Claude Fable 5.1 and Claude Mythos 5.1 • Hacker News Board

Re: Claude Fable 5.1 and Claude Mythos 5.1

#751

Post by enraged_camel » Wed, Sep 02, 2026, 3:42 AM UTC

Thaxll wrote: post #747

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.

You have a serious engineering problem if you're not able to find the source of a crash after years.

You are either seriously naive, or have never worked on any large and complex legacy codebase.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#752

Post by anyg » Wed, Sep 02, 2026, 3:47 AM UTC

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…

The biggest issue i found was the gap between the tire and rim. Otherwise, the max version is the best so far!

Re: Claude Fable 5.1 and Claude Mythos 5.1

#753

Post by freakynit » Wed, Sep 02, 2026, 3:53 AM UTC

"In biology, we’ve established an access program, developed in partnership with the US government, to enable access to Claude Mythos 5.1’s advanced biology capabilities"

Having lived through Covid, this doesn't sound so good to me.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#754

Post by parineum » Wed, Sep 02, 2026, 3:56 AM UTC

mchinen wrote: post #456

binarymax wrote: post #367

Earlier quoted context omitted.

Do you think model trainers are pelicanmaxxing now?

There was a real probe into this, seems like no: https://dylancastillo.co/posts/pelicanmaxxing.html https://news.ycombinator.com/item?id=49010129

I don't really see how replacing the vehicle and the animal is a good test.

It'd be better to just have it draw a completely, linguistically, unrelated scene.

Like, a single tree in a meadow bending in the wind.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#755

Post by monkpit » Wed, Sep 02, 2026, 3:57 AM UTC

mkl wrote: post #681

reaperducer wrote: post #604

Earlier quoted context omitted.

A pelican is a bird, not a person. The knees bend the other way.

I get what you mean, but those are the ankles. The knees are higher up and bend the same way as a person's. https://en.wikipedia.org/wiki/Bird_feet_and_legs

https://en.wikipedia.org/wiki/File:Bird_leg_and_pelvic_girdl...

A bit more direct

Re: Claude Fable 5.1 and Claude Mythos 5.1

#756

Post by supern0va » Wed, Sep 02, 2026, 4:02 AM UTC

boardwaalk wrote: post #745

I let it go a few hours on a not trivial but well-known problem, and it felt like it was just a little too plodding and just kind of mucked around a little too much and wasn't aggressive enough about getting stuff done. I asked it to wind it down and finish up and it took another hour and 15 to actually stop and commit without really getting much more done. Not very impressed here, if you can't tell. This new version…

Compaction is a setting that you control in Claude Code.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#757

Post by vinhnx » Wed, Sep 02, 2026, 4:03 AM UTC

Worth noting: Claude Fable 5.1 and Mythos 5.1 are Anthropic’s first models to watermark text outputs.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#758

Post by oliver236 » Wed, Sep 02, 2026, 4:06 AM UTC

kilroy123 wrote: post #651

madrox wrote: post #405

I am finding that I am now less interested in better models than I am in token budgets. My issue with Anthropic models now is that I don't feel like I can rely on them as a daily driver because they'll dry up before my quota resets. I am becoming dependent on AI to make a living, and I need predictable spend on it. If I know I can't use a model regularly all month, my enthusiasm is limited. I urge Anthropic to get be…

I literally only make it halfway through the week until my weekly usage runs out. This is using only Opus, no fable, and I'm on the max x20 plan. It's become ridiculous.

just buy two 20x, no?

Re: Claude Fable 5.1 and Claude Mythos 5.1

#759

Post by genxy » Wed, Sep 02, 2026, 4:10 AM UTC

This change was for them, not us. I am touching grass until next week while they get this shit sorted out. Not on my time.

Re: Claude Fable 5.1 and Claude Mythos 5.1

#760

Post by noduerme » Wed, Sep 02, 2026, 4:12 AM UTC

supermdguy wrote: post #560

noduerme wrote: post #522

I'm confused about Anthropic's pricing. Can anyone explain why Sonner 5 is $2/MTok in and Sonnet 4.6 is still $3?

They originally released it at a "temporary discounted price", then made it permanent (probably due to competitive pressure). It's still way more expensive per task, due to tokenizer changes and general verbosity.

Is it? I just did a test switch over. For my personal needs I set up a box with OpenClaw back in March, which feels like a million years ago, that's been running Sonnet 4.6 since then. With all the caching it seems like my actual cost has come out around $1 per MTok on that. I just updated my whole setup today to try Sonnet 5... so far it looks like it's using fewer tokens for similar tasks, but it's only been half a day. I'm not super interested in changing harnesses, I realize this might not be the cheapest way but I've sorta come to enjoy OpenClaw... it's relatively effortless and responsive, and brief, given full control of a machine. And it does seem to incur some significant savings with the way it manages to keep things cached.

What would you suggest as an alternative if I'm happy with the harness?