diff --git a/docs/docs/how_to/custom_tools.ipynb b/docs/docs/how_to/custom_tools.ipynb
index 4225569ab61..0e1262841a1 100644
--- a/docs/docs/how_to/custom_tools.ipynb
+++ b/docs/docs/how_to/custom_tools.ipynb
@@ -22,7 +22,7 @@
     "2. LangChain [Runnables](/docs/concepts/runnables);\n",
     "3. By sub-classing from [BaseTool](https://python.langchain.com/api_reference/core/tools/langchain_core.tools.base.BaseTool.html) -- This is the most flexible method, it provides the largest degree of control, at the expense of more effort and code.\n",
     "\n",
-    "Creating tools from functions may be sufficient for most use cases, and can be done via a simple [@tool decorator](https://python.langchain.com/api_reference/core/tools/langchain_core.tools.tool.html#langchain_core.tools.tool). If more configuration is needed-- e.g., specification of both sync and async implementations-- one can also use the [StructuredTool.from_function](https://python.langchain.com/api_reference/core/tools/langchain_core.tools.structured.StructuredTool.html#langchain_core.tools.structured.StructuredTool.from_function) class method.\n",
+    "Creating tools from functions may be sufficient for most use cases, and can be done via a simple [@tool decorator](https://python.langchain.com/api_reference/core/tools/langchain_core.tools.convert.tool.html). If more configuration is needed-- e.g., specification of both sync and async implementations-- one can also use the [StructuredTool.from_function](https://python.langchain.com/api_reference/core/tools/langchain_core.tools.structured.StructuredTool.html#langchain_core.tools.structured.StructuredTool.from_function) class method.\n",
     "\n",
     "In this guide we provide an overview of these methods.\n",
     "\n",
diff --git a/libs/partners/openai/langchain_openai/chat_models/base.py b/libs/partners/openai/langchain_openai/chat_models/base.py
index 2d580d08ccd..a264fdedba6 100644
--- a/libs/partners/openai/langchain_openai/chat_models/base.py
+++ b/libs/partners/openai/langchain_openai/chat_models/base.py
@@ -6,6 +6,7 @@ import base64
 import json
 import logging
 import os
+import re
 import sys
 import warnings
 from io import BytesIO
@@ -2011,6 +2012,12 @@ class ChatOpenAI(BaseChatOpenAI):  # type: ignore[override]
         # in September 2024 release
         if "max_tokens" in payload:
             payload["max_completion_tokens"] = payload.pop("max_tokens")
+
+        # Mutate system message role to "developer" for o-series models
+        if self.model_name and re.match(r"^o\d", self.model_name):
+            for message in payload.get("messages", []):
+                if message["role"] == "system":
+                    message["role"] = "developer"
         return payload
 
     def _should_stream_usage(
diff --git a/libs/partners/openai/tests/unit_tests/chat_models/test_base.py b/libs/partners/openai/tests/unit_tests/chat_models/test_base.py
index a7b3e5f102e..5f129ef8d37 100644
--- a/libs/partners/openai/tests/unit_tests/chat_models/test_base.py
+++ b/libs/partners/openai/tests/unit_tests/chat_models/test_base.py
@@ -881,6 +881,20 @@ def test__get_request_payload() -> None:
     payload = llm._get_request_payload(messages)
     assert payload == expected
 
+    # Test we coerce to developer role for o-series models
+    llm = ChatOpenAI(model="o3-mini")
+    payload = llm._get_request_payload(messages)
+    expected = {
+        "messages": [
+            {"role": "developer", "content": "hello"},
+            {"role": "developer", "content": "bye"},
+            {"role": "user", "content": "how are you"},
+        ],
+        "model": "o3-mini",
+        "stream": False,
+    }
+    assert payload == expected
+
 
 def test_init_o1() -> None:
     with pytest.warns(None) as record:  # type: ignore[call-overload]