diff --git a/vite.config.js b/vite.config.js
index 871b2faf6..ac4b42d51 100644
--- a/vite.config.js
+++ b/vite.config.js
@@ -59,9 +59,21 @@ function copyPdfWorker() {
   return {
     name: 'copy-pdf-worker',
     closeBundle() {
-      const src = path.resolve('node_modules/pdfjs-dist/build/pdf.worker.min.mjs');
-      const dest = path.resolve('dist/pdf.worker.min.js');
-      if (fs.existsSync(src)) fs.copyFileSync(src, dest);
+      // Never throw from here: closeBundle also runs when the build FAILED
+      // mid-render (dist/ absent) and an exception here MASKS the real build
+      // error in vite's report (seen on the Windows CI runner). Warn and skip.
+      try {
+        const src = path.resolve('node_modules/pdfjs-dist/build/pdf.worker.min.mjs');
+        const dest = path.resolve('dist/pdf.worker.min.js');
+        if (!fs.existsSync(src)) {
+          console.warn('[copy-pdf-worker] source worker missing, skipped:', src);
+          return;
+        }
+        fs.mkdirSync(path.dirname(dest), { recursive: true });
+        fs.copyFileSync(src, dest);
+      } catch (err) {
+        console.warn('[copy-pdf-worker] skipped:', err?.message ?? err);
+      }
     },
   };
 }