Why should you avoid carrying over "double-check your work" instructions to Claude Opus 5?

Claude Opus 5 already performs self-verification on its own by default, more consistently than Opus 4.8 did, so an explicit "double-check your work" instruction that was useful on the older model now layers on top of behavior the model is already doing unprompted.

The practical result is over-verification: the model spends additional tokens re-checking work it had already effectively verified, without a corresponding improvement in output quality to justify that extra cost.

Anthropic's own prompting guidance frames the fix simply - delete the blanket global instruction, and only add a scoped, specific verification instruction back in if a particular step genuinely still needs one, rather than applying a general rule that made more sense on a model without this built-in behavior.

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