Anthropic strengthens defenses against distillation attacks

Anthropic says early evidence shows its new distillation defenses reduced the amount of data obtained by distillers by approximately 90% to 99%, with extracted reasoning tokens on the platform dropping to 1/10 to 1/100 of previous levels. The defenses fall into three classes: using preserved thinking to prevent new API accounts from editing Claude's prior context and making reasoning records visible only to the organization that produced them; using a two-stage classifier to intercept extraction attempts with a false positive rate below 0.1%; and tightening rate limits and banning accounts that repeatedly attempt extraction, with charges applied to intercepted requests starting September 24. Anthropic says that on SWE-bench Verified, a model trained with summarized reasoning scored 71.8%, while one trained with full reasoning scored 80.4%. Anthropic also says Zhipu distilled the cyber capabilities of a U.S. model while developing GLM-5.3, and CAISSI assessed it as the open-weight model with the strongest cyber capabilities to date. These measures require some developers to update their integrations.