>They recently tried to upstream an improvement to zig, but were prevented from doing so because zig has a hard and fast "no AI code" rule.

And will Rust team accept their vibe coded patches?

Very likely not, if they are of similarly low quality.

No. The Rust project developers are more lenient when it comes to developing patches with AI assistance, but the amount of leniency one receives is proportional to the amount of pre-existing trust a contributor has with the project, and every PR still has to be reviewed by an independent human. A stranger dumping a zillion lines of slop in a PR is a one-way ticket to having your PR politely closed.