XML 58 R40.htm IDEA: XBRL DOCUMENT
v3.26.1

Income Taxes (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2025
Income Taxes [Abstract] |
Summary of Components of Net Loss Before Income Taxes |
| Year Ended December 31,
| 2025 |  | 2024 |  | 2023
United States | $ | (110,784) |  | $ | (96,422) |  | $ | (95,634)
Foreign |  | (6,083) |  |  | 49 |  |  | 526
Net loss before income taxes | $ | (116,867) |  | $ | (96,373) |  | $ | (95,108)
Reconciliation of Federal and Effective Tax Rate | The following table is a reconciliation of the total income tax expense computed at the U.S. federal statutory rate of 21% to the Company’s total income tax expense for the year ended December 31, 2025, in accordance with ASU 2023-09 (in thousands): ‎
| Year Ended December 31, 2025
|  | Amount |  |  | Percentage
U.S. federal statutory rate | $ | (24,542) |  |  | 21.0%
Foreign tax effects |  | 1,201 |  |  | -1.0%
Tax credits: |  |  |  |  |
R&D credits |  | (382) |  |  | 0.3%
Change in valuation allowance |  | 6,316 |  |  | -5.4%
Nontaxable or nondeductible items: |  |  |  |  |
Write-off of intercompany payable |  | 4,759 |  |  | -4.1%
Mark-to-market on warrant and derivative |  | 7,683 |  |  | -6.5%
Nondeductible executive compensation |  | 1,239 |  |  | -1.1%
Other nondeductible items |  | 2,621 |  |  | -2.2%
Other |  | 1,029 |  |  | -0.9%
Provision for income taxes | $ | (76) |  |  | 0.1%
The following table presents a reconciliation of the statutory federal rate and the Company’s effective tax rate for the years ended December 31, 2024 and 2023 in accordance with the guidance prior to ASU 2023-09 (in thousands):
| Year Ended December 31,
| 2024 |  | 2023
Tax at federal statutory rate | $ | (20,027) |  | $ | (20,003)
State taxes, net of federal benefit |  | (2,247) |  |  | (4,032)
Change in valuation allowance |  | 16,563 |  |  | 20,418
Stock-based compensation |  | 1,706 |  |  | 3,722
Mark-to-market on warrant and derivative |  | 3,482 |  |  | 1,075
R&D credits |  | (281) |  |  | (391)
Foreign rate differential |  | 41 |  |  | (50)
Other |  | 816 |  |  | (192)
Provision for income taxes | $ | 53 |  | $ | 547
Schedule of Significant Components of Net Deferred Tax Assets |
| Year Ended December 31,
| 2025 |  | 2024
Deferred tax assets: |  |  |  |  |
Net operating loss carryforwards | $ | 154,356 |  | $ | 143,066
Research and development credits |  | 7,628 |  |  | 7,111
Stock-based compensation |  | 1,586 |  |  | 1,611
Interest limitation |  | 10,651 |  |  | 8,964
Accruals and reserves |  | 5,370 |  |  | 9,502
Fixed asset and intangible asset basis |  | 3,654 |  |  | 4,615
Operating lease liabilities |  | 5,386 |  |  | 5,955
Research and development capitalization |  | 15,408 |  |  | 20,675
Total deferred tax assets |  | 204,039 |  |  | 201,499
Deferred tax liabilities: |  |  |  |  |
Capitalized contract costs |  | (2,704) |  |  | (1,556)
Operating lease right-of-use assets |  | (4,256) |  |  | (4,653)
Other |  | (109) |  |  | (66)
Total deferred tax liabilities |  | (7,069) |  |  | (6,275)
Deferred tax assets, net |  | 196,970 |  |  | 195,224
Valuation allowance |  | (196,784) |  |  | (195,224)
Net deferred taxes | $ | 186 |  | $ | —
Summary of Activity Related to Valuation Allowance |
| Year Ended December 31,
| 2025 |  | 2024 |  | 2023
Balance at beginning of period | $ | 195,224 |  | $ | 178,406 |  | $ | 157,982
Additions |  | 5,346 |  |  | 16,818 |  |  | 20,424
Deductions |  | (3,786) |  |  | — |  |  | —
Balance at end of period | $ | 196,784 |  | $ | 195,224 |  | $ | 178,406
Summary of Activity Related to Unrecognized Tax Benefits |
| Year Ended December 31,
| 2025 |  | 2024 |  | 2023
Balance at beginning of period | $ | 8,597 |  | $ | 8,188 |  | $ | 7,371
Increase related to current year tax positions |  | 552 |  |  | 558 |  |  | 817
Changes related to prior tax positions |  | 75 |  |  | (149) |  |  | —
Balance at end of period | $ | 9,224 |  | $ | 8,597 |  | $ | 8,188

X
- Definition Summary Of Components Of Net Income (Loss) Before Income Taxes [Table Text Block] + References No definition available. + Details
Name: | htfl_SummaryOfComponentsOfNetIncomeLossBeforeIncomeTaxesTableTextBlock
Namespace Prefix: | htfl_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of net deferred tax asset or liability recognized in an entity's statement of financial position, including the following: the total of all deferred tax liabilities, the total of all deferred tax assets, the total valuation allowance recognized for deferred tax assets. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the reconciliation using percentage or dollar amounts of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 231 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482663/740-10-55-231 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-12A Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-12 + Details
Name: | us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the change in unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 217 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482663/740-10-55-217 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-15A + Details
Name: | us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of valuation allowances to reduce deferred tax assets to net realizable value, including identification of the deferred tax asset more likely than not will not be fully realized and the corresponding amount of the valuation allowance. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_SummaryOfValuationAllowanceTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration