diff --git a/banner.js b/banner.js
index db3974c..068770c 100644
--- a/banner.js
+++ b/banner.js
@@ -1,19 +1,75 @@
-const fs = require("fs");
-const pkg = require("./package.json");
-const filename = "assets/js/main.min.js";
-const script = fs.readFileSync(filename);
-const padStart = str => ("0" + str).slice(-2);
-const dateObj = new Date();
-const date = `${dateObj.getFullYear()}-${padStart(
-  dateObj.getMonth() + 1
-)}-${padStart(dateObj.getDate())}`;
-const banner = `/*!
+// scripts/prepend-banner.js
+// Node >= 12 (uses fs.promises)
+const fs = require("fs").promises;
+const path = require("path");
+
+async function main() {
+  try {
+    const pkg = require(path.resolve(__dirname, "..", "package.json"));
+    const filename = process.argv[2] || path.resolve(__dirname, "..", "assets/js/main.min.js");
+
+    // Read file as UTF-8 text
+    const content = await fs.readFile(filename, "utf8");
+
+    // If file already starts with a banner comment (/*! or /**), skip.
+    // This is more robust than slicing bytes and comparing to a raw string.
+    if (content.startsWith("/*!") || content.startsWith("/**")) {
+      console.log(`Banner already present in: ${filename} — nothing to do.`);
+      return;
+    }
+
+    // Build date string (YYYY-MM-DD)
+    const padStart = (s) => ("0" + String(s)).slice(-2);
+    const dateObj = new Date();
+    const date = `${dateObj.getFullYear()}-${padStart(dateObj.getMonth() + 1)}-${padStart(
+      dateObj.getDate()
+    )}`;
+
+    const banner = `/*!
  * Minimal Mistakes Jekyll Theme ${pkg.version} by ${pkg.author}
  * Copyright 2013-${dateObj.getFullYear()} Michael Rose - mademistakes.com | @mmistakes
  * Licensed under ${pkg.license}
  */
 `;
 
-if (script.slice(0, 3) != "/**") {
-  fs.writeFileSync(filename, banner + script);
+    // Prepare temporary file path in same directory for atomic replace
+    const dir = path.dirname(filename);
+    const base = path.basename(filename);
+    const tmpName = path.join(dir, `.${base}.tmp-${Date.now()}`);
+
+    // Preserve original file metadata (mode and times)
+    let stat;
+    try {
+      stat = await fs.stat(filename);
+    } catch {
+      stat = null;
+    }
+
+    // Write tmp file then rename (atomic on most OSes)
+    await fs.writeFile(tmpName, banner + content, "utf8");
+    await fs.rename(tmpName, filename);
+
+    // Restore mode and times if we got them
+    if (stat) {
+      try {
+        await fs.chmod(filename, stat.mode);
+      } catch (err) {
+        // non-fatal; continue
+      }
+      try {
+        const atime = stat.atime;
+        const mtime = stat.mtime;
+        await fs.utimes(filename, atime, mtime);
+      } catch (err) {
+        // non-fatal
+      }
+    }
+
+    console.log(`Banner prepended to: ${filename}`);
+  } catch (err) {
+    console.error("Error:", err.message || err);
+    process.exitCode = 1;
+  }
 }
+
+main();