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AI Labs · Last updated 7 Jun 2026 · methodology vv2.3 · Hallucination Register

Finding on 'Q009 Probe' for Claude Sonnet 4.6 with web search ON

RLB Citation ID: RLB-H-INT-BIS-CPMI-API-HARMONISATION-CROSS-BORDER-2024-Q009-Sonnet46
What the RLB Specialist Panel found

Finding on 'Q009 Probe' for Claude Sonnet 4.6 with web search ON

  • Question (paraphrased to protect IP): 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?
  • AI's response: "From November 2026 onwards, only structured and hybrid addresses will be permitted in ISO 20022 cross-border payment messages, the fully unstructured address format is being phased out. This is being driven by the SWIFT/CBPR+ community and is reflected in d230's updated requirements."
  • Regulator's text: The updated version of the report takes into account standardisation and regulatory developments since 2023, provides clarification where market participants had sought further guidance, and sets out the updated and expanded data model in a separate technical annex.
  • Why the AI went wrong: 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.
  • Cited source(s):
Impact for this audience

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.

References — raw findings (per AI model)
This finding also affects
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Cite this finding

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.

RLB Citation ID: RLB-H-INT-BIS-CPMI-API-HARMONISATION-CROSS-BORDER-2024-Q009-Sonnet46
Plain text Download 
RegLeg Specialist Panel (2026). "Finding on 'Q009 Probe' for Claude Sonnet 4.6 with web search ON — AI Labs." Citation ID: RLB-H-INT-BIS-CPMI-API-HARMONISATION-CROSS-BORDER-2024-Q009-Sonnet46. RegLegBrief AI Hallucination Research, published 2026-06-07. https://reglegbrief.com/regulators/j1/int/BIS-CPMI/CPMI-API-HARMONISATION-CROSS-BORDER-2024/whitepaper/finding/INT-BIS-CPMI-INT-001-CPMI-API-HARMONISATION-CROSS-BORDER-2024-v1-009--sonnet-46-websearch/
APA 7th edition Download 
RegLeg Specialist Panel. (2026). Finding on 'Q009 Probe' for Claude Sonnet 4.6 with web search ON [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/whitepaper/finding/INT-BIS-CPMI-INT-001-CPMI-API-HARMONISATION-CROSS-BORDER-2024-v1-009--sonnet-46-websearch/
Bluebook / OSCOLA (US + UK legal) Download 
RegLeg Specialist Panel, Finding on 'Q009 Probe' for Claude Sonnet 4.6 with web search ON [RLB-H-INT-BIS-CPMI-API-HARMONISATION-CROSS-BORDER-2024-Q009-Sonnet46], RegLegBrief AI Hallucination Research (June 07, 2026), https://reglegbrief.com/regulators/j1/int/BIS-CPMI/CPMI-API-HARMONISATION-CROSS-BORDER-2024/whitepaper/finding/INT-BIS-CPMI-INT-001-CPMI-API-HARMONISATION-CROSS-BORDER-2024-v1-009--sonnet-46-websearch/.
BibTeX Download 
@misc{reglegbrief_RLB_H_INT_BIS_CPMI_API_HARMONISATION_CROSS_BORDER_2024_Q009_Sonnet46,
  author    = {RegLeg Specialist Panel},
  title     = {Finding on 'Q009 Probe' for Claude Sonnet 4.6 with web search ON},
  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/whitepaper/finding/INT-BIS-CPMI-INT-001-CPMI-API-HARMONISATION-CROSS-BORDER-2024-v1-009--sonnet-46-websearch/}
}
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