diff --git a/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/ActorTestKit.scala b/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/ActorTestKit.scala
index f8503872a2c..6b067707564 100644
--- a/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/ActorTestKit.scala
+++ b/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/ActorTestKit.scala
@@ -44,7 +44,7 @@ object ActorTestKit {
    * using default configuration from the reference.conf resources that ship with the Akka libraries.
    * The application.conf of your project is not used in this case.
    */
-  def create(): ActorTestKit =
+  @noinline def create(): ActorTestKit =
     new ActorTestKit(scaladsl.ActorTestKit(TestKitUtils.testNameFromCallStack(classOf[ActorTestKit])))
 
   /**
@@ -83,7 +83,7 @@ object ActorTestKit {
    * When the test has completed you should terminate the `ActorSystem` and
    * the testkit with [[ActorTestKit#shutdownTestKit]].
    */
-  def create(customConfig: Config): ActorTestKit =
+  @noinline def create(customConfig: Config): ActorTestKit =
     new ActorTestKit(scaladsl.ActorTestKit(TestKitUtils.testNameFromCallStack(classOf[ActorTestKit]), customConfig))
 
   /**
diff --git a/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/TestKitJunitResource.scala b/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/TestKitJunitResource.scala
index 72f7e14d323..ad7e445b6bb 100644
--- a/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/TestKitJunitResource.scala
+++ b/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/javadsl/TestKitJunitResource.scala
@@ -66,7 +66,7 @@ final class TestKitJunitResource(_kit: ActorTestKit) extends ExternalResource {
    * using default configuration from the reference.conf resources that ship with the Akka libraries.
    * The application.conf of your project is not used in this case.
    */
-  def this() = this(ActorTestKit.create(TestKitUtils.testNameFromCallStack(classOf[TestKitJunitResource])))
+  @noinline def this() = this(ActorTestKit.create(TestKitUtils.testNameFromCallStack(classOf[TestKitJunitResource])))
 
   /**
    * Use a custom [[pekko.actor.typed.ActorSystem]] for the actor system.
@@ -76,7 +76,7 @@ final class TestKitJunitResource(_kit: ActorTestKit) extends ExternalResource {
   /**
    * Use a custom config for the actor system.
    */
-  def this(customConfig: String) =
+  @noinline def this(customConfig: String) =
     this(
       ActorTestKit.create(
         TestKitUtils.testNameFromCallStack(classOf[TestKitJunitResource]),
@@ -85,13 +85,13 @@ final class TestKitJunitResource(_kit: ActorTestKit) extends ExternalResource {
   /**
    * Use a custom config for the actor system.
    */
-  def this(customConfig: Config) =
+  @noinline def this(customConfig: Config) =
     this(ActorTestKit.create(TestKitUtils.testNameFromCallStack(classOf[TestKitJunitResource]), customConfig))
 
   /**
    * Use a custom config for the actor system, and a custom [[pekko.actor.testkit.typed.TestKitSettings]].
    */
-  def this(customConfig: Config, settings: TestKitSettings) =
+  @noinline def this(customConfig: Config, settings: TestKitSettings) =
     this(ActorTestKit.create(TestKitUtils.testNameFromCallStack(classOf[TestKitJunitResource]), customConfig, settings))
 
   @Rule
diff --git a/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/scaladsl/ActorTestKit.scala b/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/scaladsl/ActorTestKit.scala
index 540998d2a8f..ffad923a50d 100644
--- a/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/scaladsl/ActorTestKit.scala
+++ b/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/scaladsl/ActorTestKit.scala
@@ -57,7 +57,7 @@ object ActorTestKit {
    * using default configuration from the reference.conf resources that ship with the Akka libraries.
    * The application.conf of your project is not used in this case.
    */
-  def apply(): ActorTestKit = {
+  @noinline def apply(): ActorTestKit = {
     val system = ActorSystem(
       ActorTestKitGuardian.testKitGuardian,
       TestKitUtils.testNameFromCallStack(classOf[ActorTestKit]),
@@ -111,7 +111,7 @@ object ActorTestKit {
    * When the test has completed you should terminate the `ActorSystem` and
    * the testkit with [[ActorTestKit#shutdownTestKit]].
    */
-  def apply(customConfig: Config): ActorTestKit = {
+  @noinline def apply(customConfig: Config): ActorTestKit = {
     val system = ActorSystem(
       ActorTestKitGuardian.testKitGuardian,
       TestKitUtils.testNameFromCallStack(classOf[ActorTestKit]),
diff --git a/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/scaladsl/ActorTestKitBase.scala b/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/scaladsl/ActorTestKitBase.scala
index 0d480148f04..a9f6b1afe57 100644
--- a/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/scaladsl/ActorTestKitBase.scala
+++ b/actor-testkit-typed/src/main/scala/org/apache/pekko/actor/testkit/typed/scaladsl/ActorTestKitBase.scala
@@ -29,7 +29,7 @@ import pekko.actor.typed.Props
 import pekko.util.Timeout
 
 object ActorTestKitBase {
-  def testNameFromCallStack(): String = TestKitUtils.testNameFromCallStack(classOf[ActorTestKitBase])
+  @noinline def testNameFromCallStack(): String = TestKitUtils.testNameFromCallStack(classOf[ActorTestKitBase])
 }
 
 /**
diff --git a/actor/src/main/mima-filters/1.1.0.backwards.excludes/future-converters.excludes b/actor/src/main/mima-filters/1.1.0.backwards.excludes/future-converters.excludes
new file mode 100644
index 00000000000..bf0a9e2c4b9
--- /dev/null
+++ b/actor/src/main/mima-filters/1.1.0.backwards.excludes/future-converters.excludes
@@ -0,0 +1,6 @@
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.FutureConverters#CompletionStageOps.asScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.FutureConverters#CompletionStageOps.asScala")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.FutureConverters#CompletionStageOps.asScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.FutureConverters#FutureOps.asJava$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.FutureConverters#FutureOps.asJava")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.FutureConverters#FutureOps.asJava$extension")
diff --git a/actor/src/main/mima-filters/1.1.0.backwards.excludes/option-converters.excludes  b/actor/src/main/mima-filters/1.1.0.backwards.excludes/option-converters.excludes 
new file mode 100644
index 00000000000..3815de9f40a
--- /dev/null
+++ b/actor/src/main/mima-filters/1.1.0.backwards.excludes/option-converters.excludes 	
@@ -0,0 +1,30 @@
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOption.toJava$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOption.toJavaPrimitive$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOption.toJava")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOption.toJavaPrimitive")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOption.toJava$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOption.toJavaPrimitive$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptional.toJavaPrimitive$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptional.toScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptional.toScala")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptional.toJavaPrimitive")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptional.toScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptional.toJavaPrimitive$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalDouble.toJavaGeneric$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalDouble.toScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalDouble.toScala")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalDouble.toJavaGeneric")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalDouble.toScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalDouble.toJavaGeneric$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalInt.toJavaGeneric$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalInt.toScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalInt.toScala")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalInt.toJavaGeneric")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalInt.toScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalInt.toJavaGeneric$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalLong.toJavaGeneric$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalLong.toScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalLong.toScala")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalLong.toJavaGeneric")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalLong.toScala$extension")
+ProblemFilters.exclude[DirectMissingMethodProblem]("org.apache.pekko.util.OptionConverters#RichOptionalLong.toJavaGeneric$extension")
diff --git a/actor/src/main/scala-2.12/org/apache/pekko/util/ByteIterator.scala b/actor/src/main/scala-2.12/org/apache/pekko/util/ByteIterator.scala
index 150fa32af86..e172cb8298e 100644
--- a/actor/src/main/scala-2.12/org/apache/pekko/util/ByteIterator.scala
+++ b/actor/src/main/scala-2.12/org/apache/pekko/util/ByteIterator.scala
@@ -38,11 +38,11 @@ object ByteIterator {
       extends ByteIterator {
     iterator =>
 
-    @inline final def len: Int = until - from
+    final def len: Int = until - from
 
-    @inline final def hasNext: Boolean = from < until
+    final def hasNext: Boolean = from < until
 
-    @inline final def head: Byte = array(from)
+    final def head: Byte = array(from)
 
     final def next(): Byte = {
       if (!hasNext) EmptyImmutableSeq.iterator.next()
@@ -206,13 +206,13 @@ object ByteIterator {
     }
     normalize()
 
-    @inline private def current: ByteArrayIterator = iterators.head
-    @inline private def dropCurrent(): Unit = { iterators = iterators.tail }
-    @inline final def clear(): Unit = { iterators = MultiByteArrayIterator.empty.iterators }
+    private def current: ByteArrayIterator = iterators.head
+    private def dropCurrent(): Unit = { iterators = iterators.tail }
+    final def clear(): Unit = { iterators = MultiByteArrayIterator.empty.iterators }
 
-    @inline final def hasNext: Boolean = current.hasNext
+    final def hasNext: Boolean = current.hasNext
 
-    @inline final def head: Byte = current.head
+    final def head: Byte = current.head
 
     final def next(): Byte = {
       val result = current.next()
diff --git a/actor/src/main/scala-2.12/org/apache/pekko/util/ByteString.scala b/actor/src/main/scala-2.12/org/apache/pekko/util/ByteString.scala
index 14a93a99873..06f7779c941 100644
--- a/actor/src/main/scala-2.12/org/apache/pekko/util/ByteString.scala
+++ b/actor/src/main/scala-2.12/org/apache/pekko/util/ByteString.scala
@@ -1047,7 +1047,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
     this
   }
 
-  @inline protected final def fillByteBuffer(len: Int, byteOrder: ByteOrder)(fill: ByteBuffer => Unit): this.type = {
+  protected final def fillByteBuffer(len: Int, byteOrder: ByteOrder)(fill: ByteBuffer => Unit): this.type = {
     fillArray(len) {
       case (array, start) =>
         val buffer = ByteBuffer.wrap(array, start, len)
@@ -1078,7 +1078,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
     _tempCapacity = _temp.length
   }
 
-  @inline private def shouldResizeTempFor(size: Int): Boolean = _tempCapacity < size || _tempCapacity == 0
+  private def shouldResizeTempFor(size: Int): Boolean = _tempCapacity < size || _tempCapacity == 0
 
   private def ensureTempSize(size: Int): Unit = {
     if (shouldResizeTempFor(size)) {
diff --git a/actor/src/main/scala-2.13/org/apache/pekko/util/ByteIterator.scala b/actor/src/main/scala-2.13/org/apache/pekko/util/ByteIterator.scala
index 5965345199e..fccd69fa0c4 100644
--- a/actor/src/main/scala-2.13/org/apache/pekko/util/ByteIterator.scala
+++ b/actor/src/main/scala-2.13/org/apache/pekko/util/ByteIterator.scala
@@ -39,11 +39,11 @@ object ByteIterator {
       extends ByteIterator {
     iterator =>
 
-    @inline final def len: Int = until - from
+    final def len: Int = until - from
 
-    @inline final def hasNext: Boolean = from < until
+    final def hasNext: Boolean = from < until
 
-    @inline final def head: Byte = array(from)
+    final def head: Byte = array(from)
 
     final def next(): Byte = {
       if (!hasNext) EmptyImmutableSeq.iterator.next()
@@ -218,13 +218,13 @@ object ByteIterator {
     }
     normalize()
 
-    @inline private def current: ByteArrayIterator = iterators.head
-    @inline private def dropCurrent(): Unit = { iterators = iterators.tail }
-    @inline final def clear(): Unit = { iterators = MultiByteArrayIterator.empty.iterators }
+    private def current: ByteArrayIterator = iterators.head
+    private def dropCurrent(): Unit = { iterators = iterators.tail }
+    final def clear(): Unit = { iterators = MultiByteArrayIterator.empty.iterators }
 
-    @inline final def hasNext: Boolean = current.hasNext
+    final def hasNext: Boolean = current.hasNext
 
-    @inline final def head: Byte = current.head
+    final def head: Byte = current.head
 
     final def next(): Byte = {
       val result = current.next()
diff --git a/actor/src/main/scala-2.13/org/apache/pekko/util/ByteString.scala b/actor/src/main/scala-2.13/org/apache/pekko/util/ByteString.scala
index 41696881436..a03fac661af 100644
--- a/actor/src/main/scala-2.13/org/apache/pekko/util/ByteString.scala
+++ b/actor/src/main/scala-2.13/org/apache/pekko/util/ByteString.scala
@@ -1097,7 +1097,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
     this
   }
 
-  @inline protected final def fillByteBuffer(len: Int, byteOrder: ByteOrder)(fill: ByteBuffer => Unit): this.type = {
+  protected final def fillByteBuffer(len: Int, byteOrder: ByteOrder)(fill: ByteBuffer => Unit): this.type = {
     fillArray(len) {
       case (array, start) =>
         val buffer = ByteBuffer.wrap(array, start, len)
@@ -1128,7 +1128,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
     _tempCapacity = _temp.length
   }
 
-  @inline private def shouldResizeTempFor(size: Int): Boolean = _tempCapacity < size || _tempCapacity == 0
+  private def shouldResizeTempFor(size: Int): Boolean = _tempCapacity < size || _tempCapacity == 0
 
   private def ensureTempSize(size: Int): Unit = {
     if (shouldResizeTempFor(size)) {
diff --git a/actor/src/main/scala-2.13+/org/apache/pekko/util/FutureConverters.scala b/actor/src/main/scala-2.13/org/apache/pekko/util/FutureConverters.scala
similarity index 100%
rename from actor/src/main/scala-2.13+/org/apache/pekko/util/FutureConverters.scala
rename to actor/src/main/scala-2.13/org/apache/pekko/util/FutureConverters.scala
diff --git a/actor/src/main/scala-2.13+/org/apache/pekko/util/OptionConverters.scala b/actor/src/main/scala-2.13/org/apache/pekko/util/OptionConverters.scala
similarity index 100%
rename from actor/src/main/scala-2.13+/org/apache/pekko/util/OptionConverters.scala
rename to actor/src/main/scala-2.13/org/apache/pekko/util/OptionConverters.scala
diff --git a/actor/src/main/scala-3/org/apache/pekko/util/ByteIterator.scala b/actor/src/main/scala-3/org/apache/pekko/util/ByteIterator.scala
index c4eed52125d..92f57e10f9f 100644
--- a/actor/src/main/scala-3/org/apache/pekko/util/ByteIterator.scala
+++ b/actor/src/main/scala-3/org/apache/pekko/util/ByteIterator.scala
@@ -39,11 +39,11 @@ object ByteIterator {
       extends ByteIterator {
     iterator =>
 
-    @inline final def len: Int = until - from
+    final def len: Int = until - from
 
-    @inline final def hasNext: Boolean = from < until
+    final def hasNext: Boolean = from < until
 
-    @inline final def head: Byte = array(from)
+    final def head: Byte = array(from)
 
     final def next(): Byte = {
       if (!hasNext) EmptyImmutableSeq.iterator.next()
@@ -215,13 +215,13 @@ object ByteIterator {
     }
     normalize()
 
-    @inline private def current: ByteArrayIterator = iterators.head
-    @inline private def dropCurrent(): Unit = { iterators = iterators.tail }
-    @inline def clear(): Unit = { iterators = MultiByteArrayIterator.empty.iterators }
+    private def current: ByteArrayIterator = iterators.head
+    private def dropCurrent(): Unit = { iterators = iterators.tail }
+    def clear(): Unit = { iterators = MultiByteArrayIterator.empty.iterators }
 
-    @inline final def hasNext: Boolean = current.hasNext
+    final def hasNext: Boolean = current.hasNext
 
-    @inline final def head: Byte = current.head
+    final def head: Byte = current.head
 
     final def next(): Byte = {
       val result = current.next()
diff --git a/actor/src/main/scala-3/org/apache/pekko/util/ByteString.scala b/actor/src/main/scala-3/org/apache/pekko/util/ByteString.scala
index 077a69770e3..9dfa1990f70 100644
--- a/actor/src/main/scala-3/org/apache/pekko/util/ByteString.scala
+++ b/actor/src/main/scala-3/org/apache/pekko/util/ByteString.scala
@@ -1097,7 +1097,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
     this
   }
 
-  @inline protected final def fillByteBuffer(len: Int, byteOrder: ByteOrder)(fill: ByteBuffer => Unit): this.type = {
+  protected final def fillByteBuffer(len: Int, byteOrder: ByteOrder)(fill: ByteBuffer => Unit): this.type = {
     fillArray(len) {
       case (array, start) =>
         val buffer = ByteBuffer.wrap(array, start, len)
@@ -1128,7 +1128,7 @@ final class ByteStringBuilder extends Builder[Byte, ByteString] {
     _tempCapacity = _temp.length
   }
 
-  @inline private def shouldResizeTempFor(size: Int): Boolean = _tempCapacity < size || _tempCapacity == 0
+  private def shouldResizeTempFor(size: Int): Boolean = _tempCapacity < size || _tempCapacity == 0
 
   private def ensureTempSize(size: Int): Unit = {
     if (shouldResizeTempFor(size)) {
diff --git a/actor/src/main/scala-3/org/apache/pekko/util/FutureConverters.scala b/actor/src/main/scala-3/org/apache/pekko/util/FutureConverters.scala
new file mode 100644
index 00000000000..b3b8e63c9b8
--- /dev/null
+++ b/actor/src/main/scala-3/org/apache/pekko/util/FutureConverters.scala
@@ -0,0 +1,37 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * license agreements; and to You under the Apache License, version 2.0:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * This file is part of the Apache Pekko project, derived from Akka.
+ */
+
+package org.apache.pekko.util
+
+import org.apache.pekko.annotation.InternalStableApi
+
+import java.util.concurrent.CompletionStage
+import scala.concurrent.Future
+
+/**
+ * INTERNAL API
+ *
+ * Remove this once Scala 2.12 support is dropped since all methods are in Scala 2.13+ stdlib
+ */
+@InternalStableApi
+private[pekko] object FutureConverters {
+  import scala.jdk.javaapi
+
+  def asJava[T](f: Future[T]): CompletionStage[T] = javaapi.FutureConverters.asJava(f)
+
+  implicit final class FutureOps[T](private val f: Future[T]) extends AnyVal {
+    inline def asJava: CompletionStage[T] = FutureConverters.asJava(f)
+  }
+
+  def asScala[T](cs: CompletionStage[T]): Future[T] = javaapi.FutureConverters.asScala(cs)
+
+  implicit final class CompletionStageOps[T](private val cs: CompletionStage[T]) extends AnyVal {
+    inline def asScala: Future[T] = FutureConverters.asScala(cs)
+  }
+}
diff --git a/actor/src/main/scala-3/org/apache/pekko/util/OptionConverters.scala b/actor/src/main/scala-3/org/apache/pekko/util/OptionConverters.scala
new file mode 100644
index 00000000000..2f2fef5c378
--- /dev/null
+++ b/actor/src/main/scala-3/org/apache/pekko/util/OptionConverters.scala
@@ -0,0 +1,77 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * license agreements; and to You under the Apache License, version 2.0:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * This file is part of the Apache Pekko project, derived from Akka.
+ */
+
+package org.apache.pekko.util
+
+import org.apache.pekko.annotation.InternalStableApi
+
+import java.util._
+import scala.jdk.OptionShape
+
+/**
+ * INTERNAL API
+ *
+ * Remove this once Scala 2.12 support is dropped since all methods are in Scala 2.13+ stdlib
+ */
+@InternalStableApi
+private[pekko] object OptionConverters {
+
+  inline final def toScala[A](o: Optional[A]): Option[A] = scala.jdk.javaapi.OptionConverters.toScala(o)
+
+  inline def toScala(o: OptionalDouble): Option[java.lang.Double] = scala.jdk.javaapi.OptionConverters.toScala(o)
+
+  inline def toScala(o: OptionalInt): Option[java.lang.Integer] = scala.jdk.javaapi.OptionConverters.toScala(o)
+
+  inline def toScala(o: OptionalLong): Option[java.lang.Long] = scala.jdk.javaapi.OptionConverters.toScala(o)
+
+  inline final def toJava[A](o: Option[A]): Optional[A] = scala.jdk.javaapi.OptionConverters.toJava(o)
+
+  implicit final class RichOptional[A](private val o: java.util.Optional[A]) extends AnyVal {
+    inline def toScala: Option[A] = scala.jdk.OptionConverters.RichOptional(o).toScala
+
+    inline def toJavaPrimitive[O](implicit shape: OptionShape[A, O]): O =
+      scala.jdk.OptionConverters.RichOptional(o).toJavaPrimitive
+  }
+
+  implicit final class RichOption[A](private val o: Option[A]) extends AnyVal {
+    inline def toJava: Optional[A] = scala.jdk.OptionConverters.RichOption(o).toJava
+
+    inline def toJavaPrimitive[O](implicit shape: OptionShape[A, O]): O =
+      scala.jdk.OptionConverters.RichOption(o).toJavaPrimitive
+  }
+
+  implicit class RichOptionalDouble(private val o: OptionalDouble) extends AnyVal {
+
+    /** Convert a Java `OptionalDouble` to a Scala `Option` */
+    inline def toScala: Option[Double] = scala.jdk.OptionConverters.RichOptionalDouble(o).toScala
+
+    /** Convert a Java `OptionalDouble` to a generic Java `Optional` */
+    inline def toJavaGeneric: Optional[Double] = scala.jdk.OptionConverters.RichOptionalDouble(o).toJavaGeneric
+  }
+
+  /** Provides conversions from `OptionalInt` to Scala `Option` and the generic `Optional` */
+  implicit class RichOptionalInt(private val o: OptionalInt) extends AnyVal {
+
+    /** Convert a Java `OptionalInt` to a Scala `Option` */
+    inline def toScala: Option[Int] = scala.jdk.OptionConverters.RichOptionalInt(o).toScala
+
+    /** Convert a Java `OptionalInt` to a generic Java `Optional` */
+    inline def toJavaGeneric: Optional[Int] = scala.jdk.OptionConverters.RichOptionalInt(o).toJavaGeneric
+  }
+
+  /** Provides conversions from `OptionalLong` to Scala `Option` and the generic `Optional` */
+  implicit class RichOptionalLong(private val o: OptionalLong) extends AnyVal {
+
+    /** Convert a Java `OptionalLong` to a Scala `Option` */
+    inline def toScala: Option[Long] = scala.jdk.OptionConverters.RichOptionalLong(o).toScala
+
+    /** Convert a Java `OptionalLong` to a generic Java `Optional` */
+    inline def toJavaGeneric: Optional[Long] = scala.jdk.OptionConverters.RichOptionalLong(o).toJavaGeneric
+  }
+}
diff --git a/actor/src/main/scala/org/apache/pekko/actor/ActorSystem.scala b/actor/src/main/scala/org/apache/pekko/actor/ActorSystem.scala
index b91961d07d5..945a3bd58d1 100644
--- a/actor/src/main/scala/org/apache/pekko/actor/ActorSystem.scala
+++ b/actor/src/main/scala/org/apache/pekko/actor/ActorSystem.scala
@@ -860,7 +860,6 @@ private[pekko] class ActorSystemImpl(
         }
       }
 
-      @inline
       private def logFatalError(message: String, cause: Throwable, thread: Thread): Unit = {
         // First log to stderr as this has the best chance to get through in an 'emergency panic' situation:
         import System.err
diff --git a/actor/src/main/scala/org/apache/pekko/actor/dungeon/Children.scala b/actor/src/main/scala/org/apache/pekko/actor/dungeon/Children.scala
index 9988d06c12b..00e9fd00ed5 100644
--- a/actor/src/main/scala/org/apache/pekko/actor/dungeon/Children.scala
+++ b/actor/src/main/scala/org/apache/pekko/actor/dungeon/Children.scala
@@ -148,7 +148,7 @@ private[pekko] trait Children { this: ActorCell =>
   /*
    * low level CAS helpers
    */
-  @inline private final def swapChildrenRefs(oldChildren: ChildrenContainer, newChildren: ChildrenContainer): Boolean =
+  private final def swapChildrenRefs(oldChildren: ChildrenContainer, newChildren: ChildrenContainer): Boolean =
     Unsafe.instance.compareAndSwapObject(this, AbstractActorCell.childrenOffset, oldChildren, newChildren)
 
   @tailrec final def reserveChild(name: String): Boolean = {
diff --git a/actor/src/main/scala/org/apache/pekko/actor/dungeon/Dispatch.scala b/actor/src/main/scala/org/apache/pekko/actor/dungeon/Dispatch.scala
index 4485b071478..99211122951 100644
--- a/actor/src/main/scala/org/apache/pekko/actor/dungeon/Dispatch.scala
+++ b/actor/src/main/scala/org/apache/pekko/actor/dungeon/Dispatch.scala
@@ -52,7 +52,7 @@ private[pekko] trait Dispatch { this: ActorCell =>
     _mailboxDoNotCallMeDirectly
   }
 
-  @inline final def mailbox: Mailbox =
+  final def mailbox: Mailbox =
     Unsafe.instance.getObjectVolatile(this, AbstractActorCell.mailboxOffset).asInstanceOf[Mailbox]
 
   @tailrec final def swapMailbox(newMailbox: Mailbox): Mailbox = {
diff --git a/actor/src/main/scala/org/apache/pekko/actor/package.scala b/actor/src/main/scala/org/apache/pekko/actor/package.scala
index c0734cf0083..6947d640d13 100644
--- a/actor/src/main/scala/org/apache/pekko/actor/package.scala
+++ b/actor/src/main/scala/org/apache/pekko/actor/package.scala
@@ -17,7 +17,7 @@ import language.implicitConversions
 
 package object actor {
   @deprecated("implicit conversion is obsolete", "Akka 2.6.13")
-  @inline implicit final def actorRef2Scala(ref: ActorRef): ScalaActorRef = ref.asInstanceOf[ScalaActorRef]
+  implicit final def actorRef2Scala(ref: ActorRef): ScalaActorRef = ref.asInstanceOf[ScalaActorRef]
   @deprecated("implicit conversion is obsolete", "Akka 2.6.13")
-  @inline implicit final def scala2ActorRef(ref: ScalaActorRef): ActorRef = ref.asInstanceOf[ActorRef]
+  implicit final def scala2ActorRef(ref: ScalaActorRef): ActorRef = ref.asInstanceOf[ActorRef]
 }
diff --git a/actor/src/main/scala/org/apache/pekko/dispatch/AbstractDispatcher.scala b/actor/src/main/scala/org/apache/pekko/dispatch/AbstractDispatcher.scala
index 08afe54e947..9e6f2af1afb 100644
--- a/actor/src/main/scala/org/apache/pekko/dispatch/AbstractDispatcher.scala
+++ b/actor/src/main/scala/org/apache/pekko/dispatch/AbstractDispatcher.scala
@@ -329,7 +329,7 @@ abstract class MessageDispatcher(val configurator: MessageDispatcherConfigurator
   /**
    * INTERNAL API
    */
-  @inline protected[pekko] final val isThroughputDeadlineTimeDefined = throughputDeadlineTime.toMillis > 0
+  protected[pekko] final val isThroughputDeadlineTimeDefined = throughputDeadlineTime.toMillis > 0
 
   /**
    * INTERNAL API
diff --git a/actor/src/main/scala/org/apache/pekko/dispatch/Mailbox.scala b/actor/src/main/scala/org/apache/pekko/dispatch/Mailbox.scala
index 088a0a33e64..b9df8ee00d7 100644
--- a/actor/src/main/scala/org/apache/pekko/dispatch/Mailbox.scala
+++ b/actor/src/main/scala/org/apache/pekko/dispatch/Mailbox.scala
@@ -121,29 +121,21 @@ private[pekko] abstract class Mailbox(val messageQueue: MessageQueue)
   @volatile
   protected var _systemQueueDoNotCallMeDirectly: SystemMessage = _ // null by default
 
-  @inline
   final def currentStatus: Mailbox.Status = Unsafe.instance.getIntVolatile(this, AbstractMailbox.mailboxStatusOffset)
 
-  @inline
   final def shouldProcessMessage: Boolean = (currentStatus & shouldNotProcessMask) == 0
 
-  @inline
   final def suspendCount: Int = currentStatus / suspendUnit
 
-  @inline
   final def isSuspended: Boolean = (currentStatus & suspendMask) != 0
 
-  @inline
   final def isClosed: Boolean = currentStatus == Closed
 
-  @inline
   final def isScheduled: Boolean = (currentStatus & Scheduled) != 0
 
-  @inline
   protected final def updateStatus(oldStatus: Status, newStatus: Status): Boolean =
     Unsafe.instance.compareAndSwapInt(this, AbstractMailbox.mailboxStatusOffset, oldStatus, newStatus)
 
-  @inline
   protected final def setStatus(newStatus: Status): Unit =
     Unsafe.instance.putIntVolatile(this, AbstractMailbox.mailboxStatusOffset, newStatus)
 
diff --git a/actor/src/main/scala/org/apache/pekko/dispatch/affinity/AffinityPool.scala b/actor/src/main/scala/org/apache/pekko/dispatch/affinity/AffinityPool.scala
index f83b5a456ae..256a1686733 100644
--- a/actor/src/main/scala/org/apache/pekko/dispatch/affinity/AffinityPool.scala
+++ b/actor/src/main/scala/org/apache/pekko/dispatch/affinity/AffinityPool.scala
@@ -72,7 +72,7 @@ private[affinity] object AffinityPool {
     private[this] var parkPeriodNs = 0L
     @volatile private[this] var idling = false
 
-    @inline private[this] def transitionTo(newState: IdleState): Unit = {
+    private[this] def transitionTo(newState: IdleState): Unit = {
       state = newState
       turns = 0
     }
diff --git a/actor/src/main/scala/org/apache/pekko/event/Logging.scala b/actor/src/main/scala/org/apache/pekko/event/Logging.scala
index 50c5bd5c1b6..2a9bb428203 100644
--- a/actor/src/main/scala/org/apache/pekko/event/Logging.scala
+++ b/actor/src/main/scala/org/apache/pekko/event/Logging.scala
@@ -485,10 +485,10 @@ object Logging {
    * Marker trait for annotating LogLevel, which must be Int after erasure.
    */
   final case class LogLevel(asInt: Int) extends AnyVal {
-    @inline final def >=(other: LogLevel): Boolean = asInt >= other.asInt
-    @inline final def <=(other: LogLevel): Boolean = asInt <= other.asInt
-    @inline final def >(other: LogLevel): Boolean = asInt > other.asInt
-    @inline final def <(other: LogLevel): Boolean = asInt < other.asInt
+    final def >=(other: LogLevel): Boolean = asInt >= other.asInt
+    final def <=(other: LogLevel): Boolean = asInt <= other.asInt
+    final def >(other: LogLevel): Boolean = asInt > other.asInt
+    final def <(other: LogLevel): Boolean = asInt < other.asInt
   }
 
   /**
diff --git a/actor/src/main/scala/org/apache/pekko/pattern/AskSupport.scala b/actor/src/main/scala/org/apache/pekko/pattern/AskSupport.scala
index e2ac3da4fc6..1cd660af22f 100644
--- a/actor/src/main/scala/org/apache/pekko/pattern/AskSupport.scala
+++ b/actor/src/main/scala/org/apache/pekko/pattern/AskSupport.scala
@@ -549,11 +549,9 @@ private[pekko] final class PromiseActorRef(
     _watchedByDoNotCallMeDirectly
   }
 
-  @inline
   private[this] def watchedBy: Set[ActorRef] =
     Unsafe.instance.getObjectVolatile(this, watchedByOffset).asInstanceOf[Set[ActorRef]]
 
-  @inline
   private[this] def updateWatchedBy(oldWatchedBy: Set[ActorRef], newWatchedBy: Set[ActorRef]): Boolean =
     Unsafe.instance.compareAndSwapObject(this, watchedByOffset, oldWatchedBy, newWatchedBy)
 
@@ -575,14 +573,11 @@ private[pekko] final class PromiseActorRef(
     case other => if (!updateWatchedBy(other, null)) clearWatchers() else other
   }
 
-  @inline
   private[this] def state: AnyRef = Unsafe.instance.getObjectVolatile(this, stateOffset)
 
-  @inline
   private[this] def updateState(oldState: AnyRef, newState: AnyRef): Boolean =
     Unsafe.instance.compareAndSwapObject(this, stateOffset, oldState, newState)
 
-  @inline
   private[this] def setState(newState: AnyRef): Unit = Unsafe.instance.putObjectVolatile(this, stateOffset, newState)
 
   override def getParent: InternalActorRef = provider.tempContainer
diff --git a/actor/src/main/scala/org/apache/pekko/pattern/CircuitBreaker.scala b/actor/src/main/scala/org/apache/pekko/pattern/CircuitBreaker.scala
index a296c8962fe..18241b70f42 100644
--- a/actor/src/main/scala/org/apache/pekko/pattern/CircuitBreaker.scala
+++ b/actor/src/main/scala/org/apache/pekko/pattern/CircuitBreaker.scala
@@ -317,7 +317,6 @@ class CircuitBreaker(
    * @param newState Next state on transition
    * @return Whether the previous state matched correctly
    */
-  @inline
   private[this] def swapState(oldState: State, newState: State): Boolean =
     Unsafe.instance.compareAndSwapObject(this, AbstractCircuitBreaker.stateOffset, oldState, newState)
 
@@ -326,14 +325,12 @@ class CircuitBreaker(
    *
    * @return Reference to current state
    */
-  @inline
   private[this] def currentState: State =
     Unsafe.instance.getObjectVolatile(this, AbstractCircuitBreaker.stateOffset).asInstanceOf[State]
 
   /**
    * Helper method for updating the underlying resetTimeout via Unsafe
    */
-  @inline
   private[this] def swapResetTimeout(oldResetTimeout: FiniteDuration, newResetTimeout: FiniteDuration): Boolean =
     Unsafe.instance.compareAndSwapObject(
       this,
@@ -344,7 +341,6 @@ class CircuitBreaker(
   /**
    * Helper method for accessing to the underlying resetTimeout via Unsafe
    */
-  @inline
   private[this] def currentResetTimeout: FiniteDuration =
     Unsafe.instance.getObjectVolatile(this, AbstractCircuitBreaker.resetTimeoutOffset).asInstanceOf[FiniteDuration]
 
diff --git a/actor/src/main/scala/org/apache/pekko/routing/RouterConfig.scala b/actor/src/main/scala/org/apache/pekko/routing/RouterConfig.scala
index ec3e3427a4d..6b5565f38ba 100644
--- a/actor/src/main/scala/org/apache/pekko/routing/RouterConfig.scala
+++ b/actor/src/main/scala/org/apache/pekko/routing/RouterConfig.scala
@@ -286,13 +286,13 @@ case object FromConfig extends FromConfig {
    * Java API: get the singleton instance
    */
   def getInstance = this
-  @inline final def apply(
+  final def apply(
       resizer: Option[Resizer] = None,
       supervisorStrategy: SupervisorStrategy = Pool.defaultSupervisorStrategy,
       routerDispatcher: String = Dispatchers.DefaultDispatcherId) =
     new FromConfig(resizer, supervisorStrategy, routerDispatcher)
 
-  @inline final def unapply(fc: FromConfig): Option[String] = Some(fc.routerDispatcher)
+  final def unapply(fc: FromConfig): Option[String] = Some(fc.routerDispatcher)
 }
 
 /**
diff --git a/actor/src/main/scala/org/apache/pekko/util/Helpers.scala b/actor/src/main/scala/org/apache/pekko/util/Helpers.scala
index 6b00bd58ed9..8e71eea283b 100644
--- a/actor/src/main/scala/org/apache/pekko/util/Helpers.scala
+++ b/actor/src/main/scala/org/apache/pekko/util/Helpers.scala
@@ -140,7 +140,7 @@ object Helpers {
    *
    * @param value The value to check.
    */
-  @inline final implicit class Requiring[A](val value: A) extends AnyVal {
+  final implicit class Requiring[A](val value: A) extends AnyVal {
 
     /**
      * Check that a condition is true. If true, return `value`, otherwise throw
@@ -149,7 +149,7 @@ object Helpers {
      * @param cond The condition to check.
      * @param msg The message to report if the condition isn't met.
      */
-    @inline def requiring(cond: Boolean, msg: => Any): A = {
+    def requiring(cond: Boolean, msg: => Any): A = {
       require(cond, msg)
       value
     }
@@ -161,7 +161,7 @@ object Helpers {
      * @param cond The function used to check the `value`.
      * @param msg The message to report if the condition isn't met.
      */
-    @inline def requiring(cond: A => Boolean, msg: => Any): A = {
+    def requiring(cond: A => Boolean, msg: => Any): A = {
       require(cond(value), msg)
       value
     }
diff --git a/actor/src/main/scala/org/apache/pekko/util/LockUtil.scala b/actor/src/main/scala/org/apache/pekko/util/LockUtil.scala
index af8c069b72f..5c8c834a9a2 100644
--- a/actor/src/main/scala/org/apache/pekko/util/LockUtil.scala
+++ b/actor/src/main/scala/org/apache/pekko/util/LockUtil.scala
@@ -18,7 +18,6 @@ import java.util.concurrent.locks.ReentrantLock
 
 final class ReentrantGuard extends ReentrantLock {
 
-  @inline
   final def withGuard[T](body: => T): T = {
     lock()
     try body
diff --git a/persistence/src/main/scala/org/apache/pekko/persistence/snapshot/SnapshotStore.scala b/persistence/src/main/scala/org/apache/pekko/persistence/snapshot/SnapshotStore.scala
index 8384e95c02b..4d944d93c40 100644
--- a/persistence/src/main/scala/org/apache/pekko/persistence/snapshot/SnapshotStore.scala
+++ b/persistence/src/main/scala/org/apache/pekko/persistence/snapshot/SnapshotStore.scala
@@ -128,7 +128,7 @@ trait SnapshotStore extends Actor with ActorLogging {
   }
 
   /** Documents intent that the sender() is expected to be the PersistentActor */
-  @inline private final def senderPersistentActor(): ActorRef = sender()
+  private final def senderPersistentActor(): ActorRef = sender()
 
   private def tryReceivePluginInternal(evt: Any): Unit =
     if (receivePluginInternal.isDefinedAt(evt)) receivePluginInternal(evt)
diff --git a/project/PekkoInlinePlugin.scala b/project/PekkoInlinePlugin.scala
new file mode 100644
index 00000000000..6f99703abcb
--- /dev/null
+++ b/project/PekkoInlinePlugin.scala
@@ -0,0 +1,47 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * license agreements; and to You under the Apache License, version 2.0:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * This file is part of the Apache Pekko project, derived from Akka.
+ */
+
+import sbt.Keys._
+import sbt._
+import sbt.plugins.JvmPlugin
+
+object PekkoInlinePlugin extends AutoPlugin {
+  override def trigger: PluginTrigger = allRequirements
+
+  override def requires: Plugins = JvmPlugin
+
+  val enabled = !sys.props.contains("pekko.no.inline")
+
+  private val flagsFor212 = Seq(
+    "-opt-inline-from:org.apache.pekko.**",
+    "-opt-inline-from:<sources>",
+    "-opt:l:inline")
+
+  private val flagsFor213 = Seq(
+    "-opt-inline-from:org.apache.pekko.**",
+    "-opt-inline-from:<sources>",
+    "-opt:l:inline")
+
+  // Optimizer not yet available for Scala3, see https://docs.scala-lang.org/overviews/compiler-options/optimizer.html
+  private val flagsFor3 = Seq()
+
+  override lazy val projectSettings = Seq(
+    Compile / scalacOptions ++= {
+      if (enabled) {
+        CrossVersion.partialVersion(scalaVersion.value) match {
+          case Some((2, n)) if n == 13 =>
+            flagsFor213
+          case Some((2, n)) if n == 12 =>
+            flagsFor212
+          case Some((3, _)) =>
+            flagsFor3
+        }
+      } else Seq.empty
+    })
+}
diff --git a/remote/src/main/scala/org/apache/pekko/remote/artery/Association.scala b/remote/src/main/scala/org/apache/pekko/remote/artery/Association.scala
index e44c30140f3..6bf999338ff 100644
--- a/remote/src/main/scala/org/apache/pekko/remote/artery/Association.scala
+++ b/remote/src/main/scala/org/apache/pekko/remote/artery/Association.scala
@@ -270,7 +270,6 @@ private[remote] class Association(
    * @param newState Next state on transition
    * @return Whether the previous state matched correctly
    */
-  @inline
   private[artery] def swapState(oldState: AssociationState, newState: AssociationState): Boolean =
     Unsafe.instance.compareAndSwapObject(this, AbstractAssociation.sharedStateOffset, oldState, newState)
 
diff --git a/remote/src/main/scala/org/apache/pekko/remote/artery/compress/TopHeavyHitters.scala b/remote/src/main/scala/org/apache/pekko/remote/artery/compress/TopHeavyHitters.scala
index 47ae15f3553..be6e27f5327 100644
--- a/remote/src/main/scala/org/apache/pekko/remote/artery/compress/TopHeavyHitters.scala
+++ b/remote/src/main/scala/org/apache/pekko/remote/artery/compress/TopHeavyHitters.scala
@@ -127,8 +127,8 @@ private[remote] final class TopHeavyHitters[T >: Null](val max: Int)(implicit cl
         v
       }
 
-      @inline private final def index: Int = heap(i)
-      @inline private final def value: T = {
+      private final def index: Int = heap(i)
+      private final def value: T = {
         val idx = index
         if (idx < 0) null else items(idx)
       }
diff --git a/slf4j/src/main/scala/org/apache/pekko/event/slf4j/Slf4jLogger.scala b/slf4j/src/main/scala/org/apache/pekko/event/slf4j/Slf4jLogger.scala
index 4cbc9a988f5..7fbc1fae372 100644
--- a/slf4j/src/main/scala/org/apache/pekko/event/slf4j/Slf4jLogger.scala
+++ b/slf4j/src/main/scala/org/apache/pekko/event/slf4j/Slf4jLogger.scala
@@ -118,7 +118,6 @@ class Slf4jLogger extends Actor with SLF4JLogging with RequiresMessageQueue[Logg
       sender() ! LoggerInitialized
   }
 
-  @inline
   final def withMdc(logSource: String, logEvent: LogEvent)(logStatement: => Unit): Unit = {
     logEvent match {
       case m: LogEventWithMarker if m.marker ne null =>