From 7914b2d04f59fd3a31fdc5fd27ea4165eb7e3675 Mon Sep 17 00:00:00 2001
From: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>
Date: Mon, 29 Jun 2026 00:43:55 -0700
Subject: [PATCH] fix: guard inert feature detection against undefined
 HTMLElement.prototype

---
 .../src/overlays/ariaHideOutside.ts           |  5 +++-
 .../test/overlays/ariaHideOutside.test.js     | 26 +++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/packages/react-aria/src/overlays/ariaHideOutside.ts b/packages/react-aria/src/overlays/ariaHideOutside.ts
index fe2b0ca4670..c2270e7e059 100644
--- a/packages/react-aria/src/overlays/ariaHideOutside.ts
+++ b/packages/react-aria/src/overlays/ariaHideOutside.ts
@@ -16,7 +16,10 @@ import {getOwnerDocument, getOwnerWindow} from '../utils/domHelpers';
 import {nodeContains} from '../utils/shadowdom/DOMFunctions';
 import {shadowDOM} from 'react-stately/private/flags/flags';
 
-const supportsInert = typeof HTMLElement !== 'undefined' && 'inert' in HTMLElement.prototype;
+const supportsInert =
+  typeof HTMLElement !== 'undefined' &&
+  HTMLElement.prototype != null &&
+  'inert' in HTMLElement.prototype;
 
 function isAlwaysVisibleNode(node: HTMLElement | SVGElement): boolean {
   return node.dataset.liveAnnouncer === 'true' || node.dataset.reactAriaTopLayer !== undefined;
diff --git a/packages/react-aria/test/overlays/ariaHideOutside.test.js b/packages/react-aria/test/overlays/ariaHideOutside.test.js
index 7c9e343b5fd..689e1e2dc03 100644
--- a/packages/react-aria/test/overlays/ariaHideOutside.test.js
+++ b/packages/react-aria/test/overlays/ariaHideOutside.test.js
@@ -914,3 +914,29 @@ describe('ariaHideOutside with shadow DOM', function () {
     });
   });
 });
+
+describe('ariaHideOutside inert feature detection', function () {
+  let originalHTMLElement = global.HTMLElement;
+
+  afterEach(function () {
+    global.HTMLElement = originalHTMLElement;
+    jest.resetModules();
+  });
+
+  it('does not throw at import time when HTMLElement.prototype is undefined', function () {
+    // Simulate bundler/SSR environments where HTMLElement is defined but its prototype is not.
+    let FakeHTMLElement = function () {};
+    FakeHTMLElement.prototype = undefined;
+    global.HTMLElement = FakeHTMLElement;
+
+    jest.resetModules();
+    expect(() => require('../../src/overlays/ariaHideOutside')).not.toThrow();
+  });
+
+  it('does not throw at import time when HTMLElement is undefined (non-DOM SSR)', function () {
+    global.HTMLElement = undefined;
+
+    jest.resetModules();
+    expect(() => require('../../src/overlays/ariaHideOutside')).not.toThrow();
+  });
+});