Definition
A reasoning token is a provider-reported token used for intermediate inference work by a reasoning model before or alongside its visible answer. Some APIs count reasoning tokens inside output-token accounting even when the user cannot see the underlying reasoning. Exposure, retention, and pricing vary by provider and model.
Distinguish it from nearby terms
Reasoning tokens are an accounting category, not proof that the model reasoned correctly. Test-time compute is the broader resource allocation; a reasoning-effort setting is a control that may change how much of that resource a model uses.
Check your understanding
A 400-token visible answer can consume far more than 400 output-accounted tokens when hidden reasoning is included.