From 730d066285e601bf81289c40a5013ef3878583c6 Mon Sep 17 00:00:00 2001
From: Mason Daugherty <mason@langchain.dev>
Date: Mon, 18 May 2026 13:33:11 -0700
Subject: [PATCH] test(standard-tests): assert `ls_model_name` honors per-call
 model override (#37504)

Adds a standard unit test so every chat-model integration verifies that
`_get_ls_params` picks up a runtime `model` kwarg instead of always
reporting the constructor default.
---
 .../langchain_openai/chat_models/azure.py     |  5 ++++-
 .../langchain_tests/unit_tests/chat_models.py | 21 +++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/libs/partners/openai/langchain_openai/chat_models/azure.py b/libs/partners/openai/langchain_openai/chat_models/azure.py
index 68bf75856ce..ef51b6e3e7f 100644
--- a/libs/partners/openai/langchain_openai/chat_models/azure.py
+++ b/libs/partners/openai/langchain_openai/chat_models/azure.py
@@ -749,7 +749,10 @@ class AzureChatOpenAI(BaseChatOpenAI):
         """Get the parameters used to invoke the model."""
         params = super()._get_ls_params(stop=stop, **kwargs)
         params["ls_provider"] = "azure"
-        if self.model_name:
+        if "model" in kwargs:
+            # Honor explicit per-call override resolved by super().
+            pass
+        elif self.model_name:
             if self.model_version and self.model_version not in self.model_name:
                 params["ls_model_name"] = (
                     self.model_name + "-" + self.model_version.lstrip("-")
diff --git a/libs/standard-tests/langchain_tests/unit_tests/chat_models.py b/libs/standard-tests/langchain_tests/unit_tests/chat_models.py
index c2c854a94af..0ebf7b4e52b 100644
--- a/libs/standard-tests/langchain_tests/unit_tests/chat_models.py
+++ b/libs/standard-tests/langchain_tests/unit_tests/chat_models.py
@@ -1105,6 +1105,27 @@ class ChatModelUnitTests(ChatModelTests):
         except ValidationError as e:
             pytest.fail(f"Validation error: {e}")
 
+    def test_standard_params_model_override(self, model: BaseChatModel) -> None:
+        """Test that `ls_model_name` reflects a per-call `model` kwarg override.
+
+        If a caller invokes the model with `model="some-other-model"` (e.g.
+        via `bind` or directly through `invoke`), the trace should report
+        that model rather than the constructor's default — otherwise
+        traces silently misattribute calls to the wrong model.
+
+        ??? question "Troubleshooting"
+
+            Subclasses that override `_get_ls_params` should read the model
+            from `kwargs` first, falling back to the configured attribute:
+            `params.get("model", self.model_name)`.
+        """
+        override = "test-model-override-sentinel"
+        ls_params = model._get_ls_params(model=override)
+        assert ls_params.get("ls_model_name") == override, (
+            "ls_model_name did not reflect the per-call `model` override; "
+            "_get_ls_params should honor kwargs['model']."
+        )
+
     def test_serdes(self, model: BaseChatModel, snapshot: SnapshotAssertion) -> None:
         """Test serialization and deserialization of the model.