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How smart is Claude Fable 5.1?

140 SI-IQ · 90% interval 136–143
Rank 8 of 80 ranked models · Plausible rank range 3–12

Claude Fable 5.1 is a model from Anthropic, released on Sep 1, 2026. Its SI-IQ is 140 (90% interval 136–143), estimated from 8 benchmark results by 2 independent evaluators. Its strongest area is Math and its weakest is Knowledge.

Facts

Developer: Anthropic
Released: Sep 1, 2026
Access: API access
Benchmarks used: 8 results from 2 evaluators
API price: $10 input / $50 output per 1M tokens (developer's price list, Oct 18, 2026)
Context window: 1,000,000 tokens

Ability by area (SI-IQ, 90% interval)

Every benchmark result we used

Each score is one value exactly as the source published it: for Epoch AI the best of its run settings, for OpenRouter the median hosting provider (the developer's own hosting when it ran the test). “Implied SI-IQ” is the ability that this single result points to; the overall SI-IQ is their precision-weighted average.

Benchmark	Area	Score	Implied SI-IQ	Evaluated by	As listed by the source	Retrieved	Source
Chess Puzzles	Reasoning	48.0%	132	Epoch AI	`claude-fable-5-1_max`	Oct 18, 2026	Epoch AI Benchmarking Hub · data file
Furniture Assembly not in index	Reasoning	70.0%	—	Epoch AI	`claude-fable-5-1_max`	Oct 18, 2026	Epoch AI Benchmarking Hub · data file
Mystery Game Puzzles	Reasoning	58.0%	141	Epoch AI	`claude-fable-5-1_max`	Oct 18, 2026	Epoch AI Benchmarking Hub · data file
FrontierMath Tier 4	Math	87.8%	143	Epoch AI	`claude-fable-5-1_max`	Oct 18, 2026	Epoch AI Benchmarking Hub · data file
FrontierMath Tiers 1–3	Math	90.2%	142	Epoch AI	`claude-fable-5-1_max`	Oct 18, 2026	Epoch AI Benchmarking Hub · data file
OTIS Mock AIME 2024–2025	Math	100.0%	142	Epoch AI	`claude-fable-5-1_max`	Oct 18, 2026	Epoch AI Benchmarking Hub · data file
GPQA Diamond (OpenRouter run)	Knowledge	88.9%	127	OpenRouter	`anthropic/claude-fable-5.1-20260831` Anthropic · first-party provider (1 of 3 rows)	Oct 18, 2026	OpenRouter benchmark datasets · data file
SimpleQA Verified	Knowledge	70.8%	150	Epoch AI	`claude-fable-5-1_max`	Oct 18, 2026	Epoch AI Benchmarking Hub · data file
τ²-bench Airline (OpenRouter run)	Agents	79.1%	137	OpenRouter	`anthropic/claude-fable-5.1-20260831` Anthropic · first-party provider (1 of 3 rows)	Oct 18, 2026	OpenRouter benchmark datasets · data file

Human preference (Arena)

On the Arena leaderboard, where people vote between two anonymous answers, Claude Fable 5.1 has a rating of 1,502 (1,496–1,508) from 14,590 votes (published Oct 15, 2026). Human preference is a different measure from benchmark ability and is not part of SI-IQ. Arena (Hugging Face)

Models with similar SI-IQ

Model	SI-IQ
GPT-5.6 SolOpenAI	140	Claude Fable 5.1 vs GPT-5.6 Sol
Gemini 4 ArgonGoogle DeepMind	140	Claude Fable 5.1 vs Gemini 4 Argon
GPT-6 SolOpenAI	140	Claude Fable 5.1 vs GPT-6 Sol
Claude Sonnet 5.5Anthropic	140	Claude Fable 5.1 vs Claude Sonnet 5.5
GPT-5.5OpenAI	138	Claude Fable 5.1 vs GPT-5.5

Computed with SI-IQ method version 1.0.0. Read the full methodology

Data sources: Arena leaderboard dataset on Hugging Face (CC BY 4.0); Epoch AI, ‘Capabilities & benchmarking’ (CC BY 4.0); API list prices via LiteLLM's price table (MIT); each price links to the developer's pricing page; Source: OpenRouter (openrouter.ai), licensed under CC BY 4.0.