Rewrite Bun in Rust has been merged • Hacker News Board

Re: Rewrite Bun in Rust has been merged

#281

Post by hxtk » Thu, May 14, 2026, 6:18 PM UTC

alfanick wrote: post #260

I'm confused. Never heard of Bun until a few days ago here on HN. It's some nodejs wrapper thingy, written in Zig, and someone decided to use LLM to rewrite it in Rust. Is this a big deal? Who is even using this software? Why is this big?

I think relatively few people are probably running Bun in production, but as a dependency management system and bundler for the JavaScript ecosystem, it's similar to `uv` from the Python ecosystem in how much faster it is compared to the most popular alternatives so it's fairly popular in that space.

Re: Rewrite Bun in Rust has been merged

#282

Post by LucidLynx » Thu, May 14, 2026, 6:18 PM UTC

Is this really the state of "software engineering" today? :/

Re: Rewrite Bun in Rust has been merged

#283

Post by philipbjorge » Thu, May 14, 2026, 6:18 PM UTC

kracket wrote: post #247

It's going to be absolute mess of total AI slop and black box that nobody understands and is going to cause more issues than it fixes.

I've done some pretty incredible things with LLMs. If this were sqlite with its exhaustive test suite... OK, I can see it.

It's hard for me to see this not becoming a pile of slop, but hey, maybe I'm wrong

Re: Rewrite Bun in Rust has been merged

#284

Post by j-pb » Thu, May 14, 2026, 6:19 PM UTC

AlienRobot wrote: post #265

j-pb wrote: post #199

Earlier quoted context omitted.

I'm pretty sure they'll miss the full developer salary that Oven used to sponsor them, which they no longer do. I'd wager one doesn't do a rewrite like that, if you are in great personal standing with the language foundation. That same "just don't use it" attitude was what drove me away from Zig btw. I would have been fine in restricting myself to a somewhat stable subset, e.g. if, loop + function calls, but they did…

I think if you use a programming language that is clearly version zero you can't complain that it's not stable...

I'm not expecting the whole language to be stable, but I expect certain parts of it to be more stable than others. E.g. control flow vs. async.

I'm not saying that they can't work that way, more power to them. But then having the expectation of anybody using it in a professional setting is also unrealistic. You can't have your cake and eat it too, either it's your personal project and you are fine with nobody using it but you, or you evangelise for people to use it, but then you also need to make at least some effort to not break their stuff on a whim, or to accept their change requests when they put in the work as was apparently the case for bun.

Tbh I don't see Zig hit 1.0 with a meaningful user-base, it's probably going to mostly get eaten by Rust or some other language and will continue to exist as a niche thing, kinda like D.

Having one of the flagship/showcase codebases rewritten to Rust in a week feels like a death knell. Either the community or the language is too unworkable if someone that heavily invested into it jumps ship, and I'm afraid it's kinda both.

Re: Rewrite Bun in Rust has been merged

#285

Post by bflesch » Thu, May 14, 2026, 6:19 PM UTC

tarruda wrote: post #40

nicce wrote: post #26

Earlier quoted context omitted.

Maybe this is the best marketing trick for Claude Code ever. Maybe there was pressure from Anthropic to do this and prove the value. Even partial success is enough to prove the value, justify the value and usage, and AI dependency even further.

And as long as Bun doesn't break Claude code, which only uses a subset of it's APIs, this might just pay out.

Running the rust version in their prod for two weeks should be long enough to catch the biggest crashes and fix them. I'll be up to bug bounty hunters to find the big one that crashes all their app servers at once.

Re: Rewrite Bun in Rust has been merged

#286

Post by moomoo11 » Thu, May 14, 2026, 6:19 PM UTC

atonse wrote: post #252

I have full faith, it's the same really smart people that built bun (Jarred and team) that have spearheaded this and are running it. So I have no reason to believe that this was done carelessly. That said, I'm still shocked and amazed that something this big is possible these days. But as we've seen multiple times now, one of the most important things your codebase can have is a solid test suite. I will continue to u…

yeah but it also made some tests pass by changing the tests. i’m not super familiar so i’ll dig more on weekend but it seems sus pending more review. i’ve had ai do similar things that i caught in manual review. cheating the test is bad.

Re: Rewrite Bun in Rust has been merged

#287

Post by lukaslalinsky » Thu, May 14, 2026, 6:20 PM UTC

Havoc wrote: post #102

How does the no async work? Would have thought Bun would need that

People were doing async I/O before coroutines existed. They are using callbacks and their own networking.

Re: Rewrite Bun in Rust has been merged

#288

Post by ifwinterco » Thu, May 14, 2026, 6:23 PM UTC

atonse wrote: post #252

I have full faith, it's the same really smart people that built bun (Jarred and team) that have spearheaded this and are running it. So I have no reason to believe that this was done carelessly. That said, I'm still shocked and amazed that something this big is possible these days. But as we've seen multiple times now, one of the most important things your codebase can have is a solid test suite. I will continue to u…

Just because it's possible, doesn't mean that it's sensible

Re: Rewrite Bun in Rust has been merged

#289

Post by ordu » Thu, May 14, 2026, 6:24 PM UTC

gm678 wrote: post #249

$ rg 'unsafe [{]' src/ | wc -l 10428 $ rg 'unsafe [{]' src/ -l | wc -l 736 Language Files Lines Code Comments Blanks ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Rust 1443 929213 732281 116293 80639 Zig 1298 711112 574563 59118 77431 TypeScript 2604 654684 510464 82254 61966 JavaScript 4370 364928 293211 36108 35609 C 111 305123 205875 79077 20171 C++ 586 262475 217111 19004 26360 C Header 779 100979…

The half of the files contain 'unsafe' keyword? It doesn't seem as a good rewrite. What is the point of rewrite into Rust, if ~half of your code is still unsafe?

Re: Rewrite Bun in Rust has been merged

#290

Post by embedding-shape » Thu, May 14, 2026, 6:25 PM UTC

vitaminCPP wrote: post #253

> +1009257 -4024 Bun is now over 1M lines of Rust code. This is approaching the size of the Rust compiler itself; except that BunJs is mostly a JavaScript interpreter wrapper + a reimplementation of the NodeJS library (Rust STD wrapper). I think BunJS is becoming the canary for software complexity management in the LLM era.

> I think BunJS is becoming the canary for software complexity management in the LLM era.

Yeah, Cursor did the same thing, bragging about how many lines of code they managed to produce for a semi-working browser, completely missing the idea where less code is better, not the other way around.