Anthropic

Claude Fable 5.1

Tool callingStructured outputReasoningImage inputFile input
Claude Fable 5.1 launch post cover

Claude model for demanding reasoning and long-horizon agentic work

Context
1M
Released
1mo ago
Input / 1M tokens
$10.00
Output / 1M tokens
$50.00
Cached input / 1M tokens
$0.25
Cache write / 1M tokens
$12.50

Sources:models.devOpenRouter

Benchmarks

DeepSWE is the primary coding benchmark where an exact model evaluation exists. Other sourced evaluations appear below; missing scores are not zero.

Not evaluated in DeepSWE 1.1 as of 2026-09-22. Results are only shown for exact model versions in the official dataset. Official leaderboard.

Other published benchmarks

EvaluationReported score and source
ARC-AGI-2
88.8%
Third-party evaluator · claude-fable-5-1_high
Reasoning effort: high
External evaluation via Epoch AI
Original-source terms apply
ARC-AGI-2
78.3%
Third-party evaluator · claude-fable-5-1_low
Reasoning effort: low
External evaluation via Epoch AI
Original-source terms apply
ARC-AGI-2
90.0%
Third-party evaluator · claude-fable-5-1_max
Reasoning effort: max
External evaluation via Epoch AI
Original-source terms apply
ARC-AGI-2
86.3%
Third-party evaluator · claude-fable-5-1_medium
Reasoning effort: medium
External evaluation via Epoch AI
Original-source terms apply
ARC-AGI-2
90.0%
Third-party evaluator · claude-fable-5-1_xhigh
Reasoning effort: xhigh
External evaluation via Epoch AI
Original-source terms apply
FrontierMath-Tier-4-v2-Private
87.8%
Epoch AI · claude-fable-5-1_max
Reasoning effort: max
Epoch AI evaluation
FrontierMath-Tiers-1-3-v2-Private
90.2%
Epoch AI · claude-fable-5-1_max
Reasoning effort: max
Epoch AI evaluation
OTIS Mock AIME 2024-2025
100.0%
Epoch AI · claude-fable-5-1_max
Reasoning effort: max
Epoch AI evaluation
SimpleQA Verified
70.8%
Epoch AI · claude-fable-5-1_max
Reasoning effort: max
Epoch AI evaluation

Benchmark compilation: Epoch AI, Capabilities & benchmarking (CC BY attribution). Scores are converted to percentages and model names matched to the Vertical Tabs catalog. Individual evaluations are credited to their original sources. External results may carry separate licences and evaluation configurations; do not interpret scores from different harnesses as directly comparable.

Specifications

Developer
Anthropic
Model family
Claude
Type
Language model
Predecessor
—
Successor
—
Released
September 1, 2026
Model ID
anthropic/claude-fable-5.1
Openness
Closed
License
—
Input modalities
text, image, file
Output modalities
text
Modality
text+image+file->text
Tokenizer
Claude
Max output tokens
128K
Knowledge cutoff
2026-06
Hugging Face
—
Source freshness
Metadata synced Oct 8, 2026, 10:17 PM UTC
Additional source evidence
Source model
anthropic/claude-fable-5-1
Source family
claude-fable
Last updated
2026-09-01
Knowledge cutoff
2026-06
Model context
1M
Model output limit
128K
Open weights
No
File attachments
Yes
Reasoning
Yes
Tool calling
Yes
Temperature control
No

Published benchmarks

BenchmarkScoreEvaluation detailsEvidence
Terminal-Bench-Science52.6 · scoreproduction safeguards with fallback · 0.1 · 2026-09-01Source
Terminal-Bench55.8 · scoreproduction safeguards with fallback · 4.0 · 2026-09-01Source
GDPval-AA1853 · Eloproduction safeguards with fallback · 2 · 2026-09-01Source
OSWorld77.9 · partial scoreAugust 2026 task release · production safeguards; interventions score zero; no fallback · 2.0 · 2026-09-01Source
OSWorld41.7 · strict success rateAugust 2026 task release · production safeguards; interventions score zero; no fallback · 2.0 · 2026-09-01Source
Humanity's Last Exam60.9 · scorewithout tools; production safeguards with fallback · 2026-09-01Source
Humanity's Last Exam65 · scorewith tools; production safeguards with fallback · 2026-09-01Source
AutomationBench31.4 · pass rateproduction safeguards with fallback · 2026-09-01Source
CursorBench73.4 · scoremax effort; production safeguards with fallback · 3.2.0 · 2026-09-01Source
Complete source record (JSON)
{
  "id": "anthropic/claude-fable-5-1",
  "name": "Claude Fable 5.1",
  "description": "Claude model for demanding reasoning and long-horizon agentic work",
  "family": "claude-fable",
  "last_updated": "2026-09-01",
  "knowledge": "2026-06",
  "attachment": true,
  "reasoning": true,
  "tool_call": true,
  "temperature": false,
  "modalities": {
    "input": [
      "text",
      "image",
      "pdf"
    ],
    "output": [
      "text"
    ]
  },
  "limit": {
    "context": 1000000,
    "output": 128000
  },
  "benchmarks": [
    {
      "name": "Terminal-Bench-Science",
      "score": 52.6,
      "source": "https://www.anthropic.com/claude-fable-and-mythos-5-1",
      "metric": "score",
      "variant": "production safeguards with fallback",
      "version": "0.1",
      "date": "2026-09-01"
    },
    {
      "name": "Terminal-Bench",
      "score": 55.8,
      "source": "https://www.anthropic.com/claude-fable-and-mythos-5-1",
      "metric": "score",
      "variant": "production safeguards with fallback",
      "version": "4.0",
      "date": "2026-09-01"
    },
    {
      "name": "GDPval-AA",
      "score": 1853,
      "source": "https://www.anthropic.com/claude-fable-and-mythos-5-1",
      "metric": "Elo",
      "variant": "production safeguards with fallback",
      "version": "2",
      "date": "2026-09-01"
    },
    {
      "name": "OSWorld",
      "score": 77.9,
      "source": "https://www.anthropic.com/claude-fable-and-mythos-5-1",
      "metric": "partial score",
      "variant": "production safeguards; interventions score zero; no fallback",
      "dataset": "August 2026 task release",
      "version": "2.0",
      "date": "2026-09-01"
    },
    {
      "name": "OSWorld",
      "score": 41.7,
      "source": "https://www.anthropic.com/claude-fable-and-mythos-5-1",
      "metric": "strict success rate",
      "variant": "production safeguards; interventions score zero; no fallback",
      "dataset": "August 2026 task release",
      "version": "2.0",
      "date": "2026-09-01"
    },
    {
      "name": "Humanity's Last Exam",
      "score": 60.9,
      "source": "https://www.anthropic.com/claude-fable-and-mythos-5-1",
      "metric": "score",
      "variant": "without tools; production safeguards with fallback",
      "date": "2026-09-01"
    },
    {
      "name": "Humanity's Last Exam",
      "score": 65,
      "source": "https://www.anthropic.com/claude-fable-and-mythos-5-1",
      "metric": "score",
      "variant": "with tools; production safeguards with fallback",
      "date": "2026-09-01"
    },
    {
      "name": "AutomationBench",
      "score": 31.4,
      "source": "https://www.anthropic.com/claude-fable-and-mythos-5-1",
      "metric": "pass rate",
      "variant": "production safeguards with fallback",
      "date": "2026-09-01"
    },
    {
      "name": "CursorBench",
      "score": 73.4,
      "source": "https://www.anthropic.com/claude-fable-and-mythos-5-1",
      "metric": "score",
      "variant": "max effort; production safeguards with fallback",
      "version": "3.2.0",
      "date": "2026-09-01"
    }
  ],
  "release_date": "2026-09-01",
  "open_weights": false
}

Infrastructure

Provider availability

All providers
ProviderEndpointContextInput /M tokensOutput /M tokensCached input /M tokensCache write /M tokensUptime 1dData handling
Amazon Bedrockamazon-bedrock1M$10.00$50.00$0.25$12.50—
ZDR: No

Training: Unknown

Prompt logging: Unknown

Retention: Unknown

Checked 2026-10-15

Amazon Bedrockamazon-bedrockBatch pricing1M$10.00$50.00$0.25$12.50—
ZDR: No

Training: Unknown

Prompt logging: Unknown

Retention: Unknown

Checked 2026-10-15

Anthropicanthropic1M$10.00$50.00$0.25$12.50100.00%
ZDR: No

Training: Unknown

Prompt logging: Unknown

Retention: Unknown

Checked 2026-10-15

AnthropicanthropicBatch pricing1M$10.00$50.00$0.25$12.50100.00%
ZDR: No

Training: Unknown

Prompt logging: Unknown

Retention: Unknown

Checked 2026-10-15

Azureazure1M$10.00$50.00$0.25$12.50100.00%
ZDR: No

Training: Unknown

Prompt logging: Unknown

Retention: Unknown

Checked 2026-10-15

AzureazureBatch pricing1M$10.00$50.00$0.25$12.50100.00%
ZDR: No

Training: Unknown

Prompt logging: Unknown

Retention: Unknown

Checked 2026-10-15

Googlegoogle-vertex/global1M$10.00$50.00$0.25$12.5099.42%
ZDR: No

Training: Unknown

Prompt logging: Unknown

Retention: Unknown

Checked 2026-10-15

Googlegoogle-vertex/globalBatch pricing1M$10.00$50.00$0.25$12.5099.20%
ZDR: No

Training: Unknown

Prompt logging: Unknown

Retention: Unknown

Checked 2026-10-15

Provider data:OpenRouter

Text provenance

Watermarked · Global

Claude text watermarking

Anthropic says newer Claude models include an invisible statistical watermark globally. It changes token selection rather than adding hidden characters.

Official explanation