US Mortgage Compliance Core · Cluster ㉑ · OpenChainGraph v0.4

US Mortgage Compliance Core

Six computational tools covering the full US residential mortgage compliance stack: Reg Z Appendix J actuarial APR (bracketed-bisection solver with fractional-period support, priced at simple interest per (b)(6)), TRID fee tolerance classification and cure computation, TRID APR accuracy verification (§1026.22(a) tolerances), QM points-and-fees test (§1026.43(e)(3) five-tier table, version-pinned 2021-2026), QM APR-APOR spread classification (§1026.43(e)(2)(vi)), and version-pinned Reg Z threshold lookup. All regulatory reference tables are baked into the kernels citing primary sources (FR citations, CFPB rule citations). Zero PII. Agent-native via MCP.

TRID · 12 CFR §1026.19 IN FORCE Reg Z APR · 12 CFR §1026.22 IN FORCE QM Rule · 12 CFR §1026.43 IN FORCE Reg Z Appendix J IN FORCE QM Tables · Version-pinned 2021-2026 HOEPA Thresholds · Version-pinned 2021-2026 First OCG §21.4 Gated Chain Live FHFA CLL 2026 · Conforming Loan Limits Fannie Mae LLPA 2025-11-01 · Version-pinned FHA MIP · HUD 4000.1 · ML 2023-05 VA Funding Fee · 38 USC §3729 · 2025-01-01 ULDD Phase 5 · Public Stencil Only

ALL IN FORCE: TRID disclosure rules (12 CFR §1026.19), Reg Z APR accuracy (§1026.22(a)), Qualified Mortgage rule (§1026.43), Reg Z Appendix J actuarial method, FHFA 2026 conforming loan limits, Fannie Mae LLPA matrix (effective 2025-11-01), FHA MIP grid (HUD ML 2023-05), and VA funding fee table (38 USC §3729, effective 2025-01-01) are all currently in force. Tables are version-pinned. Rerun check_conforming_loan_limit and verify LLPA table_version when annual announcements occur (FHFA Nov; FHA/VA Jan).

EDUCATIONAL: Outputs are decision-support computations. Not legal or compliance advice, not a regulatory filing. Verify QM threshold values against CFPB annual adjustments (Federal Register). Consult qualified mortgage counsel before relying on any result for loan production or remediation decisions.

Chain and tool matrix for US Mortgage Compliance Core: each column is a tool this guide covers, most used first, each row is one chain, and a brighter cell means more of that row's chains run through the tool. Hover a cell to list them.

Entry point: Reg Z threshold lookup

Start here when building any mortgage compliance workflow. Fetches version-pinned QM and HOEPA tables that downstream nodes consume.

ART-220 · compliance_mandate

Reg Z Threshold Lookup

Version-pinned QM points-and-fees dollar thresholds (2021-2026) and HOEPA rate-spread and points-and-fees thresholds (2021-2026). All values baked from Federal Register annual adjustments. No numeric inputs. Select table type and year. Anti-hallucination moat: agents cannot invent thresholds when pinned tables are present in context.

lookup_reg_z_thresholds IN FORCE · Annual FR Updates

Reg Z APR: computation and accuracy

Actuarial APR solver (Appendix J) and APR accuracy verifier (§1026.22(a)). Run the solver first to obtain the actual APR, then pass it to the verifier.

ART-215 · compliance_mandate

Reg Z Appendix J APR Solver

Bracketed-bisection APR solver over the Reg Z Appendix J general actuarial equation. Supports regular periodic loans, irregular payment schedules, and fractional first periods (odd days), with the odd-days fraction priced at simple interest per (b)(6) and only full unit-periods compounded. Advances and payments arrays. Narrows the bracket to 0.000001 percentage points of APR. Outputs apr_pct (4dp), periodic_rate, iterations, converged and bracketed flags, and finance_charge, and reports no rate at all when no sign-change bracket exists.

compute_reg_z_appendix_j_apr IN FORCE · Reg Z Appendix J

ART-217 · compliance_mandate

TRID APR Accuracy Verifier

Verifies APR accuracy per 12 CFR §1026.22(a). Regular transaction: 1/8 pp (0.125%) tolerance. Irregular transaction: 1/4 pp (0.250%) tolerance. Irregular = multiple advances, irregular payment periods, or demand feature. Verdicts: accurate, accurate_overstated_ok, understated_violation, overstated_violation. Flags TRID_APR_UNDERSTATED_VIOLATION.

verify_trid_apr_accuracy IN FORCE · §1026.22(a)

TRID fee tolerance and cure

Classifies fees into TRID tolerance buckets and computes the cure amount per 12 CFR §1026.19(e)(3).

ART-216 · compliance_mandate

TRID Fee Tolerance and Cure

Classifies fees into three TRID tolerance buckets: zero-tolerance (any increase is a violation, cure = full increase), ten-percent-cumulative (10% bucket total), no-tolerance-limit (no cure required). Supports dynamic fee rows. Outputs cure_amount, violations list, bucket summaries. Flags TRID_ZERO_TOLERANCE_VIOLATION and TRID_TEN_PCT_VIOLATION.

compute_trid_tolerance_cure IN FORCE · §1026.19(e)(3)

Qualified Mortgage: points-and-fees and APR-APOR spread

QM test tools per 12 CFR §1026.43(e)(3) (points-and-fees) and §1026.43(e)(2)(vi) + §1026.43(b)(4) (APR-APOR spread). Run points-and-fees first; only proceed to spread if it passes.

ART-218 · compliance_mandate

QM Points and Fees Test

Five-tier QM points-and-fees table per 12 CFR §1026.43(e)(3). Version-pinned 2021-2026 with Federal Register citations. Tier thresholds: ≥$130,461 (3%), ≥$78,277 (5%), ≥$26,092 (8%), ≥$16,058.50 (fixed $2,003), <$16,058.50 (8%), 2026 values. Active tier highlighted. Outputs pass/fail and limit. Feeds §21.4 gate in preflight chain.

check_qm_points_and_fees IN FORCE · §1026.43(e)(3)

ART-219 · compliance_mandate

QM APR-APOR Spread Classifier

Classifies QM APR-APOR spread per §1026.43(e)(2)(vi). First-lien: safe harbor ≤1.5pp, rebuttable 1.5-2.25pp, fail >2.25pp. HPCT threshold 1.5pp first / 3.5pp sub. General QM outer limit 2.25pp first / 6.5pp sub. Flags QM_APR_SPREAD_FAIL, HPCT_LOAN, QM_REBUTTABLE_PRESUMPTION. Three-zone threshold grid.

classify_qm_apr_apor_spread IN FORCE · §1026.43(e)(2)(vi)

Agency loan sizing and pricing

FHFA conforming loan limit classification, Fannie Mae DU / Freddie Mac LPA agency eligibility, and Fannie Mae LLPA stack. Run limit check first, then eligibility, then LLPA pricing for eligible loans.

ART-223 · compliance_mandate

Conforming Loan Limit Check

FHFA 2026 conforming loan limit classification by unit count and county tier. Baseline: $806,500 (1-unit). High-cost ceiling: $1,209,750 (150% of baseline). AK/HI/GU/VI always receive ceiling treatment. Optional county_limit_override for exact per-county FHFA data. Classifies as conforming, super_conforming, or jumbo. Surfaces loan_program into output for chain gate routing. Table: FHFA-CLL-2026.

check_conforming_loan_limit IN FORCE · FHFA-CLL-2026

ART-222 · compliance_mandate

Agency Eligibility Matrix

Fannie Mae DU / Freddie Mac LPA eligibility matrix. DTI caps: 50% DU/LPA, 36%/45% manual. Max LTV/CLTV/HCLTV by occupancy and purpose (purchase/rate-term/cash-out). Multi-unit overlays (2-4 unit). Second home 1-unit-only restriction. Returns ELIGIBLE or INELIGIBLE in eligible_flag. Table: FNM-LPA-ELIGIBILITY-2026-01-01.

check_agency_eligibility_matrix IN FORCE · DU/LPA Grid 2026

ART-221 · compliance_mandate

LLPA Stack Calculator

Fannie Mae public LLPA matrix (FNM-LLPA-2025-11-01). FICO-by-LTV base grid (9 LTV bands x 8 FICO bands). Purpose adjustments: cash-out refinance, second home, investment property. Property overlays: condo, subordinate financing (indexed by LTV band). FTHB waiver: primary purchase only, AMI at or below 100%, up to 1.75 pp waiver. Returns total_llpa_pct and waiver amount.

compute_llpa_stack IN FORCE · FNM-LLPA-2025-11-01

Government loan programs: FHA and VA

FHA mortgage insurance premium eligibility and cost (HUD 4000.1), VA funding fee (38 USC §3729) and residual income qualification (VA Pamphlet 26-7 Ch.4), and ULDD/ULAD structural lint (public ULDD Phase 5).

ART-224 · compliance_mandate

FHA MIP Eligibility

FHA mortgage insurance premium eligibility and cost per HUD Handbook 4000.1. UFMIP: 1.75% of base loan amount. Annual MIP grid by loan size vs $726,200 threshold, LTV, and term (ML 2023-05 / ML 2024-01). MIP duration: 11 years if original LTV at or below 90%; life-of-loan if above. Qualifying ratios: 31% front-end / 43% back-end. Max LTV by FICO tier (580 for 96.5%; 500-579 for 90%). Table: HUD-MIP-ML2023-05-ML2024-01.

compute_fha_mip_eligibility IN FORCE · HUD 4000.1 · ML 2023-05

ART-225 · compliance_mandate

VA Funding Fee and Residual Income

VA funding fee per 38 USC §3729 statutory table (first/subsequent use, three down-payment tiers: below 5%, 5-9.99%, 10%+). Purchase: 2.15%/3.30% first/subsequent below 5%. IRRRL flat: 0.50%. Exemption for service-connected disability. Residual income per VA Pamphlet 26-7 Ch.4 Table 41A (NE/MW/SO/WE regions, family size 1-5, $80/additional member). DTI benchmark: 41%. Tables: VA-FF-2025-01-01; VA-PAMPHLET-26-7-CH4-2024.

compute_va_funding_fee_residual IN FORCE · 38 USC §3729 · 2025

ART-226 · compliance_mandate

ULDD/ULAD Structural Linter

Structural lint of Fannie Mae ULDD Phase 5 and Freddie Mac ULAD required data points and enumerations. Checks 13 required field presence, 9 enum dictionaries, 7 numeric range constraints, ARM conditionality (arm_index_type required for AdjustableRate), and indicator consistency warnings. ULDD Phase 5 mandate effective 2025-07-28. Uses public ULDD/ULAD data dictionaries only, not the membership-licensed MISMO v3.x Reference Model schema. Table: ULDD-PHASE5-ULAD-1.3-2025-07-28.

lint_mismo_uldd_ulad IN FORCE · ULDD Phase 5 · 2025-07-28

HOEPA and HPML: high-cost mortgage and escrow screens

HOEPA three-trigger test (§1026.32(a)(1)) and HPML escrow requirement (§1026.35(a)+(b)). Run the high-cost screen first; the HPML screen only applies when no HOEPA trigger fires. Both consume art-220 threshold tables.

ART-234 · compliance_mandate

HOEPA High-Cost Mortgage Trigger Test

Tests all three HOEPA high-cost triggers per §1026.32(a)(1). (i) APR trigger: APOR+6.5pp first-lien, APOR+8.5pp subordinate or dwelling below $50,000. (ii) Points-and-fees trigger: 5% of loan or $1,380 floor (2026, FR 2025-22773). (iii) Prepayment penalty trigger: applies beyond 36 months or exceeds 2% of prepaid amount. Returns is_high_cost and triggers_fired. Feeds §21.4 gate in mortgage-high-cost-and-hpml-screen chain.

test_hoepa_high_cost IN FORCE · §1026.32(a)(1) · HOEPA 2026

ART-235 · compliance_mandate

HPML Escrow Requirement Test

HPML higher-priced mortgage loan definition per §1026.35(a) and escrow obligation per §1026.35(b). Spread thresholds: APOR+1.5pp first-lien standard, APOR+2.5pp jumbo, APOR+3.5pp subordinate lien. Dodd-Frank structural thresholds, unchanged since 2014. Escrow required for first-lien HPML (5-year minimum). Exemptions: rural/underserved small creditor (assets <$2B + ≤500 HPMLs), condo master policy. Returns is_hpml and escrow_required.

test_hpml_escrow IN FORCE · §1026.35(a)+(b) · Dodd-Frank

Chains: 5 chains (4 gated, 1 linear)

Five chains cover mortgage compliance, TRID remediation, agency pricing decisioning, government loan program routing, and HOEPA/HPML screening. Chains with §21.4 gates exit early or fork when a condition is met.

mortgage-compliance-preflight (§21.4 gated, 2 gates):
  ART-220 [thresholds] → ART-217 [APR GATE: understated_violation → END] → ART-218 [QM fees GATE: fail → END] → ART-219 [spread]

mortgage-apr-accuracy-and-tolerance-cure (linear):
  ART-215 [APR solver] → ART-217 [APR accuracy] → ART-216 [TRID cure]

mortgage-agency-pricing-and-eligibility (§21.4 gated, 1 gate):
  ART-223 [CLL check] → ART-222 [eligibility GATE: INELIGIBLE → END] → ART-221 [LLPA stack]

mortgage-government-loan-fit (§21.4 fork gate):
  ART-223 [CLL + program FORK: loan_program=VA → ART-225; default → ART-224]
    Branch A (VA): ART-225 [VA fee + residual] | Branch B (FHA/default): ART-224 [FHA MIP]

mortgage-high-cost-and-hpml-screen (§21.4 gated, 1 gate):
  ART-234 [HOEPA triggers GATE: is_high_cost=true → END] → ART-235 [HPML escrow]

mortgage-compliance-preflight · 4 nodes · OCG v0.8.0

Mortgage Compliance Preflight

Gated four-step preflight. Fetches version-pinned Reg Z thresholds, verifies TRID APR accuracy (exits immediately on understatement violation), checks QM points-and-fees (exits on failure), then classifies QM APR-APOR spread. Early exit prevents unnecessary downstream calls on a blocking violation.

→ ART-220 → ART-217 [GATE] → ART-218 [GATE] → ART-219

⚡ §21.4 Decision Gates (2 gates)

mortgage-apr-accuracy-and-tolerance-cure · 3 nodes · OCG v0.8.0

Mortgage APR Accuracy and Tolerance Cure

Linear three-step TRID remediation chain. Computes actual APR via Reg Z Appendix J, verifies APR accuracy against the disclosed figure, and produces a complete TRID fee tolerance cure package.

→ ART-215 → ART-217 → ART-216

mortgage-agency-pricing-and-eligibility · 3 nodes · OCG v0.8.0

Mortgage Agency Pricing and Eligibility

Gated three-step agency decisioning chain. Classifies conforming loan limit, checks DU/LPA agency eligibility (gate exits on INELIGIBLE), then computes the full LLPA cost grid for eligible loans. FHFA CLL 2026, DU/LPA eligibility, FNM LLPA 2025-11-01.

→ ART-223 → ART-222 [GATE: INELIGIBLE→END] → ART-221

⚡ §21.4 Decision Gate (1 gate)

mortgage-government-loan-fit · fork gate · OCG v0.8.0

Mortgage Government Loan Fit

Fork-gate router for government loan programs. Step 1 surfaces the loan program into output. Gate routes VA loans to VA funding fee and residual income (38 USC §3729 + Pamphlet 26-7); all others to FHA MIP eligibility (HUD 4000.1). Both branches reachable; mandatory default.

→ ART-223 [FORK: VA → ART-225 | default → ART-224]

⚡ §21.4 Fork Gate (VA/FHA router)

mortgage-high-cost-and-hpml-screen · 2 nodes · OCG v0.8.0

Mortgage High-Cost and HPML Screen

Gated two-step HOEPA/HPML screen. Step 1 tests all three HOEPA high-cost triggers (APR, points-and-fees, prepayment penalty) per §1026.32(a)(1). Gate exits immediately if any trigger fires. If no HOEPA trigger, default path continues to step 2: HPML escrow requirement per §1026.35(a)+(b). Covers rural/underserved and condo master-policy escrow exemptions.

→ ART-234 [GATE: is_high_cost=true → END] → ART-235

⚡ §21.4 Decision Gate (1 gate)

Agent integration

All 6 tools are callable via MCP at https://mcp.ainumbers.co/mcp. Use run_chain to execute a chain end-to-end, or call tools individually by mcp_name.

MCP · chain execution

run_chain

Execute mortgage-compliance-preflight or mortgage-apr-accuracy-and-tolerance-cure end-to-end over MCP. Gates in the preflight chain are evaluated server-side. Returns a composite artifact with decisions[], path_taken[], and skipped_by_gate entries for any early-exit branches.

run_chain

MCP · discovery

find_chain / find_tool

Use find_chain with query "mortgage" to discover both chains. Use find_tool with query "trid" or "qm" to discover individual nodes. Returned tool_id values can be passed directly to tools/call.

find_chain · find_tool

Regulatory references

Primary sources baked into the kernels with explicit version pinning.

Reg Z APR (Appendix J): 12 CFR §1026, Appendix J; actuarial method equation, advances/payments notation, fractional period (odd-day) treatment

TRID APR accuracy: 12 CFR §1026.22(a); 1/8 pp regular / 1/4 pp irregular; definition of irregular transaction

TRID fee tolerance: 12 CFR §1026.19(e)(3); zero-tolerance, ten-percent-cumulative, no-tolerance-limit buckets; cure timing and amount rules

QM points-and-fees: 12 CFR §1026.43(e)(3); five-tier table; annual CFPB adjustments published in the Federal Register (FR Vol. 87, 88, 89, 90 for 2022-2026 thresholds)

QM APR-APOR spread: 12 CFR §1026.43(e)(2)(vi) safe harbor / rebuttable presumption thresholds; §1026.43(b)(4) HPCT definition; §1026.43(e)(3)(ii) fee failure interaction

HOEPA high-cost triggers (§1026.32(a)(1)): 12 CFR §1026.32(a)(1); three triggers: (i) APR: APOR+6.5pp first-lien, APOR+8.5pp subordinate or dwelling below $50,000; (ii) Points-and-fees: 5% or $1,380 floor (2026, FR 2025-22773; effective 2026-01-01); (iii) Prepayment penalty: applies beyond 36 months or exceeds 2% of prepaid amount. Table: HOEPA-REGZ-2026-01-01.

HPML definition and escrow (§1026.35): Reg Z §1026.35(a)(1) HPML definition; APR exceeds APOR by 1.5pp (first-lien standard), 2.5pp (jumbo, above FHFA conforming limit), or 3.5pp (subordinate lien). Dodd-Frank structural thresholds, unchanged since 2014 (FR 2013-01730). §1026.35(b)(1) escrow requirement: first-lien HPML must maintain property-tax-and-insurance escrow for minimum 5 years. Exemptions: §1026.35(b)(2)(iii) rural/underserved area + assets below $2B + 500 or fewer first-lien HPMLs; §1026.35(b)(2)(ii) condo HOA master policy. Table: HPML-REGZ-2026-01-01.

FHFA Conforming Loan Limits 2026: 12 USC 1454 (Freddie Mac Charter §305); 12 USC 1717 (Fannie Mae Charter §304(b)); HERA 2008 §201; FHFA Annual CLL Adjustment; baseline $806,500 (1-unit); 150% ceiling $1,209,750; AK/HI/GU/VI at ceiling. Source: FHFA FullCountyLoanLimitList2026.xlsx (public). Table: FHFA-CLL-2026.

Fannie Mae Agency Eligibility (DU/LPA): Fannie Mae Selling Guide B3-2-01 (DU eligibility); Freddie Mac Guide Ch.5100 (LPA eligibility); DTI caps, LTV/CLTV/HCLTV grids by occupancy and purpose, multi-unit overlays. Table: FNM-LPA-ELIGIBILITY-2026-01-01.

Fannie Mae LLPA Matrix: Fannie Mae Selling Guide B3-4.1-02; LLPA matrix effective 2025-11-01 (public, FNM website); FICO-by-LTV base grid, purpose/property/subordinate-financing adjustments; SEL-2023-07 FTHB AMI waiver. Table: FNM-LLPA-2025-11-01.

FHA MIP (HUD 4000.1): 12 USC 1709 (FHA §203(b)); HUD Handbook 4000.1 §II.A.8; UFMIP 1.75%; annual MIP grid (ML 2023-05; ML 2024-01); 31%/43% qualifying ratios; FICO-gated max LTV (580 for 96.5%, 500-579 for 90%). Table: HUD-MIP-ML2023-05-ML2024-01.

VA Funding Fee and Residual Income: 38 USC §3729 (funding fee statutory table); 38 CFR Part 36 (VA home loans); VA Pamphlet 26-7 Ch.4 Table 41A (residual income by region and family size); exemption for service-connected disability. Tables: VA-FF-2025-01-01; VA-PAMPHLET-26-7-CH4-2024.

ULDD / ULAD structural lint: Fannie Mae ULDD Phase 5 Data Stencil (public, fanniemae.com; mandate effective 2025-07-28); Freddie Mac ULAD Data Dictionary v1.3 (public, freddiemac.com); Uniform Mortgage Data Program (UMDP); 12 USC 4501 (FHFA). Tool uses public stencils only, not the membership-licensed MISMO v3.x Reference Model. Table: ULDD-PHASE5-ULAD-1.3-2025-07-28.

All Tools · OpenChainGraph Hub · ART-215 · ART-216 · ART-217 · ART-218 · ART-219 · ART-220 · ART-221 · ART-222 · ART-223 · ART-224 · ART-225 · ART-226 · ART-234 · ART-235

Post Oak Labs · CC BY 4.0 · OpenChainGraph Suite · US Mortgage Compliance · Agency and Government Loan Pricing · HOEPA and HPML · Cluster ㉑