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fix(langchain): token detach exceptions in async contexts #1317

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Merged
hassiebp merged 1 commit into from
Sep 1, 2025
Merged

fix(langchain): token detach exceptions in async contexts #1317

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42 changes: 36 additions & 6 deletions langfuse/langchain/CallbackHandler.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,10 @@

import pydantic
from opentelemetry import context, trace
from opentelemetry.context import _RUNTIME_CONTEXT

from langfuse._client.attributes import LangfuseOtelSpanAttributes
from langfuse._client.client import Langfuse
from langfuse._client.get_client import get_client
from langfuse._client.span import (
LangfuseAgent,
Expand Down Expand Up @@ -272,7 +274,7 @@ def on_chain_start(
serialized, "chain", **kwargs
)

span = self.client.start_observation(
span = self._get_parent_observation(parent_run_id).start_observation(
name=span_name,
as_type=observation_type,
metadata=span_metadata,
Expand Down Expand Up @@ -336,6 +338,22 @@ def _deregister_langfuse_prompt(self, run_id: Optional[UUID]) -> None:
if run_id is not None and run_id in self.prompt_to_parent_run_map:
del self.prompt_to_parent_run_map[run_id]

def _get_parent_observation(
self, parent_run_id: Optional[UUID]
) -> Union[
Langfuse,
LangfuseAgent,
LangfuseChain,
LangfuseGeneration,
LangfuseRetriever,
LangfuseSpan,
LangfuseTool,
]:
if parent_run_id and parent_run_id in self.runs:
return self.runs[parent_run_id]

return self.client

def _attach_observation(
self,
run_id: UUID,
Expand Down Expand Up @@ -369,7 +387,18 @@ def _detach_observation(
token = self.context_tokens.pop(run_id, None)

if token:
context.detach(token)
try:
# Directly detach from runtime context to avoid error logging
_RUNTIME_CONTEXT.detach(token)
except Exception:
# Context detach can fail in async scenarios - this is expected and safe to ignore
# The span itself was properly ended and tracing data is correctly captured
#
# Examples:
# 1. Token created in one async task/thread, detached in another
# 2. Context already detached by framework or other handlers
# 3. Runtime context state mismatch in concurrent execution
pass

return cast(
Union[
Expand Down Expand Up @@ -591,7 +620,7 @@ def on_tool_start(
serialized, "tool", **kwargs
)

span = self.client.start_observation(
span = self._get_parent_observation(parent_run_id).start_observation(
name=self.get_langchain_run_name(serialized, **kwargs),
as_type=observation_type,
input=input_str,
Expand Down Expand Up @@ -626,8 +655,7 @@ def on_retriever_start(
observation_type = self._get_observation_type_from_serialized(
serialized, "retriever", **kwargs
)

span = self.client.start_observation(
span = self._get_parent_observation(parent_run_id).start_observation(
name=span_name,
as_type=observation_type,
metadata=span_metadata,
Expand Down Expand Up @@ -753,7 +781,9 @@ def __on_llm_action(
"prompt": registered_prompt,
}

generation = self.client.start_observation(as_type="generation", **content) # type: ignore
generation = self._get_parent_observation(parent_run_id).start_observation(
as_type="generation", **content
) # type: ignore
self._attach_observation(run_id, generation)

self.last_trace_id = self.runs[run_id].trace_id
Expand Down