How is the Bun Rewrite in Rust going?
lockwood.dev
July 27, 2026
5 min read
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65/100
Summary
Bun is undergoing a rewrite in Rust, which aims to leverage AI capabilities for the work typically done by open-source maintainers. Anthropic's AI tools, including a C compiler, are contributing to this rewrite process.
Key Takeaways
- The Bun rewrite in Rust was completed in 11 days at a cost of $165,000 for Anthropic API calls, averaging $15,000 per day.
- As of July 27, 2026, there have been no new release tags for Bun since May 12, 2026, marking an 11-week gap since the last release.
- The number of open pull requests for Bun increased from 1,277 to 2,475 within a six-week period following the rewrite.
- There is a significant involvement of Anthropic employees in the Bun project, suggesting that the costs associated with the rewrite may be higher than initially reported.
Community Sentiment
Positives
- Using an LLM to translate a project in a short time is nothing short of incredible — it shows just how far we've come in AI-assisted development.
- The Rust rewrite shipped in Claude Code and is being used by millions, proving that the project has substantial real-world impact despite the development delays.
- Taking the time to ensure software quality before a release is a smart move — rushing could jeopardize community trust.
Concerns
- Short-termism is rampant, and those who don't understand the code could face a rude awakening as AI-generated solutions often miss the mark on maintainability.
- The lack of noticeable progress from the Rust rewrite raises concerns — if no one noticed, is it really worth the effort?
- There's skepticism about whether the rewrite truly adds value, as more code doesn't necessarily translate to better functionality.
