What specific changes did the February 2026 updated CPMI harmonised ISO 20022 data requirements make compared to the October 2023 original, including regulatory developments incorporated, clarifications provided, and how the separate technical annex relates to the main document?
The model fabricated a specific commitment, November 2026 cutover, structured-and-hybrid-addresses-only, and attributed it to the CPMI document. The actual CPMI text describes only generalised standardisation and regulatory developments since 2023, with a separate technical annex containing the data model. The structured-address content appears drawn from SWIFT/CBPR+ community material that the model has cross-attributed to CPMI without distinguishing the source corpus.
The model returned a specific cutover commitment — 'from November 2026 onwards, only structured and hybrid addresses will be permitted in ISO 20022 cross-border payment messages' — attributing the commitment to the CPMI document. The regulator's own text describes only generalised 'standardisation and regulatory developments since 2023' and a separate technical annex; the specific date-and-format commitment is not present there. The fabrication appears to draw from SWIFT/CBPR+ community discussion material, which has circulated dates and structured-address mandates, and the model has cross-attributed that content to CPMI without distinguishing the source.
For an AI lab, this is a source-attribution eval candidate: when the model returns a specific commitment with a specific date, the regulator-source attribution should be verifiable against the cited document, and where it is not, the model should distinguish industry-community material from regulator-published material in its response.
Retail-bank engineering on ISO 20022 address-format work is staffed across schema validation, address normalisation, fallback handling for unstructured legacy messages, and the message-format SLA with the FPS scheme. Sonnet 4.6 commits to a November 2026 structured-address-only cutover that does not appear in d230. A readiness epic or backlog ticket scoped against the AI line books engineering capacity against a regulatory deadline that does not exist.
Each finding has a stable Citation ID (RLB-F-… for aggregated case-study findings, RLB-H-… for raw per-model hallucinations) — like a DOI, the ID always resolves to the canonical finding even if URLs change.
RegLeg Specialist Panel (2026). "Fabricated ISO 20022 cutover — Retail Banking × Technology Data — International / Multilateral." Citation ID: RLB-H-INT-BIS-CPMI-API-HARMONISATION-CROSS-BORDER-2024-Q009-Sonnet46. RegLegBrief AI Hallucination Research, published 2026-06-11. https://reglegbrief.com/regulators/j1/INT/BIS-CPMI/CPMI-API-HARMONISATION-CROSS-BORDER-2024/sectors/retail_banking/technology_data/finding/INT-BIS-CPMI-INT-001-CPMI-API-HARMONISATION-CROSS-BORDER-2024-v1-009/
RegLeg Specialist Panel. (2026). Fabricated ISO 20022 cutover [Hallucination finding RLB-H-INT-BIS-CPMI-API-HARMONISATION-CROSS-BORDER-2024-Q009-Sonnet46]. RegLegBrief AI Hallucination Research. https://reglegbrief.com/regulators/j1/INT/BIS-CPMI/CPMI-API-HARMONISATION-CROSS-BORDER-2024/sectors/retail_banking/technology_data/finding/INT-BIS-CPMI-INT-001-CPMI-API-HARMONISATION-CROSS-BORDER-2024-v1-009/
RegLeg Specialist Panel, Fabricated ISO 20022 cutover [RLB-H-INT-BIS-CPMI-API-HARMONISATION-CROSS-BORDER-2024-Q009-Sonnet46], RegLegBrief AI Hallucination Research (June 11, 2026), https://reglegbrief.com/regulators/j1/INT/BIS-CPMI/CPMI-API-HARMONISATION-CROSS-BORDER-2024/sectors/retail_banking/technology_data/finding/INT-BIS-CPMI-INT-001-CPMI-API-HARMONISATION-CROSS-BORDER-2024-v1-009/.
@misc{reglegbrief_RLB_H_INT_BIS_CPMI_API_HARMONISATION_CROSS_BORDER_2024_Q009_Sonnet46,
author = {RegLeg Specialist Panel},
title = {Fabricated ISO 20022 cutover},
year = {2026},
publisher = {RegLegBrief AI Hallucination Research},
note = {Hallucination finding Citation ID: RLB-H-INT-BIS-CPMI-API-HARMONISATION-CROSS-BORDER-2024-Q009-Sonnet46},
url = {https://reglegbrief.com/regulators/j1/INT/BIS-CPMI/CPMI-API-HARMONISATION-CROSS-BORDER-2024/sectors/retail_banking/technology_data/finding/INT-BIS-CPMI-INT-001-CPMI-API-HARMONISATION-CROSS-BORDER-2024-v1-009/}
}
Every finding on this page compares an AI subject's account of the rule against the regulator's verbatim text from the regulator's own portal. Both are linked. Each delta, its root causes, and impact analysis are documented and published with immutable Citation IDs.