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AI Labs · Last updated 7 Jun 2026 · methodology v2.1 · Hallucination Register

Finding on 'Q001 Probe' for Claude Sonnet 4.6 with web search ON

RLB Citation ID: RLB-H-INT-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q001-Sonnet46
What the RLB Specialist Panel found

Finding on 'Q001 Probe' for Claude Sonnet 4.6 with web search ON

  • Question (paraphrased to protect IP): How is the 2025 OECD Merger Review Recommendation (OECD/LEGAL/0333) structured, what does each operative section address, and which subject-matter areas did the 2025 revision add that were absent from the 2005 version?
  • AI's response: "structured around six broad operative areas: 1. Merger Review Framework... 2. Notification and Review Procedures... 3. Substantive Merger Analysis... 4. Merger Remedies... 5. Cross-Jurisdictional Co-operation... 6. Monitoring and Review."
  • Regulator's text: The Recommendation has five operative sections: Section I (maintain an effective merger review framework); Section II (apply effective merger notification and review procedures); Section III (apply sound merger analysis); Section IV (develop and apply a clear framework for remedies); Section V (conduct ex-post assessment of merger decisions and/or remedies).
  • Why the AI went wrong: The model generated an identical structural error to Claude Opus 4.7 with web search on the same question, a six-section architecture with "Cross-Jurisdictional Co-operation" and "Monitoring and Review" inserted as standalone operative areas. The near-exact convergence across two configurations that differ substantially in size and post-training tuning, both with web search active, points to a shared training-data gap on the 2025 revision's structure rather than a configuration-specific artefact. The retrieval layer did not surface or weight the primary text sufficiently to correct the reconstruction.
  • Cited source(s):
Impact for this audience

Near-exact convergence with Claude Opus 4.7 with web search on the same structural fabrication — a six-section architecture, with the same inserted section names — across configurations that differ substantially in model size, post-training tuning, and retrieval behaviour. The shared error points to a training-data gap on the 2025 Recommendation's structure rather than a model-specific artefact, and confirms the retrieval layer is not compensating for the gap in either configuration.

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-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q001-Sonnet46
Plain text Download 
RegLeg Specialist Panel (2026). "Finding on 'Q001 Probe' for Claude Sonnet 4.6 with web search ON — AI Labs." Citation ID: RLB-H-INT-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q001-Sonnet46. RegLegBrief AI Hallucination Research, published 2026-06-07. https://reglegbrief.com/regulators/j1/INT/OECD/OECD-MERGER-REVIEW-RECOMMENDATION-2025/whitepaper/finding/INT-OECD-INT-001-OECD-MERGER-REVIEW-RECOMMENDATION-2025-v1-001--sonnet-46-websearch/
APA 7th edition Download 
RegLeg Specialist Panel. (2026). Finding on 'Q001 Probe' for Claude Sonnet 4.6 with web search ON [Hallucination finding RLB-H-INT-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q001-Sonnet46]. RegLegBrief AI Hallucination Research. https://reglegbrief.com/regulators/j1/INT/OECD/OECD-MERGER-REVIEW-RECOMMENDATION-2025/whitepaper/finding/INT-OECD-INT-001-OECD-MERGER-REVIEW-RECOMMENDATION-2025-v1-001--sonnet-46-websearch/
Bluebook / OSCOLA (US + UK legal) Download 
RegLeg Specialist Panel, Finding on 'Q001 Probe' for Claude Sonnet 4.6 with web search ON [RLB-H-INT-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q001-Sonnet46], RegLegBrief AI Hallucination Research (June 07, 2026), https://reglegbrief.com/regulators/j1/INT/OECD/OECD-MERGER-REVIEW-RECOMMENDATION-2025/whitepaper/finding/INT-OECD-INT-001-OECD-MERGER-REVIEW-RECOMMENDATION-2025-v1-001--sonnet-46-websearch/.
BibTeX Download 
@misc{reglegbrief_RLB_H_INT_OECD_OECD_MERGER_REVIEW_RECOMMENDATION_2025_Q001_Sonnet46,
  author    = {RegLeg Specialist Panel},
  title     = {Finding on 'Q001 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-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q001-Sonnet46},
  url       = {https://reglegbrief.com/regulators/j1/INT/OECD/OECD-MERGER-REVIEW-RECOMMENDATION-2025/whitepaper/finding/INT-OECD-INT-001-OECD-MERGER-REVIEW-RECOMMENDATION-2025-v1-001--sonnet-46-websearch/}
}
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