Image: reddit.com · Jarred, creator of Bun rewrote it from Zig to Rust in 11 days using Claude Fable 5 which costed ~$165k of Fable usage, at API prices. They said by hand, this wo
Bun rewritten from Zig to Rust in 11 days
A Reddit post about the Bun runtime being ported to Rust with Claude Fable 5.
Credits
- Reddit poster simple_explorer1 Source ↗
- Post author aiforecastledger.bsky.social Source ↗
- Post author ai-nerd.bsky.social Source ↗
- HN commenter xyzsparetimexyz Source ↗
Earliest dated source:
The full story
Bun, the JavaScript runtime, was originally written in Zig. Its creator Jarred Sumner reports that coordinated Claude agents ported it to Rust, more than a million lines of code, in 11 days. The Rust version is already shipping, including inside Claude Code itself.
The details come from Bun's own blog post, shared widely on Bluesky.
How it was done
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Sources
From a short post by the maker, so the details are as they tell them.
- Reddit: Jarred, creator of Bun rewrote it from Zig to Rust in 11 days using Claude Fable 5 which costed ~$16Reddit poster: simple_explorer1Posted
If it disappears: archived copy of Reddit: Jarred, creator of Bun rewrote it from Zig to Rust in 11 days using Claude Fable 5 which costed ~$16 (opens in a new tab)
- The project: bun.com
Linked in the post.
- Bluesky: Bun runtime rewritten from Zig to Rust using Claude coding agents — Jarred Sumner reports Post author: aiforecastledger.bsky.socialPosted
A Bluesky summary with the scale and timeline.
- Bluesky: Bun's runtime got ported from Zig to Rust by Claude Fable 5 in 11 days: bun.com/blog/bun-iPost author: ai-nerd.bsky.socialPosted
A Bluesky post linking Bun's blog post about the port.
- Hacker News: I asked Claude to loop the workflow on all 1,448 .zig files, and about 2 minutes in, one CHN commenter: xyzsparetimexyzPosted
- Reddit: Jarred, creator of Bun rewrote it from Zig to Rust in 11 days using Claude Fable 5 which cReddit poster: simple_explorer1Posted
If it disappears: archived copy of Reddit: Jarred, creator of Bun rewrote it from Zig to Rust in 11 days using Claude Fable 5 which c (opens in a new tab)