when to implement api versioning? dont have a clue.

Hey everyone, I'm working on a new service and we've been debating API versioning. We're seeing a lot of differing opinions on when to introduce it. Some folks want to add it from day one, others say wait until we actually need it. What's your experience? Do you start with v1, or only add versioning when breaking changes are on the horizon? I'm curious about the pros and cons you've encountered.