Admin notice jumps from above the H1 to below it when created - patch03052026.diff refresh

src/wp-includes/default-filters.php

@@ -702,6 +702,10 @@
 add_action( 'load-post-new.php', 'wp_set_up_cross_origin_isolation' );
 add_action( 'load-site-editor.php', 'wp_set_up_cross_origin_isolation' );
 add_action( 'load-widgets.php', 'wp_set_up_cross_origin_isolation' );
+
+// Move the admin notices below the heading tag via server-side processing.
+add_action( 'admin_init', 'wp_move_notice_after_heading' );
+
 // Nav menu.
 add_filter( 'nav_menu_item_id', '_nav_menu_item_id_use_once', 10, 2 );
 add_filter( 'nav_menu_css_class', 'wp_nav_menu_remove_menu_item_has_children_class', 10, 4 );

src/wp-includes/functions.php

@@ -9280,6 +9280,41 @@ function wp_fast_hash(
 	return '$generic$' . sodium_bin2base64( $hashed, SODIUM_BASE64_VARIANT_URLSAFE_NO_PADDING );
 }
 
+/**
+ * Moves the admin notices below the heading tag via server-side processing.
+ * This prevents the visual glitch caused by JavaScript processing in the original fix.
+ *
+ * @since 7.x.x
+ */
+function wp_move_notice_after_heading() {
+	ob_start(
+		function ( $html ) {
+			global $pagenow;
+			if ( ! class_exists( '\Dom\HTMLDocument' ) || empty( $html ) || ! is_string( $html ) || wp_doing_ajax() || ! is_user_logged_in() ) {
+				return $html;
+			}
+
+			if ( 'admin-post.php' === $pagenow || ( defined( 'WP_CLI' ) && WP_CLI ) ) {
+				return $html;
+			}
+
+			$dom = \Dom\HTMLDocument::createFromString( $html, LIBXML_NOERROR );
+			$headerEnd = $dom->querySelector( '.wrap :is( h1, h2 )' );
+
+			$notices = $dom->querySelectorAll( 'div:is( .updated, .error, .notice ):not( .inline, .below-h2 )' );
+			if ( $headerEnd && $notices->length > 0 ) {
+				foreach ( $notices as $notice ) {
+					$headerEnd->parentNode->insertBefore( $notice, $headerEnd->nextSibling ); // phpcs:ignore WordPress.NamingConventions.ValidVariableName.UsedPropertyNotSnakeCase -- DOM API property name, cannot be renamed.
+				}
+
+				return $dom->saveHTML();
+			}
+
+			return $html;
+		}
+	);
+}
+
 /**
  * Checks whether a plaintext message matches the hashed value. Used to verify values hashed via wp_fast_hash().
  *