fix(langchain): make init_chat_model work with huggingface provider

libs/langchain_v1/langchain/chat_models/base.py

@@ -403,9 +403,16 @@ def _init_chat_model_helper(
         return ChatMistralAI(model=model, **kwargs)  # type: ignore[call-arg,unused-ignore]
     if model_provider == "huggingface":
         _check_pkg("langchain_huggingface")
-        from langchain_huggingface import ChatHuggingFace
+        from langchain_huggingface import ChatHuggingFace, HuggingFaceEndpoint
 
-        return ChatHuggingFace(model_id=model, **kwargs)
+        # Build a HuggingFaceEndpoint from the model id and wrap it in ChatHuggingFace.
+        # ChatHuggingFace expects an underlying HF LLM in `llm`, not a raw model_id.
+        llm = HuggingFaceEndpoint(
+            repo_id=model,
+            task="text-generation",
+            **kwargs,
+        )
+        return ChatHuggingFace(llm=llm)
     if model_provider == "groq":
         _check_pkg("langchain_groq")
         from langchain_groq import ChatGroq

libs/langchain_v1/tests/unit_tests/chat_models/test_chat_models.py

@@ -1,5 +1,5 @@
 import os
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any
 from unittest import mock
 
 import pytest
@@ -57,7 +57,7 @@ def test_init_missing_dep() -> None:
 
 
 def test_init_unknown_provider() -> None:
-    with pytest.raises(ValueError, match="Unsupported model_provider='bar'."):
+    with pytest.raises(ValueError, match=r"Unsupported model_provider='bar'\."):
         init_chat_model("foo", model_provider="bar")
 
 
@@ -285,3 +285,31 @@ def test_configurable_with_default() -> None:
     prompt = ChatPromptTemplate.from_messages([("system", "foo")])
     chain = prompt | model_with_config
     assert isinstance(chain, RunnableSequence)
+
+
+def test_init_chat_model_huggingface(monkeypatch: Any) -> None:
+    lhf = pytest.importorskip("langchain_huggingface")
+
+    chat_huggingface_cls = lhf.ChatHuggingFace
+    huggingface_endpoint_cls = lhf.HuggingFaceEndpoint
+
+    created: dict[str, Any] = {}
+
+    class DummyHFEndpoint(huggingface_endpoint_cls):  # type: ignore[misc, valid-type]
+        def __init__(self, *args: Any, **kwargs: Any) -> None:
+            super().__init__(**kwargs)
+            created["args"] = args
+            created["kwargs"] = kwargs
+
+    monkeypatch.setattr(lhf, "HuggingFaceEndpoint", DummyHFEndpoint)
+
+    model = init_chat_model(
+        model="microsoft/Phi-3-mini-4k-instruct",
+        model_provider="huggingface",
+        temperature=0,
+    )
+
+    assert isinstance(model, chat_huggingface_cls)
+    assert created["kwargs"]["repo_id"] == "microsoft/Phi-3-mini-4k-instruct"
+    assert created["kwargs"]["task"] == "text-generation"
+    assert created["kwargs"]["temperature"] == 0

libs/langchain_v1/tests/unit_tests/embeddings/test_base.py

@@ -88,7 +88,10 @@ def test_infer_model_and_provider_errors() -> None:
         _infer_model_and_provider("model", provider="")
 
     # Test invalid provider
-    with pytest.raises(ValueError, match="Provider 'invalid' is not supported.") as exc:
+    with pytest.raises(
+        ValueError,
+        match=r"Provider 'invalid' is not supported\.",
+    ) as exc:
         _infer_model_and_provider("model", provider="invalid")
     # Test provider list is in error
     for provider in _SUPPORTED_PROVIDERS: