upvote
A lot of AI stuff is like that, actually. GPT 2 and 3 were mainly curiosities that would get articles on tech news sites but didn’t attract much attention from the general public. But after RLHF the UX improved dramatically and ChatGPT became mainstream. A lot of MLEs underestimate how much UX matters, and the same is true for Jev.

> how do these models calculate probabilities?

The short answer is: more and better data.

The long answer is: probably the same way any other classifier does. Take your ground truth probabilities and your predicted probabilities. The gap between those is called cross entropy, which is used to push the model towards the correct probabilities.

reply
> which is used to push the model towards the correct probabilities.

The definition of "correct probability" here is usually "p=1 for the ground truth label, p=0 for all others." Which seems like an intuitive approach but if you actually think about it doesn't trivially imply the model would learn sensible distributions under uncertainty.

reply
deleted
reply
Wouldn't learning a calibrated probability distribution just be a consequence of the CE loss being a proper scoring rule? So, by construction, they are approximating the distribution of the labels. Of course in practice there might be issues with overfitting the log-likelihood and the with the labels being a finite sample of the population distribution
reply
Yes, in a sense, with some important caveats. Cross-entropy will tend to yield reasonable marginal (i.e., not class-wise, not approximately conditional) calibration for in-distribution (i.i.d. data). The challenge with LMs, and neural networks more generally, is that the resulting estimators that are based on the output logits are very brittle to covariate shifts and out-of-distribution data, and that for real applications, we often need robust estimates in high-probability regions (e.g., of class- and prediction-conditional accuracy at least some value near 1) for conditional-branching decisions (by a human or a model). (ECE is the wrong metric for that quantity.)

The various decision APIs don't give you that, and would themselves need to be recalibrated with constraints in feature-representation space over the applicable reference class, as with https://pypi.org/project/reexpress-sdm/.

reply
For a single prediction, sure. But the model doesn't make a single prediction and then stop existing. It makes an unbounded number of future predictions and under that assumption it is reasonable to expect the model to behave optimally under Bayes rule - which has a unique global minimizer at E[(Y-F(X))^2].

So counter to your claim that "It doesn't trivially imply that the model would learn sensible distributions under uncertainty" I think you need to consider what it means to optimally update a posterior under the global minimizer of the true conditional distribution.

reply
The thing I had to wrap my head around is: For a "classic" classifier, the classes are fixed and the data distribution is p(x,y). The calibration is checked over this single distribution. Jev makes the tasks part of the input, so the data distribution is p(task,x,y) and calibration is averaged over that joint distribution. What follows is that while for classic classifiers, calibration brakes down if your x was out-of-distribution, it can now also break if your task is out of distribution. The big question now is: Can subtle differences in phrasing your task already lead to this? And the only way to verify calibration is having ground truth data to validate on. Also: Calibration over p(task, x, y) means calibrated on average across tasks. Even an in-distribution task can be over- or underconfident while the average looks fine.
reply
> And the only way to verify calibration is having ground truth data to validate on

I’m not sure that’s true in real cases.

I would expect that in distribution tasks have quite consistent outcomes with variations on phrasing. I would expect that to be much less true when tasks are out of distribution. So could we randomly adjust phrasing and see how much the results change - looking less for truth but consistency?

reply
A model can be consistently over- or under-confident for similar inputs. The only way to check if it's actually calibrated is to compare against some known ground truth. I don't see any way around that.
reply
In my experience, calibration is only ever in expectation, even for a classic classifier. Any given prediction is often still over- or under-confident.
reply
> It makes an unbounded number of future predictions

nit: it's trained on finitely many samples.

> So counter to your claim that "It doesn't trivially imply that the model would learn sensible distributions under uncertainty" I think you need to consider what it means to optimally update a posterior under the global minimizer of the true conditional distribution.

Huh? That's not counter to anything I said. All I said was it's not trivially implied.

reply
From what I’ve gathered, it doesn’t work at all like a normal classifier. As in, for a classifier you’d train it for a specific task to reduce the cross entropy. So, in a hand-wavy way “the model knows the truth”. For Jev-type models it’s more like an LLM, in the sense that the “truth” is in the context you provide. But instead of producing a completion it fills in the schema. But it’s always - “given the context, the schema needs to be filled in like this”
reply
as s.o. who registered their chatgpt account on the third day after they released, I can tell you chatgpt actually became mainstream overnight.
reply
3.5, not 3
reply
> A lot of AI stuff is like that, actually.

Chain of thought was that way. DeepSeek came out, and not long thereafter everyone had adopted chain of thought.

reply
Unless I am misunderstanding you then I don't think this is correct. Chain of thought was first proposed in 2022. Assuming you mean reasoning models then the correct comparison is GPT-o1, which came out in September 2024, 2 months prior to R1 lite preview. In the next 2 months, prior to the release of the full R1 model, both qwen and gemini released reasoning models. Dario explicitly notes in early 2025 that most major labs had been working on reasoning models in 2024, and explicitly credits OAI for pulling things forward with their release.

https://darioamodei.com/post/on-deepseek-and-export-controls

> In 2024, the idea of using reinforcement learning (RL) to train models to generate chains of thought has become a new focus of scaling. Anthropic, DeepSeek, and many other companies (perhaps most notably OpenAI who released their o1-preview model in September) have found that this training greatly increases performance on certain select, objectively measurable tasks like math, coding competitions, and on reasoning that resembles these tasks.

reply
CoT is far older than DeepSeek.

I remember adding it to GPT-3.0 and getting a big boost in accuracy. It was like magic.

And then we would handcraft thoughts and inject that into the prompt so the model thinks its owns thoughts and would follow instructions much more precisely.

This was well before reasoning models, even before chat models.

reply
I wasn't suggesting they invented it. I was suggesting that they popularized it, made a huge amount of noise about it, and it seemed like after they did, there was a lot more attention on it.
reply
I think if you were paying attention at the time, CoT and ReAct loops were already "well known". Lots of GPT wrappers at the time were doing it, I remember doing CoT to help measure the calories for a recipe. The problem is tokens then were quite expensive and doing experimentation on it was pretty expensive for an individual. I once accidentally spent $20 trying to categorize a Who's Hiring post from here lol.

It was a short-lived time though. I think only a few months before Deepseek really RLed the reasoning which produced much better reasoning than just prompting a CoT out of the model.

reply
Is this true? I don't remember this and looking back it appears that Google came up with it and openai was the first to release a commercial model.
reply
Dont under estimate the power of branding/positioning/marketing. For more than a year I have been using a RL'd Qwen fine tune optimised for just taking a decision and outputting the decision number, initially I didnt have much training data so after a few manual examples I asked deepseek to make them for me and had codex train it. I compared it to jev when it first came out and it was mostly neck and neck for my use case. I can't have been the only one in fact, I'm sure there must have been other people who probably even open sourced, but I couldn't find anything. I think the question going forward will be how does one keep abreast of interesting stuff happening, now that its de-coupled from direct human labour so de-bottlenecked on production capacity - just bound by how residual time/attention one has (Terence Tao was talking about this exact predicament in the latest tyler cowen podcast).

The natural path of things, I suppose, is those that have a soapbox/distribution will just get larger...

reply
> Dont under estimate the power of branding/positioning/marketing.

You're leaving out the UX (DX, developer experience) in this.

And the better zero-shot performance when you don't have a dataset yet (could argue this falls under DX).

Not to mention the faster time-to-decision and order-of-magnitude cheaper costs.

reply
you should write a blog post about it
reply
I think its more like how LLMs caught everyone by surprise. A reasonable person would not think such a simple system would have been this effective, and yet here we are. Distilling that system down even further into a decision model again does not seem like it should work. But it seems to.

The whole system is foreign to us, and makes us rethink what "intelligence" actually is.

reply
That's how the original Transformer architecture (LaMDA) should have been released back in the day, but Google thought it would cannibalize their search revenue.
reply
Basically there is a whole host of tarpit usage of LLMs in application backends today. This is simply another case of LLMs enabling people to build what they cannot productionize or maintain.

Today developers without any AI/ML skillset can prototype a fancy new feature with LLMs, what used to require collecting and curating data to train a pipeline of ML models then serving them in production.

The problem comes when it's time to take the new feature into production. That $20 cost with prototype/beta workload is now $30k per month in LLM costs, and those hallucinations that never happened on their 200 test samples is happening 600 times per day.

They are then stuck, because they lack the knowledge and budget to build and run the production ML pipeline properly, the infra stack necessary to handle production workload. Management also doesn't understand why they have to invest in rebuilding something that "seems to work" with "outdated methods".

These system one or decision models are a step up from LLMs when it comes to this usage. Problem is that they are still difficult to work with (limited in expression power) for many application logic. Despite the initial popularity, I hear about a lot of frictions refactoring LLM based backend with them, and multiple cases of production rollbacks to LLMs already.

I think system one models is a sensible paradigm, but there is a lot more work needed above the model layer to make this work.

reply
That also makes me wonder: what other things are achieved by now and are up for grabs, and that will seem obvious in retrospect, but we don't notice it yet?

Roughly speaking, has AGI actually been achieved two years ago and we go around don't noticing that?

reply
> Which makes me wonder: how do these models calculate probabilities?

By unprincipled methods. To calibrate confidence in an answer you need a task specific calibration set. You can't pre-calibrate for tasks unknown ahead of time, which is the case for most uses of decision models.

reply
In some sense everything an LLM does is by unprincipled methods. But it works! We judge it empirically post hoc by its performance rather than relying on tuning.

Hell, human thinking is unprincipled in basically the exact same way.

reply
We were doing zero and few-shot classification with LLMs since before they could reliably complete whole sentences. It’s an easier task than generating coherent text. The model needed to be tuned for classification (not generation) and for the domain, but it would often succeed at new classification tasks with a simple description.

I guess given the huge advances in LLM since then, these models probably achieve much better accuracy on a wide range of domains with lower effort compared to what we were doing, which makes it compelling as a product. And yeah, the models probably were already good enough a few years ago too. Other factors include how easy it is to release products at high speed now, and the desire in the industry to reduce token spend.

reply
Zero-shot encoders even pre-date LLMs. People who worked in NLP in the transformers "BERT-era" may be familiar with natural language inference (NLI).

Decision models are really not much different than that, but (usually) scaled up to bigger causal models.

If you are looking to do Jev-like things with smaller models, check into NLI.

reply
You can do it with LLMs by looking at the logprobs of ('yes', 'Yes', 'YES'...) vs. ('no'...). This works for bool or whatever they call it in jev space nool I think?

You can do it manually or use ready made libs. I know there's one in python on top of vllm that can do something like this.

reply
LLM token probabilities are really poorly calibrated for decision making.

Every time I see someone saying something like "isn't this just structured output?", it's because they don't understand that probability calibration is one of the most important parts of the product, especially to understand uncertainty.

I think Jev did a pretty good job on calibration. I wonder how the fast-follow competition from OpenAI and Gemini do.

reply
Right, that's always been true for LLMs + constrained generation. It ensures syntactic correctness, but semantics are "best effort".
reply
Not reliably - look at microsoft's guidance project that did some of this.

Once a model goes through instruction fine tuning and RLVR/RLHF the log probs decorrelate from what's ground truth (given the propensity of the data seen during training)

reply
But I assume it wouldn't take much more training to make them good again - just a matter of picking the right loss function, since this sort of stuff is probably all encoded in the last layer or two anyway.
reply
I'm pretty sure these models also went through RL post-training, the question you ask still needs to be interpreted as an instruction.
reply
> I'm sort of surprised it took Jev for everyone to realize "oh yeah, this is a useful thing that we should have in our product portfolio".

Because it's especially parsimonious with token use.

reply
Why introduce a feature that would cut token use by 1000x?
reply
OpenAI was already working on a Decisions API, and Jev launched theirs quickly enough to have 1 week in the spotlight before OpenAI put theirs in beta (which works great btw).
reply
When trying it out, OpenAI's Decisions was ~2x slower, worse accuracy and more expensive. Unless used with image-related tasks, Jev is clearly superior.
reply
There were classifier models on hugging face for years though…
reply
deleted
reply