Ultrathink: Tell Claude Exactly How Hard to Think About Your Problem

Source: Dev.to

A Truth About AI

Not every question deserves the same amount of computational thought.
Asking “what’s the syntax for a for loop in Python?” shouldn’t trigger the same deep reasoning as “help me architect a distributed system for 10 million concurrent users.”

Yet most AI interactions treat every prompt the same—you get what you get, with no control over the depth of reasoning. Until now.

The Problem

Let’s be honest about how we use AI coding assistants. Our requests fall into roughly three categories:

Without explicit control, you’re leaving the thinking depth to chance. Sometimes Claude blazes through something that deserved more thought; sometimes it over‑thinks a simple question. For complex problems, shallow thinking can miss nuance, forcing you to ask follow‑up after follow‑up.

The Solution

Claude Code introduces thinking keywords that give you explicit control over reasoning depth. Just include these magic words anywhere in your prompt.

How to Use It

What This Looks Like in Practice

Example: Debugging a complex issue

I'm seeing race conditions in our payment processing. Here's the relevant code:
[code block]
The error appears intermittently, about 1 in 100 transactions.
ultrathink through potential causes and solutions.

With ultrathink engaged, Claude will:

• Analyze the code structure systematically
• Consider multiple potential race‑condition sources
• Think through timing implications
• Evaluate different locking strategies
• Consider edge cases and failure modes
• Synthesize a comprehensive response

You get an answer that reflects actual deep thought, not a quick pattern match.

Placement Is Flexible

The magic words work anywhere in your prompt:

ultrathink — what's wrong with this architecture?

Here's my code. think hard about potential security vulnerabilities.

I need to optimize this query. think about it and suggest improvements.

Pro Tips

• 🎯 Match thinking depth to problem complexity. Don’t ultrathink “how do I exit vim”—you’re wasting time. Use ultrathink for “how should I architect this microservice.”
• 🎯 Use ultrathink for code reviews. Paste a PR diff and say “ultrathink through potential issues with this change.” You’ll get a review that rivals a senior engineer’s.
• 🎯 Leverage it for architectural decisions. Before committing to a technical direction, let Claude ultrathink the implications. It’s like having a senior architect on demand.
• 🎯 Combine with context. ultrathink is most powerful when Claude has full context—share relevant files, explain constraints, describe goals—then unleash the deep thinking.

Real‑World Use Case

Marcus, a tech lead, must decide whether to adopt a microservices architecture or stick with their modular monolith.

Old approach: “Claude, should we go microservices?” → Generic “it depends” list of pros and cons.

With ultrathink:

ultrathink

We're a team of 8 developers building a B2B SaaS product.  
Current state: modular monolith, 50 K LOC, PostgreSQL, deployed on AWS ECS.  
We have 500 customers, growing 20 % MoM.

Pain points: deployments take 45 minutes, one team's changes often break another team's features, scaling specific features independently isn’t possible.

Question: Should we migrate to microservices? If yes, what's the migration strategy? If no, what should we do instead?

Claude will dive deep, weigh trade‑offs, propose migration roadmaps, and surface hidden risks—giving Marcus a decisive, well‑reasoned answer.

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Claude spends 32,000 tokens really thinking about this. The response includes:

• Analysis of whether their pain points actually require micro‑services
• Alternative solutions (better modular boundaries, feature flags, etc.)
• If micro‑services: a phased migration strategy starting with the highest‑pain areas
• Team‑structure implications
• Timeline estimates
• Warning signs that they’re moving too fast or too slow

Marcus gets an answer that would have taken a consultant a week to produce. All because he told Claude to actually think.

Conclusion

The ultrathink feature represents a fundamental shift in how we interact with AI. You’re no longer a passive recipient of whatever thinking depth the model happens to apply—you’re in control.

• Quick question? Just ask normally.
• Moderate complexity? Tell Claude to “think.”
• Complex architectural decision? Ultrathink it.

This isn’t just about getting better answers. It’s about efficiency:

• Stop wasting time on follow‑up questions that wouldn’t be necessary if Claude had thought deeper initially.
• Stop getting shallow answers to deep questions.

Tomorrow in Day 13

What happens when you’re mid‑prompt and need to ask something else urgently?
We’re covering Prompt Stashing — like git stash, but for your thoughts. Never lose a draft again. 💾

Did ultrathink level up your Claude game? Share your experience and follow along for the rest of the 31 Days of Claude Code Features!