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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

#471

Post by neosat »

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…

Can you or someone else from A\ comment on whether the conversation style is coming to Opus 5 or a future 5.1 asap as well? Currently it seems the model has been made unusable by the way it 'speaks' and there is a clear solution where it can speak better but nothing has been done about the flagship model on Pro plans. I've literally had to work on Opus 4.8 which does not have this problem and speaks fine.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#472

Post by andai »

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…

> Probably leaves no room to place Opus 5.1 anywhere.

Well it'll probably be better than Fable again, lol

Re: Claude Fable 5.1 and Claude Mythos 5.1

#473

Post by anthonypasq »

supern0va wrote: post #319
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…

>Has frontier progress finally stalled? It wouldn't surprise me if we start to see minimal performance gains from incremental changes to base models. It seems like the gains from the Opus 4.5+ incremental updates were a result of Anthropic learning a lot about post-training, the gains from RLVR, etc. If new post-training techniques are seeing diminishing returns, we could just be back to waiting for new large pretrai…

it seems to me that OpenAI is the only actual lab that truly understands reasoning. they have the best reasoning efficiency, they get pretty uniform improvements with more reasoning compared to other labs. (theres been plenty of graphs where models do worse with more reasoning), and i suspect their models are a lot smaller than we think.

i think the next gen of openAI models are going to be quite insane tbh.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#474

Post by peri-cl »

simonw wrote: post #304
swalsh wrote: post #248

Earlier quoted context omitted.

Now that it's a solved benchmark, can we get the animated version?

I didn't want to shell out for Max again, so I piped the SVG created by Max back into Fable 5.1 at its default thinking level (of high): llm logs -cx | llm -m claude-fable-5.1 -s 'animate this' Here's the result, which cost $1.37: https://tools.simonwillison.net/markdown-svg-renderer?url=ht... It's excellent!

Well, the wheels are rotating the wrong way, but other than that!

(Maybe it's a strobing artifact?)

Re: Claude Fable 5.1 and Claude Mythos 5.1

#475

Post by andai »

ThouYS wrote: post #447
madrox wrote: post #405

I am finding that I am now less interested in better models than I am in token budgets. My issue with Anthropic models now is that I don't feel like I can rely on them as a daily driver because they'll dry up before my quota resets. I am becoming dependent on AI to make a living, and I need predictable spend on it. If I know I can't use a model regularly all month, my enthusiasm is limited. I urge Anthropic to get be…

GLM 5.3-flash fits the bill

What is it equivalent to?

What kind of things are you using it for?

I haven't tested it yet but on all the benchmarks it looks like it's 5-7x slower for agentic tasks.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#476

Post by JamesSwift »

vablings wrote: post #142
jumploops wrote: post #70

> For example, in testing by the investment firm Millennium, Fable 5.1 found the cause of a rare crash on their internal systems that none of their engineers (or any other model) had been able to explain after several years of trying. Say what you will about LLM-generated code, but stories like this give me hope that software will never be as buggy as it once was.

Software will be buggier than ever but also way less buggy.

Time-to-fix is lower, but time-to-new-bug is also lower

Re: Claude Fable 5.1 and Claude Mythos 5.1

#477

Post by pkulak »

karelpeeters wrote: post #463
exabrial wrote: post #419

Anyone ever seen the SouthPark episode making fun of Game of Thrones: A Song of Ass and Fire? Anthropic's announcements reminds me of "The Dragons Are Coming" running joke. What they have done: * Nerfed Fable, as many of noted it's useless * Leverage Mythos as a marketing strategy, claiming its too good to release * Removed thought traces, one of the only useful things to make sure your prompts are working correctly…

Text watermarking has no effect on output quality, it just works by changing the explicit source of randomness that is in practice always present in LLM output sampling. See for example https://www.seangoedecke.com/ai-text-watermarking-is-not-a-b... .

> Text watermarking has no effect on output quality

It has an effect, and it's negative. It's hoped that the effect is negligible, and it probably is, but the whole point is that it has an effect.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#478

Post by george_max »

madrox wrote: post #405

I am finding that I am now less interested in better models than I am in token budgets. My issue with Anthropic models now is that I don't feel like I can rely on them as a daily driver because they'll dry up before my quota resets. I am becoming dependent on AI to make a living, and I need predictable spend on it. If I know I can't use a model regularly all month, my enthusiasm is limited. I urge Anthropic to get be…

Agreed. The area I think will become more prevalent in the future for organizations are cost per intelligence -- effectively efficiency. An unoptimized model that costs 90x more than another that is only 10-15% less intelligent is something I would say is not a good deal.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#479

Post by alin23 »

My main gripe with LLMs is the cringe AI phrasings that they use in UI elements. Pompous things like "Your keys, supercharged" or weird yoda-speak stuff like "searches the app remembers" instead of just naming the thing "Learned searches".. you know, proper GUI copy like it was done for the past decades.

I jumped when I saw a mention about "writing style improvements" so I gave it a try on a recent feature in rcmd [0]. I prompted Fable 5.1 to find these wordings and propose simpler plain language.

    For context, I recently worked with Fable to give users a way to fuzzy search and focus any browser tabs, terminal panes etc. but the UI was still a prototype full of AI writings.
It took every string including the ones I already rewrote by hand, and proposed even more weird LLM speak. Like for "Left Command conflict detected" it proposed "This keyboard can't tell left from right".

It's a very capable coding agent, but I can't understand how it can be so bad at writing. Where are all these verbal tics coming from and why is it so hard to get rid of them?

[0] https://lowtechguys.com/rcmd

Re: Claude Fable 5.1 and Claude Mythos 5.1

#480

Post by motbus3 »

velcrovan wrote: post #121
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…

I have a pet theory that the Opus prose style/smell we all have grown weary of is due at least in part to the models writing more for themselves and each other than for humans. They're packing lots of signal into fewer words and they don't care if it sounds cringe because it works better as glue in long-running tasks. I'm also thinking of the 2017 novel "Void Star" where AIs who operate everything have long since lef…

You can just get a style guide or sample and ask it to describe/distill on your Claude.md
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