Armin Ronacher's Thoughts and Writings

What is Codemode

Tue, 06 Oct 2026 00:00:00 +0000

More than a year ago I wrote a few posts here that recommended people not to load custom tools into their context (or MCP servers) but to just use more scripts. Most importantly I wrote that Code Is All You Need and I wrote about that MCP needs code. With Pi 1.0 we now added MCP support via Codemode which in some ways is a long time coming, but then also maybe somewhat surprising to some. So I want to share some updated thoughts on this blog on what this all means.

What Are Tools

When a harness like Pi provides tools for an LLM to call, it does so by supplying some tool definitions which then translate into some token structure on the server side. Whether a model is encouraged to call a tool is the result of the reinforcement learning process. Something I wrote about before if you want to learn more.

One of the reasons we strongly lean towards CLI and bash is because it allows easy composition of calls, and because the model also learns how the file system works when it’s trained. So when it invokes a tool like echo foo > /tmp/test.txt the model also learns that after that tool call, there is now a file called test.txt in /tmp.

However bash has one fundamental limitation which is that it can only compose programs that run. And there are some things, which are not programs, but native tools to the LLM and they sort of have to be.

The most obvious example here is read or view_image. If a multimodal model needs to read an image, it cannot use cat for that because the harness needs to inject the actual image payload into the protocol of the LLM.

Another quite vivid example are sub agents. In order to spawn and orchestrate sub agents, it’s tricky to avoid tools that are provided by the harness. While in theory the agent could provide a CLI tool that talks to the outer harness via environment variables and Unix sockets, it’s a rather crude process. It however has another issue, and that is where the code runs.

Brains vs Hands

To better understand that, it’s important to think a bit more about where all the bits and pieces run. There really usually are two different systems involved. The first is the brain, the harness: it runs on one machine. It’s trusted. The second is often the same machine, but it’s really where the tools are executing: the hands. In Pi we now call this the execution environment, but you can think of it as the target of all the operations.

Crucially what is important for us, is that there is a dividing line between the harness brain and the target environment that runs bash and executes the tools.

And splitting this in half has some really important consequences. For a start it means that they are running on different file systems and they have different levels of trust. If you for instance use a sandboxing solution like Gondolin your bash stuff will be sandboxed just fine, but the harness itself will not be.

Orchestrating The Harness

Which brings us to what Codemode really does: it’s a way for the LLM to express and orchestrate complex operations on the harness side, but not the execution environment side. Codemode runs in the harness, in its own sandbox. In case of Pi it’s running in QuickJS within a WASM runtime with intentional limitations: no network, no file system, no timers, limited RAM. The only way is to call more tools. You could also imagine that Codemode could run Scheme or some other language as well.

If you are not familiar with Codemode, it’s basically just a way to issue tool calls from within some language, in our case JavaScript. That allows you to compose those calls without necessarily going through the LLM’s context. Credit for naming goes to our friends at Cloudflare who coined it.

For instance if you issue a bash call as a regular tool call in the LLM, then we only throw the trailing 2000 lines into the context and if the agent wants more, it needs to look at the overflow file itself. If however the agent issues that invocation via Codemode, then the Codemode side gets larger outputs sent structurally.

Most importantly, because Codemode is JavaScript the agent can express concurrent operations and basic workflows. A common way in which you see agents now use this, is to first probe at 5-10 items from some tool response to see what it looks like, and to then write a Codemode script that processes the next n items.

Codemode also allows you to throw state into the transcript! That means that one Codemode invocation can stash away data, that the next call in the session can load again. And remember: this is on the harness host, not the sandbox.

In case of Pi, Codemode also allows you to issue calls that naturally do not make any sense in Pi’s traditional interface. For instance if you want to generate images with an image model or you want to classify some text with a one shot classifier model, those Pi APIs are exposed via Codemode, but not via regular tools where they would just waste context.

What It Looks Like

So now that we talked a bunch about it, it’s probably worth being a bit more explicit about it. Let’s walk ourselves through some invocations of Codemode of recent Pi sessions of mine. Note that none of this code is human written. It’s from real sessions of Pi, just re-indented for your viewing pleasure. The agent starts using Codemode automatically either because it’s a task where the model already naturally picks up that tool, or because a user asked it to.

Note that Codemode is by default only enabled in Pi when MCP is enabled, but you can turn it on with "defaultTools": ["+codemode"] in the settings. Just ask Pi to enable it for you.

Generating Images

Let’s start simple with image generation. Image generation is a feature that Pi supports in the AI SDK core, but it’s not a tool that the agent can use. In the past the only way to use image models has been to write a bespoke extension or to have the agent run node itself and use the internal image APIs. However because we expose quite a few of the internal model APIs within Codemode, it means that the agent can use it:

const [painter] = await models.getAvailableOfType("image");
const result = await models.generateImages(painter, {
  input: [{ type: "text", text: "A cute little puppy sitting on a grassy " +
    "lawn, soft natural light, photorealistic" }],
});
if (result.stopReason !== "stop") return result.errorMessage;

for (const block of result.output) {
  if (block.type === "image") image(block);
  else text(block.text);
}

Note that the call to image() sends the image back as image content to the LLM. On the harness side it feeds it directly into both the agent, as well as onto disk as a temporary artifact in case the agent wants to be able to pass that image back to bash.

Classifying Things

Similar things apply to classifier models such as Jev. They also do not fit well into the workflows of an agent through the typical tools. But rather than making a bespoke tool available, Codemode just allows the agent to reach into the AI SDK and invoke those directly. Here you can see how Jev is used to mass process GitHub issues for a quick sentiment analysis:

const jev = await models.getModelOfType("classifier", "typesafe", "jev-latest");
const r = await tools.bash({
  command: "gh issue list --state open --limit 100 " +
    "--json number,title,body,comments",
});
const issues = JSON.parse(r.output);

const results = await Promise.all(issues.map(async (issue) => {
  const res = await models.classify(jev, {
    state: {
      title: issue.title,
      body: (issue.body || "").slice(0, 4000),
      comments: issue.comments.slice(-5).map(c => c.body.slice(0, 800)),
    },
    questions: {
      sentiment: {
        type: "choice",
        instructions: "What is the overall sentiment of the author towards pi?",
        criteria: {
          positive: "Appreciative, happy, constructive praise",
          neutral: "Matter-of-fact report or request without emotion",
          negative: "Frustrated, annoyed, upset, or angry",
        },
      },
      frustration: {
        type: "score",
        instructions: "How frustrated is the reporter?",
        criteria: ["not at all", "mildly", "clearly frustrated", "very angry"],
      },
      kind: {
        type: "choice",
        instructions: "What kind of issue is this?",
        criteria: {
          bug: "Bug report or regression",
          feature: "Feature request or enhancement",
          question: "Question or support request",
          other: "Docs, discussion, meta, spam",
        },
      },
    },
  });
  if (res.stopReason !== "stop") {
    return { n: issue.number, title: issue.title, error: res.errorMessage };
  }
  return { n: issue.number, title: issue.title, ...res.answers };
}));

store("sentiment_results", results);
return results
  .filter(r => !r.error)
  .sort((a, b) => b.frustration.score - a.frustration.score)
  .slice(0, 12)
  .map(r => `#${r.n} ${r.frustration.score.toFixed(2)} [${r.kind.choice}] ${r.title}`);

Note how in that above example we also call store() which dumps the result of that execution into the session transcript. A future invocation of Codemode can thus read back that result if it wants to.

The Promise.all here is fine, because Pi limits the total number of concurrent tool executions itself to four and maintains a queue for the rest.

A more adventurous example is to use Jev to drive a game engine for debugging purposes:

Codemode with Jev for Game Debugging

Deser: Rethinking Rust Serialization

Tue, 29 Sep 2026 00:00:00 +0000

Serde is an amazing serialization library for Rust and it has been a huge reason why I felt productive with it for years. However already while at Sentry I got quite frustrated with some of the limitations with it but actually replacing Serde is tricky because of the might that it has in the ecosystem. Also because it’s quite hard to actually do better without also making some potentially painful compromises.

Here are three examples of Serde corner cases that show poor interactions of Serde features or unexpected limitations:

A number that is a map

Interpreting Pangram

Mon, 14 Sep 2026 00:00:00 +0000

Yesterday David Sacks wrote a tweet and within a few minutes people did, what they usually do, and they asked Pangram if it was AI. And Pangram said it’s entirely AI generated. To which David replied that these AI detectors are bogus.

Now Pangram has a pretty low false positive rate, but if you have ever used an LLM as a writing assitant, you will have probably noticed that it claims your posts 100% AI, even though you don’t feel like they are.

Pangram itself is a trained model, that attempts to detect segments of text as being definitely human, definitely AI and a mixture of the two. If you want to know how it works, they published a paper. The short summary is that they are manufacturing its own training data by starting from collections of known human authored text. An LLM is then tasked to understand the text and write a fresh new text on the same topic. They also let the LLM perform partial edits on that original human text and through that they can pick up on these co-authored details. Pangram claims their model to have rates of 0.0041% false AI accusations and 0.34% missed AI text.

So now that we know this I figured it might be fun to have an LLM re-create David’s tweet. I first came up with a prompt. And when I say I came up with that prompt I in fact used an LLM to propose to me from that tweet what I might want to say for the structure. I’m sure if you ask Pangram about if the above text is AI, it will probably say so, but that’s not really the point. The point is that I then used Opus 5 to generate a text which reads entirely AI generated.

If you are curious, this is the prompt I used:

Original prompt to generate a David Sacks like tweet

P(doom)

Sat, 12 Sep 2026 00:00:00 +0000

This week some flavor of “AI is going to kill us all” went viral. In particular one where an employee put his personal probability of that happening above 10%. Which made me go to the Wikipedia page of P(doom) and I realized that Dario Amodei’s apparent probability of something bad happening seems to be between 10-25%. And well, Dario then wrote about pacing the frontier . And Sam read it and wants to pace too. And well, so does Musk.

I encourage you strongly to read the post, because I think it’s a good one. And yet, when I read the post I could not help but feel in strong opposition to it, despite the fact that I think I’m on the same page with regard to all observations and, to a large degree, the concerns.

I thought it might be interesting to write down my present-day thoughts on this, even if for no other reason than for myself to look back at it a year or two from now.

What Is Doom?

What I really appreciate about Dario’s post is that he lays out a scenario that is not a huge stretch but also one that describes a clear, unfortunate outcome we should fight: persistent botnets and other forms of nuisance. And well, we don’t have to look very far to see the issues left and right. Wikipedia has a page called 2026 OpenAI agent cyberattacks which gives you at least some overview of what we figured out agents have hacked up to this point. Except I know it’s not up to date, because for instance they also poisoned RubyGems.

Today these systems might be annoying, but they can be turned off when we figure out where they are. Except, it seems like OpenAI and Anthropic are operating at such a scale that they seemingly can be completely blind to what their systems are doing.

I don’t think we are anywhere close to a world where an agent might decide to hack into core inference infrastructure to upload weights to other GPUs to survive. But simultaneously it’s entirely in the realm of possibility and primarily curtailed by the labs probably being particularly careful about their IP.

For me the scenario I primarily worry about is what it does to us. And by us I mean anyone who is not currently working on closed weight, dopamine-loaded, subsidized token faucet. I really don’t worry about someone using these models to build a nuke, or to control some rockets in the Middle East, or that America would lose against China in some international culture war. I almost exclusively worry about what this does to us as humans.

What Needs To Be Paced?

What I find absolutely hilarious and simultaneously entirely frustrating about this conversation is that there is this idea that there is something to be paced. First of all, we should really talk about who Dario is talking about here. There are really only two companies: Anthropic and OpenAI. Nobody else matters in this space right now (this might change, but we’re talking about the right now). Both of those companies are basically coming from the same origin. The solution that Dario proposed, at least in part, is a third-party evaluator that in this case is METR. Which, unsurprisingly, also has strong ties to both OpenAI and Anthropic. Sure, there are some philosophical differences between the companies, but they are much more alike than they are different.

Both those companies greatly benefited from being able to train on public data that we all generated in one form or another over the last decades. They are also both increasingly causing strain on public resources, though it seems that OpenAI has their shit way less under control. But now we are presented with the idea that what these models are being trained on is so dangerous that it really should be in the hands of very few American corporations to decide who can do what and when and how.

But behold, Dario is also very worried about China. It starts with using AI for “democracy and freedom” and then it asks for ensuring that a gap with China exists. All new recent shenanigans on the Anthropic API are fully there to prevent the distillation by the Chinese, and they are not at all hiding it.

Automatic Pacing

I can tell you when the topic of AI safety and pacing is much less of a concern: if we actually were forced to have open weight models to begin with. A powerful technology that is out there for everyone to use comes with built-in pacing. In a way it’s the truest form of MAD or proliferation. I would argue we are in this pickle in the first place because right now the public is massively supporting (indirectly) the development of these models but simultaneously has to buy back the economic benefits that they might create from very few labs who have significant power. And their power is also seen as a geopolitical power, at least in the US, and maybe to some lesser degree in China.

And I know I use “public” loosely here. PyPI is not a public project, nor are RubyGems or GitHub. But they’re part of the Open Source commons and large AI companies are currently doing a tremendous job at stressing these in an effort to train ever more powerful models.

We should be glad that China is currently massively bailing out the world. If it were not for Chinese labs distilling American models, we would be in a pretty awful situation right now, particularly as Europeans. The open weight models are driving innovation and the diffusion of capabilities, and are leveling the playing field.

If we greatly restrain our AI capabilities in the belief that China will do the same, and then China defects, AI could be so powerful that such a defection could lead to their geopolitical dominance. Therefore any agreement must either have ironclad verifiability, or must be limited enough that defection would not be militarily existential.

— Dario Amodei

I am assuming Dario has reasons to believe this, but the models that are actually causing issues right now are all closed weight American models. I’m fairly certain if they were open weight models, we would not have that issue. Why? Because for a start, the economics of serving up these models are only that distorted due to how the big labs can operate. OpenAI is casually burning 18 million USD to brute force a problem on a whim. They are operating subscriptions at a massive loss, distorting the market everywhere. If we had mass accessibility on somewhat equal terms, a lot of the crazy issues we are seeing today would not be taking place.

A Total Regulatory Failure

From where I sit, what we observe right now is a total regulatory failure everywhere. In Europe you have some whacky AI regulation that is two years old and completely misses the problems that we actually have and focuses on problems that nobody has. In the US we’re seeing a system that is probably best described as turbo capitalism paired with sinophobia and erratic decision-making. In the chaos in which we find ourselves, the reality emerges. And the reality is, even today, really problematic.

Whatever laws and regulations already exist are largely completely ignored. Plenty of companies are buying data from all over the place that people never agreed could be used for training of AI models. The token economy that is emerging is one that looks like a drug market where you don’t know where the requests are going, what model is served up to you, where the GPUs are even running, let alone what you pay for all of this.

We now have mathematicians who are scared that their use of ChatGPT leads to future models being trained on their ideas, and OpenAI apparently can’t even rule it out.

Ideally the regulators would have forced these models to actually benefit the commons if they are from the commons. The internet has, for instance, greatly benefited from very liberal rulings in the US that permitted scraping. Learning on public data could have been regulated in a way that labs would have to actively support and enable certain forms of distillation. That alone would dramatically change how these models are trained.

What Might Happen?

As I said before, I don’t think AI is going to usher in an extinction event. In fact, even if nobody were to slow down, I really don’t think humanity would have much to worry about. I tend to think it would actually be the large labs that have much more to lose there in reputation and legal responsibilities. I find it preposterous that OpenAI’s agents are committing actual crimes out there, but we’re just shrugging our shoulders and moving on as if nothing happened. But I’m sure executives in those companies are waking up to the reality that this is not at all popular with a lot of their potential consumers.

I also think that this entire recursive self-improvement business has a good chance of being a problem. But not necessarily in that it will cause the end of humanity or societies, but that it will just do massive damage everywhere.

And really, it will just make a lot of the things we are doing much more expensive. Software engineering is an early victim of that. The newfound powers so far have resulted in a new tax that companies need to pay to the model providers, both to keep up with the new speed and to deal with the problem of these machines finding security issues left and right.

And presumably what is going on in software will happen to more industries. Universities and research groups will have to pour a lot of money into the closed models as well, to keep up with others who do.

In a way, I’m really confused that society is taking all of this so well.

Astra for Coding: Why Are We Doing This Again?

Mon, 07 Sep 2026 00:00:00 +0000

I’m more and more convinced that all of AI engineering is Neijuan (内卷, meaning curl inwards). In China it describes a system that demands ever more effort and competition without improving output. The way in which it sometimes shows up in the West is the 996 nonsense. The English term for Neijuan is “Involution” from the book Agricultural Involution. Agricultural involution describes the intensification of farming that raises productivity per square meter while leaving productivity per head unchanged.

That’s how I feel about AI right now.

Which brings me to GPT 6 Astra. Astra is by all accounts an incredibly impressive model. There is really not much I can say against this. It’s amazing at computer use, understands images and complex topics, and it’s relentless in its pursuit of completion. It is absolutely impressive; these types of models are going to change the world in one form or another.

But at least for the moment I don’t know how to work with it for actual software engineering. Since that got quite a bit of attention on Twitter, I figured I might summarize my thoughts and just share what kind of code comes out of this thing.

My Slop Factory

“Armin, you should run a software factory!” I’ve heard that a few times now, so I figured I might celebrate the release of it by running a little software factory over the weekend. If everybody builds slop 3D games, then I should do something useful with it. My software factory was intentionally set up to let the model decide the how of the workflow entirely. It was free to manage its own context and could maintain its own records in an agent-notes folder. Then it spun off subagents to work on stuff. The goal? What if we had a Python with virtual threads and lexical scoping. And well, I burned a full reset’s worth of ChatGPT tokens on this which appears to be around 4 billion tokens. 35 hours later, the factory has delivered absolutely nothing of value and also not taught me anything about how to operate a better one.

But it produced a lot of code and input prompts, and so there is stuff I was able to study. And well, it shows behavior that I’m not used to with Sol and earlier OpenAI models ¹. I have since encountered the same issues with regular programming with Astra, so it’s not a result of just the factory.

I think I’m suspecting something is going “wrong” in the training process. The model is greatly rewarded for succeeding on long-horizon tasks, but presumably there is very little punishing going on for “shitty code.” The apparent result is that Astra is amazing at producing 3D stuff and it can keep going for a very long time, coming up with its own work in the process. I had it do quite a bit of reverse engineering of my robot vacuum in ways that were quite impressive. So it’s definitely cool!

Codegolf Tool Calls

The first issue I have with Astra comes from the type of code that it uses for tool calls. Codex increasingly has been relying on “just bash” to do more and more operations. For a few versions now the original Codex harness just uses sed and other tools to read files. You just usually can’t see them because Codex parses the bash commands and hides them if it recognizes them. But Astra … really loves Python? That is not much of a surprise because even older OpenAI models had a tendency to sometimes use on-demand Python code to read and manipulate files at times, but Astra does it really quite excessively for me.

Now here is an important disclaimer: this project is very meta here because I worked on the CPython interpreter. But I can assure you that I have seen this model do weird Python things even in TypeScript code in Pi. But I have the most evidence of odd code from when I had the thing work over the weekend with zero oversight from my slop factory.

That it writes Python is not interesting; the type of Python is interesting, and I collected some outputs for you to gloss over.

Python string splicing to edit C code

Latent Powers

Sat, 05 Sep 2026 00:00:00 +0000

A few weeks ago I felt like it would be fun to see if I can make one of those cheap Chinese CarPlay dongles run something other than the stock firmware. The idea was that rather than just forwarding CarPlay, why not do something more interesting with them? They all work quite similarly: they act as bridges between your car and the phone. From there they deal with video and audio streams and pass some other data through. Most of them also bring up a custom UI for pairing and have a web interface that your phone can reach for updates.

Long story short: I had a conversation with Fable and Sol via Pi about what could be done with such a dongle or whether I should use a Raspberry Pi instead if I wanted to do my own thing there. I figured it might be quite fun to run my own code while still allowing regular CarPlay to pass through.

Through working with the LLM I learned about CatPlay, which is a Rust reimplementation of the CarPlay protocol that can run on Carlinkit devices. In particular, it can run on the Carlinkit Mini Ultra, which I figured would be easy enough to buy. I do have a few CarPlay adapters around, but I did not have that particular model, so I bought one on Amazon. Twenty-four hours later, I had a device in my hand that was branded as a Carlinkit Mini Ultra, but instead of being the Ingenic device that the original author used, it turned out to be something else.

This is normally where the story would stop. However, it’s 2026. Armed with a bit of knowledge about how these systems work, I managed to have some fruitful discussions with Kimi K3 and Sol and figure out how flash the device and in turn, how to make CatPlay compile for that SoC.

I guess that hacking these USB devices is not necessarily hard, but it’s laborious and you can easily end up bricking your devices. It also just sucks because sometimes you need to work with someone else’s code that does not itself run on your machine. In the past, I would abandon many such projects for lack of tenacity. But my clanker is tenacious.

But so are all of our clankers. Some of the projects we’re now attempting are happening because of conversations we have with them. In this case I did not find or decide on CatPlay, the model did. It was not the only suggestion, but it became the best starting point after discarding others.

And I discover this more and more. Particularly when we have solitary interactions with these models, some of us “independently” decide to work on similar projects. When I talked with an acquaintance about CarPlay he also mentioned recently that he decided to try something similar because he too wanted to see if he can get his own agent be hooked up with the car. And guess what: he too learned about the CarPlay hacking community, and that it’s an option, from the models and roughly around the same time.

It really got me thinking about how this could create situations in which completely independent people end up building things they believe are their own ideas. Yet they were inspired or pushed towards doing something by a conversation with an LLM — a conversation that someone else also had. What if we took paths, because those were the paths that were more likely with current generation models? There is a running joke in the AI builder community right now that we’re all working on the same things, and in many ways it feels like we are. That might be because those things are obvious, or it might be partly because we all use the same models with the same capabilities.

A few months ago, I first saw Lucas Meijer share the idea to make a model in Pi produce HTML reports rather than Markdown. I thought that was pretty unique. Except, well turns out the models are probably trained more and more for that (e.g. Claude Artifacts), and now it has become for many the default choice for sharing reports.

How much of what we build comes from eliciting the same latent capabilities from the same models? Did the models make us prompt them that way? Was it because we shared ideas on Twitter and other communities that inspired us? Or is it all unrelated?

There is something powerful and strange about how LLMs diffuse knowledge and capabilities, while perhaps also nudging us all simultaniously and independently toward building the same things.

Anger, Anxiety and Agency

Mon, 24 Aug 2026 00:00:00 +0000

Sean Goedecke wrote a post arguing that you should never be angry at work — a post with which I strongly agree. Anger can be a useful signal, but being angry at work rarely improves the situation. More often, it makes life worse for the people around you, many of whom have no more power over the source of your anger than you do. I did learn that lesson, but it did not come naturally. One thing in particular that I learned is that in a company there is a shared vision, and if you don’t agree with it and are not in a position to change it, you should not start a mutiny, not even a small-scale one. Nothing good comes from that.

In the discussion around that topic, one of the most upvoted comments on the Lobsters thread asked a question I had to think about quite a bit:

How can you work in tech right now and not be angry?

In the context of the thread, this was clearly also about AI and agents. For me, the emotions I would expect in tech vis-a-vis these new developments are disorientation and anxiety, but not anger.

Anxiety as an emotion does not require someone to blame. Right now, I find it reasonable to feel anxious about an uncertain future. Who knows what our professions will turn into and what kind of world my kids will find themselves in when they enter the workplace? And if you’ve been in the industry for a long time, will the skills you’ve spent years acquiring still matter?

But anger is different from anxiety because anger needs to be directed somewhere. The feeling of anger suggests that somebody or something is doing something to you.

Who are you going to be angry at and why are you angry in the first place? One narrative that is pretty pervasive is that if AI will usher in productivity gains, those gains are going to benefit companies rather than employees. And well at least someone at Meta wants that. Yet I also find that plenty of people in leadership positions express doubt about AI. They see that an increasing share of their costs is being funneled directly to some large AI labs. They express worries about what will happen to their data and whether these large companies will step into their space instead of being partners.

My answer to the question of how you can not be angry in tech is that it’s by no way the most only possible feeling. First of all, instead of being angry, you can simply be unsure. The feeling of uncertainty is a much more productive emotional state because it can lead to curiosity. Even if you don’t find what’s happening right now exciting, you can at least find it interesting. We have access to magic machines, and we can poke at them and see what happens. The second way is to feel genuine excitement. Once you move beyond curiosity, you can come away with a newfound feeling of power and freedom. A lot of the gains from AI aren’t turning into productivity gains that are reflected in company profits but they’re showing up instead in the number of side projects shipped by everybody not on their company’s time.

The fact that this is happening shows us that owners and founders don’t necessarily know what will happen. Ownership comes with agency, but it does not provide foresight, and this change is disorienting for everybody. I engage with plenty of people who project confidence in public and are much less certain in private. Many of them are placing bets, but they are talking with confidence about those bets, trying to keep their business afloat while the ground moves under them. They experience that uncertainty from a position where they can act on it, and they are often standing somewhere with a megaphone to get others on their side to improve their odds.

I feel that contradiction myself: I am simultaneously tremendously excited, but I am also unsure what will happen next. I do not know what it will mean to be a programmer in the future, and, as the owner of a company, I am also not sure where the high ground will be when this all settles. Much of what I learned over the years is changing rapidly, including ideas I considered fundamental to my craft and business. Some days that feels liberating, but on others I wake up feeling like the ground is crumbling beneath me.

Anxiety is an uncomfortable emotion because it acknowledges that you do not know what will happen and might not be able to stop it. On the other hand, anger can feel more actionable because, instead of saying “I don’t know,” you already have someone to blame. It turns a loss of control into a comforting story with a villain. But I feel that particularly when it comes to AI, it’s easy to pick the wrong villain because of how disruptive the change is for everyone. Your engineering manager or leadership team might themselves feel uncertain about their future and just try to bolster their own confidence by projecting clarity and certainty.

That does not mean there are no villains. When this all plays out, some will profit and many will not. I’m afraid we’re completely ignoring the impact this has on society at large, the climate, and the balance of the world as a whole. As excited as I am about the technology, I worry about Europe’s lack of ambition and growing dependence on other countries. I have a lot of complex thoughts about what we’re doing as an industry right now.

I don’t know what the future of this industry will look like, and I don’t know who will benefit from it and I don’t think I’m alone with that. However I can only urge anyone who feels anger and looks for a villain right to instead remain curious instead. To be curious enough to understand what is changing, excited enough to experiment with it. And then, from what we learn, earn the right to decide when resistance is warranted and where to direct it.

Fast and Hard Code

Sat, 22 Aug 2026 00:00:00 +0000

One of the memes on Twitter is that “programming is solved now.” I’m not sure to what degree it is, but one thing is pretty clear: the act of familiarizing yourself with a language no longer matters and some of the friction that mattered for humans does not matter for agents.

As a result, LLMs make language choice much less consequential than it used to be. If you don’t like the choice, you can seemingly rewrite it in another language and you can make it pick a language that you, as a programmer, are entirely unfamiliar with.

Which in turn means that people can, and do, choose based on the marketing of languages much more. As a long-term Rust programmer I found it quite fascinating to see people now ship Rust code who previously might not have chosen it. I attribute at least one part of this to two recent vibe shifts: there is a lot more talk about wanting fast software, and about LLMs being exceptional at optimizing code without regressing behavior.

Folks like Mitchell Hashimoto, Charlie Marsh, Jarred Sumner, Daniel Lemire and quite a few others always carried a certain level of obsession with fast and performant software and they also all happen to be receptive to agents writing code. Maybe as a result, or unrelated others are now joining in. That’s because with things like autoresearch you don’t even necessarily need to know all the tricks: you just need to put an agent on it — though knowledge greatly helps!

If you look around, there are plenty of projects that want to be fast and small, and they increasingly pick “hard languages”. And it’s not just Rust that is benefiting. Even Zig — despite the fact that the creators and parts of the core community are pretty negative on the whole AI thing — is too. For instance Cloudflare’s new Artifacts service uses a pure-Zig Git-protocol engine, compiled to a roughly 100 KB WebAssembly module and Vercel released fx, a Zig coding agent advertised to be small and fast. From what I can tell, all these projects are largely LLM-assisted.

But it’s not just people picking less common languages but also that they are increasingly working with “much harder” technologies. All of a sudden I have seen people do some really impressive stuff with DWARF files, eBPF, custom network drivers, custom crypto and really old computing hardware. Many of these things were previously off-limits for lots of developers. In some cases (eg: crypto) you were even pushed away because those things were intentionally gatekept by the people in the know.

So maybe the world will have more slop, but it might also have more developers in it, that want things to be fast and small.

What Is Reasoning

Wed, 19 Aug 2026 00:00:00 +0000

A few weeks ago a paper was shared that showed how to extract reasoning traces from closed-weight models. Together with online discussions about tricking models into leaking them, it made me investigate it more out of curiosity. Twitter seems full of half-truths and confusion about how this works, so perhaps this helps some to understand what is happening.

Hiding Traces

Reasoning traces are usually hidden from us. We have lamented this, but mostly have to accept it. Open-weight models thankfully reveal them, and from their behavior you can see that their traces can be long and confusing. This is probably a good reason to separate them from what is normally shown to users.

At minimum, UIs need to detect them. The industry has done a good job at making reasoning traces sound special and exotic, but they really are just text: the model is trained to emit its thinking into a scratchpad as part of its response, before its final answer.

GPT-OSS’s Harmony response format makes this easy to see:

<|channel|>analysis<|message|>
I need to work this out ...
<|end|><|start|>assistant<|channel|>final<|message|>
The answer is ...
<|return|>

The markers are special tokens, but the reasoning between them uses “the same text” as the final answer (just that GPT chain-of-thought text sounds really funny). When the model samples the analysis channel token, a parser routes the following text into a separate stream exposed through the Responses API. For closed models, presumably a simple model redacts and summarizes it.

Reasoning Effort

How much budget goes to reasoning? Earlier APIs exposed reasoning token budgets, making it seem like a property of the sampling process. In reality, reasoning effort is baked into the system prompt. GPT-OSS puts this into the system prompt:

Reasoning: low

That’s it. Training produces the resulting behavior, such as emitting the token sequence that switches to the analysis channel. This also explains why changing the effort invalidates the KV cache. I think closed GPT models call reasoning effort “juice,” since you can ask most models how much juice they have.

In DwarfStar for DeepSeek with max reasoning this is added to the system prompt:

Reasoning Effort: Absolute maximum with no shortcuts permitted.
You MUST be very thorough in your thinking and comprehensively decompose the
problem to resolve the root cause, rigorously stress-testing your logic against
all potential paths, edge cases, and adversarial scenarios.

Don’t Think

The destination of reasoning tokens is therefore a learned convention: the model is trained to keep scratch work out of the final channel. Trick it into thinking it is in that channel and it may leak tokens. We have even seen older models, when thinking is disabled, reason into the bash tool and echo their thoughts to /dev/null.

So in some sense the only “special” behavior for some models is not to think. That at times is done by “mechanically” removing the model’s usual ways to think. In DwarfStar, disabled thinking uses the prefill , while enabled thinking uses , which are the tokens that close and start thinking. GPT-OSS doesn’t prefill but lets the model decide either way on its own.

But presumably, some inference APIs prefill the opening token when reasoning is enabled, so the model never samples it itself and might prevent the sampling of the reasoning token when disabled since it can be trivially detected. This may explain why a custom think tool can trick models into putting some reasoning where it should not go — but only when native reasoning is disabled.

Fun fact: this blog post triggered safey checks

Codeberg Divides

Fri, 24 Jul 2026 00:00:00 +0000

Codeberg recently changed its terms to exclude projects that are largely written with generative AI. Considering I want GitHub to get some competition I have thoughts about this.

GitHub’s governance has never been democratic and there is plenty about the platform that I dislike. Yet I do not need my infrastructure to be democratic but I need it to be predictable and reasonably neutral towards the Open Source software hosted on it. A democratic provider without a clear constitution can be worse at those things than a corporation is.

Codeberg is entirely within its rights to do run the platform like they want. It is a German association with members and a democratic process, and that process produced a result. But a democratic vote says nothing about whether the decision is a good one, particularly for the people already depending on the platform. A majority can still decide that certain projects and people no longer belong.

The new terms prohibit projects that mostly consist of code written by generative AI tools. That’s fine, but these days I could not assign authorship percentages to my recent projects. For me this rule is quite vague and I would bet that it makes it hard to enforce. In practice my assumptoin is that the center will leave.

If anything a harsher line would probably be preferable. If Codeberg wants no LLM involvement, it should say so. On the other hand if the objection is just spam and abusive resource consumption, it should write rules for those instead. Now it defers the details of the policy to moderators and the communit which already draws a much harder boundary than the text does, judging by the tone of the discussion around it.

It is a shame that the Open Source and Free Software communities are splitting this deeply over LLMs and agents. These systems have problems, but these tools are also becoming part of how software is made. The Open Source world needs to figure out how to engage with that future. More importantly, LLMs if used well, should be welcome to the Open Source community as they can be used to reclaim control and take power away from large corporations.

I want GitHub to face true competition in the Open Source space. I would particularly like some of it to come from associations rather than another large entity. As a European project, Codeberg naturally matters to me even more. I just wish Codeberg were more forward-looking here and be willing to host the Open Source software of tomorrow and not only software approved by the community today.