What is UltraThink in Claude Code

UltraThink is a Claude Code magic word that automatically triggers the maximum thinking budget for extended reasoning. It's a built-in feature that allocates the highest level of computational thinking time for complex problem-solving and deep analysis.

How to Use It

Add "ultrathink" to any Claude Code prompt to trigger maximum thinking budget:

Research the best approach for migrating this legacy system ultrathink
Plan the implementation strategy for this complex feature ultrathink
Analyze the codebase and recommend optimization opportunities ultrathink

I use UltraThink when facing complex architectural decisions or performance optimization challenges where thorough analysis is essential.

How UltraThink Works

Thinking Budget Hierarchy - Claude Code has built-in preprocessing that maps keywords to thinking budgets:

• "think": 4,000 tokens
• "megathink": 10,000 tokens
• "ultrathink": maximum budget

Extended Reasoning - The maximum token budget allows Claude to deeply consider alternatives, evaluate trade-offs, and iterate on solutions before responding.

Claude Code Exclusive - UltraThink only works in Claude Code's terminal interface, not in the web chat or API.

Benefits:

• Maximum Thinking Time - Highest possible computational budget for complex problems
• Deep Analysis - Thorough examination of multiple approaches and edge cases
• Quality Solutions - More robust, well-considered implementations
• Architectural Planning - Comprehensive system design and optimization strategies
• Reduced Revisions - Higher-quality initial solutions requiring fewer iterations

I reserve UltraThink for the most complex challenges where the computational cost is justified by the need for exceptional solution quality.

Revving the Engine

Combine multiple rounds of plan mode and UltraThink to get peak performance out of Claude Code. Use plan mode to structure the approach, then UltraThink for deep analysis, repeating the cycle for maximum-quality solutions.

Strategic Usage

UltraThink uses significant token budget. Reserve it for complex architectural decisions, performance optimization, or unfamiliar codebase analysis.

See Also: Plan Mode|Context Window Management|Task Agent Tools