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How is the Bun rewrite in Rust going?

lockwood.dev

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Re: How is the Bun rewrite in Rust going?

#271

Post by well_ackshually »

klausa wrote: post #84
flohofwoe wrote: post #63

Earlier quoted context omitted.

Claude Code most likely only uses a tiny fraction of Bun/Node features, so Claude Code switching to the Rust rewrite doesn't mean all that much.

Look, I understand being skeptical of the whole process; the discourse about this has been extremely tiring. But at some point if “moving one of the biggest actively maintained and used codebases to it without anyone noticing” is dismissed as “it doesn’t mean all that much”, then we’ve lost the plot a little bit somewhere.

Claude Code is 150k lines of Javascript that doesn't work particularly well. 150k isn't nearly "one of the biggest", even when filtering for actively maintained.

Re: How is the Bun rewrite in Rust going?

#272

Post by well_ackshually »

throw16180339 wrote: post #267
SoftTalker wrote: post #186

Earlier quoted context omitted.

Why is porting a program from one language to another seen as some great achievement? We had f2c in the 1990s. https://en.wikipedia.org/wiki/F2c

This isn't a valid comparison. f2c is a compiler and the output isn't intended to be human readable.

[flagged]

Re: How is the Bun rewrite in Rust going?

#273

Post by pianopatrick »

At what point should I trust projects like this?

I've heard stories of LLMs changing tests to get all the tests to pass instead of actually fixing code. So I'm not sure I trust it just because tests pass. I also think that tests do not and cannot check everything.

I also don't trust it just because it compiles in Rust. The Rust compiler does not check everything.

So at what point do projects like this cross from "untrusted" to "trusted"?

Re: How is the Bun rewrite in Rust going?

#274

Post by WD-42 »

interroboink wrote: post #260
brabel wrote: post #257

Earlier quoted context omitted.

But postmortem is literally “post death” in Latin. It’s synonymous with autopsy! I know people misuse borrowed words all the time, but come on?!

> is literally “post death” in Latin Yes; I think what I described matches that meaning? Post-death, as in: "it's over," "activity has halted," "no more work being done." Death does not necessarily have a bad/negative connotation. It's just the end of something. This is in contrast to the original comment: "something that went so wrong you had to kill it." Death does not imply something went wrong or that it happened…

> Post-death, as in: "it's over," "activity has halted," "no more work being done”

Which makes even less sense as we all know software is never done, unless it truly is dead.

Re: How is the Bun rewrite in Rust going?

#275

Post by aleksandrm »

tomlockwood wrote: post #163
Jarred wrote: post #148

Bun’s Rust rewrite shipped in Claude Code over a month ago and barely anyone noticed. Claude Code is widely used. The Rust rewrite is going well overall. In the Bun v1.4 video, I promised a certain number of newly passing Node.js tests were added to force us to improve compatibility, and that number is not true yet. The release is delayed until it is true. The PRs to make it true are up but not merged yet. Most likel…

[flagged]

https://bun.com/blog/bun-in-rust

This is from July 8, 2026. And while you did link it in your article, what else are you expecting?

Re: How is the Bun rewrite in Rust going?

#276

Post by well_ackshually »

Atotalnoob wrote: post #126
rienbdj wrote: post #44

Earlier quoted context omitted.

Anyone know why? Can’t CC run on any JS runtime?

Yes, but it’s slower on non-bun runtimes. Nowadays, I believe they bundle bun with CC They chose to use a react rendering to native TUI renderer, which was a source of a lot of performance issues. AFAIK, they have written a new renderer.

>AFAIK, they have written a new renderer.

Which is equally terrible and has earned them every single rendering engineer in the world taking the piss out of them when they proudly announced it was as complicated as rendering a video game.

Re: How is the Bun rewrite in Rust going?

#277

Post by whstl »

SuddsMcDuff wrote: post #136
whstl wrote: post #90

Earlier quoted context omitted.

I think this is perfectly fine. If you explore Github, you're gonna see thousands of abandoned game engines, compilers for made-up languages. And that has been happening since before the LLM era. I used to be part of an OS messaging board in the early 2000s and almost everyone had their own OS. A dozen people or so could even run Firefox! I remember (now legend) Terry bothering us to check out LoseThos or GodOS or wh…

> (now legend) Terry bothering us to check out LoseThos or GodOS or whatever was its name Temple OS :)

That was half memory-loss, half joke, since Terry was always changing the OSs name. Wish he was still with us, renaming it every year!

Re: How is the Bun rewrite in Rust going?

#278

Post by whstl »

boggo wrote: post #166
whstl wrote: post #90

Earlier quoted context omitted.

I think this is perfectly fine. If you explore Github, you're gonna see thousands of abandoned game engines, compilers for made-up languages. And that has been happening since before the LLM era. I used to be part of an OS messaging board in the early 2000s and almost everyone had their own OS. A dozen people or so could even run Firefox! I remember (now legend) Terry bothering us to check out LoseThos or GodOS or wh…

LoseThOS didn't burn through hundreds of thousands of dollars of expensive and environmentally questionable compute.

True! It just burned though other forum contributors patience! I miss the Terry from back in the day (early 2000s?) though.

Re: How is the Bun rewrite in Rust going?

#279

Post by sandeepkd »

Jarred wrote: post #182
lantry wrote: post #175

Earlier quoted context omitted.

Any comment on the costs estimated in the article? especially the buildkite costs?

CI has always been expensive for Bun including before the acquisition. We build for [macOS, Linux, FreeBSD, Android, Windows] x [ARM64, x64] and then run tests on multiple Linux distros with multiple shards, multiple macOS versions and Windows for each architecture. We recently started cross-compiling all the builds on Linux arm64 and that made it a little faster (I wrote a CLI tool to download the correct macOS head…

I think the question for CI costs is still out there. While I do not think it should be in tunes of thousands a day but thats the skepticism presented in the article. True costs are really important to make a good decision in situations like this. One has to consider the fact that lots of people are going to use these numbers to justify the rewrite in future.

Re: How is the Bun rewrite in Rust going?

#280

Post by qarl2 »

insanitybit wrote: post #270
qarl2 wrote: post #236

Earlier quoted context omitted.

An example of an LLM porting code is off topic to a project where the issue is entirely about an LLM porting code? Can you explain that more?

No, I don't think it warrants explanation. If you think it's on topic, I'd suggest adding more context and relating it to the parent post rather than just linking to your own project.

Ah - my bad. I thought it was obvious that a toy project facing the same issues would be a good playground for experimentation on the topics being argued.

Going forward, I will strive to not make leaps that my audience can't follow.

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