NO_LCP in PageSpeed Insights with Lighthouse 13.4.1 despite fully rendered page

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).
• Yes, my issue is not answered by other FAQs.

URL

https://www.lewisie-zp.cz/

What happened?

Related to #16934 – the issue is still reproducible in Lighthouse 13.4.1.

Still reproducible today with PSI using Lighthouse 13.4.1 / HeadlessChromium 151.0.7922.71:

URL tested: https://www.lewisie-zp.cz/

Fresh PSI report (18 Aug 2026, 19:51 CEST):
https://pagespeed.web.dev/analysis/https-www-lewisie-zp-cz/8ra3z6al45?form_factor=desktop

Both mobile and desktop finish with NO_LCP, while the filmstrip and final screenshot show the complete WooCommerce homepage rendered correctly. The same page reports normally when Lighthouse/Performance tools are run locally in Chrome DevTools.

Evidence from the Lighthouse report:

The main document returned HTTP 200 and the final URL remained unchanged.
137 requests on mobile and 153 on desktop, with no failed or HTTP 4xx/5xx requests.
is-crawlable and robots-txt both pass.
No console errors or Lighthouse run warnings.
Metrics contain lcpInvalidated: false, but no observed LCP entry.
Stable above-the-fold candidates exist: a visible static H1 and a same-origin 800×533 image with fetchpriority="high"; neither uses opacity, transform, or an entrance animation.

Could this still be a Lighthouse 13 / PSI trace regression or infrastructure issue? Please let us know which trace artifact would be most useful if you need one.

What did you expect?

Lighthouse should detect and report the Largest Contentful Paint, calculate the Total Blocking Time, and return a valid performance score when the page is fully rendered.

What have you tried?

• Repeated the PageSpeed Insights test several times on both mobile and desktop.
• Tested the same page locally using Chrome DevTools, where the Lighthouse and Performance tools work correctly.
• Verified that the main document returns HTTP 200 and that the report contains no failed HTTP 4xx/5xx requests.
• Verified that robots.txt and crawlability checks pass.
• Checked the above-the-fold elements for opacity, transforms, and entrance animations.
• Confirmed that a static H1 and a same-origin hero image are visible LCP candidates.

How were you running Lighthouse?

PageSpeed Insights

Lighthouse Version

13.4.1

Chrome Version

No response

Node Version

No response

OS

Not applicable – PageSpeed Insights

Relevant log output

Largest Contentful Paint: Error! NO_LCP

Metrics contain:
lcpInvalidated: false

No observed Largest Contentful Paint entry was recorded.

Start by reproducing the URL in PageSpeed Insights with Lighthouse 13.4.1 on both mobile and desktop, then compare the result with a local Chrome DevTools run. Inspect the PSI trace and metric output for the missing observed LCP entry; done means identifying whether the NO_LCP result is a Lighthouse regression or infrastructure issue and documenting the useful trace artifact.