From 6b0c951a44623e3889e4dddcc6d945586b8679a1 Mon Sep 17 00:00:00 2001
From: brandonkelly <brandon@pixelandtonic.com>
Date: Mon, 18 Nov 2024 12:14:01 -0800
Subject: [PATCH] Backport #16124

---
 CHANGELOG.md                | 1 +
 src/services/Structures.php | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d7e9acef03b..d1a75e3992f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - Fixed a JavaScript error that could occur on element edit pages. ([#16055](https://github.com/craftcms/cms/issues/16055))
 - Fixed a Twig deprecation error. ([#16107](https://github.com/craftcms/cms/issues/16107))
+- Fixed a bug where `craft\services\Structures::fillGapsInElements()` wasn’t working properly if the elements weren’t passed in hierarchical order. ([#16085](https://github.com/craftcms/cms/issues/16085))
 
 ## 4.13.0 - 2024-11-12
 
diff --git a/src/services/Structures.php b/src/services/Structures.php
index c537c178851..ddb75439861 100644
--- a/src/services/Structures.php
+++ b/src/services/Structures.php
@@ -155,6 +155,10 @@ public function fillGapsInElements(array &$elements): void
         $prevElement = null;
         $patchedElements = [];
 
+        // https://github.com/craftcms/cms/issues/16085
+        // don't assume that elements are in the top to bottom order
+        usort($elements, fn(ElementInterface $a, ElementInterface $b) => $a->lft <=> $b->lft);
+
         foreach ($elements as $i => $element) {
             // Did we just skip any elements?
             if (