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  <xs:element id="htfl_LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" abstract="false" name="LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_A2024TermLoanMember" abstract="true" name="A2024TermLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_PrepaymentFeeAxis" abstract="true" name="PrepaymentFeeAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="htfl_PrepaymentFeeDomain" abstract="true" name="PrepaymentFeeDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_PrepaymentsAfterSecondAnniversaryMember" abstract="true" name="PrepaymentsAfterSecondAnniversaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_PrepaymentsOnAndAfterThirdAnniversaryMember" abstract="true" name="PrepaymentsOnAndAfterThirdAnniversaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_A2024CreditAgreementMember" abstract="true" name="A2024CreditAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_UpfrontFeeMember" abstract="true" name="UpfrontFeeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_AgentFeeMember" abstract="true" name="AgentFeeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_DebtInstrumentPrepaymentFeePercentage" abstract="false" name="DebtInstrumentPrepaymentFeePercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="htfl_DebtInstrumentCovenantRepaymentUponConsummationOfInitialPublicOfferingOrSpecialPurposeAcquisitionCompaniesMaximum" abstract="false" name="DebtInstrumentCovenantRepaymentUponConsummationOfInitialPublicOfferingOrSpecialPurposeAcquisitionCompaniesMaximum" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentCovenantRepaymentUponConsummationOfInitialPublicOfferingOrSpecialPurposeAcquisitionCompaniesMinimum" abstract="false" name="DebtInstrumentCovenantRepaymentUponConsummationOfInitialPublicOfferingOrSpecialPurposeAcquisitionCompaniesMinimum" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentCovenantRepaymentUponConsummationOfInitialPublicOfferingOrSpecialPurposeAcquisitionCompaniesIfUnderwritersExerciseOptionsMinimum" abstract="false" name="DebtInstrumentCovenantRepaymentUponConsummationOfInitialPublicOfferingOrSpecialPurposeAcquisitionCompaniesIfUnderwritersExerciseOptionsMinimum" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentExitFeePercentage" abstract="false" name="DebtInstrumentExitFeePercentage" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="htfl_DebtInstrumentEarlyRepaymentFeePercentage" abstract="false" name="DebtInstrumentEarlyRepaymentFeePercentage" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="htfl_DebtInstrumentEarlyRepaymentFeeAmount" abstract="false" name="DebtInstrumentEarlyRepaymentFeeAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentNumberOfQuarterlyInstallments" abstract="false" name="DebtInstrumentNumberOfQuarterlyInstallments" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="htfl_DebtInstrumentEarlyRepaymentFeeQuarterlyInstallments" abstract="false" name="DebtInstrumentEarlyRepaymentFeeQuarterlyInstallments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentAgentFeeGross" abstract="false" name="DebtInstrumentAgentFeeGross" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentPeriodicPaymentAgentFees" abstract="false" name="DebtInstrumentPeriodicPaymentAgentFees" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentUpfrontFee" abstract="false" name="DebtInstrumentUpfrontFee" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentExitFeeAndEarlyPrepaymentFeeAmount" abstract="false" name="DebtInstrumentExitFeeAndEarlyPrepaymentFeeAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_RepaymentOfAccruedInterest" abstract="false" name="RepaymentOfAccruedInterest" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_FederalReserveBankOfNewYorkRateMember" abstract="true" name="FederalReserveBankOfNewYorkRateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_OneMonthSecuredOvernightFinancingRateSOFRMember" abstract="true" name="OneMonthSecuredOvernightFinancingRateSOFRMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_DebtInstrumentInterestRatePaidInKind" abstract="false" name="DebtInstrumentInterestRatePaidInKind" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="htfl_DebtInstrumentProRataDebtDiscount" abstract="false" name="DebtInstrumentProRataDebtDiscount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentAccretedExitFee" abstract="false" name="DebtInstrumentAccretedExitFee" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_A2025ConvertiblePromissoryNotesSettledInCashMember" abstract="true" name="A2025ConvertiblePromissoryNotesSettledInCashMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_A2025ConvertiblePromissoryNotesSettledInLieuOfCashMember" abstract="true" name="A2025ConvertiblePromissoryNotesSettledInLieuOfCashMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_A2025ConvertiblePromissoryNotesIssuedFromConversionOfPrincipalUnder2024TermLoanMember" abstract="true" name="A2025ConvertiblePromissoryNotesIssuedFromConversionOfPrincipalUnder2024TermLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_DebtInstrumentIssuedOnEmployeeBasedCompensation" abstract="false" name="DebtInstrumentIssuedOnEmployeeBasedCompensation" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_DebtInstrumentConversionPriceDiscountPercentage" abstract="false" name="DebtInstrumentConversionPriceDiscountPercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="htfl_SeriesARedeemableConvertiblePreferredStockMember" abstract="true" name="SeriesARedeemableConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_SeriesB1RedeemableConvertiblePreferredStockMember" abstract="true" name="SeriesB1RedeemableConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_SeriesB2RedeemableConvertiblePreferredStockMember" abstract="true" name="SeriesB2RedeemableConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_SeriesCRedeemableConvertiblePreferredStockMember" abstract="true" name="SeriesCRedeemableConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_SeriesDRedeemableConvertiblePreferredStockMember" abstract="true" name="SeriesDRedeemableConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_SeriesERedeemableConvertiblePreferredStockMember" abstract="true" name="SeriesERedeemableConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_SeriesFRedeemableConvertiblePreferredStockMember" abstract="true" name="SeriesFRedeemableConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_SeriesF1RedeemableConvertiblePreferredStockMember" abstract="true" name="SeriesF1RedeemableConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_RedeemableConvertiblePreferredStockVotingRightsNumberOfVotesUponConversion" abstract="false" name="RedeemableConvertiblePreferredStockVotingRightsNumberOfVotesUponConversion" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="htfl_SharesReservedForIssuanceMember" abstract="true" name="SharesReservedForIssuanceMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_CommonStockWarrantInitialTermLoanMember" abstract="true" name="CommonStockWarrantInitialTermLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_CommonStockWarrantNewMoneyTermLoanMember" abstract="true" name="CommonStockWarrantNewMoneyTermLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_CommonStockWarrantCreditAgreementMember" abstract="true" name="CommonStockWarrantCreditAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_MeasurementInputDebtYieldMember" abstract="true" name="MeasurementInputDebtYieldMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_MeasurementInputProbabilityOfBusinessCombinationOrIPOMember" abstract="true" name="MeasurementInputProbabilityOfBusinessCombinationOrIPOMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_MeasurementInputProbabilityToIncurNewDebtMember" abstract="true" name="MeasurementInputProbabilityToIncurNewDebtMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_MeasurementInputProbabilityOfChangeOfControlMember" abstract="true" name="MeasurementInputProbabilityOfChangeOfControlMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_A2025PerformanceIncentivePlanMember" abstract="true" name="A2025PerformanceIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_A2025EmployeeStockPurchasePlanMember" abstract="true" name="A2025EmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_CommonStockOutstandingPercentage" abstract="false" name="CommonStockOutstandingPercentage" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="htfl_PercentageOfVotingPowerOnClassesOfStock" abstract="false" name="PercentageOfVotingPowerOnClassesOfStock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="htfl_SanFranciscoCaliforniaMember" abstract="true" name="SanFranciscoCaliforniaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_LesseeOperatingLeaseAverageMonthlyPayment" abstract="false" name="LesseeOperatingLeaseAverageMonthlyPayment" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="htfl_JohnC.M.FarquharMember" abstract="true" name="JohnC.M.FarquharMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_CampbellD.K.RogersMember" abstract="true" name="CampbellD.K.RogersMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="htfl_JulieA.CullivanMember" abstract="true" name="JulieA.CullivanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
