diff --git a/akka-actor/src/main/scala/akka/actor/ActorCell.scala b/akka-actor/src/main/scala/akka/actor/ActorCell.scala
index 0d11d89817..347af6b5e7 100644
--- a/akka-actor/src/main/scala/akka/actor/ActorCell.scala
+++ b/akka-actor/src/main/scala/akka/actor/ActorCell.scala
@@ -18,7 +18,7 @@ import akka.dispatch.sysmsg._
 import akka.event.Logging.{ Debug, Error, LogEvent }
 import akka.japi.Procedure
 import akka.util.{ unused, Reflect }
-import akka.annotation.InternalApi
+import akka.annotation.{ InternalApi, InternalStableApi }
 import com.github.ghik.silencer.silent
 
 /**
@@ -312,6 +312,7 @@ private[akka] trait Cell {
    * schedule the actor to run, depending on which type of cell it is.
    * Is only allowed to throw Fatal Throwables.
    */
+  @InternalStableApi
   def sendMessage(msg: Envelope): Unit
 
   /**
diff --git a/akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala b/akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala
index 4ccfb24aad..6a2c34657b 100644
--- a/akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala
+++ b/akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala
@@ -8,6 +8,7 @@ import java.util.concurrent._
 import java.{ util => ju }
 
 import akka.actor._
+import akka.annotation.InternalStableApi
 import akka.dispatch.affinity.AffinityPoolConfigurator
 import akka.dispatch.sysmsg._
 import akka.event.EventStream
@@ -315,6 +316,7 @@ abstract class MessageDispatcher(val configurator: MessageDispatcherConfigurator
    *
    * INTERNAL API
    */
+  @InternalStableApi
   protected[akka] def shutdown(): Unit
 }
 
diff --git a/akka-actor/src/main/scala/akka/dispatch/Mailbox.scala b/akka-actor/src/main/scala/akka/dispatch/Mailbox.scala
index 431f46e780..73682f1e55 100644
--- a/akka-actor/src/main/scala/akka/dispatch/Mailbox.scala
+++ b/akka-actor/src/main/scala/akka/dispatch/Mailbox.scala
@@ -10,6 +10,7 @@ import java.util.concurrent.locks.ReentrantLock
 import java.util.{ Comparator, Deque, PriorityQueue, Queue }
 
 import akka.actor.{ ActorCell, ActorRef, ActorSystem, DeadLetter, InternalActorRef }
+import akka.annotation.InternalStableApi
 import akka.dispatch.sysmsg._
 import akka.event.Logging.Error
 import akka.util.Helpers.ConfigOps
@@ -448,6 +449,7 @@ private[akka] trait SystemMessageQueue {
   /**
    * Enqueue a new system message, e.g. by prepending atomically as new head of a single-linked list.
    */
+  @InternalStableApi
   def systemEnqueue(receiver: ActorRef, message: SystemMessage): Unit
 
   /**
diff --git a/akka-actor/src/main/scala/akka/dispatch/sysmsg/SystemMessage.scala b/akka-actor/src/main/scala/akka/dispatch/sysmsg/SystemMessage.scala
index 991fd30511..05f50af8c7 100644
--- a/akka-actor/src/main/scala/akka/dispatch/sysmsg/SystemMessage.scala
+++ b/akka-actor/src/main/scala/akka/dispatch/sysmsg/SystemMessage.scala
@@ -7,6 +7,7 @@ package akka.dispatch.sysmsg
 import scala.annotation.tailrec
 import akka.actor.{ ActorInitializationException, ActorRef, InternalActorRef, PossiblyHarmful }
 import akka.actor.DeadLetterSuppression
+import akka.annotation.InternalStableApi
 
 /**
  * INTERNAL API
@@ -190,6 +191,7 @@ private[akka] class EarliestFirstSystemMessageList(val head: SystemMessage) exte
  *
  * <b>NEVER SEND THE SAME SYSTEM MESSAGE OBJECT TO TWO ACTORS</b>
  */
+@InternalStableApi
 private[akka] sealed trait SystemMessage extends PossiblyHarmful with Serializable {
   // Next fields are only modifiable via the SystemMessageList value class
   @transient
diff --git a/akka-remote/src/main/scala/akka/remote/Remoting.scala b/akka-remote/src/main/scala/akka/remote/Remoting.scala
index 15afcd2053..92c9706577 100644
--- a/akka-remote/src/main/scala/akka/remote/Remoting.scala
+++ b/akka-remote/src/main/scala/akka/remote/Remoting.scala
@@ -31,6 +31,7 @@ import akka.util.OptionVal
 
 import scala.collection.immutable
 import akka.actor.ActorInitializationException
+import akka.annotation.InternalStableApi
 import akka.util.ccompat._
 import com.github.ghik.silencer.silent
 
@@ -291,6 +292,7 @@ private[remote] object EndpointManager {
   final case class Listen(addressesPromise: Promise[Seq[(AkkaProtocolTransport, Address)]]) extends RemotingCommand
   case object StartupFinished extends RemotingCommand
   case object ShutdownAndFlush extends RemotingCommand
+  @InternalStableApi
   final case class Send(
       message: Any,
       senderOption: OptionVal[ActorRef],
diff --git a/akka-stream/src/main/scala/akka/stream/impl/PhasedFusingActorMaterializer.scala b/akka-stream/src/main/scala/akka/stream/impl/PhasedFusingActorMaterializer.scala
index 5d5df9fcab..4bdf8c8bb0 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/PhasedFusingActorMaterializer.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/PhasedFusingActorMaterializer.scala
@@ -9,7 +9,7 @@ import java.util.concurrent.atomic.AtomicBoolean
 
 import akka.NotUsed
 import akka.actor.{ ActorContext, ActorRef, ActorRefFactory, ActorSystem, Cancellable, ExtendedActorSystem, PoisonPill }
-import akka.annotation.{ DoNotInherit, InternalApi }
+import akka.annotation.{ DoNotInherit, InternalApi, InternalStableApi }
 import akka.dispatch.Dispatchers
 import akka.event.{ Logging, LoggingAdapter }
 import akka.stream.Attributes.InputBuffer
@@ -429,6 +429,7 @@ private final case class SavedIslandData(
   override def materialize[Mat](_runnableGraph: Graph[ClosedShape, Mat]): Mat =
     materialize(_runnableGraph, defaultAttributes)
 
+  @InternalStableApi
   override def materialize[Mat](_runnableGraph: Graph[ClosedShape, Mat], defaultAttributes: Attributes): Mat =
     materialize(
       _runnableGraph,
@@ -612,14 +613,19 @@ private final case class SavedIslandData(
 
   def name: String
 
+  @InternalStableApi
   def materializeAtomic(mod: AtomicModule[Shape, Any], attributes: Attributes): (M, Any)
 
+  @InternalStableApi
   def assignPort(in: InPort, slot: Int, logic: M): Unit
 
+  @InternalStableApi
   def assignPort(out: OutPort, slot: Int, logic: M): Unit
 
+  @InternalStableApi
   def createPublisher(out: OutPort, logic: M): Publisher[Any]
 
+  @InternalStableApi
   def takePublisher(slot: Int, publisher: Publisher[Any]): Unit
 
   def onIslandReady(): Unit
diff --git a/akka-stream/src/main/scala/akka/stream/impl/fusing/ActorGraphInterpreter.scala b/akka-stream/src/main/scala/akka/stream/impl/fusing/ActorGraphInterpreter.scala
index 1924b98930..393fb884b3 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/fusing/ActorGraphInterpreter.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/fusing/ActorGraphInterpreter.scala
@@ -10,7 +10,7 @@ import java.util.concurrent.atomic.AtomicReference
 
 import akka.Done
 import akka.actor._
-import akka.annotation.InternalApi
+import akka.annotation.{ InternalApi, InternalStableApi }
 import akka.event.Logging
 import akka.stream._
 import akka.stream.impl.ReactiveStreamsCompliance._
@@ -55,6 +55,7 @@ import scala.util.control.NonFatal
   def props(shell: GraphInterpreterShell): Props =
     Props(new ActorGraphInterpreter(shell)).withDeploy(Deploy.local)
 
+  @InternalStableApi
   class BatchingActorInputBoundary(
       size: Int,
       shell: GraphInterpreterShell,
@@ -144,6 +145,7 @@ import scala.util.control.NonFatal
       })
     }
 
+    @InternalStableApi
     private def dequeue(): Any = {
       val elem = inputBuffer(nextInputElementCursor)
       if (elem eq null) throw new IllegalArgumentException("Internal queue must never contain a null")
@@ -160,6 +162,7 @@ import scala.util.control.NonFatal
       elem
     }
 
+    @InternalStableApi
     private def clear(): Unit = {
       java.util.Arrays.fill(inputBuffer, 0, inputBuffer.length, null)
       inputBufferElements = 0
@@ -174,6 +177,7 @@ import scala.util.control.NonFatal
       }
     }
 
+    @InternalStableApi
     def onNext(elem: Any): Unit = {
       if (!upstreamCompleted) {
         if (inputBufferElements == size) throw new IllegalStateException("Input buffer overrun")
diff --git a/akka-stream/src/main/scala/akka/stream/impl/fusing/GraphInterpreter.scala b/akka-stream/src/main/scala/akka/stream/impl/fusing/GraphInterpreter.scala
index e859aca9a1..75342a7a35 100644
--- a/akka-stream/src/main/scala/akka/stream/impl/fusing/GraphInterpreter.scala
+++ b/akka-stream/src/main/scala/akka/stream/impl/fusing/GraphInterpreter.scala
@@ -11,7 +11,7 @@ import akka.stream._
 import java.util.concurrent.ThreadLocalRandom
 
 import akka.Done
-import akka.annotation.InternalApi
+import akka.annotation.{ InternalApi, InternalStableApi }
 
 import scala.concurrent.Promise
 import scala.util.control.NonFatal
@@ -78,6 +78,7 @@ import akka.stream.snapshot._
    * @param inHandler The handler that contains the callback for input events.
    * @param outHandler The handler that contains the callback for output events.
    */
+  @InternalStableApi
   final class Connection(
       var id: Int,
       var inOwner: GraphStageLogic,
@@ -467,6 +468,7 @@ import akka.stream.snapshot._
     }
 
   // Decodes and processes a single event for the given connection
+  @InternalStableApi
   private def processEvent(connection: Connection): Unit = {
 
     // this must be the state after returning without delivering any signals, to avoid double-finalization of some unlucky stage
@@ -514,6 +516,7 @@ import akka.stream.snapshot._
     }
   }
 
+  @InternalStableApi
   private def processPush(connection: Connection): Unit = {
     if (Debug)
       println(
@@ -523,6 +526,7 @@ import akka.stream.snapshot._
     connection.inHandler.onPush()
   }
 
+  @InternalStableApi
   private def processPull(connection: Connection): Unit = {
     if (Debug)
       println(
@@ -574,6 +578,7 @@ import akka.stream.snapshot._
     if (enabled) shutdownCounter(logic.stageId) |= KeepGoingFlag
     else shutdownCounter(logic.stageId) &= KeepGoingMask
 
+  @InternalStableApi
   private[stream] def finalizeStage(logic: GraphStageLogic): Unit = {
     try {
       logic.postStop()
@@ -612,6 +617,7 @@ import akka.stream.snapshot._
     if ((currentState & OutClosed) == 0) completeConnection(connection.outOwner.stageId)
   }
 
+  @InternalStableApi
   private[stream] def fail(connection: Connection, ex: Throwable): Unit = {
     val currentState = connection.portState
     if (Debug) println(s"$Name   fail($connection, $ex) [$currentState]")
@@ -630,6 +636,7 @@ import akka.stream.snapshot._
     if ((currentState & OutClosed) == 0) completeConnection(connection.outOwner.stageId)
   }
 
+  @InternalStableApi
   private[stream] def cancel(connection: Connection): Unit = {
     val currentState = connection.portState
     if (Debug) println(s"$Name   cancel($connection) [$currentState]")