diff -u b/core/modules/system/system.module b/core/modules/system/system.module
--- b/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -173,6 +173,14 @@
       'render element' => 'elements',
       'base hook' => 'block',
     ),
+    'block__system_local_actions_block' => [
+      'base hook' => 'block',
+      'template' => 'block--system-page-actions-block',
+    ],
+    'block__system_tabs_block' => [
+      'base hook' => 'block',
+      'template' => 'block--system-page-tabs-block',
+    ],
     'system_themes_page' => array(
       'variables' => array(
         'theme_groups' => array(),
diff -u b/core/themes/classy/templates/block/block--system-local-actions-block.html.twig b/core/themes/classy/templates/block/block--system-local-actions-block.html.twig
--- b/core/themes/classy/templates/block/block--system-local-actions-block.html.twig
+++ b/core/themes/classy/templates/block/block--system-local-actions-block.html.twig
@@ -2,13 +2,11 @@
 {#
 /**
  * @file
- * Default theme implementation for local actions.
+ * Theme override for local actions.
  *
  * Available variables:
  * - action_links: Actions local to the page, such as "Add menu" on the menu
  *   administration interface.
- *
- * @ingroup themeable
  */
 #}
 {% block content %}
diff -u b/core/themes/classy/templates/block/block--system-tabs-block.html.twig b/core/themes/classy/templates/block/block--system-tabs-block.html.twig
--- b/core/themes/classy/templates/block/block--system-tabs-block.html.twig
+++ b/core/themes/classy/templates/block/block--system-tabs-block.html.twig
@@ -4,15 +4,15 @@
  * @file
- * Default theme implementation for tabs.
+ * Theme override for tabs.
  *
  * Available variables:
  * - tabs: The tabs linking to any sub-pages beneath the current page (e.g., the
- *   view and edit tabs when displaying a node).
- *
- * @ingroup themeable
+ *   view and edit tabs when displaying a node).*
  */
 #}
 {% block content %}
-  <nav class="tabs" role="navigation" aria-label="{{ 'Tabs'|t }}">
-    {{ tabs }}
-  </nav>
+  {% if tabs %}
+    <nav class="tabs" role="navigation" aria-label="{{ 'Tabs'|t }}">
+      {{ tabs }}
+    </nav>
+  {% endif %}
 {% endblock %}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/system/templates/block--system-local-actions-block.html.twig
@@ -0,0 +1,14 @@
+{% extends "@block/block.html.twig" %}
+{#
+/**
+ * @file
+ * Theme override for local actions.
+ *
+ * Available variables:
+ * - action_links: Actions local to the page, such as "Add menu" on the menu
+ *   administration interface.
+ */
+#}
+{% block content %}
+  {{ action_links }}
+{% endblock %}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/system/templates/block--system-tabs-block.html.twig
@@ -0,0 +1,14 @@
+{% extends "@block/block.html.twig" %}
+{#
+/**
+ * @file
+ * Theme override for tabs.
+ *
+ * Available variables:
+ * - tabs: The tabs linking to any sub-pages beneath the current page (e.g., the
+ *   view and edit tabs when displaying a node).*
+ */
+#}
+{% block content %}
+  {{ tabs }}
+{% endblock %}