diff --git a/src/main/scala/com/twitter/diffy/ApiController.scala b/src/main/scala/com/twitter/diffy/ApiController.scala
index 90e5cbfd3..7e0bec69b 100644
--- a/src/main/scala/com/twitter/diffy/ApiController.scala
+++ b/src/main/scala/com/twitter/diffy/ApiController.scala
@@ -33,7 +33,7 @@ class ApiController @Inject()(
     JoinedEndpoint: JoinedEndpoint,
     includeWeights: Boolean,
     excludeNoise: Boolean
-  ) =
+  ) : Map[String, Map[String, Any]] =
     Map(
       "endpoint" -> Renderer.endpoint(JoinedEndpoint.endpoint),
       "fields" ->
diff --git a/src/main/scala/com/twitter/diffy/proxy/ClientService.scala b/src/main/scala/com/twitter/diffy/proxy/ClientService.scala
index 6d2bca675..a06ce63f3 100644
--- a/src/main/scala/com/twitter/diffy/proxy/ClientService.scala
+++ b/src/main/scala/com/twitter/diffy/proxy/ClientService.scala
@@ -1,7 +1,7 @@
 package com.twitter.diffy.proxy
 
-import com.twitter.finagle.{Addr, Name, Resolver, Service}
 import com.twitter.finagle.thrift.ThriftClientRequest
+import com.twitter.finagle.{Addr, Name, Service}
 import com.twitter.util.{Time, Var}
 import org.jboss.netty.handler.codec.http.{HttpRequest, HttpResponse}
 
@@ -42,7 +42,7 @@ case class ThriftService(
     }
   }
 
-  private[this] def sizeChange(size: Int) {
+  private[this] def sizeChange(size: Int) : Unit = {
     changeCount += 1
     if (changeCount > 1) {
       changedAt = Some(Time.now)
diff --git a/src/main/scala/com/twitter/diffy/proxy/DifferenceProxy.scala b/src/main/scala/com/twitter/diffy/proxy/DifferenceProxy.scala
index b63c17cc5..3b1d5370f 100644
--- a/src/main/scala/com/twitter/diffy/proxy/DifferenceProxy.scala
+++ b/src/main/scala/com/twitter/diffy/proxy/DifferenceProxy.scala
@@ -25,12 +25,15 @@ object DifferenceProxyModule extends TwitterModule {
 }
 
 object DifferenceProxy {
+  val AllLabels: Seq[String] = Seq("primary", "secondary", "candidate")
+
   object NoResponseException extends Exception("No responses provided by diffy")
   val NoResponseExceptionFuture = Future.exception(NoResponseException)
   val log = Logger(classOf[DifferenceProxy])
 }
 
 trait DifferenceProxy {
+
   import DifferenceProxy._
 
   type Req
diff --git a/src/main/scala/com/twitter/diffy/proxy/HttpDifferenceProxy.scala b/src/main/scala/com/twitter/diffy/proxy/HttpDifferenceProxy.scala
index c5d4fdd7f..1505f3e7a 100644
--- a/src/main/scala/com/twitter/diffy/proxy/HttpDifferenceProxy.scala
+++ b/src/main/scala/com/twitter/diffy/proxy/HttpDifferenceProxy.scala
@@ -2,15 +2,17 @@ package com.twitter.diffy.proxy
 
 import java.net.SocketAddress
 
-import com.twitter.diffy.analysis.{DifferenceAnalyzer, JoinedDifferences, InMemoryDifferenceCollector}
+import com.twitter.diffy.analysis.{DifferenceAnalyzer, InMemoryDifferenceCollector, JoinedDifferences}
 import com.twitter.diffy.lifter.{HttpLifter, Message}
 import com.twitter.diffy.proxy.DifferenceProxy.NoResponseException
-import com.twitter.finagle.{Service, Http, Filter}
-import com.twitter.finagle.http.{Status, Response, Method, Request}
-import com.twitter.util.{Try, Future}
-import org.jboss.netty.handler.codec.http.{HttpResponse, HttpRequest}
+import com.twitter.diffy.proxy.http.filter.{CloneHttpRequestFilter, RefineHttpHeadersByLabelFilter}
+import com.twitter.finagle.http.{Method, Request, Response, Status}
+import com.twitter.finagle.{Filter, Http, Service}
+import com.twitter.util.{Future, Try}
+import org.jboss.netty.handler.codec.http.{HttpRequest, HttpResponse}
 
 object HttpDifferenceProxy {
+
   val okResponse = Future.value(Response(Status.Ok))
 
   val noResponseExceptionFilter =
@@ -34,8 +36,12 @@ trait HttpDifferenceProxy extends DifferenceProxy {
   override type Rep = HttpResponse
   override type Srv = HttpService
 
+
   override def serviceFactory(serverset: String, label: String) =
-    HttpService(Http.newClient(serverset, label).toService)
+    HttpService(
+      CloneHttpRequestFilter.apply.
+        andThen(RefineHttpHeadersByLabelFilter(label, DifferenceProxy.AllLabels)).
+        andThen(Http.newClient(serverset, label).toService))
 
   override lazy val server =
     Http.serve(
diff --git a/src/main/scala/com/twitter/diffy/proxy/http/filter/CloneHttpRequestFilter.scala b/src/main/scala/com/twitter/diffy/proxy/http/filter/CloneHttpRequestFilter.scala
new file mode 100644
index 000000000..7f7c0ad31
--- /dev/null
+++ b/src/main/scala/com/twitter/diffy/proxy/http/filter/CloneHttpRequestFilter.scala
@@ -0,0 +1,28 @@
+package com.twitter.diffy.proxy.http.filter
+
+import com.twitter.finagle.Filter
+import com.twitter.util.Future
+import org.jboss.netty.handler.codec.http.{DefaultHttpRequest, HttpHeaders, HttpRequest, HttpResponse}
+
+import scala.collection.JavaConverters._
+
+object CloneHttpRequestFilter {
+
+  type Req = HttpRequest
+  type Res = HttpResponse
+
+  private def mkCloneRequest(reqIn:Req, filter: (Req => Future[Res])):Future[Res] = {
+    def copyHeader(headers:HttpHeaders)(k: String, v:String) : Unit = { headers.add(k, v)}
+
+    val reqOut: DefaultHttpRequest = new DefaultHttpRequest(reqIn.getProtocolVersion, reqIn.getMethod, reqIn.getUri)
+    reqOut.setChunked(reqIn.isChunked)
+    reqOut.setContent(reqIn.getContent)
+
+    val headers = for {entry <- reqIn.headers().asScala} yield (entry.getKey, entry.getValue)
+    headers.foreach((copyHeader(reqOut.headers)_).tupled)
+
+    filter(reqOut)
+  }
+
+  def apply(): Filter[Req, Res, Req, Res] = Filter.mk(mkCloneRequest)
+}
diff --git a/src/main/scala/com/twitter/diffy/proxy/http/filter/HeaderEffect.scala b/src/main/scala/com/twitter/diffy/proxy/http/filter/HeaderEffect.scala
new file mode 100644
index 000000000..dfef107e7
--- /dev/null
+++ b/src/main/scala/com/twitter/diffy/proxy/http/filter/HeaderEffect.scala
@@ -0,0 +1,32 @@
+package com.twitter.diffy.proxy.http.filter
+
+import org.jboss.netty.handler.codec.http.HttpHeaders
+
+sealed trait HeaderEffect {
+  def apply(headers:HttpHeaders) : Unit
+}
+
+case class Rewrite(oldName:String, newName:String) extends HeaderEffect {
+  def apply(headers:HttpHeaders): Unit ={
+    val temp = headers.get(oldName)
+    headers.remove(oldName)
+    headers.set(newName, temp)
+  }
+}
+
+case class Remove( name:String) extends HeaderEffect {
+  def apply(headers:HttpHeaders): Unit = {
+    headers.remove(name)
+  }
+}
+
+object HeaderEffect {
+  def rewrite(oldName: String, newName:String): HeaderEffect = {
+    if (newName.isEmpty){
+      Remove(oldName)
+    } else {
+      Rewrite(oldName,newName)
+    }
+  }
+  def remove(oldName:String):HeaderEffect = Remove(oldName)
+}
diff --git a/src/main/scala/com/twitter/diffy/proxy/http/filter/RefineHttpHeadersByLabelFilter.scala b/src/main/scala/com/twitter/diffy/proxy/http/filter/RefineHttpHeadersByLabelFilter.scala
new file mode 100644
index 000000000..ddcf63405
--- /dev/null
+++ b/src/main/scala/com/twitter/diffy/proxy/http/filter/RefineHttpHeadersByLabelFilter.scala
@@ -0,0 +1,33 @@
+package com.twitter.diffy.proxy.http.filter
+
+import com.twitter.finagle.Filter
+import org.jboss.netty.handler.codec.http.{HttpRequest, HttpResponse}
+
+object RefineHttpHeadersByLabelFilter {
+
+  def rewriteRule(prefix:String):HeaderRule = {
+    val prefixLength = prefix.length
+    def go(name:String) = {
+      if (name.startsWith(prefix)) {
+        Some(HeaderEffect.rewrite(name, name.substring(prefixLength)))
+      } else None
+    }
+    go
+  }
+
+  def removeRule(prefix:String): HeaderRule = {
+    def go(name:String) = {
+      if (name.startsWith(prefix)) Some(HeaderEffect.remove(name))
+      else None
+    }
+    go
+  }
+
+  def apply(label: String, allLabels: Seq[String]): Filter[HttpRequest, HttpResponse, HttpRequest, HttpResponse] = {
+    val (inclusions, exclusion) = allLabels.partition(_.equalsIgnoreCase(label))
+    val rules =
+      inclusions.map(_ + "_").map(rewriteRule) ++
+        exclusion.map(_+ "_").map(removeRule)
+    RewriteHttpHeadersFilter(rules)
+  }
+}
diff --git a/src/main/scala/com/twitter/diffy/proxy/http/filter/RewriteHttpHeadersFilter.scala b/src/main/scala/com/twitter/diffy/proxy/http/filter/RewriteHttpHeadersFilter.scala
new file mode 100644
index 000000000..e8f6c6afe
--- /dev/null
+++ b/src/main/scala/com/twitter/diffy/proxy/http/filter/RewriteHttpHeadersFilter.scala
@@ -0,0 +1,29 @@
+package com.twitter.diffy.proxy.http.filter
+
+import com.twitter.finagle.Filter
+import com.twitter.util.Future
+import org.jboss.netty.handler.codec.http.{HttpHeaders, HttpResponse, HttpRequest}
+import scala.collection.JavaConverters._
+
+object RewriteHttpHeadersFilter {
+
+  def apply(rules:Seq[HeaderRule]) : Filter[HttpRequest, HttpResponse, HttpRequest, HttpResponse] = {
+    def filter(req: HttpRequest):HttpRequest = {
+      val headers: HttpHeaders = req.headers
+      val effects = for {
+        name <- headers.names().asScala
+        effect <- rules.flatMap(_(name)).headOption
+      } yield {
+        effect
+      }
+      effects.foreach(_ (headers))
+      req
+    }
+
+    def go(req: HttpRequest, next: (HttpRequest => Future[HttpResponse])): Future[HttpResponse] ={
+      next(filter(req))
+    }
+
+    Filter.mk(go)
+  }
+}
diff --git a/src/main/scala/com/twitter/diffy/proxy/http/filter/package.scala b/src/main/scala/com/twitter/diffy/proxy/http/filter/package.scala
new file mode 100644
index 000000000..ba1f0a4e3
--- /dev/null
+++ b/src/main/scala/com/twitter/diffy/proxy/http/filter/package.scala
@@ -0,0 +1,5 @@
+package com.twitter.diffy.proxy.http
+
+package object filter {
+  type HeaderRule = String => Option[HeaderEffect]
+}
diff --git a/src/test/scala/com/twitter/diffy/proxy/http/filter/CloneHttpRequestFilterSpec.scala b/src/test/scala/com/twitter/diffy/proxy/http/filter/CloneHttpRequestFilterSpec.scala
new file mode 100644
index 000000000..56eb525e0
--- /dev/null
+++ b/src/test/scala/com/twitter/diffy/proxy/http/filter/CloneHttpRequestFilterSpec.scala
@@ -0,0 +1,53 @@
+package com.twitter.diffy.proxy.http.filter;
+
+import com.twitter.diffy.ParentSpec
+import com.twitter.diffy.util.TwitterFutures
+import com.twitter.finagle.http.{Request, Response}
+import com.twitter.finagle.{Filter, Service}
+import com.twitter.util.Future
+import org.jboss.netty.handler.codec.http._
+import org.junit.runner.RunWith
+import org.scalatest.junit.JUnitRunner
+
+@RunWith(classOf[JUnitRunner])
+class CloneHttpRequestFilterSpec extends ParentSpec with TwitterFutures{
+  describe("CloneHttpRequestFilter"){
+    val subject: Filter[HttpRequest, HttpResponse, HttpRequest, HttpResponse] = CloneHttpRequestFilter.apply()
+
+    def mutateHeader(req: HttpRequest): Future[HttpResponse] = {
+      req.headers().add("mutation", "test")
+      Future.apply(Response(req))
+    }
+
+    val mutateHeaderService =subject.andThen(Service.mk(mutateHeader))
+
+
+    describe("recieving a request with no headers"){
+      def request:Request={ Request(HttpVersion.HTTP_1_1, HttpMethod.GET, "/") }
+
+      it("must prevent services which mutate the output request header from affecting the input request"){
+        val input: Request = request
+        whenReady(mutateHeaderService(input)){ _ => input.headers().names() mustNot contain("mutation") }
+      }
+      it("must preserve http method"){
+        val input = request
+        whenReady(mutateHeaderService(input)){ _ => input.method mustBe HttpMethod.GET }
+      }
+      it("must preserve http version"){
+        val input = request
+        whenReady(mutateHeaderService(input)){_ => input.version mustBe HttpVersion.HTTP_1_1 }
+      }
+
+      it("must preserve content buffer"){
+        val input = request
+        val expected = request.content.array()
+        whenReady(mutateHeaderService(input)){_ => input.content.array() mustBe expected }
+      }
+      it("must preserve chunkiness"){
+        val input = request
+        whenReady(mutateHeaderService(input)){_ => input.isChunked() mustBe false}
+
+      }
+    }
+  }
+}
diff --git a/src/test/scala/com/twitter/diffy/proxy/http/filter/RefineHttpHeadersByLabelSpec.scala b/src/test/scala/com/twitter/diffy/proxy/http/filter/RefineHttpHeadersByLabelSpec.scala
new file mode 100644
index 000000000..5cbfc65b3
--- /dev/null
+++ b/src/test/scala/com/twitter/diffy/proxy/http/filter/RefineHttpHeadersByLabelSpec.scala
@@ -0,0 +1,80 @@
+package com.twitter.diffy.proxy.http.filter
+
+import com.twitter.diffy.ParentSpec
+import com.twitter.diffy.util.TwitterFutures
+import com.twitter.finagle.http.{Request, Response}
+import com.twitter.finagle.{Filter, Service}
+import com.twitter.util.Future
+import org.jboss.netty.handler.codec.http.{HttpHeaders, HttpRequest, HttpResponse}
+import org.junit.runner.RunWith
+import org.scalatest.FunSpec
+import org.scalatest.junit.JUnitRunner
+
+import scala.collection.JavaConverters._
+
+trait HeaderTransformations extends ParentSpec with TwitterFutures {  this: FunSpec =>
+
+  def returnHeaders(req: HttpRequest): Future[HttpResponse] = {
+    val response: Response = Response(req)
+    response.headers().add(req.headers())
+    Future.apply(response)
+  }
+
+  def anEchoServiceForHeaders(subject: Filter[HttpRequest, HttpResponse, HttpRequest, HttpResponse],
+                              inputHeaders: Map[String,String],
+                              expectedHeaders: Map[String,String]): Unit ={
+    val service = subject.andThen(Service.mk(returnHeaders))
+
+    it ("must match headers"){
+      val req1: HttpRequest = Request("/")
+      val addHeader = (k:String, v:String) => req1.headers().add(k, v)
+      inputHeaders.foreach( addHeader.tupled )
+
+      def headersToMap(httpHeaders:HttpHeaders): Map[String,String] = {
+        httpHeaders.iterator().asScala.map( e=>(e.getKey,e.getValue )).toMap
+      }
+      whenReady(service(req1).map( _.headers ).map(headersToMap))( _ mustBe expectedHeaders )
+    }
+  }
+
+  def aFilterThatTargetsLabel(label:String, labelEx1:String, labelEx2:String) : Unit ={
+    describe(s"given a $label filter"){
+      val subject: Filter[HttpRequest, HttpResponse, HttpRequest, HttpResponse] =
+        RefineHttpHeadersByLabelFilter(label, List(label, labelEx1, labelEx2))
+
+      describe("given empty headers"){
+        it must behave like anEchoServiceForHeaders(subject, Map.empty, Map.empty)
+      }
+      describe("given a set of headers"){
+        val headers=Map(("A", "B"), ("C-c", "D-d"))
+        it must behave like anEchoServiceForHeaders(subject, headers, headers)
+      }
+      describe(s"given an exact $label header"){
+        it must behave like anEchoServiceForHeaders(subject, Map( (s"$label", "X")), Map((s"$label", "X")))
+      }
+      describe(s"given a $label prefixed header"){
+        it must behave like anEchoServiceForHeaders(subject, Map( (s"${label}_X", "X")), Map(("X", "X")))
+      }
+      describe(s"given a $label prefixed header with no suffix"){
+        it must behave like anEchoServiceForHeaders(subject, Map( (s"${label}_", "X")), Map.empty)
+      }
+
+      describe(s"given a $labelEx1 prefixed header"){
+        it must behave like anEchoServiceForHeaders(subject, Map( (s"${labelEx1}_X", "X")), Map.empty)
+      }
+      describe(s"given a $labelEx2 prefixed header"){
+        it must behave like anEchoServiceForHeaders(subject, Map( (s"${labelEx2}_Y", "Y")), Map.empty)
+      }
+
+    }
+  }
+
+}
+@RunWith(classOf[JUnitRunner])
+class RefineHttpHeadersByLabelSpec extends ParentSpec with TwitterFutures with HeaderTransformations {
+  describe("RefineHttpHeadersByLabelFilter"){
+    it must behave like aFilterThatTargetsLabel("primary", "candidate", "secondary")
+    it must behave like aFilterThatTargetsLabel("candidate", "primary", "secondary")
+    it must behave like aFilterThatTargetsLabel("secondary", "primary", "candidate")
+  }
+}
diff --git a/src/test/scala/com/twitter/diffy/util/TwitterFutures.scala b/src/test/scala/com/twitter/diffy/util/TwitterFutures.scala
new file mode 100644
index 000000000..cbb00d461
--- /dev/null
+++ b/src/test/scala/com/twitter/diffy/util/TwitterFutures.scala
@@ -0,0 +1,21 @@
+package com.twitter.diffy.util
+
+import com.twitter.util.{Return, Throw}
+import org.scalatest.concurrent.Futures
+
+trait TwitterFutures extends Futures {
+
+  import scala.language.implicitConversions
+
+  implicit def convertTwitterFuture[T](twitterFuture: com.twitter.util.Future[T]): FutureConcept[T] =
+    new FutureConcept[T] {
+      override def eitherValue: Option[Either[Throwable, T]] = {
+        twitterFuture.poll.map {
+          case Return(o) => Right(o)
+          case Throw(e)  => Left(e)
+        }
+      }
+      override def isCanceled: Boolean = false
+      override def isExpired: Boolean = false
+    }
+}