add langchain

libs/core/langchain_core/language_models/base.py

@@ -183,8 +183,8 @@ class BaseLanguageModel(
         """Pydantic V2 lifecycle hook called automatically after `__init__`.
 
         Seeds `metadata["versions"]` with the installed `langchain-core`
-        version so that every LLM trace carries the package version that
-        produced it.
+        (and `langchain`, if installed) versions so that every LLM trace
+        carries the package versions that produced it.
 
         Partner packages should **not** override this method. Instead, they
         should define a `@model_validator(mode="after")` that calls
@@ -206,6 +206,13 @@ class BaseLanguageModel(
 
         self._add_version("langchain-core", VERSION)
 
+        try:
+            from importlib.metadata import version as pkg_version  # noqa: PLC0415
+
+            self._add_version("langchain", pkg_version("langchain"))
+        except Exception:  # noqa: S110
+            pass
+
     def _add_version(self, pkg: str, version: str) -> None:
         """Record a package version in `metadata.versions` for tracing.
 
@@ -216,7 +223,13 @@ class BaseLanguageModel(
         Example resulting metadata:
 
         ```python
-        {"versions": {"langchain-core": "1.x.x", "langchain-openai": "1.x.x"}}
+        {
+            "versions": {
+                "langchain-core": "1.x.x",
+                "langchain": "1.x.x",
+                "langchain-openai": "1.x.x",
+            }
+        }
         ```
 
         Args:

libs/core/tests/unit_tests/language_models/chat_models/test_base.py

@@ -1312,6 +1312,36 @@ def test_add_version_with_non_dict_versions() -> None:
     assert "langchain-core" in llm.metadata["versions"]
 
 
+def test_langchain_version_in_metadata(monkeypatch: pytest.MonkeyPatch) -> None:
+    """When `langchain` is installed, its version appears in metadata."""
+    monkeypatch.setattr(
+        "importlib.metadata.version",
+        lambda pkg: (
+            "1.2.13"
+            if pkg == "langchain"
+            else (_ for _ in ()).throw(Exception(f"not found: {pkg}"))
+        ),
+    )
+    llm = FakeListChatModel(responses=["x"])
+    assert llm.metadata is not None
+    assert llm.metadata["versions"]["langchain"] == "1.2.13"
+    assert "langchain-core" in llm.metadata["versions"]
+
+
+def test_langchain_version_missing_when_not_installed(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """When `langchain` is not installed, metadata.versions has no entry."""
+    monkeypatch.setattr(
+        "importlib.metadata.version",
+        lambda pkg: (_ for _ in ()).throw(Exception(f"not found: {pkg}")),
+    )
+    llm = FakeListChatModel(responses=["x"])
+    assert llm.metadata is not None
+    assert "langchain" not in llm.metadata["versions"]
+    assert "langchain-core" in llm.metadata["versions"]
+
+
 def test_model_profiles() -> None:
     model = GenericFakeChatModel(messages=iter([]))
     assert model.profile is None