Anthropic Publishes Official Prompting Guide for Claude Opus 5.5: Calibrate Effort, Don't Max It

CodeByPoonam · x · 2026-09-25

Anthropic released an official prompting guide for Claude Opus 5.5 in its platform docs. Key points: output is 30%+ faster than Opus 5 with fewer tokens per task; start at medium effort—it already beats Opus 5's high at lower cost; thinking is always on so 'think carefully' is obsolete; unattended agents report progress mid-task and need explicit 'keep going'; mark pasted content separately from instructions; ban specific frontend patterns instead of vague 'make it unique'; the model now reads charts and screenshots accurately; the guide also covers safeguard refusals, multi-agent time signals, and multi-app workflows.

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