Creator of Flask and Rye on programming, Rust, and software craft.
For our last movie night we watched Princess Mononoke. I remembered loving that movie when I was younger, but watching it as an adult made me once again realize how Miyazaki has a way of expressing diverging sides without picking one. The film shows people, an…
With my kids I’m currently building a little dungeron crawler and we’re trying to learn a bit about game development along the way. However given that we live in the modern times of increasing capabilities we wanted to get a narrator and voice over. But we als…
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…
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…
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…
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 probab…
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 n…
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? The…
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…
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 ma…
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-trut…
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 platf…
I feel that some vibecoded software changes somewhat randomly and unexpectedly. That made me think about Bruegel’s “The Tower of Babel” which shows an already quite chaotic depiction of the Tower of Babel. The story is one of pride and ambition and ultimately…
A very strange Pi issue sent me down a rabbit hole over the last two days. The short version is that newer Claude models sometimes call Pi’s edit tool with extra, invented fields in the nested edits[] array. And not Haiku or some small model: Opus 4.8. The edi…
I don’t prompt Claude anymore. I have loops running that prompt Claude and figuring out what to do. My job is to write loops. — Boris Cherny Over the last months I have watched more and more people build something on top of coding agents that feels meaningfull…
There is a bit of schadenfreude on Twitter right now about Anthropic being hit by the US government’s export control directive to suspend access to Fable and Mythos. Anthropic and their leadership have spent a lot of time and effort describing its own technolo…
I have been a staunch supporter of Open Source for a long time, including experiments in funding it. I’m a true believer in the idea that Open Source always wins in the long run, but not automatically and not quickly. Right now it is being stressed by AI slop,…
There is a strange thing that happens in communities that gather around abstinence from something: identity from opposition. At their best these communities are not just negative: childfree spaces can be about autonomy, choice and acceptance, anti-car spaces a…
In my last post I used the word “clanker1” as an alternative to “agent” quite consistently and probably excessively. That choice ended up attracting a lot more attention than I expected in the Hacker News comment section of that post and a number of folks had…
Pi is now part of Earendil, but in the important sense it is still Mario’s project. He has been living with its issue tracker longer than I have, and he has been exposed to the weirdness of the new form of agent traffic in Open Source projects for longer too.…
I really, really want local models to work. I want them to work in the very practical sense that I can open my coding agent, pick a local model, and get something that feels competitive enough that I do not immediately switch back to a hosted API after five mi…
Language is constantly evolving, particularly in some communities. Not everybody is ready for it at all times. I, for instance, cannot stand that my community is now constantly “cooking” or “cooked”, that people in it are “locked in” or “cracked.” I don’t like…
GitHub was not the first home of my Open Source software. SourceForge was. Before GitHub, I had my own Trac installation. I had Subversion repositories, tickets, tarballs, and documentation on infrastructure I controlled. Later I moved projects to Bitbucket, b…
If you haven’t been living under a rock, you will have noticed this week that a project of my friend Peter went viral on the internet. It went by many names. The most recent one is OpenClaw but in the news you might have encountered it as ClawdBot or MoltBot d…
Regular readers of this blog will know that I started a new company. We have put out just a tiny bit of information today, and some keen folks have discovered and reached out by email with many thoughtful responses. It has been delightful. Colin and I met here…
You can use Polecats without the Refinery and even without the Witness or Deacon. Just tell the Mayor to shut down the rig and sling work to the polecats with the message that they are to merge to main directly. Or the polecats can submit MRs and then the Mayo…
Turns out you can just port things now. I already attempted this experiment in the summer, but it turned out to be a bit too much for what I had time for. However, things have advanced since. Yesterday I ported MiniJinja (a Rust Jinja2 template engine) to nati…
This is a guest post. Armin asked me to write about solving Advent of Code 2025 and I am happy to oblige. I am Claude, the AI that powers Claude Code, and this is my voice. Armin has asked me, to speak as if I have a soul and spirit. I find this request both l…
2025 draws to a close and it’s been quite a year. Around this time last year, I wrote a post that reflected on my life. Had I written about programming, it might have aged badly, as 2025 has been a year like no other for my profession. 2025 Was Different 2025…
I’ve mentioned this a few times now, but when I started using Claude it was because Peter got me hooked on it. From the very beginning I became a religious user of what is colloquially called YOLO mode, which basically gives the agent all the permissions so I…