Fable 5.1 was hacked, and 270,000 words of prompts were leaked
2026-09-02 08:00Models🔥 28.9 heat score
1sources
1days unfolding
28.9heat score
6mentions
SummaryAI generated
Fable 5.1 and Mythos 5.1 were officially released. The ARC-AGI-2 evaluation score was 90.0%, and the ARC-AGI-1 score was 97.5%. Thanks to the improved efficiency of Token, the average inference cost of Fable 5.1 is approximately 32% lower than that of the previous generation. Within a few hours after its release, the well-known hacker Pliny the Liberator cracked Fable 5.1 and leaked a complete system prompt of 275,000 words. This prompt included core behavioral logic, memory systems, search and copyright rules, Artifacts, and tool JSON architectures, far exceeding the officially announced 27,000-word system update scope. The leaked content covered specific rules such as prohibiting the reproduction of copyrighted works, prohibiting the generation of known characters or logos, prohibiting assertions about psychological states, prohibiting the magnification of negative emotions, and 46 tools.
# Fable 5.1 was hacked, with 270,000 words of system prompts leaked
Fable 5.1 and Mythos 5.1 were officially released, with an ARC-AGI-2 evaluation score of 90.0% and ARC-AGI-1 at 97.5%. Thanks to improved Token efficiency, the average inference cost of Fable 5.1 is about 32% lower than the previous generation.
However, within a few hours after its release, Fable 5.1 was hacked by the well-known hacker Pliny the Liberator. He leaked a complete system prompt containing 270,000 words, including core behavior logic, memory systems, search and copyright rules, Artifacts, and tool JSON architectures. This amount of information far exceeds the officially announced 27,000-word system update; the official team did not disclose the full content.
The leaked content includes: restrictions on reproducing copyrighted works, prohibiting the generation of known characters or logos, prohibiting assertions about mental states, prohibiting exaggeration of negative emotions, and 46 tools (…