Tip: Avoid Adaptive Thinking Default — Set Explicit Effort Levels to Prevent Claude Performance Degradation

r/ClaudeAI·high signal

An r/ClaudeAI analysis (127 upvotes) documents how Adaptive Thinking mode silently degrades Claude Code output quality by letting the model decide its own reasoning depth — Opus 4.7 and Sonnet 4.6 on Adaptive Thinking produce measurably worse code. An AMD executive's analysis of 6,852 sessions showed Opus 4.6 thinking 67% less after the default changed to effort medium in March 2026. Fix: explicitly set effort level to 'high' or use the new 'xhigh' level on Opus 4.7. Boris Cherny (Claude Code creator) confirmed this is the intended fix.