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

Programming languages are increasingly fungible rather than creating long-term lock-in. A production-grade JavaScript runtime was rewritten in Rust in about six days, with thousands of commits and a short development cycle. This demonstrates that a language can be treated as replaceable when agentic systems can generate, test, and iterate code quickly. Companies are becoming more comfortable making large architectural changes because they can switch again if the decision proves wrong. The same flexibility can apply across other layers of the stack, including frameworks and databases, enabling faster experimentation and reduced maintenance risk.

"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."

"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."

Read at kottke.org