaModule] = {
+    scalaCrossVersions.flatMap { ver =>
+      Seq(chisel(ver), stdlib.cross(ver), unipublish)
+    } ++ scalaCrossVersions.filterNot(isScala3(_)).flatMap { ver2 =>
+      Seq(
+        chisel(ver2).test,
+        firrtl.cross(ver2).test,
+        svsim.cross(ver2).test,
+        `integration-tests`.cross(ver2).test,
+        lit.utility.cross(ver2),
+        panamaconverter.cross(ver2),
+        panamalib.cross(ver2),
+        panamaom.cross(ver2)
+      )
+    }
+  }
+
+  val scalaVersion = scalaCrossVersions.head
+  val jmhVersion = "1.37"
+  val osLib = ivy"com.lihaoyi::os-lib:0.10.0"
+  val upickle = ivy"com.lihaoyi::upickle:3.3.1"
+  val firtoolResolver = ivy"org.chipsalliance::firtool-resolver:2.0.0"
+  val scalatest = ivy"org.scalatest::scalatest:3.2.19"
+  val scalacheck = ivy"org.scalatestplus::scalacheck-1-18:3.2.19.0"
+  val json4s = ivy"org.json4s::json4s-native:4.0.7"
+  val dataclass = ivy"io.github.alexarchambault::data-class:0.2.6"
+  val commonText = ivy"org.apache.commons:commons-text:1.12.0"
+  val scopt = ivy"com.github.scopt::scopt:4.1.0"
+
+  def scalaReflect(scalaVersion:  String) = ivy"org.scala-lang:scala-reflect:$scalaVersion"
+  def scalaCompiler(scalaVersion: String) = ivy"org.scala-lang:scala-compiler:$scalaVersion"
+  def scalaLibrary(scalaVersion:  String) = ivy"org.scala-lang:scala-library:$scalaVersion"
+
+  def circt(version: String, os: String, platform: String) =
+    s"https://github.com/llvm/circt/releases/download/firtool-${version}/circt-full-shared-${os}-${platform}.tar.gz"
+
+  val scala2WarnConf = Seq(
+    "msg=APIs in chisel3.internal:s",
+    "msg=Importing from firrtl:s",
+    "msg=migration to the MLIR:s",
+    "msg=method hasDefiniteSize in trait IterableOnceOps is deprecated:s", // replacement `knownSize` is not in 2.12
+    "msg=object JavaConverters in package collection is deprecated:s",
+    "msg=undefined in comment for method cf in class PrintableHelper:s",
+    // This is deprecated for external users but not internal use
+    "cat=deprecation&origin=firrtl\\.options\\.internal\\.WriteableCircuitAnnotation:s",
+    "cat=deprecation&origin=chisel3\\.util\\.experimental\\.BoringUtils.*:s",
+    "cat=deprecation&origin=chisel3\\.experimental\\.IntrinsicModule:s",
+    "cat=deprecation&origin=chisel3\\.ltl.*:s",
+    // Deprecated for external users, will eventually be removed.
+    "cat=deprecation&msg=Looking up Modules is deprecated:s",
+    // Only for testing of deprecated APIs
+    "cat=deprecation&msg=Use of @instantiable on user-defined types is deprecated:s"
+  )
+
+  // ScalacOptions
+  val scala2CommonOptions = Seq(
+    "-deprecation",
+    "-feature",
+    "-unchecked",
+    "-Werror",
+    "-Ymacro-annotations",
+    "-explaintypes",
+    "-Xcheckinit",
+    "-Xlint:infer-any",
+    "-Xlint:missing-interpolator",
+    "-language:reflectiveCalls",
+    s"-Wconf:${scala2WarnConf.mkString(",")}"
+  )
+}
+
+def compileAll() = Task.Command {
+  Task.traverse(v.buildUnits())(_.compile)()
+}
+
+trait ChiselPublishModule extends CiReleaseModule {
+  // Publish information
+  def pomSettings = PomSettings(
+    description = artifactName(),
+    organization = "org.chipsalliance",
+    url = "https://www.chisel-lang.org",
+    licenses = Seq(License.`Apache-2.0`),
+    versionControl = VersionControl.github("chipsalliance", "chisel"),
+    developers = Seq(
+      Developer("jackkoenig", "Jack Koenig", "https://github.com/jackkoenig"),
+      Developer("azidar", "Adam Izraelevitz", "https://github.com/azidar"),
+      Developer("seldridge", "Schuyler Eldridge", "https://github.com/seldridge")
+    )
+  )
+
+  override def sonatypeHost = Some(SonatypeHost.s01)
+
+  override def publishVersion = VcsVersion
+    .vcsState()
+    .format(
+      countSep = "+",
+      revHashDigits = 8,
+      untaggedSuffix = "-SNAPSHOT"
+    )
+
+}
+
+trait HasScala2MacroAnno extends CrossModuleBase {
+  override def scalacOptions = Task {
+    if (!v.isScala3(crossScalaVersion)) {
+      super.scalacOptions() ++ Agg("-Ymacro-annotations")
+    } else super.scalacOptions()
+  }
+}
+
+trait HasScala2Plugin extends CrossModuleBase {
+  import $file.plugin.Plugin
+  def pluginModule: Plugin
+
+  override def scalacOptions = Task {
+    if (!v.isScala3(crossScalaVersion)) {
+      super.scalacOptions() ++ Agg(s"-Xplugin:${pluginModule.jar().path}")
+    } else super.scalacOptions()
+  }
+
+  override def scalacPluginClasspath = Task {
+    if (!v.isScala3(crossScalaVersion)) {
+      super.scalacPluginClasspath() ++ Agg(pluginModule.jar())
+    } else super.scalacPluginClasspath()
+  }
+}
+
+trait HasJextractGeneratedSources extends JavaModule {
+
+  def jextractBinary: T[os.Path]
+
+  def includePaths: T[Seq[PathRef]]
+
+  def libraryPaths: T[Seq[PathRef]]
+
+  def header: T[PathRef]
+
+  def includeFunctions: T[Seq[String]]
+
+  def includeConstants: T[Seq[String]]
+
+  def includeStructs: T[Seq[String]]
+
+  def includeTypedefs: T[Seq[String]]
+
+  def includeUnions: T[Seq[String]]
+
+  def includeVars: T[Seq[String]]
+
+  def linkLibraries: T[Seq[String]]
+
+  def target: T[String]
+
+  def headerClassName: T[String]
+
+  def dumpAllIncludes = Task {
+    val f = os.temp()
+    os.proc(
+      Seq(jextractBinary().toString, header().path.toString)
+        ++ includePaths().flatMap(p => Seq("-I", p.path.toString))
+        ++ Seq("--dump-includes", f.toString)
+    ).call()
+    os.read.lines(f).filter(s => s.nonEmpty && !s.startsWith("#"))
+  }
+
+  override def generatedSources: T[Seq[PathRef]] = Task {
+    super.generatedSources() ++ {
+      // @formatter:off
+      os.proc(
+        Seq(jextractBinary().toString, header().path.toString)
+          ++ includePaths().flatMap(p => Seq("-I", p.path.toString))
+          ++ Seq(
+            "-t", target(),
+            "--header-class-name", headerClassName(),
+            "--source",
+            "--output", Task.dest.toString
+          ) ++ includeFunctions().flatMap(f => Seq("--include-function", f)) ++
+          includeConstants().flatMap(f => Seq("--include-constant", f)) ++
+          includeStructs().flatMap(f => Seq("--include-struct", f)) ++
+          includeTypedefs().flatMap(f => Seq("--include-typedef", f)) ++
+          includeUnions().flatMap(f => Seq("--include-union", f)) ++
+          includeVars().flatMap(f => Seq("--include-var", f)) ++
+          linkLibraries().flatMap(l => Seq("-l", l))
+      ).call(Task.dest)
+      // @formatter:on
+      Seq(PathRef(Task.dest))
+    }
+  }
+
+  override def javacOptions = Task(super.javacOptions() ++ Seq("--enable-preview", "--release", "21"))
+}
+
+trait HasCIRCTPanamaBindingModule extends JavaModule {
+  import $file.circtpanamabinding.CIRCTPanamaBinding
+  def circtPanamaBindingModule: CIRCTPanamaBinding
+
+  override def moduleDeps = super.moduleDeps ++ Some(circtPanamaBindingModule)
+  //
+  override def javacOptions = Task(super.javacOptions() ++ Seq("--enable-preview", "--release", "21"))
+
+  override def forkArgs: T[Seq[String]] = Task(
+    super.forkArgs() ++ Seq("--enable-native-access=ALL-UNNAMED", "--enable-preview")
+      ++ circtPanamaBindingModule
+        .libraryPaths()
+        .map(p => s"-Djava.library.path=${p.path}")
+  )
+}
+
+trait HasPanamaLibModule extends ScalaModule with HasCIRCTPanamaBindingModule {
+  import $file.panamalib.PanamaLib
+  def panamaLibModule: PanamaLib
+
+  def circtPanamaBindingModule = panamaLibModule.circtPanamaBindingModule
+
+  override def moduleDeps = super.moduleDeps ++ Some(panamaLibModule)
+}
+
+trait HasPanamaOMModule extends ScalaModule with HasCIRCTPanamaBindingModule {
+  import $file.panamaom.PanamaOM
+  def panamaOMModule: PanamaOM
+
+  def circtPanamaBindingModule = panamaOMModule.circtPanamaBindingModule
+
+  override def moduleDeps = super.moduleDeps ++ Some(panamaOMModule)
+}
+
+trait HasPanamaConverterModule extends ScalaModule with HasCIRCTPanamaBindingModule {
+  import $file.panamaconverter.PanamaConverter
+  def panamaConverterModule: PanamaConverter
+
+  def circtPanamaBindingModule = panamaConverterModule.circtPanamaBindingModule
+
+  override def moduleDeps = super.moduleDeps ++ Some(panamaConverterModule)
+}
+
+object chisel extends Cross[Chisel](v.scalaCrossVersions)
+
+trait Chisel extends CrossSbtModule with HasScala2MacroAnno with HasScala2Plugin with ScalafmtModule {
+  override def millSourcePath = super.millSourcePath / os.up
+  def svsimModule = svsim.cross(crossScalaVersion)
+  def coreModule = core.cross(crossScalaVersion)
+  def pluginModule = plugin.cross()
+
+  override def scalacOptions = Task {
+    if (v.isScala3(crossScalaVersion)) {
+      Seq.empty[String]
+    } else {
+      super.scalacOptions() ++ v.scala2CommonOptions
+    }
+  }
+
+  override def moduleDeps = super.moduleDeps ++ Seq(coreModule, svsimModule)
+
+  object test extends SbtTests with TestModule.ScalaTest with ScalafmtModule {
+    def ivyDeps = Agg(v.scalatest, v.scalacheck)
+
+    // Suppress Scala 3 behavior requiring explicit types on implicit definitions
+    // Note this must come before the -Wconf is warningSuppression
+    override def scalacOptions = Task { super.scalacOptions() :+ "-Wconf:cat=other-implicit-type:s" }
+  }
+}
+
+/** Aggregate project for publishing Chisel as a single artifact
+  */
+object unipublish extends ScalaModule with ChiselPublishModule {
+
+  def scalaVersion = v.scalaVersion
+
+  // This is published as chisel
+  override def artifactName = "chisel"
+
+  // Older versions of Scala do not work with newer versions of the JVM
+  // This is a hack to ensure we always use Java 8 to publish Chisel with Scala 2.13
+  // We could use Java 11 with -release 8
+  // Note that this target is used by real publishing but not by publishLocal
+  override def publishArtifacts = Task {
+    // TODO when we publish for Scala 3, only do this check for Scala 2.13
+    if (v.javaVersion != 8) {
+      throw new Exception(s"Publishing requires Java 8, current JDK is ${v.javaVersion}")
+    }
+    super.publishArtifacts
+  }
+
+  /** Publish both this project and the plugin (for the default Scala version) */
+  override def publishLocal(localIvyRepo: String = null) = Task.Command {
+    // TODO consider making this parallel and publishing all cross-versions for plugin
+    plugin.cross(v.scalaVersion).publishLocal(localIvyRepo)()
+    super.publishLocal(localIvyRepo)()
+  }
+
+  // Explicitly not using moduleDeps because that influences so many things
+  def components = Seq(firrtl.cross, svsim.cross, macros.cross, core.cross, chisel).map(_(v.scalaVersion))
+
+  /** Aggregated ivy deps to include as dependencies in POM */
+  def ivyDeps = Task { Task.traverse(components)(_.ivyDeps)().flatten }
+
+  /** Aggregated local classpath to include in jar */
+  override def localClasspath = Task { Task.traverse(components)(_.localClasspath)().flatten }
+
+  /** Aggreagted sources from all component modules */
+  def aggregatedSources = Task { Task.traverse(components)(_.allSources)().flatten }
+
+  /** Aggreagted resources from all component modules */
+  def aggregatedResources = Task { Task.traverse(components)(_.resources)().flatten }
+
+  /** Aggreagted compile resources from all component modules */
+  def aggregatedCompileResources = Task { Task.traverse(components)(_.compileResources)().flatten }
+
+  /** Aggregated sourceJar from all component modules
+    */
+  override def sourceJar: T[PathRef] = Task {
+    // This is based on the implementation of sourceJar in PublishModule, may need to be kept in sync.
+    val allDirs = aggregatedSources() ++ aggregatedResources() ++ aggregatedCompileResources()
+    createJar(allDirs.map(_.path).filter(os.exists), manifest())
+  }
+
+  // Needed for ScalaDoc
+  override def scalacOptions = v.scala2CommonOptions
+
+  def scalaDocRootDoc = Task.Source { Task.workspace / "root-doc.txt" }
+
+  def unidocOptions = Task {
+    scalacOptions() ++ Seq[String](
+      "-classpath",
+      unidocCompileClasspath().map(_.path).mkString(sys.props("path.separator")),
+      "-diagrams",
+      "-groups",
+      "-skip-packages",
+      "chisel3.internal",
+      "-diagrams-max-classes",
+      "25",
+      "-doc-version",
+      publishVersion(),
+      "-doc-title",
+      "chisel",
+      "-doc-root-content",
+      scalaDocRootDoc().path.toString,
+      "-sourcepath",
+      Task.workspace.toString,
+      "-doc-source-url",
+      unidocSourceUrl(),
+      "-language:implicitConversions",
+      "-implicits"
+    )
+  }
+
+  // Built-in UnidocModule is insufficient so we need to implement it ourselves
+  // We could factor this out into a utility
+  def unidocSourceUrl: T[String] = Task {
+    val base = "https://github.com/chipsalliance/chisel/tree"
+    val branch = if (publishVersion().endsWith("-SNAPSHOT")) "main" else s"v${publishVersion()}"
+    s"$base/$branch/€{FILE_PATH_EXT}#L€{FILE_LINE}"
+  }
+
+  def unidocVersion: T[Option[String]] = None
+
+  def unidocCompileClasspath = Task {
+    Seq(compile().classes) ++ Task.traverse(components)(_.compileClasspath)().flatten
+  }
+
+  def unidocSourceFiles = Task {
+    allSourceFiles() ++ Task.traverse(components)(_.allSourceFiles)().flatten
+  }
+
+  // Based on UnidocModule and docJar in Mill, may need to be kept in sync.
+  override def docJar = Task {
+    Task.log.info(s"Building unidoc for ${unidocSourceFiles().length} files")
+
+    val javadocDir = Task.dest / "javadoc"
+    os.makeDir(javadocDir)
+
+    val fullOptions = unidocOptions() ++
+      Seq("-d", javadocDir.toString) ++
+      unidocSourceFiles().map(_.path.toString)
+
+    zincWorker()
+      .worker()
+      .docJar(
+        scalaVersion(),
+        scalaOrganization(),
+        scalaDocClasspath(),
+        scalacPluginClasspath(),
+        fullOptions
+      ) match {
+      case true  => Result.Success(createJar(Agg(javadocDir))(Task.dest))
+      case false => Result.Failure("docJar generation failed")
+    }
+  }
+}
diff --git a/build.sc b/build.sc
deleted file mode 100644
index bce888a8d5c..00000000000
--- a/build.sc
+++ /dev/null
@@ -1,585 +0,0 @@
-import mill._
-import mill.scalalib._
-import mill.scalalib.publish._
-import mill.scalalib.scalafmt._
-import mill.api.Result
-import mill.define.Cross
-import mill.scalalib.api.ZincWorkerUtil.matchingVersions
-import mill.util.Jvm.createJar
-import $ivy.`com.lihaoyi::mill-contrib-jmh:`
-import mill.contrib.jmh.JmhModule
-import $ivy.`io.chris-kipp::mill-ci-release::0.1.10`
-import io.kipp.mill.ci.release.{CiReleaseModule, SonatypeHost}
-import de.tobiasroeser.mill.vcs.version.VcsVersion // pulled in by mill-ci-release
-
-import $file.panama
-
-object v extends Module {
-
-  val javaVersion = {
-    val rawVersion = sys.props("java.specification.version")
-    // Older versions of Java started with 1., e.g. 1.8 == 8
-    rawVersion.stripPrefix("1.").toInt
-  }
-
-  val firtoolVersion = {
-    val j = _root_.upickle.default.read[Map[String, String]](os.read(millSourcePath / os.up / "etc" / "circt.json"))
-    j("version").stripPrefix("firtool-")
-  }
-  // Java 21 only works with 2.13.11+, but Project Panama uses Java 21
-  // Only publish plugin for 2.13.11+ when using Java > 11, but still
-  // publish all versions when Java version <= 11.
-  val pluginScalaCrossVersions = {
-    val latest213 = 15
-    val java21Min213 = 11
-    val minVersion = if (javaVersion > 11) java21Min213 else 0
-    val versions = minVersion to latest213
-    val versionSeq = versions.map(v => s"2.13.$v").toSeq
-    versionSeq ++ Seq("3.3.4")
-  }
-
-  val scalaCrossVersions = Seq(
-    "2.13.15",
-    "3.3.4"
-  )
-
-  def isScala3(ver: String): Boolean = ver.startsWith("3.")
-
-  def buildUnits(): Seq[ScalaModule] = {
-    scalaCrossVersions.flatMap { ver =>
-      Seq(chisel(ver), stdlib(ver), unipublish)
-    } ++ scalaCrossVersions.filterNot(isScala3(_)).flatMap { ver2 =>
-      Seq(
-        chisel(ver2).test,
-        firrtl(ver2).test,
-        svsim(ver2).test,
-        integrationTests(ver2).test,
-        litutility(ver2),
-        panamaconverter(ver2),
-        panamalib(ver2),
-        panamaom(ver2)
-      )
-    }
-  }
-
-  val scalaVersion = scalaCrossVersions.head
-  val jmhVersion = "1.37"
-  val osLib = ivy"com.lihaoyi::os-lib:0.10.0"
-  val upickle = ivy"com.lihaoyi::upickle:3.3.1"
-  val firtoolResolver = ivy"org.chipsalliance::firtool-resolver:2.0.0"
-  val scalatest = ivy"org.scalatest::scalatest:3.2.19"
-  val scalacheck = ivy"org.scalatestplus::scalacheck-1-18:3.2.19.0"
-  val json4s = ivy"org.json4s::json4s-native:4.0.7"
-  val dataclass = ivy"io.github.alexarchambault::data-class:0.2.6"
-  val commonText = ivy"org.apache.commons:commons-text:1.12.0"
-  val scopt = ivy"com.github.scopt::scopt:4.1.0"
-
-  def scalaReflect(scalaVersion:  String) = ivy"org.scala-lang:scala-reflect:$scalaVersion"
-  def scalaCompiler(scalaVersion: String) = ivy"org.scala-lang:scala-compiler:$scalaVersion"
-  def scalaLibrary(scalaVersion:  String) = ivy"org.scala-lang:scala-library:$scalaVersion"
-
-  def circt(version: String, os: String, platform: String) =
-    s"https://github.com/llvm/circt/releases/download/firtool-${version}/circt-full-shared-${os}-${platform}.tar.gz"
-
-  val scala2WarnConf = Seq(
-    "msg=APIs in chisel3.internal:s",
-    "msg=Importing from firrtl:s",
-    "msg=migration to the MLIR:s",
-    "msg=method hasDefiniteSize in trait IterableOnceOps is deprecated:s", // replacement `knownSize` is not in 2.12
-    "msg=object JavaConverters in package collection is deprecated:s",
-    "msg=undefined in comment for method cf in class PrintableHelper:s",
-    // This is deprecated for external users but not internal use
-    "cat=deprecation&origin=firrtl\\.options\\.internal\\.WriteableCircuitAnnotation:s",
-    "cat=deprecation&origin=chisel3\\.util\\.experimental\\.BoringUtils.*:s",
-    "cat=deprecation&origin=chisel3\\.experimental\\.IntrinsicModule:s",
-    "cat=deprecation&origin=chisel3\\.ltl.*:s",
-    // Deprecated for external users, will eventually be removed.
-    "cat=deprecation&msg=Looking up Modules is deprecated:s",
-    // Only for testing of deprecated APIs
-    "cat=deprecation&msg=Use of @instantiable on user-defined types is deprecated:s"
-  )
-
-  // ScalacOptions
-  val scala2CommonOptions = Seq(
-    "-deprecation",
-    "-feature",
-    "-unchecked",
-    "-Werror",
-    "-Ymacro-annotations",
-    "-explaintypes",
-    "-Xcheckinit",
-    "-Xlint:infer-any",
-    "-Xlint:missing-interpolator",
-    "-language:reflectiveCalls",
-    s"-Wconf:${scala2WarnConf.mkString(",")}"
-  )
-}
-
-def compileAll() = T.command {
-  T.traverse(v.buildUnits())(_.compile)()
-}
-
-trait ChiselPublishModule extends CiReleaseModule {
-  // Publish information
-  def pomSettings = PomSettings(
-    description = artifactName(),
-    organization = "org.chipsalliance",
-    url = "https://www.chisel-lang.org",
-    licenses = Seq(License.`Apache-2.0`),
-    versionControl = VersionControl.github("chipsalliance", "chisel"),
-    developers = Seq(
-      Developer("jackkoenig", "Jack Koenig", "https://github.com/jackkoenig"),
-      Developer("azidar", "Adam Izraelevitz", "https://github.com/azidar"),
-      Developer("seldridge", "Schuyler Eldridge", "https://github.com/seldridge")
-    )
-  )
-
-  override def sonatypeHost = Some(SonatypeHost.s01)
-
-  override def publishVersion = VcsVersion
-    .vcsState()
-    .format(
-      countSep = "+",
-      revHashDigits = 8,
-      untaggedSuffix = "-SNAPSHOT"
-    )
-
-}
-
-trait HasScala2MacroAnno extends CrossModuleBase {
-  override def scalacOptions = T {
-    if (!v.isScala3(crossScalaVersion)) {
-      super.scalacOptions() ++ Agg("-Ymacro-annotations")
-    } else super.scalacOptions()
-  }
-}
-
-trait HasScala2Plugin extends CrossModuleBase {
-  def pluginModule: Plugin
-
-  override def scalacOptions = T {
-    if (!v.isScala3(crossScalaVersion)) {
-      super.scalacOptions() ++ Agg(s"-Xplugin:${pluginModule.jar().path}")
-    } else super.scalacOptions()
-  }
-
-  override def scalacPluginClasspath = T {
-    if (!v.isScala3(crossScalaVersion)) {
-      super.scalacPluginClasspath() ++ Agg(pluginModule.jar())
-    } else super.scalacPluginClasspath()
-  }
-}
-
-object firrtl extends Cross[Firrtl](v.scalaCrossVersions)
-
-trait Firrtl extends CrossSbtModule with Cross.Module[String] with HasScala2MacroAnno with ScalafmtModule {
-  def millSourcePath = super.millSourcePath / os.up / "firrtl"
-  def scalaVersion = crossScalaVersion
-
-  override def scalacOptions = T {
-    if (v.isScala3(crossScalaVersion)) {
-      Seq.empty[String]
-    } else {
-      v.scala2CommonOptions ++ Seq(
-        "-language:reflectiveCalls",
-        "-language:existentials",
-        "-language:implicitConversions",
-        "-Yrangepos", // required by SemanticDB compiler plugin
-        "-Xsource:3",
-        "-Xsource-features:infer-override"
-      )
-    }
-  }
-
-  val commonDeps = Agg(
-    v.scopt,
-    v.commonText,
-    v.osLib,
-    v.json4s
-  )
-
-  def ivyDeps = if (v.isScala3(crossScalaVersion)) {
-    commonDeps
-  } else {
-    commonDeps ++ Agg(v.dataclass)
-  }
-
-  object test extends SbtModuleTests with TestModule.ScalaTest with ScalafmtModule {
-    def ivyDeps = Agg(v.scalatest, v.scalacheck)
-  }
-}
-
-object svsim extends Cross[Svsim](v.scalaCrossVersions)
-trait Svsim extends CrossSbtModule with ScalafmtModule {
-  def millSourcePath = super.millSourcePath / os.up / "svsim"
-
-  override def scalacOptions = T {
-    if (v.isScala3(crossScalaVersion)) {
-      Seq.empty[String]
-    } else {
-      v.scala2CommonOptions ++ Seq(
-        "-Xsource:3",
-        "-Xsource-features:case-apply-copy-access"
-      )
-    }
-  }
-
-  object test extends SbtModuleTests with TestModule.ScalaTest with ScalafmtModule {
-    def ivyDeps = Agg(v.scalatest, v.scalacheck)
-  }
-}
-
-object macros extends Cross[Macros](v.scalaCrossVersions)
-trait Macros extends CrossSbtModule with HasScala2MacroAnno with ScalafmtModule {
-  def millSourcePath = super.millSourcePath / os.up / "macros"
-
-  override def scalacOptions = T {
-    if (v.isScala3(crossScalaVersion)) {
-      Seq.empty[String]
-    } else {
-      v.scala2CommonOptions ++ Seq(
-        "-Xsource:3"
-      )
-    }
-  }
-
-  override def ivyDeps = super.ivyDeps() ++ Seq(v.scalaReflect(crossScalaVersion))
-}
-
-object core extends Cross[Core](v.scalaCrossVersions)
-trait Core extends CrossSbtModule with HasScala2MacroAnno with ScalafmtModule {
-  def scalaVersion = crossScalaVersion
-  def millSourcePath = super.millSourcePath / os.up / "core"
-
-  override def scalacOptions = T {
-    if (v.isScala3(crossScalaVersion)) {
-      Seq.empty[String]
-    } else {
-      v.scala2CommonOptions ++ Seq(
-        "-Xsource:3"
-      )
-    }
-  }
-
-  val crossModuleDeps = Seq(firrtl(crossScalaVersion)) ++ {
-    if (v.isScala3(crossScalaVersion)) Seq.empty
-    else Seq(macros(crossScalaVersion))
-  }
-
-  override def moduleDeps = super.moduleDeps ++ crossModuleDeps
-
-  val commonDeps = Agg(
-    v.osLib,
-    v.upickle
-  )
-
-  override def ivyDeps = if (v.isScala3(crossScalaVersion)) {
-    super.ivyDeps() ++ commonDeps ++ Agg(v.firtoolResolver.withDottyCompat(scalaVersion()))
-  } else {
-    super.ivyDeps() ++ commonDeps ++ Agg(v.firtoolResolver)
-  }
-
-  // Similar to the publish version, but no dirty indicators because otherwise
-  // this file will change any time any file is changed.
-  def publishVersion = T {
-    VcsVersion
-      .vcsState()
-      .format(
-        countSep = "+",
-        revHashDigits = 8,
-        untaggedSuffix = "-SNAPSHOT",
-        dirtySep = "",
-        dirtyHashDigits = 0
-      )
-  }
-  def buildInfo = T {
-    val outputFile = T.dest / "chisel3" / "BuildInfo.scala"
-    val firtoolVersionString = "Some(\"" + v.firtoolVersion + "\")"
-    val contents =
-      s"""
-         |package chisel3
-         |case object BuildInfo {
-         |  val buildInfoPackage: String = "chisel3"
-         |  val version: String = "${publishVersion()}"
-         |  val scalaVersion: String = "${scalaVersion()}"
-         |  @deprecated("Chisel no longer uses SBT, this field will be removed.", "Chisel 7.0")
-         |  val sbtVersion: String = ""
-         |  val firtoolVersion: scala.Option[String] = $firtoolVersionString
-         |  override val toString: String = {
-         |    "buildInfoPackage: %s, version: %s, scalaVersion: %s, firtoolVersion %s".format(
-         |        buildInfoPackage, version, scalaVersion, firtoolVersion
-         |    )
-         |  }
-         |}
-         |""".stripMargin
-    os.write(outputFile, contents, createFolders = true)
-    PathRef(T.dest)
-  }
-  override def generatedSources = T {
-    super.generatedSources() :+ buildInfo()
-  }
-}
-
-object plugin extends Cross[Plugin](v.pluginScalaCrossVersions)
-trait Plugin extends CrossSbtModule with ScalafmtModule with ChiselPublishModule {
-  override def artifactName = "chisel-plugin"
-
-  // The plugin is compiled for every minor Scala version
-  override def crossFullScalaVersion = true
-
-  def millSourcePath = super.millSourcePath / os.up / "plugin"
-  def scalaLibraryIvy = v.scalaLibrary(crossScalaVersion)
-  def scalaReflectIvy = v.scalaReflect(crossScalaVersion)
-  def scalaCompilerIvy: Dep = v.scalaCompiler(crossScalaVersion)
-
-  def ivyDeps = T {
-    if (!v.isScala3(crossScalaVersion)) {
-      super.ivyDeps() ++ Agg(scalaLibraryIvy, scalaReflectIvy, scalaCompilerIvy)
-    } else {
-      super.ivyDeps()
-    }
-  }
-}
-
-object chisel extends Cross[Chisel](v.scalaCrossVersions)
-trait Chisel extends CrossSbtModule with HasScala2MacroAnno with HasScala2Plugin with ScalafmtModule {
-  override def millSourcePath = super.millSourcePath / os.up
-  def svsimModule = svsim(crossScalaVersion)
-  def coreModule = core(crossScalaVersion)
-  def pluginModule = plugin()
-
-  override def scalacOptions = T {
-    if (v.isScala3(crossScalaVersion)) {
-      Seq.empty[String]
-    } else {
-      super.scalacOptions() ++ v.scala2CommonOptions
-    }
-  }
-
-  override def moduleDeps = super.moduleDeps ++ Seq(coreModule, svsimModule)
-
-  object test extends SbtModuleTests with TestModule.ScalaTest with ScalafmtModule {
-    def ivyDeps = Agg(v.scalatest, v.scalacheck)
-
-    // Suppress Scala 3 behavior requiring explicit types on implicit definitions
-    // Note this must come before the -Wconf is warningSuppression
-    override def scalacOptions = T { super.scalacOptions() :+ "-Wconf:cat=other-implicit-type:s" }
-  }
-}
-
-object integrationTests extends Cross[IntegrationTests](v.scalaCrossVersions)
-trait IntegrationTests extends CrossSbtModule with HasScala2Plugin with ScalafmtModule {
-  def pluginModule = plugin()
-  def millSourcePath = os.pwd / "integration-tests"
-
-  object test extends SbtModuleTests with TestModule.ScalaTest with ScalafmtModule {
-    override def moduleDeps = super.moduleDeps :+ chisel().test
-    def ivyDeps = Agg(v.scalatest, v.scalacheck)
-  }
-}
-
-object stdlib extends Cross[Stdlib](v.scalaCrossVersions)
-trait Stdlib extends CrossSbtModule with HasScala2Plugin with ScalafmtModule {
-  def millSourcePath = super.millSourcePath / os.up / "stdlib"
-  def chiselModule = chisel(crossScalaVersion)
-  def pluginModule = plugin(crossScalaVersion)
-
-  override def moduleDeps = Seq(chiselModule, pluginModule)
-}
-
-object circtpanamabinding extends CIRCTPanamaBinding
-
-trait CIRCTPanamaBinding extends panama.CIRCTPanamaBindingModule {
-  def header = T(PathRef(millSourcePath / "jextract-headers.h"))
-  def circtInstallPath = T(panama.utils.circtInstallDir())
-  def jextractBinary = T(panama.utils.jextractInstallDir() / "bin" / "jextract")
-  def includePaths = T(Seq(PathRef(circtInstallPath() / "include")))
-  def libraryPaths = T(Seq(PathRef(circtInstallPath() / "lib")))
-}
-
-object panamalib extends Cross[PanamaLib](v.scalaCrossVersions)
-
-trait PanamaLib extends panama.PanamaLibModule with CrossModuleBase with ScalafmtModule {
-  def circtPanamaBindingModule = circtpanamabinding
-}
-
-object panamaom extends Cross[PanamaOM](v.scalaCrossVersions)
-
-trait PanamaOM extends panama.PanamaOMModule with CrossModuleBase with ScalafmtModule {
-  def panamaLibModule = panamalib(crossScalaVersion)
-}
-
-object panamaconverter extends Cross[PanamaConverter](v.scalaCrossVersions)
-
-trait PanamaConverter
-    extends panama.PanamaConverterModule
-    with CrossModuleBase
-    with HasScala2Plugin
-    with ScalafmtModule {
-  def panamaOMModule = panamaom(crossScalaVersion)
-  def chiselModule = chisel(crossScalaVersion)
-  def pluginModule = plugin(crossScalaVersion)
-
-  override def moduleDeps = super.moduleDeps ++ Some(chiselModule)
-}
-
-object litutility extends Cross[LitUtility](v.scalaCrossVersions)
-
-trait LitUtility extends panama.LitUtilityModule with CrossModuleBase with HasScala2Plugin with ScalafmtModule {
-  def chiselModule = chisel(crossScalaVersion)
-  def pluginModule = plugin(crossScalaVersion)
-  def millSourcePath = super.millSourcePath / os.up / "lit" / "utility"
-  def panamaConverterModule = panamaconverter(crossScalaVersion)
-  def panamaOMModule = panamaom(crossScalaVersion)
-
-  override def moduleDeps = super.moduleDeps ++ Some(chiselModule)
-}
-
-object lit extends Cross[Lit](v.scalaCrossVersions)
-
-trait Lit extends panama.LitModule with Cross.Module[String] {
-  def scalaVersion: T[String] = crossValue
-  def runClasspath: T[Seq[os.Path]] = T(litutility(crossValue).runClasspath().map(_.path))
-  def pluginJars:   T[Seq[os.Path]] = T(Seq(litutility(crossValue).panamaConverterModule.pluginModule.jar().path))
-  def javaLibraryPath: T[Seq[os.Path]] = T(
-    litutility(crossValue).panamaConverterModule.circtPanamaBindingModule.libraryPaths().map(_.path)
-  )
-  def javaHome:     T[os.Path] = T(os.Path(sys.props("java.home")))
-  def chiselLitDir: T[os.Path] = T(millSourcePath)
-  def litConfigIn:  T[PathRef] = T.source(millSourcePath / "tests" / "lit.site.cfg.py.in")
-}
-
-object benchmark extends ScalaModule with JmhModule with ScalafmtModule {
-  def scalaVersion = v.scalaVersion
-  def jmhCoreVersion = v.jmhVersion
-
-  override def moduleDeps = Seq(chisel(v.scalaVersion))
-}
-
-/** Aggregate project for publishing Chisel as a single artifact
-  */
-object unipublish extends ScalaModule with ChiselPublishModule {
-
-  def scalaVersion = v.scalaVersion
-
-  // This is published as chisel
-  override def artifactName = "chisel"
-
-  // Older versions of Scala do not work with newer versions of the JVM
-  // This is a hack to ensure we always use Java 8 to publish Chisel with Scala 2.13
-  // We could use Java 11 with -release 8
-  // Note that this target is used by real publishing but not by publishLocal
-  override def publishArtifacts = T {
-    // TODO when we publish for Scala 3, only do this check for Scala 2.13
-    if (v.javaVersion != 8) {
-      throw new Exception(s"Publishing requires Java 8, current JDK is ${v.javaVersion}")
-    }
-    super.publishArtifacts
-  }
-
-  /** Publish both this project and the plugin (for the default Scala version) */
-  override def publishLocal(localIvyRepo: String = null) = T.command {
-    // TODO consider making this parallel and publishing all cross-versions for plugin
-    plugin(v.scalaVersion).publishLocal(localIvyRepo)()
-    super.publishLocal(localIvyRepo)()
-  }
-
-  // Explicitly not using moduleDeps because that influences so many things
-  def components = Seq(firrtl, svsim, macros, core, chisel).map(_(v.scalaVersion))
-
-  /** Aggregated ivy deps to include as dependencies in POM */
-  def ivyDeps = T { T.traverse(components)(_.ivyDeps)().flatten }
-
-  /** Aggregated local classpath to include in jar */
-  override def localClasspath = T { T.traverse(components)(_.localClasspath)().flatten }
-
-  /** Aggreagted sources from all component modules */
-  def aggregatedSources = T { T.traverse(components)(_.allSources)().flatten }
-
-  /** Aggreagted resources from all component modules */
-  def aggregatedResources = T { T.traverse(components)(_.resources)().flatten }
-
-  /** Aggreagted compile resources from all component modules */
-  def aggregatedCompileResources = T { T.traverse(components)(_.compileResources)().flatten }
-
-  /** Aggregated sourceJar from all component modules
-    */
-  override def sourceJar: T[PathRef] = T {
-    // This is based on the implementation of sourceJar in PublishModule, may need to be kept in sync.
-    val allDirs = aggregatedSources() ++ aggregatedResources() ++ aggregatedCompileResources()
-    createJar(allDirs.map(_.path).filter(os.exists), manifest())
-  }
-
-  // Needed for ScalaDoc
-  override def scalacOptions = v.scala2CommonOptions
-
-  def scalaDocRootDoc = T.source { T.workspace / "root-doc.txt" }
-
-  def unidocOptions = T {
-    scalacOptions() ++ Seq[String](
-      "-classpath",
-      unidocCompileClasspath().map(_.path).mkString(sys.props("path.separator")),
-      "-diagrams",
-      "-groups",
-      "-skip-packages",
-      "chisel3.internal",
-      "-diagrams-max-classes",
-      "25",
-      "-doc-version",
-      publishVersion(),
-      "-doc-title",
-      "chisel",
-      "-doc-root-content",
-      scalaDocRootDoc().path.toString,
-      "-sourcepath",
-      T.workspace.toString,
-      "-doc-source-url",
-      unidocSourceUrl(),
-      "-language:implicitConversions",
-      "-implicits"
-    )
-  }
-
-  // Built-in UnidocModule is insufficient so we need to implement it ourselves
-  // We could factor this out into a utility
-  def unidocSourceUrl: T[String] = T {
-    val base = "https://github.com/chipsalliance/chisel/tree"
-    val branch = if (publishVersion().endsWith("-SNAPSHOT")) "main" else s"v${publishVersion()}"
-    s"$base/$branch/€{FILE_PATH_EXT}#L€{FILE_LINE}"
-  }
-
-  def unidocVersion: T[Option[String]] = None
-
-  def unidocCompileClasspath = T {
-    Seq(compile().classes) ++ T.traverse(components)(_.compileClasspath)().flatten
-  }
-
-  def unidocSourceFiles = T {
-    allSourceFiles() ++ T.traverse(components)(_.allSourceFiles)().flatten
-  }
-
-  // Based on UnidocModule and docJar in Mill, may need to be kept in sync.
-  override def docJar = T {
-    T.log.info(s"Building unidoc for ${unidocSourceFiles().length} files")
-
-    val javadocDir = T.dest / "javadoc"
-    os.makeDir(javadocDir)
-
-    val fullOptions = unidocOptions() ++
-      Seq("-d", javadocDir.toString) ++
-      unidocSourceFiles().map(_.path.toString)
-
-    zincWorker()
-      .worker()
-      .docJar(
-        scalaVersion(),
-        scalaOrganization(),
-        scalaDocClasspath(),
-        scalacPluginClasspath(),
-        fullOptions
-      ) match {
-      case true  => Result.Success(createJar(Agg(javadocDir))(T.dest))
-      case false => Result.Failure("docJar generation failed")
-    }
-  }
-}
diff --git a/circtpanamabinding/package.mill b/circtpanamabinding/package.mill
new file mode 100644
index 00000000000..81556034108
--- /dev/null
+++ b/circtpanamabinding/package.mill
@@ -0,0 +1,108 @@
+package build.circtpanamabinding
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+
+import build._
+
+object `package` extends RootModule with CIRCTPanamaBinding
+
+// Java Codegen for all declared functions.
+// All of these functions are not private API which is subject to change.
+trait CIRCTPanamaBinding extends HasJextractGeneratedSources {
+  object utils extends Module {
+    val architecture = System.getProperty("os.arch")
+    val operationSystem = System.getProperty("os.name")
+
+    val mac = operationSystem.toLowerCase.startsWith("mac")
+    val linux = operationSystem.toLowerCase.startsWith("linux")
+    val windows = operationSystem.toLowerCase.startsWith("win")
+    val amd64 = architecture.matches("^(x8664|amd64|ia32e|em64t|x64|x86_64)$")
+    val aarch64 = architecture.equals("aarch64") | architecture.startsWith("armv8")
+
+    val firtoolVersion = {
+      val j =
+        _root_.upickle.default.read[Map[String, String]](os.read(millSourcePath / os.up / os.up / "etc" / "circt.json"))
+      j("version").stripPrefix("firtool-")
+    }
+
+    def circt(version: String, os: String, platform: String) =
+      s"https://github.com/llvm/circt/releases/download/firtool-${version}/circt-full-shared-${os}-${platform}.tar.gz"
+
+    // 21, 1-2, {linux-x64, macos-x64, windows-x64}
+    // 22, 1-2, {linux-x64, macos-aarch64, macos-x64, windows-x64}
+    def jextract(jdkVersion: Int, jextractVersion: String, os: String, platform: String) =
+      s"https://download.java.net/java/early_access/jextract/21/1/openjdk-${jdkVersion}-jextract+${jextractVersion}_${os}-${platform}_bin.tar.gz"
+
+    // use Task(persistent = true) to avoid download repeatedly
+    def circtInstallDir: T[os.Path] = Task(persistent = true) {
+      Task.ctx().env.get("CIRCT_INSTALL_PATH") match {
+        case Some(dir) => os.Path(dir)
+        case None =>
+          Task.ctx().log.info("Use CIRCT_INSTALL_PATH to vendor circt")
+          val tarPath = Task.dest / "circt.tar.gz"
+          if (!os.exists(tarPath)) {
+            val url = circt(
+              firtoolVersion,
+              if (linux) "linux" else if (mac) "macos" else throw new Exception("unsupported os"),
+              // circt does not yet publish for macos-aarch64, use x64 for now
+              if (amd64 || mac) "x64" else throw new Exception("unsupported arch")
+            )
+            Task.ctx().log.info(s"Downloading circt from ${url}")
+            mill.util.Util.download(url, os.rel / "circt.tar.gz")
+            Task.ctx().log.info(s"Download Successfully")
+          }
+          os.proc("tar", "xvf", tarPath, "--strip-components=1").call(Task.dest)
+          Task.dest
+      }
+    }
+
+    // use Task(persistent = true) to avoid download repeatedly
+    def jextractInstallDir: T[os.Path] = Task(persistent = true) {
+      Task.ctx().env.get("JEXTRACT_INSTALL_PATH") match {
+        case Some(dir) => os.Path(dir)
+        case None =>
+          Task.ctx().log.info("Use JEXTRACT_INSTALL_PATH to vendor jextract")
+          val tarPath = Task.dest / "jextract.tar.gz"
+          if (!os.exists(tarPath)) {
+            val url = jextract(
+              21,
+              "1-2",
+              if (linux) "linux" else if (mac) "macos" else throw new Exception("unsupported os"),
+              // There is no macos-aarch64 for jextract 21, use x64 for now
+              if (amd64 || mac) "x64" else if (aarch64) "aarch64" else throw new Exception("unsupported arch")
+            )
+            Task.ctx().log.info(s"Downloading jextract from ${url}")
+            mill.util.Util.download(url, os.rel / "jextract.tar.gz")
+            Task.ctx().log.info(s"Download Successfully")
+          }
+          os.proc("tar", "xvf", tarPath, "--strip-components=1").call(Task.dest)
+          Task.dest
+      }
+    }
+  }
+
+  def includeConstants =
+    Task.Input(os.read.lines(millSourcePath / "includeConstants.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
+  def includeFunctions =
+    Task.Input(os.read.lines(millSourcePath / "includeFunctions.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
+  def includeStructs =
+    Task.Input(os.read.lines(millSourcePath / "includeStructs.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
+  def includeTypedefs =
+    Task.Input(os.read.lines(millSourcePath / "includeTypedefs.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
+  def includeUnions =
+    Task.Input(os.read.lines(millSourcePath / "includeUnions.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
+  def includeVars =
+    Task.Input(os.read.lines(millSourcePath / "includeVars.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
+  def linkLibraries =
+    Task.Input(os.read.lines(millSourcePath / "linkLibraries.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
+
+  def target = Task("org.llvm.circt")
+  def headerClassName = Task("CAPI")
+  def header = Task(PathRef(millSourcePath / "jextract-headers.h"))
+  def circtInstallPath = Task(utils.circtInstallDir())
+  def jextractBinary = Task(utils.jextractInstallDir() / "bin" / "jextract")
+  def includePaths = Task(Seq(PathRef(circtInstallPath() / "include")))
+  def libraryPaths = Task(Seq(PathRef(circtInstallPath() / "lib")))
+}
diff --git a/core/package.mill b/core/package.mill
new file mode 100644
index 00000000000..f1976a6e80e
--- /dev/null
+++ b/core/package.mill
@@ -0,0 +1,88 @@
+package build.core
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+import de.tobiasroeser.mill.vcs.version.VcsVersion // pulled in by mill-ci-release
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[Core](v.scalaCrossVersions)
+}
+
+trait Core extends CrossSbtModule with HasScala2MacroAnno with ScalafmtModule {
+  def scalaVersion = crossScalaVersion
+
+  def millSourcePath = super.millSourcePath / os.up
+
+  override def scalacOptions = Task {
+    if (v.isScala3(crossScalaVersion)) {
+      Seq.empty[String]
+    } else {
+      v.scala2CommonOptions ++ Seq(
+        "-Xsource:3"
+      )
+    }
+  }
+
+  val crossModuleDeps = Seq(firrtl.cross(crossScalaVersion)) ++ {
+    if (v.isScala3(crossScalaVersion)) Seq.empty
+    else Seq(macros.cross(crossScalaVersion))
+  }
+
+  override def moduleDeps = super.moduleDeps ++ crossModuleDeps
+
+  val commonDeps = Agg(
+    v.osLib,
+    v.upickle
+  )
+
+  override def ivyDeps = if (v.isScala3(crossScalaVersion)) {
+    super.ivyDeps() ++ commonDeps ++ Agg(v.firtoolResolver.withDottyCompat(scalaVersion()))
+  } else {
+    super.ivyDeps() ++ commonDeps ++ Agg(v.firtoolResolver)
+  }
+
+  // Similar to the publish version, but no dirty indicators because otherwise
+  // this file will change any time any file is changed.
+  def publishVersion = Task {
+    VcsVersion
+      .vcsState()
+      .format(
+        countSep = "+",
+        revHashDigits = 8,
+        untaggedSuffix = "-SNAPSHOT",
+        dirtySep = "",
+        dirtyHashDigits = 0
+      )
+  }
+  def buildInfo = Task {
+    val outputFile = Task.dest / "chisel3" / "BuildInfo.scala"
+    val firtoolVersionString = "Some(\"" + v.firtoolVersion + "\")"
+    val contents =
+      s"""
+         |package chisel3
+         |case object BuildInfo {
+         |  val buildInfoPackage: String = "chisel3"
+         |  val version: String = "${publishVersion()}"
+         |  val scalaVersion: String = "${scalaVersion()}"
+         |  @deprecated("Chisel no longer uses SBT, this field will be removed.", "Chisel 7.0")
+         |  val sbtVersion: String = ""
+         |  val firtoolVersion: scala.Option[String] = $firtoolVersionString
+         |  override val toString: String = {
+         |    "buildInfoPackage: %s, version: %s, scalaVersion: %s, firtoolVersion %s".format(
+         |        buildInfoPackage, version, scalaVersion, firtoolVersion
+         |    )
+         |  }
+         |}
+         |""".stripMargin
+    os.write(outputFile, contents, createFolders = true)
+    PathRef(Task.dest)
+  }
+  override def generatedSources = Task {
+    super.generatedSources() :+ buildInfo()
+  }
+}
diff --git a/firrtl/package.mill b/firrtl/package.mill
new file mode 100644
index 00000000000..ebec7ef9853
--- /dev/null
+++ b/firrtl/package.mill
@@ -0,0 +1,51 @@
+package build.firrtl
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[Firrtl](v.scalaCrossVersions)
+}
+
+trait Firrtl extends CrossSbtModule with Cross.Module[String] with HasScala2MacroAnno with ScalafmtModule {
+  def scalaVersion = crossScalaVersion
+
+  def millSourcePath = super.millSourcePath / os.up
+
+  override def scalacOptions = Task {
+    if (v.isScala3(crossScalaVersion)) {
+      Seq.empty[String]
+    } else {
+      v.scala2CommonOptions ++ Seq(
+        "-language:reflectiveCalls",
+        "-language:existentials",
+        "-language:implicitConversions",
+        "-Yrangepos", // required by SemanticDB compiler plugin
+        "-Xsource:3",
+        "-Xsource-features:infer-override"
+      )
+    }
+  }
+
+  val commonDeps = Agg(
+    v.scopt,
+    v.commonText,
+    v.osLib,
+    v.json4s
+  )
+
+  def ivyDeps = if (v.isScala3(crossScalaVersion)) {
+    commonDeps
+  } else {
+    commonDeps ++ Agg(v.dataclass)
+  }
+
+  object test extends SbtTests with TestModule.ScalaTest with ScalafmtModule {
+    def ivyDeps = Agg(v.scalatest, v.scalacheck)
+  }
+}
diff --git a/flake.lock b/flake.lock
index 69bc40050c3..ecc41d7664e 100644
--- a/flake.lock
+++ b/flake.lock
@@ -5,11 +5,11 @@
         "systems": "systems"
       },
       "locked": {
-        "lastModified": 1710146030,
-        "narHash": "sha256-SZ5L6eA7HJ/nmkzGG7/ISclqe6oZdOZTNoesiInkXPQ=",
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "b1d9ab70662946ef0850d488da1c9019f3a9752a",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
         "type": "github"
       },
       "original": {
@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1718209920,
-        "narHash": "sha256-ZMkzbuNpjKsWqUNOU0GPbtJgz0ejKfTLPcZHLd0L2+Q=",
+        "lastModified": 1736143365,
+        "narHash": "sha256-hUT7MWIF17WXwqiF7QxnQf1zRvov7CVhjLMGfTQcpW8=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "ccacd09436c6d39457eb11b451db538df72c53d9",
+        "rev": "6663da588d8b6298bed018c6bc23681f8af70399",
         "type": "github"
       },
       "original": {
diff --git a/integration-tests/package.mill b/integration-tests/package.mill
new file mode 100644
index 00000000000..12991a7d075
--- /dev/null
+++ b/integration-tests/package.mill
@@ -0,0 +1,23 @@
+package build.`integration-tests`
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[IntegrationTests](v.scalaCrossVersions)
+}
+
+trait IntegrationTests extends CrossSbtModule with HasScala2Plugin with ScalafmtModule {
+  def pluginModule = plugin.cross()
+  def millSourcePath = super.millSourcePath / os.up
+
+  object test extends SbtTests with TestModule.ScalaTest with ScalafmtModule {
+    override def moduleDeps = super.moduleDeps :+ chisel().test
+    def ivyDeps = Agg(v.scalatest, v.scalacheck)
+  }
+}
diff --git a/lit/package.mill b/lit/package.mill
new file mode 100644
index 00000000000..9b09f22adbe
--- /dev/null
+++ b/lit/package.mill
@@ -0,0 +1,46 @@
+package build.lit
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+import build.lit.utility
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[Lit](v.scalaCrossVersions)
+}
+
+trait Lit extends Module with Cross.Module[String] {
+  def millSourcePath = super.millSourcePath / os.up
+
+  def litConfig: T[PathRef] = Task {
+    os.write(
+      Task.dest / "lit.site.cfg.py",
+      os.read(litConfigIn().path)
+        .replaceAll("@SCALA_VERSION@", scalaVersion())
+        .replaceAll("@RUN_CLASSPATH@", runClasspath().mkString(","))
+        .replaceAll("@SCALA_PLUGIN_JARS@", pluginJars().mkString(","))
+        .replaceAll("@JAVA_HOME@", javaHome().toString)
+        .replaceAll("@JAVA_LIBRARY_PATH@", javaLibraryPath().mkString(","))
+        .replaceAll("@CHISEL_LIT_DIR@", chiselLitDir().toString)
+    )
+    PathRef(Task.dest)
+  }
+
+  def run(args: String*) = Task.Command(
+    os.proc("lit", litConfig().path)
+      .call(Task.dest, stdout = os.ProcessOutput.Readlines(line => Task.ctx().log.info("[lit] " + line)))
+  )
+  def scalaVersion: T[String] = crossValue
+  def runClasspath: T[Seq[os.Path]] = Task(utility.cross(crossValue).runClasspath().map(_.path))
+  def pluginJars:   T[Seq[os.Path]] = Task(Seq(utility.cross(crossValue).panamaConverterModule.pluginModule.jar().path))
+  def javaLibraryPath: T[Seq[os.Path]] = Task(
+    utility.cross(crossValue).panamaConverterModule.circtPanamaBindingModule.libraryPaths().map(_.path)
+  )
+  def javaHome:     T[os.Path] = Task(os.Path(sys.props("java.home")))
+  def chiselLitDir: T[os.Path] = Task(millSourcePath)
+  def litConfigIn:  T[PathRef] = Task.Source(millSourcePath / "tests" / "lit.site.cfg.py.in")
+}
diff --git a/lit/utility/package.mill b/lit/utility/package.mill
new file mode 100644
index 00000000000..44775dd38cf
--- /dev/null
+++ b/lit/utility/package.mill
@@ -0,0 +1,26 @@
+package build.lit.utility
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[LitUtility](v.scalaCrossVersions)
+}
+
+trait LitUtility extends ScalaModule with HasPanamaConverterModule with HasPanamaOMModule with CrossModuleBase with HasScala2Plugin with ScalafmtModule {
+  override def scalacOptions = Task { Seq("-Ymacro-annotations") }
+  override def circtPanamaBindingModule = panamaConverterModule.circtPanamaBindingModule
+
+  def chiselModule = chisel(crossScalaVersion)
+  def pluginModule = plugin.cross(crossScalaVersion)
+  def millSourcePath = super.millSourcePath / os.up
+  def panamaConverterModule = panamaconverter.cross(crossScalaVersion)
+  def panamaOMModule = panamaom.cross(crossScalaVersion)
+
+  override def moduleDeps = super.moduleDeps ++ Some(chiselModule)
+}
diff --git a/macros/package.mill b/macros/package.mill
new file mode 100644
index 00000000000..12b90c463d0
--- /dev/null
+++ b/macros/package.mill
@@ -0,0 +1,29 @@
+package build.macros
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[Macros](v.scalaCrossVersions)
+}
+
+trait Macros extends CrossSbtModule with HasScala2MacroAnno with ScalafmtModule {
+  def millSourcePath = super.millSourcePath / os.up
+
+  override def scalacOptions = Task {
+    if (v.isScala3(crossScalaVersion)) {
+      Seq.empty[String]
+    } else {
+      v.scala2CommonOptions ++ Seq(
+        "-Xsource:3"
+      )
+    }
+  }
+
+  override def ivyDeps = super.ivyDeps() ++ Seq(v.scalaReflect(crossScalaVersion))
+}
diff --git a/mill b/mill
index 9d343ff64b8..ddc0c9a41be 100755
--- a/mill
+++ b/mill
@@ -14,7 +14,7 @@
 set -e
 
 if [ -z "${DEFAULT_MILL_VERSION}" ] ; then
-  DEFAULT_MILL_VERSION="0.11.4"
+  DEFAULT_MILL_VERSION="0.12.5"
 fi
 
 
diff --git a/overlay.nix b/overlay.nix
index 2498ad5f4f9..b708348037e 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -1,10 +1,10 @@
 final: prev:
 {
   mill = (prev.mill.overrideAttrs (oldAttrs: rec {
-    version = "0.11.6";
+    version = "0.12.5";
     src = prev.fetchurl {
       url = "https://github.com/com-lihaoyi/mill/releases/download/${version}/${version}-assembly";
-      hash = "sha256-vGhjnOKvR2RdgFx3WsM217SO9gcKZknPaf7LKo3SJPU=";
+      hash = "sha256-DHslQS/uzwbZVdATQY3pqQgM51W+26x2AckQnDPVoFc=";
     };
   })).override {
     jre = final.openjdk21;
diff --git a/panama.sc b/panama.sc
deleted file mode 100644
index 12d794f4469..00000000000
--- a/panama.sc
+++ /dev/null
@@ -1,249 +0,0 @@
-import mill._
-import mill.scalalib._
-import mill.api.Result
-import mill.scalalib._
-import mill.scalalib.api.CompilationResult
-import mill.util.Jvm
-import mill.scalalib.scalafmt._
-
-import java.util
-import scala.jdk.StreamConverters.StreamHasToScala
-
-object utils extends Module {
-  val architecture = System.getProperty("os.arch")
-  val operationSystem = System.getProperty("os.name")
-
-  val mac = operationSystem.toLowerCase.startsWith("mac")
-  val linux = operationSystem.toLowerCase.startsWith("linux")
-  val windows = operationSystem.toLowerCase.startsWith("win")
-  val amd64 = architecture.matches("^(x8664|amd64|ia32e|em64t|x64|x86_64)$")
-  val aarch64 = architecture.equals("aarch64") | architecture.startsWith("armv8")
-
-  val firtoolVersion = {
-    val j = _root_.upickle.default.read[Map[String, String]](os.read(millSourcePath / os.up / "etc" / "circt.json"))
-    j("version").stripPrefix("firtool-")
-  }
-
-  def circt(version: String, os: String, platform: String) =
-    s"https://github.com/llvm/circt/releases/download/firtool-${version}/circt-full-shared-${os}-${platform}.tar.gz"
-
-  // 21, 1-2, {linux-x64, macos-x64, windows-x64}
-  // 22, 1-2, {linux-x64, macos-aarch64, macos-x64, windows-x64}
-  def jextract(jdkVersion: Int, jextractVersion: String, os: String, platform: String) =
-    s"https://download.java.net/java/early_access/jextract/21/1/openjdk-${jdkVersion}-jextract+${jextractVersion}_${os}-${platform}_bin.tar.gz"
-
-  // use T.persistent to avoid download repeatedly
-  def circtInstallDir: T[os.Path] = T.persistent {
-    T.ctx().env.get("CIRCT_INSTALL_PATH") match {
-      case Some(dir) => os.Path(dir)
-      case None =>
-        T.ctx().log.info("Use CIRCT_INSTALL_PATH to vendor circt")
-        val tarPath = T.dest / "circt.tar.gz"
-        if (!os.exists(tarPath)) {
-          val url = circt(
-            firtoolVersion,
-            if (linux) "linux" else if (mac) "macos" else throw new Exception("unsupported os"),
-            // circt does not yet publish for macos-aarch64, use x64 for now
-            if (amd64 || mac) "x64" else throw new Exception("unsupported arch")
-          )
-          T.ctx().log.info(s"Downloading circt from ${url}")
-          mill.util.Util.download(url, os.rel / "circt.tar.gz")
-          T.ctx().log.info(s"Download Successfully")
-        }
-        os.proc("tar", "xvf", tarPath, "--strip-components=1").call(T.dest)
-        T.dest
-    }
-  }
-
-  // use T.persistent to avoid download repeatedly
-  def jextractInstallDir: T[os.Path] = T.persistent {
-    T.ctx().env.get("JEXTRACT_INSTALL_PATH") match {
-      case Some(dir) => os.Path(dir)
-      case None =>
-        T.ctx().log.info("Use JEXTRACT_INSTALL_PATH to vendor jextract")
-        val tarPath = T.dest / "jextract.tar.gz"
-        if (!os.exists(tarPath)) {
-          val url = jextract(
-            21,
-            "1-2",
-            if (linux) "linux" else if (mac) "macos" else throw new Exception("unsupported os"),
-            // There is no macos-aarch64 for jextract 21, use x64 for now
-            if (amd64 || mac) "x64" else if (aarch64) "aarch64" else throw new Exception("unsupported arch")
-          )
-          T.ctx().log.info(s"Downloading jextract from ${url}")
-          mill.util.Util.download(url, os.rel / "jextract.tar.gz")
-          T.ctx().log.info(s"Download Successfully")
-        }
-        os.proc("tar", "xvf", tarPath, "--strip-components=1").call(T.dest)
-        T.dest
-    }
-  }
-}
-
-trait HasJextractGeneratedSources extends JavaModule {
-
-  def jextractBinary: T[os.Path]
-
-  def includePaths: T[Seq[PathRef]]
-
-  def libraryPaths: T[Seq[PathRef]]
-
-  def header: T[PathRef]
-
-  def includeFunctions: T[Seq[String]]
-
-  def includeConstants: T[Seq[String]]
-
-  def includeStructs: T[Seq[String]]
-
-  def includeTypedefs: T[Seq[String]]
-
-  def includeUnions: T[Seq[String]]
-
-  def includeVars: T[Seq[String]]
-
-  def linkLibraries: T[Seq[String]]
-
-  def target: T[String]
-
-  def headerClassName: T[String]
-
-  def dumpAllIncludes = T {
-    val f = os.temp()
-    os.proc(
-      Seq(jextractBinary().toString, header().path.toString)
-        ++ includePaths().flatMap(p => Seq("-I", p.path.toString))
-        ++ Seq("--dump-includes", f.toString)
-    ).call()
-    os.read.lines(f).filter(s => s.nonEmpty && !s.startsWith("#"))
-  }
-
-  override def generatedSources: T[Seq[PathRef]] = T {
-    super.generatedSources() ++ {
-      // @formatter:off
-      os.proc(
-        Seq(jextractBinary().toString, header().path.toString)
-          ++ includePaths().flatMap(p => Seq("-I", p.path.toString))
-          ++ Seq(
-            "-t", target(),
-            "--header-class-name", headerClassName(),
-            "--source",
-            "--output", T.dest.toString
-          ) ++ includeFunctions().flatMap(f => Seq("--include-function", f)) ++
-          includeConstants().flatMap(f => Seq("--include-constant", f)) ++
-          includeStructs().flatMap(f => Seq("--include-struct", f)) ++
-          includeTypedefs().flatMap(f => Seq("--include-typedef", f)) ++
-          includeUnions().flatMap(f => Seq("--include-union", f)) ++
-          includeVars().flatMap(f => Seq("--include-var", f)) ++
-          linkLibraries().flatMap(l => Seq("-l", l))
-      ).call(T.dest)
-      // @formatter:on
-      Seq(PathRef(T.dest))
-    }
-  }
-
-  override def javacOptions = T(super.javacOptions() ++ Seq("--enable-preview", "--release", "21"))
-}
-
-// Java Codegen for all declared functions.
-// All of these functions are not private API which is subject to change.
-trait CIRCTPanamaBindingModule extends HasJextractGeneratedSources {
-
-  def includeConstants =
-    T.input(os.read.lines(millSourcePath / "includeConstants.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
-  def includeFunctions =
-    T.input(os.read.lines(millSourcePath / "includeFunctions.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
-  def includeStructs =
-    T.input(os.read.lines(millSourcePath / "includeStructs.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
-  def includeTypedefs =
-    T.input(os.read.lines(millSourcePath / "includeTypedefs.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
-  def includeUnions =
-    T.input(os.read.lines(millSourcePath / "includeUnions.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
-  def includeVars =
-    T.input(os.read.lines(millSourcePath / "includeVars.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
-  def linkLibraries =
-    T.input(os.read.lines(millSourcePath / "linkLibraries.txt").filter(s => s.nonEmpty && !s.startsWith("#")))
-
-  def target = T("org.llvm.circt")
-  def headerClassName = T("CAPI")
-}
-
-trait HasCIRCTPanamaBindingModule extends JavaModule {
-  def circtPanamaBindingModule: CIRCTPanamaBindingModule
-
-  override def moduleDeps = super.moduleDeps ++ Some(circtPanamaBindingModule)
-  //
-  override def javacOptions = T(super.javacOptions() ++ Seq("--enable-preview", "--release", "21"))
-
-  override def forkArgs: T[Seq[String]] = T(
-    super.forkArgs() ++ Seq("--enable-native-access=ALL-UNNAMED", "--enable-preview")
-      ++ circtPanamaBindingModule
-        .libraryPaths()
-        .map(p => s"-Djava.library.path=${p.path}")
-  )
-}
-
-// The Scala API for PanamaBinding, API here is experimentally public to all developers
-trait PanamaLibModule extends ScalaModule with HasCIRCTPanamaBindingModule
-
-trait HasPanamaLibModule extends ScalaModule with HasCIRCTPanamaBindingModule {
-  def panamaLibModule: PanamaLibModule
-
-  def circtPanamaBindingModule = panamaLibModule.circtPanamaBindingModule
-
-  override def moduleDeps = super.moduleDeps ++ Some(panamaLibModule)
-}
-
-trait PanamaOMModule extends ScalaModule with HasPanamaLibModule
-
-trait HasPanamaOMModule extends ScalaModule with HasCIRCTPanamaBindingModule {
-  def panamaOMModule: PanamaOMModule
-
-  def circtPanamaBindingModule = panamaOMModule.circtPanamaBindingModule
-
-  override def moduleDeps = super.moduleDeps ++ Some(panamaOMModule)
-}
-
-trait PanamaConverterModule extends ScalaModule with HasPanamaOMModule
-
-trait HasPanamaConverterModule extends ScalaModule with HasCIRCTPanamaBindingModule {
-  def panamaConverterModule: PanamaConverterModule
-
-  def circtPanamaBindingModule = panamaConverterModule.circtPanamaBindingModule
-
-  override def moduleDeps = super.moduleDeps ++ Some(panamaConverterModule)
-}
-
-trait PanamaOM extends PanamaOMModule with CrossModuleBase with ScalafmtModule
-
-trait LitUtilityModule extends ScalaModule with HasPanamaConverterModule with HasPanamaOMModule {
-  override def scalacOptions = T { Seq("-Ymacro-annotations") }
-  override def circtPanamaBindingModule = panamaConverterModule.circtPanamaBindingModule
-}
-
-trait LitModule extends Module {
-  def scalaVersion:    T[String]
-  def runClasspath:    T[Seq[os.Path]]
-  def pluginJars:      T[Seq[os.Path]]
-  def javaLibraryPath: T[Seq[os.Path]]
-  def javaHome:        T[os.Path]
-  def chiselLitDir:    T[os.Path]
-  def litConfigIn:     T[PathRef]
-  def litConfig: T[PathRef] = T {
-    os.write(
-      T.dest / "lit.site.cfg.py",
-      os.read(litConfigIn().path)
-        .replaceAll("@SCALA_VERSION@", scalaVersion())
-        .replaceAll("@RUN_CLASSPATH@", runClasspath().mkString(","))
-        .replaceAll("@SCALA_PLUGIN_JARS@", pluginJars().mkString(","))
-        .replaceAll("@JAVA_HOME@", javaHome().toString)
-        .replaceAll("@JAVA_LIBRARY_PATH@", javaLibraryPath().mkString(","))
-        .replaceAll("@CHISEL_LIT_DIR@", chiselLitDir().toString)
-    )
-    PathRef(T.dest)
-  }
-  def run(args: String*) = T.command(
-    os.proc("lit", litConfig().path)
-      .call(T.dest, stdout = os.ProcessOutput.Readlines(line => T.ctx().log.info("[lit] " + line)))
-  )
-}
diff --git a/panamaconverter/package.mill b/panamaconverter/package.mill
new file mode 100644
index 00000000000..aa53f1b0cbb
--- /dev/null
+++ b/panamaconverter/package.mill
@@ -0,0 +1,28 @@
+package build.panamaconverter
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[PanamaConverter](v.scalaCrossVersions)
+}
+
+trait PanamaConverter
+    extends ScalaModule
+    with HasPanamaOMModule
+    with CrossModuleBase
+    with HasScala2Plugin
+    with ScalafmtModule {
+  def millSourcePath = super.millSourcePath / os.up
+
+  def panamaOMModule = panamaom.cross(crossScalaVersion)
+  def chiselModule = chisel(crossScalaVersion)
+  def pluginModule = plugin.cross(crossScalaVersion)
+
+  override def moduleDeps = super.moduleDeps ++ Some(chiselModule)
+}
diff --git a/panamalib/package.mill b/panamalib/package.mill
new file mode 100644
index 00000000000..0ff32e2e56f
--- /dev/null
+++ b/panamalib/package.mill
@@ -0,0 +1,20 @@
+package build.panamalib
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[PanamaLib](v.scalaCrossVersions)
+}
+
+// The Scala API for PanamaBinding, API here is experimentally public to all developers
+trait PanamaLib extends ScalaModule with HasCIRCTPanamaBindingModule with CrossModuleBase with ScalafmtModule {
+  def millSourcePath = super.millSourcePath / os.up
+
+  def circtPanamaBindingModule = circtpanamabinding
+}
diff --git a/panamaom/package.mill b/panamaom/package.mill
new file mode 100644
index 00000000000..a2d7bcd899c
--- /dev/null
+++ b/panamaom/package.mill
@@ -0,0 +1,19 @@
+package build.panamaom
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[PanamaOM](v.scalaCrossVersions)
+}
+
+trait PanamaOM extends ScalaModule with HasPanamaLibModule with CrossModuleBase with ScalafmtModule {
+  def millSourcePath = super.millSourcePath / os.up
+
+  def panamaLibModule = panamalib.cross(crossScalaVersion)
+}
diff --git a/plugin/package.mill b/plugin/package.mill
new file mode 100644
index 00000000000..45a424bc272
--- /dev/null
+++ b/plugin/package.mill
@@ -0,0 +1,34 @@
+package build.plugin
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[Plugin](v.scalaCrossVersions)
+}
+
+trait Plugin extends CrossSbtModule with ScalafmtModule with ChiselPublishModule {
+  override def artifactName = "chisel-plugin"
+
+  def millSourcePath = super.millSourcePath / os.up
+
+  // The plugin is compiled for every minor Scala version
+  override def crossFullScalaVersion = true
+
+  def scalaLibraryIvy = v.scalaLibrary(crossScalaVersion)
+  def scalaReflectIvy = v.scalaReflect(crossScalaVersion)
+  def scalaCompilerIvy: Dep = v.scalaCompiler(crossScalaVersion)
+
+  def ivyDeps = Task {
+    if (!v.isScala3(crossScalaVersion)) {
+      super.ivyDeps() ++ Agg(scalaLibraryIvy, scalaReflectIvy, scalaCompilerIvy)
+    } else {
+      super.ivyDeps()
+    }
+  }
+}
diff --git a/stdlib/package.mill b/stdlib/package.mill
new file mode 100644
index 00000000000..62088d3e72c
--- /dev/null
+++ b/stdlib/package.mill
@@ -0,0 +1,21 @@
+package build.stdlib
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[Stdlib](v.scalaCrossVersions)
+}
+
+trait Stdlib extends CrossSbtModule with HasScala2Plugin with ScalafmtModule {
+  def millSourcePath = super.millSourcePath / os.up
+  def chiselModule = chisel(crossScalaVersion)
+  def pluginModule = plugin.cross(crossScalaVersion)
+
+  override def moduleDeps = Seq(chiselModule, pluginModule)
+}
diff --git a/svsim/package.mill b/svsim/package.mill
new file mode 100644
index 00000000000..293d63370cf
--- /dev/null
+++ b/svsim/package.mill
@@ -0,0 +1,32 @@
+package build.svsim
+
+import mill._
+import mill.scalalib._
+import mill.scalalib.scalafmt._
+import mill.define.Cross
+
+import build._
+
+object `package` extends RootModule {
+  // https://github.com/com-lihaoyi/mill/issues/3693
+  object cross extends Cross[Svsim](v.scalaCrossVersions)
+}
+
+trait Svsim extends CrossSbtModule with ScalafmtModule {
+  def millSourcePath = super.millSourcePath / os.up
+
+  override def scalacOptions = Task {
+    if (v.isScala3(crossScalaVersion)) {
+      Seq.empty[String]
+    } else {
+      v.scala2CommonOptions ++ Seq(
+        "-Xsource:3",
+        "-Xsource-features:case-apply-copy-access"
+      )
+    }
+  }
+
+  object test extends SbtTests with TestModule.ScalaTest with ScalafmtModule {
+    def ivyDeps = Agg(v.scalatest, v.scalacheck)
+  }
+}