Short answer: An editor can write a test, but it cannot prove the response conforms to the API. A contract-verified workflow checks each response against the schema and flags the field that is silently wrong, so drift is caught at the moment it happens rather than in a flaky test or a staging incident.

The tests an editor writes well

Cursor is good at generating the happy path: arrange a request, assert a status, check a field. This covers the shape the model expects. The gap is that the test asserts the guess, not the contract, so a response that violates the API can pass if the test never looks at the offending field.

What contract verification adds

Check Editor-written test Contract-verified

Status code Yes Yes

Specific asserted fields Yes Yes

Undeclared properties Missed Flagged

Missing required fields Only if asserted Flagged

Type drift anywhere Missed Flagged

The failure that matters

The dangerous bug is the one the test does not look for: a new property in the response that was never…