What If Lock-In Doesn’t Matter So Much Anymore?
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.
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