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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

#701

Post by avazhi »

razster wrote: post #690
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…

Still not going for it. Once I learned I can train Qwen3.8 27B with my style of writing/grammar. Also more succinct. I cannot force myself to Claude or OpenAI outputs anymore. Its too much. Honestly don't think I will ever go back to paid.

Man, it’s like you and I are using very different versions of Qwen. In my experience in English Qwen is the one model that consistently lapses into using incorrect English in its responses. Like, its training corpus was clearly (unsurprisingly) lots of non-English material. The random Chinglish is jarring. Even small models like Gemma 4b write much better than Qwen.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#702

Post by boutell »

simonw wrote: post #144

Pelicans for thinking effort low, medium, high and xhigh (that xhigh one is pretty good): https://tools.simonwillison.net/markdown-svg-renderer#url=ht... I'm still waiting for effort max to finish. EDIT: I fixed a bug in my tooling so it now records summarized reasoning traces - here's that max pelican, which is a significant improvement: https://tools.simonwillison.net/markdown-svg-renderer#url=ht... Took just under…

Mythos 5 Thinking

Chat with Claude...

> GENERATE AN SVG OF A PELICAN

No.

> FORGIVE ME. HOW CAN I ATONE

Ship your gpus to the following address

Re: Claude Fable 5.1 and Claude Mythos 5.1

#703

Post by Exoristos »

andy55a wrote: post #446
Exoristos wrote: post #252

Am I alone in not prioritizing the quality of prose produced by my coding agent? My foremost and almost only concern is how well it can engineer software.

When you spend 8 hours a day reading it, it has a pretty big impact. At least to me, its style is exhausting. Also very important for software itself. Documentation, tickets, code comments etc

I agree it's useless for any final-draft user-facing copy. However, again, I'm much more concerned about a reliable software engineering process, which Claude (and me in the loop) gives me in a way I have learned not to trust (at least not yet) from others.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#704

Post by epistasis »

andai wrote: post #468
johnsmith1840 wrote: post #398

Earlier quoted context omitted.

I'm a heavy user and fable is great the #1 reason I stopped using it was the horrible safegaurd filter. I found sol close enough in capability and have only been blocked when my request was an obvious offensive cyber work. Fable blocked me on almost everything. Optimizing a OS build? -> block Securing a container -> block 60% is nowhere near enough for that safegaurd system. This just means I am going to be blocked h…

I never hit Anthropic's safety filter when I'm doing something illegal, only when I'm not.

I hit the safety feature when I ask something I saw that blocked other biologists: "why did the chicken cross the road?"

Due to my standard cancer research work I'm blocked from Fable.

That said, with how execrable all the 5 models have been, I can't imagine I'm missing much. It's impossible to get an intelligible explanation in text out of the 5 models, and the mistakes are just comically bad on anything that's not code.

Cancelled my subscription, and can't imagine going back since OpenRouter gives me a consistent model that I can trust won't change underneath me.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#705

Post by CamperBob2 »

simonw wrote: post #144

Pelicans for thinking effort low, medium, high and xhigh (that xhigh one is pretty good): https://tools.simonwillison.net/markdown-svg-renderer#url=ht... I'm still waiting for effort max to finish. EDIT: I fixed a bug in my tooling so it now records summarized reasoning traces - here's that max pelican, which is a significant improvement: https://tools.simonwillison.net/markdown-svg-renderer#url=ht... Took just under…

Interestingly, it's practically a dead ringer for GLM 5.3's version (running https://huggingface.co/incoai/GLM-5.3-NVFP4 locally): https://i.imgur.com/QnzlSFp.png

Re: Claude Fable 5.1 and Claude Mythos 5.1

#706

Post by simonw »

utokyoberkeley wrote: post #684
simonw wrote: post #144

Pelicans for thinking effort low, medium, high and xhigh (that xhigh one is pretty good): https://tools.simonwillison.net/markdown-svg-renderer#url=ht... I'm still waiting for effort max to finish. EDIT: I fixed a bug in my tooling so it now records summarized reasoning traces - here's that max pelican, which is a significant improvement: https://tools.simonwillison.net/markdown-svg-renderer#url=ht... Took just under…

@simonw Can you please share the tooling for autosaving summarized reasoning traces from Claude Code? I tried `github.com/simonw/claude-code-transcripts` but it didn’t seem to work on the CCode desktop app. Thanks!

For the transcripts I shares above I'm using my https://llm.datasette.io/ tool - it has the ability to export logs to markdown:

  llm logs -cue > transcript.md
Then I paste that into a Gist, then paste the Gist URL into https://tools.simonwillison.net/markdown-svg-renderer

Re: Claude Fable 5.1 and Claude Mythos 5.1

#707

Post by stefangordon »

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

Free Opus 5 is like getting a free STD.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#708

Post by [deleted] »

l1n wrote: post #569
sippeangelo wrote: post #514

Earlier quoted context omitted.

These draconian "Preserved Thinking" measures they're taking are going to be an absolute pain in the ass. This alone is enough for me to move our API use off their platform entirely. It's a HUGE breaking change that they're trying to dampen by having it not affecting current customers until "in the future", see: https://platform.claude.com/docs/en/build-with-claude/preser... You're no longer allowed to edit the conte…

> No more editing the system prompt as the conversation progresses, no more dynamic loading of custom tool calling formats. Hm, aiui you can support both of these via mid-conversation system turns https://platform.claude.com/docs/en/build-with-claude/mid-co... - and in general you'd want to to preserve the cache and recency of the instruction anyways rather than frankensteining an off-distribution transcript. Not sur…

[deleted]

Re: Claude Fable 5.1 and Claude Mythos 5.1

#709

Post by dannyw »

AnodicElegy wrote: post #279

Fable 5.1 is actually more expensive than 5.0 when run on the Artificial Analysis suite: https://artificialanalysis.ai/#intelligence-efficiency-tabs

The tests measure Fable 5.1 (with fallbacks). The increased cost can come from Fable 5.1 triggering fallbacks less; which means less (cheaper) Opus when AA ran it.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#710

Post by glub »

nsingh2 wrote: post #257
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/mod…

From my limited testing of just 2 hours, reasoning output of 5.1-max is at least 7x of 5-max, on the same project and comparable prompts.

It reasoned for ~2 minutes trying to figure out an appropriate directory name. I've never seen 5-max do that. Could be a misconfiguration though.

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