diff --git a/chatmastermind/ai_factory.py b/chatmastermind/ai_factory.py
index 36a987b..42b27c1 100644
--- a/chatmastermind/ai_factory.py
+++ b/chatmastermind/ai_factory.py
@@ -3,18 +3,20 @@ Creates different AI instances, based on the given configuration.
 """
 
 import argparse
-from typing import cast
+from typing import cast, Optional
 from .configuration import Config, AIConfig, OpenAIConfig
 from .ai import AI, AIError
 from .ais.openai import OpenAI
 
 
-def create_ai(args: argparse.Namespace, config: Config) -> AI:  # noqa: 11
+def create_ai(args: argparse.Namespace, config: Config,  # noqa: 11
+              def_ai: Optional[str] = None,
+              def_model: Optional[str] = None) -> AI:
     """
-    Creates an AI subclass instance from the given arguments
-    and configuration file. If AI has not been set in the
-    arguments, it searches for the ID 'default'. If that
-    is not found, it uses the first AI in the list.
+    Creates an AI subclass instance from the given arguments and configuration file.
+    If AI has not been set in the arguments, it searches for the ID 'default'. If
+    that is not found, it uses the first AI in the list. It's also possible to
+    specify a default AI and model using 'def_ai' and 'def_model'.
     """
     ai_conf: AIConfig
     if hasattr(args, 'AI') and args.AI:
@@ -22,6 +24,8 @@ def create_ai(args: argparse.Namespace, config: Config) -> AI:  # noqa: 11
             ai_conf = config.ais[args.AI]
         except KeyError:
             raise AIError(f"AI ID '{args.AI}' does not exist in this configuration")
+    elif def_ai:
+        ai_conf = config.ais[def_ai]
     elif 'default' in config.ais:
         ai_conf = config.ais['default']
     else:
@@ -34,6 +38,8 @@ def create_ai(args: argparse.Namespace, config: Config) -> AI:  # noqa: 11
         ai = OpenAI(cast(OpenAIConfig, ai_conf))
         if hasattr(args, 'model') and args.model:
             ai.config.model = args.model
+        elif def_model:
+            ai.config.model = def_model
         if hasattr(args, 'max_tokens') and args.max_tokens:
             ai.config.max_tokens = args.max_tokens
         if hasattr(args, 'temperature') and args.temperature: