feat(openai): add configurable base_url support with OPENAI_BASE_URL env var

- Add base_url field to OpenAIConfig with default "https://api.openai.com/v1"
- Update sample_run_config to support OPENAI_BASE_URL environment variable
- Modify get_base_url() to return configured base_url instead of hardcoded value
- Add comprehensive test suite covering:
  - Default base URL behavior
  - Custom base URL from config
  - Environment variable override
  - Config precedence over environment variables
  - Client initialization with configured URL
  - Model availability checks using configured URL

This enables users to configure custom OpenAI-compatible API endpoints
via environment variables or configuration files.

Author: mattf

docs/source/providers/inference/remote_openai.md

@@ -9,11 +9,13 @@ OpenAI inference provider for accessing GPT models and other OpenAI services.
 | Field | Type | Required | Default | Description |
 |-------|------|----------|---------|-------------|
 | `api_key` | `str \| None` | No |  | API key for OpenAI models |
+| `base_url` | `<class 'str'>` | No | https://api.openai.com/v1 | Base URL for OpenAI API |
 
 ## Sample Configuration
 
 ```yaml
 api_key: ${env.OPENAI_API_KEY:=}
+base_url: ${env.OPENAI_BASE_URL:=https://api.openai.com/v1}
 
 ```
 

llama_stack/providers/remote/inference/openai/config.py

@@ -24,9 +24,19 @@ class OpenAIConfig(BaseModel):
         default=None,
         description="API key for OpenAI models",
     )
+    base_url: str = Field(
+        default="https://api.openai.com/v1",
+        description="Base URL for OpenAI API",
+    )
 
     @classmethod
-    def sample_run_config(cls, api_key: str = "${env.OPENAI_API_KEY:=}", **kwargs) -> dict[str, Any]:
+    def sample_run_config(
+        cls,
+        api_key: str = "${env.OPENAI_API_KEY:=}",
+        base_url: str = "${env.OPENAI_BASE_URL:=https://api.openai.com/v1}",
+        **kwargs,
+    ) -> dict[str, Any]:
         return {
             "api_key": api_key,
+            "base_url": base_url,
         }

llama_stack/providers/remote/inference/openai/openai.py

@@ -65,9 +65,9 @@ def get_base_url(self) -> str:
         """
         Get the OpenAI API base URL.
 
-        Returns the standard OpenAI API base URL for direct OpenAI API calls.
+        Returns the OpenAI API base URL from the configuration.
         """
-        return "https://api.openai.com/v1"
+        return self.config.base_url
 
     async def initialize(self) -> None:
         await super().initialize()

llama_stack/templates/ci-tests/run.yaml

@@ -56,6 +56,7 @@ providers:
     provider_type: remote::openai
     config:
       api_key: ${env.OPENAI_API_KEY:=}
+      base_url: ${env.OPENAI_BASE_URL:=https://api.openai.com/v1}
   - provider_id: anthropic
     provider_type: remote::anthropic
     config:

llama_stack/templates/open-benchmark/run.yaml

@@ -16,6 +16,7 @@ providers:
     provider_type: remote::openai
     config:
       api_key: ${env.OPENAI_API_KEY:=}
+      base_url: ${env.OPENAI_BASE_URL:=https://api.openai.com/v1}
   - provider_id: anthropic
     provider_type: remote::anthropic
     config:

llama_stack/templates/starter/run.yaml

@@ -56,6 +56,7 @@ providers:
     provider_type: remote::openai
     config:
       api_key: ${env.OPENAI_API_KEY:=}
+      base_url: ${env.OPENAI_BASE_URL:=https://api.openai.com/v1}
   - provider_id: anthropic
     provider_type: remote::anthropic
     config:

tests/unit/providers/inference/test_openai_base_url_config.py

@@ -0,0 +1,125 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+import os
+from unittest.mock import AsyncMock, MagicMock, patch
+
+from llama_stack.distribution.stack import replace_env_vars
+from llama_stack.providers.remote.inference.openai.config import OpenAIConfig
+from llama_stack.providers.remote.inference.openai.openai import OpenAIInferenceAdapter
+
+
+class TestOpenAIBaseURLConfig:
+    """Test that OPENAI_BASE_URL environment variable properly configures the OpenAI adapter."""
+
+    def test_default_base_url_without_env_var(self):
+        """Test that the adapter uses the default OpenAI base URL when no environment variable is set."""
+        config = OpenAIConfig(api_key="test-key")
+        adapter = OpenAIInferenceAdapter(config)
+
+        assert adapter.get_base_url() == "https://api.openai.com/v1"
+
+    def test_custom_base_url_from_config(self):
+        """Test that the adapter uses a custom base URL when provided in config."""
+        custom_url = "https://custom.openai.com/v1"
+        config = OpenAIConfig(api_key="test-key", base_url=custom_url)
+        adapter = OpenAIInferenceAdapter(config)
+
+        assert adapter.get_base_url() == custom_url
+
+    @patch.dict(os.environ, {"OPENAI_BASE_URL": "https://env.openai.com/v1"})
+    def test_base_url_from_environment_variable(self):
+        """Test that the adapter uses base URL from OPENAI_BASE_URL environment variable."""
+        # Use sample_run_config which has proper environment variable syntax
+        config_data = OpenAIConfig.sample_run_config(api_key="test-key")
+        processed_config = replace_env_vars(config_data)
+        config = OpenAIConfig.model_validate(processed_config)
+        adapter = OpenAIInferenceAdapter(config)
+
+        assert adapter.get_base_url() == "https://env.openai.com/v1"
+
+    @patch.dict(os.environ, {"OPENAI_BASE_URL": "https://env.openai.com/v1"})
+    def test_config_overrides_environment_variable(self):
+        """Test that explicit config value overrides environment variable."""
+        custom_url = "https://config.openai.com/v1"
+        config = OpenAIConfig(api_key="test-key", base_url=custom_url)
+        adapter = OpenAIInferenceAdapter(config)
+
+        # Config should take precedence over environment variable
+        assert adapter.get_base_url() == custom_url
+
+    @patch("llama_stack.providers.utils.inference.openai_mixin.AsyncOpenAI")
+    def test_client_uses_configured_base_url(self, mock_openai_class):
+        """Test that the OpenAI client is initialized with the configured base URL."""
+        custom_url = "https://test.openai.com/v1"
+        config = OpenAIConfig(api_key="test-key", base_url=custom_url)
+        adapter = OpenAIInferenceAdapter(config)
+
+        # Mock the get_api_key method since it's delegated to LiteLLMOpenAIMixin
+        adapter.get_api_key = MagicMock(return_value="test-key")
+
+        # Access the client property to trigger AsyncOpenAI initialization
+        _ = adapter.client
+
+        # Verify AsyncOpenAI was called with the correct base_url
+        mock_openai_class.assert_called_once_with(
+            api_key="test-key",
+            base_url=custom_url,
+        )
+
+    @patch("llama_stack.providers.utils.inference.openai_mixin.AsyncOpenAI")
+    async def test_check_model_availability_uses_configured_url(self, mock_openai_class):
+        """Test that check_model_availability uses the configured base URL."""
+        custom_url = "https://test.openai.com/v1"
+        config = OpenAIConfig(api_key="test-key", base_url=custom_url)
+        adapter = OpenAIInferenceAdapter(config)
+
+        # Mock the get_api_key method
+        adapter.get_api_key = MagicMock(return_value="test-key")
+
+        # Mock the AsyncOpenAI client and its models.retrieve method
+        mock_client = MagicMock()
+        mock_client.models.retrieve = AsyncMock(return_value=MagicMock())
+        mock_openai_class.return_value = mock_client
+
+        # Call check_model_availability and verify it returns True
+        assert await adapter.check_model_availability("gpt-4")
+
+        # Verify the client was created with the custom URL
+        mock_openai_class.assert_called_with(
+            api_key="test-key",
+            base_url=custom_url,
+        )
+
+        # Verify the method was called and returned True
+        mock_client.models.retrieve.assert_called_once_with("gpt-4")
+
+    @patch.dict(os.environ, {"OPENAI_BASE_URL": "https://proxy.openai.com/v1"})
+    @patch("llama_stack.providers.utils.inference.openai_mixin.AsyncOpenAI")
+    async def test_environment_variable_affects_model_availability_check(self, mock_openai_class):
+        """Test that setting OPENAI_BASE_URL environment variable affects where model availability is checked."""
+        # Use sample_run_config which has proper environment variable syntax
+        config_data = OpenAIConfig.sample_run_config(api_key="test-key")
+        processed_config = replace_env_vars(config_data)
+        config = OpenAIConfig.model_validate(processed_config)
+        adapter = OpenAIInferenceAdapter(config)
+
+        # Mock the get_api_key method
+        adapter.get_api_key = MagicMock(return_value="test-key")
+
+        # Mock the AsyncOpenAI client
+        mock_client = MagicMock()
+        mock_client.models.retrieve = AsyncMock(return_value=MagicMock())
+        mock_openai_class.return_value = mock_client
+
+        # Call check_model_availability and verify it returns True
+        assert await adapter.check_model_availability("gpt-4")
+
+        # Verify the client was created with the environment variable URL
+        mock_openai_class.assert_called_with(
+            api_key="test-key",
+            base_url="https://proxy.openai.com/v1",
+        )