Reasoning Summaries Are Not Audit Evidence

OpenAI’s o1 system card states that hidden chain-of-thought reasoning is not shown to users; where the API exposes anything at all, it’s a model-generated summary of that reasoning, not the raw reasoning tokens themselves. Provider implementations diverge from there. OpenAI’s Responses API can return encrypted reasoning items to preserve continuity across stateless requests — clients can pass them back on subsequent calls, but cannot inspect them as plaintext. Some providers omit reasoning output entirely on certain endpoints or call types. And in agentic setups, tool calls and intermediate reasoning can end up interleaved across model events and wrapper logs, making “thought” and “action” hard to separate cleanly after the fact.