We broke our customers twice with API changes before we learned. The first time we froze in fear and stopped evolving. The second time we overcorrected and shipped too fast. What works is boring and predictable: calendar versioning with deprecation windows announced a year ahead. Versions live for exactly twenty four months. Every deprecation has a migration guide, a changelog entry, and a banner in the response headers. Customers can plan. The result: zero angry support tickets about breaking changes in eighteen months. The lesson for API teams is that your versioning strategy is a promise. Make it boring, publish it, and keep it. Boring is a feature when other people build on you.