In the past few months, progress has slowed after the initial rapid advancements, as OpenAI and Anthropic have implemented stronger anti-distillation measures, increasing the cost and difficulty of distillation by tenfold. For example, OpenAI’s GPT-6 no longer directly exposes reasoning chains, forcing distillation efforts to rely on significantly more rounds of questioning to reconstruct the model’s thought process. Information that previously required only 2–5 interactions now often demands 10 or even 30 rounds, causing API invocation costs to rise by more than fivefold. Anthropic’s new defenses reduce reasoning tokens by 90–99%, including restrictions on transferring reasoning logs across conversations, models, and accounts; deploying a two-stage classifier to detect and block extraction attempts; and implementing rate limiting or account bans for repeated probing.