diff --git a/inject-mermaid.sh b/inject-mermaid.sh
new file mode 100755
index 0000000..6d78a22
--- /dev/null
+++ b/inject-mermaid.sh
@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+# Injects mermaid.js script into HTML files that contain mermaid code blocks.
+# Usage: inject-mermaid.sh <html_directory>
+
+HTML_DIR="${1:-.}"
+
+inject_mermaid() {
+  local html_file="$1"
+  python3 - "$html_file" << 'PYEOF'
+import sys
+
+path = sys.argv[1]
+snippet = """\
+<script type="module">
+import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs';
+document.querySelectorAll('code.language-mermaid').forEach(el => {
+  const div = document.createElement('div');
+  div.className = 'mermaid';
+  div.textContent = el.textContent;
+  el.closest('pre').replaceWith(div);
+});
+mermaid.initialize({ startOnLoad: true, theme: 'dark' });
+</script>"""
+
+with open(path, encoding='utf-8') as f:
+    content = f.read()
+
+# Skip if already injected
+if 'mermaid.esm' in content:
+    sys.exit(0)
+
+# Skip if no mermaid blocks
+if 'language-mermaid' not in content:
+    sys.exit(0)
+
+new_content = content.replace('</body>', snippet + '\n</body>', 1)
+if new_content == content:
+    print(f"Warning: </body> not found in {path}", file=sys.stderr)
+    sys.exit(1)
+
+with open(path, 'w', encoding='utf-8') as f:
+    f.write(new_content)
+PYEOF
+}
+
+# Find and process all HTML files in the directory
+if command -v python3 &>/dev/null; then
+  for html_file in "$HTML_DIR"/*.html; do
+    [ -f "$html_file" ] || continue
+    [ "$(basename "$html_file")" = "index.html" ] && continue
+
+    if grep -q 'language-mermaid' "$html_file" 2>/dev/null; then
+      if ! grep -q 'mermaid.esm' "$html_file" 2>/dev/null; then
+        inject_mermaid "$html_file" && echo "  Injected mermaid.js into $(basename "$html_file")"
+      fi
+    fi
+  done
+else
+  echo "Warning: python3 not found — skipping mermaid injection"
+  exit 1
+fi