From 6d5f44219dd403877b662472f6c1d5e602f83439 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Thu, 6 Feb 2025 09:42:58 +0800
Subject: [PATCH 1/4] .

---
 build.mill                                    |  4 +-
 changelog.adoc                                |  2 +-
 contrib/playlib/src/mill/playlib/Layout.scala |  4 +-
 .../src/mill/playlib/RouterModule.scala       |  2 +-
 .../versionfile/VersionFileModule.scala       |  2 +-
 dist/package.mill                             |  2 +-
 .../modules/ROOT/pages/comparisons/maven.adoc | 10 ++--
 .../ROOT/pages/comparisons/unique.adoc        |  4 +-
 docs/package.mill                             | 10 ++--
 .../extending/jvmcode/1-subprocess/build.mill |  2 +-
 .../jvmcode/2-classloader/build.mill          |  2 +-
 example/extending/jvmcode/3-worker/build.mill |  2 +-
 .../python/1-hello-python/build.mill          |  4 +-
 .../python/2-python-modules/build.mill        |  4 +-
 .../python/3-python-module-deps/build.mill    |  4 +-
 .../python/4-python-libs-bundle/build.mill    |  4 +-
 .../typescript/1-hello-typescript/build.mill  |  2 +-
 .../2-typescript-modules/build.mill           |  2 +-
 .../typescript/3-module-deps/build.mill       |  2 +-
 .../typescript/4-npm-deps-bundle/build.mill   |  2 +-
 .../fundamentals/modules/6-modules/build.mill |  6 +--
 .../modules/8-diy-java-modules/build.mill     |  2 +-
 .../tasks/1-task-graph/build.mill             |  4 +-
 .../tasks/2-primary-tasks/build.mill          |  4 +-
 .../tasks/3-anonymous-tasks/build.mill        |  2 +-
 .../tasks/5-persistent-tasks/build.mill       |  2 +-
 .../fundamentals/tasks/6-workers/build.mill   |  2 +-
 example/javalib/module/15-jni/build.mill      |  2 +-
 example/javalib/module/7-resources/build.mill |  2 +-
 .../javalib/publishing/3-revapi/build.mill    |  2 +-
 .../module/1-common-config/build.mill         |  2 +-
 .../module/5-resources/build.mill             |  2 +-
 example/kotlinlib/module/15-jni/build.mill    |  2 +-
 .../kotlinlib/module/7-resources/build.mill   |  2 +-
 example/pythonlib/basic/1-simple/build.mill   |  2 +-
 .../basic/2-custom-build-logic/build.mill     |  2 +-
 .../pythonlib/basic/3-multi-module/build.mill |  4 +-
 .../module/1-common-config/build.mill         |  2 +-
 .../module/2-custom-tasks/build.mill          |  2 +-
 .../4-compilation-execution-flags/build.mill  |  2 +-
 .../pythonlib/module/5-resources/build.mill   |  4 +-
 .../pythonlib/module/6-pex-config/build.mill  |  2 +-
 .../2-publish-module-advanced/build.mill      |  2 +-
 .../pythonlib/testing/1-test-suite/build.mill |  6 +--
 .../pythonlib/testing/2-test-deps/build.mill  |  4 +-
 .../testing/3-integration-suite/build.mill    |  2 +-
 .../pythonlib/web/1-hello-flask/build.mill    |  2 +-
 example/pythonlib/web/2-todo-flask/build.mill |  2 +-
 .../pythonlib/web/3-hello-django/build.mill   |  2 +-
 .../pythonlib/web/4-todo-django/build.mill    |  2 +-
 .../scalalib/module/7-resources/build.mill    |  2 +-
 example/thirdparty/acyclic/build.mill         |  2 +-
 example/thirdparty/arrow/build.mill           |  6 +--
 example/thirdparty/mockito/build.mill         |  2 +-
 example/thirdparty/netty/build.mill           | 14 ++---
 .../gen-idea/resources/extended/build.mill    |  2 +-
 .../src/MultiLevelBuildTests.scala            |  2 +-
 .../selective-execution/resources/build.mill  |  4 +-
 .../watch-source-input/resources/build.mill   |  4 +-
 .../mill/javascriptlib/PublishModule.scala    |  2 +-
 .../javascriptlib/ReactScriptsModule.scala    |  6 +--
 .../javascriptlib/RsWithServeModule.scala     |  2 +-
 .../mill/javascriptlib/TypeScriptModule.scala |  2 +-
 .../mill/kotlinlib/js/KotlinJsModule.scala    |  4 +-
 .../src/mill/kotlinlib/HelloWorldTests.scala  |  2 +-
 .../mill/kotlinlib/MixedHelloWorldTests.scala |  2 +-
 .../contrib/kover/KoverModuleTests.scala      |  2 +-
 .../contrib/ktfmt/KtfmtModuleTests.scala      | 12 ++---
 .../kotlinlib/js/KotlinJsCompileTests.scala   |  6 +--
 main/define/src/mill/define/Task.scala        | 52 +++++++++++++++++++
 .../src/mill/eval/JavaCompileJarTests.scala   |  9 ++--
 .../maven/src/mill/main/maven/Modeler.scala   |  2 +-
 .../src/mill/pythonlib/PythonModule.scala     |  8 +--
 pythonlib/src/mill/pythonlib/RuffModule.scala |  2 +-
 .../src/mill/pythonlib/HelloWorldTests.scala  |  2 +-
 .../mill/pythonlib/RunBackgroundTests.scala   |  4 +-
 .../javalib/android/AndroidAppModule.scala    |  4 +-
 .../javalib/android/AndroidSdkModule.scala    |  4 +-
 scalalib/src/mill/scalalib/JavaModule.scala   |  8 +--
 .../PalantirFormatModuleTest.scala            |  2 +-
 .../javalib/revapi/RevapiModuleTests.scala    |  2 +-
 .../mill/scalalib/TestRunnerTestUtils.scala   |  2 +-
 testkit/package.mill                          |  2 +-
 .../example-test-example-project/build.mill   |  2 +-
 .../build.mill                                |  2 +-
 .../src/mill/testkit/UnitTesterTests.scala    |  2 +-
 86 files changed, 193 insertions(+), 142 deletions(-)

diff --git a/build.mill b/build.mill
index 713fba82c96..821f7dc3260 100644
--- a/build.mill
+++ b/build.mill
@@ -148,7 +148,7 @@ object Deps {
   val junitInterface = ivy"com.github.sbt:junit-interface:0.13.3"
   val commonsIo = ivy"commons-io:commons-io:2.18.0"
   val log4j2Core = ivy"org.apache.logging.log4j:log4j-core:2.24.3"
-  val osLib = ivy"com.lihaoyi::os-lib:0.11.4-M5"
+  val osLib = ivy"com.lihaoyi::os-lib:0.11.4-M6"
   val pprint = ivy"com.lihaoyi::pprint:0.9.0"
   val mainargs = ivy"com.lihaoyi::mainargs:0.7.6"
   val millModuledefsVersion = "0.11.2"
@@ -381,7 +381,7 @@ trait MillJavaModule extends JavaModule {
 
   def writeLocalTestOverrides = Task.Anon {
     for ((k, v) <- testTransitiveDeps()) {
-      os.write(Task.dest / "mill" / "local-test-overrides" / k, v, createFolders = true)
+      os.write(Task.dest / "mill/local-test-overrides" / k, v, createFolders = true)
     }
     Seq(PathRef(Task.dest))
   }
diff --git a/changelog.adoc b/changelog.adoc
index c125470dc62..5bacb513050 100644
--- a/changelog.adoc
+++ b/changelog.adoc
@@ -450,7 +450,7 @@ or `;exclude=org:*` or `;exclude=*:name` {link-pr}/3492[#3492]
 
 * Update to https://github.com/com-lihaoyi/os-lib?tab=readme-ov-file#0-10-7[OS-Lib 0.10.7] to
 allow concise multi-segment sub-paths; you can now write `os.pwd / "foo/bar/qux"` rather than
-`os.pwd / "foo" / "bar" / "qux"`
+`os.pwd / "foo/bar/qux"`
 
 * Add `JavaModule.mandatoryJavacOptions`. Those are not propagated to the inner test
 traits intentionally, since those options are typically configured by other means,
diff --git a/contrib/playlib/src/mill/playlib/Layout.scala b/contrib/playlib/src/mill/playlib/Layout.scala
index d5492e33160..46f77d61e32 100644
--- a/contrib/playlib/src/mill/playlib/Layout.scala
+++ b/contrib/playlib/src/mill/playlib/Layout.scala
@@ -5,8 +5,8 @@ import mill.scalalib._
 
 private[playlib] trait Layout extends JavaModule {
 
-  def conf = Task.Sources { millSourcePath / "conf" }
-  def app = Task.Sources { millSourcePath / "app" }
+  def conf = Task.Sources { "conf" }
+  def app = Task.Sources { "app" }
 
   override def sources = Task { app() }
   override def resources = Task { conf() }
diff --git a/contrib/playlib/src/mill/playlib/RouterModule.scala b/contrib/playlib/src/mill/playlib/RouterModule.scala
index a5f8c62af70..ec17570d8d3 100644
--- a/contrib/playlib/src/mill/playlib/RouterModule.scala
+++ b/contrib/playlib/src/mill/playlib/RouterModule.scala
@@ -9,7 +9,7 @@ import mill.{Agg, T, Task}
 
 trait RouterModule extends ScalaModule with Version {
 
-  def routes: T[Seq[PathRef]] = Task.Sources { millSourcePath / "routes" }
+  def routes: T[Seq[PathRef]] = Task.Sources { "routes" }
 
   def routeFiles = Task {
     val paths = routes().flatMap(file => os.walk(file.path))
diff --git a/contrib/versionfile/src/mill/contrib/versionfile/VersionFileModule.scala b/contrib/versionfile/src/mill/contrib/versionfile/VersionFileModule.scala
index c113b2e21a9..724631cd3a7 100644
--- a/contrib/versionfile/src/mill/contrib/versionfile/VersionFileModule.scala
+++ b/contrib/versionfile/src/mill/contrib/versionfile/VersionFileModule.scala
@@ -5,7 +5,7 @@ import mill._
 trait VersionFileModule extends Module {
 
   /** The file containing the current version. */
-  def versionFile: T[PathRef] = Task.Source(millSourcePath / "version")
+  def versionFile: T[PathRef] = Task.Source("version")
 
   /** The current version. */
   def currentVersion: T[Version] = Task { Version.of(os.read(versionFile().path).trim) }
diff --git a/dist/package.mill b/dist/package.mill
index f226bfe7999..c7929ddc68d 100644
--- a/dist/package.mill
+++ b/dist/package.mill
@@ -41,7 +41,7 @@ trait InstallModule extends build.MillPublishJavaModule {
   def installLocalCache() = Task.Command {
     val path = installLocalTask(
       Task.Anon(
-        (os.home / ".cache" / "mill" / "download" / (build.millVersion() + batExt)).toString()
+        (os.home / ".cache/mill/download" / (build.millVersion() + batExt)).toString()
       )
     )()
     Task.log.outputStream.println(path.toString())
diff --git a/docs/modules/ROOT/pages/comparisons/maven.adoc b/docs/modules/ROOT/pages/comparisons/maven.adoc
index 7b96c8a4eec..090380e2c6d 100644
--- a/docs/modules/ROOT/pages/comparisons/maven.adoc
+++ b/docs/modules/ROOT/pages/comparisons/maven.adoc
@@ -391,7 +391,7 @@ import $ivy.`ant:ant-optional:1.5.3-1`
 
 object common extends NettyModule{
   ...
-  def script = Task.Source(millSourcePath / "src" / "main" / "script")
+  def script = Task.Source("src/main/script")
   def generatedSources0 = Task {
     val shell = new groovy.lang.GroovyShell()
     val context = new java.util.HashMap[String, Object]
@@ -520,8 +520,8 @@ with the `make` command essentially being a bash script wrapped in layers of XML
 In contrast, the Mill configuration for this logic is as follows:
 
 ```scala
-def makefile = Task.Source(millSourcePath / "Makefile")
-def cSources = Task.Source(millSourcePath / "src" / "main" / "c")
+def makefile = Task.Source("Makefile")
+def cSources = Task.Source("src/main/c")
 def cHeaders = Task {
   for(p <- os.walk(cSources().path) if p.ext == "h"){
     os.copy(p, Task.dest / p.relativeTo(cSources().path), createFolders = true)
@@ -531,14 +531,14 @@ def cHeaders = Task {
 
 def make = Task {
   os.copy(makefile().path, Task.dest / "Makefile")
-  os.copy(cSources().path, Task.dest / "src" / "main" / "c", createFolders = true)
+  os.copy(cSources().path, Task.dest / "src/main/c", createFolders = true)
 
   val Seq(sourceJar) = resolveDeps(
     deps = Task.Anon(Agg(ivy"io.netty:netty-jni-util:0.0.9.Final").map(bindDependency())),
     sources = true
   )().toSeq
 
-  os.proc("jar", "xf", sourceJar.path).call(cwd = Task.dest  / "src" / "main" / "c")
+  os.proc("jar", "xf", sourceJar.path).call(cwd = Task.dest  / "src/main/c")
 
   os.proc("make").call(
     cwd = Task.dest,
diff --git a/docs/modules/ROOT/pages/comparisons/unique.adoc b/docs/modules/ROOT/pages/comparisons/unique.adoc
index 8fe5879ed9c..6f712eec5f7 100644
--- a/docs/modules/ROOT/pages/comparisons/unique.adoc
+++ b/docs/modules/ROOT/pages/comparisons/unique.adoc
@@ -176,8 +176,8 @@ them into classfiles, and then the `jar` executable to package them together int
 ```scala
 def mainClass: T[Option[String]] = Some("foo.Foo")
 
-def sources = Task.Source(millSourcePath / "src")
-def resources = Task.Source(millSourcePath / "resources")
+def sources = Task.Source("src")
+def resources = Task.Source("resources")
 
 def compile = Task {
   val allSources = os.walk(sources().path)
diff --git a/docs/package.mill b/docs/package.mill
index 272092bba2e..baec2a1585e 100644
--- a/docs/package.mill
+++ b/docs/package.mill
@@ -61,7 +61,7 @@ object `package` extends RootModule {
       envArgs = Map("CI" -> "true"),
       workingDir = workDir
     )
-    PathRef(workDir / "build" / "site")
+    PathRef(workDir / "build/site")
   }
 
   def source0 = Task.Source(millSourcePath)
@@ -69,8 +69,8 @@ object `package` extends RootModule {
   def source = Task {
     os.copy(source0().path, Task.dest, mergeFolders = true)
 
-    val pagesWd = Task.dest / "modules" / "ROOT" / "pages"
-    val partialsWd = Task.dest / "modules" / "ROOT" / "partials"
+    val pagesWd = Task.dest / "modules/ROOT/pages"
+    val partialsWd = Task.dest / "modules/ROOT/partials"
 
     os.copy(projectChangelog().path, partialsWd / "project-changelog.adoc", createFolders = true)
 
@@ -284,7 +284,7 @@ object `package` extends RootModule {
       val checkout = Task.dest / displayVersion
       os.proc("git", "clone", Task.workspace / ".git", checkout).call(stdout = os.Inherit)
       os.proc("git", "checkout", millLastTag).call(cwd = checkout, stdout = os.Inherit)
-      val outputFolder = checkout / "out" / "docs" / "source.dest"
+      val outputFolder = checkout / "out/docs/source.dest"
       os.proc("./mill", "-i", "docs.source").call(cwd = checkout, stdout = os.Inherit)
       expandDiagramsInDirectoryAdocFile(
         outputFolder,
@@ -360,7 +360,7 @@ object `package` extends RootModule {
     // only copy the "api" sub-dir; api docs contains a top-level index.html with we don't want
     val unidocSrc = if (authorMode) site.unidocLocal().path else site.unidocSite().path
     Task.log.errorStream.println(s"Copying API docs from ${unidocSrc} ...")
-    os.copy(unidocSrc, siteDir / "api" / "latest", createFolders = true)
+    os.copy(unidocSrc, siteDir / "api/latest", createFolders = true)
 
     PathRef(siteDir)
   }
diff --git a/example/extending/jvmcode/1-subprocess/build.mill b/example/extending/jvmcode/1-subprocess/build.mill
index f84e7dad5cb..82034149fa9 100644
--- a/example/extending/jvmcode/1-subprocess/build.mill
+++ b/example/extending/jvmcode/1-subprocess/build.mill
@@ -22,7 +22,7 @@ object foo extends JavaModule {
     defaultResolver().resolveDeps(Agg(ivy"org.codehaus.groovy:groovy:3.0.9"))
   }
 
-  def groovyScript = Task.Source(millSourcePath / "generate.groovy")
+  def groovyScript = Task.Source("generate.groovy")
 
   def groovyGeneratedResources = Task {
     Jvm.runSubprocess(
diff --git a/example/extending/jvmcode/2-classloader/build.mill b/example/extending/jvmcode/2-classloader/build.mill
index fb18c8643ff..7c38a3faec4 100644
--- a/example/extending/jvmcode/2-classloader/build.mill
+++ b/example/extending/jvmcode/2-classloader/build.mill
@@ -14,7 +14,7 @@ object foo extends JavaModule {
     defaultResolver().resolveDeps(Agg(ivy"org.codehaus.groovy:groovy:3.0.9"))
   }
 
-  def groovyScript = Task.Source(millSourcePath / "generate.groovy")
+  def groovyScript = Task.Source("generate.groovy")
 
   def groovyGeneratedResources = Task {
     Jvm.runClassloader(classPath = groovyClasspath().map(_.path)) { classLoader =>
diff --git a/example/extending/jvmcode/3-worker/build.mill b/example/extending/jvmcode/3-worker/build.mill
index 4de2b2214bd..fdf667119aa 100644
--- a/example/extending/jvmcode/3-worker/build.mill
+++ b/example/extending/jvmcode/3-worker/build.mill
@@ -24,7 +24,7 @@ def groovyWorker: Worker[java.net.URLClassLoader] = Task.Worker {
 }
 
 trait GroovyGenerateJavaModule extends JavaModule {
-  def groovyScript = Task.Source(millSourcePath / "generate.groovy")
+  def groovyScript = Task.Source("generate.groovy")
 
   def groovyGeneratedResources = Task {
     mill.api.ClassLoader.withContextClassLoader(groovyWorker()) {
diff --git a/example/extending/python/1-hello-python/build.mill b/example/extending/python/1-hello-python/build.mill
index ec96d797839..57b0baa7f48 100644
--- a/example/extending/python/1-hello-python/build.mill
+++ b/example/extending/python/1-hello-python/build.mill
@@ -9,7 +9,7 @@ import mill._
 def pythonExe: T[PathRef] = Task {
 
   os.call(("python3", "-m", "venv", Task.dest / "venv"))
-  val python = Task.dest / "venv" / "bin" / "python3"
+  val python = Task.dest / "venv/bin/python3"
   os.call((python, "-m", "pip", "install", "mypy==1.13.0"))
 
   PathRef(python)
@@ -19,7 +19,7 @@ def pythonExe: T[PathRef] = Task {
 
 // The `sources` task specifies the directory for Python source files (`src` folder).
 
-def sources: T[PathRef] = Task.Source(millSourcePath / "src")
+def sources: T[PathRef] = Task.Source("src")
 
 // === Type Checking
 
diff --git a/example/extending/python/2-python-modules/build.mill b/example/extending/python/2-python-modules/build.mill
index 46e8ed1f28b..0372b3aac33 100644
--- a/example/extending/python/2-python-modules/build.mill
+++ b/example/extending/python/2-python-modules/build.mill
@@ -8,13 +8,13 @@ import mill._
 
 trait PythonModule extends Module {
 
-  def sources: T[PathRef] = Task.Source(millSourcePath / "src")
+  def sources: T[PathRef] = Task.Source("src")
   def mainFileName: T[String] = Task { "main.py" }
 
   def pythonExe: T[PathRef] = Task {
 
     os.call(("python3", "-m", "venv", Task.dest / "venv"))
-    val python = Task.dest / "venv" / "bin" / "python3"
+    val python = Task.dest / "venv/bin/python3"
     os.call((python, "-m", "pip", "install", "mypy==1.13.0"))
 
     PathRef(python)
diff --git a/example/extending/python/3-python-module-deps/build.mill b/example/extending/python/3-python-module-deps/build.mill
index 09f1416ac31..d52b9c8f01b 100644
--- a/example/extending/python/3-python-module-deps/build.mill
+++ b/example/extending/python/3-python-module-deps/build.mill
@@ -13,13 +13,13 @@ trait PythonModule extends Module {
   // List of module dependencies required by this module.
   def moduleDeps: Seq[PythonModule] = Nil
 
-  def sources: T[PathRef] = Task.Source(millSourcePath / "src")
+  def sources: T[PathRef] = Task.Source("src")
   def mainFileName: T[String] = Task { "main.py" }
 
   def pythonExe: T[PathRef] = Task {
 
     os.call(("python3", "-m", "venv", Task.dest / "venv"))
-    val python = Task.dest / "venv" / "bin" / "python3"
+    val python = Task.dest / "venv/bin/python3"
     os.call((python, "-m", "pip", "install", "mypy==1.13.0"))
 
     PathRef(python)
diff --git a/example/extending/python/4-python-libs-bundle/build.mill b/example/extending/python/4-python-libs-bundle/build.mill
index 3d3b466609b..072ea6201e2 100644
--- a/example/extending/python/4-python-libs-bundle/build.mill
+++ b/example/extending/python/4-python-libs-bundle/build.mill
@@ -11,7 +11,7 @@ import mill._
 trait PythonModule extends Module {
   def moduleDeps: Seq[PythonModule] = Nil
   def mainFileName: T[String] = Task { "main.py" }
-  def sources: T[PathRef] = Task.Source(millSourcePath / "src")
+  def sources: T[PathRef] = Task.Source("src")
 
   def pythonDeps: T[Seq[String]] = Task { Seq.empty[String] }
 
@@ -22,7 +22,7 @@ trait PythonModule extends Module {
 
   def pythonExe: T[PathRef] = Task {
     os.call(("python3", "-m", "venv", Task.dest / "venv"))
-    val python = Task.dest / "venv" / "bin" / "python3"
+    val python = Task.dest / "venv/bin/python3"
     os.call((python, "-m", "pip", "install", "mypy==1.13.0", "pex==2.24.1", transitivePythonDeps()))
 
     PathRef(python)
diff --git a/example/extending/typescript/1-hello-typescript/build.mill b/example/extending/typescript/1-hello-typescript/build.mill
index 51e7fae7ae4..81c7cf5da32 100644
--- a/example/extending/typescript/1-hello-typescript/build.mill
+++ b/example/extending/typescript/1-hello-typescript/build.mill
@@ -39,7 +39,7 @@ def npmInstall = Task {
 // e.g. someone can later easily override `allSources` to add additional filtering
 // on exactly which files within the source root they wish to pick up.
 
-def sources = Task.Source(millSourcePath / "src")
+def sources = Task.Source("src")
 def allSources = Task {
   os.walk(sources().path).filter(_.ext == "ts").map(PathRef(_))
 }
diff --git a/example/extending/typescript/2-typescript-modules/build.mill b/example/extending/typescript/2-typescript-modules/build.mill
index aae72e2627f..c254acba0be 100644
--- a/example/extending/typescript/2-typescript-modules/build.mill
+++ b/example/extending/typescript/2-typescript-modules/build.mill
@@ -13,7 +13,7 @@ trait TypeScriptModule extends Module {
     PathRef(Task.dest)
   }
 
-  def sources = Task.Source(millSourcePath / "src")
+  def sources = Task.Source("src")
   def allSources = Task {
     os.walk(sources().path).filter(_.ext == "ts").map(PathRef(_))
   }
diff --git a/example/extending/typescript/3-module-deps/build.mill b/example/extending/typescript/3-module-deps/build.mill
index 5d8bdb56bd3..9680713d7a2 100644
--- a/example/extending/typescript/3-module-deps/build.mill
+++ b/example/extending/typescript/3-module-deps/build.mill
@@ -22,7 +22,7 @@ trait TypeScriptModule extends Module {
     PathRef(Task.dest)
   }
 
-  def sources = Task.Source(millSourcePath / "src")
+  def sources = Task.Source("src")
   def allSources = Task { os.walk(sources().path).filter(_.ext == "ts").map(PathRef(_)) }
 
   def compile: T[(PathRef, PathRef)] = Task {
diff --git a/example/extending/typescript/4-npm-deps-bundle/build.mill b/example/extending/typescript/4-npm-deps-bundle/build.mill
index 1fa764480b8..5a4e1bfb58e 100644
--- a/example/extending/typescript/4-npm-deps-bundle/build.mill
+++ b/example/extending/typescript/4-npm-deps-bundle/build.mill
@@ -39,7 +39,7 @@ trait TypeScriptModule extends Module {
     PathRef(Task.dest)
   }
 
-  def sources = Task.Source(millSourcePath / "src")
+  def sources = Task.Source("src")
   def allSources = Task { os.walk(sources().path).filter(_.ext == "ts").map(PathRef(_)) }
 
   def compile: T[(PathRef, PathRef)] = Task {
diff --git a/example/fundamentals/modules/6-modules/build.mill b/example/fundamentals/modules/6-modules/build.mill
index fa8fa794e17..2e5c47ca508 100644
--- a/example/fundamentals/modules/6-modules/build.mill
+++ b/example/fundamentals/modules/6-modules/build.mill
@@ -133,7 +133,7 @@ object foo2 extends FooModule {
 // module expects its input files to be on disk.
 
 trait MyModule extends Module {
-  def sources = Task.Source(millSourcePath / "sources")
+  def sources = Task.Source("sources")
   def task = Task { "hello " + os.list(sources().path).map(os.read(_)).mkString(" ") }
 }
 
@@ -238,7 +238,7 @@ object outer2 extends MyModule {
 //
 
 trait Foo extends Module {
-  def sourceRoots = Task.Sources(millSourcePath / "src")
+  def sourceRoots = Task.Sources("src")
   def sourceContents = Task {
     sourceRoots()
       .flatMap(pref => os.walk(pref.path))
@@ -249,7 +249,7 @@ trait Foo extends Module {
 }
 
 trait Bar extends Foo {
-  def additionalSources = Task.Sources(millSourcePath / "src2")
+  def additionalSources = Task.Sources("src2")
   def sourceRoots = Task { super.sourceRoots() ++ additionalSources() }
 }
 
diff --git a/example/fundamentals/modules/8-diy-java-modules/build.mill b/example/fundamentals/modules/8-diy-java-modules/build.mill
index cbab4c36e63..92ebe8d40c4 100644
--- a/example/fundamentals/modules/8-diy-java-modules/build.mill
+++ b/example/fundamentals/modules/8-diy-java-modules/build.mill
@@ -9,7 +9,7 @@ trait DiyJavaModule extends Module {
   def mainClass: T[Option[String]] = None
 
   def upstream: T[Seq[PathRef]] = Task { Task.traverse(moduleDeps)(_.classPath)().flatten }
-  def sources = Task.Source(millSourcePath / "src")
+  def sources = Task.Source("src")
 
   def compile = Task {
     val allSources = os.walk(sources().path)
diff --git a/example/fundamentals/tasks/1-task-graph/build.mill b/example/fundamentals/tasks/1-task-graph/build.mill
index 5d991e25924..fa26d93121e 100644
--- a/example/fundamentals/tasks/1-task-graph/build.mill
+++ b/example/fundamentals/tasks/1-task-graph/build.mill
@@ -6,8 +6,8 @@ import mill._
 
 def mainClass: T[Option[String]] = Some("foo.Foo")
 
-def sources = Task.Source(millSourcePath / "src")
-def resources = Task.Source(millSourcePath / "resources")
+def sources = Task.Source("src")
+def resources = Task.Source("resources")
 
 def compile = Task {
   val allSources = os.walk(sources().path)
diff --git a/example/fundamentals/tasks/2-primary-tasks/build.mill b/example/fundamentals/tasks/2-primary-tasks/build.mill
index 0cd36d99a8f..5f16e8bb768 100644
--- a/example/fundamentals/tasks/2-primary-tasks/build.mill
+++ b/example/fundamentals/tasks/2-primary-tasks/build.mill
@@ -9,8 +9,8 @@ package build
 
 import mill.{Module, T, _}
 
-def sources = Task.Source { millSourcePath / "src" }
-def resources = Task.Source { millSourcePath / "resources" }
+def sources = Task.Source { "src" }
+def resources = Task.Source { "resources" }
 
 // ``Source``s are defined using `Task.Source{...}` taking one `os.Path`, or `Task.Sources{...}`,
 // taking multiple ``os.Path``s as arguments. A ``Source``'s:
diff --git a/example/fundamentals/tasks/3-anonymous-tasks/build.mill b/example/fundamentals/tasks/3-anonymous-tasks/build.mill
index 810af932a43..2bac20ece41 100644
--- a/example/fundamentals/tasks/3-anonymous-tasks/build.mill
+++ b/example/fundamentals/tasks/3-anonymous-tasks/build.mill
@@ -5,7 +5,7 @@
 package build
 import mill._, define.Task
 
-def data = Task.Source(millSourcePath / "data")
+def data = Task.Source("data")
 
 def anonTask(fileName: String): Task[String] = Task.Anon {
   os.read(data().path / fileName)
diff --git a/example/fundamentals/tasks/5-persistent-tasks/build.mill b/example/fundamentals/tasks/5-persistent-tasks/build.mill
index fdbd5d2fed0..aec2614e7a0 100644
--- a/example/fundamentals/tasks/5-persistent-tasks/build.mill
+++ b/example/fundamentals/tasks/5-persistent-tasks/build.mill
@@ -17,7 +17,7 @@ import java.util.Arrays
 import java.io.ByteArrayOutputStream
 import java.util.zip.GZIPOutputStream
 
-def data = Task.Source(millSourcePath / "data")
+def data = Task.Source("data")
 
 def compressedData = Task(persistent = true) {
   println("Evaluating compressedData")
diff --git a/example/fundamentals/tasks/6-workers/build.mill b/example/fundamentals/tasks/6-workers/build.mill
index f19b8a7d0df..2336e4aa75c 100644
--- a/example/fundamentals/tasks/6-workers/build.mill
+++ b/example/fundamentals/tasks/6-workers/build.mill
@@ -25,7 +25,7 @@ import java.util.Arrays
 import java.io.ByteArrayOutputStream
 import java.util.zip.GZIPOutputStream
 
-def data = Task.Source(millSourcePath / "data")
+def data = Task.Source("data")
 
 def compressWorker = Task.Worker { new CompressWorker(Task.dest) }
 
diff --git a/example/javalib/module/15-jni/build.mill b/example/javalib/module/15-jni/build.mill
index f9fb34a1028..61e243fd964 100644
--- a/example/javalib/module/15-jni/build.mill
+++ b/example/javalib/module/15-jni/build.mill
@@ -6,7 +6,7 @@ import mill._, javalib._, util.Jvm
 
 object `package` extends RootModule with JavaModule {
   // Additional source folder to put C sources
-  def nativeSources = Task.Sources(millSourcePath / "native-src")
+  def nativeSources = Task.Sources("native-src")
 
   // Auto-generate JNI `.h` files from Java classes using Javac
   def nativeHeaders = Task {
diff --git a/example/javalib/module/7-resources/build.mill b/example/javalib/module/7-resources/build.mill
index fc3870c5c9c..301606779b0 100644
--- a/example/javalib/module/7-resources/build.mill
+++ b/example/javalib/module/7-resources/build.mill
@@ -4,7 +4,7 @@ import mill._, javalib._
 
 object foo extends JavaModule {
   object test extends JavaTests with TestModule.Junit4 {
-    def otherFiles = Task.Source(millSourcePath / "other-files")
+    def otherFiles = Task.Source("other-files")
 
     def forkEnv = super.forkEnv() ++ Map(
       "OTHER_FILES_DIR" -> otherFiles().path.toString
diff --git a/example/javalib/publishing/3-revapi/build.mill b/example/javalib/publishing/3-revapi/build.mill
index 7da8a9b5986..cc88e69c1e4 100644
--- a/example/javalib/publishing/3-revapi/build.mill
+++ b/example/javalib/publishing/3-revapi/build.mill
@@ -16,7 +16,7 @@ object bar extends JavaModule with RevapiModule {
 
   override def revapiConfigFiles: T[Seq[PathRef]] =
     // add Revapi config JSON file(s)
-    Task.Sources(millSourcePath / "conf/revapi.json")
+    Task.Sources("conf/revapi.json")
 
   override def revapiClasspath: T[Agg[PathRef]] = Task {
     // add folder containing logback.xml
diff --git a/example/javascriptlib/module/1-common-config/build.mill b/example/javascriptlib/module/1-common-config/build.mill
index 0ba16f29df8..610e349b885 100644
--- a/example/javascriptlib/module/1-common-config/build.mill
+++ b/example/javascriptlib/module/1-common-config/build.mill
@@ -6,7 +6,7 @@ import mill.javascriptlib._
 object foo extends TypeScriptModule {
 
   def customSource = Task {
-    Seq(PathRef(millSourcePath / "custom-src" / "foo2.ts"))
+    Seq(PathRef(millSourcePath / "custom-src/foo2.ts"))
   }
 
   def allSources = super.allSources() ++ customSource()
diff --git a/example/javascriptlib/module/5-resources/build.mill b/example/javascriptlib/module/5-resources/build.mill
index 684a3dbe4d4..6769bd40cf9 100644
--- a/example/javascriptlib/module/5-resources/build.mill
+++ b/example/javascriptlib/module/5-resources/build.mill
@@ -5,7 +5,7 @@ import ujson._
 
 object foo extends TypeScriptModule {
   object test extends TypeScriptTests with TestModule.Jest {
-    def otherFiles = Task.Source(millSourcePath / "other-files")
+    def otherFiles = Task.Source("other-files")
 
     def forkEnv = super.forkEnv() + ("OTHER_FILES_DIR" -> otherFiles().path.toString)
   }
diff --git a/example/kotlinlib/module/15-jni/build.mill b/example/kotlinlib/module/15-jni/build.mill
index 1ddadd00b0a..dac4985c1f0 100644
--- a/example/kotlinlib/module/15-jni/build.mill
+++ b/example/kotlinlib/module/15-jni/build.mill
@@ -8,7 +8,7 @@ object `package` extends RootModule with KotlinModule {
   def kotlinVersion = "1.9.24"
 
   // Additional source folder to put C sources
-  def nativeSources = Task.Sources(millSourcePath / "native-src")
+  def nativeSources = Task.Sources("native-src")
 
   // Compile C
   def nativeCompiled = Task {
diff --git a/example/kotlinlib/module/7-resources/build.mill b/example/kotlinlib/module/7-resources/build.mill
index ed509bedecd..25e2e06801a 100644
--- a/example/kotlinlib/module/7-resources/build.mill
+++ b/example/kotlinlib/module/7-resources/build.mill
@@ -7,7 +7,7 @@ object foo extends KotlinModule {
   def kotlinVersion = "1.9.24"
 
   object test extends KotlinTests with TestModule.Junit5 {
-    def otherFiles = Task.Source(millSourcePath / "other-files")
+    def otherFiles = Task.Source("other-files")
 
     def forkEnv = super.forkEnv() ++ Map(
       "OTHER_FILES_DIR" -> otherFiles().path.toString
diff --git a/example/pythonlib/basic/1-simple/build.mill b/example/pythonlib/basic/1-simple/build.mill
index 4492515b6c6..b1a250e74e9 100644
--- a/example/pythonlib/basic/1-simple/build.mill
+++ b/example/pythonlib/basic/1-simple/build.mill
@@ -3,7 +3,7 @@ import mill._, pythonlib._
 
 object foo extends PythonModule {
 
-  def mainScript = Task.Source { millSourcePath / "src" / "foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
 
   def pythonDeps = Seq("Jinja2==3.1.4")
 
diff --git a/example/pythonlib/basic/2-custom-build-logic/build.mill b/example/pythonlib/basic/2-custom-build-logic/build.mill
index 9d298926e56..dbbbde1f9f7 100644
--- a/example/pythonlib/basic/2-custom-build-logic/build.mill
+++ b/example/pythonlib/basic/2-custom-build-logic/build.mill
@@ -7,7 +7,7 @@ import mill._, pythonlib._
 
 object foo extends PythonModule {
 
-  def mainScript = Task.Source { millSourcePath / "src" / "foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
 
   /** All Python source files in this module, recursively from the source directories.*/
   def allSourceFiles: T[Seq[PathRef]] = Task {
diff --git a/example/pythonlib/basic/3-multi-module/build.mill b/example/pythonlib/basic/3-multi-module/build.mill
index 2d5002805b3..3ac3b10d9c7 100644
--- a/example/pythonlib/basic/3-multi-module/build.mill
+++ b/example/pythonlib/basic/3-multi-module/build.mill
@@ -8,11 +8,11 @@ trait MyModule extends PythonModule {
 
 object foo extends MyModule {
   def moduleDeps = Seq(bar)
-  def mainScript = Task.Source { millSourcePath / "src" / "foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
 }
 
 object bar extends MyModule {
-  def mainScript = Task.Source { millSourcePath / "src" / "bar.py" }
+  def mainScript = Task.Source { "src/bar.py" }
   def pythonDeps = Seq("Jinja2==3.1.4")
 }
 
diff --git a/example/pythonlib/module/1-common-config/build.mill b/example/pythonlib/module/1-common-config/build.mill
index 87e1001963c..e457e814cb8 100644
--- a/example/pythonlib/module/1-common-config/build.mill
+++ b/example/pythonlib/module/1-common-config/build.mill
@@ -12,7 +12,7 @@ object foo extends PythonModule {
   def pythonDeps = Seq("MarkupSafe==3.0.2", "Jinja2==3.1.4")
 
   // choose a main Script to run if there are multiple present
-  def mainScript = Task.Source { millSourcePath / "custom-src" / "foo2.py" }
+  def mainScript = Task.Source { "custom-src/foo2.py" }
 
   // Add (or replace) source folders for the module to use
   def sources = Task.Sources {
diff --git a/example/pythonlib/module/2-custom-tasks/build.mill b/example/pythonlib/module/2-custom-tasks/build.mill
index 9a4a73e6883..4731ac56153 100644
--- a/example/pythonlib/module/2-custom-tasks/build.mill
+++ b/example/pythonlib/module/2-custom-tasks/build.mill
@@ -15,7 +15,7 @@ object foo extends PythonModule {
 
   def pythonDeps = Seq("argparse==1.4.0", "jinja2==3.1.4")
 
-  def mainScript = Task.Source { millSourcePath / "src" / "foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
 
   def generatedSources: T[Seq[PathRef]] = Task {
     val destPath = Task.dest / "generatedSources"
diff --git a/example/pythonlib/module/4-compilation-execution-flags/build.mill b/example/pythonlib/module/4-compilation-execution-flags/build.mill
index e72e192271f..6387ac7425a 100644
--- a/example/pythonlib/module/4-compilation-execution-flags/build.mill
+++ b/example/pythonlib/module/4-compilation-execution-flags/build.mill
@@ -2,7 +2,7 @@ package build
 import mill._, pythonlib._
 
 object `package` extends RootModule with PythonModule {
-  def mainScript = Task.Source { millSourcePath / "src" / "foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
   def pythonOptions = Seq("-Wall", "-Xdev")
   def forkEnv = Map("MY_ENV_VAR" -> "HELLO MILL!")
 }
diff --git a/example/pythonlib/module/5-resources/build.mill b/example/pythonlib/module/5-resources/build.mill
index 9bf431557f0..2d279a35dab 100644
--- a/example/pythonlib/module/5-resources/build.mill
+++ b/example/pythonlib/module/5-resources/build.mill
@@ -2,13 +2,13 @@ package build
 import mill._, pythonlib._
 
 object foo extends PythonModule {
-  def mainScript = Task.Source { millSourcePath / "src" / "foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
 
   def resources = Task.Sources { super.resources() ++ Seq(PathRef(millSourcePath / "custom")) }
 
   object test extends PythonTests with TestModule.Unittest {
 
-    def otherFiles = Task.Source(millSourcePath / "other-files")
+    def otherFiles = Task.Source("other-files")
 
     def forkEnv: T[Map[String, String]] =
       super.forkEnv() ++ Map("OTHER_FILES_DIR" -> otherFiles().path.toString)
diff --git a/example/pythonlib/module/6-pex-config/build.mill b/example/pythonlib/module/6-pex-config/build.mill
index c9a094a0e23..f219fffc584 100644
--- a/example/pythonlib/module/6-pex-config/build.mill
+++ b/example/pythonlib/module/6-pex-config/build.mill
@@ -7,7 +7,7 @@ import mill._, pythonlib._
 
 object foo extends PythonModule {
   // This Script will be the entry point for the bundle
-  def mainScript = Task.Source { millSourcePath / "src" / "foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
 
   // These Dependencies will be used in the bundle
   def pythonDeps = Seq("pyfiglet==1.0.2", "termcolor==2.5.0")
diff --git a/example/pythonlib/publishing/2-publish-module-advanced/build.mill b/example/pythonlib/publishing/2-publish-module-advanced/build.mill
index beb0354f58c..530ef71f1f5 100644
--- a/example/pythonlib/publishing/2-publish-module-advanced/build.mill
+++ b/example/pythonlib/publishing/2-publish-module-advanced/build.mill
@@ -39,7 +39,7 @@ object `package` extends RootModule with PythonModule with PublishModule {
   def publishVersion = "0.0.3"
 
   // you could also reference an existing setup.py file directly, e.g.
-  // `def setup = Task.Source { millSourcePath / "setup.py" }`
+  // `def setup = Task.Source { "setup.py" }`
   def setup = Task {
     val str =
       s"""#from setuptools import setup
diff --git a/example/pythonlib/testing/1-test-suite/build.mill b/example/pythonlib/testing/1-test-suite/build.mill
index d440ffc1454..9bed86884c6 100644
--- a/example/pythonlib/testing/1-test-suite/build.mill
+++ b/example/pythonlib/testing/1-test-suite/build.mill
@@ -2,9 +2,9 @@ package build
 import mill._, pythonlib._
 
 object foo extends PythonModule {
-  def mainScript = Task.Source { millSourcePath / "src/foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
   object test extends PythonTests with TestModule.Unittest {
-    def mainScript = Task.Source { millSourcePath / "src/test_foo.py" }
+    def mainScript = Task.Source { "src/test_foo.py" }
   }
 }
 
@@ -51,7 +51,7 @@ OK
 // details on how to use each one from the command line.
 
 object bar extends PythonModule {
-  def mainScript = Task.Source { millSourcePath / "src/bar.py" }
+  def mainScript = Task.Source { "src/bar.py" }
   object test extends PythonTests with TestModule.Pytest
 }
 
diff --git a/example/pythonlib/testing/2-test-deps/build.mill b/example/pythonlib/testing/2-test-deps/build.mill
index f78cdcd6b20..561de57a3e3 100644
--- a/example/pythonlib/testing/2-test-deps/build.mill
+++ b/example/pythonlib/testing/2-test-deps/build.mill
@@ -6,7 +6,7 @@ import mill._, pythonlib._
 
 object foo extends PythonModule {
 
-  def mainScript = Task.Source { millSourcePath / "src/foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
 
   def moduleDeps = Seq(bar)
 
@@ -23,7 +23,7 @@ object foo extends PythonModule {
 
 object bar extends PythonModule {
 
-  def mainScript = Task.Source { millSourcePath / "src/bar.py" }
+  def mainScript = Task.Source { "src/bar.py" }
 
   object test extends PythonTests with TestModule.Unittest
 
diff --git a/example/pythonlib/testing/3-integration-suite/build.mill b/example/pythonlib/testing/3-integration-suite/build.mill
index b0fbfa5e764..f6f6118a97e 100644
--- a/example/pythonlib/testing/3-integration-suite/build.mill
+++ b/example/pythonlib/testing/3-integration-suite/build.mill
@@ -7,7 +7,7 @@ import mill._, pythonlib._
 
 object foo extends PythonModule {
 
-  def mainScript = Task.Source { millSourcePath / "src/foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
 
   object test extends PythonTests with TestModule.Unittest
 
diff --git a/example/pythonlib/web/1-hello-flask/build.mill b/example/pythonlib/web/1-hello-flask/build.mill
index 661c36a9b70..2cf31d9324c 100644
--- a/example/pythonlib/web/1-hello-flask/build.mill
+++ b/example/pythonlib/web/1-hello-flask/build.mill
@@ -6,7 +6,7 @@ import mill._, pythonlib._
 
 object foo extends PythonModule {
 
-  def mainScript = Task.Source { millSourcePath / "src/foo.py" }
+  def mainScript = Task.Source { "src/foo.py" }
 
   def pythonDeps = Seq("flask==3.1.0")
 
diff --git a/example/pythonlib/web/2-todo-flask/build.mill b/example/pythonlib/web/2-todo-flask/build.mill
index ac903686234..ccd697a8219 100644
--- a/example/pythonlib/web/2-todo-flask/build.mill
+++ b/example/pythonlib/web/2-todo-flask/build.mill
@@ -7,7 +7,7 @@ import mill._, pythonlib._
 
 object todo extends PythonModule {
 
-  def mainScript = Task.Source { millSourcePath / "src/app.py" }
+  def mainScript = Task.Source { "src/app.py" }
 
   def pythonDeps = Seq("flask==3.1.0", "Flask-SQLAlchemy==3.1.1", "Flask-WTF==1.2.2")
 
diff --git a/example/pythonlib/web/3-hello-django/build.mill b/example/pythonlib/web/3-hello-django/build.mill
index cd85cfc7afa..4c323cb96f7 100644
--- a/example/pythonlib/web/3-hello-django/build.mill
+++ b/example/pythonlib/web/3-hello-django/build.mill
@@ -6,7 +6,7 @@ import mill._, pythonlib._
 
 object foo extends PythonModule {
 
-  def mainScript = Task.Source { millSourcePath / "src/manage.py" }
+  def mainScript = Task.Source { "src/manage.py" }
 
   def pythonDeps = Seq("django==5.1.4")
 
diff --git a/example/pythonlib/web/4-todo-django/build.mill b/example/pythonlib/web/4-todo-django/build.mill
index b992704855f..2f0cc218267 100644
--- a/example/pythonlib/web/4-todo-django/build.mill
+++ b/example/pythonlib/web/4-todo-django/build.mill
@@ -6,7 +6,7 @@ import mill._, pythonlib._
 
 object todo extends PythonModule {
 
-  def mainScript = Task.Source { millSourcePath / "src/manage.py" }
+  def mainScript = Task.Source { "src/manage.py" }
 
   def pythonDeps = Seq("django==5.1.4")
 
diff --git a/example/scalalib/module/7-resources/build.mill b/example/scalalib/module/7-resources/build.mill
index 62d82a99035..03c8243b4fc 100644
--- a/example/scalalib/module/7-resources/build.mill
+++ b/example/scalalib/module/7-resources/build.mill
@@ -12,7 +12,7 @@ object foo extends ScalaModule {
     def ivyDeps = Agg(ivy"com.lihaoyi::utest:0.8.5")
     def testFramework = "utest.runner.Framework"
 
-    def otherFiles = Task.Source(millSourcePath / "other-files")
+    def otherFiles = Task.Source("other-files")
 
     def forkEnv = super.forkEnv() ++ Map(
       "OTHER_FILES_DIR" -> otherFiles().path.toString
diff --git a/example/thirdparty/acyclic/build.mill b/example/thirdparty/acyclic/build.mill
index cabfc027b20..b6867c9857d 100644
--- a/example/thirdparty/acyclic/build.mill
+++ b/example/thirdparty/acyclic/build.mill
@@ -39,7 +39,7 @@ trait AcyclicModule extends CrossScalaModule with PublishModule {
   def compileIvyDeps = Agg(Deps.scalaCompiler(crossScalaVersion))
 
   object test extends ScalaTests with TestModule.Utest {
-    def sources = Task.Sources(millSourcePath / "src", millSourcePath / "resources")
+    def sources = Task.Sources("src", "resources")
     def ivyDeps = Agg(Deps.utest, Deps.scalaCompiler(crossScalaVersion))
   }
 }
diff --git a/example/thirdparty/arrow/build.mill b/example/thirdparty/arrow/build.mill
index 7fb0b31bb37..cc9475a71e2 100644
--- a/example/thirdparty/arrow/build.mill
+++ b/example/thirdparty/arrow/build.mill
@@ -135,10 +135,10 @@ object `package` extends RootModule {
       override def sources: T[Seq[PathRef]] = Task.Sources {
         val sourcesRootPath = millSourcePath / "src"
         var sources = Seq("common", platformCrossSuffix)
-          .map(platform => PathRef(sourcesRootPath / s"${platform}Main" / "kotlin"))
+          .map(platform => PathRef(sourcesRootPath / s"${platform}Main/kotlin"))
           .filter(p => os.exists(p.path))
         if (platformCrossSuffix != "jvm") {
-          val nonJvmSourcesPath = sourcesRootPath / "nonJvmMain" / "kotlin"
+          val nonJvmSourcesPath = sourcesRootPath / "nonJvmMain/kotlin"
           if (os.exists(nonJvmSourcesPath)) {
             sources ++= Seq(PathRef(nonJvmSourcesPath))
           }
@@ -163,7 +163,7 @@ object `package` extends RootModule {
         override def sources: T[Seq[PathRef]] = Task.Sources {
           val sourcesRootPath = outer.millSourcePath / "src"
           Seq("common", outer.platformCrossSuffix)
-            .map(platform => PathRef(sourcesRootPath / s"${platform}Test" / "kotlin"))
+            .map(platform => PathRef(sourcesRootPath / s"${platform}Test/kotlin"))
             .filter(p => os.exists(p.path))
         }
       }
diff --git a/example/thirdparty/mockito/build.mill b/example/thirdparty/mockito/build.mill
index e1adef2960d..6e1dd2eec1f 100644
--- a/example/thirdparty/mockito/build.mill
+++ b/example/thirdparty/mockito/build.mill
@@ -228,7 +228,7 @@ object `package` extends RootModule with MockitoModule {
 //      trait BundleModule extends MockitoModule{
 //        def bundleName: String = millModuleSegments.last.value
 //        override def millSourcePath = `osgi-test`.millSourcePath
-//        def sources = Task.Sources(millSourcePath / "src" / bundleName / "java")
+//        def sources = Task.Sources("src" / bundleName / "java")
 //
 //        def manifest = super.manifest().add(
 //          "Bundle-Name" -> bundleName,
diff --git a/example/thirdparty/netty/build.mill b/example/thirdparty/netty/build.mill
index 8e4551032e4..5079d147252 100644
--- a/example/thirdparty/netty/build.mill
+++ b/example/thirdparty/netty/build.mill
@@ -85,7 +85,7 @@ trait NettyModule extends NettyBaseModule {
 
 trait NettyJniModule extends NettyModule {
   def jniLibraryName: T[String]
-  def cSources = Task.Source(millSourcePath / "src/main/c")
+  def cSources = Task.Source("src/main/c")
   def resources = Task {
     os.copy(clang().path, Task.dest / "META-INF/native" / jniLibraryName(), createFolders = true)
     Seq(PathRef(Task.dest))
@@ -245,7 +245,7 @@ object common extends NettyModule {
     ivy"org.jctools:jctools-core:4.0.5"
   )
 
-  def script = Task.Source(millSourcePath / "src/main/script")
+  def script = Task.Source("src/main/script")
   def generatedSources0 = Task {
     val shell = new groovy.lang.GroovyShell()
 
@@ -456,7 +456,7 @@ object `testsuite-native` extends NettyTestSuiteModule {
     `transport-native-epoll`
   )
   def testModuleDeps = Seq(`resolver-dns-classes-macos`)
-  override def sources = Task.Sources(millSourcePath / "src/test/java")
+  override def sources = Task.Sources("src/test/java")
 }
 
 object `testsuite-native-image` extends NettyTestSuiteModule {
@@ -493,7 +493,7 @@ object `testsuite-osgi` extends NettyTestSuiteModule {
     `transport-udt`
   )
 
-  override def sources = Task.Sources(millSourcePath / "src/test/java")
+  override def sources = Task.Sources("src/test/java")
 
   def ivyDeps = super.ivyDeps() ++ Agg(
     ivy"org.apache.felix:org.apache.felix.configadmin:1.9.14",
@@ -506,7 +506,7 @@ object `testsuite-osgi` extends NettyTestSuiteModule {
 
 object `testsuite-shading` extends NettyTestSuiteModule {
   def moduleDeps = Seq(common)
-  override def sources = Task.Sources(millSourcePath / "src/test/java")
+  override def sources = Task.Sources("src/test/java")
 }
 
 object transport extends NettyModule {
@@ -556,8 +556,8 @@ object `transport-native-unix-common` extends NettyModule {
   def moduleDeps = Seq(common, buffer, transport)
   def ivyDeps = Agg(ivy"org.junit.jupiter:junit-jupiter-api:5.9.0")
 
-  def makefile = Task.Source(millSourcePath / "Makefile")
-  def cSources = Task.Source(millSourcePath / "src/main/c")
+  def makefile = Task.Source("Makefile")
+  def cSources = Task.Source("src/main/c")
   def cHeaders = Task {
     for (p <- os.walk(cSources().path) if p.ext == "h") {
       os.copy(p, Task.dest / p.relativeTo(cSources().path), createFolders = true)
diff --git a/integration/ide/gen-idea/resources/extended/build.mill b/integration/ide/gen-idea/resources/extended/build.mill
index 3a6d98db685..2bcc972d3e9 100644
--- a/integration/ide/gen-idea/resources/extended/build.mill
+++ b/integration/ide/gen-idea/resources/extended/build.mill
@@ -52,7 +52,7 @@ trait HelloWorldModule extends scalalib.ScalaModule {
         Seq(
           // whole file
           IdeaConfigFile(
-            os.sub / "runConfigurations" / "testrun.xml",
+            os.sub / "runConfigurations/testrun.xml",
             None,
             Seq(Element("test"))
           ),
diff --git a/integration/invalidation/multi-level-editing/src/MultiLevelBuildTests.scala b/integration/invalidation/multi-level-editing/src/MultiLevelBuildTests.scala
index d44eed2bb88..60b28b4e96f 100644
--- a/integration/invalidation/multi-level-editing/src/MultiLevelBuildTests.scala
+++ b/integration/invalidation/multi-level-editing/src/MultiLevelBuildTests.scala
@@ -110,7 +110,7 @@ trait MultiLevelBuildTests extends UtestIntegrationTestSuite {
     // restarts behave as expected:
     if (clientServerMode) {
       // Only one server should be running at any point in time
-      val Seq(serverFolder) = os.list(tester.workspacePath / "out" / "mill-server")
+      val Seq(serverFolder) = os.list(tester.workspacePath / "out/mill-server")
 
       // client-server mode should never restart in these tests and preserve the same process,
       val currentServerId = os.read(serverFolder / "serverId")
diff --git a/integration/invalidation/selective-execution/resources/build.mill b/integration/invalidation/selective-execution/resources/build.mill
index 4b0bf9d6068..fed58b7238b 100644
--- a/integration/invalidation/selective-execution/resources/build.mill
+++ b/integration/invalidation/selective-execution/resources/build.mill
@@ -1,7 +1,7 @@
 import mill._
 
 object foo extends Module {
-  def fooTask = Task.Source(millSourcePath / "foo.txt")
+  def fooTask = Task.Source("foo.txt")
 
   def fooHelper(p: os.Path) = {
     "fooHelper " + os.read(p)
@@ -15,7 +15,7 @@ object foo extends Module {
 
 object bar extends mill.define.TaskModule {
   // make sure it works with private tasks as well
-  private def barTask = Task.Source(millSourcePath / "bar.txt")
+  private def barTask = Task.Source("bar.txt")
 
   def barHelper(p: os.Path) = {
     "barHelper " + os.read(p)
diff --git a/integration/invalidation/watch-source-input/resources/build.mill b/integration/invalidation/watch-source-input/resources/build.mill
index 5d6b57c4248..662cbfe87ac 100644
--- a/integration/invalidation/watch-source-input/resources/build.mill
+++ b/integration/invalidation/watch-source-input/resources/build.mill
@@ -3,8 +3,8 @@ import mill._
 
 println("Setting up build.mill")
 
-def foo = Task.Sources(millSourcePath / "foo1.txt", millSourcePath / "foo2.txt")
-def bar = Task.Source(millSourcePath / "bar.txt")
+def foo = Task.Sources("foo1.txt", "foo2.txt")
+def bar = Task.Source("bar.txt")
 
 def qux = Task {
   val fooMsg = "Running qux foo contents " + foo().map(p => os.read(p.path)).mkString(" ")
diff --git a/javascriptlib/src/mill/javascriptlib/PublishModule.scala b/javascriptlib/src/mill/javascriptlib/PublishModule.scala
index b035c6bd183..b8b8756295e 100644
--- a/javascriptlib/src/mill/javascriptlib/PublishModule.scala
+++ b/javascriptlib/src/mill/javascriptlib/PublishModule.scala
@@ -131,7 +131,7 @@ trait PublishModule extends TypeScriptModule {
   private def pubGenSources: T[Unit] = Task {
     val allGeneratedSources = pubBaseModeGenSources() ++ pubModDepsGenSources()
     allGeneratedSources.foreach { target =>
-      val destination = publishDir().path / "typescript" / "generatedSources" / target.path.last
+      val destination = publishDir().path / "typescript/generatedSources" / target.path.last
       os.makeDir.all(destination / os.up)
       os.copy.over(
         target.path,
diff --git a/javascriptlib/src/mill/javascriptlib/ReactScriptsModule.scala b/javascriptlib/src/mill/javascriptlib/ReactScriptsModule.scala
index e569a24e873..14268b7a6fe 100644
--- a/javascriptlib/src/mill/javascriptlib/ReactScriptsModule.scala
+++ b/javascriptlib/src/mill/javascriptlib/ReactScriptsModule.scala
@@ -71,7 +71,7 @@ trait ReactScriptsModule extends TypeScriptModule {
     val npm = npmInstall().path
     val combinedPaths = compilerOptionsPaths() ++ Seq(
       "*" -> npm / "node_modules",
-      "typescript" -> npm / "node_modules" / "typescript"
+      "typescript" -> npm / "node_modules/typescript"
     )
 
     val combinedCompilerOptions: Map[String, ujson.Value] = compilerOptions() ++ Map(
@@ -108,7 +108,7 @@ trait ReactScriptsModule extends TypeScriptModule {
   override def bundle: Target[PathRef] = Task {
     val compiled = compile()._1.path
     os.call(
-      ("node", compiled / "node_modules" / "react-scripts" / "bin" / "react-scripts.js", "build"),
+      ("node", compiled / "node_modules/react-scripts/bin/react-scripts.js", "build"),
       cwd = compiled,
       stdout = os.Inherit,
       env = forkEnv()
@@ -142,7 +142,7 @@ trait ReactScriptsModule extends TypeScriptModule {
     os.call(
       (
         "node",
-        (compiled / "node_modules" / "react-scripts" / "bin" / "react-scripts.js").toString,
+        (compiled / "node_modules/react-scripts/bin/react-scripts.js").toString,
         "test",
         "--watchAll=false"
       ),
diff --git a/javascriptlib/src/mill/javascriptlib/RsWithServeModule.scala b/javascriptlib/src/mill/javascriptlib/RsWithServeModule.scala
index fa7aa8cf972..61fc110ce2c 100644
--- a/javascriptlib/src/mill/javascriptlib/RsWithServeModule.scala
+++ b/javascriptlib/src/mill/javascriptlib/RsWithServeModule.scala
@@ -15,7 +15,7 @@ trait RsWithServeModule extends ReactScriptsModule {
     val env = forkEnv()
     os.call(
       (
-        (compiled / "node_modules" / "serve" / "bin" / "serve.js").toString,
+        (compiled / "node_modules/serve/bin/serve.js").toString,
         "-s",
         build,
         "-l",
diff --git a/javascriptlib/src/mill/javascriptlib/TypeScriptModule.scala b/javascriptlib/src/mill/javascriptlib/TypeScriptModule.scala
index 01830c0fcd5..f75b5e65202 100644
--- a/javascriptlib/src/mill/javascriptlib/TypeScriptModule.scala
+++ b/javascriptlib/src/mill/javascriptlib/TypeScriptModule.scala
@@ -50,7 +50,7 @@ trait TypeScriptModule extends Module { outer =>
     PathRef(Task.dest)
   }
 
-  def sources: T[PathRef] = Task.Source(millSourcePath / "src")
+  def sources: T[PathRef] = Task.Source("src")
 
   def resources: T[Seq[PathRef]] = Task { Seq(PathRef(millSourcePath / "resources")) }
 
diff --git a/kotlinlib/src/mill/kotlinlib/js/KotlinJsModule.scala b/kotlinlib/src/mill/kotlinlib/js/KotlinJsModule.scala
index 71cbdda4c84..3e1c5473e7d 100644
--- a/kotlinlib/src/mill/kotlinlib/js/KotlinJsModule.scala
+++ b/kotlinlib/src/mill/kotlinlib/js/KotlinJsModule.scala
@@ -486,11 +486,11 @@ trait KotlinJsModule extends KotlinModule { outer =>
     // otherwise with random versions there is a possibility to have conflict
     // between the versions of the shared transitive deps
     private def mochaModule = Task {
-      PathRef(nodeModulesDir().path / "node_modules" / "mocha" / "bin" / "mocha.js")
+      PathRef(nodeModulesDir().path / "node_modules/mocha/bin/mocha.js")
     }
 
     private def sourceMapSupportModule = Task {
-      PathRef(nodeModulesDir().path / "node_modules" / "source-map-support" / "register.js")
+      PathRef(nodeModulesDir().path / "node_modules/source-map-support/register.js")
     }
 
     // endregion
diff --git a/kotlinlib/test/src/mill/kotlinlib/HelloWorldTests.scala b/kotlinlib/test/src/mill/kotlinlib/HelloWorldTests.scala
index b169e96bfcd..86b636cad37 100644
--- a/kotlinlib/test/src/mill/kotlinlib/HelloWorldTests.scala
+++ b/kotlinlib/test/src/mill/kotlinlib/HelloWorldTests.scala
@@ -89,7 +89,7 @@ object HelloWorldTests extends TestSuite {
     test("failures") {
       val eval = testEval()
 
-      val mainJava = HelloWorldKotlin.millSourcePath / "main" / "src" / "Hello.kt"
+      val mainJava = HelloWorldKotlin.millSourcePath / "main/src/Hello.kt"
 
       HelloWorldKotlin.main.crossModules.foreach(m => {
 
diff --git a/kotlinlib/test/src/mill/kotlinlib/MixedHelloWorldTests.scala b/kotlinlib/test/src/mill/kotlinlib/MixedHelloWorldTests.scala
index 77c58237fff..b0c3c6970fa 100644
--- a/kotlinlib/test/src/mill/kotlinlib/MixedHelloWorldTests.scala
+++ b/kotlinlib/test/src/mill/kotlinlib/MixedHelloWorldTests.scala
@@ -76,7 +76,7 @@ object MixedHelloWorldTests extends TestSuite {
       MixedHelloWorldKotlin.main.crossModules.foreach(m => {
 
         val mainJava =
-          MixedHelloWorldKotlin.millSourcePath / "main" / "src" / "hello" / "KotlinHello.kt"
+          MixedHelloWorldKotlin.millSourcePath / "main/src/hello/KotlinHello.kt"
 
         val Right(_) = eval.apply(m.compile)
 
diff --git a/kotlinlib/test/src/mill/kotlinlib/contrib/kover/KoverModuleTests.scala b/kotlinlib/test/src/mill/kotlinlib/contrib/kover/KoverModuleTests.scala
index eee518be48c..842a36429a9 100644
--- a/kotlinlib/test/src/mill/kotlinlib/contrib/kover/KoverModuleTests.scala
+++ b/kotlinlib/test/src/mill/kotlinlib/contrib/kover/KoverModuleTests.scala
@@ -13,7 +13,7 @@ object KoverModuleTests extends TestSuite {
 
   val kotlinVersion = "1.9.24"
 
-  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "contrib" / "kover"
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "contrib/kover"
 
   object module extends TestBaseModule {
 
diff --git a/kotlinlib/test/src/mill/kotlinlib/contrib/ktfmt/KtfmtModuleTests.scala b/kotlinlib/test/src/mill/kotlinlib/contrib/ktfmt/KtfmtModuleTests.scala
index b1a8afe2c62..4f29b90f409 100644
--- a/kotlinlib/test/src/mill/kotlinlib/contrib/ktfmt/KtfmtModuleTests.scala
+++ b/kotlinlib/test/src/mill/kotlinlib/contrib/ktfmt/KtfmtModuleTests.scala
@@ -17,7 +17,7 @@ object KtfmtModuleTests extends TestSuite {
   def tests: Tests = Tests {
 
     val (before, after) = {
-      val root = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "contrib" / "ktfmt"
+      val root = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "contrib/ktfmt"
       (root / "before", root / "after")
     }
 
@@ -25,7 +25,7 @@ object KtfmtModuleTests extends TestSuite {
       assert(
         checkState(
           afterFormat(before, style = "kotlin"),
-          after / "style" / "kotlin"
+          after / "style/kotlin"
         )
       )
     }
@@ -34,7 +34,7 @@ object KtfmtModuleTests extends TestSuite {
       assert(
         checkState(
           afterFormat(before, style = "google"),
-          after / "style" / "google"
+          after / "style/google"
         )
       )
     }
@@ -43,7 +43,7 @@ object KtfmtModuleTests extends TestSuite {
       assert(
         checkState(
           afterFormat(before, style = "meta"),
-          after / "style" / "meta"
+          after / "style/meta"
         )
       )
     }
@@ -65,7 +65,7 @@ object KtfmtModuleTests extends TestSuite {
     test("ktfmt - explicit files") {
       checkState(
         afterFormat(before, sources = Seq(module.sources)),
-        after / "style" / "kotlin"
+        after / "style/kotlin"
       )
     }
 
@@ -74,7 +74,7 @@ object KtfmtModuleTests extends TestSuite {
       assert(
         checkState(
           afterFormatAll(before),
-          after / "style" / "kotlin"
+          after / "style/kotlin"
         )
       )
     }
diff --git a/kotlinlib/test/src/mill/kotlinlib/js/KotlinJsCompileTests.scala b/kotlinlib/test/src/mill/kotlinlib/js/KotlinJsCompileTests.scala
index aa992797679..ad5cf303e76 100644
--- a/kotlinlib/test/src/mill/kotlinlib/js/KotlinJsCompileTests.scala
+++ b/kotlinlib/test/src/mill/kotlinlib/js/KotlinJsCompileTests.scala
@@ -34,8 +34,8 @@ object KotlinJsCompileTests extends TestSuite {
       val irDir = result.value.classes.path
       assert(
         os.isDir(irDir),
-        os.exists(irDir / "default" / "manifest"),
-        os.exists(irDir / "default" / "linkdata" / "package_foo"),
+        os.exists(irDir / "default/manifest"),
+        os.exists(irDir / "default/linkdata/package_foo"),
         !os.walk(irDir).exists(_.ext == "klib")
       )
     }
@@ -43,7 +43,7 @@ object KotlinJsCompileTests extends TestSuite {
     test("failures") {
       val eval = testEval()
 
-      val compilationUnit = module.foo.millSourcePath / "src" / "foo" / "Hello.kt"
+      val compilationUnit = module.foo.millSourcePath / "src/foo/Hello.kt"
 
       val Right(_) = eval.apply(module.foo.compile)
 
diff --git a/main/define/src/mill/define/Task.scala b/main/define/src/mill/define/Task.scala
index be7857fde6c..ab0a4e7b250 100644
--- a/main/define/src/mill/define/Task.scala
+++ b/main/define/src/mill/define/Task.scala
@@ -65,6 +65,9 @@ object Task extends TaskBase {
   def Sources(values: Result[Seq[PathRef]])(implicit ctx: mill.define.Ctx): Target[Seq[PathRef]] =
     macro Target.Internal.sourcesImpl2
 
+  def Sources(values: os.SubPath*)(implicit ctx: mill.define.Ctx): Target[Seq[PathRef]] =
+    macro Target.Internal.sourcesImpl3
+
   /**
    * Similar to [[Source]], but only for a single source file or folder. Defined
    * using `Task.Source`.
@@ -75,6 +78,10 @@ object Task extends TaskBase {
   def Source(value: Result[PathRef])(implicit ctx: mill.define.Ctx): Target[PathRef] =
     macro Target.Internal.sourceImpl2
 
+
+  def Source(value: os.SubPath)(implicit ctx: mill.define.Ctx): Target[PathRef] =
+    macro Target.Internal.sourceImpl3
+
   /**
    * [[InputImpl]]s, normally defined using `Task.Input`, are [[NamedTask]]s that
    * re-evaluate every time Mill is run. This is in contrast to [[TargetImpl]]s
@@ -476,6 +483,29 @@ object Target extends TaskBase {
       )
     }
 
+    def sourcesImpl3(c: Context)(values: c.Expr[os.SubPath]*)(ctx: c.Expr[mill.define.Ctx])
+    : c.Expr[Target[Seq[PathRef]]] = {
+      import c.universe._
+      val wrapped =
+        for (value <- values.toList)
+          yield Applicative.impl0[Task, PathRef, mill.api.Ctx](c)(
+            reify(Result.Success(PathRef(ctx.splice.millSourcePath / value.splice))).tree
+          ).tree
+
+      val taskIsPrivate = isPrivateTargetOption(c)
+
+      mill.define.Cacher.impl0[SourcesImpl](c)(
+        reify(
+          new SourcesImpl(
+            Target.sequence(c.Expr[List[Task[PathRef]]](q"_root_.scala.List(..$wrapped)").splice),
+            ctx.splice,
+            taskIsPrivate.splice
+          )
+        )
+      )
+    }
+
+
     def sourceImpl1(c: Context)(value: c.Expr[Result[os.Path]])(ctx: c.Expr[mill.define.Ctx])
         : c.Expr[Target[PathRef]] = {
       import c.universe._
@@ -515,6 +545,28 @@ object Target extends TaskBase {
       )
     }
 
+    def sourceImpl3(c: Context)(value: c.Expr[os.SubPath])(ctx: c.Expr[mill.define.Ctx])
+    : c.Expr[Target[PathRef]] = {
+      import c.universe._
+
+      val wrapped =
+        Applicative.impl0[Task, PathRef, mill.api.Ctx](c)(
+          reify(Result.Success(PathRef(ctx.splice.millSourcePath / value.splice))).tree
+        )
+
+      val taskIsPrivate = isPrivateTargetOption(c)
+
+      mill.define.Cacher.impl0[Target[PathRef]](c)(
+        reify(
+          new SourceImpl(
+            wrapped.splice,
+            ctx.splice,
+            taskIsPrivate.splice
+          )
+        )
+      )
+    }
+
     def inputImpl[T: c.WeakTypeTag](c: Context)(value: c.Expr[T])(
         w: c.Expr[upickle.default.Writer[T]],
         ctx: c.Expr[mill.define.Ctx]
diff --git a/main/eval/test/src/mill/eval/JavaCompileJarTests.scala b/main/eval/test/src/mill/eval/JavaCompileJarTests.scala
index 7f3322fa1e9..6b563014aab 100644
--- a/main/eval/test/src/mill/eval/JavaCompileJarTests.scala
+++ b/main/eval/test/src/mill/eval/JavaCompileJarTests.scala
@@ -22,12 +22,11 @@ object JavaCompileJarTests extends TestSuite {
   val javacSrcPath = resourceFolder / "examples/javac"
 
   val tests = Tests {
-
     test("javac") {
       object Build extends TestBaseModule {
-        def sourceRootPath = millSourcePath / "src"
-        def readmePath = millSourcePath / "readme.md"
-        def resourceRootPath = millSourcePath / "resources"
+        def sourceRootPath: os.SubPath = "src"
+        def readmePath: os.SubPath = "readme.md"
+        def resourceRootPath: os.SubPath = "resources"
 
         // sourceRoot -> allSources -> classFiles
         //                                |
@@ -68,7 +67,7 @@ object JavaCompileJarTests extends TestSuite {
       def eval[T](t: Task[T]) = evaluator.apply(t)
       def check(targets: Agg[Task[_]], expected: Agg[Task[_]]) = evaluator.check(targets, expected)
 
-      def append(path: os.Path, txt: String) = os.write.append(path, txt)
+      def append(path: os.SubPath, txt: String) = os.write.append(millSourcePath / path, txt)
 
       check(
         targets = Agg(jar),
diff --git a/main/init/maven/src/mill/main/maven/Modeler.scala b/main/init/maven/src/mill/main/maven/Modeler.scala
index 7446b439f03..57c779ac5a3 100644
--- a/main/init/maven/src/mill/main/maven/Modeler.scala
+++ b/main/init/maven/src/mill/main/maven/Modeler.scala
@@ -64,7 +64,7 @@ object Modeler {
   }
 
   def defaultLocalRepository: LocalRepository =
-    new LocalRepository((os.home / ".m2" / "repository").toIO)
+    new LocalRepository((os.home / ".m2/repository").toIO)
 
   def defaultRemoteRepositories: Seq[RemoteRepository] =
     Seq(
diff --git a/pythonlib/src/mill/pythonlib/PythonModule.scala b/pythonlib/src/mill/pythonlib/PythonModule.scala
index 94182a138fe..b7a3dfe414c 100644
--- a/pythonlib/src/mill/pythonlib/PythonModule.scala
+++ b/pythonlib/src/mill/pythonlib/PythonModule.scala
@@ -43,7 +43,7 @@ trait PythonModule extends PipModule with TaskModule { outer =>
    */
   def pythonExe: T[PathRef] = Task {
     os.call((hostPythonCommand(), "-m", "venv", Task.dest / "venv"))
-    val python = Task.dest / "venv" / "bin" / "python3"
+    val python = Task.dest / "venv/bin/python3"
     os.call((python, "-m", "pip", "install", pipInstallArgs().args), stdout = os.Inherit)
     PathRef(python)
   }
@@ -53,17 +53,17 @@ trait PythonModule extends PipModule with TaskModule { outer =>
    *
    * Python modules will be defined relative to these directories.
    */
-  def sources: T[Seq[PathRef]] = Task.Sources { millSourcePath / "src" }
+  def sources: T[Seq[PathRef]] = Task.Sources { "src" }
 
   /**
    * The folders where the resource files for this module live.
    */
-  def resources: T[Seq[PathRef]] = Task.Sources { millSourcePath / "resources" }
+  def resources: T[Seq[PathRef]] = Task.Sources { "resources" }
 
   /**
    * The python script to run. This file may not exist if this module is only a library.
    */
-  def mainScript: T[PathRef] = Task.Source { millSourcePath / "src" / "main.py" }
+  def mainScript: T[PathRef] = Task.Source { "src/main.py" }
 
   override def pythonToolDeps: T[Seq[String]] = Task {
     super.pythonToolDeps() ++ Seq("mypy==1.13.0", "pex==2.24.1")
diff --git a/pythonlib/src/mill/pythonlib/RuffModule.scala b/pythonlib/src/mill/pythonlib/RuffModule.scala
index 79ea6b15cd0..bfa3d8e799d 100644
--- a/pythonlib/src/mill/pythonlib/RuffModule.scala
+++ b/pythonlib/src/mill/pythonlib/RuffModule.scala
@@ -17,7 +17,7 @@ trait RuffModule extends PythonModule {
    * Configuration file to use when running ruff. If this file does not exist,
    * ruff will use the default settings.
    */
-  def ruffConfigFile: T[PathRef] = Task.Source(millSourcePath / "ruff.toml")
+  def ruffConfigFile: T[PathRef] = Task.Source("ruff.toml")
 
   /**
    * Global command line options to pass to ruff. These are passed in before any
diff --git a/pythonlib/test/src/mill/pythonlib/HelloWorldTests.scala b/pythonlib/test/src/mill/pythonlib/HelloWorldTests.scala
index a15882bd5f3..c14d371c996 100644
--- a/pythonlib/test/src/mill/pythonlib/HelloWorldTests.scala
+++ b/pythonlib/test/src/mill/pythonlib/HelloWorldTests.scala
@@ -16,7 +16,7 @@ object HelloWorldTests extends TestSuite {
 
     object qux extends PythonModule {
       override def moduleDeps: Seq[PythonModule] = Seq(foo)
-      override def mainScript = Task.Source(millSourcePath / "src" / "qux.py")
+      override def mainScript = Task.Source("src/qux.py")
       object test extends PythonTests with TestModule.Unittest
     }
   }
diff --git a/pythonlib/test/src/mill/pythonlib/RunBackgroundTests.scala b/pythonlib/test/src/mill/pythonlib/RunBackgroundTests.scala
index cd020cfda6c..dc045339fd4 100644
--- a/pythonlib/test/src/mill/pythonlib/RunBackgroundTests.scala
+++ b/pythonlib/test/src/mill/pythonlib/RunBackgroundTests.scala
@@ -8,7 +8,7 @@ object RunBackgroundTests extends TestSuite {
 
   object HelloWorldPython extends TestBaseModule {
     object foo extends PythonModule {
-      override def mainScript = Task.Source(millSourcePath / "src" / "foo.py")
+      override def mainScript = Task.Source("src/foo.py")
     }
   }
 
@@ -32,7 +32,7 @@ object RunBackgroundTests extends TestSuite {
 
       while (lock.probe()) sleepIfTimeAvailable("File never locked by python subprocess")
 
-      os.remove.all(eval.outPath / "foo" / "runBackground.dest")
+      os.remove.all(eval.outPath / "foo/runBackground.dest")
 
       while (!lock.probe()) {
         sleepIfTimeAvailable("File never unlocked after runBackground.dest removed")
diff --git a/scalalib/src/mill/javalib/android/AndroidAppModule.scala b/scalalib/src/mill/javalib/android/AndroidAppModule.scala
index 5b853e92b5f..c77f08699ca 100644
--- a/scalalib/src/mill/javalib/android/AndroidAppModule.scala
+++ b/scalalib/src/mill/javalib/android/AndroidAppModule.scala
@@ -89,7 +89,7 @@ trait AndroidAppModule extends JavaModule {
     super.repositoriesTask() :+ AndroidSdkModule.mavenGoogle
   }
 
-  override def sources: T[Seq[PathRef]] = Task.Sources(millSourcePath / "src/main/java")
+  override def sources: T[Seq[PathRef]] = Task.Sources("src/main/java")
 
   /**
    * Provides access to the Android SDK configuration.
@@ -99,7 +99,7 @@ trait AndroidAppModule extends JavaModule {
   /**
    * Provides os.Path to an XML file containing configuration and metadata about your android application.
    */
-  def androidManifest: Task[PathRef] = Task.Source(millSourcePath / "src/main/AndroidManifest.xml")
+  def androidManifest: Task[PathRef] = Task.Source("src/main/AndroidManifest.xml")
 
   /**
    * Name of the release keystore file. Default is not set.
diff --git a/scalalib/src/mill/javalib/android/AndroidSdkModule.scala b/scalalib/src/mill/javalib/android/AndroidSdkModule.scala
index 9f082cddd47..4882c331663 100644
--- a/scalalib/src/mill/javalib/android/AndroidSdkModule.scala
+++ b/scalalib/src/mill/javalib/android/AndroidSdkModule.scala
@@ -86,7 +86,7 @@ trait AndroidSdkModule extends Module {
    */
   def lintToolPath: T[PathRef] = Task {
     installAndroidSdkComponents()
-    PathRef(sdkPath().path / "cmdline-tools" / "latest" / "bin" / "lint")
+    PathRef(sdkPath().path / "cmdline-tools/latest/bin/lint")
   }
 
   /**
@@ -290,7 +290,7 @@ trait AndroidSdkModule extends Module {
             case _ => false
           })
           .maxBy(_._2.head.toInt)._1
-        sdkManagerPath = latestCmdlineToolsPath / "bin" / "sdkmanager"
+        sdkManagerPath = latestCmdlineToolsPath / "bin/sdkmanager"
       }
     }
     Some(sdkManagerPath).filter(os.exists)
diff --git a/scalalib/src/mill/scalalib/JavaModule.scala b/scalalib/src/mill/scalalib/JavaModule.scala
index 8a166bef3e4..39f70348241 100644
--- a/scalalib/src/mill/scalalib/JavaModule.scala
+++ b/scalalib/src/mill/scalalib/JavaModule.scala
@@ -825,20 +825,20 @@ trait JavaModule
   /**
    * The folders where the source files for this module live
    */
-  def sources: T[Seq[PathRef]] = Task.Sources { millSourcePath / "src" }
+  def sources: T[Seq[PathRef]] = Task.Sources { "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: T[Seq[PathRef]] = Task.Sources { millSourcePath / "resources" }
+  def resources: T[Seq[PathRef]] = Task.Sources { "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: T[Seq[PathRef]] = Task.Sources { millSourcePath / "compile-resources" }
+  def compileResources: T[Seq[PathRef]] = Task.Sources { "compile-resources" }
 
   /**
    * Folders containing source files that are generated rather than
@@ -1106,7 +1106,7 @@ trait JavaModule
    * on the doc tool that is actually used.
    * @see [[docSources]]
    */
-  def docResources: T[Seq[PathRef]] = Task.Sources(millSourcePath / "docs")
+  def docResources: T[Seq[PathRef]] = Task.Sources("docs")
 
   /**
    * Control whether `docJar`-target should use a file to pass command line arguments to the javadoc tool.
diff --git a/scalalib/test/src/mill/javalib/palantirformat/PalantirFormatModuleTest.scala b/scalalib/test/src/mill/javalib/palantirformat/PalantirFormatModuleTest.scala
index 9068459c23e..9be06859e48 100644
--- a/scalalib/test/src/mill/javalib/palantirformat/PalantirFormatModuleTest.scala
+++ b/scalalib/test/src/mill/javalib/palantirformat/PalantirFormatModuleTest.scala
@@ -11,7 +11,7 @@ object PalantirFormatModuleTest extends TestSuite {
   def tests: Tests = Tests {
 
     val (before, after) = {
-      val root = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "javalib" / "palantirformat"
+      val root = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "javalib/palantirformat"
       (root / "before", root / "after")
     }
 
diff --git a/scalalib/test/src/mill/javalib/revapi/RevapiModuleTests.scala b/scalalib/test/src/mill/javalib/revapi/RevapiModuleTests.scala
index f59127b8cdc..ec5332791a5 100644
--- a/scalalib/test/src/mill/javalib/revapi/RevapiModuleTests.scala
+++ b/scalalib/test/src/mill/javalib/revapi/RevapiModuleTests.scala
@@ -11,7 +11,7 @@ object RevapiModuleTests extends TestSuite {
 
   def tests: Tests = Tests {
 
-    val root = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "javalib" / "revapi"
+    val root = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "javalib/revapi"
     val conf = root / "conf"
     val textReport = "report.txt"
 
diff --git a/scalalib/test/src/mill/scalalib/TestRunnerTestUtils.scala b/scalalib/test/src/mill/scalalib/TestRunnerTestUtils.scala
index 06a6eca9f19..d36037751eb 100644
--- a/scalalib/test/src/mill/scalalib/TestRunnerTestUtils.scala
+++ b/scalalib/test/src/mill/scalalib/TestRunnerTestUtils.scala
@@ -107,7 +107,7 @@ object TestRunnerTestUtils {
       moduleName: String,
       action: String = "test"
   ): JUnitReportMatch = {
-    val reportPath: Path = outPath / moduleName / s"$action.dest" / "test-report.xml"
+    val reportPath: Path = outPath / moduleName / s"$action.dest/test-report.xml"
     val reportXML = XML.loadFile(reportPath.toIO)
     new JUnitReportMatch {
       override def shouldHave(statuses: (Int, Status)*): Unit = {
diff --git a/testkit/package.mill b/testkit/package.mill
index e25bd3311dc..c1e4fda9711 100644
--- a/testkit/package.mill
+++ b/testkit/package.mill
@@ -8,7 +8,7 @@ object `package` extends RootModule with build.MillPublishScalaModule {
 
   def sources =
     super.sources() ++
-      Seq(PathRef(build.millSourcePath / "mill-build" / "src"))
+      Seq(PathRef(build.millSourcePath / "mill-build/src"))
 
   def forkEnv =
     super.forkEnv() ++ Map("MILL_EXECUTABLE_PATH" -> build.dist.launcher().path.toString())
diff --git a/testkit/test/resources/example-test-example-project/build.mill b/testkit/test/resources/example-test-example-project/build.mill
index 4a30be3ff78..e75ff8a6d11 100644
--- a/testkit/test/resources/example-test-example-project/build.mill
+++ b/testkit/test/resources/example-test-example-project/build.mill
@@ -1,7 +1,7 @@
 package build
 import mill._
 
-def testSource = Task.Source(millSourcePath / "source-file.txt")
+def testSource = Task.Source("source-file.txt")
 def testTask = Task { os.read(testSource().path).toUpperCase() }
 
 /** Usage
diff --git a/testkit/test/resources/integration-test-example-project/build.mill b/testkit/test/resources/integration-test-example-project/build.mill
index 896b7ac6fe7..fa1e358efc0 100644
--- a/testkit/test/resources/integration-test-example-project/build.mill
+++ b/testkit/test/resources/integration-test-example-project/build.mill
@@ -1,5 +1,5 @@
 package build
 import mill._
 
-def testSource = Task.Source(millSourcePath / "source-file.txt")
+def testSource = Task.Source("source-file.txt")
 def testTask = Task { os.read(testSource().path).toUpperCase() }
diff --git a/testkit/test/src/mill/testkit/UnitTesterTests.scala b/testkit/test/src/mill/testkit/UnitTesterTests.scala
index 96aeb9c66c5..975dc3e2a86 100644
--- a/testkit/test/src/mill/testkit/UnitTesterTests.scala
+++ b/testkit/test/src/mill/testkit/UnitTesterTests.scala
@@ -20,7 +20,7 @@ object UnitTesterTests extends TestSuite {
 
     test("sources") {
       object build extends TestBaseModule {
-        def testSource = Task.Source(millSourcePath / "source-file.txt")
+        def testSource = Task.Source("source-file.txt")
         def testTask = Task { os.read(testSource().path).toUpperCase() }
       }
 

From f15d3ab0ca0043dfd0d88191b5bc6c57dccc31db Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Thu, 6 Feb 2025 10:50:44 +0800
Subject: [PATCH 2/4] .

---
 example/pythonlib/testing/2-test-deps/build.mill          | 6 ++++--
 example/thirdparty/arrow/build.mill                       | 4 ++--
 scalalib/test/src/mill/scalalib/TestRunnerTestUtils.scala | 2 +-
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/example/pythonlib/testing/2-test-deps/build.mill b/example/pythonlib/testing/2-test-deps/build.mill
index 561de57a3e3..1d5123f4854 100644
--- a/example/pythonlib/testing/2-test-deps/build.mill
+++ b/example/pythonlib/testing/2-test-deps/build.mill
@@ -49,13 +49,15 @@ object bar extends PythonModule {
 
 > ./mill foo.test
 ...Using BarTestUtils.bar_assert_equals...
-...test_equal_string (test.TestScript...)...ok...
+...test_equal_string (test.TestScript...)...
+ ...ok...
 ...Ran 1 test...
 ...OK...
 
 > ./mill bar.test
 ...Using BarTestUtils.bar_assert_equals...
-...test_mean (test.TestScript...)...ok...
+...test_mean (test.TestScript...)...
+ ...ok...
 ...Ran 1 test...
 ...OK...
 
diff --git a/example/thirdparty/arrow/build.mill b/example/thirdparty/arrow/build.mill
index cc9475a71e2..4da424f68a1 100644
--- a/example/thirdparty/arrow/build.mill
+++ b/example/thirdparty/arrow/build.mill
@@ -135,7 +135,7 @@ object `package` extends RootModule {
       override def sources: T[Seq[PathRef]] = Task.Sources {
         val sourcesRootPath = millSourcePath / "src"
         var sources = Seq("common", platformCrossSuffix)
-          .map(platform => PathRef(sourcesRootPath / s"${platform}Main/kotlin"))
+          .map(platform => PathRef(sourcesRootPath / s"${platform}Main" / "kotlin"))
           .filter(p => os.exists(p.path))
         if (platformCrossSuffix != "jvm") {
           val nonJvmSourcesPath = sourcesRootPath / "nonJvmMain/kotlin"
@@ -163,7 +163,7 @@ object `package` extends RootModule {
         override def sources: T[Seq[PathRef]] = Task.Sources {
           val sourcesRootPath = outer.millSourcePath / "src"
           Seq("common", outer.platformCrossSuffix)
-            .map(platform => PathRef(sourcesRootPath / s"${platform}Test/kotlin"))
+            .map(platform => PathRef(sourcesRootPath / s"${platform}Test" / "kotlin"))
             .filter(p => os.exists(p.path))
         }
       }
diff --git a/scalalib/test/src/mill/scalalib/TestRunnerTestUtils.scala b/scalalib/test/src/mill/scalalib/TestRunnerTestUtils.scala
index d36037751eb..06a6eca9f19 100644
--- a/scalalib/test/src/mill/scalalib/TestRunnerTestUtils.scala
+++ b/scalalib/test/src/mill/scalalib/TestRunnerTestUtils.scala
@@ -107,7 +107,7 @@ object TestRunnerTestUtils {
       moduleName: String,
       action: String = "test"
   ): JUnitReportMatch = {
-    val reportPath: Path = outPath / moduleName / s"$action.dest/test-report.xml"
+    val reportPath: Path = outPath / moduleName / s"$action.dest" / "test-report.xml"
     val reportXML = XML.loadFile(reportPath.toIO)
     new JUnitReportMatch {
       override def shouldHave(statuses: (Int, Status)*): Unit = {

From 846521a334f701192cb203785277eb592cd2b6f7 Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Thu, 6 Feb 2025 10:57:38 +0800
Subject: [PATCH 3/4] .

---
 main/define/src/mill/define/Task.scala | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/main/define/src/mill/define/Task.scala b/main/define/src/mill/define/Task.scala
index ab0a4e7b250..10f0ef6ad77 100644
--- a/main/define/src/mill/define/Task.scala
+++ b/main/define/src/mill/define/Task.scala
@@ -78,7 +78,6 @@ object Task extends TaskBase {
   def Source(value: Result[PathRef])(implicit ctx: mill.define.Ctx): Target[PathRef] =
     macro Target.Internal.sourceImpl2
 
-
   def Source(value: os.SubPath)(implicit ctx: mill.define.Ctx): Target[PathRef] =
     macro Target.Internal.sourceImpl3
 
@@ -484,7 +483,7 @@ object Target extends TaskBase {
     }
 
     def sourcesImpl3(c: Context)(values: c.Expr[os.SubPath]*)(ctx: c.Expr[mill.define.Ctx])
-    : c.Expr[Target[Seq[PathRef]]] = {
+        : c.Expr[Target[Seq[PathRef]]] = {
       import c.universe._
       val wrapped =
         for (value <- values.toList)
@@ -505,7 +504,6 @@ object Target extends TaskBase {
       )
     }
 
-
     def sourceImpl1(c: Context)(value: c.Expr[Result[os.Path]])(ctx: c.Expr[mill.define.Ctx])
         : c.Expr[Target[PathRef]] = {
       import c.universe._
@@ -546,7 +544,7 @@ object Target extends TaskBase {
     }
 
     def sourceImpl3(c: Context)(value: c.Expr[os.SubPath])(ctx: c.Expr[mill.define.Ctx])
-    : c.Expr[Target[PathRef]] = {
+        : c.Expr[Target[PathRef]] = {
       import c.universe._
 
       val wrapped =

From ea93872e8793967e50d03cdf8c90cf960cb1a1ce Mon Sep 17 00:00:00 2001
From: Li Haoyi <haoyi.sg@gmail.com>
Date: Thu, 6 Feb 2025 14:26:07 +0800
Subject: [PATCH 4/4] Update build.mill

---
 example/pythonlib/testing/2-test-deps/build.mill | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/example/pythonlib/testing/2-test-deps/build.mill b/example/pythonlib/testing/2-test-deps/build.mill
index 1d5123f4854..4e0b46bbccf 100644
--- a/example/pythonlib/testing/2-test-deps/build.mill
+++ b/example/pythonlib/testing/2-test-deps/build.mill
@@ -50,14 +50,14 @@ object bar extends PythonModule {
 > ./mill foo.test
 ...Using BarTestUtils.bar_assert_equals...
 ...test_equal_string (test.TestScript...)...
- ...ok...
+...ok...
 ...Ran 1 test...
 ...OK...
 
 > ./mill bar.test
 ...Using BarTestUtils.bar_assert_equals...
 ...test_mean (test.TestScript...)...
- ...ok...
+...ok...
 ...Ran 1 test...
 ...OK...