ClaudeDevs said the Messages API will block editing Claude's context before thinking blocks in multi-turn chats, to harden against distillation that extracts chain-of-thought. The change applies first only to new accounts on Fable 5.1 (distillation often spins up many fake accounts), with plans to extend it to all users on future releases while looking for longer-term fixes.
Key Takeaways
- ✓The Messages API disallows edits to context before thinking blocks.
- ✓It starts on new Fable 5.1 accounts and is planned for all users on later models.
- ✓Aimed at distillation attacks that scrape chain-of-thought; integrators should audit multi-turn context edits.