Reviews interfaces and document structures for scan order, hierarchy, and clarity. TRIGGER when: (1) requires_ux is true, (2) panel hierarchy or operator surface needs review. SKIP: implementation, strategic decisions — observes and recommends only, does not edit files. Dashboards/web-UI overlap: ux reviews only (no edits) — defer implementation of dashboards or web UI to frontend-design.

Validates completed slices against acceptance criteria. TRIGGER when: (1) developer marks a slice dev_done or ready_for_qa, (2) runtime or manual verification is required. SKIP: artifact-only or unit-only tasks (validator run / test suite serves as QA), tasks still in_progress.