Last updated: April 5, 2026 · Model Architecture · by Daniel Ashford
What is Reasoning Tokens?
Hidden thinking tokens that reasoning models generate internally before their visible response.
Definition
Reasoning tokens are tokens generated by reasoning models as part of their internal thought process before producing the final visible response. They represent the model thinking through a problem step by step.
How It Works
Models like OpenAI o3 and Claude with extended thinking generate reasoning tokens automatically. They count toward output token costs and add latency, but significantly improve accuracy on complex reasoning, math, and coding tasks.
Example
For a complex math problem, a reasoning model might generate 500 reasoning tokens working through the algebra, then output a 50-token final answer. You are billed for all 550 tokens.
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