Python: Add base_url support to OpenAI settings and improve initialization (#788)

Co-authored-by: Chris <66376200+crickman@users.noreply.github.com>

python/packages/main/agent_framework/openai/_chat_client.py

@@ -427,7 +427,9 @@ class OpenAIChatClient(OpenAIConfigMixin, OpenAIBaseChatClient):
             async_client: An existing client to use. (Optional)
             instruction_role: The role to use for 'instruction' messages, for example,
                 "system" or "developer". If not provided, the default is "system".
-            base_url: The optional base URL to use. If provided will override the standard value for a OpenAI connector.
+            base_url: The optional base URL to use. If provided will override
+                the standard value for a OpenAI connector,
+                the env vars or .env file value.
             env_file_path: Use the environment settings file as a fallback
                 to environment variables. (Optional)
             env_file_encoding: The encoding of the environment settings file. (Optional)
@@ -435,6 +437,7 @@ class OpenAIChatClient(OpenAIConfigMixin, OpenAIBaseChatClient):
         try:
             openai_settings = OpenAISettings(
                 api_key=SecretStr(api_key) if api_key else None,
+                base_url=base_url,
                 org_id=org_id,
                 chat_model_id=ai_model_id,
                 env_file_path=env_file_path,
@@ -456,11 +459,11 @@ class OpenAIChatClient(OpenAIConfigMixin, OpenAIBaseChatClient):
         super().__init__(
             ai_model_id=openai_settings.chat_model_id,
             api_key=openai_settings.api_key.get_secret_value() if openai_settings.api_key else None,
+            base_url=openai_settings.base_url if openai_settings.base_url else None,
             org_id=openai_settings.org_id,
             default_headers=default_headers,
             client=async_client,
             instruction_role=instruction_role,
-            base_url=base_url,
         )
 
     @classmethod

python/packages/main/agent_framework/openai/_shared.py

@@ -78,6 +78,8 @@ class OpenAISettings(AFBaseSettings):
     Attributes:
         api_key: OpenAI API key, see https://platform.openai.com/account/api-keys
             (Env var OPENAI_API_KEY)
+        base_url: The base URL for the OpenAI API.
+            (Env var OPENAI_BASE_URL)
         org_id: This is usually optional unless your account belongs to multiple organizations.
             (Env var OPENAI_ORG_ID)
         chat_model_id: The OpenAI chat model ID to use, for example, gpt-3.5-turbo or gpt-4.
@@ -106,6 +108,7 @@ class OpenAISettings(AFBaseSettings):
     env_prefix: ClassVar[str] = "OPENAI_"
 
     api_key: SecretStr | None = None
+    base_url: str | None = None
     org_id: str | None = None
     chat_model_id: str | None = None
     responses_model_id: str | None = None

python/packages/main/tests/openai/test_openai_chat_client.py

@@ -80,6 +80,22 @@ def test_init_base_url(openai_unit_test_env: dict[str, str]) -> None:
     assert str(open_ai_chat_completion.client.base_url) == "http://localhost:1234/v1/"
 
 
+def test_init_base_url_from_settings_env() -> None:
+    """Test that base_url from OpenAISettings environment variable is properly used."""
+    # Set environment variable for base_url
+    with patch.dict(
+        os.environ,
+        {
+            "OPENAI_API_KEY": "dummy",
+            "OPENAI_CHAT_MODEL_ID": "gpt-5",
+            "OPENAI_BASE_URL": "https://custom-openai-endpoint.com/v1",
+        },
+    ):
+        client = OpenAIChatClient()
+        assert client.ai_model_id == "gpt-5"
+        assert str(client.client.base_url) == "https://custom-openai-endpoint.com/v1/"
+
+
 @pytest.mark.parametrize("exclude_list", [["OPENAI_CHAT_MODEL_ID"]], indirect=True)
 def test_init_with_empty_model_id(openai_unit_test_env: dict[str, str]) -> None:
     with pytest.raises(ServiceInitializationError):