fix(langchain): extract model name for ChatHuggingFace (#1728)

Author: vismaytiwari

langfuse/langchain/utils.py

@@ -97,6 +97,7 @@ def _extract_model_name(
         ("ChatCohere", "model", None),
         ("Cohere", "model", None),
         ("HuggingFaceHub", "model", None),
+        ("ChatHuggingFace", "model_id", None),
         ("ChatAnyscale", "model_name", None),
         ("TextGen", "model", "text-gen"),
         ("Ollama", "model", None),

tests/unit/test_langchain_utils.py

@@ -0,0 +1,44 @@
+"""Unit tests for langfuse.langchain.utils model-name extraction."""
+
+import pytest
+
+from langfuse.langchain.utils import _extract_model_name
+
+_MODEL_ID = "Qwen/Qwen2.5-Coder-32B-Instruct"
+
+
+def _chat_huggingface_serialized(inner_repr: str) -> dict:
+    """Mirror ``langchain_core.load.dumpd(ChatHuggingFace(...))``.
+
+    ChatHuggingFace is not LangChain-serializable, so it serializes to a
+    ``not_implemented`` stub with no ``kwargs``; the model id is only available
+    inside the ``repr`` string as ``model_id='...'``.
+    """
+    return {
+        "lc": 1,
+        "type": "not_implemented",
+        "id": [
+            "langchain_huggingface",
+            "chat_models",
+            "huggingface",
+            "ChatHuggingFace",
+        ],
+        "repr": f"ChatHuggingFace(llm={inner_repr}, model_id='{_MODEL_ID}')",
+        "name": "ChatHuggingFace",
+    }
+
+
+@pytest.mark.parametrize(
+    "inner_repr",
+    [
+        f"HuggingFaceEndpoint(repo_id='{_MODEL_ID}', model='{_MODEL_ID}', task='text-generation')",
+        f"HuggingFaceHub(repo_id='{_MODEL_ID}')",
+        # HuggingFacePipeline exposes its own model_id, so the repr carries two
+        # model_id='...' occurrences; re.search picks the first (inner) one.
+        f"HuggingFacePipeline(model_id='{_MODEL_ID}')",
+    ],
+)
+def test_extract_model_name_chat_huggingface(inner_repr: str):
+    serialized = _chat_huggingface_serialized(inner_repr)
+
+    assert _extract_model_name(serialized) == _MODEL_ID