diff --git a/core/lib/Drupal/Core/Ajax/AjaxSubscriber.php b/core/lib/Drupal/Core/Ajax/AjaxSubscriber.php
new file mode 100644
index 0000000..7d2ed7b
--- /dev/null
+++ b/core/lib/Drupal/Core/Ajax/AjaxSubscriber.php
@@ -0,0 +1,41 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Ajax\AjaxSubscriber.
+ */
+
+namespace Drupal\Core\Ajax;
+
+use Symfony\Component\HttpKernel\KernelEvents;
+use Symfony\Component\HttpKernel\Event\GetResponseEvent;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * Subscribes to the kernel request event to add the Ajax media type.
+ *
+ * @param \Symfont\Component\HttpKernel\Event\GetResponseEvent $event
+ *   The event to process.
+ */
+class AjaxSubscriber implements EventSubscriberInterface {
+
+  /**
+   * Registers Ajax formats with the Request class.
+   */
+  public function onKernelRequest(GetResponseEvent $event) {
+    $request = $event->getRequest();
+    $request->setFormat('ajax', 'application/vnd.drupal-ajax');
+  }
+
+  /**
+   * Registers the methods in this class that should be listeners.
+   *
+   * @return array
+   *   An array of event listener definitions.
+   */
+  static function getSubscribedEvents(){
+    $events[KernelEvents::REQUEST][] = array('onKernelRequest', 50);
+    return $events;
+  }
+
+}
\ No newline at end of file
diff --git a/core/lib/Drupal/Core/AjaxController.php b/core/lib/Drupal/Core/AjaxController.php
new file mode 100644
index 0000000..31259fb
--- /dev/null
+++ b/core/lib/Drupal/Core/AjaxController.php
@@ -0,0 +1,79 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\AjaxController.
+ */
+
+namespace Drupal\Core;
+
+use Drupal\Core\Ajax\AjaxResponse;
+use Drupal\Core\Ajax\InsertCommand;
+use Drupal\Core\Ajax\PrependCommand;
+use Symfony\Component\DependencyInjection\ContainerAware;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Default controller for ajax requests.
+ */
+class AjaxController extends ContainerAware {
+
+  /**
+   * Controller method for AJAX content.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request object.
+   * @param callable $_content
+   *   The callable that returns the content of the ajax response.
+   *
+   * @return \Symfony\Component\HttpFoundation\Response
+   *   A response object.
+   */
+  public function content(Request $request, $_content) {
+
+    // @todo When we have a Generator, we can replace the forward() call with
+    // a render() call, which would handle ESI and hInclude as well.  That will
+    // require an _internal route.  For examples, see:
+    // https://github.com/symfony/symfony/blob/master/src/Symfony/Bundle/FrameworkBundle/Resources/config/routing/internal.xml
+    // https://github.com/symfony/symfony/blob/master/src/Symfony/Bundle/FrameworkBundle/Controller/InternalController.php
+    $attributes = clone $request->attributes;
+    $controller = $_content;
+
+    // We need to clean up the derived information and such so that the
+    // subrequest can be processed properly without leaking data through.
+    $attributes->remove('system_path');
+    $attributes->remove('_content');
+    $attributes->remove('_legacy');
+
+    // Remove the accept header so the subrequest does not end up back in this
+    // controller.
+    $request->headers->remove('accept');
+
+    $response = $this->container->get('http_kernel')->forward($controller, $attributes->all(), $request->query->all());
+    // For successful (HTTP status 200) responses.
+    if ($response->isOk()) {
+      // If there is already an AjaxResponse, then return it without
+      // manipulation.
+      if (!($response instanceof AjaxResponse)) {
+        // Pull the content out of the response.
+        $content = $response->getContent();
+        // A page callback could return a render array or a string.
+        $html = is_string($content) ? $content : drupal_render($content);
+        $response = new AjaxResponse();
+        // The selector for the insert command is NULL as the new content will
+        // replace the element making the ajax call. The default 'replaceWith'
+        // behavior can be changed with #ajax['method'].
+        $response->addCommand(new InsertCommand(NULL, $html));
+        $status_messages = theme('status_messages');
+        if (!empty($status_messages)) {
+          $response->addCommand(new PrependCommand(NULL, $status_messages));
+        }
+      }
+    }
+    return $response;
+  }
+}
+
+
diff --git a/core/lib/Drupal/Core/ContentNegotiation.php b/core/lib/Drupal/Core/ContentNegotiation.php
index 1695de9..5dfefc2 100644
--- a/core/lib/Drupal/Core/ContentNegotiation.php
+++ b/core/lib/Drupal/Core/ContentNegotiation.php
@@ -36,16 +36,11 @@ public function getContentType(Request $request) {
       return 'iframeupload';
     }
 
-    // AJAX calls need to be run through ajax rendering functions
-    elseif ($request->isXmlHttpRequest()) {
-      return 'ajax';
-    }
-
     // Check all formats, it HTML is found return it.
     $first_found_format = FALSE;
     foreach ($request->getAcceptableContentTypes() as $mime_type) {
       $format = $request->getFormat($mime_type);
-      if ($format === 'html') {
+      if ($format === 'html' || $format === 'ajax') {
         return $format;
       }
       if (!is_null($format) && !$first_found_format) {
diff --git a/core/lib/Drupal/Core/CoreBundle.php b/core/lib/Drupal/Core/CoreBundle.php
index 88b25bf..b59be66 100644
--- a/core/lib/Drupal/Core/CoreBundle.php
+++ b/core/lib/Drupal/Core/CoreBundle.php
@@ -304,7 +304,10 @@ public function build(ContainerBuilder $container) {
     $container->register('plugin.manager.condition', 'Drupal\Core\Condition\ConditionManager');
 
     $container->register('kernel_destruct_subscriber', 'Drupal\Core\EventSubscriber\KernelDestructionSubscriber')
-      ->addMethodCall('setContainer', array(new Reference('service_container')))
+      ->addMethodCall('setContainer', array(new Reference('service_container')));
+
+    // Register Ajax event subscriber.
+    $container->register('ajax.subscriber', 'Drupal\Core\Ajax\AjaxSubscriber')
       ->addTag('event_subscriber');
 
     $container->addCompilerPass(new RegisterMatchersPass());
diff --git a/core/lib/Drupal/Core/EventSubscriber/RouteProcessorSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/RouteProcessorSubscriber.php
index 0061530..58387b2 100644
--- a/core/lib/Drupal/Core/EventSubscriber/RouteProcessorSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/RouteProcessorSubscriber.php
@@ -37,8 +37,11 @@ public function __construct(ContentNegotiation $negotiation) {
    */
   public function onRequestSetController(GetResponseEvent $event) {
     $request = $event->getRequest();
-
-    if (!$request->attributes->has('_controller') && $this->negotiation->getContentType($request) === 'html') {
+    if (!$request->attributes->has('_content') && $this->negotiation->getContentType($request) == 'ajax') {
+      $request->attributes->set('_content', $request->attributes->get('_controller'));
+      $request->attributes->set('_controller', '\Drupal\Core\AjaxController::content');
+    }
+    elseif (!$request->attributes->has('_controller') && $this->negotiation->getContentType($request) === 'html') {
       $request->attributes->set('_controller', '\Drupal\Core\HtmlPageController::content');
     }
   }
@@ -55,4 +58,5 @@ static function getSubscribedEvents() {
 
     return $events;
   }
+
 }
diff --git a/core/misc/ajax.js b/core/misc/ajax.js
index 53351ad..7ca4463 100644
--- a/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -208,6 +208,9 @@ Drupal.ajax = function (base, element, element_settings) {
       }
     },
     dataType: 'json',
+    accepts: {
+      json: 'application/vnd.drupal-ajax'
+    },
     type: 'POST'
   };