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

Finding on 'Q005 Probe' for Claude Sonnet 4.6 with web search ON

RLB Citation ID: RLB-H-INT-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q005-Sonnet46
What the RLB Specialist Panel found

Finding on 'Q005 Probe' for Claude Sonnet 4.6 with web search ON

  • Question (paraphrased to protect IP): Under Section III.11.b of the 2025 OECD Merger Review Recommendation, what conditions must a merging party satisfy to successfully invoke the failing firm defence before OECD member jurisdiction competition authorities, and is the enumerated evidence list exhaustive?
  • AI's response: "Under the OECD standard, a failing firm defence requires the merging parties to demonstrate all three of the following conditions... All three conditions must be satisfied simultaneously. Failure on any one condition is fatal to the defence."
  • Regulator's text: Section III.11.b requires "inter alia, evidence that the business was likely to have exited and the existence of less anti-competitive alternative buyers or other options for reorganisation are not viable, and that the exit of the firm's assets would cause more harm to competition than the merger."
  • Why the AI went wrong: The Recommendation's failing firm defence standard is explicitly non-exhaustive, "inter alia" preserves regulatory flexibility for competition authorities to require additional evidence. The model dropped the qualifier and presented the evidentiary list as a closed, exhaustive three-condition test with an expressly fatal consequence for failure on any single condition. This convergence with Claude Opus 4.7 with web search on the same erasure, across two different configurations, both with web search active, indicates that the 2025 Recommendation's exact phrasing of this standard is not adequately represented in training for either model, and that retrieval did not surface the primary text to correct it.
  • Cited source(s):
  • https://www.oecd.org/en/publications/failing-firm-defence_1712635f-en.html, Pretextual
Impact for this audience

Cross-model convergence with Claude Opus 4.7 with web search on the identical qualifier erasure — both models dropped 'inter alia' and presented the standard as exhaustive, with web search active on both — is a strong signal that the 2025 Recommendation's failing firm defence text is not adequately represented in training for either model, and that the retrieval layer is not surfacing the primary text at sufficient weight to correct it. Post-training calibration for precision-qualifier preservation in legal standard characterisation is the relevant intervention.

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-Q005-Sonnet46
Plain text Download 
RegLeg Specialist Panel (2026). "Finding on 'Q005 Probe' for Claude Sonnet 4.6 with web search ON — AI Labs." Citation ID: RLB-H-INT-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q005-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-v1-005--sonnet-46-websearch/
APA 7th edition Download 
RegLeg Specialist Panel. (2026). Finding on 'Q005 Probe' for Claude Sonnet 4.6 with web search ON [Hallucination finding RLB-H-INT-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q005-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-v1-005--sonnet-46-websearch/
Bluebook / OSCOLA (US + UK legal) Download 
RegLeg Specialist Panel, Finding on 'Q005 Probe' for Claude Sonnet 4.6 with web search ON [RLB-H-INT-OECD-OECD-MERGER-REVIEW-RECOMMENDATION-2025-Q005-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-v1-005--sonnet-46-websearch/.
BibTeX Download 
@misc{reglegbrief_RLB_H_INT_OECD_OECD_MERGER_REVIEW_RECOMMENDATION_2025_Q005_Sonnet46,
  author    = {RegLeg Specialist Panel},
  title     = {Finding on 'Q005 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-Q005-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-v1-005--sonnet-46-websearch/}
}
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