Anthropic launches Fable 5.2, beating GPT-6 Astra on FrontierSWE at 69.9%

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Anthropic has launched Fable 5.2 for open-ended technical work and Mythos 5.2 for cybersecurity engineering. Anthropic reports Fable 5.2 at 69.9% on FrontierSWE v2, versus Fable 5.1’s 56.3% and GPT-6 Astra’s 65.5%.

Here's what changed:

• Fable 5.2 scored 49.1% on FrontierCode 2.0 at Xhigh effort, versus Opus 5.5’s 45.5% and GPT-6 Astra’s 42.8%, Anthropic reports.
• High effort put Fable 5.2 about level with Opus 5.5’s best score at roughly half the cost per task, Anthropic says.
• Standard pricing is $8 input and $40 output per million tokens. Fast mode doubles those prices for up to 2.5x faster token generation.
• Fable 5.2 can advise smaller Claude models on harder problems or delegate simpler work to them.

One catch: Mythos 5.2 access is gated to vetted organizations.

Try it: Use claude-fable-5-2 on the Claude Platform. Also available via Vercel, Amazon Web Services, LiteLLM

Sources: anthropic.com