[diffusion] feat: support loading mixed w4a8 text encoders (#36037)

docs/cookbook/diffusion/MiniMax/MiniMax-H3.mdx

@@ -958,6 +958,17 @@ linear layers use FP8 while embeddings, normalization, and the vision tower
 remain BF16. This is an approximate serve-time choice and is incompatible with
 the strict `quality="high"` deployment contract.
 
+The mixed W4A8 community encoder follows the same component-path contract:
+
+```bash Overlay
+--component-paths.text_encoder \
+  Winnougan/MiniMax-H3-INT4_Convrot_ComfyUI/qwen3vl_32b_minimax_h3-w4a8_convrot.safetensors
+```
+
+Install `comfy-kitchen>=0.2.27` and omit `--quantization`. SGLang automatically
+loads its W4A8 language linears and tensorwise INT8 embedding; the unmarked
+vision tower remains BF16.
+
 </Tab>
 
 <Tab title="Encoder scheduling">

docs/docs/sglang-diffusion/quantization.mdx

@@ -195,10 +195,10 @@ backend.
     <tr>
       <td><code>comfy-w4a8-convrot</code></td>
       <td>Safetensors with serialized <code>asym_w4a8_int8</code> layer metadata and packed weights</td>
-      <td><code>--transformer-weights-path</code></td>
+      <td><code>--transformer-weights-path</code> or <code>--component-paths.text_encoder</code></td>
-      <td>MiniMax-H3 FL2VA / Ref2VA DiTs</td>
+      <td>MiniMax-H3 FL2VA / Ref2VA DiTs and its native Qwen3-VL encoder</td>
       <td><code>comfy-kitchen&gt;=0.2.27</code></td>
-      <td>Auto-detected; omit <code>--quantization</code>. Requires SM80+ and validates packed weights, group/channel scales, and optional codebooks before model construction. TP must preserve ConvRot group boundaries; offload is supported and FSDP is not.</td>
+      <td>Auto-detected; omit <code>--quantization</code>. Requires SM80+ and validates packed weights, group/channel scales, and optional codebooks before model construction. Mixed encoder files may keep their embedding tensorwise INT8. TP must preserve ConvRot group boundaries; offload is supported and FSDP is not.</td>
     </tr>
     <tr>
       <td><code>qvg-kv</code></td>

python/sglang/multimodal_gen/runtime/layers/quantization/configs/base_config.py

@@ -46,6 +46,10 @@ class QuantizationConfig(SRTQuantizationConfig):
         """Whether a row-parallel shard preserves this format's input layout."""
         return True
 
+    def quantizes_embedding(self, prefix: str) -> bool:
+        """Whether this checkpoint config owns the named embedding table."""
+        return False
+
     def remap_checkpoint_prefixes(self, param_names_mapping: dict) -> None:
         """Translate checkpoint module names to the native model namespace."""
         return

python/sglang/multimodal_gen/runtime/layers/quantization/configs/kitchen_w4a8_config.py

@@ -16,8 +16,12 @@ from sglang.multimodal_gen.runtime.layers.quantization.configs.base_config impor
     QuantizeMethodBase,
 )
 from sglang.multimodal_gen.runtime.layers.quantization.kitchen_w4a8 import (
+    KitchenInt8EmbeddingMethod,
     KitchenW4A8LinearMethod,
 )
+from sglang.multimodal_gen.runtime.layers.vocab_parallel_embedding import (
+    VocabParallelEmbedding,
+)
 from sglang.multimodal_gen.runtime.platforms import current_platform
 
 
@@ -44,10 +48,15 @@ class KitchenW4A8Config(QuantizationConfig):
         self.selected: list[str] = []
 
         for prefix, marker in layer_markers.items():
-            if marker.get("format") != "asym_w4a8_int8":
+            marker_format = marker.get("format")
+            if marker_format == "int8_tensorwise" and marker.get(
+                "_is_tensorwise_scalar"
+            ):
+                continue
+            if marker_format != "asym_w4a8_int8":
                 raise ValueError(
                     f"Unsupported Comfy W4A8 format for {prefix!r}: "
-                    f"{marker.get('format')!r}"
+                    f"{marker_format!r}"
                 )
             if marker.get("convrot") is not True:
                 raise ValueError(
@@ -80,11 +89,24 @@ class KitchenW4A8Config(QuantizationConfig):
     def get_quant_method(
         self, layer: torch.nn.Module, prefix: str
     ) -> QuantizeMethodBase | None:
+        marker = self.layer_markers.get(prefix)
+        if isinstance(layer, VocabParallelEmbedding):
+            if marker is None:
+                return None
+            if marker.get("format") != "int8_tensorwise" or not marker.get(
+                "_is_tensorwise_scalar"
+            ):
+                raise ValueError(
+                    f"Unsupported quantized embedding marker for {prefix!r}: {marker}"
+                )
+            self.selected.append(prefix)
+            return KitchenInt8EmbeddingMethod()
         if not isinstance(layer, LinearBase):
             return None
-        marker = self.layer_markers.get(prefix)
         if marker is None:
             return UnquantizedLinearMethod()
+        if marker.get("format") != "asym_w4a8_int8":
+            raise ValueError(f"Unsupported quantized linear marker for {prefix!r}")
 
         group_size = int(marker.get("group_size", 16))
         convrot_group_size = int(marker.get("convrot_groupsize", 256))
@@ -120,7 +142,7 @@ class KitchenW4A8Config(QuantizationConfig):
         self, prefix: str, input_size_per_partition: int
     ) -> bool:
         marker = self.layer_markers.get(prefix)
-        if marker is None:
+        if marker is None or marker.get("format") != "asym_w4a8_int8":
             return True
         return self._supports_input_size(
             input_size_per_partition,
@@ -130,3 +152,11 @@ class KitchenW4A8Config(QuantizationConfig):
 
     def get_scaled_act_names(self) -> list[str]:
         return []
+
+    def quantizes_embedding(self, prefix: str) -> bool:
+        marker = self.layer_markers.get(prefix)
+        return bool(
+            marker is not None
+            and marker.get("format") == "int8_tensorwise"
+            and marker.get("_is_tensorwise_scalar")
+        )

python/sglang/multimodal_gen/runtime/layers/quantization/kitchen_w4a8.py

@@ -14,6 +14,23 @@ try:
 except ImportError:  # pragma: no cover - optional dependency
     w4a8_int8_linear = None
 
+_OUTPUT_DTYPE_CODE = {torch.float32: 0, torch.float16: 1, torch.bfloat16: 2}
+
+
+def _register_weight(
+    layer: torch.nn.Module,
+    name: str,
+    shape: tuple[int, ...],
+    dtype: torch.dtype,
+    weight_attrs: dict,
+    parallel_dims: dict[str, int] | None = None,
+) -> None:
+    weight = Parameter(torch.empty(shape, dtype=dtype), requires_grad=False)
+    if parallel_dims is not None:
+        set_weight_attrs(weight, parallel_dims)
+    set_weight_attrs(weight, weight_attrs)
+    layer.register_parameter(name, weight)
+
 
 class KitchenW4A8LinearMethod(LinearMethodBase):
     """Load packed INT4 weights and execute the W4A8 ConvRot kernel."""
@@ -36,21 +53,6 @@ class KitchenW4A8LinearMethod(LinearMethodBase):
         self.has_codebook = has_codebook
         self.has_correction = has_correction
 
-    @staticmethod
-    def _register_weight(
-        layer: torch.nn.Module,
-        name: str,
-        shape: tuple[int, ...],
-        dtype: torch.dtype,
-        weight_attrs: dict,
-        parallel_dims: dict[str, int] | None = None,
-    ) -> None:
-        weight = Parameter(torch.empty(shape, dtype=dtype), requires_grad=False)
-        if parallel_dims is not None:
-            set_weight_attrs(weight, parallel_dims)
-        set_weight_attrs(weight, weight_attrs)
-        layer.register_parameter(name, weight)
-
     def create_weights(
         self,
         layer: torch.nn.Module,
@@ -70,7 +72,7 @@ class KitchenW4A8LinearMethod(LinearMethodBase):
             )
 
         output_size_per_partition = sum(output_partition_sizes)
-        self._register_weight(
+        _register_weight(
             layer,
             "weight",
             (output_size_per_partition, input_size_per_partition // 2),
@@ -78,7 +80,7 @@ class KitchenW4A8LinearMethod(LinearMethodBase):
             extra_weight_attrs,
             {"input_dim": 1, "output_dim": 0},
         )
-        self._register_weight(
+        _register_weight(
             layer,
             "weight_s_rel",
             (output_size_per_partition, input_size_per_partition // self.group_size),
@@ -86,7 +88,7 @@ class KitchenW4A8LinearMethod(LinearMethodBase):
             extra_weight_attrs,
             {"input_dim": 1, "output_dim": 0},
         )
-        self._register_weight(
+        _register_weight(
             layer,
             "weight_s_channel",
             (output_size_per_partition,),
@@ -95,7 +97,7 @@ class KitchenW4A8LinearMethod(LinearMethodBase):
             {"output_dim": 0},
         )
         if self.has_codebook:
-            self._register_weight(
+            _register_weight(
                 layer,
                 "weight_codebook",
                 (16,),
@@ -105,7 +107,7 @@ class KitchenW4A8LinearMethod(LinearMethodBase):
         else:
             layer.register_parameter("weight_codebook", None)
         if self.has_correction:
-            self._register_weight(
+            _register_weight(
                 layer,
                 "weight_correction",
                 (
@@ -146,4 +148,62 @@ class KitchenW4A8LinearMethod(LinearMethodBase):
         return output
 
 
-__all__ = ["KitchenW4A8LinearMethod"]
+class KitchenInt8EmbeddingMethod(LinearMethodBase):
+    """Gather and dequantize only the selected rows of a tensorwise INT8 table."""
+
+    def __init__(self) -> None:
+        try:
+            torch.ops.comfy_kitchen.dequantize_int8_embedding
+        except AttributeError as exc:
+            raise ImportError(
+                "Tensorwise INT8 embeddings require comfy-kitchen>=0.2.27 "
+                "(`pip install -U comfy-kitchen`)."
+            ) from exc
+
+    def create_weights(
+        self,
+        layer: torch.nn.Module,
+        input_size_per_partition: int,
+        output_partition_sizes: list[int],
+        input_size: int,
+        output_size: int,
+        params_dtype: torch.dtype,
+        **extra_weight_attrs,
+    ) -> None:
+        del input_size, output_size
+        self.output_dtype = params_dtype
+        _register_weight(
+            layer,
+            "weight",
+            (sum(output_partition_sizes), input_size_per_partition),
+            torch.int8,
+            extra_weight_attrs,
+            {"input_dim": 1, "output_dim": 0},
+        )
+        _register_weight(
+            layer,
+            "weight_scale",
+            (),
+            torch.float32,
+            extra_weight_attrs,
+        )
+
+    def apply(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        bias: torch.Tensor | None = None,
+    ) -> torch.Tensor:
+        raise NotImplementedError("Kitchen INT8 embedding weights support lookup only")
+
+    def embedding(self, layer: torch.nn.Module, input_: torch.Tensor) -> torch.Tensor:
+        return torch.ops.comfy_kitchen.dequantize_int8_embedding(
+            layer.weight,
+            layer.weight_scale,
+            input_,
+            0,
+            _OUTPUT_DTYPE_CODE[self.output_dtype],
+        )
+
+
+__all__ = ["KitchenInt8EmbeddingMethod", "KitchenW4A8LinearMethod"]

python/sglang/multimodal_gen/runtime/loader/component_loaders/text_encoder_loader.py

@@ -34,6 +34,9 @@ from sglang.multimodal_gen.runtime.layers.quantization.configs.base_config impor
 from sglang.multimodal_gen.runtime.layers.quantization.configs.kitchen_int8_config import (
     KitchenInt8Config,
 )
+from sglang.multimodal_gen.runtime.layers.quantization.configs.kitchen_w4a8_config import (
+    KitchenW4A8Config,
+)
 from sglang.multimodal_gen.runtime.loader.component_loaders.component_loader import (
     ComponentCheckpointUnsupportedError,
     ComponentLoader,
@@ -133,13 +136,13 @@ def _get_encoder_quant_config(
                 mapping_fn = get_param_names_mapping(mapping)
 
                 def name_mapper(name: str) -> str:
-                    mapped_name, merge_index, _ = mapping_fn(name)
+                    mapped_name, merge_index, _ = mapping_fn(f"{name}.weight")
                     if merge_index is not None:
                         raise ValueError(
                             "Comfy quantized component weights cannot use a "
                             "stacked parameter-name mapping"
                         )
-                    return mapped_name
+                    return mapped_name.removesuffix(".weight")
 
         markers = inspect_comfy_quant_markers(
             [component_weights_path],
@@ -308,7 +311,7 @@ def _require_quantized_encoder_layers(
             f"The native {type(model).__name__} implementation does not construct "
             f"quantized linear layers for {component_name!r}"
         )
-    if isinstance(quant_config, (ComfyFp8Config, KitchenInt8Config)):
+    if isinstance(quant_config, (ComfyFp8Config, KitchenInt8Config, KitchenW4A8Config)):
         missing = set(quant_config.layer_markers) - set(quant_config.selected)
         if missing:
             raise ComponentCheckpointUnsupportedError(

python/sglang/multimodal_gen/runtime/models/encoders/qwen3vl.py

@@ -27,6 +27,9 @@ from sglang.multimodal_gen.runtime.layers.quantization.weight_only_fp8 import (
     WeightOnlyFP8Linear,
     WeightOnlyFP8RowParallelLinear,
 )
+from sglang.multimodal_gen.runtime.layers.vocab_parallel_embedding import (
+    VocabParallelEmbedding,
+)
 from sglang.multimodal_gen.runtime.loader.weight_utils import default_weight_loader
 from sglang.multimodal_gen.runtime.models.encoders.base import TextEncoder
 from sglang.multimodal_gen.runtime.models.encoders.qwen3vl_vision import (
@@ -504,6 +507,18 @@ class Qwen3VLTextModel(nn.Module):
         self.padding_idx = config.pad_token_id
         self.vocab_size = config.vocab_size
 
+        embedding_prefix = add_prefix("embed_tokens", prefix)
+        if quant_config is not None and quant_config.quantizes_embedding(
+            embedding_prefix
+        ):
+            self.embed_tokens = VocabParallelEmbedding(
+                config.vocab_size,
+                config.hidden_size,
+                params_dtype=torch.get_default_dtype(),
+                quant_config=quant_config,
+                prefix=embedding_prefix,
+            )
+        else:
             self.embed_tokens = nn.Embedding(
                 config.vocab_size, config.hidden_size, self.padding_idx
             )

python/sglang/multimodal_gen/runtime/utils/quantization_utils.py

@@ -211,6 +211,14 @@ def inspect_comfy_quant_markers(
             continue
         weight_dtype, weight_shape = checkpoint_meta[f"{prefix}.weight"]
         scale_dtype, scale_shape = checkpoint_meta[f"{prefix}.weight_scale"]
+        if weight_dtype == "I8" and scale_dtype == "F32" and scale_shape == ():
+            if len(weight_shape) != 2:
+                raise ValueError(
+                    f"Comfy tensorwise INT8 layer {prefix!r} needs a 2D weight, "
+                    f"got {weight_shape}"
+                )
+            marker["_is_tensorwise_scalar"] = True
+            continue
         if weight_dtype != "I8" or scale_dtype != "F32":
             raise ValueError(
                 f"Comfy INT8 layer {prefix!r} needs I8 weights and F32 scales, "
@@ -243,6 +251,8 @@ def resolve_comfy_checkpoint_quantization(
         return KitchenInt8Config(layer_markers=layer_markers)
     if formats == ["asym_w4a8_int8"]:
         return KitchenW4A8Config(layer_markers)
+    if formats == ["asym_w4a8_int8", "int8_tensorwise"]:
+        return KitchenW4A8Config(layer_markers)
     if formats == ["float8_e4m3fn"]:
         return ComfyFp8Config(layer_markers)
     if formats == ["mxfp8"]:

python/sglang/multimodal_gen/test/unit/test_text_encoder_loader.py

@@ -13,6 +13,9 @@ from sglang.multimodal_gen.runtime.layers.linear import LinearBase
 from sglang.multimodal_gen.runtime.layers.quantization.configs.kitchen_int8_config import (
     KitchenInt8Config,
 )
+from sglang.multimodal_gen.runtime.layers.quantization.configs.kitchen_w4a8_config import (
+    KitchenW4A8Config,
+)
 from sglang.multimodal_gen.runtime.layers.quantization.fp8 import Fp8Config
 from sglang.multimodal_gen.runtime.loader.component_loaders.component_loader import (
     ComponentCheckpointUnsupportedError,
@@ -30,6 +33,7 @@ from sglang.multimodal_gen.runtime.models.encoders.minimax_h3_qwen3vl import (
     MiniMaxH3ConditioningProjection,
     MiniMaxH3Qwen3VLEncoder,
 )
+from sglang.multimodal_gen.runtime.models.encoders.qwen3vl import Qwen3VLTextModel
 
 
 class TestTextEncoderClassResolution(unittest.TestCase):
@@ -80,6 +84,41 @@ class TestTextEncoderClassResolution(unittest.TestCase):
         # e.g. CLIP/Mistral/Qwen text encoders are not encoder-decoder.
         self.assertIs(self._resolve(False, ["CLIPTextModel"]), transformers.AutoModel)
 
+    def test_qwen_text_model_constructs_checkpoint_owned_embedding(self):
+        config = SimpleNamespace(
+            pad_token_id=0,
+            vocab_size=64,
+            hidden_size=256,
+            num_hidden_layers=0,
+            rms_norm_eps=1e-6,
+        )
+        quant_config = mock.Mock()
+        quant_config.quantizes_embedding.return_value = True
+        replacement = nn.Embedding(64, 256)
+        with mock.patch(
+            "sglang.multimodal_gen.runtime.models.encoders.qwen3vl."
+            "VocabParallelEmbedding",
+            return_value=replacement,
+        ) as embedding_cls:
+            model = Qwen3VLTextModel(
+                config,
+                quant_config=quant_config,
+                use_tensor_parallel=True,
+                prefix="model.language_model",
+            )
+
+        self.assertIs(model.embed_tokens, replacement)
+        quant_config.quantizes_embedding.assert_called_once_with(
+            "model.language_model.embed_tokens"
+        )
+        embedding_cls.assert_called_once_with(
+            64,
+            256,
+            params_dtype=torch.get_default_dtype(),
+            quant_config=quant_config,
+            prefix="model.language_model.embed_tokens",
+        )
+
     def test_unknown_architecture_falls_back_to_automodel(self):
         self.assertIs(self._resolve(True, ["NotARealClass"]), transformers.AutoModel)
 
@@ -358,6 +397,60 @@ class TestTextEncoderQuantization(unittest.TestCase):
             {"model.language_model.layers.0.self_attn.q_proj"},
         )
 
+    def test_mixed_w4a8_weight_file_maps_embedding_and_linear_markers(self):
+        self.get_quant_config.return_value = None
+        layers = {
+            "model.embed_tokens": {"format": "int8_tensorwise"},
+            "model.layers.0.mlp.down_proj": {
+                "format": "asym_w4a8_int8",
+                "convrot": True,
+                "group_size": 16,
+                "convrot_groupsize": 256,
+            },
+        }
+        with tempfile.NamedTemporaryFile(suffix=".safetensors") as checkpoint:
+            save_file(
+                {
+                    "model.embed_tokens.weight": torch.ones((4, 256), dtype=torch.int8),
+                    "model.embed_tokens.weight_scale": torch.tensor(0.25),
+                    "model.layers.0.mlp.down_proj.weight": torch.ones(
+                        (2, 128), dtype=torch.int8
+                    ),
+                    "model.layers.0.mlp.down_proj.weight_s_rel": torch.ones(
+                        (2, 16), dtype=torch.float8_e4m3fn
+                    ),
+                    "model.layers.0.mlp.down_proj.weight_s_channel": torch.ones(2),
+                    "model.layers.0.mlp.down_proj.weight_codebook": torch.ones(16),
+                },
+                checkpoint.name,
+                metadata={"_quantization_metadata": json.dumps({"layers": layers})},
+            )
+            model_config = SimpleNamespace(quant_config=None)
+            with mock.patch(
+                "sglang.multimodal_gen.runtime.loader.component_loaders."
+                "text_encoder_loader.get_quant_config_from_safetensors_metadata",
+                return_value=None,
+            ):
+                _configure_encoder_quantization(
+                    model_config,
+                    MiniMaxH3Qwen3VLEncoder,
+                    {},
+                    "/model/text_encoder",
+                    checkpoint.name,
+                    "text_encoder",
+                )
+
+        self.assertIsInstance(model_config.quant_config, KitchenW4A8Config)
+        self.assertTrue(
+            model_config.quant_config.quantizes_embedding(
+                "model.language_model.embed_tokens"
+            )
+        )
+        self.assertIn(
+            "model.language_model.layers.0.mlp.down_proj",
+            model_config.quant_config.layer_markers,
+        )
+
     def test_encoder_must_use_native_loader(self):
         model_config = SimpleNamespace(quant_config=None)
         with self.assertRaisesRegex(