Claude restricts context editing in multi-turn conversations to prevent distillation attacks

ClaudeDevs · x · 2026-09-02

To hinder distillation attacks targeting the model's chain of thought, Anthropic has updated the Messages API: it is no longer possible to edit Claude's context prior to thinking blocks in multi-turn conversations. This change currently applies only to new accounts using Fable 5.1, with plans to roll it out to all users in future releases.

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