[Model][3/N] Automatic conversion of CrossEncoding model

docs/models/supported_models.md

@@ -477,19 +477,28 @@ If your model is not in the above list, we will try to automatically convert the
 
 Specified using `--task score`.
 
-| Architecture                          | Models            | Example HF Models                                                                    | [V1](gh-issue:8779)   |
-|---------------------------------------|-------------------|--------------------------------------------------------------------------------------|-----------------------|
-| `BertForSequenceClassification`       | BERT-based        | `cross-encoder/ms-marco-MiniLM-L-6-v2`, etc.                                         |                       |
-| `Qwen3ForSequenceClassification`      | Qwen3-based       | `tomaarsen/Qwen3-Reranker-0.6B-seq-cls`, `Qwen/Qwen3-Reranker-0.6B` (see note), etc. | ✅︎                     |
-| `RobertaForSequenceClassification`    | RoBERTa-based     | `cross-encoder/quora-roberta-base`, etc.                                             |                       |
-| `XLMRobertaForSequenceClassification` | XLM-RoBERTa-based | `BAAI/bge-reranker-v2-m3`, etc.                                                      |                       |
+| Architecture                          | Models            | Example HF Models                                                                    | [V1](gh-issue:8779) |
+|---------------------------------------|-------------------|--------------------------------------------------------------------------------------|---------------------|
+| `BertForSequenceClassification`       | BERT-based        | `cross-encoder/ms-marco-MiniLM-L-6-v2`, etc.                                         |                     |
+| `Qwen2ForSequenceClassification`      | Qwen2-based       | `mixedbread-ai/mxbai-rerank-base-v2` (see note), etc.                                | ✅︎                  |
+| `Qwen3ForSequenceClassification`      | Qwen3-based       | `tomaarsen/Qwen3-Reranker-0.6B-seq-cls`, `Qwen/Qwen3-Reranker-0.6B` (see note), etc. | ✅︎                  |
+| `RobertaForSequenceClassification`    | RoBERTa-based     | `cross-encoder/quora-roberta-base`, etc.                                             |                     |
+| `XLMRobertaForSequenceClassification` | XLM-RoBERTa-based | `BAAI/bge-reranker-v2-m3`, etc.                                                      |                     |
+
+!!! note
+    Load the official original `mxbai-rerank-v2` by using the following command.
+
+    ```bash
+    vllm serve mixedbread-ai/mxbai-rerank-base-v2 --hf_overrides '{"architectures": ["Qwen2ForSequenceClassification"],"classifier_from_token": ["0", "1"], "method": "from_2_way_softmax"}'
+    ```
 
 !!! note
     Load the official original `Qwen3 Reranker` by using the following command. More information can be found at: <gh-file:examples/offline_inference/qwen3_reranker.py>.
 
     ```bash
     vllm serve Qwen/Qwen3-Reranker-0.6B --hf_overrides '{"architectures": ["Qwen3ForSequenceClassification"],"classifier_from_token": ["no", "yes"],"is_original_qwen3_reranker": true}'
     ```
+
 [](){ #supported-mm-models }
 
 ## List of Multimodal Language Models

tests/models/language/pooling/test_embedding.py

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 import os
+from typing import Optional
 
 import pytest
 
@@ -74,6 +75,13 @@ def test_models(
         vllm_extra_kwargs["override_pooler_config"] = \
             PoolerConfig(pooling_type="MEAN", normalize=False)
 
+    max_model_len: Optional[int] = 512
+    if model in [
+            "sentence-transformers/all-MiniLM-L12-v2",
+            "sentence-transformers/stsb-roberta-base-v2"
+    ]:
+        max_model_len = None
+
     # The example_prompts has ending "\n", for example:
     # "Write a short story about a robot that dreams for the first time.\n"
     # sentence_transformers will strip the input texts, see:
@@ -87,7 +95,7 @@ def test_models(
 
     with vllm_runner(model,
                      task="embed",
-                     max_model_len=512,
+                     max_model_len=max_model_len,
                      **vllm_extra_kwargs) as vllm_model:
         vllm_outputs = vllm_model.embed(example_prompts)
 

tests/models/language/pooling/test_gte.py

@@ -56,10 +56,16 @@
                    enable_test=False),
 ]
 
+V1FlashAttentionImpNotSupported = [
+    "Alibaba-NLP/gte-Qwen2-1.5B-instruct", "Alibaba-NLP/gte-modernbert-base"
+]
+
 
 @pytest.mark.parametrize("model_info", MODELS)
-def test_embed_models_mteb(hf_runner, vllm_runner,
-                           model_info: EmbedModelInfo) -> None:
+def test_embed_models_mteb(hf_runner, vllm_runner, model_info: EmbedModelInfo,
+                           monkeypatch) -> None:
+    if model_info.name in V1FlashAttentionImpNotSupported:
+        monkeypatch.setenv("VLLM_USE_V1", "0")
 
     vllm_extra_kwargs: dict[str, Any] = {}
     if model_info.architecture == "GteNewModel":
@@ -71,8 +77,10 @@ def test_embed_models_mteb(hf_runner, vllm_runner,
 
 @pytest.mark.parametrize("model_info", MODELS)
 def test_embed_models_correctness(hf_runner, vllm_runner,
-                                  model_info: EmbedModelInfo,
-                                  example_prompts) -> None:
+                                  model_info: EmbedModelInfo, example_prompts,
+                                  monkeypatch) -> None:
+    if model_info.name in V1FlashAttentionImpNotSupported:
+        monkeypatch.setenv("VLLM_USE_V1", "0")
 
     vllm_extra_kwargs: dict[str, Any] = {}
     if model_info.architecture == "GteNewModel":

tests/models/language/pooling/test_mxbai_rerank.py

@@ -0,0 +1,84 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+from typing import Any
+
+import pytest
+import torch
+
+from tests.conftest import HfRunner
+
+from .mteb_utils import RerankModelInfo, mteb_test_rerank_models
+
+RERANK_MODELS = [
+    RerankModelInfo("mixedbread-ai/mxbai-rerank-base-v2",
+                    architecture="Qwen2ForSequenceClassification",
+                    dtype="float32",
+                    enable_test=True),
+    RerankModelInfo("mixedbread-ai/mxbai-rerank-large-v2",
+                    architecture="Qwen2ForSequenceClassification",
+                    dtype="float32",
+                    enable_test=False)
+]
+
+
+class MxbaiRerankerHfRunner(HfRunner):
+
+    def __init__(self,
+                 model_name: str,
+                 dtype: str = "auto",
+                 *args: Any,
+                 **kwargs: Any) -> None:
+        from transformers import AutoModelForCausalLM, AutoTokenizer
+        super().__init__(model_name, dtype, auto_cls=AutoModelForCausalLM)
+
+        self.tokenizer = AutoTokenizer.from_pretrained(model_name,
+                                                       padding_side='left')
+        self.yes_loc = self.tokenizer.convert_tokens_to_ids("1")
+        self.no_loc = self.tokenizer.convert_tokens_to_ids("0")
+
+    def predict(self, prompts: list[list[str]], *args,
+                **kwargs) -> torch.Tensor:
+
+        def process_inputs(pairs):
+            inputs = self.tokenizer(pairs,
+                                    padding=False,
+                                    truncation='longest_first',
+                                    return_attention_mask=False)
+            for i, ele in enumerate(inputs['input_ids']):
+                inputs['input_ids'][i] = ele
+            inputs = self.tokenizer.pad(inputs,
+                                        padding=True,
+                                        return_tensors="pt")
+            for key in inputs:
+                inputs[key] = inputs[key].to(self.model.device)
+            return inputs
+
+        @torch.no_grad()
+        def compute_logits(inputs):
+            logits = self.model(**inputs).logits[:, -1, :]
+            yes_logits = logits[:, self.yes_loc]
+            no_logits = logits[:, self.no_loc]
+            logits = yes_logits - no_logits
+            scores = logits.float().sigmoid()
+            return scores
+
+        scores = []
+        for prompt in prompts:
+            inputs = process_inputs([prompt])
+            score = compute_logits(inputs)
+            scores.append(score[0].item())
+        return torch.Tensor(scores)
+
+
+@pytest.mark.parametrize("model_info", RERANK_MODELS)
+def test_rerank_models_mteb(vllm_runner, model_info: RerankModelInfo) -> None:
+    vllm_extra_kwargs: dict[str, Any] = {}
+    if model_info.architecture == "Qwen2ForSequenceClassification":
+        vllm_extra_kwargs["hf_overrides"] = {
+            "architectures": ["Qwen2ForSequenceClassification"],
+            "classifier_from_token": ["0", "1"],
+            "method": "from_2_way_softmax",
+        }
+
+    mteb_test_rerank_models(MxbaiRerankerHfRunner, vllm_runner, model_info,
+                            vllm_extra_kwargs)

vllm/config.py

@@ -466,6 +466,9 @@ def __post_init__(self) -> None:
                     "affect the random state of the Python process that "
                     "launched vLLM.", self.seed)
 
+        # Keep set served_model_name before maybe_model_redirect(self.model)
+        self.served_model_name = get_served_model_name(self.model,
+                                                       self.served_model_name)
         self.model = maybe_model_redirect(self.model)
         # The tokenizer is consistent with the model by default.
         if self.tokenizer is None:
@@ -609,8 +612,6 @@ def __post_init__(self) -> None:
 
         self.original_max_model_len = self.max_model_len
         self.max_model_len = self.get_and_verify_max_len(self.max_model_len)
-        self.served_model_name = get_served_model_name(self.model,
-                                                       self.served_model_name)
         self.multimodal_config = self._init_multimodal_config()
         if not self.skip_tokenizer_init:
             self._verify_tokenizer_mode()
@@ -1420,7 +1421,7 @@ def is_multimodal_model(self) -> bool:
 
     @property
     def is_cross_encoder(self) -> bool:
-        return self.registry.is_cross_encoder_model(self.architectures)
+        return self.task == "classify"
 
     @property
     def use_mla(self) -> bool:
@@ -4762,6 +4763,12 @@ def try_verify_and_update_config(self):
         if cls is not None:
             cls.verify_and_update_config(self)
 
+        if self.model_config.task == "classify":
+            # Maybe convert ForCausalLM into ForSequenceClassification model.
+            from vllm.model_executor.models.adapters import (
+                SequenceClassificationConfig)
+            SequenceClassificationConfig.verify_and_update_config(self)
+
     def __str__(self):
         return (
             f"model={self.model_config.model!r},"

vllm/model_executor/models/adapters.py

@@ -2,14 +2,17 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 from collections.abc import Iterable
-from typing import TYPE_CHECKING, Any, Optional, TypeVar, Union
+from typing import TYPE_CHECKING, Any, Optional, TypeVar, Union, cast
 
 import torch
 import torch.nn as nn
 
+from vllm.model_executor.models.config import VerifyAndUpdateConfig
+
 from .interfaces_base import VllmModelForPooling, is_pooling_model
 
 if TYPE_CHECKING:
+    from vllm.config import VllmConfig
     from vllm.model_executor.layers.pooler import PoolingType
 
 _T = TypeVar("_T", bound=type[nn.Module])
@@ -39,7 +42,6 @@ def _create_pooling_model_cls(
     default_softmax: bool,
 ) -> _T:
     # Lazy import
-    from vllm.config import VllmConfig
     from vllm.model_executor.layers.pooler import Pooler, PoolerOutput
     from vllm.model_executor.pooling_metadata import PoolingMetadata
 
@@ -162,7 +164,6 @@ def as_seq_cls_model(cls: _T) -> _T:
         return cls
 
     # Lazy import
-    from vllm.config import VllmConfig
     from vllm.model_executor.layers.linear import RowParallelLinear
     from vllm.model_executor.layers.pooler import PoolerOutput, PoolingType
     from vllm.model_executor.models.interfaces import SupportsCrossEncoding
@@ -193,6 +194,7 @@ def __init__(
             config = vllm_config.model_config.hf_config
             quant_config = vllm_config.quant_config
 
+            self.vllm_config = vllm_config
             self.task = vllm_config.model_config.task
             self.pooling_type = (
                 vllm_config.model_config.pooler_config.pooling_type)
@@ -242,6 +244,17 @@ def get_logits(hidden_states):
                 ]
                 return PoolerOutput(outputs=pooled_outputs)
 
+        def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]):
+            tokens = getattr(self.config, "classifier_from_token", None)
+            method = getattr(self.config, "method", None)
+
+            if tokens is None and method is None:
+                return super().load_weights(weights)
+            else:
+                # Online convert ForCausalLM into
+                # ForSequenceClassification model.
+                return seq_cls_model_loader(self, weights)
+
 
     ModelForSequenceClassification.__name__ = \
         _get_pooling_model_name(cls.__name__, "ForSequenceClassification")
@@ -277,3 +290,86 @@ def as_reward_model(cls: _T) -> _T:
         _get_pooling_model_name(cls.__name__, "ForReward")
 
     return ModelForReward  # type: ignore
+
+
+class SequenceClassificationConfig(VerifyAndUpdateConfig):
+
+    @staticmethod
+    def verify_and_update_config(vllm_config: "VllmConfig") -> None:
+        config = vllm_config.model_config.hf_config
+        method = getattr(config, "method", None)
+        tokens = getattr(config, "classifier_from_token", None)
+
+        if method is None:
+            return
+
+        assert tokens is not None
+        assert method in SEQ_CLS_LOAD_METHODS, f"method {method} not supported"
+
+        if method == "from_2_way_softmax":
+            assert len(tokens) == 2
+            config.num_labels = 1
+        else:
+            config.num_labels = len(tokens)
+
+
+def load_weights_using_from_2_way_softmax(
+        model, weights: Iterable[tuple[str, torch.Tensor]]):
+    # refer to https://huggingface.co/Qwen/Qwen3-Reranker-0.6B/discussions/3
+    from vllm.model_executor.layers.vocab_parallel_embedding import (
+        ParallelLMHead)
+    from vllm.model_executor.models.utils import AutoWeightsLoader
+
+    model_config = model.vllm_config.model_config
+    tokens = getattr(model.config, "classifier_from_token", [])
+    tokens = cast(list[int], tokens)
+    assert len(tokens) == 2
+
+    device = model.score.weight.device
+
+    if model.config.tie_word_embeddings:
+        model.lm_head = model.model.embed_tokens
+    else:
+        model.lm_head = ParallelLMHead(model.config.vocab_size,
+                                       model.config.hidden_size,
+                                       quant_config=model.quant_config)
+
+    loader = AutoWeightsLoader(model)
+    loaded_weights = loader.load_weights(weights)
+
+    from vllm.transformers_utils.tokenizer import get_tokenizer
+    tokenizer = get_tokenizer(model_config.tokenizer,
+                              revision=model_config.tokenizer_revision,
+                              tokenizer_mode=model_config.tokenizer_mode,
+                              trust_remote_code=model_config.trust_remote_code)
+
+    false_id = tokenizer.convert_tokens_to_ids(tokens[0])
+    true_id = tokenizer.convert_tokens_to_ids(tokens[1])
+    weight = model.lm_head.weight.data[true_id].to(device).to(
+        torch.float32) - model.lm_head.weight.data[false_id].to(device).to(
+            torch.float32)
+    model.score.weight.data.copy_(weight)
+
+    del model.lm_head
+    loaded_weights.add("score.weight")
+    loaded_weights.discard("lm_head.weight")
+    return loaded_weights
+
+
+SEQ_CLS_LOAD_METHODS = {
+    "from_2_way_softmax": load_weights_using_from_2_way_softmax,
+}
+
+
+def seq_cls_model_loader(model, weights: Iterable[tuple[str, torch.Tensor]]):
+    # Online convert ForCausalLM into ForSequenceClassification model.
+    # - from_2_way_softmax:
+    #   - Qwen3ForCausalLM
+    #     - Qwen3-Reranker
+    #   - Qwen2ForCausalLM
+    #     - mxbai-rerank-v2
+
+    config = model.vllm_config.model_config.hf_config
+    method = getattr(config, "method", None)
+    assert method in SEQ_CLS_LOAD_METHODS, f"method {method} not supported"
+    return SEQ_CLS_LOAD_METHODS[method](model, weights)

vllm/model_executor/models/config.py

@@ -167,7 +167,7 @@ def verify_and_update_config(vllm_config: "VllmConfig") -> None:
         assert tokens is not None and len(tokens) == 2, \
             ("Try loading the original Qwen3 Reranker?, see: "
              "https://github.com/vllm-project/vllm/tree/main/examples/offline_inference/qwen3_reranker.py")
-        config.num_labels = 1
+        vllm_config.model_config.hf_config.method = "from_2_way_softmax"
 
 
 class SnowflakeGteNewModelConfig(VerifyAndUpdateConfig):