diff --git a/src/vision_worker/main.py b/src/vision_worker/main.py
index 25311be..c86d665 100644
--- a/src/vision_worker/main.py
+++ b/src/vision_worker/main.py
@@ -10,6 +10,7 @@ import asyncio
 import io
 import json
 import os
+import re
 from pathlib import Path
 
 import numpy as np
@@ -61,6 +62,8 @@ def _resolve_recipe_dir(recipe_dir: str | None) -> Path | None:
     root = Path(os.environ.get("VISION_RECIPES_ROOT", _RECIPES_ROOT_DEFAULT)).resolve()
     if (
         Path(rel).is_absolute()
+        # #46: lettera di unita (C:/x) rifiutata su ogni OS; UNC coperto da startswith("\\")
+        or re.match(r"^[A-Za-z]:", rel)
         or rel.startswith(("/", "\\"))
         or ".." in Path(rel.replace("\\", "/")).parts
     ):