All four affect whether people can use the product.
Baseline → candidate → controlled environment → diff → human decision
An intentional design change should be approved, not silently accepted or automatically called a bug.
Check:
At each viewport, test:
AI can spot possible visual issues.
Confirm with viewport details, DOM/accessibility evidence, keyboard behavior, screenshots, or a human review.
Review the launch preview at 1440px, 768px and 375px plus keyboard-only package selection.
Deliver: annotated evidence and user-impact findings.
At 375px width, the launch preview extends beyond the viewport. Record its measured width and affected content; do not infer a nonexistent overlay or focus trap.
Specific user. Specific condition. Observable impact.
Write one accessibility test that an automated color check would miss.