diff --git a/modules/bloop-rifle/src/main/scala/scala/build/bloop/BuildServer.scala b/modules/bloop-rifle/src/main/scala/scala/build/bloop/BuildServer.scala
index baeed691a7..ae0eb793f5 100644
--- a/modules/bloop-rifle/src/main/scala/scala/build/bloop/BuildServer.scala
+++ b/modules/bloop-rifle/src/main/scala/scala/build/bloop/BuildServer.scala
@@ -3,4 +3,3 @@ package scala.build.bloop
 import ch.epfl.scala.bsp4j
 
 trait BuildServer extends bsp4j.BuildServer with bsp4j.ScalaBuildServer with bsp4j.JavaBuildServer
-    with ScalaDebugServer
diff --git a/modules/bloop-rifle/src/main/scala/scala/build/bloop/ScalaDebugServer.scala b/modules/bloop-rifle/src/main/scala/scala/build/bloop/ScalaDebugServer.scala
deleted file mode 100644
index 8f54089aa8..0000000000
--- a/modules/bloop-rifle/src/main/scala/scala/build/bloop/ScalaDebugServer.scala
+++ /dev/null
@@ -1,11 +0,0 @@
-package scala.build.bloop;
-
-import ch.epfl.scala.bsp4j.{DebugSessionAddress, DebugSessionParams}
-import org.eclipse.lsp4j.jsonrpc.services.JsonRequest
-
-import java.util.concurrent.CompletableFuture;
-
-trait ScalaDebugServer {
-  @JsonRequest("debugSession/start")
-  def buildTargetDebugSession(params: DebugSessionParams): CompletableFuture[DebugSessionAddress]
-}
diff --git a/modules/bloop-rifle/src/main/scala/scala/build/bloop/ScalaDebugServerForwardStubs.scala b/modules/bloop-rifle/src/main/scala/scala/build/bloop/ScalaDebugServerForwardStubs.scala
deleted file mode 100644
index b964048d41..0000000000
--- a/modules/bloop-rifle/src/main/scala/scala/build/bloop/ScalaDebugServerForwardStubs.scala
+++ /dev/null
@@ -1,13 +0,0 @@
-package scala.build.bloop
-
-import ch.epfl.scala.{bsp4j => b}
-
-import java.util.concurrent.CompletableFuture
-
-trait ScalaDebugServerForwardStubs extends ScalaDebugServer {
-  protected def forwardTo: ScalaDebugServer
-  override def buildTargetDebugSession(
-    params: b.DebugSessionParams
-  ): CompletableFuture[b.DebugSessionAddress] =
-    forwardTo.buildTargetDebugSession(params)
-}
diff --git a/modules/build/src/main/scala/scala/build/bsp/BspClient.scala b/modules/build/src/main/scala/scala/build/bsp/BspClient.scala
index f5c6ed18dc..22a9ed9268 100644
--- a/modules/build/src/main/scala/scala/build/bsp/BspClient.scala
+++ b/modules/build/src/main/scala/scala/build/bsp/BspClient.scala
@@ -199,7 +199,7 @@ class BspClient(
         diag.relatedInformation.foreach { relatedInformation =>
           val location = new Location(path.toNIO.toUri.toASCIIString, range)
           val related  = new b.DiagnosticRelatedInformation(location, relatedInformation.message)
-          bDiag.setRelatedInformation(related)
+          bDiag.setRelatedInformation(List(related).asJava)
         }
         bDiag.setSeverity(diag.severity.toBsp4j)
         bDiag.setSource("scala-cli")
diff --git a/modules/build/src/main/scala/scala/build/bsp/BspImpl.scala b/modules/build/src/main/scala/scala/build/bsp/BspImpl.scala
index cc3281037f..9b2a381ef6 100644
--- a/modules/build/src/main/scala/scala/build/bsp/BspImpl.scala
+++ b/modules/build/src/main/scala/scala/build/bsp/BspImpl.scala
@@ -10,7 +10,7 @@ import java.io.{InputStream, OutputStream}
 import java.util.concurrent.{CompletableFuture, Executor}
 import scala.build.*
 import scala.build.EitherCps.{either, value}
-import scala.build.bloop.{BloopServer, ScalaDebugServer}
+import scala.build.bloop.BloopServer
 import scala.build.compiler.BloopCompiler
 import scala.build.errors.{BuildException, Diagnostic, ParsingInputsException}
 import scala.build.internal.{Constants, CustomCodeWrapper}
@@ -423,7 +423,7 @@ final class BspImpl(
     bloopSession.update(null, currentBloopSession, "BSP server already initialized")
 
     val actualLocalServer: b.BuildServer with b.ScalaBuildServer with b.JavaBuildServer
-      with ScalaDebugServer with ScalaScriptBuildServer with HasGeneratedSources =
+      with ScalaScriptBuildServer with HasGeneratedSources =
       new BuildServerProxy(
         () => bloopSession.get().bspServer,
         () => onReload()
diff --git a/modules/build/src/main/scala/scala/build/bsp/BspServer.scala b/modules/build/src/main/scala/scala/build/bsp/BspServer.scala
index 4ca0b9b662..d02aed74aa 100644
--- a/modules/build/src/main/scala/scala/build/bsp/BspServer.scala
+++ b/modules/build/src/main/scala/scala/build/bsp/BspServer.scala
@@ -9,7 +9,6 @@ import java.util.concurrent.{CompletableFuture, TimeUnit}
 import java.util as ju
 
 import scala.build.Logger
-import scala.build.bloop.{ScalaDebugServer, ScalaDebugServerForwardStubs}
 import scala.build.internal.Constants
 import scala.build.options.Scope
 import scala.concurrent.{Future, Promise}
@@ -17,13 +16,12 @@ import scala.jdk.CollectionConverters.*
 import scala.util.Random
 
 class BspServer(
-  bloopServer: b.BuildServer & b.ScalaBuildServer & b.JavaBuildServer & ScalaDebugServer,
+  bloopServer: b.BuildServer & b.ScalaBuildServer & b.JavaBuildServer,
   compile: (() => CompletableFuture[b.CompileResult]) => CompletableFuture[b.CompileResult],
   logger: Logger,
   presetIntelliJ: Boolean = false
 ) extends b.BuildServer with b.ScalaBuildServer with b.JavaBuildServer with BuildServerForwardStubs
     with ScalaScriptBuildServer
-    with ScalaDebugServerForwardStubs
     with ScalaBuildServerForwardStubs with JavaBuildServerForwardStubs
     with HasGeneratedSourcesImpl {
 
@@ -108,7 +106,12 @@ class BspServer(
       logger.debug(s"invalid target in Test request: $target")
     params
   }
-
+  private def check(params: b.DebugSessionParams): params.type = {
+    val invalidTargets = params.getTargets.asScala.filter(!validTarget(_))
+    for (target <- invalidTargets)
+      logger.debug(s"invalid target in Test request: $target")
+    params
+  }
   private def mapGeneratedSources(res: b.SourcesResult): Unit = {
     val gen = generatedSources.values.toVector
     for {
@@ -123,8 +126,7 @@ class BspServer(
     }
   }
 
-  protected def forwardTo
-    : b.BuildServer & b.ScalaBuildServer & b.JavaBuildServer & ScalaDebugServer = bloopServer
+  protected def forwardTo: b.BuildServer & b.ScalaBuildServer & b.JavaBuildServer = bloopServer
 
   private val supportedLanguages: ju.List[String] = List(
     "scala",
@@ -215,6 +217,10 @@ class BspServer(
   override def buildTargetTest(params: b.TestParams): CompletableFuture[b.TestResult] =
     super.buildTargetTest(check(params))
 
+  override def debugSessionStart(params: b.DebugSessionParams)
+    : CompletableFuture[b.DebugSessionAddress] =
+    super.debugSessionStart(check(params))
+
   override def workspaceBuildTargets(): CompletableFuture[b.WorkspaceBuildTargetsResult] =
     super.workspaceBuildTargets().thenApply { res =>
       maybeUpdateProjectTargetUri(res)
diff --git a/modules/build/src/main/scala/scala/build/bsp/BuildServerForwardStubs.scala b/modules/build/src/main/scala/scala/build/bsp/BuildServerForwardStubs.scala
index 0f0727ae12..3cab5a4ffc 100644
--- a/modules/build/src/main/scala/scala/build/bsp/BuildServerForwardStubs.scala
+++ b/modules/build/src/main/scala/scala/build/bsp/BuildServerForwardStubs.scala
@@ -70,6 +70,11 @@ trait BuildServerForwardStubs extends b.BuildServer {
     forwardTo.buildTargetTest(params)
       .handle(fatalExceptionHandler("buildTargetTest", params))
 
+  override def debugSessionStart(params: b.DebugSessionParams)
+    : CompletableFuture[b.DebugSessionAddress] =
+    forwardTo.debugSessionStart(params)
+      .handle(fatalExceptionHandler("debugSessionStart", params))
+
   override def workspaceBuildTargets(): CompletableFuture[b.WorkspaceBuildTargetsResult] =
     forwardTo.workspaceBuildTargets()
       .handle(fatalExceptionHandler("workspaceBuildTargets"))
diff --git a/modules/build/src/main/scala/scala/build/bsp/BuildServerProxy.scala b/modules/build/src/main/scala/scala/build/bsp/BuildServerProxy.scala
index 1cb0493bdb..a0e66d0e25 100644
--- a/modules/build/src/main/scala/scala/build/bsp/BuildServerProxy.scala
+++ b/modules/build/src/main/scala/scala/build/bsp/BuildServerProxy.scala
@@ -4,7 +4,6 @@ import ch.epfl.scala.{bsp4j => b}
 
 import java.util.concurrent.CompletableFuture
 
-import scala.build.bloop.ScalaDebugServer
 import scala.build.options.Scope
 import scala.build.{GeneratedSource, Inputs}
 
@@ -12,7 +11,7 @@ class BuildServerProxy(
   bspServer: () => BspServer,
   onReload: () => CompletableFuture[Object]
 ) extends b.BuildServer with b.ScalaBuildServer with b.JavaBuildServer
-    with ScalaDebugServer with ScalaScriptBuildServer with HasGeneratedSources {
+    with ScalaScriptBuildServer with HasGeneratedSources {
   override def buildInitialize(params: b.InitializeBuildParams)
     : CompletableFuture[b.InitializeBuildResult] = bspServer().buildInitialize(params)
 
@@ -67,9 +66,9 @@ class BuildServerProxy(
 
   override def buildTargetJavacOptions(params: b.JavacOptionsParams)
     : CompletableFuture[b.JavacOptionsResult] = bspServer().buildTargetJavacOptions(params)
-
-  override def buildTargetDebugSession(params: b.DebugSessionParams)
-    : CompletableFuture[b.DebugSessionAddress] = bspServer().buildTargetDebugSession(params)
+  override def debugSessionStart(params: b.DebugSessionParams)
+    : CompletableFuture[b.DebugSessionAddress] =
+    bspServer().debugSessionStart(params)
 
   override def buildTargetWrappedSources(params: WrappedSourcesParams)
     : CompletableFuture[WrappedSourcesResult] = bspServer().buildTargetWrappedSources(params)
diff --git a/modules/build/src/main/scala/scala/build/bsp/LoggingBuildServer.scala b/modules/build/src/main/scala/scala/build/bsp/LoggingBuildServer.scala
index f158d17147..f05968fc51 100644
--- a/modules/build/src/main/scala/scala/build/bsp/LoggingBuildServer.scala
+++ b/modules/build/src/main/scala/scala/build/bsp/LoggingBuildServer.scala
@@ -41,6 +41,9 @@ trait LoggingBuildServer extends b.BuildServer {
     underlying.buildTargetSources(pprint.err.log(params)).logF
   override def buildTargetTest(params: b.TestParams): CompletableFuture[b.TestResult] =
     underlying.buildTargetTest(pprint.err.log(params)).logF
+  override def debugSessionStart(params: b.DebugSessionParams)
+    : CompletableFuture[b.DebugSessionAddress] =
+    underlying.debugSessionStart(pprint.err.log(params)).logF
   override def workspaceBuildTargets(): CompletableFuture[b.WorkspaceBuildTargetsResult] =
     underlying.workspaceBuildTargets().logF
   override def workspaceReload(): CompletableFuture[Object] =
diff --git a/modules/build/src/main/scala/scala/build/bsp/package.scala b/modules/build/src/main/scala/scala/build/bsp/package.scala
index fc2ba59c46..05ccc91cee 100644
--- a/modules/build/src/main/scala/scala/build/bsp/package.scala
+++ b/modules/build/src/main/scala/scala/build/bsp/package.scala
@@ -1,10 +1,10 @@
 package scala.build
 
-import ch.epfl.scala.{bsp4j => b}
+import ch.epfl.scala.bsp4j as b
+import ch.epfl.scala.bsp4j.SourcesItem
 
 import java.util.concurrent.CompletableFuture
-
-import scala.jdk.CollectionConverters._
+import scala.jdk.CollectionConverters.*
 
 package object bsp {
 
@@ -44,7 +44,10 @@ package object bsp {
 
   implicit class SourcesResultExt(private val res: b.SourcesResult) extends AnyVal {
     def duplicate(): b.SourcesResult =
-      new b.SourcesResult(res.getItems().asScala.toList.map(_.duplicate()).asJava)
+      new b.SourcesResult(
+        res.getItems().asScala.toList
+          .map((item: SourcesItem) => item.duplicate()).asJava
+      )
   }
 
   implicit class BuildTargetCapabilitiesExt(
@@ -102,7 +105,9 @@ package object bsp {
     def duplicate(): b.Diagnostic = {
       val diag0 = new b.Diagnostic(diag.getRange.duplicate(), diag.getMessage)
       diag0.setCode(diag.getCode)
-      diag0.setRelatedInformation(Option(diag.getRelatedInformation).map(_.duplicate()).orNull)
+      diag0.setRelatedInformation(
+        Option(diag.getRelatedInformation).map(_.asScala.map(_.duplicate()).asJava).orNull
+      )
       diag0.setSeverity(diag.getSeverity)
       diag0.setSource(diag.getSource)
       diag0
diff --git a/modules/cli/src/main/scala/scala/cli/internal/CliLogger.scala b/modules/cli/src/main/scala/scala/cli/internal/CliLogger.scala
index 99f9264b5c..fb3118333c 100644
--- a/modules/cli/src/main/scala/scala/cli/internal/CliLogger.scala
+++ b/modules/cli/src/main/scala/scala/cli/internal/CliLogger.scala
@@ -15,6 +15,7 @@ import scala.build.internal.CustomProgressBarRefreshDisplay
 import scala.build.{ConsoleBloopBuildClient, Logger, Position}
 import scala.collection.mutable
 import scala.scalanative.{build => sn}
+import scala.jdk.CollectionConverters._
 
 class CliLogger(
   val verbosity: Int,
@@ -88,7 +89,7 @@ class CliLogger(
         } {
           val location = new Location(filePath.toNIO.toUri.toASCIIString, range)
           val related  = new b.DiagnosticRelatedInformation(location, info.message)
-          diag.setRelatedInformation(related)
+          diag.setRelatedInformation(List(related).asJava)
         }
 
         for (file <- f.path) {
diff --git a/modules/integration/src/test/scala/scala/cli/integration/BspTestDefinitions.scala b/modules/integration/src/test/scala/scala/cli/integration/BspTestDefinitions.scala
index 8f6e2581e5..2f6fc6daa4 100644
--- a/modules/integration/src/test/scala/scala/cli/integration/BspTestDefinitions.scala
+++ b/modules/integration/src/test/scala/scala/cli/integration/BspTestDefinitions.scala
@@ -1180,7 +1180,7 @@ abstract class BspTestDefinitions(val scalaVersionOpt: Option[String])
             strictlyCheckMessage = false
           )
 
-          val relatedInformation = updateActionableDiagnostic.getRelatedInformation()
+          val relatedInformation = updateActionableDiagnostic.getRelatedInformation().asScala.head
           expect(relatedInformation.getMessage.contains("com.lihaoyi::os-lib:"))
           expect(
             relatedInformation.getLocation().getUri() == (root / fileName).toNIO.toUri.toASCIIString
diff --git a/project/deps.sc b/project/deps.sc
index add929e85d..e138b488fb 100644
--- a/project/deps.sc
+++ b/project/deps.sc
@@ -68,7 +68,7 @@ object Deps {
   def asm      = ivy"org.ow2.asm:asm:9.3"
   // Force using of 2.13 - is there a better way?
   def bloopConfig      = ivy"io.github.alexarchambault.bleep:bloop-config_2.13:1.5.3-sc-1"
-  def bsp4j            = ivy"ch.epfl.scala:bsp4j:2.0.0"
+  def bsp4j            = ivy"ch.epfl.scala:bsp4j:2.1.0-M1"
   def caseApp          = ivy"com.github.alexarchambault:case-app_2.13:2.1.0-M15"
   def collectionCompat = ivy"org.scala-lang.modules::scala-collection-compat:2.8.1"
   // Force using of 2.13 - is there a better way?