Claude Fable 5.1
MultimodalClaude Fable 5.1 is Anthropic's generally available, production-safeguarded deployment of the same underlying weights as the trusted-access Claude Mythos 5.1. It targets demanding reasoning and long-horizon agentic work with a 1M-token context window, 128K max output, and adaptive thinking always enabled, and it leads self-reported launch results on Terminal-Bench 4.0 and Humanity's Last Exam. First-party pricing matches Fable 5 at $10/$50 per million tokens with cache reads cut to $0.25 per million.
Key Specifications
Timeline
Technical Specifications
Pricing & Availability
Benchmark Results
Model performance metrics across various tests and benchmarks
Other Tests
License & Metadata
Compare Claude Fable 5.1
All comparisonsArticles about Claude Fable 5.1
GPT-6 Astra drove a real Toyota through a cone course once in three attempts. Nobody else finished.
Four frontier models drove a real Toyota through a cone course. GPT-6 Astra finished once in three attempts, at 0.42 m/s and $7.74; no other model finished.
GPT-6 Astra scored 95% on a real robot arm — then tied Fable 5.1 when precision mattered
RobotCurve's real-robot eval: GPT-6 Astra scores 95% on a block-into-bowl task versus Claude Fable 5.1's 40% — then both stall at 10% on precision insertion.
FrontierMath Erdős: GPT-6 Astra solved 2 of 68 open problems while rivals scored zero
Epoch AI benchmarked models on 68 significant unsolved Erdős problems formalized in Lean. A pre-release GPT-6 Astra solved two. Everyone else scored zero.
Claude Fable 5.1 is the first model above SimpleBench's 83.7% human baseline
Claude Fable 5.1 scored 86.6% on SimpleBench, clearing the benchmark's 83.7% non-specialized human baseline — the first model of any lab to cross that line.
'What are these benchmarks': r/singularity pushes back on Claude Fable 5.1's launch table
r/singularity met Claude Fable 5.1's launch benchmark table with 'what are these benchmarks' — new evals, self-reported scores, and safety routing under fire.
Claude Fable 5.1 and Mythos 5.1 arrive with a 75% cache cut and a 20% per-task markup
Anthropic released Claude Fable 5.1 and Mythos 5.1 — one model behind two safeguard tiers. Cache reads fell 75%, yet measured per-task costs rose about a fifth.
Fable 5.1 claims a 373-year-old cipher solved in 44 minutes. Nobody has checked it
Vals AI claims Claude Fable 5.1 solved Urquhart's 373-year-old Cyphral Distich in 44 minutes. No expert has verified it — the mechanism is the real story.
Similar Models
All ModelsClaude Fable 5
Anthropic
Claude Sonnet 5
Anthropic
Claude Haiku 5.5
Anthropic
Claude Opus 5
Anthropic
Claude Mythos Preview
Anthropic
Claude 3.5 Sonnet
Anthropic
Claude 3 Opus
Anthropic
Claude Opus 4.6
Anthropic
Recommendations are based on similarity of characteristics: developer organization, multimodality, parameter size, and benchmark performance. Choose a model to compare or go to the full catalog to browse all available AI models.