diff --git a/build.sbt b/build.sbt
index 3e7aa0ad3..542ad398c 100644
--- a/build.sbt
+++ b/build.sbt
@@ -620,6 +620,7 @@ lazy val actionsProj = (project in file("main-actions"))
       // an internal (sbt.internal) type not meant for external consumption.
       exclude[DirectMissingMethodProblem]("sbt.internal.WorkerConnection.valueOf"),
       exclude[DirectMissingMethodProblem]("sbt.internal.WorkerConnection.values"),
+      exclude[DirectMissingMethodProblem]("sbt.internal.*"),
     ),
   )
   .dependsOn(lmCore)
diff --git a/internal/util-core/src/main/scala/sbt/internal/util/Util.scala b/internal/util-core/src/main/scala/sbt/internal/util/Util.scala
index 12a897222..602af1ad7 100644
--- a/internal/util-core/src/main/scala/sbt/internal/util/Util.scala
+++ b/internal/util-core/src/main/scala/sbt/internal/util/Util.scala
@@ -13,7 +13,7 @@ import java.util.Locale
 
 import scala.collection.concurrent.TrieMap
 import scala.reflect.Selectable.reflectiveSelectable
-import scala.util.Properties
+import scala.util.{ Properties, Try }
 
 object Util:
   def makeList[T](size: Int, value: T): List[T] = List.fill(size)(value)
@@ -50,6 +50,8 @@ object Util:
     ()
   }
 
+  def ignoreTry[A](f: => A): Unit = ignoreResult(Try(f))
+
   lazy val isMac: Boolean =
     System.getProperty("os.name").toLowerCase(Locale.ENGLISH).contains("mac")
 
diff --git a/lm-core/src/main/scala/sbt/internal/librarymanagement/LMSysProp.scala b/lm-core/src/main/scala/sbt/internal/librarymanagement/LMSysProp.scala
index 209e0cd11..6eb5e4b96 100644
--- a/lm-core/src/main/scala/sbt/internal/librarymanagement/LMSysProp.scala
+++ b/lm-core/src/main/scala/sbt/internal/librarymanagement/LMSysProp.scala
@@ -9,10 +9,11 @@ package sbt
 package internal
 package librarymanagement
 
+import java.io.File
 import java.util.Locale
 import scala.util.control.NonFatal
 
-object LMSysProp {
+object LMSysProp:
   def booleanOpt(name: String): Option[Boolean] =
     sys.props.get(name).flatMap { x =>
       x.toLowerCase(Locale.ENGLISH) match {
@@ -63,4 +64,12 @@ object LMSysProp {
   lazy val maxPublishAttempts: Int =
     java.lang.Integer.getInteger("sbt.repository.publish.attempts", 3)
 
-}
+  /**
+   * Ivy home directory: `sbt.ivy.home`, then `ivy.home`, else `user.home/.ivy2`.
+   */
+  lazy val defaultIvyHome: File =
+    def prop(name: String): Option[String] = sys.props.get(name).map(_.trim).filter(_.nonEmpty)
+    prop("sbt.ivy.home").orElse(prop("ivy.home")) match
+      case Some(home) => File(home)
+      case None       => File(sbt.io.Path.userHome, ".ivy2")
+end LMSysProp
diff --git a/lm-coursier/src/main/scala/lmcoursier/internal/ResolutionParams.scala b/lm-coursier/src/main/scala/lmcoursier/internal/ResolutionParams.scala
index 1c91acdd4..2ee909b0f 100644
--- a/lm-coursier/src/main/scala/lmcoursier/internal/ResolutionParams.scala
+++ b/lm-coursier/src/main/scala/lmcoursier/internal/ResolutionParams.scala
@@ -8,6 +8,7 @@ import coursier.core.*
 import coursier.params.rule.Strict
 import lmcoursier.FallbackDependency
 import lmcoursier.definitions.ToCoursier
+import sbt.internal.librarymanagement.LMSysProp
 import coursier.util.Task
 
 import scala.collection.mutable
@@ -114,7 +115,7 @@ object ResolutionParams {
     val ivyHome = sys.props
       .get("ivy.home")
       .orElse(ivyHomeOpt.map(_.getAbsoluteFile.toURI.getPath))
-      .getOrElse(new File(sys.props("user.home")).toURI.getPath + ".ivy2")
+      .getOrElse(LMSysProp.defaultIvyHome.getAbsoluteFile.toURI.getPath)
 
     val sbtIvyHome = sys.props.getOrElse(
       "sbt.ivy.home",
diff --git a/lm-coursier/src/main/scala/lmcoursier/internal/ResolutionRun.scala b/lm-coursier/src/main/scala/lmcoursier/internal/ResolutionRun.scala
index 04859ed5f..f6ed25f13 100644
--- a/lm-coursier/src/main/scala/lmcoursier/internal/ResolutionRun.scala
+++ b/lm-coursier/src/main/scala/lmcoursier/internal/ResolutionRun.scala
@@ -1,6 +1,7 @@
 package lmcoursier.internal
 
-import coursier.{ Resolution, Resolve }
+import coursier.{ CoursierEnv, Resolution, Resolve }
+import coursier.cache.CacheEnv
 import coursier.cache.internal.ThreadUtil
 import coursier.cache.loggers.{ FallbackRefreshDisplay, ProgressBarRefreshDisplay, RefreshLogger }
 import coursier.core.*
@@ -8,8 +9,9 @@ import coursier.error.ResolutionError
 import coursier.error.ResolutionError.CantDownloadModule
 import coursier.ivy.IvyRepository
 import coursier.maven.MavenRepositoryLike
+import coursier.params.Mirror
 import coursier.params.rule.RuleResolution
-import coursier.util.Task
+import coursier.util.{ EnvValues, Task }
 import sbt.util.Logger
 
 import scala.annotation.nowarn
@@ -19,6 +21,35 @@ import scala.collection.mutable
 // private[coursier]
 object ResolutionRun {
 
+  /**
+   * Mirrors from the coursier configuration, plus the ones of Maven's settings.xml
+   * only when COURSIER_MAVEN_SETTINGS (or coursier.maven-settings) is set explicitly,
+   * since a settings.xml mirror of `*` would otherwise shadow the resolvers of the build.
+   * See https://github.com/sbt/sbt/issues/9821
+   */
+  lazy val defaultMirrors: Seq[Mirror] =
+    CoursierEnv.defaultMirrors(
+      CoursierEnv.mirrors.read(),
+      CoursierEnv.mirrorsExtra.read(),
+      CoursierEnv.scalaCliConfig.read(),
+      CacheEnv.configDir.read()
+    ) ++
+      mavenSettingsMirrors(
+        CoursierEnv.mavenSettings.read(),
+        CoursierEnv.mavenHome.read(),
+        CoursierEnv.mavenHomeFallback.read()
+      )
+
+  private[lmcoursier] def mavenSettingsMirrors(
+      mavenSettings: EnvValues,
+      mavenHome: EnvValues,
+      mavenHomeFallback: EnvValues
+  ): Seq[Mirror] =
+    val explicit = mavenSettings.env.orElse(mavenSettings.prop).exists(_.trim.nonEmpty)
+    if explicit then
+      CoursierEnv.defaultMavenSettingsMirrors(mavenSettings, mavenHome, mavenHomeFallback)
+    else Nil
+
   private def resolution(
       params: ResolutionParams,
       verbosityLevel: Int,
@@ -103,6 +134,7 @@ object ResolutionRun {
           },
           boms = params.boms,
           repositories = repositories,
+          mirrors = defaultMirrors,
           resolutionParams = params.params
             .addForceVersion(
               (if (isSandboxConfig) Nil
diff --git a/lm-coursier/src/test/scala/lmcoursier/internal/ResolutionRunSpec.scala b/lm-coursier/src/test/scala/lmcoursier/internal/ResolutionRunSpec.scala
index a3ad3f4e0..64d4b9f03 100644
--- a/lm-coursier/src/test/scala/lmcoursier/internal/ResolutionRunSpec.scala
+++ b/lm-coursier/src/test/scala/lmcoursier/internal/ResolutionRunSpec.scala
@@ -1,11 +1,16 @@
 package lmcoursier.internal
 
+import coursier.CoursierEnv
 import coursier.core.{ Module, ModuleName, Organization, Resolution }
 import coursier.error.ResolutionError.CantDownloadModule
+import coursier.util.EnvValues
 import coursier.version.VersionConstraint
+import sbt.io.IO
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
+import java.io.File
+
 class ResolutionRunSpec extends AnyFunSuite with Matchers:
 
   private def cantDownload(errors: String*): CantDownloadModule =
@@ -37,3 +42,48 @@ class ResolutionRunSpec extends AnyFunSuite with Matchers:
       "Server returned HTTP response code: 404 for URL: https://repo.example.com/org/mod/1.0/mod-1.0.pom"
     )
     ResolutionRun.isTransientResolutionError(err) shouldBe false
+
+  private val unset = EnvValues(None, None)
+
+  private def withMirrorOfAll(f: File => Unit): Unit =
+    IO.withTemporaryDirectory: dir =>
+      IO.write(
+        new File(dir, "settings.xml"),
+        """<settings>
+          |  <mirrors>
+          |    <mirror>
+          |      <id>internal</id>
+          |      <url>https://nexus.example.com/repository/maven-public</url>
+          |      <mirrorOf>*</mirrorOf>
+          |    </mirror>
+          |  </mirrors>
+          |</settings>
+          |""".stripMargin
+      )
+      f(dir)
+
+  test("settings.xml mirrors are ignored unless the Maven settings are set explicitly"):
+    withMirrorOfAll: dir =>
+      val mavenHome = EnvValues(Some(dir.getAbsolutePath), None)
+      assert(CoursierEnv.defaultMavenSettingsMirrors(unset, mavenHome, unset).nonEmpty)
+      assert(ResolutionRun.mavenSettingsMirrors(unset, mavenHome, unset).isEmpty)
+
+  test("settings.xml mirrors are read when the Maven settings are set explicitly"):
+    withMirrorOfAll: dir =>
+      val settings = new File(dir, "settings.xml").getAbsolutePath
+      assert(
+        ResolutionRun.mavenSettingsMirrors(EnvValues(Some(settings), None), unset, unset).size == 1
+      )
+      assert(
+        ResolutionRun.mavenSettingsMirrors(EnvValues(None, Some(settings)), unset, unset).size == 1
+      )
+      val mavenHome = EnvValues(Some(dir.getAbsolutePath), None)
+      assert(
+        ResolutionRun
+          .mavenSettingsMirrors(EnvValues(Some("true"), None), mavenHome, unset)
+          .size == 1
+      )
+      assert(
+        ResolutionRun.mavenSettingsMirrors(EnvValues(Some("false"), None), mavenHome, unset).isEmpty
+      )
+end ResolutionRunSpec
diff --git a/main-actions/src/main/scala/sbt/internal/WorkerExchange.scala b/main-actions/src/main/scala/sbt/internal/WorkerExchange.scala
index fe22ca67c..eae02d416 100644
--- a/main-actions/src/main/scala/sbt/internal/WorkerExchange.scala
+++ b/main-actions/src/main/scala/sbt/internal/WorkerExchange.scala
@@ -24,8 +24,9 @@ import scala.sys.process.{ BasicIO, Process, ProcessIO }
 import scala.collection.mutable
 import scala.collection.concurrent.TrieMap
 import scala.collection.mutable.ListBuffer
-import scala.concurrent.{ Await, Promise }
+import scala.concurrent.{ Await, Future, Promise }
 import scala.concurrent.duration.*
+import scala.util.Try
 import scala.util.control.NonFatal
 
 object WorkerExchange:
@@ -83,11 +84,13 @@ object WorkerExchange:
       IO.classLocationPath(classOf[Gson]).toFile,
     )
     val inputRef = Promise[OutputStream]()
+    val responsesRead = Promise[Unit]()
     def runAccepter(out: OutputStream, in: InputStream): Unit =
       inputRef.success(out)
       val scanner = Scanner(in, "UTF-8")
       while scanner.hasNextLine() do notifyListeners(scanner.nextLine())
-    val (connArgs, closer): (Seq[String], Option[AutoCloseable]) = connectionType match
+      responsesRead.trySuccess(())
+    val (connArgs, closer) = connectionType match
       case WorkerConnection.Tcp =>
         val serverSocket = Retry(ServerSocket(0, 1, loopback))
         val accepter = Thread(() => {
@@ -130,20 +133,24 @@ object WorkerExchange:
     val onStdoutLine: String => Unit = connectionType match
       case WorkerConnection.Stdio => notifyListeners
       case _                      => (line) => scala.Console.out.println(line)
+    def readStdout(stdout: InputStream): Unit =
+      BasicIO.processFully(onStdoutLine)(stdout)
+      if connectionType == WorkerConnection.Stdio then responsesRead.trySuccess(())
     val processIo = ProcessIO(
       in = (input) =>
         (connectionType match
           case WorkerConnection.Stdio => inputRef.success(input)
           case _                      => ()
         ),
-      out = BasicIO.processFully(onStdoutLine),
+      out = readStdout,
       err = BasicIO.processFully((line) => scala.Console.err.println(line)),
     )
     val forkWithIo = fo.withOutputStrategy(OutputStrategy.CustomInputOutput(processIo))
     val p = Fork.java.fork(forkWithIo, options)
     val forkTimeout = fo.connectionTimeout.getOrElse(30.seconds)
     val input = Await.result(inputRef.future, forkTimeout)
-    WorkerProxy(input, p, options, closer)
+    WorkerProxy(input, p, options, closer, responsesRead.future)
+  end startWorker
 
   /** Generates a fresh path suitable for binding a `WorkerConnection.Ipc` socket. */
   def newIpcSocketPath(): NioPath =
@@ -178,6 +185,7 @@ class WorkerProxy(
     val process: Process,
     val options: Seq[String],
     closer: Option[AutoCloseable],
+    responsesRead: Future[Unit],
 ) extends AutoCloseable:
   lazy val inputStream = PrintStream(input)
   def close(): Unit =
@@ -194,11 +202,21 @@ class WorkerProxy(
 
   val watch = Thread(() => {
     while process.isAlive() do Thread.sleep(100)
+    Try(Await.ready(responsesRead, WorkerProxy.responseDrainTimeout))
     WorkerExchange.listeners.foreach(_.notifyExit(process))
   })
   watch.start()
 end WorkerProxy
 
+object WorkerProxy:
+  /**
+   * How long to keep reading a worker's responses after it exits, before reporting the exit.
+   * The reader reaches end of stream as soon as it has consumed everything the worker wrote;
+   * the bound only matters for a worker that died before connecting.
+   */
+  private val responseDrainTimeout = 10.seconds
+end WorkerProxy
+
 abstract class WorkerResponseListener extends Function1[String, Unit]:
   def notifyExit(p: Process): Unit
 
diff --git a/main-command/src/main/scala/sbt/internal/AtomicCloseable.scala b/main-command/src/main/scala/sbt/internal/AtomicCloseable.scala
new file mode 100644
index 000000000..f4dc92fa3
--- /dev/null
+++ b/main-command/src/main/scala/sbt/internal/AtomicCloseable.scala
@@ -0,0 +1,47 @@
+/*
+ * sbt
+ * Copyright 2023, Scala center
+ * Copyright 2011 - 2022, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt
+package internal
+
+import java.util.concurrent.atomic.AtomicReference
+
+import sbt.internal.util.Util
+
+/** Holds a closeable that a caller replaces, and closes the one it replaces. */
+private[sbt] class AtomicCloseable[A >: Null <: AutoCloseable](val ref: AtomicReference[A])
+    extends AnyVal:
+  def get: A = ref.get
+  def set(c: A): Unit = AtomicCloseable.close(ref.getAndSet(c))
+  def close(): Unit = AtomicCloseable.close(AtomicCloseable.release(ref))
+
+  /** Keeps the value another caller put here, and closes the one this caller built. */
+  def setIfEmpty(ctor: => A): A =
+    var obj = ref.get
+    if obj eq null then
+      val value = ctor
+      require(value ne null, "AtomicCloseable.setIfEmpty: `ctor` must not return null")
+      while obj eq null do obj = if ref.compareAndSet(null, value) then value else ref.get
+      if obj ne value then AtomicCloseable.close(value)
+    obj
+end AtomicCloseable
+
+private[sbt] object AtomicCloseable:
+  def apply[A >: Null <: AutoCloseable](): AtomicCloseable[A] =
+    new AtomicCloseable(new AtomicReference[A])
+
+  def apply[A >: Null <: AutoCloseable](c: A): AtomicCloseable[A] =
+    new AtomicCloseable(new AtomicReference[A](c))
+
+  def close(obj: AutoCloseable): Unit =
+    if obj ne null then Util.ignoreTry(obj.close())
+
+  def release[A >: Null <: AutoCloseable](ref: AtomicReference[A]): A =
+    ref.getAndSet(null)
+
+end AtomicCloseable
diff --git a/main-command/src/main/scala/sbt/internal/server/Server.scala b/main-command/src/main/scala/sbt/internal/server/Server.scala
index e71d6e643..692399aa8 100644
--- a/main-command/src/main/scala/sbt/internal/server/Server.scala
+++ b/main-command/src/main/scala/sbt/internal/server/Server.scala
@@ -46,7 +46,7 @@ private[sbt] object Server {
 
   def start(
       connection: ServerConnection,
-      onIncomingSocket: (Socket, ServerInstance) => Unit,
+      onIncomingSocket: (AtomicReference[Socket], ServerInstance) => Unit,
       log: Logger
   ): ServerInstance =
     new ServerInstance { self =>
@@ -109,14 +109,19 @@ private[sbt] object Server {
               running.set(true)
               p.success(())
               while (running.get()) {
+                val clientSocket = AtomicCloseable[Socket]()
                 try {
-                  val socket = serverSocket.accept()
-                  onIncomingSocket(socket, self)
+                  clientSocket.set(serverSocket.accept())
+                  onIncomingSocket(clientSocket.ref, self)
                 } catch {
+                  case scala.util.control.NonFatal(e) if clientSocket.get ne null =>
+                    log.error(s"sbt server failed to serve a client: $e")
+                    log.trace(e)
                   case e: IOException if Option(e.getMessage).exists(_.contains("connect")) =>
                   case _: SocketTimeoutException          => // its ok
                   case _: SocketException if !running.get => // the server is shutting down
                 }
+                clientSocket.close()
               }
               serverSocketHolder.get match {
                 case null =>
diff --git a/main-command/src/test/scala/sbt/internal/AtomicCloseableSpec.scala b/main-command/src/test/scala/sbt/internal/AtomicCloseableSpec.scala
new file mode 100644
index 000000000..d26f1096f
--- /dev/null
+++ b/main-command/src/test/scala/sbt/internal/AtomicCloseableSpec.scala
@@ -0,0 +1,72 @@
+/*
+ * sbt
+ * Copyright 2023, Scala center
+ * Copyright 2011 - 2022, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package sbt
+package internal
+
+import verify.BasicTestSuite
+
+object AtomicCloseableSpec extends BasicTestSuite:
+  class Probe extends AutoCloseable:
+    var closed: Boolean = false
+    override def close(): Unit = closed = true
+  end Probe
+
+  test("a holder built around a value"):
+    val probe = new Probe
+    val holder = AtomicCloseable(probe)
+    assert(holder.get == probe)
+    assert(!probe.closed)
+    holder.close()
+    assert(probe.closed)
+
+  test("a value that replaces another closes it"):
+    val holder = AtomicCloseable[Probe]()
+    val first, second = new Probe
+    holder.set(first)
+    holder.set(second)
+    assert(first.closed)
+    assert(!second.closed)
+    assert(holder.get == second)
+
+  test("closing empties the holder"):
+    val holder = AtomicCloseable[Probe]()
+    val probe = new Probe
+    holder.set(probe)
+    holder.close()
+    assert(probe.closed)
+    assert(holder.get == null)
+
+  test("closing an empty holder does nothing"):
+    AtomicCloseable[Probe]().close()
+
+  test("a holder that has a value keeps it"):
+    val holder = AtomicCloseable[Probe]()
+    val first = new Probe
+    holder.set(first)
+    val second = new Probe
+    assert(holder.setIfEmpty(second) == first)
+    assert(!first.closed)
+    assert(!second.closed)
+
+  test("a holder that has no value takes the one it is given"):
+    val holder = AtomicCloseable[Probe]()
+    val probe = new Probe
+    assert(holder.setIfEmpty(probe) == probe)
+    assert(holder.get == probe)
+    assert(!probe.closed)
+
+  test("a value that loses a race is closed"):
+    val holder = AtomicCloseable[Probe]()
+    val winner, loser = new Probe
+    // the holder fills while this caller builds its own value
+    val result = holder.setIfEmpty { holder.set(winner); loser }
+    assert(result == winner)
+    assert(loser.closed)
+    assert(!winner.closed)
+end AtomicCloseableSpec
diff --git a/main/src/main/scala/sbt/coursierint/LMCoursier.scala b/main/src/main/scala/sbt/coursierint/LMCoursier.scala
index 70233ac7e..faa3c2664 100644
--- a/main/src/main/scala/sbt/coursierint/LMCoursier.scala
+++ b/main/src/main/scala/sbt/coursierint/LMCoursier.scala
@@ -61,7 +61,7 @@ object LMCoursier {
         sys.env
           .get("LOCALAPPDATA")
           .map(absoluteFile)
-          .getOrElse(absoluteFile(sys.props("user.home")) / "AppData" / "Local")
+          .getOrElse(sbt.io.Path.userHome.getAbsoluteFile / "AppData" / "Local")
       base / "Coursier" / "Cache" / "v1"
     }
     sys.props
diff --git a/main/src/main/scala/sbt/internal/CommandExchange.scala b/main/src/main/scala/sbt/internal/CommandExchange.scala
index 889c358ca..36fd5339e 100644
--- a/main/src/main/scala/sbt/internal/CommandExchange.scala
+++ b/main/src/main/scala/sbt/internal/CommandExchange.scala
@@ -205,19 +205,21 @@ private[sbt] final class CommandExchange {
     lazy val enableBsp = s.get(bspEnabled).getOrElse(true)
     lazy val portfile = s.baseDir / "project" / "target" / "active.json"
 
-    def onIncomingSocket(socket: Socket, instance: ServerInstance): Unit = {
+    def onIncomingSocket(socket: AtomicReference[Socket], instance: ServerInstance): Unit = {
       val name = newNetworkName
       Terminal.consoleLog(s"new client connected: $name")
       val channel =
         new NetworkChannel(
           name,
-          socket,
+          socket.get,
           auth,
           instance,
           handlers,
           mkAskUser(name),
         )
       subscribe(channel)
+      channel.start()
+      AtomicCloseable.release(socket) // i took over
     }
     if (server.isEmpty && firstInstance.get) {
       val h = Hash.halfHashString(IO.toURI(portfile).toString)
diff --git a/main/src/main/scala/sbt/internal/SysProp.scala b/main/src/main/scala/sbt/internal/SysProp.scala
index 41369c245..ae90de146 100644
--- a/main/src/main/scala/sbt/internal/SysProp.scala
+++ b/main/src/main/scala/sbt/internal/SysProp.scala
@@ -202,7 +202,7 @@ object SysProp:
   def secondaryIdleTimeoutSec: Long = long("sbt.server.secondaryIdleTimeout", 600L)
 
   private def file(value: String): File = new File(value)
-  private def home: File = file(sys.props("user.home"))
+  private def home: File = sbt.io.Path.userHome
 
   /**
    * Default directory for global sbt config (plugins, settings). Respects XDG Base Directory
diff --git a/main/src/main/scala/sbt/internal/server/NetworkChannel.scala b/main/src/main/scala/sbt/internal/server/NetworkChannel.scala
index 05809670b..341848eeb 100644
--- a/main/src/main/scala/sbt/internal/server/NetworkChannel.scala
+++ b/main/src/main/scala/sbt/internal/server/NetworkChannel.scala
@@ -965,8 +965,10 @@ final class NetworkChannel(
   private[sbt] def isAttached: Boolean = attached.get
   private[sbt] def isInitialized: Boolean = initialized
 
-  thread.start()
-  writeThread.start()
+  private[sbt] def start(): Unit =
+    thread.start()
+    writeThread.start()
+
 }
 
 object NetworkChannel {
diff --git a/main/src/test/scala/sbt/internal/server/NetworkChannelSpec.scala b/main/src/test/scala/sbt/internal/server/NetworkChannelSpec.scala
index 83a043243..7443d40b8 100644
--- a/main/src/test/scala/sbt/internal/server/NetworkChannelSpec.scala
+++ b/main/src/test/scala/sbt/internal/server/NetworkChannelSpec.scala
@@ -13,7 +13,10 @@ import java.net.{ InetAddress, ServerSocket, Socket }
 import sbt.{ State, StandardMain }
 import sbt.internal.util.{ AttributeMap, ConsoleOut, GlobalLogging, MainAppender, Terminal, Util }
 import sbt.internal.util.Terminal.TerminalImpl
+import sbt.internal.protocol.JsonRpcRequestMessage
 import sbt.protocol.Serialization
+import sjsonnew.support.scalajson.unsafe.Parser
+import scala.concurrent.duration.*
 import scala.jdk.CollectionConverters.*
 import scala.util.Using
 import verify.BasicTestSuite
@@ -78,6 +81,31 @@ object NetworkChannelSpec extends BasicTestSuite:
       val outcome = whileInterrupted(StandardMain.exchange.removeChannel(channel))
       assertSucceededAndStillInterrupted(outcome)
 
+  test("an attach sent before the channel is subscribed still attaches the client"):
+    withServerState:
+      withChannelThreadsJoined:
+        withLoopbackConnection: (client, connection) =>
+          client.getOutputStream.write(attachRequest)
+          client.getOutputStream.flush()
+          Using.resource(newChannel(connection, Seq(VirtualTerminal.handler))): channel =>
+            Thread.sleep(acceptThreadDelay.toMillis)
+            StandardMain.exchange.subscribe(channel)
+            channel.start()
+            assert(eventually(channel.isAttached), "the attach request was dropped")
+
+  private val acceptThreadDelay = 200.millis
+
+  private def attachRequest: Array[Byte] =
+    val params = Parser.parseUnsafe("""{"interactive": false}""")
+    Serialization.serializeRequestMessage(
+      JsonRpcRequestMessage("2.0", "attach-id", Serialization.attach, Some(params))
+    )
+
+  private def eventually(condition: => Boolean): Boolean =
+    val deadline = 5.seconds.fromNow
+    while !condition && deadline.hasTimeLeft() do Thread.sleep(10)
+    condition
+
   private type Outcome = (thrown: Option[Exception], stillInterrupted: Boolean)
 
   private given Using.Releasable[NetworkChannel] = _.shutdown(false)
@@ -104,7 +132,7 @@ object NetworkChannelSpec extends BasicTestSuite:
   private def withAttachedClient[A](test: NetworkChannel => A): A =
     withServerState:
       withChannelThreadsJoined:
-        withLoopbackConnection: connection =>
+        withLoopbackConnection: (_, connection) =>
           Using.resource(attachedChannel(connection))(test)
 
   private def withChannelThreadsJoined[A](f: => A): A =
@@ -120,26 +148,30 @@ object NetworkChannelSpec extends BasicTestSuite:
     thread.getName.startsWith("sbt-networkchannel-") ||
       thread.getName.startsWith(s"sbt-$channelName-")
 
-  private def attachedChannel(connection: Socket): NetworkChannel =
-    val channel = new NetworkChannel(
+  private def newChannel(connection: Socket, handlers: Seq[ServerHandler]): NetworkChannel =
+    new NetworkChannel(
       name = channelName,
       connection = connection,
       auth = Set.empty,
       instance = null,
-      handlers = Nil,
+      handlers = handlers,
       mkUIThreadImpl = (_, _) => null,
     )
+
+  private def attachedChannel(connection: Socket): NetworkChannel =
+    val channel = newChannel(connection, Nil)
+    channel.start()
     val attachRequestId = "attached-id"
     channel.setInteractive(attachRequestId, value = false)
     channel
 
-  private def withLoopbackConnection[A](f: Socket => A): A =
+  private def withLoopbackConnection[A](f: (Socket, Socket) => A): A =
     val loopback = InetAddress.getLoopbackAddress
     val anyFreePort = 0
     val backlog = 1
     Using.resource(new ServerSocket(anyFreePort, backlog, loopback)): server =>
-      Using.resource(new Socket(loopback, server.getLocalPort)): _ =>
-        Using.resource(server.accept())(f)
+      Using.resource(new Socket(loopback, server.getLocalPort)): client =>
+        Using.resource(server.accept())(f(client, _))
 
   private def withServerState[A](f: => A): A =
     val previous = StandardMain.exchange.withState(Option(_))
diff --git a/project/Dependencies.scala b/project/Dependencies.scala
index de79d1712..5e3108724 100644
--- a/project/Dependencies.scala
+++ b/project/Dependencies.scala
@@ -12,7 +12,7 @@ object Dependencies {
     sys.env.get("BUILD_VERSION") orElse sys.props.get("sbt.build.version")
 
   // sbt modules
-  val ioVersion = nightlyVersion.getOrElse("1.13.4")
+  val ioVersion = nightlyVersion.getOrElse("1.13.5")
   val zincVersion = nightlyVersion.getOrElse("2.0.4")
 
   private val sbtIO = "org.scala-sbt" %% "io" % ioVersion
diff --git a/sbt-app/src/sbt-test/tests/fork-slow-listener/build.sbt b/sbt-app/src/sbt-test/tests/fork-slow-listener/build.sbt
new file mode 100644
index 000000000..9f889b515
--- /dev/null
+++ b/sbt-app/src/sbt-test/tests/fork-slow-listener/build.sbt
@@ -0,0 +1,11 @@
+scalaVersion := "3.9.0"
+Test / fork := true
+libraryDependencies += "org.scalameta" %% "munit" % "1.0.4" % Test
+
+Test / testListeners += new TestsListener:
+  def doInit(): Unit = ()
+  def startGroup(name: String): Unit = ()
+  def testEvent(event: TestEvent): Unit = Thread.sleep(50)
+  def endGroup(name: String, t: Throwable): Unit = ()
+  def endGroup(name: String, result: TestResult): Unit = ()
+  def doComplete(finalResult: TestResult): Unit = ()
diff --git a/sbt-app/src/sbt-test/tests/fork-slow-listener/src/test/scala/ManyTests.scala b/sbt-app/src/sbt-test/tests/fork-slow-listener/src/test/scala/ManyTests.scala
new file mode 100644
index 000000000..9f1ae0f39
--- /dev/null
+++ b/sbt-app/src/sbt-test/tests/fork-slow-listener/src/test/scala/ManyTests.scala
@@ -0,0 +1,2 @@
+class ManyTests extends munit.FunSuite:
+  (1 to 40).foreach(i => test(s"test $i")(assert(i < 40)))
diff --git a/sbt-app/src/sbt-test/tests/fork-slow-listener/test b/sbt-app/src/sbt-test/tests/fork-slow-listener/test
new file mode 100644
index 000000000..5a9f22365
--- /dev/null
+++ b/sbt-app/src/sbt-test/tests/fork-slow-listener/test
@@ -0,0 +1 @@
+-> test
diff --git a/zinc-lm-integration/src/main/scala/sbt/internal/inc/ZincComponentCompiler.scala b/zinc-lm-integration/src/main/scala/sbt/internal/inc/ZincComponentCompiler.scala
index 9ea5d12e8..26d83f852 100644
--- a/zinc-lm-integration/src/main/scala/sbt/internal/inc/ZincComponentCompiler.scala
+++ b/zinc-lm-integration/src/main/scala/sbt/internal/inc/ZincComponentCompiler.scala
@@ -11,7 +11,7 @@ package internal
 package inc
 
 import sbt.internal.inc.classpath.ClasspathUtil
-import sbt.internal.librarymanagement.JsonUtil
+import sbt.internal.librarymanagement.{ JsonUtil, LMSysProp }
 import sbt.internal.util.{ BufferedLogger, FullLogger }
 import sbt.io.IO
 import sbt.librarymanagement.*
@@ -171,12 +171,7 @@ private[sbt] object ZincComponentCompiler {
     new ZincCompilerBridgeProvider(None, manager, dependencyResolution, scalaJarsTarget)
 
   private final val LocalIvy =
-    (sys.props.get("sbt.ivy.home") match {
-      case Some(home) =>
-        if (home.endsWith("/")) home
-        else home + "/"
-      case _ => s"$${user.home}/.ivy2/"
-    }) + "local/" + Resolver.localBasePattern
+    Resolver.resolvePattern(LMSysProp.defaultIvyHome.toString, "local/" + Resolver.localBasePattern)
 
   final val LocalResolver: Resolver = {
     val toUse = Vector(LocalIvy)