stop overriding caller's ls_integration in ls trace

libs/core/langchain_core/language_models/chat_models.py

@@ -738,10 +738,10 @@ class BaseChatModel(BaseLanguageModel[AIMessage], ABC):
 
             params = self._get_invocation_params(stop=stop, **kwargs)
             options = {"stop": stop, **kwargs, **ls_structured_output_format_dict}
-            inheritable_metadata = {
-                **(config.get("metadata") or {}),
-                **self._get_ls_params_with_defaults(stop=stop, **kwargs),
-            }
+            inheritable_metadata = self._merge_inheritable_metadata(
+                config.get("metadata") or {},
+                self._get_ls_params_with_defaults(stop=stop, **kwargs),
+            )
             callback_manager = CallbackManager.configure(
                 config.get("callbacks"),
                 self.callbacks,
@@ -867,10 +867,10 @@ class BaseChatModel(BaseLanguageModel[AIMessage], ABC):
 
         params = self._get_invocation_params(stop=stop, **kwargs)
         options = {"stop": stop, **kwargs, **ls_structured_output_format_dict}
-        inheritable_metadata = {
-            **(config.get("metadata") or {}),
-            **self._get_ls_params_with_defaults(stop=stop, **kwargs),
-        }
+        inheritable_metadata = self._merge_inheritable_metadata(
+            config.get("metadata") or {},
+            self._get_ls_params_with_defaults(stop=stop, **kwargs),
+        )
         callback_manager = AsyncCallbackManager.configure(
             config.get("callbacks"),
             self.callbacks,
@@ -1002,10 +1002,10 @@ class BaseChatModel(BaseLanguageModel[AIMessage], ABC):
 
         params = self._get_invocation_params(stop=stop, **kwargs)
         options = {"stop": stop, **kwargs, **ls_structured_output_format_dict}
-        inheritable_metadata = {
-            **(config.get("metadata") or {}),
-            **self._get_ls_params_with_defaults(stop=stop, **kwargs),
-        }
+        inheritable_metadata = self._merge_inheritable_metadata(
+            config.get("metadata") or {},
+            self._get_ls_params_with_defaults(stop=stop, **kwargs),
+        )
         callback_manager = CallbackManager.configure(
             config.get("callbacks"),
             self.callbacks,
@@ -1136,10 +1136,10 @@ class BaseChatModel(BaseLanguageModel[AIMessage], ABC):
 
         params = self._get_invocation_params(stop=stop, **kwargs)
         options = {"stop": stop, **kwargs, **ls_structured_output_format_dict}
-        inheritable_metadata = {
-            **(config.get("metadata") or {}),
-            **self._get_ls_params_with_defaults(stop=stop, **kwargs),
-        }
+        inheritable_metadata = self._merge_inheritable_metadata(
+            config.get("metadata") or {},
+            self._get_ls_params_with_defaults(stop=stop, **kwargs),
+        )
         callback_manager = AsyncCallbackManager.configure(
             config.get("callbacks"),
             self.callbacks,
@@ -1547,6 +1547,30 @@ class BaseChatModel(BaseLanguageModel[AIMessage], ABC):
         ls_params["ls_integration"] = "langchain_chat_model"
         return ls_params
 
+    @staticmethod
+    def _merge_inheritable_metadata(
+        inherited: dict[str, Any], ls_params: LangSmithParams
+    ) -> dict[str, Any]:
+        """Merge model `ls_params` into inherited run metadata.
+
+        Replacing "last-writer-wins" policy for `ls_integration`.
+        If a caller already set one on the run metadata, keep it instead of
+        overriding with the chat model default.
+        Mirrors langgraph, which sets `ls_integration` only when it is absent.
+
+        Args:
+            inherited: Run metadata inherited from the invocation config.
+            ls_params: LangSmith params for this chat model, including the
+                default `ls_integration`.
+
+        Returns:
+            The merged metadata, preserving any inherited `ls_integration`.
+        """
+        merged: dict[str, Any] = {**inherited, **ls_params}
+        if inherited.get("ls_integration"):
+            merged["ls_integration"] = inherited["ls_integration"]
+        return merged
+
     def _get_llm_string(self, stop: list[str] | None = None, **kwargs: Any) -> str:
         if self.is_lc_serializable():
             params = {**kwargs, "stop": stop}
@@ -1617,10 +1641,10 @@ class BaseChatModel(BaseLanguageModel[AIMessage], ABC):
 
         params = self._get_invocation_params(stop=stop, **kwargs)
         options = {"stop": stop, **ls_structured_output_format_dict}
-        inheritable_metadata = {
-            **(metadata or {}),
-            **self._get_ls_params_with_defaults(stop=stop, **kwargs),
-        }
+        inheritable_metadata = self._merge_inheritable_metadata(
+            metadata or {},
+            self._get_ls_params_with_defaults(stop=stop, **kwargs),
+        )
 
         callback_manager = CallbackManager.configure(
             callbacks,
@@ -1743,10 +1767,10 @@ class BaseChatModel(BaseLanguageModel[AIMessage], ABC):
 
         params = self._get_invocation_params(stop=stop, **kwargs)
         options = {"stop": stop, **ls_structured_output_format_dict}
-        inheritable_metadata = {
-            **(metadata or {}),
-            **self._get_ls_params_with_defaults(stop=stop, **kwargs),
-        }
+        inheritable_metadata = self._merge_inheritable_metadata(
+            metadata or {},
+            self._get_ls_params_with_defaults(stop=stop, **kwargs),
+        )
 
         callback_manager = AsyncCallbackManager.configure(
             callbacks,

libs/core/tests/unit_tests/language_models/chat_models/test_base.py

@@ -1362,6 +1362,18 @@ async def test_user_lc_versions_metadata_survives_merge_async() -> None:
         assert "langchain-core" in run_metadata["lc_versions"]
 
 
+def test_caller_ls_integration_survives_merge() -> None:
+    """A caller-supplied `ls_integration` is not overridden by the model default."""
+    llm = FakeListChatModel(responses=["hello"])
+    user_config: RunnableConfig = {"metadata": {"ls_integration": "my-integration"}}
+
+    with collect_runs() as cb:
+        llm.invoke([HumanMessage(content="hi")], config=user_config)
+        assert len(cb.traced_runs) == 1
+        run_metadata = cb.traced_runs[0].extra["metadata"]
+        assert run_metadata["ls_integration"] == "my-integration"
+
+
 def test_user_lc_versions_metadata_survives_merge_stream() -> None:
     """Stream variant: user-provided `lc_versions` metadata merges with model's."""
     llm = _VersionedFakeModel(responses=["hello"])

libs/langchain_v1/langchain/agents/factory.py

@@ -1778,9 +1778,10 @@ def create_agent(
     # Set recursion limit to 9_999
     # https://github.com/langchain-ai/langgraph/issues/7313
     config: RunnableConfig = {"recursion_limit": 9_999}
-    config["metadata"] = {"ls_integration": "langchain_create_agent"}
+    # Don't bake ls_integration here: it would override an outer integration's
+    # value inherited ambiently through the parent run tree.
     if name:
-        config["metadata"]["lc_agent_name"] = name
+        config["metadata"] = {"lc_agent_name": name}
 
     middleware_transformers = [t for m in middleware for t in getattr(m, "transformers", ())]
 

libs/langchain_v1/tests/unit_tests/agents/test_injected_runtime_create_agent.py

@@ -279,7 +279,8 @@ def test_tool_runtime_config_access() -> None:
     assert config_data["config_exists"] is True
     assert "config_keys" in config_data
     assert config_data["recursion_limit"] == 9999
-    assert config_data["metadata"]["ls_integration"] == "langchain_create_agent"
+    # create_agent no longer bakes ls_integration; it defers to the caller.
+    assert "ls_integration" not in (config_data["metadata"] or {})
 
     tool_message = result["messages"][2]
     assert isinstance(tool_message, ToolMessage)