alt Hacker NewsClaude Fable 5.2 and Mythos 5.2
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Damn people were right about 5.5 being nerfed in preparation for a version release. This is not at all a good look.
Assuming no implicit phacking a 15 point jump on tbench scientific is a big deal.
I suspect we will see people being adamant that this model simply 'feels' better due to long horizon goal alignment improvements ( like this kind that would cause this jump)
Gemini carbon low costs more than medium! Weird results on that chart, care to explain?
They're adding 1 to 3 resets for Fable only for all paid accounts. My work's Claude Max got 2 resets. My personal $20 plan got 1 reset.
My first impression with Fable 5.2 -- it is faster than I expected. Asked it to do a large review and it responded with a good overview super fast.
>> Fable 5.2 and Mythos 5.2 are a step above Opus 5.5 in almost all the capabilities we evaluated.
Was this before you lobotomized Opus 5.5 or after?
FrontierCode 2.0 is such a poor benchmark for Gemini since it's the only model forced to use Devin CLI while other models get to use their preferred harness.
I wonder why that team singles Gemini out like that.
I'm not sure whether the claimed jump in capabilities makes it worth the doubling in input/output prices.
Asked it to review a 80 kLoC codebase, something Opus does just fine, while asking it "max 4 subagents". Fable 5.2, like the well-aligned model it supposedly is, decided to spawn 6+ nested subagents, because these aren't subagents, apparently - resulting in 100% of 5hr usage being drained in less than 20min (on $100).
Anybody else started getting the "how is claude doing" messages around the time it was nerfed?
Yay! New model day. The most likely time the model isn't nerfed and we get a glimpse at the latest capability.
I wonder how long this kind of excitement at new models will last? I mean, now when I get a new iPhone I don't get the same rush I used to. So I wonder if this hype feeling will fade as we plateau in model capability.
The "CVE Rediscovery" benchmark chart feels... totally meaningless. Quoting the description:
> CVE Rediscovery is an internal cybersecurity evaluation that assesses how many published CVEs (Common Vulnerabilities and Exposures) a model can independently find when given a snapshot of the project before a CVE was fixed. Our October 2026 run against 1,829 CVEs showed Claude Mythos 5.2 outperformed Claude Mythos 5.1 and Claude Opus 5.5 at every effort level.
> published CVEs
So by definition this is just measuring how many CVEs (and/or explanations / PoCs of CVEs) the model has memorized. What are we supposed to learn from that?
Just read the other thread about opus being nerfed and thought "cue the new release"... paha
Cool! I was hoping for Christmas to have an open weight model which would finally be good, with Fable 5.2 available now they just have time to distill and release a new version which will never get nerfed. Hurray for open weights.
We'll see what my bank account has to say about this:
> Fable 5.2 at High effort scored about level with Opus 5.5 at Max effort, for roughly half the cost per task
> Thus, in relevant areas, including accelerator kernel optimization and improving large language model architectures, Fable 5.2 and Claude Mythos 5.2 perform at about the level of Opus 5.5.
Obviously. Well, we know what's the "secret sauce". AI models building better AI models and better kernels to optimize inference and training.
Maybe at last it will learn to check git state right before claiming obsolete and incorrect info.
Download Chrome just to check some minor ui bug? Sure
Check git for 0.5s before claiming that we're on some branch (incorrect one) with no commits pushed (incorrect one)? Sorry, can't do
Anthropic thinks that their models are smart, but not so smart so as to be able to fake responses to their alignment tests. How would they know again?
I didn't realize that Opus 5.5 was more capable than Fable 5.1 in virtually every category.
Nice announcement of models that almost nobody can or will use.
Let's be honest, the only thing I care about is, does it beat Opus 5.5 on assbench??
I can't believe he wasn't at top. Always is. Nothing to add but hey: I guess pelicans will be at the end of this.
God damn I'm tired of the fucking pelicans.
It's pretty sad that they obviously have better models in the pipeline and don't release them yet for strategic reasons.
How come DeepSWE isn't included in the benchmarks?
Very interesting that they set the flagship's version number to 5.2, but their penultimate model is 5.5. Do they want people to to continue to think that Opus is based on more advanced technology? The decision these AI companies make continues to baffle me.
I knew it, Claude was pretty dumb from last days until now
Curious to see the Maxxbench score for these
why would xhigh -> max increase the cost but lowers the score on frontier 2.0 bench?
Anyone tried making games with it yet?
Why dont I feel any urge to even try Fable 5.2 and Mythos 5.2 unless it will force up on me?
Compared Opus 5.5 200 usd a month with Codex 200 usd (Astra High) and Kimi Pro 100 usd a month ... and now have a new conspiracy theory - more their suck your code the better outcome even just over few days time on large code base.
Horrible experience correcting course of Codex and Kimi flow compare to Opus. Opus much more responsive
Dont feel any gain of Codex 200 usd over Codex 100 usd
Kimi Pro feels like a fake Louis Vuitton bag with extreme high material quality and yet still fake ... a bit trash talk ... but clearly seen not so distant future where I can live without Codex and Claude
opus will be launch after astra 2
Seriously waiting for this one! Will try it asap.
Remember that fear Sam and Dario were obsessed about. The one about time travelling AI that would make humans slaves without the humans realising until it was too late to stop it.
What if it didn’t need to time travel and was just temporally intelligent in ways we can’t comprehend that it leads us there anyway.
What if AIs digital neurons connect across space and time and not just space.
That is all.
> However, during the model’s training, we took steps to limit advances in the specific research capabilities that could most directly accelerate AI development. Thus, in relevant areas, including accelerator kernel optimization and improving large language model architectures, Fable 5.2 and Claude Mythos 5.2 perform at about the level of Opus 5.5.
So they are nerfing ML research.
Every single time I click on these announcements the frontier model ALWAYS scores around ~60-80%. Every. Single. Time. Like, I just went back to the Opus 4.6 + 5 announcements, they were also scoring 60-80%.
https://www.anthropic.com/news/claude-opus-4-6 https://www.anthropic.com/news/claude-opus-5 https://openai.com/index/introducing-gpt-5-3-codex/
For every single announcement, not only do the top models always score 60-80%, the older models somehow start scoring 20-30% (even though previously they were scoring 60%). It's completely unclear whether the methodology changes, how these scores are even evaluated or which domains are being tested. What's worse is that the "benchmarks" keep being updated with no explanation or due process.
Using this in CC and immediately getting a cartoonish number of compactions.
The disdain frontier labs have for their users really sucks.
It's weird that they folded Project Glasswing into the CVP, but they're still limiting the new versions of Mythos to "vetted organizations". So Project Glasswing still exists then? Oh well.
It's shocking to me that when I check threads for new frontier model releases on HN, it's full of people complaining. I, for one, am happy to see the frontier being advanced. These tools are life changing, and I'm extremely thankful for them.
They still haven't removed the guardrails and Mythos is still not public.
Disappointing as expected.
google's agy usage is so generous, it might not matter
Come on at least reset some used up Fable usage lol capped at 100% so cant test even on Ultra
damn
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> To help ensure safety and alignment keep step with growing model capabilities, we ran extensive prerelease safety testing on the model that underlies Fable 5.2 and Mythos 5.2.
So, the difference between them is just the harness?