Armin Ronacher
@mitsuhiko.at
Creator of Flask • earendil.com ♥︎ writing and giving talks • Excited about AI • Husband and father of three • Inhabits Vienna; Liberal Spirit • “more nuanced in person” • More AI content on https://x.com/mitsuhiko
More stuff: https://mitsuhiko.at/
More stuff: https://mitsuhiko.at/
Pinned
Armin Ronacher
@mitsuhiko.at
· Nov 11
Blog
lucumr.pocoo.org
Hi! In a prior life I built a lot of Python tools and libraries. I created Flask, Werkzeug, Jinja2 and many more. I worked on Sphinx and Pygments. In the years since I did a lot more Rust. For the last 10 years I spent my life working on @sentry.io.
You can find my blog here: lucumr.pocoo.org
You can find my blog here: lucumr.pocoo.org
I carry this query utility with me from codebase to codebase. I know that a version of this already exists in many libraries, but I really like how simple it is and it also covers identifiers.
November 9, 2025 at 7:52 AM
I carry this query utility with me from codebase to codebase. I know that a version of this already exists in many libraries, but I really like how simple it is and it also covers identifiers.
On the weekend I talked with @baro.dev on why Agentic Coding works for me, an not quite for him. www.youtube.com/watch?v=EZhj...
Talking Agentic Engineering with Giovanni
YouTube video by Armin Ronacher
www.youtube.com
November 4, 2025 at 7:46 PM
On the weekend I talked with @baro.dev on why Agentic Coding works for me, an not quite for him. www.youtube.com/watch?v=EZhj...
I'm surprised by is how many people that I'm interviewing mentioning that they don't use coding agents due to cost for their side projects. There are in fact free agents. Amp Code has a free tier and at the moment you can use Grok fast, still for free on OpenCode and others.
November 3, 2025 at 1:31 PM
I'm surprised by is how many people that I'm interviewing mentioning that they don't use coding agents due to cost for their side projects. There are in fact free agents. Amp Code has a free tier and at the moment you can use Grok fast, still for free on OpenCode and others.
I wrote a bit about my sidequest at Earendil: Building Absurd which implements durable execution (𝚞𝚜𝚎 𝚠𝚘𝚛𝚔𝚏𝚕𝚘𝚠, Temporal, Inngest, etc.) on just Postgres. How it works and why I like it. lucumr.pocoo.org/2025/11/3/ab...
Absurd Workflows: Durable Execution With Just Postgres
Durable execution with just postgres.
lucumr.pocoo.org
November 3, 2025 at 8:53 AM
I wrote a bit about my sidequest at Earendil: Building Absurd which implements durable execution (𝚞𝚜𝚎 𝚠𝚘𝚛𝚔𝚏𝚕𝚘𝚠, Temporal, Inngest, etc.) on just Postgres. How it works and why I like it. lucumr.pocoo.org/2025/11/3/ab...
Does anyone know if there is a convenient way to programmatically invoke MCP tools registered with Claude? I don’t think there is a way to do this through the agent SDK. I’m trying to wire up some shit here that does not involve inference.
November 1, 2025 at 3:47 PM
Does anyone know if there is a convenient way to programmatically invoke MCP tools registered with Claude? I don’t think there is a way to do this through the agent SDK. I’m trying to wire up some shit here that does not involve inference.
One UX quirk of uuid7 and tagged IDs is they the leading characters are low entropy so ID shortening doesn’t work. I think I dislike ellipsis in the middle. What are good options?
October 22, 2025 at 10:59 AM
One UX quirk of uuid7 and tagged IDs is they the leading characters are low entropy so ID shortening doesn’t work. I think I dislike ellipsis in the middle. What are good options?
“Regulation Isn't the European Trap — Resignation Is […] When you're step 3 of 10, act like step 10 depends on you. Own the handoff. Move same day.” lucumr.pocoo.org/2025/10/21/e...
Regulation Isn’t the European Trap — Resignation Is
The difference between business in Europe and the US.
lucumr.pocoo.org
October 21, 2025 at 12:50 PM
“Regulation Isn't the European Trap — Resignation Is […] When you're step 3 of 10, act like step 10 depends on you. Own the handoff. Move same day.” lucumr.pocoo.org/2025/10/21/e...
Next release of minijinja should support free threading in the Python binding. I think so at least, but I would love to have someone check if there is more that needs more to be done here! github.com/mitsuhiko/mi...
Add free threading support (#841) · mitsuhiko/minijinja@68f4457
github.com
October 19, 2025 at 10:11 PM
Next release of minijinja should support free threading in the Python binding. I think so at least, but I would love to have someone check if there is more that needs more to be done here! github.com/mitsuhiko/mi...
Modern Open Source social dynamics are bizarre. I found a small bug in Karpathy's minichat tokenizer but the repo is full of low effort issues and pull requests so my default response now is to just leave it.
October 19, 2025 at 6:37 PM
Modern Open Source social dynamics are bizarre. I found a small bug in Karpathy's minichat tokenizer but the repo is full of low effort issues and pull requests so my default response now is to just leave it.
It's kinda cool how far you can get with pg_tgrm and tsvector, but at the same time, the expectations in full text search are so much higher in 2025 that I'm almost a bit disappointed.
October 18, 2025 at 8:56 PM
It's kinda cool how far you can get with pg_tgrm and tsvector, but at the same time, the expectations in full text search are so much higher in 2025 that I'm almost a bit disappointed.
Prototyping with AI is easy. Shipping with it is… messy. I sit down with @1st1 to argue both sides: vibe coding vs real engineering, context limits, bad tests, and the open-source trust challenges. www.youtube.com/watch?v=VcBZ...
Talking AI and Agentic Coding with Yury Selivanov
YouTube video by Armin Ronacher
www.youtube.com
October 18, 2025 at 11:16 AM
Prototyping with AI is easy. Shipping with it is… messy. I sit down with @1st1 to argue both sides: vibe coding vs real engineering, context limits, bad tests, and the open-source trust challenges. www.youtube.com/watch?v=VcBZ...
I've been experimenting with single-tool agents that solve problems by writing, running and discarding code and nothing else. Doing that is much more fascinating, useful and simple than you would think. Weekend write-up here: lucumr.pocoo.org/2025/10/17/c...
Building an Agent That Leverages Throwaway Code
Revisiting agents writing code for non code purposes.
lucumr.pocoo.org
October 18, 2025 at 7:08 AM
I've been experimenting with single-tool agents that solve problems by writing, running and discarding code and nothing else. Doing that is much more fascinating, useful and simple than you would think. Weekend write-up here: lucumr.pocoo.org/2025/10/17/c...
As an outsider I'm a bit confused now. Is Remix 3 trying to be a new take on solid.js? The code examples make it look like it does not use react at all? (Or at least not sure how that would work with react)
October 13, 2025 at 11:50 AM
As an outsider I'm a bit confused now. Is Remix 3 trying to be a new take on solid.js? The code examples make it look like it does not use react at all? (Or at least not sure how that would work with react)
I still really want to record a video with me and another programmer who is not getting value out of AI. Goal is to have a good discussion about our approaches and learnings.
October 12, 2025 at 12:09 PM
I still really want to record a video with me and another programmer who is not getting value out of AI. Goal is to have a good discussion about our approaches and learnings.
Now I want to know: why did it take Canada until 2023 to join the Apostille Convention?
October 11, 2025 at 9:07 PM
Now I want to know: why did it take Canada until 2023 to join the Apostille Convention?
Reposted by Armin Ronacher
For an AI startup today, what language would be the best choice: Python, TypeScript, Go or Rust?
Armin Ronacher is a great person to answer: a longtime open source contributor, creator of Flask (a Python fullstack framework), and he's building his AI startup. Spoiler: he's not using Python for it.
Armin Ronacher is a great person to answer: a longtime open source contributor, creator of Flask (a Python fullstack framework), and he's building his AI startup. Spoiler: he's not using Python for it.
October 8, 2025 at 9:13 PM
For an AI startup today, what language would be the best choice: Python, TypeScript, Go or Rust?
Armin Ronacher is a great person to answer: a longtime open source contributor, creator of Flask (a Python fullstack framework), and he's building his AI startup. Spoiler: he's not using Python for it.
Armin Ronacher is a great person to answer: a longtime open source contributor, creator of Flask (a Python fullstack framework), and he's building his AI startup. Spoiler: he's not using Python for it.
The @pragmaticengineer.com episode with me is online. Talking all about errors, programming languages and agents. www.youtube.com/watch?v=45kV...
Python, Go, Rust, TypeScript and AI with Armin Ronacher
YouTube video by The Pragmatic Engineer
www.youtube.com
October 8, 2025 at 7:28 PM
The @pragmaticengineer.com episode with me is online. Talking all about errors, programming languages and agents. www.youtube.com/watch?v=45kV...
I recorded a one hour video of me implementing a thing for one of our code bases with codex and claude. It might be boring in the first 15 minutes, but I went through most of it.
youtube.com/watch?v=X8M6...
youtube.com/watch?v=X8M6...
Armin Ronacher ⇌ on X: "Weekend is coming up, so might take some time to share some agentic coding stuff on a video or blog post. Anything you're curious about in particular?" / X
Weekend is coming up, so might take some time to share some agentic coding stuff on a video or blog post. Anything you're curious about in particular?
x.com
October 4, 2025 at 5:00 PM
I recorded a one hour video of me implementing a thing for one of our code bases with codex and claude. It might be boring in the first 15 minutes, but I went through most of it.
youtube.com/watch?v=X8M6...
youtube.com/watch?v=X8M6...
Weekend is coming up, so might take some time to share some agentic coding stuff on a video or blog post. Anything you're curious about in particular?
October 2, 2025 at 9:50 PM
Weekend is coming up, so might take some time to share some agentic coding stuff on a video or blog post. Anything you're curious about in particular?
Reposted by Armin Ronacher
Going after OSS projects that are openly governed isn't going to do what you want it to. Vercel makes its money from its hosting platform and paid products. OSS is not a paid product and while contributes goodwill doesn't directly impact the bottomline. And these project's reach well exceed Vercel.
fuck vercel, fuck Next.js, fuck Svelte, fuck Turborepo, fuck SWR, fuck SWC
Posing with the architect of a genocide for sales leads is an insane and deeply immoral stance
these projects cannot separate themselves from the CEO of the company who funds them
Posing with the architect of a genocide for sales leads is an insane and deeply immoral stance
these projects cannot separate themselves from the CEO of the company who funds them
September 30, 2025 at 4:29 PM
Going after OSS projects that are openly governed isn't going to do what you want it to. Vercel makes its money from its hosting platform and paid products. OSS is not a paid product and while contributes goodwill doesn't directly impact the bottomline. And these project's reach well exceed Vercel.
“Is 90% of code going to be written by AI? I don’t know. What I do know is, that for me, on this project, the answer is already yes.” lucumr.pocoo.org/2025/9/29/90...
90%
AI is writing 90% of the code I was in charge of
lucumr.pocoo.org
September 29, 2025 at 10:48 AM
“Is 90% of code going to be written by AI? I don’t know. What I do know is, that for me, on this project, the answer is already yes.” lucumr.pocoo.org/2025/9/29/90...
My oldest and me are making a 3d printed bb8. So far we didn't make it very far, but we wanted to spray paint it, so I needed a cutout. Turns out Claude Code is great at writing OpenSCAD files. Still kinda blown away.
September 28, 2025 at 1:13 PM
My oldest and me are making a 3d printed bb8. So far we didn't make it very far, but we wanted to spray paint it, so I needed a cutout. Turns out Claude Code is great at writing OpenSCAD files. Still kinda blown away.
I don't know if you've ever been in the situation of working on a visa (or knew someone who did). Shit stressful as it is. Preventing you from traveling abroad, unless your employer pay a hundred thousand dollars, is fucked up. I hope I'm misinterpreting this. www.whitehouse.gov/presidential...
Restriction on Entry of Certain Nonimmigrant Workers
BY THE PRESIDENT OF THE UNITED STATES OF AMERICA A PROCLAMATION The H-1B nonimmigrant visa program was created to bring temporary workers into the United
www.whitehouse.gov
September 20, 2025 at 10:30 AM
I don't know if you've ever been in the situation of working on a visa (or knew someone who did). Shit stressful as it is. Preventing you from traveling abroad, unless your employer pay a hundred thousand dollars, is fucked up. I hope I'm misinterpreting this. www.whitehouse.gov/presidential...
Some thoughts on the weekends on “what is a foreigner anyways?” — I'm arguing that there are significant differences in how for instance Austria and the US think about what foreigners are and why that might be.
lucumr.pocoo.org/2025/9/14/wh...
lucumr.pocoo.org/2025/9/14/wh...
What’s a Foreigner?
Thoughts on immigration.
lucumr.pocoo.org
September 14, 2025 at 11:10 AM
Some thoughts on the weekends on “what is a foreigner anyways?” — I'm arguing that there are significant differences in how for instance Austria and the US think about what foreigners are and why that might be.
lucumr.pocoo.org/2025/9/14/wh...
lucumr.pocoo.org/2025/9/14/wh...
This platform is unbearable today.
September 11, 2025 at 4:14 PM
This platform is unbearable today.