CoT controllability evals seem very under-elicited

The CoTControl eval asks reasoning models to follow formatting constraints in their chain-of-thought (e.g. write in all lowercase, avoid a specific word) while solving questions. Models seem to mostly be pretty bad at this: recent models score between 0-30% with the exception of Mythos Preview[1]. OpenAI and Anthropic have used this eval in recent system cards (GPT-5.5, Fable 5) to argue that their current frontier models are pretty bad at shaping their CoTs in ways that would reduce monitorabil...