Qualitative taste validation.

humans (not agents) test for taste / UX / defect discovery, not just correctness. Delivered either via a dedicated usability research service (Netizen Experience, UserTesting, Lookback, Maze, PlaybookUX) or via your own user base through canary releases and A/B tests. Catches what automated tests can't: is this confusing? Does this feel wrong? Would a real user hit this edge case?