Digging through Opus 4.6-to-5 system prompt diffs: the stubborn 'Honestly' instruction

dbreunig · x · 2026-09-08

dbreunig went down a system prompt rabbit-hole, tracking when instructions arrived and dropped between Claude Opus 4.6 and 5. One notable finding: the 'Honestly' instruction proved stubborn, persisting across versions — a small window into how vendors steer model behavior via prompts.

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