Chrome/Edge >=146 throws: TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
Author: hthoCreated Mar 20, 2026Updated Mar 25, 2026
LabelsTYPE: bug
What is your Scenario?
Our tests run on a (self-hosted) headless azure-pipeline agent. They started to fail when we updated the browsers to Chrome/Edge 146. I can't reproduce the problem locally. The problem appears for tests in our on-premise application - not for very basic pages. Hence I can't create a minimal working example, because I have no way to properly debug the app, when the error occurs.
What is the Current behavior?
About 90% of our tests fail on one of the first actions/assertions of the test.
The error message is:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34BTW: The stack trace is only available if I run chrome with the --disable-web-security flag.
What is the Expected behavior?
The tests should not fail because of the exception in Hammerhead. There should not be an exception like this in Hammerhead.
What is the public URL of the test page? (attach your complete example)
- There is none
- This is a complex on-premise application
- I cant create a minimal working example because the tests only fail in our pipeline, where I can't use a debugger.
What is your TestCafe test code?
import { Selector } from "testcafe";
fixture("Dummy")
.page(`http://localhost:16700/index.htm`)
.before(async() => {
// a simplification to report the bug
await new Promise<void>((resolve, reject) => {
setTimeout(resolve, 120_000);
});
})
.beforeEach(async(t) => {
// await t.debug();
await t.resizeWindow(1024, 768);
})
.afterEach(async(t) => {
// we need this later
console.log(await t.getBrowserConsoleMessages());
});
for (let i = 1; i <= 10; i++) {
test(`test (Attempt #${i})`, async(t) => {
await t.expect(Selector(`[pweb-name="NavigationCurrentView"]`).textContent).eql("0");
});
}Your complete configuration file
none
Your complete test report
> testcafe chrome:"azure-pipelines/PortableBrowsers/chrome/chrome-146-72/GoogleChromePortable.exe --disable-web-security" --headless ./Integrationstestprojekte/WebVisuPictures/dummy.tc.ts
Running tests in:
- Chrome 146.0.0.0 / Windows Server 2022
Dummy
{ log: [], info: [], warn: [], error: [] }
√ test (Attempt #1)
× test (Attempt #2)
1) - Error in fixture.beforeEach hook -
A JavaScript error occurred on "http://localhost:16700/index.htm".
Repeat test actions in the browser and check the console for errors.
Enable the “skipJsErrors” option to ignore JavaScript errors during test execution. Learn more: "https://testcafe.io/documentation/404038/recipes/debugging/skip-javascript-errors"
If the website only throws this error when you test it with TestCafe, please create a new issue at:
"https://github.com/DevExpress/testcafe/issues/new?template=bug-report.md".
JavaScript error details:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34
Browser: Chrome 146.0.0.0 / Windows Server 2022
8 | setTimeout(resolve, 120_000);
9 | });
10 | })
11 | .beforeEach(async(t) => {
12 | // await t.debug();
> 13 | await t.resizeWindow(1024, 768);
14 | })
15 | .afterEach(async(t) => {
16 | // we need this later
17 | console.log(await t.getBrowserConsoleMessages());
18 | });
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:13:11)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:8:71)
at __awaiter (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:4:12)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:11:25)
× test (Attempt #3)
1) - Error in fixture.beforeEach hook -
A JavaScript error occurred on "http://localhost:16700/index.htm".
Repeat test actions in the browser and check the console for errors.
Enable the “skipJsErrors” option to ignore JavaScript errors during test execution. Learn more: "https://testcafe.io/documentation/404038/recipes/debugging/skip-javascript-errors"
If the website only throws this error when you test it with TestCafe, please create a new issue at:
"https://github.com/DevExpress/testcafe/issues/new?template=bug-report.md".
JavaScript error details:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34
Browser: Chrome 146.0.0.0 / Windows Server 2022
8 | setTimeout(resolve, 120_000);
9 | });
10 | })
11 | .beforeEach(async(t) => {
12 | // await t.debug();
> 13 | await t.resizeWindow(1024, 768);
14 | })
15 | .afterEach(async(t) => {
16 | // we need this later
17 | console.log(await t.getBrowserConsoleMessages());
18 | });
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:13:11)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:8:71)
at __awaiter (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:4:12)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:11:25)
× test (Attempt #4)
1) - Error in fixture.beforeEach hook -
A JavaScript error occurred on "http://localhost:16700/index.htm".
Repeat test actions in the browser and check the console for errors.
Enable the “skipJsErrors” option to ignore JavaScript errors during test execution. Learn more: "https://testcafe.io/documentation/404038/recipes/debugging/skip-javascript-errors"
If the website only throws this error when you test it with TestCafe, please create a new issue at:
"https://github.com/DevExpress/testcafe/issues/new?template=bug-report.md".
JavaScript error details:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34
Browser: Chrome 146.0.0.0 / Windows Server 2022
8 | setTimeout(resolve, 120_000);
9 | });
10 | })
11 | .beforeEach(async(t) => {
12 | // await t.debug();
> 13 | await t.resizeWindow(1024, 768);
14 | })
15 | .afterEach(async(t) => {
16 | // we need this later
17 | console.log(await t.getBrowserConsoleMessages());
18 | });
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:13:11)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:8:71)
at __awaiter (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:4:12)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:11:25)
× test (Attempt #5)
1) - Error in fixture.beforeEach hook -
A JavaScript error occurred on "http://localhost:16700/index.htm".
Repeat test actions in the browser and check the console for errors.
Enable the “skipJsErrors” option to ignore JavaScript errors during test execution. Learn more: "https://testcafe.io/documentation/404038/recipes/debugging/skip-javascript-errors"
If the website only throws this error when you test it with TestCafe, please create a new issue at:
"https://github.com/DevExpress/testcafe/issues/new?template=bug-report.md".
JavaScript error details:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34
Browser: Chrome 146.0.0.0 / Windows Server 2022
8 | setTimeout(resolve, 120_000);
9 | });
10 | })
11 | .beforeEach(async(t) => {
12 | // await t.debug();
> 13 | await t.resizeWindow(1024, 768);
14 | })
15 | .afterEach(async(t) => {
16 | // we need this later
17 | console.log(await t.getBrowserConsoleMessages());
18 | });
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:13:11)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:8:71)
at __awaiter (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:4:12)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:11:25)
× test (Attempt #6)
1) - Error in fixture.beforeEach hook -
A JavaScript error occurred on "http://localhost:16700/index.htm".
Repeat test actions in the browser and check the console for errors.
Enable the “skipJsErrors” option to ignore JavaScript errors during test execution. Learn more: "https://testcafe.io/documentation/404038/recipes/debugging/skip-javascript-errors"
If the website only throws this error when you test it with TestCafe, please create a new issue at:
"https://github.com/DevExpress/testcafe/issues/new?template=bug-report.md".
JavaScript error details:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34
Browser: Chrome 146.0.0.0 / Windows Server 2022
8 | setTimeout(resolve, 120_000);
9 | });
10 | })
11 | .beforeEach(async(t) => {
12 | // await t.debug();
> 13 | await t.resizeWindow(1024, 768);
14 | })
15 | .afterEach(async(t) => {
16 | // we need this later
17 | console.log(await t.getBrowserConsoleMessages());
18 | });
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:13:11)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:8:71)
at __awaiter (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:4:12)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:11:25)
× test (Attempt #7)
1) - Error in fixture.beforeEach hook -
A JavaScript error occurred on "http://localhost:16700/index.htm".
Repeat test actions in the browser and check the console for errors.
Enable the “skipJsErrors” option to ignore JavaScript errors during test execution. Learn more: "https://testcafe.io/documentation/404038/recipes/debugging/skip-javascript-errors"
If the website only throws this error when you test it with TestCafe, please create a new issue at:
"https://github.com/DevExpress/testcafe/issues/new?template=bug-report.md".
JavaScript error details:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34
Browser: Chrome 146.0.0.0 / Windows Server 2022
8 | setTimeout(resolve, 120_000);
9 | });
10 | })
11 | .beforeEach(async(t) => {
12 | // await t.debug();
> 13 | await t.resizeWindow(1024, 768);
14 | })
15 | .afterEach(async(t) => {
16 | // we need this later
17 | console.log(await t.getBrowserConsoleMessages());
18 | });
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:13:11)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:8:71)
at __awaiter (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:4:12)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:11:25)
× test (Attempt #8)
1) - Error in fixture.beforeEach hook -
A JavaScript error occurred on "http://localhost:16700/index.htm".
Repeat test actions in the browser and check the console for errors.
Enable the “skipJsErrors” option to ignore JavaScript errors during test execution. Learn more: "https://testcafe.io/documentation/404038/recipes/debugging/skip-javascript-errors"
If the website only throws this error when you test it with TestCafe, please create a new issue at:
"https://github.com/DevExpress/testcafe/issues/new?template=bug-report.md".
JavaScript error details:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34
Browser: Chrome 146.0.0.0 / Windows Server 2022
8 | setTimeout(resolve, 120_000);
9 | });
10 | })
11 | .beforeEach(async(t) => {
12 | // await t.debug();
> 13 | await t.resizeWindow(1024, 768);
14 | })
15 | .afterEach(async(t) => {
16 | // we need this later
17 | console.log(await t.getBrowserConsoleMessages());
18 | });
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:13:11)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:8:71)
at __awaiter (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:4:12)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:11:25)
× test (Attempt #9)
1) - Error in fixture.beforeEach hook -
A JavaScript error occurred on "http://localhost:16700/index.htm".
Repeat test actions in the browser and check the console for errors.
Enable the “skipJsErrors” option to ignore JavaScript errors during test execution. Learn more: "https://testcafe.io/documentation/404038/recipes/debugging/skip-javascript-errors"
If the website only throws this error when you test it with TestCafe, please create a new issue at:
"https://github.com/DevExpress/testcafe/issues/new?template=bug-report.md".
JavaScript error details:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34
Browser: Chrome 146.0.0.0 / Windows Server 2022
8 | setTimeout(resolve, 120_000);
9 | });
10 | })
11 | .beforeEach(async(t) => {
12 | // await t.debug();
> 13 | await t.resizeWindow(1024, 768);
14 | })
15 | .afterEach(async(t) => {
16 | // we need this later
17 | console.log(await t.getBrowserConsoleMessages());
18 | });
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:13:11)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:8:71)
at __awaiter (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:4:12)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:11:25)
× test (Attempt #10)
1) - Error in fixture.beforeEach hook -
A JavaScript error occurred on "http://localhost:16700/index.htm".
Repeat test actions in the browser and check the console for errors.
Enable the “skipJsErrors” option to ignore JavaScript errors during test execution. Learn more: "https://testcafe.io/documentation/404038/recipes/debugging/skip-javascript-errors"
If the website only throws this error when you test it with TestCafe, please create a new issue at:
"https://github.com/DevExpress/testcafe/issues/new?template=bug-report.md".
JavaScript error details:
TypeError: Cannot read properties of null (reading 'hammerhead|shadow-ui-element')
at isShadowUIElement (http://localhost:56889/hammerhead.js:3583:22)
at _onFocus (http://localhost:56889/hammerhead.js:40330:52)
at http://localhost:56889/hammerhead.js:39672:34
Browser: Chrome 146.0.0.0 / Windows Server 2022
8 | setTimeout(resolve, 120_000);
9 | });
10 | })
11 | .beforeEach(async(t) => {
12 | // await t.debug();
> 13 | await t.resizeWindow(1024, 768);
14 | })
15 | .afterEach(async(t) => {
16 | // we need this later
17 | console.log(await t.getBrowserConsoleMessages());
18 | });
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:13:11)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:8:71)
at __awaiter (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:4:12)
at <anonymous> (C:\a\2\s\Integrationstestprojekte\WebVisuPictures\dummy.tc.ts:11:25)
9/10 failed (2m 26s)Screenshots
No response
Steps to Reproduce
none
TestCafe version
3.7.4
Node.js version
20.20.1
Command-line arguments
testcafe chrome:"azure-pipelines/PortableBrowsers/chrome/chrome-146-72/GoogleChromePortable.exe --disable-web-security" --headless ./Integrationstestprojekte/WebVisuPictures/dummy.tc.ts
Browser name(s) and version(s)
Chrome 146, Edge 146
Platform(s) and version(s)
Windows Server 2022
Other
I created a patch for testcafe-hammerhead, that fixes the problem and logs some debug-information:
diff --git a/node_modules/testcafe-hammerhead/lib/client/hammerhead.min.js b/node_modules/testcafe-hammerhead/lib/client/_hammerhead.min.js
similarity index 100%
rename from node_modules/testcafe-hammerhead/lib/client/hammerhead.min.js
rename to node_modules/testcafe-hammerhead/lib/client/_hammerhead.min.js
diff --git a/node_modules/testcafe-hammerhead/lib/client/hammerhead.js b/node_modules/testcafe-hammerhead/lib/client/hammerhead.js
index c01ff46..d0d65c3 100644
--- a/node_modules/testcafe-hammerhead/lib/client/hammerhead.js
+++ b/node_modules/testcafe-hammerhead/lib/client/hammerhead.js
@@ -3218,12 +3218,25 @@
var doc = currentDocument || document;
var activeElement = nativeMethods.documentActiveElementGetter.call(doc);
var el = isDomElement(activeElement) ? activeElement : doc.body;
- while (el && el.shadowRoot) {
+ var result = el;
+ while (result && result.shadowRoot) {
// esliSource: DevExpress/testcafe