Feat: default OpenAI chat to Responses API where possible (#66)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: cosminacho

packages/uipath_langchain_client/CHANGELOG.md

@@ -2,6 +2,11 @@
 
 All notable changes to `uipath_langchain_client` will be documented in this file.
 
+## [1.9.3] - 2026-04-20
+
+### Changed
+- `get_chat_model()` now defaults to the OpenAI Responses API (`ApiFlavor.RESPONSES`) when discovery does not specify a flavor for an OpenAI chat model. Explicit `api_flavor=` on the call and BYOM-discovered flavors still take precedence. The LiteLLM client still defaults to chat-completions for OpenAI because LiteLLM 1.83.x drops the injected httpx `client` when its acompletion→aresponses bridge fires, which breaks async auth against the UiPath gateway.
+
 ## [1.9.2] - 2026-04-17
 
 ### Changed

packages/uipath_langchain_client/src/uipath_langchain_client/__version__.py

@@ -1,3 +1,3 @@
 __title__ = "UiPath LangChain Client"
 __description__ = "A Python client for interacting with UiPath's LLM services via LangChain."
-__version__ = "1.9.2"
+__version__ = "1.9.3"

packages/uipath_langchain_client/src/uipath_langchain_client/factory.py

@@ -124,6 +124,10 @@ def get_chat_model(
 
     match discovered_vendor_type:
         case VendorType.OPENAI:
+            # OpenAI chat defaults to the Responses API when no flavor is specified.
+            if api_flavor is None:
+                api_flavor = ApiFlavor.RESPONSES
+
             if model_family == ModelFamily.OPENAI:
                 from uipath_langchain_client.clients.openai.chat_models import (
                     UiPathAzureChatOpenAI,

tests/cassettes.db

@@ -1,10 +1,12 @@
+from unittest.mock import MagicMock
+
 import pytest
 from uipath_langchain_client.clients.normalized.chat_models import UiPathChat
 from uipath_langchain_client.clients.normalized.embeddings import UiPathEmbeddings
 from uipath_langchain_client.factory import get_chat_model, get_embedding_model
 
 from tests.langchain.conftest import COMPLETION_MODEL_NAMES, EMBEDDING_MODEL_NAMES
-from uipath.llm_client.settings import UiPathBaseSettings
+from uipath.llm_client.settings import ApiFlavor, UiPathBaseSettings
 
 
 @pytest.mark.vcr
@@ -44,3 +46,85 @@ def test_get_embedding_model_custom_class(
         )
         assert embedding_model is not None
         assert isinstance(embedding_model, UiPathEmbeddings)
+
+
+class TestFactoryDefaultApiFlavor:
+    """Unit tests for the default api_flavor picked by the chat factory.
+
+    The factory returns concrete LangChain model classes whose construction is
+    non-trivial. Instead of fully instantiating them, we patch the concrete
+    classes with a sentinel that captures the kwargs the factory passes.
+    """
+
+    def _captured_kwargs(
+        self,
+        monkeypatch: pytest.MonkeyPatch,
+        model_info: dict,
+        **factory_kwargs,
+    ) -> dict:
+        settings = MagicMock()
+        settings.get_model_info.return_value = model_info
+        captured: dict = {}
+
+        class _StubModel:
+            def __init__(self, **kwargs):
+                captured.update(kwargs)
+
+        monkeypatch.setattr(
+            "uipath_langchain_client.clients.openai.chat_models.UiPathChatOpenAI",
+            _StubModel,
+        )
+        monkeypatch.setattr(
+            "uipath_langchain_client.clients.openai.chat_models.UiPathAzureChatOpenAI",
+            _StubModel,
+        )
+        get_chat_model(
+            model_name=model_info["modelName"],
+            client_settings=settings,
+            **factory_kwargs,
+        )
+        return captured
+
+    def test_openai_chat_defaults_to_responses_when_no_flavor_discovered(
+        self, monkeypatch: pytest.MonkeyPatch
+    ):
+        """UiPath-owned OpenAI (apiFlavor=null) should default to the Responses API."""
+        captured = self._captured_kwargs(
+            monkeypatch,
+            {
+                "modelName": "gpt-4o",
+                "vendor": "OpenAi",
+                "apiFlavor": None,
+                "modelFamily": "OpenAi",
+            },
+        )
+        assert captured["api_flavor"] == ApiFlavor.RESPONSES
+
+    def test_openai_chat_respects_user_api_flavor_override(self, monkeypatch: pytest.MonkeyPatch):
+        """Explicit api_flavor from the caller still wins over the default."""
+        captured = self._captured_kwargs(
+            monkeypatch,
+            {
+                "modelName": "gpt-4o",
+                "vendor": "OpenAi",
+                "apiFlavor": None,
+                "modelFamily": "OpenAi",
+            },
+            api_flavor=ApiFlavor.CHAT_COMPLETIONS,
+        )
+        assert captured["api_flavor"] == ApiFlavor.CHAT_COMPLETIONS
+
+    def test_openai_chat_respects_discovered_byom_chat_completions(
+        self, monkeypatch: pytest.MonkeyPatch
+    ):
+        """BYOM-discovered chat-completions still maps to chat-completions."""
+        captured = self._captured_kwargs(
+            monkeypatch,
+            {
+                "modelName": "custom-gpt",
+                "vendor": "OpenAi",
+                "apiFlavor": "OpenAiChatCompletions",
+                "modelFamily": None,
+            },
+        )
+        assert captured["api_flavor"] == ApiFlavor.CHAT_COMPLETIONS