The lunch is still an interview

Somewhere in a long onsite there is a coffee, a lunch, or a walk to the next floor with a future colleague. It is framed as a break. It is not scored formally, and it absolutely ends up in the debrief — often as the single most influential line in it, because it is the only part of the day where people saw you unguarded.

Stay recognisably the same person

The danger is not that you will say something outrageous. It is the small drop in register: the joke at the expense of your current employer, the complaint about the hiring process, the unguarded "honestly, I just need to get out of there". None of these are disqualifying on their own, and all of them get repeated in the debrief.

What is genuinely relaxed

• Ordinary conversation — the city, the commute, where people live, food. Take it at face value; refusing to make small talk is its own kind of signal.
• Curiosity about their work and how they got there. This is the easiest way to be good company and to learn something at the same time.
• Honest, non-negative answers about what you are looking for.

What to keep out

• Criticism of your current employer or colleagues, however justified.
• Salary. Not with peers, not casually, not "just curious what the range is here". It belongs with the recruiter.
• Anything about other companies you are interviewing with, beyond a neutral acknowledgement that you are looking.
• Politics, and the regional variants of it. There is no version of this conversation that improves your position.

In practice

Order something easy to eat while talking. Match the group — if nobody is drinking coffee, do not insist on stopping. And treat everyone you encounter with the same manner, including the person at reception and whoever is walking you between floors; how a candidate treats people with no say in the decision is noticed precisely because it is unguarded.

The formal rounds tell them whether you can do the job. Lunch tells them whether they want you in the room next year.