Anthropic Reveals Claude Code's 'UltraThink' Mode

Anthropic released extensive documentation on best practices for their Claude Code CLI coding agent tool. A fascinating tip reveals that using words like "think," "think hard," etc., triggers extended thinking modes. These phrases directly correlate to different thinking budgets; "ultrathink" allocates a massive 31999 tokens, while "think" uses only 4000. Code analysis shows these keywords trigger functions assigning varying token counts, impacting Claude's thinking depth and output. This suggests "ultrathink" isn't a Claude model feature, but rather a Claude Code-specific enhancement.