diff --git a/src/hooks/useDeleteTransactions.ts b/src/hooks/useDeleteTransactions.ts
index 7d7053710e5f..f46e2fc2e887 100644
--- a/src/hooks/useDeleteTransactions.ts
+++ b/src/hooks/useDeleteTransactions.ts
@@ -5,8 +5,8 @@ import {useSearchStateContext} from '@components/Search/SearchContext';
 import {getIOURequestPolicyID} from '@libs/actions/IOU';
 import {deleteMoneyRequest} from '@libs/actions/IOU/DeleteMoneyRequest';
 import {getIOUActionForTransactions} from '@libs/actions/IOU/Duplicate';
-import {updateSplitTransactions} from '@libs/actions/IOU/Split';
 import {initSplitExpenseItemData} from '@libs/actions/IOU/SplitExpenseItems';
+import {updateSplitTransactions} from '@libs/actions/IOU/SplitTransactionUpdate';
 import getNonEmptyStringOnyxID from '@libs/getNonEmptyStringOnyxID';
 import {getOriginalMessage, isMoneyRequestAction} from '@libs/ReportActionsUtils';
 import {getActiveGroupSearchHashes} from '@libs/SearchUIUtils';
diff --git a/src/libs/actions/IOU/Split.ts b/src/libs/actions/IOU/Split.ts
index e458b900efc4..c1b83adfe9ab 100644
--- a/src/libs/actions/IOU/Split.ts
+++ b/src/libs/actions/IOU/Split.ts
@@ -1,21 +1,12 @@
 import {fastMerge} from 'expensify-common';
 // eslint-disable-next-line no-restricted-imports
 import {InteractionManager} from 'react-native';
-import type {NullishDeep, OnyxCollection, OnyxEntry, OnyxInputValue, OnyxUpdate} from 'react-native-onyx';
+import type {OnyxCollection, OnyxEntry, OnyxInputValue, OnyxUpdate} from 'react-native-onyx';
 import Onyx from 'react-native-onyx';
 import type {ValueOf} from 'type-fest';
 import ReceiptGeneric from '@assets/images/receipt-generic.png';
-import type {SearchActionsContextValue, SearchStateContextValue} from '@components/Search/types';
 import * as API from '@libs/API';
-import type {
-    CompleteSplitBillParams,
-    CreateDistanceRequestParams,
-    RevertSplitTransactionParams,
-    SplitBillParams,
-    SplitTransactionParams,
-    SplitTransactionSplitsParam,
-    StartSplitBillParams,
-} from '@libs/API/parameters';
+import type {CompleteSplitBillParams, CreateDistanceRequestParams, SplitBillParams, StartSplitBillParams} from '@libs/API/parameters';
 import {WRITE_COMMANDS} from '@libs/API/types';
 import DateUtils from '@libs/DateUtils';
 import {deferOrExecuteWrite} from '@libs/deferredLayoutWrite';
@@ -23,31 +14,14 @@ import {getMicroSecondOnyxErrorWithTranslationKey} from '@libs/ErrorUtils';
 import {calculateAmount as calculateIOUAmount, updateIOUOwnerAndTotal} from '@libs/IOUUtils';
 import {formatPhoneNumber} from '@libs/LocalePhoneNumber';
 import * as Localize from '@libs/Localize';
-import Log from '@libs/Log';
 import isReportTopmostSplitNavigator from '@libs/Navigation/helpers/isReportTopmostSplitNavigator';
-import isSearchTopmostFullScreenRoute from '@libs/Navigation/helpers/isSearchTopmostFullScreenRoute';
-import Navigation, {navigationRef} from '@libs/Navigation/Navigation';
+import Navigation from '@libs/Navigation/Navigation';
 import {roundToTwoDecimalPlaces} from '@libs/NumberUtils';
 import * as NumberUtils from '@libs/NumberUtils';
 import Parser from '@libs/Parser';
 import {addSMSDomainIfPhoneNumber} from '@libs/PhoneNumber';
-import {getDistanceRateCustomUnitRate} from '@libs/PolicyUtils';
+import {getReportActionHtml, getReportActionText} from '@libs/ReportActionsUtils';
 import {
-    getAllReportActions,
-    getIOUActionForReportID,
-    getIOUActionForTransactionID,
-    getLastVisibleAction,
-    getOriginalMessage,
-    getReportAction,
-    getReportActionHtml,
-    getReportActionText,
-    isActionOfType,
-    isAddCommentAction,
-    isDeletedAction,
-    isMoneyRequestAction,
-} from '@libs/ReportActionsUtils';
-import {
-    buildOptimisticAddCommentReportAction,
     buildOptimisticChatReport,
     buildOptimisticCreatedReportAction,
     buildOptimisticExpenseReport,
@@ -55,7 +29,6 @@ import {
     buildOptimisticIOUReportAction,
     buildOptimisticMoneyRequestEntities,
     buildOptimisticReportPreview,
-    canUserPerformWriteAction as canUserPerformWriteActionReportUtils,
     generateReportID,
     getChatByParticipants,
     getParsedComment,
@@ -63,48 +36,36 @@ import {
     getReportOrDraftReport,
     getTransactionDetails,
     hasViolations as hasViolationsReportUtils,
-    isArchivedReport,
     isExpenseReport,
     isMoneyRequestReport as isMoneyRequestReportReportUtils,
     isOneOnOneChat,
     isOptimisticPersonalDetail,
     isPolicyExpenseChat as isPolicyExpenseChatReportUtil,
-    navigateBackOnDeleteTransaction,
     shouldCreateNewMoneyRequestReport as shouldCreateNewMoneyRequestReportReportUtils,
-    updateOptimisticParentReportAction,
     updateReportPreview,
 } from '@libs/ReportUtils';
 import type {OptimisticChatReport} from '@libs/ReportUtils';
 import playSound, {SOUNDS} from '@libs/Sound';
-import {addOptimization, isTracking, setPendingSubmitFollowUpAction} from '@libs/telemetry/submitFollowUpAction';
+import {addOptimization, setPendingSubmitFollowUpAction} from '@libs/telemetry/submitFollowUpAction';
 import {
     buildOptimisticTransaction,
-    getChildTransactions,
     getUpdatedTransaction,
     isDistanceExpenseType,
     isDistanceRequest as isDistanceRequestTransactionUtils,
-    isOnHold,
-    isPerDiemRequest as isPerDiemRequestTransactionUtils,
     isScanRequest as isScanRequestTransactionUtils,
 } from '@libs/TransactionUtils';
 import {buildOptimisticPolicyRecentlyUsedTags} from '@userActions/Policy/Tag';
-import {notifyNewAction, setDeleteTransactionNavigateBackUrl} from '@userActions/Report';
+import {notifyNewAction} from '@userActions/Report';
 import {sanitizeWaypointsForAPI} from '@userActions/Transaction';
-import {removeDraftSplitTransaction, removeDraftTransaction} from '@userActions/TransactionEdit';
+import {removeDraftTransaction} from '@userActions/TransactionEdit';
 import CONST from '@src/CONST';
-import NAVIGATORS from '@src/NAVIGATORS';
 import ONYXKEYS from '@src/ONYXKEYS';
-import ROUTES from '@src/ROUTES';
-import SCREENS from '@src/SCREENS';
 import type * as OnyxTypes from '@src/types/onyx';
-import type {Attendee, Participant, Split, SplitExpense} from '@src/types/onyx/IOU';
-import type {CurrentUserPersonalDetails} from '@src/types/onyx/PersonalDetails';
+import type {Attendee, Participant, Split} from '@src/types/onyx/IOU';
 import type RecentlyUsedTags from '@src/types/onyx/RecentlyUsedTags';
 import type {OnyxData} from '@src/types/onyx/Request';
-import type {SearchResultDataType} from '@src/types/onyx/SearchResults';
 import type {Receipt, ReceiptSource, SplitShares, TransactionChanges, WaypointCollection} from '@src/types/onyx/Transaction';
 import {isEmptyObject} from '@src/types/utils/EmptyObject';
-import {getCleanUpTransactionThreadReportOnyxData} from './DeleteMoneyRequest';
 import {
     buildMinimalTransactionForFormula,
     buildOnyxDataForMoneyRequest,
@@ -114,7 +75,6 @@ import {
     getAllTransactionDrafts,
     getAllTransactions,
     getMoneyRequestInformation,
-    getMoneyRequestParticipantsFromReport,
     getMoneyRequestPolicyTags,
     getPolicyTagsData,
     getReceiptError,
@@ -125,12 +85,9 @@ import {
     mergePolicyRecentlyUsedCategories,
     mergePolicyRecentlyUsedCurrencies,
 } from './index';
-import type {BuildOnyxDataForMoneyRequestKeys, MoneyRequestInformationParams, OneOnOneIOUReport, StartSplitBilActionParams} from './index';
-import {getDeleteTrackExpenseInformation} from './TrackExpense';
+import type {BuildOnyxDataForMoneyRequestKeys, OneOnOneIOUReport, StartSplitBilActionParams} from './index';
 import type BasePolicyParams from './types/BasePolicyParams';
 import type BaseTransactionParams from './types/BaseTransactionParams';
-import {getUpdateMoneyRequestParams} from './UpdateMoneyRequest';
-import type {UpdateMoneyRequestDataKeys} from './UpdateMoneyRequest';
 
 type IOURequestType = ValueOf<typeof CONST.IOU.REQUEST_TYPE>;
 
@@ -207,38 +164,6 @@ type CreateSplitsAndOnyxDataParams = {
     personalDetails: OnyxEntry<OnyxTypes.PersonalDetailsList>;
 };
 
-type UpdateSplitTransactionsParams = {
-    allTransactionsList: OnyxCollection<OnyxTypes.Transaction>;
-    allReportsList: OnyxCollection<OnyxTypes.Report>;
-    allReportNameValuePairsList: OnyxCollection<OnyxTypes.ReportNameValuePairs>;
-    allSnapshots?: OnyxCollection<OnyxTypes.SearchResults>;
-    transactionData: {
-        reportID: string;
-        originalTransactionID: string;
-        splitExpenses: SplitExpense[];
-        splitExpensesTotal: number | undefined;
-    };
-    searchContext?: (Partial<SearchStateContextValue & SearchActionsContextValue> & {activeGroupSearchHashes?: number[]}) | undefined;
-    policyCategories: OnyxTypes.PolicyCategories | undefined;
-    policy: OnyxTypes.Policy | undefined;
-    policyRecentlyUsedCategories: OnyxTypes.RecentlyUsedCategories | undefined;
-    iouReport: OnyxEntry<OnyxTypes.Report>;
-    firstIOU: OnyxEntry<OnyxTypes.ReportAction> | undefined;
-    isASAPSubmitBetaEnabled: boolean;
-    currentUserPersonalDetails: CurrentUserPersonalDetails;
-    transactionViolations: OnyxCollection<OnyxTypes.TransactionViolation[]>;
-    quickAction: OnyxEntry<OnyxTypes.QuickAction>;
-    policyRecentlyUsedCurrencies: string[];
-    iouReportNextStep: OnyxEntry<OnyxTypes.ReportNextStepDeprecated>;
-    betas: OnyxEntry<OnyxTypes.Beta[]>;
-    isFromSplitExpensesFlow?: boolean;
-    policyTags: OnyxTypes.PolicyTagLists;
-    personalDetails: OnyxEntry<OnyxTypes.PersonalDetailsList>;
-    transactionReport: OnyxEntry<OnyxTypes.Report>;
-    expenseReport: OnyxEntry<OnyxTypes.Report>;
-    isOffline: boolean;
-};
-
 type SplitBillActionsParams = {
     participants: Participant[];
     currentUserLogin: string;
@@ -1152,1293 +1077,6 @@ function completeSplitBill(
     notifyNewAction(chatReportID, undefined, true);
 }
 
-function updateSplitTransactions({
-    allTransactionsList,
-    allReportsList,
-    allReportNameValuePairsList,
-    allSnapshots,
-    transactionData,
-    searchContext,
-    policyCategories,
-    policy,
-    policyRecentlyUsedCategories,
-    iouReport,
-    firstIOU,
-    isASAPSubmitBetaEnabled,
-    currentUserPersonalDetails,
-    transactionViolations,
-    quickAction,
-    policyRecentlyUsedCurrencies,
-    iouReportNextStep,
-    isFromSplitExpensesFlow,
-    betas,
-    policyTags,
-    personalDetails,
-    transactionReport,
-    expenseReport,
-    isOffline,
-}: UpdateSplitTransactionsParams) {
-    const chatReport = allReportsList?.[`${ONYXKEYS.COLLECTION.REPORT}${expenseReport?.chatReportID}`];
-    const expenseReportParentChat = getReportOrDraftReport(chatReport?.parentReportID);
-    const originalTransactionID = transactionData?.originalTransactionID ?? CONST.IOU.OPTIMISTIC_TRANSACTION_ID;
-    const originalTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`];
-    const originalTransactionDetails = getTransactionDetails(originalTransaction);
-    const autoParticipants = getMoneyRequestParticipantsFromReport(expenseReport, currentUserPersonalDetails.accountID);
-    // Delegate split edit can reach this flow without the workspace expense chat in Onyx.
-    const fallbackPolicyParticipant =
-        autoParticipants.length === 0 && !chatReport && expenseReport?.chatReportID && expenseReport?.policyID
-            ? {
-                  accountID: 0,
-                  reportID: expenseReport.chatReportID,
-                  isPolicyExpenseChat: true,
-                  selected: true,
-                  policyID: expenseReport.policyID,
-              }
-            : undefined;
-    const participants = fallbackPolicyParticipant ? [fallbackPolicyParticipant] : autoParticipants;
-    let fallbackPolicyParentChatReport = expenseReportParentChat;
-    if (!fallbackPolicyParentChatReport && chatReport && isPolicyExpenseChatReportUtil(chatReport)) {
-        fallbackPolicyParentChatReport = chatReport;
-    }
-    if (!fallbackPolicyParentChatReport && fallbackPolicyParticipant) {
-        fallbackPolicyParentChatReport = {
-            reportID: fallbackPolicyParticipant.reportID,
-            type: CONST.REPORT.TYPE.CHAT,
-            chatType: CONST.REPORT.CHAT_TYPE.POLICY_EXPENSE_CHAT,
-            policyID: fallbackPolicyParticipant.policyID,
-            ownerAccountID: expenseReport?.ownerAccountID,
-        } as OnyxTypes.Report;
-    }
-    const splitExpenses = transactionData?.splitExpenses ?? [];
-
-    // Get all children once (including orphaned), then filter for non-orphaned
-    const allChildTransactions = getChildTransactions(allTransactionsList, allReportsList, originalTransactionID, true);
-    const originalChildTransactions = allChildTransactions.filter((tx) => tx?.reportID !== CONST.REPORT.UNREPORTED_REPORT_ID);
-    const processedChildTransactionIDs: string[] = [];
-
-    const splitExpensesTotal = transactionData?.splitExpensesTotal ?? 0;
-
-    const isCreationOfSplits = originalChildTransactions.length === 0;
-    const hasEditableSplitExpensesLeft = splitExpenses.some((expense) => (expense.statusNum ?? 0) < CONST.REPORT.STATUS_NUM.SUBMITTED);
-    // Don't revert split if there are orphaned children (reportID '0') - they're still part of the split
-    const isReverseSplitOperation =
-        splitExpenses.length === 1 && originalChildTransactions.length > 0 && hasEditableSplitExpensesLeft && allChildTransactions.length === originalChildTransactions.length;
-
-    let splitThreadComments: OnyxTypes.ReportAction[] = [];
-    let splitTransactionThreadReportID: string | undefined;
-
-    if (isReverseSplitOperation) {
-        const revertSplitTransactionID = splitExpenses.at(0)?.transactionID;
-        const revertSplitTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${revertSplitTransactionID}`];
-        const revertSplitReportActions = getAllReportActions(revertSplitTransaction?.reportID);
-        const revertSplitIOUAction = revertSplitTransactionID ? getIOUActionForTransactionID(Object.values(revertSplitReportActions ?? {}), revertSplitTransactionID) : undefined;
-        splitTransactionThreadReportID = revertSplitIOUAction?.childReportID;
-        if (splitTransactionThreadReportID) {
-            const splitTransactionThreadActions = getAllReportActions(splitTransactionThreadReportID);
-            splitThreadComments = Object.values(splitTransactionThreadActions).filter(
-                (action): action is OnyxTypes.ReportAction =>
-                    isActionOfType(action, CONST.REPORT.ACTIONS.TYPE.ADD_COMMENT) && !isDeletedAction(action) && (action.actorAccountID ?? CONST.DEFAULT_NUMBER_ID) > 0,
-            );
-        }
-    }
-
-    let changesInReportTotal = 0;
-    // Validate custom unit rate before proceeding with split
-    const customUnitRateID = originalTransaction?.comment?.customUnit?.customUnitRateID;
-    const isPerDiem = isPerDiemRequestTransactionUtils(originalTransaction);
-
-    if (customUnitRateID && policy && !isPerDiem && isCreationOfSplits && !isFromSplitExpensesFlow) {
-        const customUnitRate = getDistanceRateCustomUnitRate(policy, customUnitRateID);
-
-        // If the rate doesn't exist or is disabled, show an error and return early
-        if (!customUnitRate?.enabled) {
-            // Show error to user
-            Onyx.merge(`${ONYXKEYS.COLLECTION.SPLIT_TRANSACTION_DRAFT}${originalTransactionID}`, {
-                errors: getMicroSecondOnyxErrorWithTranslationKey('iou.error.invalidRate'),
-            });
-            return;
-        }
-    }
-
-    const splits: SplitTransactionSplitsParam =
-        splitExpenses.map((split) => {
-            const currentDescription = getParsedComment(Parser.htmlToMarkdown(split.description ?? ''));
-            changesInReportTotal += split.amount;
-            return {
-                amount: split.amount,
-                category: split.category ?? '',
-                tag: split.tags?.[0] ?? '',
-                created: split.created,
-                merchant: split?.merchant ?? '',
-                transactionID: split.transactionID,
-                comment: {
-                    comment: currentDescription,
-                },
-                reimbursable: split?.reimbursable,
-                billable: split?.billable,
-                quantity: split.customUnit?.quantity ?? undefined,
-                customUnitRateID: split.customUnit?.customUnitRateID,
-                odometerStart: split.odometerStart,
-                odometerEnd: split.odometerEnd,
-                waypoints: split.waypoints,
-            };
-        }) ?? [];
-    changesInReportTotal -= splitExpensesTotal;
-
-    const onyxData: OnyxData<BuildOnyxDataForMoneyRequestKeys | UpdateMoneyRequestDataKeys> = {
-        successData: [],
-        failureData: [],
-        optimisticData: [],
-    };
-
-    // The split transactions can be in different reports, so we need to calculate the total for each report.
-    const reportTotals = new Map<string, number>();
-    const expenseReportID = expenseReport?.reportID;
-
-    if (expenseReportID) {
-        const expenseReportKey = `${ONYXKEYS.COLLECTION.REPORT}${expenseReportID}`;
-        const expenseReportTotal = allReportsList?.[expenseReportKey]?.total ?? expenseReport?.total ?? 0;
-        reportTotals.set(expenseReportID, expenseReportTotal - changesInReportTotal);
-    }
-
-    for (const expense of splitExpenses) {
-        const splitExpenseReportID = expense.reportID;
-        if (!splitExpenseReportID || reportTotals.has(splitExpenseReportID)) {
-            continue;
-        }
-
-        const splitExpenseReport = allReportsList?.[`${ONYXKEYS.COLLECTION.REPORT}${splitExpenseReportID}`];
-        reportTotals.set(splitExpenseReportID, splitExpenseReport?.total ?? 0);
-    }
-
-    let updatedReportPreviewAction: Partial<OnyxTypes.ReportAction> | undefined;
-    const originalReportPreviewAction = getReportPreviewAction(expenseReport?.chatReportID, expenseReport?.reportID);
-    const transactionReportActions = getAllReportActions(firstIOU?.childReportID);
-    const expenseReportNameValuePairs = allReportNameValuePairsList?.[`${ONYXKEYS.COLLECTION.REPORT_NAME_VALUE_PAIRS}${expenseReport?.reportID}`];
-    const isArchivedExpenseReport = isArchivedReport(expenseReportNameValuePairs);
-    const canUserPerformWriteAction = chatReport ? !!canUserPerformWriteActionReportUtils(chatReport, isArchivedExpenseReport) : true;
-    const lastVisibleAction = getLastVisibleAction(expenseReport?.reportID, canUserPerformWriteAction);
-    const isTransactionOnHold = isOnHold(originalTransaction);
-    const holdReportAction = getReportAction(firstIOU?.childReportID, `${originalTransaction?.comment?.hold ?? ''}`);
-
-    let holdCommentReportAction: OnyxTypes.ReportAction<'ADDCOMMENT'> | undefined;
-    const allCommentActionsFromOriginalTransactionThread: Array<OnyxTypes.ReportAction<'ADDCOMMENT'>> = [];
-    for (const action of Object.values(transactionReportActions ?? {})) {
-        if (!isAddCommentAction(action)) {
-            continue;
-        }
-
-        if (holdReportAction && !(holdCommentReportAction?.timestamp && holdReportAction?.timestamp === holdCommentReportAction.timestamp)) {
-            // The HOLD report action and its corresponding comment share the same `timestamp` value.
-            if (holdReportAction.timestamp !== undefined && holdReportAction.timestamp === action.timestamp) {
-                holdCommentReportAction = action;
-            } else if (action.created >= holdReportAction.created && (!holdCommentReportAction || holdCommentReportAction.created >= action.created)) {
-                // If `timestamp` is unavailable, fall back to finding the comment whose `created` value
-                // is greater than and closest to that of the holdReportAction.
-                holdCommentReportAction = action;
-            }
-        }
-
-        if (isDeletedAction(action) || action.pendingAction === CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE) {
-            continue;
-        }
-        allCommentActionsFromOriginalTransactionThread.push(action);
-    }
-    // We will pre-sort to ensure that comments are inserted in the correct order.
-    allCommentActionsFromOriginalTransactionThread.sort((a, b) => (a.created > b.created ? 1 : -1));
-
-    const updateParentActions = (iouAction: OnyxTypes.ReportAction, childVisibleActionCountToAdd: number) => {
-        if (childVisibleActionCountToAdd <= 0) {
-            return undefined;
-        }
-
-        const updatedIOUAction = updateOptimisticParentReportAction(iouAction, iouAction.created, CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD, childVisibleActionCountToAdd);
-
-        if (originalReportPreviewAction) {
-            const nextUpdatedReportPreviewAction = updateOptimisticParentReportAction(
-                (updatedReportPreviewAction ?? originalReportPreviewAction) as OnyxTypes.ReportAction,
-                lastVisibleAction?.childLastVisibleActionCreated ?? lastVisibleAction?.created ?? '',
-                CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
-                childVisibleActionCountToAdd,
-            ) as Partial<OnyxTypes.ReportAction>;
-            nextUpdatedReportPreviewAction.reportActionID = originalReportPreviewAction.reportActionID;
-            updatedReportPreviewAction = nextUpdatedReportPreviewAction;
-        }
-
-        return updatedIOUAction;
-    };
-    const pushUpdatedReportPreviewActionToOnyxData = () => {
-        if (!updatedReportPreviewAction) {
-            return;
-        }
-
-        onyxData.optimisticData?.push({
-            onyxMethod: Onyx.METHOD.MERGE,
-            key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${chatReport?.reportID}`,
-            value: {
-                [updatedReportPreviewAction?.reportActionID ?? CONST.DEFAULT_NUMBER_ID]: updatedReportPreviewAction,
-            },
-        });
-
-        onyxData.failureData?.push({
-            onyxMethod: Onyx.METHOD.MERGE,
-            key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${chatReport?.reportID}`,
-            value: {
-                [updatedReportPreviewAction?.reportActionID ?? CONST.DEFAULT_NUMBER_ID]: {
-                    childVisibleActionCount: originalReportPreviewAction?.childVisibleActionCount,
-                    childCommenterCount: originalReportPreviewAction?.childCommenterCount,
-                    childLastVisibleActionCreated: originalReportPreviewAction?.childLastVisibleActionCreated,
-                    childOldestFourAccountIDs: originalReportPreviewAction?.childOldestFourAccountIDs,
-                },
-            },
-        });
-    };
-
-    // Collect optimistic child transactions to add to the search snapshot (forward split only)
-    const optimisticChildSnapshotEntries: SearchResultDataType = {};
-    const optimisticChildSnapshotKeys: Array<`${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}`> = [];
-
-    for (const [index, splitExpense] of splitExpenses.entries()) {
-        const existingTransactionID = isReverseSplitOperation ? originalTransactionID : splitExpense.transactionID;
-        const splitTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`];
-        if (splitTransaction) {
-            processedChildTransactionIDs.push(splitTransaction.transactionID);
-        }
-
-        const splitReportActions = getAllReportActions(isReverseSplitOperation ? expenseReport?.reportID : splitTransaction?.reportID);
-        const currentReportAction = Object.values(splitReportActions).find((action) => {
-            const transactionID = isMoneyRequestAction(action) ? (getOriginalMessage(action)?.IOUTransactionID ?? CONST.DEFAULT_NUMBER_ID) : CONST.DEFAULT_NUMBER_ID;
-            return transactionID === existingTransactionID;
-        });
-
-        const splitExpenseMerchant = splitExpense.merchant ?? '';
-
-        const requestMoneyInformation = {
-            participantParams: {
-                participant: participants.at(0) ?? ({} as Participant),
-                payeeEmail: currentUserPersonalDetails?.login ?? '',
-                payeeAccountID: currentUserPersonalDetails?.accountID ?? CONST.DEFAULT_NUMBER_ID,
-            },
-            policyParams: {
-                policy,
-                policyCategories,
-                policyTags,
-            },
-            transactionParams: {
-                amount: Math.abs(originalTransaction?.amount ?? 0),
-                modifiedAmount: splitExpense.amount ?? 0,
-                currency: originalTransactionDetails?.currency ?? CONST.CURRENCY.USD,
-                created: splitExpense.created,
-                merchant: splitExpenseMerchant,
-                comment: splitExpense.description,
-                category: splitExpense.category,
-                tag: splitExpense.tags?.[0],
-                originalTransactionID,
-                attendees: splitTransaction?.comment?.attendees ?? originalTransactionDetails?.attendees,
-                source: CONST.IOU.TYPE.SPLIT,
-                linkedTrackedExpenseReportAction: currentReportAction,
-                pendingAction: splitTransaction ? null : CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
-                pendingFields: splitTransaction ? splitTransaction.pendingFields : undefined,
-                reimbursable: originalTransactionDetails?.reimbursable,
-                taxCode: originalTransactionDetails?.taxCode,
-                taxAmount: calculateIOUAmount(splitExpenses.length - 1, originalTransactionDetails?.taxAmount ?? 0, originalTransactionDetails?.currency ?? CONST.CURRENCY.USD, false),
-                taxValue: originalTransactionDetails?.taxValue,
-                billable: originalTransactionDetails?.billable,
-                waypoints: splitExpense.waypoints,
-                customUnit: splitExpense.customUnit,
-                // For distance transactions, also pass distance from customUnit.quantity so buildOptimisticTransaction sets it correctly
-                distance: splitExpense.customUnit?.quantity,
-                odometerStart: splitExpense.odometerStart,
-                odometerEnd: splitExpense.odometerEnd,
-            },
-            parentChatReport: fallbackPolicyParentChatReport,
-            existingTransaction: originalTransaction,
-            isASAPSubmitBetaEnabled,
-            currentUserAccountIDParam: currentUserPersonalDetails?.accountID,
-            currentUserEmailParam: currentUserPersonalDetails?.login ?? '',
-            transactionViolations,
-            quickAction,
-            policyRecentlyUsedCurrencies,
-            betas,
-            personalDetails,
-        } as MoneyRequestInformationParams;
-
-        if (isReverseSplitOperation) {
-            requestMoneyInformation.transactionParams = {
-                amount: splitExpense.amount ?? 0,
-                currency: originalTransactionDetails?.currency ?? CONST.CURRENCY.USD,
-                created: splitExpense.created,
-                merchant: splitExpense.merchant ?? '',
-                comment: splitExpense.description,
-                category: splitExpense.category,
-                tag: splitExpense.tags?.[0],
-                attendees: originalTransactionDetails?.attendees as Attendee[],
-                linkedTrackedExpenseReportAction: currentReportAction,
-                taxCode: originalTransactionDetails?.taxCode,
-                taxAmount: calculateIOUAmount(splitExpenses.length - 1, originalTransactionDetails?.taxAmount ?? 0, originalTransactionDetails?.currency ?? CONST.CURRENCY.USD, false),
-                taxValue: originalTransactionDetails?.taxValue,
-                billable: originalTransactionDetails?.billable,
-                waypoints: splitExpense.waypoints,
-                customUnit: splitExpense.customUnit,
-                // For distance transactions, also pass distance from customUnit.quantity so buildOptimisticTransaction sets it correctly
-                distance: splitExpense.customUnit?.quantity ?? undefined,
-                odometerStart: splitExpense.odometerStart,
-                odometerEnd: splitExpense.odometerEnd,
-            };
-            requestMoneyInformation.existingTransaction = undefined;
-        }
-
-        const {participantParams, policyParams, transactionParams, parentChatReport, existingTransaction} = requestMoneyInformation;
-        const parsedComment = getParsedComment(Parser.htmlToMarkdown(transactionParams.comment ?? ''));
-        transactionParams.comment = parsedComment;
-
-        const {
-            transactionThreadReportID,
-            createdReportActionIDForThread,
-            transaction: optimisticTransactionFromGetMoneyRequest,
-            onyxData: moneyRequestInformationOnyxData,
-            iouAction,
-        } = getMoneyRequestInformation({
-            participantParams,
-            parentChatReport,
-            policyParams: {
-                ...policyParams,
-                // eslint-disable-next-line @typescript-eslint/no-deprecated
-                policyTagList: getMoneyRequestPolicyTags({moneyRequestReportID: splitExpense?.reportID, parentChatReport, participant: participantParams.participant}),
-            },
-            transactionParams,
-            moneyRequestReportID: splitExpense?.reportID,
-            existingTransaction,
-            existingTransactionID,
-            newReportTotal: reportTotals.get(splitExpense?.reportID ?? String(CONST.DEFAULT_NUMBER_ID)) ?? 0,
-            newNonReimbursableTotal: (transactionReport?.nonReimbursableTotal ?? 0) - changesInReportTotal,
-            isSplitExpense: true,
-            currentReportActionID: !isReverseSplitOperation ? currentReportAction?.reportActionID : undefined,
-            isASAPSubmitBetaEnabled,
-            currentUserAccountIDParam: currentUserPersonalDetails?.accountID,
-            currentUserEmailParam: currentUserPersonalDetails?.login ?? '',
-            transactionViolations,
-            quickAction,
-            shouldGenerateTransactionThreadReport: true,
-            policyRecentlyUsedCurrencies,
-            betas,
-            personalDetails,
-        });
-
-        let updateMoneyRequestParamsOnyxData: OnyxData<UpdateMoneyRequestDataKeys> = {};
-        const currentSplit = splits.at(index);
-
-        // For existing split transactions, update the field change messages
-        // For new transactions, skip this step
-        if (splitTransaction) {
-            const transactionChanges = {
-                ...currentSplit,
-                comment: currentSplit?.comment?.comment,
-                customUnitRateID: currentSplit?.customUnitRateID ?? CONST.CUSTOM_UNITS.FAKE_P2P_ID,
-            } as TransactionChanges;
-
-            const existing = getTransactionDetails(splitTransaction);
-            const oldTransactionChanges = {
-                ...existing,
-                quantity: splitTransaction.comment?.customUnit?.quantity ?? existing?.distance,
-            } as TransactionChanges;
-
-            if (currentSplit) {
-                currentSplit.reimbursable = splitTransaction.reimbursable;
-                currentSplit.billable = splitTransaction.billable;
-            }
-
-            for (const key of Object.keys(transactionChanges)) {
-                const newValue = transactionChanges[key as keyof typeof transactionChanges];
-                const oldValue = oldTransactionChanges?.[key as keyof typeof oldTransactionChanges];
-                if (newValue === oldValue) {
-                    delete transactionChanges[key as keyof typeof transactionChanges];
-                    // Ensure we pass the currency to getUpdateMoneyRequestParams as well, so the amount message is created correctly
-                } else if (key === 'amount') {
-                    transactionChanges.currency = originalTransactionDetails?.currency;
-                } else if (key === 'waypoints') {
-                    // For waypoints, we need to compare the stringified version of the arrays since they are arrays of objects
-                    const newWaypoints = JSON.stringify(transactionChanges.waypoints);
-                    const oldWaypoints = JSON.stringify(oldTransactionChanges?.waypoints);
-                    if (newWaypoints === oldWaypoints) {
-                        delete transactionChanges.waypoints;
-                    }
-                }
-            }
-
-            if (isReverseSplitOperation) {
-                delete transactionChanges.transactionID;
-            }
-
-            if (Object.keys(transactionChanges).length > 0) {
-                const transactionThreadReport = getAllReports()?.[`${ONYXKEYS.COLLECTION.REPORT}${isReverseSplitOperation ? splitExpense?.reportID : transactionThreadReportID}`];
-                const transactionIOUReport = getAllReports()?.[`${ONYXKEYS.COLLECTION.REPORT}${splitExpense?.reportID ?? transactionThreadReport?.parentReportID}`];
-                const {onyxData: moneyRequestParamsOnyxData, params} = getUpdateMoneyRequestParams({
-                    transactionID: existingTransactionID,
-                    transactionThreadReport,
-                    iouReport: transactionIOUReport,
-                    transactionChanges,
-                    policy,
-                    policyTagList: policyTags ?? null,
-                    // TODO: Replace getPolicyTagsData (https://github.com/Expensify/App/issues/72721) with useOnyx hook
-                    // eslint-disable-next-line @typescript-eslint/no-deprecated
-                    reportPolicyTags: getPolicyTagsData(transactionIOUReport?.policyID),
-                    policyCategories: policyCategories ?? null,
-                    newTransactionReportID: splitExpense?.reportID,
-                    policyRecentlyUsedCategories,
-                    currentUserAccountIDParam: currentUserPersonalDetails?.accountID,
-                    currentUserEmailParam: currentUserPersonalDetails?.login ?? '',
-                    isASAPSubmitBetaEnabled,
-                    iouReportNextStep,
-                    isSplitTransaction: true,
-                    isOffline,
-                });
-                if (currentSplit) {
-                    currentSplit.modifiedExpenseReportActionID = params.reportActionID;
-                }
-                updateMoneyRequestParamsOnyxData = moneyRequestParamsOnyxData;
-            }
-            // For new split transactions, set the reportID once the transaction and associated report are created
-        } else if (currentSplit) {
-            currentSplit.reportID = splitExpense?.reportID;
-        }
-
-        if (currentSplit) {
-            currentSplit.transactionThreadReportID = transactionThreadReportID;
-            currentSplit.createdReportActionIDForThread = createdReportActionIDForThread;
-            currentSplit.splitReportActionID = iouAction.reportActionID;
-        }
-
-        // Copy comments to the transaction report thread of the split expense
-        const optimisticDataComments: Array<OnyxUpdate<BuildOnyxDataForMoneyRequestKeys>> = [];
-        const successDataComments: Array<OnyxUpdate<BuildOnyxDataForMoneyRequestKeys>> = [];
-        const failureDataComments: Array<OnyxUpdate<BuildOnyxDataForMoneyRequestKeys>> = [];
-        const addCommentToSplitTransactionThread = (commentAction: OnyxTypes.ReportAction) => {
-            const newReportActionID = NumberUtils.rand64();
-            // delegateAccountIDParam: will be threaded in PR 11; buildOptimisticAddCommentReportAction falls back to module-level Onyx.connect value (https://github.com/Expensify/App/issues/66425)
-            const reportComment = buildOptimisticAddCommentReportAction({
-                text: '',
-                actorAccountID: commentAction.actorAccountID,
-                reportID: transactionThreadReportID,
-                reportActionID: newReportActionID,
-                delegateAccountIDParam: undefined,
-            });
-            const reportActionComment = {
-                ...reportComment.reportAction,
-                created: DateUtils.getDBTime(),
-                message: commentAction.message,
-                originalMessage: getOriginalMessage(commentAction),
-            };
-
-            optimisticDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
-                value: {[newReportActionID]: reportActionComment},
-            });
-            successDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
-                value: {[newReportActionID]: {pendingAction: null, isOptimisticAction: null}},
-            });
-            failureDataComments.push({onyxMethod: Onyx.METHOD.MERGE, key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`, value: {[newReportActionID]: null}});
-
-            if (currentSplit) {
-                currentSplit.copiedComments ??= {};
-                currentSplit.copiedComments[commentAction.reportActionID] = newReportActionID;
-            }
-        };
-
-        // An internal helper to find transaction violations within onyxUpdates.
-        // If one exists, it modifies the value for the update instead of adding a new one.
-        const updateTransactionViolationsOnyxData = (
-            targetTransactionID: string,
-            onyxUpdates: Array<OnyxUpdate<BuildOnyxDataForMoneyRequestKeys | UpdateMoneyRequestDataKeys>> | undefined,
-            fallbackViolations: OnyxTypes.TransactionViolation[],
-        ) => {
-            const transactionViolationsKey = `${ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS}${targetTransactionID}` as typeof ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS;
-            const latestViolationUpdate = onyxUpdates?.findLast((update) => update.key === transactionViolationsKey) as OnyxUpdate<typeof ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS>;
-            const baseViolations = latestViolationUpdate && 'value' in latestViolationUpdate && Array.isArray(latestViolationUpdate.value) ? latestViolationUpdate.value : fallbackViolations;
-            const nextViolations = [
-                ...baseViolations.filter((violation) => violation.name !== CONST.VIOLATIONS.HOLD),
-                {name: CONST.VIOLATIONS.HOLD, type: CONST.VIOLATION_TYPES.VIOLATION, showInReview: true},
-            ];
-
-            if (latestViolationUpdate && 'value' in latestViolationUpdate) {
-                latestViolationUpdate.value = nextViolations;
-                return;
-            }
-
-            optimisticDataComments.push({
-                onyxMethod: Onyx.METHOD.SET,
-                key: transactionViolationsKey,
-                value: nextViolations,
-            });
-
-            failureDataComments.push({
-                onyxMethod: Onyx.METHOD.SET,
-                key: transactionViolationsKey,
-                value: fallbackViolations,
-            });
-        };
-        const addHoldToTransactionThread = (commentAction?: OnyxTypes.ReportAction) => {
-            if (!holdReportAction) {
-                return;
-            }
-            // Generate new IDs and timestamps for each split
-            const newHoldReportActionID = NumberUtils.rand64();
-            const timestamp = DateUtils.getDBTime();
-
-            // Create new optimistic hold report action with new ID and timestamp, keeping other information
-            const newHoldReportAction = {
-                ...holdReportAction,
-                reportActionID: newHoldReportActionID,
-                created: timestamp,
-                pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
-                timestamp: undefined,
-            };
-
-            const newHoldReportActionCommentID = commentAction ? NumberUtils.rand64() : undefined;
-            const newHoldReportActionComment =
-                commentAction && newHoldReportActionCommentID
-                    ? {
-                          ...commentAction,
-                          reportActionID: newHoldReportActionCommentID,
-                          created: DateUtils.addMillisecondsFromDateTime(timestamp, 1),
-                          pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
-                          timestamp: undefined,
-                      }
-                    : undefined;
-
-            // Add to optimisticData for this split's reportActions
-            optimisticDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
-                value: {
-                    [newHoldReportActionID]: newHoldReportAction,
-                    ...(newHoldReportActionCommentID && newHoldReportAction ? {[newHoldReportActionCommentID]: newHoldReportActionComment} : {}),
-                },
-            });
-
-            optimisticDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`,
-                value: {
-                    comment: {
-                        hold: newHoldReportActionID,
-                    },
-                },
-            });
-
-            // Add successData to clear pendingAction after API call succeeds
-            successDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
-                value: {
-                    [newHoldReportActionID]: {pendingAction: null},
-                    ...(newHoldReportActionCommentID ? {[newHoldReportActionCommentID]: {pendingAction: null}} : {}),
-                },
-            });
-
-            // Add failureData to remove optimistic hold report actions if the request fails
-            failureDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
-                value: {
-                    [newHoldReportActionID]: null,
-                    ...(newHoldReportActionCommentID ? {[newHoldReportActionCommentID]: null} : {}),
-                },
-            });
-            failureDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`,
-                value: {
-                    comment: {
-                        hold: splitTransaction?.comment?.hold ?? null,
-                    },
-                },
-            });
-
-            // Add hold transaction violation to optimisticData
-            updateTransactionViolationsOnyxData(
-                existingTransactionID,
-                updateMoneyRequestParamsOnyxData.optimisticData ?? moneyRequestInformationOnyxData.optimisticData,
-                transactionViolations?.[`${ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS}${existingTransactionID}`] ?? [],
-            );
-
-            if (currentSplit) {
-                currentSplit.holdReportActionID = newHoldReportActionID;
-                currentSplit.holdReportActionCommentID = newHoldReportActionCommentID;
-            }
-        };
-
-        let updatedIOUAction: Partial<OnyxTypes.ReportAction> | undefined;
-        const copyCommentsAndHoldState = ({commentActions, isSourceTransactionOnHold}: {commentActions: OnyxTypes.ReportAction[]; isSourceTransactionOnHold: boolean}) => {
-            let hasInsertedHoldState = !isSourceTransactionOnHold || !holdReportAction;
-
-            for (const commentAction of commentActions) {
-                if (!hasInsertedHoldState && holdReportAction && commentAction.reportActionID === holdCommentReportAction?.reportActionID) {
-                    addHoldToTransactionThread(commentAction);
-                    hasInsertedHoldState = true;
-                    continue;
-                }
-
-                addCommentToSplitTransactionThread(commentAction);
-            }
-
-            // If the commentAction is not found, it means the action has been deleted.
-            // We call insertHoldState here to ensure the hold state is always added.
-            if (!hasInsertedHoldState) {
-                addHoldToTransactionThread();
-            }
-        };
-
-        if (isCreationOfSplits && transactionThreadReportID && firstIOU?.childReportID) {
-            copyCommentsAndHoldState({
-                commentActions: allCommentActionsFromOriginalTransactionThread,
-                isSourceTransactionOnHold: isTransactionOnHold,
-            });
-            updatedIOUAction = updateParentActions(iouAction, firstIOU.childVisibleActionCount ?? 0);
-        }
-
-        // When isReverseSplitOperation is true, we move all comments from the remaining transaction to the original transaction
-        if (isReverseSplitOperation && transactionThreadReportID) {
-            const remainingTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${splitExpense.transactionID}`];
-            const remainTransactionThreadReportAction = getIOUActionForReportID(splitExpense.reportID, splitExpense.transactionID);
-            const allReportActions = getAllReportActions(remainTransactionThreadReportAction?.childReportID);
-            const isRemainingTransactionOnHold = isOnHold(remainingTransaction);
-            const remainingHoldReportAction = getReportAction(remainTransactionThreadReportAction?.childReportID, `${remainingTransaction?.comment?.hold ?? ''}`);
-
-            const optimisticActionsData: OnyxTypes.ReportActions = {};
-            const successActionsData: Record<string, Record<string, null>> = {};
-            const failureActionsData: Record<string, null> = {};
-
-            for (const action of Object.values(allReportActions)) {
-                if (!isAddCommentAction(action) || isDeletedAction(action) || action.pendingAction === CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE) {
-                    continue;
-                }
-                optimisticActionsData[action.reportActionID] = {...action, pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD};
-                successActionsData[action.reportActionID] = {pendingAction: null, isOptimisticAction: null};
-                failureActionsData[action.reportActionID] = null;
-            }
-            if (isRemainingTransactionOnHold && remainingHoldReportAction) {
-                optimisticActionsData[remainingHoldReportAction.reportActionID] = {...remainingHoldReportAction, pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD};
-                successActionsData[remainingHoldReportAction.reportActionID] = {pendingAction: null, isOptimisticAction: null};
-                failureActionsData[remainingHoldReportAction.reportActionID] = null;
-
-                optimisticDataComments.push({
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`,
-                    value: {
-                        comment: {
-                            hold: remainingHoldReportAction.reportActionID,
-                        },
-                    },
-                });
-
-                failureDataComments.push({
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`,
-                    value: {
-                        comment: {
-                            hold: splitTransaction?.comment?.hold ?? null,
-                        },
-                    },
-                });
-
-                // Add hold transaction violation to optimisticData
-                updateTransactionViolationsOnyxData(
-                    existingTransactionID,
-                    updateMoneyRequestParamsOnyxData.optimisticData ?? moneyRequestInformationOnyxData.optimisticData,
-                    transactionViolations?.[`${ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS}${existingTransactionID}`] ?? [],
-                );
-            }
-            optimisticDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
-                value: optimisticActionsData,
-            });
-
-            successDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
-                value: successActionsData,
-            });
-
-            failureDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
-                value: failureActionsData,
-            });
-
-            updatedIOUAction = updateParentActions(iouAction, remainTransactionThreadReportAction?.childVisibleActionCount ?? 0);
-        }
-
-        if (updatedIOUAction) {
-            optimisticDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.reportID}`,
-                value: {[iouAction.reportActionID]: updatedIOUAction},
-            });
-            failureDataComments.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.reportID}`,
-                value: {
-                    [iouAction.reportActionID]: {
-                        childVisibleActionCount: iouAction.childVisibleActionCount,
-                        childCommenterCount: iouAction.childCommenterCount,
-                        childLastVisibleActionCreated: null,
-                        childOldestFourAccountIDs: null,
-                    },
-                },
-            });
-        }
-
-        // Ensure merchant from splitExpense is preserved in optimisticData for new and existing transactions
-        const transactionIDFromOptimistic = optimisticTransactionFromGetMoneyRequest?.transactionID;
-        if (transactionIDFromOptimistic && moneyRequestInformationOnyxData.optimisticData) {
-            const transactionUpdate = moneyRequestInformationOnyxData.optimisticData.find((update) => update.key === `${ONYXKEYS.COLLECTION.TRANSACTION}${transactionIDFromOptimistic}`);
-            if (transactionUpdate && 'value' in transactionUpdate && typeof transactionUpdate.value === 'object' && transactionUpdate.value !== null) {
-                const transactionUpdateValue = transactionUpdate.value as OnyxTypes.Transaction;
-                const expectedMerchant = optimisticTransactionFromGetMoneyRequest?.merchant;
-                if (expectedMerchant && transactionUpdateValue.merchant !== expectedMerchant) {
-                    transactionUpdateValue.merchant = expectedMerchant;
-                    // For distance transactions, also update modifiedMerchant to ensure consistency
-                    if (isDistanceRequestTransactionUtils(transactionUpdateValue)) {
-                        transactionUpdateValue.modifiedMerchant = expectedMerchant;
-                    }
-                }
-            }
-        }
-
-        // Collect the optimistic child transaction for snapshot update (forward split only)
-        if (!isReverseSplitOperation && optimisticTransactionFromGetMoneyRequest) {
-            const childTransactionID = optimisticTransactionFromGetMoneyRequest.transactionID;
-            const transactionKey: `${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}` = `${ONYXKEYS.COLLECTION.TRANSACTION}${childTransactionID}`;
-            // Use the transaction value from optimisticData if available (it may have merchant fixes applied),
-            // otherwise fall back to the raw optimistic transaction
-            const transactionUpdate = moneyRequestInformationOnyxData.optimisticData?.find((update) => update.key === transactionKey);
-            const snapshotTransaction =
-                transactionUpdate && 'value' in transactionUpdate && typeof transactionUpdate.value === 'object' && transactionUpdate.value !== null
-                    ? (transactionUpdate.value as OnyxTypes.Transaction)
-                    : optimisticTransactionFromGetMoneyRequest;
-            optimisticChildSnapshotEntries[transactionKey] = snapshotTransaction;
-            optimisticChildSnapshotKeys.push(transactionKey);
-        }
-
-        onyxData.optimisticData?.push(...(moneyRequestInformationOnyxData.optimisticData ?? []), ...(updateMoneyRequestParamsOnyxData.optimisticData ?? []), ...optimisticDataComments);
-        onyxData.successData?.push(...(moneyRequestInformationOnyxData.successData ?? []), ...(updateMoneyRequestParamsOnyxData.successData ?? []), ...successDataComments);
-        onyxData.failureData?.push(...(moneyRequestInformationOnyxData.failureData ?? []), ...(updateMoneyRequestParamsOnyxData.failureData ?? []), ...failureDataComments);
-    }
-
-    // All transactions that were deleted in the split list will be marked as deleted in onyx
-    const undeletedTransactions = originalChildTransactions.filter(
-        (currentTransaction) => !processedChildTransactionIDs.includes(currentTransaction?.transactionID ?? CONST.IOU.OPTIMISTIC_TRANSACTION_ID),
-    );
-
-    for (const undeletedTransaction of undeletedTransactions) {
-        const splitTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${undeletedTransaction?.transactionID}`];
-        const splitReportActions = getAllReportActions(splitTransaction?.reportID);
-        const reportNameValuePairs = allReportNameValuePairsList?.[`${ONYXKEYS.COLLECTION.REPORT_NAME_VALUE_PAIRS}${splitTransaction?.reportID}`];
-        const splitTransactionReport = allReportsList?.[`${ONYXKEYS.COLLECTION.REPORT}${splitTransaction?.reportID}`];
-        const isReportArchived = isArchivedReport(reportNameValuePairs);
-        const currentReportAction = Object.values(splitReportActions).find((action) => {
-            const transactionID = isMoneyRequestAction(action) ? (getOriginalMessage(action)?.IOUTransactionID ?? CONST.DEFAULT_NUMBER_ID) : CONST.DEFAULT_NUMBER_ID;
-            return transactionID === undeletedTransaction?.transactionID;
-        });
-
-        if (!currentReportAction) {
-            Log.warn(`[Split] Can't find the report action for transaction ${undeletedTransaction?.transactionID} in report ${splitTransaction?.reportID}`);
-            continue;
-        }
-
-        // For a reverse split operation (i.e. deleting one transaction from a 2-split), the other split(undeleted)
-        // transaction also gets marked for deletion optimistically. This causes the undeleted split to remain visible,
-        // resulting in 3 transactions(deleted, undeleted, and original) being shown at the same time when offline.
-        // Since original transaction will be reverted and both splits will eventually be deleted, we remove
-        // the undeleted split entirely instead of marking it for deletion.
-        const forceDeleteSplitTransactionID = isReverseSplitOperation ? splitExpenses.at(0)?.transactionID : undefined;
-
-        const {
-            optimisticData: deleteExpenseOptimisticData,
-            failureData: deleteExpenseFailureData,
-            successData: deleteExpenseSuccessData,
-        } = getDeleteTrackExpenseInformation(
-            splitTransactionReport,
-            undeletedTransaction?.transactionID,
-            currentReportAction,
-            undefined,
-            currentUserPersonalDetails.accountID,
-            undefined,
-            undefined,
-            undefined,
-            undefined,
-            isReportArchived || undeletedTransaction?.transactionID === forceDeleteSplitTransactionID,
-        );
-
-        // getDeleteTrackExpenseInformation only handles deleting the transaction report thread, so we need to update the report preview action here
-        if (originalReportPreviewAction) {
-            const cleanUpTransactionThreadReportOnyxData = getCleanUpTransactionThreadReportOnyxData({
-                shouldDeleteTransactionThread: false,
-                reportAction: currentReportAction,
-                updatedReportPreviewAction: (updatedReportPreviewAction ?? originalReportPreviewAction) as OnyxTypes.ReportAction,
-                shouldAddUpdatedReportPreviewActionToOnyxData: false,
-                currentUserAccountID: currentUserPersonalDetails.accountID,
-            });
-            updatedReportPreviewAction = cleanUpTransactionThreadReportOnyxData.updatedReportPreviewAction;
-        }
-
-        onyxData.optimisticData?.push(...(deleteExpenseOptimisticData ?? []));
-        onyxData.successData?.push(...(deleteExpenseSuccessData ?? []));
-        onyxData.failureData?.push(...(deleteExpenseFailureData ?? []));
-    }
-
-    if (isReverseSplitOperation) {
-        const deletedSplitSnapshotKeys = originalChildTransactions.reduce<Array<`${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}`>>((acc, childTransaction) => {
-            if (!childTransaction?.transactionID) {
-                return acc;
-            }
-
-            acc.push(`${ONYXKEYS.COLLECTION.TRANSACTION}${childTransaction.transactionID}`);
-            return acc;
-        }, []);
-
-        if (deletedSplitSnapshotKeys.length > 0) {
-            const snapshotKeysToUpdate = new Set<`${typeof ONYXKEYS.COLLECTION.SNAPSHOT}${string}`>();
-            const currentSearchHash = searchContext?.currentSearchHash;
-            const activeGroupSearchHashes = searchContext?.activeGroupSearchHashes ?? [];
-
-            if (currentSearchHash !== undefined && currentSearchHash >= 0) {
-                snapshotKeysToUpdate.add(`${ONYXKEYS.COLLECTION.SNAPSHOT}${currentSearchHash}` as const);
-            }
-
-            for (const searchHash of activeGroupSearchHashes) {
-                if (searchHash >= 0) {
-                    snapshotKeysToUpdate.add(`${ONYXKEYS.COLLECTION.SNAPSHOT}${searchHash}` as const);
-                }
-            }
-
-            const relevantSnapshotKeys = Array.from(snapshotKeysToUpdate).filter((snapshotKey) => {
-                const snapshot = allSnapshots?.[snapshotKey];
-                if (!snapshot?.data) {
-                    return false;
-                }
-
-                return deletedSplitSnapshotKeys.some((deletedSplitSnapshotKey) => Object.hasOwn(snapshot.data, deletedSplitSnapshotKey));
-            });
-
-            const originalSnapshotTransactionKey = `${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}` as const;
-            const revertedOriginalTransactionUpdate = [...(onyxData.optimisticData ?? [])].reverse().find((update) => {
-                return update.key === originalSnapshotTransactionKey && update.value && typeof update.value === 'object' && 'reportID' in update.value;
-            });
-            const revertedOriginalTransaction = revertedOriginalTransactionUpdate?.value as OnyxTypes.Transaction | undefined;
-
-            for (const snapshotKey of relevantSnapshotKeys) {
-                const previousSnapshotData = allSnapshots?.[snapshotKey]?.data;
-                const optimisticSnapshotData: Partial<Record<`${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}`, OnyxTypes.Transaction | null>> = {};
-                const failureSnapshotData: Partial<Record<`${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}`, OnyxTypes.Transaction | null>> = {};
-
-                for (const deletedSplitSnapshotKey of deletedSplitSnapshotKeys) {
-                    optimisticSnapshotData[deletedSplitSnapshotKey] = null;
-                    failureSnapshotData[deletedSplitSnapshotKey] = previousSnapshotData?.[deletedSplitSnapshotKey] ?? null;
-                }
-
-                if (revertedOriginalTransaction) {
-                    optimisticSnapshotData[originalSnapshotTransactionKey] = revertedOriginalTransaction;
-                    failureSnapshotData[originalSnapshotTransactionKey] = previousSnapshotData?.[originalSnapshotTransactionKey] ?? null;
-                }
-
-                onyxData.optimisticData?.push({
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: snapshotKey,
-                    value: {
-                        data: optimisticSnapshotData,
-                    },
-                });
-                onyxData.failureData?.push({
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: snapshotKey,
-                    value: {
-                        data: failureSnapshotData,
-                    },
-                });
-            }
-        }
-    }
-
-    if (!isReverseSplitOperation) {
-        // Use SET to update originalTransaction more quickly in Onyx as compared to MERGE to prevent UI inconsistency
-        onyxData.optimisticData?.push({
-            onyxMethod: Onyx.METHOD.SET,
-            key: `${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`,
-            value: {
-                ...originalTransaction,
-                reportID: CONST.REPORT.SPLIT_REPORT_ID,
-            },
-        });
-
-        onyxData.failureData?.push({
-            onyxMethod: Onyx.METHOD.MERGE,
-            key: `${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`,
-            value: originalTransaction ?? null,
-        });
-
-        if (firstIOU) {
-            const updatedReportAction = {
-                [firstIOU.reportActionID]: {
-                    pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE,
-                    previousMessage: firstIOU.message,
-                    message: [
-                        {
-                            type: 'COMMENT',
-                            html: '',
-                            text: '',
-                            isEdited: true,
-                            isDeletedParentAction: true,
-                        },
-                    ],
-                    originalMessage: {
-                        IOUTransactionID: null,
-                    },
-                    errors: null,
-                },
-            };
-
-            const {optimisticData, successData, failureData} = getCleanUpTransactionThreadReportOnyxData({
-                transactionThreadID: firstIOU.childReportID,
-                shouldDeleteTransactionThread: true,
-                reportAction: firstIOU,
-                updatedReportPreviewAction: updatedReportPreviewAction as OnyxTypes.ReportAction,
-                currentUserAccountID: currentUserPersonalDetails.accountID,
-            });
-
-            onyxData.optimisticData?.push(...optimisticData);
-            onyxData.optimisticData?.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${iouReport?.reportID}`,
-                value: updatedReportAction,
-            });
-
-            onyxData.successData?.push(...successData);
-
-            onyxData.failureData?.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${iouReport?.reportID}`,
-                value: {
-                    [firstIOU.reportActionID]: {
-                        ...firstIOU,
-                        pendingAction: null,
-                    },
-                },
-            });
-            onyxData.failureData?.push(...failureData);
-        } else {
-            pushUpdatedReportPreviewActionToOnyxData();
-        }
-
-        // Build the snapshot data update: remove original transaction and add child transactions
-        const optimisticSnapshotData: SearchResultDataType = {
-            [`${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`]: null,
-            ...optimisticChildSnapshotEntries,
-        };
-
-        // On failure, restore the original transaction and remove the child transactions
-        // Initializing as an empty typed object to allow dynamic key assignment resolves TypeScript type inference issue
-        const failureSnapshotData: NullishDeep<SearchResultDataType> = {};
-        failureSnapshotData[`${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`] = originalTransaction ?? null;
-        for (const childKey of optimisticChildSnapshotKeys) {
-            failureSnapshotData[childKey] = null;
-        }
-
-        onyxData.optimisticData?.push({
-            onyxMethod: Onyx.METHOD.MERGE,
-            key: `${ONYXKEYS.COLLECTION.SNAPSHOT}${searchContext?.currentSearchHash}`,
-            value: {
-                data: optimisticSnapshotData,
-            },
-        });
-
-        onyxData.failureData?.push({
-            onyxMethod: Onyx.METHOD.MERGE,
-            key: `${ONYXKEYS.COLLECTION.SNAPSHOT}${searchContext?.currentSearchHash}`,
-            value: {
-                data: failureSnapshotData,
-            },
-        });
-    } else {
-        onyxData.optimisticData?.push({
-            onyxMethod: Onyx.METHOD.MERGE,
-            key: `${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`,
-            value: {
-                errors: null,
-            },
-        });
-        pushUpdatedReportPreviewActionToOnyxData();
-        const isLastTransactionInReport = Object.values(allTransactionsList ?? {}).filter((itemTransaction) => itemTransaction?.reportID === expenseReportID).length === 1;
-        if (isLastTransactionInReport) {
-            onyxData.optimisticData?.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT}${transactionData.reportID}`,
-                value: {
-                    reportID: null,
-                    pendingFields: {
-                        preview: CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE,
-                    },
-                },
-            });
-            onyxData.successData?.push({
-                onyxMethod: Onyx.METHOD.SET,
-                key: `${ONYXKEYS.COLLECTION.REPORT}${transactionData.reportID}`,
-                value: null,
-            });
-            onyxData.failureData?.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT}${transactionData.reportID}`,
-                value: {
-                    reportID: transactionData.reportID,
-                    pendingFields: null,
-                },
-            });
-            if (expenseReport?.parentReportID && expenseReport?.parentReportActionID) {
-                onyxData.optimisticData?.push({
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.parentReportID}`,
-                    value: {
-                        [expenseReport?.parentReportActionID]: {
-                            pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE,
-                        },
-                    },
-                });
-                onyxData.successData?.push({
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.parentReportID}`,
-                    value: {
-                        [expenseReport?.parentReportActionID]: {
-                            pendingAction: null,
-                        },
-                    },
-                });
-                onyxData.failureData?.push({
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.parentReportID}`,
-                    value: {
-                        [expenseReport?.parentReportActionID]: {
-                            pendingAction: null,
-                        },
-                    },
-                });
-            }
-        }
-
-        const originalTransactionThreadReportID = splits.at(0)?.transactionThreadReportID;
-        const iouActionReportActionID = splits.at(0)?.splitReportActionID;
-        if (splitThreadComments.length > 0 && originalTransactionThreadReportID && splitTransactionThreadReportID && iouActionReportActionID && expenseReportID) {
-            const optimisticMovedComments: Record<string, OnyxTypes.ReportAction> = {};
-            const optimisticRemovedComments: Record<string, null> = {};
-            const successMovedComments: OnyxCollection<NullishDeep<OnyxTypes.ReportAction>> = {};
-            const failureMovedCommentsRemoval: Record<string, null> = {};
-            const failureRestoredComments: Record<string, OnyxTypes.ReportAction> = {};
-
-            const commenterAccountIDs = new Set<number>();
-            let latestCommentCreated = '';
-
-            for (const comment of splitThreadComments) {
-                optimisticMovedComments[comment.reportActionID] = {
-                    ...comment,
-                    reportID: originalTransactionThreadReportID,
-                    pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
-                };
-                optimisticRemovedComments[comment.reportActionID] = null;
-                successMovedComments[comment.reportActionID] = {pendingAction: null};
-                failureMovedCommentsRemoval[comment.reportActionID] = null;
-                failureRestoredComments[comment.reportActionID] = comment;
-
-                if (comment.actorAccountID && comment.actorAccountID > 0) {
-                    commenterAccountIDs.add(comment.actorAccountID);
-                }
-                if (comment.created && comment.created > latestCommentCreated) {
-                    latestCommentCreated = comment.created;
-                }
-            }
-
-            onyxData.optimisticData?.push(
-                {
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${originalTransactionThreadReportID}`,
-                    value: optimisticMovedComments,
-                },
-                {
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${splitTransactionThreadReportID}`,
-                    value: optimisticRemovedComments,
-                },
-                {
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReportID}`,
-                    value: {
-                        [iouActionReportActionID]: {
-                            childVisibleActionCount: splitThreadComments.length,
-                            childCommenterCount: commenterAccountIDs.size,
-                            childLastVisibleActionCreated: latestCommentCreated,
-                            childOldestFourAccountIDs: [...commenterAccountIDs].slice(0, 4).join(','),
-                        },
-                    },
-                },
-            );
-
-            onyxData.successData?.push({
-                onyxMethod: Onyx.METHOD.MERGE,
-                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${originalTransactionThreadReportID}`,
-                value: successMovedComments,
-            });
-
-            onyxData.failureData?.push(
-                {
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${originalTransactionThreadReportID}`,
-                    value: failureMovedCommentsRemoval,
-                },
-                {
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${splitTransactionThreadReportID}`,
-                    value: failureRestoredComments,
-                },
-                {
-                    onyxMethod: Onyx.METHOD.MERGE,
-                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReportID}`,
-                    value: {
-                        [iouActionReportActionID]: {
-                            childVisibleActionCount: 0,
-                            childCommenterCount: 0,
-                            childLastVisibleActionCreated: '',
-                            childOldestFourAccountIDs: '',
-                        },
-                    },
-                },
-            );
-        }
-    }
-
-    if (isReverseSplitOperation) {
-        const parameters = {
-            ...splits.at(0),
-            comment: splits.at(0)?.comment?.comment,
-            waypoints: splits.at(0)?.waypoints ? JSON.stringify(splits.at(0)?.waypoints) : undefined,
-        } as RevertSplitTransactionParams;
-        API.write(WRITE_COMMANDS.REVERT_SPLIT_TRANSACTION, parameters, onyxData);
-    } else {
-        // Prepare splitApiParams for the Transaction_Split API call which requires a specific format for the splits
-        // The format is: splits[0][amount], splits[0][category], splits[0][tag] etc.
-        const splitApiParams = {} as Record<string, string | number | boolean>;
-        for (const [i, split] of splits.entries()) {
-            for (const [key, value] of Object.entries(split)) {
-                splitApiParams[`splits[${i}][${key}]`] = value !== null && typeof value === 'object' ? JSON.stringify(value) : value;
-            }
-        }
-
-        const splitParameters: SplitTransactionParams = {
-            ...splitApiParams,
-            transactionID: originalTransactionID,
-        };
-
-        if (isCreationOfSplits) {
-            // eslint-disable-next-line rulesdir/no-multiple-api-calls
-            API.write(WRITE_COMMANDS.SPLIT_TRANSACTION, splitParameters, onyxData);
-        } else {
-            // eslint-disable-next-line rulesdir/no-multiple-api-calls
-            API.write(WRITE_COMMANDS.UPDATE_SPLIT_TRANSACTION, splitParameters, onyxData);
-        }
-    }
-    // eslint-disable-next-line @typescript-eslint/no-deprecated
-    InteractionManager.runAfterInteractions(() => removeDraftSplitTransaction(originalTransactionID));
-}
-
-function updateSplitTransactionsFromSplitExpensesFlow(params: UpdateSplitTransactionsParams) {
-    // Detect if this will be a reverse split that deletes the expense report.
-    // When splits are reduced to 1, updateSplitTransactions performs a reverse split which
-    // optimistically deletes the expense report if it's the last transaction. We need to
-    // set the navigate-back URL before the deletion to prevent the "Not Found" page.
-    const splitExpenses = params.transactionData?.splitExpenses ?? [];
-    const originalTransactionID = params.transactionData?.originalTransactionID ?? CONST.IOU.OPTIMISTIC_TRANSACTION_ID;
-    const allChildTransactions = getChildTransactions(params.allTransactionsList, params.allReportsList, originalTransactionID, true);
-    const originalChildTransactions = allChildTransactions.filter((tx) => tx?.reportID !== CONST.REPORT.UNREPORTED_REPORT_ID);
-    const hasEditableSplitExpensesLeft = splitExpenses.some((expense) => (expense.statusNum ?? 0) < CONST.REPORT.STATUS_NUM.SUBMITTED);
-    const isReverseSplitOperation =
-        splitExpenses.length === 1 && originalChildTransactions.length > 0 && hasEditableSplitExpensesLeft && allChildTransactions.length === originalChildTransactions.length;
-    const expenseReportID = params.expenseReport?.reportID;
-    const isLastTransactionInReport =
-        isReverseSplitOperation && Object.values(params.allTransactionsList ?? {}).filter((itemTransaction) => itemTransaction?.reportID === expenseReportID).length === 1;
-    const fallbackReportID = params.expenseReport?.chatReportID ?? params.expenseReport?.parentReportID;
-
-    if (isLastTransactionInReport && fallbackReportID) {
-        setDeleteTransactionNavigateBackUrl(ROUTES.REPORT_WITH_ID.getRoute(fallbackReportID));
-    }
-
-    updateSplitTransactions({...params, isFromSplitExpensesFlow: true});
-    const isSearchPageTopmostFullScreenRoute = isSearchTopmostFullScreenRoute();
-    const transactionThreadReportID = params.firstIOU?.childReportID;
-    const transactionThreadReportScreen = Navigation.getReportRouteByID(transactionThreadReportID);
-
-    // Reset selected transactions in search after saving split expenses
-    const searchFullScreenRoutes = navigationRef.getRootState()?.routes.findLast((route) => route.name === NAVIGATORS.SEARCH_FULLSCREEN_NAVIGATOR);
-    const lastRoute = searchFullScreenRoutes?.state?.routes?.at(-1);
-    const isUserOnSearchPage = isSearchTopmostFullScreenRoute() && lastRoute?.name === SCREENS.SEARCH.ROOT;
-    if (isUserOnSearchPage) {
-        params?.searchContext?.clearSelectedTransactions?.(undefined, true);
-    } else {
-        params?.searchContext?.clearSelectedTransactions?.(true);
-    }
-
-    if (isSearchPageTopmostFullScreenRoute || !params.transactionReport?.parentReportID) {
-        Navigation.navigateBackToLastSuperWideRHPScreen();
-
-        // After the modal is dismissed, remove the transaction thread report screen
-        // to avoid navigating back to a report removed by the split transaction.
-        requestAnimationFrame(() => {
-            if (!transactionThreadReportScreen?.key) {
-                return;
-            }
-
-            Navigation.removeScreenByKey(transactionThreadReportScreen.key);
-        });
-
-        return;
-    }
-
-    // When the reverse split deletes the expense report, use the backward navigation pattern
-    // (dismissToSuperWideRHP + goBack) instead of dismissModalWithReport. This naturally pops
-    // stale screens from the stack instead of leaving them behind.
-    if (isLastTransactionInReport && fallbackReportID) {
-        const backRoute = ROUTES.REPORT_WITH_ID.getRoute(fallbackReportID);
-        navigateBackOnDeleteTransaction(backRoute);
-
-        // Remove the transaction thread report screen to avoid navigating back to a removed report
-        requestAnimationFrame(() => {
-            if (!transactionThreadReportScreen?.key) {
-                return;
-            }
-            Navigation.removeScreenByKey(transactionThreadReportScreen.key);
-        });
-
-        return;
-    }
-
-    const targetReportID = params.expenseReport?.reportID ?? String(CONST.DEFAULT_NUMBER_ID);
-
-    if (isTracking()) {
-        setPendingSubmitFollowUpAction(CONST.TELEMETRY.SUBMIT_FOLLOW_UP_ACTION.DISMISS_MODAL_AND_OPEN_REPORT, targetReportID);
-    }
-    Navigation.dismissModalWithReport({reportID: targetReportID});
-
-    // After the modal is dismissed, remove the transaction thread report screen
-    // to avoid navigating back to a report removed by the split transaction.
-    requestAnimationFrame(() => {
-        if (!transactionThreadReportScreen?.key) {
-            return;
-        }
-        Navigation.removeScreenByKey(transactionThreadReportScreen.key);
-    });
-}
-
 /**
  * Sets the `splitShares` map that holds individual shares of a split bill
  */
@@ -3448,8 +2086,6 @@ export {
     splitBill,
     splitBillAndOpenReport,
     startSplitBill,
-    updateSplitTransactions,
-    updateSplitTransactionsFromSplitExpensesFlow,
     adjustRemainingSplitShares,
     setDraftSplitTransaction,
     setIndividualShare,
@@ -3457,4 +2093,4 @@ export {
     resetSplitShares,
 };
 
-export type {CreateDistanceRequestInformation, SplitBillActionsParams, UpdateSplitTransactionsParams};
+export type {CreateDistanceRequestInformation, SplitBillActionsParams};
diff --git a/src/libs/actions/IOU/SplitTransactionUpdate.ts b/src/libs/actions/IOU/SplitTransactionUpdate.ts
new file mode 100644
index 000000000000..892df2ab762e
--- /dev/null
+++ b/src/libs/actions/IOU/SplitTransactionUpdate.ts
@@ -0,0 +1,1382 @@
+// eslint-disable-next-line no-restricted-imports
+import {InteractionManager} from 'react-native';
+import type {NullishDeep, OnyxCollection, OnyxEntry, OnyxUpdate} from 'react-native-onyx';
+import Onyx from 'react-native-onyx';
+import type {SearchActionsContextValue, SearchStateContextValue} from '@components/Search/types';
+import {write as apiWrite} from '@libs/API';
+import type {RevertSplitTransactionParams, SplitTransactionParams, SplitTransactionSplitsParam} from '@libs/API/parameters';
+import {WRITE_COMMANDS} from '@libs/API/types';
+import DateUtils from '@libs/DateUtils';
+import {getMicroSecondOnyxErrorWithTranslationKey} from '@libs/ErrorUtils';
+import {calculateAmount as calculateIOUAmount} from '@libs/IOUUtils';
+import Log from '@libs/Log';
+import isSearchTopmostFullScreenRoute from '@libs/Navigation/helpers/isSearchTopmostFullScreenRoute';
+import Navigation, {navigationRef} from '@libs/Navigation/Navigation';
+import {rand64} from '@libs/NumberUtils';
+import Parser from '@libs/Parser';
+import {getDistanceRateCustomUnitRate} from '@libs/PolicyUtils';
+import {
+    getAllReportActions,
+    getIOUActionForReportID,
+    getIOUActionForTransactionID,
+    getLastVisibleAction,
+    getOriginalMessage,
+    getReportAction,
+    isActionOfType,
+    isAddCommentAction,
+    isDeletedAction,
+    isMoneyRequestAction,
+} from '@libs/ReportActionsUtils';
+import {
+    buildOptimisticAddCommentReportAction,
+    canUserPerformWriteAction as canUserPerformWriteActionReportUtils,
+    getParsedComment,
+    getReportOrDraftReport,
+    getTransactionDetails,
+    isArchivedReport,
+    isPolicyExpenseChat as isPolicyExpenseChatReportUtil,
+    navigateBackOnDeleteTransaction,
+    updateOptimisticParentReportAction,
+} from '@libs/ReportUtils';
+import {isTracking, setPendingSubmitFollowUpAction} from '@libs/telemetry/submitFollowUpAction';
+import {getChildTransactions, isDistanceRequest as isDistanceRequestTransactionUtils, isOnHold, isPerDiemRequest as isPerDiemRequestTransactionUtils} from '@libs/TransactionUtils';
+import {setDeleteTransactionNavigateBackUrl} from '@userActions/Report';
+import {removeDraftSplitTransaction} from '@userActions/TransactionEdit';
+import CONST from '@src/CONST';
+import NAVIGATORS from '@src/NAVIGATORS';
+import ONYXKEYS from '@src/ONYXKEYS';
+import ROUTES from '@src/ROUTES';
+import SCREENS from '@src/SCREENS';
+import type * as OnyxTypes from '@src/types/onyx';
+import type {Attendee, Participant, SplitExpense} from '@src/types/onyx/IOU';
+import type {CurrentUserPersonalDetails} from '@src/types/onyx/PersonalDetails';
+import type {OnyxData} from '@src/types/onyx/Request';
+import type {SearchResultDataType} from '@src/types/onyx/SearchResults';
+import type {TransactionChanges} from '@src/types/onyx/Transaction';
+import {getCleanUpTransactionThreadReportOnyxData} from './DeleteMoneyRequest';
+import {getAllReports, getMoneyRequestInformation, getMoneyRequestParticipantsFromReport, getMoneyRequestPolicyTags, getPolicyTagsData, getReportPreviewAction} from './index';
+import type {BuildOnyxDataForMoneyRequestKeys, MoneyRequestInformationParams} from './index';
+import {getDeleteTrackExpenseInformation} from './TrackExpense';
+import {getUpdateMoneyRequestParams} from './UpdateMoneyRequest';
+import type {UpdateMoneyRequestDataKeys} from './UpdateMoneyRequest';
+
+type UpdateSplitTransactionsParams = {
+    allTransactionsList: OnyxCollection<OnyxTypes.Transaction>;
+    allReportsList: OnyxCollection<OnyxTypes.Report>;
+    allReportNameValuePairsList: OnyxCollection<OnyxTypes.ReportNameValuePairs>;
+    allSnapshots?: OnyxCollection<OnyxTypes.SearchResults>;
+    transactionData: {
+        reportID: string;
+        originalTransactionID: string;
+        splitExpenses: SplitExpense[];
+        splitExpensesTotal: number | undefined;
+    };
+    searchContext?: (Partial<SearchStateContextValue & SearchActionsContextValue> & {activeGroupSearchHashes?: number[]}) | undefined;
+    policyCategories: OnyxTypes.PolicyCategories | undefined;
+    policy: OnyxTypes.Policy | undefined;
+    policyRecentlyUsedCategories: OnyxTypes.RecentlyUsedCategories | undefined;
+    iouReport: OnyxEntry<OnyxTypes.Report>;
+    firstIOU: OnyxEntry<OnyxTypes.ReportAction> | undefined;
+    isASAPSubmitBetaEnabled: boolean;
+    currentUserPersonalDetails: CurrentUserPersonalDetails;
+    transactionViolations: OnyxCollection<OnyxTypes.TransactionViolation[]>;
+    quickAction: OnyxEntry<OnyxTypes.QuickAction>;
+    policyRecentlyUsedCurrencies: string[];
+    iouReportNextStep: OnyxEntry<OnyxTypes.ReportNextStepDeprecated>;
+    betas: OnyxEntry<OnyxTypes.Beta[]>;
+    isFromSplitExpensesFlow?: boolean;
+    policyTags: OnyxTypes.PolicyTagLists;
+    personalDetails: OnyxEntry<OnyxTypes.PersonalDetailsList>;
+    transactionReport: OnyxEntry<OnyxTypes.Report>;
+    expenseReport: OnyxEntry<OnyxTypes.Report>;
+    isOffline: boolean;
+};
+
+function updateSplitTransactions({
+    allTransactionsList,
+    allReportsList,
+    allReportNameValuePairsList,
+    allSnapshots,
+    transactionData,
+    searchContext,
+    policyCategories,
+    policy,
+    policyRecentlyUsedCategories,
+    iouReport,
+    firstIOU,
+    isASAPSubmitBetaEnabled,
+    currentUserPersonalDetails,
+    transactionViolations,
+    quickAction,
+    policyRecentlyUsedCurrencies,
+    iouReportNextStep,
+    isFromSplitExpensesFlow,
+    betas,
+    policyTags,
+    personalDetails,
+    transactionReport,
+    expenseReport,
+    isOffline,
+}: UpdateSplitTransactionsParams) {
+    const chatReport = allReportsList?.[`${ONYXKEYS.COLLECTION.REPORT}${expenseReport?.chatReportID}`];
+    const expenseReportParentChat = getReportOrDraftReport(chatReport?.parentReportID);
+    const originalTransactionID = transactionData?.originalTransactionID ?? CONST.IOU.OPTIMISTIC_TRANSACTION_ID;
+    const originalTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`];
+    const originalTransactionDetails = getTransactionDetails(originalTransaction);
+    const autoParticipants = getMoneyRequestParticipantsFromReport(expenseReport, currentUserPersonalDetails.accountID);
+    // Delegate split edit can reach this flow without the workspace expense chat in Onyx.
+    const fallbackPolicyParticipant =
+        autoParticipants.length === 0 && !chatReport && expenseReport?.chatReportID && expenseReport?.policyID
+            ? {
+                  accountID: 0,
+                  reportID: expenseReport.chatReportID,
+                  isPolicyExpenseChat: true,
+                  selected: true,
+                  policyID: expenseReport.policyID,
+              }
+            : undefined;
+    const participants = fallbackPolicyParticipant ? [fallbackPolicyParticipant] : autoParticipants;
+    let fallbackPolicyParentChatReport = expenseReportParentChat;
+    if (!fallbackPolicyParentChatReport && chatReport && isPolicyExpenseChatReportUtil(chatReport)) {
+        fallbackPolicyParentChatReport = chatReport;
+    }
+    if (!fallbackPolicyParentChatReport && fallbackPolicyParticipant) {
+        fallbackPolicyParentChatReport = {
+            reportID: fallbackPolicyParticipant.reportID,
+            type: CONST.REPORT.TYPE.CHAT,
+            chatType: CONST.REPORT.CHAT_TYPE.POLICY_EXPENSE_CHAT,
+            policyID: fallbackPolicyParticipant.policyID,
+            ownerAccountID: expenseReport?.ownerAccountID,
+        } as OnyxTypes.Report;
+    }
+    const splitExpenses = transactionData?.splitExpenses ?? [];
+
+    // Get all children once (including orphaned), then filter for non-orphaned
+    const allChildTransactions = getChildTransactions(allTransactionsList, allReportsList, originalTransactionID, true);
+    const originalChildTransactions = allChildTransactions.filter((tx) => tx?.reportID !== CONST.REPORT.UNREPORTED_REPORT_ID);
+    const processedChildTransactionIDs: string[] = [];
+
+    const splitExpensesTotal = transactionData?.splitExpensesTotal ?? 0;
+
+    const isCreationOfSplits = originalChildTransactions.length === 0;
+    const hasEditableSplitExpensesLeft = splitExpenses.some((expense) => (expense.statusNum ?? 0) < CONST.REPORT.STATUS_NUM.SUBMITTED);
+    // Don't revert split if there are orphaned children (reportID '0') - they're still part of the split
+    const isReverseSplitOperation =
+        splitExpenses.length === 1 && originalChildTransactions.length > 0 && hasEditableSplitExpensesLeft && allChildTransactions.length === originalChildTransactions.length;
+
+    let splitThreadComments: OnyxTypes.ReportAction[] = [];
+    let splitTransactionThreadReportID: string | undefined;
+
+    if (isReverseSplitOperation) {
+        const revertSplitTransactionID = splitExpenses.at(0)?.transactionID;
+        const revertSplitTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${revertSplitTransactionID}`];
+        const revertSplitReportActions = getAllReportActions(revertSplitTransaction?.reportID);
+        const revertSplitIOUAction = revertSplitTransactionID ? getIOUActionForTransactionID(Object.values(revertSplitReportActions ?? {}), revertSplitTransactionID) : undefined;
+        splitTransactionThreadReportID = revertSplitIOUAction?.childReportID;
+        if (splitTransactionThreadReportID) {
+            const splitTransactionThreadActions = getAllReportActions(splitTransactionThreadReportID);
+            splitThreadComments = Object.values(splitTransactionThreadActions).filter(
+                (action): action is OnyxTypes.ReportAction =>
+                    isActionOfType(action, CONST.REPORT.ACTIONS.TYPE.ADD_COMMENT) && !isDeletedAction(action) && (action.actorAccountID ?? CONST.DEFAULT_NUMBER_ID) > 0,
+            );
+        }
+    }
+
+    let changesInReportTotal = 0;
+    // Validate custom unit rate before proceeding with split
+    const customUnitRateID = originalTransaction?.comment?.customUnit?.customUnitRateID;
+    const isPerDiem = isPerDiemRequestTransactionUtils(originalTransaction);
+
+    if (customUnitRateID && policy && !isPerDiem && isCreationOfSplits && !isFromSplitExpensesFlow) {
+        const customUnitRate = getDistanceRateCustomUnitRate(policy, customUnitRateID);
+
+        // If the rate doesn't exist or is disabled, show an error and return early
+        if (!customUnitRate?.enabled) {
+            // Show error to user
+            Onyx.merge(`${ONYXKEYS.COLLECTION.SPLIT_TRANSACTION_DRAFT}${originalTransactionID}`, {
+                errors: getMicroSecondOnyxErrorWithTranslationKey('iou.error.invalidRate'),
+            });
+            return;
+        }
+    }
+
+    const splits: SplitTransactionSplitsParam =
+        splitExpenses.map((split) => {
+            const currentDescription = getParsedComment(Parser.htmlToMarkdown(split.description ?? ''));
+            changesInReportTotal += split.amount;
+            return {
+                amount: split.amount,
+                category: split.category ?? '',
+                tag: split.tags?.[0] ?? '',
+                created: split.created,
+                merchant: split?.merchant ?? '',
+                transactionID: split.transactionID,
+                comment: {
+                    comment: currentDescription,
+                },
+                reimbursable: split?.reimbursable,
+                billable: split?.billable,
+                quantity: split.customUnit?.quantity ?? undefined,
+                customUnitRateID: split.customUnit?.customUnitRateID,
+                odometerStart: split.odometerStart,
+                odometerEnd: split.odometerEnd,
+                waypoints: split.waypoints,
+            };
+        }) ?? [];
+    changesInReportTotal -= splitExpensesTotal;
+
+    const onyxData: OnyxData<BuildOnyxDataForMoneyRequestKeys | UpdateMoneyRequestDataKeys> = {
+        successData: [],
+        failureData: [],
+        optimisticData: [],
+    };
+
+    // The split transactions can be in different reports, so we need to calculate the total for each report.
+    const reportTotals = new Map<string, number>();
+    const expenseReportID = expenseReport?.reportID;
+
+    if (expenseReportID) {
+        const expenseReportKey = `${ONYXKEYS.COLLECTION.REPORT}${expenseReportID}`;
+        const expenseReportTotal = allReportsList?.[expenseReportKey]?.total ?? expenseReport?.total ?? 0;
+        reportTotals.set(expenseReportID, expenseReportTotal - changesInReportTotal);
+    }
+
+    for (const expense of splitExpenses) {
+        const splitExpenseReportID = expense.reportID;
+        if (!splitExpenseReportID || reportTotals.has(splitExpenseReportID)) {
+            continue;
+        }
+
+        const splitExpenseReport = allReportsList?.[`${ONYXKEYS.COLLECTION.REPORT}${splitExpenseReportID}`];
+        reportTotals.set(splitExpenseReportID, splitExpenseReport?.total ?? 0);
+    }
+
+    let updatedReportPreviewAction: Partial<OnyxTypes.ReportAction> | undefined;
+    const originalReportPreviewAction = getReportPreviewAction(expenseReport?.chatReportID, expenseReport?.reportID);
+    const transactionReportActions = getAllReportActions(firstIOU?.childReportID);
+    const expenseReportNameValuePairs = allReportNameValuePairsList?.[`${ONYXKEYS.COLLECTION.REPORT_NAME_VALUE_PAIRS}${expenseReport?.reportID}`];
+    const isArchivedExpenseReport = isArchivedReport(expenseReportNameValuePairs);
+    const canUserPerformWriteAction = chatReport ? !!canUserPerformWriteActionReportUtils(chatReport, isArchivedExpenseReport) : true;
+    const lastVisibleAction = getLastVisibleAction(expenseReport?.reportID, canUserPerformWriteAction);
+    const isTransactionOnHold = isOnHold(originalTransaction);
+    const holdReportAction = getReportAction(firstIOU?.childReportID, `${originalTransaction?.comment?.hold ?? ''}`);
+
+    let holdCommentReportAction: OnyxTypes.ReportAction<'ADDCOMMENT'> | undefined;
+    const allCommentActionsFromOriginalTransactionThread: Array<OnyxTypes.ReportAction<'ADDCOMMENT'>> = [];
+    for (const action of Object.values(transactionReportActions ?? {})) {
+        if (!isAddCommentAction(action)) {
+            continue;
+        }
+
+        if (holdReportAction && !(holdCommentReportAction?.timestamp && holdReportAction?.timestamp === holdCommentReportAction.timestamp)) {
+            // The HOLD report action and its corresponding comment share the same `timestamp` value.
+            if (holdReportAction.timestamp !== undefined && holdReportAction.timestamp === action.timestamp) {
+                holdCommentReportAction = action;
+            } else if (action.created >= holdReportAction.created && (!holdCommentReportAction || holdCommentReportAction.created >= action.created)) {
+                // If `timestamp` is unavailable, fall back to finding the comment whose `created` value
+                // is greater than and closest to that of the holdReportAction.
+                holdCommentReportAction = action;
+            }
+        }
+
+        if (isDeletedAction(action) || action.pendingAction === CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE) {
+            continue;
+        }
+        allCommentActionsFromOriginalTransactionThread.push(action);
+    }
+    // We will pre-sort to ensure that comments are inserted in the correct order.
+    allCommentActionsFromOriginalTransactionThread.sort((a, b) => (a.created > b.created ? 1 : -1));
+
+    const updateParentActions = (iouAction: OnyxTypes.ReportAction, childVisibleActionCountToAdd: number) => {
+        if (childVisibleActionCountToAdd <= 0) {
+            return undefined;
+        }
+
+        const updatedIOUAction = updateOptimisticParentReportAction(iouAction, iouAction.created, CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD, childVisibleActionCountToAdd);
+
+        if (originalReportPreviewAction) {
+            const nextUpdatedReportPreviewAction = updateOptimisticParentReportAction(
+                (updatedReportPreviewAction ?? originalReportPreviewAction) as OnyxTypes.ReportAction,
+                lastVisibleAction?.childLastVisibleActionCreated ?? lastVisibleAction?.created ?? '',
+                CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
+                childVisibleActionCountToAdd,
+            ) as Partial<OnyxTypes.ReportAction>;
+            nextUpdatedReportPreviewAction.reportActionID = originalReportPreviewAction.reportActionID;
+            updatedReportPreviewAction = nextUpdatedReportPreviewAction;
+        }
+
+        return updatedIOUAction;
+    };
+    const pushUpdatedReportPreviewActionToOnyxData = () => {
+        if (!updatedReportPreviewAction) {
+            return;
+        }
+
+        onyxData.optimisticData?.push({
+            onyxMethod: Onyx.METHOD.MERGE,
+            key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${chatReport?.reportID}`,
+            value: {
+                [updatedReportPreviewAction?.reportActionID ?? CONST.DEFAULT_NUMBER_ID]: updatedReportPreviewAction,
+            },
+        });
+
+        onyxData.failureData?.push({
+            onyxMethod: Onyx.METHOD.MERGE,
+            key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${chatReport?.reportID}`,
+            value: {
+                [updatedReportPreviewAction?.reportActionID ?? CONST.DEFAULT_NUMBER_ID]: {
+                    childVisibleActionCount: originalReportPreviewAction?.childVisibleActionCount,
+                    childCommenterCount: originalReportPreviewAction?.childCommenterCount,
+                    childLastVisibleActionCreated: originalReportPreviewAction?.childLastVisibleActionCreated,
+                    childOldestFourAccountIDs: originalReportPreviewAction?.childOldestFourAccountIDs,
+                },
+            },
+        });
+    };
+
+    // Collect optimistic child transactions to add to the search snapshot (forward split only)
+    const optimisticChildSnapshotEntries: SearchResultDataType = {};
+    const optimisticChildSnapshotKeys: Array<`${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}`> = [];
+
+    for (const [index, splitExpense] of splitExpenses.entries()) {
+        const existingTransactionID = isReverseSplitOperation ? originalTransactionID : splitExpense.transactionID;
+        const splitTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`];
+        if (splitTransaction) {
+            processedChildTransactionIDs.push(splitTransaction.transactionID);
+        }
+
+        const splitReportActions = getAllReportActions(isReverseSplitOperation ? expenseReport?.reportID : splitTransaction?.reportID);
+        const currentReportAction = Object.values(splitReportActions).find((action) => {
+            const transactionID = isMoneyRequestAction(action) ? (getOriginalMessage(action)?.IOUTransactionID ?? CONST.DEFAULT_NUMBER_ID) : CONST.DEFAULT_NUMBER_ID;
+            return transactionID === existingTransactionID;
+        });
+
+        const splitExpenseMerchant = splitExpense.merchant ?? '';
+
+        const requestMoneyInformation = {
+            participantParams: {
+                participant: participants.at(0) ?? ({} as Participant),
+                payeeEmail: currentUserPersonalDetails?.login ?? '',
+                payeeAccountID: currentUserPersonalDetails?.accountID ?? CONST.DEFAULT_NUMBER_ID,
+            },
+            policyParams: {
+                policy,
+                policyCategories,
+                policyTags,
+            },
+            transactionParams: {
+                amount: Math.abs(originalTransaction?.amount ?? 0),
+                modifiedAmount: splitExpense.amount ?? 0,
+                currency: originalTransactionDetails?.currency ?? CONST.CURRENCY.USD,
+                created: splitExpense.created,
+                merchant: splitExpenseMerchant,
+                comment: splitExpense.description,
+                category: splitExpense.category,
+                tag: splitExpense.tags?.[0],
+                originalTransactionID,
+                attendees: splitTransaction?.comment?.attendees ?? originalTransactionDetails?.attendees,
+                source: CONST.IOU.TYPE.SPLIT,
+                linkedTrackedExpenseReportAction: currentReportAction,
+                pendingAction: splitTransaction ? null : CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
+                pendingFields: splitTransaction ? splitTransaction.pendingFields : undefined,
+                reimbursable: originalTransactionDetails?.reimbursable,
+                taxCode: originalTransactionDetails?.taxCode,
+                taxAmount: calculateIOUAmount(splitExpenses.length - 1, originalTransactionDetails?.taxAmount ?? 0, originalTransactionDetails?.currency ?? CONST.CURRENCY.USD, false),
+                taxValue: originalTransactionDetails?.taxValue,
+                billable: originalTransactionDetails?.billable,
+                waypoints: splitExpense.waypoints,
+                customUnit: splitExpense.customUnit,
+                // For distance transactions, also pass distance from customUnit.quantity so buildOptimisticTransaction sets it correctly
+                distance: splitExpense.customUnit?.quantity,
+                odometerStart: splitExpense.odometerStart,
+                odometerEnd: splitExpense.odometerEnd,
+            },
+            parentChatReport: fallbackPolicyParentChatReport,
+            existingTransaction: originalTransaction,
+            isASAPSubmitBetaEnabled,
+            currentUserAccountIDParam: currentUserPersonalDetails?.accountID,
+            currentUserEmailParam: currentUserPersonalDetails?.login ?? '',
+            transactionViolations,
+            quickAction,
+            policyRecentlyUsedCurrencies,
+            betas,
+            personalDetails,
+        } as MoneyRequestInformationParams;
+
+        if (isReverseSplitOperation) {
+            requestMoneyInformation.transactionParams = {
+                amount: splitExpense.amount ?? 0,
+                currency: originalTransactionDetails?.currency ?? CONST.CURRENCY.USD,
+                created: splitExpense.created,
+                merchant: splitExpense.merchant ?? '',
+                comment: splitExpense.description,
+                category: splitExpense.category,
+                tag: splitExpense.tags?.[0],
+                attendees: originalTransactionDetails?.attendees as Attendee[],
+                linkedTrackedExpenseReportAction: currentReportAction,
+                taxCode: originalTransactionDetails?.taxCode,
+                taxAmount: calculateIOUAmount(splitExpenses.length - 1, originalTransactionDetails?.taxAmount ?? 0, originalTransactionDetails?.currency ?? CONST.CURRENCY.USD, false),
+                taxValue: originalTransactionDetails?.taxValue,
+                billable: originalTransactionDetails?.billable,
+                waypoints: splitExpense.waypoints,
+                customUnit: splitExpense.customUnit,
+                // For distance transactions, also pass distance from customUnit.quantity so buildOptimisticTransaction sets it correctly
+                distance: splitExpense.customUnit?.quantity ?? undefined,
+                odometerStart: splitExpense.odometerStart,
+                odometerEnd: splitExpense.odometerEnd,
+            };
+            requestMoneyInformation.existingTransaction = undefined;
+        }
+
+        const {participantParams, policyParams, transactionParams, parentChatReport, existingTransaction} = requestMoneyInformation;
+        const parsedComment = getParsedComment(Parser.htmlToMarkdown(transactionParams.comment ?? ''));
+        transactionParams.comment = parsedComment;
+
+        const {
+            transactionThreadReportID,
+            createdReportActionIDForThread,
+            transaction: optimisticTransactionFromGetMoneyRequest,
+            onyxData: moneyRequestInformationOnyxData,
+            iouAction,
+        } = getMoneyRequestInformation({
+            participantParams,
+            parentChatReport,
+            policyParams: {
+                ...policyParams,
+                // eslint-disable-next-line @typescript-eslint/no-deprecated
+                policyTagList: getMoneyRequestPolicyTags({moneyRequestReportID: splitExpense?.reportID, parentChatReport, participant: participantParams.participant}),
+            },
+            transactionParams,
+            moneyRequestReportID: splitExpense?.reportID,
+            existingTransaction,
+            existingTransactionID,
+            newReportTotal: reportTotals.get(splitExpense?.reportID ?? String(CONST.DEFAULT_NUMBER_ID)) ?? 0,
+            newNonReimbursableTotal: (transactionReport?.nonReimbursableTotal ?? 0) - changesInReportTotal,
+            isSplitExpense: true,
+            currentReportActionID: !isReverseSplitOperation ? currentReportAction?.reportActionID : undefined,
+            isASAPSubmitBetaEnabled,
+            currentUserAccountIDParam: currentUserPersonalDetails?.accountID,
+            currentUserEmailParam: currentUserPersonalDetails?.login ?? '',
+            transactionViolations,
+            quickAction,
+            shouldGenerateTransactionThreadReport: true,
+            policyRecentlyUsedCurrencies,
+            betas,
+            personalDetails,
+        });
+
+        let updateMoneyRequestParamsOnyxData: OnyxData<UpdateMoneyRequestDataKeys> = {};
+        const currentSplit = splits.at(index);
+
+        // For existing split transactions, update the field change messages
+        // For new transactions, skip this step
+        if (splitTransaction) {
+            const transactionChanges = {
+                ...currentSplit,
+                comment: currentSplit?.comment?.comment,
+                customUnitRateID: currentSplit?.customUnitRateID ?? CONST.CUSTOM_UNITS.FAKE_P2P_ID,
+            } as TransactionChanges;
+
+            const existing = getTransactionDetails(splitTransaction);
+            const oldTransactionChanges = {
+                ...existing,
+                quantity: splitTransaction.comment?.customUnit?.quantity ?? existing?.distance,
+            } as TransactionChanges;
+
+            if (currentSplit) {
+                currentSplit.reimbursable = splitTransaction.reimbursable;
+                currentSplit.billable = splitTransaction.billable;
+            }
+
+            for (const key of Object.keys(transactionChanges)) {
+                const newValue = transactionChanges[key as keyof typeof transactionChanges];
+                const oldValue = oldTransactionChanges?.[key as keyof typeof oldTransactionChanges];
+                if (newValue === oldValue) {
+                    delete transactionChanges[key as keyof typeof transactionChanges];
+                    // Ensure we pass the currency to getUpdateMoneyRequestParams as well, so the amount message is created correctly
+                } else if (key === 'amount') {
+                    transactionChanges.currency = originalTransactionDetails?.currency;
+                } else if (key === 'waypoints') {
+                    // For waypoints, we need to compare the stringified version of the arrays since they are arrays of objects
+                    const newWaypoints = JSON.stringify(transactionChanges.waypoints);
+                    const oldWaypoints = JSON.stringify(oldTransactionChanges?.waypoints);
+                    if (newWaypoints === oldWaypoints) {
+                        delete transactionChanges.waypoints;
+                    }
+                }
+            }
+
+            if (isReverseSplitOperation) {
+                delete transactionChanges.transactionID;
+            }
+
+            if (Object.keys(transactionChanges).length > 0) {
+                const transactionThreadReport = getAllReports()?.[`${ONYXKEYS.COLLECTION.REPORT}${isReverseSplitOperation ? splitExpense?.reportID : transactionThreadReportID}`];
+                const transactionIOUReport = getAllReports()?.[`${ONYXKEYS.COLLECTION.REPORT}${splitExpense?.reportID ?? transactionThreadReport?.parentReportID}`];
+                const {onyxData: moneyRequestParamsOnyxData, params} = getUpdateMoneyRequestParams({
+                    transactionID: existingTransactionID,
+                    transactionThreadReport,
+                    iouReport: transactionIOUReport,
+                    transactionChanges,
+                    policy,
+                    policyTagList: policyTags ?? null,
+                    // TODO: Replace getPolicyTagsData (https://github.com/Expensify/App/issues/72721) with useOnyx hook
+                    // eslint-disable-next-line @typescript-eslint/no-deprecated
+                    reportPolicyTags: getPolicyTagsData(transactionIOUReport?.policyID),
+                    policyCategories: policyCategories ?? null,
+                    newTransactionReportID: splitExpense?.reportID,
+                    policyRecentlyUsedCategories,
+                    currentUserAccountIDParam: currentUserPersonalDetails?.accountID,
+                    currentUserEmailParam: currentUserPersonalDetails?.login ?? '',
+                    isASAPSubmitBetaEnabled,
+                    iouReportNextStep,
+                    isSplitTransaction: true,
+                    isOffline,
+                });
+                if (currentSplit) {
+                    currentSplit.modifiedExpenseReportActionID = params.reportActionID;
+                }
+                updateMoneyRequestParamsOnyxData = moneyRequestParamsOnyxData;
+            }
+            // For new split transactions, set the reportID once the transaction and associated report are created
+        } else if (currentSplit) {
+            currentSplit.reportID = splitExpense?.reportID;
+        }
+
+        if (currentSplit) {
+            currentSplit.transactionThreadReportID = transactionThreadReportID;
+            currentSplit.createdReportActionIDForThread = createdReportActionIDForThread;
+            currentSplit.splitReportActionID = iouAction.reportActionID;
+        }
+
+        // Copy comments to the transaction report thread of the split expense
+        const optimisticDataComments: Array<OnyxUpdate<BuildOnyxDataForMoneyRequestKeys>> = [];
+        const successDataComments: Array<OnyxUpdate<BuildOnyxDataForMoneyRequestKeys>> = [];
+        const failureDataComments: Array<OnyxUpdate<BuildOnyxDataForMoneyRequestKeys>> = [];
+        const addCommentToSplitTransactionThread = (commentAction: OnyxTypes.ReportAction) => {
+            const newReportActionID = rand64();
+            // delegateAccountIDParam: will be threaded in PR 11; buildOptimisticAddCommentReportAction falls back to module-level Onyx.connect value (https://github.com/Expensify/App/issues/66425)
+            const reportComment = buildOptimisticAddCommentReportAction({
+                text: '',
+                actorAccountID: commentAction.actorAccountID,
+                reportID: transactionThreadReportID,
+                reportActionID: newReportActionID,
+                delegateAccountIDParam: undefined,
+            });
+            const reportActionComment = {
+                ...reportComment.reportAction,
+                created: DateUtils.getDBTime(),
+                message: commentAction.message,
+                originalMessage: getOriginalMessage(commentAction),
+            };
+
+            optimisticDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
+                value: {[newReportActionID]: reportActionComment},
+            });
+            successDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
+                value: {[newReportActionID]: {pendingAction: null, isOptimisticAction: null}},
+            });
+            failureDataComments.push({onyxMethod: Onyx.METHOD.MERGE, key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`, value: {[newReportActionID]: null}});
+
+            if (currentSplit) {
+                currentSplit.copiedComments ??= {};
+                currentSplit.copiedComments[commentAction.reportActionID] = newReportActionID;
+            }
+        };
+
+        // An internal helper to find transaction violations within onyxUpdates.
+        // If one exists, it modifies the value for the update instead of adding a new one.
+        const updateTransactionViolationsOnyxData = (
+            targetTransactionID: string,
+            onyxUpdates: Array<OnyxUpdate<BuildOnyxDataForMoneyRequestKeys | UpdateMoneyRequestDataKeys>> | undefined,
+            fallbackViolations: OnyxTypes.TransactionViolation[],
+        ) => {
+            const transactionViolationsKey = `${ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS}${targetTransactionID}` as typeof ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS;
+            const latestViolationUpdate = onyxUpdates?.findLast((update) => update.key === transactionViolationsKey) as OnyxUpdate<typeof ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS>;
+            const baseViolations = latestViolationUpdate && 'value' in latestViolationUpdate && Array.isArray(latestViolationUpdate.value) ? latestViolationUpdate.value : fallbackViolations;
+            const nextViolations = [
+                ...baseViolations.filter((violation) => violation.name !== CONST.VIOLATIONS.HOLD),
+                {name: CONST.VIOLATIONS.HOLD, type: CONST.VIOLATION_TYPES.VIOLATION, showInReview: true},
+            ];
+
+            if (latestViolationUpdate && 'value' in latestViolationUpdate) {
+                latestViolationUpdate.value = nextViolations;
+                return;
+            }
+
+            optimisticDataComments.push({
+                onyxMethod: Onyx.METHOD.SET,
+                key: transactionViolationsKey,
+                value: nextViolations,
+            });
+
+            failureDataComments.push({
+                onyxMethod: Onyx.METHOD.SET,
+                key: transactionViolationsKey,
+                value: fallbackViolations,
+            });
+        };
+        const addHoldToTransactionThread = (commentAction?: OnyxTypes.ReportAction) => {
+            if (!holdReportAction) {
+                return;
+            }
+            // Generate new IDs and timestamps for each split
+            const newHoldReportActionID = rand64();
+            const timestamp = DateUtils.getDBTime();
+
+            // Create new optimistic hold report action with new ID and timestamp, keeping other information
+            const newHoldReportAction = {
+                ...holdReportAction,
+                reportActionID: newHoldReportActionID,
+                created: timestamp,
+                pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
+                timestamp: undefined,
+            };
+
+            const newHoldReportActionCommentID = commentAction ? rand64() : undefined;
+            const newHoldReportActionComment =
+                commentAction && newHoldReportActionCommentID
+                    ? {
+                          ...commentAction,
+                          reportActionID: newHoldReportActionCommentID,
+                          created: DateUtils.addMillisecondsFromDateTime(timestamp, 1),
+                          pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
+                          timestamp: undefined,
+                      }
+                    : undefined;
+
+            // Add to optimisticData for this split's reportActions
+            optimisticDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
+                value: {
+                    [newHoldReportActionID]: newHoldReportAction,
+                    ...(newHoldReportActionCommentID && newHoldReportAction ? {[newHoldReportActionCommentID]: newHoldReportActionComment} : {}),
+                },
+            });
+
+            optimisticDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`,
+                value: {
+                    comment: {
+                        hold: newHoldReportActionID,
+                    },
+                },
+            });
+
+            // Add successData to clear pendingAction after API call succeeds
+            successDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
+                value: {
+                    [newHoldReportActionID]: {pendingAction: null},
+                    ...(newHoldReportActionCommentID ? {[newHoldReportActionCommentID]: {pendingAction: null}} : {}),
+                },
+            });
+
+            // Add failureData to remove optimistic hold report actions if the request fails
+            failureDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
+                value: {
+                    [newHoldReportActionID]: null,
+                    ...(newHoldReportActionCommentID ? {[newHoldReportActionCommentID]: null} : {}),
+                },
+            });
+            failureDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`,
+                value: {
+                    comment: {
+                        hold: splitTransaction?.comment?.hold ?? null,
+                    },
+                },
+            });
+
+            // Add hold transaction violation to optimisticData
+            updateTransactionViolationsOnyxData(
+                existingTransactionID,
+                updateMoneyRequestParamsOnyxData.optimisticData ?? moneyRequestInformationOnyxData.optimisticData,
+                transactionViolations?.[`${ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS}${existingTransactionID}`] ?? [],
+            );
+
+            if (currentSplit) {
+                currentSplit.holdReportActionID = newHoldReportActionID;
+                currentSplit.holdReportActionCommentID = newHoldReportActionCommentID;
+            }
+        };
+
+        let updatedIOUAction: Partial<OnyxTypes.ReportAction> | undefined;
+        const copyCommentsAndHoldState = ({commentActions, isSourceTransactionOnHold}: {commentActions: OnyxTypes.ReportAction[]; isSourceTransactionOnHold: boolean}) => {
+            let hasInsertedHoldState = !isSourceTransactionOnHold || !holdReportAction;
+
+            for (const commentAction of commentActions) {
+                if (!hasInsertedHoldState && holdReportAction && commentAction.reportActionID === holdCommentReportAction?.reportActionID) {
+                    addHoldToTransactionThread(commentAction);
+                    hasInsertedHoldState = true;
+                    continue;
+                }
+
+                addCommentToSplitTransactionThread(commentAction);
+            }
+
+            // If the commentAction is not found, it means the action has been deleted.
+            // We call insertHoldState here to ensure the hold state is always added.
+            if (!hasInsertedHoldState) {
+                addHoldToTransactionThread();
+            }
+        };
+
+        if (isCreationOfSplits && transactionThreadReportID && firstIOU?.childReportID) {
+            copyCommentsAndHoldState({
+                commentActions: allCommentActionsFromOriginalTransactionThread,
+                isSourceTransactionOnHold: isTransactionOnHold,
+            });
+            updatedIOUAction = updateParentActions(iouAction, firstIOU.childVisibleActionCount ?? 0);
+        }
+
+        // When isReverseSplitOperation is true, we move all comments from the remaining transaction to the original transaction
+        if (isReverseSplitOperation && transactionThreadReportID) {
+            const remainingTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${splitExpense.transactionID}`];
+            const remainTransactionThreadReportAction = getIOUActionForReportID(splitExpense.reportID, splitExpense.transactionID);
+            const allReportActions = getAllReportActions(remainTransactionThreadReportAction?.childReportID);
+            const isRemainingTransactionOnHold = isOnHold(remainingTransaction);
+            const remainingHoldReportAction = getReportAction(remainTransactionThreadReportAction?.childReportID, `${remainingTransaction?.comment?.hold ?? ''}`);
+
+            const optimisticActionsData: OnyxTypes.ReportActions = {};
+            const successActionsData: Record<string, Record<string, null>> = {};
+            const failureActionsData: Record<string, null> = {};
+
+            for (const action of Object.values(allReportActions)) {
+                if (!isAddCommentAction(action) || isDeletedAction(action) || action.pendingAction === CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE) {
+                    continue;
+                }
+                optimisticActionsData[action.reportActionID] = {...action, pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD};
+                successActionsData[action.reportActionID] = {pendingAction: null, isOptimisticAction: null};
+                failureActionsData[action.reportActionID] = null;
+            }
+            if (isRemainingTransactionOnHold && remainingHoldReportAction) {
+                optimisticActionsData[remainingHoldReportAction.reportActionID] = {...remainingHoldReportAction, pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD};
+                successActionsData[remainingHoldReportAction.reportActionID] = {pendingAction: null, isOptimisticAction: null};
+                failureActionsData[remainingHoldReportAction.reportActionID] = null;
+
+                optimisticDataComments.push({
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`,
+                    value: {
+                        comment: {
+                            hold: remainingHoldReportAction.reportActionID,
+                        },
+                    },
+                });
+
+                failureDataComments.push({
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.TRANSACTION}${existingTransactionID}`,
+                    value: {
+                        comment: {
+                            hold: splitTransaction?.comment?.hold ?? null,
+                        },
+                    },
+                });
+
+                // Add hold transaction violation to optimisticData
+                updateTransactionViolationsOnyxData(
+                    existingTransactionID,
+                    updateMoneyRequestParamsOnyxData.optimisticData ?? moneyRequestInformationOnyxData.optimisticData,
+                    transactionViolations?.[`${ONYXKEYS.COLLECTION.TRANSACTION_VIOLATIONS}${existingTransactionID}`] ?? [],
+                );
+            }
+            optimisticDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
+                value: optimisticActionsData,
+            });
+
+            successDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
+                value: successActionsData,
+            });
+
+            failureDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${transactionThreadReportID}`,
+                value: failureActionsData,
+            });
+
+            updatedIOUAction = updateParentActions(iouAction, remainTransactionThreadReportAction?.childVisibleActionCount ?? 0);
+        }
+
+        if (updatedIOUAction) {
+            optimisticDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.reportID}`,
+                value: {[iouAction.reportActionID]: updatedIOUAction},
+            });
+            failureDataComments.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.reportID}`,
+                value: {
+                    [iouAction.reportActionID]: {
+                        childVisibleActionCount: iouAction.childVisibleActionCount,
+                        childCommenterCount: iouAction.childCommenterCount,
+                        childLastVisibleActionCreated: null,
+                        childOldestFourAccountIDs: null,
+                    },
+                },
+            });
+        }
+
+        // Ensure merchant from splitExpense is preserved in optimisticData for new and existing transactions
+        const transactionIDFromOptimistic = optimisticTransactionFromGetMoneyRequest?.transactionID;
+        if (transactionIDFromOptimistic && moneyRequestInformationOnyxData.optimisticData) {
+            const transactionUpdate = moneyRequestInformationOnyxData.optimisticData.find((update) => update.key === `${ONYXKEYS.COLLECTION.TRANSACTION}${transactionIDFromOptimistic}`);
+            if (transactionUpdate && 'value' in transactionUpdate && typeof transactionUpdate.value === 'object' && transactionUpdate.value !== null) {
+                const transactionUpdateValue = transactionUpdate.value as OnyxTypes.Transaction;
+                const expectedMerchant = optimisticTransactionFromGetMoneyRequest?.merchant;
+                if (expectedMerchant && transactionUpdateValue.merchant !== expectedMerchant) {
+                    transactionUpdateValue.merchant = expectedMerchant;
+                    // For distance transactions, also update modifiedMerchant to ensure consistency
+                    if (isDistanceRequestTransactionUtils(transactionUpdateValue)) {
+                        transactionUpdateValue.modifiedMerchant = expectedMerchant;
+                    }
+                }
+            }
+        }
+
+        // Collect the optimistic child transaction for snapshot update (forward split only)
+        if (!isReverseSplitOperation && optimisticTransactionFromGetMoneyRequest) {
+            const childTransactionID = optimisticTransactionFromGetMoneyRequest.transactionID;
+            const transactionKey: `${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}` = `${ONYXKEYS.COLLECTION.TRANSACTION}${childTransactionID}`;
+            // Use the transaction value from optimisticData if available (it may have merchant fixes applied),
+            // otherwise fall back to the raw optimistic transaction
+            const transactionUpdate = moneyRequestInformationOnyxData.optimisticData?.find((update) => update.key === transactionKey);
+            const snapshotTransaction =
+                transactionUpdate && 'value' in transactionUpdate && typeof transactionUpdate.value === 'object' && transactionUpdate.value !== null
+                    ? (transactionUpdate.value as OnyxTypes.Transaction)
+                    : optimisticTransactionFromGetMoneyRequest;
+            optimisticChildSnapshotEntries[transactionKey] = snapshotTransaction;
+            optimisticChildSnapshotKeys.push(transactionKey);
+        }
+
+        onyxData.optimisticData?.push(...(moneyRequestInformationOnyxData.optimisticData ?? []), ...(updateMoneyRequestParamsOnyxData.optimisticData ?? []), ...optimisticDataComments);
+        onyxData.successData?.push(...(moneyRequestInformationOnyxData.successData ?? []), ...(updateMoneyRequestParamsOnyxData.successData ?? []), ...successDataComments);
+        onyxData.failureData?.push(...(moneyRequestInformationOnyxData.failureData ?? []), ...(updateMoneyRequestParamsOnyxData.failureData ?? []), ...failureDataComments);
+    }
+
+    // All transactions that were deleted in the split list will be marked as deleted in onyx
+    const undeletedTransactions = originalChildTransactions.filter(
+        (currentTransaction) => !processedChildTransactionIDs.includes(currentTransaction?.transactionID ?? CONST.IOU.OPTIMISTIC_TRANSACTION_ID),
+    );
+
+    for (const undeletedTransaction of undeletedTransactions) {
+        const splitTransaction = allTransactionsList?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${undeletedTransaction?.transactionID}`];
+        const splitReportActions = getAllReportActions(splitTransaction?.reportID);
+        const reportNameValuePairs = allReportNameValuePairsList?.[`${ONYXKEYS.COLLECTION.REPORT_NAME_VALUE_PAIRS}${splitTransaction?.reportID}`];
+        const splitTransactionReport = allReportsList?.[`${ONYXKEYS.COLLECTION.REPORT}${splitTransaction?.reportID}`];
+        const isReportArchived = isArchivedReport(reportNameValuePairs);
+        const currentReportAction = Object.values(splitReportActions).find((action) => {
+            const transactionID = isMoneyRequestAction(action) ? (getOriginalMessage(action)?.IOUTransactionID ?? CONST.DEFAULT_NUMBER_ID) : CONST.DEFAULT_NUMBER_ID;
+            return transactionID === undeletedTransaction?.transactionID;
+        });
+
+        if (!currentReportAction) {
+            Log.warn(`[Split] Can't find the report action for transaction ${undeletedTransaction?.transactionID} in report ${splitTransaction?.reportID}`);
+            continue;
+        }
+
+        // For a reverse split operation (i.e. deleting one transaction from a 2-split), the other split(undeleted)
+        // transaction also gets marked for deletion optimistically. This causes the undeleted split to remain visible,
+        // resulting in 3 transactions(deleted, undeleted, and original) being shown at the same time when offline.
+        // Since original transaction will be reverted and both splits will eventually be deleted, we remove
+        // the undeleted split entirely instead of marking it for deletion.
+        const forceDeleteSplitTransactionID = isReverseSplitOperation ? splitExpenses.at(0)?.transactionID : undefined;
+
+        const {
+            optimisticData: deleteExpenseOptimisticData,
+            failureData: deleteExpenseFailureData,
+            successData: deleteExpenseSuccessData,
+        } = getDeleteTrackExpenseInformation(
+            splitTransactionReport,
+            undeletedTransaction?.transactionID,
+            currentReportAction,
+            undefined,
+            currentUserPersonalDetails.accountID,
+            undefined,
+            undefined,
+            undefined,
+            undefined,
+            isReportArchived || undeletedTransaction?.transactionID === forceDeleteSplitTransactionID,
+        );
+
+        // getDeleteTrackExpenseInformation only handles deleting the transaction report thread, so we need to update the report preview action here
+        if (originalReportPreviewAction) {
+            const cleanUpTransactionThreadReportOnyxData = getCleanUpTransactionThreadReportOnyxData({
+                shouldDeleteTransactionThread: false,
+                reportAction: currentReportAction,
+                updatedReportPreviewAction: (updatedReportPreviewAction ?? originalReportPreviewAction) as OnyxTypes.ReportAction,
+                shouldAddUpdatedReportPreviewActionToOnyxData: false,
+                currentUserAccountID: currentUserPersonalDetails.accountID,
+            });
+            updatedReportPreviewAction = cleanUpTransactionThreadReportOnyxData.updatedReportPreviewAction;
+        }
+
+        onyxData.optimisticData?.push(...(deleteExpenseOptimisticData ?? []));
+        onyxData.successData?.push(...(deleteExpenseSuccessData ?? []));
+        onyxData.failureData?.push(...(deleteExpenseFailureData ?? []));
+    }
+
+    if (isReverseSplitOperation) {
+        const deletedSplitSnapshotKeys = originalChildTransactions.reduce<Array<`${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}`>>((acc, childTransaction) => {
+            if (!childTransaction?.transactionID) {
+                return acc;
+            }
+
+            acc.push(`${ONYXKEYS.COLLECTION.TRANSACTION}${childTransaction.transactionID}`);
+            return acc;
+        }, []);
+
+        if (deletedSplitSnapshotKeys.length > 0) {
+            const snapshotKeysToUpdate = new Set<`${typeof ONYXKEYS.COLLECTION.SNAPSHOT}${string}`>();
+            const currentSearchHash = searchContext?.currentSearchHash;
+            const activeGroupSearchHashes = searchContext?.activeGroupSearchHashes ?? [];
+
+            if (currentSearchHash !== undefined && currentSearchHash >= 0) {
+                snapshotKeysToUpdate.add(`${ONYXKEYS.COLLECTION.SNAPSHOT}${currentSearchHash}` as const);
+            }
+
+            for (const searchHash of activeGroupSearchHashes) {
+                if (searchHash >= 0) {
+                    snapshotKeysToUpdate.add(`${ONYXKEYS.COLLECTION.SNAPSHOT}${searchHash}` as const);
+                }
+            }
+
+            const relevantSnapshotKeys = Array.from(snapshotKeysToUpdate).filter((snapshotKey) => {
+                const snapshot = allSnapshots?.[snapshotKey];
+                if (!snapshot?.data) {
+                    return false;
+                }
+
+                return deletedSplitSnapshotKeys.some((deletedSplitSnapshotKey) => Object.hasOwn(snapshot.data, deletedSplitSnapshotKey));
+            });
+
+            const originalSnapshotTransactionKey = `${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}` as const;
+            const revertedOriginalTransactionUpdate = [...(onyxData.optimisticData ?? [])].reverse().find((update) => {
+                return update.key === originalSnapshotTransactionKey && update.value && typeof update.value === 'object' && 'reportID' in update.value;
+            });
+            const revertedOriginalTransaction = revertedOriginalTransactionUpdate?.value as OnyxTypes.Transaction | undefined;
+
+            for (const snapshotKey of relevantSnapshotKeys) {
+                const previousSnapshotData = allSnapshots?.[snapshotKey]?.data;
+                const optimisticSnapshotData: Partial<Record<`${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}`, OnyxTypes.Transaction | null>> = {};
+                const failureSnapshotData: Partial<Record<`${typeof ONYXKEYS.COLLECTION.TRANSACTION}${string}`, OnyxTypes.Transaction | null>> = {};
+
+                for (const deletedSplitSnapshotKey of deletedSplitSnapshotKeys) {
+                    optimisticSnapshotData[deletedSplitSnapshotKey] = null;
+                    failureSnapshotData[deletedSplitSnapshotKey] = previousSnapshotData?.[deletedSplitSnapshotKey] ?? null;
+                }
+
+                if (revertedOriginalTransaction) {
+                    optimisticSnapshotData[originalSnapshotTransactionKey] = revertedOriginalTransaction;
+                    failureSnapshotData[originalSnapshotTransactionKey] = previousSnapshotData?.[originalSnapshotTransactionKey] ?? null;
+                }
+
+                onyxData.optimisticData?.push({
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: snapshotKey,
+                    value: {
+                        data: optimisticSnapshotData,
+                    },
+                });
+                onyxData.failureData?.push({
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: snapshotKey,
+                    value: {
+                        data: failureSnapshotData,
+                    },
+                });
+            }
+        }
+    }
+
+    if (!isReverseSplitOperation) {
+        // Use SET to update originalTransaction more quickly in Onyx as compared to MERGE to prevent UI inconsistency
+        onyxData.optimisticData?.push({
+            onyxMethod: Onyx.METHOD.SET,
+            key: `${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`,
+            value: {
+                ...originalTransaction,
+                reportID: CONST.REPORT.SPLIT_REPORT_ID,
+            },
+        });
+
+        onyxData.failureData?.push({
+            onyxMethod: Onyx.METHOD.MERGE,
+            key: `${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`,
+            value: originalTransaction ?? null,
+        });
+
+        if (firstIOU) {
+            const updatedReportAction = {
+                [firstIOU.reportActionID]: {
+                    pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE,
+                    previousMessage: firstIOU.message,
+                    message: [
+                        {
+                            type: 'COMMENT',
+                            html: '',
+                            text: '',
+                            isEdited: true,
+                            isDeletedParentAction: true,
+                        },
+                    ],
+                    originalMessage: {
+                        IOUTransactionID: null,
+                    },
+                    errors: null,
+                },
+            };
+
+            const {optimisticData, successData, failureData} = getCleanUpTransactionThreadReportOnyxData({
+                transactionThreadID: firstIOU.childReportID,
+                shouldDeleteTransactionThread: true,
+                reportAction: firstIOU,
+                updatedReportPreviewAction: updatedReportPreviewAction as OnyxTypes.ReportAction,
+                currentUserAccountID: currentUserPersonalDetails.accountID,
+            });
+
+            onyxData.optimisticData?.push(...optimisticData);
+            onyxData.optimisticData?.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${iouReport?.reportID}`,
+                value: updatedReportAction,
+            });
+
+            onyxData.successData?.push(...successData);
+
+            onyxData.failureData?.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${iouReport?.reportID}`,
+                value: {
+                    [firstIOU.reportActionID]: {
+                        ...firstIOU,
+                        pendingAction: null,
+                    },
+                },
+            });
+            onyxData.failureData?.push(...failureData);
+        } else {
+            pushUpdatedReportPreviewActionToOnyxData();
+        }
+
+        // Build the snapshot data update: remove original transaction and add child transactions
+        const optimisticSnapshotData: SearchResultDataType = {
+            [`${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`]: null,
+            ...optimisticChildSnapshotEntries,
+        };
+
+        // On failure, restore the original transaction and remove the child transactions
+        // Initializing as an empty typed object to allow dynamic key assignment resolves TypeScript type inference issue
+        const failureSnapshotData: NullishDeep<SearchResultDataType> = {};
+        failureSnapshotData[`${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`] = originalTransaction ?? null;
+        for (const childKey of optimisticChildSnapshotKeys) {
+            failureSnapshotData[childKey] = null;
+        }
+
+        onyxData.optimisticData?.push({
+            onyxMethod: Onyx.METHOD.MERGE,
+            key: `${ONYXKEYS.COLLECTION.SNAPSHOT}${searchContext?.currentSearchHash}`,
+            value: {
+                data: optimisticSnapshotData,
+            },
+        });
+
+        onyxData.failureData?.push({
+            onyxMethod: Onyx.METHOD.MERGE,
+            key: `${ONYXKEYS.COLLECTION.SNAPSHOT}${searchContext?.currentSearchHash}`,
+            value: {
+                data: failureSnapshotData,
+            },
+        });
+    } else {
+        onyxData.optimisticData?.push({
+            onyxMethod: Onyx.METHOD.MERGE,
+            key: `${ONYXKEYS.COLLECTION.TRANSACTION}${originalTransactionID}`,
+            value: {
+                errors: null,
+            },
+        });
+        pushUpdatedReportPreviewActionToOnyxData();
+        const isLastTransactionInReport = Object.values(allTransactionsList ?? {}).filter((itemTransaction) => itemTransaction?.reportID === expenseReportID).length === 1;
+        if (isLastTransactionInReport) {
+            onyxData.optimisticData?.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT}${transactionData.reportID}`,
+                value: {
+                    reportID: null,
+                    pendingFields: {
+                        preview: CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE,
+                    },
+                },
+            });
+            onyxData.successData?.push({
+                onyxMethod: Onyx.METHOD.SET,
+                key: `${ONYXKEYS.COLLECTION.REPORT}${transactionData.reportID}`,
+                value: null,
+            });
+            onyxData.failureData?.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT}${transactionData.reportID}`,
+                value: {
+                    reportID: transactionData.reportID,
+                    pendingFields: null,
+                },
+            });
+            if (expenseReport?.parentReportID && expenseReport?.parentReportActionID) {
+                onyxData.optimisticData?.push({
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.parentReportID}`,
+                    value: {
+                        [expenseReport?.parentReportActionID]: {
+                            pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.DELETE,
+                        },
+                    },
+                });
+                onyxData.successData?.push({
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.parentReportID}`,
+                    value: {
+                        [expenseReport?.parentReportActionID]: {
+                            pendingAction: null,
+                        },
+                    },
+                });
+                onyxData.failureData?.push({
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReport?.parentReportID}`,
+                    value: {
+                        [expenseReport?.parentReportActionID]: {
+                            pendingAction: null,
+                        },
+                    },
+                });
+            }
+        }
+
+        const originalTransactionThreadReportID = splits.at(0)?.transactionThreadReportID;
+        const iouActionReportActionID = splits.at(0)?.splitReportActionID;
+        if (splitThreadComments.length > 0 && originalTransactionThreadReportID && splitTransactionThreadReportID && iouActionReportActionID && expenseReportID) {
+            const optimisticMovedComments: Record<string, OnyxTypes.ReportAction> = {};
+            const optimisticRemovedComments: Record<string, null> = {};
+            const successMovedComments: OnyxCollection<NullishDeep<OnyxTypes.ReportAction>> = {};
+            const failureMovedCommentsRemoval: Record<string, null> = {};
+            const failureRestoredComments: Record<string, OnyxTypes.ReportAction> = {};
+
+            const commenterAccountIDs = new Set<number>();
+            let latestCommentCreated = '';
+
+            for (const comment of splitThreadComments) {
+                optimisticMovedComments[comment.reportActionID] = {
+                    ...comment,
+                    reportID: originalTransactionThreadReportID,
+                    pendingAction: CONST.RED_BRICK_ROAD_PENDING_ACTION.ADD,
+                };
+                optimisticRemovedComments[comment.reportActionID] = null;
+                successMovedComments[comment.reportActionID] = {pendingAction: null};
+                failureMovedCommentsRemoval[comment.reportActionID] = null;
+                failureRestoredComments[comment.reportActionID] = comment;
+
+                if (comment.actorAccountID && comment.actorAccountID > 0) {
+                    commenterAccountIDs.add(comment.actorAccountID);
+                }
+                if (comment.created && comment.created > latestCommentCreated) {
+                    latestCommentCreated = comment.created;
+                }
+            }
+
+            onyxData.optimisticData?.push(
+                {
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${originalTransactionThreadReportID}`,
+                    value: optimisticMovedComments,
+                },
+                {
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${splitTransactionThreadReportID}`,
+                    value: optimisticRemovedComments,
+                },
+                {
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReportID}`,
+                    value: {
+                        [iouActionReportActionID]: {
+                            childVisibleActionCount: splitThreadComments.length,
+                            childCommenterCount: commenterAccountIDs.size,
+                            childLastVisibleActionCreated: latestCommentCreated,
+                            childOldestFourAccountIDs: [...commenterAccountIDs].slice(0, 4).join(','),
+                        },
+                    },
+                },
+            );
+
+            onyxData.successData?.push({
+                onyxMethod: Onyx.METHOD.MERGE,
+                key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${originalTransactionThreadReportID}`,
+                value: successMovedComments,
+            });
+
+            onyxData.failureData?.push(
+                {
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${originalTransactionThreadReportID}`,
+                    value: failureMovedCommentsRemoval,
+                },
+                {
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${splitTransactionThreadReportID}`,
+                    value: failureRestoredComments,
+                },
+                {
+                    onyxMethod: Onyx.METHOD.MERGE,
+                    key: `${ONYXKEYS.COLLECTION.REPORT_ACTIONS}${expenseReportID}`,
+                    value: {
+                        [iouActionReportActionID]: {
+                            childVisibleActionCount: 0,
+                            childCommenterCount: 0,
+                            childLastVisibleActionCreated: '',
+                            childOldestFourAccountIDs: '',
+                        },
+                    },
+                },
+            );
+        }
+    }
+
+    if (isReverseSplitOperation) {
+        const parameters = {
+            ...splits.at(0),
+            comment: splits.at(0)?.comment?.comment,
+            waypoints: splits.at(0)?.waypoints ? JSON.stringify(splits.at(0)?.waypoints) : undefined,
+        } as RevertSplitTransactionParams;
+        apiWrite(WRITE_COMMANDS.REVERT_SPLIT_TRANSACTION, parameters, onyxData);
+    } else {
+        // Prepare splitApiParams for the Transaction_Split API call which requires a specific format for the splits
+        // The format is: splits[0][amount], splits[0][category], splits[0][tag] etc.
+        const splitApiParams = {} as Record<string, string | number | boolean>;
+        for (const [i, split] of splits.entries()) {
+            for (const [key, value] of Object.entries(split)) {
+                splitApiParams[`splits[${i}][${key}]`] = value !== null && typeof value === 'object' ? JSON.stringify(value) : value;
+            }
+        }
+
+        const splitParameters: SplitTransactionParams = {
+            ...splitApiParams,
+            transactionID: originalTransactionID,
+        };
+
+        if (isCreationOfSplits) {
+            apiWrite(WRITE_COMMANDS.SPLIT_TRANSACTION, splitParameters, onyxData);
+        } else {
+            apiWrite(WRITE_COMMANDS.UPDATE_SPLIT_TRANSACTION, splitParameters, onyxData);
+        }
+    }
+    // eslint-disable-next-line @typescript-eslint/no-deprecated
+    InteractionManager.runAfterInteractions(() => removeDraftSplitTransaction(originalTransactionID));
+}
+
+function updateSplitTransactionsFromSplitExpensesFlow(params: UpdateSplitTransactionsParams) {
+    // Detect if this will be a reverse split that deletes the expense report.
+    // When splits are reduced to 1, updateSplitTransactions performs a reverse split which
+    // optimistically deletes the expense report if it's the last transaction. We need to
+    // set the navigate-back URL before the deletion to prevent the "Not Found" page.
+    const splitExpenses = params.transactionData?.splitExpenses ?? [];
+    const originalTransactionID = params.transactionData?.originalTransactionID ?? CONST.IOU.OPTIMISTIC_TRANSACTION_ID;
+    const allChildTransactions = getChildTransactions(params.allTransactionsList, params.allReportsList, originalTransactionID, true);
+    const originalChildTransactions = allChildTransactions.filter((tx) => tx?.reportID !== CONST.REPORT.UNREPORTED_REPORT_ID);
+    const hasEditableSplitExpensesLeft = splitExpenses.some((expense) => (expense.statusNum ?? 0) < CONST.REPORT.STATUS_NUM.SUBMITTED);
+    const isReverseSplitOperation =
+        splitExpenses.length === 1 && originalChildTransactions.length > 0 && hasEditableSplitExpensesLeft && allChildTransactions.length === originalChildTransactions.length;
+    const expenseReportID = params.expenseReport?.reportID;
+    const isLastTransactionInReport =
+        isReverseSplitOperation && Object.values(params.allTransactionsList ?? {}).filter((itemTransaction) => itemTransaction?.reportID === expenseReportID).length === 1;
+    const fallbackReportID = params.expenseReport?.chatReportID ?? params.expenseReport?.parentReportID;
+
+    if (isLastTransactionInReport && fallbackReportID) {
+        setDeleteTransactionNavigateBackUrl(ROUTES.REPORT_WITH_ID.getRoute(fallbackReportID));
+    }
+
+    updateSplitTransactions({...params, isFromSplitExpensesFlow: true});
+    const isSearchPageTopmostFullScreenRoute = isSearchTopmostFullScreenRoute();
+    const transactionThreadReportID = params.firstIOU?.childReportID;
+    const transactionThreadReportScreen = Navigation.getReportRouteByID(transactionThreadReportID);
+
+    // Reset selected transactions in search after saving split expenses
+    const searchFullScreenRoutes = navigationRef.getRootState()?.routes.findLast((route) => route.name === NAVIGATORS.SEARCH_FULLSCREEN_NAVIGATOR);
+    const lastRoute = searchFullScreenRoutes?.state?.routes?.at(-1);
+    const isUserOnSearchPage = isSearchTopmostFullScreenRoute() && lastRoute?.name === SCREENS.SEARCH.ROOT;
+    if (isUserOnSearchPage) {
+        params?.searchContext?.clearSelectedTransactions?.(undefined, true);
+    } else {
+        params?.searchContext?.clearSelectedTransactions?.(true);
+    }
+
+    if (isSearchPageTopmostFullScreenRoute || !params.transactionReport?.parentReportID) {
+        Navigation.navigateBackToLastSuperWideRHPScreen();
+
+        // After the modal is dismissed, remove the transaction thread report screen
+        // to avoid navigating back to a report removed by the split transaction.
+        requestAnimationFrame(() => {
+            if (!transactionThreadReportScreen?.key) {
+                return;
+            }
+
+            Navigation.removeScreenByKey(transactionThreadReportScreen.key);
+        });
+
+        return;
+    }
+
+    // When the reverse split deletes the expense report, use the backward navigation pattern
+    // (dismissToSuperWideRHP + goBack) instead of dismissModalWithReport. This naturally pops
+    // stale screens from the stack instead of leaving them behind.
+    if (isLastTransactionInReport && fallbackReportID) {
+        const backRoute = ROUTES.REPORT_WITH_ID.getRoute(fallbackReportID);
+        navigateBackOnDeleteTransaction(backRoute);
+
+        // Remove the transaction thread report screen to avoid navigating back to a removed report
+        requestAnimationFrame(() => {
+            if (!transactionThreadReportScreen?.key) {
+                return;
+            }
+            Navigation.removeScreenByKey(transactionThreadReportScreen.key);
+        });
+
+        return;
+    }
+
+    const targetReportID = params.expenseReport?.reportID ?? String(CONST.DEFAULT_NUMBER_ID);
+
+    if (isTracking()) {
+        setPendingSubmitFollowUpAction(CONST.TELEMETRY.SUBMIT_FOLLOW_UP_ACTION.DISMISS_MODAL_AND_OPEN_REPORT, targetReportID);
+    }
+    Navigation.dismissModalWithReport({reportID: targetReportID});
+
+    // After the modal is dismissed, remove the transaction thread report screen
+    // to avoid navigating back to a report removed by the split transaction.
+    requestAnimationFrame(() => {
+        if (!transactionThreadReportScreen?.key) {
+            return;
+        }
+        Navigation.removeScreenByKey(transactionThreadReportScreen.key);
+    });
+}
+
+export {updateSplitTransactions, updateSplitTransactionsFromSplitExpensesFlow};
+
+export type {UpdateSplitTransactionsParams};
diff --git a/src/pages/iou/SplitExpensePage.tsx b/src/pages/iou/SplitExpensePage.tsx
index 5e760646b158..dc25c1848197 100644
--- a/src/pages/iou/SplitExpensePage.tsx
+++ b/src/pages/iou/SplitExpensePage.tsx
@@ -29,7 +29,6 @@ import useResponsiveLayout from '@hooks/useResponsiveLayout';
 import useThemeStyles from '@hooks/useThemeStyles';
 import {getIOURequestPolicyID} from '@libs/actions/IOU';
 import {getIOUActionForTransactions} from '@libs/actions/IOU/Duplicate';
-import {updateSplitTransactionsFromSplitExpensesFlow} from '@libs/actions/IOU/Split';
 import {
     addSplitExpenseField,
     clearSplitTransactionDraftErrors,
@@ -38,6 +37,7 @@ import {
     initSplitExpenseItemData,
     updateSplitExpenseAmountField,
 } from '@libs/actions/IOU/SplitExpenseItems';
+import {updateSplitTransactionsFromSplitExpensesFlow} from '@libs/actions/IOU/SplitTransactionUpdate';
 import {convertToBackendAmount} from '@libs/CurrencyUtils';
 import DateUtils from '@libs/DateUtils';
 import {canUseTouchScreen} from '@libs/DeviceCapabilities';
diff --git a/tests/actions/IOUTest.ts b/tests/actions/IOUTest.ts
index f73939e3bbd8..64d052648c2c 100644
--- a/tests/actions/IOUTest.ts
+++ b/tests/actions/IOUTest.ts
@@ -24,7 +24,8 @@ import {
     shouldOptimisticallyUpdateSearch,
 } from '@libs/actions/IOU';
 import {putOnHold} from '@libs/actions/IOU/Hold';
-import {completeSplitBill, splitBill, startSplitBill, updateSplitTransactionsFromSplitExpensesFlow} from '@libs/actions/IOU/Split';
+import {completeSplitBill, splitBill, startSplitBill} from '@libs/actions/IOU/Split';
+import {updateSplitTransactionsFromSplitExpensesFlow} from '@libs/actions/IOU/SplitTransactionUpdate';
 import {requestMoney, trackExpense} from '@libs/actions/IOU/TrackExpense';
 import {removeMoneyRequestOdometerImage, setMoneyRequestOdometerImage} from '@libs/actions/OdometerTransactionUtils';
 import initOnyxDerivedValues from '@libs/actions/OnyxDerived';
diff --git a/tests/actions/IOUTest/SplitTest.ts b/tests/actions/IOUTest/SplitTest.ts
index d4acfc090a9f..ec8ad0d6e574 100644
--- a/tests/actions/IOUTest/SplitTest.ts
+++ b/tests/actions/IOUTest/SplitTest.ts
@@ -14,15 +14,7 @@ import {WRITE_COMMANDS} from '@libs/API/types';
 import {rand64} from '@libs/NumberUtils';
 import {getIOUActionForReportID, getOriginalMessage, isActionOfType, isAddCommentAction, isMoneyRequestAction} from '@libs/ReportActionsUtils';
 import {buildOptimisticIOUReportAction, getAncestors, getReportOrDraftReport} from '@libs/ReportUtils';
-import {
-    completeSplitBill,
-    createDistanceRequest,
-    setDraftSplitTransaction,
-    splitBill,
-    startSplitBill,
-    updateSplitTransactions,
-    updateSplitTransactionsFromSplitExpensesFlow,
-} from '@userActions/IOU/Split';
+import {completeSplitBill, createDistanceRequest, setDraftSplitTransaction, splitBill, startSplitBill} from '@userActions/IOU/Split';
 import {
     addSplitExpenseField,
     evenlyDistributeSplitExpenseAmounts,
@@ -33,6 +25,7 @@ import {
     updateSplitExpenseAmountField,
     updateSplitExpenseField,
 } from '@userActions/IOU/SplitExpenseItems';
+import {updateSplitTransactions, updateSplitTransactionsFromSplitExpensesFlow} from '@userActions/IOU/SplitTransactionUpdate';
 import CONST from '@src/CONST';
 import IntlStore from '@src/languages/IntlStore';
 import DateUtils from '@src/libs/DateUtils';
diff --git a/tests/unit/DomainSelectorsTest.ts b/tests/unit/DomainSelectorsTest.ts
index ae9a1624bfa9..b5527c593e41 100644
--- a/tests/unit/DomainSelectorsTest.ts
+++ b/tests/unit/DomainSelectorsTest.ts
@@ -402,9 +402,7 @@ describe('domainSelectors', () => {
                 validated: true,
                 accountID: 1,
                 email: 'test@example.com',
-                // eslint-disable-next-line @typescript-eslint/naming-convention
                 [key1]: {shared: {'123': null}, enableRestrictedPrimaryLogin: false, enableRestrictedPolicyCreation: false},
-                // eslint-disable-next-line @typescript-eslint/naming-convention
                 [key2]: {shared: {'123': 'read'}, enableRestrictedPrimaryLogin: false, enableRestrictedPolicyCreation: false},
             } as unknown as Domain;
 
@@ -420,7 +418,6 @@ describe('domainSelectors', () => {
                 validated: true,
                 accountID: 1,
                 email: 'test@example.com',
-                // eslint-disable-next-line @typescript-eslint/naming-convention
                 [key1]: {shared: {'123': null}, enableRestrictedPrimaryLogin: false, enableRestrictedPolicyCreation: false},
             } as unknown as Domain;
 
