Anthropic Claude Extended Thinking(2025年・Claude 3.7+)。Thinking budget設定(thinking.budget_tokens 1024-32k)・Visible thinking trace(reasoning可視化)・Interleaved thinking(2025年・tool use間挟む reasoning)・Math/Code/Science domain改善大(GPQA Diamond +10%)・Latency増加(thinking分・3-30s typical)・Pricing: thinking tokens billing対象($75/Mtok Opus output同価)・Anthropic SDK Python: thinking={"type":"enabled","budget_tokens":4096}・Streaming支援・2026年 reasoning model時代核機能、o1/o3類似実装。