Root causes, not patches
Anthropic says the model is smart enough to fix the underlying cause of a software problem instead of taking the shortcut that produces poorer work.
Anthropic released Claude Fable 5.1 on September 1, 2026, together with Claude Mythos 5.1. They are the same model: Mythos is restricted to trusted access programs, Fable 5.1 is the version anyone can use. It improves on Fable 5 across the board, most of all in agentic coding, long-running workflows and knowledge work, with a 1 million token context. On avots.ai you use Claude Fable 5.1 pay per use, no Claude plan, and the same balance also covers GPT-6 Astra, Gemini, Kimi K3 and 40+ image, video and music models.
| Claude Fable 5.1 | Claude Fable 5 | Claude Mythos 5.1 | |
|---|---|---|---|
| Best for | agentic coding, long workflows, analysis | the previous flagship | cybersecurity and life sciences research |
| Price per 1M in / out | $10 / $50 | $10 / $50 | trusted access only |
| Cache read per 1M | $0.25 | $1 | trusted access only |
| Context window | 1M tokens | 1M tokens | 1M tokens |
| Input | text, images, PDFs | text, images, PDFs | text, images, PDFs |
| On avots.ai | pay per use | pay per use | not available to the public |
Mythos-class means the tier above Opus. Fable 5.1 carries the same intelligence with additional safety measures for dual-use capabilities, which is what makes it generally available. Anthropic estimates typical workloads about 25 percent cheaper than on Fable 5 because cache reads dropped fourfold. Keep Opus 5 or Sonnet 5 in the same picker for everyday tasks.
Anthropic says the model is smart enough to fix the underlying cause of a software problem instead of taking the shortcut that produces poorer work.
The biggest gains are in agentic coding and runs that last hours: long refactors, front-end and visual code, finance and analysis tasks.
Same list price as Fable 5, but cache reads fell from 1 to 0.25 USD per million tokens, about a quarter off typical workloads.
Plans and summaries are shorter than Fable 5's, and the cybersecurity safeguards block 60 percent fewer legitimate requests, including vulnerability discovery.
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Claude Fable 5.1 in @AvotsAIbot, same balance, from any phone.
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1,000 tokens cost 0.99 EUR and a short Fable reply costs a small part of them. The same balance unlocks Opus 5, Sonnet 5, GPT-6 Astra, Gemini, Kimi K3, Veo video and Nano Banana images.
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OpenAI's answer, released the same week: the new flagship and its Pro mode, pay per use.
Anthropic's Opus tier: the everyday flagship below Fable, pay per use.
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