I worked for almost three years on a team of five, and the four of us who weren't the manager had dinner together at least twice a week. We finished each other's sentences. We knew each other's apartments. When the company restructured and the team broke up, I assumed two of those people would be in my life forever. One of them is. Two of them I have not seen since the year we left, despite living in the same city. I think about that gap a lot. The line between a coworker and a friend turns out to be invisible until you accidentally cross it in one direction or the other.

The cleanest test I have found happens at the end of a project. When the deadline is gone and the shared problem is gone, do you still seek each other out. If the answer is yes, you were friends who happened to work together. If the answer is no, you were collaborators who liked each other, which is its own valuable thing and not a downgrade. Many of us confuse the two during the project itself, because shared deadlines can feel like intimacy. They aren't always.

Office friendships also carry a weight that pure friendships don't. You will eventually disagree about strategy, about headcount, about who gets credit. A real friend can absorb a strong professional disagreement and still text you on the weekend. A friendly coworker often cannot, because the disagreement was the relationship. Knowing which one you have ahead of time saves both of you a lot of confusion when the inevitable conflict arrives.

The reason office friendships sometimes feel more intense than non work ones is that they happen in a high contact, high stakes environment. You see this person every day. You watch them under pressure. You witness moments of quiet competence and small failures that no one outside the team will ever see. Shared difficulty creates closeness fast. The closeness is real. It is also tied to the context. Forgetting the second part is what makes people overestimate the friendship after the team, the project, or the company changes shape.

Reentering an old office friendship from outside the company is a strange experience. The shorthand still works. The jokes still land. But the conversation has fewer obvious topics, and both of you can feel it. The friendships that survive past this point usually do so because at least one person makes a deliberate effort to find new ground. New restaurants, new walks, new questions about the parts of life that don't involve the old job. If neither of you puts in that work, the relationship doesn't really fail. It just becomes a fond memory you bump into every couple of years.

What I would tell my younger self, if I could send a message back to that team of five, is to not assume the relationships will hold automatically. Pick the one or two you actually want to keep. Send the first message in the month after the team breaks up, when both of you still have the shorthand and neither of you has filled the gap with new colleagues. The friendships I lost from that period weren't lost because we stopped caring. They were lost because nobody picked up the phone in the first ninety days, and after the first ninety days, the relationship had quietly stopped being a friendship and become a fond memory.