fix: prevent DefaultConfig template values from leaking into user model_list entries

pkg/config/config.go

@@ -499,6 +499,20 @@ func LoadConfig(path string) (*Config, error) {
 		return nil, err
 	}
 
+	// Pre-scan the JSON to check how many model_list entries the user provided.
+	// Go's JSON decoder reuses existing slice backing-array elements rather than
+	// zero-initializing them, so fields absent from the user's JSON (e.g. api_base)
+	// would silently inherit values from the DefaultConfig template at the same
+	// index position. We only reset cfg.ModelList when the user actually provides
+	// entries; when count is 0 we keep DefaultConfig's built-in list as fallback.
+	var tmp Config
+	if err := json.Unmarshal(data, &tmp); err != nil {
+		return nil, err
+	}
+	if len(tmp.ModelList) > 0 {
+		cfg.ModelList = nil
+	}
+
 	if err := json.Unmarshal(data, cfg); err != nil {
 		return nil, err
 	}