design-ux — usability audit (heuristic evaluation)

Usability ≠ aesthetics. design-system/design-spatial make it look right; this checks whether a first-timer can do the task without being told how. Use it whenever a UI "sucks to use," needs a paragraph of instructions, or before shipping anything interactive.

Rule 0 — fresh eyes, on the rendered artifact (inherited from design-spatial §1)

Never self-grade. The builder rationalizes its own UI. Render the live UI in its default first-load state (not a hand-arranged screenshot), capture an interaction trace of the primary task, and have a separate judge (a subagent/VLM that did NOT build it) score it. A described list of changes is not an audit — the audit is a fresh judge hunting for what's wrong on the real screen.

The procedure

1. Name the primary task(s) the UI exists for (e.g. "trim a clip and set its speed, then export"). The audit is relative to these, not to abstract prettiness.
2. Render default state + trace the task. Screenshot the first-load UI (wide AND narrow — overflow gate from design-spatial §2). Then actually perform the primary task and screenshot each step.
3. Score every heuristic (table below) on the artifact: pass / violation, severity (blocker / major / minor), a specifically located finding, and a concrete fix. Separate judge does this.
4. Prioritize: blockers → majors → minors; cluster fixes that touch the same surface.
5. Fix, then RE-RENDER and RE-SCORE. Do not claim fixed without re-auditing the new artifact (verify-outputs-rule).

Heuristics — score each (Nielsen's 10, 1994) + interaction add-ons