When would you choose Claude Sonnet 5's xhigh effort over Claude Opus 5 entirely?

Choose Sonnet 5 at xhigh when a task needs meaningfully deeper reasoning than Sonnet 5's high effort provides, but the task still fits comfortably within Sonnet-class capability and doesn't specifically require Opus-level judgment on long-context or highly novel problems.

This is generally the more cost-efficient path when the underlying task type is one Sonnet 5 handles well at lower effort already - pushing the effort dial up on a model that's fundamentally well suited to the task, rather than switching to a more expensive model tier entirely.

The signal to switch models instead of continuing to raise Sonnet 5's effort is when xhigh, or max, still isn't producing the needed quality, or when cost at that effort level is already approaching Opus-tier pricing without a corresponding quality payoff - at that point, an Opus-class model is likely to be the better-value choice rather than squeezing more out of Sonnet 5's ceiling.

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