From 3cc58f959b5f27eb48fb86daa6b3da079ce8ab1f Mon Sep 17 00:00:00 2001
From: Eugene Yurtsev <eyurtsev@gmail.com>
Date: Tue, 18 Aug 2026 12:30:24 -0400
Subject: [PATCH] x

---
 libs/core/langchain_core/tracers/core.py      | 18 ++++-
 .../tracers/test_automatic_metadata.py        | 81 +++++++++++++++++++
 2 files changed, 98 insertions(+), 1 deletion(-)

diff --git a/libs/core/langchain_core/tracers/core.py b/libs/core/langchain_core/tracers/core.py
index 6af82ea9d9..e4a3954362 100644
--- a/libs/core/langchain_core/tracers/core.py
+++ b/libs/core/langchain_core/tracers/core.py
@@ -350,13 +350,29 @@ class _TracerCore(ABC):
         return llm_run
 
     def _attach_gateway_metadata(self, run: Run, response: LLMResult) -> None:
-        """Promote LangSmith gateway metadata from the response to run metadata."""
+        """Promote LangSmith gateway metadata from the response to run metadata.
+
+        When a request is routed through the LangSmith gateway, the resolved
+        provider and model may differ from the static values captured in the
+        run's `ls_provider` / `ls_model_name` at start time. When the gateway
+        reports them, they take precedence so the trace reflects what actually
+        served the request.
+        """
         gateway_metadata = _extract_gateway_metadata(response)
         if gateway_metadata is None:
             return
         metadata = run.extra.setdefault("metadata", {})
         metadata[_GATEWAY_RUN_METADATA_KEY] = gateway_metadata
 
+        provider = gateway_metadata.get("provider")
+        if provider:
+            metadata["ls_provider"] = provider
+        # Route-based calls report the served model as `selected_model`; simple
+        # calls report it as `model`.
+        model = gateway_metadata.get("selected_model") or gateway_metadata.get("model")
+        if model:
+            metadata["ls_model_name"] = model
+
     def _errored_llm_run(
         self, error: BaseException, run_id: UUID, response: LLMResult | None = None
     ) -> Run:
diff --git a/libs/core/tests/unit_tests/tracers/test_automatic_metadata.py b/libs/core/tests/unit_tests/tracers/test_automatic_metadata.py
index 47f8362811..22875ce421 100644
--- a/libs/core/tests/unit_tests/tracers/test_automatic_metadata.py
+++ b/libs/core/tests/unit_tests/tracers/test_automatic_metadata.py
@@ -192,6 +192,87 @@ def test_complete_llm_run_attaches_gateway_metadata() -> None:
     assert completed_run.extra["metadata"]["ls_gateway_info"] == gateway_info
 
 
+def test_complete_llm_run_gateway_metadata_overrides_ls_params() -> None:
+    """Gateway provider/model override the static `ls_*` run metadata."""
+    tracer = MockTracerCore()
+    run = _make_run("test-gateway-override-run-id")
+    run.extra = {"metadata": {"ls_provider": "openai", "ls_model_name": "gpt-5.6"}}
+    tracer.run_map[str(run.id)] = run
+
+    gateway_info = {"provider": "anthropic", "model": "claude-opus-5"}
+    response = LLMResult(
+        generations=[
+            [
+                ChatGeneration(
+                    message=AIMessage(content="Test"),
+                    generation_info={GATEWAY_METADATA_RESPONSE_KEY: gateway_info},
+                )
+            ]
+        ]
+    )
+
+    completed_run = tracer._complete_llm_run(response=response, run_id=run.id)
+
+    metadata = completed_run.extra["metadata"]
+    assert metadata["ls_provider"] == "anthropic"
+    assert metadata["ls_model_name"] == "claude-opus-5"
+    assert metadata["ls_gateway_info"] == gateway_info
+
+
+def test_complete_llm_run_gateway_metadata_prefers_selected_model() -> None:
+    """`selected_model` (route-based served model) wins over `model`."""
+    tracer = MockTracerCore()
+    run = _make_run("test-gateway-selected-model-run-id")
+    run.extra = {"metadata": {"ls_model_name": "gpt-5.6"}}
+    tracer.run_map[str(run.id)] = run
+
+    gateway_info = {
+        "provider": "openai",
+        "model": "gpt-5.6",
+        "selected_model": "gpt-5.6-mini",
+    }
+    response = LLMResult(
+        generations=[
+            [
+                ChatGeneration(
+                    message=AIMessage(content="Test"),
+                    generation_info={GATEWAY_METADATA_RESPONSE_KEY: gateway_info},
+                )
+            ]
+        ]
+    )
+
+    completed_run = tracer._complete_llm_run(response=response, run_id=run.id)
+
+    assert completed_run.extra["metadata"]["ls_model_name"] == "gpt-5.6-mini"
+
+
+def test_complete_llm_run_gateway_metadata_preserves_ls_params_when_absent() -> None:
+    """Static `ls_*` values are kept when the gateway omits provider/model."""
+    tracer = MockTracerCore()
+    run = _make_run("test-gateway-partial-run-id")
+    run.extra = {"metadata": {"ls_provider": "openai", "ls_model_name": "gpt-5.6"}}
+    tracer.run_map[str(run.id)] = run
+
+    gateway_info = {"outcome": "success"}
+    response = LLMResult(
+        generations=[
+            [
+                ChatGeneration(
+                    message=AIMessage(content="Test"),
+                    generation_info={GATEWAY_METADATA_RESPONSE_KEY: gateway_info},
+                )
+            ]
+        ]
+    )
+
+    completed_run = tracer._complete_llm_run(response=response, run_id=run.id)
+
+    metadata = completed_run.extra["metadata"]
+    assert metadata["ls_provider"] == "openai"
+    assert metadata["ls_model_name"] == "gpt-5.6"
+
+
 def test_complete_llm_run_no_gateway_metadata() -> None:
     """No gateway metadata is attached when the response carries none."""
     tracer = MockTracerCore()