This is the reference for prompt engineering with current Claude models, including Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Opus 4.6, Claude Sonnet 5, Claude Sonnet 4.6, and Claude Haiku 4.5. The page is organized in three parts:
Model-specific guidance first: where a single model behaves differently and what to change in your prompt.
Techniques for all current models after that: general principles, output and formatting, tool use, thinking, and agentic systems.
Migration considerations last, for prompts moving from earlier generations.
For an overview of model capabilities, see the models overview. For Claude Fable 5.1 capabilities and API changes, see What's new in Claude Fable 5.1. For Claude Fable 5 capabilities and API changes, see Introducing Claude Fable 5 and Claude Mythos 5. For details on what's new in Claude Sonnet 5, see What's new in Claude Sonnet 5. For details on what's new in Claude Opus 5, see What's new in Claude Opus 5. For migration guidance, see the Migration guide.