fix(skills): address nitpick comments on frontend-a11y

scripts/hooks/cost-tracker.js

@@ -20,54 +20,15 @@
  * Each row therefore represents the cumulative session total up to that point.
  * To get per-session cost, take the last row per session_id. To get per-day
  * spend, aggregate.
- *
- * Harness-cost contract (optional, opt-in by the statusline):
- *   If the user's statusline (which receives `cost.total_cost_usd` directly
- *   from Claude Code) writes `{ts, cost_usd}` to
- *   `<os.tmpdir()>/harness-cost-<session_id>.json` on each render, this hook
- *   prefers that authoritative value over the transcript-sum estimate when
- *   the cache is fresh (≤ 300s). The transcript-sum is kept as a safe
- *   fallback because:
- *     - the hard-coded rate table cannot represent Opus 4.7's >200K-token
- *       2x tier or the 1h-cache 2x tier (under-counts on long sessions);
- *     - summing the full transcript double-counts work done across
- *       `--resume` boundaries while `cost.total_cost_usd` is per-process.
- *   Absent a writer, behavior is unchanged.
  */
 
 'use strict';
 
 const fs = require('fs');
-const os = require('os');
 const path = require('path');
 const { ensureDir, appendFile, getClaudeDir } = require('../lib/utils');
 const { sanitizeSessionId } = require('../lib/session-bridge');
 
-const HARNESS_COST_MAX_AGE_SECONDS = 300;
-
-/**
- * Read authoritative harness cost from the per-session cache file.
- * @param {string} sessionId
- * @param {number} maxAgeSeconds
- * @returns {number|null} cost in USD, or null on miss / stale / parse error
- */
-function readHarnessCost(sessionId, maxAgeSeconds) {
-  if (!sessionId) return null;
-  try {
-    const fp = path.join(os.tmpdir(), `harness-cost-${sessionId}.json`);
-    if (!fs.existsSync(fp)) return null;
-    const obj = JSON.parse(fs.readFileSync(fp, 'utf8'));
-    const ts = Number(obj && obj.ts);
-    const cost = Number(obj && obj.cost_usd);
-    if (!Number.isFinite(ts) || !Number.isFinite(cost) || cost < 0) return null;
-    const age = Math.floor(Date.now() / 1000) - ts;
-    if (age < 0 || age > maxAgeSeconds) return null;
-    return cost;
-  } catch {
-    return null;
-  }
-}
-
 // Approximate per-1M-token billing rates (USD).
 // Cache creation: 1.25x input rate. Cache read: 0.1x input rate.
 const RATE_TABLE = {
@@ -164,23 +125,13 @@ process.stdin.on('end', () => {
     } = usageTotals || {};
 
     const rates = getRates(model);
-    const transcriptCostUsd = Math.round((
+    const estimatedCostUsd = Math.round((
       (inputTokens      / 1e6) * rates.in +
       (outputTokens     / 1e6) * rates.out +
       (cacheWriteTokens / 1e6) * rates.cacheWrite +
       (cacheReadTokens  / 1e6) * rates.cacheRead
     ) * 1e6) / 1e6;
 
-    // Prefer the harness's authoritative `cost.total_cost_usd` when the
-    // statusline has written it to the per-session cache (see contract in
-    // the file header). The harness number reflects API-billed truth
-    // (correct rates, 1h-cache 2x, >200K tier 2x) and is per-process so it
-    // does not drift across `--resume`. Cache miss → transcript-sum.
-    const harnessCost = readHarnessCost(sessionId, HARNESS_COST_MAX_AGE_SECONDS);
-    const estimatedCostUsd = harnessCost !== null
-      ? Math.round(harnessCost * 1e6) / 1e6
-      : transcriptCostUsd;
-
     const metricsDir = path.join(getClaudeDir(), 'metrics');
     ensureDir(metricsDir);
 

skills/frontend-a11y/SKILL.md

@@ -0,0 +1,446 @@
+---
+name: frontend-a11y
+description: >
+  Accessibility patterns for React and Next.js — semantic HTML, ARIA attributes,
+  form labeling, keyboard navigation, focus management, and screen reader support.
+  Use when building any interactive UI component or form.
+origin: community
+---
+
+# Frontend Accessibility Patterns
+
+Practical accessibility patterns for React and Next.js. Covers the issues most commonly flagged in code review: missing form labels, incorrect ARIA usage, non-semantic interactive elements, and broken keyboard navigation.
+
+## When to Activate
+
+- Building or reviewing form components (`<input>`, `<select>`, `<textarea>`)
+- Creating interactive elements (modals, dropdowns, tooltips, tabs)
+- Using `<div>` or `<span>` with `onClick`
+- Adding `aria-*` attributes to any element
+- Implementing keyboard navigation or focus management
+- Receiving accessibility feedback from code review tools (CodeRabbit, ESLint a11y)
+- Building components that must support screen readers
+
+## Form Accessibility
+
+Missing `htmlFor` / `id` pairing and disconnected error messages are the most common issues flagged in code review.
+
+### Label Connection
+
+```tsx
+// BAD: label has no connection to input — screen readers cannot associate them
+<label>Email</label>
+<input type="email" />
+
+// GOOD: htmlFor matches input id
+<label htmlFor="email">Email</label>
+<input id="email" type="email" />
+```
+
+### Required Fields
+
+```tsx
+// BAD: visual-only asterisk conveys nothing to screen readers
+<label htmlFor="email">Email *</label>
+<input id="email" type="email" />
+
+// GOOD: required enables native browser validation; aria-required signals it to screen readers
+<label htmlFor="email">
+  Email <span aria-hidden="true">*</span>
+</label>
+<input id="email" type="email" required aria-required="true" />
+```
+
+### Error Messages
+
+```tsx
+// BAD: error text exists visually but is not linked to the input
+<input id="email" type="email" />
+<span className="error">Invalid email address</span>
+
+// GOOD: aria-describedby connects input to its error message
+// aria-invalid signals the invalid state to screen readers
+<input
+  id="email"
+  type="email"
+  aria-describedby="email-error"
+  aria-invalid={!!error}
+/>
+{error && (
+  <span id="email-error" role="alert">
+    {error}
+  </span>
+)}
+```
+
+### Complete Accessible Form
+
+```tsx
+interface LoginFormProps {
+  onSubmit: (email: string, password: string) => void;
+}
+
+export function LoginForm({ onSubmit }: LoginFormProps) {
+  const [email, setEmail] = useState('');
+  const [password, setPassword] = useState('');
+  const [errors, setErrors] = useState<{ email?: string; password?: string }>({});
+
+  const handleSubmit = (e: React.FormEvent) => {
+    e.preventDefault();
+    const newErrors: typeof errors = {};
+    if (!email) newErrors.email = 'Email is required';
+    if (!password) newErrors.password = 'Password is required';
+    if (Object.keys(newErrors).length) {
+      setErrors(newErrors);
+      return;
+    }
+    onSubmit(email, password);
+  };
+
+  return (
+    <form onSubmit={handleSubmit} noValidate>
+      <div>
+        <label htmlFor="email">
+          Email <span aria-hidden="true">*</span>
+        </label>
+        <input
+          id="email"
+          type="email"
+          value={email}
+          onChange={e => setEmail(e.target.value)}
+          aria-required="true"
+          aria-describedby={errors.email ? 'email-error' : undefined}
+          aria-invalid={!!errors.email}
+          autoComplete="email"
+        />
+        {errors.email && (
+          <span id="email-error" role="alert">
+            {errors.email}
+          </span>
+        )}
+      </div>
+
+      <div>
+        <label htmlFor="password">
+          Password <span aria-hidden="true">*</span>
+        </label>
+        <input
+          id="password"
+          type="password"
+          value={password}
+          onChange={e => setPassword(e.target.value)}
+          aria-required="true"
+          aria-describedby={errors.password ? 'password-error' : undefined}
+          aria-invalid={!!errors.password}
+          autoComplete="current-password"
+        />
+        {errors.password && (
+          <span id="password-error" role="alert">
+            {errors.password}
+          </span>
+        )}
+      </div>
+
+      <button type="submit">Log in</button>
+    </form>
+  );
+}
+```
+
+## Semantic HTML
+
+Use the element that matches the intent. Screen readers and keyboard users depend on native semantics.
+
+```tsx
+// BAD: div has no role, no keyboard support, no accessible name
+<div onClick={handleClick}>Submit</div>
+
+// GOOD: button is focusable, activates on Enter/Space, announces as "button"
+<button type="button" onClick={handleClick}>Submit</button>
+```
+
+```tsx
+// BAD: non-semantic navigation
+<div onClick={() => navigate('/home')}>Home</div>
+
+// GOOD: anchor supports right-click, middle-click, and keyboard navigation
+<a href="/home">Home</a>
+```
+
+```tsx
+// BAD: heading hierarchy skipped (h1 to h4)
+<h1>Dashboard</h1>
+<h4>Recent Activity</h4>
+
+// GOOD: sequential heading levels
+<h1>Dashboard</h1>
+<h2>Recent Activity</h2>
+```
+
+## ARIA Attributes
+
+Use ARIA only when native HTML semantics are insufficient. Wrong ARIA is worse than no ARIA.
+
+### aria-label vs aria-labelledby
+
+```tsx
+// aria-label: inline string label — use when no visible label text exists
+<button aria-label="Close modal">
+  <XIcon />
+</button>
+
+// aria-labelledby: references another element's text — use when a visible label exists
+<section aria-labelledby="section-title">
+  <h2 id="section-title">Recent Orders</h2>
+  {/* content */}
+</section>
+```
+
+### aria-describedby
+
+```tsx
+// Provides supplementary description beyond the label
+<button
+  aria-describedby="delete-warning"
+  onClick={handleDelete}
+>
+  Delete account
+</button>
+<p id="delete-warning">This action cannot be undone.</p>
+```
+
+### aria-live for Dynamic Content
+
+```tsx
+// Use aria-live to announce content that updates without a page reload
+// polite: waits for user to finish current action before announcing
+// assertive: interrupts immediately — use only for urgent errors
+
+export function StatusMessage({ message, isError }: { message: string; isError?: boolean }) {
+  return (
+    <div role="status" aria-live={isError ? 'assertive' : 'polite'} aria-atomic="true">
+      {message}
+    </div>
+  );
+}
+```
+
+### aria-expanded and aria-controls
+
+```tsx
+export function Accordion({ title, children }: { title: string; children: React.ReactNode }) {
+  const [isOpen, setIsOpen] = useState(false);
+  const contentId = useId();
+
+  return (
+    <div>
+      <button aria-expanded={isOpen} aria-controls={contentId} onClick={() => setIsOpen(prev => !prev)}>
+        {title}
+      </button>
+      <div id={contentId} hidden={!isOpen}>
+        {children}
+      </div>
+    </div>
+  );
+}
+```
+
+## Keyboard Navigation
+
+Every interactive element must be reachable and operable by keyboard alone.
+
+### Custom Dropdown
+
+```tsx
+export function Dropdown({ options, onSelect }: { options: string[]; onSelect: (value: string) => void }) {
+  const [isOpen, setIsOpen] = useState(false);
+  const [activeIndex, setActiveIndex] = useState(0);
+  const listId = useId();
+
+  if (!options.length) return null;
+
+  const handleKeyDown = (e: React.KeyboardEvent) => {
+    switch (e.key) {
+      case 'ArrowDown':
+        e.preventDefault();
+        setActiveIndex(i => Math.min(i + 1, options.length - 1));
+        break;
+      case 'ArrowUp':
+        e.preventDefault();
+        setActiveIndex(i => Math.max(i - 1, 0));
+        break;
+      case 'Enter':
+      case ' ':
+        e.preventDefault();
+        if (isOpen) onSelect(options[activeIndex]);
+        setIsOpen(prev => !prev);
+        break;
+      case 'Escape':
+        setIsOpen(false);
+        break;
+    }
+  };
+
+  return (
+    <div
+      role="combobox"
+      aria-expanded={isOpen}
+      aria-haspopup="listbox"
+      aria-controls={listId}
+      tabIndex={0}
+      onKeyDown={handleKeyDown}
+      onClick={() => setIsOpen(prev => !prev)}
+    >
+      <span>{options[activeIndex]}</span>
+      {isOpen && (
+        <ul id={listId} role="listbox">
+          {options.map((option, index) => (
+            <li
+              key={option}
+              role="option"
+              aria-selected={index === activeIndex}
+              onClick={() => {
+                onSelect(option);
+                setIsOpen(false);
+              }}
+            >
+              {option}
+            </li>
+          ))}
+        </ul>
+      )}
+    </div>
+  );
+}
+```
+
+## Focus Management
+
+Focus must move logically when UI state changes — especially for modals and route transitions.
+
+### Modal Focus Restoration
+
+> This example covers initial focus and restoration. For a full focus trap (Tab/Shift+Tab cycling within the modal), use a library like [`focus-trap-react`](https://github.com/focus-trap/focus-trap-react) which handles edge cases like dynamic content and nested portals.
+
+```tsx
+export function Modal({ isOpen, onClose, title, children }: { isOpen: boolean; onClose: () => void; title: string; children: React.ReactNode }) {
+  const modalRef = useRef<HTMLDivElement>(null);
+  const previousFocusRef = useRef<HTMLElement | null>(null);
+
+  useEffect(() => {
+    if (isOpen) {
+      // Save currently focused element and move focus into modal
+      previousFocusRef.current = document.activeElement as HTMLElement;
+      modalRef.current?.focus();
+    } else {
+      // Restore focus to the element that opened the modal
+      previousFocusRef.current?.focus();
+    }
+  }, [isOpen]);
+
+  if (!isOpen) return null;
+
+  return (
+    <div ref={modalRef} role="dialog" aria-modal="true" aria-labelledby="modal-title" tabIndex={-1} onKeyDown={e => e.key === 'Escape' && onClose()}>
+      <h2 id="modal-title">{title}</h2>
+      {children}
+      <button onClick={onClose}>Close</button>
+    </div>
+  );
+}
+```
+
+## Images and Icons
+
+```tsx
+// BAD: decorative icon announced as unlabeled image
+<img src="/icon.svg" />
+
+// GOOD: decorative image hidden from screen readers
+<img src="/decoration.png" alt="" aria-hidden="true" />
+
+// GOOD: meaningful image with descriptive alt text
+<img src="/chart.png" alt="Monthly revenue increased 23% from January to March" />
+
+// GOOD: icon button with accessible label
+<button aria-label="Delete item">
+  <TrashIcon aria-hidden="true" />
+</button>
+```
+
+## Reduced Motion
+
+Respect users who have requested reduced motion in their OS settings.
+
+```tsx
+export function useReducedMotion(): boolean {
+  const [prefersReduced, setPrefersReduced] = useState(false);
+
+  useEffect(() => {
+    const mq = window.matchMedia('(prefers-reduced-motion: reduce)');
+    setPrefersReduced(mq.matches);
+    const handler = (e: MediaQueryListEvent) => setPrefersReduced(e.matches);
+    mq.addEventListener('change', handler);
+    return () => mq.removeEventListener('change', handler);
+  }, []);
+
+  return prefersReduced;
+}
+
+// Usage
+export function AnimatedCard({ children }: { children: React.ReactNode }) {
+  const reduceMotion = useReducedMotion();
+
+  return (
+    <div
+      style={{
+        transition: reduceMotion ? 'none' : 'transform 300ms ease'
+      }}
+    >
+      {children}
+    </div>
+  );
+}
+```
+
+## Anti-Patterns
+
+```tsx
+// BAD: onClick on non-interactive element with no keyboard support
+<div onClick={handleClick}>Click me</div>
+
+// BAD: aria-label on a div that has no role
+<div aria-label="Navigation">...</div>
+
+// BAD: placeholder used as a substitute for label
+<input placeholder="Enter your email" />
+
+// BAD: positive tabIndex creates unpredictable tab order
+<button tabIndex={3}>Submit</button>
+
+// BAD: aria-hidden on a focusable element — keyboard users get trapped
+<button aria-hidden="true">Open</button>
+
+// BAD: role="button" on div without keyboard handler
+<div role="button" onClick={handleClick}>Submit</div>
+// Missing: tabIndex={0}, onKeyDown for Enter/Space
+```
+
+## Checklist
+
+Before submitting any interactive component for review:
+
+- [ ] Every `<input>`, `<select>`, and `<textarea>` has a connected `<label>` via `htmlFor`/`id`
+- [ ] Error messages are linked with `aria-describedby` and marked `role="alert"`
+- [ ] No `onClick` on `<div>` or `<span>` without `role`, `tabIndex`, and `onKeyDown`
+- [ ] Icon-only buttons have `aria-label`
+- [ ] Decorative images use `alt=""` and `aria-hidden="true"`
+- [ ] Modals restore focus on close (for full focus trapping with Tab/Shift+Tab cycling, use a library like `focus-trap-react`)
+- [ ] Dynamic content updates use `aria-live`
+- [ ] `prefers-reduced-motion` is respected for animations
+
+## Related Skills
+
+- `frontend-patterns` — general React component and state patterns
+- `design-system` — design token and component consistency
+- `motion-ui` — animation patterns with accessibility considerations

tests/hooks/cost-tracker.test.js

@@ -215,93 +215,6 @@ function runTests() {
     fs.rmSync(tmpHome, { recursive: true, force: true });
   }) ? passed++ : failed++);
 
-  // 8. Prefers harness-cost cache value over transcript-sum when fresh
-  (test('prefers fresh harness-cost cache over transcript estimate', () => {
-    const tmpHome = makeTempDir();
-    const sessionId = 'harness-fresh-' + Date.now();
-    const transcriptPath = path.join(tmpHome, 'session.jsonl');
-    writeTranscript(transcriptPath, [
-      {
-        type: 'assistant',
-        message: {
-          model: 'claude-opus-4-20250514',
-          usage: {
-            input_tokens: 10000,
-            output_tokens: 5000,
-            cache_creation_input_tokens: 200000,
-            cache_read_input_tokens: 1000000,
-          },
-        },
-      },
-    ]);
-    const harnessCachePath = path.join(os.tmpdir(), `harness-cost-${sessionId}.json`);
-    const nowEpoch = Math.floor(Date.now() / 1000);
-    fs.writeFileSync(
-      harnessCachePath,
-      JSON.stringify({ ts: nowEpoch, cost_usd: 1.23 }),
-      'utf8'
-    );
-
-    try {
-      const result = runScript(
-        { session_id: sessionId, transcript_path: transcriptPath },
-        withTempHome(tmpHome)
-      );
-      assert.strictEqual(result.code, 0, `Expected exit code 0, got ${result.code}`);
-
-      const metricsFile = path.join(tmpHome, '.claude', 'metrics', 'costs.jsonl');
-      const row = JSON.parse(fs.readFileSync(metricsFile, 'utf8').trim());
-      assert.strictEqual(row.estimated_cost_usd, 1.23, 'Expected harness cost to win');
-      // Token totals still reflect the transcript scan
-      assert.strictEqual(row.input_tokens, 10000, 'Token totals should still come from transcript');
-      assert.strictEqual(row.output_tokens, 5000, 'Token totals should still come from transcript');
-    } finally {
-      try { fs.unlinkSync(harnessCachePath); } catch { /* best-effort */ }
-      fs.rmSync(tmpHome, { recursive: true, force: true });
-    }
-  }) ? passed++ : failed++);
-
-  // 9. Ignores stale harness-cost cache and falls back to transcript estimate
-  (test('ignores stale harness-cost cache (>300s) and uses transcript estimate', () => {
-    const tmpHome = makeTempDir();
-    const sessionId = 'harness-stale-' + Date.now();
-    const transcriptPath = path.join(tmpHome, 'session.jsonl');
-    writeTranscript(transcriptPath, [
-      {
-        type: 'assistant',
-        message: {
-          model: 'claude-sonnet-4-20250514',
-          usage: { input_tokens: 1000, output_tokens: 500 },
-        },
-      },
-    ]);
-    const harnessCachePath = path.join(os.tmpdir(), `harness-cost-${sessionId}.json`);
-    const staleEpoch = Math.floor(Date.now() / 1000) - 3600;
-    fs.writeFileSync(
-      harnessCachePath,
-      JSON.stringify({ ts: staleEpoch, cost_usd: 999.99 }),
-      'utf8'
-    );
-
-    try {
-      const result = runScript(
-        { session_id: sessionId, transcript_path: transcriptPath },
-        withTempHome(tmpHome)
-      );
-      assert.strictEqual(result.code, 0, `Expected exit code 0, got ${result.code}`);
-
-      const metricsFile = path.join(tmpHome, '.claude', 'metrics', 'costs.jsonl');
-      const row = JSON.parse(fs.readFileSync(metricsFile, 'utf8').trim());
-      assert.notStrictEqual(row.estimated_cost_usd, 999.99, 'Stale cache must not win');
-      assert.ok(row.estimated_cost_usd > 0, 'Expected fallback transcript estimate to be positive');
-      // Sonnet rates: 1000/1e6*3 + 500/1e6*15 ≈ $0.011 — well below the 999.99 stale value
-      assert.ok(row.estimated_cost_usd < 1, 'Expected small transcript estimate, not the stale 999.99');
-    } finally {
-      try { fs.unlinkSync(harnessCachePath); } catch { /* best-effort */ }
-      fs.rmSync(tmpHome, { recursive: true, force: true });
-    }
-  }) ? passed++ : failed++);
-
   console.log(`\nResults: Passed: ${passed}, Failed: ${failed}`);
   process.exit(failed > 0 ? 1 : 0);
 }