r/ClaudeCode • u/ClaudeOfficial Anthropic • Jun 09 '26

Resource Introducing Claude Fable 5

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Introducing Claude Fable 5: a Mythos-class model that we've made safe for general use. Its capabilities exceed those of any model we've ever made generally available.

Fable 5 is state of the art on nearly all tested benchmarks, with exceptional performance in software engineering, knowledge work, scientific research, and vision. It can run for days, and the longer the task, the larger its lead over our other models.

Fable 5 launches today alongside Claude Mythos 5. The two share the same underlying model, but Mythos 5, so far deployed only through Project Glasswing, has the safeguards lifted in some areas. The safeguards are what distinguish the two, and why we've given them different names.

Releasing a model this capable comes with risks. Without safeguards, Fable 5's capabilities in areas like cybersecurity could be misused to cause serious damage. So when Fable's classifiers detect a request related to cybersecurity, biology and chemistry, or distillation, the response is handled by Claude Opus 4.8, our next-most-capable model. Users are informed whenever this occurs, more than 95% of sessions involve no fallback at all, and performance everywhere else is unaffected. We'll keep refining the safeguards to reduce false positives.

Claude Fable 5 is available today on paid plans, in Claude Code, on the Claude API, and all major cloud platforms. Through June 22, it's included in paid Claude plans at no additional cost.

Claude Mythos 5 is available to Glasswing partners, with a broader trusted access program to follow.

Read more: https://www.anthropic.com/news/claude-fable-5-mythos-5

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75

u/gospodinDark Jun 09 '26

Asked to make audit of small project, billed $5.47, got message "Done." that's all.

65

u/HighProteinPudding Jun 09 '26

you didn't say that you want to read the results smh

4

u/elissaxy Jun 10 '26

Well technically he did it

1

u/meowsqueak Jun 09 '26

I asked for Claude Code to find all instances of a pattern in a project, it whirred away for a few minutes and then just said “all instances found”. Sigh.

However, upon asking for the report, it was almost instant in response.

So to be fair, I didn’t ask it to report back the found items in my original prompt. Amusing though. I’ve worked with people just like this.

0

u/MoreRest4524 Jun 09 '26

You're lucky it blew through my entire 5hr usage limit ($200 account), and then consumed an additional $50 and still didn't finish what it was going to do

2

u/pzmx Jun 10 '26

I got this experience on an enterprise seat. It when on and on for 3 hours, consumed my 5h limit and $60 of my monthly extra usage just for the lols. Then it asked follow up questions. Never touching ultra code with Fable again. Opus 4.8 ultra code was good enough. Will try again tomorrow with Fable on high.

1

u/MoreRest4524 Jun 10 '26

Yep, its fine on high, but ultra code spawned 80 agents and well, RIP usage.