基本信息

要点解读

这是什么

这是一期播客访谈，邀请麻省理工学院研究者亚历克斯·张，讨论递归语言模型、GPU 内核优化、多智能体系统设计以及 AI 研究品味等话题。

用在哪里

适合关注大语言模型架构演进、智能体系统构建、以及 AI 前沿研究方向的工程师和研究人员了解当前行业动态。

可以推断的

推测：在学术环境中，选择与工业界主流不同的研究课题可能更容易产生独特的学术影响力。

推测：当前的模型能力可能尚未被现有系统设计充分挖掘，系统层面的改进与模型本身的能力提升同样值得关注。

来源摘要/节选

Last call for regular tickets for AI Engineer NYC! As an exclusive for Latent Space subscribers, the first 30 of you can take a 30% off code if it helps - for new tickets only, no refunds! See you in 2 weeks!

While we tend to cover industry on the pod, every so often we celebrate a clearly emerging superstar PhD. In 2024 we featured Shunyu Yao, who went on to build Operator at OpenAI and is now Chief AI Scientist of Tencent. In 2025 we featured Jack Morris, who went on to cofound Engram at $600m and is now a leading voice on continual learning.

This year we are proud to feature the work of Alex Zhang of MIT.

From GPU kernels and KernelBench to Recursive Language Models, Mismanaged Geniuses, and massive multi-agent swarms, Alex Zhang is exploring how much capability we’re leaving on the table by wrapping increasingly powerful models in primitive systems.

RLMs took over the timeline early this year:

and an RLM based harness was the first to ~solve ARC-AGI-3 before OpenAI’s Astra:

and is even today, influencing new research that has more extreme implications than RLMs:

We go deep on GPU Mode and AI-written kernels, research taste and why academics should take bets industry labs won’t, GEV and alternatives to the standard autoregressive language model, and the idea of harnesses as compositional generalizers. Alex explains RLMs, context offloading, programmatic subagent calling, Prime Agent, persistent subagents, and why the “language model” of the future may actually be an invisible swarm of agents underneath a simple interface. We also discuss OpenAI’s massive agent experiments, Kimi swarms, open-ended research at Sakana AI, speculative programmatic tool calling, capability overhang, Neuralese, and where Alex thinks the next big research opportunities may lie.

We discuss:

Why AI-generated GPU kernels still leave substantial room for human expertise

How one expert insight can potentially replace enormous amounts of brute-force token search

Why PhD students should take research bets that initially look trivial, weird, or pointless

What SWE-bench, RLMs, ReAct, and Quiet-STaR reveal about research taste

GEV and why a language model does not have to mean an autoregressive text-to-text decoder

Why Claude Code, Codex, and Pi are structurally more similar than they look

How harness design can improve compositional generalization across tasks and domains

RLMs: context offloading, code execution, recursive subagents, and shared memory

Prime Agent, continual harnesses, and persistent agent-to-agent communication

Why the model you query in the future may secretly be an entire swarm or scaffold

OpenAI’s 10,000-agent experiment, 130B output tokens, and ~$40M-equivalent problem solving

Why much of an agent swarm may be wasted search — and why convergence is still hard

Kimi versus OpenAI and different approaches to multi-agent systems

Open-endedness, Sakana AI, and finding hidden gems in enormous amounts of generated work

Why current frontier models may already have a large capability overhang

Speculative programmatic tool calling and overlapping tool execution with generation

Whether English, code, or an entirely new “Neuralese” constrains how models reason

AI for science, fast-moving benchmarks, and how Alex chooses what research problems to bet on

Alex Zhang

Website: alexzhang13.github.io

X: @a1zhang

Timestamps

00:00:00 Introduction

00:00:49 GPU Mode, KernelBench, and AI-Written Kernels

00:07:38 Human Expertise vs. Brute-Force AI Search

00:13:20 Research Taste and Taking Big Bets

00:19:28 GEV and Rethinking the Language Model

00:29:03 Video Game Agents and the Harness Problem

00:31:01 Why Claude Code, Codex, and Pi Are So Similar

00:36:42 Harnesses as Compositional Generalizers

00:44:24 RLMs Explained

00:52:01 Prime Agent and Persistent Subagents

00:57:41 RLMs in the Wild

01:00:30 OpenAI Swarms and the Future of Language Models

01:07:26 Open-Endedness and Sakana AI

01:15:52 Kimi vs. OpenAI Agent Swarms

01:20:06 Capability Overhang and Speculative Tool Calling

01:28:19 Neuralese, Future Research, and AI for Science

Transcript

Introduction: Alex Zhang, RLMs, and GPU Mode

Swyx [00:00:00]: All right, we’re here in the studio with Alex Zhang, I guess most famously of, RLMs, but you have a few other affiliations. Welcome to the show.

Alex Zhang [00:00:12]: Yeah. Thank you for having me.

Swyx [00:00:13]: Yeah. I guess GPU Mode as well?

Alex Zhang [00:00:15]: Yes, GPU Mode as well.

Swyx [00:00:16]: You were shepherded in by Mark Saroufim. Not everyone gets that kind of welcome.

Alex Zhang [00:00:19]: Yep. Yeah. Yeah. I’m very close to all the people in GPU Mode, so yeah

Swyx [00:00:23]: Yeah

Alex Zhang [00:00:23]: We often end up working together in various capacities, like even beyond just GPU Mode itself, so.

Swyx [00:00:29]: Yeah. Can we explain, so people who are not that close Don’t know about this. It’s just a– it’s a Discord. It used to be focused on, I guess, CUDA Mode, and then generalized a little bit. it was started by Mark.

Alex Zhang [00:00:41]: Yep.

Swyx [00:00:42]: It was basically like. To me, it’s like the hiring pipeline of the PyTorch team.

Swyx [00:00:45]: And then you left PyTorch.

Alex Zhang [00:00:47]: Yep.

Alex Zhang [00:00:49]: Yeah. So it used to be, I think, it started actually around when I was in college, in like 2023. I think it was started by Mark, Andreas, and Jeremy Howard. The original premise was just like, it was a GPU– or it was a Discord dedicated to learning how to write GPU kernels, and they had, like, lectures. That was basically the extent of it. and I got interested in it because I was writing GPU kernels. It was actually out of, like, pure chance. I was interning at Snapchat at the time, and

From CUDA Mode to GPU Mode

Swyx [00:01:22]: Rexis.

Alex Zhang [00:01:23]: Yeah, I was very bored with Rexis. So, they had a project where, like, they were interested in writing. It was this paper called Infinite Attention. It was like a Google paper.

Swyx [00:01:35]: Yes, we’ve covered it on Paper Club.

Alex Zhang [00:01:36]: Yes, yeah. So I was interested in whether or not you could write specialized kernels for it at Snapchat. it didn’t. Nothing really came of it, but I joined GPU Mode. At the time, it was called CUDA Mode, I think for, like, legal reasons or something, they changed the name. But I met Mark, I met Matei, I met a bunch of other people that were very involved in the community. And then Mark had pitched this idea called Popcorn, which was now what you see as the leaderboard today. But the general idea was like. I think all of us had this, like, intuition that GPU programming is, like, very similar to if you guys have done, like, competitive programming. It’s a, it’s a not. I don’t mean to say, like, they’re transferable skills.

Popcorn, KernelBench, and Automating GPU Kernels

Swyx [00:02:17]: You have constraints. You code golf a little bit.

Alex Zhang [00:02:19]: Yep.

Swyx [00:02:19]: Yeah.

Alex Zhang [00:02:19]: Yeah. And there’s like. There’s actually a surprisingly small space of optimizations that people do. and there’s actually not that many kernels per se that people are interested in optimizing. And so we kind of had this thought that, like, if you had enough data, like, in the same way that Codeforces, there’s millions of problems. If you could do this with GPU code, like, you could scale and automate kind of GPU kernel development, which for researchers is a huge deal. ‘Cause I think one of the bigger bottlenecks. Like, if you look at, like, Mamba, for example, like, they release the paper with kernels because otherwise, like, you can’t really use it in any meaningful way? And not everyone has, like, a Tri Dao on their team. So we’re very interested in this. KernelBench kind of spawned from that too, of like, can we get LLMs to automate, GPU kernel code? And I think that was like a. It was a very fun time. It was like between college and my PhD, and yeah, I had a really pleasant time doing stuff with GPU Mode. Now I kind of just help with the lectures sometimes. I’m not as involved, and I think in general, like, we don’t have as many competitions as we used to. But, yeah, I still keep in touch a lot with everyone there.

Swyx [00:03:27]: Is there a friendly rivalry? Because I think the previous community that used to do this was like MLSys, MLPerf

Alex Zhang [00:03:32]: Yeah

Swyx [00:03:32]: Kind of thing. Is there a friendly rivalry? Is this like just new generation MLPerf, or what’s going on?

Alex Zhang [00:03:38]: The nice thing about GPU Mode is that it is also a community in the sense that, like, a lot of the lectures are very easy enough for a beginner to follow and ask questions and things like that. And, like, the competitions are, like, somewhat, not secondary, but, like, you can participate in them to learn. I think with a lot of, like, MLSys, MLPerf kind of benchmarks, like, for the most part, like, only serious labs and companies participate. Like, seriously in them, at least. That was my understanding of it. I could be wrong. But I think also beyond GPU Mode now, one thing that has been really exciting is there’s a lot more websites and, like, people that work on hosting competitions. Like, I think there’s this.

Alex Zhang [00:04:21]: I think there’s this website called, like, LeetGPU or something, and it’s like leet code for GPU problems.

Swyx [00:04:26]: Wow.

Alex Zhang [00:04:26]: There’s, like, other ones that I’ve. Like, we’ve, we’ve seen. Like, there’s many that have kind of spawned and, like, talked on GPU Mode, and like, it’s very exciting in the sense that I think GPU programming used to be super niche, like when I was interested in it. And the only reason I got interested in it was Tri Dao gave a talk at Princeton because he was, applying for faculty. he is faculty there now, but I listened to his talk on FlashAttention in like 2023, and I was like, “Wow, this is like the coolest thing ever.”

Alex Zhang [00:04:56]: And I was like, “This is like. This is what everyone should be working on.” I guess, like, vLLM and stuff had come out too, and it was like, “Oh, we should be writing kernels.” But now it’s like, everyone writes kernels. Like, everyone. It’s, it’s. I think it’s actually almost saturated in some sense, as a field.

AI-Written Kernels and the Verification Gap

Vibhu [00:05:11]: Any interesting takes for people that wanna get into it? So I think one of the biggest news is GPT-5.6 Wrote more efficient kernels, so Terra and, Luna could be 80% cheaper.

Alex Zhang [00:05:24]: Yeah.

Vibhu [00:05:25]: And then we’ve seen other competitions where people are, like, setting records, and they’re like, “We’re doing some auto research loop,” and these are people that don’t have a background

Alex Zhang [00:05:34]: Yep

Vibhu [00:05:34]: In any kernel writing, right?

Alex Zhang [00:05:36]: Yeah. So even on the GPU Mode leaderboard, if you look at, like, a lot of the recent problems, almost all the solutions are AI generated. However, you’ll notice on the leaderboard. So there’s this guy named Gauners who’s, like, a very, like, regular member of GPU Mode. We’ve always known for a long time that he’s, like, a super cracked, like, GPU kernel writer. One thing we discovered on this leaderboard is, like, almost ev– Like, he also used AI to help him with these solutions, but for the most part, like, he helped prompt and move it in certain directions. we found that, like, his kernel was, like, basically the only one in, like, the top 10 that was actually stable in, like, actual, like. end-to-end systems. And it does bring into question, like, it’s not. Like, GPU kernels have a verification problem. Like, we’ve kind of known this. It’s been a problem since KernelBench was released. Like, there’s a lot of reward hacking that goes on. But you al– Yeah, you also notice, like, the lines of code is a lot smaller, but

Vibhu [00:06:33]: Yeah, I was gonna ask, is that noticeable, or is it just

Alex Zhang [00:06:36]: Yeah, no, it’s, it’s

Vibhu [00:06:36]: Okay

Alex Zhang [00:06:36]: It’s definitely, like, very important, and I think, like, it’s, it’s really interesting that still there’s a lot of alpha in being good at writing GPU kernels.

Vibhu [00:06:44]: Okay, so there is a gap from verifying

Alex Zhang [00:06:45]: There definitely is, yeah. I think, like. And this applies to a lot of AI systems as well. Like, I think, even with the most recent, like, math proofs and stuff, like, it doesn’t necessarily mean mathematicians are obsolete. these companies still hire mathematicians, like, to do, whether it be, like, data labeling work or even just, like, steering the models to solve problems. Like, there is still a lot of alpha in being, like, knowledgeable in these things, so.

Swyx [00:07:12]: Is it just knowledge, or is it also there is just more planning, and is there, an emergent style of planning that works better?

Alex Zhang [00:07:22]: I think it’s, it’s a mix of. Maybe this is what you mean, like intuition for

Swyx [00:07:27]: Something like that

Alex Zhang [00:07:28]: How to solve the problems.

Swyx [00:07:29]: Like, for example, I always diagram my code.

Alex Zhang [00:07:31]: Yeah.

Swyx [00:07:31]: Right?

Alex Zhang [00:07:31]: Yeah.

Swyx [00:07:31]: And then, like, if there’s a part of the diagram I don’t understand, I work until I understand it. Otherwise, I, it’s not allowed.

Alex Zhang [00:07:37]: Yeah.

Swyx [00:07:38]: Yeah.

Alex Zhang [00:07:38]: So I think it’s, like, it’s a mix of those things of, like, the people who work. Like, the people who know how to look at these problems and how to solve them, like, also know how to use AI to do them. Because, like, you’re acting as a very strong verifier. Like, if you are knowled- or if what to do and you are also. Like, I think the thing that we’ve kind of discovered with all these agent swarms and things like this is, like, when you throw enough compute at a problem, you, like, can sufficiently explore solutions to that problem. But oftentimes, like, maybe you can burn, like, 100 billion or a trillion tokens on something, but if you bring in someone who knows something about the problem, they can uncover something for the model that would, like, erase that one trillion token spend. it’s not, it’s not super clear, like, what exactly the trends are here. But I think, like, there are so many problems in the wild still right now that we want to solve, and, like, we can’t afford to just always, throw as much compute as possible at it. Like, there is still an efficiency aspect of all of these things that is super important.

Speed-of-Light Limits, Memory, and Megakernels

Swyx [00:08:41]: Is there, like, a theoretical right answer that you just calculate based on physics, and then you just get close to the physics limit?

Alex Zhang [00:08:49]: Yes. So for GPU kernels, you can compute. It’s actually not that easy to compute sometimes, like, depending on how complex the problem is. Like, for matrix multiplication, it’s very easy to compute, this, like, speed-of-light kind of, estimate of what the fastest kernel can be. And, like, this is also assuming, like, maybe all of your, all your data starts on the CPU, or maybe it starts in DRAM, on the GPU, et cetera. Like, this changes these numbers slightly, but

Swyx [00:09:18]: The transfers and all these things, yeah.

Alex Zhang [00:09:20]: Yeah. But I will say, like, it’s not clear, though, like, in a lot of cases if it’s even possible to hit this theoretical number, if that makes sense. Like, this is assuming, like, perfect overlapping and transfer of data, and, like, there’s maybe some bottleneck that you can’t get around. But often, the kernels are not even close. Like, that we write are not nearly close enough to this number to be, like, meaningful at all.

Swyx [00:09:43]: Yeah. And is it speed that matters? Do you also care about, obviously memory, which

Alex Zhang [00:09:48]: Mm

Swyx [00:09:48]: Feeds into speed? Do you care about power consumption? So one of my, one of our top pods of the year was Geoff Dean, who was like, “Actually, I just tracked the microjoules or, like, the nanojoules, picojoules.”

Alex Zhang [00:09:59]: Yeah, it’s often picojoules today.

Swyx [00:10:01]: Picojoules.

Alex Zhang [00:10:01]: Yeah.

Swyx [00:10:01]: Do you care about that?

Alex Zhang [00:10:03]: So I don’t.

Alex Zhang [00:10:04]: Yeah. I guess maybe I’m not, I’m not as

Swyx [00:10:06]: But everything here is speed, right? Like

Alex Zhang [00:10:07]: Everything here is speed

Swyx [00:10:08]: Nobody’s counting picojoules.

Alex Zhang [00:10:09]: But I– There’s a caveat here, which is, I think, like, there is speed in the context of a single kernel, and there is speed in the context of a larger problem, like maybe the N10 model. Because, like, one thing to consider, and this is why it’s important to talk about what speed-of-light is referring to, because in these cases for the kernels, like, we always start with everything in, like HBM, for example, right? But you can imagine that, like, an end-to-end like an end-to-end model, what you might wanna do between two layers is, like, you might sacrifice the speed of the first operation to keep things in the cache for the second operation. And, like, these are things that, like, you can’t really get out of, in isolation with, like, these kinds of kernels. And, people call this, like, the fusion or, like, the

Swyx [00:11:01]: Megakernel

Alex Zhang [00:11:02]: Kernel fusion problem. Yeah, or, like, megakernel stuff. And it generally only applies, like, when you are, like, memory-bound in most cases. But this is something that, like, also there is this question of, like, as these models get better, like, should we just be generating like, megakernels? Is that, like, what we want?

Vibhu [00:11:20]: What’s, what’s your take?

Alex Zhang [00:11:21]: I think that this is really difficult because you need the data to do this. And I think, like, I have yet to see an example in the wild of, like, we bootstrap the ability to solve a very difficult class of problems without any examples. and I think, like, the other reason why I think maybe this isn’t that interesting is that at the level of an individual kernel, A, like, they’re not that, they’re not as complex, but B, you’re somewhat confident that there’s not as much structure in a single kernel. But, like, in a megakernel, like, I would be more inclined to believe that, like, a compiler would be better here. Like, some compiler over, like, higher level- Ops makes sense, because in general, like actually, I think mega kernels are very, like the pieces are very composable of like the individual kernels. There’s some areas where you might wanna do like weird fusions and everything, but in general, I think these are cases that like a compiler can probably handle. And there is a company that’s working on this from what I understand that has given some talks on GPU mode as well.

Swyx [00:12:28]: Yeah, I wanna basically cluster all the GPU mode discussions here because obviously there’s other parts

Alex Zhang [00:12:32]: Right.

Swyx [00:12:32]: That we need to move on to.

Vibhu [00:12:33]: I think there is something to plug. You guys do host a lot of really good lectures. They’re all on YouTube. People can follow. And you

Alex Zhang [00:12:39]: Yes

Vibhu [00:12:39]: Lead quite a bit of it. You’re still quite involved.

Alex Zhang [00:12:41]: I used to. sometimes I still do. I think they’re mostly Mark. Mark is the one who usually does them. Matei does sometimes as well, but, yeah, I highly recommend them. They are extremely good resources. Like, I think it’s kind of crazy how much people share on there, so yeah.

Swyx [00:12:59]: ‘Cause like if you’re there, like you’re very, like you’re exactly the right audience?

Alex Zhang [00:13:03]: Yes, exactly.

Swyx [00:13:03]: Like this isn’t gonna reach the mainstream.

Alex Zhang [00:13:04]: And there’s a lot of like introductory material as well, that we’ve put on, that I think is useful for people.

Benchmarks, Princeton, and Research Taste

Swyx [00:13:10]: KernelBench was kind of influential. I just wanna see like, that was last year.

Alex Zhang [00:13:13]: Yep.

Swyx [00:13:14]: What other ongoing work do you wanna shout out that people should pay attention to? ‘Cause obviously you’re involved in this

Alex Zhang [00:13:20]: Yep

Swyx [00:13:20]: Field.

Alex Zhang [00:13:20]: Yeah. I will give maybe the background story of like I am actually involved in a lot of benchmarks, or I used to be, maybe prior to my PhD. It started because I was at Princeton. I worked with the SWE-bench team there.

Swyx [00:13:33]: John, Carlos

Alex Zhang [00:13:33]: John, Carlos

Swyx [00:13:34]: Ofir

Alex Zhang [00:13:34]: And Ofir. They’re all great. Like

Swyx [00:13:36]: Karthik

Alex Zhang [00:13:36]: I love them. Yeah.

Swyx [00:13:37]: There’s basically this, like I think people don’t understand how much benchmarks come from the same group

Alex Zhang [00:13:42]: Yeah

Swyx [00:13:42]: At Princeton.

Alex Zhang [00:13:44]: It is crazy.

Swyx [00:13:45]: Do Xun Yu?

Alex Zhang [00:13:45]: Yes. Yeah.

Swyx [00:13:46]: We had him on a pod before. Now he’s like running Tencent.

Alex Zhang [00:13:48]: Yeah, now he’s like, he’s like a superstar. when I met him, so he was advising my friend Michael Tang, who is now at Anthropic, but they worked together a lot. We were like the two undergrads in Karthik’s lab. I– And then some others joined later as well. But yeah, Xun Yu is great. I did not know he was like such a superstar until like later on, like after I left, but

Swyx [00:14:12]: Yeah. like, okay, so there are very few PhD students. Like yours is like the next one. Like once a year, we feature someone like who is like basically entire PhD, has been like on target.

Swyx [00:14:25]: There’s not that many of them. Xun Yu was like clearly one of them. And, Jack Morris is another one. And like, we talked, before the show, we talked about research taste.

Swyx [00:14:33]: Right? Like somehow some grad students just have a very blessed career where like, yeah, mostly like, yep, this is like going to stick around, relevant, everyone should know this.

Alex Zhang [00:14:42]: Yeah.

Swyx [00:14:42]: And then others, just nothing.

Alex Zhang [00:14:44]: I think this is also true of like even people within like industry labs as well. I think it’s just like grad students are a lot more visible. So you just see, like you see, like, there are some people who

Swyx [00:14:56]: Yeah, you can publish

Alex Zhang [00:14:57]: Who really like get lucky and like, or it’s, it’s a mix of being lucky and also being very smart and things like that. I think like with research taste as well, like I think it gets developed through opportunities, at least in my case. Like I got– I was very fortunate to have like taken the path that I took, like working at Princeton and then like later, like finding my like Omar at MIT. Like he’s a fantastic advisor. I will say, though, I find that the most successful research from grad students or like in academia comes when people care about problems that maybe like most people in industry are not looking at. I think this is the issue that like a lot of grad students work on things that benefit, like that look good to an industry lab. Like for example, they’ll work on some, like some benchmark that’s really popular now. I think benchmarks in 2023 were a very different story than benchmarks now. There are a lot of people that work on like harnesses and like meta-harnesses and like specific harnesses for XYZ task. And when you really think about it, the reason someone would work on this is like maybe there’s like a clear goal shaped around the models that we have today of like, this is what I want to see. But like, I’ll give, I’ll give the like RLM, like the recursive language model paper as an example, because I think like it’s a super simple idea. I think when it came out as well, like there were a lot of people that were like, when they see something like that, they’re like, “What is even the purpose of this?”

Swyx [00:16:27]: Or like too

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