When to use extended thinking — and when it's a waste
Extended thinking makes Claude noticeably better on hard problems. But most tasks don't need it, and using it everywhere will slow you down and cost more.
Extended thinking is one of those features that sounds obviously useful — Claude thinks harder before answering, so it gets better results — until you realise that "thinking harder" takes longer and costs more tokens, and most of your prompts don't need it.
Here's how to decide when it's actually worth it.
What extended thinking actually does
When you enable extended thinking, Claude works through the problem step by step before giving its answer. You can see the reasoning — including where it changed its mind or caught an error. It's not just more words. It's a different process.
The result is meaningfully better on certain types of problems. On others, it's overkill.
Use it when the problem has hidden complexity
Extended thinking pays off most on:
Multi-step reasoning. Problems where you have to get step 3 right to get step 5 right. Financial models, legal analysis, anything that chains dependencies.
Ambiguous or contradictory inputs. When the information you've given Claude is incomplete or internally inconsistent, extended thinking helps Claude surface that explicitly rather than glossing over it.
High-stakes decisions. When the cost of a wrong answer is high enough that taking extra time is worth it. Strategic analysis, risk assessments, anything you're going to act on directly.
Tasks where you've been getting inconsistent results. If Claude keeps giving you different answers to the same question, extended thinking often produces more stable, considered outputs.
Don't use it for routine work
For most everyday tasks — writing a first draft, answering a factual question, reformatting something, summarising a document — standard Claude is fast, accurate, and perfectly sufficient. Extended thinking adds latency you don't need.
Think of it like the difference between asking a colleague a quick question versus booking a meeting to work through a problem together. Both are right in different situations. Using the meeting format for every question is just inefficient.
A practical rule
If you'd be comfortable reading just the final answer without understanding how Claude got there, you don't need extended thinking. If you'd want to check the reasoning — because the problem is hard enough that the path matters — turn it on.
The goal is appropriate depth. Not always deep, not always shallow.
Further reading
- Extended thinking guide — Anthropic Docs