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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

#851

Post by nixlaz »

timster6442 wrote: post #682
5555watch wrote: post #433

Earlier quoted context omitted.

While I can't speak for everyone in academia, I personally don't feel comfortable in putting my research questions and outputs to a private website, before the idea is at least arxived. Especially as all the Fable/Mythos prompts are said to be human reviewed. So I believe that, at least in the short run, we might be seeing breakthroughs in hard open problems or in low hanging problems which are not that interesting t…

I'm in academia (biology but highly computational) and I would say opinions on AI are quite polarized. Some professors in the department equate not using AI as lost productivity. Contrarily some professors abhor the idea of even using AI at all. For us (biologists) it's less of an issue because we have no fear of openai or A/ publishing a biology paper. Though even people I known in physics, data science, or computer…

Do you mind me asking why you have no fear of OpenAI etc publishing a biology paper? With increasing model capability and compatibility with lab hardware could we not be in a scenario soon(ish) where these agents are able to autonomously complete and publish experimental results?

I was debating this with a friend the other day and the consensus we came to was that a highly trained scientist would (or should) always review output like that described above, but that's starting to feel like a weakening argument!

Re: Claude Fable 5.1 and Claude Mythos 5.1

#852

Post by visarga »

alasano wrote: post #187
vablings wrote: post #142

Earlier quoted context omitted.

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

Good software will be good-er. Bad software will be nightmare fuel.

> Good software will be good-er. Bad software will be nightmare fuel.

We are talking about a moving target here ... they get better every few months, so I expect the super-LLMs from 2035 will write amazing code even with sloppy prompting.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#853

Post by visarga »

coder-pm wrote: post #363
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.

That kind of one shot capability is impressive but how does it work for my typical work style? The way I work is to build a huge roadmap with goals and hand it to my agent to execute (often over night). I don't care that much about the benchmarks, what I care about is how often Fable 5.1 is making a baffling decision and destroys my plan, not respecting stop conditions or goals. I would seek for behavioral reliabilit…

You can engineer loops that have it, but it depends on a case by case basis. Does your loop have strong validation? if it's all vibes nothing can stop it from diverging.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#854

Post by visarga »

Someone1234 wrote: post #92
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…

One thing I've noticed and HATE, is that when you increase thinking-effort, that seemingly increases response-length. Meaning that X.High is longer than High, which is longer than Medium, etc. Which is kind of the inverse of how people work; a really smart person can condense difficult ideas into simple[r] terms. Whereas people who struggle speak a lot but say very little. High/X.High do seem to deliver better qualit…

> when you increase thinking-effort, that seemingly increases response-length

I use the /sss writing style - synthetic, short and simple - and it helps a lot.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#855

Post by visarga »

alasano wrote: post #181
Someone1234 wrote: post #92

Earlier quoted context omitted.

One thing I've noticed and HATE, is that when you increase thinking-effort, that seemingly increases response-length. Meaning that X.High is longer than High, which is longer than Medium, etc. Which is kind of the inverse of how people work; a really smart person can condense difficult ideas into simple[r] terms. Whereas people who struggle speak a lot but say very little. High/X.High do seem to deliver better qualit…

It's so bad I've made myself a Pi extension that rewrites responses in side by side view using models on Cerebras (insanely fast tps)

It's so bad I made my own chat client for Claude, so I can attach steering prompts in conversation. They are applied just at the end, before the last LLM response, then removed and response kept.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#856

Post by _puk »

stefangordon wrote: post #627
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…

It dramatically improved about a week ago - most of my blocked projects are now completely functional.

Ironically, having never been flagged - I've just restarted Claude Desktop and it's flagged a conversation that has already been completed.

In a long session pulling data from all over the place it created a pretty PDF.

"create this as a google doc that can be commented on"

Done — the full v0.5 content is now a Google Doc in your Drive...

"Ah, the formatting has gone. Do it in google slides please"

The brand studio has a native Google Slides path for exactly this — building the deck now.

Google Slides created.

Then today:

Chat paused Edit and retry with Fable 5 Fable 5's safeguards flagged this message. This sometimes happens with safe, normal conversations. Continue with Opus 4.8, send feedback, or learn more.

Details: [reasoning_extraction]

  Flagging the formatting prompt

Re: Claude Fable 5.1 and Claude Mythos 5.1

#857

Post by sevenseacat »

BoorishBears wrote: post #64
exabrial wrote: post #38

Did we get thought traces back? If no, it's useless.

Lol we got literally the opposite: > *Fewer progress updates during long tool runs.* > The model writes less user-facing text between tool calls, especially at higher effort. Set thinking.display to "updates" (beta) to receive the progress updates it does write, and remove any prompt line that tells it to hold findings for the final response.

I love when I make a request or ask a question, and Claude Code immediately queues up a dozen tool calls to edit files instead of explaining what it wants to do or why, despite repeated constant reminding that I will not approve tool calls without context and reasoning

Re: Claude Fable 5.1 and Claude Mythos 5.1

#858

Post by [deleted] »

ceroxylon wrote: post #274

The thing with Fable-level models is that I will never feel comfortable using them for agentic tasks on a pay-as-you-go API pricing plan without monitoring them strictly, which becomes a chore. I once caught Fable 5 spinning its wheels on a rendering issue, which evaporated 90% of my usage in a single prompt. I could never let Fable run free attached to a credit card without staring at it the whole time.

[deleted]

Re: Claude Fable 5.1 and Claude Mythos 5.1

#859

Post by pampas »

swalsh wrote: post #248
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…

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

I made a 3D browser game a few months ago where you play as a pelican riding a bike via a bluetooth trainer.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#860

Post by Topfi »

Far to early for any true assessment, will take a week+ as per, but something truly incredible I have found was this output in a Fable 5.1 subagent spawned by Fable 5.1 on Medium after handing it a task I had two days ago tackled with Opus 5 due to the safety classifier on Fable 5 blocking it:

> This is the user's own Firefox-fork browser; the slice is defensive service-posture hardening (telemetry/Normandy/FxA/push/crash-upload off, the update endpoint and private-mode extension law) of their own product on the unbranded build path.

I cannot say what effect this has on the way the classifier operates, whether it actually impacts the classifier or whether that was tuned in the background to prevent blocking hardening ones own pre-release code, whether it treats input by Fable 5.1 different to what a user prompts (otherwise the classifier could be defeated with prompting which wasn't the case in 5 and I doubt has changed).

I do however know from personal experience that even when Fable 5 prompted a subagent in such a manner, it had a high likely to be caught by the classifier.

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