From 7c71f575a978de506719717e288edba7d8f57643 Mon Sep 17 00:00:00 2001
From: LegenDairy <devaangadee@gmail.com>
Date: Tue, 11 Aug 2026 20:41:02 +0530
Subject: [PATCH] fix(langfuse): record rerank output in OTEL spans

---
 .../integrations/langfuse/langfuse_otel.py    |  7 +++++
 .../integrations/test_langfuse_otel.py        | 27 +++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/litellm/integrations/langfuse/langfuse_otel.py b/litellm/integrations/langfuse/langfuse_otel.py
index 7de42c00ede..86eca9d8a0e 100644
--- a/litellm/integrations/langfuse/langfuse_otel.py
+++ b/litellm/integrations/langfuse/langfuse_otel.py
@@ -169,6 +169,13 @@ class LangfuseOtelLogger(OpenTelemetry):
                         safe_dumps(output_data),
                     )
 
+        results: Final = response_obj.get("results", [])
+        if results:
+            safe_set_attribute(
+                span,
+                LangfuseSpanAttributes.OBSERVATION_OUTPUT.value,
+                safe_dumps(results),
+            )
         output: Final = response_obj.get("output", [])
         if output:
             output_items_data: Final[list[dict]] = []
diff --git a/tests/test_litellm/integrations/test_langfuse_otel.py b/tests/test_litellm/integrations/test_langfuse_otel.py
index 28f138c7acd..af6dab0d78f 100644
--- a/tests/test_litellm/integrations/test_langfuse_otel.py
+++ b/tests/test_litellm/integrations/test_langfuse_otel.py
@@ -291,6 +291,33 @@ class TestLangfuseOtelIntegration:
                 actual == expect_output
             ), "Mismatch in observation input/output OTEL attributes."
 
+    def test_set_langfuse_specific_attributes_with_rerank_results(self):
+        from litellm.types.integrations.langfuse_otel import LangfuseSpanAttributes
+        from litellm.types.rerank import RerankResponse
+
+        response_obj = RerankResponse(
+            id="rerank-test",
+            results=[
+                {"index": 2, "relevance_score": 0.98},
+                {"index": 0, "relevance_score": 0.41},
+            ],
+        )
+
+        with patch(
+            "litellm.integrations.arize._utils.safe_set_attribute"
+        ) as mock_safe_set_attribute:
+            LangfuseOtelLogger._set_langfuse_specific_attributes(
+                MagicMock(), {}, response_obj
+            )
+
+        output_calls = [
+            call
+            for call in mock_safe_set_attribute.call_args_list
+            if call.args[1] == LangfuseSpanAttributes.OBSERVATION_OUTPUT.value
+        ]
+        assert len(output_calls) == 1
+        assert json.loads(output_calls[0].args[2]) == response_obj.results
+
     def test_set_langfuse_specific_attributes_with_tool_calls(self):
         """Test that _set_langfuse_specific_attributes correctly sets observation.output with tool calls in Langfuse format."""
         from litellm.types.integrations.langfuse_otel import LangfuseSpanAttributes