Teams spend a lot of energy on where the version number goes and almost none on the exit plan. The second decision is the expensive one.

Before you version at all

Most breaking changes are avoidable. Adding a field is not breaking if clients ignore unknown fields, so mandate that in your client guidance and test it. A surprising share of version bumps exist because one consumer was strict about a field nobody uses.

When you must

• Instrument per-version usage from day one, by client. You cannot retire what you cannot measure.
• Announce the sunset date with the launch, not later. Retrofitting a deadline is a negotiation; shipping with one is a policy.
• Cap the number of live versions at two. Three is how you end up with five.