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Anthropic · Frontier

Claude Fable 5.1

Added Sep 1, 2026

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Use in the app

Claude Fable 5.1 improves on Fable 5 across agentic coding, long-running workflows, front-end and visual code generation, finance, analysis, and knowledge work, with more concise plans and summaries. Anthropic retains prompts and outputs for 30 days; Zero Data Retention is not available.

  • Reasoning
  • Tools
  • Vision
  • Structured output
  • PDF input
Input
Text, Images
Output
Text
Reasoning effort
low · medium · high · xhigh · max
Discovery tier
Frontier

Pricing

USD per 1M tokens
Input
$10.00
Output
$50.00
Cache read
$0.25
Cache write
$12.50
$20.00 for a 1-hour cache

Reference prices as published by the model provider. API example

Specifications

Context window
1M
Max output
128K
Average output (7 days)
2.3K tokens
Longer than 93% of 473 models

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TryGemini 4 ArgonMuse WonderKimi K3.1 ProAll 3

Public evaluations

Benchmarks

Independent evaluation results, with how each score ranks among the models in the Noumen catalog.

Intelligence Index

53.4

Tested at max reasoning effort

Better than 98% of 326 scored models

3.8Catalog models by score55.1

Indexes

  • Coding Index

    81.6

    Composite of the coding evaluations

    Better than 99% of 168 scored models

Agentic work

  • AutomationBench-AA

    59.4%

    Workflow automation, penalized for guardrail violations

    Better than 78% of 173 scored models

  • AutomationBench-AA tasks completed

    32.1%

    Workflows finished end to end without a guardrail violation

    Better than 90% of 173 scored models

  • Harvey LAB-AAv1.1

    6.4%

    Legal tasks passed in full, with no material hallucination

    Better than 89% of 29 scored models

  • AA-Briefcasev1.1

    1,671 Elo

    Agentic knowledge work, rated head to head

    Better than 96% of 166 scored models

  • GDPval-AAv2.1

    1,755 Elo

    Economically valuable occupational tasks, rated head to head

    Better than 97% of 187 scored models

Document reasoning

  • GDP.pdf

    26.2%

    Professional reasoning over PDF documents, all-pass rate

    Better than 90% of 171 scored models

  • AA-LCRv1.1

    85.3%

    Reasoning across long documents

    Better than 97% of 309 scored models

  • MLCR-AA

    15.6%

    Long-context reasoning over medical records

    Better than 66% of 121 scored models

Reasoning and knowledge

  • Humanity’s Last Exam

    59.1%

    Expert-level questions across academic fields

    Better than 99% of 323 scored models

  • GPQA Diamond

    93.7%

    Graduate-level science questions

    Better than 94% of 291 scored models

Coding

  • Terminal-Benchv4.0

    52.0%

    Practical software engineering in a terminal

    Better than 95% of 171 scored models

  • SciCode

    63.1%

    Scientific computing in Python

    Better than 99% of 174 scored models

Legacy evaluations

  • AA-LCR (unversioned)

    85.3%

    Long-context reasoning, earlier grading

    Better than 97% of 309 scored models

Scores from Artificial Analysis, updated Oct 26, 2026. Claude Fable 5.1 was tested at max reasoning effort; compare scores measured at the same effort.Artificial Analysis

Live routing data

Performance and reliability

Recent averages across requests routed for this model. Your own speed depends on prompt length, reasoning effort and load.

Throughput
103.0 tok/s
Faster than 64% of 256 models
Time to first token
8.4 s
Quicker than 12% of 256 models
Prompt cache hits
15.3%
About $8.50 per 1M input tokens with caching
Request success (24h)
99.0%
Reliable

Cache hits are the share of input tokens recently served from a prompt cache across all requests. They are not a forecast of your own hit rate.

Hourly request success · last 72 hoursLowest hour 87.8%
  • Healthy (98% or more)
  • Degraded (90–98%)
  • Down (under 90%)
  • No requests

Developers

Use it through the API

Noumen’s API is OpenAI-compatible: any Chat Completions client works with a base URL and a key.

Read the quickstart
curl https://www.noumen.xyz/api/v1/chat/completions \
  -H "Authorization: Bearer $NOUMEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-fable-5.1",
    "reasoning_effort": "medium",
    "messages": [{ "role": "user", "content": "Explain this stack trace." }]
  }'
import os
from openai import OpenAI

client = OpenAI(base_url="https://www.noumen.xyz/api/v1", api_key=os.environ["NOUMEN_API_KEY"])
reply = client.chat.completions.create(
    model="anthropic/claude-fable-5.1",
    messages=[{"role": "user", "content": "Explain this stack trace."}],
)
print(reply.choices[0].message.content)

Anthropic

Other Anthropic models, starting with the same family.