diff --git a/CLEAN_CODE_ANALYSIS.md b/CLEAN_CODE_ANALYSIS.md
index 5c25292..4362b4c 100644
--- a/CLEAN_CODE_ANALYSIS.md
+++ b/CLEAN_CODE_ANALYSIS.md
@@ -485,7 +485,7 @@ styles/
   - [x] Introduce a lightweight CSS lint configuration (`stylelint` + [`.stylelintrc.json`](.stylelintrc.json:1)) scoped to `styles/**/*.css` to enforce:
     - No ID selectors in plugin CSS.
     - A small, explicit set of allowed class prefixes for plugin and layout classes (`coalesce-`, `backlinks-`, `markdown-`, `theme-`, `is-`, `has-`, `no-`).
-  - [ ] Optionally add a simple “unused selector” check in CI (build + grep for key class names in HTML/DOM tests).
+  - [x] Add a simple “unused selector” check via `npm run lint:css:unused` using [`scripts/check-unused-css.mjs`](scripts/check-unused-css.mjs:1), which heuristically reports plugin-scoped CSS classes not referenced in `src/**/*.ts`/`.js` files (informational only; does not fail the build).
 
 This plan keeps the runtime surface unchanged (still a single `dist/styles.css`) while making the CSS layout more modular and slice-aware.
 
diff --git a/package.json b/package.json
index 403a636..932ef2a 100644
--- a/package.json
+++ b/package.json
@@ -10,7 +10,8 @@
 		"test": "jest",
 		"test:watch": "jest --watch",
 		"test:coverage": "jest --coverage",
-		"lint:css": "stylelint \"styles/**/*.css\""
+		"lint:css": "stylelint \"styles/**/*.css\"",
+		"lint:css:unused": "node scripts/check-unused-css.mjs"
 	},
 	"keywords": [],
 	"author": "",
diff --git a/scripts/check-unused-css.mjs b/scripts/check-unused-css.mjs
new file mode 100644
index 0000000..5078b4a
--- /dev/null
+++ b/scripts/check-unused-css.mjs
@@ -0,0 +1,124 @@
+#!/usr/bin/env node
+import { promises as fs } from 'fs';
+import path from 'path';
+
+const ROOT = process.cwd();
+const CSS_DIR = path.join(ROOT, 'styles');
+const SRC_DIR = path.join(ROOT, 'src');
+
+const SKIP_DIRS = ['node_modules', '.git', 'dist'];
+const SOURCE_EXTS = ['.ts', '.tsx', '.js', '.jsx'];
+
+async function collectFiles(dir, exts) {
+  const files = [];
+  async function walk(current) {
+    let entries;
+    try {
+      entries = await fs.readdir(current, { withFileTypes: true });
+    } catch {
+      return;
+    }
+    for (const entry of entries) {
+      const full = path.join(current, entry.name);
+      if (entry.isDirectory()) {
+        if (SKIP_DIRS.some(skip => full.includes(path.sep + skip + path.sep))) {
+          continue;
+        }
+        await walk(full);
+      } else if (exts.some(ext => full.endsWith(ext))) {
+        files.push(full);
+      }
+    }
+  }
+  await walk(dir);
+  return files;
+}
+
+async function collectCssFiles() {
+  return collectFiles(CSS_DIR, ['.css']);
+}
+
+async function collectSourceFiles() {
+  return collectFiles(SRC_DIR, SOURCE_EXTS);
+}
+
+function extractClassesFromCss(css) {
+  const classRegex = /\.([a-zA-Z0-9_-]+)/g;
+  const classes = new Set();
+  let match;
+  while ((match = classRegex.exec(css)) !== null) {
+    const name = match[1];
+    if (/^(coalesce|backlinks|markdown|theme|is|has|no)-/.test(name)) {
+      classes.add(name);
+    }
+  }
+  return classes;
+}
+
+async function buildFileCache(files) {
+  const cache = new Map();
+  for (const file of files) {
+    try {
+      const content = await fs.readFile(file, 'utf8');
+      cache.set(file, content);
+    } catch {
+      // ignore read errors
+    }
+  }
+  return cache;
+}
+
+function isClassUsedInSources(className, sourceCache) {
+  for (const content of sourceCache.values()) {
+    if (content.includes(className)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+async function main() {
+  console.log('[coalesce] CSS unused-selector check starting...');
+
+  const cssFiles = await collectCssFiles();
+  const sourceFiles = await collectSourceFiles();
+
+  if (cssFiles.length === 0) {
+    console.log('[coalesce] No CSS files found under styles/');
+    return;
+  }
+
+  const sourceCache = await buildFileCache(sourceFiles);
+
+  const allClasses = new Set();
+  for (const cssFile of cssFiles) {
+    const css = await fs.readFile(cssFile, 'utf8');
+    const classes = extractClassesFromCss(css);
+    for (const cls of classes) {
+      allClasses.add(cls);
+    }
+  }
+
+  const possiblyUnused = [];
+  for (const cls of allClasses) {
+    const used = isClassUsedInSources(cls, sourceCache);
+    if (!used) {
+      possiblyUnused.push(cls);
+    }
+  }
+
+  if (possiblyUnused.length === 0) {
+    console.log('[coalesce] No obvious unused plugin CSS classes found.');
+  } else {
+    console.log('[coalesce] Potentially unused plugin CSS classes (heuristic):');
+    for (const cls of possiblyUnused) {
+      console.log('  - .' + cls);
+    }
+    console.log('[coalesce] Review these and remove any truly unused selectors. This check is informational and does not fail the build.');
+  }
+}
+
+main().catch((err) => {
+  console.error('[coalesce] CSS unused-selector check failed:', err);
+  process.exitCode = 1;
+});
\ No newline at end of file