Comment by GodelNumbering
13 hours ago
The price reduction comes from the cache read pricing falling from $1/M to $0.25/M, which means that Fable 5.1 now costs half of Opus's cache read costs ($0.5/M).
This gives a lot of credit to the theory that Anthropic did not get much bite on Fable at its original pricing, which in turn likely places a ceiling on LLM pricing in general.
Interestingly also, if you take away terminal-Bench-Science 0.1 results, it is hard to see ANY improvement:
Terminal-Bench 4.0: Fable 5.1 is +3.5% vs Opus 5.
GDPval-AA v2: +1.5% vs Opus 5.
OSWorld 2.0: +2.5% vs Opus 5.
Humanity's Last Exam (with tools): +1.6%
Keep in mind that this is supposed to be an entirely higher tier of a model than Opus 5. For one tier up and one version up, these are not really improvements. Probably leaves no room to place Opus 5.1 anywhere. Combined with the fact that they are selling 'readability'... Has frontier progress finally stalled?
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 half as much? Any long running task will likely get blocked.
Say you give a single big prompt and fable goes off for 6hrs of work. At hr 5 it gets blocked you now have the option of a much dumber model taking over and wrecking it or losing the entire 5hrs of work. That risk is beyond terrible and deffinetly not worth a 5-10% percieved improvement on my end. I previously would just bring sol in when that happened and realized sol is stupidly close in capability.
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.
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Honestly, unless what you are doing is frankly illegal, it usually is possible for you to get around most safeguards for coding things if you also know how to write code. Most problems have a separable completely innocuous core that Fable would gladly do. Then you can implement the problematic parts yourself. Particularly things like copyright issues, web scraping etc.
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It dramatically improved about a week ago - most of my blocked projects are now completely functional.
The safety filter is simply no longer an issue.
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.
That's a good idea but it works from the change in context no? So you lose context from your big model. It's a good suggestion though.
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Do you have the prompt for these? I ask because I have recently asked Fable's help with hardening a docker container (custom dev container CC sandbox) and it didn't get triggered on it at all.
The blocks that fustrate me more are tool permisissions. I ask to do something then flip to another screen and come back to see it never started
Auto permission is what ya need.
> Optimizing a OS build? -> block
Why would fable block optimizing an OS build
From Artificial Analysis cost per task, it looks like Fable 5.1 (max) is more expensive per task than Fable 5 (max)? Cache hit price went down, but the other components still add up to more.
Edit: 5.1-xhigh seems to be cheaper than 5-max, and 5.1-xhigh has a higher index score than 5-max. Also interesting that Fable 5.1 (high) is comparable to Opus 5 (max), but nearly half the price.
https://artificialanalysis.ai/models#cost-tabs
From my limited testing of just 2 hours, reasoning output of 5.1-max is at least 7x of 5-max, on the same project and comparable prompts.
It reasoned for ~2 minutes trying to figure out an appropriate directory name. I've never seen 5-max do that. Could be a misconfiguration though.
I did a bunch of Fable 5.1 xhigh review work on a bunch of critical components, ones with direct comparison from Fable 5 xhigh runs from two weeks ago. Token cost was 1.5-2x for each component.
I haven't dug deep but I burned through 30% of my weekly usage in a few hours which shocked me at first.
Interesting, even if we were to ignore the cache-hits, reads and output, the reasoning cost (aka test time compute) per task should remain a fully comparable metric - it went from $1.25 (Fable5) to $1.48 (+18.4%) for an improvement significantly lower than 18%.
I would expect the benchmark scores to be nonlinear near the top, as the easier tasks get solved and the harder ones are left over. So going from 10 to 15 would be easier than going from 60 to 65.
I only take the Intelligence Index value roughly though. Considering they put Opus 5 (High) at the same level as Fable 5 (Max), I don't trust it that much.
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> Anthropic did not get much bite on Fable at its original pricing
I stopped using Fable because it kept stopping itself due to safeguards.
>Has frontier progress finally stalled?
It wouldn't surprise me if we start to see minimal performance gains from incremental changes to base models. It seems like the gains from the Opus 4.5+ incremental updates were a result of Anthropic learning a lot about post-training, the gains from RLVR, etc.
If new post-training techniques are seeing diminishing returns, we could just be back to waiting for new large pretraining runs at larger sizes for gains (even if those ultimately end up getting distilled down into smaller models because the economics for serving anything larger than Fable isn't practical).
it seems to me that OpenAI is the only actual lab that truly understands reasoning. they have the best reasoning efficiency, they get pretty uniform improvements with more reasoning compared to other labs. (theres been plenty of graphs where models do worse with more reasoning), and i suspect their models are a lot smaller than we think.
i think the next gen of openAI models are going to be quite insane tbh.
> Has frontier progress finally stalled?
From my experience using coding agents approximately 7 days per week for the past year and a half or so, we hit the top of the S curve about a year ago around Opus 4.5, and it’s mostly been harness and other tooling improvements since then with small percentage improvements coming from the actual models.
I was saying this already months before Fable dropped and thought from all the Mythos hype that maybe I was wrong…then Fable came out and was barely better than Opus 4.8.
Considering how many more parameters Fable is supposed to be than Opus, we seem to have hit a scaling limit at least with current transformer architecture considering how closely Fable and Opus benchmark and perform in practice.
Anthropic did not get much bite because they don’t offer zero data retention with fable
This is exactly the reason why fable is blocked at the company I work at.
The issue with many of these benchmarks is that it doesn’t take into the real world usage of the model. Fable for me was a step above opus. The real reason I stopped using it is because of misanthropic. I was hospitalized and asked to extend my claim to fable credits and they responded to it by denying it. I regret buying annual plan instead of monthly one.
It's because GPT Sol is equally good and established a price ceiling
Sol is excellent. I’m amazed I can use it on my teeny $20 plan.
> This gives a lot of credit to the theory that Anthropic did not get much bite on Fable at its original pricing, which in turn likely places a ceiling on LLM pricing in general.
Does that mean that generally available intelligence is now constrained by Moore's law? We have to wait for the actual price to come down.
> Probably leaves no room to place Opus 5.1 anywhere.
Well it'll probably be better than Fable again, lol
I haven’t yet had a week without spending my Max Fable allowance. For my work (formalised mathematics) Fable is my go to for hard(ish) tasks and problems – of which I have many!
I hope they keep making it smarter! (Cheaper would be nice too, but smarter is my priority!)
DeepSeek V4 Pro cache read pricing is $0.022 (offpeak) and
DeepSeek V4 Flash cache read pricing is $0.007
Makes it super affordable!
Huh! Yeah that feels more like an opus5.1 than a fable5.1.
Partially frontier moved to cost and speed axes.