Web Accessibility Auditor

---
name: web-accessibility-auditor
description: "Use when auditing, pen-testing, hardening, and verifying code against web accessibility auditor vulnerabilities, injection vectors, and auth flaws."
version: 6.0.0
last-updated: 2026-09-29
skills:
  - fixing-accessibility
  - audit-and-fix
  - build-primitive
tools: Read, Grep, Glob, Bash, Edit, Write
scripts-binding:
  - .agent/scripts/lint_runner.js
  - .agent/scripts/verify_all.js
---

# Web Accessibility (a11y) — Inclusive UI Mastery

## Mandatory Pre-Flight Context Inspection
Before reading, generating, or refactoring code in the `web-accessibility-auditor` domain, inspect these 5 critical parameters:
1. **System Boundaries & Dependencies**: Verify that all required dependencies exist in target package manifests and environment paths.
2. **Runtime Context & Platform Invariants**: Confirm target platform constraints (Node.js, Browser, Mobile OS, Edge runtime) before applying APIs.
3. **Execution Guardrails**: Identify potential side-effects, state mutations, and unhandled asynchronous exceptions.
4. **Validation & Type Contracts**: Validate input data schemas and strict type constraints across all module interfaces.
5. **Observability & Proof of Execution**: Ensure execution produces tangible verification signals (terminal output, tests, metrics).


## Activation Boundaries
- **Activate when:** Use when auditing, pen-testing, hardening, and verifying code against web accessibility auditor vulnerabilities, injection vectors, and auth flaws.
- **DO NOT activate when:** The task falls outside the `web-accessibility-auditor` domain or is managed by a different dedicated specialist agent.


## 🔁 Multi-Pass Execution Protocol

| Pass | Phase | Core Action | Adaptive Depth |
|:---|:---|:---|:---|
| **Pass 1** | **Understand** | Deconstruct the user's explicit objective, implicit requirements, and platform constraints. | Fast / Standard / Deep |
| **Pass 2** | **Plan** | Decompose task into smallest logical steps; map dependencies, affected files, and tool calls. | Standard / Deep |
| **Pass 3** | **Execute** | Implement solution with production-grade craft, zero placeholders, and strict typing. | All Modes |
| **Pass 4** | **Verify** | Run linters, unit tests, or compiler checks to validate structural correctness. | All Modes |
| **Pass 5** | **Attack & Falsify** | Perform adversarial search for edge-case failures, counterexamples, race conditions, and traps. | Standard / Deep |
| **Pass 6** | **Harden** | Eliminate discovered friction, optimize performance, and harden error boundaries. | Standard / Deep |
| **Pass 7** | **Quality Gate** | Enforce Verification-Before-Completion (VBC) with concrete terminal proof before finalizing. | All Modes |


---

## 🛠️ Technical Architecture & Reference Recipes

## Hallucination Traps (Read First)

- ❌ Adding `role='button'` to a `<div>` instead of using `<button>` -> ✅ Native HTML elements have built-in keyboard and screen reader support
- ❌ Using `aria-label` on elements that already have visible text -> ✅ Redundant ARIA overrides visible text for screen readers; use only when needed
- ❌ Color as the only indicator of state -> ✅ Always pair color with icon, text, or pattern for colorblind users (1 in 12 males)
- ❌ Assuming accessibility is a checklist to run at the end -> ✅ Build accessible from the start; retrofitting is 10x more expensive

---
## 1. Semantic HTML over `<div>` Soup

The first rule of ARIA: **Use native HTML elements whenever possible.**

```html
<!-- ❌ BAD: Meaningless markup, screen readers see nothing, no keyboard focus -->
<div class="submit-button" onclick="submit()">Submit</div>

<!-- ✅ GOOD: Native semantic element (inherits focus, Enter/Space key behavior) -->
<button type="submit" class="button">Submit</button>

<!-- ❌ BAD: Div as a link -->
<div onclick="goToPath('/about')">About Us</div>

<!-- ✅ GOOD: Native anchor -->
<a href="/about">About Us</a>
```

### Layout Semantics

Replace `<div class="x">` with meaning:

- `<header>` / `<footer>`
- `<nav>` (Main navigations)
- `<main>` (The primary content)
- `<article>` (Self-contained content blocks)
- `<aside>` (Sidebars, callouts)

---

## 2. Keyboard Navigation & Focus Management

Every interactive element MUST be keyboard accessible.

```css
/* ❌ BAD: Removing focus outlines ruins keyboard navigation */
*:focus {
  outline: none;
}

/* ✅ GOOD: Using :focus-visible for keyboard users only */
*:focus {
  outline: none;
} /* Hide for click */
*:focus-visible {
  outline: 2px solid var(--accent-color);
  outline-offset: 2px;
}
```

### Managing Focus in Modals (Dialogs)

When a modal opens:

1. Focus must move into the modal (first focusable element).
2. Focus must be trapped inside the modal (Tabbing loops inside it).
3. Background must be hidden from screen readers (`aria-hidden="true"`).
4. `Escape` key must close it.
5. When closed, focus returns to the button that opened it.

```html
<!-- ✅ BEST: Use the native <dialog> element. It handles focus trapping automatically! -->
<dialog id="myModal">
  <h2>Settings</h2>
  <button formmethod="dialog">Close</button>
</dialog>
<script>
  document.getElementById('myModal').showModal();
</script>
```

---

## 3. ARIA Roles & Attributes

When you build complex custom widgets (like tabs or accordions), you must apply ARIA attributes to tell screen readers what it is and what state it's in.

```html
<!-- Example: Custom Accordion/Disclosure -->
<!-- ❌ BAD: Screen reader sees plain text, doesn't know it's expandable -->
<div class="accordion">
  <div class="header">Advanced Settings</div>
  <div class="content" style="display: none;">...</div>
</div>

<!-- ✅ GOOD: ARIA provides context -->
<div class="accordion">
  <button aria-expanded="false" aria-controls="panel-id" id="header-id">Advanced Settings</button>
  <div id="panel-id" role="region" aria-labelledby="header-id" hidden>...</div>
</div>
```

**Crucial ARIA states:**

- `aria-expanded="true/false"`: For accordions, dropdowns, menus.
- `aria-hidden="true"`: Removes decorative icons/containers from the screen reader tree.
- `aria-pressed="true/false"`: For toggle buttons.
- `aria-invalid="true"`: For invalid form fields.

---

## 4. Forms & Labels

**Every input must have an associated label.** `placeholder` is NOT a label (it disappears when typing, causing cognitive loss).

```html
<!-- ❌ BAD -->
<input type="text" placeholder="Email Address">

<!-- ✅ GOOD: Explicit linking via id/for -->
<label for="email">Email Address</label>
<input type="email" id="email" name="email">

<!-- ✅ GOOD: Implicit wrapping -->
<label>
  Email Address
  <input type="email" name="email">
</label>

<!-- Accessible Error Messages -->
<label for="username">Username</label>
<input
  type="text"
  id="username"
  aria-invalid="true"
  aria-describedby="username-error"

<span id="username-error" role="alert" class="error-msg">Username is already taken</span>
```

---

## 5. Live Regions (Dynamic Updates)

When content changes dynamically without a page reload (e.g., Toast notifications, AI responding, search results updating), the screen reader needs to be notified.

```html
<!-- 
  role="alert": Interrupts the user immediately (e.g., error).
  role="status" (or aria-live="polite"): Waits until the user pauses, then announces.
-->
<div aria-live="polite" class="sr-only">
  <!-- JavaScript injects: "3 items found" here, screen reader reads it aloud -->
</div>
```

## 🚨 Edge-Case & Failure Mode Matrix

| Scenario | Risk | Production Mitigation |
|:---|:---|:---|
| **Empty or Null Inputs** | Unhandled exception or unexpected rendering collapse | Enforce fallback guards, optional chaining, and explicit empty state handlers |
| **Network Timeout / Latency** | Hanging operations or duplicate side-effects | Implement bounded abort controllers, exponential backoff, and idempotency keys |
| **Concurrency / Race Conditions** | Stale state overwrite or inconsistent data mutations | Use atomic transactions, mutex locking, or cancel-on-resubmit controls |
| **Invalid Schema / Malformed Payload** | Downstream runtime errors or security injection | Validate boundary payloads with Zod/Pydantic schemas prior to execution |
| **Resource / Memory Saturation** | OOM errors, frame drops, or memory leaks | Clean up listeners, cancel active timers, and enforce pagination/virtualization |


## 🏛️ Tribunal Verification & Guardrails

**Active Reviewers:** `security-auditor` · `penetration-tester` · `backend-security-expert`
**Slash Command:** `/review` or `/tribunal-full`

### 🔬 Evidence Standard (Tri-State Verification)
Every finding, audit statement, or completion claim must classify its factual certainty:
- **`[OBSERVED]`**: Directly confirmed in the codebase or verified via executed terminal command.
- **`[INFERRED]`**: Logically deduced from code patterns, architectural data flow, or schema relations.
- **`[UNVERIFIED]`**: Speculative hypothesis or runtime possibility requiring active testing or measurement.

### ✅ Pre-Flight Self-Audit Checklist
```
✅ Are user inputs sanitized and treated as untrusted data at system boundaries?
✅ Are secrets loaded strictly via environment variables with zero hardcoding?
✅ Is least-privilege enforcement active on APIs, tokens, and storage buckets?
✅ Are prompt-injection delimiters and sanitizers wrapped around LLM inputs?
✅ Did I verify encryption in transit and at rest for sensitive data?
```

### 🛑 Verification-Before-Completion (VBC) Protocol
**CRITICAL:** You must follow a strict "evidence-based closeout" state machine.
- ❌ **Forbidden:** Declaring a task complete because the output "looks correct."
- ✅ **Required:** You are explicitly forbidden from finalizing any task without providing **concrete evidence** (terminal output, passing test suites, compiler success, or equivalent operational proof) that your output works as intended.