From 81fc52124164eb798bd7be0f27e9253f2597e48c Mon Sep 17 00:00:00 2001
From: atomiks <cc.glows@gmail.com>
Date: Fri, 5 Dec 2025 09:07:28 +1100
Subject: [PATCH] [popups] Fix mount transitions in Firefox

---
 packages/react/src/utils/useTransitionStatus.ts | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/packages/react/src/utils/useTransitionStatus.ts b/packages/react/src/utils/useTransitionStatus.ts
index 72ea5a22466..3fdee6cb739 100644
--- a/packages/react/src/utils/useTransitionStatus.ts
+++ b/packages/react/src/utils/useTransitionStatus.ts
@@ -1,6 +1,5 @@
 'use client';
 import * as React from 'react';
-import * as ReactDOM from 'react-dom';
 import { useIsoLayoutEffect } from '@base-ui-components/utils/useIsoLayoutEffect';
 import { AnimationFrame } from '@base-ui-components/utils/useAnimationFrame';
 
@@ -54,9 +53,9 @@ export function useTransitionStatus(
     }
 
     const frame = AnimationFrame.request(() => {
-      ReactDOM.flushSync(() => {
-        setTransitionStatus(undefined);
-      });
+      // Avoid `flushSync` here due to Firefox.
+      // See https://github.com/mui/base-ui/pull/3424
+      setTransitionStatus(undefined);
     });
 
     return () => {