> What’s your threat model here? People making up elaborate lies about code they’ve written?

Likely people making up elaborate lies about code they didn't write. It's trivial to push code of which you are not the author.

I can’t imagine a situation where you couldn’t work that out with five minutes of casual conversation about the codebase but maybe I’m naive.

Which is why the interviewer should ask specific and thoughtful questions about the project, so they can gauge the candidate's level of understanding. This concern could also be addressed by introducing a trial period.

>This concern could also be addressed by introducing a trial period.

Why would I leave a stable well paying job for a job that basically says they don't trust me enough to not fire me in two weeks?

> Why would I leave a stable well paying job Well, why are you doing that in the first place? Maybe the new opportunity is worth it or the current one is so bad that it's worth it.

At least they’re honest about it. Unless you’ve got some kind of contract in place (or live somewhere where this is prohibited by law) your current employer could fire you in 2 weeks if they didn’t like your performance, too. They could do it this afternoon even.

I have heard of someone trying and pass off repos forked into their github account as their own work. A quick google or even just looking at the commit history in their fork made it obvious it wasnt true.

Manipulating one or more git repos to claim it as yours then ensuring your lie is not uncovered by googling would be technically challenging enough that those who could do probably don't need to.