Federal tax / Library

The federal tax engine as a library

The engine behind POST /api/federal-tax is also a library you run inside your own application (libfedtax 1.6.0, engine 2.3.2, tax year 2026): the same C code, the same rules, the same citations and the same output, byte for byte. No network call, no per-request latency, and no household data leaving your system. It is the sibling of the state tax engine library.

One engine, two doors

The JSON entry point (qcft_compute_json) is the API's own request parser, field table, engine call and response builder, compiled unchanged: for any request it returns the bytes the API returns, including the 400 body of a refusal. The schema and rules documents (GET /api/federal-tax/schema and /rules) are there too, byte for byte. The typed entry point (qcft_compute) takes a C struct and returns the result's figures; it runs the API's own parser and evaluator on the request, so a refused typed request carries the API's message.

What you get

Artefact	Size	For
`libfedtax-1.6.0-linux-x86_64.tar.gz`	687 KB	C/C++ and any language with a C FFI: libfedtax.so.1, libfedtax.a, the header, a CMake package and pkg-config
`quantcalc-fedtax-1.6.0.tgz`	249 KB	npm: WebAssembly, ESM glue and TypeScript types (Node 18 or later, browsers, workers)
`quantcalc_fedtax-1.6.0-py3-none-manylinux2014_x86_64.manylinux_2_17_x86_64.whl`	311 KB	Python 3.9 or later: one wheel for every CPython version, typed
`libfedtax-1.6.0-src.tar.gz`	406 KB	the C source drop, when the licence includes source

Thin bindings for Go, Rust, Java, .NET and Swift call the JSON entry point of the same shared library. Sizes measured on the 1.6.0 release build (engine 2.3.2) of 2026-10-11; every artefact is rebuilt byte for byte from the same commit, with SHA-256 checksums and a manifest of the pinned toolchains (the archive timestamps come from the last commit that touched the engine or the library, so sizes can move by a few bytes between commits).

Without the citations

Each full response carries the official sources of every step on the return, with their checked quotes. A build without them answers every request as the full library does, minus rules.sources and rules.unsourced (the blocks includeSources: false leaves out); every figure is the same. The sources stay published on the sources page.

Artefact	Size	For
`libfedtax-nosources-1.6.0-linux-x86_64.tar.gz`	399 KB	the C library without the citations
`quantcalc-fedtax-nosources-1.6.0.tgz`	172 KB	npm @quantcalc/fedtax-nosources
`quantcalc_fedtax_nosources-1.6.0-py3-none-manylinux2014_x86_64.manylinux_2_17_x86_64.whl`	192 KB	Python distribution quantcalc-fedtax-nosources (import name quantcalc_fedtax)
`libfedtax-nosources-1.6.0-src.tar.gz`	406 KB	the source drop, built without the citations

Size budgets are enforced on every release build (bytes, measured and budget):

Binary	Full	Without citations
libfedtax.so.1, stripped	1,071,104 (budget 1,276,000)	538,624 (budget 642,000)
libfedtax.a	1,474,312 (budget 1,754,000)	687,680 (budget 819,000)
fedtax.wasm, raw	659,217 (budget 784,000)	379,928 (budget 452,000)
npm WebAssembly + glue + wrapper + layout, gzipped	225,854 (budget 269,000)	145,811 (budget 174,000)

The typed request

The typed request is generated from the API's field table, so it has one member per request field and nothing else. When the API gains a field, a regeneration and a rebuild add it at the end of the struct, and the build fails until that is done. The offsets below are the library's binary interface: they never move within a major version.

Kind	C type	Not sent
one of the listed strings	`int32_t` (index)	`QCFT_ENUM_ABSENT`
whole number	`int32_t`	`QCFT_INT_ABSENT`
boolean	`int32_t`	`QCFT_BOOL_ABSENT`
amount	`double`	`QCFT_ABSENT`
list of {year, taxable, nontaxable}	`_count` + `qcft_roth_conversion[16]`	count `QCFT_LIST_ABSENT`
up to 4 amounts	`_count` + `double[4]`	count `QCFT_LIST_ABSENT`
up to 4 dates	`_count` + `int32_t[4]` (YYYYMMDD)	count `QCFT_LIST_ABSENT`
a later tax year {year, inflation or cpiFactor, awiFactor, indexing}	`qcft_projection` (year, indexing, inflation, cpi_factor, awi_factor)	year `QCFT_INT_ABSENT`
amount_list12	see `include/quantcalc/fedtax.h`	see `include/quantcalc/fedtax.h`

JSON field	C member	Kind	Offset
`filingStatus`	`filing_status`	one of the listed strings: `single`, `mfj`, `married_filing_jointly`, `mfs`, `married_filing_separately`, `hoh`, `head_of_household`, `qss`, `qualifying_surviving_spouse`	8
`age`	`age`	whole number	12
`spouseAge`	`spouse_age`	whole number	16
`mfsLivedApart`	`mfs_lived_apart`	boolean	20
`iraDistributions`	`ira_distributions`	amount	24
`rothConversion`	`roth_conversion`	amount	32
`pension`	`pension`	amount	40
`otherOrdinaryIncome`	`other_ordinary_income`	amount	48
`shortTermGains`	`short_term_gains`	amount	56
`longTermGains`	`long_term_gains`	amount	64
`socialSecurityGross`	`social_security_gross`	amount	72
`taxExemptInterest`	`tax_exempt_interest`	amount	80
`includeSources`	`include_sources`	boolean	88
`birthMonth`	`birth_month`	whole number	92
`blindCount`	`blind_count`	whole number	96
`saltIncomeOrSalesTax`	`salt_income_or_sales_tax`	amount	104
`saltRealEstateTax`	`salt_real_estate_tax`	amount	112
`saltPersonalPropertyTax`	`salt_personal_property_tax`	amount	120
`otherTaxes`	`other_taxes`	amount	128
`mortgageInterest`	`mortgage_interest`	amount	136
`investmentInterest`	`investment_interest`	amount	144
`charityCash`	`charity_cash`	amount	152
`charityCashDaf`	`charity_cash_daf`	amount	160
`charityCapitalGainProperty`	`charity_capital_gain_property`	amount	168
`medicalExpenses`	`medical_expenses`	amount	176
`otherItemized`	`other_itemized`	amount	184
`itemizeMode`	`itemize_mode`	one of the listed strings: `auto`, `itemize`, `standard`	192
`mfsSpouseItemizes`	`mfs_spouse_itemizes`	boolean	196
`employerPlanDistribution`	`employer_plan_distribution`	amount	200
`separationYearAge`	`separation_year_age`	whole number	208
`publicSafetyEmployee`	`public_safety_employee`	boolean	212
`seppDistribution`	`sepp_distribution`	amount	216
`disabled`	`disabled`	boolean	224
`iraBasis`	`ira_basis`	amount	232
`iraYearEndValue`	`ira_year_end_value`	amount	240
`rothDistribution`	`roth_distribution`	amount	248
`rothContributions`	`roth_contributions`	amount	256
`rothFirstContributionYear`	`roth_first_contribution_year`	whole number	264
`rothConversions`	`roth_conversions`	list of {year, taxable, nontaxable}	268
`iraBalancePriorYearEnd`	`ira_balance_prior_year_end`	amount	656
`spouseSoleBeneficiary`	`spouse_sole_beneficiary`	boolean	664
`beneficiarySpouseAge`	`beneficiary_spouse_age`	whole number	668
`rmdShortfall`	`rmd_shortfall`	amount	672
`rmdShortfallCorrected`	`rmd_shortfall_corrected`	boolean	680
`priorYearTax`	`prior_year_tax`	amount	688
`priorYearAgi`	`prior_year_agi`	amount	696
`priorYearFullYearReturn`	`prior_year_full_year_return`	boolean	704
`withholding`	`withholding`	amount	712
`estimatedPayments`	`estimated_payments`	up to 4 amounts	720
`estimatedPaymentDates`	`estimated_payment_dates`	up to 4 dates	760
`taxableInterest`	`taxable_interest`	amount	784
`ordinaryDividends`	`ordinary_dividends`	amount	792
`qualifiedDividends`	`qualified_dividends`	amount	800
`capitalLossRules`	`capital_loss_rules`	boolean	808
`capitalLossCarryoverShortTerm`	`capital_loss_carryover_short_term`	amount	816
`capitalLossCarryoverLongTerm`	`capital_loss_carryover_long_term`	amount	824
`taxTable`	`tax_table`	boolean	832
`birthDay`	`birth_day`	whole number	836
`spouseBirthMonth`	`spouse_birth_month`	whole number	840
`spouseBirthDay`	`spouse_birth_day`	whole number	844
`governmental457bDistribution`	`governmental_457b_distribution`	amount	848
`nonqualifiedAnnuity`	`nonqualified_annuity`	amount	856
`saltSalesTaxElected`	`salt_sales_tax_elected`	boolean	864
`capitalGainDistributions`	`capital_gain_distributions`	amount	872
`rate28Gain`	`rate_28_gain`	amount	880
`unrecapturedSection1250Gain`	`unrecaptured_section_1250_gain`	amount	888
`wages`	`wages`	amount	896
`socialSecurityWages`	`social_security_wages`	amount	904
`medicareWages`	`medicare_wages`	amount	912
`socialSecurityWithheld`	`social_security_withheld`	amount	920
`medicareTaxWithheld`	`medicare_tax_withheld`	amount	928
`employerCount`	`employer_count`	whole number	936
`selfEmploymentIncome`	`self_employment_income`	amount	944
`selfEmploymentSstb`	`self_employment_sstb`	boolean	952
`sepContribution`	`sep_contribution`	amount	960
`seHealthInsurance`	`se_health_insurance`	amount	968
`qbiW2Wages`	`qbi_w2_wages`	amount	976
`qbiUbia`	`qbi_ubia`	amount	984
`spouseWages`	`spouse_wages`	amount	992
`spouseSocialSecurityWages`	`spouse_social_security_wages`	amount	1000
`spouseMedicareWages`	`spouse_medicare_wages`	amount	1008
`spouseSocialSecurityWithheld`	`spouse_social_security_withheld`	amount	1016
`spouseMedicareTaxWithheld`	`spouse_medicare_tax_withheld`	amount	1024
`spouseEmployerCount`	`spouse_employer_count`	whole number	1032
`spouseSelfEmploymentIncome`	`spouse_self_employment_income`	amount	1040
`spouseSelfEmploymentSstb`	`spouse_self_employment_sstb`	boolean	1048
`spouseSepContribution`	`spouse_sep_contribution`	amount	1056
`spouseSeHealthInsurance`	`spouse_se_health_insurance`	amount	1064
`spouseQbiW2Wages`	`spouse_qbi_w2_wages`	amount	1072
`spouseQbiUbia`	`spouse_qbi_ubia`	amount	1080
`qualifiedTips`	`qualified_tips`	amount	1088
`qualifiedOvertime`	`qualified_overtime`	amount	1096
`foreignTaxPaid`	`foreign_tax_paid`	amount	1104
`foreignSourceOrdinaryIncome`	`foreign_source_ordinary_income`	amount	1112
`foreignSourceQualifiedIncome`	`foreign_source_qualified_income`	amount	1120
`foreignTaxCarryover`	`foreign_tax_carryover`	amount	1128
`ftcMethod`	`ftc_method`	one of the listed strings: `auto`, `election`, `form1116`	1136
`foreignIncomeOnPayeeStatements`	`foreign_income_on_payee_statements`	boolean	1140
`amtFtcSimplifiedElection`	`amt_ftc_simplified_election`	boolean	1144
`privateActivityBondInterest`	`private_activity_bond_interest`	amount	1152
`incentiveStockOptions`	`incentive_stock_options`	amount	1160
`amtDispositionAdjustment`	`amt_disposition_adjustment`	amount	1168
`amtOtherAdjustments`	`amt_other_adjustments`	amount	1176
`taxableStateRefund`	`taxable_state_refund`	amount	1184
`projection`	`projection`	a later tax year {year, inflation or cpiFactor, awiFactor, indexing}: `law`, `inflation`	1192
`beneficiaryDistribution`	`beneficiary_distribution`	amount	1224
`rentalNetIncome`	`rental_net_income`	amount	1232
`rentalPriorYearUnallowedLoss`	`rental_prior_year_unallowed_loss`	amount	1240
`rentalActiveParticipation`	`rental_active_participation`	boolean	1248
`realEstateProfessional`	`real_estate_professional`	boolean	1252
`childTaxCreditChildren`	`child_tax_credit_children`	whole number	1256
`otherDependents`	`other_dependents`	whole number	1260
`eitcQualifyingChildren`	`eitc_qualifying_children`	whole number	1264
`eitcSeparatedSpouse`	`eitc_separated_spouse`	boolean	1268
`saversContributions`	`savers_contributions`	amount	1272
`saversDistributions`	`savers_distributions`	amount	1280
`fullTimeStudent`	`full_time_student`	boolean	1288
`taxableDisabilityIncome`	`taxable_disability_income`	amount	1296
`spouseSaversContributions`	`spouse_savers_contributions`	amount	1304
`spouseSaversDistributions`	`spouse_savers_distributions`	amount	1312
`spouseFullTimeStudent`	`spouse_full_time_student`	boolean	1320
`spouseTaxableDisabilityIncome`	`spouse_taxable_disability_income`	amount	1328
`nontaxablePensions`	`nontaxable_pensions`	amount	1336
`inheritedBalancePriorYearEnd`	`inherited_balance_prior_year_end`	amount	1344
`inheritedAccountType`	`inherited_account_type`	one of the listed strings: `traditional`, `roth`	1352
`inheritedOwnerBirthYear`	`inherited_owner_birth_year`	whole number	1356
`inheritedOwnerBirthMonth`	`inherited_owner_birth_month`	whole number	1360
`inheritedOwnerDeathYear`	`inherited_owner_death_year`	whole number	1364
`inheritedOwnerDiedOnOrAfterRbd`	`inherited_owner_died_on_or_after_rbd`	boolean	1368
`inheritedBeneficiaryType`	`inherited_beneficiary_type`	one of the listed strings: `designated`, `spouse`, `minorChild`, `disabled`, `chronicallyIll`, `notMoreThan10YearsYounger`, `noDesignatedBeneficiary`	1372
`inheritedBeneficiaryBirthYear`	`inherited_beneficiary_birth_year`	whole number	1376
`inheritedElection`	`inherited_election`	one of the listed strings: `none`, `tenYearRule`, `treatAsOwn`	1380
`inheritedDistribution`	`inherited_distribution`	amount	1384
`inheritedShortfallCorrected`	`inherited_shortfall_corrected`	boolean	1392
`inheritedOwnerDistributedInDeathYear`	`inherited_owner_distributed_in_death_year`	amount	1400
`wagesByPeriod`	`wages_by_period`	up to 4 amounts	1408
`spouseWagesByPeriod`	`spouse_wages_by_period`	up to 4 amounts	1448
`selfEmploymentIncomeByPeriod`	`self_employment_income_by_period`	up to 4 amounts	1488
`spouseSelfEmploymentIncomeByPeriod`	`spouse_self_employment_income_by_period`	up to 4 amounts	1528
`iraDistributionsByPeriod`	`ira_distributions_by_period`	up to 4 amounts	1568
`rothConversionByPeriod`	`roth_conversion_by_period`	up to 4 amounts	1608
`pensionByPeriod`	`pension_by_period`	up to 4 amounts	1648
`otherOrdinaryIncomeByPeriod`	`other_ordinary_income_by_period`	up to 4 amounts	1688
`shortTermGainsByPeriod`	`short_term_gains_by_period`	up to 4 amounts	1728
`longTermGainsByPeriod`	`long_term_gains_by_period`	up to 4 amounts	1768
`capitalGainDistributionsByPeriod`	`capital_gain_distributions_by_period`	up to 4 amounts	1808
`taxableInterestByPeriod`	`taxable_interest_by_period`	up to 4 amounts	1848
`ordinaryDividendsByPeriod`	`ordinary_dividends_by_period`	up to 4 amounts	1888
`qualifiedDividendsByPeriod`	`qualified_dividends_by_period`	up to 4 amounts	1928
`socialSecurityGrossByPeriod`	`social_security_gross_by_period`	up to 4 amounts	1968
`rentalNetIncomeByPeriod`	`rental_net_income_by_period`	up to 4 amounts	2008
`inheritedDistributionByPeriod`	`inherited_distribution_by_period`	up to 4 amounts	2048
`withholdingByPeriod`	`withholding_by_period`	up to 4 amounts	2088
`charityCarryoverCash1`	`charity_carryover_cash_1`	amount	2128
`charityCarryoverCash2`	`charity_carryover_cash_2`	amount	2136
`charityCarryoverCash3`	`charity_carryover_cash_3`	amount	2144
`charityCarryoverCash4`	`charity_carryover_cash_4`	amount	2152
`charityCarryoverCash5`	`charity_carryover_cash_5`	amount	2160
`charityCarryoverProperty1`	`charity_carryover_property_1`	amount	2168
`charityCarryoverProperty2`	`charity_carryover_property_2`	amount	2176
`charityCarryoverProperty3`	`charity_carryover_property_3`	amount	2184
`charityCarryoverProperty4`	`charity_carryover_property_4`	amount	2192
`charityCarryoverProperty5`	`charity_carryover_property_5`	amount	2200
`marketplacePremiums`	`marketplace_premiums`	amount_list12	2208
`marketplaceSlcspPremiums`	`marketplace_slcsp_premiums`	amount_list12	2312
`marketplaceAdvancePayments`	`marketplace_advance_payments`	amount_list12	2416
`taxFamilySize`	`tax_family_size`	whole number	2520
`povertyGuidelineState`	`poverty_guideline_state`	one of the listed strings: `contiguous`, `alaska`, `hawaii`	2524
`dependentsModifiedAgi`	`dependents_modified_agi`	amount	2528
`ptcEstimatedIncomeException`	`ptc_estimated_income_exception`	boolean	2536
`ptcMfsException`	`ptc_mfs_exception`	boolean	2540
`k1PassiveIncome`	`k1_passive_income`	amount	2544
`k1PassivePriorYearUnallowedLoss`	`k1_passive_prior_year_unallowed_loss`	amount	2552
`k1NonpassiveIncome`	`k1_nonpassive_income`	amount	2560
`k1NonpassiveTrading`	`k1_nonpassive_trading`	boolean	2568
`estateTrustIncome`	`estate_trust_income`	amount	2576
`estateTrustPassive`	`estate_trust_passive`	boolean	2584
`estateTrustPriorYearUnallowedLoss`	`estate_trust_prior_year_unallowed_loss`	amount	2592
`partnershipSeEarnings`	`partnership_se_earnings`	amount	2600
`spousePartnershipSeEarnings`	`spouse_partnership_se_earnings`	amount	2608
`k1QualifiedBusinessIncome`	`k1_qualified_business_income`	amount	2616
`k1QbiW2Wages`	`k1_qbi_w2_wages`	amount	2624
`k1QbiUbia`	`k1_qbi_ubia`	amount	2632
`k1QbiSstb`	`k1_qbi_sstb`	boolean	2640
`k1QbiActive`	`k1_qbi_active`	boolean	2644
`nonqualifiedAnnuitySepp`	`nonqualified_annuity_sepp`	amount	2648
`nonqualifiedAnnuityDeath`	`nonqualified_annuity_death`	amount	2656
`nonqualifiedAnnuityOtherException`	`nonqualified_annuity_other_exception`	amount	2664
`traditionalIraContributions`	`traditional_ira_contributions`	amount	2672
`traditionalIraPriorExcess`	`traditional_ira_prior_excess`	amount	2680
`traditionalIraDistributionsIncluded`	`traditional_ira_distributions_included`	amount	2688
`traditionalIraPriorExcessWithdrawn`	`traditional_ira_prior_excess_withdrawn`	amount	2696
`traditionalIraCorrectiveWithdrawal`	`traditional_ira_corrective_withdrawal`	amount	2704
`traditionalIraValue`	`traditional_ira_value`	amount	2712
`rothIraContributions`	`roth_ira_contributions`	amount	2720
`rothIraPriorExcess`	`roth_ira_prior_excess`	amount	2728
`rothIraDistributions`	`roth_ira_distributions`	amount	2736
`rothIraCorrectiveWithdrawal`	`roth_ira_corrective_withdrawal`	amount	2744
`rothIraValue`	`roth_ira_value`	amount	2752
`hsaContributions`	`hsa_contributions`	amount	2760
`hsaCoverage`	`hsa_coverage`	one of the listed strings: `none`, `self`, `family`	2768
`hsaLimit`	`hsa_limit`	amount	2776
`hsaPriorExcess`	`hsa_prior_excess`	amount	2784
`hsaTaxableDistributions`	`hsa_taxable_distributions`	amount	2792
`hsaCorrectiveWithdrawal`	`hsa_corrective_withdrawal`	amount	2800
`hsaValue`	`hsa_value`	amount	2808
`spouseTraditionalIraContributions`	`spouse_traditional_ira_contributions`	amount	2816
`spouseTraditionalIraPriorExcess`	`spouse_traditional_ira_prior_excess`	amount	2824
`spouseTraditionalIraDistributionsIncluded`	`spouse_traditional_ira_distributions_included`	amount	2832
`spouseTraditionalIraPriorExcessWithdrawn`	`spouse_traditional_ira_prior_excess_withdrawn`	amount	2840
`spouseTraditionalIraCorrectiveWithdrawal`	`spouse_traditional_ira_corrective_withdrawal`	amount	2848
`spouseTraditionalIraValue`	`spouse_traditional_ira_value`	amount	2856
`spouseRothIraContributions`	`spouse_roth_ira_contributions`	amount	2864
`spouseRothIraPriorExcess`	`spouse_roth_ira_prior_excess`	amount	2872
`spouseRothIraDistributions`	`spouse_roth_ira_distributions`	amount	2880
`spouseRothIraCorrectiveWithdrawal`	`spouse_roth_ira_corrective_withdrawal`	amount	2888
`spouseRothIraValue`	`spouse_roth_ira_value`	amount	2896
`spouseHsaContributions`	`spouse_hsa_contributions`	amount	2904
`spouseHsaCoverage`	`spouse_hsa_coverage`	one of the listed strings: `none`, `self`, `family`	2912
`spouseHsaLimit`	`spouse_hsa_limit`	amount	2920
`spouseHsaPriorExcess`	`spouse_hsa_prior_excess`	amount	2928
`spouseHsaTaxableDistributions`	`spouse_hsa_taxable_distributions`	amount	2936
`spouseHsaCorrectiveWithdrawal`	`spouse_hsa_corrective_withdrawal`	amount	2944
`spouseHsaValue`	`spouse_hsa_value`	amount	2952
`coverdellContributions`	`coverdell_contributions`	amount	2960
`coverdellLimit`	`coverdell_limit`	amount	2968
`coverdellPriorExcess`	`coverdell_prior_excess`	amount	2976
`coverdellDistributions`	`coverdell_distributions`	amount	2984
`coverdellCorrectiveWithdrawal`	`coverdell_corrective_withdrawal`	amount	2992
`coverdellValue`	`coverdell_value`	amount	3000
`archerMsaContributions`	`archer_msa_contributions`	amount	3008
`archerMsaLimit`	`archer_msa_limit`	amount	3016
`archerMsaPriorExcess`	`archer_msa_prior_excess`	amount	3024
`archerMsaDistributions`	`archer_msa_distributions`	amount	3032
`archerMsaCorrectiveWithdrawal`	`archer_msa_corrective_withdrawal`	amount	3040
`archerMsaValue`	`archer_msa_value`	amount	3048
`ableContributions`	`able_contributions`	amount	3056
`ableLimit`	`able_limit`	amount	3064
`ableCorrectiveWithdrawal`	`able_corrective_withdrawal`	amount	3072
`ableValue`	`able_value`	amount	3080
`trumpAccountExcess`	`trump_account_excess`	amount	3088
`trumpAccountExcessDistributed`	`trump_account_excess_distributed`	amount	3096
`trumpAccountExcessEarnings`	`trump_account_excess_earnings`	amount	3104
`selfEmployedQualifiedTips`	`self_employed_qualified_tips`	amount	3112
`spouseSelfEmployedQualifiedTips`	`spouse_self_employed_qualified_tips`	amount	3120

With the state engine

The state tax library (libstatetax 1.13.2) carries this engine: its JSON entry point answers computeFederal: true as POST /api/state-tax does, with the federal engine supplying the federal figures the state rules read. It is one binary, so the two engines are always the same version.

The same answer, checked on every build

A parity gate runs on every release build (make dist) and every make check. On 2026-10-11 (engine 2.3.2) it sent a generated corpus of 34,659 requests (18,704 computed, 15,955 refused: every filing status and age gate, every one of the 245 request fields at and past its limits, extended returns, every refusal the API makes, malformed bodies) through four surfaces: the C library, the WebAssembly package, the Python package and the API's own request handler. All four must produce the same bytes for every request, and the 19,987 requests the typed entry point can express must give the same document through it. make check also runs the whole test suite under address, undefined-behaviour and thread sanitizers, fuzzes both entry points, and checks that the binary exports only its own functions.

Performance

Measured 2026-10-01 (engine 2.0.0) on Intel Core i7-12800H, one core; 4,934,741 typed calls a second on 8 threads. Host load average at the start: 1.64 / 2.07 / 2.55 (1 / 5 / 15 minutes). A shared 20-thread host that other agents' test suites often keep busy: `make bench` was run when the 1-minute load average had fallen to the value recorded here. The single-thread rows are pinned to core 0 (taskset).

Surface	Call	Calls a second	Microseconds a call
C	typed (qcft_compute)	795,392	1.3
C	JSON, includeSources false	25,429	39.3
C	JSON, the full document with its sources	6,485	154.2
C	JSON, an extended return with its sources	3,243	308.4
WebAssembly (Node)	typed (compute)	232,151	4.3
WebAssembly (Node)	JSON, includeSources false	13,401	74.6
WebAssembly (Node)	JSON, the full document	3,457	289.3
Python	typed (compute)	64,793	15.4
Python	typed, compute_batch of 1,000	72,172	13.9
Python	JSON, the full document	5,608	178.3

Most of a JSON call is building and printing the document, and the sources are most of the document: send includeSources: false, or use the typed entry point, when a response does not need them.

Versions and updates

The library version follows semantic versioning (additions are minor versions; a break is a new major version with a new shared-library name); the engine version, reported as engineVersion, moves whenever a rule, rate or threshold moves; the tax year is the law the build encodes.

Licence

The library is licensed commercially. Ask at [email protected].