Predicting thinking time in Reasoning models

Abstract: Reasoning models that produce long, hidden chains of thought have emerged as powerful tools for complex, reasoning-intensive tasks\citep{deepseekai2025deepseekr1incentivizingreasoningcapability, openai2024openaio1card}. However, this paradigm introduces a new user experience challenge: users have little insight into how much time the model will spend reasoning before returning an answer. This unpredictability, can lead to user frustration and is likely to compound as LLMs can produce increasingly long tasks asynchronously \citep{kwa2025measuringaiabilitycomplete}. In this paper, we introduce and evaluate methods for both online and offline prediction of model "thinking time," aiming to develop a practical "progress bar for reasoning." We discuss the implications for user interaction and future research directions.