fix(openai): capture reasoning_effort and verbosity in model parameters

langfuse/openai.py

@@ -30,7 +30,7 @@
 from dataclasses import dataclass
 from datetime import datetime
 from inspect import isawaitable, isclass
-from typing import Any, Optional, cast
+from typing import Any, Dict, Optional, cast
 
 from openai import _types as openai_types
 from openai._types import NotGiven
@@ -494,6 +494,36 @@ def _extract_chat_response(kwargs: Any) -> Any:
     return response
 
 
+def _parse_reasoning_model_parameters(
+    resource: OpenAiDefinition, kwargs: Any
+) -> Dict[str, Any]:
+    """Collect reasoning-model request params as flat model parameters.
+
+    Chat Completions accepts `reasoning_effort` and `verbosity` at the top level,
+    while the Responses API nests them under `reasoning` and `text`.
+    """
+    if resource.object in ("Responses", "AsyncResponses"):
+        reasoning = kwargs.get("reasoning", None)
+        text = kwargs.get("text", None)
+        candidates = {
+            "reasoning_effort": _get_attr_or_item(reasoning, "effort"),
+            "reasoning_summary": _get_attr_or_item(reasoning, "summary"),
+            "verbosity": _get_attr_or_item(text, "verbosity"),
+            "max_output_tokens": kwargs.get("max_output_tokens", None),
+        }
+    else:
+        candidates = {
+            "reasoning_effort": kwargs.get("reasoning_effort", None),
+            "verbosity": kwargs.get("verbosity", None),
+        }
+
+    return {
+        key: value
+        for key, value in candidates.items()
+        if value is not None and not _is_not_given(value)
+    }
+
+
 def _get_langfuse_data_from_kwargs(resource: OpenAiDefinition, kwargs: Any) -> Any:
     default_name = (
         "OpenAI-embedding" if resource.type == "embedding" else "OpenAI-generation"
@@ -646,6 +676,10 @@ def _get_langfuse_data_from_kwargs(resource: OpenAiDefinition, kwargs: Any) -> A
         if parsed_service_tier is not None:
             modelParameters["service_tier"] = parsed_service_tier
 
+        modelParameters.update(_parse_reasoning_model_parameters(resource, kwargs))
+        if "max_output_tokens" in modelParameters:
+            modelParameters.pop("max_tokens", None)
+
     langfuse_prompt = kwargs.get("langfuse_prompt", None)
 
     return {

tests/unit/test_openai.py

@@ -1167,6 +1167,77 @@ async def test_openai_async_stream_captures_service_tier_from_chunks(
     assert model_parameters["temperature"] == 0
 
 
+def test_chat_completion_captures_reasoning_parameters(
+    langfuse_memory_client, get_span, json_attr
+):
+    openai_client = lf_openai.OpenAI(api_key="test")
+    response = _make_chat_response()
+
+    with patch.object(openai_client.chat.completions, "_post", return_value=response):
+        openai_client.chat.completions.create(
+            name="unit-openai-reasoning-params",
+            model="gpt-5",
+            messages=[{"role": "user", "content": "1 + 1 = ?"}],
+            reasoning_effort="minimal",
+            verbosity="low",
+        )
+
+    langfuse_memory_client.flush()
+    span = get_span("unit-openai-reasoning-params")
+
+    model_parameters = json_attr(
+        span, LangfuseOtelSpanAttributes.OBSERVATION_MODEL_PARAMETERS
+    )
+    assert model_parameters["reasoning_effort"] == "minimal"
+    assert model_parameters["verbosity"] == "low"
+
+
+def test_chat_completion_reasoning_parameters_absent_by_default(
+    langfuse_memory_client, get_span, json_attr
+):
+    from openai._types import NOT_GIVEN
+
+    openai_client = lf_openai.OpenAI(api_key="test")
+    response = _make_chat_response()
+
+    with patch.object(openai_client.chat.completions, "_post", return_value=response):
+        openai_client.chat.completions.create(
+            name="unit-openai-reasoning-params-absent",
+            model="gpt-4o-mini",
+            messages=[{"role": "user", "content": "1 + 1 = ?"}],
+            reasoning_effort=NOT_GIVEN,
+        )
+
+    langfuse_memory_client.flush()
+    span = get_span("unit-openai-reasoning-params-absent")
+
+    model_parameters = json_attr(
+        span, LangfuseOtelSpanAttributes.OBSERVATION_MODEL_PARAMETERS
+    )
+    assert "reasoning_effort" not in model_parameters
+    assert "verbosity" not in model_parameters
+
+
+def test_responses_kwargs_capture_reasoning_parameters():
+    data = lf_openai_module._get_langfuse_data_from_kwargs(
+        SimpleNamespace(type="chat", object="Responses"),
+        {
+            "model": "gpt-5",
+            "input": "1 + 1 = ?",
+            "reasoning": {"effort": "high", "summary": "auto"},
+            "text": {"verbosity": "high", "format": {"type": "text"}},
+            "max_output_tokens": 256,
+        },
+    )
+
+    model_parameters = data["model_parameters"]
+    assert model_parameters["reasoning_effort"] == "high"
+    assert model_parameters["reasoning_summary"] == "auto"
+    assert model_parameters["verbosity"] == "high"
+    assert model_parameters["max_output_tokens"] == 256
+    assert "max_tokens" not in model_parameters
+
+
 def test_embedding_model_parameters_do_not_include_service_tier(
     langfuse_memory_client, get_span, json_attr
 ):