feat: Add enable_model_discovery to enable/disable model discovery on startup

docs/docs/providers/inference/remote_vllm.mdx

@@ -20,6 +20,7 @@ Remote vLLM inference provider for connecting to vLLM servers.
 | `api_token` | `str \| None` | No | fake | The API token |
 | `tls_verify` | `bool \| str` | No | True | Whether to verify TLS certificates. Can be a boolean or a path to a CA certificate file. |
 | `refresh_models` | `<class 'bool'>` | No | False | Whether to refresh models periodically |
+| `enable_model_discovery` | `<class 'bool'>` | No | True | Whether to enable model discovery from the vLLM server |
 
 ## Sample Configuration
 
@@ -28,4 +29,5 @@ url: ${env.VLLM_URL:=}
 max_tokens: ${env.VLLM_MAX_TOKENS:=4096}
 api_token: ${env.VLLM_API_TOKEN:=fake}
 tls_verify: ${env.VLLM_TLS_VERIFY:=true}
+enable_model_discovery: ${env.VLLM_ENABLE_MODEL_DISCOVERY:=true}
 ```

llama_stack/distributions/ci-tests/run.yaml

@@ -31,6 +31,7 @@ providers:
       max_tokens: ${env.VLLM_MAX_TOKENS:=4096}
       api_token: ${env.VLLM_API_TOKEN:=fake}
       tls_verify: ${env.VLLM_TLS_VERIFY:=true}
+      enable_model_discovery: ${env.VLLM_ENABLE_MODEL_DISCOVERY:=true}
   - provider_id: ${env.TGI_URL:+tgi}
     provider_type: remote::tgi
     config:

llama_stack/distributions/postgres-demo/run.yaml

@@ -16,6 +16,7 @@ providers:
       max_tokens: ${env.VLLM_MAX_TOKENS:=4096}
       api_token: ${env.VLLM_API_TOKEN:=fake}
       tls_verify: ${env.VLLM_TLS_VERIFY:=true}
+      enable_model_discovery: ${env.VLLM_ENABLE_MODEL_DISCOVERY:=true}
   - provider_id: sentence-transformers
     provider_type: inline::sentence-transformers
   vector_io:

llama_stack/distributions/starter-gpu/run.yaml

@@ -31,6 +31,7 @@ providers:
       max_tokens: ${env.VLLM_MAX_TOKENS:=4096}
       api_token: ${env.VLLM_API_TOKEN:=fake}
       tls_verify: ${env.VLLM_TLS_VERIFY:=true}
+      enable_model_discovery: ${env.VLLM_ENABLE_MODEL_DISCOVERY:=true}
   - provider_id: ${env.TGI_URL:+tgi}
     provider_type: remote::tgi
     config:

llama_stack/distributions/starter/run.yaml

@@ -31,6 +31,7 @@ providers:
       max_tokens: ${env.VLLM_MAX_TOKENS:=4096}
       api_token: ${env.VLLM_API_TOKEN:=fake}
       tls_verify: ${env.VLLM_TLS_VERIFY:=true}
+      enable_model_discovery: ${env.VLLM_ENABLE_MODEL_DISCOVERY:=true}
   - provider_id: ${env.TGI_URL:+tgi}
     provider_type: remote::tgi
     config:

llama_stack/providers/inline/inference/meta_reference/inference.py

@@ -71,6 +71,9 @@ async def openai_completion(self, *args, **kwargs):
     async def should_refresh_models(self) -> bool:
         return False
 
+    async def enable_model_discovery(self) -> bool:
+        return True
+
     async def list_models(self) -> list[Model] | None:
         return None
 

llama_stack/providers/inline/inference/sentence_transformers/sentence_transformers.py

@@ -52,6 +52,9 @@ async def shutdown(self) -> None:
     async def should_refresh_models(self) -> bool:
         return False
 
+    async def enable_model_discovery(self) -> bool:
+        return True
+
     async def list_models(self) -> list[Model] | None:
         return [
             Model(

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

@@ -34,6 +34,10 @@ class VLLMInferenceAdapterConfig(RemoteInferenceProviderConfig):
         default=False,
         description="Whether to refresh models periodically",
     )
+    enable_model_discovery: bool = Field(
+        default=True,
+        description="Whether to enable model discovery from the vLLM server",
+    )
 
     @field_validator("tls_verify")
     @classmethod
@@ -59,4 +63,5 @@ def sample_run_config(
             "max_tokens": "${env.VLLM_MAX_TOKENS:=4096}",
             "api_token": "${env.VLLM_API_TOKEN:=fake}",
             "tls_verify": "${env.VLLM_TLS_VERIFY:=true}",
+            "enable_model_discovery": "${env.VLLM_ENABLE_MODEL_DISCOVERY:=true}",
         }

llama_stack/providers/remote/inference/vllm/vllm.py

@@ -283,6 +283,11 @@ async def should_refresh_models(self) -> bool:
         return self.config.refresh_models
 
     async def list_models(self) -> list[Model] | None:
+        log.debug(f"VLLM list_models called, enable_model_discovery={self.config.enable_model_discovery}")
+        if not self.config.enable_model_discovery:
+            log.debug("VLLM list_models returning None due to enable_model_discovery=False")
+            return None
+
         models = []
         async for m in self.client.models.list():
             model_type = ModelType.llm  # unclear how to determine embedding vs. llm models
@@ -337,13 +342,43 @@ async def register_model(self, model: Model) -> Model:
             model = await self.register_helper.register_model(model)
         except ValueError:
             pass  # Ignore statically unknown model, will check live listing
+
+        # Check if provider enables model discovery before making HTTP request
+        if not self.config.enable_model_discovery:
+            log.debug("Model discovery disabled for vLLM: Trusting model exists")
+            # Warn if API key is set but model discovery is disabled
+            if self.config.api_token:
+                log.warning(
+                    "Model discovery is disabled but VLLM_API_TOKEN is set. "
+                    "If you're not using model discovery, you may not need to set the API token. "
+                    "Consider removing VLLM_API_TOKEN from your configuration or setting enable_model_discovery=true."
+                )
+            return model
+
         try:
             res = self.client.models.list()
         except APIConnectionError as e:
             raise ValueError(
                 f"Failed to connect to vLLM at {self.config.url}. Please check if vLLM is running and accessible at that URL."
             ) from e
-        available_models = [m.id async for m in res]
+
+        try:
+            available_models = [m.id async for m in res]
+        except Exception as e:
+            # Provide helpful error message for model discovery failures
+            log.error(f"Model discovery failed with the following output from vLLM server: {e}.\n")
+            log.error(
+                f"Model discovery failed: This typically occurs when a provider (like vLLM) is configured "
+                f"with model discovery enabled but the provider server doesn't support the /models endpoint. "
+                f"To resolve this, either:\n"
+                f"1. Check that {self.config.url} correctly points to the vLLM server, or\n"
+                f"2. Ensure your provider server supports the /v1/models endpoint and if authenticated that VLLM_API_TOKEN is set, or\n"
+                f"3. Set enable_model_discovery=false for the problematic provider in your configuration\n"
+            )
+            raise ValueError(
+                f"Model discovery failed for vLLM at {self.config.url}. Please check the server configuration and logs."
+            ) from e
+
         if model.provider_resource_id not in available_models:
             raise ValueError(
                 f"Model {model.provider_resource_id} is not being served by vLLM. "

llama_stack/providers/utils/inference/model_registry.py

@@ -100,6 +100,9 @@ async def list_models(self) -> list[Model] | None:
     async def should_refresh_models(self) -> bool:
         return False
 
+    async def enable_model_discovery(self) -> bool:
+        return True
+
     def get_provider_model_id(self, identifier: str) -> str | None:
         return self.alias_to_provider_id_map.get(identifier, None)
 

llama_stack/providers/utils/inference/openai_mixin.py

@@ -425,3 +425,6 @@ async def check_model_availability(self, model: str) -> bool:
 
     async def should_refresh_models(self) -> bool:
         return False
+
+    async def enable_model_discovery(self) -> bool:
+        return True

tests/unit/distribution/routers/test_routing_tables.py

@@ -52,6 +52,9 @@ async def unregister_model(self, model_id: str):
     async def should_refresh_models(self):
         return False
 
+    async def enable_model_discovery(self):
+        return True
+
     async def list_models(self):
         return [
             Model(

tests/unit/providers/inference/test_remote_vllm.py

@@ -636,27 +636,75 @@ async def test_should_refresh_models():
     Test the should_refresh_models method with different refresh_models configurations.
 
     This test verifies that:
-    1. When refresh_models is True, should_refresh_models returns True regardless of api_token
-    2. When refresh_models is False, should_refresh_models returns False regardless of api_token
+    1. When refresh_models is True, should_refresh_models returns True
+    2. When refresh_models is False, should_refresh_models returns False
     """
 
-    # Test case 1: refresh_models is True, api_token is None
-    config1 = VLLMInferenceAdapterConfig(url="http://test.localhost", api_token=None, refresh_models=True)
+    # Test case 1: refresh_models is True
+    config1 = VLLMInferenceAdapterConfig(url="http://test.localhost", refresh_models=True)
     adapter1 = VLLMInferenceAdapter(config1)
     result1 = await adapter1.should_refresh_models()
     assert result1 is True, "should_refresh_models should return True when refresh_models is True"
 
-    # Test case 2: refresh_models is True, api_token is empty string
-    config2 = VLLMInferenceAdapterConfig(url="http://test.localhost", api_token="", refresh_models=True)
+    # Test case 2: refresh_models is False
+    config2 = VLLMInferenceAdapterConfig(url="http://test.localhost", refresh_models=False)
     adapter2 = VLLMInferenceAdapter(config2)
     result2 = await adapter2.should_refresh_models()
-    assert result2 is True, "should_refresh_models should return True when refresh_models is True"
+    assert result2 is False, "should_refresh_models should return False when refresh_models is False"
 
-    # Test case 3: refresh_models is True, api_token is "fake" (default)
-    config3 = VLLMInferenceAdapterConfig(url="http://test.localhost", api_token="fake", refresh_models=True)
+
+async def test_enable_model_discovery_flag():
+    """
+    Test the enable_model_discovery flag functionality.
+
+    This test verifies that:
+    1. When enable_model_discovery is True (default), list_models returns models from the server
+    2. When enable_model_discovery is False, list_models returns None without calling the server
+    """
+
+    # Test case 1: enable_model_discovery is True (default)
+    config1 = VLLMInferenceAdapterConfig(url="http://test.localhost", enable_model_discovery=True)
+    adapter1 = VLLMInferenceAdapter(config1)
+    adapter1.__provider_id__ = "test-vllm"
+
+    # Mock the client.models.list() method
+    with patch.object(VLLMInferenceAdapter, "client", new_callable=PropertyMock) as mock_client_property:
+        mock_client = MagicMock()
+
+        async def mock_models_list():
+            yield OpenAIModel(id="test-model-1", created=1, object="model", owned_by="test")
+            yield OpenAIModel(id="test-model-2", created=2, object="model", owned_by="test")
+
+        mock_client.models.list.return_value = mock_models_list()
+        mock_client_property.return_value = mock_client
+
+        models = await adapter1.list_models()
+        assert models is not None, "list_models should return models when enable_model_discovery is True"
+        assert len(models) == 2, "Should return 2 models"
+        assert models[0].identifier == "test-model-1"
+        assert models[1].identifier == "test-model-2"
+        mock_client.models.list.assert_called_once()
+
+    # Test case 2: enable_model_discovery is False
+    config2 = VLLMInferenceAdapterConfig(url="http://test.localhost", enable_model_discovery=False)
+    adapter2 = VLLMInferenceAdapter(config2)
+    adapter2.__provider_id__ = "test-vllm"
+
+    # Mock the client.models.list() method
+    with patch.object(VLLMInferenceAdapter, "client", new_callable=PropertyMock) as mock_client_property:
+        mock_client = MagicMock()
+        mock_client_property.return_value = mock_client
+
+        models = await adapter2.list_models()
+        assert models is None, "list_models should return None when enable_model_discovery is False"
+        mock_client.models.list.assert_not_called()
+
+    # Test case 3: enable_model_discovery defaults to True
+    config3 = VLLMInferenceAdapterConfig(url="http://test.localhost")
     adapter3 = VLLMInferenceAdapter(config3)
-    result3 = await adapter3.should_refresh_models()
-    assert result3 is True, "should_refresh_models should return True when refresh_models is True"
+    adapter3.__provider_id__ = "test-vllm"
+    result3 = await adapter3.enable_model_discovery()
+    assert result3 is True, "enable_model_discovery should return True by default"
 
     # Test case 4: refresh_models is True, api_token is real token
     config4 = VLLMInferenceAdapterConfig(url="http://test.localhost", api_token="real-token-123", refresh_models=True)
@@ -670,6 +718,22 @@ async def test_should_refresh_models():
     result5 = await adapter5.should_refresh_models()
     assert result5 is False, "should_refresh_models should return False when refresh_models is False"
 
+    # Mock the client.models.list() method
+    with patch.object(VLLMInferenceAdapter, "client", new_callable=PropertyMock) as mock_client_property:
+        mock_client = MagicMock()
+
+        async def mock_models_list():
+            yield OpenAIModel(id="default-model", created=1, object="model", owned_by="test")
+
+        mock_client.models.list.return_value = mock_models_list()
+        mock_client_property.return_value = mock_client
+
+        models = await adapter3.list_models()
+        assert models is not None, "list_models should return models when enable_model_discovery defaults to True"
+        assert len(models) == 1, "Should return 1 model"
+        assert models[0].identifier == "default-model"
+        mock_client.models.list.assert_called_once()
+
 
 async def test_provider_data_var_context_propagation(vllm_inference_adapter):
     """

tests/unit/server/test_access_control.py

@@ -32,6 +32,7 @@ async def test_setup(cached_disk_dist_registry):
     mock_inference.__provider_spec__ = MagicMock()
     mock_inference.__provider_spec__.api = Api.inference
     mock_inference.register_model = AsyncMock(side_effect=_return_model)
+    mock_inference.enable_model_discovery = AsyncMock(return_value=True)
     routing_table = ModelsRoutingTable(
         impls_by_provider_id={"test_provider": mock_inference},
         dist_registry=cached_disk_dist_registry,