Opus 4.8 runs leaked Claude Fable 5 prompt
A user on X reported that the system prompt for Anthropic's unreleased Claude Fable 5 model was leaked. Someone reportedly ran this leaked system prompt on an Opus 4.8 model and claimed the resulting output was approximately 90% similar to the real Claude Fable 5 model.
The leak of a flagship model's system prompt highlights significant security challenges in protecting intellectual property for AI labs. It highlights the critical role system prompts play in defining model behavior and output quality, suggests that Opus 4.8 is capable of replicating newer model behaviors when provided with the right instructions, and raises concerns about internal security and prompt protection mechanisms at AI companies.
DISCOVERED
3h ago
2026-06-15
PUBLISHED
3h ago
2026-06-15
RELEVANCE
AUTHOR
codewithimanshu