[Core] Support multiple tasks per model (#20771)

Signed-off-by: NickLucche <nlucches@redhat.com>
Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>
Co-authored-by: DarkLight1337 <tlleungac@connect.ust.hk>

tests/test_config.py

@@ -54,7 +54,7 @@ def test_get_field():
         ("jason9693/Qwen2.5-1.5B-apeach", "pooling", "classify"),
         ("cross-encoder/ms-marco-MiniLM-L-6-v2", "pooling", "classify"),
         ("Qwen/Qwen2.5-Math-RM-72B", "pooling", "reward"),
-        ("openai/whisper-small", "transcription", "transcription"),
+        ("openai/whisper-small", "generate", "transcription"),
     ],
 )
 def test_auto_task(model_id, expected_runner_type, expected_task):
@@ -69,7 +69,11 @@ def test_auto_task(model_id, expected_runner_type, expected_task):
     )
 
     assert config.runner_type == expected_runner_type
-    assert config.task == expected_task
+
+    if config.runner_type == "pooling":
+        assert config.task == expected_task
+    else:
+        assert expected_task in config.supported_tasks
 
 
 @pytest.mark.parametrize(
@@ -98,11 +102,50 @@ def test_score_task(model_id, expected_runner_type, expected_task):
     assert config.task == expected_task
 
 
+@pytest.mark.parametrize(("model_id", "expected_runner_type", "expected_task"),
+                         [
+                             ("Qwen/Qwen2.5-1.5B-Instruct", "draft", "auto"),
+                         ])
+def test_draft_task(model_id, expected_runner_type, expected_task):
+    config = ModelConfig(
+        model_id,
+        runner="draft",
+        tokenizer=model_id,
+        seed=0,
+        dtype="float16",
+    )
+
+    assert config.runner_type == expected_runner_type
+    assert config.task == expected_task
+
+
+@pytest.mark.parametrize(
+    ("model_id", "expected_runner_type", "expected_task"),
+    [
+        ("openai/whisper-small", "generate", "transcription"),
+    ],
+)
+def test_transcription_task(model_id, expected_runner_type, expected_task):
+    config = ModelConfig(
+        model_id,
+        task="transcription",
+        tokenizer=model_id,
+        tokenizer_mode="auto",
+        trust_remote_code=False,
+        seed=0,
+        dtype="float16",
+    )
+
+    assert config.runner_type == expected_runner_type
+    assert config.task == expected_task
+
+
 @pytest.mark.parametrize(("model_id", "bad_task"), [
     ("Qwen/Qwen2.5-Math-RM-72B", "generate"),
+    ("Qwen/Qwen3-0.6B", "transcription"),
 ])
 def test_incorrect_task(model_id, bad_task):
-    with pytest.raises(ValueError, match=r"does not support the .* task"):
+    with pytest.raises(ValueError, match=r"does not support task=.*"):
         ModelConfig(
             model_id,
             task=bad_task,

vllm/config.py

@@ -91,24 +91,19 @@ logger = init_logger(__name__)
 ConfigT = TypeVar("ConfigT", bound=ConfigType)
 
 TaskOption = Literal["auto", "generate", "embedding", "embed", "classify",
-                     "score", "reward", "transcription"]
+                     "score", "reward", "transcription", "draft"]
 
-_ResolvedTask = Literal["generate", "embed", "classify", "reward", "draft",
-                        "transcription"]
+_ResolvedTask = Literal["generate", "transcription", "pooling", "embed",
+                        "classify", "reward", "draft"]
 
-RunnerType = Literal["generate", "pooling", "draft", "transcription"]
+RunnerOption = Literal["auto", "generate", "pooling", "draft"]
 
-_RUNNER_TASKS: dict[RunnerType, list[_ResolvedTask]] = {
-    "generate": ["generate"],
-    "pooling": ["embed", "classify", "reward"],
-    "draft": ["draft"],
-    "transcription": ["transcription"],
-}
+RunnerType = Literal["generate", "pooling", "draft"]
 
-_TASK_RUNNER: dict[_ResolvedTask, RunnerType] = {
-    task: runner
-    for runner, tasks in _RUNNER_TASKS.items()
-    for task in tasks
+_RUNNER_TASKS: dict[RunnerType, list[_ResolvedTask]] = {
+    "generate": ["generate", "transcription"],
+    "pooling": ["pooling", "embed", "classify", "reward"],
+    "draft": [],
 }
 
 
@@ -234,11 +229,14 @@ class ModelConfig:
     """Name or path of the Hugging Face model to use. It is also used as the
     content for `model_name` tag in metrics output when `served_model_name` is
     not specified."""
-    task: Literal[TaskOption, Literal["draft"]] = "auto"
-    """The task to use the model for. Each vLLM instance only supports one
-    task, even if the same model can be used for multiple tasks. When the model
-    only supports one task, "auto" can be used to select it; otherwise, you
-    must specify explicitly which task to use."""
+    runner: RunnerOption = "auto"
+    """The type of model runner to use. Each vLLM instance only supports one
+    model runner, even if the same model can be used for multiple types."""
+    task: TaskOption = "auto"
+    """The task to use the model for. If the model supports more than one
+    model runner, this is used to select which model runner to run.
+
+    Note that the model may support other tasks using the same model runner."""
     tokenizer: SkipValidation[str] = None  # type: ignore
     """Name or path of the Hugging Face tokenizer to use. If unspecified, model
     name or path will be used."""
@@ -553,10 +551,41 @@ class ModelConfig:
         self.hf_image_processor_config = get_hf_image_processor_config(
             self.model, hf_token=self.hf_token, revision=self.revision)
 
-        supported_tasks, task = self._resolve_task(self.task)
-        self.supported_tasks = supported_tasks
-        self.task = task
-        if self.task in ("draft", "generate"):
+        # For pooling models, self.task is used to indicate the
+        # user-selected task
+        if self.task == "score":
+            if self.registry.is_cross_encoder_model(self.architectures):
+                self.task = "classify"
+            else:
+                self.task = "embed"
+        elif self.task == "embedding":
+            msg = ("The 'embedding' task has been renamed to 'embed', please "
+                   "use the new name. The old name will be removed in v1.0.")
+            warnings.warn(msg, DeprecationWarning, stacklevel=2)
+
+            self.task = "embed"
+
+        all_supported_tasks = self._get_supported_tasks(self.task)
+        logger.debug("Tasks supported by runner type: %s", all_supported_tasks)
+        supported_runner_types = self._get_supported_runner_types(
+            all_supported_tasks)
+        runner_type = self._resolve_runner(self.runner, self.task,
+                                           supported_runner_types,
+                                           all_supported_tasks)
+
+        logger.debug("Selected runner type: %s", runner_type)
+        # For pooling models, self.task is used to indicate the
+        # user-selected task
+        if runner_type == "pooling" and self.task == "auto":
+            selected_task = all_supported_tasks[runner_type][-1]
+            assert selected_task != "pooling"
+            self.task = selected_task
+        self.supported_runner_types = supported_runner_types
+        self.runner_type = runner_type
+        self.supported_tasks = all_supported_tasks[runner_type]
+
+        if self.runner_type in ("draft",
+                                "generate") and self.task != "transcription":
             self.truncation_side = "left"
         else:
             self.truncation_side = "right"
@@ -780,11 +809,10 @@ class ModelConfig:
                 f"one of {get_args(TokenizerMode)}.")
         self.tokenizer_mode = tokenizer_mode
 
-    def _get_preferred_task(
+    def _get_preferred_pooling_task(
         self,
         architectures: list[str],
-        supported_tasks: set[_ResolvedTask],
-    ) -> Optional[_ResolvedTask]:
+    ) -> _ResolvedTask:
         model_id = self.model
         if get_pooling_config(model_id, self.revision):
             return "embed"
@@ -795,92 +823,136 @@ class ModelConfig:
 
         suffix_to_preferred_task: list[tuple[str, _ResolvedTask]] = [
             # Other models follow this pattern
-            ("ForCausalLM", "generate"),
-            ("ForConditionalGeneration", "generate"),
             ("ForSequenceClassification", "classify"),
-            ("ChatModel", "generate"),
-            ("LMHeadModel", "generate"),
             ("EmbeddingModel", "embed"),
             ("RewardModel", "reward"),
         ]
         _, arch = self.registry.inspect_model_cls(architectures)
 
         for suffix, pref_task in suffix_to_preferred_task:
-            if arch.endswith(suffix) and pref_task in supported_tasks:
+            if arch.endswith(suffix):
                 return pref_task
 
-        return None
+        return "embed"
 
-    def _resolve_task(
+    def _get_supported_generation_tasks(
         self,
-        task_option: Literal[TaskOption, Literal["draft"]],
-    ) -> tuple[set[_ResolvedTask], _ResolvedTask]:
-        if task_option == "draft":
-            return {"draft"}, "draft"
+        task_option: TaskOption,
+    ) -> list[_ResolvedTask]:
+        registry = self.registry
+        architectures = self.architectures
+
+        if registry.is_transcription_only_model(architectures):
+            return ["transcription"]
+
+        supported_tasks = list[_ResolvedTask]()
+        if registry.is_text_generation_model(architectures):
+            supported_tasks.append("generate")
+
+            if registry.is_transcription_model(architectures):
+                supported_tasks.append("transcription")
+
+        return supported_tasks
 
+    def _get_supported_pooling_tasks(
+        self,
+        task_option: TaskOption,
+    ) -> list[_ResolvedTask]:
         registry = self.registry
         architectures = self.architectures
 
-        runner_support: dict[RunnerType, bool] = {
-            # NOTE: Listed from highest to lowest priority,
-            # in case the model supports multiple of them
-            "transcription": registry.is_transcription_model(architectures),
-            "generate": registry.is_text_generation_model(architectures),
-            "pooling": registry.is_pooling_model(architectures),
+        supported_tasks = list[_ResolvedTask]()
+        if registry.is_pooling_model(architectures):
+            supported_tasks.append("pooling")
+
+            # For now, users must specify the task (other than "pooling")
+            # to use for pooling models
+            if task_option == "auto":
+                preferred_task = self._get_preferred_pooling_task(
+                    architectures)
+
+                supported_tasks.append(preferred_task)
+            elif task_option in _RUNNER_TASKS["pooling"]:
+                supported_tasks.append(cast(_ResolvedTask, task_option))
+
+        return supported_tasks
+
+    def _get_supported_tasks(
+        self,
+        task_option: TaskOption,
+    ) -> dict[RunnerType, list[_ResolvedTask]]:
+        return {
+            "generate": self._get_supported_generation_tasks(task_option),
+            "pooling": self._get_supported_pooling_tasks(task_option),
+            "draft": ["draft"]
         }
-        supported_runner_types_lst: list[RunnerType] = [
-            runner_type
-            for runner_type, is_supported in runner_support.items()
-            if is_supported
-        ]
 
-        supported_tasks_lst: list[_ResolvedTask] = [
-            task for runner_type in supported_runner_types_lst
-            for task in _RUNNER_TASKS[runner_type]
-        ]
-        supported_tasks = set(supported_tasks_lst)
+    def _get_supported_runner_types(
+        self,
+        supported_tasks: dict[RunnerType, list[_ResolvedTask]],
+    ) -> set[RunnerType]:
+        return {
+            runner
+            for runner, runner_tasks in supported_tasks.items()
+            if len(runner_tasks) > 0
+        }
 
-        if task_option == "auto":
-            selected_task = next(iter(supported_tasks_lst))
+    def _resolve_runner(
+        self,
+        runner_option: RunnerOption,
+        task_option: TaskOption,
+        supported_runner_types: set[RunnerType],
+        supported_tasks: dict[RunnerType, list[_ResolvedTask]],
+    ) -> RunnerType:
+        if not supported_runner_types:
+            raise ValueError("This model does not support any model runners!")
+
+        if runner_option != "auto":
+            if runner_option not in supported_runner_types:
+                raise ValueError(
+                    f"This model does not support runner={runner_option!r}. "
+                    f"Available runners: {supported_runner_types}")
 
-            if len(supported_tasks_lst) > 1:
-                preferred_task = self._get_preferred_task(
-                    architectures, supported_tasks)
-                if preferred_task is not None:
-                    selected_task = preferred_task
+            return runner_option
 
-                logger.info(
-                    "This model supports multiple tasks: %s. "
-                    "Defaulting to '%s'.", supported_tasks, selected_task)
-        else:
-            if task_option == "score":
-                if not runner_support["pooling"]:
-                    msg = (f"This model does not support the '{task_option}' "
-                           f"task. Supported tasks: {supported_tasks}")
-                    raise ValueError(msg)
-                if self.registry.is_cross_encoder_model(architectures):
-                    task_option = "classify"
-                else:
-                    task_option = "embed"
+        if task_option != "auto":
+            for runner, runner_tasks in supported_tasks.items():
+                if task_option in runner_tasks:
+                    return runner
             else:
-                # Aliases
-                if task_option == "embedding":
-                    msg = ("The 'embedding' task has been renamed to "
-                           "'embed', please use the new name. The old name "
-                           "will be removed in v1.0.")
-                    warnings.warn(msg, DeprecationWarning, stacklevel=2)
+                task_runner: RunnerType = next(
+                    runner for runner, tasks in _RUNNER_TASKS.items()
+                    if task_option in tasks)
+                raise ValueError(
+                    f"This model does not support task={task_option!r}. "
+                    f"Available tasks for runner={task_runner!r}: "
+                    f"{supported_tasks[task_runner]}")
 
-                    task_option = "embed"
+        suffix_to_preferred_runner: list[tuple[str, RunnerType]] = [
+            ("ForCausalLM", "generate"),
+            ("ForConditionalGeneration", "generate"),
+            ("ChatModel", "generate"),
+            ("LMHeadModel", "generate"),
+            ("ForSequenceClassification", "pooling"),
+            ("EmbeddingModel", "pooling"),
+            ("RewardModel", "pooling"),
+        ]
+        _, arch = self.registry.inspect_model_cls(self.architectures)
 
-            if task_option not in supported_tasks:
-                msg = (
-                    f"This model does not support the '{task_option}' task. "
-                    f"Supported tasks: {supported_tasks}")
-                raise ValueError(msg)
+        for suffix, pref_runner in suffix_to_preferred_runner:
+            if arch.endswith(suffix) and pref_runner in supported_runner_types:
+                return pref_runner
 
-            selected_task = task_option
+        if "classify" in supported_tasks.get("pooling", []):
+            # When multiple pooling tasks are present, default to
+            # pooling (eg cross-encoder) for non-standard architectures.
+            return "pooling"
+        if "generate" in supported_runner_types:
+            return "generate"
+        if "pooling" in supported_runner_types:
+            return "pooling"
 
-        return supported_tasks, selected_task
+        raise AssertionError("This line should not be reached")
 
     def _parse_quant_hf_config(self):
         quant_cfg = getattr(self.hf_config, "quantization_config", None)
@@ -1449,14 +1521,6 @@ class ModelConfig:
     def use_mla(self) -> bool:
         return self.is_deepseek_mla and not envs.VLLM_MLA_DISABLE
 
-    @property
-    def supported_runner_types(self) -> set[RunnerType]:
-        return {_TASK_RUNNER[task] for task in self.supported_tasks}
-
-    @property
-    def runner_type(self) -> RunnerType:
-        return _TASK_RUNNER[cast(_ResolvedTask, self.task)]
-
     @property
     def is_v1_compatible(self) -> bool:
         architectures = getattr(self.hf_config, "architectures", [])
@@ -2694,7 +2758,7 @@ class SpeculativeConfig:
             if self.model is not None:
                 self.draft_model_config = ModelConfig(
                     model=self.model,
-                    task="draft",
+                    runner="draft",
                     tokenizer=self.target_model_config.tokenizer,
                     tokenizer_mode=self.target_model_config.tokenizer_mode,
                     trust_remote_code=self.target_model_config.

vllm/entrypoints/llm.py

@@ -454,20 +454,19 @@ class LLM:
             considered legacy and may be deprecated in the future. You should
             instead pass them via the `inputs` parameter.
         """
-        runner_type = self.llm_engine.model_config.runner_type
-        if runner_type not in ["generate", "transcription"]:
+        model_config = self.llm_engine.model_config
+        runner_type = model_config.runner_type
+        if runner_type != "generate":
             messages = [
-                "LLM.generate() is only supported for (conditional) generation "
-                "models (XForCausalLM, XForConditionalGeneration).",
+                "LLM.generate() is only supported for generative models."
             ]
 
-            supported_runner_types = self.llm_engine.model_config \
-                .supported_runner_types
-            if "generate" in supported_runner_types:
+            if "generate" in model_config.supported_runner_types:
                 messages.append(
                     "Your model supports the 'generate' runner, but is "
                     f"currently initialized for the '{runner_type}' runner. "
-                    "Please initialize vLLM using `--task generate`.")
+                    "Please initialize vLLM using `--task generate` or "
+                    "`--task transcription`.")
 
             raise ValueError(" ".join(messages))
 
@@ -1091,13 +1090,12 @@ class LLM:
             considered legacy and may be deprecated in the future. You should
             instead pass them via the `inputs` parameter.
         """
-        runner_type = self.llm_engine.model_config.runner_type
+        model_config = self.llm_engine.model_config
+        runner_type = model_config.runner_type
         if runner_type != "pooling":
             messages = ["LLM.encode() is only supported for pooling models."]
 
-            supported_runner_types = self.llm_engine.model_config \
-                .supported_runner_types
-            if "pooling" in supported_runner_types:
+            if "pooling" in model_config.supported_runner_types:
                 messages.append(
                     "Your model supports the 'pooling' runner, but is "
                     f"currently initialized for the '{runner_type}' runner. "
@@ -1119,13 +1117,13 @@ class LLM:
             # Use default pooling params.
             pooling_params = PoolingParams()
         elif isinstance(pooling_params, PoolingParams):
-            pooling_params.verify(self.llm_engine.model_config)
+            pooling_params.verify(model_config)
         else:
             for pooling_param in pooling_params:
-                pooling_param.verify(self.llm_engine.model_config)
+                pooling_param.verify(model_config)
 
-        tokenization_kwargs: dict[str, Any] = {}
-        _validate_truncation_size(self.llm_engine.model_config.max_model_len,
+        tokenization_kwargs = dict[str, Any]()
+        _validate_truncation_size(model_config.max_model_len,
                                   truncate_prompt_tokens, tokenization_kwargs)
 
         self._validate_and_add_requests(
@@ -1178,9 +1176,10 @@ class LLM:
             A list of `EmbeddingRequestOutput` objects containing the
             embedding vectors in the same order as the input prompts.
         """
-        if self.llm_engine.model_config.task != "embed":
-            raise ValueError(
-                "Embedding API is only enabled for `--task embed`")
+        model_config = self.llm_engine.model_config
+        if "embed" not in model_config.supported_tasks:
+            raise ValueError("Embedding API is not supported by this model. "
+                             "Please set `--task embed`.")
 
         items = self.encode(prompts,
                             truncate_prompt_tokens=truncate_prompt_tokens,
@@ -1223,9 +1222,11 @@ class LLM:
             A list of `ClassificationRequestOutput` objects containing the
             embedding vectors in the same order as the input prompts.
         """
-        if self.llm_engine.model_config.task != "classify":
+        model_config = self.llm_engine.model_config
+        if "classify" not in model_config.supported_tasks:
             raise ValueError(
-                "Classification API is only enabled for `--task classify`")
+                "Classification API is not supported by this model. "
+                "Please set `--task classify`.")
 
         items = self.encode(prompts,
                             use_tqdm=use_tqdm,
@@ -1392,13 +1393,12 @@ class LLM:
             A list of `ScoringRequestOutput` objects containing the
             generated scores in the same order as the input prompts.
         """
-        runner_type = self.llm_engine.model_config.runner_type
+        model_config = self.llm_engine.model_config
+        runner_type = model_config.runner_type
         if runner_type != "pooling":
             messages = ["LLM.score() is only supported for pooling models."]
 
-            supported_runner_types = self.llm_engine.model_config \
-                .supported_runner_types
-            if "pooling" in supported_runner_types:
+            if "pooling" in model_config.supported_runner_types:
                 messages.append(
                     "Your model supports the 'pooling' runner, but is "
                     f"currently initialized for the '{runner_type}' runner. "
@@ -1407,12 +1407,13 @@ class LLM:
 
             raise ValueError(" ".join(messages))
 
-        if self.llm_engine.model_config.task not in ("embed", "classify"):
-            raise ValueError("Score API is only enabled for "
-                             "`--task embed or --task classify`.")
+        if all(t not in model_config.supported_tasks
+               for t in ("embed", "classify")):
+            raise ValueError("Score API is not supported by this model. "
+                             "Please set `--task embed` or `--task classify`.")
 
-        if (self.llm_engine.model_config.task == "classify"
-                and self.llm_engine.model_config.hf_config.num_labels != 1):
+        if (model_config.task == "classify"
+                and getattr(model_config.hf_config, "num_labels", 0) != 1):
             raise ValueError("Score API is only enabled for num_labels == 1.")
 
         # the tokenizer for models such as

vllm/entrypoints/openai/api_server.py

@@ -1520,7 +1520,7 @@ async def init_app_state(
         reasoning_parser=args.reasoning_parser,
         enable_prompt_tokens_details=args.enable_prompt_tokens_details,
         enable_force_include_usage=args.enable_force_include_usage,
-    ) if model_config.runner_type == "generate" else None
+    ) if "generate" in model_config.supported_tasks else None
     state.openai_serving_chat = OpenAIServingChat(
         engine_client,
         model_config,
@@ -1537,7 +1537,7 @@ async def init_app_state(
         reasoning_parser=args.reasoning_parser,
         enable_prompt_tokens_details=args.enable_prompt_tokens_details,
         enable_force_include_usage=args.enable_force_include_usage,
-    ) if model_config.runner_type == "generate" else None
+    ) if "generate" in model_config.supported_tasks else None
     state.openai_serving_completion = OpenAIServingCompletion(
         engine_client,
         model_config,
@@ -1545,7 +1545,7 @@ async def init_app_state(
         request_logger=request_logger,
         return_tokens_as_token_ids=args.return_tokens_as_token_ids,
         enable_force_include_usage=args.enable_force_include_usage,
-    ) if model_config.runner_type == "generate" else None
+    ) if "generate" in model_config.supported_tasks else None
     state.openai_serving_pooling = OpenAIServingPooling(
         engine_client,
         model_config,
@@ -1553,7 +1553,7 @@ async def init_app_state(
         request_logger=request_logger,
         chat_template=resolved_chat_template,
         chat_template_content_format=args.chat_template_content_format,
-    ) if model_config.runner_type == "pooling" else None
+    ) if "pooling" in model_config.supported_tasks else None
     state.openai_serving_embedding = OpenAIServingEmbedding(
         engine_client,
         model_config,
@@ -1561,22 +1561,24 @@ async def init_app_state(
         request_logger=request_logger,
         chat_template=resolved_chat_template,
         chat_template_content_format=args.chat_template_content_format,
-    ) if model_config.task == "embed" else None
+    ) if "embed" in model_config.supported_tasks else None
     state.openai_serving_classification = ServingClassification(
         engine_client,
         model_config,
         state.openai_serving_models,
         request_logger=request_logger,
-    ) if model_config.task == "classify" else None
+    ) if "classify" in model_config.supported_tasks else None
 
-    enable_serving_reranking = (model_config.task == "classify" and getattr(
-        model_config.hf_config, "num_labels", 0) == 1)
+    enable_serving_reranking = ("classify" in model_config.supported_tasks
+                                and getattr(model_config.hf_config,
+                                            "num_labels", 0) == 1)
     state.openai_serving_scores = ServingScores(
         engine_client,
         model_config,
         state.openai_serving_models,
-        request_logger=request_logger) if (
-            model_config.task == "embed" or enable_serving_reranking) else None
+        request_logger=request_logger,
+    ) if ("embed" in model_config.supported_tasks
+          or enable_serving_reranking) else None
 
     state.openai_serving_tokenization = OpenAIServingTokenization(
         engine_client,
@@ -1591,13 +1593,13 @@ async def init_app_state(
         model_config,
         state.openai_serving_models,
         request_logger=request_logger,
-    ) if model_config.runner_type == "transcription" else None
+    ) if "transcription" in model_config.supported_tasks else None
     state.openai_serving_translation = OpenAIServingTranslation(
         engine_client,
         model_config,
         state.openai_serving_models,
         request_logger=request_logger,
-    ) if model_config.runner_type == "transcription" else None
+    ) if "transcription" in model_config.supported_tasks else None
     state.task = model_config.task
 
     state.enable_server_load_tracking = args.enable_server_load_tracking

vllm/entrypoints/openai/run_batch.py

@@ -348,7 +348,7 @@ async def main(args):
         chat_template=None,
         chat_template_content_format="auto",
         enable_prompt_tokens_details=args.enable_prompt_tokens_details,
-    ) if model_config.runner_type == "generate" else None
+    ) if "generate" in model_config.supported_tasks else None
     openai_serving_embedding = OpenAIServingEmbedding(
         engine,
         model_config,
@@ -356,17 +356,19 @@ async def main(args):
         request_logger=request_logger,
         chat_template=None,
         chat_template_content_format="auto",
-    ) if model_config.task == "embed" else None
+    ) if "embed" in model_config.supported_tasks else None
 
-    enable_serving_reranking = (model_config.task == "classify" and getattr(
-        model_config.hf_config, "num_labels", 0) == 1)
+    enable_serving_reranking = ("classify" in model_config.supported_tasks
+                                and getattr(model_config.hf_config,
+                                            "num_labels", 0) == 1)
 
-    openai_serving_scores = (ServingScores(
+    openai_serving_scores = ServingScores(
         engine,
         model_config,
         openai_serving_models,
         request_logger=request_logger,
-    ) if (model_config.task == "embed" or enable_serving_reranking) else None)
+    ) if ("embed" in model_config.supported_tasks
+          or enable_serving_reranking) else None
 
     tracker = BatchProgressTracker()
     logger.info("Reading batch from %s...", args.input_file)

vllm/model_executor/models/interfaces.py

@@ -694,6 +694,12 @@ class SupportsTranscription(Protocol):
 
     supports_transcription: ClassVar[Literal[True]] = True
 
+    supports_transcription_only: ClassVar[bool] = False
+    """
+    Transcription models can opt out of text generation by setting this to
+    `True`.
+    """
+
     @classmethod
     def get_generation_prompt(cls, audio: np.ndarray,
                               stt_config: SpeechToTextConfig, language: str,

vllm/model_executor/models/registry.py

@@ -284,6 +284,7 @@ class _ModelInfo:
     is_hybrid: bool
     has_noops: bool
     supports_transcription: bool
+    supports_transcription_only: bool
     supports_v0_only: bool
 
     @staticmethod
@@ -299,6 +300,8 @@ class _ModelInfo:
             is_attention_free=is_attention_free(model),
             is_hybrid=is_hybrid(model),
             supports_transcription=supports_transcription(model),
+            supports_transcription_only=(supports_transcription(model) and
+                                         model.supports_transcription_only),
             supports_v0_only=supports_v0_only(model),
             has_noops=has_noops(model),
         )
@@ -573,6 +576,13 @@ class _ModelRegistry:
         model_cls, _ = self.inspect_model_cls(architectures)
         return model_cls.supports_transcription
 
+    def is_transcription_only_model(
+        self,
+        architectures: Union[str, list[str]],
+    ) -> bool:
+        model_cls, _ = self.inspect_model_cls(architectures)
+        return model_cls.supports_transcription_only
+
     def is_v1_compatible(
         self,
         architectures: Union[str, list[str]],

vllm/model_executor/models/whisper.py

@@ -772,6 +772,9 @@ class WhisperForConditionalGeneration(nn.Module, SupportsTranscription,
         ".fc2.": ".mlp.fc2."
     })
 
+    # Whisper only supports audio-conditioned generation.
+    supports_transcription_only = True
+
     @classmethod
     def validate_language(cls, language: str) -> bool:
         if language in ISO639_1_SUPPORTED_LANGS: