# Extended thinking

**Source:** https://promtable.com/glossary/extended-thinking

> Extended thinking is Anthropic's flag on Claude that allocates a configurable budget of internal reasoning tokens before the user-visible answer — enabling deeper reasoning on hard problems for a higher cost.

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Extended thinking is Anthropic's flag on Claude that allocates a configurable budget of internal reasoning tokens before the user-visible answer — enabling deeper reasoning on hard problems for a higher cost.

Anthropic's equivalent of OpenAI's o-series reasoning. When you enable extended thinking with a token budget (e.g. 8,000 tokens), Claude runs an internal chain-of-thought that the user never sees before emitting the final answer. The technique materially improves performance on math, code, planning, and multi-step reasoning. By 2026 it's a per-call setting on Claude 4.x. Best practice: route by task — disable extended thinking for chat and extraction, enable with a 4K-8K budget for hard reasoning, escalate to 16K only when measured quality warrants the cost.

## When to use

- Math, code, planning, multi-step reasoning.
- Agent step decisions where one wrong step cascades.

## Common mistakes

- Adding explicit "think step by step" instructions when extended thinking is enabled — often hurts quality.
- Running every query with extended thinking — costs and latency blow up.

## Related terms

- [reasoning-model](https://promtable.com/glossary/reasoning-model)
- [reasoning-tokens](https://promtable.com/glossary/reasoning-tokens)
- [chain-of-thought](https://promtable.com/glossary/chain-of-thought)

*Last updated: 2026-06-01*
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Original page: https://promtable.com/glossary/extended-thinking
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