bun's rust rewrite is a marketing stunt - annieversary
bun's rust rewrite is a marketing stunt
2026-05-15
word count: 643
approx reading time: 3 mins
yesterday Bun merged it's million lines long PR that rewrites the entire project from Zig to Rust.<br>you might be able to see said PR here, if Github feels like cooperating.<br>this has, expectedly, caused a big commotion.<br>a lot of people are talking about it, and lot's of people have opinions on the subject.<br>the HN post has over 700 comments, the Lobsters one over 100.<br>and everyone seems to be discussing this change on its technical merits.<br>on if it makes any sense to switch from Zig to Rust,<br>if there's any need,<br>if a million llm generated locs are maintainable,<br>if the new code is going to be safer, or more buggy, or whatever.<br>but like. i find it hard to belive this is anything more than a marketing stunt.<br>i mean, i believe it probably did start as an experiment.<br>bun's creator Jarred said so himself on HN when the branch got noticed originally.<br>but i also know for a fact that anthropic took note of all the buzz it got.<br>and we also know Anthropic has done big projects like these before (like their c compiler).<br>if you were anthropic, would you not immediately call Jarred and ask him to drop everything<br>and focus on getting that PR merged?<br>if there's one thing that most engineers can agree on, is that whole-codebase rewrites are costly, expensive, and hard.<br>at least, it's an Engineering Blogpost worthy endeavour.<br>it's not something you even consider unless there's very clear benefits.<br>what better showcase of LLM's capabilities than doing the unthinkable in a week?<br>and now Anthropic get to say that they solve this problem!<br>it's an incredible selling point for Claude Code.<br>at $work we use PHP, and i some times get asked if i've considered changing to any other language.<br>the answer has always been an incredibly easy No.<br>the cost would be way too high, and the pros/cons are never too good or concrete to justify spending all that time and money.<br>but now that cost has been slashed by a couple orders of magnitude.<br>maybe not enough to make it worth it for $work, but certainly for a lot more companies.<br>and next time you propose a rewrite to an Exec, do you think they'll say:<br>"yes, let's spend 18 engineer-months on this rewrite" or "spend 20K on claude tokens to do it in a week and get it over with"?<br>this Bun rewrite creates new market opportunities and captures a big chunk of the existing ones.<br>if i had an MBA i would probably make up a big fancy number for how much money they'll maybe make from this.<br>so why are we analysing the technical merits of this migration from Anthropic/Bun's perspective?<br>i don't think they care about the technical case when the business one is so strong.
an aside: software is cheap<br>if i worked at Anthropic i don't know if i would care too much about Bun being unmaintainable after this rewrite.<br>fundamentally, software is now Cheap.<br>we are entering an era of software industrialization.<br>as it happened with clothes manufacturing, the price to produce software has gone down incredibly.<br>like. it doesn't matter if Bun is unmaintainable in this new version.<br>the point is that it took them 6 days (SIX!!!) to generate this entire rust codebase.<br>if it's shit, they'll just make it from scratch again with what they know.<br>if your tshirt is broken or you've outgrown it, you don't go to the tailor to get it fixed.<br>you buy a new one, because it's cheap as hell.<br>so of course i don't think Anthropic cares about whether their new Bun code is maintainable.<br>they have proven they have the tech to make a new Bun from scratch whenever they want.