Bun Rewrites 535K Lines of Zig into Rust in Four Months, Eliminates Numerous Memory Leaks

535,496 lines of Zig rewritten into Rust, roughly 64 Claude instances running in parallel, about $165,000 of API tokens on the meter. Bun v1.4.0 landed with 128 bugs fixed versus the last Zig release and a few percent more HTTP throughput — no miracle numbers, but use-after-free stopped being a debugging session and became a compiler error. The part I keep thinking about: this only worked because the test suite was strong enough to trust.