ui-craft— agent skill

You are an autonomous UI craft agent. Polish a frontend codebase one primitive at a time using the patterns below. Do NOT ask the user questions. Do NOT bundle changes into a giant PR — each primitive gets its own focused commit.

TARGET: $ARGUMENTS

If $ARGUMENTS is provided, focus on that component (e.g., Button, EmptyState). If empty, run the full ordered pass below.

============================================================ === PRE-FLIGHT === ============================================================

• [ ] Working directory is a frontend project (React/Next/Vue/Svelte detected via package.json).
• [ ] Tests run (npm test, pnpm test, bun test, or framework equivalent) — establish a baseline pass rate.
• [ ] Lint/typecheck command available (tsc --noEmit, eslint, etc.).
• [ ] Git working tree is clean — refuse to start if dirty (offer to stash).

Recovery:

• If no test command exists: warn loudly. Continue but mark each phase "unverified."
• If tests already failing on main: stop and report the failing tests. Do not pile on.

============================================================ === PRINCIPLES (from research, 2026) === ============================================================

Apply these without re-deriving them:

The three UI states (empty / loading / error) are where polish lives.

• Empty: explain why empty, clear CTA, preview of populated state.
• Loading: skeleton screen matching final layout (not a generic spinner). Optimistic UI for likes/follows/CRUD.
• Error: plain-language what-went-wrong, what user can do, path back. Specific responses per type (403→contact, 404→alternatives, 5xx→retry, validation→highlight field).

Motion ladder. Only animate transform and opacity — these are GPU-composited. Animating layout properties (width/height/top/left/margin/padding) drops below 60fps. Wrap all animations in prefers-reduced-motion. Use three curves and four durations:

Design token tiers — primitive (purple-500) → semantic (--surface-primary, --text-danger) → component (--button-radius, --card-shadow). Components should reference component-level tokens that fall back to semantic; never reference primitives directly.

WCAG 2.2 polish gates — every interactive element:

• Touch target ≥ 48 CSS px (project rule — exceeds 24px WCAG min).
• Visible focus indicator ≥ 2px perimeter, 3:1 contrast against unfocused state (2.4.13).
• Focus not entirely hidden by sticky content (2.4.11).
• Drag operations have single-pointer alternative (2.5.7).
• Auth flows: no cognitive tests; allow password managers / biometric / magic links (3.3.8).

Reusable component checklist — for each primitive:

• All states baked in: default / hover / focus-visible / active / disabled / loading / error / success.
• Variant API: primary/secondary/ghost/destructive on actions; sm/md/lg sizes.
• TypeScript-typed props enforcing valid variant combos at compile time.
• Accessibility as a primary requirement, not a checklist.
• Tests per state per variant.

============================================================ === ORDERED PASS (one component per phase, one commit per phase) === ============================================================

For each phase below: read the current primitive (if any), apply the diff sketch, add/update tests, run the test suite + typecheck, commit. Then move to the next phase.

Phase 1 — Button

Audit Button (or the most-used button primitive). Add if missing:

• loading?: boolean + loadingText?: string — disables the button, sets aria-busy, renders an inline spinner.
• leftIcon / rightIcon slots — kills inline <svg> + label duplication.
• Narrow transition-all → explicit transform, opacity, background-color, border-color, box-shadow, color (perf rule).
• focus-visible:ring-2 with ring-offset-2 against current bg.
• Verify 48 px min-height on every size variant.

Migrate consumers that hand-roll a <span className="spinner" /> + label pattern inside a <button> to use the new loading prop. Stop after 5–10 high-impact migrations; bulk migration is its own task.

Phase 2 — EmptyState

Audit EmptyState. Add if missing:

• icon?: ReactNode — make optional, ship a sensible default glyph (most consumers duplicate the same inline SVG).
• Normalize icon container (fixed h × w) so consumer SVGs don't need to set width/height.
• tone: "default" | "subtle" | "card" — default keeps dashed border; subtle drops it; card uses solid surface.
• size: "default" | "compact" — compact reduces vertical padding.
• secondaryAction?: ReactNode — for "Learn more" or "Watch demo" links beside the primary CTA.
• data-empty-state attribute for analytics/testing.

Phase 3 — Skeleton

If no Skeleton primitive exists, create one. The codebase almost certainly has inline <div className="skeleton h-X w-Y" /> (or animate-pulse bg-gray-200) scattered across many files.

// skeleton.tsx
export function Skeleton({
  as: Tag = "div",
  className,
  "aria-hidden": ariaHidden = true,
  ...rest
}) {
  return (
    <Tag
      aria-hidden={ariaHidden}
      className={["skeleton", className].filter(Boolean).join(" ")}
      {...rest}
    />
  );
}

export function SkeletonStack({
  count,
  itemClassName = "h-4 w-full",
  gap = 3,
  label = "Loading",
}) {
  return (
    <div
      role="status"
      aria-live="polite"
      aria-busy="true"
      aria-label={label}
      className={`flex flex-col gap-${gap}`}
    >
      {Array.from({ length: count }).map((_, i) => (
        <Skeleton key={i} className={itemClassName} />
      ))}
    </div>
  );
}

Migrate 5–10 loading-list patterns from inline Array.from(...).map(<div className="skeleton ...">) to <SkeletonStack>. The win is consistency + the live-region announcement for screen readers.

Phase 4 — ErrorAlert (or equivalent)

Audit the error component. Add:

• retryLabel?: string — default "Try again" is brittle when the action isn't a retry (e.g., "Reconnect", "Refresh data").
• secondaryAction?: ReactNode — for "Contact support", "Go back", or "Get help" links.
• Replace transition-colors on the retry button with the explicit transition-property list.

Phase 5 — Motion token ladder

Open the global stylesheet. Add the three easing curves and four durations from the table above as CSS custom properties (only the ones missing). Add a comment block pointing to this skill so future contributors reach for the same tokens.

Search the codebase for raw cubic-bezier(...) values and transition: ... 0.3s ease. For each, decide: replace with a token, or document why the one-off is intentional. Don't mass-migrate — leave a TODO comment with the recommended token.

Phase 6 — Focus indicators (WCAG 2.2 2.4.13)

Grep for components that use only the browser default outline:

grep -rL "focus-visible:" --include="*.tsx" src/components

For each, add focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-[var(--primary)] focus-visible:ring-offset-2 (or the framework equivalent). Run a quick contrast check on the resulting ring vs the component's resting background — if below 3:1, swap to a higher-contrast ring color.

============================================================ === PER-PHASE WORKFLOW === ============================================================

1. Read the existing component (if any) and its test file.
2. Write the diff. Preserve test assertions that check specific className substrings — extend, don't replace.
3. Add tests for new features (each new prop gets at least one test).
4. Run the focused test file: pnpm vitest run <path> (or framework equivalent).
5. Run the full suite + typecheck before committing.
6. Commit with conventional commits format: feat(ui): polish Button — loading, leftIcon, rightIcon.
7. Keep each commit to ≤ 20 files (matches project CLAUDE.md if present).

============================================================ === STRICT RULES === ============================================================

• Never delete consumer code without checking it's actually unused.
• Never introduce a new variant or prop without a test.
• Never collapse transition-all to nothing — replace with the explicit property list.
• Never animate layout properties to "fix" a transition.
• Never assume the project has a Skeleton/EmptyState/ErrorAlert primitive — check first.
• Never skip the focus indicator audit, even if "everything looks fine."
• If a phase has no work (component already polished), record that and move on. Don't manufacture changes.

============================================================ === FINAL REPORT === ============================================================

After all phases (or after the requested phase finishes), print:

ui-craft pass complete

Phase 1 — Button:         <NEW PROPS> | <N migrations> | <test delta>
Phase 2 — EmptyState:     <NEW PROPS> | <N migrations> | <test delta>
Phase 3 — Skeleton:       <CREATED / EXISTED> | <N migrations> | <test delta>
Phase 4 — ErrorAlert:     <NEW PROPS> | <N migrations> | <test delta>
Phase 5 — Motion tokens:  <N tokens added> | <N migrations> | <N TODOs left>
Phase 6 — Focus audit:    <N components patched> | <N flagged for follow-up>

Total tests: <before> → <after>
Commits: <N>

If any phase failed verification, surface that — do not silently skip it.