diff --git a/lib/pkgcomposer.py b/lib/pkgcomposer.py
index 722cc42..28aace4 100644
--- a/lib/pkgcomposer.py
+++ b/lib/pkgcomposer.py
@@ -1,6 +1,7 @@
 import json
 import os
 import shutil
+import subprocess
 import sys
 
 if sys.version_info >= (3, 14):
@@ -45,4 +46,14 @@ class PkgComposer:
         shutil.copy2(src, f"{self.workdir}/bundle/{dst}", follow_symlinks=False)
 
     def add_dir(self, src: str, dst: str, merge: bool = False):
-        shutil.copytree(src, f"{self.workdir}/bundle/{dst}", dirs_exist_ok=merge)
+        target = f"{self.workdir}/bundle/{dst}"
+        if not os.path.exists(src):
+            raise FileNotFoundError(f"Source directory not found: {src}")
+        os.makedirs(os.path.dirname(target), exist_ok=True)
+        if merge and os.path.exists(target) and os.path.isdir(target):
+            cmd = ["cp", "-a", f"{src}/.", target]
+        else:
+            cmd = ["cp", "-a", src, target]
+        result = subprocess.run(cmd, capture_output=True, text=True)
+        if result.returncode != 0:
+            raise RuntimeError(f"cp command failed: {result.stderr}")