UltraThink Overview

Aug 29, 2025

Overview

This lecture covers UltraThink, a Claude Code feature that enables maximum computational reasoning for solving complex coding and architectural problems.

What is UltraThink

  • UltraThink is a Claude Code keyword that triggers the highest level of computational thinking time ("thinking budget") for deep analysis.
  • It is specifically designed for tackling complex problem-solving and extended reasoning tasks in Claude Code.

Usage Instructions

  • Add "ultrathink" to the end of any Claude Code prompt to initiate maximum thinking budget.
  • Common use cases include architectural decisions, system migrations, and performance optimizations.

How UltraThink Works

  • Claude Code maps keywords to different thinking budgets: "think" (4,000 tokens), "megathink" (10,000 tokens), "ultrathink" (maximum allowed).
  • UltraThink allows the system to thoroughly evaluate alternatives and iterate on solutions before responding.
  • UltraThink is exclusive to the Claude Code terminal interface and does not work in the web chat or API.

Benefits and Strategic Usage

  • Provides the maximum computational time for in-depth problem analysis and high-quality solutions.
  • Recommended for complex tasks that justify higher computational costs.
  • Helps reduce the need for multiple solution revisions by increasing initial solution quality.
  • Particularly useful for architectural planning, optimization, and analyzing unfamiliar codebases.

Combining UltraThink with Other Features

  • UltraThink can be paired with Opus Plan Mode to maximize planning and execution efficiency.
  • Alternating between plan mode and UltraThink can further enhance solution quality.

Key Terms & Definitions

  • UltraThink — Magic word in Claude Code that triggers the highest computational thinking budget.
  • Thinking Budget — The number of tokens allocated for reasoning in Claude Code responses.
  • Opus Plan Mode — A planning feature in Claude Code that structures complex problem approaches.
  • Plan Mode — A tool for strategy structuring within Claude Code.

Action Items / Next Steps

  • Practice adding "ultrathink" to sample prompts in the Claude Code terminal.
  • Reserve UltraThink for complex engineering challenges where extra computational depth is needed.
  • Explore combining UltraThink with Opus Plan Mode for intricate planning and execution tasks.