Rewriting Bun in Rust

Bun, the fast all-in-one JavaScript tool used by millions, just pulled off a full-blown language swap: founder Jarred Sumner says the project is being rewritten from Zig into Rust, with help from Anthropic’s unreleased Claude Fable 5. On paper, that’s a huge software story. But in the comments, the real show was the chaos, suspicion, and victory laps.

Some readers treated the post like a blockbuster reveal; others called it a giant ad for Anthropic’s AI. One of the sharpest reactions basically said: so this is the sales pitch now — what once took “hundreds of developers” can supposedly be done by one person with Fable. That instantly turned the discussion into a fight over whether the rewrite was an engineering milestone, an AI flex, or both. Another mini-drama: people had assumed a weaker model was doing the work, and commenters argued that this misunderstanding fueled a lot of the early skepticism.

Then came the Zig discourse, and wow, people did not hold back. One viral-style take said it was a terrible look for Zig if a “naive rewrite” fixed leaks, improved stability, cut the app size by 20%, and made it faster too. Ouch. But Bun fans clapped back with jokes about rumors of Bun’s death being “greatly exaggerated,” especially after the reveal that Claude Code already uses the Rust version. Even the blog’s fancy AI-made animations got side-eye: cute, thematic, maybe a little hard to read. In short, the rewrite landed — but the comment section turned it into AI propaganda accusations, language-war sniping, and meme-ready survival jokes.