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Claude Fable 5.1

Anthropicfamily · Claudeplatform.claude.com/docs/en/models/fable-5-1/ove

For demanding reasoning and long-horizon agentic work

Open in Graph
data quality76

Updated 3 h ago · first seen 11 Sept 2026

model_01M293V7EK3CVA2J99BHKR8PHG

Overview

Identity

Canonical model
Yesidentity confidence: mediumOne row per real model release. Artifacts (checkpoints, quantisations, conversions) and folded evaluation variants point here.
Official checkpoints
None recorded — closed weightsofficial_checkpoints = hf_repo identifiers carried by the model itself; artifacts are separate entities pointing here through canonical_id.
Artifacts
None recordedSeparate entities (checkpoint · quantization · conversion · packaging) pointing to this model through canonical_id.
Provider deployments
2
API aliases
anthropic/claude-fable-5.1claude-fable-5-1claude-fable-5-1-highclaude-fable-5-1-lowclaude-fable-5-1-mediumclaude-fable-5-1-xhighIdentifiers under which providers and evaluators refer to this model.
Folded evaluation variants
5Effort / thinking variants (…-high, …-non-reasoning) are result configurations of this model, not separate models. Their old URLs redirect here.

Openness

Closed / proprietary— weights not available; 7 dimensions unknown.

Weights are not available; the model is reachable only through an API or a product.

  • Weights

    No

  • Inference code

    —

  • Training code

    —

  • Training data

    —

  • Dataset

    —

  • Commercial use

    —

  • Redistribution

    —

  • Derivatives

    —

dimensions marked null are unknown, not false

Key facts

Release date

Source:Claude Developer Platform docsT1observed 14 h agohigh

Status

Source:Claude Developer Platform docsT1observed 14 h agohigh

Knowledge cutoff

Source:Claude Developer Platform docsT1observed 14 h agohigh

Retirement date

Source:Claude Developer Platform docsT1observed 14 h agohigh

Official page
platform.claude.com/docs/en/models/fable-5-1/overview

Source:Claude Developer Platform docsT1observed 14 h agohigh

API model id

Source:Claude Developer Platform docsT1observed 14 h agohigh

Openrouter id

Source:OpenRouter public model & pricing listingT2observed 13 h agomedium

Architecture

Tokenizer

Source:OpenRouter public model & pricing listingT2observed 13 h agomedium

Training data cutoff

Source:Claude Developer Platform docsT1observed 14 h agohigh

Capabilities

Modalities

Modalities
textimage
Input
textimage
Output
text

Capabilities

  • Tool calling

    Yes

    Claude Developer Platform docs · T1

  • Structured output

    Yes

    OpenRouter public model & pricing listing · T2

  • Reasoning

    Yes

    OpenRouter public model & pricing listing · T2

  • Vision

    Yes

    Claude Developer Platform docs · T1

  • Audio

    Unavailable

  • Fine-tuning available

    Unavailable

Context window

Source:Claude Developer Platform docsT1observed 14 h agohigh

Max output

Source:Claude Developer Platform docsT1observed 14 h agohigh

Knowledge cutoff

Source:Claude Developer Platform docsT1observed 14 h agohigh

Tokenizer

Source:OpenRouter public model & pricing listingT2observed 13 h agomedium

Benchmarks68

Compare with another model →

Comparable same task and conditions · Partially comparable same task, conditions differ (effort, temperature, judge) · Not comparable different variant or metric

Benchmark results grouped by comparability group
Benchmark · groupBest scoreTrustConfigurationResultsvs leaderEvaluatedSource
Terminal-Benchagentic · accuracy · variant=v2.1 · evaluator=Artificial AnalysisIndependentevaluatorArtificial Analysisvariantv2.1reasoning_effortmaxconditions differ across rows → partially comparable10non-primary groupobs. 12 Sept 2026artificialanalysis.aiT2
Terminal-Benchagentic · accuracy · variant=v4.0 · evaluator=Artificial AnalysisIndependentevaluatorArtificial Analysisvariantv4.0reasoning_effortxhighconditions differ across rows → partially comparable10non-primary groupobs. 12 Sept 2026artificialanalysis.aiT2
LiveBench Agentic Codingcoding · average score · variant=Agentic CodingOfficial boardvariantAgentic Codingreasoning_effortmaxrelease2026-06-25conditions differ across rows → partially comparable1−11.2 ptvs DeepSeek-V4.1-Flash25 Jun 2026livebench.aiT2
LiveBench Codingcoding · average score · variant=CodingOfficial boardvariantCodingreasoning_effortmaxrelease2026-06-25conditions differ across rows → partially comparable1current leader25 Jun 2026livebench.aiT2
SciCodecoding · accuracy · evaluator=Artificial AnalysisIndependentevaluatorArtificial Analysisreasoning_effortmaxconditions differ across rows → partially comparable10current leaderobs. 12 Sept 2026artificialanalysis.aiT2
Artificial Analysis Intelligence Indexcomposite · indexIndependentreasoning_effortmaxversion4.3conditions differ across rows → partially comparable10current leaderobs. 12 Sept 2026artificialanalysis.aiT2
LiveBenchgeneral · global_averageOfficial boardreasoning_effortmaxrelease2026-06-25conditions differ across rows → partially comparable1current leader25 Jun 2026livebench.aiT2
LiveBench Data Analysisgeneral · average score · variant=Data AnalysisOfficial boardvariantData Analysisreasoning_effortmaxrelease2026-06-25conditions differ across rows → partially comparable1−2.70 ptvs gpt-6-astra25 Jun 2026livebench.aiT2
LiveBench Languagegeneral · average score · variant=LanguageOfficial boardvariantLanguagereasoning_effortmaxrelease2026-06-25conditions differ across rows → partially comparable1−1.18 ptvs Claude Fable 525 Jun 2026livebench.aiT2
LiveBench Instruction Followinginstruction-following · average score · variant=IFOfficial boardvariantIFreasoning_effortmaxrelease2026-06-25conditions differ across rows → partially comparable1−8.42 ptvs Gemini 3.8 Flash25 Jun 2026livebench.aiT2
Humanity's Last Examknowledge · accuracy · evaluator=Artificial AnalysisIndependentevaluatorArtificial Analysisreasoning_effortmaxconditions differ across rows → partially comparable10current leaderobs. 12 Sept 2026artificialanalysis.aiT2
LiveBench Mathematicsmath · average score · variant=MathematicsOfficial boardvariantMathematicsreasoning_effortmaxrelease2026-06-25conditions differ across rows → partially comparable1current leader25 Jun 2026livebench.aiT2
GPQA Diamondreasoning · accuracy · variant=Diamond · evaluator=Artificial AnalysisIndependentevaluatorArtificial AnalysisvariantDiamondreasoning_effortmaxconditions differ across rows → partially comparable5non-primary groupobs. 12 Sept 2026artificialanalysis.aiT2
GPQA Diamondreasoning · accuracy · variant=GPQA Diamond · evaluator=Artificial AnalysisIndependentevaluatorArtificial AnalysisvariantGPQA Diamond5−2.52 ptvs gpt-6-astraobs. 11 Sept 2026artificialanalysis.aiT2
LiveBench Reasoningreasoning · average score · variant=ReasoningOfficial boardvariantReasoningreasoning_effortmaxrelease2026-06-25conditions differ across rows → partially comparable1−0.96 ptvs gpt-6-astra25 Jun 2026livebench.aiT2

Current rows only, grouped by benchmark → canonical metric → comparability group (task configuration). Effort variants folded into this model appear as rows of the same group. 68 current rows in total. “vs leader” compares with the current leader of the benchmark's primary group only; other groups are not directly comparable. Comparability rules →

Providers & Pricing5

All offers in the price terminal →
Provider deployments, cheapest output first
ProviderContextInput / 1MCached inCache writeOutput / 1MNative unitsStatusObservedSource
Anthropic APIcheapest outputanthropic/claude-fable-5.1:batch1Mout 128K$0.125$6.25—active4 h agosince 11 Sept 2026openrouter.aiT2
OpenRouteranthropic/claude-fable-5.1:batch1Mout 128K$0.125$6.25—active1 h agosince 12 Sept 2026openrouter.aiT2
Anthropic API—$0.25$12.5cache_write_1h_per_mtok=20active14 h agosince 11 Sept 2026platform.claude.comT1
Anthropic APIanthropic/claude-fable-5.11Mout 128K$0.25$12.5—active4 h agosince 11 Sept 2026openrouter.aiT2
OpenRouteranthropic/claude-fable-5.11Mout 128K$0.25$12.5—active1 h agosince 12 Sept 2026openrouter.aiT2

USD per 1M tokens as published by each provider; native units (per-request fees, flex/priority tiers) are kept verbatim. Rows are append-only — every price change is kept in the history below. Cost of a workload →

Price history

Step lines per provider; amber markers are recorded changes. Click a marker or a row for the evidence behind that price.

Output price · USD / 1M tokens 2 providers

Output price history of Claude Fable 5.1$0$20$40$60Sept 26Sept 26Sept 26Sept 26Anthropic API: first observed → $50 · 11 Sept 2026Anthropic API: $50 → $25 · 11 Sept 2026OpenRouter: first observed → $50 · 12 Sept 2026OpenRouter: $50 → $25 · 12 Sept 2026
  • Anthropic API
  • OpenRouter
  • OpenRouter$50 → $2512 Sept 2026
  • OpenRouterfirst observed $5012 Sept 2026
  • Anthropic API$50 → $2511 Sept 2026
  • Anthropic APIfirst observed $5011 Sept 2026

Input price · USD / 1M tokens 2 providers

Input price history of Claude Fable 5.1$0$2$4$6$8$10$12Sept 26Sept 26Sept 26Sept 26Anthropic API: first observed → $10 · 11 Sept 2026Anthropic API: $10 → $5 · 11 Sept 2026OpenRouter: first observed → $10 · 12 Sept 2026OpenRouter: $10 → $5 · 12 Sept 2026
  • Anthropic API
  • OpenRouter
  • OpenRouter$10 → $512 Sept 2026
  • OpenRouterfirst observed $1012 Sept 2026
  • Anthropic API$10 → $511 Sept 2026
  • Anthropic APIfirst observed $1011 Sept 2026

Versions & Artifacts0

Version history

Context windowfirst observation only

11 Sept 2026current

Knowledge cutofffirst observation only

11 Sept 2026current

Max outputfirst observation only

11 Sept 2026current

Opennessfirst observation only

11 Sept 2026current

Statusfirst observation only

11 Sept 2026current

Each hop is a claim: click a value for its source, tier and observation time. Nothing is overwritten — a new observation closes the previous claim.

Artifacts 0

No artifact (checkpoint, quantisation, conversion or packaging) points to this model yet.

Timeline30

Full timeline →

Change history

Temporal, append-only claims: a new observation closes the previous claim instead of overwriting it. Rewind the record with the as-of picker.
1 claims · 1 propertiesShow all properties

Aa opennessaa_openness1

Claim history for Aa openness
ValueValid from → toStatusSourceConfidenceExtractor
proprietary → currentcurrentArtificial AnalysisT2mediumdeterministic

Claims are temporal and append-only: a new observation closes the previous claim (valid_to) instead of overwriting it. Conflicting claims from different sources are kept side by side and flagged — never averaged. Methodology →

Provenance

Attributed facts

37

Source tiers

T1T226 / 11

Freshest observation

3 h ago

Conflicts

10 flagged

Source documents 6

Source documents
SourceDocumentTypeTierLast observedSnapshots
Claude Developer Platform docsdocs.claude.com/en/docs/about-claude/models/overview.md model_docsT1· Official2 h ago1
Claude Developer Platform docsdocs.claude.com/en/docs/about-claude/pricing.md pricingT1· Official2 h ago1
Claude Developer Platform docsplatform.claude.com/docs/en/models/fable-5-1/overview.md model_pageT1· Official14 h ago1
OpenRouter public model & pricing listingopenrouter.ai/api/v1/models catalogueT2· Quality secondary1 h ago10
Artificial Analysisartificialanalysis.ai/leaderboards/models leaderboardT2· Quality secondary3 h ago2
LiveBenchlivebench.ai/table_2026_06_25.csv leaderboardT2· Quality secondary12 h ago1

Tier 1 = official/primary, 2 = quality secondary, 3 = community, 4 = unverified. Every snapshot is archived; see all sources and the methodology.

Data quality (76/100) measures how well AI Atlas knows this entity — completeness, primary-source ratio, freshness, conflicts — never how good the model is. Methodology →