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Lms24
added this pull request to stack #24904
October 2, 2026 12:58
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The replay CLS event used the CLS score as its timestamp, so it always landed a fraction of a millisecond after page load. Use the start time of the last layout shift instead, like the CLS span in tracing does. This also picks the time origin from when the shift happened. Co-Authored-By: Claude <noreply@anthropic.com>
Like CLS, the replay INP event used the metric value as its timestamp. For INP that value is a duration, so the event landed shortly after page load. Use the start time of the interaction instead. Co-Authored-By: Claude <noreply@anthropic.com>
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The Replay integration adding web vital breadcrumbs used the metric value as the timestamp for CLS and INP web vitals. This is incorrect because that value is a score for CLS and a duration for INP, so both events always landed just after page load. This was a pre-existing bug, but it showed up during work on #23054. With this PR, CLS goes at the last layout shift and INP at the interaction, like we already do with spans in tracing. Both also get the time origin from when that happened, so they stay correct after a clock drift correction. A CLS of 0 has no layout shift, so it stays at the time origin.