Anthropic Releases Claude Fable 5.2 and Mythos 5.2: Price Cut to $8/$40 per Million Tokens, a Record 49.1% on FrontierCode 2.0 Among Released Models, and 1,000 Agents Formalizing Fermat's Last Theorem in 30 Hours
At 18:58 UTC on November 9 (2:58 a.m. on November 10 SGT), the official Claude account released Claude Fable 5.2 and Claude Mythos 5.2. They are the same underlying model: Fable ships with cybersecurity and biology safeguards and is open to all paid plans, the Claude Platform and the major clouds, while Mythos drops some of those safeguards and is offered only to vetted organizations through the Cyber and Life Sciences Verification Programs. Pricing falls from Fable 5.1's $10/$50 to $8/$40 per million input/output tokens, output is up to 30% faster, and an optional fast mode generates up to 2.5x faster for $16/$80. By Anthropic's numbers, Fable 5.2 at Xhigh effort scores 49.1% on FrontierCode 2.0, ahead of Opus 5.5 (45.5%) and GPT-6 Astra (42.8%); at High effort it matches Opus 5.5's best for about half the cost per task. The API model name is claude-fable-5-2.

Key Takeaways
- Pricing: $8 / $40 per million input/output tokens, 20% cheaper than Fable 5.1's $10 / $50; fast mode generates up to 2.5x faster at $16 / $80
- Coding (Anthropic's numbers): FrontierCode 2.0 at Xhigh effort 49.1% (Opus 5.5 45.5%, GPT-6 Astra 42.8%); at High effort 45.3%, matching Opus 5.5's best for about half the cost per task; FrontierSWE v2 69.9%
- Long-running agents: 1,000 Fable 5.2 agents formalized Fermat's Last Theorem in Lean in 30 hours, while Opus 5.5 in the same setup finished only 26% in 18 hours; one engineer had it coordinate over 1,000 subagents for 8 days to build a prototype OS that boots on a laptop
- Other scores (Anthropic's numbers): RoboDojo Sim 64.9% (Fable 5.1 27.6%), HLE with tools 74.2%, OSWorld 2.1 89.3%, Remote Labor Index 41.3%; Mythos 5.2 CVE Rediscovery 89.6%
- Safeguards: Fable and Mythos are the same model; Fable 5.2's classifiers block about 55% less often than 5.1's; the preserved thinking anti-distillation feature now applies to all accounts




