Armin Ronacher
Software engineering
Creator of Flask, Sentry VP of Engineering. Writes on software engineering paradigm shifts.
Recent activity
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The Tower Keeps Rising
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 ambition and ultimately why people no longer speak the same language. But it is also a story about the unity that makes technological progress work. The text begins with a technology upgrade: And they said one to another, Go to
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Better Models: Worse Tools
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 edit itself is usually correct but the arguments do not match the schema as the model invents made-up keys and Pi thus rejects the tool call and asks to try again. That alone is not too surprising as models emit malformed tool calls some
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The Coming Loop
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 meaningfully different from just using a coding agent. Some of this happens on top of Pi which is cool to see for sure! The pattern is the same everywhere though: work is put into a queue of sorts, a machine picks it up, attempts it, stops, and then s
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Dangerous Technology For Americans Only
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 technology as dangerous and in need of strict controls and regulation. Now that the US government appears to have taken that framing seriously and told them to turn it off for foreign nationals I can see why people are making fun of that sit
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Gaslighting Openness
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, shifting contributor dynamics, the falling cost of producing code, and large companies learning to close doors behind them. A lot of that battle today is manipulation of the narrative. Opinion makers on social media and in business
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Communities of Not
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 about safer streets and transit, and LLM-skeptical developer spaces about the future of labor, code quality and slop 1 . But the thing being refused often does not go away and instead becomes the main subject of the community’s identit
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Clanker: A Word For The Machine
In my last post I used the word “clanker 1 ” 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 a very strong reaction: to them it sounded like a slur, in one case even something adjacent to the n-word. That reaction surprised me somewhat, but it also made me realize that I should write down what I mean by th
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Building Pi With Pi
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. This post is mostly a reflection of my own experience after spending more time in the tracker, using Pi to work on Pi, and watching what I have learned about it so far. Slop Issues Unsurprisingly, we are using Pi to build Pi. That sou
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Pushing Local Models With Focus And Polish
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 minutes. There are a lot of reasons why I want this, but the biggest quite frankly is that we’re so early with this stuff, and the thought of locking all the experimentation away from the average developer really upsets me. Frustratingl
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Content for Content’s Sake
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 it, because the use of the words primarily signals membership of a group rather than one’s individuality. But some of the changes to that language might now be coming from … machi
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