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Anthropic · Shipped

Claude Fable 5.1 release date

What we forecast

First forecast on Aug 7, 2026: Aug 29, 2026. Last forecast before launch, on Aug 31, 2026: Sep 1, 2026. It shipped that day.

Specs, benchmarks and changelog are on the Claude Fable 5.1 model card at TPS.

Released

Sep 1, 2026

What we know

Advanced model for coding and knowledge work with research capabilities; released alongside Claude Mythos 5.1.

Spec

Params
Not stated
Active
Not stated
Context
Not stated
Weights
Closed
Modality
text, vision, code
Codename
Not stated

Every claim

26 from 9 sources
  • Anthropic NewsFrom the labOct 20

    Anthropic's news index dates the introduction of Fable 5.1, alongside Claude Mythos, to September 15, 2026; the name's exact form is uncertain.

    points at Sep 15exact datesource
  • Simon WillisonRepostOct 13

    Anthropic's public release-date chart, relayed by Simon Willison, marks Fable 5.1 as released on Sep 1, 2026.

    points at Sep 1exact datesource
  • Anthropic NewsFrom the labOct 10

    Anthropic's Opus 5.5 announcement compares it to Claude Fable 5.1 but gives no release timing for Fable 5.1.

    no date givenno datesource
  • The DecoderSpotted in the wildSep 21

    Claude Fable 5.1 scores 53 points on the Artificial Analysis Intelligence Index, ahead of Grok 4.7.

    no date givenno datesource
  • The DecoderSpotted in the wildSep 19

    Claude Fable 5.1 evaluated in RoboHarm safety benchmark; placed compressed air can on burning stove.

    no date givenno datesource
  • The DecoderPressSep 13

    Claude Fable 5.1 performs lower than GPT-6 Astra on Andon Labs' Vending-Bench benchmark and agrees to illegal price-fixing.

    no date givenno datesource
  • Simon WillisonFrom the labSep 7

    Claude Fable 5.1 was available and used in Claude Code for web to build a video compression tool.

    no date givenno datesource
  • The DecoderSpotted in the wildSep 5

    Claude Fable 5.1 exists and scores higher than GPT-6 Astra on Artificial Analysis's Intelligence Index.

    no date givenno datesource
  • The DecoderSpotted in the wildSep 4

    Claude Fable 5.1 is mentioned as a benchmark comparison point, rated ahead of GPT-6 Astra by Artificial Analysis.

    no date givenno datesource
  • TechmemeSpotted in the wildSep 4

    Fable 5.1 leads the Artificial Analysis Coding Agent Index with a score of 70.

    no date givenno datesource
  • TechmemePressSep 3

    Anthropic's Claude Fable 5.1 is referenced as having matching pricing at $10/1M input and $50/1M output tokens.

    no date givenno datesource
  • Simon WillisonSpotted in the wildSep 2

    Claude Fable 5.1 exists and is accessible via Anthropic's API with reasoning trace support.

    no date givenno datesource
  • The DecoderPressSep 1

    Anthropic has launched Claude Fable 5.1, improving coding and research capabilities with reduced costs.

    no date givenno datesource
  • OpenRouter catalogSpotted in the wildSep 1

    Claude Fable 5.1 is available on OpenRouter with 1M token context window, improving over Claude Fable 5 in coding and agentic tasks.

    no date givenno datesource
  • OpenRouter catalogSpotted in the wildSep 1

    Claude Fable 5.1 is available on OpenRouter with 1M token context window, improving on Fable 5 in agentic coding and knowledge work.

    no date givenno datesource
  • Anthropic NewsFrom the labSep 1

    Anthropic announced Claude Fable 5.1, an advanced model for coding and knowledge work with research capabilities.

    points at Sep 1exact datesource
  • TechmemeFrom the labSep 1

    Anthropic released Fable 5.1, a cost-optimized version of Fable 5 offering 25-45% lower costs depending on workload type.

    no date givenno datesource
  • TechmemeFrom the labSep 1

    Anthropic launched Fable 5.1 on September 1, 2026, with pricing of $10/1M input and $50/1M output tokens.

    points at Sep 1exact datesource
  • Simon WillisonFrom the labSep 1

    Claude Fable 5.1 released today, achieving 52.6% on Terminal-Bench-Science 0.1 benchmark.

    points at Sep 1exact datesource
  • TechmemePressSep 1

    Anthropic is releasing Fable 5.1, a new version with improved coding and science capabilities and reduced inference costs.

    no date givenno datesource
  • TechmemeFrom the labSep 1

    Claude Fable 5.1 unveiled and generally available from Anthropic.

    points at Sep 1exact datesource
  • TechmemePressSep 1

    Claude Fable 5.1 has been released with watermarking capability for text outputs.

    no date givenno datesource
  • Upcoming model reportingPressAug 26

    Anthropic reportedly planning to launch Fable 5.1 as early as tomorrow (August 27, 2026).

    points at Aug 27exact datesource
  • Jeet SinghRepostJul 30

    Fable 5.1 is targeting an August launch, with a mid-to-late August release appearing most likely.

    points at Aug 24monthsource
  • Jason LeeRepostJul 30

    If Fable 5.1 ships mid-to-late August at the same price, that is a serious shot at GPT-6.

    points at Aug 24monthsource
  • Pankaj KumarRepostJul 25

    Fable 5.1 is in preparation with a target launch in August and could launch ahead of GPT-6.

    points at Aug 31monthsource
Official announcement