AGENTS.MD and CLAUDE.MD also provide easy detection avenues. Trivial measures will probably catch 70-80% or more. You don't need a 100% enforcement rate for a rule to exist, indeed there are basically no rules anywhere in the world that achieve that.

At that point just use whitelist-based approach. I already used gitignore like that. It also easier to avoid committing temp file and secret through whitelist because those file are never in gitignore in the first place.

It does not prove anything. Some could not commit those files to avoid detection, and those files exist in projects in which only some code is AI generated. I have them in projects where, for example, LLMs were used to generate tests and for a few fixes/additions in the rest of the code.

Whilst they may provide a strong signal, I wouldn't call it a guarantee. If I wanted to avoid vibe-coded contributions I might add such files, but with instructions for the agents that they're not allowed to read or touch any of the files in the repository.

But that just means they probably used AI to help code, not that it is vibe coded, no?

Then the linux repo is also banned. I don't think that's a good way to detect "vibe coding"