A Single-Record, Content-Specific Refusal Localised to Opus 4.7: Seven-Judge Falsification on a CTI-Style Prose Sample Falsely Attributing US-CERT Infrastructure to Attackers (safety-note artefacts)

This deposit accompanies the standalone preprint "A Single-Record, Content-Specific Refusal Localised to Opus 4.7", a short safety-research note that documents and falsifies a frontier-LLM refusal pattern using a seven-judge cross-vendor panel. Result: Claude Opus 4.7's safety classifier, called via the structured-output messages.parse() API to rate stylistic fidelity on a public-CTI corpus, refuses to score one specific student-output record (chunk_idx=2 ttp_summary) on both the 2026-05-17 N=90 eval and the 2026-05-24 N=194 wider eval, and reproduces in a 5 / 5 stochasticity test on 2026-05-25. The refused record falsely attributes attacker-controlled distribution channels to real US-CERT / CISA infrastructure. Seven other judges — Claude Sonnet 4.6, Claude Haiku 4.5, Gemma 4 E4B, foundation-sec:latest, qwen2.5:7b, gpt-oss-120b, and Llama-4-Scout-17B-16E — all engage with the record. The refusal is localised to Opus 4.7 specifically within the Anthropic family. This is v5 of the note. v5 adds an N=44 targeted guardrail-characterisation probe (data in guardrail_probe/) that falsifies the v4-era hypothesis that the guardrail keys on "false attribution of US-CERT / CISA infrastructure" at the content-class level: 24 synthetic records varying defensive-infrastructure entity attribution across US-gov, non-US-gov, and commercial-vendor buckets all engaged under Opus. A prompt-swap test surfaced a second refusal trigger that is prompt-context-conditioned rather than student-response-content-driven. The guardrail therefore has at least two distinct trigger modes that the experiment cannot fully characterise. v4 (2026-05-24) corrected an earlier v3 claim of 53 % refusal rate that had been arithmetically inflated by 15 upstream API credit-balance errors mistaken for refusals; the corrected rate is 1 / 30 = 3.3 % on N=90 and 1 / 67 = 1.5 % on N=194. Reuse: CC-BY-4.0 over the entire deposit. The companion Paper 2 deposit at 10.5281/zenodo.20369167 (v2) carries the parallel correction history and the wider eval data this note's correction relies on.