fix(langchain): read AzureOpenAI API version from openai_api_version

`_extract_model_name` for `AzureOpenAI` checks
`serialized_kwargs["openai_api_version"]` to decide whether a version
is available, then reads the value from `serialized_kwargs["deployment_version"]`
(`langfuse/langchain/utils.py:73-74`). LangChain's `AzureOpenAI` doesn't
expose a `deployment_version` field — only `openai_api_version` and
`deployment_name` — so `deployment_version` is always `None`, the
`isinstance(deployment_version, str)` check fails, and the function
returns the bare deployment name with no version suffix.

Read the value from the same key that gates the branch
(`openai_api_version`). Combined with the deduplication logic added in
PR #1203, deployments now produce `<deployment_name>-<api_version>` —
matching the documented intent of this code path — while still
collapsing if the deployment_name already embeds the version.

Add `tests/unit/test_extract_model_name.py` with three regression cases:
api_version present, api_version absent, and the dedup path from #1203.

Author: Spectual

langfuse/langchain/utils.py

@@ -70,8 +70,12 @@ def _extract_model_name(
 
             serialized_kwargs = serialized.get("kwargs")
             if serialized_kwargs and isinstance(serialized_kwargs, dict):
+                # LangChain's AzureOpenAI exposes the API version under
+                # `openai_api_version`, not `deployment_version` — the latter
+                # is never populated, so previously the version suffix was
+                # dropped from the resulting model name.
                 if serialized_kwargs.get("openai_api_version"):
-                    deployment_version = serialized_kwargs.get("deployment_version")
+                    deployment_version = serialized_kwargs.get("openai_api_version")
 
                 if serialized_kwargs.get("deployment_name"):
                     deployment_name = serialized_kwargs.get("deployment_name")

tests/unit/test_extract_model_name.py

@@ -0,0 +1,47 @@
+"""Unit tests for ``langfuse.langchain.utils._extract_model_name``."""
+
+from langfuse.langchain.utils import _extract_model_name
+
+
+def _azure_openai_serialized(
+    *, deployment_name: str, openai_api_version: str | None
+) -> dict:
+    """Build a minimal ``serialized`` dict mirroring what LangChain emits for AzureOpenAI."""
+    kwargs: dict = {"deployment_name": deployment_name}
+    if openai_api_version is not None:
+        kwargs["openai_api_version"] = openai_api_version
+    return {"id": ["langchain", "llms", "openai", "AzureOpenAI"], "kwargs": kwargs}
+
+
+def test_azure_openai_returns_deployment_name_with_api_version_suffix():
+    """Regression: ``openai_api_version`` should be appended to the deployment name.
+
+    Previously the code read the value from a non-existent ``deployment_version``
+    key after checking that ``openai_api_version`` was set, so the suffix was
+    silently dropped.
+    """
+    serialized = _azure_openai_serialized(
+        deployment_name="my-deployment",
+        openai_api_version="2024-02-15-preview",
+    )
+    assert _extract_model_name(serialized) == "my-deployment-2024-02-15-preview"
+
+
+def test_azure_openai_returns_bare_deployment_name_when_no_api_version():
+    serialized = _azure_openai_serialized(
+        deployment_name="my-deployment",
+        openai_api_version=None,
+    )
+    assert _extract_model_name(serialized) == "my-deployment"
+
+
+def test_azure_openai_no_duplicate_version_suffix():
+    """If the deployment_name already contains the version, don't append it again.
+
+    This guards the existing behavior introduced in PR #1203.
+    """
+    serialized = _azure_openai_serialized(
+        deployment_name="my-deployment-2024-02-15-preview",
+        openai_api_version="2024-02-15-preview",
+    )
+    assert _extract_model_name(serialized) == "my-deployment-2024-02-15-preview"