LCP measurement reported without the LCP DOM element

[thefoxis]

FAQ

• Yes, my issue is not about variability or throttling.
• Yes, my issue is not about a specific accessibility audit (file with axe-core instead).

URL

https://www.crunchbase.com/

What happened?

Steps to reproduce

1. Run a Performance Lighthouse test on https://www.crunchbase.com/ in Chrome Developer Tools.
2. Observe that LCP measurement is reported without the LCP DOM element being specified.

Screenshots

What did you expect?

When Largest Contentful Paint measurement is available, the LCP element should always be listed (since the measurement is derived based on finding a specific element).

TL:DR; there should never be a case where there's a measurement and no element specified (or the other way around).

What have you tried?

I've ran numerous tests to confirm it's not a one-off behavior. It happens either persistently (every DevTools test) or intermittently, but in a semi-persistent manner. I was also able to reproduce it in Calibre, see this publicly available test ¹:

I wasn’t able to reproduce it on PSI (web.dev/measure), perhaps because it runs on newer Lighthouse version (10.0.2), but I'm unable to speculate the reasoning.

---

How were you running Lighthouse?

Chrome DevTools

Lighthouse Version

Lighthouse 9.6.8

Chrome Version

Version 111.0.5563.64 (Official Build) (arm64)

Node Version

No response

OS

Mac

Relevant log output

No response

Footnotes

1. You can either look for the Largest Contentful Paint element audit, or filter by LCP-related audits. ↩

[adamraine]

I was able to reproduce this, but I'm having a hard time debugging because of the "Verify that you are human" screen. It sometimes doesn't believe that I am human (possibly because Lighthouse is controlling Chrome automatically?)

[thefoxis]

@adamraine I thought the human check might be an issue here, but it's hard to reproduce, I agree. if I test manually an encounter the confirmation screen, then press the press & hold button to confirm, and conduct testing afterwards, i still results in no LCP element, even though I've gone through the human checks 🧐 in that case, I would have thought it'd be resolved?

one workaround I thought of would be to pass a cookie during the test to bypass the human check, but I still think Lighthouse fails in an unexpected way here 😅

[adamraine]

We are getting a "No node with given ID found" error when we try and resolve the node. Not entirely clear why this is happening though since Lighthouse should account for nodes being removed during page load. Next step would be to create a minimum repro, this could be an issue with Chrome.

[thefoxis]

hey, are there any updates on this? 🙏🏻

[adamraine]

I was able to create a repro and filed an upstream bug:

https://bugs.chromium.org/p/chromium/issues/detail?id=1445244