diff --git a/docs/features/llm.md b/docs/features/llm.md
index 31648144..d38ce39d 100644
--- a/docs/features/llm.md
+++ b/docs/features/llm.md
@@ -95,7 +95,7 @@ SessionLocal = sessionmaker(bind=engine)
 
 client = ChatOpenAI(model="gpt-4o-mini")
 
-mem = Memori(conn=SessionLocal).llm.register(client)
+mem = Memori(conn=SessionLocal).llm.register(chatopenai=client)
 mem.attribution(entity_id="user_123", process_id="langchain_agent")
 
 response = client.invoke("Hello")
diff --git a/docs/troubleshooting.md b/docs/troubleshooting.md
index 41af8646..6ddf150c 100644
--- a/docs/troubleshooting.md
+++ b/docs/troubleshooting.md
@@ -485,7 +485,7 @@ def get_sqlite_connection():
     return sqlite3.connect("memori.db")
 
 chat = ChatOpenAI()
-mem = Memori(conn=get_sqlite_connection).llm.register(chat)
+mem = Memori(conn=get_sqlite_connection).llm.register(chatopenai=chat)
 mem.attribution(entity_id="user-123", process_id="my-app")
 ```
 
diff --git a/memori/llm/_registry.py b/memori/llm/_registry.py
index 95fcdab1..5d8eab30 100644
--- a/memori/llm/_registry.py
+++ b/memori/llm/_registry.py
@@ -39,6 +39,15 @@ def client(self, client_obj: Any, config) -> BaseClient:
             if matcher(client_obj):
                 return client_class(config)
 
+        module = type(client_obj).__module__
+        if module.startswith("langchain"):
+            class_name = type(client_obj).__name__
+            param_hint = class_name.lower()
+            raise RuntimeError(
+                f"LangChain models require named parameters. "
+                f"Use: llm.register({param_hint}=client) instead of llm.register(client)"
+            )
+
         raise RuntimeError(
             f"Unsupported LLM client type: {type(client_obj).__module__}.{type(client_obj).__name__}"
         )
diff --git a/tests/llm/test_llm_registry.py b/tests/llm/test_llm_registry.py
index fd0bd8a3..bdfc6f11 100644
--- a/tests/llm/test_llm_registry.py
+++ b/tests/llm/test_llm_registry.py
@@ -49,3 +49,22 @@ def test_llm_adapter_raises_for_unsupported_provider():
 
     with pytest.raises(RuntimeError, match="Unsupported LLM provider"):
         Registry().adapter("mistral", "mistral")
+
+
+def test_llm_client_raises_helpful_error_for_langchain():
+    """Test that LangChain clients produce a helpful error message."""
+
+    class MockLangChainClient:
+        pass
+
+    MockLangChainClient.__module__ = "langchain_openai.chat_models.base"
+    MockLangChainClient.__name__ = "ChatOpenAI"
+
+    mock_client = MockLangChainClient()
+    mock_config = None
+
+    with pytest.raises(
+        RuntimeError,
+        match=r"LangChain models require named parameters.*llm\.register\(chatopenai=client\)",
+    ):
+        Registry().client(mock_client, mock_config)