# Reasoning Model

> A model optimized to spend more inference effort on multi-step reasoning, math, code, or planning.

- Category: Reasoning & Inference
- Stage: Rising
- Also called: Reasoner, Thinking model
- Canonical: https://www.joelcsaji.com/ai-dictionary/reasoning-model

## Plain English

It pauses longer to solve harder problems.

## Example

A reasoning model is selected for a complex debugging task while a faster model handles simple classification.

## Why it matters

Reasoning models changed product design because latency, cost, and answer quality can now be traded explicitly.

## Related

- [Test-Time Compute](https://www.joelcsaji.com/ai-dictionary/test-time-compute)
- [Model Routing](https://www.joelcsaji.com/ai-dictionary/model-routing)
- [Chain-of-Thought](https://www.joelcsaji.com/ai-dictionary/chain-of-thought)

## Sources

- [Stanford HAI: 2026 AI Index](https://hai.stanford.edu/ai-index/2026-ai-index-report)
- [Anthropic: Building Effective Agents](https://www.anthropic.com/engineering/building-effective-agents)