Interesting observation by Mitchell Hashimoto (creator of Vagrant and Ghostty) on how a company’s or product’s choice of programming language matters less in the age of agentic programming:
On the interesting side is how fungible programming languages are nowadays. Programming languages used to be LOCK IN, and they’re increasingly not so. You think the Bun rewrite in Rust is good for Rust? Bun has shown they can be in probably any language they want in roughly a week or two. Rust is expendable. It’s useful until it’s not then it can be thrown out. That’s interesting!
Hashimoto is talking about this complete rewrite of Bun (a Javascript/Typescript toolkit that’s owned by Anthropic and includes “a fast JavaScript runtime designed as a drop-in replacement for Node.js”) in a completely different programming language (Rust) in just 6 days.
6,755 commits, branch name claude/phase-a-port, PR opened May 8th, merged May 14th.
Six days. A full rewrite of a production-grade JS runtime, merged in six days.
Let that number sit in your mind for a second.
Whether or not you think that taking this six-day-old code completely rewritten & tested mostly by LLMs and deploying it in production is a good idea, it’s something that many more companies are comfortable doing. Simon Willison riffing on Hashimoto’s thoughts:
I was talking to someone who worked for a medium sized technology company with a pair of legacy/legendary iPhone and Android apps.
They told me they had just completed a coding-agent driven rewrite of both apps to React Native.
I asked why they chose that, given that coding agents presumably drive down the cost of maintaining separate iPhone and Android apps.
They said that React Native has improved a lot over the past few years and covered everything their apps needed to do.
And… if it turned out to be the wrong decision, they could just port back to native in the future.
This also applies to other layers of the tech stack (database, etc.) to various extents as well as to some other types of software, e.g. it’s trivial to export your bookmarks from one bookmark manager to another if they both have APIs or import/export capabilities — or, with a bit more effort, you can write your own.
BTW, this also goes for the big AI companies — it’s pretty easy to switch between different flagship models or to the increasingly powerful local models.
A couple of weeks ago, AI company Anthropic published the constitution that they use to train their Claude LLM (“under a Creative Commons CC0 1.0 Deed, meaning it can be freely used by anyone for any purpose without asking for permission”). From the company’s news release:
We’re publishing a new constitution for our AI model, Claude. It’s a detailed description of Anthropic’s vision for Claude’s values and behavior; a holistic document that explains the context in which Claude operates and the kind of entity we would like Claude to be.
The constitution is a crucial part of our model training process, and its content directly shapes Claude’s behavior. Training models is a difficult task, and Claude’s outputs might not always adhere to the constitution’s ideals. But we think that the way the new constitution is written — with a thorough explanation of our intentions and the reasons behind them — makes it more likely to cultivate good values during training.
The full document is 80+ pages, but the news release does a decent job in summarizing what’s in it.
Claude’s constitution is the foundational document that both expresses and shapes who Claude is. It contains detailed explanations of the values we would like Claude to embody and the reasons why. In it, we explain what we think it means for Claude to be helpful while remaining broadly safe, ethical, and compliant with our guidelines. The constitution gives Claude information about its situation and offers advice for how to deal with difficult situations and tradeoffs, like balancing honesty with compassion and the protection of sensitive information. Although it might sound surprising, the constitution is written primarily for Claude. It is intended to give Claude the knowledge and understanding it needs to act well in the world.
We treat the constitution as the final authority on how we want Claude to be and to behave — that is, any other training or instruction given to Claude should be consistent with both its letter and its underlying spirit. This makes publishing the constitution particularly important from a transparency perspective: it lets people understand which of Claude’s behaviors are intended versus unintended, to make informed choices, and to provide useful feedback. We think transparency of this kind will become ever more important as AIs start to exert more influence in society.
Casey Newton and Kevin Roose recently interviewed the primary author of the constitution, philosopher Amanda Askell, for the Hard Fork podcast (the segment starts at ~25min).
Newton says the document reads like “a letter from a parent to a child maybe who’s leaving for college”:
And it’s like, we hope that you take with you the values that you grew up with. And we know we’re not going to be there to help you through every little thing, but we trust you. And good luck.
Both the constitution and the conversation with Askell are fascinating, no matter where you lie on the AI debate continuum. You might also be interested in this video of Askell answering questions from Claude users about her work:
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