Claude Prompting Best Practices

Opus 4.5/4.6 Behavioral Characteristics

Opus 4.5+ has specific behavioral characteristics that affect prompt design:

• Highly responsive to system prompts - Emphatic language causes overtriggering
• Stricter instruction adherence - Won't infer implied requests; needs explicit direction
• Sensitive to "think" word - When extended thinking is disabled, triggers unintended behavior
• Tendency to over-engineer - May create extra files, unnecessary abstractions, or unrequested features
• May skip code exploration - Can propose solutions without reading relevant files

Core Principles

Use Positive Framing

Describe what to do rather than what to avoid. Negative prompting can backfire.

Soften Emphatic Language