Claude Opus 5 Introduces Five-Level Effort Parameter to Balance Cost and Performance

Anthropic launched Claude Opus 5 on July 24, 2026, featuring an API request parameter called 'effort' that controls how much internal reasoning the model performs before generating a response. The parameter offers five levels — low, medium, high, xhigh, and max — with 'high' set as the default, meaning all requests without explicit configuration will consume thinking tokens and incur higher costs. Unlike previous versions, Opus 5 applies adaptive thinking by default, making it a notable cost shift for developers migrating from Opus 4.8, where default requests did not use thinking. Anthropic has recalibrated what each effort level means in Opus 5, so settings from Opus 4.8 cannot be transferred directly and must be retested. Pricing remains the same at $5 per million input tokens and $25 per million output tokens, but thinking tokens count toward output, making effort selection a significant cost lever for high-volume pipelines.