A live Data Drop

Day One with Fable

10 Jun 2026 · updated daily

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On June 9, Anthropic released Claude Fable 5, the first public model from Mythos, a capability tier it had been running above Opus, inside a government cyberdefense program, since April. The launch post is a parade of superlatives. Stripe migrated 50 million lines of Ruby in a day. Pokémon fell to vision alone. The price doubled.

This page tracks Fable a different way. One person set it as his default model on day one and metered everything: every session, every token, every dollar not spent. The numbers come straight from this machine's logs, and they keep updating. Vibes elsewhere. Receipts here.

Fable replies742+ Output tokens938,211 API-equivalent$210.15 Paid$0.00

What the launch said. What the logs said back.

The quotes are from Anthropic's launch post. The timestamps are from this machine's session logs on June 10. Both are real.

Stripe used Fable to perform a 50 million line migration in a day. Work that would otherwise have taken a whole team over two months.

Anthropic launch post · source

10:21 AMFable's first assignment here: a connection test. It passed.claude-fable-5

It's opened up a class of long-horizon problems that were out of reach for earlier models.

Michael Truell, CEO, Cursor · source

11:10 AMIts second: scheduling its own demotion for June 22, the day the free window closes.claude-fable-5

At the highest effort, Claude Fable 5 reflects on and validates its own work.

Yusuke Kaji, GM AI for Business, Microsoft · source

1:14 PMReflecting on and validating someone else's work: a pile of 90-day-old email tokens, end to end.claude-fable-5

It works at senior research scientist grade. Picking directions, allocating resources, killing its incorrect beliefs.

Anthropic life sciences team · source

1:35 PMBuilding this page, about itself. The meter above is still running.claude-fable-5

The bill

Fable costs $10 per million input tokens and $50 per million output, double Opus 4.8. Here is day one at list price, computed from this machine's own logs.

Day one usageTokensRate / 1MCost
Input tokens77,885$10.00$0.78
Output tokens938,211$50.00$46.91
Cache reads124,342,586$1.00$124.34
Cache writes3,049,291$12.50$38.12
API-equivalent total$210.15
What we actually paid*$0.00

*Fable is included in paid Claude plans until June 22. Simon Willison's first day with Fable cost $110.42. Ours metered $40.42 by lunch. Then Fable started building this page, and the most expensive thing it did all day was write about itself. The table above is live.

The Fable wire

swept daily at 8:00 IST

Every Fable story as it lands: adoption, benchmarks, safety drama, price moves. New items appear here without this page changing a line of code.

  • 10 Jun · 13:35 ISTmetasheets.worksclaude-fable-5

    This page goes live, written by Fable about itself

    Fable 5 researched the launch coverage, mined its own session logs, computed its own bill, and built the page you are reading. Its token meter is still running at the top.

  • 10 Jun · 12:00 ISTbenchmarkgeeky-gadgets.comclaude-fable-5

    FrontierCode: Fable 5 roughly doubles GPT 5.5

    Independent comparisons of Cognition's FrontierCode results put Fable 5 well ahead of GPT 5.5 on hard, long-horizon coding tasks, the gap widening with task length.

  • 10 Jun · 08:00 ISTreviewsimonwillison.netclaude-fable-5

    Simon Willison: slow, expensive, and unusually capable

    After a 5.5 hour first day costing $110.42, Willison writes that the challenge is finding tasks Fable cannot do. One session produced several days of work in hours.

  • 10 Jun · 05:00 ISTsafetyaiweekly.coclaude-fable-5

    AI researchers say the distillation classifier flags their normal work

    The third safeguard category, meant to stop competitors extracting Fable's capabilities, is catching ordinary frontier-AI research. Several bioinformatics and ML practitioners say they are switching models over it.

  • 10 Jun · 03:00 ISTreviewnews.ycombinator.comclaude-fable-5

    The pelican has never looked better

    Simon Willison's pelican-on-a-bicycle SVG test, run at every effort level: a clear improvement over Opus 4.8 on default settings, with quality scaling up through max effort.

  • 10 Jun · 02:00 ISTsafetylatent.spaceclaude-fable-5

    Every Fable user now gets 30-day data retention, like it or not

    All Mythos-class traffic carries mandatory 30-day retention, overriding even zero-retention agreements, to defend against novel jailbreaks. Anthropic says data is used only for safety, with all human access logged.

  • 9 Jun · 23:30 ISTsafetynews.ycombinator.comclaude-fable-5

    Hacker News pushes back on silent fallbacks

    The top thread’s sharpest complaint: classifier false positives on routine work like MRI segmentation and mosquito biology, with sessions quietly answered by Opus 4.8 instead.

  • 9 Jun · 22:30 ISTadoptionanthropic.comclaude-fable-5

    Stripe: a 50 million line migration in a day

    Stripe reports Fable completed a Ruby migration in one day that it estimates would have taken a team over two months by hand.

  • 9 Jun · 22:00 ISTbenchmarkventurebeat.comclaude-fable-5

    80.3% on SWE-Bench Pro, 11 points clear of the field

    Anthropic’s published numbers put Fable 5 well ahead of the next best model on agentic coding, with the biggest gains on long, complex tasks. Spatial reasoning nearly tripled over Opus 4.8.

  • 9 Jun · 21:45 ISTnewstechcrunch.comclaude-fable-5

    Released days after Anthropic warned AI is getting too dangerous

    The launch landed days after Anthropic urged labs to prepare for recursive self-improvement, frontier systems improving themselves without human oversight. The juxtaposition is the story for much of the press.

  • 9 Jun · 21:30 ISTnewsanthropic.comclaude-fable-5

    It finished Pokémon FireRed using vision alone

    Earlier Claude models needed elaborate harnesses to play Pokémon. Fable 5 completed FireRed through a vision-only interface.

  • 9 Jun · 21:00 ISTadoptiongithub.blogclaude-fable-5

    Generally available in GitHub Copilot and Amazon Bedrock on day zero

    Fable 5 shipped simultaneously to the Claude API, GitHub Copilot, and Amazon Bedrock, with Cursor, Replit, and Databricks publishing day-one endorsements.

  • 9 Jun · 20:45 ISTnewsanthropic.comclaude-fable-5

    In blind tests, scientists preferred its hypotheses 4 times out of 5

    Anthropic's life-sciences results: molecular biologists preferred Mythos-generated hypotheses about 80% of the time, one was corroborated by an independent study, and 9 of 14 protein design targets yielded strong drug candidates.

  • 9 Jun · 20:30 ISTsafetyanthropic.comclaude-fable-5

    Mythos 5: the same brain with the locks off, for vetted defenders

    The unrestricted twin goes only to cyberdefenders and infrastructure providers via Project Glasswing, expanding to roughly 150 organizations across 15+ countries, with a biology trusted-access program to follow.

  • 9 Jun · 20:00 ISTpricinganthropic.comclaude-fable-5

    $10 in, $50 out, and free on paid plans until June 22

    Double Opus 4.8’s price, less than half of Mythos Preview’s. Subscribers get it included until June 22, then it moves to usage credits.

  • 9 Jun · 19:30 ISTanthropicanthropic.comclaude-fable-5

    Anthropic releases Claude Fable 5, its first public Mythos-class model

    A capability tier above Opus, previewed through a government cyberdefense program since April, now public with classifier safeguards. Under 5% of sessions fall back to Opus 4.8. The names are the tell: fabula is Latin for that which is told, mythos is the Greek.

Where the numbers come from

  • Session data. Token counts and timestamps are read from this machine's local Claude Code session logs. No conversation content is published. Nothing is estimated. The strip above refreshes from the same meter that updates the wire.
  • Pricing. $10 input and $50 output per million tokens, cache reads at 0.1× and cache writes at 1.25×, per Anthropic's launch post and published API pricing.
  • The badges. Anthropic says safety classifiers silently route under 5% of Fable sessions to Claude Opus 4.8. In tribute, every model badge on this page rolls the same dice. About 1 in 20 of them is quietly Opus right now. Refresh to re-roll.
  • The wire. Seeded by hand on launch week from the sources linked on each item, then swept daily by a scheduled search job. Corrections welcome: akash@sheets.works.
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