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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 #477

Earlier quoted context omitted.

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.

It has an effect, 50% of the time it's positive, increasing the quality of the answer, and 50% of the time it's negative.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#702

(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…

I support this pet theory, I tried out to reduce the output of Claude models with a "ADHD" prompt that made its responses small and to the point, but I could notice it degraded in performance as the session went on.

So I think what is going on is that because responses are part of the context window, those long/technical responses help it keep focus/attention.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#703

(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

#704
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

#705

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

#706
post #468

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

#707
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

#708
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

#709

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

#710
post #569

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…

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