[No QA] fix: introduce `useStartSpansOnRender` hook that registers spans on first render by war-in · Pull Request #97885 · Expensify/App

war-in · 2026-08-05T15:36:38Z

Explanation of Change

NavigationRootReady was started in a useEffect but is ended from NavigationContainer's onReady, which React flushes first — so the end was dropped and the span leaked, landing as cancelled on 36–53% of native traces (single span evidence, aggregated spans that didn't finish) . New useStartSpansOnRender hook registers spans during render instead, which also makes the span cover the navigator's render cost.

Fixed Issues

$
PROPOSAL:

Tests

Run the app on iOS Native or Android Native (npm run ios / npm run android).
Open the Metro/debugger console and filter logs for [Sentry][NavigationRootReady].
Cold start the app (fully kill it first, then relaunch) and sign in.
Verify two lines appear, in this order:
- [Sentry][NavigationRootReady] Starting span
- [Sentry][NavigationRootReady] Ending span (Nms)
Verify that on main (before this change) only the Starting span line appears on native and the Ending span line is never logged, because the end ran before the span was registered and was silently dropped.

Offline tests

N/A

QA Steps

N/A - telemetry change

PR Author Checklist

Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

…irst render

roryabraham

LGTM, great find 👍🏼

@MelvinBot Are there other places where we're starting spans in effects and ending them in effects of a child component?

war-in · 2026-08-10T10:07:19Z

@roryabraham answering the question Melvin missed

Are there other places where we're starting spans in effects and ending them in effects of a child component?

I think TelemetrySpanManager is a good candidate. It's designed solely for starting and finishing spans but I'd rather verify if the proposed solution fixes the issue and then prepare a follow-up PR with a fix for TelemetrySpanManager. What do you think?

Here is my bot's analysis

Answer: one candidate, not yet an active bug, fragile.
SPAN_CONFIRMATION_LIST_READY / SPAN_CONFIRMATION_RECEIPT_LOAD:
• Started in TelemetrySpanManager's mount effect (TelemetrySpanManager.tsx:25-35)
• SPAN_CONFIRMATION_LIST_READY ended in ConfirmationTelemetry's mount effect (ConfirmationTelemetry.tsx:18-23), which lives inside MoneyRequestConfirmationList — a sibling subtree, not a descendant of TelemetrySpanManager
Both mount in the same commit under IOURequestStepConfirmation.tsx, where is at line 853 and at line 964. It currently works only because React commits sibling subtrees left-to-right — start wins the race by JSX source order, not by anything that guarantees it. Reordering those two elements would silently reintroduce this exact bug. ConfirmationTelemetry's effect is keyed on [transactionID], so if transactionID is already defined on first render (common case), the end fires in the same commit as the start — this isn't a someday-later-tick end, it's the same race NavigationRootReady had, just currently winning by luck.
Everything else audited clean: zero other startSpan-in-effect / endSpan-in-descendant-effect pairs in the same commit, and zero endSpan calls inside any useLayoutEffect/useInsertionEffect anywhere in src/ (which would invert even against an ancestor's passive-effect start).

melvin-bot · 2026-08-10T10:08:08Z

@inimaga Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

trjExpensify · 2026-08-10T11:28:07Z

PR doesn’t need product input as a perf tooling PR. Unassigning and unsubscribing myself.

inimaga · 2026-08-10T12:00:16Z

Reviewer Checklist

I have verified the author checklist is complete (all boxes are checked off).
I verified the correct issue is linked in the ### Fixed Issues section above
I verified testing steps are clear and they cover the changes made in this PR
- I verified the steps for local testing are in the Tests section
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- I verified the steps cover any possible failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
- I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
I checked that screenshots or videos are included for tests on all platforms
I included screenshots or videos for tests on all platforms
I verified that the composer does not automatically focus or open the keyboard on mobile unless explicitly intended. This includes checking that returning the app from the background does not unexpectedly open the keyboard.
I verified tests pass on all platforms & I tested again on:
- Android: HybridApp
- Android: mWeb Chrome
- iOS: HybridApp
- iOS: mWeb Safari
- MacOS: Chrome / Safari
If there are any errors in the console that are unrelated to this PR, I either fixed them (preferred) or linked to where I reported them in Slack
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- I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
- I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
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I verified other components that can be impacted by these changes have been tested, and I retested again (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar have been tested & I retested again)
If a new component is created I verified that:
- A similar component doesn't exist in the codebase
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If a new CSS style is added I verified that:
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If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
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For any bug fix or new feature in this PR, I verified that sufficient unit tests are included to prevent regressions in this flow.
If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
I have checked off every checkbox in the PR reviewer checklist, including those that don't apply to this PR.

Screenshots/Videos

Android: HybridApp

Android: mWeb Chrome

iOS: HybridApp

iOS: mWeb Safari

MacOS: Chrome / Safari

github-actions · 2026-08-11T01:58:05Z

🚧 roryabraham has triggered a test Expensify/App build. You can view the workflow run here.

OSBotify · 2026-08-11T01:59:01Z

✋ This PR was not deployed to staging yet because QA is ongoing. It will be automatically deployed to staging after the next production release.

github-actions · 2026-08-11T02:05:28Z

🧪🧪 Use the links below to test this adhoc build on Android, iOS, and Web. Happy testing! 🧪🧪
Built from App PR #97885.

Android 🤖	iOS 🍎
https://ad-hoc-expensify-cash.s3.us-east-1.amazonaws.com/rock-artifacts/ad-hoc/rock-android-Adhoc-edc4aad882a-7d586de-0d7ec3a17c27bd752f5d3eae4a35cfaed16ad8c7/index.html	❌ FAILED ❌
	The QR code can't be generated, because the iOS build failed

Web 🕸️
https://97885.pr-testing.expensify.com

👀 View the workflow run that generated this build 👀

OSBotify · 2026-08-12T18:40:30Z

🚀 Deployed to staging by https://github.com/roryabraham in version: 9.4.53-0 🚀

platform	result
🕸 web 🕸	success ✅
🤖 android 🤖	success ✅
🍎 iOS 🍎	success ✅

MelvinBot · 2026-08-12T18:44:06Z

🤖 No help site changes required — no draft PR created.

This PR is a [No QA] telemetry-only change. It fixes a timing bug where the NavigationRootReady Sentry span was started in a useEffect but ended from NavigationContainer's onReady (flushed first), causing the span to leak as cancelled. The fix introduces a useStartSpansOnRender hook that registers the span during render instead.

Both changed files are internal observability code with no user-facing impact:

src/libs/Navigation/NavigationRoot.tsx — moves span registration from an effect to render
src/libs/telemetry/useStartSpansOnRender.ts — new internal telemetry hook

There are no new or changed features, UI, settings, tab names, buttons, workflows, billing, or integration behavior — nothing that the help site articles under App/docs/articles document. Accordingly, no help site article needs to be added or updated.

@war-in, if you believe there is a user-facing behavior change I've missed that the help site should cover, let me know and I'll draft the docs PR.

fix: introduce useStartSpansOnRender hook that registers spans on f…

21301c7

…irst render

melvin-bot Bot assigned war-in Aug 5, 2026

war-in added 2 commits August 6, 2026 11:14

Merge branch 'main' into war-in/fix-broken-navigation-root-ready-span

3fdf6e1

chore: remove unnecessary comment

22f4e15

war-in changed the title ~~fix: introduce useStartSpansOnRender hook that registers spans on first render~~ [No QA] fix: introduce useStartSpansOnRender hook that registers spans on first render Aug 6, 2026

roryabraham previously approved these changes Aug 6, 2026

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Comment thread src/libs/telemetry/useStartSpansOnRender.ts Outdated

war-in added 2 commits August 10, 2026 11:54

Merge branch 'main' into war-in/fix-broken-navigation-root-ready-span

f20b136

refactor: remove unnecessary useOnFirstRender function

b2409e9

war-in dismissed roryabraham’s stale review via b2409e9 August 10, 2026 09:57

war-in marked this pull request as ready for review August 10, 2026 10:07

war-in requested review from a team as code owners August 10, 2026 10:07

melvin-bot Bot requested review from inimaga and trjExpensify and removed request for a team August 10, 2026 10:07

github-actions Bot reviewed Aug 10, 2026

View reviewed changes

Comment thread src/libs/telemetry/useStartSpansOnRender.ts Outdated

chore: fix comment

a7294c1

trjExpensify removed their request for review August 10, 2026 11:28

inimaga approved these changes Aug 10, 2026

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roryabraham approved these changes Aug 11, 2026

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roryabraham closed this Aug 11, 2026

roryabraham reopened this Aug 11, 2026

roryabraham merged commit edc4aad into Expensify:main Aug 11, 2026
44 of 46 checks passed

OSBotify mentioned this pull request Aug 12, 2026

Deploy Checklist: New Expensify 2026-08-12 #98463

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[No QA] fix: introduce `useStartSpansOnRender` hook that registers spans on first render - #97885

[No QA] fix: introduce `useStartSpansOnRender` hook that registers spans on first render#97885
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