feat: Add --junior-model argument and plumb it into Model()

aider/args.py

@@ -190,6 +190,14 @@ def get_parser(default_config_files, git_root):
             " depends on --model)"
         ),
     )
+    group.add_argument(
+        "--junior-model",
+        metavar="JUNIOR_MODEL",
+        default=None,
+        help=(
+            "Specify the model to use for junior tasks (default depends on --model)"
+        ),
+    )
     group.add_argument(
         "--show-model-warnings",
         action=argparse.BooleanOptionalAction,

aider/main.py

@@ -533,7 +533,7 @@ def main(argv=None, input=None, output=None, force_git_root=None, return_coder=F
         if os.environ.get("ANTHROPIC_API_KEY"):
             args.model = "claude-3-5-sonnet-20240620"
 
-    main_model = models.Model(args.model, weak_model=args.weak_model)
+    main_model = models.Model(args.model, weak_model=args.weak_model, junior_model=args.junior_model)
 
     if args.verbose:
         io.tool_output("Model info:")

aider/models.py

@@ -597,10 +597,11 @@ def get_model_info(model):
 
 
 class Model(ModelSettings):
-    def __init__(self, model, weak_model=None):
+    def __init__(self, model, weak_model=None, junior_model=None):
         self.name = model
         self.max_chat_history_tokens = 1024
         self.weak_model = None
+        self.junior_model = None
 
         self.info = self.get_model_info(model)
 
@@ -621,6 +622,11 @@ class Model(ModelSettings):
         else:
             self.get_weak_model(weak_model)
         
+        if junior_model is False:
+            self.junior_model_name = None
+        else:
+            self.get_junior_model(junior_model)
+
     def get_model_info(self, model):
         return get_model_info(model)
 
@@ -692,6 +698,26 @@ class Model(ModelSettings):
     def commit_message_models(self):
         return [self.weak_model, self]
 
+    def get_junior_model(self, provided_junior_model_name):
+        # If junior_model_name is provided, override the model settings
+        if provided_junior_model_name:
+            self.junior_model_name = provided_junior_model_name
+
+        if not self.junior_model_name:
+            self.junior_model = self
+            return
+
+        if self.junior_model_name == self.name:
+            self.junior_model = self
+            return
+
+        self.junior_model = Model(
+            self.junior_model_name,
+            weak_model=False,
+            junior_model=False,
+        )
+        return self.junior_model
+
     def tokenizer(self, text):
         return litellm.encode(model=self.name, text=text)