nx_iso20022_lib.nx

nx_iso20022_lib.nx -- F989: ISO 20022 payment-message parse + integrity validation. 2026 is the inflection: Fedwire migrated to ISO 20022 in July 2025 and Swift ends MT coexistence in November. A pain.001 (customer credit-transfer initiation) carries its OWN integrity fields -- NbOfTxs (the declared transaction count) and CtrlSum (the declared total). The sovereign property here is that these are CHECKED against the actual message content, never trusted: a corrupted or TAMPERED payment file -- one where an amount was altered but the control sum was not -- is REJECTED by construction. Money is integer minor units; a control sum is compared to the exact cent, no float, no tolerance. FAIL-CLOSED: a missing required field (NbOfTxs / CtrlSum) is a rejection, not a default -- a payment message you cannot validate is a payment message you do not process. SCOPE (declared, honest): this parses element text and validates the two internal-integrity invariants. Full XSD schema validation, namespace resolution, and variable-fraction-digit currencies (this assumes 2 fraction digits, correct for USD/EUR/most) are DECLARED follow-ons, not silently handled. DRY: composes nx_matter_lib (sys_*/mt_*). A validated message feeds nx_ledger as transfers. license_tier: ORIGINAL LIB.