Mortgage Compliance Preflight

Note (dated 2026-08-04): a chain composes independent computations performed in an analytical order. No step's output is carried into the next step by the execution model; each step computes from its own declared inputs. This is true of every chain on this site, including chains whose per-step copy below reads as a data handoff.

Gated four-step mortgage compliance 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. The first live OpenChainGraph chain to use §21.4 decision gates — early exit prevents unnecessary downstream calls when a blocking violation is detected.

OpenChainGraph · 4 Steps compliance mandate · §21.4 Gates Hash-Anchored §4 chain_depth:4 Client-Side · Zero PII

Chain Stages · 4 Steps · 2 Decision Gates (§21.4)

1 ROOT node

Reg Z Threshold Lookup art-220-reg-z-threshold-lookup

Version-pinned threshold tables feed downstream QM and TRID nodes

MCP Call · lookup_reg_z_thresholds

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "lookup_reg_z_thresholds",
    "arguments": {
      "table": "qm_points_fees",
      "year": 2026
    }
  },
  "id": 1
}

↓

2 GATE node §21.4 gate

TRID APR Accuracy Verifier art-217-trid-apr-accuracy

APR accuracy verdict — gate exits chain on understated_violation

△ Gate: if /verdict == "understated_violation" → END | else → Step 3

MCP Call · verify_trid_apr_accuracy

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "verify_trid_apr_accuracy",
    "arguments": {
      "disclosed_apr_pct": 6.875,
      "actual_apr_pct": 6.82
    }
  },
  "id": 2
}

↓

3 GATE node §21.4 gate

QM Points and Fees Test art-218-qm-points-and-fees

QM points-and-fees pass/fail — gate exits chain on fail

△ Gate: if /pass == false → END | else → Step 4

MCP Call · check_qm_points_and_fees

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "check_qm_points_and_fees",
    "arguments": {
      "loan_amount": 450000,
      "total_points_and_fees": 12000,
      "table_year": 2026
    }
  },
  "id": 3
}

↓

4 TERMINAL node

QM APR-APOR Spread Classifier art-219-qm-apr-apor-spread

QM APR-APOR spread classification — final stage (only reached if gates 2 and 3 pass)

MCP Call · classify_qm_apr_apor_spread

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "classify_qm_apr_apor_spread",
    "arguments": {
      "apr_pct": 6.875,
      "apor_pct": 5.0,
      "lien_type": "first",
      "loan_type": "fixed",
      "qm_fees_passed": true
    }
  },
  "id": 4
}

Question: Before this file is priced as a QM, do the points and fees clear the 2026 cap? Run the AINumbers MCP tool `run_chain` with {"chain":"mortgage-compliance-preflight"} and read `art-218-qm-points-and-fees.pass`. Re-run with `inputs` for `art-218-qm-points-and-fees`, reusing the values that result echoed, with `points_and_fees` set to 15000. Compare the same field. Verify: call `verify_execution_hash` (https://mcp.ainumbers.co/mcp) with `claimed_hash` set to `composite_execution_hash` and the full `composite_artifact`. Ledger, for a human re-check: https://ledger.ainumbers.co/ PII rule: send synthetic or anonymised inputs only. The MCP server runs these kernels and logs no payloads. Chain page: https://ainumbers.co/chaingraph/chains/mortgage-compliance-preflight.html

Mortgage Compliance Preflight

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