Model evaluation report

System Card: Claude Fable 5.2 & Claude Mythos 5.2

Anthropic · Published 2026-11-09

A system card is the model developer’s report describing the model, its evaluations, and its limitations.

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Results and research linked to this document
Type	Evidence
Paper / report	Claude Fable 5.2 and Mythos 5.2: AI research and development evaluation context Source details Primary publication source

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Source ID: src-anthropic-fable-mythos52-card-20261109
Source type: Primary
Original URL: https://www.anthropic.com/document/claude-fable-5-2-mythos-5-2-system-card
Retrieved URL: https://assets.claude.com/27d60918d218125e7504bc7354c4b4626ec56b11.pdf
Last updated by publisher: Not reported
Access status: available
Retrieved: 2026-11-10T21:30:36.104252Z
Document fingerprint: bb548a5db76349a67a0e65b84f36ddd15c19c3d5819eb3028460955682bfc259
Based on original bytes. Used to detect changes to the source.

2026-11-10T21:36:07Z · success: Original23,887,562-byte PDF retained after web size failure. Executive summary and AI-R&D sections2.3.2-2.3.6(pp33-41) checked; complete AECI figure2.3.5.3.B(page38) pixels/axes/legend/caption inspected. This is not full-card review or experimental replication.