Contract Verification Gate
A provider's pipeline stage that replays every consumer's recorded expectations and fails the build if any would break.
Contract testing only prevents outages if the verification blocks something. The gate is the mechanism: before a provider can be promoted, its pipeline retrieves the current expectations of every registered consumer, replays them against the candidate build, and fails on any unmet expectation.
This shifts the discovery of a breaking change from the consumer's environment, hours or days later, to the provider's own pipeline, minutes after the change was written and while its author still has the context.
Two operational details determine whether it works at scale. First, the gate must know which consumer versions matter — verifying against every expectation ever recorded means a long-dead consumer blocks the provider forever, so the registry has to track what is actually deployed. Second, a genuinely intended breaking change must have a route through: usually versioning the interface and running both, with the gate enforcing that the old expectations still pass until the last consumer has moved.