Fix - Merge expenses prompts for attendee selection even when both expenses have the same attendee

[FitseTLT]

Explanation of Change

When merging two expenses that have the same attendee, the merge flow wrongly prompted the user to pick an attendee. Two things caused it:

1. Every manual expense creation/edit optimistically stamped the current user as a default attendee (comment.attendees = [you]), even though the backend only persists attendees the user explicitly selects. So two otherwise-identical expenses could hold [you] in optimistic Onyx while the synced value was empty — a phantom difference.
2. The merge conflict detector (getMergeableDataAndConflictFields) compared attendees without applying the report-owner fallback that the display path (buildMergeFieldsData) uses. So an empty attendee list compared as [] instead of [owner], producing a false conflict against an expense whose attendee resolves to that same owner.

This PR:

• Removes the optimistic default-attendee stamp from initMoneyRequest (MoneyRequest.ts) and buildOptimisticTransactionAndCreateDraft (TransactionEdit.ts), so optimistic data matches the backend. Display is unchanged because getAttendees still falls back to the report owner when the stored list is empty.
• Threads the report-owner fallback into getMergeableDataAndConflictFields and applies it at every merge entry point — the details page, the receipt-review page, and the direct/bulk merge action — so attendee conflict detection matches what the UI displays and stops flagging identical attendees.

Fixed Issues

$ #94700
PROPOSAL: #94700 (comment)

Tests

1. Create a workspace with the Attendee Tracking feature enabled.
2. Create two expenses in that workspace with the same merchant and the same (default) attendee.
3. Select one expense and start the Merge action; pick the other expense and continue.
4. Verify the "Select the details you want to keep" page does NOT show an Attendee section (attendees are identical, so there is no conflict).
5. Verify the merge completes and the attendee is retained.
6. Repeat with two expenses that have DIFFERENT explicit attendees and verify the Attendee section IS still shown so the user can choose.

• Verify that no errors appear in the JS console

Offline tests

Same as tests.

QA Steps

Same as tests.

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover 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 tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that comments were added to code that is not self explanatory
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  • 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
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
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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.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user 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.

Screenshots/Videos

Android: Native

2026-07-21.16-24-58.mp4

Android: mWeb Chrome

2026-07-21.00-03-22.mp4

iOS: Native

iOS: mWeb Safari

2026-07-21.00-05-18.mp4

MacOS: Chrome / Safari

2026-07-20.23-59-48.mp4

[melvin-bot]

@sobitneupane 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]

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[codecov]

Codecov Report

❌ Looks like you've decreased code coverage for some files. Please write tests to increase, or at least maintain, the existing level of code coverage. See our documentation here for how to interpret this table.

Files with missing lines	Coverage Δ
src/hooks/useReceiptScanDrop.tsx	46.34% <ø> (ø)
src/hooks/useResetIOUType.ts	97.29% <ø> (-0.08%)	⬇️
src/hooks/useSelectedTransactionsActions.ts	78.03% <100.00%> (+0.08%)	⬆️
src/libs/MergeTransactionUtils.ts	79.65% <100.00%> (ø)
src/libs/actions/IOU/MoneyRequest.ts	74.22% <100.00%> (ø)
src/libs/actions/TransactionEdit.ts	75.25% <100.00%> (ø)
src/pages/Share/SubmitDetailsPage.tsx	88.50% <100.00%> (ø)
...ages/TransactionMerge/DynamicDetailsReviewPage.tsx	0.00% <ø> (ø)
...inbox/report/ReportActionCompose/useReceiptDrop.ts	48.78% <ø> (ø)
...p/IOURequestStepScan/components/ScanFromReport.tsx	71.42% <ø> (ø)
... and 7 more
... and 6 files with indirect coverage changes

[sobitneupane]

@FitseTLT Could you please merge main?

[JmillsExpensify]

LGTM

[sobitneupane]

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
  • I verified the steps for Staging and/or Production testing are in the QA steps section
  • 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
• I verified proper code patterns were followed (see Reviewing the code)
  • I verified that comments were added to code that is not self explanatory
  • 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
• I verified that this PR follows the guidelines as stated in the Review Guidelines
• 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:
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  • The component has the minimum amount of code necessary for its purpose, and it is broken down into smaller components in order to separate concerns and functions
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG)
• 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.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• 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

Screen.Recording.2026-07-25.at.21.34.35.mov

Android: mWeb Chrome

Screen.Recording.2026-07-25.at.21.36.40.mov

iOS: HybridApp

Screen.Recording.2026-07-25.at.21.51.33.mov

iOS: mWeb Safari

Screen.Recording.2026-07-25.at.21.43.53.mov

MacOS: Chrome / Safari

Screen.Recording.2026-07-25.at.21.11.46.mov

Screen.Recording.2026-07-25.at.21.15.31.mov

Screen.Recording.2026-07-25.at.21.16.45.mov

[luacmartins]

@FitseTLT conflicts

[FitseTLT]

@luacmartins

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[MelvinBot]

🤖 Help site review: no docs changes required.

This PR is a bug fix to the merge-expenses conflict detector — it stops the "Select the details you want to keep" step from prompting for an attendee when both expenses already resolve to the same attendee (by removing the optimistic default-attendee stamp and applying the report-owner fallback during conflict detection). It doesn't add features, rename anything, or change any user-facing labels, settings, or workflow.

The relevant help article, How to Merge Duplicate Expenses, already describes the corrected behavior — including this FAQ, which matches this fix exactly:

Why was I not asked to choose which expense details to apply to the final expense?
If both expenses already have the same details, the final expense keeps those values automatically.

I also checked Adding Attendees and searched the docs — nothing documents an automatic/default attendee on expense creation, so removing the optimistic stamp doesn't contradict any published article.

Since this brings the app in line with what the docs already say, no draft PR was created.

@FitseTLT, please confirm you agree no help site changes are needed. If you think an article should be updated (e.g. added detail about attendees during merge), reply with @MelvinBot and what you'd like changed and I'll open a draft PR.

[OSBotify]

🚀 Deployed to production by https://github.com/roryabraham in version: 9.4.52-11 🚀

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

Bundle Size Analysis (Sentry):

• Android