Contract tests that survive vendor churn

Vendors rotate contacts; schemas drift quietly. Contract tests only earn their keep when they plug into the same CI gates that already block merges—not when they live in a forgotten spreadsheet. We outline a lightweight matrix pairing producers, consumers, and compatibility expectations. Each pairing gets a minimal fixture set plus an explicit owner on your side—even if that owner is a rotating contractor. We also cover sunset clauses: when to retire tests whose services no longer exist, and how to sound an alarm when silent skips creep into pipelines. Teams in Seoul and Busan adopted the matrix approach without introducing new SaaS vendors—important when procurement cycles lag engineering reality.