My Thoughts on the Bun Rust Rewrite - Andrew Kelley

Andrew Kelley - My Thoughts on the Bun Rust Rewrite (2026 Jul 09)

My Thoughts on the Bun Rust Rewrite

Context: Rewriting Bun in Rust

History

When Jarred joined the Zig community about 5 years ago, I described him as<br>someone who had strong "beginner energy". That is, he moved fast and tried a<br>lot of different stuff, jumping head first into problems that he was not yet<br>equipped to solve, leading to mediocre outcomes in terms of engineering, but<br>learning a whole heck of a lot in the process. I see it as quite a healthy<br>attitude, particularly for young people and students. This is the best way to<br>level up and learn new things.

As he focused his efforts on Bun he began to attract attention. JavaScript<br>being the most popular programming language in the world, there are a lot of<br>potential eyeballs on a promising new toolchain.

This attention could have been harnessed in a few different ways. For<br>example, he could have easily achieved a solid living via crowdfunding, even<br>for San Francisco standards. But having graduated from the Thiel Fellowship<br>school of thought rather than university, he was essentially groomed from<br>a young age into uncritically embracing the Silicon Valley mindset, and he took<br>venture capital.

From the beginning, Jarred was appreciative towards the Zig project. He<br>credited Zig on the Bun website for the project's performance achievements. He<br>set up a monthly donation to<br>Zig Software Foundation that amounted to<br>$60,000 per year. He didn't have to do either of those things, but he did,<br>and it was pretty cool of him. Even in<br>his blog post that I'm referencing,<br>he expresses what I perceive as sincere grattitude towards the Zig project.

However, once Bun became a VC-backed startup, he started racing towards the<br>finish line. Now, instead of working on a free and open source project, learning<br>and growing with the community, Jarred was running a business. It was at this<br>point - when he suddenly became a manager - that this "beginner energy" started<br>to hit differently for me. It's one thing to<br>choose a poor work-life balance for oneself; a different thing entirely to<br>demand it of others:

"Oven is going to be a grind, especially the first nine months or so. If<br>work-life balance means a lot of time spent not working, it's probably not a<br>good fit."

Fun fact: people talk to each other.

I talked to those who interviewed for a job at Oven. I talked to<br>people who worked there. Those people talked to each other. Everybody talked to<br>everybody. The grapevine was large and healthy and full of juicy grapes, and<br>all those grapes contained the juice of the same message: Jarred was a<br>stinky manager. Poor communication, unrealistic expectations, low empathy, no<br>experience. Just a total shit show, from an employment perspective.

Consequently, although Zig community members were eager to find work coding<br>in Zig on the clock, most of the talent pool steered clear of Oven and Bun.

At the same time, a rift between Zig and Jarred started widening. His singular<br>focus on productivity and his startup's exit strategy was increasingly at odds<br>with my longer term vision for the Zig project. I remember he kept nagging me<br>to drop all my other priorities and work on a Language Server Protocol<br>implementation and VSCode integration, while I had bigger plans.

The main problem, however, was code quality.

The Zig team regularly checks in on our users' projects. We read source code<br>to find out how the language is affecting users, we test changes to see how<br>problematic breakage might be, and we check for performance regressions.

We became increasingly horrified at the programming practices we saw in<br>Bun's codebase. Hacks on top of hacks.<br>Abuse of assertions.<br>Most of all, recklessly speeding past feature after feature<br>with very little time taken for reflection and elimination of bugs and<br>technical debt. Jarred was already writing slop well before he had access to<br>LLMs. Now, it's not our business to police what our users do, but you may have noticed<br>people screaming in our faces about memory safety constantly. You can imagine<br>how we might want to put some social distance between ourselves and a project<br>whose irresponsible software engineering practices invite the exact kind of<br>criticism that people are eager to level.

We made futile attempts to guide them towards better programming practices.<br>There were a few exceptional heroes who did their very best in a dysfunctional<br>company. You know who you are. But you can't stop a rising tide.

By this time, we all felt at ZSF that Bun was a net liability, and this was<br>before RoboBun became the #1 contributor. Along with the discomfort of<br>the publicly presumed poster child for Zig programming language actually being<br>the prime example of How Not To Write Zig Code, at some point they would sell<br>out (let's be honest, their vague "sell some cloud something" business plan was<br>a farce from the get-go), we would receive some negative...