diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index 44a175ec1ca..6547eaa21e6 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -1102,6 +1102,10 @@ def format_chat_chunks(self):
             chunks.system = [
                 dict(role="system", content=main_sys),
             ]
+        elif self.main_model.use_developer_message:
+            chunks.system = [
+                dict(role="developer", content=main_sys),
+            ]
         else:
             chunks.system = [
                 dict(role="user", content=main_sys),
diff --git a/aider/models.py b/aider/models.py
index c8dcfdfbc1f..95e9a5f23bc 100644
--- a/aider/models.py
+++ b/aider/models.py
@@ -95,6 +95,7 @@ class ModelSettings:
     cache_control: bool = False
     caches_by_default: bool = False
     use_system_prompt: bool = True
+    use_developer_message: bool = False
     use_temperature: bool = True
     streaming: bool = True
     editor_model_name: Optional[str] = None
@@ -674,6 +675,19 @@ class ModelSettings:
         reminder="sys",
         editor_edit_format="editor-diff",
     ),
+    ModelSettings(
+        "openrouter/openai/o1",
+        "diff",
+        weak_model_name="openrouter/openai/gpt-4o-mini",
+        use_repo_map=True,
+        lazy=True,
+        reminder="sys",
+        editor_edit_format="editor-diff",
+        use_system_prompt=False,
+        use_temperature=False,
+        use_developer_message = True
+    ),
+
     ModelSettings(
         "openai/o1-mini",
         "whole",