Claude Fable 5.1 and Claude Mythos 5.1

The safeguards and required extra retention is still not gone. Further more they are working to create separate tiers of access with the new biology program instead of giving everyone equal access to AI. Anthropic once again are showing they can not be trusted.

"Price. Fable 5.1 will cost an estimated 25% less than Fable 5 for typical workloads, wherever usage is billed by token. This is because we’re reducing our pricing on cache reads (where the model reads inputs that have already been processed and stored). For highly agentic work, the savings will often be much larger—up to approximately 45%."

They show this off, but artificial analysis contradicts the statement. Fable 5 cost $3.14 per task, while 5.1 cost $3.69 -- around a 15% jump in pricing.

https://artificialanalysis.ai/

These, IMO, are marginal improvements for a more expensive model. I stopped using Claude ~3 months back; its outputs are too jargoned, it makes architectural decisions that are not right, and it's incredibly pricey for what it is. Each decision it makes, it acts as if a problem as major as world hunger has been solved. And the overly verbose code comments, strange commit descriptions, duplicate code, and slop it generates -- which I know is not specific to Fable -- is just too much for me.

I found the best is to use something like Deepseek V4 Flash -- with a fast TPS provider -- and work on the code myself. For agentic work with computer use, GLM 5.3 flash with Hermes Desktop works well.

The most remarkable thing here is just how close Opus 5 is on most of these benchmarks.

"Democratization" through AI means that everyone has to pay a monthly Anthropic tax and only a small secret guild gets access to the real model.

Jane Street is a partner? How sad indeed. Anthropic could front run them because they leak all the data.

Strange that the system card carefully seems to avoid any benchmark where you can also find scores for GLM, Qwen. There's barely any overlap with GPT 5.6 benchmarks. Just these:

    Model              HLE w/tools   GDPval-AA v2 
    Claude Fable 5.1   65.0          1853
    GPT-5.6 Sol        64.5          ~1711-1730
    GLM-5.3            62.5          1769
    DeepSeek V4 Pro    60.0          1590
    Kimi K3            59.8          1682
    Qwen3.8-Max        56.2          1739

Should've just named them both Guardrails 5.1 and be done with it.

> The watermark doesn't change the meaning, quality, or readability of the output

how?

the counterbalance to the AI doomers has always been the fact that everyone has equal access to AI. i hate this new world where Anthropic believe they should be the ones to decide who gets access to super intelligence and who doesn't.

Don't care unless it is priced in as other models.

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.

Why would anyone use Antropic with these prices and full of bullshit safeguards, where chinese models rarely have any at all and massively cheaper? You can't even ask it to pentest auth code it itself has written.

When is Astra launching?

$50/M output is wild as hell - I haven't been using anthropics models for months now but who is paying for these tokens??? How can you justify spending that much money?

Interesting that they seem to have gone all-in on science, and life sciences in particular. Improvements to coding performance seem marginal, although cost savings are very welcome.

Curious to see how Astra does.

> Enterprise Frontier Safeguards (EFS)

Sounds like some serious nonsense. "Tell me you want the government to retain access to my data without saying it explicitly."

Looks like agentic coding plateaued, and agentic scientific research is the new hype?

> Denser prose in places.

Really? Interesting choice. Pretty much every CLAUDE.md file I have starts with something about Hemingway, terseness and treating every word you use like you're carving it on your own back, but different strokes for different folks. I suppose I haven't heard from anyone who enjoys how wordy Claude is because they aren't done writing their post yet.

This seems like a welcome change: Claude Fable 5.1 also supports changing effort mid-conversation with a per-message output_config, which preserves the prompt cache.

Unfortunately, I just canceled my max account.

Unfortunately, for them.

I think what’s the industry is interested to see now isn’t “the best and latest super intelligent frontier model ever!!”, but rather the ability to run good enough models locally or better, on consumer or laptop grade specs. So I am not that impressed, plus haven’t used Claude for a while nor planning to, their models are useless with their “safe guards”.

According to Artificial Analysis, 5.1 cost 56% MORE than 5, $8523 vs $5455. Yes cache cost is lower but it was MUCH more verbose: 140M vs 83M output tokens.

This directly contradicts what Anthropic is presenting here. Yes it scores higher but that's to be expected from a new release. It's the opposite of what OpenAI has been doing which was reducing costs, increasing efficiency.

Fable 5: https://artificialanalysis.ai/models/claude-fable-5 Fable 5.1: https://artificialanalysis.ai/models/claude-fable-5-1

> Hey Cl… Your limit has been reached.

Goes to show what a farce the supposed paradigm shift from Mythos and Fable was. All marketing, as always.

> Claude Fable 5.1 follows explicit tool instructions reliably.

Moving stuff out the API into prompt engineering is obviously less reliable but necessary for progression to 'actual intelligence'. Will be interesting to see if it really is solid.

At least half the changes are just anti-distillation strategies...

Thank the heavens for quota resets

I am not sure if Fable is worth it, at least with version 5 vs Opus 5. Opus beats Fable in quite a few benchmarks and at twice the cost I just haven't seen it provide noticeably better results compared to Opus. Has anyone noticed big differences? I did notice Opus maybe making more mistakes repeatedly but I don't have hard numbers on this. I hope Fable 5.1 brings noticeable improvements. I am giving it a go now on my 20x Max plan on a problem that Opus 5 has struggled for more than week now and has made very slow progress with regular regressions on the way.

The biggest change is the price cut of course.

This feels kind of petty, but what is going on with those fuckass clouds in the background? Did no one notice how uncanny that whole thing looks?

Zero data retention coming soon!

... with the condition that you store 100% of your data and make it available to the US government and possible others.

The guardrails are horrendous for cybersecurity. you will get booted quickly down to Opus 4.8

Reads like AI slop, surprised they can’t see it in their blog post. No human wants to read in such prose

Has anyone been able to get anything substantial done with Fable in the first place? I more or less had totally given up on using it since the alignment checks were so sensitive that it pretty much always threw me back to Opus.

weary of trying this model out after the amount of requests Fable 5 sent to Opus 5 which created for a terrible UX IMO.

While haiku is almost one year old. What a joke

aaaaand its blocked from doing even basic tasks in biotech...

do you think we'll go a full year without a new haiku lol

So bullshit safeguards are still there.

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Hi Claude, please cure aging, make no mistakes

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