Anthropic · Released Sep 1, 2026Claude Fable 5.1
Claude model for demanding reasoning and long-horizon agentic work.
- Capability
- 164.8ECI · #4 of 148
- Input
- $10.00per 1M tokens
- Output
- $50.00per 1M tokens
- Context
- 1M128K max output
What it costs
- Input
- $10.00per million tokens
- Output
- $50.00per million tokens
- Cached input
- $0.25per million tokens
- Cache write
- $12.50per million tokens
- Blended (3:1)
- $20.00pricier than 96% of priced models
Typical monthly bills
| Monthly usage | Estimated cost |
|---|---|
| Side project2M input + 0.5M output tokens | $45.00 |
| Team assistant25M input + 5M output tokens | $500.00 |
| Production app250M input + 50M output tokens | $5,000 |
Official Anthropic API price, as listed on models.dev.
Independent benchmarks
#4 of 148 scored models
The shaded band is Epoch AI’s confidence range (161.8–169.1); the tick marks the median scored model.
Scores from Epoch AI, run independently of Anthropic.
The details
- Lab
- Anthropic
- Released
- Sep 1, 2026
- Knowledge cutoff
- Jun 2026
- Context window
- 1,000,000 tokens
- Max output
- 128,000 tokens
- Inputs
- Text, Images, PDFs
- Output
- Text
- Reasoning
- Adjustable effort low · medium · high · xhigh · max
- Tool calling
- Yes
- Structured output
- Yes
- Weights
- Proprietary
- API model ID
claude-fable-5-1on Anthropic- Availability
- 29 API providerslisted on models.dev
What Anthropic claims
Published by the lab at launch. Settings vary, so compare these only with care.
| Benchmark | Score | Setting | Source |
|---|---|---|---|
| Terminal-Bench-Science v0.1 | 52.6 | production safeguards with fallback | Source |
| Terminal-Bench v4.0 | 55.8 | production safeguards with fallback | Source |
| GDPval-AA v2 | 1853 Elo | production safeguards with fallback | Source |
| OSWorld v2.0 | 77.9 | production safeguards; interventions score zero; no fallback | Source |
| OSWorld v2.0 | 41.7 strict success rate | production safeguards; interventions score zero; no fallback | Source |
| Humanity's Last Exam | 60.9 | without tools; production safeguards with fallback | Source |
| Humanity's Last Exam | 65 | with tools; production safeguards with fallback | Source |
| AutomationBench | 31.4 | production safeguards with fallback | Source |
| CursorBench v3.2.0 | 73.4 | max effort; production safeguards with fallback | Source |
More from Anthropic
About Claude Fable 5.1
How much does Claude Fable 5.1 cost?
Claude Fable 5.1 costs $10.00 input / $50.00 output per million tokens (official Anthropic API price). Cached input is $0.25 per million tokens, and writing to the cache costs $12.50. At a 3:1 input-to-output mix that is $20.00 per million tokens, more expensive than 96% of the 360 priced models we track.
What is the context window of Claude Fable 5.1?
Claude Fable 5.1 accepts up to 1,000,000 tokens per request and can write up to 128,000 tokens in one response.
How good is Claude Fable 5.1?
Epoch AI gives Claude Fable 5.1 a Capabilities Index score of 164.8 (likely range 161.8–169.1), ranking it #4 of 148 models Epoch has scored. Epoch AI benchmark results: FrontierMath Tiers 1–3 90.2%, OTIS Mock AIME 2024–2025 100%, SimpleQA Verified 70.8%.
Is Claude Fable 5.1 open source?
No. Claude Fable 5.1 is proprietary; you use it through Anthropic’s API or partner platforms.
What inputs does Claude Fable 5.1 support?
Claude Fable 5.1 accepts text, images and PDFs and replies in text. It is a reasoning model with low, medium, high, xhigh and max effort settings, supports tool calling and can return structured JSON output.
When was Claude Fable 5.1 released?
Anthropic released Claude Fable 5.1 on Sep 1, 2026. Its training data runs to Jun 2026.
What are the best alternatives to Claude Fable 5.1?
The closest current models from other labs on capability, price and release date are GPT-6 Astra (OpenAI, ECI 166.5, $10.00 / $50.00), Kimi K3 (Moonshot AI, ECI 157.6, $3.00 / $15.00), Grok 4.6 (xAI, ECI 156.6, $2.00 / $6.00) and Qwen3.8 Max (Alibaba (Qwen), ECI 156.6, $2.00 / $6.00).