# Claude Fable 5 review: what the new Mythos model gets right (and very wrong)

> Source: <https://www.lennysnewsletter.com/p/claude-fable-5-review-what-the-new>
> Published: 2026-06-09 18:32:03+00:00

Claude Fable 5 is the first Mythos-class intelligence model to be generally available, and I got early access to test it before launch. I walk through what Anthropic is promising, what actually stood out when I used it on real work, and where I think it fits in your AI stack.

**Listen or watch on YouTube, Spotify, or Apple Podcasts**

### In this episode, we cover:

([00:00](https://www.youtube.com/watch?v=IREnr4I89Ho)) Introduction: Fable 5 is finally here

([00:31](https://www.youtube.com/watch?v=IREnr4I89Ho&t=31s)) What Anthropic says about the model

([05:14](https://www.youtube.com/watch?v=IREnr4I89Ho&t=314s)) Token-intensive by design

([06:28](https://www.youtube.com/watch?v=IREnr4I89Ho&t=388s)) Safety classifiers and the new fallback concept

([07:46](https://www.youtube.com/watch?v=IREnr4I89Ho&t=466s)) Is this or is this not Mythos?

([08:30](https://www.youtube.com/watch?v=IREnr4I89Ho&t=510s)) New product launches: Managed Agents and more

([09:20](https://www.youtube.com/watch?v=IREnr4I89Ho&t=560s)) Crushing benchmarks

([09:55](https://www.youtube.com/watch?v=IREnr4I89Ho&t=595s)) What it’s actually like to use (the good and the bad)

([11:40](https://www.youtube.com/watch?v=IREnr4I89Ho&t=700s)) Test 1: product graph spec

([12:56](https://www.youtube.com/watch?v=IREnr4I89Ho&t=776s)) Test 2: designing a skills registry

([14:04](https://www.youtube.com/watch?v=IREnr4I89Ho&t=844s)) Conservative on execution

([14:43](https://www.youtube.com/watch?v=IREnr4I89Ho&t=883s)) Test 3: multi-agent orchestration

([15:39](https://www.youtube.com/watch?v=IREnr4I89Ho&t=939s)) My takeaways

### Tools referenced:

• Claude Fable 5: [https://www.anthropic.com/news/claude-fable-5-mythos-5](https://www.anthropic.com/news/claude-fable-5-mythos-5)

• Claude Managed Agents: [https://platform.claude.com/docs/en/managed-agents/overview](https://platform.claude.com/docs/en/managed-agents/overview)

### Other reference:

• SWBench Pro benchmark: [https://www.swebench.com/](https://www.swebench.com/)

### Where to find Claire Vo:

ChatPRD: [https://www.chatprd.ai/](https://www.chatprd.ai/)

Website: [https://clairevo.com/](https://clairevo.com/)

LinkedIn: [https://www.linkedin.com/in/clairevo/](https://www.linkedin.com/in/clairevo/)

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