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  <xs:element id="htfl_MeasurementInputProbabilityOfBusinessCombinationOrIPOMember" abstract="true" name="MeasurementInputProbabilityOfBusinessCombinationOrIPOMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"></xs:element>
  <xs:element id="htfl_MeasurementInputProbabilityOfChangeOfControlMember" abstract="true" name="MeasurementInputProbabilityOfChangeOfControlMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"></xs:element>
  <xs:element id="htfl_A2025PerformanceIncentivePlanMember" abstract="true" name="A2025PerformanceIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"></xs:element>
  <xs:element id="htfl_A2025EmployeeStockPurchasePlanMember" abstract="true" name="A2025EmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"></xs:element>
  <xs:element id="htfl_SanFranciscoCaliforniaMember" abstract="true" name="SanFranciscoCaliforniaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"></xs:element>
  <xs:element id="htfl_ContractCostsPolicyTextBlock" name="ContractCostsPolicyTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_RevenueFromContractWithCustomerRemainingPerformanceObligationsPolicyTextBlock" name="RevenueFromContractWithCustomerRemainingPerformanceObligationsPolicyTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_RevenueFromContractWithCustomerContractLiabilitiesPolicyTextBlock" name="RevenueFromContractWithCustomerContractLiabilitiesPolicyTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_ConvertibleDebtDisclosureTextBlock" name="ConvertibleDebtDisclosureTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_RedeemableConvertiblePreferredStockDisclosureTextBlock" name="RedeemableConvertiblePreferredStockDisclosureTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_CommonStockWarrantLiabilityAbstract" name="CommonStockWarrantLiabilityAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_NumberOfMajorCustomers" name="NumberOfMajorCustomers" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_NoCustomerMember" name="NoCustomerMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_BusinessOverviewTable" name="BusinessOverviewTable" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_BusinessOverviewLineItems" name="BusinessOverviewLineItems" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_AccountingPoliciesTable" name="AccountingPoliciesTable" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_AccountingPoliciesLineItems" name="AccountingPoliciesLineItems" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_TenantImprovementAllowanceUnused" name="TenantImprovementAllowanceUnused" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_EmployeeWhoOwnsMoreThanTenPercentOfVotingPowerOfAllClassesOfStockMember" name="EmployeeWhoOwnsMoreThanTenPercentOfVotingPowerOfAllClassesOfStockMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_ThresholdOfVotingPowerInCompanyThatTriggersIncreaseInMinimumExercisePriceOfShareBasedPaymentAwards" name="ThresholdOfVotingPowerInCompanyThatTriggersIncreaseInMinimumExercisePriceOfShareBasedPaymentAwards" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_IncentiveStockOptionsMember" name="IncentiveStockOptionsMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_TrancheTwoThroughThirtySevenMember" name="TrancheTwoThroughThirtySevenMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_TrancheOneThroughThirtySevenMember" name="TrancheOneThroughThirtySevenMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_TrancheOneThroughFortyEightMember" name="TrancheOneThroughFortyEightMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_UnderwriterMember" name="UnderwriterMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_ProceedsFromIssuanceInitialPublicOfferingGross" name="ProceedsFromIssuanceInitialPublicOfferingGross" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_LesseeOepratingSubleaseInitialOccupancyPercentage" name="LesseeOepratingSubleaseInitialOccupancyPercentage" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_LesseeOperatingSubleaseAnnualBaseRent" name="LesseeOperatingSubleaseAnnualBaseRent" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_LesseeOperatingSubleaseLetterOfCreditProvidedInPlaceOfSecurityDeposit" name="LesseeOperatingSubleaseLetterOfCreditProvidedInPlaceOfSecurityDeposit" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_LesseeOperatingLeaseMonthlyPayment" name="LesseeOperatingLeaseMonthlyPayment" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_ConvertibleNotesDerivativeLiabilityMember" name="ConvertibleNotesDerivativeLiabilityMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_MoneyMarketFundsIncludedInCashEquivalentsMember" name="MoneyMarketFundsIncludedInCashEquivalentsMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_MoneyMarketFundsIncludedInRestrictedCashNoncurrentMember" name="MoneyMarketFundsIncludedInRestrictedCashNoncurrentMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue" name="AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughTwoYearsFairValue" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_DebtSecuritiesAvailableForSaleMatuirtyPeriod" name="DebtSecuritiesAvailableForSaleMatuirtyPeriod" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_RohnertParkCaliforniaMember" name="RohnertParkCaliforniaMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_NotesConverted" name="NotesConverted" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_CreditAgreement2024Member" name="CreditAgreement2024Member" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_AmendedCreditAgreement2024Member" name="AmendedCreditAgreement2024Member" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_NonCashInterestCharges" name="NonCashInterestCharges" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_CommonStockWarrantMember" name="CommonStockWarrantMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_WarrantsExercisedFairValueTransferredToStockholdersEquity" name="WarrantsExercisedFairValueTransferredToStockholdersEquity" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_CommonStockCapitalSharesReservedForFutureIssuanceAnnualPercentageIncrease" name="CommonStockCapitalSharesReservedForFutureIssuanceAnnualPercentageIncrease" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_EmployeeStockOwnershipPlanCommonStockPurchasePriceAsPercentageOfFairMarketValue" name="EmployeeStockOwnershipPlanCommonStockPurchasePriceAsPercentageOfFairMarketValue" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_ScheduleOfAdditionalInformationRelatedToOperatingLeasesTableTextBlock" name="ScheduleOfAdditionalInformationRelatedToOperatingLeasesTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" name="LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_PaymentOfDeferredOfferingCosts" name="PaymentOfDeferredOfferingCosts" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_ConvertibleDebtIssuanceCostsIncurredDuringNoncashOrPartialNoncashTransaction" name="ConvertibleDebtIssuanceCostsIncurredDuringNoncashOrPartialNoncashTransaction" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element>
  <xs:element id="htfl_LesseeOperatingLeaseMonthlyPaymentAmendedLeaseTerm" name="LesseeOperatingLeaseMonthlyPaymentAmendedLeaseTerm" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema"></xs:element></schema>
