Anthropic's site source code leaks Mythos 5.5; Fable 5.5 briefly appeared in LiteLLM
VraserX · x · 2026-11-02
Users dug up traces of unreleased Anthropic models from public code:
- Website source: The HTML of anthropic.com's Mythos page contains six references to "Mythos 5.5" while the visible text still says 5.1; a report notes a hidden reference lists Mythos 5.5 as its most capable model class for high-stakes cybersecurity and biology research.
- LiteLLM logs: On Oct 13 an automated sync added an azureai/claude-fable-5.5 pricing entry, only to remove it 24 hours later citing "Azure does not list this model."
Two independent clues point the same way: Anthropic likely ships Mythos 5.5 and Fable 5.5 soon, setting up a head-to-head with OpenAI's rumored GPT-6.2 Astra. Unconfirmed by Anthropic.
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