Latent Space: The AI Engineer Podcast

A few years ago, Caltech Prof. Anima Anandkumar set out to develop the first open-source weather model with AI. Talking to experts in the field, she was met with skepticism. Weather is chaotic, physics simulations are hard, have been developed for decades, and require supercomputers, the data just isn’t there. Despite reservations, Anima went forth and built. Within a year her team had developed FourCastNet, a predictive model that is competitive with the best physics-based simulations available. Thanks to Anima, and her follow up work, anyone can now predict weather accurately over a short timescale using consumer grade GPUs.
In the fifteen or so science episodes we’ve released on Latent.Space, we’ve covered atoms, molecules, materials, biology, and math. Anima is a pioneer in studying physical systems that are continuous. Weather, fusion, and fluid or heat flow are huge areas of science that are extremely difficult to model: they are large, chaotic, and fundamentally multi-scale. This is a field the AI community has somewhat neglected, but one we expect will grow fast. We plan to cover large physical systems more in coming episodes.
One thing you can glean from Anima’s work is that this area of AI resists the scaling ideas that have permeated the rest of the field. The data isn’t there: open source datasets in many of these domains are limited to tens or hundreds of thousands of examples, far from what token-hungry transformers need. Even worse, the resolution that physics demands pushes the context length into the hundreds of billions, so you can’t just throw more tokens at the problem. That isn’t a ceiling though, just a slower road: progress here comes from building in structure and inductive biases. Sorry for all you bitter-lesson-pilled language modelers.
“If each dimension is even a few hundred grid points, which is where industrial scale starts... we’re talking hundreds of billions to even a trillion context length. So forget ever having a transformer for anything of this scale, all of the world’s compute will not be enough.”
The math underneath
To tackle these systems, Anima pioneered a technique known as Neural Operators, one of the most beautiful theoretical developments in AI of the last decade. These allow you to combine data and physical laws to enable multi-scale inputs and outputs. We’re no longer modeling a grid, we’re modeling a function that evolves over many scales. This allows Anima and crew to build in priors based upon physical intuition.
To see how physical priors are still helpful for AI modeling, let’s revisit the problem of weather forecasting on a global scale. The earth is a sphere, which meant that accurate modeling involved using the right basis set — the Spherical Harmonics. Run a weather model on a grid and it blows up fast. Move to the natural basis for the problem and it stays stable far longer, long enough to roll out months ahead instead of days. Anima’s Fourier Neural Operator learns directly in this frequency domain, and its spherical variant powers FourCastNet 3, which models the weather across the whole globe and keeps running stably far into the future.
The physical world is forgiving
Anima explored Neural Operators across other physical domains too, and one striking observation is that the physical world is more forgiving than you’d expect. In fusion, a few thousand samples are enough to predict plasma disruptions, and to do it a million times faster than traditional simulation.
None of this is a rejection of scale, it is a different route to it. Anima ultimately still wants to build a “foundation model for physics”, a model that spans many phenomena and does both simulation and design. You get there by building in the structure the physical world already has, not by waiting for data that will never exist. It is a start, and it will take longer than the token-driven parts of AI, because for the physical world tokens were never the answer.
“All of the things that work with deep learning, let’s take them, but make them a bit more principled.”
Weather is only the beginning
Neural operators and weather modeling were a personal passion of mine, so we’ve spent much of this blog and the episode exploring this work. Anima has done so much more! In the episode, we cover several other recent developments from Anima:
* Anima has a series of works integrating neural networks and automated proof techniques. We talk about TorchLean, a new framework that lets you write PyTorch-style networks inside the proof assistant Lean and formally verify them. This is a major step for proving bounds on neural networks, something that would be really important for someone trying to, e.g., add a neural network as part of the control loop to their fusion reactor!
* Anima was recently appointed to the United Nations Scientific Advisory Board! We talk with her about her goals of bringing evidence-based viewpoints to policy, and how AI in scientific domains can improve people’s lives all over the world.
This episode has something for every AI or science nerd! Elegant math? ✅ Old school harmonic analysis? ✅ Fundamental developments in modern AI? ✅ Practical ways of modeling the physical world? ✅
Give it a watch!


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When we first dicsussed the Summer of Simulative AI in 2024 we knew it would be a brief summer, but it has recently come back with a vengeance with SimGym in April and now Simile AI’s $2B Series B, backed by GreenOaks and Index Ventures with prominent backers like Fei-Fei Li and Andrej Karpathy, running tens of millions of simulations for Fortune 100 clients like CVS and 85–99% accuracy vs human focus groups.
Time to catch up on why this Second Summer of simulation is working!
From creating Smallville, the landmark 2023 paper on Generative Agents that showed AI characters could remember, plan, socialize, and develop emergent behaviors, to now building foundation models of human behavior, Joon Sung Park is trying to answer a much bigger question: what if we could simulate the world before making decisions in it? In this episode, the Simile co-founder and CEO joins us to unpack the path from generative agents to digital twins, why today’s frontier models still fail to capture how humans actually behave, and what it would take to eventually simulate all 8 billion people on Earth.
We go deep on Simile’s approach to modeling human behavior: long-form interviews, observational and transaction data, randomized controlled trials, population-level and individual-level models, and post-training on the causal mechanisms behind why people make decisions. Joon explains how his research created digital twins that reproduced human behavior and attitudes 85% as accurately as people reproduced their own responses, why models optimized to be rational can be bad simulations of irrational humans, and why understanding “social physics” may require changing model weights rather than simply prompting frontier LLMs.
We also explore the much larger ambition behind simulation: testing products and policies before deploying them, finding counterintuitive paths toward desired outcomes, modeling emergent behavior across entire societies, and potentially tackling problems like climate change, democratic instability, and UBI. Joon reflects on scaling laws for simulation, the economics of data-center-scale simulated worlds, the connection to Thomas Schelling and psychohistory, why simulation is surprisingly similar to painting, and whether we might already be living in one.
We discuss:
* How Smallville and Generative Agents led to Simile
* Why Joon’s team asked: “What if we can just recreate the world that we live in?”
* Why useful personal agents require deep models of their users
* Memory architectures, Markdown files, and the limits of prompting
* “Social physics” and behavioral foundation models
* Why web data captures what people say more than what they actually do
* Interviews, transactions, observational data, and randomized controlled trials
* Why predicting the future matters less than understanding how to shape it
* How Simile creates representative simulated populations
* Simulation versus prediction and the connection to Foundation’s psychohistory
* How to evaluate simulations instead of simply stacking LLM hallucinations
* Creating digital twins of 1,000 real people and reaching 85% behavioral accuracy
* Why frontier models can struggle to reproduce real human behavior
* Why good simulations need to reproduce human biases and mistakes
* Post-training models on randomized controlled trials
* Population-level versus individual-level simulation
* Scaling laws for human simulation
* The long-term ambition to simulate all 8 billion people on Earth
* Whether simulations could help solve climate change or detect collapsing democracy
* Thomas Schelling and the history of agent-based modeling
* Why future simulations could require an entire data center
* Multi-agent simulations and what happens when simulated people interact
* Replacing expensive human panels with synthetic populations
* Why market research is only the starting point for simulation
* Why Joon sees simulation as surprisingly similar to painting
* Using simulation to study questions like UBI
* Whether we are already living in a simulation
* Why AGI and simulation may be the twin technologies of advanced civilizations
Joon Sung Park
* LinkedIn: https://www.linkedin.com/in/joonspark
* X: https://x.com/joon_s_pk
* Website: https://www.joonsungpark.com
* Simile: https://www.simile.com
Timestamps
00:00:00 Introduction and Joon’s Path from Art to AI
00:01:46 Smallville, Generative Agents, and the Origins of Simulation
00:05:03 “Let’s Just Create a World” and the Future of Personal Agents
00:09:53 Social Physics and Behavioral Foundation Models
00:14:08 Prediction vs. Simulation: How Do You Shape the Future?
00:16:59 How Simile Models Real People and Populations
00:25:35 Evaluating Simulations, Digital Twins, and 85% Accuracy
00:30:23 Post-Training Models to Reproduce Human Behavior
00:40:04 Scaling Laws and Simulating 8 Billion People
00:43:10 From Schelling to Society-Scale Agent Simulations
00:46:13 The Cost and Economics of Simulating the World
00:52:05 Real-World Use Cases, Synthetic Populations, and the Market
00:57:27 The Future of Simulation, Painting, and UBI
01:04:23 Are We Already Living in a Simulation?
01:06:08 Building Simile and Hiring
Transcript
Introduction: Joon Sung Park, Simile, and the Story So Far
Vibhu [00:00:00]: Today, we have Joon in the podcast. Excited to kick this one off. Very exciting company. I wanna kick off and ask you the question, talk us through the story of your life. How have you gotten here?
Joon [00:00:13]: Yeah, for sure. I’m really excited to be here. A story of my life. So I was born in Korea, and I lived there for a good 11 years or so of my life, and then my family moved to Boston. So we moved when I was 11, and my parents were doctors, so they were going through their postdoctoral studies. My dad was a surgeon, so he was doing his sabbatical years at the Boston Children’s Hospital. So I grew up there, not too close to tech. I was very much a music and artsy, painting kind of guy.
Vibhu [00:00:49]: Painting.
Joon [00:00:49]: Exactly. I got into painting a little bit later, in high school, but that’s what I used to do. And then I grew up mostly in the East Coast after Korea. So I lived a good number of years in New Hampshire, and then I went to college in Pennsylvania. And I got into more of this tech scene, in college. So I was originally trained to be an artist. I thought that would be my professional career. So it wasn’t a hobby. It was like, “Hey, let’s make a living out of this.” And then gradually, I got really interested in this idea of, hey, the greatest artist often creates their own medium, and the best medium that we had available today was in computation. So I decided to go deeper into that, and one thing led to another, and we can go deeper into this, but I decided that research was something that I gradually got interested in, and here I am.
Smallville, Generative Agents, and the 2023 Breakout Paper
Swyx [00:01:46]: So there’s a lot that you packed into the research components. You had one of the best papers of 2023, which was the generative agents paper, commonly known as the Smallville paper.
Swyx [00:01:58]: Feel free to call back to anything else that you mentioned, but most people would have heard of you from this. Do you have any statistics on how many people have, like, read it? arXiv gives you something, right? Some stats.
Joon [00:02:10]: Yeah, it’s a good question. How many people have read it, I’m not sure.
Joon [00:02:14]: I know we do keep track of citations, and they are going up quite fast.
Swyx [00:02:23]: Yeah, Google Scholar has 7,200 citations.
Vibhu [00:02:25]: I feel like it made a bigger hit than that, and it was a pretty instrumental paper. It got cited so many times.
Swyx [00:02:34]: It is frequently the answer when people ask, “What is the best paper you’ve read recently?” It’s this one.
Vibhu [00:02:39]: I thought the memory component was pretty underrated. It was a very good early memory system, and one of the biggest papers.
Foundation Models and the Search for Killer Applications
Joon [00:02:47]: Yeah, so maybe I can talk a little bit about how this particular paper came together. So when I got into research, it was back in 2020 when I started my PhD program at Stanford, and that was the year, when we were about to get GPT-3 to be available. So we already had GPT-2, and you could sense that there was this new class of models that was just becoming available in the market, and the team got very intrigued. And the general consensus was, “Well, is this model going to be useful for anything?” “It’s really strange that these models are not trained to do any particular task.” But we decided to take a bet. So a large group of scholars at Stanford, and it was led by one of my co-founders, Percy Liang, and we came together
Swyx [00:03:35]: Who coined foundation models.
Joon [00:03:36]: Who coined the term foundation models. We wrote this paper, where that term came from called Opportunities and Risks of Foundation Models. And during that process, really the thing that I started to think deeply about was, here is a model that is fundamentally new in our ecosystem. The reason why this was new was it wasn’t, again, trained to do anything in particular, but its premise was it could do anything and everything. It was like a stem cell, if you were to take a biology analogy. And I got really interested in this idea that, well, if we were to really think about what are the killer applications that this particular technology would enable, what would that be? Many of my colleagues were using this for simple classification, simple generations. Interesting that these models can do that, but from an interaction perspective, not that interesting. We’ve known how to do that for many decades. And what we came down to was these models are trained on this very broad data from the web, right? So these are human behavioral data. It’s social media, Wikipedia, all these data. So if you poke at the right angle, then you could see human behavior that would just pop out that’s quite realistic, and we’ve never seen that before.
The Time Machine Game and Recreating the World
Joon [00:04:45]: So that got us really interested. The exercise that we decided to do, with this particular group of colleagues, Michael Bernstein, Percy Liang, and myself, who ended up becoming my co-founder at Simile, we sat down and we played this game that we call the time machine game.
Joon [00:05:03]: Imagine we were to get on a time machine and fast-forward 10 years and look back. What would have been the single application that will have mattered that would be the most interesting and inspiring? And when we thought, “Well, what if we can just recreate the world that we live in?” it’s really hard to get more ambitious than that. Like, let’s just create a world.
Joon [00:05:24]: And that’s where we started. And initially, we had this paper that was a precursor to the generative agents paper called Social Simulacra.
Swyx [00:05:32]: Before you go further, were there other candidates for the most ambitious thing in the time machine exercise? What was number two or number three?
Personal Agents, User Models, and Why Simulation Came First
Joon [00:05:44]: There is a close second that we were considering, which ended up becoming more of these automation tools, especially the vision around really personalized agents that would do things for you.
Swyx [00:05:59]: That’s also happening.
Joon [00:06:00]: It’s also happening. But it was interesting for us, right, in that the reason why, we decided to go with the idea of simulation, one, I was a huge science fiction nerd, and this idea of creating simulation, I was personally really just fascinated. I loved the idea. It’s really cool to see, like, a game town like this and just see these agents live in it. But at the same time, my bet was if you were to create a really amazing personal assistant out of this technology, what you need first is an amazing model of your users. So I told a model, “Hey, can you go buy late dinner for me?” And it orders Hawaiian pizza, and I do not like pineapples on my pizza. Then it totally failed. The way for it to not make that mistake is only by having a deep understanding of who I am. And I gave a very simple and dumb example here, but you can imagine how this core understanding of people is instrumental. This is how, if we have our family and closest friends, they have a good mental model of who we are. That’s the basis of our social connection. So our bet also was this technology around simulation, creating accurate representation of people ought to precede the more complex agents that would automate the world that we live in. So that was the bet. But that was a very close second, and I’m still very much fascinated by it. I think there’s a lot of interesting work that’s going around. My hot take here, though, is I don’t think we’ve seen a true personal assistant that’s useful, in ways that meet the ambition of that particular line of work. I think there are early applications that are interesting, and if you talk to even ChatGPT nowadays or Claude, they know a lot about us. So a lot of the generation it’s doing, I do think it’s much more tailored, but I think the ambition is quite large in that field, and I don’t think we quite have all the right ingredients just yet.
Swyx [00:08:01]: So OpenClaw and these personal agents, what do you want to see from them that they don’t currently have?
Memory, Markdown, and the Limits of Prompting
Joon [00:08:09]: I do think it’s slowly getting there, but I do generally want them to have much deeper understanding of the person. Right now, you look at the models. OpenClaw, what it’s leveraging is a Markdown file, and I think it’s quite clever, right? So if you look at the generative agents paper, this was the same intuition that we had, where initially when we were creating the memory architecture for the generative agents, and, like, this is, like, back in 2022, so we didn’t really quite have the idea of even agentive architecture or the term agent. But the intuition that we shared with some of the work that’s coming out today was we initially thought, “Well, do we want to make the memory into, let’s say, knowledge graph? Do we want to train a bespoke model?” All of these things. And what we decided to do was, “No. Just forget about all this.” These language models are quite good at modeling text and understanding and reasoning about text. So just put everything in a Markdown file or a text file. You’re done. I thought that was quite interesting that we could do that, and there’s a lot of strength in doing that. But also, there are limitations. It’s the way you retrieve and make sense of data that’s extremely large, it takes a lot of work. So I think that technology is getting better. I also do, however, think, there are certain things you just cannot shape just by prompting the model. So to some degree, you do need to touch the parameters of the model itself. So there is this work that I do think does need to happen, and it is happening. The question is, how far can we take it? How do we source data, and how do you also create an ecosystem where people are continuously feeding data to this model so it’s learning about you?
Vibhu [00:09:50]: What’s the intuition between why you need to do it in the model?
Social Physics and Behavior Foundation Models
Joon [00:09:53]: My intuition behind the actual when do you train or even post-train a model versus just prompt a model is if the model has to learn the underlying physics of the world that it’s operating in. So it has to learn new social physics. The places where it doesn’t have to train are the places where it already has the physics. We trust the physics. It already has the base statistics, but it’s just trying to react to an environment. Then I think you can just prompt your way into getting the actions out of it. I don’t think the models that are out in the open have yet learned the complete mapping of social physics of humanity. This is one of the core theses of Simile, right? And one of the core reasons why that is the case is if you look at the data that the model was trained on, these models were trained on the web data, like, whatever was available on the web. And these are really interesting data sets, but they are fundamentally the self-exposed attitudinal data with some behavior data that’s sprinkled around here and there. And it has yet to learn the really deep behavioral nature of people, not just what people say they do online, but what they do in real life. And this is one of what I would consider to be the dark knowledge of humanity that we haven’t quite captured. And it’s these data that would also need to get factored into the model creation.
Vibhu [00:11:21]: You call it behavior foundation model.
Vibhu [00:11:23]: There’s a good one-liner here, but outside of that, what type of data do you need? What are you changing on the model level? How do you go about modeling, doing a behavior foundation model?
The Three Data Buckets: Interviews, Behavior, and Causality
Joon [00:11:35]: We think about data in three buckets. So one bucket is interview data. It’s quite interesting. Rich qualitative data is interesting. It’s not behavioral, but we would literally ask people, “Hey, tell me the story of your life.”
Vibhu [00:11:53]: It’s just what we’re doing here exactly.
Joon [00:11:54]: The question that you all asked at the beginning of this interview literally is the question we also ask. And we ask our participants to go a little bit deeper, than how far I went. Maybe I can give more of my life story in lieu of this. But the reason why that data is interesting is by learning about this very long-tail information about people, you get a lot of texture around this model, like, this person as a model. So even understanding their childhood memory or even their trauma, their first love, these things, quite informative in ways that’s really hard to predict. So that’s one. Then there are two tranches of what I would consider to be the behavioral data. One kind of behavioral data is observational. So these might be like transaction data, or these might be data that you can get by scraping the web, right? So you can imagine why these data sets would be interesting, right, because they give you the base statistics of people’s behavior.
Joon [00:12:55]: But then there is the last category of data, that I personally think is perhaps the most important, which is the data that describes the causal mechanism, the whys of people. Some of this is covered by the interview data, the qualitative, because people talk about why they made certain decisions. But really, where you get to see the most behavioral aspect of this is in randomized controlled trials, like RCTs. Imagine you have the same setup, but you have a few different variables that you are trying to tweak. Can you get realistic human behavior out of it in ways where, imagine you had this particular option. Imagine you’re even trying to choose whether you’re going to drink coffee or not. The day you drink coffee versus the day you didn’t drink coffee, does your behavior change? That’s a data set that describes a causal mechanism. This is quite important in modeling people. The reason why this is important is oftentimes when people come to us, or not just to us, but the reason why people are interested in simulation isn’t because they want to predict the future. If you’re trying to win against the stock market, predicting the future is interesting.
Prediction vs. Simulation: Shaping the Future
Joon [00:14:08]: But most people, most decision-makers, what they want to know is, how can we shape the future? It doesn’t really help you to hear that your sales are going to tank in two quarters. They’re just gonna say, “Wow, that sucks.” What they want to know is, well, what do we need to do now to avoid that future? That’s the causal mechanism. And this is also very hard data to come by, right, because the world is our ground truth, but it happens once. So in a very controlled setup where everything is equal except for one variable, this kind of data set rarely happens. So this is a reason why this data set is both hard to come by and quite important if you’re trying to model human behavior.
Swyx [00:14:50]: So behavior, I think, is the hardest data set to acquire. What is out there? What is even possible? You’re not going to know a lot of details about my life. I don’t even have data for myself on my own health or habits, and I just don’t log everything. So how can you have that data?
Joon [00:15:14]: So we run a lot of randomized controlled trials.
Swyx [00:15:17]: But you put people in the lab, they watch them sleep, or what?
Joon [00:15:20]: We do care a lot about the consent process. People know that we invite them to be a member of this community to both share data and have themselves represented in different forms. But we bring a lot of people to the lab, or virtual lab, where we design experiments that would pose them real behavioral decisions. And often in these experimental setups, what makes the difference between what is attitudinal versus behavioral is whether the stake in your decision is real. That’s ultimately what makes it behavioral. So in these setups, we are inspired by our colleagues in social sciences, psychology, and so forth. So when they run studies, the techniques they utilize is imagine there’s an online store that you’re inviting people to come by. Then whatever they purchase in this experiment, they actually get that item delivered. Like, these are the things that make the stakes real. So we run a lot of these experiments, and we also do partner with firms. Right now, we also have customers who are quite excited to at least give us a glimpse of the behaviors that their users exhibit so that we can get a little bit deeper understanding of how people behave in these different platforms.
How Customers Use Simile: Populations, Queries, and Experiments
Vibhu [00:16:39]: I think on the customer side, they have a lot of data about their users, who has bought. They have the action data.
Vibhu [00:16:47]: Can you walk us through an example of what someone comes to you for? What questions would they want solved? Do you customize a model for them? Do you have something off the shelf? What does that look like?
Joon [00:16:59]: Today, when people leverage our models, it’s often to better understand the population of their interest. So usually, the start of the relationship, we come together and hear about what population they want us to model, right? So it might be that if you’re a CPG company that’s selling to all of the US, then maybe it’s fairly straightforward. You want to model the gen pop of the US. But at the same time, if there is a vertical or if there’s a market that they’re trying to go into, imagine, they want to better understand, let’s say, people in their 20s and 30s living in California. That’s a much more specific population. So we hear about this population, and we go recruit these people, with consent, and with incentives, and we collect some of their data and create a model of these people. Then what our product allows you to do is query them. So it can take as input a filter that is a description of the population that you want to talk to, just like the one I just mentioned, and an environment. The environment can literally be survey questions, behavioral experiments, It can be A/B testing. Oftentimes, the core use cases are things like concept testing, to start with. But also, people sometimes want to do focus groups or one of the fun use cases that we also serve is even modeling things like earnings calls for public companies.
Joon [00:18:21]: So these are the use cases that we often start with.
Swyx [00:18:23]: Concept testing, is that an established term? I’ve never heard of concept testing.
Concept Testing, Gallup, and Politics
Joon [00:18:27]: Yeah. So it has to do with they have, let’s say, different messaging, different products, different ideas.
Swyx [00:18:32]: It’s like a marketing exercise.
Swyx [00:18:33]: Okay, got it. Got it. Politics?
Joon [00:18:36]: We do, have a strategic partnership with Gallup, and of course, Gallup is deep into policy space and so forth. Right now, we have not worked deeply with politics, like that area just yet, however.
Swyx [00:18:49]: I’m curious if there is demand or if they really would have different needs that somehow fundamentally don’t mix with your existing, users or people.
Joon [00:19:00]: I think there’s certainly demand.
Joon [00:19:02]: But we are very much mindful of how this technology gets adopted and the societal impact that we’ll end up having with this technology. And I do see politics as an area where a company has to be particularly thoughtful about the way they operate and make impact. So this is where we also want to make sure that we form enough of guardrail and perspective on how to leverage this technology before we go on to serve markets like the politics.
Swyx [00:19:29]: I’ll give people an example. one of my favorite shows is The West Wing. I don’t know if people have watched.
Swyx [00:19:34]: One of the key storylines is, like, the president has, multiple sclerosis, but they haven’t. they need to figure out how to disclose it. So they run a poll with a fake governor and ask people to respond on the poll,
Counterfactuals, Polling, and When Simulation Is Useful
Swyx [00:19:47]: They try to make decisions based on the results of that poll on, like, how well they’ll be received, like where, how should we play this?
Swyx [00:19:54]: And I’m like, well, I think those counterfactual things, I would use a simulation for this if I could trust it.
Joon [00:20:01]: For sure.
Joon [00:20:02]: In that show, how’d it go?
Swyx [00:20:04]: In that show, it was, like a foregone conclusion. They were like, “We know it’s bad. We just don’t know how bad.” And then the poll came back. It was like, “It’s really bad.” And then they just did it anyway.
Joon [00:20:14]: Part of it is to show, right? So you’re, you’re looking at the idea
Swyx [00:20:17]: Maximizing drama.
Joon [00:20:18]: How bad could it be? Oh, it’s horrible.
Swyx [00:20:20]: And to some extent, I think that is part of the trick of the, or the challenge or with being a customer of yours, which is that if I know it’s. if I roughly know and can intuit
Swyx [00:20:35]: What the effect is going to be, do I need you? What sensitivity of it, of effect do I need in order to make a decision, right? So for example, if I, my approval rating is 50%
Swyx [00:20:48]: And I, they have this negative piece, news item comes out, and it drops to 30.
Swyx [00:20:52]: If it drops to 20, if it drops to 40, do I care? No. It, I know it drops. It’s negative. So when do I care about simulations?
Joon [00:21:01]: You do something that’s clearly bad, that’s not popular, and people don’t like you, like, yeah, it’s like
Swyx [00:21:05]: You don’t need a simulation.
Joon [00:21:07]: Yeah. Well, so there are a couple of things. one is, there are use cases where, like every day, developers, designers, policymakers, marketers, every single day, they create assets. They create new products. And turns out, it’s many of the decisions in hindsight is obvious. Yes, of course this is bad, but we still run those studies because understanding the magnitude and understanding how acute something is quite difficult, even if, we feel like, of course, like this makes sense. this is the reason why we make so many mistakes. Like, every time somebody goes online and say something that has huge backlash, you look at that and like, “What an idiot.” However, it’s tough. That’s one. There’s also another aspect here, which is, again, this is the reason why simulation is different from prediction. In simulation, in the ideal case scenario. So what simulation is trying to show is it’s trying to show each step of the way or each step that we need to take to get to a certain outcome, right? So in the most advanced simulations, sometimes the next step that we’re suggesting might be quite counterintuitive. The analogy that I sometimes give, and I ground it in a more realistic example, but, I, as I mentioned, I’m a huge fan of science fiction, and I don’t know how, many of the audience members have read, like, things like the Foundation series by Asimov.
Simulation as a Path, Not Just a Prediction
Swyx [00:22:37]: Oh, yeah. We’ve mentioned psychohistory a number of times.
Joon [00:22:39]: Okay, fantastic. So I might be, talking to the right crew. If you read Foundation series, literally the first act is there’s a group of scientists who have found out that, “Oh, our galactic empire is going to collapse, and we’re going to have 30,000 years of unrest.” And they run psychohistory, the simulator that tries to teach them, “Okay, how can we keep this unrest to a 1,000 years?” And they plan this out, and the first step of that plan is to get the scientists who say, “Okay, this is coming,” exiled into this random place in this, galax- galaxy.
Swyx [00:23:18]: Terminus.
Joon [00:23:19]: Exactly. And that’s so counterintuitive. Like, what a strange move that you literally sent the group of scientists who was raising voice around this potential collapse of galactic empire into nowhere. How is that the right first move? Well, it turns out in this particular simulation, that was the move.
Joon [00:23:40]: It’s these things, right? And the reason why these reasoning is possible is because you’re showing the step function or each step that results in a particular outcome. So really what simulation allows you to do in its highest form is you give it not a problem or question, like what would people answer to the survey? That’s not what we do. What we tell it is, “Here is a goal that we have. In the context of foundation, we want to keep the unrest to a 1,000 years. What is the path that we need to take now to get to that particular future?” And that’s what simulation allows you to do. Now, translating that into real market, imagine you’re a automobile company and you’re about to release a, EV, and you’re trying to understand, well, how do we market EV, to make sure that our stock price goes up? But what if the answer comes down that, well, you can market your EV in XYZ way, but that might change people’s perception around the cars that’s not EV and make your overall sales to go down. Not very intuitive, especially all you’re trying to optimize is EV salesss, and that’s the only thing that you’re tracking, then that might result in a completely wrong solution, or at least different solution than what you would have expected, whether it’s right or wrong.
Joon [00:24:57]: That’s the power of simulation.
Swyx [00:24:58]: For listeners, we covered a similar topic with Mikhail Parakhin from Shopify, where they are working on SimGym. I don’t know if he ever talked to you about it. it’s very similar.
Joon [00:25:07]: I
Swyx [00:25:07]: The goal is increased conversion, but then the journey is very unusual.
Joon [00:25:12]: Journey is unusual.
Swyx [00:25:12]: Yeah. The-- He’s trying to look for interventions on a shopping trajectory, which is similar to what you’re saying. Like, it’s not about the attitudinal, is your word for it.
Swyx [00:25:24]: It’s about behavior.
Joon [00:25:25]: It’s about behavior.
Swyx [00:25:25]: And that’s exactly the difference, right? It’s, like, not about the near-term direction about-- but it’s more about, like, how do you affect multiple turns of interactions.
Vibhu [00:25:35]: You had a good quote at the start about this as well. It’s not about people wanting to know the outcome. It’s about how they can change it, change the way to get there, something like that. But I wanna take it back to how do we know this is grounded? Like
Grounding and Evaluating Digital Twins
Vibhu [00:25:47]: How do you run evals? How do you test that simulations come through? if I was to do the same thing that you described with, say, your favorite LLM, Opus, GPT-5.6, have some agent to map out these things
Vibhu [00:26:02]: How different are the answers we would get if I give it the same goal, the same objective, make a decent system? You’re saying that you need to change the model weight. You have your own solution to this. But how far off are we, and how do you check if it’s grounded? you have some interesting stuff on your site that points to how you run real evals, but if you could take us through that side. I think that’s one of the big concerns that people have. They’re like, “LLMs hallucinate.”
Vibhu [00:26:27]: “You’re just hallucinating layer after layer,” right?
Joon [00:26:30]: The way we do this, and this is the paper that we worked on after the generative agents paper that really became the, at least for Simile and also the field of simulation and synthetic panels, really became the foundation. Yeah, this is the paper. the paper is called Generative Agent Simulations of 1000 People. Here’s what we’ve done. For this paper, we brought 1,000 people that’s representatively sampled from the US to a virtual lab. And what we have done was we spent two hours collecting fairly wide-ranging data. In this particular study, we focused a lot on this interview data, that was, whose script was taken from this project called American Voices Project. And then we would also pair that with a lot of behavior data and so forth, whatever we can collect within two hours. And then we would send these people away for a couple of weeks. And during that time, I would use this data to create their digital twins. And I would bring the humans, participants back after 2 weeks and have them complete a battery of surveys, experiments, behavior studies. So we have the list here, which included things like behavioral economics games. We would run literally, like, Big Five personality test, General Social Survey. We would also go ahead and run the randomized controlled trials that were published on PNAS. And we would have their digital twins predict how the source individuals would have acted in these studies and surveys. And this is where we could replicate people’s behaviors and attitudes 85 percent as accurately as people would replicate their own. So that was the first really paper that gave this validated results that we can model individuals in an accurate way. And what we ended up finding now, of course, in AI space, so this paper came out at the end of 2024. AI space, a year and a half, 2 years, that’s a lifetime.
85% Accuracy and Why Frontier Models Miss Human Behavior
Swyx [00:28:24]: Yeah. Just, for listeners who are not seeing the YouTube, I just wanna say, like, the headline figure is 85 percent accuracy, like, which is a big improvement over all the other
Swyx [00:28:34]: Methods that you showed.
Joon [00:28:36]: But the part that was particularly striking to us, especially as we improved this technology even further, was the generative AI models like ChatGPT, Claude that’s coming out, it does give you the right foundation. However, what they do not consider is the true attitudinal and behavioral aspect of people, especially in the population that you care about. So what these models are really good at today is they’re trying to become the super rational, objective machines, right? So you go get their data from places like Mercor, Scale. You talk to professional programmers, scientists to create model that’s amazing at reasoning. That’s what they do. Simile doesn’t care about any of this. The models that we’re talking about here, what we’re trying to create are models that are as dumb as I am, right? So if I make some mistakes, the model has to make the same mistake.
Swyx [00:29:34]: Oh, that’s very hard.
Joon [00:29:35]: That’s very hard.
Swyx [00:29:36]: You’re solving Murphy’s paradox.
Joon [00:29:37]: That’s exactly. And this is a completely different data and training objective. This is also where we see quite a bit of discrepancy in the performance in human behavior prediction between the frontier models, Simile’s model, and the models being created in this space, where in some cases, the model performance of frontier models go all the way down to 20, 30 percent, especially if you go into that more niche population on topics that our customers would care about. On more gen pop, it might be around 50 to 60 percent. So it’s not very robust. Like, you wouldn’t want to make your decision off of these and these findings. If you can bring that up to 85 percent, that is ultimately what people end up getting very excited about.
Swyx [00:30:20]: Yeah. Do we wanna keep going on the paper, routes?
Joon [00:30:23]: Yeah, for sure. So the last one, was an interesting one. So this, paper was the follow-up paper that we had, to the 1000 agents paper, where the idea was now can we augment the models even further and post-train a model based on a lot of randomized controlled trials? So this was an interesting one. The data is always the most interesting part of modeling in many ways. The data that we got here was there’s this, there’s this platform called Open Science Framework. So some, the audience might be familiar with this. And there has been, especially in the social sciences over the past 5 years or so, there has been this concern around replicability of studies. And so it was a bit of a crisis, the scientists acknowledged, where we rerun the study and we don’t see the same finding.
Post-Training on RCTs and Replication Studies
Vibhu [00:31:12]: Oof.
Joon [00:31:12]: It’s tough. And the reason why it’s there-- that was often the case was there’s this survival bias where the papers that get published often need to maintain what we call the value of less than 0.05 in the experiments that we ran. That suggests that only-- there’s only 5% chance that the results that we saw is false positive. But the tricky part was all the papers that were not published, and there’s still a 5% chance that whatever we publish is totally just randomly generated. Like, there’s a 5% chance that, hey, this effect is not real, but it just happened to be real because of the sampling bias. So because of that, what scientists started to do was they started to register their studies. So before running an experiment, they would go to this platform and say, “Here is the data. Here is the population that we’re collecting, and here’s the hypotheses.” And they would just say, “Here is our hypothesis.” Like, “This is what we believe.” And you cannot retroactively change those hypotheses. This is what gives us more scientific statistical confidence that whatever effect that you ended up seeing is true. So that ended up creating this really interesting platform where there’s one platform that has now contains tens of thousands of real-world experiments and hypotheses. And a lot of these are really high-quality, like, professionally designed behavior studies and random- randomized controlled trials. So we got the data and the studies from this platform and used that to make a point. And this particular, model is not, something that we’re serving commercially because this was a part of the open science. But this particular data set, helped us make a point that by collecting a lot of these randomized controlled trials, that are really well-designed, we can make significant improvement in model’s capability to predict human behaviors. So that’s what this paper was about.
Vibhu [00:33:10]: Is this stuff done on a individual level? Like, do I need to tune the model per individual, per company? Is there foundation model changes and then some slight post-training? Anything you can share there?
Population-Level vs. Individual-Level Models
Joon [00:33:21]: So this particular model was trained. the data we had at the level of individuals, but this particular model was trained. We experimented with both. And this is what we end up doing at Simile too. We always train 2, distinct model. One is what we call the population-level model. The other is what we call the individual-level model. And both take very similar input, which is the description of a subpopulation or individual and a stimuli. In this particular work, we’ve done the same. Here, the results that we are reporting are much more geared towards individuals because we do think that is a harder task in many ways, but that’s what we have done.
Vibhu [00:34:02]: You seen anything on the questions that humans can solve that models can’t solve? So like
Human Biases, Mundane Choices, and What Models Miss
Vibhu [00:34:09]: Currently, it’s, I live 5 minutes walk away from a car wash. It’s a 10-minute drive. Should I walk or drive?
Joon [00:34:16]: Huh.
Vibhu [00:34:16]: The model will say, “Oh, walk to the car wash.” And, you don’t have your car.
Vibhu [00:34:20]: Is anything like this a problem in simulation? You would assume, like, very simple for human to think about, but if the model is saying you should walk to the car wash, anything here?
Joon [00:34:32]: It’s less, what can we solve, but I think it’s more about what biases or mistakes do people make that models miss. Like, imagine that you are, like the. When I was still at Stanford, I lived in Palo Alto. So it’s about, I would say, 40-minute walk from the campus. You ask the model, “Okay, let’s go home. What can I, what can I do?” It would likely call an Uber or, give me, the bus time. But for the longest time, I really liked walking back. And the reason why I wanted to do that was not for efficiency. It really helped me think. And I like to walk for, half an hour or 40 minutes or so a day, where I just get to, just think about ideas, research, just get lost in my thoughts. That’s very human activity. Unless the model has seen that and understands the importance of that activity, it would miss these kinds of features. So that I think, is fundamentally what we’re trying to model. Like, what is fundamentally human might not be the most efficient thing to do, might not be the right thing to do, but things that make us who we are.
Swyx [00:35:43]: I’m curious if, there are some data sets that you really want that would materially help you. One version of this may be interesting, which is more valuable to you to acquire as a data set, all of LinkedIn, all of Twitter, all of Facebook?
What Data Matters: Social Media, Transactions, and Facebook
Joon [00:35:57]: It’s a little bit hard to rank, in part because, there’s, there’s this product saying where no feedback is wrong because it teaches you something about your users. Doesn’t matter what feedback.
Joon [00:36:11]: I think it’s a little bit like that.
Swyx [00:36:12]: So just whatever is bigger.
Vibhu [00:36:13]: What about a different domain? Say it was. What about all of Amazon data?
Joon [00:36:17]: Oh, yeah.
Vibhu [00:36:18]: Shopping data, right?
Joon [00:36:18]: Shopping data. So Amazon data is interesting in that it’s very much behavioral, although, like, what people do on social media, you could squint and say that is also behavioral. But the transaction data is always interesting. It is also most commonly available, however.
Joon [00:36:33]: If we were to look at purely social media, like if you really, if I were, if I had to really pick, Facebook likely is interesting because I do think it is most a default version of people. Because you go to LinkedIn, it’s very much professional environment. So people put up their, they have their guards up, right? And that still is interesting because that is true human attitude and behavior, but it is not your base state. you go to Twitter- Twitter, people have their own crazy personas, or depending on who you are. Like, my Twitter profile and, persona is very much, initially was I was very much an academic. “Hey, I’m here to share my studies.” Now, I share, things that’s related to Simile. But Facebook is one of those more private space where people just connect with their friends. In that way, I do think it shows you a little bit more about who that person is. So if I had to pick, I’d likely pick, Facebook.
Swyx [00:37:30]: Yeah. And you’re interested in, like, the whole person and their background and philosophy. I, is it too clinical or too machine learning-oriented to just say this is just ways to inject variance and biases? The broad question, is, like, is this any better than a randomized, like, combinatorial explosion version? So we have a link to the Tencent
Billion Personas, Synthetic Demographics, and Bespoke Data
Swyx [00:37:54]: Billion persona paper, where they did not do any of the groundwork that you are doing.
Swyx [00:37:59]: They just did like a cross matrix of here’s all the professions in the world, here’s all the people, possible backgrounds in the world, do a dot product across all of them, and that’s it. That’s your prompt for a billion people.
Swyx [00:38:12]: This will do something. I don’t know if it’ll do what you do, but it gets you some way, some percent of the way there.
Joon [00:38:18]: So this was an interesting paper. Like, what I admired about this paper when it came out was the scale. And you do gradually want to be able to simulate really large societies and interactions. So the scale is definitely admirable. it is relying heavily on the known statistics that went into training the model. So to the extent that you believe that statistics is correct, this is not a bad way to go about this. But the thesis here, and this is something that we also have seen in the market, like if this works, then we have solved simulation.
Joon [00:38:54]: It,
Swyx [00:38:55]: Because I survey, like, okay, 5% of the US population is in construction.
Swyx [00:39:01]: The other 5% is in medicine, whatever, right? And then you just keep going down the list, and then you do the other side. 5% has, like, the big 5 personality
Swyx [00:39:08]: Of, like, neurotic or whatever. That’s it.
Joon [00:39:11]: That’s it. So if you believe that the underlying data set and the platform that we’re leveraging has all the right statistics, then this will have solved it. you’re at that point merely retrieving the knowledge that is already embedded in the model, in the model parameters. That’s not, unfortunately, what we see, where there is such detailed and also niche knowledge about people that if you just take one example, it might feel very mundane, but it’s quite rich when you put together, that you do need to do a lot of bespoke data collection to better understand people. And this is also, I think what makes this particular, job fun, which you want to deeply understand people, and the process of deeply understanding them requires a lot of attention to the details. And you do need to pay attention to and pay respect to the daily lives that people lead.
Scaling Simulation: From Thousands to Societies
Vibhu [00:40:04]: I wanna talk about scaling simulation.
Vibhu [00:40:07]: So what can’t we simulate, what can we simulate, and how does scaling affect this? So how big are the models? What if we go from, 8B, like, couple 100 billion
Vibhu [00:40:18]: Like billion000 parameters, billion000? Do we get scaling? Any interesting emergence? Like, at a certain scale, at a certain amount of training, you uncover anything unusual and any learnings from that?
Joon [00:40:31]: What we are seeing is at Simile, so we do post-train our own model. The thing that we’re seeing is the early glimpse of scaling law in simulations. The more data about humans and more compute you ingest, you start to get predictive and predictable gains of the model performance in simulating it, simulating people.
Vibhu [00:40:51]: Ooh. We need a scaling law curve.
Joon [00:40:52]: It’s scaling law. Whenever you find it’s a beautiful thing. And we’re starting to see the glimpse of it, which is quite exciting. But if you talk about the ambition of simulation as a whole, it’s not merely about building a model. It’s about building a model, then creating the agents that become the individuals in a much larger ecosystem. So they’re creating this multi-agent simulation. Down the line, you want these multi-agent simulation to also live in a very rich environment, right? What we are really trying to get to at that point is, hey, can we create. All right, let’s do a time machine game again, and 5 years, 10 years into the future, can we create a simulation of 8 billion people living on Earth? I think that’s quite interesting. And that really is the vision. And once you get to that state, the questions that you can help answer for the society also start to change from my perspective. The answers are fundamentally about emergence of the emergent behavior of society and large groups of people.
Joon [00:41:53]: So the questions that I get excited by, and maybe this is a stodgy- a bit. I have my, academic side of me.
Joon [00:42:01]: And for me, it’s questions like, can we help solve climate change? If you look at climate change as a problem space, this is what we, like social scientists would often call it the wicked problems, problem where you have many actors with competing incentives for trying to make a very complex decision and coordinating that coordination decision. Very difficult to really solve in real life, which is also the reason why we couldn’t solve it. Can simulation help us solve that? Another one is, can we understand the signals for collapsing democracy, or can we understand or can we uncover the origin story of the monetary system? These are societal questions that we never really had a good way of answering. If we can create simulations of our society, you have to believe that these are the problems that we can solve. So that’s really the ambition of this field. And, I also think, yes, I think there’s a Nobel Prize to be won there, which wouldn’t be surprising. And I think there’s some amazing societal impact that we can have to help people make better decisions.
Climate Change, Democracy, and Societal Simulation
Swyx [00:43:04]: Nobel Prize in economics?
Joon [00:43:06]: In economics.
Swyx [00:43:06]: Oh, I see. I see. Rooting for you to write that paper.
Joon [00:43:10]: One of these days. But, one of the scholars that I was deeply inspired by, When I was coming into the space of simulation, is this scholar, named Thomas Schelling.
Schelling, Agent-Based Models, and the Nobel Prize
Swyx [00:43:23]: Schelling point?
Joon [00:43:24]: So the canonical example of the work that he’s done was he was one of the creators of agent-based modeling. So this was, like, in the 1970s and 80s. It’s very early days, but this was truly one of the first exemplars of simulations. And one of the canonical model from that time, and of course many of these simulations are trying to tackle the societal problems that’s most relevant for their era, it was called the model of segregation. So racial segregation was a big topic, that, we cared about. And what they’ve done was they created this grid world where they had red dots and blue dots. And these dots were, back in the day, like, they were the agents, and they had a simple rule that governed their behavior. If certain percentage of your neighbors are of different color and if that goes above certain threshold, then you move to a new location at random.
Joon [00:44:21]: One of the striking finding of this paper or this agent-based model was for the longest time, people thought the segregation within society was caused by explicit and overt racism.
Joon [00:44:34]: But if you look at this model, people’s preference towards living with people of the same color, that preference can be very minute.
Joon [00:44:42]: But the very small difference causes the society to segregate completely over time. This was very counterintuitive for a lot of people. And this particular work ended up informing housing policies. Mixed income housing, got really inspired by this work. And Thomas Schelling ends up winning the Nobel Prize for having laid the groundwork for very early versions of simulations. The opportunity that I do see here in the more scientific terms, is agent-based models for the longest, had impact in the 1980s, 90s, to some extent, early 2000s, but it has now gotten forgotten by the community a little bit. Because as you can imagine, red dots and blue dots is not really a rich description of people.
Joon [00:45:31]: But with the emergence of things like generative AI and, in particular, generative agents, we do have an opportunity to create these agent-based models that are high fidelity enough to help us make really complex decisions. And that’s the opportunity that I see. If that truly works, then yes, that is the work that will result in a Nobel Prize.
Swyx [00:45:53]: Yeah. For what it’s worth, and I grew up in Singapore. 80% of Singapore is in public housing, and public housing has, enforced racial quotas for exactly that reason, which is very interesting. okay, so we talk about scaling, we talk about all these, the agent possible applications.
Cost, Reuse, and the Economics of Simulation
Swyx [00:46:13]: I’m scared about the cost. if you even-- let’s just keep it to the US, about 8 billion people.
Swyx [00:46:21]: But, how much does it cost to model so many hundreds of millions of people?
Joon [00:46:26]: Oftentimes today, we don’t start at that scale, this stage of the, of industry and simulation as technology. But we can get our users extremely rich and meaningful insights even by modeling thousands, tens of thousands of people. And today what we do is every week we are collecting data on the scale of tens of thousands people’s data, and we have panel partnerships that gets us to tens of millions of people globally. So that’s what we do today.
Swyx [00:46:55]: And just as a side note once you’ve collected one person for one study
Swyx [00:46:59]: Can you reuse that same person for all the subsequent studies?
Joon [00:47:03]: That’s exactly right.
Swyx [00:47:03]: Okay.
Joon [00:47:04]: The beauty of this model and these agents is the fact that they are domain-agnostic.
Joon [00:47:08]: That what you’re really trying to understand is what is the fundamental nature of these people? What’s their social physics? And there are a lot of, a lot of, people that does change over time. Like, even, like, even things like, how many times have you gone have you been to, like, CVS the past week? that will change. But there’s so many traits about people that are also known to never change. Like, your risk tolerance doesn’t really change over time. It’s very consistent. So it’s these things that we’re trying to learn. But the scale we are operating is right now hundreds or, tens of thousands to hundreds of thousands. And in many of the core use cases that we are deployed in, and this is more than enough population, to cover those. Really, at that point, what you care about is less the number of people, but more do you have the right subpopulation of interest covered? And this is also the reason why people want a larger sample. It’s not because they want, stronger statistical guarantees. It’s more that can they filter down to any population of their interest. However, you can also imagine in 10 years, if we truly believe that the compute is going to scale, that we’ll have much more availability for compute, and our ambition for simulation is also going to scale accordingly, there’s definitely a reason for us to create an entire data center worth of simulations.
Joon [00:48:35]: Or in my hunch here is I do think in the next some number of years, we will start creating simulations that will cost as much as training a foundation model. But perhaps it’s going to be so valuable to the society that it would be a no-brainer. Right now, even today, like, we are training bunch of new foundation model just so we can say we trained one and we spent tens of millions. But if we can create a simulation at the level of society that would solve climate change, I would run that today. I would raise the money right now just to run that.
Multi-Agent Simulation and Social Influence
Swyx [00:49:10]: Amazing. the follow-up question is, does it also compound if you let the simulations talk to each other?
Swyx [00:49:18]: Or do they already do that today? They don’t, right, as far as I understand?
Joon [00:49:22]: It depends on what simulation you’re trying to run.
Joon [00:49:24]: In the multi-agent simulation setup, the agents do talk to each other.
Swyx [00:49:28]: Right, which is exactly Smallville, right?
Joon [00:49:29]: That’s right.
Swyx [00:49:30]: But a lot of times, for example, in commerce, you’re just by yourself, so there’s no point talking. which is way cheaper.
Vibhu [00:49:37]: But they use all these levels, right? Like, you decide what you will buy based on what other people around you buy and talk about, right?
Swyx [00:49:43]: It depends.
Vibhu [00:49:44]: It depends.
Swyx [00:49:45]: Again, I’m, I’m coming at this from a cost point of view. I’m like, “Oh my God.” Like
Vibhu [00:49:48]: I think
Swyx [00:49:49]: If there is, like, some combinatorial thing of, like, thousands of people talking to thousands of people, then that one million X’s might cost.
Vibhu [00:49:56]: I have a very different view as the cost point aside. Like, running these studies in reality is a lot more expensive, right? Running any study like this is you gotta have people do it, you gotta sign people up. It’s very expensive and sometimes, like, not feasible to run the study.
Vibhu [00:50:14]: But the outcome or the decisions you make are very expensive on them, right? So spend X million on something that, the overall process costs 100 million might as well, right? There’s, there’s a lot of value to be had there. It’s a small cost, but I’m excited on the cost side.
Joon [00:50:33]: To some extent, and when you deploy technology, you often want to deploy in a way where you can replace existing budget or you can make things more efficient, and that is the best way to deploy. However, the way you capture the long-term value of the technology is making the argument that, no, it’s the upside, that by making this better decision using simulation, you have saved yourself or made yourself hundreds of millions or even billions of dollars, and that’s a case to be made.
Vibhu [00:51:06]: Random tangent question. So if you’re doing a lot of inference, a lot of model multi-agent stuff, are you at the point where it makes sense to, train a model that’ very sparse? You’re expecting to do multi-million dollar runs. Are you thinking about this in model architecture standpoint or inference efficiency, or, you’re still at the research phase of it works, we’re not super there yet?
Joon [00:51:34]: Efficiency, we do think quite a bit about. this is technology that is deployed now in some of the largest enterprise companies in the world, and we do process significant number of queries, that are trying to, simulate the populations in the world. So efficiency is a consistent thing. we don’t want to over-optimize too early, so I wouldn’t say, like, this is the higher bid Right now, but this is definitely something that we think pretty carefully about.
Swyx [00:52:05]: Yeah. Are there other case studies? So we, you talked about CVS, talked about Gallup, Deloitte, Wealthfront.
Efficiency, Enterprise Use, and Real-World Case Studies
Joon [00:52:12]: Wealthfront is an interesting one, because one of the things they were trying to do, they were one of the first customers that wanted to do product testing that goes beyond just asking people what they think about, let’s say, behavior experiments and so forth. So there, really what we had to do was reason about multimodal input, so images, but also you can also imagine, like, these agents traversing through Figma mockups or websites. So some of the things that our agents can also do is it can be given a domain, like, or, like, a website URL and go use it for a while. It’s these things. And Wealthfront was one of the first, customers, that was very excited about this possibility.
Vibhu [00:52:53]: What have people been asking? Like, is there any demand that we have not covered? Like, UI testing, right?
Vibhu [00:52:59]: I wanna try a new. I wanna ship a new feature, test the UI, simulate how people will do it. Any interesting things that you’re seeing demand for?
Product Testing, Websites, and Synthetic Panels
Joon [00:53:08]: Today, a lot of the demand does come from like, the places where people have historically used human panels, we can now replace with agents, and these synthetic populations. And this is not replacing human panel. in many ways, the simulation that Simile is building is grounded. So the way that I think about this is we are trying to represent humanity at scale. And in that way, the use cases are what we would expect, but it’s the scale of deployment that surprises me.
Joon [00:53:44]: Turns out there are so many decisions that people make every day in these organizations, groups, and we want to be able to say, “We listen to people. We have consulted our users.” But in reality, that is rarely the case because getting to people and asking them many questions, it’s difficult. It’s both costly, time-consuming, but most importantly, people are just not available. If I had to answer 1000 survey questions for this one particular, vendor, even if I wanted to do that, like, I would never do it. And that’s very much the case. What simulation can do is ensure that the voices of people are always represented in rooms where the decisions for them is made, right? So all the stakeholders of this particular product launch, ideally they’re consulted. That’s what this technology really is trying to enable.
Market Size, TAM, and Human Decision-Making
Swyx [00:54:39]: In my mind, that means it skews towards more consumer focus, right? Like, anything with a wide enough customer base where you do benefit from the diversity that you represent. What are some rough statistics, just for people who are not familiar with this market in general, what’s the market size that. I’m sure you have some, like, rough numbers. market size is, like, a vague question
Swyx [00:55:01]: But, like, how much do people spend?
Joon [00:55:03]: So market research is a $100 billion industry.
Joon [00:55:06]: But the thing about simulation is not a tool for market research. Simulation is a tool for human decision-making. So the question around what is a TAM here is quite tricky, right? Because it’s easy to say, “Well, market research TAM is roughly 100 million or 100 billion.” so is it a TAM? And not really, right? Because in many ways, you’re trying to inform all human decision-making. You’re trying to inform every decision that are made about humans for humans. What is a TAM for that? It’s really unclear. And I’ll be honest. Like, I have a scientific background, I have a research background, so I didn’t come into the field calculating, oh, what is the TAM for human decision-making? But I just had to assume, well, if we can inform every decision that is made about human for human, that has to be big.
Swyx [00:55:58]: Some- something valuable.
Joon [00:55:59]: Exactly.
Swyx [00:55:59]: To some extent, you are a unicorn founder now, and you have to care as a CEO. But, like, I do think, like, yeah, when you go into these boardrooms with people that you’re quoting millions of dollars of contracts for, like, you have to say, “Well, here’s what you spend on humans-”
Swyx [00:56:15]: “. And here’s what we save you, and it’s 85% similar.”
Joon [00:56:19]: And certainly, the value case, is something that we care deeply about. Like, what is the value that we provide to the users and the decision-makers? But this is also where, like, as a founder, I think valuation only tells one very superficial aspect of the story, and I try not to think too much about valuation, in general, because that’s not what also motivates a team or certainly doesn’t. I’m, I-- Again, the interesting thing about researchers is we are happy living in academia, getting paid next to. we get paid okay. we don’t get paid that much, as a researcher here in academia, but it’s the impact and it’s the, it’s the value that we can provide to the individuals and the society that really drives us. And in that way, ultimately what drives us is the impact. Does the simulation we provide have a real impact in people’s decision-making in ways that progresses our society forward? If the answer is yes, then yes. that has to be great business, and we see that in numbers, and we do care deeply about that upside story, but that’s the heart of it.
Where Simulation Goes Next
Vibhu [00:57:27]: Do you have any timeline predictions? So we talked about scaling laws of simulations.
Vibhu [00:57:33]: You brought up, okay, maybe one day we can simulate how to solve climate change.
Vibhu [00:57:38]: Where are we now?
Vibhu [00:57:40]: If that’s not the end state, what is an end state, and what does progress look like?
Joon [00:57:45]: So what I sometimes tell people is simulation as industry, it feels a lot like where GPT-3.5, GPT-4 was, for the AGI saga, which is we have now technology that is powerful enough to do real damage on the verticals that we are tackling. At the same time, there’s a lot of progress that is yet to come. And that’s, I think, where this is. So the way I see it, I do think there will continue to be breakthroughs both in data, in algorithms, and there will be much more aggressive scaling that will also happen over the next few years. But I think that’s roughly where we are.
Swyx [00:58:27]: I think that was about the rough set of topics. Anything else that we should have asked you or you wish people asked you more about Simile?
Simulation as Painting and Understanding Human Essence
Joon [00:58:38]: I think the, what’s, for me, what’s quite fascinating about simulation, it is very impactful technology, but it is also very interesting technology, both in terms of, like, what it means for human society, our philosophy. And the way I sometimes interpret simulation is. So going back to my background, I as I mentioned earlier, I started my career as a painter. it was a professional pursuit, and I did oil painting, for figures. So I got my training originally in the realism studios, and that’s what I spent a lot of my, years, doing. Simulation is a lot like painting, right? The best paintings teach you something deep about the subject that you’re trying to represent. And it is always not a perfect representation. It-- No painting is perfect. There’s always some small differences and discrepancy, but what it does is it tries to highlight the thing that matters the most about the subject.
Swyx [00:59:47]: The essential
Joon [00:59:49]: The essential essence.
Swyx [00:59:49]: Yes. He, you, he’s brought up some of your work.
Vibhu [00:59:53]: Just nice to put it up.
Joon [00:59:54]: Yeah. So these are some of the works. So this is from, my, personal website that I maintain when, I was still a researcher.
Swyx [01:00:00]: I think a lot of people will say, like a Picasso, like anything postmodern is, like, very much focused on the essence.
Swyx [01:00:09]: Right. yeah, but I don’t know if any one of these evokes something that you like to tell the story of.
Joon [01:00:15]: No, it’s one of those things where, each of these paintings, drawings, whatever it may be, it is trying to surface something about the subject that you feel deeply about onto the surface. when I was a painter, and artist, the topic that I cared really deeply about was, the more mundane aspect of human lives. This shows up in some of the, some of the work that I’ve done, where, like, I did this entire study of a rural town where I went around and took photos of people for not really doing anything special, but just living their everyday lives. I thought that was the most interesting thing. I’m somebody who has this perspective where, the world is oriented around this fractal shape, and you have two choices to understand the fractal shape. You either go outward and try to explore as much as you can to understand the broader shape of the fractal, or you go inward because, the outward resembles the inward, shapes. And understanding the mundane aspect of it was very much that. Simulation has a lot of this, right? You’re trying to understand even the most mundane aspect of people. When put together- teaches you something really deep about that individual and the society. So I think that’s what’s interesting about simulation, the way, the same way that AGI helped us better understand or really think critically about humanity and human intelligence, simulation is really an exercise of understanding more about human society and our collective lives. So that I find to be, yeah, particularly interesting.
Swyx [01:01:56]: Yeah. Now you’re reminding me that some of the best biographers, documentarians, and even photographers, they’re taking a photo of you.
Swyx [01:02:05]: But before I take a photo of you, I must spend-- I must, like, follow you for a week just to understand you?
Swyx [01:02:11]: Which some artists, some do. Part of your work, there’s a very famous book called Working. I don’t know if you’ve, been referred to it before.
Swyx [01:02:18]: It’s very famous, like, to the point of having a Wikipedia page
Swyx [01:02:23]: About this like, really depth understanding and interview of people as they, about their lives, which seems mundane, but is told in a very, compelling way. Yeah, 1970s as well.
Joon [01:02:34]: Okay. It was an amazing decade.
Vibhu [01:02:39]: Before closing question
UBI, Future Questions, and the Value of Simulation
Swyx [01:02:41]: Okay, here we go
Vibhu [01:02:41]: You said that you started Simile with your 10-year question, right? If we do that now, 10 years down, what can we simulate? What would you simulate if, like, if you’ve made significant progress, are there any questions outside of the ones that we brought up? Any- anything that you think is most impactful? Anything that you would go vision 10 years out?
Joon [01:03:03]: In many ways, as I mentioned, I am somebody who is very much impact-driven. So the what would inspire me is I would want to ask, 10 years later, what would be the most important societal question that we as a society have to ask? I would love to tackle that. Like, do we need UBI? That could be an interesting one.
Swyx [01:03:24]: Ooh, has anyone done that?
Joon [01:03:25]: Well, we were thinking about it.
Vibhu [01:03:27]: Can we get access? Can we just
Swyx [01:03:28]: So OpenAI, this is, like, just trivia now. Like, OpenAI, or I think Sam Altman funded a study on this
Swyx [01:03:35]: In Africa, and the answer was no.
Joon [01:03:37]: The answer was no. But, what, was it something about the implementation?
Swyx [01:03:41]: Yeah, I know. It was a skill issue.
Joon [01:03:43]: Or was it something about, But this is the thing. See, when Sam
Vibhu [01:03:46]: Funny news article
Joon [01:03:46]: Altman funded this particular,
Swyx [01:03:50]: He spent 14 million dollars? Oh my God.
Vibhu [01:03:52]: It’s a little more.
Joon [01:03:52]: Quite a bit. But this is the thing. This is the reason why you want to run a simulation. You spend 5 years, 40 million dollars on this one study and have one finding, but if you can run simulation many times instantly, then that’s the value.
Swyx [01:04:07]: I feel like that one could-- you could have done in a simulation. Like, if you can do the housing study, you can do the UBI one. Like, I, come on.
Vibhu [01:04:13]: I think sometimes people will spend the money because they wanna verify what you think, right? Like, sometimes you just wanna. Is it right? Like, you gotta test it.
Swyx [01:04:23]: Okay, closing question. What are the chances we are in a simulation right now?
Are We Already in a Simulation?
Joon [01:04:28]: So it’s a fun question, and I assert at some point I just answer, yeah, we’re definitely in a simulation. But what I do, feel, however, is, whether we are in a simulation or not, that, I don’t think that makes our experience any less real. And I think that’s fundamentally, like, what I believe in. Maybe we live in a simulation, maybe not, but for
Swyx [01:04:48]: It’s real to us. Yeah.
Joon [01:04:49]: Yeah. For me, I don’t really care.
Swyx [01:04:50]: Yeah. Unless you die and you wake up in, like, the level higher or below.
Joon [01:04:55]: That would be interesting.
Vibhu [01:04:55]: I feel like you wouldn’t care. Once you die, then you find out you’re in a higher level.
Joon [01:05:01]: I worry about it when I die.
Swyx [01:05:04]: I think the other thing that. Okay, so I like the mathematical answer to this, which is, like, the, sheer number of possibilities that you are in a simulation far outweigh the sheer number of possibilities that you’re not.
Swyx [01:05:16]: Except for the simplest answer, which is, it is computationally very expensive to have you be a simulation. okay, great. You’ve been very generous with your time. Congrats on all your success. I met you just after your Smallville paper and had no idea that you could build, like, such an enormous company. And then now you’re like, “Well, it’s a $100 billion market, but that’s just where we’re starting.” So this is, very exciting.
Vibhu [01:05:42]: I think $100 billion market was not the term. That was only part of it.
Swyx [01:05:45]: Yeah, exactly. It’s, if you’re thinking too small.
Joon [01:05:48]: Well, I do believe that, maybe my final note here might be, again, I love science fiction. You look at any advanced civilization in science fictions, there’s 2 twin pillar, technology. One’s AGI in some form, and the other is simulation. So I think the market’s pretty big here.
Simile as Research Lab and Product Company
Vibhu [01:06:08]: Tell us about the company. You guys just raised a lot. You’re half a research lab, half a company. you’re hiring. Where are you based?
Joon [01:06:15]: Yeah. So we’re based in Mission Rock, so not too far away from, where we are right now. So we’re in SF, but we are also bicoastal. So we have our, team. I would say our headquarter is in SF, and we have a lot of our technical talent in SF, and we do have a smaller office that just opened up in New York. We are, as a company, an interesting one in that today, there are AI neo labs and then there are AI product companies. Simile truly is both. So this is a company that was founded by 4 founders, myself, Michael Bernstein, Percy Liang, Lainie Yallen. Michael, Percy, and I are all researchers. So of course, Michael was one of the authors of the ImageNet, kickstarted the AI revolution back in 2013, has been instrumental in human-centered AI. Percy coined the term foundation model, and is a, one of the greats of the AI researchers today. And Lanie is my business counterpart, where she led some of the fastest-growing AI native companies from their seed to A and B. But we have this DNA at the company where the vision of the technology that we’re creating is continuously developing, that we are getting people who were my lab mates. We are about 60 people right now.
Joon [01:07:28]: 15%, almost 20% of the company population are just my lab mates from Microsoft Research lab.
Joon [01:07:36]: And we It’s quite fun because many of them then had gone on to OpenAI, Google Gemini, and these places. And so it’s been a few years since we really got together and had a chance to work together. But now they’re coming back and really building out this vision that I find to be quite exciting, and that excitement is shared. So there’s that motion at Simile where we are a group of researchers trying to do something that no one is working on that we find to be the most impactful potentially. But at the same time, this is, again, technology that can make impact today. So we have an amazing group of engineers, product people, and designers, who are sitting here with us trying to imagine what does it look like to help people understand what simulation can do and make real-world decisions with this. Having both and then deploying it to some of the largest customers in the world today, it feels quite unique.
Swyx [01:08:30]: Yeah, it’s very compelling. One part of it was this is the call to action. Like, who are you hiring? You’ve done part of it, which is you have-- you’ve got a very talented group. Who are you hiring? Like, what roles?
Hiring and Closing
Joon [01:08:41]: So honestly, at this point, we’re hiring across
Swyx [01:08:43]: Everything
Joon [01:08:43]: All, section. we are always excited to bring on, amazing research talent.
Joon [01:08:49]: So if you’re interested in working with, our lab mates, we are always welcoming of amazing, researchers. But also we, hire, amazing engineers, that some of whom I, like, I respect the most. Many of them come from places where we have personal connections with, so many of the members are from Figma, Notion, Rive, and so forth, but also more broadly from the companies that we as a team have really admired. So engineers both in the product side, infra side, we’re all looking for those hires.
Swyx [01:09:24]: Well, lots of people. I think you made a really good case. So thanks, and, we’ll see you in the simulation.
Joon [01:09:30]: Amazing.
Joon [01:09:31]: See you all there.


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This January, four big AI × Pharma tools deals were announced at the huge JPM Pharma conference that takes over San Francisco every year. OpenAI-backed Chai Discovery (now worth $4B) was somehow at the heart despite being all of 2 years old.
The Science team is proud to bring you the first podcast with cofounder Matt McPartlon and product lead Neil Patil to tell the full story!

Editor’s note: not to be confused with Chai AI, which was another top pod of ours.
Pharma suddenly doing big AI tools deals
For the non-pharma people, JPM is JP Morgan’s annual conference for pharma deal-making that takes over San Francisco for a week in January with hundreds of side events, etc. It’s a big thing.
Tools deals for pharma are also a big (new) thing: companies that start as AI for Pharma usually end up building their own drug pipelines instead, and the reason is something like this: convincing pharma to use your tool requires proof that your tool works. Proof means good targets, maybe with good clinical validation. If you have that, then it’s easier to raise money (with a known, if long path to commercialization) or sell (e.g payment in biobucks) for a specific target than it is to sell to lots of companies on a promise that it will work across their portfolios.
The “we’ll just partner / build our own drug” optionality proved to be the only good path up until January. What changed? In short, the tools got good enough for drug design teams to trust.
Good-enough-to-trust unlocks the ability to scale discovery: get more, better candidates into the lab and animal trials faster. More screening for toxicity, better delivery, etc. This means that what you push to the clinic is more likely to succeed.
Tools also unlock new capabilities: mechanisms that are very hard or impossible to develop using lab-based discovery. Designing an antibody that precisely triggers a very specific molecular cascade takes many years of trial and error. Designing bi-specific antibodies (that bind to two different proteins) is similarly difficult. Good design tools can unlock this.
RJ: The fact that the quality of the model has jumped means you’re enabling things you just plain couldn’t do. So it’s a step change. It’s not an efficiency argument at all, or not so much.
Matt: Yeah, exactly. It’s kind of interesting, even for us — it took me a while to believe in the thesis, actually. I talked to Josh for months before Chai started... It’s like, can I beat a mouse, and then can I do what mice can’t do? And then how many levels of interaction can you just keep building on top of that?
Everyone playing in the structural / binding space has an angle here, and some will be better than others, but Chai is pointing to a different unlock: getting good molecules right out of the gate (meaning they don’t then need as much lab work) means that the iteration time is faster. This turns science into engineering: you can design your systems to reduce friction and hill climb towards one-shotting molecules all the way to the clinic.
This, per-se, is not a new thesis: a16z articulated a version of this in 2020. What has changed is that structural models became binding models (how well doesn’t this molecule bind to this molecule, aka “binding affinity). Binding models unlock design, which has been steadily improving. Chai’s observation is that for engineering problems the best product tends to win, and good technology is a necessary but not sufficient condition.
Photoshop for molecules
With that in mind Chai has invested heavily in partnerships that allow them to learn from their Pharma counterparts.
What is kind of cool about working so closely and supporting so many of these partners is we get to really learn about what is the stuff that would be helpful in research. So rather than doing research in a vacuum, based on what would hypothetically be cool, we're able to do informed research based on what our partners have just been organically asking us for help with.
— Neil Patil, (Chai product lead)
This means better UX, such as a molecule editor that is more like a CAD or graphics design program than a chatbot.
Their approach has paid off: since June, Chai has announced three more major deals: Lilly, Novartis, argenx, plus an expansion of their Eli Lily program. This episode is too full of quotable moments for a short blog, so tune in to learn about
* Why protein tokens have the highest downstream value of any token
* Climbing levels of abstraction as models improve
* How Pharma, VC, and research are all just portfolio optimization
* How better tech changes the whole portfolio
* How relentless focus on simplicity leads to scale
Plus much more!


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Watch the full episode on YouTube:

We first covered Baseten last year when DeepSeek mania was at peak hype. Now they have raised a monster $13B round and become one of the new cohort of AI Infra decacorns that are (with Nvidia, Intel, and the semis complex) chief beneficiaries of the Inference Inflection.
We return to Baseten at the peak of the 2026 edition of Open Weights debate. Ali has published a viral breakdown of Kimi K3:
And since you last saw him, Philip has spoken at AI Engineer and written the definitive book on Inference Engineering spotted all over SF:
Three years ago, inference engineering barely existed as a category.
Today, it is one of the most critical disciplines in AI. Inference engineering inherently tackles a different question than standard model training: “How do you turn those weights from training into a product that is fast, reliable, and affordable at scale?” Focusing on these creates an entirely new optimization problem.
In one recent GLM-5.2 experiment, quantizing more of the model actually preserved its benchmark quality while increasing throughput by 20%, because the errors introduced in different layers could cancel each other out.
Inference is no longer just the final step after training. It is becoming its own engineering discipline, with its own research problems, infrastructure, and increasingly specialized roles.
In this episode, Baseten’s Philip Kiely and Ali Taha join swyx and Vibhu to explain what actually happens after a new open model is released and what it takes to turn “we generated a token” into a fast, reliable, production-ready API.
We go deep on cache-aware routing, disaggregated prefill and decode, quantization, speculative decoding, KV-cache movement, model parallelism, GPU kernels, and the race to make frontier models up to 10× faster. Philip and Ali explain why inference optimizations can still produce gains of 20%, 100%, or even 200%; how quantization errors can cancel one another out; why identical weights can behave differently across clusters; and how Baseten grafted a Kimi vision encoder onto GLM-5.2 without changing the underlying language model.
The conversation then expands beyond LLMs into NVIDIA Dynamo, mega kernels, Rubin, AI-specific chips, local inference, video generation, diffusion versus autoregressive models, and the enormous compute barrier to generating coherent long-form video. Finally, we explore the convergence of training and inference, continual learning through persistent KV cache, and the emerging loop where models help optimize the infrastructure that runs them.
We discuss:
* What happens when a 200,000-token request enters an inference system
* Cache-aware routing and reusing previously computed KV cache
* Why prefill and decode are increasingly handled by different GPUs
* When dedicated deployments become cheaper and more reliable than shared APIs
* How speculative decoding uses a smaller model to accelerate a larger one
* Tool calling, structured outputs, and what LLMs actually do
* What it takes to support a new open model on day zero
* Grafting Kimi’s vision encoder onto GLM-5.2
* Retrofitting inefficient model layers with components from other architectures
* Why models sometimes collapse into repeating the same token
* How hardware, kernels, and race conditions create nondeterministic failures
* Preserving model fidelity while making inference faster
* How quantization errors can cancel each other out
* Why inference optimizations still deliver gains of 20%, 100%, and 200%
* How optimized serving can make a model up to 10× faster
* NVIDIA Dynamo, KV-aware routing, and distributed model serving
* Speculative decoding the speculative decoder
* Why local AI is about making models less dumb while data-center AI is about making them less slow
* Tensor, expert, and pipeline parallelism across GPUs
* Hardware-aware model design, auto-tuning, and the case against mega kernels
* Rubin and why inference is becoming a systems problem
* Whether modern GPUs are evolving into programmable AI ASICs
* Why enormous models like Kimi K3 require GB300-class hardware
* Why open-source video generation still trails Veo, Kling, and other closed models
* The quadratic attention bottleneck behind long-form AI video
* Autoregressive video, real-time generation, and compounding quality drift
* Why future video systems may combine autoregressive and diffusion architectures
* Training for inference and inference for training
* Continuous post-training, deployment, evaluation, and improvement loops
* How GLM-5.2 helped optimize the kernels serving GLM-5.2 itself
* Why faster networking could unlock dramatically faster decoding
* Continual learning, KV-cache compaction, and persistent model memory
Show Notes
* How to build a day-0 API for Kimi K3
* 22580: From GPT2 to Kimi3, Explained
Philip Kiely
* LinkedIn: https://www.linkedin.com/in/philipkiely
* X: https://x.com/philipkiely
* Inference Engineering: https://www.baseten.co/inference-engineering/
Ali Taha
* LinkedIn: https://www.linkedin.com/in/aliestaha/
* X: https://x.com/waterloointern
Timestamps
00:00:00 Introduction and the 200K-Token Prompt
00:03:18 Dedicated Deployments, Speculative Decoding, and Tool Calling
00:11:26 Launching Production-Ready Open Models
00:19:06 Model Retrofits, Failure Modes, and Nondeterminism
00:28:22 Quantization and Canceling Errors
00:32:15 The Race to 10× Faster Inference
00:40:48 Dynamo, Speculation, and Local vs. Data-Center AI
00:50:18 Model Parallelism, Auto-Tuning, and Mega Kernels
01:00:55 Rubin, GPUs vs. ASICs, and Custom AI Chips
01:10:03 Giant Models and the Limits of GPU Memory
01:12:42 AI Video, Quadratic Attention, and Autoregressive Generation
01:21:47 Audio, Images, and Diffusion Models
01:27:32 Training, Self-Optimizing Models, and Continual Learning
01:40:06 Closing Thoughts
Transcript
Introduction: Baseten, Waterloo Intern, and Inference Engineering
Swyx [00:00:00]: Okay, we’re here in the studio with Philip, old friend from Inference Engineering, the book, as well as Baseten and everything that you’ve done, you and I have done before, as well as Ali. Welcome.
Ali [00:00:15]: Pleasure to meet you.
Swyx [00:00:15]: Waterloo intern.
Ali [00:00:16]: Waterloo intern, always.
Swyx [00:00:17]: When did you get “Waterloo intern” as a handle?
Ali [00:00:19]: As a handle? Oh.
Ali [00:00:20]: I think the rebranding happened mid-March. When I saw it was open, I was like, “I have to take it. Up for grabs.”
Philip [00:00:26]: The problem is that Ali is really good at his job and is not gonna be an intern much longer.
Philip [00:00:30]: So we have to figure out who’s gonna get the handle.
Ali [00:00:33]: Well, I’ll pass the torch over to the next intern.
Swyx [00:00:34]: Oh, okay. It can be, like, you just pass it to another Waterloo grad.
Ali [00:00:37]: To another Waterloo intern. No, bruh.
Philip [00:00:39]: Yeah.
Ali [00:00:39]: Intern.
Swyx [00:00:40]: Intern, yeah.
Ali [00:00:40]: And no.
Philip [00:00:41]: You gotta get an intern from Waterloo.
Ali [00:00:42]: Yeah, I’ve gotta get an intern from Waterloo.
Swyx [00:00:44]: Right.
Ali [00:00:44]: But they have to follow the path.
Swyx [00:00:45]: Oh, it could, but it could come from Baseten, so it’s like whoever Baseten gets from Waterloo.
Ali [00:00:48]: Right.
Swyx [00:00:49]: Has the title of Waterloo.
Ali [00:00:50]: It stays in the ecosystem.
Philip [00:00:51]: Exactly.
Ali [00:00:52]: Halfway through the internship, you either get it or you’re out.
Philip [00:00:55]: You should also do, like, a big graduation ceremony where you change the handle.
Ali [00:00:59]: Just say it.
Philip [00:00:59]: For everybody.
Swyx [00:01:00]: You guys are good at ceremonies, clearly. We had a nice launch of the book, very successful. But before we get into all that, I wanna start off with a fun question for you. Okay, you’re an expert inference engineer. What happens when I send a long query, say two hundred thousand tokens into Baseten’s inference? What’s the process of query through GPU model routing, balancing, all that? What is all the stuff that we don’t think about?
Long Context Requests, KV Cache, and Cache-Aware Routing
Philip [00:01:26]: With a long query specifically, the first thing that I’m gonna ask is, “Have you sent me this query before, or at least part of it?” and I really hope you have, because it’s gonna be a lot easier for me and a lot cheaper for you. So the first thing that we’re gonna look at is some cache-aware routing, where we’re going to see, we probably have a number of instances, a number of replicas up serving whatever model you’re hitting. We want to send this one to something with, number one, available prefill workers, and number two, ideally some cached input already there so that we can skip prefill on at least part of these two hundred thousand tokens. If you’re doing two hundred thousand tokens, it’s probably coding or a multi-turn agent or something where you would expect to have that cached. If you don’t, we’re gonna have to send it to a prefill worker. We’ve at least on certain models disaggregated prefill and decode, so you’re going to have one set of GPUs that’s solely going to process the input, create the KV cache, and get you your first token, and then that’s going to be passed over to a separate set of GPUs, which is going to run decode. We’re going to iteratively make those tokens. We’re probably going to have some speculator model in front of that. I’m going to assume that you’re doing coding, and because of that, our speculator model, which assumes you’re doing coding, is gonna have a high draft token acceptance rate. If I’m wrong and you’re asking me to summarize every Harry Potter book, it’s gonna be slower. And then we stream that output to you and account for it, charge you, a couple of pennies and say, “Hey, would you like to send another one?”
Swyx [00:03:04]: Except Baseten doesn’t charge by pennies.
Philip [00:03:07]: Well, yeah, we charge. I’m assuming that we’re talking about the public model APIs. If you are setting up a dedicated deployment, then yeah, it’s not pennies.
Public APIs vs. Dedicated Deployments
Swyx [00:03:18]: Yeah, one of the key differentiators when I was talking with Baseten initially was that people who want very high volume just need to rent by the box, ‘cause then it’s up to you to figure out how to saturate the box.
Ali [00:03:31]: And more often than not, it’s, like, way cheaper if you’re pushing, like, millions of tokens per hour, if you just pay per hour instead of pay per token.
Philip [00:03:37]: Yeah, they do. I think that we’ve increasingly seen a lot of demand for the pay per token APIs, just because everyone wants to try open models, and then once they find a use case that’s really sticky, then they move over to dedicated.
Swyx [00:03:51]: Is there a best practice on when it’s time to swap over?
Philip [00:03:54]: Couple reasons. Yeah, reliability, that’s a big one, right?
Ali [00:03:57]: Like, if they have a very specific use case, they want you to train something specifically for them, like they want their own spec dec, for instance, for their own traffic.
Swyx [00:04:04]: Spec dec is speculative decoding.
Speculative Decoding and Custom Speculators
Ali [00:04:05]: Speculative decoding, yeah.
Swyx [00:04:07]: You have to explain.
Ali [00:04:07]: Sorry. Like, speculative decoding is like, if you have a huge model, right? And so the model is going to be generating one token at a time every single turn, every single forward pass. So we attach, like, this little, like, parasite, like this layer that goes on top of the model, and this model just has to predict. It does three very fast autoregressive forward passes, and it will predict, like, three certain tokens, and then you do one forward stage over the entire original model in order to see if those predictions were correct or not, and then you accept them or you reject them. Now, this draft model is traffic specific, so if you, like, Philip said, if you’re summarizing Harry Potter books, I can train exclusively that draft model on Harry Potter books, and I can guarantee you that I’m gonna accept the three tokens every single time. And so with that case, I increase your decode speed. I wouldn’t be able to provide this to you if you’re a shared endpoint
Swyx [00:04:53]: Yeah
Ali [00:04:53]: ‘cause I have no idea if you’re doing Harry Potter, if you’re doing coding, if you’re doing English. We don’t know. Also, there was a thing in the book that mentioned that if they really cared about a specific threshold, chapter four, I think. Do you remember that?
Philip [00:05:06]: Yeah. The things that you can do is you can set a specific, like, batch sizing, a specific, like, parallelism strategy if you’re trying to optimize for, like, throughput versus latency. You can. Maybe a NVFP4 quant doesn’t pass your benchmarks and you wanna run a model at higher precision, you could do that. There’s just a bunch of reasons why you might wanna have your own endpoint and the biggest one, of course, just being, like, you don’t have to deal with someone else doing a hundred million tokens of benchmarking traffic at the endpoint when you happen to be trying to serve your users.
Swyx [00:05:40]: Yeah. I think one thing that is. That is a classic journey. Like, it’s people is asking the, what happens when you type Google into the browser. Tool calling, is that just, you’re generating JSON or is there more complication beyond that?
Tool Calling, JSON, and Structured Outputs
Ali [00:05:58]: Certain customers that we have, they have their own post-trained models, and so they demand a tool calling that’s not just, like parse a file or go find the weather. It’s something that’s very specific and you have to do post-training on this. And if the post-training on the model is not good or if the quantization after the post-training to get the inference to be fast, the model will struggle reading the JSON file and reading the tool calling. But it doesn’t require its own like sandbox. It’s not like it’s going to use that tool calling to like escape a sandbox or like it doesn’t have to be contained. It can just be a normal dedicated deployment. The challenge with tool calling more and more seems to be that the companies want certain tool calling which is a very sensitive thing to train. And because you’re dealing with all of the JSON outputs, if it doesn’t like close the end of the request in a very certain manner, you end up with a model that did the tool calling and like the thinking and so as a result of that, it didn’t see the result and just hallucinated the result as it decoded. That seems to be the most challenging thing with tool calling, not really the sandboxes model.
Philip [00:06:56]: Yeah, that’s a challenge on the training side and then on the inference side, there’s work that you can do to scope the possible output. So we published this at this point close to two years ago, the solution to this problem which is you make a state machine and you use that to constrain the output to a specific format. So this is the structured output problem. If you remember back
Swyx [00:07:27]: Yeah, the specific grammar is,
Philip [00:07:29]: Yeah, exactly
Swyx [00:07:30]: GML had this thing.
Philip [00:07:31]: Yeah. So it’s like the old-school “make sure this is only JSON”, return only JSON or
Swyx [00:07:38]: Yeah
Philip [00:07:38]: Grandma’s gonna die type of prompts.
Swyx [00:07:39]: Is it BNF grammar? At some point OpenAI had released a thing that was like, yeah, if you want to constrain your output, write BNF grammar, back as NOR.
Philip [00:07:47]: In our inference system, it’s just a specified output format. And you get the guarantee that your output’s gonna be structured along that format. And so applying that to tool calls can like help cut down on. You can still call the wrong tool or call no tool. It doesn’t solve the certainty problem but it at least solves the output structuring problem
Swyx [00:08:10]: Yeah
Philip [00:08:10]: Within tool calls.
Swyx [00:08:12]: And MCP is just another form of tool, right.
Philip [00:08:14]: Yeah, exactly.
Swyx [00:08:15]: As far as there’s no special thing there.
Philip [00:08:16]: The thing I’m always like explaining to people is the LLM is not capable of doing anything. It’s only capable of making suggestions of what to do and then if those suggestions are formatted in a certain way and applied to a system that knows what to do with them, then an action occurs.
Swyx [00:08:32]: Yeah. Part of the fun stuff is, this is solved outside of tool calling too. Like in an agent loop if the output is not correct or you’re right, like reasoning, tool calling was done in the reasoning trace, just be like, “Oh, I don’t know what to do. Let me just try again.” And it might get there after a few tries. And on your point of training, sometimes this is harder in smaller models, so you don’t have the same exact quality output
Ali [00:08:56]: Right.
Swyx [00:08:57]: When you just swap from a big model, right?
Ali [00:08:59]: Yeah. I will say that, before, I think we need to go back to inference engineering proper.
Ali [00:09:04]: But, I had expected that something would replace JSON because it’s hard to stream JSON ‘cause JSON must be complete and you must have open and close brackets and everything. So it’s hard to parse something or validate something while it’s being streamed. So people invented all sorts of things that are like, I forget the name of some of these alternatives, but it’s something like TOML, something like YAML. But JSON seems to be dominant still.
Philip [00:09:30]: The JSON outputs aren’t that long, right? Like you could have a long-- ‘cause tool calls also contain the arguments in them and perhaps for a certain tool you might pass like a very long argument. But my impression of the median tool call is that it’s a relatively small number of tokens, right? So I would expect that speculators are generally fairly good at something as formatted as JSON. And so you would have like a pretty fast decode step there and that the streaming wouldn’t be as valuable, but maybe I’m wrong about that.
Ali [00:10:02]: I think you’re also bounded by the software or that the model is gonna integrate with if the software is built with JSON for the tool calls or if the company that you’- if your customer says that this is how our software works and our tools are interfaced with JSON, you can ask them to like, change their software and say like, “Yeah, this is gonna be better for the model.” but like with the right training shouldn’t be that much of a difference. Also more profitable if it outputs more tokens probably.
Swyx [00:10:25]: Depends on your business model.
Swyx [00:10:27]: It really depends. But I will say that, as a writer with like experience a lot with generated output, I do try to move from text to JSON text which is very long JSON, right? Like there’s paragraphs in every field because I’m trying to structure it, right?
Philip [00:10:44]: Right.
Swyx [00:10:44]: I want you to first make factual statements, then make opinions then make bullet point summaries, have dates, have entity references have your sources for references, all these things. Anyway, so these are things that like I think people who really experiment with structural output have to really care about. But, let’s, let’s recurse up the stack a little bit. Before we started recording, you mentioned something really cool, which is that there’s a lot of engineering that-- inference engineering that goes on when a new model provider releases a new model, right? So let’s call it GLM-5.2, Kimi K3. I had previously assumed, especially if it’s like, well, GLM 5 to 5.1 to GLM-5.2, like that you’ve supported them before. Is it that much work?
What It Takes to Support a New Open Model
Ali [00:11:26]: It’s a lot of work.
Swyx [00:11:28]: Yeah. Okay. So like, a lot of people, all you guys, right whenever a new model launch like, people rush to say like, “Oh, Hugging Face supports this, Fireworks supports this, Spacetime supports this,” and I’m like, “Yeah, of course we support it.” But what goes into that? What goes into
Philip [00:11:40]: I think it’s more than just support it too, right? It benefits the consumer a lot. Like I think it was with Kimi K2.5 or GLM-5.2 the latest, there was an inference war, right? X provider is at 90 tokens a second. The next day we’re at 150. The next
Swyx [00:11:55]: I kinda kicked that off with the GLM-5.2.
Swyx [00:11:58]: I wrote a Twitter article about. It got like half a million views,
Ali [00:12:02]: Based on being number
Swyx [00:12:03]: Yeah
Ali [00:12:04]: Or it’s for something else.
Swyx [00:12:05]: Yeah. Which,
Ali [00:12:06]: Oh my God
Swyx [00:12:07]: Which then got everyone really excited about, hey, how can we, bend tracks a little bit further and,
Philip [00:12:14]: There’s a difference between support the model, as in I can make a token out of this model, and support a model, as in I have a production-ready API from this model.
Philip [00:12:26]: Getting to the point of I can make a token out of this model is not that hard because generally the, open source inference engines, vLLM, SGLang of the world oftentimes even receive weights ahead of time, maintainers do, or the people making the model merge PRs to ensure support. So you generally can, just get it working on the standard open source stack without too much pain in most cases. The challenge is, every inference company is gonna have own proprietary stack. Some open source components, some in-house stuff. And for any arbitrary model, there’s going to be some new stuff. Sometimes you get lucky, like K, two five to two six was, like, pretty similar.
Quantization, Speculators, and Production Readiness
Ali [00:13:16]: Yeah. It was pure continued post-training
Philip [00:13:18]: Yeah
Ali [00:13:18]: If I remember correctly.
Philip [00:13:19]: Even in those cases, there’s still stuff you have to do. You have to redo the quantization work. You’re taking the model from. Generally, these models are not released in NVFP4, and we want them to be in NVFP4 for maximum Blackwell compatibility. So we have to perform that quantization, and, calibrate the quantization to make sure that we’re not causing any regression in the model’s intelligence. And then we also have to train the speculator, as we’ve talked about. Generally, we have. We have ZDR, zero data retention on our model APIs, so we don’t know exactly the traffic that people are sending us, but we know what’s popular. We know that coding use cases are popular. We know that agents, agentic use cases are popular. So we can get public data sets that are representative of that traffic and train general speculators. Now, with speculators today, you need to train the speculator using the base model itself because you’re getting hidden states out of the model from running inference on these specific prompts, and that is the training data you use to create the speculator. So there’s that process which you need the real model weights for. And then there’s of course just the process of, standing up all the infrastructure behind it, loading all this stuff, testing it. And then when there’s a new model with a newer architecture, I think that, like, the DeepSeek models tend to be the most challenging as they have, like, the most novel architectural stuff going on, model after model. But every new model has something. Kimi K2 had. Oh, sorry, GLM-5.2 had
Ali [00:14:53]: Sparse attention.
Philip [00:14:54]: Yeah,
Ali [00:14:54]: Yeah
Philip [00:14:54]: the DSA.
Ali [00:14:55]: Right. Which is brought from DeepSeek.
Philip [00:14:57]: Yeah. And
Ali [00:14:59]: So you can copy-paste then?
Philip [00:15:01]: It kind
Ali [00:15:01]: I don’t know how this works.
Philip [00:15:02]: So, like we had to, like, build support for that into our runtime. And you’re right, like it is really interesting the way that all of these open source labs borrow from each other. For example, like GLM-5.2 doesn’t have vision. So something that, Haley, a guy on our team, if we could take a look at this, he, like, grafted the Kimi vision encoder onto GLM-5.2.
Retrofitting Vision into GLM-5.2
Ali [00:15:27]: We’ll be training the projector.
Philip [00:15:28]: Exactly. So if you think about, like, the encoder, there’s the encoder, which is the part that looks at the image and turns it into latent information, and then there’s the projector which like
Ali [00:15:38]: You can say latent space. It’s okay.
Philip [00:15:41]: And then there’s the projector that maps it onto, the model itself, and then there’s the model weights. You don’t wanna mess with the model weights because you run a chance of making the model dumber at something else for the purpose of giving it vision. So instead, Haley started with just a projector, which is only a handful of millions of parameters.
Ali [00:16:02]: That would be, yeah.
Philip [00:16:02]: Yeah.
Ali [00:16:03]: Can you show the training one?
Ali [00:16:04]: Like the way it groks
Philip [00:16:05]: Yeah
Ali [00:16:06]: Very interesting.
Philip [00:16:06]: And maybe
Ali [00:16:07]: That right there
Philip [00:16:07]: Maybe Ali, you should take it from here. You’ve got a better
Ali [00:16:10]: Ooh, double the sand
Philip [00:16:11]: Understanding of this than I do.
Ali [00:16:11]: Yeah. You can see, like, he. The way he trained this is really cool. At the beginning, he was training it using just like, “Here’s a picture of a mountain. Can you describe what’s in this mountain?” And that caused it just like the first, learning walls. Like here you can see this all we’re trying to teach it is to translate the encoded. Like it’s already taken the encoder from Kimi K. It’s taken the image. It’
Philip [00:16:31]: Yeah. Frozen
Ali [00:16:31]: Frozen
Philip [00:16:32]: With adapter.
Ali [00:16:32]: Exactly.
Philip [00:16:33]: Yeah.
Ali [00:16:33]: So the brain is frozen and the eyes are frozen. It’s just we’re trying
Philip [00:16:37]: Align
Ali [00:16:38]: Interconnect between the eye and the brain, right? So the projector. And so you take the tokens and then he’s like, “Oh, can you describe what’s in this image?” And he’s like, “Oh, it’s a mountain,” or it’s a person or it’s a human, whatever the case is. But that didn’t cause complete understanding. So he changed it such that every image was associated with a data set of questions. Like, does this image have a white male? Does this image have birds in the top corner? Does this image have a scientist in it? All of that stuff. And it would have to answer questions correctly. And using not just training on describing an image, but being able to answer question, another question, answer over time. Like you can see the grokking, which is like genuinely insane, that retrofitting vision into a large LLM can learn to that extent. And even for images that it doesn’t perform well on, for instance, if you ask it a picture of like Stephen Hawking, “Who is this?” Maybe it doesn’t get it, but it will say something like, “This is Albert Einstein.” Like it still understands
Philip [00:17:25]: Close enough
Ali [00:17:26]: That this is a scientist who is a man who has, some significant achievements, all that stuff. So that’s like really cool.
Philip [00:17:32]: Yeah. So, we’ve covered Hao Tian before, who the author of the LLaVA paper that did this, a while ago. And I think that’s very foundational work for anyone who hasn’t done vision work before.
Ali [00:17:41]: Same with the CLIP and MetaCLIP, where you go from just captioning to building out questions
Philip [00:17:47]: Right
Ali [00:17:47]: Off the image and how much better you can get performance.
Philip [00:17:50]: Right. Right. Right. Yeah. But what’s, what’s so exciting about this is if you look at a model like this. Now, this is a little bit more of a research project. It’s not. It got to 56% on MMLU Pro, I think. So not quite frontier. But if you’re running this model, you haven’t suffered any loss on your GLM-5.2 quality. If you don’t have an image, it’ll just behave exactly the way it used to. And ultimately
Ali [00:18:14]: Which in the inference code you literally do not include the other part, right?
Philip [00:18:18]: Yeah. You would just skip the encoder if you don’t have an image input.
Ali [00:18:22]: Okay.
Philip [00:18:22]: Just confirming.
Philip [00:18:23]: Yeah
Ali [00:18:23]: Does it affect a lot on the overall inference side? Like you’re not adding much, you’re adding a very small vision encoder. These are typically like
Philip [00:18:30]: They’re super fine
Ali [00:18:31]: Less than a billion parameters, right?
Philip [00:18:32]: Yeah. It’s, - There’s a little bit less standardization among vision encoders
Swyx [00:18:37]: Yeah
Philip [00:18:37]: So the support matrix can be a little bit, sparser. But overall, yeah, it’s a pretty, it’s a pretty minor component of the overall system. And ultimately what you get out of the system is all of a sudden you have Kimi Vision, GLM weights, and DeepSeek attention all in one model.
Open Source Model Grafting and Franken-Merges
Philip [00:18:56]: And that’s, I think, a lot of the power and beauty of open source, is that you can take all of these different components and combine them together into a system that’s better than anyone
Swyx [00:19:05]: Yeah
Philip [00:19:05]: Can be individually.
Swyx [00:19:06]: People used to say that you would also do Franken-merges where you would take like
Philip [00:19:10]: Yeah
Swyx [00:19:10]: Layers from each model.
Swyx [00:19:11]: Does anyone do that anymore?
Ali [00:19:13]: Well, to your point previously when you were mentioning like, the work that goes into supporting a model when it first comes out, like GLM-5.2 or MiniMax M3 or whatever the case is. Sometimes you do have to like, you do have to switch out some things. Like, for instance, the MiniMax M3 head uses full attention, and with full attention you end up with this like insane bottleneck in spec dec ‘cause you’re doing auto-regressive token generation for three tokens, and you’re doing this like N squared over all of the tokens that are in your sequence. Your KV cache is like very large because it’s not sparse, it’s not top K. So we find it better to like, okay, we’re gonna replace this, we’re gonna replace this layer with a layer from another model that’s using like GQA, for instance. And then just with the right training, you can get it to have the same acceptance rate. So it is very possible to retrofit layers from other models and very much needed. If a layer is like inefficient, the training just becomes the challenge, like how do you ensure that you train it properly? Which again to your earlier point is like the mesh between training and inference. As in like you need very good training in order to do fast inference. That’s like, I feel like more and more becoming true.
Swyx [00:20:21]: Yeah. Anything else on the support side when you say like get it to fully production ready?
Loop Detection, Race Conditions, and Non-Determinism
Philip [00:20:26]: Yeah. I think that there’s also a question of just, we can test a model to a pretty extensive degree, but we’re trying to get it out quickly and then you see a bunch of other people test it and you get interesting results. There was an issue with, GLM briefly where we had some like mode collapses where it would just output the same token over and over again for certain prompts on certain temperatures. Like once you expose an endpoint to the real world, there’s going to be, so many more varieties of things given to it that you’re able to, discover and patch things. So it’s not just a, day zero process, it’s then like for the first week, for the first month, if a model remains popular, like how do you both fix bugs and then continue to push the envelope on performance?
Ali [00:21:21]: What do you mean you don’t want your model outputting S?
Swyx [00:21:24]: Is there loop detection on that stuff, by the way? It still happens like quite a lot, which is surprising.
Ali [00:21:30]: We have like we, in our endpoint, like if a model was to output the same token like four plus times, we just cut the generation. We say like, “Oh, sorry, this-- Like try again,” or like we will reprocess the request. ‘Cause we know then, like if it, like if, yeah, it’s four times the same token, it’s probably collapsed.
Swyx [00:21:45]: Yeah. Is there a way to opt out in case I really want that?
Ali [00:21:48]: You want that?
Ali [00:21:50]: I think there’s a way that we have to handle it. I’m not exactly certain, but I feel like in certain models, like when they output something like you can imagine, like a table for instance, and so they want, they wanna draw like 12 dashes and 12 dashes. Yeah, I think there’s a way for that to happen. I think we only do it on certain tokens. Like we exclude certain special characters.
Swyx [00:22:07]: Yeah.
Ali [00:22:07]: So we only do it on like certain like S is the most common almost. GLM-5.2
Swyx [00:22:11]: Oh
Ali [00:22:11]: And I think it was DSV 4 as well. Like you’d just have like looping issues where like you literally
Swyx [00:22:17]: It
Ali [00:22:17]: Just have like S.
Swyx [00:22:18]: Yeah. Is there a special, something special about S? No, just randomly
Ali [00:22:21]: It just seems to be the one token involved.
Swyx [00:22:23]: Yeah. And it’
Philip [00:22:24]: Is there
Swyx [00:22:24]: And it’s only temperature 0
Ali [00:22:27]: No
Swyx [00:22:27]: Even at other temperatures
Ali [00:22:27]: Even at like 0.9 or whatever, it will still, it will still collapse.
Swyx [00:22:30]: That’s weird, right?
Ali [00:22:30]: It’s, it is an inference problem to be honest, like a software problem. Like oftentimes, the image you run will-- like NVIDIA will release an image for instance, and if we will upstream the changes from their latest TensorRT-LLM image into our stack, we’ll find that it fixes it. Or oftentimes this will only happen in an inference engine that you’re using like SGLang. But if you were to switch to vLLM, that isn’t the case. So it seems to be like an extremely like deterministic software issue and not really a model issue. It’s not like a weights problem. Like I’- we’ll say like, “Oh, it’s a problem with the quant. We did PTQ wrong,” right? But that isn’t, that doesn’t make sense because the same weights used with a different inference engine does not repeat the problem. And sometimes it’s, the kernels that are being used in the backend have like these very subtle sometimes race conditions, where if you were to use this model hosted on one cluster, you will never get this problem.
Swyx [00:23:19]: Oh my God.
Ali [00:23:19]: But if you host it on a different cluster, you will. And the reason is the KV cache transfer from a node to node in that one cluster is using a slower interconnect than the node to node in another cluster. So that exposes the race, whereas in another cluster it doesn’t. So then you end up just like, okay, this model is not gonna be hosted on this cluster. We’re gonna host it on, another cluster because that cluster exposed that problem. But then it ends up with like, okay, is it the software? Is it the model weights or is it the hardware?
Swyx [00:23:42]: There is a thing about this with temperature 0 still not being deterministic, right?
Ali [00:23:46]: Right.
Swyx [00:23:46]: Mostly because of hardware. Even at temperature 0 same model, you won’t always get the same output.
Swyx [00:23:52]: Even-- But I’m surprised by the race condition one because, I thought PyTorch was a graph that like guarantees that you at least, execute things in the right order.
Ali [00:24:02]: Well, yeah, true. Like I’m not, I’m not saying that there is. Like well, you have things like PTL optimizations where like you can start a kernel before the end of the previous kernel, and that’s like ‘cause you want to do that because there’s
Swyx [00:24:12]: It’s like pipelining
Ali [00:24:12]: Expense. Exactly.
Swyx [00:24:13]: Yeah.
Ali [00:24:13]: But it’- But you don’t do it cleanly. Like you overlap a little bit of the execution. No, it is very possible that the kernel itself, like that one block that is supposed to be running in this instance of time, that kernel itself has a race condition. For instance, like a missing barrier. Like often if you’re designing a kernel and you want it to make it to be very fast, if you don’t test it extensively, you’ll, you’ll have certain threads access data points from registers before they’ve been written to by other threads
Swyx [00:24:36]: Yeah
Ali [00:24:36]: For example, because like your barrier is wrong or your synchronization was wrong. But yeah, like the testing itself is very difficult in those like, and
Swyx [00:24:42]: And there’s no like borrow checker
Ali [00:24:45]: What does that mean?
Swyx [00:24:46]: Like Rust. Like the. If you’re trying to have like memory safety It sounds like a comparable problem.
Ali [00:24:52]: Well, yes, but you’re working in CUDA, right, NVIDIA GPUs. Like- You just need a higher level language like modular Maybe that’s what modular is supposed to do. I don’t know.
Quantization Quality and Vendor Fidelity
Vibhu [00:25:00]: How do you see keeping quality of the model? So you talked about all these steps of, okay, you gotta do quantization, train your own speculative decoder
Ali [00:25:07]: Right
Vibhu [00:25:07]: Run on different hardware. Looking at other model providers, okay, you kicked off a inference speed race on the consumer end. What goes into keeping quality the same across them, right? Sure, you can run benchmarks
Ali [00:25:22]: Yeah
Vibhu [00:25:22]: But, like, how do you determine how much quantization are there standards? What goes into
Philip [00:25:27]: There’s a few things on quality. Most inference optimizations are lossless. KV caching, for example. You are just recomputing or preventing recomputing the same values. Speculation, of course, if a draft token is wrong, it gets rejected. The main lossy optimization is quantization. And that really comes down to, number one, data format, number two, which parts of the model you choose to quantize, which layers, and number three, like doing a lot of calibration on the quantized weights, to ensure that you’re preserving all the outliers. There’s other tricks that you can do, though. A big one is long context, ‘cause one thing you asked at, right at the beginning is, “Oh, what’s gonna happen if I send a 200,000 token request in?” So with a long input sequence, you need to, store a lot more information. You need to process a lot more tokens. And so even if a model has a context of a certain length, you might, as an inference provider, choose to build an API with a shorter context length, and of course a full length one as well. Because if someone doesn’t need the full million token context, for example, you can get them better performance. I don’t know if that’s exactly like quality of the model. The way that I think about quality is to what degree are we faithfully serving the original model? If you think of a golden implementation of a model that performs exactly the way the model is designed to perform, I think of quality as how close are we getting to that, 100% fidelity of the model.
Philip [00:27:13]: You can also, of course, think about quality from the training side and how do you push yourself past 100%. But when I think about purely inference optimizations, it’s getting faster while staying as close to that 100% fidelity mark as possible. And certainly our standard internally is that, like you should not be able to tell the difference between our API and a, official API. I think Kimi in particular does a good job of vendor benchmarking here
Ali [00:27:41]: Yes
Philip [00:27:41]: Where they have
Ali [00:27:42]: They released an actual vendor benchmark.
Philip [00:27:43]: Exactly, yeah.
Ali [00:27:44]: ‘Cause they accused, some people, Amazon? There was some provider that was not doing very well on Kimi’s benchmark.
Philip [00:27:50]: Yeah.
Philip [00:27:51]: So, with Reflect we probably
Vibhu [00:27:52]: This was a long time ago, right?
Philip [00:27:54]: No.
Ali [00:27:54]: Yeah, like three
Vibhu [00:27:55]: They also
Ali [00:27:55]: Four, five months ago
Vibhu [00:27:57]: This also happened with, I don’t remember which model, but they pulled out quite a few, and then they started a whole chart about this. It might have been
Philip [00:28:03]: Kimi Vendor Verifier.
Ali [00:28:04]: Yeah.
Philip [00:28:05]: Yeah.
Ali [00:28:05]: Yeah, ‘cause you, ‘cause you’d be pissed, right? Like if you’
Philip [00:28:07]: Yeah.
Ali [00:28:07]: If like if I’m a consumer and I’m using like Amazon’s endpoint for instance, and I’ve used Kimi and I’m like, “Oh my God, like this is bad,” I’m not gonna say, “Oh, Amazon quantized the model in a bad way.” I’m gonna say, “Oh, Kimi sucks.” Right?
Philip [00:28:17]: Yeah.
Ali [00:28:17]: So it seems like that makes sense.
Philip [00:28:19]: Yeah, they care. They care.
Vibhu [00:28:21]: Justifiably.
Ali [00:28:21]: Yeah, justifiably.
Vibhu [00:28:22]: This is probably a stupid question, but just checking, has anything improved from main quantization?
Philip [00:28:28]: Yeah.
Vibhu [00:28:28]: Like, is quantization always strictly worse?
Ali [00:28:30]: Well technically
Vibhu [00:28:32]: No
Ali [00:28:32]: It’s a lossy. Quantization
Philip [00:28:33]: Yeah
Ali [00:28:33]: Is a lossy, it’s a lossy implementation.
Philip [00:28:36]: Speed improves
Vibhu [00:28:36]: Speed improves.
Ali [00:28:37]: It the number, like
Vibhu [00:28:38]: No, I’ always look for inverse scaling laws.
Philip [00:28:40]: Yeah.
Ali [00:28:40]: Yeah.
Vibhu [00:28:40]: This is something I learned from Noam Brown, where like things that normally act in one direction sometimes do.
Philip [00:28:45]: Well, technically when you run a benchmark, because these models are deterministic, sometimes your,
Ali [00:28:52]: Yeah
Philip [00:28:52]: NVFP4 quant is like, two basis points higher than your
Ali [00:28:56]: No, it’s noise. It’s noise.
Philip [00:28:57]: Yeah, exactly. I’m like, yeah, it’s, it’s within. That’s why I always say within margin of error.
Philip [00:29:01]: And I stopped saying that because everyone assumes that what is, well, within some margin of error, we’re barely inside of that to the worst, so we’re saying. But yeah, sometimes it’s just like, gives you a higher output score. But like Ali said, that’s noise. To my knowledge, you’re not necessarily making the results better. You’re just trying to, again, like keep your fidelity as close to 100% to the original model.
Layer Selection, KL Divergence, and Better Quantization
Ali [00:29:27]: There is, to your point, research that we did on MP. I don’t know if you are able to pull
Philip [00:29:31]: Yeah
Ali [00:29:32]: A tweet we did. One of our research interns, Joshua, I think it’s a tweet on how we have 20% better quantized GLM-5.2 than NVIDIA. Essentially what we found throughout like this month research is, okay, quantization is a lossy. It’s. You’re compressing the data from, occupying 16 bits to occupying, four bits, for instance. And so you’re losing some information, and you’re trying to minimize that. And so when I say that I’m gonna quantize the model, my job becomes how do I find the layers that I can quantize, and how to find the layers to not. For instance, with image models, I don’t quantize modulation layers, and I don’t quantize out projections because those two are. Like out projection is what you see as the user. Modulation is what the model sees or understands. Right, exactly. And so to his paper, do you have the. It doesn’t have the. Yeah. It’s a long paper. I don’t know if I can find
Vibhu [00:30:25]: If there’s a part to search or it’s probably in the thread.
Ali [00:30:28]: It’s probably in the thread.
Vibhu [00:30:29]: Yeah.
Ali [00:30:29]: But the long and the short is it is very possible that quantizing more of the model makes the results. Like if I have a model that I quantize layers one, five, and 10, and another model where I only quantize layers one and It is possible that the model in which I quantized more information is going to perform better because the quantization errors have canceled out. And so what Joshua showed in his mathematical proof where he had like a verifier in, is that you can predict which layers are going to have quantization errors that will cancel out with each other, and you choose to quantize those layers. And so the result of doing this mathematical quantization is you end up with a model that’s 20% more quantized than another provider, so you get 20% more throughput of it because there’s more layers than running an NVFP4, and your quality is better than that other quant because the layers that you chose to quantize have their errors cancel out, like one layer skewed to the right one layer skewed to the left, one layer skewed to the right. Your final logits distribution is more similar to the original distribution of the model, so you have better fidelity. And so the way we proved this was with KL divergence. So instead of just scoring on the benchmarks, we scored the KL divergence between the logit distribution of the quantized model and the logit distribution of the original full precision model, and we showed that with this technique we get. If your probability distribution on the logits which token it wants to select is more of the same as the original model, you’re probably gonna end up staying true to the original model. So yeah, so it seems like previously before this, it seemed like the industry was, well, the more you quantize, the worse it’s gonna be, ‘cause the more loss you introduce. That’s not exactly, not necessarily true. So yeah, doesn’t improve it, but can cancel out.
Philip [00:31:57]: I think it might be this, but reminds me a good bit about pruning where you can prune off certain layers.
Philip [00:32:03]: But very interesting. Didn’t know this was a whole paper you guys put out.
Ali [00:32:06]: It’s. Fun fact, it was originally 72 pages, this paper, and then we decided
Philip [00:32:11]: Wow
Ali [00:32:11]: We can’t tell. We couldn’t release it. So it’s now 45.
Swyx [00:32:15]: Still 39 pages, so very substantive. We talked about evals and all these things and, like what’s possible in terms of speedup? Like it’s like probably like the number
Inference Speedups and Benchmarking
Swyx [00:32:25]: Thing that people do wanna care about, and it’s something that you wrote about in your post. Like official API is 70 tokens per second, and you push it up to 90. Is that like a normal thing?
Philip [00:32:36]: So what’s cool about working in inference, the reason that I think inference is going to be a useful place to do engineering for a long time, is that if you look at highly optimized domains like, say, finance, if you’re in finance, you measure how much better you got in basis points. It’s like, “Oh, I got five basis points better, like twentieth of 1% better,” that’s huge news because everything is so optimized. When we publish optimizations, it’s 20%, it’s 100% it’s 200%. So there’s still probably like a lot further to go, honestly. Like you’ll, you’ll know that inference is pretty much solved when researchers start publishing about how they got 1% faster at something.
Swyx [00:33:19]: Which by the way, because I am from the finance background, in the ‘70s, that was the margin at the time. When you did quantitative finance research, you would find
Ali [00:33:27]: And like 20%, tens of percent.
Swyx [00:33:29]: That’s. Yes.
Philip [00:33:29]: Yeah.
Swyx [00:33:30]: And now it’
Philip [00:33:31]: Tiny fractions
Swyx [00:33:32]: For those people interested, look up Andrew Lo’s paper. He had a really interesting illustration of quant, stat arb, distribution, narrowing down from like those kinds of 20% differences in the ‘70s, down to nothing today, which is very cool.
Philip [00:33:48]: Exactly, and we’re at the beginning of the same type of thing. Now benchmarking is hard. I think anyone will tell you that, and benchmarking provider speeds is hard because there’s so many variables that go into it. What hardware are you using? How much load do you have on the system? What’s the exact nature of the prompts and input and output sequence lengths? All that stuff. But overall, when you start stacking these improvements, you’re looking at multiples. You can look at it. The most common form, of course, is TPS, tokens per second, which is bad naming by us in the industry, ‘cause there’s two tokens per second. There’s tokens per second, the throughput number, and the latency number.
Ali [00:34:31]: TTMT, yeah.
Philip [00:34:32]: Like total tokens per second out of the, out of the GPU as a throughput number. Most people only care about tokens per second as the latency number, which we should call ITL, intertoken latency, but we don’t.
Philip [00:34:44]: Anyway, so you can imagine a standard API without many optimizations for a 1 trillion parameter model operating somewhere in the 30 to 50 tokens per second range for reasonable traffic profile. And we generally see the goal of, pushing to 10X that. But, not necessarily day zero, but by stacking enough optimizations, if you have, say like four optimizations, each of which doubles performance. Or sorry, three optimizations, each of which doubles performance, then you stack that up, that’s an 8X gain. That’s the order of magnitude that we’re working with in this space. We’re trying to make things substantially faster, not just go from like 70 to 90.
Swyx [00:35:38]: Are you saying you’ve. You have done that?
Philip [00:35:40]: So let’s say you have as a reasonable baseline, 30 or 40 tokens per second. You can achieve 10X that. So like on GLM-5.2, if you run it unquantized, perhaps on H100s even, and you’re just using an off-the-shelf inference engine with no particular optimizations, no speculator, nothing extra around like KV routing, no disaggregation, you’re, you’re probably, yeah, looking at that like 30 to 40. You think that’s like a reasonable baseline?
Swyx [00:36:12]: Right. Right.
Philip [00:36:12]: To get to something like 10X, there’s a lot of trade-offs that you’re making. If we’re running at more like a 300, 400 tokens per second range, you are using the best hardware possible. You have a optimized speculator. You have done all of your quantization work. You are Seeing a pretty high cache hit rate. You are running with a reasonably small batch size and a parallelism configuration that is tuned for latency versus throughput, but it is possible. So the spreads that you see if you, like, go on artificial analysis or you go on OpenRouter and you look at, the worst provider to the best provider, oftentimes can hit that range. 10X is of course very aggressive. It’s oftentimes maybe more of a four to six times improvement. But that’s the performance that makes us really excited, is when we can get these huge gains, not just go from 70 to 90 tokens.
Stacking Optimizations: NVFP4, Speculation, and Disaggregation
Ali [00:37:19]: It’s also, like, hardware dependent. Like, if
Philip [00:37:20]: Yeah
Ali [00:37:20]: If you have a thing where you’re serving it on just, like, a node of H100s and then you throw, like, you shard the model across, like, four nodes of B200s. Like, you can definitely increase the speed with just throwing more hardware at it. Like, normalizing for the same exact hardware and the same number of GPUs.
Philip [00:37:35]: Yeah. Then you’re looking at, like, a two to 4X improvement
Ali [00:37:38]: Right. Right
Philip [00:37:38]: Depending on the inference optimizations. So yeah, it’s. Some of it’s, what’s the call, and some of it’s who’s the driver.
Vibhu [00:37:46]: If you break down the two to 4X, say the example is run GLM-5.2
Ali [00:37:51]: Yeah
Vibhu [00:37:51]: On B200s
Ali [00:37:53]: Yeah
Vibhu [00:37:53]: Single node, right? What’s, like, the cost trade-off for effort to get, like, the last bit of juice out versus what should people just think of, right?
Ali [00:38:01]: Spectre quantization. Yeah.
Vibhu [00:38:03]: Spectre quantization.
Ali [00:38:04]: That’s, that’s, that’s like 95%. Like
Vibhu [00:38:06]: And how far does that get you? And how easy is that for the average person to do? So say right I wanna throw the weights of GLM-5.2 on a node of B200s, how easy is it to find speculative decoder- decoder model or already quantized model? How much work goes into it?
Philip [00:38:23]: If you’re doing it up front, it’s quite a lot of work. If you’re doing it today, there’s going to be people who have published things that you can just, you can just grab some NVFP4 weights. You can grab a speculator. Yeah, if we’re thinking about, like, what are the 2Xs we’re stacking, going from, BF16 to NVFP4 is, it’s not quite a 2X, right? It’s like. I think it’s about, like, 30 to 40%, from 16 to 8, and then another 30 to 40% multiplied from, 8 to 4. So that doesn’t quite get you a 2X, but, like, roughly a 2X. Speculator, roughly a 2X. Disagg on top of that if you’re able to get enough hardware and put enough traffic through it, another roughly a 2X. And then you add in some, double-digit percent increase from having just a better runtime with, the latest kernels and stuff behind it. And that’s how it stacks up.
Ali [00:39:21]: Yeah
Philip [00:39:21]: So building each of those, like, building the, quantized weights is, for someone who really knows what they’re doing, hours to days of work. Building the speculator, again, like, hours to days of work. And the, disagg setup, hours to days. Well okay, but like once you have
Ali [00:39:39]: Once set up. Once set up. Yeah
Philip [00:39:40]: Yeah, getting disagg working for the first time, I’m saying, of course, is very difficult.
Philip [00:39:44]: The marginal implementation
Ali [00:39:48]: Like, if you’re just grabbing, like if you are a person, like just a normal consumer who has access to, like, a node of B200s and you’re wondering, “How can I just host it myself?” You don’t need to quantize the model yourself. There’s always gonna be, like, an open source quantized checkpoint. NVIDIA’s gonna push one out if no one else does. You. Usually, the providers will have their own spec dec that they’ve trained as well. You don’t need to train your own spec dec. You can just use that as well.
Philip [00:40:09]: Yeah. Like, GLM-5.2 has its own MTP.
Ali [00:40:13]: Right. Right.
Vibhu [00:40:14]: What’s multi token prediction?
Philip [00:40:15]: Yes.
Ali [00:40:16]: I’m just
Vibhu [00:40:16]: Can you explain that?
Ali [00:40:16]: I’m just an expert.
Ali [00:40:18]: I can do it for you in case I get it wrong?
Vibhu [00:40:20]: No.
Vibhu [00:40:21]: Yeah, you should correct if we’re wrong, but their multi-token prediction can be used for self-speculative decoding.
Ali [00:40:27]: I’m not sure. I’m not gonna correct that.
Vibhu [00:40:28]: Okay. I’m semi-confident in that
Ali [00:40:30]: Okay. Yeah
Vibhu [00:40:30]: But someone can check. But it’s useful to paint the story of, okay, not just the average person, but say a company wants to switch from serverless inference I wanna throw this up on. I wanna rent some GPUs, throw it up. These are the steps you take to do significantly faster than just put it behind vLLM.
Ali [00:40:48]: Right.
Vibhu [00:40:49]: I was waiting for a mention of Dynamo.
Vibhu [00:40:51]: I feel like, that’s supposed to be the baseline that you measure against.
Dynamo, KV Routing, and Disaggregation Toolkits
Philip [00:40:55]: I would think of Dynamo as less of a box system and more of a toolkit for building with. So when we talk about doing aware routing, when we talk about doing KV offloading, when we talk about doing, PD disaggregation, Dynamo fundamentally is. By the way, Dynamo is an open source library from NVIDIA.
Ali [00:41:17]: We’ve done a pod with Kyle
Philip [00:41:18]: Okay
Ali [00:41:19]: Kyle Cranin.
Philip [00:41:19]: Cool. So then your listeners know then that it supports all the different inference frameworks. And it is multi hardware, which is interesting.
Ali [00:41:28]: But it’s just a router, it’s not like an optimizer layer.
Philip [00:41:30]: Yeah. All it does, like, what Dynamo is good at, it is a library for moving information around your cluster, around your hardware. So if you have, KV cache on one place and you need it to be somewhere else, Dynamo coordinates NIXL for you to move that around.
Philip [00:41:49]: That doesn’t mean that, like, out of the box, you just say, “Pip install Dynamo,” and then you get, like, a massive performance speed up. It’s more of a developer toolkit.
Ali [00:42:01]: Yeah. I would have said it would. It comes with a set of defaults that you can then swap out.
Philip [00:42:06]: It does. If the industry at large, I think, was, like, rolling out all of these deployments, standard, then I think it would be, like, a credible baseline. But, we’ve got to, we’ve got to benchmark against, like, what we’re seeing in the wild.
Speculative Decoding Methods: Medusa, EAGLE, n-Gram, and Spec-Spec
Vibhu [00:42:23]: I did wanna talk a little bit more about PD disagg, because that is probably, like, number three after quantized and speculative decoding. In your book though, I was just gonna pull out the book.
Philip [00:42:31]: Yeah.
Vibhu [00:42:32]: Like section 522 on Medusa, 523 on EAGLE
Philip [00:42:35]: Yeah
Vibhu [00:42:36]: 524 on gram.
Philip [00:42:37]: It’s 55, would be disaggregation
Ali [00:42:42]: Yeah. Well, no, I just wanted to dwell a little bit
Philip [00:42:44]: Yeah
Ali [00:42:44]: The other. Like, so what do you choose to include? What do you choose to not to include? Because there was all these other techniques.
Philip [00:42:51]: Yeah.
Ali [00:42:51]: Are these still relevant? Because I think they came out, like, a year and a half ago maybe.
Vibhu [00:42:55]: Medusa is quite old.
Philip [00:42:56]: Yeah, Medusa’s old.
Ali [00:42:58]: It was old.
Vibhu [00:42:58]: But is it in the book as a good, here’s
Philip [00:43:01]: Baseline
Vibhu [00:43:01]: Baseline vanilla understand it?
Philip [00:43:02]: Like you should know this.
Vibhu [00:43:03]: Like I read the paper, I’m like, “ it makes so much sense.”
Philip [00:43:05]: Yeah.
Philip [00:43:05]: So with the book, I had a couple goals. One was to give people just a working vocabulary for the space as a whole, and the other was to give them some intuition about how each of these techniques works. As I mentioned in my AI Engineer talk, which is the first public addendum to this, the speculation space has moved much faster than everything else. So yeah, even at the time that I wrote the book Medusa, I very much included as a way for people to understand how the space evolved rather than what the most modern technique is. And now of course, there’s DFlash, dSpark. There’s, there’s newer techniques even than EAGLE, although EAGLE is still very commonly used.
Ali [00:43:51]: SpecSpecta.
Philip [00:43:52]: Yes. Speculative decoding.
Vibhu [00:43:54]: What can

Ali [00:43:56]: Oh, it’s a paper by Tri Dao and it’s like, it’s doing speculative decoding
Vibhu [00:44:00]: Huh
Ali [00:44:01]: For the speculative decoder.
Philip [00:44:02]: Oh, in spec- oh my God.
Ali [00:44:02]: It’s literally just an another. It’s like, yeah, that’s the most simple way to explain it, and it seems like he got trivial speed ups there. But it seems that the complexity with training, it’s almost like in our mind at least, it’s almost as complex as training GANs. Like it’s like a very delicate balance and oftentimes you, it’s just but yeah, it’s literally speculative decoding on speculative decoding.
Vibhu [00:44:21]: Speculative.
Ali [00:44:22]: Yeah. We saw this paper.
Vibhu [00:44:24]: It’s interesting, right?
Ali [00:44:24]: Yeah.
Vibhu [00:44:24]: I wouldn’t even expect it to be very particular to train, I would
Ali [00:44:29]: Right.
Vibhu [00:44:29]: The naive part of me is like, okay, train speculative decoder.
Ali [00:44:32]: But like, and it makes sense, like the whole idea of speculative decoding is you. It’s like, it’s like almost like the iPhone auto predict version but for a normal model, right? Like you’re just, you’re just, generating three tokens and you’re like, okay, I’ll do prefill on them. And so you save those three turns for your original model. Now your speculative decoder is doing three turns of auto regression, so why not just have an even smaller model?
Ali [00:44:53]: The other question there is what are the size of speculators? So say for
Philip [00:44:58]: Right. It’s like a billion parameters.
Ali [00:45:01]: Like for MiniMax, it’s. Yeah. It’s like one layer. It’s like one 60th of the original model usually.
Philip [00:45:06]: Yeah. I think we should do a paper when we get back to the office.
Philip [00:45:10]: Speculative
Ali [00:45:11]: Speculative
Philip [00:45:11]: Decoding.
Ali [00:45:13]: No, it’s, it does seem like how, when do you stop? But then it also seems like if you’re able to train spec-spec decode for instance, right? Like if you’re able to have a small model that is accurately predicts what the intermediate speculator is gonna predict, that is able to predict what the original target model’s gonna predict, then why not just use that smallest model directly, right?
Vibhu [00:45:34]: Yeah. This is
Ali [00:45:35]: Like it seems like
Vibhu [00:45:35]: Adjacent to the routing problem.
Ali [00:45:36]: Right.
Vibhu [00:45:36]: Yeah.
Ali [00:45:36]: Right.
Philip [00:45:37]: The thing with speculators is one of the practical constraints on using them is that you do have to run a small model on the same hardware that you’re running the big model on. There is a orchestration and resource competition problem inherent in that, and that is one of the constraints on speculation in general, is that draft tokens cost resources to create and cost software complexity to manage. And so if you have like infinitely recursive speculators, you add in quite a bit of that complexity on the actual implementation within the inference engine as well, not just in the training process.
Vibhu [00:46:17]: I was gonna say, I would wonder if you could do similar, like distillation and pruning of, it’s the same thing, it’s just a model. Can we not just distill a lot of the weights, quantize the speculator, out of my domain? The question that also comes up is, this is all for big server workloads, right? How much of this applies to, say I have this MacBook, I wanna run Gemma really efficiently. Similar problems, not the same?
Local AI vs. Data Center Inference
Philip [00:46:45]: Pretty different. I talked to Selo, about this on his podcast a couple weeks ago. The difference between inference engineering for the data center and for production workloads versus inference engineering for local AI, is that we start with fundamentally like different constraints and different goals. With local AI, it’s how do I fit this model onto my hardware and then make it less dumb? And with data center influence, it’s how do I load this model and then make it less slow? And we care about less dumb, and they care about less slow. But the local AI inference engineering ecosystem, I think has a lot for us to learn from in the data center space. They are experts in various forms of quantization, including dynamic quantization that we just don’t touch, in the pruning, in the distillation, in the, layer removal. There’
Ali [00:47:42]: Layer removal matters less.
Philip [00:47:43]: Yeah. There’
Ali [00:47:44]: No one loves pruning really.
Philip [00:47:45]: Yeah. Well, but the, but they do
Vibhu [00:47:46]: Which is surprising, right? But that’s, that’s a whole different thing
Philip [00:47:48]: Just to fit something on the laptop.
Ali [00:47:50]: Right.
Philip [00:47:50]: So yeah, it’s a, it’s an interesting, it’s an interesting space. Not necessarily that like their techniques make sense for us to do in the data center, because we have different resources and different goals, but more that the process as well as the openness of that field is something to, admire.
Ali [00:48:12]: Yeah. Like to your point, like, certain optimizations that would. Like for instance, Turbo Quantum Sharper, like it made such huge hype on that and we did like a whole deep dive on Twitter and like said, what is it? How does it work? Why is it good or not? And it took off and it was implemented on local devices because your memory bandwidth is so slow on like a MacBook, for instance. But try putting the same thing on like an NVIDIA GPU on a B200 Turbo quant would not be. Like, it would not be used. Like, NVIDIA - Like, NVIDIA made it clear that this is not a good optimization, and we’ve seen it firsthand where the overhead of doing dequantization, quantization of, in the kernel itself with turbo quant kernel, each end is much slower than the time that you save from doing the bandwidth. ‘Cause on the B200s, you have like 3.5 terabytes per second. You don’t need decrease the storage that much. You don’t need to do, FP4 KV cache. You don’t need to use a requant. There’s, there’s, there’s better optimizations to be made. But on Edge devices, it’s extremely important, it’s extremely useful. So, seems to be, like, different optimizations there, but then they’re all uniquely combined with like all you wanna quantize the model, you wanna do speculative decoding, like certain common prefixes with both
Philip [00:49:18]: Principles.
Ali [00:49:19]: Yeah, exactly. Exactly. Exactly.
Philip [00:49:20]: They also do a lot of work on, model parallelism, especially over, heterogeneous topology, where you have, some sparks and they are wired together with, Ethernet, DGX sparks.
Ali [00:49:35]: Yeah, this is the Exo Labs guys.
Philip [00:49:36]: Yeah. You have, a number of, Mac Minis stacked up.
Philip [00:49:41]: There’s, the inter. They. One thing that I think we both have to deal with, although they have to deal with a lot more is the interconnect between machines. Which is why, like, one thing that we do a lot is work with tensor parallelism.
Philip [00:49:56]: And that’s where, you are using all of the, all eight GPUs, and sharding the model across it. Tensor parallelism is not a good fit for local AI because it assumes a very high bandwidth interconnects like NVLink. Was, they might be forced to do something like pipeline parallelism, which we’re never gonna do unless we’re doing some kind
Ali [00:50:16]: Yeah. For image
Philip [00:50:17]: Multi-node inference.
Ali [00:50:18]: But since you mentioned it, I wasn’t sure if we were gonna cover it, but let’s briefly explain tensor parallelism and expert parallelism, since you have very nice images.
Tensor, Expert, and Pipeline Parallelism
Philip [00:50:25]: You wanna pull the book?
Ali [00:50:26]: Yeah.
Philip [00:50:26]: Yeah. Let’s, let’s get
Ali [00:50:27]: So I just wanna show a few images.
Philip [00:50:29]: Yeah. Shout out to Luke from Baseten’s design team for making these beautiful images. Oh, that’s a, that’s. Before we get into this, just one other difference is we talk a lot about the active parameters of a mixture of experts model, and for local inference folks, that matters a lot because if you have a batch size of one, you’re only activating that many parameters. When we
Ali [00:50:51]: Yes. I was gonna
Philip [00:50:52]: Inference in the data center
Ali [00:50:52]: I was gonna bring that in the diffusion conversation.
Philip [00:50:54]: Yeah.
Philip [00:50:55]: Yeah. We, I, when we go through like a MoE model, and we host it, for an API, we assume that all parameters are gonna be active because
Ali [00:51:06]: You’re batching
Philip [00:51:06]: Throughout your batch
Ali [00:51:07]: Yeah
Philip [00:51:07]: You’re gonna, you’re gonna hit everything. Cool. So broadly, tensor parallelism you can do with any model. Expert parallelism, you can only do with MoE models. Effectively all models today are MoE models, that are,
Ali [00:51:21]: Sort
Philip [00:51:22]: At least all models large enough that you would care to parallelize them across multiple GPUs. So that’s, that nuance is less important now. With expert parallelism, the idea is you put the entire expert on a GPU. Generally, you have more experts than GPUs, so you might put like N experts per GPU, like eight experts per GPU or whatever. And then you replicate the router, which the router is very small, across each of the GPUs. And then by moving the generation from expert to expert, with each expert being inside a GPU, they’re not competing for resources. You massively increase the throughput that you’re capable of doing, and the, GPU connection is not as important ‘cause there’s not as much communication. Tensor parallelism requires that you are able to do this like all gather, all reduce. So you shard the model across the GPUs entirely. And then for each step, you’re combining the results of each of the GPUs, which is why the interconnect matters a lot, and it is generally. Of course, this is a, this is a very high-level generalization. There’s a lot of places where this is not correct. But generally, TP is helpful for latency, and in many cases, you will use some combination of these two parallelisms, across the model rather than just, like, picking one or the other. Do you wanna add some color there?
Ali [00:52:50]: Like, yeah, usually, like in a model, it’s not. They’re not mutually exclusive. You do tensor parallelism and you’ll do expert parallelism. Pipeline parallelism less solely, it seems to me like we never use pipeline parallelism.
Philip [00:52:58]: Yeah. The only reason you would have to do pipeline parallelism, which is where you separate like different layers and you put like half the layers on one hardware and half on another, is if you are forced to do multi-node inference, because a model is bigger than you have the. Like let’s say, let’s say you’re doing a deployment on H100s for whatever reason, and you’re putting a trillion-parameter model on there. You have to use multiple nodes of H100, and so you. - Because the interconnect is so slow between the nodes, the only viable way to parallelize there is pipeline, but then you would do expert and tensor within each node.
Ali [00:53:36]: And the limiting factor for H100s is HBM?
Philip [00:53:39]: Yeah. They just don’t have enough
Ali [00:53:40]: How much? What’s the magic numbers that we need
Philip [00:53:43]: Like on a B200 is 180 gigabytes per GPU, and then a node of eight, so you’re talking like 180 times eight. And the FP4, so each parameter takes half a byte, so that’s 800 gigabytes. On a H100, it’s like 140?
Ali [00:53:56]: It’s 80.
Philip [00:53:57]: It’s 80?
Ali [00:53:57]: Yeah.
Philip [00:53:57]: Oof.
Ali [00:53:58]: Yeah.
Philip [00:53:58]: I’m old. I’ve been doing this a long time. I remember H100 specs.
Ali [00:54:04]: Yeah.
Philip [00:54:04]: No, so one thing
Ali [00:54:06]: You wanna tell me about the T4s?
Philip [00:54:07]: The T4s. Oh my God.
Ali [00:54:08]: Let me tell you what it was like to run a model on a T4 back in the day.
Ali [00:54:12]: One thing I was surprised to see that more people didn’t do, Jamba. I don’t know if you guys remember Jamba from AI ‘21. They would specifically pick a hardware, and then they designed the arc dimensions for the hardware, and then it would saturate the hardware. Like, it makes sense. And like, somehow all these models don’t do that.
Hardware-Aware Inference and Auto-Tuning
Philip [00:54:32]: Don’t they do this for the training side, though?
Ali [00:54:35]: I don’t know.
Ali [00:54:36]: Sorry,
Philip [00:54:36]: Training. For training the model.
Ali [00:54:37]: Like deciding which GPU, which
Philip [00:54:39]: Yeah. Well, how
Ali [00:54:40]: Yeah, they do And with training, it’s more of like a math. Like you can run the math- Yeah and see the flops and maximize it. With inference, it’s more of like an auto-tuning, like if you like GPU kernel auto-tuning. But like it’s like you define that, “Oh, I have two GPUs. I can do TP1, TP2, EP1, EP2,” for instance, right? And you. So that gives you like total of like two squared combinations, and then you just like you shadow the same traffic, like real prod traffic, and you just see which configuration gives you the best TPM and TPS, and then just use that. I don’t like the fact that it’s, you cannot reason about which one’s gonna give you the best performance or that there isn’t one specific configuration that’s always best. But it seems like auto-tuning is just the way that you find the best one. And with kernels and GPU kernels, it’s much of the same. After you design your kernel and you design your configuration, how many threads do you launch? How many, how much shared memory do you use? You just auto-tune. You just sweep the parameter space on the side, and this is the best one empirically. But yeah, but they are combined. They’re not just entirely- Yeah like separation. There’s a few bits of training that are like hardware targeted. If you look at, for example, NVIDIA Nemotron models, they run very well on Blackwell. That’s, that’s unsurprising. So there’s some degree of that, but I think that most open labs are trying to make models that can be run on as wide of hardware as possible rather than targeting just like a single chip. I see. For usefulness. Yeah. Okay, one more thing while this chart is still up. All gather, all reduce is expensive. One of the things that is a movement in Silicon Valley is mega kernels, just keep fusing kernels. I don’t know. Is it that simple? Well, I, like a fused kernel can’t save you. Like here with tensor parallelism, you’re. The half the matrix is on one GPU and the other half is on another, and if I need the entire matrix in order to do like a nonlinear operation in the next step, which is, for instance, like if I’m doing attention, I need the softmax, or I need to do like exponentiation, I need to have the entire row. So I need to know what the partial result was from GPU 2 and what the partial result was from GPU 1 in order to be able to do the softmax in the next stage. So I, like I have to make them communicate with each other, even if I had a fused kernel, because of the nonlinearities within each one. Also with like mega kernels, like honestly, I’m, I’m, I’m very bearish Ooh on, I’ll be honest. Like- Please. No, it’s just like mega kernels, it was a good research direction, and it seems like a very. Like intuitively, theoretically, it’s nice. Like, oh, like you have a lot of launch overhead from launching- Just- one kernel- Yeah, just keep fusing it moving the data. Just fuse everything together. But yeah, but like the kernel complexity itself is very difficult to write a very optimized mega kernel. It’s, it’s very difficult to do so. And even the, like not to name any companies, but like even the companies that have worked or people that I’ve spoken to who work at companies that do fused mega kernels, they very often don’t end up running those in production because the TensorRT-LLM and modular kernels that launch are faster because you can optimize each individual component, and you can just have them parallelize with each other. With the Rubins, I don’t know if you guys saw the Rubins Twitter post yesterday, but they’re also, Rubins? Like- No, like Rubin, like the GPU. NVIDIA GPU the, yeah, GPU. Yeah. They have a Twitter account for Rubins only? No. Okay. I was like, “What are you talking about?” Yeah. Sorry. One of the tech leads at NVIDIA is like launched a Twitter post said like, “We’re pulling the curtain on Rubin, and here’s the, here’s the specs.” And the third tweet showed, like not to get too technical into it, I and I need to read it much more, but the GPU is designed in such a way that it kills mega kernels. You don’t need to use mega kernels that much anymore. So it seems like that entire research field goes into like, won’t be continued, but yeah. Can I speculate about Rubin for a minute, please? Go. I’ve been through now, we And by the way, they are covered in the book. Yeah. But yeah, they- Well, they’re covered in the book in the sense that like I am aware- The Wikipedia entry from the blog post- Yeah that Rubin is going to happen in the future. And you even had the name of the one, Feynman. Yeah, it’s like, “Hey, this is gonna “ I was like, “This is very up to date.” Like I’m trying to future-proof this thing, okay? I don’t wanna publish a new one until like next year or something. Anyway, so we were discussing the degree to which I am old. And I’ve now been through three hardware launch cycles. I’ve been through the Ampere launch cycle, the Hopper launch cycle, and the, Blackwell launch cycle. Now, when I say launch cycle, I don’t necessarily mean like the actual shipping of the hardware. Like Ampere’s were racked up well before I got in this industry. But there is a lot of time between hardware being racked up and hardware being feasible for inference. So if you look at like the original vLLM and SGLang, vLLM especially, like that was written targeting Ampere and then had to be updated for Hopper, updated for Blackwell. With each of these cycles, it becomes faster and more urgent, but also substantially more complicated. When I look ahead to, what’s going to be new with Rubin, I think that like Dynamo gives me a lot of technical hints around like what kinds of work is going to be very valuable. We’re continuing some trends from Blackwell, right? NVFP4 is big. The amount of compute that they have behind NVFP4 tensor cores is massive. We’ll, we’re gonna talk about video, I think, at some point, and that’s the big barrier there. You’ve got, much faster memory bandwidth, but which was the same thing that made Blackwell so good. But the big thing is more systems thinking. You have more emphasis on the CPU to GPU interconnect, more emphasis on the interconnect between GPUs, and when you look at Dynamo, it’s a system entirely designed around how do I move the KV cache to where it needs to be when it needs to get there? So I think that themes around like KV cache offloading, KV-aware routing, and disaggregation are going to be substantially more important in the Rubin era, which means that inference engineering becomes not just a like CUDA kernel problem, but also like a very traditional hardware infrastructure problem, which is something, we’ve been building toward for a long time, and something that’s like very exciting to me because we’re gonna see
Mega Kernels, Rubin, and the Future of GPU Systems
Philip [01:00:55]: Multiple domains colliding and the ability to reason from the kernel level, like up to the hardware level and back down is going to be very valuable.
Ali [01:01:05]: I will take what Phil said one step further, into that. It’s, I think, trending towards becoming exclusively an infrastructure problem, where like problems of PD disagg, Training, spec dec. But troiting kernels is not going to be much of a problem because the GPU is moving more towards being an ASIC, where it’- you’re just, you’re just trying to orchestrate what happens on the GPU, but you’re not controlling it thread by thread level. And you see this with like QTAL, QDSL, like you’re, you’re just working at levels of like tiles of data, but you’re no longer working at controlling what each thread does on the GPU that’s being taken care of for you. So do you agree that a GPU and future GPUs are trending more and more towards becoming ASICs that just need to be launched and then they do the data operation based on your conversations with other people?
GPUs, ASICs, and Specialized Hardware
Swyx [01:01:50]: Oh, yeah, no. That is a section of the market.
Ali [01:01:55]: Right.
Swyx [01:01:55]: And ASICs can do, a lot more performance for only their workload.
Ali [01:02:01]: Right.
Swyx [01:02:01]: And the G in GPU makes them continue to be very general.
Philip [01:02:05]: Yeah. The, - I think that there’s like a spectrum
Swyx [01:02:08]: It’s graphics,
Philip [01:02:09]: Yeah.
Swyx [01:02:09]: I keep saying this, I have to correct myself in case people come at me for getting the G wrong.
Philip [01:02:14]: Yeah. It’s like, it’s like a spectrum, right? Of a very general purpose compute to something like a Taalas, where you’ve got the hardware built for a specific set of model weights.
Ali [01:02:26]: The weights burned
Swyx [01:02:27]: The weights
Ali [01:02:27]: Into the chip.
Swyx [01:02:28]: Yeah.
Ali [01:02:28]: No loading.
Philip [01:02:29]: I don’- I wouldn’t say that like, that we’re, we’re, we’re going all the way there. It’s more like along the spectrum, it’s a step in the direction of more specialization within the hardware.
Swyx [01:02:40]: Yeah. I’m curious, I feel like he was driving towards something.
Ali [01:02:43]: My point is being bearish on. Like, you say, like everything else apart from burning the weights into the chip. Burning weights into the chip is like impractical because you wanna fine-tune, you wanna optimize, you wanna quantize, you wanna release new checkpoints of the model. If it’s burned into the chip’s useless in like a month or two, right? My point is: How can you - like seeing NVIDIA more and more specialized, like take its GPUs from a general programming paradigm where you’re just-- it’s a general computer that you can use to program threads, and with every new generation, you’re putting more and more specialized instructions, specialized tensor cores, specialized, MMA instructions, things that will allow you to just control it almost as an ASIC, almost as a collection of ASICs.
Ali [01:03:22]: How can you look at this trend and then still be bullish on companies that are coming up with ASICs for AI?
Ali [01:03:30]: In the sense that, in the sense
Swyx [01:03:31]: Yeah, because they’re, they’re
Ali [01:03:33]: Right.
Swyx [01:03:33]: They’re, they’re evolving towards that direction.
Ali [01:03:34]: They’re almost evolving towards - Like as an Rubin, comp- Like compared to Ampere or, a T4, Rubin is an ASIC. It is, it’s just a thing that is used
Swyx [01:03:47]: Programmable ASIC?
Ali [01:03:48]: Yeah. It’s like - Yeah, like you can program, like I, like. It’s very controversial to call it an ASIC. It is a GPU. It is - It is general. It does have threads. I can write CUDA to control it and change its operations. But it has the systolic arrays and tensor cores and TMAs and tensor memory, and it has these things that are almost exclusively useful for loading model weights. It has, tensor core instructions that are almost exclusively shaped around the head dimensions of models that exist in the market today. To say that you’re gonna come up with an ASIC and you’re gonna etch something into it, well, but the next architecture is gonna be useless.
Philip [01:04:19]: Yeah, I don’t know. I don’t know. I think that the thing to remember is just how long these hardware cycles are.
Ali [01:04:25]: Yeah.
Philip [01:04:25]: So if a chip is coming out today, that means the design process for it was kicked off years ago. And they’- at NVIDIA, they’ve done a very good job of predicting where the market is going to go and,
Swyx [01:04:38]: They have the most information
Ali [01:04:40]: For sure.
Philip [01:04:41]: Of course. But if you look at, there being public open source model architectures that look more or less like early versions of the one today, Rubin’s honestly the first chip that was fully built in that world. And so you can see a lot of the understanding of the shape of the workload that this chip’s going to be asked to do in the way it’s designed.
Swyx [01:05:04]: Yeah. Okay. So I’m not gonna be the best person to directly answer those questions. I think these are very fair questions that - the first one that’s based on Rubin that like I’ve, heard artic-articulated so well. I do think that, I will make a case for a vertically integrated model lab ASICs.
Swyx [01:05:24]: So like the OpenAI, Broadcom, what-whatever, Jalapeño
Philip [01:05:27]: Sure. Yeah
Swyx [01:05:28]: Chip, which like totally makes sense. Like, so - we first had this on the pod with, Martin Casado, where he was like, “Look, if you have a trillion-dollar or five hundred billion dollar training then take fifty billion of that and make a ASIC. Like it’s fine. Like you will get more than ten percent efficiency from the ASIC.” And like that makes sense.
Philip [01:05:46]: Right.
Swyx [01:05:46]: Right? So like a model-specific chip, yes. But ASIC companies, the interesting thing is I feel like you are focus-- you’re hyper-focusing on like you say, like the Taalas stuff.
Philip [01:05:58]: Right.
Swyx [01:05:58]: They are doing a lot more like, surface area engineering or like the actual allocations of memory and hardware and like the communication between chips that, probably still won’t be touched by Rubin, but I don’t know the details.
Philip [01:06:14]: I see. I see.
Swyx [01:06:15]: They-- Typically, they often talk about things that I would expect to have bigger orders of magnitude than would be programmably accomplished by whatever Rubin does. But who know-- who knows?
Ali [01:06:26]: No, I see.
Ali [01:06:28]: Yeah. It seems,
Swyx [01:06:29]: Yeah, like think about what - what are the real blockers to ten x to one thousand x faster inference. It is not the stuff that can be rearranged, just within the existing GPU design.
Ali [01:06:41]: Inter communication.
Swyx [01:06:42]: Yeah.
Ali [01:06:43]: Okay.
Swyx [01:06:43]: Like these guys are aiming for three hundred thousand tokens per second. They’re not f*****g around. Like,
Ali [01:06:49]: Might have to put on some X6.
Philip [01:06:50]: Maybe. I think, it is interesting to me that you’re so bearish on so much of this kernel engineering work, given how much of it you’ve been doing recently.
Ali [01:06:59]: Right. Right. But like the more I do it, the more it just seems to me that
Swyx [01:07:01]: It’s not mega
Philip [01:07:02]: I would also add like
Vibhu [01:07:04]: There’s generations of models being out, right? I think on your guys’ end, you see a lot of, okay, one day it’s GLM, Kimi, DeepSeek, MiniMax, throw in the others. Some are doing completely different stuff, right? Gemma, no encoder. The latest thinking machines is all from scratch. But when you look at the other side, like how long have we been on the GPT-5 generation, right?
Philip [01:07:26]: Right.
Vibhu [01:07:26]: They’ve been serving that thing for quite a while. Sure, there’s maybe more training. There’s, there’s different checkpoints, but like you can squeeze quite a bit out and you do a multi-billion dollar train run. If you can make it X percent more efficient, they serve it for a while. Same with, say, the Claude 5 set, family, right?
Philip [01:07:44]: Like if they release a new model, like if they release GPT-6 now or whatever
Model Longevity, Open Source, and Enterprise Reliability
Vibhu [01:07:47]: Yeah
Philip [01:07:47]: And they release a new model every year, and - well, we don’t know, but if we assume that they’re changing some bits of the architecture and not just doing like post-training, like you’re gonna be spending fifty billion dollars a year every single year coming out with new ASICs for the model and throwing out the ASICs of the previous year away.
Vibhu [01:08:03]: Yeah. Yeah. Easy.
Swyx [01:08:05]: So I think, okay, I would slightly disagree based on my again,
Philip [01:08:09]: Yeah
Swyx [01:08:09]: It’s all secondhand, on the longevity of a model.
Philip [01:08:12]: Right.
Swyx [01:08:12]: There’s still people out there using 4o.
Vibhu [01:08:14]: Yeah.
Swyx [01:08:14]: Yeah, Llama. Not Llama 2, but Llama 3. I still see Llama 3 workloads.
Vibhu [01:08:18]: Yeah.
Swyx [01:08:18]: Because if it’s done, if it’s trusted, don’t change it.
Vibhu [01:08:22]: If it works.
Philip [01:08:24]: Which is one of the promises of open source, right? Like the whole 4o, save 4o movement. Like you don’t gotta have a save Llama 3 movement. You just gotta have an eight one hundred somewhere.
Vibhu [01:08:34]: I think at some point there’s also the question of, okay, if a model can do enough and use enough tool calls and be agentic enough, can it just web search, tool search write code? Do you really need to keep squeezing more? We will because you guys will make it cheap and fast and smaller, and I can swap it in. But at some level, like you give me GLM-5.2 today or say whatever 120 B model, I can run with it for quite a while, right?
Philip [01:08:59]: This is assuming like you don’t need intelligence.
Vibhu [01:09:02]: I think there’s a lot of intelligence where we
Swyx [01:09:03]: You need reliability and predictability. Like I’m in enterprise like like this is tried and tested. It is signed off by like my five thousand stakeholders.
Philip [01:09:11]: Right.
Swyx [01:09:11]: Like I’m not touching it.
Philip [01:09:12]: It runs a batch job every and I like the results.
Swyx [01:09:16]: Yeah.
Philip [01:09:16]: The results are predictable. Yeah.
Vibhu [01:09:18]: Yeah. It doesn’t make sense to keep using them. Like stuff gets sparser, cheaper, better.
Philip [01:09:23]: Right.
Vibhu [01:09:23]: But that doesn’t mean that old models, GLM 50 isn’t usable, right?
Vibhu [01:09:28]: If we hit a stall, say, for whatever reason, there’s still a lot that can be squeezed out.
Swyx [01:09:34]: We’re gonna run out of time. I did wanna also make sure. Yeah. Yes, we happen to have this diagram. Pull. Compare this versus any Cerebras diagram, right? I don’t think Edge10, medics have put out public, charts yet. But the complete the real estate is very different. The size is very different, right? This is not wafer scale, right? This there’s probably like, I don’t know, a few hundred of these on a wafer. I don’t, I don’t know how big
Philip [01:09:55]: Right.
Swyx [01:09:55]: The comparison is. But like, it is a, it is a very like real estate allocation
Vibhu [01:10:00]: Yeah
Swyx [01:10:00]: Difference.
Philip [01:10:01]: Few dozen, I would say.
Swyx [01:10:03]: Few dozen. Yeah.
Vibhu [01:10:03]: Before we move from hardware, I have two quick questions. One, the latest Kimi, which is really big, three trillion
Kimi Scale, GB300, and KV Cache Limits
Philip [01:10:09]: Yeah
Vibhu [01:10:09]: Doesn’t fit on most hardware on single node.
Philip [01:10:12]: Yes.
Swyx [01:10:12]: You need GB300 to fit it on a single node.
Vibhu [01:10:14]: You need GB300 or AMD.
Philip [01:10:20]: It’s simple math. NVFP4, two point eight trillion parameters, one point four terabytes. The GB300s have, two hundred and eighty-eight gigabytes each. So across eight of those, you have enough room for the model, and honestly like. So the other thing with GPU VRAM math is you have to leave space for the KV cache, and that’s going to depend on, to some degree, on the context length. So when a model is both has a very large number of parameters and a very long context length, you’re like fighting over space. Which is why, the KV cache offloading, would become like a more salient topic, I think, with these huge models. ‘cause you just, you’re very crunched for space.
Vibhu [01:11:10]: With the Rubin, you now have what? NVL 72 rack
Philip [01:11:15]: What?
Vibhu [01:11:15]: 20 terabytes of your
Philip [01:11:16]: Yeah. Now you still have NVL 72 on, Blackwell as well, but, you can’t necessarily assume you’re gonna do inference on that.
Philip [01:11:24]: There’s a whole lot more 8X racks in the world than there are NVL 72s.
Vibhu [01:11:30]: Yeah. My last quick question on hardware was, do you notice anything with hardware generations for new trained base models? So one of the things you said for efficiency is you can swap hardware. That’s one of the 2X gains. When we see new stuff coming out training-wise on Rubin, any changes on logs? Does this affect what type of models we will be seeing when these are more available? And can
Philip [01:11:56]: They get bigger. Like people understand the ceiling that you have in terms of how many parameters of a model you can run, given the latest inference hardware, and that forms a ceiling. And so, for example, when DeepSeek R1 came out, it was six hundred and seventy-one billion parameters, which at the time was really huge and I think did a lot to push us to really quickly adopt Blackwell and get good at serving on Blackwell. So yeah, it’s, it’s mostly in my mind about, model size and then about matching the architecture and the native quantization to the target hardware, like we talked about with like, all Nemotron models or NVFP4, for example.
Vibhu [01:12:42]: So we talked a lot about LLMs.
Video Diffusion, Attention, and Autoregressive Video
Vibhu [01:12:46]: You have a lot more in the book. What about audio, video? What’s the other side of inference engineering? Ali, you’re pretty big in video diffusion.
Philip [01:12:53]: Video diffusions, I think, are like they’re just shaped. A lot of the stuff that you can think about, reason about with LLMs being autoregressive. With video diffusion, it’s, it’s not the case. For instance, you don’t
Ali [01:13:04]: You don’t do batching. - every request just comes in on one GPU and it serves one GPU. You don’t have to shard. The models are a lot, are a lot smaller, like Wan 2.2, for instance, is a twenty billion parameter model. You don’t need to worry about. So it’s like orders of magnitude smaller than the best LLMs. And it’s one of those spaces where the open source models are. Like with LLMs, we see Kimica 3 is almost comparable to, Mythos or like GPT 5.5. The difference between the best open source LLM and best open closed-source LLM is very small. Like it used to be six months. I don’t think it’s six months anymore. I think it’s like almost on parity. Video models are definitely not. There’s a huge gap. If you look at the best video that you can generate today with an open source model like Wan 2.2 versus something like with Kling or Veo, difference is night and day. So it creates this disparity where media companies will choose to go most of the time to closed source models.
Ali [01:13:58]: For instance if I were to tell you, “Hey, I can generate an entire three-hour movie for you with this model, and I’ll optimize it so that you only have to pay me ten dollars.” But if they were to do it on a closed source, they’d have to pay a thousand dollars, which is a hundred x. Like I’m a hundred x cheaper, but it’s still a thousand dollars. They’re still gonna choose to do all of their cuts with Veo and Kling. So the. It’s like a chicken and egg cycle where less demand causes less innovation in the field, causes, less open source checkpoints to be released. And some of the labs that were releasing open source models like Wan will have closed sourced their latest models, like Wan 2.7 is not open source. We’re still on Wan 2.2. The challenge with video models especially is the number of tokens. So video models, you want to generate a high quality model, a high quality video. So let’s say you’re doing sixteen frames per second, that’s like the absolute minimum you’ll do, and let’s say you’ll do like 480p video. So you can think about your like dimensions and I think I have like a good, just like a diagram that shows the number, the sheer number of tokens, right? Let’s say you’re looking at like just one video of like, Sparta 300 or whatever. So let’s say we’re looking at like four frames, right? Those four frames of that video, if you go just. If you’re doing full attention, if you go a bit up, like you’re looking at, 480p by 720 by 81 frames in just five seconds, because 16 FPS by five, right? And then you compress it down to latent space, but you’re still doing 30 by like 50 by 21 tokens.
Vibhu [01:15:25]: Yeah.
Ali [01:15:25]: Which means that for attention, for just five seconds, you’re running attention on 35,000 tokens, right? So the attention becomes such a huge bottleneck. And because it’s O(n²), if you’re doing like-- if you extend that to like ten seconds, well, it’s just squared, 20 seconds, 30 seconds. So to generate a good cut scene of like one minute, it’s almost impossible to do within the same compute time. And it’s just, it’s, it becomes unfeasible. You can’t do it. And so you end up with moving towards two directions. Either you decide to do attention on the entire video at once, in which case you are forced to do sparse attention. So if you scroll back down to the origin, the video image, like you can see whereas on the left, for instance, I would be doing full attention where every single token in that Sparta 300 scene attends to every single other token, as you can see the sheer number of like red patches. On the right, I’m only attending to each token only attends to like the top K or top 12.5% that’s important to it, which can be like spatial. So like, the token that represents the crown attends to like the head, the face, and then the head on the other frame and the previous frame, temporal locality, spatial locality, that thing. This results in terrible video quality and the whole point of the post or the article here is to show like how you can train and you can do all these things, but you will still suffer in your quality a little bit. So you end up with one of two things. Either you bite the bullet, you have huge compute, and you do full attention over like a million tokens because you’re trying to generate like two minutes of video, or you move towards autoregressive video. Autoregressive video seems to me like that is the bet that the future’s gonna be making, but there are no good open source autoregressive video models out there today. And that seems to be the. If you want to get like an hour movie, if you want to see video models generating like an, like, Hollywood level movies, they have to be autoregressive in order to exceed that five second frame. Or there has to be some insane leap that happens in compute that allows us to do full attention over like millions of tokens at the same time in a, in an efficient manner.
Vibhu [01:17:10]: Even millions of tokens, it’s like you’re, you’re quadratic, so you’re gonna get there really quick.
Ali [01:17:15]: Right.
Vibhu [01:17:15]: I think, can you explain the pros and cons trade-offs of autoregressive? So one that comes to mind is, the consistency across frames.
Ali [01:17:23]: Right.
Vibhu [01:17:23]: You will. Ten minutes into generating autoregressive diffusion, you’re gonna forget. But what are pros and cons of this?
Ali [01:17:30]: Well, like autoregressive LLMs, you can take a lot of your. Oh, sorry, autoregressive diffusion models. You can take a lot of your optimizations that we discussed with LLMs, like spec dec and stuff like that, and you can apply it there. And you can, if you have a very high quality scaled up model, there is no reason why I can’t stream the outputs as in I can show you the first frame and then I’m like GPT back in 2022 when you were. Like now it’s almost like shots the text, but back then you could read and it’s generating as you read. With video models, you can watch and it’s generating as you watch. You it generates the frames and so token by token generation will allow us to scale a lot up and apply the attention mechanisms there. The downsides is every single autoregressive video model is s**t. It’s just terrible quality. If I, like, it’s just if you put, if you put the quality of any opens like Wan 2.2 versus any other autoregressive model, you can see like a video generated by Wan 2.2 is like, a cat and dog fighting. Autoregressive model will give you like degraded Tom and Jerry quality. I don’t know. The solution to generating long output then becomes, “Okay, we’re not gonna use autoregressive model. We’re gonna.” If you look at some of the things that like Grok Imagine or Grok Video does, and they do it really well, is they’ll, they’ll try to stitch these, seven second chunks together. And so you generate seven seconds and then you’re like, “Okay, I’m gonna. Can you extend this video?” And they’ll chunk two videos together. Open source doesn’t seem to have the tricks that they have there and by definition it’s closed source. We don’t know what they’re doing. But the closest you can get is taking the last frame of a video and feeding it into like a text and image to video where it will take the text, the prompt, and it will take the image of the last frame, and you’ll ask it to generate the next five seconds. And that’s like how you can extend this level of a model to generate like a movie, where you’re just, you’re constantly streaming frame by frame. But you get a drift. So you start with like you take the image, and then you generate a video, and then that next five-second video is like lower quality, and the third chunk is like even lower, and the fourth chunk is even lower. And like sometimes you’ll see things where like the new video is like just ever so slightly darker than the first one, and the next one is darker than the second one until like twenty-five seconds and you have black screen.
Ali [01:19:31]: Like it’s just. It’s, it’s - We tried to have a demo that would show this, but it was like-- it was extremely embarrassing to show. Like we just decided not to because it seemed to like. But it is, I think models will get there. They just need to, in my mind, scale up significantly and move towards being autoregressive. But the training techniques don’t seem to be clear there.
Swyx [01:19:50]: For those - who are interested in Grok Imagine, we did a pod with Ethan Ha from that team
Ali [01:19:54]: Right.
Swyx [01:19:55]: Who dropped a little-- a few hints, but not that not enough that we can fully reconstruct everything.
Ali [01:20:00]: Right.
Philip [01:20:00]: Specifically on this part, - he explains a bit about that.
Swyx [01:20:02]: Yeah. So we talked about memory and, longer context and all these things.
Ali [01:20:06]: But as far as I know, they’- it’s not autoregressive, even though like no one in industry is autoregressive.
Swyx [01:20:11]: Yeah.
Ali [01:20:11]: It seems to be, yeah.
Philip [01:20:12]: The key thing to understand between a autoregressive model and a diffusion model is that diffusion attention goes in both directions, while autoregression, it only goes forward in the sequence. So that’s why you see this like going off the rails behavior, both in. If you naively construct a video generation model as simply generating a linear sequence of frames, you can’t then go back in that sequence and fix something to make the whole thing consistent. While, of course, the reason that we need all this latent space for the video model is, like you said, we keep all the tokens in memory, we iterate over that full sequence, and you can adjust the past in order to make the future make sense. So if we think about the architecture that’s gonna get us there to these longer, richer sequences, it’s probably, like you said, gonna be a mix of the autoregressive and the diffusion, working together to do what each piece is good at.
Ali [01:21:10]: Well, if you get. Like you intuitively get why. So like English, for instance, or just writing in language, it’s like it’s just left to right. You can stream your tokens, you can stream your chain of thought. Just even as a human, you write like you just. You write and then you think about what’s the next thing you’re gonna generate, and then you write that, and then you think about your ideas, and then you generate forward. And sure, you can argue that as you write, you need to go back and you wanna edit some things, but you need to do that, less often than you’d think. Whereas with video, there is no sequential. The pixel in the top left corner of the video and the pixel in the bottom right corner of the video, they both need to attend to each other to understand how the video quality is gonna be almost as equally. Whereas with text, you don’t need that as much.
Philip [01:21:47]: Is there a parallel to audio? Like I’m not a hundred percent confident on this, but there was a point about a year ago where there was Audio LM, there’s diffusion for audio and autoregressive, and for the points you mentioned, mostly on the inference side, even though they’re shorter clips, most music is three to five minutes
Audio, Diffusion Text, and Cross-Modality Lessons
Ali [01:22:04]: Yeah
Philip [01:22:04]: We’ve swapped over to autoregressive Yeah, I can’t speak to music, but speech is autoregressive.
Ali [01:22:11]: Speech.
Philip [01:22:11]: You, effectively. This was even back with like the Orpheus architecture a year and a half ago. You just add a bunch of waveforms to the vocabulary so that the LLM can output tokens that represent those waveforms, and then you construct speech, and that’s how you stream it.
Ali [01:22:28]: That’s it. Wow.
Philip [01:22:29]: That’s my AIE talk from 2025.
Ali [01:22:32]: Nice. Nice. But it’s - with audio, it’s not the same challenge, though, is it? Because you. Like audio is solved with an LLM that generates everything. Like with audio, it’s still a transcript that you can generate with an LLM.
Philip [01:22:43]: Yeah.
Ali [01:22:43]: So your audio model just needs to like transcribe it, text to speech.
Philip [01:22:47]: For music, there was a phase of a trade-off between diffusion for music
Ali [01:22:52]: Right
Philip [01:22:52]: Autoregressive, and they were both pretty on par. There’s probably more pros and cons to either. I just wanted to poke and see if you had takes.
Ali [01:22:59]: Yeah, I don’t know about music specifically.
Philip [01:23:01]: Oh, well.
Ali [01:23:01]: What-- with what you said about editing you writing, I think my editor would tell me I need to do that more often and go back and fix things. I can imagine music or poetry, for example, where you have a rhyming scheme, and you might wanna go back and make a change to make it, to make it easier to set up a rhyme that you wanna make later on. There being some advantage to being able to attend in both directions. But yeah, to my knowledge, I very much bifurcate this inference problem into the autoregressive models, which have a set of constraints and techniques, and the diffusion models, which have a set of constraints and techniques. And, I think of text, embedding, voice in and voice out as being in the autoregressive side, and then image and video being in the diffusion side. There’s some overlap between the two. It’s not a perfect split, but that’s the broad categorization I use.
Swyx [01:24:02]: I should point out, I think it’s confirmed, right, Nano Banana and, GPT Image are autoregressive image.
Philip [01:24:07]: It’s this blended approach that we’re talking about, but in the image space, it hasn’t like made its way over to the video space, at least in the open source world.
Swyx [01:24:19]: Yeah. But like I assume that’s not too far away if that is possible
Philip [01:24:23]: Right.
Swyx [01:24:23]: On the. At least the Qwen Image guys are trying it.
Philip [01:24:26]: Yeah. Yeah. With
Swyx [01:24:27]: Yeah
Philip [01:24:28]: I’m really excited for Qwen Image 3. I hope they open source it.
Swyx [01:24:31]: And then I should also mention on the diffusion for tech side, there’s been some movement, not a lot.
Philip [01:24:37]: Yeah. We’ve got Mercury,
Swyx [01:24:39]: You host Mercury?
Philip [01:24:40]: Yeah.
Swyx [01:24:40]: Nice. Nice. Nice
Philip [01:24:41]: Diffusion Gemma is open source.
Swyx [01:24:44]: Yeah.
Philip [01:24:45]: And then, yeah
Swyx [01:24:47]: And we on the science pod, we just have been releasing, some, virtual cell models that use diffusion as well.
Philip [01:24:53]: Yeah. They have built. It’s definitely still in the cheap, fast tokens, world.
Swyx [01:25:01]: Yeah.
Philip [01:25:01]: We’re trying
Swyx [01:25:03]: It’- I think it’s the wrong marketing, and I’ve told them this before. I was like: “Look, like you’re not gonna beat the optimizations that, the other LLMs are gonna do, but you can have different APIs. Like you should be able to use it differently than chat response.”
Ali [01:25:19]: Me also.
Swyx [01:25:20]: Because it’s diffusion. Because you can do like. What is like context-free guidance for diffusion look like?
Swyx [01:25:26]: For text. Like give me a give me a poem, give me a plot structure that like diffuses into place
Philip [01:25:33]: Exactly. So that’s where, like I mentioned with poetry, for example, where you might want to ensure consistency across UIMs. I’ve done a lot of LLM sonnets. It used to be one of my to benchmarks, and even models today
Swyx [01:25:46]: They cannot count. Yeah
Philip [01:25:47]: Yeah, they don’t get the syllables right. And if you can attend across all of the different tokens, you can get the syllables right.
Swyx [01:25:55]: Yeah. And, David Holtz from Midjourney was, investing in text diffusion. I don’t think anything came out of it, but like the idea was that you can storyboard a long movie, and then you can generate the scenes with video- normal video gen. But the idea of like coherence across a thing that would just appear where like the end should attend to the start and you should not have this auto-regressive path dependency does make sense in principle. Just the API should be different. The marketing should be different.
Ali [01:26:24]: None of the most heavily used open source or closed source models use diffusion. But isn’t that like Like doesn’t that point to almost like
Swyx [01:26:31]: It is. It’s chicken and egg because what if you just give it more scale?
Ali [01:26:36]: What’s the, what’s the largest diffusion LLM?
Swyx [01:26:38]: I don’t think it’s very big.
Philip [01:26:40]: I don’t know the parameter count on this one, but diffusion Gemma
Swyx [01:26:42]: Like under 20B. I don’t know
Philip [01:26:43]: Diffusion Gemma is not large.
Vibhu [01:26:44]: I think it’s a 20-something.
Swyx [01:26:46]: Yeah. And yeah.
Ali [01:26:47]: Oh, it’
Swyx [01:26:47]: Like you haven’t tried.
Vibhu [01:26:49]: You haven’t given it a big and you haven’t,
Swyx [01:26:51]: So it’s like very unfair
Vibhu [01:26:51]: Diffusion Gemma is a 25B and it’s old
Philip [01:26:54]: And that’s what I’m saying is like for its size, it does pretty well, in terms of, in terms of quality.
Ali [01:27:01]: It’s almost like the same challenge with video models that have the same size. It’s like you’re comparing it to models that are much larger in scale.
Swyx [01:27:07]: Yeah. Well, unless you do the whole thing where you have a text, backbone and then
Ali [01:27:12]: Right. Right.
Swyx [01:27:12]: You like glom some decoder thing that, does that. Like, - so we started off the podcast doing this for the inverse direction from image to text.
Ali [01:27:22]: Right.
Swyx [01:27:23]: And I think like it’s, it’s roughly intuitive that you can do the opposite direction.
Ali [01:27:27]: I agree.
Ali [01:27:28]: I see it. I see it.
Swyx [01:27:29]: Yeah. The, we’re, we’re speculating on research in general.
Ali [01:27:32]: Yeah.
Swyx [01:27:32]: One part that we can end off with this is the topic of your talk where, inference engineering used to just be like, let’s take an open model, make the GPU go
Training for Inference and Inference for Training
Swyx [01:27:43]: And then that’s it. That’s the job of Baseten. Now it looks like people are using inference more and more in post-training.
Ali [01:27:50]: Yes.
Swyx [01:27:51]: Yeah.
Ali [01:27:51]: And training and inference.
Philip [01:27:53]: Yes. It’s training for inference and inference for training both have become big topics.
Ali [01:27:58]: Well, inference for training in the sense that like you just need, you need to do, you need to do rollouts when you’re doing like RL training runs. And so if your rollouts are taking a long time, if like, you’re using a vLLM for instance, or as opposed to vLLM or if the model that you’re trying to train is not supported in vLLM and you have to fall back to an older inference engine, your rollouts are gonna be slow and you don’t wanna do training on rollouts that are too off policy, so you have to wait for them so you bottleneck your entire training pipeline. And so like the techniques that we do inference optimizations for, will help them there. The training for inference mostly comes down to like just the spec dec training, EAGLE training, and sometimes post-training. For instance, if you want to quantize a model, you’ll quantize it down to like NVFP4.
Ali [01:28:43]: How do you like sometimes you get lucky and you can just do PTQ and that works. Sometimes you quantize it down to NVFP4 and the model is terrible, like the quality is too bad. And you have to do post-training on the model in order to make it understand that it’s going to now be an NVFP4 and let it still output the same logits. You can do this with normal SFT, PC, quantization aware training, all of that stuff. But more and more so we’re seeing techniques like NVIDIA released a quantization aware distillation paper where you establish a version of the model that’s in NVFP4 and a version of the model that’s in full precision, and then you’ll do distillation training based on the logits of the two models in order to make the FP4 model understand. And so more and more of the team, the engineers, like of the inference engineers that work on our team, they have to be very familiar with like training techniques and just being fine writing training pipelines for it. Yeah, it just seems like, they’re meshing together in a sense.
Swyx [01:29:36]: Well, it’s, coming together.
Philip [01:29:38]: Yeah, absolutely. If you think about the ultimate goal potentially of having a continuous improvement system . Yeah, it’s, it’s funny, but at the same time it’s also happening and I think within a few months to a couple years, like a lot of leading agent builders are going to have these loops like really up and running in production where you are doing inference, learning from the inference. We for a long time have been like learning from inference as it’s live and dynamically adjusting the system. Any dynamic adjustment is going to beat a static configuration across, your, exact config, across your speculator, across that thing. And then the, you can take the traces that you’re generating from your product, continuously post-train the model, roll those out, A/B test, get better signal, get better model, get better product. That loop is really promising. The technologies and the infrastructure to build it are coming along quickly. And so the unification between training and inference, I think, is only going to accelerate.
Swyx [01:31:01]: I was chuckling, but I wasn’- I didn’t think it was funny. Like it’s real. Like one of the big things for AIE World’s Fair was that, we have, RSI into AGI is the rough tagline. Which like, yeah, we have, I saw you pull a parameter golf. Like we have models training models and, the next step is models training, - or optimizing their own inference, which is funny. I wonder if, models will be like on policy better at training themselves than training models that they are unfamiliar with. This-- these are all like very interesting open areas of research.
Models Optimizing Their Own Inference
Philip [01:31:36]: One big part of my job a couple years ago was for any arbitrary model that came out on Hugging Face, writing a config foot and getting it up and running. And now the get-it-up-and-running config is shottable.
Philip [01:31:50]: And so, I don’t have to do that anymore. Yeah, that’s not exactly a model optimizing its own influence so much as a model, like being able to read the SGLang docs. But, yeah,
Ali [01:32:01]: Well, we do see it. We do see it like
Philip [01:32:03]: Yeah
Ali [01:32:03]: With GLM-5.2 for instance. GLM-5.2 is very good at writing GPU kernels. And so for like-- It was very funny internally, we had a GLM-5.2 endpoint that we were using to, like that we plugged in our cloud code harness, so every engineer on team uses like our GLM-5.2. And it will do a forward pass on the GLM-5.2 instance of the node, and then it will get the profile trace, and it will analyze it, and it will find the kernels that are the bottlenecks in SGLang, and then it will write the new kernels, and then we’ll do another profiling trace, and when it’s done, it uploads the image to our thing, and then we can pull that image down and repeat the cycle. And so for quite a bit of time, we had like literally GLM-5.2 optimizing
Philip [01:32:44]: Writing and optimizing all of GLM-5.2
Ali [01:32:46]: A GLM-5.2. And like some of the GPU kernels that were on GLM-5.2 within our inference engine is written by GLM-5.2, and the trace and the kernels were guided by GLM-5.2 as the driver. So it seems like. I do see, I do see that circle being there. I think a bit more time is needed. There’s definitely a lot of things that it can’t do. The models just aren’t there yet, even though they’re like really smart. Like, they still try to like reward hack their way into like the cheapest or like they’re very-- like they’re not good at like decision-making almost it seems. But yeah, I do. Like yeah, like a model optimizing its inference is already a thing that happens.
Philip [01:33:20]: Do you think GLM-5.2 was uniquely good at optimizing itself or did it just happen to be the best coding model that we had access to it would do an equally good job of optimizing,
Ali [01:33:31]: Would
Philip [01:33:31]: A DeepSeek or a Kimi or something?
Ali [01:33:34]: Well, to Swyx’s point, maybe it’s gonna be off policy when it tries to optimize
Philip [01:33:37]: Will it secretly hurt DeepSeek?
Ali [01:33:40]: To try to boost itself.
Philip [01:33:41]: Ooh.
Ali [01:33:42]: That’
Philip [01:33:42]: No, for what it’s worth, I don’t believe that.
Ali [01:33:44]: Yeah.
Philip [01:33:44]: But it’s just. Let’s just find out.
Ali [01:33:45]: It’s an interesting. Yeah.
Philip [01:33:47]: Just, you have more compute than me. Just
Ali [01:33:49]: Just go try it
Philip [01:33:50]: Try it. Yeah. Any other upcoming trends in inference engineering that we didn’t cover? Like right now, - ‘cause you guys are so close to
Future Trends: Modalities, Scale, Networking, and Continual Learning
Ali [01:33:58]: Yeah
Philip [01:33:58]: You can see it, that the world-- rest of the world doesn’t know about. The big ones are obvious. Models get bigger. Hardware gets more powerful. Users get used to a certain level of speed and demand a higher one. I think that some things I’m excited about are systems level. We still have a lot to think about in terms of composing multiple models together. If you think about a voice agent, there’s three to five models involved in that and the communication between those models. There’s a lot of new modalities that are coming out. There’s like the Cosmos, the new world model. There’s more research. Speech to speech is still like not entirely a thing, but it’s getting, it’s getting closer. There’s gonna be just a lot of new modalities to build around, which is gonna be exciting. And then, yeah, I think that the other thing to solve, which is something we’ve been solving for a long time and are not done with yet, is just going to be continuing to operate at another 10X scale as an industry. If you think about the degree of usage that AI has worldwide compared to, some of the more mature technologies both on consumer and business, it’s pretty clear that there could be multiple 10Xs more of demand. If you look at the infrastructure work industry-wide, it’s been stood up very quickly to meet a unprecedented spike in demand that is like not stopping. So yeah, there’s just a lot of problems to solve around like long tail reliability and, figuring out where we’re gonna get the next like 10X and 100X of tokens from.
Ali [01:35:49]: I’m gonna say, it’s gonna be a really boring answer, but I think the answer is just faster next, like faster network chip communications. It seems to me that like more and more memory is the bottleneck. You wanna have larger models. Right now, when you’re doing serving at large, you have to transfer KV cache from one node to another. But the way that you do that is you tran- you find the KV cache, you find where it is, you transfer it to another node, you put it on that node’s memory, and then you transfer it from that node’s memory into the GPU, and for like into the tensor cores of the GPU. So there’s like a stage transfer here that makes it such that you’re very bottlenecked with just KV cache transfers at large, which affects the time of decode and PD disagg. You have to do this because the HBM is so - it’s like extremely fast, like 4.5 terabytes per second as opposed to. Like, which is like magnitudes better than NIC communication speed. If you were to somehow be able to, in like this theoretical dreamland, have extremely fast NICs, you could, in theory, spare that HBM, and you could just transfer KV cache trans like directly from one node to another. This would give you like almost 100X speed up when you’re doing this aggregated serving between nodes and nodes. I’m not familiar with the technical challenges of making NICs faster. I’m certain there’s a reason why they’re like orders of magnitude
Ali [01:36:59]: Smaller, like slower than, like HBM. But if someone were to figure that out, it would literally be like a - like two orders of magnitude faster to do decode. That would be my take.
Philip [01:37:12]: Be a good trip.
Ali [01:37:12]: Cool.
Philip [01:37:13]: I don’t know if you have a nomination for things that are trends. I got one.
Ali [01:37:18]: Cool.
Philip [01:37:19]: So I think inference engineering for continual learning. So what if you just, like if you just had the idea that you are supposed to learn from everything that you ever process, do you do anything differently? Or do you just have the same paradigm of like, well, stick it in a memory.md, and then like it somehow gets consumed in KV cache, and like this system works, it’s not broken. Or like how do you like reshape inference so that it learns while you inference?
KV Cache Compaction and Continual Learning
Ali [01:37:48]: Yeah. I think maybe one relevant topic there is your absolute best fund in the entire world’s work on KV compaction Correctly
Swyx [01:37:55]: Like what changes?
Ali [01:37:56]: What changes when
Swyx [01:37:57]: If you’re trying to continual learn
Ali [01:37:58]: There’s two takes, and there was like Charlie and I had this Twitter, argument where the. Like continual learning could take one of two paths. It could either be that the model learns and so it’s continuously pushing its new knowledge into its weights. In that case, you just need to have, like your inference just needs to continually fetch new weights or yeah, like you just literally need to do fetch new writes and reads of weights. Or the other path, which is you do KV cache compaction. And if you
Swyx [01:38:28]: And there’s a LoRA layer if you just only update LoRAs.
Ali [01:38:31]: Yeah, exactly. Exactly.
Swyx [01:38:31]: Which is, that’s the gram approach
Ali [01:38:33]: Yes
Swyx [01:38:33]: Which we covered.
Ali [01:38:34]: The argument against doing weight pushing is that you can only fix one hop knowledge, as in you can only
Swyx [01:38:39]: Yeah
Ali [01:38:39]: Feed it a new feature of like, “Oh, what is the best university in the world?” The best university in the world is Waterloo. But then a second derivative
Swyx [01:38:46]: That’s not changing.
Ali [01:38:47]: That’s not changing. That’s not changing. But like a second derivative question of which university should I hire an intern from? So if that the best university in the world is Waterloo, then the answer should be Waterloo. But if I wasn’t just shotting the question and I was to ask it to like use its knowledge to think and then give me a second answer, or like, “Should I hire an intern from Waterloo or MIT?” It’d be like, “Oh yeah, both are good.” But no, like I liter- I just edited in your knowledge base that Waterloo is the best. Why didn’t you use that to do reasoning? So that’s the fundamental problem with trying to change a fact in an MLP within the weight. KV cache compaction fixes that. With KV cache, or like rather not KV cache compaction, but like if you’re able to have something like the still paper which we came out with, which is you’re able to make your KV almost infinite, and you’re able to compact in such a way that you don’t lose any of the knowledge. In that case, you can do continual learning, and you can solve continual learning. And this as a, it’s a result of, this argument that Charlie and I had, that I do concede that his point was correct, and I do see that KV cache is the way forward. And in that case, I don’t think inference is going to change that much because we still use KV cache and inference. You’re just gonna update the KV cache, but it’s gonna be like an additional step, but nothing changes in the weight, so nothing changes in inference time. Nothing changes the spec that I had.
Swyx [01:39:58]: Okay. Surprisingly great answer. We have it up on the blog. It’s a relatively recent blog, so, we can. People can go see it.
Closing: The Book, Baseten, and Inference Engineering
Ali [01:40:06]: Hyperverve
Swyx [01:40:07]: Yeah. Otherwise, this is super enjoyable chat. I know we’ve like already gone two hours.
Philip [01:40:11]: Wow. I didn’t even realize.
Swyx [01:40:12]: Like time flies. Yeah.
Philip [01:40:13]: Yeah. So much we didn’t even cover.
Swyx [01:40:15]: Yeah. This is like, we also wanted to talk about the book and all that, but you’ve covered the book.
Philip [01:40:18]: Yeah, everyone knows about the book.
Ali [01:40:22]: Yeah.
Swyx [01:40:22]: High- highest ROI thing in the history of Baseten, right? For the hour.
Ali [01:40:27]: Without a doubt. Without a doubt.
Philip [01:40:28]: Yeah.
Ali [01:40:28]: Absolutely.
Swyx [01:40:29]: So congrats on that. I, and we’ve covered that in our meetup
Ali [01:40:32]: Yeah
Swyx [01:40:32]: Which we can publish separately. But no, thank you to you guys for being so generous for sharing. I think it’s a fun conversation that, we don’t get to have enough. I think inference engineering, we never really covered head on, and so to have you guys come on, is a treat.
Philip [01:40:47]: Always.
Ali [01:40:47]: It was amazing.
Philip [01:40:48]: Yeah. Thanks. Thanks for having us, and hopefully in a year everything shifts, and we can, come back and say everything we were wrong about.
Swyx [01:40:56]: Yeah. Yeah. I’m excited for this mega kernels comment to get out and see what’ see what people say.
Philip [01:41:00]: We gotta stir stuff.
Ali [01:41:02]: Should I go into hiding? I know I’m gonna get like the mega kernel community after me.
Philip [01:41:05]: Yeah. One thing I really respect about you is you are not willing. You are not, scared to kick the hornet’s nest, ever.
Swyx [01:41:12]: It’s not, I don’t think it’s that controversial. I don’t know. We’ll see.
Ali [01:41:18]: We’ll see. We’ll see.
Swyx [01:41:19]: All right. Thanks, guys.
Philip [01:41:21]: Thanks.
Ali [01:41:21]: No, thank you so much.


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There are roughly 100x more people who use code than who can write code. As code that “just works” becomes easier to generate, this group may be the biggest prize of all — if you can get the agentic interface right.
A key trend we have been tracking over at AINews is the absolute explosion in Codex usage this year, with MAU now up >10x from Jan 2026. Less than two weeks after their July 9th launch, OpenAI said ChatGPT Work and Codex had reached 10M users combined (as we cover in the pod, Codex now powers ChatGPT Work, so all ChatGPT Work users are now users of the Codex harness, even if they aren’t traditional engineers) — showing the early innings of what happens when you graduate from coding agents to knowledge work agents:
We’ve been calling out how coding agents are “breaking containment” to do everything else this year to power every other part of knowledge work - and it started with the org chart, with a major reorg last month that amounted to two of Codex’s most prominent leaders, Greg and Tibo, taking responsibility over product and ChatGPT specifically, completing a “Superapp” consolidation cycle first discussed in March.
With these updates Codex is no longer just a coding tool. In June, OpenAI said knowledge workers already accounting for roughly 20% of Codex’s user base and growing more than 3x as quickly as developers. A product dedicated for knowledge workers was being pulled out of the Codex team.
However, knowledge work has a different set of problems and environments than coding. For decades, knowledge work has been scattered across different primitives like documents for writing, spreadsheets for analysis, slide decks for communication, and specialized applications for everything else. ChatGPT Work now enables users to work across every primitive with agents. Instead of opening an application and manually operating its features, the user can describe an outcome and collaborates with an agent that can assemble the tools, context, and artifact needed to reach it.
From building no-code products at Airtable to leading Productivity Engineering at OpenAI, Akshay Nathan has spent much of his career trying to make the power of software accessible to people who do not write code. In this episode, Akshay joins swyx and Vibhu to unpack the launch of ChatGPT Work, why Codex unexpectedly took off among non-developers inside OpenAI, and the company’s broader plan to bring useful agents from software engineers to knowledge workers and eventually everyone.
We go deep on the shared agent harness behind Codex and ChatGPT Work, why OpenAI brought the experiences together without making them identical, and how persistent computers, artifacts, Sites, plugins, memory, and sub-agents are changing what people can delegate to AI. Akshay explains why some teams are replacing decks and spreadsheets with interactive websites, how agents can gather context across code, Slack, documents, and local files, and what OpenAI learned from personal-agent products like OpenClaw.
Side note: also don’t miss Abhihek’s sandbox track keynote at AIE, which now powers a lot of the sandboxing for ChatGPT Work… and yes was also broken by an unreleased OpenAI model in the recent HuggingFace incident.
Akshay also reflects on how AI is transforming product development itself: why more people will become generalists with a specialty, why ideas and taste become the bottlenecks when almost anyone can build, why LLMs still struggle to generate genuinely grounded new ideas, and why teams must distinguish increased motion from actual progress.
We discuss:
* Why Codex unexpectedly took off among non-developers inside OpenAI
* Why employees felt like using Codex gave them a new superpower
* The product insight that led OpenAI to build ChatGPT Work
* Why Codex and ChatGPT Work share the same underlying agent harness
* How their UX, Git visibility, artifacts, and sandboxing defaults differ
* Why OpenAI merged its agent experiences instead of building separate products
* How AI is blurring the boundaries between engineering, design, strategy, and operations
* Why OpenAI wants the default model configuration to work for most users
* When power users should use deeper reasoning, Ultra, or multi-agent modes
* Artifacts, agentic spreadsheets, and creating high-fidelity work products
* Why interactive Sites may replace decks and spreadsheets
* The challenge of designing a simple interface for an agent that can build almost anything
* Why users should retry tasks that models could not handle three or six months ago
* How AI can gather context for performance reviews without replacing human judgment
* The OpenAI automation that turns internal Slack and document activity into memes
* What reaching ten million ChatGPT Work and Codex users means for the product
* How OpenClaw inspired persistent environments, scheduled tasks, and personal agents
* Using ChatGPT for financial planning, budgeting, workouts, meals, and household management
* The design tradeoffs behind sub-agents and how much of their work users should see
* ChatGPT memory, Chronicle, and long-term context
* Why AI may make more people generalists with deep specialties
* Why ideas and taste become more important when almost anyone can build
* Why LLMs still struggle with the instruction “bring me new ideas”
* Measuring productivity through quality at-bats instead of commits, tokens, or pull requests
* The critical difference between AI-generated motion and meaningful progress
Akshay Nathan
* LinkedIn: https://www.linkedin.com/in/akshaynathan/
* X: https://x.com/akshaynathan_
Timestamps
00:00:00 Introduction and Bringing the Power of Code to Everyone
00:01:33 Joining OpenAI and Preserving a Startup Culture
00:02:40 What OpenAI Learned from Enterprise AI Adoption
00:05:28 Why OpenAI Built ChatGPT Work
00:07:17 Codex vs. ChatGPT Work and the Shared Agent Harness
00:12:07 Why OpenAI Merged Its Agent Experiences
00:16:24 Models, Reasoning Levels, and Choosing the Right Default
00:20:26 Artifacts, Agentic Spreadsheets, and Model–Product Collaboration
00:24:22 Why Sites Could Replace Decks and Spreadsheets
00:30:08 Designing an Agent That Can Build Almost Anything
00:34:28 From Developer Agents to Knowledge Work—and Everyone
00:36:07 Power-User Advice and AI-Assisted Performance Reviews
00:40:41 OpenAI’s Internal AI Memes and the Ten-Million-User Launch
00:44:39 OpenClaw, Personal Agents, and ChatGPT as an Operating System
00:50:24 Sub-Agents, Ultra Mode, and How Much Control Users Need
00:54:39 ChatGPT Memory, Personalization, and Chronicle
01:00:19 How AI Is Reshaping Product Development and Tech Roles
01:03:15 Ideas, Taste, and Why LLMs Struggle to Generate New Ideas
01:04:42 Measuring Productivity, Quality At-Bats, and Motion vs. Progress
Transcript
Introduction: Akshay Nathan, ChatGPT Work, and the No-Code Arc
Swyx [00:00:00]: We’re here in the studio with Akshay from OpenAI. Welcome.
Akshay Nathan [00:00:07]: Thank you.
Swyx [00:00:08]: And with our trusty co-host, Vibhu. So you recently launched ChatGPT Work. You lead Core Product Engineering. It’s been a long journey, into all this. I find it very interesting that you started with no code or low code, with Walrus and Airtable. And to some extent, ChatGPT Work is like the super app of super apps of, well, here is the ultimate no code. You just write a prompt.
Akshay Nathan [00:00:32]: Yeah. It’s funny how things come, full circle. I think for a long time in my career, I started my career working consumer fintech, but then after that, like, there’s this hypothesis that, the things that we were able to do with code, like, as engineers, like, if we could bring that to many more people in a more, accessible way, then that would be truly magical. We were working on a startup. It’s funny, like, before LLMs, before vision LLMs, on how to do automated testing with AI. It was just kinda jank, back then, but doing what we can, and then worked at Airtable for a while on the same thesis that, like, if we can bring a database or the primitives behind a database to people, that’d be really useful to them. But once LLMs came onto the scene, it became clear that, this was the missing piece, like, the missing technology required to, like, bring the magic of code to everyone without them having to know what’s going on underneath the hood. And so, like, I think this launch and a lot of the stuff that we’ve been up to is, like, the manifestation of that.
From Walrus and Airtable to OpenAI
Vibhu [00:01:33]: How was stuff when you joined? So you joined OpenAI 2023. Now we’ve got, so much more stuff, so ChatGPT, Codex app, ChatGPT Work. Have things changed?
Joining OpenAI and What Hasn’t Changed
Akshay Nathan [00:01:44]: I think the more interesting thing is how things haven’t changed. Like, one, I joined I remember when I joined, it was, like, five hundred people. One thing I was worried about was, like, I was looking for something, more early stage and, like, was it gonna feel startup enough? And I joined, and I was like, “This feels even more startup-y than I could ever imagine.” And, like, that really hasn’t changed even till now. I think the, like, level of, like, bottoms-up ambition and, like, the ability of anyone to, like, do anything or have an idea and ship it is really cool. But on the, like, mission side, I think what was really compelling to me is this mission of, bringing frontier intelligence to everyone. Like, building AGI and then bringing it to everyone. And, I think acknowledging back then that, like, that vision is gonna, not be a linear progression. Like, we’re probably gonna, like, try different products and have different things that succeed and don’t. But the vision has stayed the same, and the mission has stayed the same, and we’re starting to see the pieces, fall together, and that’s really cool.
Enterprise Lessons: No One-Size-Fits-All AI
Swyx [00:02:40]: You worked on Enterprise. What A lot of people never touch ChatGPT Enterprise. What is something that you learned from there that you’re bringing into your work now?
Akshay Nathan [00:02:52]: I think how there’s no one-size-fits-all solution in Enterprise. I remember in the early days of ChatGPT Enterprise, like, when we talked to customers and, like, everyone. That was, like, when I think it was a year after ChatGPT was released, and everyone was so excited to bring, AI into their enterprise. And, there were all these teams being stood up. It was, like, the AI deployment team with, like, these enormous budgets. And if you asked anyone, like, what were they excited about? Like, what were they excited about solving? Like, at first, you’d get, like, kinda like the baseline answers of, like, “Yeah, we have all this context and data and all this stuff.” But then if you ask them, like, “What was, like, a discrete use case that, like, they want AI to enable in their workplace?” You get such a different, like, variance, like, explosion of, different types of answers. And it’s interesting, like, you using, like, these models and these products, you have this box, and you can say anything to it, which is the magic. But it’on the flip side, it also means that, like, you don’t know what to do with it. And in Enterprise, I think a big part of that is, like, meeting the users where they are, like, what use case were they trying to solve, and then teaching them how they can use AI to, like, gain leverage there.
Swyx [00:03:56]: Do you meaningfully differentiate that from forward-deployed engineering?
Akshay Nathan [00:04:01]: I think there is the go-to-market side of it and then there is the product side of it. I think you need someone on the product side. And I think, like, however good we get at FDE motion, like, I think at the end of the day, if we have a user who’s, like, looking at their computer or looking at their phone, like, it’s our job in the product to, like, be enabling them and showing them where to go. So we’re really excited about that.
Vibhu [00:04:24]: Do you think there’s been changes, over the past three years of adoption? So there have been, step function changes. You have reasoning models and whatnot. Is there still the same problems of Enterprise has black box, don’t know what to do with it, or have things changed?
Adoption, Agents, and the Next 10x Market
Akshay Nathan [00:04:39]: We’re seeing now that, like, there’s this huge uptake, right? Everyone is extremely excited about it. It feels like, many people are, millions, hundreds of millions of people are using ChatGPT. They understand, like, how generally to work with AI. But then, like, every time, like, a new capability gets unlocked, so now, like, we’re seeing with agents, like, there is probably a contingent of, like, early adopters still who, truly get it, who are like, “ we you can do anything. You just have to make sure the right context is there, it’s connected to the right tools, and that you are supervising it, but, like, anything is possible.” But then there’s, like, this, like, 10x or 100x bigger market where, like, they don’t yet get that, or they don’t yet see that. And so I think that’s the next stage here. So to answer your question, like, I think the adoption is there and growing fast, but I think the opportunity is, like, far bigger than that. That’s where we wanna play, especially with ChatGPT Work.
ChatGPT Work, Codex, and the Super App Merge
Swyx [00:05:27]: Yeah. well, let’s, let’s skip ahead to ChatGPT Work. only, like, a month ago or so, announced. what was the decision process that led into it? there was this, overall merging of the super app. Is that what we’re officially calling it? you deprecated the browser as well. Just, summarize your last, like, couple months of working on this thing.
Akshay Nathan [00:05:50]: Yeah. It feels like forever now, but it’s only been a few months. I think maybe the one, impetus that, like- Is most salient is when we release Codex, or even internally had Codex, like, it was really surprising to us, I think we recently put out some stats on this, that there was this, like, real inflection of, like, adoption among non-developers at OpenAI. And, I, through this product development process, like, would go to, like, these UXR sessions to talk to people internally. And the thing that stuck out to me is, like, one, like, you go talk to, like, strategic finance or marketing or whatever, and they’re all using Codex for, their use cases. That part’s cool, but the thing that really stuck out to me is how proud people were that they were using Codex. Like, how, like
Swyx [00:06:34]: It’s like, “I’m not supposed to be using it, but I am.”
Akshay Nathan [00:06:36]: It was that. It was, like, that they were, early to this, like, new thing, but it was also this thing of, like, they felt like they had a superpower, right? And, what we recognized then is that, like, the power of Codex, the power of agents, like, we already had this massive distribution base of people who have, come to know and love ChatGPT. Like, how do we show that to them? Like, how do we bring it to them? Which is, like, a hard product problem, and it’s, like, a tricky thing, right? There’s many ways you can go about it. And so that’s what we called the Merge and the Super App over time, and ultimately launched it in ChatGPT Work, is how do we do that? But it came from that initial realization that, like, the power was not only for developers, like, much earlier than probably even we thought. Like, it could be extended to everyone.
Swyx [00:07:17]: How do you see the products differently? So, like, who is it for, right? So Codex started out even CLI, then app. Now there’s a merge of ChatGPT Codex and ChatGPT Work, so is it the opening for the average user, for enterprise, for work? How do you position it?
Akshay Nathan [00:07:36]: I think we want to get it to position it for if you’re doing work-related things, for lack of a better word, right?
Who ChatGPT Work Is For
Akshay Nathan [00:07:42]: I think productivity is what, like, the pillar that I support. Like, that’s the name of the team. And the reason for that, the reason we call it productivity and not, like, enterprise or, like, work or something like that, is because there’s also personal productivity, right? And, like, I think ChatGPT Work is I’ve seen people do things in their personal lives that you wouldn’t classify as, like, work technically, but, like, these agents are, super capable for. Like, one recent example that someone posted about, on our Slack is, like, someone had, like, a missed package, like they didn’t receive it, and then they got, like, the picture of it, from Amazon or whoever the courier was, and they, like, asked ChatGPT Work to, like, find out where that package is. And, like, the agent, is extremely tenacious and, like, took the image and, like, looked at a bunch of, like, listings around their neighborhood and figured out exactly the apartment complex in which the package was, like, gave them some information. And so, like, I think there’s all these things that, like, you, work-related or productivity-related things, I think that’s what we want the product to be. You asked about Codex. I think we think Codex is, a durable brand, but we have a principle that, like, the user we don’t want a user to get stuck in a tab or an experience where they don’t get the power of the product. And so, like, everything that you can do, in the Codex portion of the product on desktop, you can do in ChatGPT Work and vice versa. But we made some opinionated product decisions on, like, how much of the Git state, if you’re in a Git repo, do we wanna expose to the end user? Or how much do we wanna make the experience of seeing the agents thinking, like, diff forward so that you get exposed to the diffs out of the box. And then, like, on the safety side, like, how do we wanna think about, like, sandboxing and making sure that we have the right defaults in one state versus the other? So, there’s, like, some opinions that go behind that, but we do want We don’t want the user to need to choose which experience they’re in.
Swyx [00:09:26]: That is a good goal for AGI, right? Like, people don’t want, like, to hide to choose what version of AGI they want. They just want the AGI to decide for them. can I get an answer or, like It’s not super clear to me. Is the Codex harness and the ChatGPT Work harness the same? Is it just UI affordances, or are there prompt level or even deeper differences?
Shared Harness, Different UX: Codex vs. Work
Akshay Nathan [00:09:49]: So the harness is the same. The harness is shared. on In both of the products, we made improvements to the harness to make it good for knowledge work, especially as it relates to plug-ins or computer use or artifacts. You get that power regardless of which experience you’re in. On the UX side, there’s opinionated takes that we have when you’re in Codex mode, what the UX should be how the UX should behave, and some stuff around the sandbox like I mentioned, but the underlying harness and capabilities should be the same.
Swyx [00:10:16]: I’m just kinda curious. Maybe we can, -- Is there a query that we can run that would look different in the two modes?
Akshay Nathan [00:10:23]: Yeah. I tried to create, like ask it to create, like, a retirement calculator spreadsheet or something, in both modes. And then in Codex mode, you might have to be in a repo for this, but you’ll see, like, the diffs of, like, the sheet that it’s creating and stuff like that, and the file edits. But in Work you won’t be able to see that.
Swyx [00:10:42]: I think that’s, that’s super clear. And then also the other thing I wanted to dive into was your, the productivity team. what else is there? first of all, what are the top-level teams other than productivity? Isn’t productivity everything?
Productivity Teams and Core Chat
Akshay Nathan [00:10:55]: So
Swyx [00:10:55]: Science?
Akshay Nathan [00:10:55]: We have a team focused on ChatGPT. Like, the core chat experience, for consumer, which is like, not, I think all productivity. Like, there’People are using ChatGPT every day for search to, figure out how to write messages to loved ones, to think about, how to, like, learn a new topic, et cetera. And so there’s so much more inside to create images. And there’s so much more in chat that, the hundreds of millions of users are using that warrants, like, a very dedicated effort. And there’s teams focused on enterprise and infrastructure and API and stuff like that, so.
Swyx [00:11:33]: I will bring it up.
Retirement Calculator Demo and Git-First UX
Swyx [00:11:34]: Yeah. So I have them both running. This is ChatGPT Work. There’s a Codex version here. I picked “Five Little Ducks” song, so this will take a while.
Akshay Nathan [00:11:43]: Huh.
Swyx [00:11:43]: I think we’ll just keep it in the background and, as they finish, we’ll look into some of the differences.
Akshay Nathan [00:11:48]: Yeah. But immediately, I think if you flip back to the Codex version you’ll see that,
Swyx [00:11:53]: That it assumes
Akshay Nathan [00:11:54]: Like the
Swyx [00:11:54]: It assumes Git. Yeah. Yeah.
Akshay Nathan [00:11:56]: The, like, dynamic island assumes that you’re in a Git repo. And you might miss some stuff because some of it is, like, in the actual chain of thought with those changes and how we display that, but yeah.
Swyx [00:12:07]: Is there an unintuitive like, is there a thing that you wanted to ship and then you got feedback, and you were like, “No, let’s not do it?” Like, what’s the thinking behind that?
Why Merge the Experiences
Akshay Nathan [00:12:14]: In, ChatGPT Work?
Akshay Nathan [00:12:17]: I think one direction we could have gone with this is, like, keeping the experiences, like, completely separate. So it’s like, why
Swyx [00:12:22]: Different apps.
Akshay Nathan [00:12:23]: Exactly, like different apps or even in the same app, like different, completely different experiences. Like, why merge it all? Like, what is. Codex, people love. Like, why bring these products together? And I think the intuition here is that, like, all of our jobs are, like, changing dramatically with AI. Like, for, like, every few months, like, I feel like I wake up, and I’m, like, doing a completely different thing than I was doing a few months ago. And my hypothesis here is that, or I should say our hypothesis is that, like, part of what we’re, we’re building, this technology is giving people leverage. Like, the things, maybe it’s the more mundane parts of your job or parts that, like, if you were able to automate, you’d be able to share more ideas faster or whatever, like, you’re able to do now. And because of that, like, that might blur the lines between someone who’s, like, only writing code or creating strategy docs or, planning events or, helping with marketing or doing podcasts or whatever, right? And so, like, these things are gonna get blurred over time. And so, like, trying to draw a hard boundary based on, like, the who you are is gonna be, is gonna be tough. And, like, we should enable users to choose, but we shouldn’t box them in. And so a lot of the work that went in here, like, keeping the primitives the same, like for example, plugins are, like, unified across, this product and ChatGPT and the cloud, was because of that. It’s this thesis that, like, eventually things are gonna come together and we don’t wanna be Like, we wanna be prescriptive about when to be in either experience, but we don’t want to box anyone in.
Swyx [00:13:45]: I wonder if there’s users who are very tuned to the old ChatGPT harness that is effectively now replaced by the Codex harness. I can’t imagine what that was, but maybe they’re more the more conversational side. Can you compare and contrast the two harnesses? ‘Cause only you’ve seen it.
Akshay Nathan [00:14:02]: Yeah. I think ChatGPT, the existing harness, like, still exists today. Like, it exists in this app,
Harness Engineering: ChatGPT vs. Codex
Swyx [00:14:08]: The classic, right?
Akshay Nathan [00:14:09]: The
Vibhu [00:14:09]: You just start a new chat, and you don’t go under Work, right?
Akshay Nathan [00:14:13]: Yeah. If you start
Vibhu [00:14:13]: So
Akshay Nathan [00:14:14]: A new chat and go to chat, then you’re, you’re talking to ChatGPT with the instant model.
Vibhu [00:14:16]: Oh, we can technically do another. But on instant.
Swyx [00:14:21]: Yeah. So this one’s not gonna code or it’s gonna be in line. It’s on a in line in a sandbox.
Akshay Nathan [00:14:26]: It’ll
Vibhu [00:14:27]: Oh, that’s cool
Akshay Nathan [00:14:27]: We try to push you to go to Work if you’re creating a spreadsheet. Yeah, but this is
Swyx [00:14:30]: And this is a router decision? Sorry. Is it a router decision?
Akshay Nathan [00:14:34]: This is the decision that, the model is making, and then, like it sees that you’re able to. or you’re trying to do something that would be better served in Work mode. But I think your question was like, what are the advantages of, like, the chat, like ChatGPT chat harness?
Swyx [00:14:48]: It’s more broadly, like, I wanna, do an oral history of harness engineering. Right? the ChatGPT harness lasted us from, let’s call it the ‘01 era, until now, and now it’s being replaced by the Codex harness effectively. And they’re, they’re overlapping somewhat, but I’m curious what changed if there is.
Akshay Nathan [00:15:10]: My perspective on this is, like, there’s, there’s, there’s there’s like a constant process of, like, divergence, convergence, divergence, convergence. And in chat, like, many of the use cases I was talking about before, like, search or learning, I think we’re, we’re really optimizing for latency and optimizing for personality and, like, different things that, over time, like the product The reason people love ChatGPT is because we’ve been optimizing for those things and working on them for so long. Codex, what we learned was that, like, if you give the agent access to this infinitely flexible environment as a computer, it can do really powerful things. And so when we think about, like, okay, well, for knowledge work, like, what is which mode should we choose? It was like it felt more natural to us to bring that to this, like, computer environment and, maybe abstract some of the details of this computer away from users who might not be used to that, but, like, give them that same power. But ultimately, I think that we want the power in all places, right? We wanna meet people where they are. So I’m sure there’ll be work down the road in order to get things to be, equivalently capable in all scenarios. But it’s just a question of, like, what we’ve been focusing on the product on historically and what we’re focusing on now.
Models, Defaults, and the Reasoning Slider
Vibhu [00:16:24]: I think alongside that, outside of just harness and when to use Codex, ChatGPT, or Work, there’s also the new models you’ve released, right? any guidance there? So people love to min-max what to use, like only use Terra on high reasoning versus, for this, you wanna use Sol here, ignore all these
Akshay Nathan [00:16:44]: There’s 32 options.
Vibhu [00:16:46]: But, that being said, for people that are expanding, so, productivity trying stuff for work that don’t have the breakdown of what all this is what’s, what’s the advice, right?
Akshay Nathan [00:16:59]: Well, I think before the advice, like the first thing is, like, none of this would be possible without these models. Like, the, I think you asked earlier, like, what was, like, the inspiration for work and, like, early on, like I mentioned, like, what we were seeing with Codex, but that was also because the models were getting infinitely more capable. That’s happening again. I think it’s like another step function jump now. And to answer the question on advice, like we want this default to be the best possible. Like, we wanna be opinionated about the default, and so we’ve we’ve chosen a default that we think is gonna be the best for everyone. And, we have for power users options under the hood. We could One could argue that there might be too many right now, and we’re, working on simplifying it. But you can extend, the reasoning level, and you can change between the different model classes if you need to, but the default should be the best for most use cases. So my advice to most people would be to stick to that. And then, if you reach a situation in which you think that you could, you wanna try, a different configuration, if you’re not seeing either the efficiency on the cost side or the quality on the intelligence side, then you can change the defaults and see if you can get something better. But we think that the default should be good enough.
Swyx [00:18:09]: I have, I’m just gonna run something by you since you have way more experience than me. I’ve recently been doing Sol Lite but with goal, with the idea that the goal augments the reasoning effort, but with more terminations and turns.
Swyx [00:18:24]: Is that a good way to think about it as opposed to Sol Ultra or Sol, Extra High?
Akshay Nathan [00:18:29]: Yeah. It’s hard to say because
Swyx [00:18:31]: Yeah. It’s like an interaction effect.
Akshay Nathan [00:18:33]: exactly. It’s like there’s a preference on, for you as an individual, like how do you like to collaborate with the models? Like how many of those like terminations, as you call them, do you want where, you can steer or make sure that it’s doing the right thing?
Akshay Nathan [00:18:46]: I think generally people should try whatever works for them. I think that like using Ultra or the like multi-agent setups are best for like when you have like tasks that are either incredibly complicated, like open explorations or very paralyzable. I think even for tasks using goal, I think is best for tasks that you’ll be able to make consistent progress in a way that’s verifiable over time. But I think for most tasks, they don’t fall into either of those buckets. And so like at least when they’re starting, and so that’s why I think the best first step is like trying it with the default configuration and then seeing like where you wanna go from there.
Swyx [00:19:29]: Right. You guys worked on a slider, which is super helpful for reducing the amount of panic.
Vibhu [00:19:36]: It’s nice on mobile at least. There’s a nice slider there.
Swyx [00:19:38]: It’s nicer.
Vibhu [00:19:39]: I haven’t tried it.
Swyx [00:19:40]: So you have the advanced view there, but if you click advanced view. Yeah.
Vibhu [00:19:44]: Ooh, it’s just a nice slider. Yeah.
Swyx [00:19:46]: Very pretty, very colorful.
Akshay Nathan [00:19:48]: Yeah. The idea was here was like reduce it to like one dimension even though there’s multiple dimensions, right? Try to project it onto a single dimension for the user. Like, something from that represents like, speed and efficiency on one side and then like quality and thoroughness on the other side.
Artifacts, Spreadsheets, and the Work Launch
Swyx [00:20:04]: I am just puzzled that it uses Sol so much, like the lower
Vibhu [00:20:07]: No
Swyx [00:20:07]: Grounds I would’ve used
Vibhu [00:20:08]: I think the slider, if I’m not mistaken, is
Swyx [00:20:09]: Terra.
Vibhu [00:20:10]: Oh, it is.
Swyx [00:20:11]: Yeah. See? So they preset Terra to only be the light one. But like I think a lot of people would more people should use Terra. One, because Sol keeps running out of capacity.
Vibhu [00:20:22]: I’m the reason. Here’s ten minutes of our
Swyx [00:20:24]: There you go
Vibhu [00:20:25]: Retirement calculator.
Swyx [00:20:26]: Oh, that’s the Excel thing working for you.
Vibhu [00:20:28]: This is,
Swyx [00:20:28]: Oh my God. Look at that
Vibhu [00:20:28]: This is work, and then Codex is still cooking, so we’ll get back into it. I think it’ll be interesting to see the thought process, the reasoning, and also, this is eight minutes on work. Codex is still cooking.
Swyx [00:20:41]: Yeah. And by the way, so I’ve, do Gabriel Chua? He’s part of the OpenAI Singapore team. He showed me this, and I was like pretty shocked that this looks like Excel. It edits Excel files. You never paid an Excel license, right? Like, but somehow this is like workable and it’s agentic Excel.
Akshay Nathan [00:21:01]: Yeah. one of the big like pushes that we made for this launch was like artifacts, right?
Akshay Nathan [00:21:05]: Like both on the model side, like I think if you compare this with GPT-5.5 and GPT-5.4 before that, you’ll see that there’s been pretty dramatic improvements in the quality of these artifacts and then also on the product side.
Vibhu [00:21:16]: The UX side is also crazy, like hosted sites and whatnot. No longer needing to host your own little webpage, like it
Swyx [00:21:23]: Oh, I have a story about that. I can do, a separate thing. I’ll need to take the visuals here, but we-we’ll, we’ll cut to that later. Was there co-training, because you were moving making this big move and you launched GPT-5.6 on the same day as ChatGPT Work? Was there influence between the model training teams and the harness teams, or did they did the launch dates just happen to line up the same day?
Akshay Nathan [00:21:46]: I think the we collaborate heavily with the research teams, and I think that’s like one of the most magical parts of the job, like the most fun parts of the job. But yeah, just using artifacts as an example. Like, a lot of what you’re seeing, like underneath the hood, there’s a lot of work that went into making sure that like, we had the right infra to be able to train the models to get better at this. And then on the product side, like had the right experience for users to be able to collaborate with the model on an artifact like this. In fact, like this whole viewer, like the intuition here is that like, it’s not necessarily that you wouldn’t need an Excel license. This is stage one, right? Like, this is probably not what you meant when you’re like making a retirement calculator.
Vibhu [00:22:24]: Yeah, you can iterate very easily. Yeah.
Akshay Nathan [00:22:24]: You wanna iterate and like when you’re seeing it, and if this thing is high fidelity to like what you would see in or what your coworkers would see if you were to send this to Sean, like that I think makes it so easier and makes you trust the product in terms of iteration.
Vibhu [00:22:39]: When you say coworkers would see, do you see a multiplayer, multi-team collaboration with artifacts? Any things you guys think about that?
Multiplayer Artifacts and Collaboration
Swyx [00:22:46]: You can already share it, right?
Akshay Nathan [00:22:48]: Yeah. It’s inter It’s something that, we’re actively thinking about. one thing that, we’ve noticed internally without talking too much about the roadmap is that like there’s many times when someone will ping me about something, and I will ask ChatGPT Work the question, and then I’ll ping them back the answer.
Akshay Nathan [00:23:04]: And then I’ll be thinking like
Vibhu [00:23:04]: Like the simplest would be, the three of us are just all on one hosted.
Akshay Nathan [00:23:07]: Exactly. And I’ll think about like was I required in this loop or and then maybe it was, rephrase like what they were asking or pulled from certain context or whatever. But like, when I gave them back the answer, that process was also lossy, right? Like I gave them just like my interpretation of what ChatGPT Work cooked up. But like underneath the hood, there’s so much context like in the rollout and stuff that could be interesting.
Vibhu [00:23:28]: Yeah, it’s
Swyx [00:23:28]: So like the answer was preemptively respond to every inbound request?
Akshay Nathan [00:23:33]: No, it was just like literally like this is what I do sometimes as my job.
Swyx [00:23:36]: I know you copy-paste and then you’re just a message forwarding service
Akshay Nathan [00:23:39]: Yeah. Yeah, exactly
Swyx [00:23:39]: From AI to AI.
Vibhu [00:23:40]: But I think it’s interesting, right? It helps people understand the capability of what you can ask and delegate that oftentimes people don’t realize until they try or someone shows you, and then you’re like, “Oh, okay. Okay, I see.”
Swyx [00:23:52]: I think it’s als there’s also like a, light security issue, where like you’re the permissions layer. Like yes, I could query everything that you query, and I could get an automated response, but maybe I’m not supposed to see it. And that there’s no way I would know because I’m not supposed to know what I don’t know.
Akshay Nathan [00:24:07]: Especially as like, with ChatGPT Work, we’re, we’re asking you to connect your plug-ins and, it’s pulling from your local files and stuff like that. Like the amount of context that the agent has access to is like- Deeply personal and like that’s something I think we need to preserve, so that’ll be definitely a challenge.
Swyx [00:24:22]: There’s Excel, there’s PowerPoint, there’s Docs, the, grand trio of work. What other formats of work do you think about? like you worked on Airtable. Is there a future where there’s like OpenAI Airtable? Like what does that look like if you ever ended up doing it?
Akshay Nathan [00:24:41]: It’s a really good question. I think,
Formats of Work: Sites as Knowledge Artifacts
Akshay Nathan [00:24:43]: one that you didn’t bring up was Sites, and I think that was
Swyx [00:24:46]: Sites
Akshay Nathan [00:24:46]: A core part of this launch. There’s one side of Sites that I think people commonly talk about, especially on Twitter and stuff or X, of like, this like prototyping tool. And like we saw that happen with this launch even. The model slider that you guys were referencing earlier, like that was developed almost fully in a Site. Like, the collaboration between design and engineering and product on that was like on a site where we play with, the affordance and figure out how it feels and all of that. But the other aspect that I think is a little bit less talked about is like Sites as like an artifact for knowledge work. I was talking to someone the other day who’s on like our corporate finance team, and like we were mentioning how like now when they have these reports that they’re, they’re working on as a team month to month, historically those things were in slide decks and in spreadsheets, and now they’re just in Sites. And like Sites is the mechanism that they collaborate across the team. And the reason is ‘cause it’s like, it’s like somewhat higher bandwidth. Like, at these tools like PowerPoint and Excel are like infinitely flexible, but at some point you reach the boundary of like either as a human you may not know how to use some feature or something, or the product itself doesn’t support it. But with a site you can do anything. You ask for anything and you can get that. once people see that magic, I think it’s been really valuable.
Swyx [00:26:02]: Yeah, let me show you my case study. this involves all the hot topics including ChatGPT Work, but also GPT-5.6 token billionaires and token maxing and Sites and auto research. I’m a fan of this game called Strata. It’s, it’s like a little board game that you
Sites, Auto Research, and Research Dashboards
Swyx [00:26:17]: That you play with, physical blocks, that come on top of it like that. So over the weekend I took like thirty photos and just threw into ChatGPT. one point seven billion tokens later, out comes this site with a fully playable thing
Akshay Nathan [00:26:32]: Wow
Swyx [00:26:32]: With 3D, block placement and everything. Because it requires physical blocks and I needed friends to train on it so they can get better, so I can play against them. But also, I could also, do things like train an AI on it and that’s, that
Akshay Nathan [00:26:45]: That’s your auto research
Swyx [00:26:46]: That gets into auto research. So, you want to train your own AIs, and then make sure they self-play against, each other. I need to set both AIs. So this is AI versus AI, and they’re, they’re gonna self-play. the AIs start out bad and then you want to define a loss function and get good. I wasn’t gonna supervise all this. I was at, I was down in San Mateo, attending a conference. What I ended up doing was, auto researching and on this and creating benchmarks and that there was just way too many parameters for me to read. So I started asking it for a site, and it’s created this lab, panel. Where is there a, is there a shortcut for a site that is created?
Akshay Nathan [00:27:28]: You should be able to go in the sidebar to Sites, top of the sidebar. The left sidebar.
Swyx [00:27:33]: This one? Oh, left?
Akshay Nathan [00:27:35]: Yeah. Just scroll all the way to the top.
Swyx [00:27:36]: Oh. Oh, it says Sites. Oh, there you go. Yeah.
Akshay Nathan [00:27:39]: Ooh.
Swyx [00:27:40]: So it create, it creates the sites. I don’t, I don’t think this is, it is exactly what I wanted, but let me show you what it popped up, right? Like I think as a research artifact, it is very important to communicate, exactly, what is being done. Outputs this thing which I eventually started publishing. So I moved it off of Sites because I wanted more, database and infrastructure than Sites afforded me. But this is like a research output that you can start to mess with and like try to think about like what hyperparameters are you tuning for training AIs. And like I was trying to make like scaling laws and everything and doing all sorts of like game optimization stuff. And the fact that you can just throw this up as a research artifact, like I no longer need to read ChatGPT output. I read Site output. But then there’s also a huge sprawl. Like look at how long this thing is. There’s so many numbers. It is pretty overwhelming, so then I have to start pruning it from there. But, it’s an interesting transition from Markdown effectively that you’re putting out to, you’re putting out a whole functional site.
Akshay Nathan [00:28:41]: I think Markdown just isn’t that optimal for people to read, right? Might as well just write HTML website and I don’t know. I think you can do a lot with customizing this, right? You have your skills that explain what you want. Like I noticed they’re quite verbose. I don’t need a lot of this information.
Swyx [00:28:57]: It’s very verbose.
Akshay Nathan [00:28:58]: So and then the nice thing of having a site side by side is, you just iterate on what you want and what you don’t, right?
Swyx [00:29:05]: Yeah. I don’t know if, any that triggers any stories for you of how it’s run internally. Am I doing this right?
Akshay Nathan [00:29:11]: Yeah. I think that this is like a workflow that we’re seeing like all different types of teams use, where like the canonical artifact that was previously a deck or something is now becoming a site. And like with a site you, because it’s just HTML, you can like. It’s infinitely flexible. And so, if you want to give more prominence to a certain thing that like in a slide deck would, feel like it was buried, like you can do that. You can have it be like the hero image, right? And so I think that like, people are starting to see that. There’s more work to be done to make these things like much more easier, easy to collaborate on. You mentioned that they’re very, they’re long and verbose, could be broken up. I’m sure that there’s still something to do there.
Swyx [00:29:53]: They’re super long. Yeah.
Akshay Nathan [00:29:54]: Yeah. But I think we’re starting to see that like there is this aspect of this is a really interesting, format, for people to use, that’s like much more flexible than what they ever had before.
Swyx [00:30:07]: I think your job also comes becomes meta. You’re not designing the products. You’re designing a product to make products, and I’m curious how you manage that.
Designing a Product That Makes Products
Akshay Nathan [00:30:18]: I think one thing that we’ve been Like when we look at the UX, like that we’ve been thinking a lot about is how can we balance like simplicity with capability? Like if we’re designing a product, like you said, that like is made to make up build other things, right? You can build so many different things. But we can’t put that all in front of you because you’ll get overwhelmed.
Vibhu [00:30:41]: Yes.
Akshay Nathan [00:30:41]: And so we had similar problem or similar challenges even Chat-with ChatGPT, but especially now, like when there’s so much that can be done, I think the balance that we’re constantly trying to strike is like, how can we give the user enough of a UI surface where, they can be expressive, they can tell the agent what they need, they can verify that it’s using the right tools, it’s pulling from the right sources, et cetera, but then it gets out of the way. And then how can we build the right system such that we can show them instead of telling them what can be done? Because so much of this is gonna be like, how do they discover the next use case and the next one after that if they really want to be super powered by the AI.
Games, Private Evals, and Show-Don’Tell
Vibhu [00:31:19]: Yeah. It’s interesting. I feel like everyone also just has a different way to do it, right? I made a similar version of this same game. I didn’t take any pictures of board or rule game. I threw in at goal eighteen minutes, fifty-three seconds later, a lot of tokens later, I’ve got a similar version. not with all the auto research and whatnot, but
Akshay Nathan [00:31:39]: You gotta do all the latest trends.
Vibhu [00:31:40]: And yeah, I did it with, did it with Codex, not Work, but it’s interesting, right?
Akshay Nathan [00:31:45]: Yeah. And this is GPT Image generating the pro avatars. Very good for game design. Like
Vibhu [00:31:51]: And
Akshay Nathan [00:31:52]: A lot of game designers were like really into GPT Image for assets.
Vibhu [00:31:54]: I will say like the broader takeaway probably is the reason that we do this is more so just to test the tools, right? Like, this was also a test for GPT-5.6 came out. I had done the game on GPT-5.5, right? The ability for me to no longer need it to. I had to feed it the rules. It’s, it’s a pretty niche game. It couldn’t find how to do this on its own.
Akshay Nathan [00:32:15]: Oh, yeah.
Vibhu [00:32:15]: GPT-5.6
Akshay Nathan [00:32:16]: It is out-of-distribution, which is why I was also very keen on testing the GPT-5.6 capability.
Vibhu [00:32:21]: But, this is just as work comes out, as new things come out, these are just our side ways to test things, right?
Akshay Nathan [00:32:27]: Yeah. It’s some private eval. That is not this private.
Vibhu [00:32:31]: But also valuable because now you can send this to your friends and I learned about this game through seeing this.
Akshay Nathan [00:32:36]: It’s a hard game. He’s very good.
Vibhu [00:32:39]: It’s good to when no one is competing with you. But yes, it’s a classic RL problem of like self-play, bootstrapping your game AI. yeah, you see how easily work becomes personal and personal becomes work because the thing I do for personal, it directly informs people I work with because I showed it to them. They were like, “Oh, you can do that with GPT?” Which like I imagine is the growth strategy.
Akshay Nathan [00:33:02]: Yeah. The show not tell is a big piece that, I think we’ve we’re not still not fully cracked of like, showing people all the things that they can do with the product versus like trying to teach that to them through like, articles or onboarding or whatever.
Akshay Nathan [00:33:18]: So meeting them in the moment.
Vibhu [00:33:19]: It’s a career risk for me, because I used to be in developer relations, right? Where your job is to show, and then you’re like, “What do you mean? You don’t, you don’t need.” your job is to tell. And then. But the product people are like, “Well, we don’t need you if our product is intuitive enough.” So
Akshay Nathan [00:33:37]: Yeah. that’s the magic of the models. So you can tailor the telling or the showing to like specifically what the user needs, like what they care about, what they’ve done in the past, exactly where they are on the adoption journey. So I think that’s like gonna be a super big opportunity.
Vibhu [00:33:50]: Seems easier and easier now to tailor custom showing, right? People have different use cases. As much as you said you don’t wanna segment different people into different buckets, right? It’s also not that hard to for people that are in different categories. But the question, is you said your team is more broadly on. What was the term you used? Productivity?
From Developers to Knowledge Work to Everyone
Akshay Nathan [00:34:12]: Productivity.
Vibhu [00:34:12]: Productivity. So how
Akshay Nathan [00:34:12]: Which is now work.
Vibhu [00:34:14]: Is it work? Is there another distribution that we’re not hitting? Is there a group of people that will have something different than ChatGPT, Codex or Work? Is there more that the mass isn’t targeting?
Akshay Nathan [00:34:28]: I see it as like a sequencing, like. The vision is like bring useful agents to everyone. We started with like developers. Like developers historically are like early adopters that are willing to put up with more friction, set things up, et cetera. Like that’s where, Codex started. I think the next opportunity is like what we call general knowledge work, all the other functions around developers. I think when you go from developers to this segment, like there’s inherent challenges with like, this show not tell thing that we’re talking about, making the product more understandable, bringing in new capabilities that matter more for this cohort than matter for developers, things like artifacts, things like computer use, et cetera. And then I think like the same learnings, like similarly how we took the learnings from developers and brought it to, general knowledge work, the next stage will be like taking the learnings from general knowledge work and bringing it to everyone no matter what they’re doing in their lives. And we’re already seeing that a little bit. Like this game example that you have is, something that’s like on the border of like fun and personal life to, your professional life. I use ChatGPT Work full-time at home for everything, like for whatever I’m doing. I used it the other day to come up with a meal plan and like, save that on the like computer environment that it has and something that I can continue going back to. Like is everyone doing that yet? Probably not because the thing says work on it, but eventually, we wanna get people there.
Vibhu [00:35:51]: ChatGPT life.
Akshay Nathan [00:35:52]: Yeah, exactly. ChatGPT cooking. But I think there’s a lot of, there’s a lot of opportunity there, but I see it as like, we’re, we’re built we built a foundation in software engineering, and we’re gonna take the same learnings that we take from software engineering to knowledge work to everyone.
Vibhu [00:36:07]: Do you have any power user advice? I feel like, there’s a group of people that will live it, use it for everything, stay on it twenty four-seven. And then there’s a bit of a gap between that crew and people that, okay, I use it for work. I use it occasionally. Sometimes I type questions. any advice, any learnings, anything you recommend or just, takeaways that you’ve found that help bridge that gap?
Power User Advice: Push the Frontier of Imagination
Akshay Nathan [00:36:30]: I think a couple things that I’ve seen is like, one, that it really helps to broaden your imagination of what’s possible, and this has been a learning even for me. Like, the technology has progressed so fast that, something that, like, even three months ago, like, no way the models can do this. Like, now it’s like, wow, it’s like it can. Like,
Swyx [00:36:52]: Give an example
Akshay Nathan [00:36:52]: We’re going through right now our, like, review cycle internally, and, people always talked about this as, like, a thing that the models are good at and like, there’s a cliché of like: Okay, like, no one wants to be writing reviews and, like, we just use AI to do it. But in all seriousness
Swyx [00:37:09]: And it can evaluate it as well.
Akshay Nathan [00:37:10]: Yeah, exactly. In all seriousness, before it was, like, just, like, slop and, like, I think it was helpful, but, not super productive. Now I’ve found that, like, the model can do a much better job than me, especially in this environment of, like, pulling context on, like, what people are up to, how they’ve like the things that they’ve done to make a difference, highlighting like, wins that they’ve had that, like, I might may not even have seen. It has access to, like, everything, right? Like the code, like, things that they’ve caught, reviews, Slack, everything. And so it’s, like, incredibly powerful in that domain and, like, just like six months ago, the last time we did this cycle, like, I didn’t even I tried using it, but it was not at all helpful. And this time it’s been, like, incredibly helpful and, like, so I think continuing to push the frontier of imagination of what’s possible, even if you tried something before, I think is maybe the my biggest piece of advice. The other, thing is, like, the more you put in, especially in this environment where, like, the model has access to everything on your computer or in ChatGPT Work, like you can create, artifacts over time and save them in your library and, like, the model will continue having access to those. Like, the more information you give it about whatever domain you’re in, whether it’s your life or your work, the more valuable it becomes, and it’ll become valuable in, like, ways that might surprise you. Like, it might pull from context in a way that, may be proactive and that you might not even have thought about. But it needs to have access to those, to that those tools or that context first.
Reviews, Agentic Search, and Context Gathering
Swyx [00:38:27]: One thing I just wanna talk about the review stuff because I’m still that’s a very sensitive thing and you’re, you’re a founder, you’ve managed people, you’ve hired people. As manager myself, I’m very reticent to put out any LLM-generated things especially when it comes to people, ‘cause it feels like you don’t care.
Swyx [00:38:46]: Presumably at OpenAI, people are more open to being eval rated by GPT. But are there any unofficial rules around this? Like, what’s the etiquette?
Akshay Nathan [00:38:57]: Oh, I think the etiquette is that, like, I would never write something via, like, well, solely via AI and, like, present it as, like, a review for someone. What I was talking about is more, like, gathering context. That’s the place where it’s incredibly helpful.
Swyx [00:39:08]: So it’s just search.
Akshay Nathan [00:39:09]: Yeah, exactly.
Swyx [00:39:09]: It’s agentic search. Yeah.
Akshay Nathan [00:39:10]: It’s like agentic search, but, that you can tailor and steer much more capably than you could before, ‘cause, like, the thing is it’s all there’s a flywheel happening, right? Because of Codex, people are able to do, and because of ChatGPT, people are able to do so much more now than ever before. And if you’re able to do so much more, it’s easy to miss things as well. And so, like, I think we need to use these same tools to keep up with all the impact that people are having and understand, where we can be helpful.
Swyx [00:39:39]: I think the thing, like, I run a small company, so easy to search, but at the scale of OpenAI with the amount of messages that you guys put in Slack, do you think that it misses things?
Remembering What Humans Miss
Akshay Nathan [00:39:50]: Probably, but I think that I also miss things.
Swyx [00:39:52]: Like, it doesn’t matter, right?
Vibhu [00:39:53]: I think sometimes it’s
Swyx [00:39:53]: Like it’s, as it needs to be human-level
Akshay Nathan [00:39:54]: It’s all relative, right? Yeah.
Vibhu [00:39:56]: Sometimes it’s nice when it finds things you wouldn’t, right? Like right now, my Codex system prompts, they’re set up in such a way that every project I have has a secret- separate, notes MD, and it just writes learnings to there. And then the global one can pull from all these. So sometimes it’ll be like: Oh, there’s this project you did like four months ago. Here’s a note that we had, and it randomly pulls it back into context that I would never do, I haven’t thought about.
Vibhu [00:40:20]: And I’m like, okay, this is quite superhuman, right? Like, stuff that would. And, it’ll save like hours on chunking of stuff or find something that’s already been done. I’m like, as much as it might miss stuff, I would too, but it’s very useful when it finds stuff. And I have like a very, non-super engineered solution to this. It’s just marked down files that get pulled whenever they want.
Akshay Nathan [00:40:41]: Yeah. I have a funny anecdote about this. Like, recently gearing up to this launch, the team has been, really cooking on it for a couple months, and over that time, like there’s so much conversation and chatter going on in Slack and Docs and elsewhere. And, one of the members of the team set up this, scheduled tasks, like automation to like look at everything that’s going on and, like, come up with the best memes and then post it in one of our shared channels. And like, there are two cool things about this. Like, the first is, like, I think the models are, over time, like starting to become like funny.
Swyx [00:41:13]: Funny. Nice.
Akshay Nathan [00:41:13]: Whereas like, a year ago, like that was not at all the case. The second is, it was what you were saying, like they find things that in surprising ways that you may not have thought of and like create connections that you may not have thought of. And that really helps with like the meme generation because then you can see something that, genuinely surprises you and, is funny in that way. So yeah, that’s like not like the most productive, use of this the technology, but it does it does uncover this, like this capability that’s emerging, which is just like to find information that you otherwise would not know of.
Launch Momentum and the 10 Million User Milestone
Swyx [00:41:43]: Talking about the launch, I think, I have pretty much said this is the most successful launch in a long time. I think even more successful personally than 5.0, and they’re announcing ten million users. Does it feel different? You’ve been through a lot of launches.
Akshay Nathan [00:41:58]: I think it feels like a culmination. Well, I think two things. One, it feels like a culmination, like I was mentioning earlier, like this like vision mission that we’ve been on for a long time. Like I said, we saw the magic of Codex internally, and then we’re like extremely excited to bring this to many more people and to see it working, to like see us reach, the distribution goal, numbers that you mentioned, like I think that’s like huge and super exciting. The flip side of that is like, there’s so much more to do too. Like, that’s also really exciting. Like, ChatGPT as a whole, like the this product that, everyone almost equates to AI and like loves, has hundreds of millions of users. And so like ten million is really cool, but like we need to get this to everyone. Like, we need everyone to feel this magic. And so that’s the next step from here. But yeah, I think extremely pumped about how it’s going so far and the opportunities.
Swyx [00:42:46]: Awesome. I did want to also Because I’ve, I’ve, I’ve been tracking the number closely, it transitioned at some point from just Codex users to Codex plus ChatGPT Work, because they’re same harness. The whole point is that you don’t, you can’t, count them separately. Do you have roughly a billion, ChatGPT users? Why did it just jump to one billion right away? Like, isn’t that the default on ChatGPT or no?
Codex, ChatGPT Work, and the Developer Brand
Akshay Nathan [00:43:11]: We don’t default you into ChatGPT Work if you’re on ChatGPT
Swyx [00:43:14]: If you’re free. Yeah
Akshay Nathan [00:43:15]: It’s also only available to paid users right now. And I think there’s like a process of, educating users of what is the value of this product, having them try it, learning from their feedback, and making it better over time. But the goal is to, get as many of the people who love ChatGPT today to like feel the power of ChatGPT Work. But I think it’ll be a journey.
Swyx [00:43:36]: Yeah. And Codex will still be alive as a brand for the foreseeable future. And we’ll just toggle between them as needed for UI stuff.
Akshay Nathan [00:43:44]: Yeah, I think it’s even stronger point than that. Like, I think we fully intend to like, treat developer. Like, developers have been, a core market for us for so long, and like there’s, there’s so much more that we can do to make Codex great specifically for, software development, and we’ll continue to do that. This doesn’t take away from that at all. If anything, it should increase the utility of something like Codex, because now you can move seamlessly between writing a diff to creating an artifact or, doing a search over your factor.
Swyx [00:44:11]: I do wonder how much this terminology leaks to the non-technical user. Like, do they have to learn to say artifact if I want artifact? Or.
Akshay Nathan [00:44:20]: It’s funny, like we call it artifacts internally ‘cause that’s what the teams call it.
Swyx [00:44:23]: It’s nice. Yeah.
Akshay Nathan [00:44:23]: But like externally, like no one says that, no one calls it an artifact. But I think that people like often, like describe things, whatever they’re used to, right? So if, ChatGPT Work is good at creating slides, they’ll say ChatGPT Work is good at creating slides, and that’s what we want.
OpenClaw, Personal OS, and Persistent Computers
Swyx [00:44:38]: One big Another, it’s July of twenty-six. One big thing that also happens in, for OpenAI was OpenClaw, and that’s I think a lot of people’s first time really maxing a agent for personal stuff, but also crossing over to work in essence same way. As far as I understand, OpenClaw is still independent, but did you go through your own OpenClaw moments? Were there any lessons you took from OpenClaw to Codex or back? Whatever.
Akshay Nathan [00:45:06]: I think there’s a lot of inspiration. I did go through my own OpenClaw moment. I,
Swyx [00:45:10]: Yeah, tell the story
Akshay Nathan [00:45:10]: Me and my wife like set up an OpenClaw to like try to manage everything in our house. Not that there’s like a ton, but it was like quite useful. We gave it a calendar. It started, creating events for us and stuff. At some point, the laptop that we were running on, it died and never got a chance to pick it back up. But there was a lot of inspiration there, like, in ChatGPT Work, in web and mobile, like you get access to this like persistent computer environment where, you can store files, and those files stay around between sessions. And the idea is to be able to enable use cases like this. one of the members of our team uses ChatGPT Work for what they used OpenClaw from before, and then feel like it has like completely transitioned, which is like, workout planning and like meal tracking. which again, it’s like a work-related thing, right? It’s like not work necessarily, but it’s like in personal productivity space. But it has all the same primitives. So it has scheduled tasks. It has the ability to store files on a file system. It has the ability to like reference those things over time. And so you start to see the same types of use cases emerge, which has been really cool.
Swyx [00:46:14]: Is there a point that ChatGPT Work completely replaces OpenClaw? they’re independent, so.
Akshay Nathan [00:46:20]: Yeah, I’m, I’m not close to it, so I can’t speak to the OpenClaw roadmap, but I don’t think so. I think that there’s gonna be, there’s always a need for like this like incredible, like open source technology that team has built. And I think that we can draw inspiration, in the product and, ChatGPT, I think many more people have like heard about and used ChatGPT than have used OpenClaw. And if we can take the magic from OpenClaw and bring it to them, I think that’ll be a success. I think that like one thing on the ChatGPT Work side that we feel strongly about is that like the core experience is that you come to this product and you have a conversation, start a session, whatever you wanna call it, with this agent. And the magic of the product is that you can do anything in that moment. And we would like to create a product where you don’t have to click a button or to go to a different place, whatever, and you can get whatever functionality exists in, your finances app or where or any other product like in this one place. And so that’s the goal. It’s like it we want an extensible system with plugins where you can connect to the tools that you need in order to be able to accomplish like a financial task, where you can, if you’re doing like science work, like we have an ability to like extend the system in such that you can like write the tech and it performs well. There’ll always be like products that we support that are best in class at those things, but we want as much of the magic as possible in that core experience.
Swyx [00:47:45]: Yeah. Do you think that you can do everything you used to do with Wealthfront in ChatGPT Finance?
Finance, Data Access, and Centralized Context
Akshay Nathan [00:47:50]: I tried it. like ChatGPT doesn’t yet custody, cash and assets for me. So that part, no, not yet. But I, there was like a whole component of like retirement planning and, like financial planning and budgeting and stuff that, we were looking into when I was there. And like with the finances plugin, like that’s all possible with ChatGPT today. So, I feel like at least that component’s replaced for me.
Swyx [00:48:17]: I haven’t really plugged it in yet. I’m somewhat scared to look at the answer. Like that’s honestly like the same reason for health and finances. Like I’m like, no.
Akshay Nathan [00:48:27]: It’s really good. It’s really cool how we were talking about like the agentic search aspect a little bit earlier, but like, it’s really cool how like, in conventional UX, like if the more power you wanna give to a user, the more like knobs and bells and whistles you need to add. Like, for like these finance and budgeting apps, like there’s always like a bunch of the different filters and like search bars and stuff like that. But like now, like with the right
Vibhu [00:48:48]: Connect-connectivity to the right data, you can have whatever you want. You can ask any question you want and into that box and get the answer, and I think that’s super powerful.
Akshay Nathan [00:48:57]: I think it’s also nice to just have it centralized in one space, right? You have different health apps. I have one for a smart scale, a watch, all these different things. It’s just nice to centrally co-locate it.
Vibhu [00:49:08]: Which is, part of the whole thing of OpenClaw, right? Like that you would have, personal OS, which presumably ChatGPT wants to become. I do think that just relying on, like, just-in-time pulling of data for, let’s say, through via MCP, CLI, API, whatever you do, still not enough. Like I come from a bit of a data engineering background, like you still want like a data warehouse or some caching or semantic layer. do you feel that or do you already have that?
Akshay Nathan [00:49:40]: I can’t speak to like all the details on how everything works, but I think it depends on the access pattern, right? Like if you want an answer immediately, then yes, it’s very difficult to do that if you need to pull from all of these sources. But a lot of the like use cases that we wanna enable in ChatGPT Work aren’t necessarily something that you need immediately. It’s more like a task that you want the agent to go and do, and that’s gonna take a certain amount of time. And, with things like programmatic tool calling and stuff now, like some of that time and sub-agents and stuff, like some of that is also parallelizable. And so it’s possible I think it’s very possible that there’s a, the ceiling on what can be done, with MCPs and like calling out to these third-party services has been raised substantially. So we’re really excited about that.
Sub-Agents, Ultra, and Product Design Tradeoffs
Vibhu [00:50:23]: You mentioned sub-agents. I gotta double-click on that. Ultra is a new mode. You have special affordances in ChatGPT itself to show off the agents. Can’t really do much with them, to be honest. Like just watch. what have been, what have been your experiences, any design issues that you would call out to other builders building with sub-agents?
Akshay Nathan [00:50:45]: I think it’s goes back to the balance that I was raising earlier about like, showing builders the power of the tool, but also creating enough of an abstraction to not overwhelm them. I think with sub-agents, the thing that we wanted to show is that you can take a task that, has many parallel tracks or, is complicated in a way that, sub-agents can handle, and this product is for you. Like, the model can accomplish those goals or try to accomplish those goals. And so like that’s the point of like showing them in the product and that’s where we-we’ve gone with the design. There’s another, iteration of this where like you can see exactly what they’re doing and things like that, which I think is like, could converge on like overwhelming, with information. And so this is like the deliberate trade-off that we made for now.
Vibhu [00:51:33]: You do display quite a lot of transcripts.
Akshay Nathan [00:51:35]: Right. Right.
Vibhu [00:51:36]: Or do you
Akshay Nathan [00:51:36]: I think it’s hidden by default though, right?
Vibhu [00:51:37]: Do you want to display more than that?
Akshay Nathan [00:51:38]: No, it’s hidden by default. Yeah.
Vibhu [00:51:39]: Some people could want more. So I’m one of those people that will throw a lot of stuff at goal, and pretty much every goal I’ll tell it to use sub-agents. Seems redundant, right? But every time I’m like, “Okay, use sub-agents where possible.” And I have a lot of people, a lot of friends that recommend and do the same. Whereas I’ll sometimes talk to people that are like, “Okay, this is where I want you to use sub-agents for this sub-task,” and I’m sure they would appreciate seeing into how they’re being used. For me, it’s primarily like two things, right? One is net time efficiency, so span out across sub-agents. Two is probably cost, right?
Vibhu [00:52:15]: Don’t use big, expensive model. Offload to a lot of smaller, cheaper models. And some people want that level of control. So if you have repetition in what you’re doing, right? Say I want something built where I want it to consistently do this every day, I might wanna go in and fine-tune sub-agents here, sub-agents there. So you can see both, but I think if I’m not mistaken, it’s hidden by default. There’s a dropdown that goes a lot where I’m like, okay I’m just gonna keep, using.
Akshay Nathan [00:52:41]: Oh, you can change the model that they use.
Vibhu [00:52:42]: I know I tell them to be steered. I’ll say my I know Anthropic offers this in Cloud Code. You can tell Fable to use Sonnet or Opus to use Sonnet as sub-agent, so pretty trivial thing. You tell it to span out sub-agents with Sonnet, it’s cheaper, faster. I would assume if it’s not there, it could be built there. But I think there’s a side of
Akshay Nathan [00:53:02]: It’s too many toggles.
Vibhu [00:53:04]: It’s not a toggle. It’s just, you tell it in chat.
Akshay Nathan [00:53:07]: You’re prompting it. Yeah.
Vibhu [00:53:07]: The way I do it is prompt it, right? And I think this is something that gets abstracted unless it’s something you built for repetition, right? So if I’m building something, say that’s, podcast prep, right? Research into people, do a very deep extensive research, that I might wanna configure to cheaper, faster model just for web search, right? I can see a world in which you want both. I think the default is pretty good right now, where it’s hidden, but you can drop down and get some more info into what’s done.
Vibhu [00:53:34]: I know people talked a lot about it on GPT-5.6’s launch. this thing loves to use a lot of sub-agents and causes the ChatGPT app to just crash because it’s so processor-heavy. But,
Akshay Nathan [00:53:47]: For what it’s worth, that’s not my experience. Yeah, I haven’t had a crash from sub-agents.
Vibhu [00:53:52]: I haven’t either. I have We both have big laptops. But I know people brought it up. There was a topic of discussion that we didn’t see the same, but it is another vibe eval, right? People are like, “Okay, the amount of sub-agents Sol is wanting is crazy.” And I’m like, “I think this is okay. I think it’s good.” But just stuff people bring up.
Akshay Nathan [00:54:12]: I think when we launched the product too, we weren’t as opinion about like who is Ultra for and like when should they be using it. And since then we’ve made some changes to like, require you to turn it on and find it in the advanced setting ‘cause that’s who it is for. It’s for like power users who understand what’s gonna happen because it also, depending on your use case, can use more of your limits as well.
Vibhu [00:54:33]: Yes.
Akshay Nathan [00:54:33]: So that’s where I think a lot of the feedback was coming from.
Vibhu [00:54:36]: It’s okay. Reset the limits. Always reset the limits.
Akshay Nathan [00:54:39]: Well, it’s, today we’re resetting because of this. I wanna change topics to one last piece of the harness, memory. A lot of people are commenting on memory recently. ChatGPT’s new memory system used to suck, it’s not very good. And then this guy also the same thing, and Samir, who you presumably work with
Memory, Chronicle, and Personalized Context
Akshay Nathan [00:54:55]: Talking about memory. What can you say there? I think that, Samir and the team have made a ton of and then the research teams have made a ton of, updates and improvements over time. I think when I talk to friends, family members about what they love about ChatGPT, like the fact that it knows them, that they feel like their ChatGPT is their ChatGPT, I think comes up probably number one. In ChatGPT Work, in the Cloud, like by default, all conversations like inherit from your ChatGPT memory, so you’ll know they’ll know context about you, and they’ll also be able to write back to this memory.
Vibhu [00:55:27]: With it, like a small text write. Like you tell me when you’re writing, right? Is it
Akshay Nathan [00:55:31]: No, it’s part of the same like memory V3 system that we launched.
Vibhu [00:55:36]: Yeah, Memory V3, yeah.
Akshay Nathan [00:55:37]: So I think that’s been really powerful because, going from ChatGPT to ChatGPT Work feels like an extension of what I’ve already been doing with the product for sometimes many years. So that’s been awesome, and it’s awesome to see that like people are recognizing the improvements here.
Vibhu [00:55:51]: Is there So it’s a retrieval problem, right? Like, are you retrieving the right things? Are you over-focusing on the wrong things? Is there like a more false positive or false negative, if that makes sense? Like, what’s the bigger problem?
Akshay Nathan [00:56:05]: So I don’t work on memory directly so it’s hard to say what the bigger problem is with like certainty. But I think you’re right. I think that like, the there’s two sides of it. It’s like, making sure it knows things about you, but then also having the EQ to like bring those things up at the right moments proactively or surprising you in ways that are positive, not negative.
Akshay Nathan [00:56:21]: So I think it’s a very challenging problem, but something that I think we feel very there’s a huge opportunity to get right, which is like why we’ve made like big investments in it.
Vibhu [00:56:29]: How do you see the side of, okay, when you’re building ChatGPT for work different than the regular chat app, different than Codex, managing memory across different projects, collaboration and whatnot, how do you see the side of what’s separate from the harness, right? So if I have four threads on one project any learnings on how to build memory systems there? For background as well, to steer it a bit, is when you do chat style applications, I’d say you have a lot of one-offs, right?
Vibhu [00:56:58]: When you switch to work it might be something you’re doing for a month, something you do a lot, right? Now, as I add more sessions, there’s a lot more than just single-threaded, right?
Vibhu [00:57:08]: And there might be memory there.
Akshay Nathan [00:57:10]: I think first I challenge that like the depth of the memory or the like value of it is like fundamentally different across chat and work. Like it is true that like, there are a lot of like shorter sessions on chat, but I think, the ChatGPT, the product has had like a ton of longevity, in, as long as this technology has been around and people use it for work-related, like productivity-related things already today. And so I think we found that there’s a lot of value. I found this my personal usage, like all these one-offs add up over time into something like quite durable and like quite a good representation of who I am. I know like from time to time, something will go viral on X about like, ChatGPT telling you everything it knows about you, and people are always surprised like how deep that is.
Vibhu [00:57:55]: The fun roast me?
Akshay Nathan [00:57:57]: Exactly. So like, I think like the That’s all to say that like I think there’s a lot of depth there in the existing, ChatGPT product, and so that’s why I think we think it’s valuable to bring into the work product. But the other reason I brought that up is because I think like hopefully we can use some of the same fundamental primitives and systems to extend memory here as well, and I know this is something that the team that focuses on this is like working through right now.
Vibhu [00:58:20]: I wanted to bring up one element of memory, which I honestly don’t really use much, and I’m curious if you do: Chronicle, which was, is up on screen right now. It’s a super memory or like what is it?
Akshay Nathan [00:58:33]: I think the idea is that like it can learn from, how you’re using your computer and like it’s another input source, into memory. And, I think it’s, experimental right now and something that like isn’t default off. But I’d recommend that you try it. I think that it’s like quite interesting how It goes back to a conversation we were having earlier on like, you were asking like, “Does it Can ChatGPT miss things?” Like does it, on Slack, when it’s searching, does it miss things? ‘Cause there’s such a volume of stuff, right? And like it’I, you can ask the same question about like everything that you’re doing on your computer. Like, is it gonna know everything that you’re doing? Is it gonna capture the intent and stuff like that? Probably not, but like it probably will find things that you might not know about. And then if it can surface those to you in relevant times, in proactive ways, like when you’re doing tasks, and I found at least that it can be quite helpful. So it’s worth trying.
Vibhu [00:59:24]: So mostly for insights and longer term.
Akshay Nathan [00:59:27]: Yeah, exactly. Like insights and it builds context that makes, that can make you more productive on certain tasks. But it’s, it’s hard to describe without feeling it.
Vibhu [00:59:37]: I will say you can feel it pretty well. Like the idea of what they’re saying here, right? Just check through my memories or check through my logs and add skills. Pretty underrated, right?
Akshay Nathan [00:59:48]: But that’s automations. You can repeat that using a cron job. Checking through your memories and creating skills. But I think the creation of the memories from Chronicle itself is like what’s different. It’s like you have much deeper memories because you have Chronicle on.
Vibhu [01:00:01]: It’s there. I don’t use it much, but maybe I just, I need more examples. I imagine you guys use a lot of it internally, so I’m always fishing for use cases.
Akshay Nathan [01:00:10]: I would just try turning it on and then like
Vibhu [01:00:13]: It just auto works? Like it
Akshay Nathan [01:00:14]: Yeah, and seeing like where it might start helping you. I think you’d be surprised.
Vibhu [01:00:18]: Yeah. Amazing. I think that was, about it in terms of like the overall, coverage of ChatGPT Work. I think there’s been a lot of like good progress and discussion on building and all these things. There’s a lot of like ex-founders in the community, in OpenAI as well. Do you think that things have changed a lot? like your overall reflection of building, pre-AI and post-AI.
Akshay Nathan [01:00:44]: I think things have changed a ton. I think it’s like super exciting to see how quickly you can go to, from idea to something real today. whereas like even before, like I think, five, 10 years ago, like it’s fast if you were scrappy and, like, willing to build the minimal viable thing. But, like, now the extent of what you can build is, like, much broader. And I think that also, like, what we’ve seen internally building is, like, that gives you an opportunity to validate much more quickly, to talk to users, to talk to internal doctors, et cetera, and, like, make sure you’re on the right track. And, like, that loop I think has been has become more closed than ever before, and that’s, like, a win for product development. I think it’s a win for consumers and users too because ideally that means they’re getting much more better much better products out the gate.
Building Before and After AI
Vibhu [01:01:32]: Does it mean your teams are smaller?
Akshay Nathan [01:01:33]: I think there’s much more to do now. So I think people can accomplish more individually or in a small team than they were that would require more people than before. But there’s, at the same time, there’s also more to do, so I think the teams are much more ambitious.
Vibhu [01:01:50]: Have you seen any changes in scopes of roles and building teams and how we used to have teams, say, a few years ago versus what ideal teams look like now?
Akshay Nathan [01:01:58]: I think we’ve seen a blurring in the lines between, like, the typical product development functions, like between, like, EM/PM, engineer, designer, et cetera. Like
Vibhu [01:02:08]: Yeah, I wanna bring up this quote. There will be, only four jobs left in tech. There’s AI slop cannon, the people who just, like, they’ll burn a bunch of tokens. And then there is SRE, the people who. people who are more responsible. There’s grown-ups who sell things, and then there’s hot people.
Akshay Nathan [01:02:27]: This is an interesting take. I think my suspicion is that there’s everything everyone will be, like, shaped in a way, in that, like, AI will enable everyone to become a generalist. Like, things that, like, I never would be able to, like, come up with a design before and, like, even now, like, I don’t have maybe, like, the visual taste required, but I can iterate on something with the help of AI. But then people will have a specialty, and that’s, like, the straight line in the T or the upward line in the T. And so, like, you can have a specialty that you’re interested in. With the help of AI, you can go deeper and become better at over time, but then you’ll also be a generalist. And so with that foundation, the way you can accomplish is, like, almost limitless.
Team Shape, Shaped Builders, and Taste
Vibhu [01:03:07]: What are you bottlenecked by in terms of specialties? Like, do you need more designers? Do you need more slop cannons? Do you need more hot people?
Akshay Nathan [01:03:15]: I think the bottleneck some becomes, like, ideas and taste. I think because anyone can build now, I think, it really is the era of, like, bottoms-up ambition. And because there’s so much to be built, like, you’re always gonna be bottlenecked by, the amount of ideas and amount of things that you’re doing at any given time.
Vibhu [01:03:37]: Do you think models help solve that?
Akshay Nathan [01:03:39]: Models?
Vibhu [01:03:40]: Yeah. I have the example of, like, I have a front-end design skill that’s like, they give me four drastically different examples of what this looks like. Sure, it burns a lot of tokens, but. And then I’ll mostly just condense down, “Okay, I like this part. I like this part. Let’s draw these together.” And it’s like, yeah, I had a vision, but, like, I don’t know.
Akshay Nathan [01:04:01]: I would say that the one automation that I would love to work and it doesn’t work is bring me new ideas, right? somehow LLMs are just not it. One interesting part about ideas is, like, they’re not, like, in a vacuum. It’s, like, not. They usually come from somewhere and, like, in product development, like, they’re coming from talking to users or reacting to, friction that you’re seeing or feedback, building on some foundation that you already had planned out before, whatever. And so I think that’s where, like, I think there will always be value in these, like, generalists that we talked about, like, closing that loop and then having coming up with those ideas that are grounded in that feedback or talking to users, whatever it is.
Defining and Measuring Productivity
Vibhu [01:04:41]: Cool. You were gonna. You lead the productivity team. How do you define productivity?
Akshay Nathan [01:04:46]: I think our mission is to make it possible for people to do things that they weren’t able to do before. And right now we’re thinking about it from the perspective of knowledge work. And so when I look at knowledge work, I think about people are no longer siloed by their roles. They’re no longer siloed by maybe the, background or training that they have. Like, no matter what function you’re in, you can suddenly build things. You can suddenly get access to data that you otherwise might not be able to interpret, et cetera. And then I think that extends to your personal life, where we want to give you leverage at the end of the day. Like, we want the models and the product to be able to give you leverage so that you can, create time for yourself to do the things that you love.
Vibhu [01:05:25]: Does that also translate to a way to measure productivity? Like, what is new?
Akshay Nathan [01:05:29]: The end is
Vibhu [01:05:30]: How do you measure leverage?
Akshay Nathan [01:05:31]: I think we haven’t figured this out yet. Part of the reason is it’s so diverse. Everyone has different goals, and really the true measurement is, like, their ability to achieve that goal. Did we help you or did we not?
Akshay Nathan [01:05:44]: And it’s very difficult without knowing what that goal is up front and also tailoring it for every individual.
Vibhu [01:05:48]: And the thumbs up and thumbs down from ChatGPT doesn’t give you anything, right?
Akshay Nathan [01:05:52]: You don’t know if they’re thumbs downing the content of the answer, the vibe of it
Vibhu [01:05:56]: Oh, yeah
Akshay Nathan [01:05:56]: Whether or not it helped them with their goal. I think that’s difficult. But it’s something that I think we will need to figure out and the industry at large will need to figure out because, that’s how we measure success, if this is what we’re, we’re
Vibhu [01:06:06]: Do you think it’s changed, productivity and how you measure it? you said there’s a lot more work that can be done, a lot more scope. has it changed?
Akshay Nathan [01:06:15]: I think it was always true that what you really wanted to measure is, like, was your team, was the individual, were you personally able to hit the goal, or are you closer to hitting that, whatever your goal is, right? But I think previously we used proxies for this. So, like, code commits or
Vibhu [01:06:31]: Lines of code
Akshay Nathan [01:06:31]: Lines of code or whatever.
Vibhu [01:06:33]: Story points.
Akshay Nathan [01:06:34]: Yeah, exactly. Story points. And, like
Vibhu [01:06:36]: They’re coming back, by the way.
Akshay Nathan [01:06:38]: maybe. But that is for a part of the change. And, like, I think with AI now, those proxies starting to fall apart. Like, you, the number of tokens you use or the number of pull requests you make are, like, no longer, like, maybe as hypercorrelated with that, is your team able to hit the goal or are they on track to hit their goals? So I think we’ll need to come up with new, measurements.
Vibhu [01:07:02]: For the managers listening, give them one thing to try.
At-Bats, Motion vs. Progress, and Closing
Akshay Nathan [01:07:06]: I think for me, what’s important is like at-bats. Are we as a team building the muscle to have not just quantity of at-bats, but quality? Like, are we able to go all the way from, like, generating an idea, building it out, getting the feedback, reacting to that feedback, validating or invalidating the hypothesis, going on to the next idea? Are we able to do that really efficiently? And like, that goes to like, the actual like code that’s being written or the designs that are being made or the specs that are being written, whatever, but also the culture of the team. Like, do we have the humility and, are able to like go through that process many times and stay motivated and excited throughout that? so that’s the thing that like I think is important now, especially when we’re on the frontier of this technology and like there’s so much to build, there’s so much to do. That’s probably the most important thing that we look at.
Vibhu [01:07:54]: Any traps people fall into around measuring productivity with your teamwork on. I feel like there’s a lot of, okay, we added a lot of LMs. We have dashboards for this and that, but not much has changed, right?
Akshay Nathan [01:08:06]: That is the trap, yes.
Vibhu [01:08:09]: And the broader source of the question is for the managers and teams building, how should they approach this?
Akshay Nathan [01:08:18]: I think maybe the trap is like conflating motion and progress. I think motion is much easier now than ever before because of the tooling that we have. But progress requires you to be like very prescriptive and deliberate about like what you’re trying to achieve, and it goes back to our question of measurement, right? Like you wrote we were talking about like, can we, OpenAI, like figure out how to measure productivity for our users? That’s, that’s a very hard problem because of the diversity. But like as a team, like you should have a really prescriptive and deliberate view on like what progress looks like for you and for your team. And if you don’t have that, then it’s very easy to conflate these two things.
Vibhu [01:08:57]: I think at-bats is a really great thing. I’m, I’m really glad. I like the discussion between motion and progress. I think that’s a quote that we’re gonna feature on the write-up. You’ve been very generous with your time. Thank you so much and congrats on ten million.
Akshay Nathan [01:09:08]: Yeah, thank you for having me.
Vibhu [01:09:09]: The next one at a hundred in two months. Two weeks. Thank you.


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