Claude Fable 5.1
Rank of 2705from #5
Known for
The hardest coding and research work, where a cheaper model's evals come up short.
Anthropic's most capable model that anyone can buy, released 1 September 2026. Built for long-horizon agentic work and the coding tasks where Opus 5 at max effort still falls short.
What it does8
- 1M-token context, 128K output
- Adaptive thinking with per-message effort control
- Effort can change mid-conversation without a new session
- Cache reads at a quarter of Fable 5's price
- Cyber safety classifiers refuse far less on defensive security work
- Invisible watermark on generated text, with a detection API in preview
- Text and image in, text out
- Same $10 / $50 list price as Fable 5
From Claude Fable 5.1’s own site. Not used for ranking.
68index score · LLMs
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