Claude Opus 4.6 effort=low parameter causes lazy agent behavior

Claude Opus 4.6's effort parameter behaves differently than similar settings from other AI providers, causing unexpected agent behavior when set to low.

Key Findings

Testing revealed that with effort=low, Claude Opus 4.6 exhibited significantly lazier behavior than expected:

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

The source notes that bumping to effort=medium fixed all these issues. According to the documentation, Anthropic's effort parameter controls general behavioral effort, not just reasoning depth like OpenAI's reasoning.effort=low or Gemini's thinking_level=low.

Important Distinction

This isn't a bug but a documented difference in implementation. The effort parameter in Claude Opus 4.6 has broader scope than equivalent parameters from other providers. This means you can't treat effort as a drop-in replacement for reasoning.effort or thinking_level when working across different AI providers.

The testing was conducted with the expectation that effort=low would behave similarly to other providers' low-effort settings, but the actual behavior was more extreme, leading to agents that were not just thinking less but acting lazier overall.