Claude Extended Thinking予算戦略。budget_tokens設定: 1024(quick・simple math)・4096(default・standard reasoning)・16384(complex math・science PhD)・32768(extreme・research grade)・Pricing: thinking tokens output同価($75/Mtok Opus・$15 Sonnet)・1 query 8k thinking ≈ $0.60・100 query/day = $60/月・Cost管理: Claude Sonnet 4.6 thinking推奨(Opus比 -80% cost)・Caching併用 -90%・Use case判断: Math/Science yes・Coding subtle改善・Q&A unnecessary多・Extended Thinking on/off toggle per request・2026年 reasoning model時代必修、AI cost engineering重要。