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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

#231

Post by windexh8er »

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…

Same here. I still have access until my account churns but Anthropic has huge issues comparative to everyone else with token / usage burn down. K3 Swarm also delivers better results than Fable at a fraction of utilization. The Pro plan is definitely not worth it anymore and if I do want to burn some money I can always just leverage the API. But Anthropic went from simply amazing last year to a dumpster fire in less than 6 months for my use cases, anyway.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#232

Post by rcr-anti »

"Distillation is a safety risk, since the distilled capabilities can subsequently be released without adequate safeguards."

Can't believe they haven't at least figured out better messaging. If we take them at their word, it's hard not to read it as a messiah complex, that they think they're the only ones capable or worthy of making these decisions. I don't believe them, but I wouldn't be surprised if the articulated reason is a version of "distillation is a safety risk because we might lose the race".

Plus, completely deaf to the recent OpenAI-HF hack incident. Recall, defenders were categorically unable to use western frontier models in their response.

I was originally going to complain about the chem and bio guards still being too onerous, but I'll admit the projects Fable 5 categorically refused to work on are now usable, at least not rejecting on first prompt because the word "virology" was in a git commit (absolutely serious, in one repo it triggered on literally any prompt, eventually traced to the system prompt loading git commit history). Still, them trying to get into the biomed business while walling off the capabilities to the public reeks. Why sell the segments that are actually valuable if you can capture the value yourself!

Re: Claude Fable 5.1 and Claude Mythos 5.1

#233

Post by elictronic »

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…

Complicated technical language is an easy way to increase perceived accuracy of tests and reviews by external reviewers. When we are talking about single % differences this has an effect.

Feels like crap to me though.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#234

Post by ctoth »

pixl97 wrote: post #145
belval wrote: post #86

Earlier quoted context omitted.

As a fervent Claude Code user who made the switch to GPT 5.6 Sol over Opus 5 over hard-to-read prose this makes me happy. I love your product but the current models are very hard to work with if you need to do a lot of context switching. Brevity is key.

>Brevity is key Which is something the providers that are trying to watermark their texts can't afford. Superfluous replies give much more opportunity to further encode this junk information.

This ... is not how this works. The model is not speaking longer to watermark anything.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#235

Post by Tepix »

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…

DeepSeek V4 Pro cache read pricing is $0.022 (offpeak) and

DeepSeek V4 Flash cache read pricing is $0.007

Makes it super affordable!

Re: Claude Fable 5.1 and Claude Mythos 5.1

#236

Post by unshavedyak »

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…

And word on Opus 5.1 for writing style? I am on the edge of switching to OpenAI due to this horrid writing style. If Fable is better, great - but i can't even use that at work.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#237

Post by pram »

Someone1234 wrote: post #150
rybosworld wrote: post #61

Instead of a new model that's going to have unreasonably shallow usage limits, I wish they would: 1) address the claude 20x plan usage being only 6-7x the ceiling of the claude pro plan 2) either fix opus 5, make it completely free, or delete it entirely

I'm legitimately out of the loop; what is going on/broken with Opus 5?

The comments it makes are so bad, long, and incomprehensible I just strip them all with sed these days.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#238

Post by boc »

echelon wrote: post #149
PedroBatista wrote: post #125

Earlier quoted context omitted.

This post and comment makes me believe "science" is the new "code" for Anthropic now that the code advantage is mostly gone and lost for OpenAI, ie. they got much better and Claude become significantly worse over these months.

IMO, Codex is worse than Claude with Fable. At least at Rust. That said, the open source models are not bad and I'm looking forward to more tools and products built on top of them. Code review, security review, etc. Anthropic needs to change how it treats users though. I'm increasingly put off by Dario, the rug pulling, the lies, and the attempts to regulate open weights. I'm going to bail if this doesn't change. The…

Small reminder that the US government rug-pulled Fable, not Dario. Lots of the safety guards that users find annoying/objectionable were the results of negotiations to get the model back online after the US government forced them to take it down.

Maybe Dario should have just "donated" $1M to Trump's inauguration fund like Altman, Meta, Amazon, Microsoft, Tim Cook, Elon, and Google. There's a reason they are the odd man out with this current Administration.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#239

Post by rcr-anti »

eckr wrote: post #143

"Claude Mythos 5.1 is identical to Fable 5.1, but it offers more permissive safeguards for vetted individuals and organizations" Then why does it have separate datapoints for Terminal Bench, and score higher? Something doesn't add up here??

Artificial Analysis at least reports the results with fallback to an inferior model. So presumably Opus 5, and the score should be between Mythos 5.1 and that other model.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#240

Post by dezgeg »

Trasmatta wrote: post #95
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…

> More work to be done (and we will!) but reading better prose makes me so much happier. I assume this work will be done for Opus as well? Opus has seemingly gotten progressively worse at its prose and technical writing with each version. I've stopped using Claude entirely for now, because it manages to turn even the simplest technical explanation into the most obtuse and obfuscated word salad imaginable. People orig…

Yeah, for all the hate Gemini gets, at least it isn't obsessed with adding comments and it's output is more readable than recent Claude's.
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