Armin Ronacher's Thoughts and Writings
Armin Ronacher — Creator of Flask, Rye, and uv
Personal blog of the Flask creator on Python, tooling, and software design.
lucumr.pocoo.orgMost software that exists today does not forget. Creating software that remembers is easy, but designing software that deliberately "forgets" is a bit more complex.
The personal blog of Armin Ronacher, creator of Flask, Jinja2, and more recently Rye and uv for Python packaging. His posts tackle software philosophy with unusual depth — whether arguing that software should intentionally forget data, questioning async/await orthodoxy, or reflecting on the uncomfortable relationship between open source and money. He writes like someone who's built enough to have earned strong opinions.
Written by Armin Ronacher.
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English
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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 s...
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 the...
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 si...
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...
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 slop1. 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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One of the most thoughtful voices in the Python and Rust ecosystems. If you want to think more carefully about the tools you use and the tradeoffs they make, Armin's writing will challenge you.