Anthropic Releases Mythos 5.2 and Fable 5.2 Amid RSI Concerns

What happened

Anthropic released Mythos 5.2 and Fable 5.2, citing improvements in coding, reasoning, vision, and user communication. Fable now costs $8 per million input tokens, returns responses 30% faster, and supports zero data retention policies through Enterprise Frontier Safeguards. The release follows a METR report suggesting internal models were speeding Anthropic’s AI progress by roughly 2x; Anthropic also described challenges in evaluating models’ real-world behavior and covert capabilities.

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The story so far

Anthropic released Claude Fable 5.2 and Claude Mythos 5.2, lowering API prices to $8 per million input tokens and $40 per million output tokens, from $10 and $50. Anthropic says both models improve coding, reasoning, and vision, and that Fable produces responses faster than version 5.1. Fable is available to paid users with safeguards for risky cybersecurity and biology tasks; Mythos is limited to organizations approved through Anthropic’s verification programs. The launch reports cite strong benchmark results, including Fable’s first-place score on Artificial Analysis’ Intelligence Index v5 at its highest compute tier. Those figures come from the named benchmark evaluations; Anthropic’s prerelease examples also include software migrations, electronic devices, and physics problems. TechCrunch reports that an optional faster serving mode costs twice as much, while the lower API prices apply to standard use.