diff --git a/PW_FT_classification/main.py b/PW_FT_classification/main.py
index ec66333a1..4caa2236e 100644
--- a/PW_FT_classification/main.py
+++ b/PW_FT_classification/main.py
@@ -55,8 +55,27 @@ def main(
     """
 
     # GPU configuration: set up GPUs based on availability and user specification
-    gpus = gpus if torch.cuda.is_available() else None
-    gpus = [int(i) for i in gpus.split(',')]
+    if torch.cuda.is_available():
+        # Sanitize and validate the GPU list provided via CLI
+        if gpus is None:
+            parsed_gpus = None
+        else:
+            tokens = [token.strip() for token in str(gpus).split(",") if token.strip()]
+            if not tokens:
+                # Empty or whitespace-only input: fall back to CPU
+                parsed_gpus = None
+            else:
+                try:
+                    parsed_gpus = [int(token) for token in tokens]
+                except ValueError as exc:
+                    raise typer.BadParameter(
+                        f"Invalid GPU list '{gpus}'. Expected a comma-separated list of integers, e.g. '0,1,2'."
+                    ) from exc
+        gpus = parsed_gpus
+    else:
+        # If no CUDA devices are available, set gpus to None to indicate CPU usage
+        # PyTorch Lightning Trainer will default to CPU if devices is None
+        gpus = None
 
     # Environment variable setup for numpy multi-threading. It is important to avoid cpu and ram issues.
     os.environ["OMP_NUM_THREADS"] = str(np_threads)