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+<!DOCTYPE html>
+<title>
+  Single-line column flex fragmentation: column balancing with forced break
+  w/ vertical writing-mode.
+</title>
+<link rel="help" href="https://drafts.csswg.org/css-flexbox-1/#pagination">
+<link rel="match" href="../../reference/ref-filled-green-100px-square.xht">
+<style>
+  #flex {
+    display: flex;
+    flex-direction: column;
+    background: green;
+    block-size: 100px;
+  }
+  #flex > div {
+    inline-size: 25px;
+    background: green;
+    flex: none;
+  }
+</style>
+<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
+<div style="writing-mode: vertical-rl;">
+  <div style="inline-size: 100px; block-size: 100px; background: red;">
+    <div style="inline-size: 100px; columns: 4; column-gap: 0; position: relative;">
+      <div id="flex">
+        <div style="block-size: 5px;"></div>
+        <div style="block-size: 10px; break-before: column;"></div>
+        <div style="block-size: 5px;">
+          <div style="block-size: 90px; inline-size: 25px; background: green;"></div>
+        </div>
+        <div style="block-size: 85px;"></div>
+        <div style="block-size: 5px;"></div>
+        <div style="block-size: 10px; break-before: column;"></div>
+        <div style="block-size: 5px;">
+          <div style="block-size: 90px; inline-size: 25px; background: green;"></div>
+        </div>
+      </div>
+      <div style="position: absolute; right: 5px; top: 50px; block-size: 95px; inline-size: 25px; background: green;"></div>
+    </div>
+  </div>
+</div>