Finding and fixing a bug yourself with the agent off: read the error, make a guess, test the guess, narrow it down. You don't have to be quick. You have to have a method, and be able to say what it is as you go.
Agents get stuck in loops, trying the same fix in new words. That is the moment a person is needed, and some interviews create it on purpose. If you have only ever watched an agent debug, you will feel this one, so practise it before someone is watching.
Say it to your agent
“Stop. You have tried the same fix twice, and a third try won't help. Write down what we know: the exact error, the last commit where it worked, your top two hypotheses, and the one command that tells them apart. Don't change any code. I'll run it myself.”