System Card: Claude Mythos Preview April 7, 2026 anthropic.com Changelog April 8, 2026 ● Corrected two model name typos. ● Removed a quote from Section 7.9 that was attributed to Claude Mythos Preview but actually came from Claude Opus 4.6. ● Revised naming in Section 2.3.6 to disambiguate Anthropic’s internal fork of ECI ...