diff --git a/library/Icinga/Web/Controller/ActionController.php b/library/Icinga/Web/Controller/ActionController.php
index d4fcb7a8d..df6dce1a1 100644
--- a/library/Icinga/Web/Controller/ActionController.php
+++ b/library/Icinga/Web/Controller/ActionController.php
@@ -122,7 +122,6 @@ class ActionController extends Zend_Controller_Action
             ->_setInvokeArgs($invokeArgs);
         $this->_helper = new Zend_Controller_Action_HelperBroker($this);
 
-        $this->handlerBrowserWindows();
         $moduleName = $this->getModuleName();
         $this->view->defaultTitle = static::DEFAULT_TITLE;
         $this->view->translationDomain = $moduleName !== 'default' ? $moduleName : 'icinga';
@@ -229,25 +228,12 @@ class ActionController extends Zend_Controller_Action
     public function Window()
     {
         if ($this->window === null) {
-            $this->window = new Window(
-                $this->_request->getHeader('X-Icinga-WindowId', Window::UNDEFINED)
-            );
+            $this->window = Window::getInstance();
         }
+
         return $this->window;
     }
 
-    protected function handlerBrowserWindows()
-    {
-        if ($this->isXhr()) {
-            $id = $this->_request->getHeader('X-Icinga-WindowId', null);
-
-            if ($id === Window::UNDEFINED) {
-                $this->window = new Window($id);
-                $this->_response->setHeader('X-Icinga-WindowId', Window::generateId());
-            }
-        }
-    }
-
     protected function reloadCss()
     {
         $this->reloadCss = true;
diff --git a/library/Icinga/Web/Request.php b/library/Icinga/Web/Request.php
index 4a3246d5f..064ce6335 100644
--- a/library/Icinga/Web/Request.php
+++ b/library/Icinga/Web/Request.php
@@ -114,12 +114,7 @@ class Request extends Zend_Controller_Request_Http
      */
     public function protectId($id)
     {
-        if (! isset($this->uniqueId)) {
-            $windowId = $this->getHeader('X-Icinga-WindowId');
-            $this->uniqueId = empty($windowId) ? Window::generateId() : $windowId;
-        }
-
-        return $id . '-' . $this->uniqueId;
+        return $id . '-' . Window::getInstance()->getContainerId();
     }
 
     public function getPost($key = null, $default = null)
diff --git a/library/Icinga/Web/Response.php b/library/Icinga/Web/Response.php
index 88d9e2302..d869f8f09 100644
--- a/library/Icinga/Web/Response.php
+++ b/library/Icinga/Web/Response.php
@@ -61,6 +61,13 @@ class Response extends Zend_Controller_Response_Http
      */
     protected $rerenderLayout = false;
 
+    /**
+     * Whether to send the current window ID to the client
+     *
+     * @var bool
+     */
+    protected $overrideWindowId = false;
+
     /**
      * Get the auto-refresh interval
      *
@@ -237,6 +244,29 @@ class Response extends Zend_Controller_Response_Http
         return $this;
     }
 
+    /**
+     * Get whether to send the current window ID to the client
+     *
+     * @return bool
+     */
+    public function getOverrideWindowId()
+    {
+        return $this->overrideWindowId;
+    }
+
+    /**
+     * Set whether to send the current window ID to the client
+     *
+     * @param bool $overrideWindowId
+     *
+     * @return $this
+     */
+    public function setOverrideWindowId($overrideWindowId = true)
+    {
+        $this->overrideWindowId = $overrideWindowId;
+        return $this;
+    }
+
     /**
      * Entry point for HTTP responses in JSON format
      *
@@ -262,6 +292,9 @@ class Response extends Zend_Controller_Response_Http
                     $this->setHeader('X-Icinga-Rerender-Layout', 'yes', true);
                 }
             }
+            if ($this->getOverrideWindowId()) {
+                $this->setHeader('X-Icinga-WindowId', Window::getInstance()->getId(), true);
+            }
             if ($this->getRerenderLayout()) {
                 $this->setHeader('X-Icinga-Container', 'layout', true);
             }
diff --git a/library/Icinga/Web/Window.php b/library/Icinga/Web/Window.php
index e6f1a05e1..158483a06 100644
--- a/library/Icinga/Web/Window.php
+++ b/library/Icinga/Web/Window.php
@@ -3,29 +3,63 @@
 
 namespace Icinga\Web;
 
-use Icinga\Web\Session;
+use Icinga\Application\Icinga;
+use Icinga\Web\Session\SessionNamespace;
 
 class Window
 {
     const UNDEFINED = 'undefined';
 
+    /** @var Window */
+    protected static $window;
+
+    /** @var string */
     protected $id;
 
+    /** @var string */
+    protected $containerId;
+
     public function __construct($id)
     {
-        $this->id = $id;
+        $parts = explode('_', $id, 2);
+        if (isset($parts[1])) {
+            $this->id = $parts[0];
+            $this->containerId = $id;
+        } else {
+            $this->id = $id;
+        }
     }
 
+    /**
+     * Get whether the window's ID is undefined
+     *
+     * @return bool
+     */
     public function isUndefined()
     {
         return $this->id === self::UNDEFINED;
     }
 
+    /**
+     * Get the window's ID
+     *
+     * @return string
+     */
     public function getId()
     {
         return $this->id;
     }
 
+    /**
+     * Get the container's ID
+     *
+     * @return string
+     */
+    public function getContainerId()
+    {
+        return $this->containerId ?: $this->id;
+    }
+
     /**
      * Return a window-aware session by using the given prefix
      *
@@ -38,29 +72,54 @@ class Window
     {
         $session = Session::getSession();
 
-        $identifier = $prefix . '_' . $this->id;
+        $identifier = $prefix . '_' . $this->getId();
         if ($reset && $session->hasNamespace($identifier)) {
             $session->removeNamespace($identifier);
         }
+
         $namespace = $session->getNamespace($identifier);
         $nsUndef = $prefix . '_' . self::UNDEFINED;
 
-        if (!$reset && $this->id !== self::UNDEFINED && $session->hasNamespace($nsUndef)) {
-            // We do not have any window-id on the very first request. Now we add
+        if (! $reset && ! $this->isUndefined() && $session->hasNamespace($nsUndef)) {
+            // We may not have any window-id on the very first request. Now we add
             // all values from the namespace, that has been created in this case,
             // to the new one and remove it afterwards.
             foreach ($session->getNamespace($nsUndef) as $name => $value) {
                 $namespace->set($name, $value);
             }
+
             $session->removeNamespace($nsUndef);
         }
 
         return $namespace;
     }
 
+    /**
+     * Generate a random string
+     *
+     * @return string
+     */
     public static function generateId()
     {
         $letters = 'abcefghijklmnopqrstuvwxyz';
         return substr(str_shuffle($letters), 0, 12);
     }
+
+    /**
+     * @return Window
+     */
+    public static function getInstance()
+    {
+        if (! isset(static::$window)) {
+            $id = Icinga::app()->getRequest()->getHeader('X-Icinga-WindowId');
+            if (empty($id) || $id === static::UNDEFINED) {
+                Icinga::app()->getResponse()->setOverrideWindowId();
+                $id = static::generateId();
+            }
+
+            static::$window = new Window($id);
+        }
+
+        return static::$window;
+    }
 }