harden - SKILL.md Agent Skill

name: harden description: "Production-readiness pass — audits and implements the full non-happy-path matrix: loading skeletons, empty states, error messages, partial data, i18n, offline, permissions, and first-run guidance. Use when preparing a surface for production or when the user says "it crashes on empty data" / "there's no loading state" / "harden this". Invoke when the user asks for harden on their UI, or mentions 'harden' alongside design / UI / frontend work."

Context: this sub-skill is one lens of the broader ui-craft skill. If the ui-craft skill is also installed, read its SKILL.md first for Discovery + Anti-Slop + Craft Test, then apply the specific lens below.

Harden the UI at the target the user described for production. Load the ui-craft skill.

Coverage matrix — check every key surface:

Loading — skeletons match the final layout (no CLS on resolve), shown after ~200ms to avoid flash on fast responses. Never a generic centered spinner when a skeleton is possible.
Empty — purposeful: one line explaining why it's empty + one clear primary action. Illustration optional, CTA mandatory.
Error — inline, actionable. "Save failed. Try again / Copy error / Contact support" — never just "Something went wrong." Surface the what and the next step.
Partial data — — (em dash) for missing metrics, never N/A or null or 0 when the value is truly unknown.
Long content — truncation with title tooltip, text-overflow: ellipsis, container queries for constrained regions. Test with a 120-character name.
i18n — no hardcoded strings, ~1.3× text expansion slack for German, narrower glyphs for CJK, RTL flip consideration for icons with direction.
Offline / slow — optimistic UI with reconciliation on failure; skeleton persists past timeout with a "still loading…" affordance.
Permission — what happens when the user lacks access: disabled vs hidden. Always surface a "why" (tooltip, inline helper) when disabled.
Zero-state → first-run — inline hints beat 5-step tours. Guide within the surface, not over it.

Knob-agnostic — correctness is not tunable. Run the full matrix regardless of CRAFT_LEVEL / MOTION_INTENSITY / VISUAL_DENSITY.

References to read: references/accessibility.md (keyboard + screen reader paths), references/copy.md (error and empty-state voice), references/motion.md Rendering Performance section (skeleton motion + reduced-motion).

Output: a per-surface checklist marking each of the 9 items as present / missing / partial. Then edit the code to fix what's missing. Print the Review Format table showing fixes. End with a "still at risk" list for anything you couldn't safely auto-fix (requires backend, requires design decision, requires translation files).