diff --git a/aider/main.py b/aider/main.py
index 25b023fc9..9d843644d 100644
--- a/aider/main.py
+++ b/aider/main.py
@@ -343,7 +343,15 @@ def main(argv=None, input=None, output=None, force_git_root=None, return_coder=F
     model_def_files = list(map(str, model_def_files))
     model_def_files = list(dict.fromkeys(model_def_files))
     print(f"model_def_files: {model_def_files}")
-    models.register_models(model_def_files)
+    try:
+        model_files_loaded=models.register_models(model_def_files)
+        if len(model_files_loaded) > 0:
+            io.tool_output(f"Loaded {len(model_files_loaded)} model files")
+            for model_file in model_files_loaded:
+                io.tool_output(f"  - {model_file}")
+    except Exception as e:
+        io.tool_error(f"Error loading model info/cost: {e}")
+        return 1
 
     main_model = models.Model(args.model, weak_model=args.weak_model)
 
diff --git a/aider/models.py b/aider/models.py
index 1a96bb5b3..852aac7ba 100644
--- a/aider/models.py
+++ b/aider/models.py
@@ -427,18 +427,21 @@ class Model:
         return res
 
 def register_models(model_def_fnames):
+    model_files_loaded = []
     for model_def_fname in model_def_fnames:
         if not os.path.exists(model_def_fname):
             continue
-        print(f"Registering model definition from {model_def_fname}")
+        model_files_loaded.append(model_def_fname)
         try:
             with open(model_def_fname, "r") as model_def_file:
                 model_def = json.load(model_def_file)
         except json.JSONDecodeError as e:
-            print(f"Error opening/decoding model definition: {e}")
+            raise Exception(f"Error loading model definition from {model_def_fname}: {e}")
 
         litellm.register_model(model_def)
 
+    return model_files_loaded
+
 def validate_variables(vars):
     missing = []
     for var in vars: