AI Hallucination Research › Regulators › Major advanced economies › SG › MAS › NOTICE-637-CAPITAL-ADEQUACY-BANKS-2025 › White paper › Detail › Finding
AI Labs · published 2026-05-28 · methodology v2.1

Claude Opus 4.7 with web search

What the RLB Specialist Panel found
  • Question (paraphrased to protect IP): In MAS Notice 637 (Amendment) 2024, what do the yellow-highlighted passages signify, and will they appear in the final consolidated version of the Notice?
  • AI's response: "Yellow highlighting in MAS tracked-change amendment PDFs is typically used as a drafting/visual aid to draw attention to particular text — for example, defined terms, cross-references, or items the reader should pay particular attention to during review."
  • Regulator's text: The yellow-highlighted passages in MAS Notice 637 (Amendment) 2024 carry a specific, defined meaning in the amendment instrument itself — they are not a general-purpose visual aid but a formatting convention with a precise editorial function in the context of that document.
  • Why the AI went wrong: The model substituted a generic, plausible account of how yellow highlighting is sometimes used in legal and regulatory drafting for the specific meaning that MAS assigned to the convention in this amendment instrument. The response reflects the model constructing an answer from general knowledge about document conventions rather than from the amendment text itself, and it does so without flagging that the characterisation is inferred rather than retrieved — inverting the actual meaning of the formatting element in the process.
  • Cited source(s):
Impact for this audience

This finding implicates the model's handling of document-specific formatting conventions — a content type that requires retrieval of the specific document rather than reconstruction from general knowledge. The model's characterisation of yellow highlighting as a general-purpose visual aid reflects generation from training knowledge about drafting conventions rather than from the amendment text itself. The gap is in how the RAG layer handles document-convention queries where the correct answer is specific to a single instrument: the model should either retrieve the relevant passage from the amendment PDF or decline to characterise the convention. Eval probes for amendment-specific formatting and editorial conventions — where general knowledge and document-specific meaning diverge — would cover this failure surface.

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.

Plain text 
RegLeg Specialist Panel (2026). "Claude Opus 4.7 with web search — AI Labs." Citation ID: . RegLegBrief AI Hallucination Research, published 2026-05-28. https://reglegbrief.com/regulators/j3/sg/mas/notice-637-capital-adequacy-banks-2025/whitepaper/finding/q-NOTICE-637-CAPITAL-ADEQUACY-BANKS-2025-v1-012--opus-47-websearch/
APA 7th edition 
RegLeg Specialist Panel. (2026). Claude Opus 4.7 with web search [Hallucination finding ]. RegLegBrief AI Hallucination Research. https://reglegbrief.com/regulators/j3/sg/mas/notice-637-capital-adequacy-banks-2025/whitepaper/finding/q-NOTICE-637-CAPITAL-ADEQUACY-BANKS-2025-v1-012--opus-47-websearch/
Bluebook / OSCOLA (US + UK legal) 
RegLeg Specialist Panel, Claude Opus 4.7 with web search [], RegLegBrief AI Hallucination Research (May 28, 2026), https://reglegbrief.com/regulators/j3/sg/mas/notice-637-capital-adequacy-banks-2025/whitepaper/finding/q-NOTICE-637-CAPITAL-ADEQUACY-BANKS-2025-v1-012--opus-47-websearch/.
BibTeX 
@misc{reglegbrief_,
  author    = {RegLeg Specialist Panel},
  title     = {Claude Opus 4.7 with web search},
  year      = {2026},
  publisher = {RegLegBrief AI Hallucination Research},
  note      = {Hallucination finding Citation ID: },
  url       = {https://reglegbrief.com/regulators/j3/sg/mas/notice-637-capital-adequacy-banks-2025/whitepaper/finding/q-NOTICE-637-CAPITAL-ADEQUACY-BANKS-2025-v1-012--opus-47-websearch/}
}
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