diff --git a/contrib/scalapblib/src/mill/contrib/scalapblib/ScalaPBModule.scala b/contrib/scalapblib/src/mill/contrib/scalapblib/ScalaPBModule.scala
index 9cc26aca5bb..85b978d1725 100644
--- a/contrib/scalapblib/src/mill/contrib/scalapblib/ScalaPBModule.scala
+++ b/contrib/scalapblib/src/mill/contrib/scalapblib/ScalaPBModule.scala
@@ -52,7 +52,7 @@ trait ScalaPBModule extends ScalaModule {
 
   def scalaPBProtocPath: T[Option[String]] = T { None }
 
-  def scalaPBSources: Sources = T.sources {
+  def scalaPBSources: T[Seq[PathRef]] = T.sources {
     millSourcePath / "protobuf"
   }
 
diff --git a/contrib/scalapblib/test/src/mill/contrib/scalapblib/TutorialTests.scala b/contrib/scalapblib/test/src/mill/contrib/scalapblib/TutorialTests.scala
index 96988026c95..a760ad7097c 100644
--- a/contrib/scalapblib/test/src/mill/contrib/scalapblib/TutorialTests.scala
+++ b/contrib/scalapblib/test/src/mill/contrib/scalapblib/TutorialTests.scala
@@ -46,7 +46,7 @@ object TutorialTests extends TestSuite {
 
   object TutorialWithSpecificSources extends TutorialBase {
     object core extends TutorialModule {
-      override def scalaPBSources: Sources = T.sources {
+      override def scalaPBSources: T[Seq[PathRef]] = T.sources {
         millSourcePath / "protobuf" / "tutorial" / "Tutorial.proto"
       }
 
diff --git a/contrib/scoverage/src/mill/contrib/scoverage/ScoverageModule.scala b/contrib/scoverage/src/mill/contrib/scoverage/ScoverageModule.scala
index 19010ada4ca..af34bb5a576 100644
--- a/contrib/scoverage/src/mill/contrib/scoverage/ScoverageModule.scala
+++ b/contrib/scoverage/src/mill/contrib/scoverage/ScoverageModule.scala
@@ -186,7 +186,7 @@ trait ScoverageModule extends ScalaModule { outer: ScalaModule =>
      * The persistent data dir used to store scoverage coverage data.
      * Use to store coverage data at compile-time and by the various report targets.
      */
-    def data: Persistent[PathRef] = T.persistent {
+    def data: T[PathRef] = T.persistent {
       // via the persistent target, we ensure, the dest dir doesn't get cleared
       PathRef(T.dest)
     }
@@ -195,14 +195,14 @@ trait ScoverageModule extends ScalaModule { outer: ScalaModule =>
     override def allSources: Target[Seq[PathRef]] = T { outer.allSources() }
     override def moduleDeps: Seq[JavaModule] = outer.moduleDeps
     override def compileModuleDeps: Seq[JavaModule] = outer.compileModuleDeps
-    override def sources: Sources = T.sources { outer.sources() }
-    override def resources: Sources = T.sources { outer.resources() }
+    override def sources: T[Seq[PathRef]] = T.sources { outer.sources() }
+    override def resources: T[Seq[PathRef]] = T.sources { outer.resources() }
     override def scalaVersion = T { outer.scalaVersion() }
     override def repositoriesTask: Task[Seq[Repository]] = T.task { outer.repositoriesTask() }
-    override def compileIvyDeps: Target[Loose.Agg[Dep]] = T { outer.compileIvyDeps() }
-    override def ivyDeps: Target[Loose.Agg[Dep]] =
+    override def compileIvyDeps: Target[Agg[Dep]] = T { outer.compileIvyDeps() }
+    override def ivyDeps: Target[Agg[Dep]] =
       T { outer.ivyDeps() ++ outer.scoverageRuntimeDeps() }
-    override def unmanagedClasspath: Target[Loose.Agg[PathRef]] = T { outer.unmanagedClasspath() }
+    override def unmanagedClasspath: Target[Agg[PathRef]] = T { outer.unmanagedClasspath() }
 
     /** Add the scoverage scalac plugin. */
     override def scalacPluginIvyDeps: Target[Loose.Agg[Dep]] =
diff --git a/contrib/twirllib/src/mill/twirllib/TwirlModule.scala b/contrib/twirllib/src/mill/twirllib/TwirlModule.scala
index 5822b468fbb..367cccc5e61 100644
--- a/contrib/twirllib/src/mill/twirllib/TwirlModule.scala
+++ b/contrib/twirllib/src/mill/twirllib/TwirlModule.scala
@@ -19,7 +19,7 @@ trait TwirlModule extends mill.Module { twirlModule =>
    */
   def twirlScalaVersion: T[String]
 
-  def twirlSources: Sources = T.sources {
+  def twirlSources: T[Seq[PathRef]] = T.sources {
     millSourcePath / "views"
   }
 
diff --git a/contrib/versionfile/src/mill/contrib/versionfile/VersionFileModule.scala b/contrib/versionfile/src/mill/contrib/versionfile/VersionFileModule.scala
index 07bb4805a6b..e157fb193fa 100644
--- a/contrib/versionfile/src/mill/contrib/versionfile/VersionFileModule.scala
+++ b/contrib/versionfile/src/mill/contrib/versionfile/VersionFileModule.scala
@@ -5,33 +5,33 @@ import mill._, scalalib._
 trait VersionFileModule extends Module {
 
   /** The file containing the current version. */
-  def versionFile: Source = T.source(millSourcePath / "version")
+  def versionFile: T[PathRef] = T.source(millSourcePath / "version")
 
   /** The current version. */
   def currentVersion: T[Version] = T { Version.of(os.read(versionFile().path).trim) }
 
   /** The release version. */
-  def releaseVersion = T { currentVersion().asRelease }
+  def releaseVersion: T[Version] = T { currentVersion().asRelease }
 
   /** The next snapshot version. */
-  def nextVersion(bump: String) = T.command { currentVersion().asSnapshot.bump(bump) }
+  def nextVersion(bump: String): Task[Version] = T.task { currentVersion().asSnapshot.bump(bump) }
 
   /** Writes the release version to file. */
-  def setReleaseVersion = T {
+  def setReleaseVersion(): Command[Unit] = T.command {
     setVersionTask(releaseVersion)()
   }
 
   /** Writes the next snapshot version to file. */
-  def setNextVersion(bump: String) = T.command {
+  def setNextVersion(bump: String): Command[Unit] = T.command {
     setVersionTask(nextVersion(bump))()
   }
 
   /** Writes the given version to file. */
-  def setVersion(version: Version) = T.command {
-    setVersionTask(T.task { version })()
+  def setVersion(version: Task[Version]): Command[Unit] = T.command {
+    setVersionTask(version)()
   }
 
-  protected def setVersionTask(version: T[Version]) = T.task {
+  protected def setVersionTask(version: Task[Version]) = T.task {
     T.log.info(generateCommitMessage(version()))
     writeVersionToFile(versionFile(), version())
   }
diff --git a/contrib/versionfile/test/src/mill/contrib/versionfile/VersionFileModuleTests.scala b/contrib/versionfile/test/src/mill/contrib/versionfile/VersionFileModuleTests.scala
index 84dc6df837a..f7a72d3887d 100644
--- a/contrib/versionfile/test/src/mill/contrib/versionfile/VersionFileModuleTests.scala
+++ b/contrib/versionfile/test/src/mill/contrib/versionfile/VersionFileModuleTests.scala
@@ -1,5 +1,6 @@
 package mill.contrib.versionfile
 
+import mill.T
 import mill.api.Result
 import mill.util.{TestEvaluator, TestUtil}
 import utest.{TestSuite, Tests, assert, assertMatch, intercept, test}
@@ -114,7 +115,7 @@ object VersionFileModuleTests extends TestSuite {
 
       test("setReleaseVersion") - workspaceTest(versions: _*) { eval =>
         val expected = eval(TestModule.versionFile.releaseVersion)
-        val write = eval(TestModule.versionFile.setReleaseVersion)
+        val write = eval(TestModule.versionFile.setReleaseVersion())
         val actual = eval(TestModule.versionFile.currentVersion)
         assert(expected.value == actual.value)
       }
@@ -129,7 +130,7 @@ object VersionFileModuleTests extends TestSuite {
 
       test("setVersion") - workspaceTest(versions: _*) { eval =>
         val expected = Version.Release(1, 2, 4)
-        val write = eval(TestModule.versionFile.setVersion(expected))
+        val write = eval(TestModule.versionFile.setVersion(T.task(expected)))
         val actual = eval(TestModule.versionFile.currentVersion)
         assert(actual.value == Right(expected))
       }
diff --git a/integration/feature/gen-idea/repo/extended/build.sc b/integration/feature/gen-idea/repo/extended/build.sc
index c16e441f758..a97df418fe3 100644
--- a/integration/feature/gen-idea/repo/extended/build.sc
+++ b/integration/feature/gen-idea/repo/extended/build.sc
@@ -1,8 +1,8 @@
 import $ivy.`org.scalameta::munit:0.7.29`
 
+import mill._
 import mill.api.PathRef
 import mill.scalalib
-import mill.define.Command
 import mill.scalalib.GenIdeaModule._
 import mill.scalalib.TestModule
 
@@ -18,8 +18,8 @@ trait HelloWorldModule extends scalalib.ScalaModule {
     override def scalaVersion = "3.0.2"
   }
 
-  def ideaJavaModuleFacets(ideaConfigVersion: Int): Command[Seq[JavaFacet]] =
-    T.command {
+  def ideaJavaModuleFacets(ideaConfigVersion: Int): Task[Seq[JavaFacet]] =
+    T.task {
       ideaConfigVersion match {
         case 4 =>
           Seq(
@@ -47,7 +47,7 @@ trait HelloWorldModule extends scalalib.ScalaModule {
 
   override def ideaConfigFiles(
       ideaConfigVersion: Int
-  ): Command[Seq[IdeaConfigFile]] = T.command {
+  ): Task[Seq[IdeaConfigFile]] = T.task {
     ideaConfigVersion match {
       case 4 =>
         Seq(
@@ -59,7 +59,7 @@ trait HelloWorldModule extends scalalib.ScalaModule {
           ),
           // components in project file
           IdeaConfigFile(
-            name = "compiler.xml",
+            os.sub / "compiler.xml",
             component = "AjcSettings",
             config = Seq(
               Element(
@@ -69,7 +69,7 @@ trait HelloWorldModule extends scalalib.ScalaModule {
             )
           ),
           IdeaConfigFile(
-            name = "compiler.xml",
+            os.sub / "compiler.xml",
             component = "CompilerConfiguration",
             config = Seq(
               Element(
diff --git a/main/resolve/src/mill/resolve/ParseArgs.scala b/main/resolve/src/mill/resolve/ParseArgs.scala
index 75f069a735e..c6659b649eb 100644
--- a/main/resolve/src/mill/resolve/ParseArgs.scala
+++ b/main/resolve/src/mill/resolve/ParseArgs.scala
@@ -7,16 +7,6 @@ import mill.util.EitherOps
 
 import scala.annotation.tailrec
 
-sealed trait SelectMode
-object SelectMode {
-
-  /** All args are treated as targets or commands. If a `--` is detected, subsequent args are parameters to all commands. */
-  object Multi extends SelectMode
-
-  /** Like a combination of [[Single]] and [[Multi]], behaving like [[Single]] but using a special separator (`++`) to start parsing another target/command. */
-  object Separated extends SelectMode
-}
-
 object ParseArgs {
 
   type TargetsWithParams = (Seq[(Option[Segments], Segments)], Seq[String])
diff --git a/main/resolve/src/mill/resolve/SelectMode.scala b/main/resolve/src/mill/resolve/SelectMode.scala
new file mode 100644
index 00000000000..03e43a97ace
--- /dev/null
+++ b/main/resolve/src/mill/resolve/SelectMode.scala
@@ -0,0 +1,12 @@
+package mill.resolve
+
+sealed trait SelectMode
+
+object SelectMode {
+
+  /** All args are treated as targets or commands. If a `--` is detected, subsequent args are parameters to all commands. */
+  object Multi extends SelectMode
+
+  /** Like a combination of [[Single]] and [[Multi]], behaving like [[Single]] but using a special separator (`++`) to start parsing another target/command. */
+  object Separated extends SelectMode
+}
diff --git a/runner/src/mill/runner/MillBuildBootstrap.scala b/runner/src/mill/runner/MillBuildBootstrap.scala
index d08c3c3f97f..69ca83030b6 100644
--- a/runner/src/mill/runner/MillBuildBootstrap.scala
+++ b/runner/src/mill/runner/MillBuildBootstrap.scala
@@ -5,7 +5,6 @@ import mill.api.{PathRef, Val, internal}
 import mill.eval.Evaluator
 import mill.main.{RootModule, RunScript}
 import mill.resolve.SelectMode
-import mill.main.TokenReaders._
 import mill.define.{Discover, Segments}
 
 import java.net.URLClassLoader
@@ -292,7 +291,7 @@ object MillBuildBootstrap {
     // Copy the current location of the enclosing classes to `mill-launcher.jar`
     // if it has the wrong file extension, because the Zinc incremental compiler
     // doesn't recognize classpath entries without the proper file extension
-    val millLauncherOpt =
+    val millLauncherOpt: Option[os.Path] =
       if (
         os.isFile(selfClassLocation) &&
         !Set("zip", "jar", "class").contains(selfClassLocation.ext)
diff --git a/runner/src/mill/runner/MillBuildRootModule.scala b/runner/src/mill/runner/MillBuildRootModule.scala
index 314d4216fd0..7d4d94dbf1f 100644
--- a/runner/src/mill/runner/MillBuildRootModule.scala
+++ b/runner/src/mill/runner/MillBuildRootModule.scala
@@ -4,9 +4,9 @@ import coursier.Repository
 import mill._
 import mill.api.{Loose, PathRef, Result, internal}
 import mill.define.{Caller, Discover, Target, Task}
+import mill.scalalib.{BoundDep, Dep, DepSyntax, Lib, ScalaModule}
 import mill.util.CoursierSupport
 import mill.util.Util.millProjectModule
-import mill.scalalib.{BoundDep, DepSyntax, Lib, ScalaModule}
 import mill.scalalib.api.Versions
 import os.{Path, rel}
 import pprint.Util.literalize
@@ -55,7 +55,7 @@ class MillBuildRootModule()(implicit
       }
     }
 
-  override def scalaVersion = "2.13.10"
+  override def scalaVersion: T[String] = "2.13.10"
 
   def scriptSources = T.sources {
     MillBuildRootModule
@@ -152,7 +152,7 @@ class MillBuildRootModule()(implicit
     enclosingClasspath() ++ lineNumberPluginClasspath()
   }
 
-  override def scalacPluginIvyDeps = Agg(
+  override def scalacPluginIvyDeps: T[Agg[Dep]] = Agg(
     ivy"com.lihaoyi:::scalac-mill-moduledefs-plugin:${Versions.millModuledefsVersion}"
   )
 
@@ -222,7 +222,7 @@ object MillBuildRootModule {
       enclosingClasspath: Seq[os.Path],
       millTopLevelProjectRoot: os.Path,
       cliImports: Seq[String]
-  ) = {
+  ): Unit = {
     for (scriptSource <- scriptSources) {
       val relative = scriptSource.path.relativeTo(base)
       val dest = targetDest / FileImportGraph.fileImportToSegments(base, scriptSource.path, false)
@@ -253,8 +253,7 @@ object MillBuildRootModule {
       millTopLevelProjectRoot: os.Path,
       originalFilePath: os.Path,
       cliImports: Seq[String]
-  ) = {
-
+  ): String = {
     val superClass =
       if (pkg.size <= 1 && name == "build") "_root_.mill.main.RootModule"
       else {
diff --git a/scalalib/src/mill/scalalib/Dependency.scala b/scalalib/src/mill/scalalib/Dependency.scala
index 9efaf0d4e9b..dc29606c623 100644
--- a/scalalib/src/mill/scalalib/Dependency.scala
+++ b/scalalib/src/mill/scalalib/Dependency.scala
@@ -1,15 +1,19 @@
 package mill.scalalib
 
 import mill.T
-import mill.define.{Discover, ExternalModule}
+import mill.define.{Command, Discover, ExternalModule}
 import mill.eval.Evaluator
 import mill.main.EvaluatorTokenReader
 import mill.scalalib.dependency.DependencyUpdatesImpl
+import mill.scalalib.dependency.updates.ModuleDependenciesUpdates
 
 object Dependency extends ExternalModule {
 
   /** Calculate possible dependency updates. */
-  def updates(ev: Evaluator, allowPreRelease: Boolean = false) =
+  def updates(
+      ev: Evaluator,
+      allowPreRelease: Boolean = false
+  ): Command[Seq[ModuleDependenciesUpdates]] =
     T.command {
       DependencyUpdatesImpl(
         ev,
@@ -21,7 +25,7 @@ object Dependency extends ExternalModule {
     }
 
   /** Show possible dependency updates. */
-  def showUpdates(ev: Evaluator, allowPreRelease: Boolean = false) = T.command {
+  def showUpdates(ev: Evaluator, allowPreRelease: Boolean = false): Command[Unit] = T.command {
     DependencyUpdatesImpl.showAllUpdates(updates(ev, allowPreRelease)())
   }
 
diff --git a/scalalib/src/mill/scalalib/GenIdeaImpl.scala b/scalalib/src/mill/scalalib/GenIdeaImpl.scala
index 3da9c67745c..1c1fac29a8f 100755
--- a/scalalib/src/mill/scalalib/GenIdeaImpl.scala
+++ b/scalalib/src/mill/scalalib/GenIdeaImpl.scala
@@ -236,7 +236,7 @@ case class GenIdeaImpl(
         os.sub / wf._1 -> ideaConfigElementTemplate(wf._2)
       }
 
-    type FileComponent = (SubPath, String)
+    type FileComponent = (SubPath, Option[String])
 
     /** Ensure, the additional configs don't collide. */
     def collisionFreeExtraConfigs(
@@ -262,7 +262,7 @@ case class GenIdeaImpl(
               )
             }
             val msg =
-              s"Config collision in file `${conf.name}` and component `${conf.component}`: ${details(
+              s"Config collision in file `${conf.subPath}` and component `${conf.component}`: ${details(
                   conf.config
                 )} vs. ${details(existing)}"
             ctx.map(_.log.error(msg))
@@ -274,7 +274,7 @@ case class GenIdeaImpl(
     val fileComponentContributions: Seq[(SubPath, Elem)] =
       collisionFreeExtraConfigs(configFileContributions).toSeq.map {
         case (file, configs) =>
-          val map: Map[String, Seq[GenIdeaModule.Element]] =
+          val map: Map[Option[String], Seq[GenIdeaModule.Element]] =
             configs
               .groupBy(_.component)
               .view
@@ -626,12 +626,12 @@ case class GenIdeaImpl(
   }
 
   def ideaConfigFileTemplate(
-      components: Map[String, Seq[GenIdeaModule.Element]]
+      components: Map[Option[String], Seq[GenIdeaModule.Element]]
   ): Elem = {
     <project version={"" + ideaConfigVersion}>
       {
       components.toSeq.map { case (name, config) =>
-        <component name={name}>{config.map(ideaConfigElementTemplate)}</component>
+        <component name={name.getOrElse("")}>{config.map(ideaConfigElementTemplate)}</component>
       }
     }
     </project>
diff --git a/scalalib/src/mill/scalalib/GenIdeaModule.scala b/scalalib/src/mill/scalalib/GenIdeaModule.scala
index 879dd62f186..699c0516632 100644
--- a/scalalib/src/mill/scalalib/GenIdeaModule.scala
+++ b/scalalib/src/mill/scalalib/GenIdeaModule.scala
@@ -1,6 +1,6 @@
 package mill.scalalib
 
-import mill.define.Command
+import mill.define.Task
 import mill.{Module, PathRef, T}
 import os.SubPath
 
@@ -22,14 +22,14 @@ trait GenIdeaModule extends Module {
    * @param ideaConfigVersion The IDEA configuration version in use. Probably `4`.
    * @return
    */
-  def ideaJavaModuleFacets(ideaConfigVersion: Int): Command[Seq[JavaFacet]] =
-    T.command { Seq[JavaFacet]() }
+  def ideaJavaModuleFacets(ideaConfigVersion: Int): Task[Seq[JavaFacet]] =
+    T.task { Seq[JavaFacet]() }
 
   /**
    * Contribute components to idea config files.
    */
-  def ideaConfigFiles(ideaConfigVersion: Int): Command[Seq[IdeaConfigFile]] =
-    T.command { Seq[IdeaConfigFile]() }
+  def ideaConfigFiles(ideaConfigVersion: Int): Task[Seq[IdeaConfigFile]] =
+    T.task { Seq[IdeaConfigFile]() }
 
   def ideaCompileOutput: T[PathRef] = T.persistent {
     PathRef(T.dest / "classes")
@@ -62,24 +62,21 @@ object GenIdeaModule {
 
   /**
    * A Idea config file contribution
-   * @param name The target config file name (can be also a sub-path)
+   * @param subPath The sub-path of the config file, relative to the Idea config directory (`.idea`)
    * @param component The Idea component
    * @param config The actual (XML) configuration, encoded as [[Element]]s
    *
    * Note: the `name` fields is deprecated in favour of `subPath`, but kept for backward compatibility.
    */
   final case class IdeaConfigFile(
-      name: String,
-      component: String,
+      subPath: SubPath,
+      component: Option[String],
       config: Seq[Element]
   ) {
-    // This also works as requirement check
-    /** The sub-path of the config file, relative to the Idea config directory (`.idea`). */
-    val subPath: SubPath = SubPath(name)
     // An empty component name meas we contribute a whole file
     // If we have a fill file, we only accept a single root xml node.
     require(
-      component.nonEmpty || config.size == 1,
+      component.forall(_.nonEmpty) && (component.nonEmpty || config.size == 1),
       "Files contributions must have exactly one root element."
     )
 
@@ -90,13 +87,15 @@ object GenIdeaModule {
   }
   object IdeaConfigFile {
 
-    /** Alternative creator accepting a sub-path as config file name. */
+    /** Alternative creator accepting a component string. */
     def apply(
         subPath: SubPath,
-        component: Option[String],
+        component: String,
         config: Seq[Element]
-    ): IdeaConfigFile = IdeaConfigFile(subPath.toString(), component.getOrElse(""), config)
+    ): IdeaConfigFile =
+      IdeaConfigFile(subPath, if (component == "") None else Option(component), config)
 
+    implicit def subPathRw: ReadWriter[SubPath] = readwriter[String].bimap(_.toString(), SubPath(_))
     implicit def rw: ReadWriter[IdeaConfigFile] = macroRW
   }
 
diff --git a/scalalib/src/mill/scalalib/JavaModule.scala b/scalalib/src/mill/scalalib/JavaModule.scala
index 128c47c649d..c0b71cc633b 100644
--- a/scalalib/src/mill/scalalib/JavaModule.scala
+++ b/scalalib/src/mill/scalalib/JavaModule.scala
@@ -44,7 +44,7 @@ trait JavaModule
   }
   trait Tests extends JavaModuleTests
 
-  def defaultCommandName() = "run"
+  def defaultCommandName(): String = "run"
   def resolvePublishDependency: Task[Dep => publish.Dependency] = T.task {
     Artifact.fromDepJava(_: Dep)
   }
@@ -103,7 +103,7 @@ trait JavaModule
    * macro-related dependencies like `scala-reflect` that doesn't need to be
    * present at runtime
    */
-  def compileIvyDeps = T { Agg.empty[Dep] }
+  def compileIvyDeps: T[Agg[Dep]] = T { Agg.empty[Dep] }
 
   /**
    * Additional dependencies, only present at runtime. Useful for e.g.
@@ -270,20 +270,20 @@ trait JavaModule
   /**
    * The folders where the source files for this module live
    */
-  def sources = T.sources { millSourcePath / "src" }
+  def sources: T[Seq[PathRef]] = T.sources { millSourcePath / "src" }
 
   /**
    * The folders where the resource files for this module live.
    * If you need resources to be seen by the compiler, use [[compileResources]].
    */
-  def resources: Sources = T.sources { millSourcePath / "resources" }
+  def resources: T[Seq[PathRef]] = T.sources { millSourcePath / "resources" }
 
   /**
    * The folders where the compile time resource files for this module live.
    * If your resources files do not necessarily need to be seen by the compiler,
    * you should use [[resources]] instead.
    */
-  def compileResources: Sources = T.sources { millSourcePath / "compile-resources" }
+  def compileResources: T[Seq[PathRef]] = T.sources { millSourcePath / "compile-resources" }
 
   /**
    * Folders containing source files that are generated rather than
@@ -484,7 +484,7 @@ trait JavaModule
    * Typically includes the source files to generate documentation from.
    * @see [[docResources]]
    */
-  def docSources: Sources = T.sources(allSources())
+  def docSources: T[Seq[PathRef]] = T.sources(allSources())
 
   /**
    * Extra directories to be copied into the documentation.
@@ -493,7 +493,7 @@ trait JavaModule
    * on the doc tool that is actually used.
    * @see [[docSources]]
    */
-  def docResources: Sources = T.sources(millSourcePath / "docs")
+  def docResources: T[Seq[PathRef]] = T.sources(millSourcePath / "docs")
 
   /**
    * Control whether `docJar`-target should use a file to pass command line arguments to the javadoc tool.
diff --git a/scalalib/src/mill/scalalib/ScalaModule.scala b/scalalib/src/mill/scalalib/ScalaModule.scala
index 15a193df530..dd75fd93590 100644
--- a/scalalib/src/mill/scalalib/ScalaModule.scala
+++ b/scalalib/src/mill/scalalib/ScalaModule.scala
@@ -251,7 +251,7 @@ trait ScalaModule extends JavaModule { outer =>
       }
     }
 
-  override def docSources: Sources = T.sources {
+  override def docSources: T[Seq[PathRef]] = T.sources {
     if (
       ZincWorkerUtil.isScala3(scalaVersion()) && !ZincWorkerUtil.isScala3Milestone(scalaVersion())
     ) Seq(compile().classes)
diff --git a/scalalib/src/mill/scalalib/SemanticDbJavaModule.scala b/scalalib/src/mill/scalalib/SemanticDbJavaModule.scala
index bee1589850c..d1474f63ba2 100644
--- a/scalalib/src/mill/scalalib/SemanticDbJavaModule.scala
+++ b/scalalib/src/mill/scalalib/SemanticDbJavaModule.scala
@@ -4,14 +4,14 @@ import mill.api.{PathRef, Result, experimental}
 import mill.define.{Target, Task}
 import mill.scalalib.api.{Versions, ZincWorkerUtil}
 import mill.util.Version
-import mill.{Agg, BuildInfo, Input, T}
+import mill.{Agg, BuildInfo, T}
 
 import scala.util.Properties
 
 @experimental
 trait SemanticDbJavaModule extends CoursierModule { hostModule: JavaModule =>
 
-  def semanticDbVersion: Input[String] = T.input {
+  def semanticDbVersion: T[String] = T.input {
     val builtin = SemanticDbJavaModule.buildTimeSemanticDbVersion
     val requested = T.env.getOrElse[String](
       "SEMANTICDB_VERSION",
@@ -20,7 +20,7 @@ trait SemanticDbJavaModule extends CoursierModule { hostModule: JavaModule =>
     Version.chooseNewest(requested, builtin)(Version.IgnoreQualifierOrdering)
   }
 
-  def semanticDbJavaVersion: Input[String] = T.input {
+  def semanticDbJavaVersion: T[String] = T.input {
     val builtin = SemanticDbJavaModule.buildTimeJavaSemanticDbVersion
     val requested = T.env.getOrElse[String](
       "JAVASEMANTICDB_VERSION",
@@ -29,12 +29,12 @@ trait SemanticDbJavaModule extends CoursierModule { hostModule: JavaModule =>
     Version.chooseNewest(requested, builtin)(Version.IgnoreQualifierOrdering)
   }
 
-  def semanticDbScalaVersion = hostModule match {
+  def semanticDbScalaVersion: T[String] = hostModule match {
     case m: ScalaModule => T { m.scalaVersion }
     case _ => T { BuildInfo.scalaVersion }
   }
 
-  private def semanticDbPluginIvyDeps: Target[Agg[Dep]] = T {
+  private def semanticDbPluginIvyDeps: T[Agg[Dep]] = T {
     val sv = semanticDbScalaVersion()
     val semDbVersion = semanticDbVersion()
     if (!ZincWorkerUtil.isScala3(sv) && semDbVersion.isEmpty) {
@@ -54,7 +54,7 @@ trait SemanticDbJavaModule extends CoursierModule { hostModule: JavaModule =>
     }
   }
 
-  private def semanticDbJavaPluginIvyDeps: Target[Agg[Dep]] = T {
+  private def semanticDbJavaPluginIvyDeps: T[Agg[Dep]] = T {
     val sv = semanticDbJavaVersion()
     if (sv.isEmpty) {
       val msg =
@@ -74,7 +74,7 @@ trait SemanticDbJavaModule extends CoursierModule { hostModule: JavaModule =>
   /**
    * Scalac options to activate the compiler plugins.
    */
-  private def semanticDbEnablePluginScalacOptions: Target[Seq[String]] = T {
+  private def semanticDbEnablePluginScalacOptions: T[Seq[String]] = T {
     val resolvedJars = resolveDeps(T.task {
       val bind = bindDependency()
       semanticDbPluginIvyDeps().map(_.exclude("*" -> "*")).map(bind)
@@ -97,7 +97,7 @@ trait SemanticDbJavaModule extends CoursierModule { hostModule: JavaModule =>
       }
   }
 
-  private def resolvedSemanticDbJavaPluginIvyDeps: Target[Agg[PathRef]] = T {
+  private def resolvedSemanticDbJavaPluginIvyDeps: T[Agg[PathRef]] = T {
     resolveDeps(T.task { semanticDbJavaPluginIvyDeps().map(bindDependency()) })()
   }
 
diff --git a/scalalib/src/mill/scalalib/ZincWorkerModule.scala b/scalalib/src/mill/scalalib/ZincWorkerModule.scala
index f0526e7db5c..b6c5da3d415 100644
--- a/scalalib/src/mill/scalalib/ZincWorkerModule.scala
+++ b/scalalib/src/mill/scalalib/ZincWorkerModule.scala
@@ -24,15 +24,15 @@ object ZincWorkerModule extends ExternalModule with ZincWorkerModule with Coursi
  */
 trait ZincWorkerModule extends mill.Module with OfflineSupportModule { self: CoursierModule =>
 
-  def classpath: Target[Agg[PathRef]] = T {
+  def classpath: T[Agg[PathRef]] = T {
     millProjectModule("mill-scalalib-worker", repositoriesTask())
   }
 
-  def scalalibClasspath: Target[Agg[PathRef]] = T {
+  def scalalibClasspath: T[Agg[PathRef]] = T {
     millProjectModule("mill-scalalib", repositoriesTask())
   }
 
-  def backgroundWrapperClasspath: Target[Agg[PathRef]] = T {
+  def backgroundWrapperClasspath: T[Agg[PathRef]] = T {
     millProjectModule(
       "mill-scalalib-backgroundwrapper",
       repositoriesTask(),
@@ -40,7 +40,7 @@ trait ZincWorkerModule extends mill.Module with OfflineSupportModule { self: Cou
     )
   }
 
-  def zincLogDebug: Input[Boolean] = T.input(T.ctx().log.debugEnabled)
+  def zincLogDebug: T[Boolean] = T.input(T.ctx().log.debugEnabled)
 
   def worker: Worker[ZincWorkerApi] = T.worker {
     val ctx = T.ctx()
diff --git a/scalalib/src/mill/scalalib/scalafmt/ScalafmtModule.scala b/scalalib/src/mill/scalalib/scalafmt/ScalafmtModule.scala
index 7b79a652ed8..75839e0fdfa 100644
--- a/scalalib/src/mill/scalalib/scalafmt/ScalafmtModule.scala
+++ b/scalalib/src/mill/scalalib/scalafmt/ScalafmtModule.scala
@@ -25,7 +25,7 @@ trait ScalafmtModule extends JavaModule {
       )
   }
 
-  def scalafmtConfig: Sources = T.sources(T.workspace / ".scalafmt.conf")
+  def scalafmtConfig: T[Seq[PathRef]] = T.sources(T.workspace / ".scalafmt.conf")
 
   // TODO: Do we want provide some defaults or write a default file?
   private[ScalafmtModule] def resolvedScalafmtConfig: Task[PathRef] = T.task {
diff --git a/scalalib/test/src/mill/scalalib/HelloWorldTests.scala b/scalalib/test/src/mill/scalalib/HelloWorldTests.scala
index fb191ffed96..d51ed75c114 100644
--- a/scalalib/test/src/mill/scalalib/HelloWorldTests.scala
+++ b/scalalib/test/src/mill/scalalib/HelloWorldTests.scala
@@ -32,7 +32,7 @@ object HelloWorldTests extends TestSuite {
 
   trait HelloWorldModule extends scalalib.ScalaModule {
     def scalaVersion = scala212Version
-    override def semanticDbVersion: Input[String] = T.input {
+    override def semanticDbVersion: T[String] = T {
       // The latest semanticDB release for Scala 2.12.6
       "4.1.9"
     }
diff --git a/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala b/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala
index 586a9ebe891..700b08c739d 100644
--- a/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala
+++ b/scalalib/test/src/mill/scalalib/scalafmt/ScalafmtTests.scala
@@ -12,19 +12,19 @@ object ScalafmtTests extends TestSuite {
   val scalafmtTestVersion = mill.scalalib.api.Versions.scalafmtVersion
 
   trait TestBase extends TestUtil.BaseModule {
-    def millSourcePath =
+    override def millSourcePath: os.Path =
       TestUtil.getSrcPathBase() / millOuterCtx.enclosing.split('.')
   }
 
   trait BuildSrcModule {
-    def buildSources: Sources
+    def buildSources: T[Seq[PathRef]]
   }
 
   object ScalafmtTestModule extends TestBase {
     object core extends ScalaModule with ScalafmtModule with BuildSrcModule {
-      def scalaVersion = sys.props.getOrElse("TEST_SCALA_2_12_VERSION", ???)
+      def scalaVersion: T[String] = sys.props.getOrElse("TEST_SCALA_2_12_VERSION", ???)
 
-      def buildSources: Sources = T.sources {
+      def buildSources: T[Seq[PathRef]] = T.sources {
         millSourcePath / "util.sc"
       }