Claude Opus 4.6's effort=low parameter differs from other providers' low-reasoning modes

Claude Opus 4.6's effort parameter behaves differently than similar settings from other AI providers. While OpenAI's reasoning.effort=low and Gemini's thinking_level=low primarily control reasoning depth, Anthropic's effort=low parameter controls general behavioral effort.

Key differences in behavior

When set to effort=low, Claude Opus 4.6 exhibited several specific behaviors that differed from expectations:

• Made fewer tool calls than expected
• Was less thorough in cross-referencing information
• Effectively ignored parts of system prompts instructing it how to do web research
• Agents returned confidently wrong answers because they stopped looking for information

These issues were resolved by bumping the parameter to effort=medium. The behavior is documented by Anthropic, confirming it's not a bug but an intentional design choice.

Practical implications

This means developers cannot treat Anthropic's effort parameter as a drop-in replacement for OpenAI's reasoning.effort or Gemini's thinking_level when working across multiple AI providers. The source material raises the question of whether reasoning and behavioral effort should be separate controls or bundled together as Anthropic has implemented.

The original post includes trace examples and full details available at https://everyrow.io/blog/claude-effort-parameter.