GoKawiilAnthropic publishes prompting guide for Claude Opus 5.5
Anthropic released documentation detailing how to prompt its Claude Opus 5.5 model, highlighting behavioral differences from Claude Opus 5 including effort calibration, thinking behavior, and handling of unattended multiagent tasks. The guide notes Opus 5.5 generates output over 30% faster than its predecessor while typically using fewer tokens to complete the same task, and that existing Opus 5 prompts should still work without modification.
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The faster, more token-efficient output suggests Anthropic is optimizing Opus 5.5 for large-scale agentic workflows, such as long-running code audits or migrations run with minimal human oversight, according to the company's own testing claims. Early tester feedback cited in the guide, including improved code review accuracy, indicates developers may see fewer false alarms and clearer explanations, though these are third-party impressions rather than independently verified benchmarks.
- Claude Opus 5.5 outputs tokens over 30% faster than Opus 5 while often using fewer tokens overall.
- Existing prompts built for Opus 5 are expected to remain compatible without changes.
- Anthropic reports Opus 5.5 at default medium effort matched or beat Opus 5's high-effort performance on coding tasks in testing.
Source: platform.claude.com, 2026-09-28
Published there as: “Prompting Claude Opus 5.5”
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