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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

#902
post #520

I’ll be very excited to try it out and see the actual improvement in writing style. The denser writing style probably won’t bother me. Anthropic seems to be listening to community complaint on HN about how the writing style is grating. And apparently the solution from Anthropic is to add this block to every conversation!? > Mannered prose substitutes metaphor and flourish for direct statement. Instead of "a parameter…

> this point earns its keep.

This and 'load-bearing' anywhere are just awful. Anthropic would do well to stop inserting their poor writing taste into models.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#903

(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…

> People have been correctly excited about the many "sudden" breakthroughs LLMs are making in Maths That people ARE making, surely not machines. Like Terence Tao or Knuts did using the tool to their advantage, for example it would have been impossible for me to prove the same thing Tao did with an LLM. Same reason I believe programmers won't go away

This isn’t true in math; see the proof of Crouzeix’s conjecture which was done by GPT 5.6 Sol in response to a prompt from a neurosurgery resident who had no deep math background, was learning that subject to better understand radiology, and thought it sounded like a cool theorem.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#904

(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…

> similar developments in other scientific domains The classifier is too strict. It's rare to be able to complete a project without being permanently relegated to Opus. I'd expect that the domains where this accelerates progress will be fairly limited.

Yeah, this feature is only useful to scientists who work at institutions that have deals with Anthropic to use the models without the classifiers.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#905
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…

You know you can just... change this right? What a weird thing to cancel over. I have in my global CLAUDE.md something to the effect of I have ADHD and give me succinct responses with headings and lists etc, works great.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#906

(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…

Thank you for commenting here and having the guts to face the nerderati! I'm a Claude Max user. I've never been able to use Fable as my work in medical physics involves both particle physics, biochemistry and biology from Python bivitticus to clinical medicine. I am not a US citizen and work in Europe. Will Fable 5.1 work on any of my problems? Fable 5 refuses outright. Is there anyone I can ask for a review or adjus…

I’m in the US and my entire account became unusable for any type of questions with Fable because I had research questions about modeling antibody-antigen binding and abstract chemical dynamics. Nothing close to biosafety related, pure, basic textbook level biophysics. Had to cancel my Max plan and switch to OpenAI which so far has a much less ridiculous classifier.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#907

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…

The last time i ran into that issue it suggested to make sure that a Fable AGENT took over the long-horizon task because, for some reason, agents in a session don't get blocked for security reasons. This may not always be possible, but it worked for me.

Don't fall for this. Agents silently downgrade unless you explicitly block the behavior. I built a little harness for Chatgpt, grok and Claude to do design review feedback rounds where one holds the pen and the other 2 send feedback, then rotate if no convergence. I built a thing into it to track if model swaps happen. Happens to Claude all the time. The other two, never.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#908

Earlier quoted context omitted.

> I am becoming dependent on AI to make a living IMO, if you depend on AI to make a living, I'd invest in hardware for local inference, and learn on how to effectively make a living using AI inference you control, on hardware you control. Sure, economically speaking it's way cheaper to use one of these heavily subsidised services (for now), and their models are faster and more capable, but if your livelihood depends…

It's okay to be a prepper, but you don't have to be. Assuming access to internet, water, electricity and increasingly AI is a entirely fine way to live. It might not be anthropic which you will want to use but current capability models will be abundant and access readily available.

I don't read that recommendation as prepping. If I were to start an earthworks business I likely would rent heavy equipment at first, but once I get the business going I'd likely begin to buy my own machines.

That's not prepping in the sense of having a bunker full of canned beans. Its taking control of a key piece of my business, and likely saving money in the long run.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#909

(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 quit your job? You guys are destroying everything good about life for little payoff except to yourselves.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#910
post #304
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!

I find it interesting that you put the instruction ("animate this") in the system prompt, while the prompt just had the existing SVG and no actual instructions on what to do with it. Anthropic's consumer-facing tools generally don't let you do this, unless maybe you're particularly clever with Claude Code command line flags (you can start Claude Code with a custom system prompt).

Do you think this had a substantial effect on the output?

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