Make langchain core optional (#80)

* Make langchain-core an optional dependency

* Improve missing package logs

* Add CHANGELOG

* Fix log level

* Fix tests

Author: rads-1996

CHANGELOG.md

@@ -5,21 +5,29 @@
 ## Bugs Fixed
 - Reverted [#81](https://github.com/microsoft/opentelemetry-distro-python/pull/81): baggage propagation now requires `enable_a365=True` and respects `ENABLE_A365_OBSERVABILITY_EXPORTER` as before.
 
+### Other Changes
+- Make `langchain-core` an optional dependency. The LangChain instrumentation
+  is now installable via `pip install microsoft-opentelemetry[langchain]` and
+  fails silently with a one-time warning when `langchain-core` is not
+  installed.
+
+
 ## 0.1.0b2 (2026-04-28)
 
 ### Bugs Fixed
 - Ensure baggage properties propagate to child spans for all exporters
   ([#81](https://github.com/microsoft/opentelemetry-distro-python/pull/81))
 
+
 ## 0.1.0b1 (2026-04-27)
 
 ### Features Added
 
 - Ensure baggage properties propagate to child spans when the console exporter is chosen and A365 exporter is disabled
   ([#74](https://github.com/microsoft/opentelemetry-distro-python/pull/74))
 - Disable web-framework / HTTP-client instrumentations
-  (`django`, `fastapi`, `flask`, `psycopg2`, `requests`, `urllib`, `urllib3`)
-  by default when A365 is enabled. GenAI instrumentations
+  (`django`, `fastapi`, `flask`, `psycopg2`, `requests`, `urllib`, `urllib3`,
+  `azure_sdk`) by default when A365 is enabled. GenAI instrumentations
   (`langchain`, `openai`, `openai_agents`, `semantic_kernel`,
   `agent_framework`) remain enabled. Users can override either default via
   `instrumentation_options`.

pyproject.toml

@@ -40,7 +40,6 @@ dependencies = [
     "opentelemetry-instrumentation-openai-agents-v2==0.1.0",
     "opentelemetry-instrumentation-openai-v2==2.3b0",
     "opentelemetry-resource-detector-azure<1.0.0,>=0.1.5",
-    "langchain-core>=0.2.0",
     "wrapt>=1.0",
     "opentelemetry-util-genai>=0.3b0",
     "microsoft-agents-activity>=0.9.0",
@@ -51,6 +50,9 @@ dependencies = [
 ]
 
 [project.optional-dependencies]
+langchain = [
+    "langchain-core>=0.2.0",
+]
 test = [
     "pytest>=8.0",
     "pytest-cov>=5.0",

src/microsoft/opentelemetry/_genai/_langchain/_tracer_instrumentor.py

@@ -16,22 +16,33 @@
 from typing import Any
 from uuid import UUID
 
-import langchain_core
-import langchain_core.callbacks
-import langchain_core.runnables.config
 import opentelemetry.trace as trace_api
-from langchain_core.callbacks import BaseCallbackManager
 from opentelemetry._logs import get_logger as get_otel_logger
 from opentelemetry.instrumentation.instrumentor import BaseInstrumentor  # type: ignore[attr-defined]
 from opentelemetry.trace import Span
-from wrapt import wrap_function_wrapper
-
-from microsoft.opentelemetry._genai._langchain._tracer import LangChainTracer
 
 logger = logging.getLogger(__name__)
 
 _INSTRUMENTS: str = "langchain-core >= 0.2.0"
 
+try:
+    import langchain_core
+    import langchain_core.callbacks
+    import langchain_core.runnables.config
+    from langchain_core.callbacks import BaseCallbackManager
+    from wrapt import wrap_function_wrapper
+
+    from microsoft.opentelemetry._genai._langchain._tracer import LangChainTracer
+
+    langchain_available = True
+except ImportError:  # pragma: no cover - exercised only when langchain-core absent
+    langchain_available = False
+    logger.warning(
+        "LangChain instrumentation is disabled because 'langchain-core' is not "
+        "installed. Install the optional extra with "
+        "`pip install microsoft-opentelemetry[langchain]` to enable it."
+    )
+
 
 class LangChainInstrumentor(BaseInstrumentor):
     """Attaches a LangChainTracer to every new BaseCallbackManager."""
@@ -47,6 +58,8 @@ def instrumentation_dependencies(self) -> Collection[str]:
         return (_INSTRUMENTS,)
 
     def _instrument(self, **kwargs: Any) -> None:
+        if not langchain_available:
+            return
         tracer_provider = kwargs.get("tracer_provider")
         tracer = trace_api.get_tracer(
             __name__,
@@ -83,6 +96,8 @@ def _instrument(self, **kwargs: Any) -> None:
         )
 
     def _uninstrument(self, **kwargs: Any) -> None:
+        if not langchain_available:
+            return
         if self._original_cb_init is not None:
             langchain_core.callbacks.BaseCallbackManager.__init__ = self._original_cb_init  # type: ignore[assignment]
         self._original_cb_init = None

tests/langchain/test_tracer.py

@@ -7,16 +7,22 @@
 from unittest.mock import MagicMock, patch
 from uuid import uuid4
 
-from microsoft.opentelemetry._genai._langchain._tracer import (
+import pytest
+
+pytest.importorskip("langchain_core")
+
+from microsoft.opentelemetry._genai._langchain._tracer import (  # noqa: E402  # pylint: disable=wrong-import-position
     LangChainTracer,
     _update_span,
     get_attributes_from_context,
 )
-from microsoft.opentelemetry._genai._langchain._utils import (
+from microsoft.opentelemetry._genai._langchain._utils import (  # noqa: E402  # pylint: disable=wrong-import-position
     EXECUTE_TOOL_OPERATION_NAME,
     INVOKE_AGENT_OPERATION_NAME,
 )
 
+pytest.importorskip("langchain_core")
+
 _NOW = datetime.datetime(2024, 6, 1, 12, 0, 0, tzinfo=datetime.timezone.utc)
 _NOW_END = datetime.datetime(2024, 6, 1, 12, 0, 1, tzinfo=datetime.timezone.utc)
 

tests/langchain/test_tracer_instrumentor.py

@@ -10,6 +10,9 @@
     _BaseCallbackManagerInit,
 )
 
+import pytest
+
+pytest.importorskip("langchain_core")
 
 class TestLangChainInstrumentor(TestCase):
     def setUp(self):
@@ -95,6 +98,30 @@ def test_get_ancestors_returns_empty_when_not_instrumented(self, mock_wrap, mock
         inst = LangChainInstrumentor()
         self.assertEqual(inst.get_ancestors(uuid4()), [])
 
+    @patch("microsoft.opentelemetry._genai._langchain._tracer_instrumentor.langchain_available", False)
+    @patch("microsoft.opentelemetry._genai._langchain._tracer_instrumentor.wrap_function_wrapper")
+    @patch("microsoft.opentelemetry._genai._langchain._tracer_instrumentor.logger")
+    def test_instrument_skips_when_langchain_unavailable(self, mock_logger, mock_wrap):
+        """When langchain-core is not installed, _instrument logs a debug message and no-ops."""
+        inst = LangChainInstrumentor()
+        inst._instrument()
+        mock_wrap.assert_not_called()
+        self.assertIsNone(inst._tracer)
+        mock_logger.debug.assert_called_once()
+        debug_msg = mock_logger.debug.call_args[0][0]
+        self.assertIn("langchain-core", debug_msg)
+        # Should NOT log a warning here (the import-time warning already fired).
+        mock_logger.warning.assert_not_called()
+
+    @patch("microsoft.opentelemetry._genai._langchain._tracer_instrumentor.langchain_available", False)
+    def test_uninstrument_no_op_when_langchain_unavailable(self):
+        """_uninstrument is a safe no-op when langchain-core is not installed."""
+        inst = LangChainInstrumentor()
+        # Should not raise
+        inst._uninstrument()
+        self.assertIsNone(inst._tracer)
+        self.assertIsNone(inst._original_cb_init)
+
 
 class TestBaseCallbackManagerInit(TestCase):
     def test_adds_tracer_to_handlers(self):

tests/langchain/test_utils.py

@@ -7,7 +7,11 @@
 from unittest import TestCase
 from unittest.mock import MagicMock, patch
 
-from microsoft.opentelemetry._genai._langchain._utils import (
+import pytest
+
+pytest.importorskip("langchain_core")
+
+from microsoft.opentelemetry._genai._langchain._utils import (  # noqa: E402  # pylint: disable=wrong-import-position
     DictWithLock,
     CHAT_OPERATION_NAME,
     EXECUTE_TOOL_OPERATION_NAME,