Bun merges Rust rewrite, drops Zig

This is a watershed moment for "agentic" development, proving AI can migrate mission-critical systems infrastructure in days rather than years.

• –Over 1,000,000 lines of code ported with 99.8% test parity in just 10 days using specialized Claude Code rules.
• –Transition from Zig to Rust targets long-standing stability issues, sacrificing Zig's manual control for Rust's safety guarantees.
• –The initial "canary" release relies on 15,000 unsafe blocks, prioritizing logic replication over idiomatic Rust for the first phase.
• –Anthropic's "bet on Bun" positions the runtime as the primary engine for its burgeoning ecosystem of AI agents and developer tools.