feat(browser): Start a navigation span for bfcache restores - #23748
Draft
logaretm wants to merge 1 commit into
Draft
feat(browser): Start a navigation span for bfcache restores#23748logaretm wants to merge 1 commit into
logaretm wants to merge 1 commit into
Conversation
logaretm
force-pushed
the
awad/bfcache-navigation-span
branch
from
August 28, 2026 18:39
c306449 to
831a206
Compare
Contributor
size-limit report 📦
|
logaretm
force-pushed
the
awad/bfcache-navigation-span
branch
from
August 31, 2026 16:03
831a206 to
d7cd440
Compare
logaretm
force-pushed
the
awad/bfcache-navigation-span
branch
from
September 8, 2026 14:56
d7cd440 to
e67604c
Compare
… bfcache Prototype. A bfcache restore resurrects the frozen document, so there is no document load and no usable history event: `popstate` either doesn't fire or is swallowed, because the URL is unchanged from when the page was frozen. Two independent guards in the existing path suppress it, neither written with bfcache in mind, so there is no small nudge that gets a span out of it. Without one, everything after the restore joins the trace the page had before it was frozen, separated by however long it sat in the cache. That misattributes errors, breadcrumbs, clicks and fetches, not just the web vitals that prompted this. The span is started from a `pageshow` listener in `browserTracingIntegration` rather than `bfcacheIntegration`, so it does not depend on an opt-in integration that is about hit/miss diagnostics. It is gated on `instrumentNavigation` and on by default. It carries `browser.navigation.type: bfcache`. A restore is near-instant, so without a way to filter these out they would drag navigation duration percentiles down exactly the way bfcache vitals would have dragged LCP. The span deliberately starts at the `pageshow` event rather than from `PerformanceNavigationTiming`, which is not replaced on restore and still describes the original document load. Known gap, pinned by a test: `bfcacheIntegration` registers its own `pageshow` listener from `setupOnce`, which core always runs before every `afterAllSetup`, so its hit/miss metric is emitted before this span exists and still lands on the pre-freeze trace.
logaretm
force-pushed
the
awad/bfcache-navigation-span
branch
from
September 8, 2026 14:57
e67604c to
08b4500
Compare
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Starts a navigation span when the page is restored from the back/forward cache.
A restore resurrects the frozen document, so there is no document load and no usable history event:
popstateeither doesn't fire or is swallowed because the URL is unchanged. Without a span of its own, everything after the restore joins the trace the page had before it was frozen, which misattributes errors and breadcrumbs as much as vitals.It lives in
browserTracingIntegrationrather thanbfcacheIntegrationso it doesn't depend on an opt-in integration being enabled, and carriesbrowser.navigation.type: bfcachesince a restore is near-instant and would otherwise drag navigation duration percentiles down with no way to tell it apart.Stacked on #23425.