[Awaiting checklist] [$250] Public Room - Green line “new message” line appears when scrolling up quickly

[jponikarchuk]

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Version Number: 9.2.31-0
Reproducible in staging?: Yes
Reproducible in production?: Yes
If this was caught during regression testing, add the test name, ID and link from BrowserStack: https://test-management.browserstack.com/projects/2219752/test-runs/TR-1292/folder/13176964/41237764/952582380
Email or phone of affected tester (no customers): N/A
Issue reported by: Applause Internal Team
Device used: iPhone 13 / iOS 18.5, iPhone 13 / Safari, Samsung Galaxy A52 / Android 14
App Component: Other

Action Performed:

Precondition: Log out of New Expensify

1. Navigate to this link as anon user - https://staging.new.expensify.com/r/2091104345528462 (user clicked the link from other app)
2. Quickly scroll to the top of the conversation

Expected Result:

no green line appeared as the message is not the new message

Actual Result:

when I quickly scroll to the top, every time when the conversation is paused to load the older conversation, there's a green line indicating as new message

Workaround:

Unknown

Platforms:

• Android: App
• Android: mWeb Chrome
• iOS: App
• iOS: mWeb Safari
• iOS: mWeb Chrome
• Windows: Chrome
• MacOS: Chrome / Safari
• MacOS: Desktop

Screenshots/Videos

1.mp4

View all open jobs on GitHub

Upwork Automation - Do Not Edit

• Upwork Job URL: https://www.upwork.com/jobs/~021978416808958492292
• Upwork Job ID: 1978416808958492292
• Last Price Increase: 2025-10-15

Issue Owner

Current Issue Owner: @thesahindia

[melvin-bot]

Triggered auto assignment to @twisterdotcom (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details. Please add this bug to a GH project, as outlined in the SO.

[paulnjs]

Proposal

Please re-state the problem that we are trying to solve in this issue.

Public Room - Green line “new message” line appears when scrolling up quickly

What is the root cause of that problem?

• The initial state for unreadMarkerTime is '' because report.lastReadTime is undefined at that time:
  

  App/src/pages/home/report/ReportActionsList.tsx

  Line 240 in e95b3e6

  const [unreadMarkerTime, setUnreadMarkerTime] = useState(reportLastReadTime);

  
  As a result, the unread marker logic treats all messages as new during the loading process.

App/src/pages/home/report/ReportActionsList.tsx

Lines 283 to 289 in e95b3e6

	shouldDisplayNewMarkerOnReportAction({
	message: reportAction,
	nextMessage: nextAction,
	isEarliestReceivedOfflineMessage,
	accountID,
	prevSortedVisibleReportActionsObjects,
	unreadMarkerTime,

What changes do you think we should make in order to solve the problem?

We should ensure that the unreadMarkerTime state is correctly initialized once report.lastReadTime becomes available. The following logic can be added:

const reportLastReadTime = useMemo(() => report.lastReadTime ?? '', [report]);
const [unreadMarkerTime, setUnreadMarkerTime] = useState(reportLastReadTime);

useEffect(() => {
    if (!unreadMarkerTime && reportLastReadTime) {
        setUnreadMarkerTime(reportLastReadTime);
    }
}, [reportLastReadTime]);

This ensures that the unread marker only gets set once and remains consistent throughout the scroll, preventing false "new message" indicators.

What specific scenarios should we cover in automated tests to prevent reintroducing this issue in the future?

What alternative solutions did you explore? (Optional)

[melvin-bot]

Job added to Upwork: https://www.upwork.com/jobs/~021978416808958492292

[melvin-bot]

Triggered auto assignment to Contributor-plus team member for initial proposal review - @thesahindia (External)

[lorretheboy]

🚨 Edited by proposal-police: This proposal was edited at 2025-10-15 13:16:17 UTC.

Proposal

Please re-state the problem that we are trying to solve in this issue.

Public Room - Green line “new message” line appears when scrolling up quickly

What is the root cause of that problem?

For anonymous users, report.lastReadTime is undefined which then causes unreadMarkerTime to be initialized as an empty string ''. This makes ALL non-created messages appear as "unread" during conversation loading. Therefore, green unread markers appear incorrectly every time the conversation pauses to load older messages

App/src/pages/home/report/ReportActionsList.tsx

Line 225 in 045400e

const reportLastReadTime = report.lastReadTime ?? '';

What changes do you think we should make in order to solve the problem?

We should prevent unread markers for anonymous users entirely, since they don't have read/unread state

Add early return here

        if (isAnonymousUser) {
            return [null, -1];
        }

And here

        if (isAnonymousUser) {
            return;
        }

Include anonymous check here as well

if (isAnonymousUser || unreadMarkerReportActionID) {

App/src/pages/home/report/ReportActionsList.tsx

Line 322 in 045400e

if (unreadMarkerReportActionID) {

What alternative solutions did you explore? (Optional)

Reminder: Please use plain English, be brief and avoid jargon. Feel free to use images, charts or pseudo-code if necessary. Do not post large multi-line diffs or write walls of text. Do not create PRs unless you have been hired for this job.

[github-actions]

⚠️ @lorretheboy Thanks for your proposal. Please update it to follow the proposal template, as proposals are only reviewed if they follow that format (note the mandatory sections).

[dangrous]

can handle internal review on this one when it's ready!