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Claude Fable 5.1 and Claude Mythos 5.1

anthropic.com

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Re: Claude Fable 5.1 and Claude Mythos 5.1

#251

Post by dpkirchner »

peab wrote: post #191
tarr11 wrote: post #35

“ Claude Fable 5.1's writing is generally a step up from earlier Claude models, with fewer stock phrases and less unexplained jargon. In some cases, though, its prose is denser than Claude Fable 5's: sentences run longer and there are fewer paragraph breaks.” I cancelled my pro max Claude subscription last week; codex is much more succinct. I am curious if this is getting better. I don’t think Anthropic realizes that…

I just can't stand how often Claude says something like "And the honest part? It's..." Like, were the other parts not honest? I don't understand how Anthropic let it get like this, it's been such a clear regression

If you ask it why it uses the term honest so much it'll tell you it was actually trained not to. lol

Re: Claude Fable 5.1 and Claude Mythos 5.1

#254

Post by theletterf »

felixrieseberg wrote: post #69

(I work at Anthropic) Beyond all the benchmarks, I think Fable 5.1 is a big improvement in writing style. It sounds a lot less stereotypically like other Claude models, has (imho) a much more natural style, and responds to my style instructions more reliably. More work to be done (and we will!) but reading better prose makes me so much happier. Another point I expect not to get much attention until it all happens at…

Docs engineer here. Nice to read about writing style: would you consider creating a writing benchmark at some point? I guess y'all are painfully aware of the load-bearing issues (pun intended).

Re: Claude Fable 5.1 and Claude Mythos 5.1

#255

Post by caconym_ »

> We’re introducing Claude Fable 5.1 and Claude Mythos 5.1. They’re the world’s most advanced models for coding and knowledge work—and their research capabilities offer an early glimpse of how AI models will contribute to scientific progress.

I'm not an emdash hater but this isn't how you use them. It should be a comma.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#256

Post by sroussey »

unglaublich wrote: post #170
dabinat wrote: post #147

> This required us to add a watermark—a numerical way of determining the likelihood that Claude was involved in writing a piece of text—to the outputs of models released after August 2, 2026. As we recently explained, this watermark is invisible to anyone who does not have the detection API. It has no practical impact on the quality or content of Claude’s outputs and contains no information about the user, their orga…

It does change the output, they never said it did not. They said it would not _noticeably_ affect performance.

Which is a lie. Or vacuous statement as Claude might say these days.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#257

Post by nsingh2 »

GodelNumbering wrote: post #139

The price reduction comes from the cache read pricing falling from $1/M to $0.25/M, which means that Fable 5.1 now costs half of Opus's cache read costs ($0.5/M). This gives a lot of credit to the theory that Anthropic did not get much bite on Fable at its original pricing, which in turn likely places a ceiling on LLM pricing in general. Interestingly also, if you take away terminal-Bench-Science 0.1 results, it is h…

From Artificial Analysis cost per task, it looks like Fable 5.1 (max) is more expensive per task than Fable 5 (max)? Cache hit price went down, but the other components still add up to more.

Edit: 5.1-xhigh seems to be cheaper than 5-max, and 5.1-xhigh has a higher index score than 5-max. Also interesting that Fable 5.1 (high) is comparable to Opus 5 (max), but nearly half the price.

https://artificialanalysis.ai/models#cost-tabs

Re: Claude Fable 5.1 and Claude Mythos 5.1

#258

Post by sscaryterry »

eigenblake wrote: post #226

I am absolutely thrilled that they reset weekly limits. I have been experimenting with highly autonomous work (5+ hours continuous) and fable seems excellent at this, especially when using subagents. I ran out of Fable capacity and was bummed out that my experiment would take longer to complete. Now I'm super happy I get to continue it

Codex has this all the time. No 5 hour limits either.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#259

Post by vessenes »

felixrieseberg wrote: post #69

(I work at Anthropic) Beyond all the benchmarks, I think Fable 5.1 is a big improvement in writing style. It sounds a lot less stereotypically like other Claude models, has (imho) a much more natural style, and responds to my style instructions more reliably. More work to be done (and we will!) but reading better prose makes me so much happier. Another point I expect not to get much attention until it all happens at…

Felix, just poking at this, and it is MUCH more pleasant to talk to, thanks to your teammates for the work.
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