The Rise and Fall of Jev

Alex Ewerlöf

Oct 19, 2026

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This is a quick note on how the industry’s reaction to Jev reveals the desperate state of AI. I’ll dissect:

What is Jev, how was it hyped and why Jev spread like mass hysteria?

What the noteworthy innovations are since ChatGPT brought “AI” to the mainstream?

How is the industry starved from real innovation?

What we’re still missing after 4 years of revolution incremental improvements?

By the end, you should be able to tell whether we’re in a bubble and how to be prepared.

But if you were clever enough to ignore it, here’s what actually matters:

Jev is basically a general purpose classifier (e.g. quick judgement). What makes it interesting is that you don’t have to train it with a lot of data (although that lack of special-purpose training negatively impacts its utility).

Calling it a “decision model” is a bit far fetched especially since it cannot even see (rival open-weight models have multi-modal features) or reason (that’s how it’s so cheap).

The idea behind Jev isn’t new! The idea of non-autoregressive decision models with RL goes back more than a year ago. The original author is pissed but as we’ll see drama is an inseparable part of AI hype.

I want to walk you through the emotional roller-coaster I went through when I read their announcement via hackernews:

At OpenAI, I helped build the methods that made language models useful at following instructions and talking with people. That work ended up as the research behind ChatGPT.

😎 So the founder was behind ChatGPT, one of the fastest-growing products in history. I’m listening…

At the time, I thought maybe chat models would lead to AGI, but despite the hype it became obvious to me that there was something really big missing.

After two years in stealth, countless technical challenges, and research breakthroughs… I am beyond excited to announce

😱 Spit it out! I’m beyond excited to read this…

TypeSafe AI is releasing our first System One Model

Do you understand what you’re talking about? Here’s my recollection of how Daniel Kahneman defined the two systems:

System one: fast, cheap (in terms of computational power), emotional, unconscious and judgmental.

System two: slow, expensive (takes more brain power), logical, conscious, and more elaborate.

If Jev is system one then LM is system two? It can’t even handle logical reasoning!

Most importantly Jev came with another interesting framing:

Hallucination is one of the biggest problems with the current generation of language models but no hallucination doesn’t mean the response is logically correct. In Jev’s context, it just means that the output matches the schema.

Technically conventional language models can gain this ability by bolting a control loop (e.g., type checker, JSON schema parser) on top. Jev does this much faster and without reasoning. It’s in the name:

We named Jev after William Stanley Jevons. We expect machine intelligence to follow a similar path to coal, after steam-engine efficiency led to an increase in demand.

I don’t know Jev’s architecture because in the true ex-"Open”AI employee tradition, not much is released (probably in the name of “safety” or “moat”). But that doesn’t stop them from dropping jargons:

We built a new […] training method we call Reinforcement Learning for Calibrated Decisions (RLCD).

Note: RLCD rhymes with the “traditional” methods:

RLHF: Reinforcement Learning with Human Feedback

RLVR: Reinforcement Learning with Verifiable Rewards

Jev is neither small nor an LLM, hence being off the intelligence Pareto curve.

Fortunately, there’s no shortage of similar models, some of them with even better performance (Laya, Kev, Nimble, NanoJev, etc.)

Name dropping: former ChatGPT creator, Jevons’ paradox, Pareto curve, System one

Big claim: cannot hallucinate, exponentially faster and cheaper, entirely new stack, amazing benchmarks and demos

Ambiguity and jargon: no useful implementation details on the “new training algorithm” or RLCD dataset

Drama: Laya showed this idea in 1.5 years prior to Jev’s launch

OK, I think at this point we’ve seen this pattern enough to recognize it. I actually think Jev’s team kicked it up a notch to a comical level. Whether their marketing is written by LLM or not, they nailed it.

Source: Latent Space Podcast on Youtube

Fortunately, Jev’s initial noise died off almost at the same speed that it blew up. I can only speculate that as more people experimented with it, we realized:

It cannot hallucinate, but it can still be wrong. It is even more wrong than conventional language models, and in that sense “system one” is the right naming. Although I consider all current generations of language models system one (even the reasoning models) because they do not really reason in the sense that’s expected of system two.

It is cheaper, but there are open-weight models that beat it in performance/cost ratio (depending on the task). What makes Jev different than frontier-level LLMs is the fact that you can actually run it at the edge (e.g. locally) with matching quality.

Jev is not completely hype, we just went from “Peak of Inflated Expectations” to the “Trough of Disillusionment” in record time:

Wikipedia: Gartner Hype Cycle

I really don’t want to bash Jev, but I want to use it as an example of where we are, as an industry.

I was one of the lucky few who got access to GPT-2 when it was invitation-only.

As a senior tech lead, I allocate part of my time to scout new tech and experiment in order to stay relevant. Prior to that, I had experienced IBM Watson and a bunch of other products so it wasn’t a big deal for me personally.

I was actually underwhelmed by GPT-2 because at the time it could:

… that was it really! 😄 I don’t remember more than that. So I moved on…

Then I saw someone create a turn-based dialogue from one of these models and to spice it up, they added an avatar to it. I thought it was creepy and funny.

Then Blake Lemoine came out claiming Google’s language model named LaMDA was conscious. Unsurprisingly, this started a philosophical discussion that’s still ongoing on the side. Again, I didn’t give it too much thought.

BUT, Sam Altman, having spent a few years at the startup accelerator (Y Combinator), saw an opportunity. Specifically the chat application seems to have got his attention and soon ChatGPT was announced.

At the time, I thought it was a cool way to turn their token prediction model into a user-friendly product for the masses.

Personally, I couldn’t use it seriously because:

Poor quality: it didn’t know what it didn’t know, so it just winged it (AKA hallucination). Although the rise of “prompt engineering” and “reasoning models” promised to reduce this issue.

Privacy: I had been working with computers for 2+ decades at the time and live by the mantra that “if it’s possible, assume it happened”. Meaning if OpenAI is technically capable of storing my conversation, I cannot trust it enough to share any company IP or private information with it.

I vividly remember the backlash Google got for their multi-modal demo when people realized it wasn’t recorded in real-time! Those were the days when even a small deception would be a conspiracy.

When llama.cpp came out I got a gaming machine with an NVIDIA card (AI machines weren’t a thing back then) to build with AI.

Meanwhile people discovered that language models can generate code It was tedious to copy/paste it so we got the early versions of a harness.

Quickly after, we got “function calls” which allowed the models to do stuff!

I was using VS Code at the time and the hype was hard to ignore even though my company at the time had a strict policy against using AI tools (yes! hard to believe that just 3-4 years ago companies prioritized IP over velocity).

I remember paying for a Copilot subscription out of pocket and using VS Code insider on my open source projects.

I was so frustrated that I shared this meme on the company Slack:

Meanwhile there was drama at OpenAI (Ilya was part of a coup that fired their CEO, then Satya was playing 4D chess while Elon was lawyering up). It was a sh*tshow which is exactly how it managed to capture the interest of non-techies, a trend that continues to today with “almighty rogue AI” hacking others while whistle-blowers and alarmists rise speak of existential threat!

Simultaneously premature AI products were creating dramas of their own (assisting crimes, cheating, etc.) and AI bros anthropomorphize the tool as if it had desires of its own (my read: they want to judge accountability).

There’s also circular investment, pentagon drama, chip wars, autonomous killer drones, etc. but in the spirit of brevity, let’s stick to the technical side of things.

Then Peter Steinberger, a veteran developer who was away from computers due to burnout, created an AI companion, which brought the Agents (LM that can do stuff) to the mainstream.

Let’s speed through the other incremental improvements:

Larger parameter size unlocks emergent properties that are hard to explain by analyzing the micro level architecture (mostly leading to sophisticated perceived behavior but also jagged alignment).

Larger context windows improve accuracy (although the practical limit is much smaller than the theoretical size).

Multimodal models enable generating voice, music, pictures, and videos while increasingly more models can understand these modalities.

MCP abstracts away the implementation and enables different AI products to use the tools needed to do productive work.

ACP, sub-agents and various orchestration techniques allow larger tasks to be planned and broken into smaller pieces.

Sandboxes help improve security and isolate unwanted side effects of agentic workflows and when they fall short, there’s HITL (but we still haven’t solved the approval fatigue).

Skills, web search and web access allow agents to access information that’s outside their training data or knowledge cut-off date.

Various memory architectures and consolidation techniques enable the models to recall what they learn.

Chinese labs showed us more efficient ways to train and run the models.

Feedback loops and scratchpads improve the model’s perceived quality by running part of the verification closer to the model.

AI Fluency Leveling

Alex Ewerlöf

·

Jan 30

Read full story

This is good progress, no question about it. But I think a part of the reason AI is a hot topic is all the drama surrounding it:

Geopolitics: unlike the US economy which is primarily service-based, China is a manufacturing behemoth. Up until DeepSeek discovered that it can manipulate stock and AI investment by diffusing the compute equation, I don’t think China had a solid AI plan. Now they do. Good old American sanctions target their chip import but China (being run by engineers) made huge strides recently both in chip manufacturing but also in model architecture. Meanwhile AI is used in warfare from drones to intelligence (and mass surveillance back home). In the best seller How the mighty falls, Collins lists 5 stages of demise: a) Hubris Born of Success, b) Undisciplined Pursuit of More, c) Denial of Risk and Peril, d) Grasping for Salvation, e) Capitulation to Irrelevance or Death. Those same stages apply to a falling empires and in this case US has bet big on AI while China diffuses US’s massive bet with open-weight models. Consumers win for now.

Safety: we got used to the “rogue AI” narrative where the AI vendors aren’t held accountable for breaking into other companies and government institutes. Why would we? It’s an open secret that the training data wasn’t legally obtained anyway (and there are multiple class action lawsuits to prove that). On top of it, there have been multiple cases where people lost their lives due to AI — and I’m not even counting “vibe war”. (yes, I actually put an em-dash there!) 🙃

Impact on jobs: software engineering is low-hanging fruit for AI automation due to its