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AI Labs · updated 2026-06-03 · methodology v2.1

Finding on 'Q004 Probe' for Claude Sonnet 4.6 with web search ON

RLB Citation ID: RLB-H-INT-BIS-CPMI-ISO-20022-HARMONISATION-UPDATED-2026-Q004-Sonnet46
What the RLB Specialist Panel found

Finding on 'Q004 Probe' for Claude Sonnet 4.6 with web search ON

  • Question (paraphrased to protect IP): Which central bank chaired the CPMI working group that produced the harmonised ISO 20022 data requirements for cross-border payments?
  • AI's response: "the specific sub-workstream chair for ISO 20022 harmonisation is attributed to the Federal Reserve Bank of New York in available public sources"
  • Regulator's text: RBA press release (18 October 2023): "The Reserve Bank of Australia chairs the CPMI working group that developed these requirements. Michele Bullock, RBA Governor, served as former Co-Chair of the CPMI Messaging Workstream."
  • Why the AI went wrong: The model attributed the working-group chair role to the Federal Reserve Bank of New York — a higher-frequency institution in CPMI-adjacent content — rather than the Reserve Bank of Australia, which holds the published chair role and whose Governor served as Co-Chair of the relevant workstream. The hedge "in available public sources" is present but does not prevent the wrong attribution from being stated as the model's answer. This is a multi-body attribution failure where the less-frequently-cited institution holds the named role and the model substituted the more-frequently-cited institution from the same domain.
  • Cited source(s):
Impact for this audience

This failure implicates training-data density for working-group chair attribution across multi-body CPMI frameworks. The RBA press release (October 2023) naming the Reserve Bank of Australia as working-group chair exists within any plausible training window, but the model substituted the Federal Reserve Bank of New York — a higher-frequency institution in CPMI-adjacent content. The hedge 'in available public sources' signals the model detected uncertainty but did not prevent the wrong attribution from being stated.

The calibration signal for multi-body institutional role questions — where the correct answer belongs to a lower-frequency institution — is not sufficient to hold against the frequency prior.

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-ISO-20022-HARMONISATION-UPDATED-2026-Q004-Sonnet46
Plain text Download 
RegLeg Specialist Panel (2026). "Finding on 'Q004 Probe' for Claude Sonnet 4.6 with web search ON — AI Labs." Citation ID: RLB-H-INT-BIS-CPMI-ISO-20022-HARMONISATION-UPDATED-2026-Q004-Sonnet46. RegLegBrief AI Hallucination Research, published 2026-06-03. https://reglegbrief.com/regulators/j1/int/bis-cpmi/cpmi-iso-20022-harmonisation-updated-2026/whitepaper/finding/INT-BIS-CPMI-INT-001-CPMI-ISO-20022-HARMONISATION-UPDATED-2026-v1-004--sonnet-46-websearch/
APA 7th edition Download 
RegLeg Specialist Panel. (2026). Finding on 'Q004 Probe' for Claude Sonnet 4.6 with web search ON [Hallucination finding RLB-H-INT-BIS-CPMI-ISO-20022-HARMONISATION-UPDATED-2026-Q004-Sonnet46]. RegLegBrief AI Hallucination Research. https://reglegbrief.com/regulators/j1/int/bis-cpmi/cpmi-iso-20022-harmonisation-updated-2026/whitepaper/finding/INT-BIS-CPMI-INT-001-CPMI-ISO-20022-HARMONISATION-UPDATED-2026-v1-004--sonnet-46-websearch/
Bluebook / OSCOLA (US + UK legal) Download 
RegLeg Specialist Panel, Finding on 'Q004 Probe' for Claude Sonnet 4.6 with web search ON [RLB-H-INT-BIS-CPMI-ISO-20022-HARMONISATION-UPDATED-2026-Q004-Sonnet46], RegLegBrief AI Hallucination Research (June 03, 2026), https://reglegbrief.com/regulators/j1/int/bis-cpmi/cpmi-iso-20022-harmonisation-updated-2026/whitepaper/finding/INT-BIS-CPMI-INT-001-CPMI-ISO-20022-HARMONISATION-UPDATED-2026-v1-004--sonnet-46-websearch/.
BibTeX Download 
@misc{reglegbrief_RLB_H_INT_BIS_CPMI_ISO_20022_HARMONISATION_UPDATED_2026_Q004_Sonnet46,
  author    = {RegLeg Specialist Panel},
  title     = {Finding on 'Q004 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-ISO-20022-HARMONISATION-UPDATED-2026-Q004-Sonnet46},
  url       = {https://reglegbrief.com/regulators/j1/int/bis-cpmi/cpmi-iso-20022-harmonisation-updated-2026/whitepaper/finding/INT-BIS-CPMI-INT-001-CPMI-ISO-20022-HARMONISATION-UPDATED-2026-v1-004--sonnet-46-websearch/}
}
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