fix(otel v2): map the caller's Langfuse user, session and tags onto the root and generation spans

`langfuse_otel` (OTel v2) only carried `trace_name` from the caller's metadata, so `metadata.trace_user_id` / `session_id` / `tags` (and the `langfuse_trace_user_id` / `langfuse_session_id` proxy headers) never reached Langfuse's user, session and tags fields. Widen the typed caller boundary to `TraceControls`, map it through one `LangfuseMapper.trace_attributes` table on both the root observation and the generation span, and keep `team_id` / `team_alias` proxy-authoritative

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/integrations/otel/langfuse_logger.py

@@ -6,9 +6,9 @@ from litellm.integrations.otel.logger import OpenTelemetryV2
 from litellm.integrations.otel.mappers.langfuse import (
     LANGFUSE_OBSERVATION_INPUT,
     LANGFUSE_OBSERVATION_OUTPUT,
-    LANGFUSE_TRACE_NAME,
+    LangfuseMapper,
 )
-from litellm.integrations.otel.model.metadata import caller_trace_name
+from litellm.integrations.otel.model.metadata import caller_trace_controls
 from litellm.integrations.otel.model.request_io import request_input, response_output, stream_output
 from litellm.integrations.otel.plumbing.context import request_root_span
 
@@ -18,14 +18,13 @@ if TYPE_CHECKING:
 
 
 class LangfuseOpenTelemetryV2(OpenTelemetryV2):
-    """Names the trace from the request. Langfuse reads ``langfuse.trace.name`` off the root observation,
-    and the proxy's root span is still recording when the LLM call starts."""
+    """Stamps the caller's trace controls (name, user, session, tags) on the request. Langfuse reads them off
+    the root observation, and the proxy's root span is still recording when the LLM call starts."""
 
     def log_pre_api_call(self, model: str, messages: object, kwargs: Mapping[str, object]) -> None:
         root: Final = request_root_span()
-        name: Final = caller_trace_name(kwargs)
-        if root is not None and root.is_recording() and name is not None:
-            root.set_attribute(LANGFUSE_TRACE_NAME, name)
+        if root is not None and root.is_recording():
+            root.set_attributes(LangfuseMapper.trace_attributes(caller_trace_controls(kwargs)))
         super().log_pre_api_call(model, messages, kwargs)
 
 

litellm/integrations/otel/logger.py

@@ -554,7 +554,7 @@ class OpenTelemetryV2(CustomLogger):
             capture_content=self.config.capture_span_content,
             time_to_first_chunk_seconds=call.time_to_first_chunk_seconds,
             request_route=request_root_http_route(),
-            trace_name=call.trace_name,
+            trace=call.trace,
         )
         end_time_ns: Final = to_ns(end_time)
         if carrier is not None and carrier.span is not None:

litellm/integrations/otel/mappers/langfuse.py

@@ -5,12 +5,14 @@ Langfuse ingests OTLP spans and reads from its own vendor namespace
 ``GenAIMapper`` to send canonical + Langfuse-flavored spans simultaneously.
 
 Every attribute is declared as a ``key -> extractor`` table entry (one callable
-per mapping operation): ``_LLM_CALL_ATTRS`` for scalars and ``_BLOB_ATTRS`` for
-the JSON-serialized payloads. ``_llm_call`` just applies both tables.
+per mapping operation): ``_LLM_CALL_ATTRS`` for scalars, ``_TRACE_ATTRS`` for the
+caller's trace controls (shared with the root observation), and ``_BLOB_ATTRS`` for
+the JSON-serialized payloads. ``_llm_call`` just applies the three tables.
 """
 
 import json
-from collections.abc import Callable
+from collections.abc import Callable, Mapping
+from types import MappingProxyType
 from typing import Final
 
 from litellm.integrations.otel.mappers.base import AttributeMap, AttrValue, SpanData
@@ -20,6 +22,7 @@ from litellm.integrations.otel.mappers.utils import (
     output_messages,
     serialize_messages,
 )
+from litellm.integrations.otel.model.metadata import TraceControls
 from litellm.integrations.otel.model.payloads import (
     LLMCallSpanData,
     LLMRequestParams,
@@ -29,6 +32,9 @@ from litellm.integrations.otel.model.payloads import (
 LANGFUSE_OBSERVATION_INPUT: Final = "langfuse.observation.input"
 LANGFUSE_OBSERVATION_OUTPUT: Final = "langfuse.observation.output"
 LANGFUSE_TRACE_NAME: Final = "langfuse.trace.name"
+LANGFUSE_TRACE_USER_ID: Final = "user.id"
+LANGFUSE_TRACE_SESSION_ID: Final = "session.id"
+LANGFUSE_TRACE_TAGS: Final = "langfuse.trace.tags"
 
 
 class LangfuseMapper:
@@ -37,11 +43,19 @@ class LangfuseMapper:
         "langfuse.observation.model.name": lambda d: d.request_model or None,
         "langfuse.observation.metadata.provider": lambda d: d.provider or None,
         "langfuse.observation.id": lambda d: d.identity.call_id or None,
-        LANGFUSE_TRACE_NAME: lambda d: d.trace_name or None,
         "langfuse.trace.metadata.team_id": lambda d: d.identity.team_id or None,
         "langfuse.trace.metadata.team_alias": lambda d: d.identity.team_alias or None,
     }
 
+    _TRACE_ATTRS: Mapping[str, Callable[[TraceControls], AttrValue | None]] = MappingProxyType(
+        {
+            LANGFUSE_TRACE_NAME: lambda t: t.name or None,
+            LANGFUSE_TRACE_USER_ID: lambda t: t.user_id or None,
+            LANGFUSE_TRACE_SESSION_ID: lambda t: t.session_id or None,
+            LANGFUSE_TRACE_TAGS: lambda t: t.tags or None,
+        }
+    )
+
     # Sub-tables folded into their respective JSON blobs.
     _MODEL_PARAMS: dict[str, Callable[[LLMRequestParams], AttrValue | None]] = {
         "temperature": lambda rp: rp.temperature,
@@ -77,9 +91,14 @@ class LangfuseMapper:
             case _:
                 return {}
 
+    @classmethod
+    def trace_attributes(cls, trace: TraceControls) -> AttributeMap:
+        return collect(cls._TRACE_ATTRS, trace)
+
     @classmethod
     def _llm_call(cls, data: LLMCallSpanData) -> AttributeMap:
         return {
             **collect(cls._LLM_CALL_ATTRS, data),
+            **cls.trace_attributes(data.trace),
             **collect(cls._BLOB_ATTRS, data),
         }

litellm/integrations/otel/model/metadata.py

@@ -36,7 +36,7 @@ model. They coincide on the SDK path, which is correct.
 
 from __future__ import annotations
 
-from collections.abc import Iterator, Mapping
+from collections.abc import Iterator, Mapping, Sequence
 from dataclasses import dataclass, field
 from types import MappingProxyType
 from typing import TYPE_CHECKING, Any, Final, cast
@@ -48,7 +48,20 @@ from litellm.integrations.otel.model.utils import as_str, to_seconds
 if TYPE_CHECKING:
     from litellm.types.utils import StandardLoggingPayload
 
-LANGFUSE_TRACE_NAME_HEADER: Final = "langfuse_trace_name"
+LANGFUSE_HEADER_PREFIX: Final = "langfuse_"
+
+
+@dataclass(frozen=True, slots=True)
+class TraceControls:
+    """The caller's trace-level Langfuse controls: ``metadata.trace_name`` / ``trace_user_id`` / ``session_id`` /
+    ``tags`` on the request (SDK or proxy body), with the proxy's ``langfuse_<control>`` headers winning over the
+    body for the scalar ones. Mutation controls (``trace_id``, ``existing_trace_id``, ``update_trace_keys``) are
+    deliberately not carried."""
+
+    name: str | None = None
+    user_id: str | None = None
+    session_id: str | None = None
+    tags: tuple[str, ...] = ()
 
 
 @dataclass(frozen=True)
@@ -217,7 +230,7 @@ class LLMCallEvent:
     # needs to be reasonable for a span that never gets closed (a leak).
     provisional_span_name: str
     time_to_first_chunk_seconds: float | None
-    trace_name: str | None
+    trace: TraceControls
 
     @classmethod
     def from_dict(cls, kwargs: Mapping[str, Any]) -> LLMCallEvent:
@@ -234,29 +247,41 @@ class LLMCallEvent:
             upstream_started=kwargs.get("api_call_start_time") is not None,
             provisional_span_name=f"{operation.value} {model}".strip(),
             time_to_first_chunk_seconds=time_to_first_chunk_seconds(kwargs),
-            trace_name=caller_trace_name(kwargs),
+            trace=caller_trace_controls(kwargs),
         )
 
 
-def caller_trace_name(kwargs: Mapping[str, object]) -> str | None:
+def caller_trace_controls(kwargs: Mapping[str, object]) -> TraceControls:
     request: Final = _as_str_mapping(kwargs.get("litellm_params"))
     if request is None:
-        return None
+        return TraceControls()
     proxy_request: Final = _as_str_mapping(request.get("proxy_server_request"))
-    headers: Final = _as_str_mapping(proxy_request.get("headers")) if proxy_request is not None else None
-    from_header: Final = as_str(headers.get(LANGFUSE_TRACE_NAME_HEADER)) if headers is not None else None
-    if from_header:
-        return from_header
-    return next(
-        (
-            name
-            for key in ("metadata", "litellm_metadata")
-            if (metadata := _as_str_mapping(request.get(key))) is not None
-            and (name := as_str(metadata.get("trace_name")))
-        ),
-        None,
+    headers: Final = (_as_str_mapping(proxy_request.get("headers")) if proxy_request is not None else None) or {}
+    bodies: Final = tuple(
+        metadata
+        for key in ("metadata", "litellm_metadata")
+        if (metadata := _as_str_mapping(request.get(key))) is not None
     )
 
+    def scalar(control: str) -> str | None:
+        from_header: Final = as_str(headers.get(f"{LANGFUSE_HEADER_PREFIX}{control}"))
+        if from_header:
+            return from_header
+        return next((value for body in bodies if (value := as_str(body.get(control)))), None)
+
+    return TraceControls(
+        name=scalar("trace_name"),
+        user_id=scalar("trace_user_id"),
+        session_id=scalar("session_id"),
+        tags=next((tags for body in bodies if (tags := _str_items(body.get("tags")))), ()),
+    )
+
+
+def _str_items(value: object) -> tuple[str, ...]:
+    if not isinstance(value, (list, tuple)):
+        return ()
+    return tuple(item for item in cast("Sequence[object]", value) if isinstance(item, str) and item)
+
 
 def time_to_first_chunk_seconds(kwargs: Mapping[str, Any]) -> float | None:
     """Seconds from the upstream request being issued (``api_call_start_time``)

litellm/integrations/otel/model/payloads.py

@@ -13,6 +13,7 @@ from urllib.parse import urlsplit
 from litellm.integrations.otel.model.metadata import (
     RequestContext,
     RequestIdentity,
+    TraceControls,
 )
 from litellm.integrations.otel.model.semconv import (
     GenAIOperation,
@@ -387,7 +388,7 @@ class LLMCallSpanData:
     output_type: GenAIOutputType | None = None
     call_type: str | None = None
     request_route: str | None = None
-    trace_name: str | None = None
+    trace: TraceControls = field(default_factory=TraceControls)
 
     @classmethod
     def from_standard_logging_payload(
@@ -396,7 +397,7 @@ class LLMCallSpanData:
         capture_content: bool = False,
         time_to_first_chunk_seconds: float | None = None,
         request_route: str | None = None,
-        trace_name: str | None = None,
+        trace: TraceControls | None = None,
     ) -> LLMCallSpanData:
         params: Final = cast(Mapping[str, object], payload.get("model_parameters") or {})
         # The single parse of the request's metadata — the request-vs-provider
@@ -438,7 +439,7 @@ class LLMCallSpanData:
             output_type=resolve_output_type(call_type),
             call_type=call_type or None,
             request_route=request_route or context.identity.request_route,
-            trace_name=trace_name,
+            trace=trace or TraceControls(),
         )
 
 

tests/test_litellm/integrations/otel/test_langfuse_logger.py

@@ -42,6 +42,7 @@ from litellm.types.utils import (  # noqa: E402
 INPUT_ATTR: Final = "langfuse.observation.input"
 OUTPUT_ATTR: Final = "langfuse.observation.output"
 TRACE_NAME_ATTR: Final = "langfuse.trace.name"
+TRACE_CONTROL_ATTRS: Final = (TRACE_NAME_ATTR, "user.id", "session.id", "langfuse.trace.tags")
 CHAT_DATA: Final = {"model": "gpt-5.4-mini", "messages": [{"role": "user", "content": "ping"}]}
 
 
@@ -374,6 +375,99 @@ def test_unnamed_request_leaves_the_trace_name_off_both_spans():
     assert TRACE_NAME_ATTR not in root_attrs and TRACE_NAME_ATTR not in generation_attrs
 
 
+@pytest.mark.parametrize("capture", ["span_only", "no_content"])
+def test_body_metadata_user_session_and_tags_land_on_the_root_and_the_generation(capture):
+    logger, exporter = _logger(capture=capture)
+
+    root_attrs, generation_attrs = _run_named_request(
+        logger,
+        exporter,
+        {
+            "metadata": {
+                "trace_user_id": "user-42",
+                "session_id": "session-7",
+                "tags": ["prod", "eval", "nightly"],
+                "user_api_key_team_id": "team-from-proxy",
+            },
+            "proxy_server_request": {"headers": {}},
+        },
+    )
+
+    for attrs in (root_attrs, generation_attrs):
+        assert attrs["user.id"] == "user-42"
+        assert attrs["session.id"] == "session-7"
+        assert tuple(attrs["langfuse.trace.tags"]) == ("prod", "eval", "nightly")
+        assert TRACE_NAME_ATTR not in attrs
+
+
+def test_langfuse_user_and_session_headers_beat_body_metadata_on_both_spans():
+    logger, exporter = _logger()
+
+    root_attrs, generation_attrs = _run_named_request(
+        logger,
+        exporter,
+        {
+            "metadata": {"trace_user_id": "from-body", "session_id": "from-body"},
+            "proxy_server_request": {
+                "headers": {"langfuse_trace_user_id": "from-header", "langfuse_session_id": "from-header-s"}
+            },
+        },
+    )
+
+    for attrs in (root_attrs, generation_attrs):
+        assert attrs["user.id"] == "from-header"
+        assert attrs["session.id"] == "from-header-s"
+
+
+def test_caller_metadata_cannot_override_the_proxy_team_identity():
+    logger, exporter = _logger()
+    response: Final = ModelResponse(choices=[Choices(message=Message(role="assistant", content="pong"))])
+    litellm_params: Final = {
+        "metadata": {"trace_user_id": "u", "trace_metadata": {"team_id": "spoofed"}, "team_id": "spoofed"}
+    }
+    logger.log_pre_api_call(
+        model="gpt-5.4-mini", messages=[], kwargs={"litellm_call_id": "call_1", "litellm_params": litellm_params}
+    )
+    payload: Final = {
+        "call_type": "acompletion",
+        "custom_llm_provider": "openai",
+        "model": "gpt-5.4-mini",
+        "messages": CHAT_DATA["messages"],
+        "response": response.model_dump(),
+        "status": "success",
+        "litellm_call_id": "call_1",
+        "metadata": {
+            "user_api_key_team_id": "real-team",
+            "user_api_key_team_alias": "real-alias",
+            "team_id": "spoofed",
+            "team_alias": "spoofed",
+        },
+        "hidden_params": {},
+    }
+    asyncio.run(
+        logger.async_log_success_event(
+            {"standard_logging_object": payload, "litellm_params": litellm_params}, response, None, None
+        )
+    )
+
+    attrs: Final = dict(exporter.get_finished_spans()[0].attributes or {})
+    assert attrs["user.id"] == "u"
+    assert attrs["langfuse.trace.metadata.team_id"] == "real-team"
+    assert attrs["langfuse.trace.metadata.team_alias"] == "real-alias"
+    assert "langfuse.trace.metadata" not in attrs and "langfuse.trace.id" not in attrs
+
+
+def test_a_request_without_trace_controls_stamps_none_of_them():
+    logger, exporter = _logger()
+
+    root_attrs, generation_attrs = _run_named_request(
+        logger, exporter, {"metadata": {"user_api_key_team_id": "t1", "tags": []}, "proxy_server_request": {"headers": {}}}
+    )
+
+    assert set(TRACE_CONTROL_ATTRS).isdisjoint(root_attrs)
+    assert set(TRACE_CONTROL_ATTRS).isdisjoint(generation_attrs)
+
+
 @pytest.mark.parametrize(
     ("capture", "mappers"),
     [("no_content", ("genai", "langfuse")), ("span_only", ("genai",))],

tests/test_litellm/integrations/otel/test_otel_v2_sources_of_truth.py

@@ -28,7 +28,7 @@ from litellm.integrations.otel import (
 )
 from litellm.integrations.otel.mappers.genai import GenAIMapper
 from litellm.integrations.otel.model import spans as spans_mod
-from litellm.integrations.otel.model.metadata import LLMCallEvent, caller_trace_name
+from litellm.integrations.otel.model.metadata import LLMCallEvent, TraceControls, caller_trace_controls
 from litellm.integrations.otel.model.payloads import (
     LLMCallSpanData,
     RequestIdentity,
@@ -743,15 +743,62 @@ def test_request_identity_falls_back_to_legacy_team_keys():
     ids=["header", "body", "anthropic-body", "header-beats-body", "blank-header-falls-through", "neither", "empty"],
 )
 def test_caller_trace_name_prefers_the_langfuse_header_over_body_metadata(request_data, expected):
-    assert caller_trace_name({"litellm_params": request_data}) == expected
-    assert LLMCallEvent.from_dict({"litellm_params": request_data}).trace_name == expected
+    assert caller_trace_controls({"litellm_params": request_data}).name == expected
+    assert LLMCallEvent.from_dict({"litellm_params": request_data}).trace.name == expected
 
 
-def test_llm_span_data_carries_the_caller_trace_name():
-    data: Final = LLMCallSpanData.from_standard_logging_payload(_sample_payload(), trace_name="nightly-eval")
+@pytest.mark.parametrize(
+    ("request_data", "expected"),
+    [
+        (
+            {"metadata": {"trace_user_id": "u-body", "session_id": "s-body", "tags": ["a", "b", "c"]}},
+            TraceControls(user_id="u-body", session_id="s-body", tags=("a", "b", "c")),
+        ),
+        (
+            {
+                "proxy_server_request": {
+                    "headers": {"langfuse_trace_user_id": "u-header", "langfuse_session_id": "s-header"}
+                },
+                "metadata": {"trace_user_id": "u-body", "session_id": "s-body"},
+            },
+            TraceControls(user_id="u-header", session_id="s-header"),
+        ),
+        (
+            {"litellm_metadata": {"trace_user_id": "u-anthropic", "session_id": "s-anthropic", "tags": ["x"]}},
+            TraceControls(user_id="u-anthropic", session_id="s-anthropic", tags=("x",)),
+        ),
+        (
+            {"metadata": {"tags": ["kept", 7, "", None, "also-kept"]}},
+            TraceControls(tags=("kept", "also-kept")),
+        ),
+        ({"metadata": {"tags": "not-a-list", "trace_user_id": "", "session_id": 12}}, TraceControls(session_id="12")),
+        (
+            {
+                "metadata": {
+                    "trace_id": "forced",
+                    "existing_trace_id": "forced",
+                    "update_trace_keys": ["name"],
+                    "trace_metadata": {"team_id": "spoofed"},
+                    "user_api_key_team_id": "t1",
+                }
+            },
+            TraceControls(),
+        ),
+        ({}, TraceControls()),
+    ],
+    ids=["body", "headers-beat-body", "anthropic-body", "non-string-tags-dropped", "scalar-coercion", "mutation-controls-ignored", "empty"],
+)
+def test_caller_trace_controls_carry_user_session_and_tags(request_data, expected):
+    assert caller_trace_controls({"litellm_params": request_data}) == expected
+    assert LLMCallEvent.from_dict({"litellm_params": request_data}).trace == expected
 
-    assert data.trace_name == "nightly-eval"
-    assert LLMCallSpanData.from_standard_logging_payload(_sample_payload()).trace_name is None
+
+def test_llm_span_data_carries_the_caller_trace_controls():
+    controls: Final = TraceControls(name="nightly-eval", user_id="u1", session_id="s1", tags=("a", "b"))
+    data: Final = LLMCallSpanData.from_standard_logging_payload(_sample_payload(), trace=controls)
+
+    assert data.trace == controls
+    assert LLMCallSpanData.from_standard_logging_payload(_sample_payload()).trace == TraceControls()
 
 
 def test_llm_span_carries_proxy_request_route():

tests/test_litellm/integrations/otel/test_otel_v2_vendor_mappers.py

@@ -18,6 +18,7 @@ from litellm.integrations.otel.mappers import (
     WeaveMapper,
     resolve_mappers,
 )
+from litellm.integrations.otel.model.metadata import TraceControls
 from litellm.integrations.otel.model.payloads import (
     LLMCallSpanData,
     LLMRequestParams,
@@ -135,8 +136,35 @@ def test_langfuse_mapper_observation_attrs():
 
 
 def test_langfuse_mapper_names_the_trace_from_the_caller():
-    assert LangfuseMapper().map(_llm_call(trace_name="nightly-eval"))["langfuse.trace.name"] == "nightly-eval"
-    assert "langfuse.trace.name" not in LangfuseMapper().map(_llm_call(trace_name=None))
+    named = LangfuseMapper().map(_llm_call(trace=TraceControls(name="nightly-eval")))
+    assert named["langfuse.trace.name"] == "nightly-eval"
+    assert "langfuse.trace.name" not in LangfuseMapper().map(_llm_call(trace=TraceControls()))
+
+
+def test_langfuse_mapper_carries_the_caller_user_session_and_tags():
+    controls = TraceControls(user_id="u-42", session_id="s-7", tags=("prod", "eval", "nightly"))
+    attrs = LangfuseMapper().map(_llm_call(trace=controls))
+
+    assert attrs["user.id"] == "u-42"
+    assert attrs["session.id"] == "s-7"
+    assert attrs["langfuse.trace.tags"] == ("prod", "eval", "nightly")
+    assert attrs["langfuse.trace.metadata.team_id"] == "t1"
+    assert attrs["langfuse.trace.metadata.team_alias"] == "team one"
+
+
+def test_langfuse_mapper_omits_unset_trace_controls():
+    attrs = LangfuseMapper().map(_llm_call(trace=TraceControls(user_id="", session_id=None, tags=())))
+
+    assert {"user.id", "session.id", "langfuse.trace.tags", "langfuse.trace.name"}.isdisjoint(attrs)
+
+
+def test_langfuse_trace_attributes_match_between_root_and_generation():
+    controls = TraceControls(name="n", user_id="u", session_id="s", tags=("t",))
+    generation = LangfuseMapper().map(_llm_call(trace=controls))
+
+    root = LangfuseMapper.trace_attributes(controls)
+    assert root == {"langfuse.trace.name": "n", "user.id": "u", "session.id": "s", "langfuse.trace.tags": ("t",)}
+    assert all(generation[key] == value for key, value in root.items())
 
 
 def test_langfuse_mapper_skips_when_no_messages():