core/modules/big_pipe/big_pipe.module              | 12 ++++-----
 .../HtmlResponseBigPipeSubscriber.php              | 29 ++++++++++++++--------
 core/modules/big_pipe/src/Render/BigPipe.php       | 27 ++++++++------------
 3 files changed, 34 insertions(+), 34 deletions(-)

diff --git a/core/modules/big_pipe/big_pipe.module b/core/modules/big_pipe/big_pipe.module
index f25b2a3..f76c5f5 100644
--- a/core/modules/big_pipe/big_pipe.module
+++ b/core/modules/big_pipe/big_pipe.module
@@ -54,11 +54,11 @@ function big_pipe_form_user_login_form_alter(&$form, FormStateInterface $form_st
  * After build handler for user_login_form().
  */
 function big_pipe_form_after_build($form, FormStateInterface $form_state) {
-  // This is tricky: We want Form API to default big_pipe_has_js to 1 in
-  // case it gets not send. We also want to set the value of the HTML element
-  // to 0 and add <noscript> tags.
-  // So in case the user has JS disabled, the noscript is parsed and
-  // big_pipe_has_js is send with '0', else it is not send at all and FAPI falls
+  // This is tricky: we want Form API to 'default big_pipe_has_js' to '1' in
+  // case it is not sent. We also want to set the value of the HTML element
+  // to '0' and wrap it in a <noscript> tag.
+  // So in case the user has JavaScript disabled, the <noscript> is parsed and
+  // 'big_pipe_has_js' is sent with '0', else it is not sent and Form API falls
   // back to the default value, which is '1'.
   $form['big_pipe_has_js']['#value'] = '0';
   $form['big_pipe_has_js']['#prefix'] = Markup::create('<noscript>');
@@ -69,7 +69,7 @@ function big_pipe_form_after_build($form, FormStateInterface $form_state) {
 /**
  * Form submission handler for user_login_form().
  *
- * Store if the user has javascript available in the SESSION.
+ * Remember whether the user has JavaScript enabled in this session.
  */
 function big_pipe_form_set_js_check($form, FormStateInterface $form_state) {
   $current_user = \Drupal::currentUser();
diff --git a/core/modules/big_pipe/src/EventSubscriber/HtmlResponseBigPipeSubscriber.php b/core/modules/big_pipe/src/EventSubscriber/HtmlResponseBigPipeSubscriber.php
index 1abf0b9..ee2d120 100644
--- a/core/modules/big_pipe/src/EventSubscriber/HtmlResponseBigPipeSubscriber.php
+++ b/core/modules/big_pipe/src/EventSubscriber/HtmlResponseBigPipeSubscriber.php
@@ -15,7 +15,7 @@
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
 /**
- * HTML response subscriber to replace the Response with a BigPipe Response.
+ * Response subscriber to replace the HtmlResponse with a BigPipeResponse.
  */
 class HtmlResponseBigPipeSubscriber implements EventSubscriberInterface {
 
@@ -37,7 +37,7 @@ public function __construct(BigPipeInterface $big_pipe) {
   }
 
   /**
-   * Processes placeholders for HTML responses.
+   * Adds markers to the response necessary for the BigPipe render strategy.
    *
    * @param \Symfony\Component\HttpKernel\Event\FilterResponseEvent $event
    *   The event to process.
@@ -58,17 +58,16 @@ public function onRespondEarly(FilterResponseEvent $event) {
       $scripts_bottom_placeholder = $attachments['html_response_attachment_placeholders']['scripts_bottom'];
       $content = $response->getContent();
 
-      // Remove any existing markers.
-      $content = str_replace('<drupal-big-pipe-scripts-bottom-wrapper>', '', $content);
-
-      // Wrap scripts_bottom placeholder with a marker.
-      $content = str_replace($scripts_bottom_placeholder, '<drupal-big-pipe-scripts-bottom-wrapper>' . $scripts_bottom_placeholder . '<drupal-big-pipe-scripts-bottom-wrapper>', $content);
+      // Wrap the scripts_bottom placeholder with a marker before and after,
+      // because \Drupal\big_pipe\Render\BigPipe needs to be able to parse out
+      // that placeholder for the "HalfPipe" render strategy.
+      $content = str_replace($scripts_bottom_placeholder, '<drupal-big-pipe-scripts-bottom-marker>' . $scripts_bottom_placeholder . '<drupal-big-pipe-scripts-bottom-marker>', $content);
       $response->setContent($content);
     }
   }
 
   /**
-   * Processes placeholders for HTML responses.
+   * Transforms a HtmlResponse to a BigPipeResponse.
    *
    * @param \Symfony\Component\HttpKernel\Event\FilterResponseEvent $event
    *   The event to process.
@@ -87,7 +86,7 @@ public function onRespond(FilterResponseEvent $event) {
     if (empty($attachments['big_pipe_placeholders'])) {
       // Remove our marker again.
       $content = $response->getContent();
-      $content = str_replace('<drupal-big-pipe-scripts-bottom-wrapper>', '', $content);
+      $content = str_replace('<drupal-big-pipe-scripts-bottom-marker>', '', $content);
       $response->setContent($content);
       return;
     }
@@ -101,6 +100,9 @@ public function onRespond(FilterResponseEvent $event) {
     $big_pipe_response->setContent($response->getContent());
     $big_pipe_response->addCacheableDependency($response->getCacheableMetadata());
 
+    // Add header to support streaming on NGINX + php-fpm (nginx >= 1.5.6).
+    $big_pipe_response->headers->set('X-Accel-Buffering', 'no');
+
     // Inject the placeholders and service into the response.
     $big_pipe_response->setBigPipePlaceholders($attachments['big_pipe_placeholders']);
     $big_pipe_response->setBigPipeService($this->bigPipe);
@@ -117,10 +119,15 @@ public function onRespond(FilterResponseEvent $event) {
    * {@inheritdoc}
    */
   public static function getSubscribedEvents() {
-    // Run after placeholder strategies.
+    // Run after HtmlResponsePlaceholderStrategySubscriber (priority 5), i.e.
+    // after BigPipeStrategy has been applied, but before normal (priority 0)
+    // response subscribers have been applied, because by then it'll be too late
+    // to transform it into a BigPipeResponse.
     $events[KernelEvents::RESPONSE][] = ['onRespondEarly', 3];
-    // Run as pretty much last subscriber.
+
+    // Run as the last possible subscriber.
     $events[KernelEvents::RESPONSE][] = ['onRespond', -10000];
+
     return $events;
   }
 
diff --git a/core/modules/big_pipe/src/Render/BigPipe.php b/core/modules/big_pipe/src/Render/BigPipe.php
index 78c758c..2fd58e3 100644
--- a/core/modules/big_pipe/src/Render/BigPipe.php
+++ b/core/modules/big_pipe/src/Render/BigPipe.php
@@ -73,27 +73,20 @@ public function __construct(RendererInterface $renderer, AttachmentsResponseProc
    * {@inheritdoc}
    */
   public function sendContent($content, $attachments, array $placeholders) {
-    // Split scripts_bottom section out.
-    $t = explode('<drupal-big-pipe-scripts-bottom-wrapper>', $content, 3);
-    assert('count($t) == 3', 'There are exactly three segments.');
+    // Extract the scripts_bottom markup; the HalfPipe render strategy needs to
+    // be able to update it.
+    $t = explode('<drupal-big-pipe-scripts-bottom-marker>', $content, 3);
+    assert('count($t) == 3', 'There is content before and after scripts_bottom.');
     $scripts_bottom = $t[1];
     unset($t[1]);
     $content = implode('', $t);
 
     // Split it up in various chunks.
-    $split = '<!-- X-RENDER-CACHE-BIG-PIPE-SPLIT -->';
-    if (strpos($content, $split) === FALSE) {
-      $split = '</body>';
-    }
-    $page_parts = explode($split, $content);
-
+    $page_parts = explode('</body>', $content);
     if (count($page_parts) !== 2) {
       throw new \LogicException("You need to have only one body or one <!-- X-RENDER-CACHE-BIG-PIPE-SPLIT --> tag in your html.html.twig template file.");
     }
 
-    // Support streaming on NGINX + php-fpm (nginx >= 1.5.6).
-    header('X-Accel-Buffering: no');
-
     $half_pipe_placeholders = [];
 
     if (empty($_SESSION['big_pipe_has_js'])) {
@@ -125,7 +118,8 @@ public function sendContent($content, $attachments, array $placeholders) {
           print $this->renderer->renderRoot($variables_extra['scripts']);
         }
 
-        // Update the bottom attachments with no ajax page state.
+        // Now that the placeholders have been rendered using the HalfPipe
+        // render strategy, recalculate the scripts_bottom markup.
         $variables = $this->htmlResponseAttachmentsProcessor->processAssetLibraries($all_attachments, [ 'scripts_bottom' => TRUE ]);
         $scripts_bottom = $this->renderer->renderRoot($variables['scripts_bottom']);
       }
@@ -135,13 +129,13 @@ public function sendContent($content, $attachments, array $placeholders) {
       ob_end_flush();
     }
 
-    // Print the bottom attachments.
+    // Send the JavaScript at the bottom of the page.
     print $scripts_bottom;
 
     flush();
 
     if (empty($placeholders)) {
-      print $split;
+      print '</body>';
       print $page_parts[1];
       return;
     }
@@ -208,8 +202,7 @@ public function sendContent($content, $attachments, array $placeholders) {
     // Send the stop signal.
     print '    <script type="application/json" data-big-pipe-stop="1"></script>' . "\n";
     print '  </div>' . "\n";
-
-    print $split;
+    print '</body>';
     print $page_parts[1];
 
     return $this;