Model releasesAugust 20, 2026Impact
Claude Fable 5.1 pushes deep reasoning further
Anthropic's Fable 5.1, its slow, deliberate reasoning model, set records on frontier reasoning benchmarks and very long agentic tasks.
Why it matters
Fable leads our hardest reasoning races. For research and analysis where accuracy matters more than speed, it is the model to beat.
The details
- Fable 5.1 leads our reasoning and long-horizon agent races by dominant margins, plus distributed systems among coding races.
- It is slower and pricier than Opus, by design.
Models in this story
Provenance: Lab announcement; independent evaluations confirm. Illustrative placeholder story.