Always attach some URL/target data point to fetch/xhr/request errors

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The Sentry Chief Product Officer has brought to our attention that Fetch errors sometimes suck. (example that will expire in 90 days)

We technically have a stack trace here but sourcemaps are broken so the user has basically no idea what fetch request failed. It's very hard to gauge from breadcrumbs what exact request failed.

Side note, the fetch call that failed looked like fetch(""). We render this as in the product, you guessed it "". Which is crap because it actually means the request went to the current route. We should at least coerce that string to URL(fetchTarget, window.location.href).toString() in the SDK.

big

@s1gr1d

Found 1 more spot , i think xhr.open('GET', '') is never instrumented, because the check in xhr.ts is !url, which treats an empty string like an unparseable argument. fetch('') does get a breadcrumb and span.

sentry-javascript/packages/browser-utils/src/instrumentation/xhr.ts

Lines 54 to 56 in 90a71e7

    
           if (!method || !url) { 
        
             return originalOpen.apply(xhrOpenThisArg, xhrOpenArgArray); 
        
           }

Should i open a small PR that only bails when the URL can't be parsed (url === undefined)? - @s1gr1d wdyt should empty-URL XHRs stay uninstrumented?

Good find, yes please! fetch('') is already instrumented, so XHR should match and bailing only on url === undefined sounds correct.

Can you also handle the breadcrumb URL in the same PR (your question from the first comment, now hidden)? Once xhr.open('GET', '') is instrumented, its breadcrumb would show "" too (same as fetch).

When we resolve the url with location.href (like your PR #25784 does) and then stripping query and fragment (stripUrlQueryAndFragment in core) we can get the path without leaking params into breadcrumbs.

opened a PR with both changes, take a look when you get a chance.

fix(browser): Instrument empty-URL XHR and show the page URL in bread…

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Always attach some URL/target data point to fetch/xhr/request errors #13168

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	if (!method \|\| !url) {
	return originalOpen.apply(xhrOpenThisArg, xhrOpenArgArray);
	}

Always attach some URL/target data point to fetch/xhr/request errors #13168

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kunal649 commented on Oct 20, 2026

3 remaining items

lforst commented on Oct 20, 2026

kunal649 commented on Oct 28, 2026

s1gr1d commented on Nov 6, 2026

kunal649 commented on Nov 7, 2026

kunal649 commented on Nov 12, 2026

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