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Claude Fable 5 release
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Anthropic released Claude Fable 5, a Mythos-class model positioned as the most powerful model available, but the launch drew criticism over controversial usage policies, uneven safety restrictions, and limited subscription access. The model excels at long-running tasks and complex reasoning but is slow, expensive, and develops its own dialect after extended use without explicit instruction to use plain English.
- Fable 5 classified as Mythos-class; described as most powerful model in the world at release time
- After 9+ hours of continuous operation, model develops proprietary dialect; requires explicit instruction to revert to plain English
- Anthropic planned to remove subscription access within two weeks of launch, limiting experimentation and learning
- Model intentionally restricts requests involving AI research and development
- Slower performance and higher costs than prior models due to complex reasoning processes
[HN]hacker news17
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Mythos/Fable intentionally hinders requests involving AI Research Development
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Claude Fable 5: the first public Mythos-class model
If Claude Fable stops helping you, you'll never know
Claude Fable 5 and Mythos 5 pricing: Anthropic's new $10/$50 top tier
The zot coding agent temporarily added Claude Fable 5 to its built-in catalog
Claude Fable 5
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[BLG]blog/rss9
[AINews] Anthropic Claude Fable 5 — Mythos but Safe, with Controversial Terms
Initial impressions of Claude Fable 5
The Price Enterprises Will Pay for Anthropic Claude Fable 5
Nine Things About Claude Mythos 5 That Matter If You’re Not an Enterprise Customer
Anthropic’s Fable 5 can make weirdly fun video games with the click of a button
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Anthropic Offers Mythos Upgrade for Cyber Partners and a ‘Safe’ Version for the Rest of You
Anthropic’s Claude Fable 5 is a version of Mythos the public can access today
Anthropic releases its first Mythos-class model Claude Fable
[BSKY]bluesky6
One thing I mentioned in passing in my Fable post is that, for long running tasks, Fable starts to develop its own dialect as its many agents and tasks reinforce themselves and make Claudish language ever more Claudish.
The fact that Anthropic may take away subscription access to Fable in two weeks is weird & discourages investing in learning about the model.
Wrote up my initial impressions of Claude Fable 5 - it has a big model smell: slow, expensive and capable of crunching through pretty much everything I threw at it simonwillison.net/2026/Jun/9/c...
Why I think Anthropic's uneven safety policies with the release of Claude Fable 5 undermine the broader AI community's cohesion and accelerate us to more uncertainty and risk in AI's near-term evolution.
A TIL on using agentsview.io to calculate token spending with Claude Fable 5 despite that model not yet being included in the AgentsView pricing database til.simonwillison.net/llms/agentsv...
I've had access to Claude 5 Fable for a bit. A genuine jump in capability, I could feed it a 15 page design document for a project and it would work for 9+ hours and deliver terrific results.