This document defines Reasoning Claim Tokens (RCTs) as a governance primitive designed to address this gap. RCTs capture discrete, time-indexed reasoning claims expressed by AI models during inference, without intervening in or explaining internal model logic. They provide a model-agnostic, reconstructable record of expressed reasoning sufficient to support audit, legal review, and risk governance. RCTs are positioned as evidentiary artifacts, not optimization tools, and are intended to govern external AI representations where internal model access is unavailable.