diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..eeea9f5
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,17 @@
+name: CI
+on:
+  pull_request:
+    branches: [main]
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+      - run: npm ci
+      - run: npx playwright install --with-deps chromium
+      - run: npm run validate
+      - run: npm run export:images
+      - run: npm run export:pptx
diff --git a/CLAUDE.md b/CLAUDE.md
index d41dc51..d1a5c58 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -149,12 +149,14 @@ ai-agent-patterns/
 │   └── svg/
 │       └── pattern-*.svg
 ├── scripts/
+│   ├── validate-patterns.js
 │   ├── export-images.js
 │   ├── export-pptx.js
 │   └── export-pdf.js
 └── .github/
     └── workflows/
-        └── deploy.yml   ← GitHub Pages deploy action
+        ├── deploy.yml   ← GitHub Pages deploy action
+        └── ci.yml       ← PR validation (schema + export smoke test)
 ```
 
 ---
@@ -190,6 +192,31 @@ jobs:
 
 ---
 
+## GitHub Actions — PR validation
+
+Path: `.github/workflows/ci.yml`
+
+Runs on every pull request targeting `main`. Two layers of validation,
+both driven by loading `index.html` in headless Chromium so they exercise
+the real `PATTERNS` data and renderer rather than a separate copy:
+
+1. `npm run validate` (`scripts/validate-patterns.js`) — checks every
+   pattern against the schema documented above (required fields, valid
+   `cat`/`group`/`kind` enums, `members` present when `kind` is set,
+   no duplicate names, and that every distinct `statefulness` value has
+   a matching entry in `STATEFULNESS_INFO` so the tooltip never renders
+   empty).
+2. `npm run export:images` / `npm run export:pptx` — runs the real export
+   scripts end-to-end as a smoke test. A thrown error here means the
+   renderer or PATTERNS data broke something the schema check can't see
+   (e.g. a layout exception), not just a malformed field.
+
+This does not catch visual regressions (e.g. a node clipped at the edge
+of its SVG `viewBox`) — only crashes and schema violations. Visual
+changes to the diagrams still need a manual screenshot check.
+
+---
+
 ## README (generate this)
 
 Claude Code should generate a `README.md` that includes:
diff --git a/package.json b/package.json
index b5d793a..22c0afe 100644
--- a/package.json
+++ b/package.json
@@ -4,6 +4,7 @@
   "private": true,
   "description": "Export tooling for the AI Agent Design Patterns interactive reference",
   "scripts": {
+    "validate": "node scripts/validate-patterns.js",
     "export:images": "node scripts/export-images.js",
     "export:pptx": "node scripts/export-pptx.js"
   },
diff --git a/scripts/validate-patterns.js b/scripts/validate-patterns.js
new file mode 100644
index 0000000..64904ed
--- /dev/null
+++ b/scripts/validate-patterns.js
@@ -0,0 +1,103 @@
+const path = require('path');
+const { chromium } = require('playwright');
+
+const ROOT = path.resolve(__dirname, '..');
+const INDEX_HTML = path.join(ROOT, 'index.html');
+
+const GROUPS = new Set(['single', 'multi']);
+const CATS = new Set(['llm', 'tool', 'data', 'multi']);
+const FLOW_CATS = new Set(['neutral', 'llm', 'tool', 'data', 'multi']);
+const KINDS = new Set(['parallel', 'branch']);
+const REQUIRED_STRING_FIELDS = [
+  'section', 'group', 'name', 'sub', 'cat', 'catLabel',
+  'desc', 'uses', 'complexity', 'agents', 'loops', 'statefulness',
+];
+
+function errorsForPattern(p, i) {
+  const errs = [];
+  const where = `PATTERNS[${i}]${p && p.name ? ` (${p.name})` : ''}`;
+
+  for (const field of REQUIRED_STRING_FIELDS) {
+    if (typeof p[field] !== 'string' || p[field].trim() === '') {
+      errs.push(`${where}: missing or empty "${field}"`);
+    }
+  }
+  if (!GROUPS.has(p.group)) errs.push(`${where}: invalid group "${p.group}"`);
+  if (!CATS.has(p.cat)) errs.push(`${where}: invalid cat "${p.cat}"`);
+  if (p.loop !== undefined && typeof p.loop !== 'boolean') {
+    errs.push(`${where}: "loop" must be a boolean if present`);
+  }
+  if (!Array.isArray(p.flow) || p.flow.length === 0) {
+    errs.push(`${where}: "flow" must be a non-empty array`);
+    return errs;
+  }
+
+  p.flow.forEach((step, j) => {
+    const stepWhere = `${where}.flow[${j}]`;
+    if (typeof step.label !== 'string' || step.label.trim() === '') {
+      errs.push(`${stepWhere}: missing or empty "label"`);
+    }
+    if (!FLOW_CATS.has(step.cat)) {
+      errs.push(`${stepWhere}: invalid cat "${step.cat}"`);
+    }
+    if (step.kind !== undefined) {
+      if (!KINDS.has(step.kind)) {
+        errs.push(`${stepWhere}: invalid kind "${step.kind}"`);
+      }
+      if (!Array.isArray(step.members) || step.members.length === 0) {
+        errs.push(`${stepWhere}: "members" must be a non-empty array when "kind" is set`);
+      } else if (step.members.some((m) => typeof m !== 'string' || m.trim() === '')) {
+        errs.push(`${stepWhere}: "members" must contain only non-empty strings`);
+      }
+    }
+  });
+
+  return errs;
+}
+
+async function main() {
+  const browser = await chromium.launch();
+  const page = await browser.newPage();
+  await page.goto(`file://${INDEX_HTML}`);
+  const { patterns, statefulnessInfo } = await page.evaluate(() => ({
+    patterns: PATTERNS,
+    statefulnessInfo: typeof STATEFULNESS_INFO !== 'undefined' ? STATEFULNESS_INFO : null,
+  }));
+  await browser.close();
+
+  const errors = [];
+
+  if (!Array.isArray(patterns) || patterns.length === 0) {
+    errors.push('PATTERNS must be a non-empty array');
+  } else {
+    patterns.forEach((p, i) => errors.push(...errorsForPattern(p, i)));
+
+    const names = patterns.map((p) => p.name).filter(Boolean);
+    const dupes = names.filter((n, i) => names.indexOf(n) !== i);
+    if (dupes.length) {
+      errors.push(`Duplicate pattern name(s): ${[...new Set(dupes)].join(', ')}`);
+    }
+
+    if (statefulnessInfo) {
+      const statefulnessValues = new Set(patterns.map((p) => p.statefulness).filter(Boolean));
+      for (const value of statefulnessValues) {
+        if (!statefulnessInfo[value]) {
+          errors.push(`No STATEFULNESS_INFO entry for statefulness value "${value}" — the tooltip will be empty`);
+        }
+      }
+    }
+  }
+
+  if (errors.length) {
+    console.error(`Found ${errors.length} problem(s) in PATTERNS:\n`);
+    errors.forEach((e) => console.error(`  - ${e}`));
+    process.exit(1);
+  }
+
+  console.log(`PATTERNS schema OK (${patterns.length} patterns).`);
+}
+
+main().catch((err) => {
+  console.error(err);
+  process.exit(1);
+});