feat: Validate custom authentication path and method in auth_config

agentflow_cli/src/app/loader.py

@@ -1,6 +1,8 @@
 import importlib
 import inspect
 import logging
+import os
+from pathlib import Path
 
 from agentflow.checkpointer import BaseCheckpointer
 from agentflow.graph import CompiledGraph
@@ -197,6 +199,24 @@ async def attach_all_modules(
     if auth_config:
         method = auth_config.get("method", None)
         path = auth_config.get("path", None)
+        if not path or not method:
+            raise ValueError("Both 'method' and 'path' must be specified in auth_config.")
+
+        # Extract file path before the ':' for existence check
+        module_or_path = path.split(":", 1)[0] if ":" in path else path
+
+        # Simple handling: if it appears to be a filesystem path, use it; otherwise
+        # convert dotted module path to a file path like src/auth/custom_auth.py
+        if os.path.sep in module_or_path or module_or_path.endswith(".py"):
+            file_path = Path(module_or_path)
+        elif "." in module_or_path and os.path.sep not in module_or_path:
+            file_path = Path(module_or_path.replace(".", os.path.sep) + ".py")
+        else:
+            file_path = Path(module_or_path)
+
+        if not file_path.exists():
+            raise ValueError(f"Custom auth path does not exist: {module_or_path}")
+
         if method == "custom":
             auth_backend = load_auth(
                 path,