Fix: include 1:1 DM participants in OpenReport so stale optimistic reportIDs self-heal

src/libs/ReportUtils.ts

@@ -2847,6 +2847,26 @@ function isOneOnOneChat(report: OnyxEntry<Report>, currentUserAccountID?: number
     );
 }
 
+/**
+ * Returns the other participant of a cached 1:1 DM as OpenReport participant info, so the server can
+ * resolve a stale/optimistic reportID to the real chat (returned as preexistingReportID) instead of
+ * failing with "Report not found". Returns an empty list for any report that is not a 1:1 DM.
+ */
+function getOneOnOneChatParticipants(
+    report: OnyxEntry<Report>,
+    personalDetails: OnyxEntry<PersonalDetailsList>,
+    currentUserAccountID: number | undefined,
+): Array<{login: string; accountID: number}> {
+    if (!currentUserAccountID || !isOneOnOneChat(report, currentUserAccountID)) {
+        return [];
+    }
+    return Object.keys(report?.participants ?? {})
+        .map(Number)
+        .filter((accountID) => accountID !== currentUserAccountID)
+        .map((accountID) => ({login: personalDetails?.[accountID]?.login ?? '', accountID}))
+        .filter((participant) => !!participant.login);
+}
+
 /**
  * Checks if the current user is a payer of the expense
  */
@@ -14247,6 +14267,7 @@ export {
     getNonHeldAndFullAmount,
     getReimbursableTotal,
     getUnheldReimbursableTotal,
+    getOneOnOneChatParticipants,
     getOptimisticDataForAncestors,
     getOriginalReportID,
     getOutstandingChildRequest,

src/pages/inbox/ReportFetchHandler.tsx

@@ -23,6 +23,7 @@ import type {CancelHandle} from '@libs/Navigation/TransitionTracker';
 import {isSupportedInviteOnboardingChoice, isSupportedPendingInviteOnboarding} from '@libs/OnboardingUtils';
 import {getFilteredReportActionsForReportView, getIOUActionForReportID, getOneTransactionThreadReportID, isCreatedAction} from '@libs/ReportActionsUtils';
 import {
+    getOneOnOneChatParticipants,
     isChatThread,
     isHiddenForCurrentUser,
     isMoneyRequestReport,
@@ -199,7 +200,10 @@ function ReportFetchHandler() {
             return;
         }
 
-        openReport({reportID: reportIDFromRoute, introSelected, reportActionID: reportActionIDFromRoute, betas, hasReportActions, currentUserAccountID});
+        // For a cached 1:1 DM, pass the other participant so the server can resolve a stale/optimistic
+        // reportID to the real chat (via preexistingReportID) instead of failing with "Report not found".
+        const dmParticipants = getOneOnOneChatParticipants(report, personalDetails, currentUserAccountID);
+        openReport({reportID: reportIDFromRoute, introSelected, reportActionID: reportActionIDFromRoute, participants: dmParticipants, betas, hasReportActions, currentUserAccountID});
     });
 
     const createOneTransactionThread = useEffectEvent(() => {

tests/actions/ReportTest.ts

@@ -5217,6 +5217,29 @@ describe('actions/Report', () => {
         });
     });
 
+    describe('openReport with participants', () => {
+        it('should send passed participants as emailList/accountIDList so the server can resolve a stale optimistic reportID', async () => {
+            global.fetch = TestHelper.createGlobalFetchMock();
+            const REPORT_ID = 'dm1';
+
+            Report.openReport({
+                reportID: REPORT_ID,
+                introSelected: undefined,
+                betas: undefined,
+                hasReportActions: true,
+                currentUserAccountID: 1,
+                participants: [{login: 'other@test.com', accountID: 2}],
+            });
+            await waitForBatchedUpdates();
+
+            TestHelper.expectAPICommandToHaveBeenCalledWith(WRITE_COMMANDS.OPEN_REPORT, 0, {
+                reportID: REPORT_ID,
+                emailList: 'other@test.com',
+                accountIDList: '2',
+            });
+        });
+    });
+
     describe('setOptimisticTransactionThread', () => {
         it('should set optimistic transaction thread data with the provided parameters', async () => {
             const reportID = 'report12';

tests/unit/ReportUtilsTest.ts

@@ -116,6 +116,7 @@ import {
     getMovedTransactionMessage,
     getNextApproverAccountID,
     getNonHeldAndFullAmount,
+    getOneOnOneChatParticipants,
     getOriginalReportID,
     getOutstandingChildRequest,
     getParentNavigationSubtitle,
@@ -11599,6 +11600,39 @@ describe('ReportUtils', () => {
         });
     });
 
+    describe('getOneOnOneChatParticipants', () => {
+        const OTHER_ACCOUNT_ID = 222;
+        const personalDetailsList: PersonalDetailsList = {
+            [OTHER_ACCOUNT_ID]: {accountID: OTHER_ACCOUNT_ID, login: 'other@test.com'},
+        };
+        const dmReport: Report = {
+            ...createRandomReport(0, undefined),
+            type: CONST.REPORT.TYPE.CHAT,
+            policyID: CONST.POLICY.ID_FAKE,
+            participants: buildParticipantsFromAccountIDs([currentUserAccountID, OTHER_ACCOUNT_ID]),
+        };
+
+        it('should return the other participant of a 1:1 DM with their login and accountID', () => {
+            expect(getOneOnOneChatParticipants(dmReport, personalDetailsList, currentUserAccountID)).toEqual([{login: 'other@test.com', accountID: OTHER_ACCOUNT_ID}]);
+        });
+
+        it('should return an empty list for reports that are not 1:1 DMs', () => {
+            const roomReport: Report = {
+                ...createRandomReport(1, CONST.REPORT.CHAT_TYPE.POLICY_ADMINS),
+                participants: buildParticipantsFromAccountIDs([currentUserAccountID, OTHER_ACCOUNT_ID]),
+            };
+            expect(getOneOnOneChatParticipants(roomReport, personalDetailsList, currentUserAccountID)).toEqual([]);
+        });
+
+        it('should return an empty list when the other participant has no known login', () => {
+            expect(getOneOnOneChatParticipants(dmReport, {}, currentUserAccountID)).toEqual([]);
+        });
+
+        it('should return an empty list when currentUserAccountID is missing', () => {
+            expect(getOneOnOneChatParticipants(dmReport, personalDetailsList, undefined)).toEqual([]);
+        });
+    });
+
     describe('getReportNotificationPreference', () => {
         it('should read the notification preference of the passed currentUserAccountID', () => {
             const report: Report = {