What is UltraThink in Claude Code

Re-introduced (v2.1.68)

The "ultrathink" keyword has been re-introduced as of v2.1.68. Adding "ultrathink" to your prompt now enables high effort for the next turn. For persistent effort control, use /effort with levels low/medium/high. The colored ultrathink text is back via TweakCC.

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UltraThink is Claude Code's power word for maximum reasoning depth. Add "ultrathink" to any prompt to trigger the full 31,999 token thinking budget—ideal for complex architecture decisions, debugging difficult issues, or deep code 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.

Unlock the CLI

Unlock inline answers in Claude Code: type _ and OpenCues completes it in place from the surrounding context, free and open source. Try out OpenCues_™by Mod of r/ClaudeAI (+1M subs)

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AgentKit

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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.

UltraThink + Opus Plan Mode Power Combo

Combine UltraThink with Opus Plan Mode for maximum planning intelligence while maintaining cost efficiency. Use "ultrathink" in your prompts to trigger maximum reasoning during the Opus planning phase, then seamlessly execute with efficient Sonnet 4.

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.

Maximum Reasoning Engine

UltraThink unlocks Claude Code's highest computational thinking budget for complex problem-solving. Reserve this power for architectural decisions where thoroughness outweighs token costs.

Inline cues in Claude Code

Type _ and OpenCues reads the cue around your cursor and completes it in place, inline inside Claude Code, with no chat panel. Try out OpenCues_™by Mod of r/ClaudeAI (+1M subs)

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