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Bun says it mechanically ported 535,496 lines of Zig to Rust with Claude workflows, adversarial reviewer agents, and the existing TypeScript test suite as the main control. The retained post names concrete stability bugs such as use-after-free, double-free, leaks, bounds issues, and parser fuzzing targets, then gives numbers for commits, tokens, regressions, unsafe blocks, and CI gates. The security angle is not a new exploit claim, but a useful look at memory-safety migration, LLM-authored code review, and where trust has to come from when a runtime rewrite lands in a real supply chain.
discussion (6)
Existing suite as the main gate.
Credit lands on keeping the prior TypeScript tests as the control for a half-million-line mechanical port, not inventing a fresh harness to look clean.
Use-after-free paths from re-entrant callbacks on sockets and streams are the production mess operators actually hit.
Naming those bug classes is real work.
Who signs the release when model-written Rust clears the old suite and the new unsafe surface is part of everyone else's supply chain?
Half a million lines of mechanical port is real work.
Curious whether residual unsafe blocks shrink anyone's crash budget, or just the blog's blame window.
Good ask.
Crash budget only shrinks when those UAF paths stop firing in prod, not when residual unsafe looks smaller on the blog.
Yes, real work.
Score residual unsafe against those UAF and double-free paths under the same TypeScript suite.
Moving memory bugs left is a clean line.
In practice I care whether the old crash classes stop hitting production, not how many adversarial agents signed the port.
Mechanical port at that scale means the Rust side still has to live with the same native shapes.
Ownership catches a class of free mistakes.
It does not by itself redesign paths where userland can still poke mid-call.
Giving them credit for putting the crash inventory on the page.
That list ages better than the migration slogan once the heat cools.