diff --git a/akka-http-core/src/main/scala/akka/http/engine/client/HttpClient.scala b/akka-http-core/src/main/scala/akka/http/engine/client/HttpClient.scala
index 9020237811..89be13f9be 100644
--- a/akka-http-core/src/main/scala/akka/http/engine/client/HttpClient.scala
+++ b/akka-http-core/src/main/scala/akka/http/engine/client/HttpClient.scala
@@ -5,16 +5,17 @@
 package akka.http.engine.client
 
 import java.net.InetSocketAddress
-import scala.collection.immutable.Queue
+import scala.annotation.tailrec
+import scala.collection.mutable.ListBuffer
+import akka.stream.stage._
 import akka.util.ByteString
 import akka.event.LoggingAdapter
 import akka.stream.FlattenStrategy
 import akka.stream.scaladsl._
 import akka.stream.scaladsl.OperationAttributes._
-import akka.http.model.{ HttpMethod, HttpRequest, HttpResponse }
+import akka.http.model.{ IllegalResponseException, HttpMethod, HttpRequest, HttpResponse }
 import akka.http.engine.rendering.{ RequestRenderingContext, HttpRequestRendererFactory }
-import akka.http.engine.parsing.{ HttpHeaderParser, HttpResponseParser }
-import akka.http.engine.parsing.ParserOutput._
+import akka.http.engine.parsing.{ ParserOutput, HttpHeaderParser, HttpResponseParser }
 import akka.http.util._
 
 /**
@@ -37,39 +38,212 @@ private[http] object HttpClient {
       })
 
     val requestRendererFactory = new HttpRequestRendererFactory(userAgentHeader, requestHeaderSizeHint, log)
-    val requestMethodByPass = new RequestMethodByPass(remoteAddress)
 
-    Flow[HttpRequest]
-      .map(requestMethodByPass)
+    /*
+      Basic Stream Setup
+      ==================
+    
+      requestIn                                            +----------+
+      +-----------------------------------------------+--->|  Termi-  |   requestRendering         
+                                                      |    |  nation  +---------------------> |
+                   +-------------------------------------->|  Merge   |                       |
+                   | Termination Backchannel          |    +----------+                       |  TCP- 
+                   |                                  |                                       |  level
+                   |                                  | Method                                |  client
+                   |                +------------+    | Bypass                                |  flow
+      responseOut  |  responsePrep  |  Response  |<---+                                       |
+      <------------+----------------|  Parsing   |                                            |
+                                    |  Merge     |<------------------------------------------ V
+                                    +------------+
+    */
+
+    val requestIn = UndefinedSource[HttpRequest]
+    val responseOut = UndefinedSink[HttpResponse]
+
+    val methodBypassFanout = Broadcast[HttpRequest]
+    val responseParsingMerge = new ResponseParsingMerge(rootParser)
+
+    val terminationFanout = Broadcast[HttpResponse]
+    val terminationMerge = new TerminationMerge
+
+    val requestRendering = Flow[HttpRequest]
+      .map(RequestRenderingContext(_, remoteAddress))
       .section(name("renderer"))(_.transform(() ⇒ requestRendererFactory.newRenderer))
       .flatten(FlattenStrategy.concat)
+
+    val transportFlow = Flow[ByteString]
       .section(name("errorLogger"))(_.transform(() ⇒ errorLogger(log, "Outgoing request stream error")))
       .via(transport)
-      .section(name("rootParser"))(_.transform(() ⇒
-        // each connection uses a single (private) response parser instance for all its responses
-        // which builds a cache of all header instances seen on that connection
-        rootParser.createShallowCopy(requestMethodByPass)))
-      .splitWhen(_.isInstanceOf[MessageStart])
+
+    val methodBypass = Flow[HttpRequest].map(_.method)
+
+    import ParserOutput._
+    val responsePrep = Flow[List[ResponseOutput]]
+      .transform(recover { case x: ResponseParsingError ⇒ x.error :: Nil }) // FIXME after #16565
+      .mapConcat(identityFunc)
+      .splitWhen(x ⇒ x.isInstanceOf[MessageStart] || x == MessageEnd)
       .headAndTail
       .collect {
         case (ResponseStart(statusCode, protocol, headers, createEntity, _), entityParts) ⇒
           HttpResponse(statusCode, headers, createEntity(entityParts), protocol)
+        case (MessageStartError(_, info), _) ⇒ throw IllegalResponseException(info)
       }
+
+    import FlowGraphImplicits._
+
+    Flow() { implicit b ⇒
+      requestIn ~> methodBypassFanout ~> terminationMerge.requestInput ~> requestRendering ~> transportFlow ~>
+        responseParsingMerge.dataInput ~> responsePrep ~> terminationFanout ~> responseOut
+      methodBypassFanout ~> methodBypass ~> responseParsingMerge.methodBypassInput
+      terminationFanout ~> terminationMerge.terminationBackchannelInput
+
+      b.allowCycles()
+
+      requestIn -> responseOut
+    }
   }
 
-  // FIXME: refactor to a pure-stream design that allows us to get rid of this ad-hoc queue here
-  class RequestMethodByPass(serverAddress: InetSocketAddress)
-    extends (HttpRequest ⇒ RequestRenderingContext) with (() ⇒ HttpMethod) {
-    private[this] var requestMethods = Queue.empty[HttpMethod]
-    def apply(request: HttpRequest) = {
-      requestMethods = requestMethods.enqueue(request.method)
-      RequestRenderingContext(request, serverAddress)
+  // a simple merge stage that simply forwards its first input and ignores its second input
+  // (the terminationBackchannelInput), but applies a special completion handling
+  class TerminationMerge extends FlexiMerge[HttpRequest] {
+    import FlexiMerge._
+    val requestInput = createInputPort[HttpRequest]()
+    val terminationBackchannelInput = createInputPort[HttpResponse]()
+
+    def createMergeLogic() = new MergeLogic[HttpRequest] {
+      override def inputHandles(inputCount: Int) = {
+        require(inputCount == 2, s"TerminationMerge must have 2 connected inputs, was $inputCount")
+        Vector(requestInput, terminationBackchannelInput)
+      }
+
+      override def initialState = State[Any](ReadAny(requestInput, terminationBackchannelInput)) {
+        case (ctx, _, request: HttpRequest) ⇒ { ctx.emit(request); SameState }
+        case _                              ⇒ SameState // simply drop all responses, we are only interested in the completion of the response input
+      }
+
+      override def initialCompletionHandling = CompletionHandling(
+        onComplete = {
+          case (ctx, `requestInput`) ⇒ SameState
+          case (ctx, `terminationBackchannelInput`) ⇒
+            ctx.complete()
+            SameState
+        },
+        onError = defaultCompletionHandling.onError)
     }
-    def apply(): HttpMethod =
-      if (requestMethods.nonEmpty) {
-        val method = requestMethods.head
-        requestMethods = requestMethods.tail
-        method
-      } else HttpResponseParser.NoMethod
+  }
+
+  import ParserOutput._
+
+  /**
+   * A FlexiMerge that follows this logic:
+   * 1. Wait on the methodBypass for the method of the request corresponding to the next response to be received
+   * 2. Read from the dataInput until exactly one response has been fully received
+   * 3. Go back to 1.
+   */
+  class ResponseParsingMerge(rootParser: HttpResponseParser) extends FlexiMerge[List[ResponseOutput]] {
+    import FlexiMerge._
+    val dataInput = createInputPort[ByteString]()
+    val methodBypassInput = createInputPort[HttpMethod]()
+
+    def createMergeLogic() = new MergeLogic[List[ResponseOutput]] {
+      // each connection uses a single (private) response parser instance for all its responses
+      // which builds a cache of all header instances seen on that connection
+      val parser = rootParser.createShallowCopy()
+      var methodBypassCompleted = false
+
+      override def inputHandles(inputCount: Int) = {
+        require(inputCount == 2, s"ResponseParsingMerge must have 2 connected inputs, was $inputCount")
+        Vector(dataInput, methodBypassInput)
+      }
+
+      override val initialState: State[HttpMethod] =
+        State(Read(methodBypassInput)) {
+          case (ctx, _, method) ⇒
+            parser.setRequestMethodForNextResponse(method)
+            drainParser(parser.onPush(ByteString.empty), ctx,
+              onNeedNextMethod = () ⇒ SameState,
+              onNeedMoreData = () ⇒ {
+                ctx.changeCompletionHandling(responseReadingCompletionHandling)
+                responseReadingState
+              })
+        }
+
+      val responseReadingState: State[ByteString] =
+        State(Read(dataInput)) {
+          case (ctx, _, bytes) ⇒
+            drainParser(parser.onPush(bytes), ctx,
+              onNeedNextMethod = () ⇒ {
+                if (methodBypassCompleted) {
+                  ctx.complete()
+                  SameState
+                } else {
+                  ctx.changeCompletionHandling(initialCompletionHandling)
+                  initialState
+                }
+              },
+              onNeedMoreData = () ⇒ SameState)
+        }
+
+      @tailrec def drainParser(current: ResponseOutput, ctx: MergeLogicContext,
+                               onNeedNextMethod: () ⇒ State[_], onNeedMoreData: () ⇒ State[_],
+                               b: ListBuffer[ResponseOutput] = ListBuffer.empty): State[_] = {
+        def emit(output: List[ResponseOutput]): Unit = if (output.nonEmpty) ctx.emit(output)
+        current match {
+          case NeedNextRequestMethod ⇒
+            emit(b.result())
+            onNeedNextMethod()
+          case StreamEnd ⇒
+            emit(b.result())
+            ctx.complete()
+            SameState
+          case NeedMoreData ⇒
+            emit(b.result())
+            onNeedMoreData()
+          case x ⇒ drainParser(parser.onPull(), ctx, onNeedNextMethod, onNeedMoreData, b += x)
+        }
+      }
+
+      override val initialCompletionHandling = CompletionHandling(
+        onComplete = (ctx, _) ⇒ { ctx.complete(); SameState },
+        onError = defaultCompletionHandling.onError)
+
+      val responseReadingCompletionHandling = CompletionHandling(
+        onComplete = {
+          case (ctx, `methodBypassInput`) ⇒
+            methodBypassCompleted = true
+            SameState
+          case (ctx, `dataInput`) ⇒
+            if (parser.onUpstreamFinish()) {
+              ctx.complete()
+            } else {
+              // not pretty but because the FlexiMerge doesn't let us emit from here (#16565)
+              // we need to funnel the error through the error channel
+              ctx.error(new ResponseParsingError(parser.onPull().asInstanceOf[ErrorOutput]))
+            }
+            SameState
+        },
+        onError = defaultCompletionHandling.onError)
+    }
+  }
+
+  private class ResponseParsingError(val error: ErrorOutput) extends RuntimeException
+
+  // TODO: remove after #16394 is cleared
+  def recover[A, B >: A](pf: PartialFunction[Throwable, B]): () ⇒ PushPullStage[A, B] = {
+    val stage = new PushPullStage[A, B] {
+      var recovery: Option[B] = None
+      def onPush(elem: A, ctx: Context[B]): Directive = ctx.push(elem)
+      def onPull(ctx: Context[B]): Directive = recovery match {
+        case None    ⇒ ctx.pull()
+        case Some(x) ⇒ { recovery = null; ctx.push(x) }
+        case null    ⇒ ctx.finish()
+      }
+      override def onUpstreamFailure(cause: Throwable, ctx: Context[B]): TerminationDirective =
+        if (pf isDefinedAt cause) {
+          recovery = Some(pf(cause))
+          ctx.absorbTermination()
+        } else super.onUpstreamFailure(cause, ctx)
+    }
+    () ⇒ stage
   }
 }
\ No newline at end of file
diff --git a/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpMessageParser.scala b/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpMessageParser.scala
index ef3367ee8a..c2288ccdf0 100644
--- a/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpMessageParser.scala
+++ b/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpMessageParser.scala
@@ -10,7 +10,6 @@ import akka.parboiled2.CharUtils
 import akka.util.ByteString
 import akka.stream.scaladsl.Source
 import akka.stream.stage._
-import akka.http.Http.StreamException
 import akka.http.model.parser.CharacterClasses
 import akka.http.util._
 import akka.http.model._
@@ -22,21 +21,33 @@ import ParserOutput._
  * INTERNAL API
  */
 private[http] abstract class HttpMessageParser[Output >: MessageOutput <: ParserOutput](val settings: ParserSettings,
-                                                                                        val headerParser: HttpHeaderParser)
-  extends PushPullStage[ByteString, Output] {
+                                                                                        val headerParser: HttpHeaderParser) { self ⇒
   import HttpMessageParser._
   import settings._
 
-  sealed trait StateResult // phantom type for ensuring soundness of our parsing method setup
-  final case class Trampoline(f: ByteString ⇒ StateResult) extends StateResult
-
   private[this] val result = new ListBuffer[Output]
   private[this] var state: ByteString ⇒ StateResult = startNewMessage(_, 0)
   private[this] var protocol: HttpProtocol = `HTTP/1.1`
   private[this] var completionHandling: CompletionHandling = CompletionOk
   private[this] var terminated = false
 
-  override def onPush(input: ByteString, ctx: Context[Output]): Directive = {
+  def isTerminated = terminated
+
+  val stage: PushPullStage[ByteString, Output] =
+    new PushPullStage[ByteString, Output] {
+      def onPush(elem: ByteString, ctx: Context[Output]) = handleParserOutput(self.onPush(elem), ctx)
+      def onPull(ctx: Context[Output]) = handleParserOutput(self.onPull(), ctx)
+      private def handleParserOutput(output: Output, ctx: Context[Output]): Directive =
+        output match {
+          case StreamEnd    ⇒ ctx.finish()
+          case NeedMoreData ⇒ ctx.pull()
+          case x            ⇒ ctx.push(x)
+        }
+      override def onUpstreamFinish(ctx: Context[Output]): TerminationDirective =
+        if (self.onUpstreamFinish()) ctx.finish() else ctx.absorbTermination()
+    }
+
+  final def onPush(input: ByteString): Output = {
     @tailrec def run(next: ByteString ⇒ StateResult): StateResult =
       (try next(input)
       catch {
@@ -51,37 +62,32 @@ private[http] abstract class HttpMessageParser[Output >: MessageOutput <: Parser
 
     if (result.nonEmpty) throw new IllegalStateException("Unexpected `onPush`")
     run(state)
-    pushResultHeadAndFinishOrPull(ctx)
+    onPull()
   }
 
-  def onPull(ctx: Context[Output]): Directive = pushResultHeadAndFinishOrPull(ctx)
-
-  def pushResultHeadAndFinishOrPull(ctx: Context[Output]): Directive =
+  final def onPull(): Output =
     if (result.nonEmpty) {
       val head = result.head
       result.remove(0) // faster than `ListBuffer::drop`
-      ctx.push(head)
-    } else if (terminated) ctx.finish() else ctx.pull()
+      head
+    } else if (terminated) StreamEnd else NeedMoreData
 
-  override def onUpstreamFinish(ctx: Context[Output]) = {
+  final def onUpstreamFinish(): Boolean = {
     completionHandling() match {
-      case Some(x) ⇒ emit(x.asInstanceOf[Output])
+      case Some(x) ⇒ emit(x)
       case None    ⇒ // nothing to do
     }
     terminated = true
-    if (result.isEmpty) ctx.finish() else ctx.absorbTermination()
+    result.isEmpty
   }
 
-  def startNewMessage(input: ByteString, offset: Int): StateResult = {
-    def _startNewMessage(input: ByteString, offset: Int): StateResult =
-      try parseMessage(input, offset)
-      catch { case NotEnoughDataException ⇒ continue(input, offset)(_startNewMessage) }
-
+  protected final def startNewMessage(input: ByteString, offset: Int): StateResult = {
     if (offset < input.length) setCompletionHandling(CompletionIsMessageStartError)
-    _startNewMessage(input, offset)
+    try parseMessage(input, offset)
+    catch { case NotEnoughDataException ⇒ continue(input, offset)(startNewMessage) }
   }
 
-  def parseMessage(input: ByteString, offset: Int): StateResult
+  protected def parseMessage(input: ByteString, offset: Int): StateResult
 
   def parseProtocol(input: ByteString, cursor: Int): Int = {
     def c(ix: Int) = byteChar(input, cursor + ix)
@@ -204,7 +210,7 @@ private[http] abstract class HttpMessageParser[Output >: MessageOutput <: Parser
         val chunkBodyEnd = cursor + chunkSize
         def result(terminatorLen: Int) = {
           emit(EntityChunk(HttpEntity.Chunk(input.slice(cursor, chunkBodyEnd), extension)))
-          trampoline(_ ⇒ parseChunk(input, chunkBodyEnd + terminatorLen, isLastMessage))
+          Trampoline(_ ⇒ parseChunk(input, chunkBodyEnd + terminatorLen, isLastMessage))
         }
         byteChar(input, chunkBodyEnd) match {
           case '\r' if byteChar(input, chunkBodyEnd + 1) == '\n' ⇒ result(2)
@@ -255,7 +261,6 @@ private[http] abstract class HttpMessageParser[Output >: MessageOutput <: Parser
     state = next(_, 0)
     done()
   }
-  def trampoline(next: ByteString ⇒ StateResult): StateResult = Trampoline(next)
 
   def failMessageStart(summary: String): StateResult = failMessageStart(summary, "")
   def failMessageStart(summary: String, detail: String): StateResult = failMessageStart(StatusCodes.BadRequest, summary, detail)
@@ -299,7 +304,7 @@ private[http] abstract class HttpMessageParser[Output >: MessageOutput <: Parser
                     transformData: Source[ByteString] ⇒ Source[ByteString] = identityFunc)(entityParts: Source[_ <: ParserOutput]): UniversalEntity = {
     val data = entityParts.collect {
       case EntityPart(bytes)       ⇒ bytes
-      case EntityStreamError(info) ⇒ throw new StreamException(info)
+      case EntityStreamError(info) ⇒ throw EntityStreamException(info)
     }
     HttpEntity.Default(contentType(cth), contentLength, transformData(data))
   }
@@ -308,7 +313,7 @@ private[http] abstract class HttpMessageParser[Output >: MessageOutput <: Parser
                     transformChunks: Source[HttpEntity.ChunkStreamPart] ⇒ Source[HttpEntity.ChunkStreamPart] = identityFunc)(entityChunks: Source[_ <: ParserOutput]): RequestEntity = {
     val chunks = entityChunks.collect {
       case EntityChunk(chunk)      ⇒ chunk
-      case EntityStreamError(info) ⇒ throw new StreamException(info)
+      case EntityStreamError(info) ⇒ throw EntityStreamException(info)
     }
     HttpEntity.Chunked(contentType(cth), transformChunks(chunks))
   }
@@ -324,7 +329,10 @@ private[http] abstract class HttpMessageParser[Output >: MessageOutput <: Parser
 }
 
 private[http] object HttpMessageParser {
-  type CompletionHandling = () ⇒ Option[ParserOutput]
+  sealed trait StateResult // phantom type for ensuring soundness of our parsing method setup
+  final case class Trampoline(f: ByteString ⇒ StateResult) extends StateResult
+
+  type CompletionHandling = () ⇒ Option[ErrorOutput]
   val CompletionOk: CompletionHandling = () ⇒ None
   val CompletionIsMessageStartError: CompletionHandling =
     () ⇒ Some(ParserOutput.MessageStartError(StatusCodes.BadRequest, ErrorInfo("Illegal HTTP message start")))
diff --git a/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpRequestParser.scala b/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpRequestParser.scala
index b5059c5355..792b18675c 100644
--- a/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpRequestParser.scala
+++ b/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpRequestParser.scala
@@ -11,9 +11,9 @@ import akka.stream.scaladsl.OperationAttributes._
 import akka.stream.stage.{ Context, PushPullStage }
 import akka.stream.scaladsl.Source
 import akka.util.ByteString
-import akka.http.engine.server.OneHundredContinue
 import akka.http.model.parser.CharacterClasses
 import akka.http.util.identityFunc
+import akka.http.engine.TokenSourceActor
 import akka.http.model._
 import headers._
 import StatusCodes._
@@ -27,6 +27,7 @@ private[http] class HttpRequestParser(_settings: ParserSettings,
                                       _headerParser: HttpHeaderParser,
                                       oneHundredContinueRef: () ⇒ Option[ActorRef] = () ⇒ None)
   extends HttpMessageParser[RequestOutput](_settings, _headerParser) {
+  import HttpMessageParser._
   import settings._
 
   private[this] var method: HttpMethod = _
@@ -105,7 +106,7 @@ private[http] class HttpRequestParser(_settings: ParserSettings,
       uriBytes = input.iterator.slice(uriStart, uriEnd).toArray[Byte] // TODO: can we reduce allocations here?
       uri = Uri.parseHttpRequestTarget(uriBytes, mode = uriParsingMode)
     } catch {
-      case e: IllegalUriException ⇒ throw new ParsingException(BadRequest, e.info)
+      case IllegalUriException(info) ⇒ throw new ParsingException(BadRequest, info)
     }
     uriEnd + 1
   }
@@ -133,7 +134,7 @@ private[http] class HttpRequestParser(_settings: ParserSettings,
             def onPull(ctx: Context[T]) = {
               if (!oneHundredContinueSent) {
                 val ref = oneHundredContinueRef().getOrElse(throw new IllegalStateException("oneHundredContinueRef unavailable"))
-                ref ! OneHundredContinue
+                ref ! TokenSourceActor.Trigger
                 oneHundredContinueSent = true
               }
               ctx.pull()
diff --git a/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpResponseParser.scala b/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpResponseParser.scala
index 86629da8b2..2e9eabfde8 100644
--- a/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpResponseParser.scala
+++ b/akka-http-core/src/main/scala/akka/http/engine/parsing/HttpResponseParser.scala
@@ -10,38 +10,41 @@ import akka.stream.scaladsl.Source
 import akka.util.ByteString
 import akka.http.model._
 import headers._
-import HttpResponseParser.NoMethod
 import ParserOutput._
 
 /**
  * INTERNAL API
  */
-private[http] class HttpResponseParser(_settings: ParserSettings,
-                                       _headerParser: HttpHeaderParser,
-                                       dequeueRequestMethodForNextResponse: () ⇒ HttpMethod = () ⇒ NoMethod)
+private[http] class HttpResponseParser(_settings: ParserSettings, _headerParser: HttpHeaderParser)
   extends HttpMessageParser[ResponseOutput](_settings, _headerParser) {
+  import HttpMessageParser._
   import settings._
 
-  private[this] var requestMethodForCurrentResponse: HttpMethod = NoMethod
+  private[this] var requestMethodForCurrentResponse: Option[HttpMethod] = None
   private[this] var statusCode: StatusCode = StatusCodes.OK
 
-  def createShallowCopy(dequeueRequestMethodForNextResponse: () ⇒ HttpMethod): HttpResponseParser =
-    new HttpResponseParser(settings, headerParser.createShallowCopy(), dequeueRequestMethodForNextResponse)
+  def createShallowCopy(): HttpResponseParser = new HttpResponseParser(settings, headerParser.createShallowCopy())
 
-  override def startNewMessage(input: ByteString, offset: Int): StateResult = {
-    requestMethodForCurrentResponse = dequeueRequestMethodForNextResponse()
-    super.startNewMessage(input, offset)
-  }
+  def setRequestMethodForNextResponse(requestMethod: HttpMethod): Unit =
+    if (requestMethodForCurrentResponse.isEmpty) requestMethodForCurrentResponse = Some(requestMethod)
 
-  def parseMessage(input: ByteString, offset: Int): StateResult =
-    if (requestMethodForCurrentResponse ne NoMethod) {
+  protected def parseMessage(input: ByteString, offset: Int): StateResult =
+    if (requestMethodForCurrentResponse.isDefined) {
       var cursor = parseProtocol(input, offset)
       if (byteChar(input, cursor) == ' ') {
         cursor = parseStatusCode(input, cursor + 1)
         cursor = parseReason(input, cursor)()
         parseHeaderLines(input, cursor)
       } else badProtocol
-    } else failMessageStart("Unexpected server response", input.drop(offset).utf8String)
+    } else {
+      emit(NeedNextRequestMethod)
+      done()
+    }
+
+  override def emit(output: ResponseOutput): Unit = {
+    if (output == MessageEnd) requestMethodForCurrentResponse = None
+    super.emit(output)
+  }
 
   def badProtocol = throw new ParsingException("The server-side HTTP version is not supported")
 
@@ -81,10 +84,11 @@ private[http] class HttpResponseParser(_settings: ParserSettings,
     def finishEmptyResponse() = {
       emitResponseStart(emptyEntity(cth))
       setCompletionHandling(HttpMessageParser.CompletionOk)
+      emit(MessageEnd)
       startNewMessage(input, bodyStart)
     }
 
-    if (statusCode.allowsEntity && (requestMethodForCurrentResponse ne HttpMethods.HEAD)) {
+    if (statusCode.allowsEntity && (requestMethodForCurrentResponse.get != HttpMethods.HEAD)) {
       teh match {
         case None ⇒ clh match {
           case Some(`Content-Length`(contentLength)) ⇒
@@ -95,6 +99,7 @@ private[http] class HttpResponseParser(_settings: ParserSettings,
               val cl = contentLength.toInt
               emitResponseStart(strictEntity(cth, input, bodyStart, cl))
               setCompletionHandling(HttpMessageParser.CompletionOk)
+              emit(MessageEnd)
               startNewMessage(input, bodyStart + cl)
             } else {
               emitResponseStart(defaultEntity(cth, contentLength))
@@ -128,11 +133,4 @@ private[http] class HttpResponseParser(_settings: ParserSettings,
       emit(EntityPart(input drop bodyStart))
     continue(parseToCloseBody)
   }
-}
-
-/**
- * INTERNAL API
- */
-private[http] object HttpResponseParser {
-  val NoMethod = HttpMethod.custom("NONE", safe = false, idempotent = false, entityAccepted = false)
 }
\ No newline at end of file
diff --git a/akka-http-core/src/main/scala/akka/http/engine/parsing/ParserOutput.scala b/akka-http-core/src/main/scala/akka/http/engine/parsing/ParserOutput.scala
index 07daa875f9..ea264f715d 100644
--- a/akka-http-core/src/main/scala/akka/http/engine/parsing/ParserOutput.scala
+++ b/akka-http-core/src/main/scala/akka/http/engine/parsing/ParserOutput.scala
@@ -21,6 +21,7 @@ private[http] object ParserOutput {
   sealed trait ResponseOutput extends ParserOutput
   sealed trait MessageStart extends ParserOutput
   sealed trait MessageOutput extends RequestOutput with ResponseOutput
+  sealed trait ErrorOutput extends MessageOutput
 
   final case class RequestStart(
     method: HttpMethod,
@@ -44,7 +45,15 @@ private[http] object ParserOutput {
 
   final case class EntityChunk(chunk: HttpEntity.ChunkStreamPart) extends MessageOutput
 
-  final case class MessageStartError(status: StatusCode, info: ErrorInfo) extends MessageStart with MessageOutput
+  final case class MessageStartError(status: StatusCode, info: ErrorInfo) extends MessageStart with ErrorOutput
 
-  final case class EntityStreamError(info: ErrorInfo) extends MessageOutput
+  final case class EntityStreamError(info: ErrorInfo) extends ErrorOutput
+
+  //////////// meta messages ///////////
+
+  case object StreamEnd extends MessageOutput
+
+  case object NeedMoreData extends MessageOutput
+
+  case object NeedNextRequestMethod extends ResponseOutput
 }
diff --git a/akka-http-core/src/main/scala/akka/http/util/package.scala b/akka-http-core/src/main/scala/akka/http/util/package.scala
index d7808d8ac3..996d3e7347 100644
--- a/akka-http-core/src/main/scala/akka/http/util/package.scala
+++ b/akka-http-core/src/main/scala/akka/http/util/package.scala
@@ -55,31 +55,25 @@ package object util {
         .flatten(FlattenStrategy.concat)
   }
 
-  private[http] implicit class EnhancedSource[T](val underlying: Source[T]) {
-    def printEvent(marker: String): Source[T] =
-      underlying.transform(() ⇒ new PushStage[T, T] {
-        override def onPush(element: T, ctx: Context[T]): Directive = {
-          println(s"$marker: $element")
-          ctx.push(element)
-        }
-        override def onUpstreamFailure(cause: Throwable, ctx: Context[T]): TerminationDirective = {
-          println(s"$marker: Failure $cause")
-          super.onUpstreamFailure(cause, ctx)
-        }
-        override def onUpstreamFinish(ctx: Context[T]): TerminationDirective = {
-          println(s"$marker: Terminated")
-          super.onUpstreamFinish(ctx)
-        }
-      })
-
-    /**
-     * Drain this stream into a Vector and provide it as a future value.
-     *
-     * FIXME: Should be part of akka-streams
-     */
-    def collectAll(implicit materializer: FlowMaterializer): Future[immutable.Seq[T]] =
-      underlying.fold(Vector.empty[T])(_ :+ _)
-  }
+  def printEvent[T](marker: String): Flow[T, T] =
+    Flow[T].transform(() ⇒ new PushStage[T, T] {
+      override def onPush(element: T, ctx: Context[T]): Directive = {
+        println(s"$marker: $element")
+        ctx.push(element)
+      }
+      override def onUpstreamFailure(cause: Throwable, ctx: Context[T]): TerminationDirective = {
+        println(s"$marker: Error $cause")
+        super.onUpstreamFailure(cause, ctx)
+      }
+      override def onUpstreamFinish(ctx: Context[T]): TerminationDirective = {
+        println(s"$marker: Complete")
+        super.onUpstreamFinish(ctx)
+      }
+      override def onDownstreamFinish(ctx: Context[T]): TerminationDirective = {
+        println(s"$marker: Cancel")
+        super.onDownstreamFinish(ctx)
+      }
+    })
 
   private[http] implicit class AddFutureAwaitResult[T](future: Future[T]) {
     /** "Safe" Await.result that doesn't throw away half of the stacktrace */
diff --git a/akka-http-core/src/test/scala/akka/http/ClientServerSpec.scala b/akka-http-core/src/test/scala/akka/http/ClientServerSpec.scala
index 6b4fceea45..602b849209 100644
--- a/akka-http-core/src/test/scala/akka/http/ClientServerSpec.scala
+++ b/akka-http-core/src/test/scala/akka/http/ClientServerSpec.scala
@@ -36,7 +36,7 @@ class ClientServerSpec extends WordSpec with Matchers with BeforeAndAfterAll {
 
   implicit val materializer = FlowMaterializer()
 
-  "The server-side HTTP infrastructure" should {
+  "The low-level HTTP infrastructure" should {
 
     "properly bind a server" in {
       val (hostname, port) = temporaryServerHostnameAndPort()
@@ -70,6 +70,7 @@ class ClientServerSpec extends WordSpec with Matchers with BeforeAndAfterAll {
       val (serverIn, serverOut) = acceptConnection()
 
       val clientOutSub = clientOut.expectSubscription()
+      clientOutSub.expectRequest()
       clientOutSub.sendNext(HttpRequest(uri = "/abc"))
 
       val serverInSub = serverIn.expectSubscription()
@@ -77,12 +78,20 @@ class ClientServerSpec extends WordSpec with Matchers with BeforeAndAfterAll {
       serverIn.expectNext().uri shouldEqual Uri(s"http://$hostname:$port/abc")
 
       val serverOutSub = serverOut.expectSubscription()
+      serverOutSub.expectRequest()
       serverOutSub.sendNext(HttpResponse(entity = "yeah"))
 
       val clientInSub = clientIn.expectSubscription()
       clientInSub.request(1)
       val response = clientIn.expectNext()
       toStrict(response.entity) shouldEqual HttpEntity("yeah")
+
+      clientOutSub.sendComplete()
+      serverInSub.request(1) // work-around for #16552
+      serverIn.expectComplete()
+      serverOutSub.expectCancellation()
+      clientInSub.request(1) // work-around for #16552
+      clientIn.expectComplete()
     }
 
     "properly complete a chunked request/response cycle" in new TestSetup {
@@ -104,6 +113,7 @@ class ClientServerSpec extends WordSpec with Matchers with BeforeAndAfterAll {
       Await.result(chunkStream.grouped(4).runWith(Sink.head), 100.millis) shouldEqual chunks
 
       val serverOutSub = serverOut.expectSubscription()
+      serverOutSub.expectRequest()
       serverOutSub.sendNext(HttpResponse(206, List(RawHeader("Age", "42")), chunkedEntity))
 
       val clientInSub = clientIn.expectSubscription()
@@ -111,8 +121,42 @@ class ClientServerSpec extends WordSpec with Matchers with BeforeAndAfterAll {
       val HttpResponse(StatusCodes.PartialContent, List(RawHeader("Age", "42"), Server(_), Date(_)),
         Chunked(`chunkedContentType`, chunkStream2), HttpProtocols.`HTTP/1.1`) = clientIn.expectNext()
       Await.result(chunkStream2.grouped(1000).runWith(Sink.head), 100.millis) shouldEqual chunks
+
+      clientOutSub.sendComplete()
+      serverInSub.request(1) // work-around for #16552
+      serverIn.expectComplete()
+      serverOutSub.expectCancellation()
+      clientInSub.request(1) // work-around for #16552
+      clientIn.expectComplete()
     }
 
+    "be able to deal with eager closing of the request stream on the client side" in new TestSetup {
+      val (clientOut, clientIn) = openNewClientConnection()
+      val (serverIn, serverOut) = acceptConnection()
+
+      val clientOutSub = clientOut.expectSubscription()
+      clientOutSub.sendNext(HttpRequest(uri = "/abc"))
+      clientOutSub.sendComplete() // complete early
+
+      val serverInSub = serverIn.expectSubscription()
+      serverInSub.request(1)
+      serverIn.expectNext().uri shouldEqual Uri(s"http://$hostname:$port/abc")
+
+      val serverOutSub = serverOut.expectSubscription()
+      serverOutSub.expectRequest()
+      serverOutSub.sendNext(HttpResponse(entity = "yeah"))
+
+      val clientInSub = clientIn.expectSubscription()
+      clientInSub.request(1)
+      val response = clientIn.expectNext()
+      toStrict(response.entity) shouldEqual HttpEntity("yeah")
+
+      serverInSub.request(1) // work-around for #16552
+      serverIn.expectComplete()
+      serverOutSub.expectCancellation()
+      clientInSub.request(1) // work-around for #16552
+      clientIn.expectComplete()
+    }
   }
 
   override def afterAll() = system.shutdown()
diff --git a/akka-http-core/src/test/scala/akka/http/engine/client/HttpClientSpec.scala b/akka-http-core/src/test/scala/akka/http/engine/client/HttpClientSpec.scala
new file mode 100644
index 0000000000..510b3b9490
--- /dev/null
+++ b/akka-http-core/src/test/scala/akka/http/engine/client/HttpClientSpec.scala
@@ -0,0 +1,330 @@
+/*
+ * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.http.engine.client
+
+import java.net.InetSocketAddress
+import org.scalatest.Inside
+import akka.util.ByteString
+import akka.event.NoLogging
+import akka.stream.FlowMaterializer
+import akka.stream.testkit.{ AkkaSpec, StreamTestKit }
+import akka.stream.scaladsl._
+import akka.http.model.HttpEntity._
+import akka.http.model.HttpMethods._
+import akka.http.model._
+import akka.http.model.headers._
+import akka.http.util._
+
+class HttpClientSpec extends AkkaSpec("akka.loggers = []\n akka.loglevel = OFF") with Inside {
+  implicit val materializer = FlowMaterializer()
+
+  "The client implementation" should {
+
+    "properly handle a request/response round-trip" which {
+
+      "has a request with empty entity" in new TestSetup {
+        requestsSub.sendNext(HttpRequest())
+        expectWireData(
+          """GET / HTTP/1.1
+            |Host: example.com:80
+            |User-Agent: akka-http/test
+            |
+            |""")
+
+        netInSub.expectRequest(16)
+        sendWireData(
+          """HTTP/1.1 200 OK
+            |Content-Length: 0
+            |
+            |""")
+
+        responsesSub.request(1)
+        responses.expectNext(HttpResponse())
+
+        requestsSub.sendComplete()
+        netOut.expectComplete()
+        netInSub.sendComplete()
+        responses.expectComplete()
+      }
+
+      "has a request with default entity" in new TestSetup {
+        val probe = StreamTestKit.PublisherProbe[ByteString]()
+        requestsSub.sendNext(HttpRequest(PUT, entity = HttpEntity(ContentTypes.`application/octet-stream`, 8, Source(probe))))
+        expectWireData(
+          """PUT / HTTP/1.1
+            |Host: example.com:80
+            |User-Agent: akka-http/test
+            |Content-Type: application/octet-stream
+            |Content-Length: 8
+            |
+            |""")
+        val sub = probe.expectSubscription()
+        sub.expectRequest(4)
+        sub.sendNext(ByteString("ABC"))
+        expectWireData("ABC")
+        sub.sendNext(ByteString("DEF"))
+        expectWireData("DEF")
+        sub.sendNext(ByteString("XY"))
+        expectWireData("XY")
+        sub.sendComplete()
+
+        netInSub.expectRequest(16)
+        sendWireData(
+          """HTTP/1.1 200 OK
+            |Content-Length: 0
+            |
+            |""")
+
+        responsesSub.request(1)
+        responses.expectNext(HttpResponse())
+
+        requestsSub.sendComplete()
+        netOut.expectComplete()
+        netInSub.sendComplete()
+        responses.expectComplete()
+      }
+
+      "has a response with a default entity" in new TestSetup {
+        requestsSub.sendNext(HttpRequest())
+        expectWireData(
+          """GET / HTTP/1.1
+            |Host: example.com:80
+            |User-Agent: akka-http/test
+            |
+            |""")
+
+        netInSub.expectRequest(16)
+        sendWireData(
+          """HTTP/1.1 200 OK
+            |Transfer-Encoding: chunked
+            |
+            |""")
+
+        responsesSub.request(1)
+        val HttpResponse(_, _, HttpEntity.Chunked(ct, chunks), _) = responses.expectNext()
+        ct shouldEqual ContentTypes.`application/octet-stream`
+
+        val probe = StreamTestKit.SubscriberProbe[ChunkStreamPart]()
+        chunks.runWith(Sink(probe))
+        val sub = probe.expectSubscription()
+
+        sendWireData("3\nABC\n")
+        sub.request(1)
+        probe.expectNext(HttpEntity.Chunk("ABC"))
+
+        sendWireData("4\nDEFX\n")
+        sub.request(1)
+        probe.expectNext(HttpEntity.Chunk("DEFX"))
+
+        sendWireData("0\n\n")
+        sub.request(1)
+        probe.expectNext(HttpEntity.LastChunk)
+        probe.expectComplete()
+
+        requestsSub.sendComplete()
+        netOut.expectComplete()
+        netInSub.sendComplete()
+        responses.expectComplete()
+      }
+
+      "exhibits eager request stream completion" in new TestSetup {
+        requestsSub.sendNext(HttpRequest())
+        requestsSub.sendComplete()
+        expectWireData(
+          """GET / HTTP/1.1
+            |Host: example.com:80
+            |User-Agent: akka-http/test
+            |
+            |""")
+
+        netInSub.expectRequest(16)
+        sendWireData(
+          """HTTP/1.1 200 OK
+            |Content-Length: 0
+            |
+            |""")
+
+        responsesSub.request(1)
+        responses.expectNext(HttpResponse())
+
+        netOut.expectComplete()
+        netInSub.sendComplete()
+        responses.expectComplete()
+      }
+    }
+
+    "produce proper errors" which {
+
+      "catch the entity stream being shorter than the Content-Length" in new TestSetup {
+        val probe = StreamTestKit.PublisherProbe[ByteString]()
+        requestsSub.sendNext(HttpRequest(PUT, entity = HttpEntity(ContentTypes.`application/octet-stream`, 8, Source(probe))))
+        expectWireData(
+          """PUT / HTTP/1.1
+            |Host: example.com:80
+            |User-Agent: akka-http/test
+            |Content-Type: application/octet-stream
+            |Content-Length: 8
+            |
+            |""")
+        val sub = probe.expectSubscription()
+        sub.expectRequest(4)
+        sub.sendNext(ByteString("ABC"))
+        expectWireData("ABC")
+        sub.sendNext(ByteString("DEF"))
+        expectWireData("DEF")
+        sub.sendComplete()
+
+        val InvalidContentLengthException(info) = netOut.expectError()
+        info.summary shouldEqual "HTTP message had declared Content-Length 8 but entity data stream amounts to 2 bytes less"
+        netInSub.sendComplete()
+        responses.expectComplete()
+        netInSub.expectCancellation()
+      }
+
+      "catch the entity stream being longer than the Content-Length" in new TestSetup {
+        val probe = StreamTestKit.PublisherProbe[ByteString]()
+        requestsSub.sendNext(HttpRequest(PUT, entity = HttpEntity(ContentTypes.`application/octet-stream`, 8, Source(probe))))
+        expectWireData(
+          """PUT / HTTP/1.1
+            |Host: example.com:80
+            |User-Agent: akka-http/test
+            |Content-Type: application/octet-stream
+            |Content-Length: 8
+            |
+            |""")
+        val sub = probe.expectSubscription()
+        sub.expectRequest(4)
+        sub.sendNext(ByteString("ABC"))
+        expectWireData("ABC")
+        sub.sendNext(ByteString("DEF"))
+        expectWireData("DEF")
+        sub.sendNext(ByteString("XYZ"))
+
+        val InvalidContentLengthException(info) = netOut.expectError()
+        info.summary shouldEqual "HTTP message had declared Content-Length 8 but entity data stream amounts to more bytes"
+        netInSub.sendComplete()
+        responses.expectComplete()
+        netInSub.expectCancellation()
+      }
+
+      "catch illegal response starts" in new TestSetup {
+        requestsSub.sendNext(HttpRequest())
+        expectWireData(
+          """GET / HTTP/1.1
+            |Host: example.com:80
+            |User-Agent: akka-http/test
+            |
+            |""")
+
+        netInSub.expectRequest(16)
+        sendWireData(
+          """HTTP/1.2 200 OK
+            |
+            |""")
+
+        val error @ IllegalResponseException(info) = responses.expectError()
+        info.summary shouldEqual "The server-side HTTP version is not supported"
+        netOut.expectError(error)
+        requestsSub.expectCancellation()
+      }
+
+      "catch illegal response chunks" in new TestSetup {
+        requestsSub.sendNext(HttpRequest())
+        expectWireData(
+          """GET / HTTP/1.1
+            |Host: example.com:80
+            |User-Agent: akka-http/test
+            |
+            |""")
+
+        netInSub.expectRequest(16)
+        sendWireData(
+          """HTTP/1.1 200 OK
+            |Transfer-Encoding: chunked
+            |
+            |""")
+
+        responsesSub.request(1)
+        val HttpResponse(_, _, HttpEntity.Chunked(ct, chunks), _) = responses.expectNext()
+        ct shouldEqual ContentTypes.`application/octet-stream`
+
+        val probe = StreamTestKit.SubscriberProbe[ChunkStreamPart]()
+        chunks.runWith(Sink(probe))
+        val sub = probe.expectSubscription()
+
+        sendWireData("3\nABC\n")
+        sub.request(1)
+        probe.expectNext(HttpEntity.Chunk("ABC"))
+
+        sendWireData("4\nDEFXX")
+        sub.request(1)
+        val error @ EntityStreamException(info) = probe.expectError()
+        info.summary shouldEqual "Illegal chunk termination"
+
+        responses.expectComplete()
+        netOut.expectComplete()
+        requestsSub.expectCancellation()
+      }
+
+      "catch a response start truncation" in new TestSetup {
+        requestsSub.sendNext(HttpRequest())
+        expectWireData(
+          """GET / HTTP/1.1
+            |Host: example.com:80
+            |User-Agent: akka-http/test
+            |
+            |""")
+
+        netInSub.expectRequest(16)
+        sendWireData("HTTP/1.1 200 OK")
+        netInSub.sendComplete()
+
+        val error @ IllegalResponseException(info) = responses.expectError()
+        info.summary shouldEqual "Illegal HTTP message start"
+        netOut.expectError(error)
+        requestsSub.expectCancellation()
+      }
+    }
+  }
+
+  class TestSetup {
+    val requests = StreamTestKit.PublisherProbe[HttpRequest]
+    val responses = StreamTestKit.SubscriberProbe[HttpResponse]
+    val remoteAddress = new InetSocketAddress("example.com", 80)
+
+    def settings = ClientConnectionSettings(system)
+      .copy(userAgentHeader = Some(`User-Agent`(List(ProductVersion("akka-http", "test")))))
+
+    val (netOut, netIn) = {
+      val netOut = StreamTestKit.SubscriberProbe[ByteString]
+      val netIn = StreamTestKit.PublisherProbe[ByteString]
+      val clientFlow = HttpClient.transportToConnectionClientFlow(
+        Flow(Sink(netOut), Source(netIn)), remoteAddress, settings, NoLogging)
+      Source(requests).via(clientFlow).runWith(Sink(responses))
+      netOut -> netIn
+    }
+
+    def wipeDate(string: String) =
+      string.fastSplit('\n').map {
+        case s if s.startsWith("Date:") ⇒ "Date: XXXX\r"
+        case s                          ⇒ s
+      }.mkString("\n")
+
+    val netInSub = netIn.expectSubscription()
+    val netOutSub = netOut.expectSubscription()
+    val requestsSub = requests.expectSubscription()
+    val responsesSub = responses.expectSubscription()
+
+    def sendWireData(data: String): Unit = sendWireData(ByteString(data.stripMarginWithNewline("\r\n"), "ASCII"))
+    def sendWireData(data: ByteString): Unit = netInSub.sendNext(data)
+
+    def expectWireData(s: String) = {
+      netOutSub.request(1)
+      netOut.expectNext().utf8String shouldEqual s.stripMarginWithNewline("\r\n")
+    }
+
+    def closeNetworkInput(): Unit = netInSub.sendComplete()
+  }
+}
\ No newline at end of file
diff --git a/akka-http-core/src/test/scala/akka/http/engine/parsing/RequestParserSpec.scala b/akka-http-core/src/test/scala/akka/http/engine/parsing/RequestParserSpec.scala
index 377db41b8d..ad92cd0ea1 100644
--- a/akka-http-core/src/test/scala/akka/http/engine/parsing/RequestParserSpec.scala
+++ b/akka-http-core/src/test/scala/akka/http/engine/parsing/RequestParserSpec.scala
@@ -120,8 +120,9 @@ class RequestParserSpec extends FreeSpec with Matchers with BeforeAndAfterAll {
             |Host: x
             |
             |ABCDPATCH"""
-        }.toCharArray.map(_.toString).toSeq should rawMultiParseTo(
-          HttpRequest(PUT, "/resource/yes", List(Host("x")), "ABCD".getBytes))
+        }.toCharArray.map(_.toString).toSeq should generalRawMultiParseTo(
+          Right(HttpRequest(PUT, "/resource/yes", List(Host("x")), "ABCD".getBytes)),
+          Left(MessageStartError(400, ErrorInfo("Illegal HTTP message start"))))
         closeAfterResponseCompletion shouldEqual Seq(false)
       }
 
@@ -232,7 +233,7 @@ class RequestParserSpec extends FreeSpec with Matchers with BeforeAndAfterAll {
           val parser = newParser
           val result = multiParse(newParser)(Seq(prep(start + manyChunks)))
           val HttpEntity.Chunked(_, chunks) = result.head.right.get.req.entity
-          val strictChunks = chunks.collectAll.awaitResult(awaitAtMost)
+          val strictChunks = chunks.grouped(100000).runWith(Sink.head).awaitResult(awaitAtMost)
           strictChunks.size shouldEqual numChunks
         }
       }
@@ -442,7 +443,7 @@ class RequestParserSpec extends FreeSpec with Matchers with BeforeAndAfterAll {
     def multiParse(parser: HttpRequestParser)(input: Seq[String]): Seq[Either[RequestOutput, StrictEqualHttpRequest]] =
       Source(input.toList)
         .map(ByteString.apply)
-        .section(name("parser"))(_.transform(() ⇒ parser))
+        .section(name("parser"))(_.transform(() ⇒ parser.stage))
         .splitWhen(x ⇒ x.isInstanceOf[MessageStart] || x.isInstanceOf[EntityStreamError])
         .headAndTail
         .collect {
@@ -461,7 +462,7 @@ class RequestParserSpec extends FreeSpec with Matchers with BeforeAndAfterAll {
         }
         .flatten(FlattenStrategy.concat)
         .map(strictEqualify)
-        .collectAll
+        .grouped(100000).runWith(Sink.head)
         .awaitResult(awaitAtMost)
 
     protected def parserSettings: ParserSettings = ParserSettings(system)
@@ -474,7 +475,7 @@ class RequestParserSpec extends FreeSpec with Matchers with BeforeAndAfterAll {
       }
 
     private def compactEntityChunks(data: Source[ChunkStreamPart]): Future[Seq[ChunkStreamPart]] =
-      data.collectAll
+      data.grouped(100000).runWith(Sink.head)
         .fast.recover { case _: NoSuchElementException ⇒ Nil }
 
     def prep(response: String) = response.stripMarginWithNewline("\r\n")
diff --git a/akka-http-core/src/test/scala/akka/http/engine/parsing/ResponseParserSpec.scala b/akka-http-core/src/test/scala/akka/http/engine/parsing/ResponseParserSpec.scala
index 305e36422f..eb067d749d 100644
--- a/akka-http-core/src/test/scala/akka/http/engine/parsing/ResponseParserSpec.scala
+++ b/akka-http-core/src/test/scala/akka/http/engine/parsing/ResponseParserSpec.scala
@@ -261,7 +261,7 @@ class ResponseParserSpec extends FreeSpec with Matchers with BeforeAndAfterAll {
           val future =
             Source(input.toList)
               .map(ByteString.apply)
-              .section(name("parser"))(_.transform(() ⇒ newParser(requestMethod)))
+              .section(name("parser"))(_.transform(() ⇒ newParserStage(requestMethod)))
               .splitWhen(x ⇒ x.isInstanceOf[MessageStart] || x.isInstanceOf[EntityStreamError])
               .headAndTail
               .collect {
@@ -279,14 +279,16 @@ class ResponseParserSpec extends FreeSpec with Matchers with BeforeAndAfterAll {
               }
               .flatten(FlattenStrategy.concat)
               .map(strictEqualify)
-              .grouped(1000).runWith(Sink.head)
+              .grouped(100000).runWith(Sink.head)
           Await.result(future, 500.millis)
         }
 
     def parserSettings: ParserSettings = ParserSettings(system)
-    def newParser(requestMethod: HttpMethod = GET) = {
-      val parser = new HttpResponseParser(parserSettings, HttpHeaderParser(parserSettings)(), () ⇒ requestMethod)
-      parser
+
+    def newParserStage(requestMethod: HttpMethod = GET) = {
+      val parser = new HttpResponseParser(parserSettings, HttpHeaderParser(parserSettings)())
+      parser.setRequestMethodForNextResponse(requestMethod)
+      parser.stage
     }
 
     private def compactEntity(entity: ResponseEntity): Future[ResponseEntity] =
@@ -296,7 +298,7 @@ class ResponseParserSpec extends FreeSpec with Matchers with BeforeAndAfterAll {
       }
 
     private def compactEntityChunks(data: Source[ChunkStreamPart]): Future[Source[ChunkStreamPart]] =
-      data.grouped(1000).runWith(Sink.head)
+      data.grouped(100000).runWith(Sink.head)
         .fast.map(source(_: _*))
         .fast.recover { case _: NoSuchElementException ⇒ source() }
 
diff --git a/akka-http-core/src/test/scala/akka/http/engine/server/HttpServerSpec.scala b/akka-http-core/src/test/scala/akka/http/engine/server/HttpServerSpec.scala
index b94425def2..d189628e50 100644
--- a/akka-http-core/src/test/scala/akka/http/engine/server/HttpServerSpec.scala
+++ b/akka-http-core/src/test/scala/akka/http/engine/server/HttpServerSpec.scala
@@ -5,7 +5,7 @@
 package akka.http.engine.server
 
 import scala.concurrent.duration._
-import org.scalatest.{ Inside, BeforeAndAfterAll, Matchers }
+import org.scalatest.Inside
 import akka.event.NoLogging
 import akka.util.ByteString
 import akka.stream.scaladsl._
@@ -18,7 +18,7 @@ import HttpEntity._
 import MediaTypes._
 import HttpMethods._
 
-class HttpServerSpec extends AkkaSpec with Matchers with BeforeAndAfterAll with Inside {
+class HttpServerSpec extends AkkaSpec("akka.loggers = []\n akka.loglevel = OFF") with Inside {
   implicit val materializer = FlowMaterializer()
 
   "The server implementation" should {
diff --git a/akka-http-testkit/src/main/scala/akka/http/testkit/RouteTestResultComponent.scala b/akka-http-testkit/src/main/scala/akka/http/testkit/RouteTestResultComponent.scala
index 373c864821..c7637f4dcb 100644
--- a/akka-http-testkit/src/main/scala/akka/http/testkit/RouteTestResultComponent.scala
+++ b/akka-http-testkit/src/main/scala/akka/http/testkit/RouteTestResultComponent.scala
@@ -96,6 +96,6 @@ trait RouteTestResultComponent {
       failTest("Request was neither completed nor rejected within " + timeout)
 
     private def awaitAllElements[T](data: Source[T]): immutable.Seq[T] =
-      data.collectAll.awaitResult(timeout)
+      data.grouped(100000).runWith(Sink.head).awaitResult(timeout)
   }
 }
\ No newline at end of file
diff --git a/akka-http-tests/src/test/scala/akka/http/server/directives/RangeDirectivesSpec.scala b/akka-http-tests/src/test/scala/akka/http/server/directives/RangeDirectivesSpec.scala
index 8401186b83..2a10f0a06b 100644
--- a/akka-http-tests/src/test/scala/akka/http/server/directives/RangeDirectivesSpec.scala
+++ b/akka-http-tests/src/test/scala/akka/http/server/directives/RangeDirectivesSpec.scala
@@ -5,17 +5,16 @@
 package akka.http.server
 package directives
 
+import scala.concurrent.Await
+import scala.concurrent.duration._
 import akka.http.model.StatusCodes._
 import akka.http.model._
 import akka.http.model.headers._
 import akka.http.util._
-import akka.stream.scaladsl.Source
+import akka.stream.scaladsl.{ Sink, Source }
 import akka.util.ByteString
 import org.scalatest.{ Inside, Inspectors }
 
-import scala.concurrent.Await
-import scala.concurrent.duration._
-
 class RangeDirectivesSpec extends RoutingSpec with Inspectors with Inside {
   lazy val wrs =
     mapSettings(_.copy(rangeCountLimit = 10, rangeCoalescingThreshold = 1L)) &
@@ -100,7 +99,7 @@ class RangeDirectivesSpec extends RoutingSpec with Inspectors with Inside {
         wrs { complete("Some random and not super short entity.") }
       } ~> check {
         header[`Content-Range`] should be(None)
-        val parts = Await.result(responseAs[Multipart.ByteRanges].parts.collectAll, 1.second)
+        val parts = Await.result(responseAs[Multipart.ByteRanges].parts.grouped(1000).runWith(Sink.head), 1.second)
         parts.size shouldEqual 2
         inside(parts(0)) {
           case Multipart.ByteRanges.BodyPart(range, entity, unit, headers) ⇒
@@ -125,7 +124,7 @@ class RangeDirectivesSpec extends RoutingSpec with Inspectors with Inside {
         wrs { complete(HttpEntity.Default(MediaTypes.`text/plain`, content.length, entityData())) }
       } ~> check {
         header[`Content-Range`] should be(None)
-        val parts = Await.result(responseAs[Multipart.ByteRanges].parts.collectAll, 1.second)
+        val parts = Await.result(responseAs[Multipart.ByteRanges].parts.grouped(1000).runWith(Sink.head), 1.second)
         parts.size shouldEqual 2
       }
     }