Andrew Kelley Shares Thoughts on Bun's Rust Rewrite
Original: My Thoughts on the Bun Rust Rewrite
Why This Matters
The commentary highlights tensions between VC-driven development speed and open-source code quality standards in the JavaScript tooling ecosystem.
Zig creator Andrew Kelley published a personal account of his history with Bun and its founder Jarred Sumner, offering critical commentary on Bun's codebase quality, management culture, and the decision to rewrite Bun in Rust instead of continuing with Zig.
Zig programming language creator Andrew Kelley published a blog post responding to Bun's announced rewrite in Rust. Kelley recounts his early impressions of Bun founder Jarred Sumner, describing him as someone with 'beginner energy' who learned quickly but moved recklessly. He notes that Bun credited Zig for performance achievements and that Sumner donated approximately $60,000 per year to the Zig Software Foundation — actions Kelley acknowledges as genuinely generous.
However, Kelley states that once Bun became VC-backed, priorities shifted dramatically. He criticizes Sumner's management style, citing reports from interviewees and employees describing poor communication, unrealistic expectations, and low empathy. Kelley says most Zig community members with interest in professional Zig work avoided Oven (Bun's parent company) as a result.
Kelley also describes a growing technical rift. He says the Zig team, which monitors user codebases to track language impact, became 'increasingly horrified' at Bun's code quality — describing it as 'hacks on top of hacks,' assertion abuse, and accumulation of unaddressed technical debt. He adds that Sumner 'was already writing slop well before he had access to LLMs.' The post frames the Rust rewrite as an outcome shaped by these compounding organizational and technical problems.