Anthropic website source code leaks unrestrained Claude Mythos 5.5, pricing starts at $10/M input tokens
kimmonismus · x · 2026-11-01
kimmonismus received an anonymous tip revealing 'Claude Mythos 5.5' already listed in the HTML source of Anthropic's official website — apparently an unreleased model.
The leaked page describes the Mythos class as Anthropic's most capable models for cybersecurity and biology research, restricted to vetted organizations: Mythos 5 launched in June, went unavailable, had export controls lifted in July after US government approval, was followed by Mythos 5.1 in September, and an expanded Cyber Verification Program in October covering Opus 5.5, Sonnet 5.5, and Mythos 5.1. Mythos 5.1 pricing starts at $10/M input and $50/M output tokens, and Claude Security now runs on Mythos 5.1.
Mythos 5.5 appearing in source code suggests the next tier of this restricted-access line is in preparation. Unconfirmed third-party leak.
Related event: Anthropic Site Code Leaks Claude Mythos 5.5, With Fable 5.5 Also Surfacing(11 posts)→
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