Bun 1.4 Rust rewrite is not looking good

I care about Bun. I have been rooting for it since the initial release in 2022. I switched all my development from Node to Bun. I used it in the development of the Nue framework and now with my new project Hertta.

The last three months have not looked good for Bun. It started as one of the most impressive individual engineering projects I have seen, but has now turned into this weird AI-powered creature with continuous false promises and an increasingly frustrated community.

In the next version of Bun

In the next version of Bun used to be a positive tweet to watch for. For years it meant a feature had been implemented, tested, and would ship in a few days. This changed after the Rust rewrite. Now the posts are false promises about the upcoming release:

It’s now three months and counting since the last stable release, the longest gap in Bun’s history since 2022. Nothing unusual there. Software slips, that’s normal. It’s just that an account which used to communicate with real dates and real numbers has switched to vibing. And the user reaction is what you’d expect after constant false promises:

Bun on GitHub

The Bun 1.4 rewrite is a big bet on AI. In the past month, 15.8k commits came from robobun, 1.6k commits from autofix-ci[bot], and 790 commits from Jarred.

The project has over 5k open pull requests, which is the largest number of pull requests I’ve seen. For comparison, OpenClaw has 2.2k, and React has 441. GitHub recommends staying under 1,000 open PRs against a single branch before mergeability checks start timing out.

The biggest worry is, of course, the code itself. In the early days Jarred’s work was inspirational. I thought he was a true Zig talent, until I read Zig creator Andrew Kelley’s thoughts on the Bun rewrite:

What was the problem with Zig?

This rewrite is the most closely watched real-world test of whether AI agents can take over a production codebase with a human mostly directing rather than reading. Anthropic’s own reputation is also on the line: if this goes well, it is real proof of what agentic coding can do. If it goes badly, it will send a signal in the opposite direction.

The number of unsafe blocks in the Rust code suggests the rewrite did not deliver the memory safety that was given as the reason for doing the rewrite in the first place. Instead this rewrite feels more like an Anthropic ad.

And was Zig really the problem? Bun’s early identity was built on Zig: its performance, its fast compile times, its low friction, its direct memory control with a small team.

It feels like Jarred and Anthropic decided early on that this was going to be written in Rust, and used Zig’s memory issues as the excuse to let the world know how powerful Claude is. A rewrite like this would make great headlines, and it certainly did. Now we’re looking at the long tail of issues from the rewrite they didn’t prepare for.

Maybe Bun should have put that same AI-assisted effort into disciplined, human-understood Zig instead of a full language change. I never saw Jarred seriously engage with this option.

And ‘tomorrow’ has come and gone. Still no v1.4.

¯\_(ツ)_/¯