diff --git a/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php b/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php
index 53b914b..d0a4ecd 100644
--- a/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php
+++ b/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php
@@ -223,9 +223,7 @@ public function renderResponse(array $main_content, Request $request, RouteMatch
             continue;
           }
 
-          // Ensure we don't render another placeholder.
-          $placeholder_elements['#cache_no_placeholder'] = TRUE;
-          $placeholder_markup = $this->renderer->render($placeholder_elements, TRUE);
+          $placeholder_markup = $this->renderer->renderPlaceholder($placeholder, $placeholder_elements, TRUE);
 
           if ($placeholder_markup == '') {
             continue;
diff --git a/core/lib/Drupal/Core/Render/Renderer.php b/core/lib/Drupal/Core/Render/Renderer.php
index a22fc6f..29911cf 100644
--- a/core/lib/Drupal/Core/Render/Renderer.php
+++ b/core/lib/Drupal/Core/Render/Renderer.php
@@ -134,6 +134,21 @@ public function renderPlain(&$elements) {
 
   /**
    * {@inheritdoc}
+   * @todo Need to fix the interface for that.
+   */
+  public function renderPlaceholder($placeholder, &$elements, $is_root_call = FALSE) {
+    if (isset($this->placeholderData[$placeholder])) {
+      // Replace $elements with the statically cached data.
+      $elements = $this->placeholderData[$placeholder];
+    }
+
+    $elements['#cache_no_placeholder'] = TRUE;
+    return $this->render($elements, $is_root_call);
+  }
+
+
+  /**
+   * {@inheritdoc}
    */
   public function render(&$elements, $is_root_call = FALSE) {
     // Since #pre_render, #post_render, #post_render_cache callbacks and theme
@@ -552,9 +567,7 @@ protected function processPlaceholders(array &$elements) {
     foreach ($elements['#cache']['placeholders'] as $placeholder => $placeholder_elements) {
       // @todo Move to static placeholdering strategy.
       if (isset($this->placeholderData[$placeholder])) {
-        $cached_element = $this->placeholderData[$placeholder];
-        $cached_element['#cache_no_placeholder'] = TRUE;
-        $markup = $this->doRender($cached_element);
+        $markup = $this->renderPlaceholder($placeholder, $placeholder_elements);
         $elements['#markup'] = str_replace('<div id="' . $placeholder . '"></div>', $markup, $elements['#markup']);
         unset($elements['#cache']['placeholders'][$placeholder]);
       }
@@ -563,8 +576,7 @@ protected function processPlaceholders(array &$elements) {
       global $process_remaining_placeholders;
 
       if (isset($process_remaining_placeholders)) {
-        $placeholder_elements['#cache_no_placeholder'] = TRUE;
-        $markup = $this->doRender($placeholder_elements);
+        $markup = $this->renderPlaceholder($placeholder, $placeholder_elements);
         $elements['#markup'] = str_replace('<div id="' . $placeholder . '"></div>', $markup, $elements['#markup']);
         unset($elements['#cache']['placeholders'][$placeholder]);
       }
@@ -639,7 +651,7 @@ protected function cacheGet(array $elements, $is_recursive = FALSE) {
     }
 
     // Do we need to create a placeholder?
-    if (!empty($cache_redirect['#cache_placeholder']) || (isset($elements['#cache']['max-age']) && $elements['#cache']['max-age'] == 0)) {
+    if (!empty($cache_redirect['#cache_placeholder']) || !empty($cached_element['#cache_placeholder']) || (isset($elements['#cache']['max-age']) && $elements['#cache']['max-age'] == 0)) {
       $elements['#cache_placeholder'] = TRUE;
     }
 
@@ -677,6 +689,7 @@ protected function checkPlaceholders(array $placeholders) {
         $cached_placeholders[$placeholder] = $this->placeholderData[$placeholder];
         continue;
       }
+      $elements['#cache_no_placeholder'] = TRUE;
       $cached_placeholders[$placeholder] = $this->cacheGet($elements);
     }
 
@@ -750,7 +763,6 @@ protected function cacheSet(array &$elements, array $pre_bubbling_elements) {
     $cid = $this->createCacheID($elements);
 
     $data = $this->getCacheableRenderArray($elements);
-
     $bin = isset($elements['#cache']['bin']) ? $elements['#cache']['bin'] : 'render';
     $expire = ($elements['#cache']['max-age'] === Cache::PERMANENT) ? Cache::PERMANENT : (int) $this->requestStack->getMasterRequest()->server->get('REQUEST_TIME') + $elements['#cache']['max-age'];
     $cache = $this->cacheFactory->get($bin);
@@ -762,6 +774,12 @@ protected function cacheSet(array &$elements, array $pre_bubbling_elements) {
     if (!isset($pre_bubbling_elements['#cache_no_placeholder']) && $pre_bubbling_cid && ($cid || isset($pre_bubbling_elements['#pre_render_cache']))) {
       // Check if we want to placeholder.
       if (!empty($elements['#cache_placeholder']) || (isset($elements['#cache']['max-age']) && $elements['#cache']['max-age'] == 0)) {
+        // Ensure bubbling works correctly by copying the render cache properties over.
+        $data = [
+          'rendered' => $data,
+          '#cache_placeholder' => TRUE,
+        ];
+        $data['#cache'] = $pre_bubbling_elements['#cache'];
         $elements = $this->createRenderCacheArrayPlaceholder($pre_bubbling_elements, $data);
 
         // Now update the #cache_redirect array or create it.
@@ -961,6 +979,10 @@ protected function cacheSet(array &$elements, array $pre_bubbling_elements) {
         $data['#cache']['contexts'] = $merged_cache_contexts;
       }
     }
+    // If there is a hint to use a placeholder, keep that in the cache entry.
+    if (!empty($pre_bubbling_elements['#cache_placeholder']) || !empty($elements['#cache_placeholder'])) {
+      $data['#cache_placeholder'] = TRUE;
+    }
     $cache->set($cid, $data, $expire, Cache::mergeTags($data['#cache']['tags'], ['rendered']));
   }
 
diff --git a/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php b/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
index 77c354a..7dba56c 100644
--- a/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
+++ b/core/modules/system/src/Plugin/Block/SystemBrandingBlock.php
@@ -193,6 +193,7 @@ public function build() {
     $build['site_slogan']['#debug'] = TRUE;
 */
     $build['site_slogan']['#cache']['contexts'] = ['user'];
+    $build['site_slogan']['#cache']['tags'] = ['site_branding_block_custom'];
 
 //    $build['site_slogan']['dynamic'] = [ '#markup' => '<div>It is: ' . time(NULL) . '</div>' ];
     $build['site_slogan']['dynamic'] = [ '#pre_render_cache' => [get_class($this) . '::buildDynamic' => []] ];
@@ -201,6 +202,20 @@ public function build() {
     // This is a stage, where a placeholder can be created.
     $build['site_slogan']['dynamic']['#cache']['keys'] = [ 'fabian', 'site-branding-dynamic' ];
 
+// Cacheable per route thing.
+    $build['site_slogan']['cacheable_per_route'] = [
+      '#pre_render' => [
+        [$this, 'buildCacheable'],
+      ],
+    ];
+    // @todo Setting the [route] here confuses the renderer.
+    $build['site_slogan']['cacheable_per_route']['#cache']['contexts'] = [ 'route' ];
+
+    // We don't want the route to bubble up: too dynamic.
+    //$build['site_slogan']['cacheable_per_route']['#cache_placeholder'] = TRUE;
+    $build['site_slogan']['cacheable_per_route']['#cache']['keys'] = [ 'fabian', 'site-branding-cacheable' ];
+    $build['site_slogan']['cacheable_per_route']['#cache']['tags'] = ['site_branding_cacheable_custom'];
+
     return $build;
   }
 
@@ -214,6 +229,14 @@ public static function buildDynamic($build, $context) {
     return $build;
   }
 
+  public function buildCacheable($build) {
+    $build['#markup'] = '<div>The current path is: ' . \Drupal::service('path.current')->getPath() . '</div>';
+    $build['#cache']['contexts'] = ['route'];
+    $build['#cache_placeholder'] = TRUE;
+    usleep(500*1000);
+    return $build;
+  }
+
   /**
    * {@inheritdoc}
    */