Your Service Passes All Tests But Breaks Production: Detecting Inter-Service API Regression

TL;DR: The most dangerous bugs in microservices are not inside a service. They are between services. A code change can make a service pass all its local tests while silently altering what it sends to downstream APIs: different payload, missing header, changed error format. These regressions are invisible to unit tests, hard to catch with contract tests, and expensive in production. BitDive detects them by capturing real HTTP exchanges in execution traces and comparing them before and after a code change. The Bug That All Tests Miss Here is a scenario every microservices team has experienced at least once: A developer updates a shared library or changes a DTO mapping. All unit tests pass. The integration test suite is green. The service deploys to production. Hours later: a downstream service starts throwing deserialization errors, or silently processing wrong data. The root cause: the service changed how it interacts with other services at the HTTP level. The actual bytes it sends over