OpenAI finds accidental chain-of-thought grading in several RL runs but no clear monitorability loss

OpenAI reports that its automated system found accidental chain-of-thought grading in RL runs for several released models, including GPT-5.4 Thinking and GPT-5.4 mini. Its analysis found no clear reduction in CoT monitorability, though the company says subtler effects cannot be ruled out. OpenAI says it still avoids grading CoTs during RL and has fixed the affected reward pathways.