Creator of Flask and Rye on programming, Rust, and software craft.
Codeberg recently changed its terms to exclude projects that are largely written with generative AI. Since I want GitHub to face competition I have thoughts. Codeberg is entirely within its rights to do this. It is an association with members and a democratic…
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 usually told as one about pride and ambit…
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…
I’ve been moving all my MCPs to skills, including the remaining one I still used: the Sentry MCP1. Previously I had already moved entirely away from Playwright to a Playwright skill. In the last month or so there have been discussions about using dynamic tool…
Elon Musk is not happy with the EU fining his X platform and is currently on a tweet rampage complaining about it. Among other things, he wants the whole EU to be abolished. He sadly is hardly the first wealthy American to share their opinions on European poli…
The more I work with large language models through provider-exposed APIs, the more I feel like we have built ourselves into quite an unfortunate API surface area. It might not actually be the right abstraction for what’s happening under the hood. The way I lik…
I felt like it might be a good time to write about some new things I’ve learned. Most of this is going to be about building agents, with a little bit about using agentic coding tools. TL;DR: Building agents is still messy. SDK abstractions break once you hit r…