What is the default effort level for Claude Opus 5?

Claude Opus 5 defaults to high effort on the API, which Anthropic positions as fitting most everyday coding and chat use cases without further tuning.

This same high default is shared with Claude Fable 5, so both models start from a comparable baseline of effort unless a request explicitly dials it up or down.

Because effort levels were recalibrated between Opus 4.8 and Opus 5, teams that previously tuned an explicit effort setting on Opus 4.8 are advised to re-run an effort comparison on their own evaluations against Opus 5, rather than assuming the same label still costs or behaves the same way.

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