LCP element span does not correlate with LCP vertical mark in waterfall

serglom21 commented 4 weeks ago

Is there an existing issue for this?

[x] I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
[x] I have reviewed the documentation https://docs.sentry.io/
[x] I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/remix

SDK Version

8.25.0

Framework Version

No response

Link to Sentry event

No response

Reproduction Example/SDK Setup

No response

Steps to Reproduce

Customer Case

Sentry reports the LCP value for a page load and the LCP element that contributed to the value. However, the LCP value for the pageload itself does not match with the end of the span of the LCP element in the waterfall

Expected Result

I would expect the LCP element span to finish at the same timeframe as the reported value of the LCP vital for the page load

Actual Result

The LCP element span finishes way before the time that Sentry reports as the LCP for the pageload

Lms24 commented 3 weeks ago

Backlogging to triage after hackweek

Lms24 commented 2 weeks ago

This might be related to some weird LCP/FCP/FP value normalization code we have in the SDK. I will investigate if we can remove this logic as it's massively screwing up web vital accuracy.

getsentry / sentry-javascript