[langchain] flag to enable context propagation (composability)

[mikeldking]

Right now context propagation is disabled for langchain as it can become troublesome when spans get orphaned (I believe). This is the line in question (https://github.com/Arize-ai/openinference/blob/6f8ec172647c48d9a15218cf248651df37f[…]angchain/src/openinference/instrumentation/langchain/_tracer.py)

This makes langchain not composable however and we need to solve this problem as it seems to come up often. Notably the more recent MCP propagation is impossible.

[mikeldking]

Going to try to see if it works on conjunction with: https://github.com/langchain-ai/langchain-mcp-adapters

[mikeldking]

OTEL context doesn't seem to be able to be attached in a meaningful way:

Traceback (most recent call last):
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/__init__.py", line 155, in detach
    _RUNTIME_CONTEXT.detach(token)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/contextvars_context.py", line 53, in detach
    self._current_context.reset(token)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
ValueError: <Token var=<ContextVar name='current_context' default={} at 0x104a315d0> at 0x106ba6700> was created in a different Context
Failed to detach context
Traceback (most recent call last):
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/__init__.py", line 155, in detach
    _RUNTIME_CONTEXT.detach(token)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/contextvars_context.py", line 53, in detach
    self._current_context.reset(token)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
ValueError: <Token var=<ContextVar name='current_context' default={} at 0x104a315d0> at 0x106b929c0> was created in a different Context
Failed to detach context
Traceback (most recent call last):
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/__init__.py", line 155, in detach
    _RUNTIME_CONTEXT.detach(token)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/contextvars_context.py", line 53, in detach
    self._current_context.reset(token)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
ValueError: <Token var=<ContextVar name='current_context' default={} at 0x104a315d0> at 0x106a87b00> was created in a different Context
attaching otel context
attaching token
Failed to detach context
Traceback (most recent call last):
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/__init__.py", line 155, in detach
    _RUNTIME_CONTEXT.detach(token)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/contextvars_context.py", line 53, in detach
    self._current_context.reset(token)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
ValueError: <Token var=<ContextVar name='current_context' default={} at 0x104a315d0> at 0x106a29ac0> was created in a different Context
Failed to detach context
Traceback (most recent call last):
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/__init__.py", line 155, in detach
    _RUNTIME_CONTEXT.detach(token)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/contextvars_context.py", line 53, in detach
    self._current_context.reset(token)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
ValueError: <Token var=<ContextVar name='current_context' default={} at 0x104a315d0> at 0x106a9a640> was created in a different Context
Failed to detach context
Traceback (most recent call last):
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/__init__.py", line 155, in detach
    _RUNTIME_CONTEXT.detach(token)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/Users/mikeldking/anaconda3/envs/langgraph-mcp/lib/python3.13/site-packages/opentelemetry/context/contextvars_context.py", line 53, in detach
    self._current_context.reset(token)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^