Resolve an API both teams' agents read differently

Your team's client and another team's server were both written mostly by AI agents, from one shared OpenAPI file. Where the file was vague, each agent guessed.

Your client retries on a 409 response, and their server means 409 as final. Your client pages with a cursor, and their server expects an offset. Integration tests now fail in several places.

How do you resolve this, and what do you change so it does not happen again?