diff --git a/package.json b/package.json
index cf44ebe9b..619883cae 100644
--- a/package.json
+++ b/package.json
@@ -42,8 +42,8 @@
   "scripts": {
     "build:skills": "bun run scripts/build.js --skip-root-sync",
     "build:skills:release": "bun run scripts/build.js",
-    "build": "bun run build:skills && mkdir -p build/_data && rm -rf build/_data/dist && cp -R dist build/_data/dist",
-    "build:release": "bun run build:skills:release && mkdir -p build/_data && rm -rf build/_data/dist && cp -R dist build/_data/dist",
+    "build": "node scripts/build-static-html-parsers.js --check && bun run build:skills && mkdir -p build/_data && rm -rf build/_data/dist && cp -R dist build/_data/dist",
+    "build:release": "node scripts/build-static-html-parsers.js --check && bun run build:skills:release && mkdir -p build/_data && rm -rf build/_data/dist && cp -R dist build/_data/dist",
     "build:browser": "node scripts/build-browser-detector.js",
     "build:static-html-parsers": "node scripts/build-static-html-parsers.js",
     "build:extension": "node scripts/build-extension.js",
diff --git a/scripts/build-static-html-parsers.js b/scripts/build-static-html-parsers.js
index ee51e4415..9bf785cda 100644
--- a/scripts/build-static-html-parsers.js
+++ b/scripts/build-static-html-parsers.js
@@ -5,9 +5,11 @@
  * by bundling htmlparser2, css-select, css-tree, and domutils for skill/plugin installs.
  *
  * Run: node scripts/build-static-html-parsers.js
+ * Check: node scripts/build-static-html-parsers.js --check
  */
 
 import fs from 'fs';
+import os from 'node:os';
 import path from 'path';
 import { fileURLToPath } from 'url';
 import { spawnSync } from 'node:child_process';
@@ -18,29 +20,48 @@ const ROOT = path.resolve(__dirname, '..');
 const ENTRY = path.join(__dirname, 'lib/static-html-parsers.entry.mjs');
 const OUT_DIR = path.join(ROOT, 'cli/engine/vendor');
 const OUTPUT = path.join(OUT_DIR, 'static-html-parsers.mjs');
-
-fs.mkdirSync(OUT_DIR, { recursive: true });
-
-const result = spawnSync(
-  'bun',
-  ['build', ENTRY, '--outfile', OUTPUT, '--target', 'node', '--format', 'esm'],
-  { cwd: ROOT, encoding: 'utf8' },
-);
-
-if (result.status !== 0) {
-  process.stderr.write(result.stderr || result.stdout || 'bun build failed\n');
-  process.exit(result.status ?? 1);
-}
-
-const bundled = fs.readFileSync(OUTPUT, 'utf8');
-const output = `/**
+const HEADER = `/**
  * GENERATED -- do not edit. Source: scripts/lib/static-html-parsers.entry.mjs
  * Rebuild: node scripts/build-static-html-parsers.js
  *
  * Bundles htmlparser2, css-select, css-tree, and domutils for skill/plugin installs.
  * Third-party licenses: see NOTICE.md.
  */
-${bundled}`;
+`;
 
-fs.writeFileSync(OUTPUT, output);
-console.log(`Generated ${path.relative(ROOT, OUTPUT)} (${(output.length / 1024).toFixed(1)} KB)`);
+function generate(outfile) {
+  fs.mkdirSync(path.dirname(outfile), { recursive: true });
+  const result = spawnSync(
+    'bun',
+    ['build', ENTRY, '--outfile', outfile, '--target', 'node', '--format', 'esm'],
+    { cwd: ROOT, encoding: 'utf8' },
+  );
+  if (result.status !== 0) {
+    process.stderr.write(result.stderr || result.stdout || 'bun build failed\n');
+    process.exit(result.status ?? 1);
+  }
+  const output = HEADER + fs.readFileSync(outfile, 'utf8');
+  fs.writeFileSync(outfile, output);
+  return output;
+}
+
+if (process.argv.includes('--check')) {
+  const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'impeccable-static-html-parsers-'));
+  const tmpFile = path.join(tmpDir, 'static-html-parsers.mjs');
+  try {
+    const fresh = generate(tmpFile);
+    const committed = fs.readFileSync(OUTPUT, 'utf8');
+    if (fresh !== committed) {
+      process.stderr.write(
+        'cli/engine/vendor/static-html-parsers.mjs is stale. Run: node scripts/build-static-html-parsers.js\n',
+      );
+      process.exit(1);
+    }
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
+  process.exit(0);
+}
+
+generate(OUTPUT);
+console.log(`Generated ${path.relative(ROOT, OUTPUT)} (${(fs.statSync(OUTPUT).size / 1024).toFixed(1)} KB)`);
diff --git a/scripts/test-suites.mjs b/scripts/test-suites.mjs
index ec2b2c47c..31c190e3a 100644
--- a/scripts/test-suites.mjs
+++ b/scripts/test-suites.mjs
@@ -25,7 +25,7 @@ export const SUITES = {
     description: 'Build, provider transforms, CLI helpers, context, and storage unit tests.',
     triggers: [
       ...COMMON_INFRA_PATTERNS,
-      /^scripts\/(?!benchmark-detector|build-browser-detector|build-static-html-parsers|build-extension)/,
+      /^scripts\/(?!benchmark-detector|build-browser-detector|build-static-html-parsers|build-extension|lib\/static-html-parsers\.entry)/,
       /^skill\/(SKILL\.src\.md|agents\/|reference\/|scripts\/(cleanup-deprecated|comp-diff|comp-spec|build-phase|font-match|data\/font-index|concept-seed|generate-image|context|context-signals|critique-storage|design-parser|doctor|hook|impeccable-paths|is-generated|lib\/(artifact-schema|png|raster|image-metrics|font-fingerprint|font-index|hero-checks|composition-catalog|concept-catalog|provider|staleness|staleness-deep|staleness-notice|surface-briefs|target-slug|template-extensions)|pin|surface-brief))/,
       /^README(\.npm)?\.md$/,
       /^cli\/bin\//,
@@ -96,6 +96,7 @@ export const SUITES = {
       /^cli\/engine\//,
       /^extension\/(background|content|detector|devtools|popup|manifest\.json)/,
       /^scripts\/(benchmark-detector|build-browser-detector|build-static-html-parsers|build-extension)\.js$/,
+      /^scripts\/lib\/static-html-parsers\.entry\.mjs$/,
       /^site\/(pages\/detector|public\/antipattern|data\/anti-patterns-catalog\.js)/,
       /^tests\/fixtures\/antipatterns/,
     ],
diff --git a/tests/lib/detector-bundle.test.js b/tests/lib/detector-bundle.test.js
index 5c10789ff..60ace6920 100644
--- a/tests/lib/detector-bundle.test.js
+++ b/tests/lib/detector-bundle.test.js
@@ -1,4 +1,5 @@
 import { describe, expect, test } from 'bun:test';
+import { spawnSync } from 'node:child_process';
 import fs from 'fs';
 import path from 'path';
 import { readSourceFiles } from '../../scripts/lib/utils.js';
@@ -19,6 +20,31 @@ describe('skill detector bundle', () => {
     expect(scriptNames.has('detector/vendor/static-html-parsers.mjs')).toBe(true);
   });
 
+  test('static HTML parser vendor bundle matches a fresh rebuild', () => {
+    const result = spawnSync(
+      process.execPath,
+      [path.join(ROOT, 'scripts/build-static-html-parsers.js'), '--check'],
+      { cwd: ROOT, encoding: 'utf8' },
+    );
+    expect(result.status).toBe(0);
+  });
+
+  test('static HTML parser --check fails when the vendor bundle is stale', () => {
+    const vendor = path.join(ROOT, 'cli/engine/vendor/static-html-parsers.mjs');
+    const original = fs.readFileSync(vendor, 'utf8');
+    try {
+      fs.writeFileSync(vendor, original.replace('htmlparser2', 'htmlparser2-stale'));
+      const result = spawnSync(
+        process.execPath,
+        [path.join(ROOT, 'scripts/build-static-html-parsers.js'), '--check'],
+        { cwd: ROOT, encoding: 'utf8' },
+      );
+      expect(result.status).toBe(1);
+    } finally {
+      fs.writeFileSync(vendor, original);
+    }
+  });
+
   test('critique references the bundled detector command', () => {
     const critique = fs.readFileSync(path.join(ROOT, 'skill/reference/critique.md'), 'utf-8');