[diffusion] feat: support loading self-describing quanto int8 encoders (#36052)

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

@@ -969,6 +969,19 @@ 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.
 
+The same component option accepts a self-describing Quanto qint8 file without
+an additional quantization flag:
+
+```bash Overlay
+--component-paths.text_encoder \
+  DeepBeepMeep/MiniMax-H3/Qwen3-VL-32B-Instruct/Qwen3-VL-32B-Instruct-layer50_quanto_bf16_int8.safetensors
+```
+
+This variant keeps the declared language and vision linear weights in qint8
+storage, then dequantizes only the active matrix for BF16/FP16 linear math. Use
+it as a memory option, not as an INT8 throughput claim. The embedded Quanto map
+is the selector; adding `--quantization` would describe a different operation.
+
 </Tab>
 
 <Tab title="Encoder scheduling">

docs/docs/sglang-diffusion/quantization.mdx

@@ -200,6 +200,14 @@ backend.
       <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. 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>quanto-int8</code></td>
+      <td>One native encoder safetensors file with an embedded Quanto quantization map</td>
+      <td>An explicit weight file through <code>--component-paths.&lt;component&gt;</code></td>
+      <td>Native encoders whose mapped linear layers consume every declared qint8 entry; MiniMax-H3's Qwen3-VL encoder is supported</td>
+      <td>None</td>
+      <td>Auto-detected weight-only qint8 storage. Each active matrix is dequantized to the compute dtype for the ordinary linear operation, so this reduces stored/resident weight memory rather than promising INT8 GEMM speed. TP and offload are supported; FSDP is not.</td>
+    </tr>
     <tr>
       <td><code>qvg-kv</code></td>
       <td>Unquantized model with runtime causal KV-cache compression</td>

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

@@ -36,6 +36,7 @@ class QuantizationConfig(SRTQuantizationConfig):
     # for quantization frameworks with a separate quantized model provided, e.g. Nunchaku
     quantized_model_path: str | None = None
     checkpoint_uses_native_qkv_layout: bool = False
+    supports_srt_linear_layers: bool = False
 
     def get_scaled_act_names(self) -> list[str]:
         return []

python/sglang/multimodal_gen/runtime/layers/quantization/configs/quanto_int8_config.py

@@ -0,0 +1,194 @@
+# SPDX-License-Identifier: Apache-2.0
+"""Config and checkpoint admission for Optimum Quanto qint8 weights."""
+
+from __future__ import annotations
+
+import base64
+import json
+from collections.abc import Callable
+from typing import Any
+
+import torch
+from safetensors import safe_open
+
+from sglang.multimodal_gen.runtime.layers.linear import (
+    LinearBase as DiffusionLinearBase,
+)
+from sglang.multimodal_gen.runtime.layers.linear import (
+    UnquantizedLinearMethod as DiffusionUnquantizedLinearMethod,
+)
+from sglang.multimodal_gen.runtime.layers.quantization.configs.base_config import (
+    QuantizationConfig,
+    QuantizeMethodBase,
+)
+from sglang.multimodal_gen.runtime.layers.quantization.quanto_int8 import (
+    QuantoInt8LinearMethod,
+)
+from sglang.srt.layers.linear import LinearBase as SrtLinearBase
+from sglang.srt.layers.quantization.unquant import (
+    UnquantizedLinearMethod as SrtUnquantizedLinearMethod,
+)
+
+_FLOAT_DTYPES = {"BF16", "F16", "F32"}
+
+
+class QuantoInt8Config(QuantizationConfig):
+    """Dispatch linears declared qint8 in an Optimum Quanto quantization map."""
+
+    supports_srt_linear_layers = True
+
+    def __init__(self, layer_prefixes: set[str]) -> None:
+        super().__init__()
+        self.layer_prefixes = layer_prefixes
+        self.selected: set[str] = set()
+
+    @classmethod
+    def get_name(cls) -> str:
+        return "quanto_int8"
+
+    @classmethod
+    def get_supported_act_dtypes(cls) -> list[torch.dtype]:
+        return [torch.bfloat16, torch.float16]
+
+    @classmethod
+    def get_min_capability(cls) -> int:
+        return 0
+
+    @staticmethod
+    def get_config_filenames() -> list[str]:
+        return []
+
+    @classmethod
+    def from_config(cls, config: dict[str, Any]) -> QuantoInt8Config:
+        raise ValueError(
+            "QuantoInt8Config must be constructed from safetensors metadata"
+        )
+
+    def get_quant_method(
+        self, layer: torch.nn.Module, prefix: str
+    ) -> QuantizeMethodBase | None:
+        if isinstance(layer, DiffusionLinearBase):
+            unquantized_method = DiffusionUnquantizedLinearMethod
+        elif isinstance(layer, SrtLinearBase):
+            unquantized_method = SrtUnquantizedLinearMethod
+        else:
+            return None
+        if prefix not in self.layer_prefixes:
+            return unquantized_method()
+        self.selected.add(prefix)
+        return QuantoInt8LinearMethod()
+
+
+def inspect_quanto_int8_checkpoint(
+    file_path: str,
+    param_name_mapper: Callable[[str], str] | None = None,
+) -> QuantoInt8Config | None:
+    """Validate a self-describing Quanto qint8 safetensors checkpoint."""
+
+    with safe_open(file_path, framework="pt", device="cpu") as checkpoint:
+        metadata = checkpoint.metadata() or {}
+        if metadata.get("quantization_format") != "quanto":
+            return None
+
+        encoded_map = metadata.get("quantization_map_base64")
+        if encoded_map is None:
+            raise ValueError("Quanto checkpoint is missing quantization_map_base64")
+        try:
+            quantization_map = json.loads(
+                base64.b64decode(encoded_map, validate=True).decode("utf-8")
+            )
+        except (ValueError, UnicodeDecodeError, json.JSONDecodeError) as error:
+            raise ValueError("Invalid Quanto quantization_map_base64") from error
+        if not isinstance(quantization_map, dict) or not quantization_map:
+            raise ValueError("Quanto quantization map must be a non-empty object")
+        if not all(
+            isinstance(prefix, str) and isinstance(spec, dict)
+            for prefix, spec in quantization_map.items()
+        ):
+            raise ValueError("Quanto quantization map entries must be named objects")
+
+        checkpoint_keys = set(checkpoint.keys())
+        data_suffix = ".weight._data"
+        data_prefixes = {
+            name.removesuffix(data_suffix)
+            for name in checkpoint_keys
+            if name.endswith(data_suffix)
+        }
+        map_prefixes = set(quantization_map)
+        if data_prefixes != map_prefixes:
+            missing_map = data_prefixes - map_prefixes
+            missing_data = map_prefixes - data_prefixes
+            raise ValueError(
+                "Quanto tensor/map prefixes do not match: "
+                f"missing metadata={sorted(missing_map)[:5]}, "
+                f"missing tensors={sorted(missing_data)[:5]}"
+            )
+
+        mapped_prefixes: set[str] = set()
+        for prefix, quantization in quantization_map.items():
+            if quantization.get("weights") != "qint8":
+                raise ValueError(
+                    f"Unsupported Quanto weight type for {prefix!r}: "
+                    f"{quantization.get('weights')!r}"
+                )
+            if quantization.get("activations") != "none":
+                raise ValueError(
+                    f"Quanto activation quantization is not supported for {prefix!r}"
+                )
+
+            names = {
+                "data": f"{prefix}.weight._data",
+                "scale": f"{prefix}.weight._scale",
+                "input": f"{prefix}.input_scale",
+                "output": f"{prefix}.output_scale",
+            }
+            missing = set(names.values()) - checkpoint_keys
+            if missing:
+                raise ValueError(
+                    f"Quanto layer {prefix!r} is missing tensors: {sorted(missing)}"
+                )
+            if f"{prefix}.weight" in checkpoint_keys:
+                raise ValueError(
+                    f"Quanto layer {prefix!r} contains both packed and dense weights"
+                )
+
+            data_slice = checkpoint.get_slice(names["data"])
+            scale_slice = checkpoint.get_slice(names["scale"])
+            data_shape = tuple(data_slice.get_shape())
+            scale_shape = tuple(scale_slice.get_shape())
+            if data_slice.get_dtype() != "I8" or len(data_shape) != 2:
+                raise ValueError(
+                    f"Quanto layer {prefix!r} needs a 2D I8 weight, got "
+                    f"{data_slice.get_dtype()} {data_shape}"
+                )
+            if scale_slice.get_dtype() not in _FLOAT_DTYPES or scale_shape != (
+                data_shape[0],
+                1,
+            ):
+                raise ValueError(
+                    f"Quanto layer {prefix!r} has incompatible scale "
+                    f"{scale_slice.get_dtype()} {scale_shape}"
+                )
+            for scale_name in (names["input"], names["output"]):
+                scale = checkpoint.get_slice(scale_name)
+                if (
+                    scale.get_dtype() not in _FLOAT_DTYPES
+                    or tuple(scale.get_shape()) != ()
+                ):
+                    raise ValueError(
+                        f"Quanto auxiliary scale {scale_name!r} must be a float scalar"
+                    )
+
+            mapped_prefix = (
+                param_name_mapper(prefix) if param_name_mapper is not None else prefix
+            )
+            if mapped_prefix in mapped_prefixes:
+                raise ValueError(
+                    f"Quanto layers collide after parameter mapping at {mapped_prefix!r}"
+                )
+            mapped_prefixes.add(mapped_prefix)
+
+    return QuantoInt8Config(mapped_prefixes)
+
+
+__all__ = ["QuantoInt8Config", "inspect_quanto_int8_checkpoint"]

python/sglang/multimodal_gen/runtime/layers/quantization/quanto_int8.py

@@ -0,0 +1,87 @@
+# SPDX-License-Identifier: Apache-2.0
+"""Runtime operations for serialized Optimum Quanto qint8 weights."""
+
+from __future__ import annotations
+
+from collections.abc import Iterable, Iterator
+from typing import Any
+
+import torch
+import torch.nn.functional as F
+from torch.nn.parameter import Parameter
+
+from sglang.multimodal_gen.runtime.layers.linear import (
+    LinearMethodBase,
+)
+from sglang.multimodal_gen.runtime.utils.weight_attrs import set_weight_attrs
+
+
+class QuantoInt8LinearMethod(LinearMethodBase):
+    """Keep qint8 weights packed and dequantize only the active matrix."""
+
+    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: Any,
+    ) -> None:
+        weight = Parameter(
+            torch.empty(
+                sum(output_partition_sizes),
+                input_size_per_partition,
+                dtype=torch.int8,
+            ),
+            requires_grad=False,
+        )
+        set_weight_attrs(weight, {"input_dim": 1, "output_dim": 0})
+        set_weight_attrs(weight, extra_weight_attrs)
+        layer.register_parameter("weight", weight)
+
+        weight_scale = Parameter(
+            torch.empty(
+                sum(output_partition_sizes),
+                1,
+                dtype=params_dtype,
+            ),
+            requires_grad=False,
+        )
+        set_weight_attrs(weight_scale, {"output_dim": 0})
+        set_weight_attrs(weight_scale, extra_weight_attrs)
+        layer.register_parameter("weight_scale", weight_scale)
+
+    def apply(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        bias: torch.Tensor | None = None,
+    ) -> torch.Tensor:
+        weight = layer.weight.to(dtype=x.dtype)
+        weight.mul_(layer.weight_scale.to(dtype=x.dtype))
+        return F.linear(x, weight, bias)
+
+
+def normalize_quanto_int8_weights(
+    weights: Iterable[tuple[str, torch.Tensor]],
+) -> Iterator[tuple[str, torch.Tensor]]:
+    """Translate flattened Quanto tensors to native linear parameter names."""
+
+    for name, tensor in weights:
+        if name.endswith((".input_scale", ".output_scale")):
+            if tensor.numel() != 1 or tensor.item() != 1:
+                raise ValueError(f"Quanto weight-only scale {name!r} must equal 1")
+            continue
+        if name.endswith(".weight._data"):
+            name = name.removesuffix("._data")
+        elif name.endswith(".weight._scale"):
+            name = name.removesuffix("._scale") + "_scale"
+        yield name, tensor
+
+
+__all__ = [
+    "QuantoInt8LinearMethod",
+    "normalize_quanto_int8_weights",
+]

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

@@ -37,6 +37,13 @@ from sglang.multimodal_gen.runtime.layers.quantization.configs.kitchen_int8_conf
 from sglang.multimodal_gen.runtime.layers.quantization.configs.kitchen_w4a8_config import (
     KitchenW4A8Config,
 )
+from sglang.multimodal_gen.runtime.layers.quantization.configs.quanto_int8_config import (
+    QuantoInt8Config,
+    inspect_quanto_int8_checkpoint,
+)
+from sglang.multimodal_gen.runtime.layers.quantization.quanto_int8 import (
+    normalize_quanto_int8_weights,
+)
 from sglang.multimodal_gen.runtime.loader.component_loaders.component_loader import (
     ComponentCheckpointUnsupportedError,
     ComponentLoader,
@@ -85,6 +92,10 @@ from sglang.multimodal_gen.runtime.weights.source import (
 )
 from sglang.multimodal_gen.utils import PRECISION_TO_TYPE
 from sglang.srt.environ import envs
+from sglang.srt.layers.linear import LinearBase as SrtLinearBase
+from sglang.srt.layers.quantization.unquant import (
+    UnquantizedLinearMethod as SrtUnquantizedLinearMethod,
+)
 
 logger = init_logger(__name__)
 
@@ -122,6 +133,23 @@ def _get_encoder_quant_config(
     model_cls: type[nn.Module] | None = None,
 ):
     quant_config = get_quant_config(component_config, component_model_path)
+    name_mapper = None
+    if model_cls is not None:
+        mapping = vars(model_cls).get("param_names_mapping", {})
+        if mapping:
+            mapping_fn = get_param_names_mapping(mapping)
+
+            def name_mapper(name: str) -> str:
+                # Layer-prefix metadata omits the suffix that many model
+                # mappings use to delimit a parameter name.
+                mapped_name, merge_index, _ = mapping_fn(f"{name}.weight")
+                if merge_index is not None:
+                    raise ValueError(
+                        "Serialized quantized component weights cannot use a "
+                        "stacked parameter-name mapping"
+                    )
+                return mapped_name.removesuffix(".weight")
+
     if (
         quant_config is None
         and component_weights_path != component_model_path
@@ -131,21 +159,11 @@ def _get_encoder_quant_config(
             component_weights_path
         )
     if quant_config is None and component_weights_path.endswith(".safetensors"):
-        name_mapper = None
+        quant_config = inspect_quanto_int8_checkpoint(
-        if model_cls is not None:
+            component_weights_path,
-            mapping = vars(model_cls).get("param_names_mapping", {})
+            param_name_mapper=name_mapper,
-            if mapping:
-                mapping_fn = get_param_names_mapping(mapping)
-
-                def name_mapper(name: str) -> str:
-                    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.removesuffix(".weight")
+        if quant_config is None:
-
             markers = inspect_comfy_quant_markers(
                 [component_weights_path],
                 param_name_mapper=name_mapper,
@@ -298,10 +316,13 @@ def _process_quantized_encoder_weights(
 ) -> int:
     processed_layers = 0
     for module in model.modules():
-        if not isinstance(module, LinearBase):
+        if not isinstance(module, (LinearBase, SrtLinearBase)):
             continue
         quant_method = module.quant_method
-        if quant_method is None or isinstance(quant_method, UnquantizedLinearMethod):
+        if quant_method is None or isinstance(
+            quant_method,
+            (UnquantizedLinearMethod, SrtUnquantizedLinearMethod),
+        ):
             continue
 
         origin_device = _module_tensor_device(module)
@@ -334,9 +355,12 @@ def _require_quantized_encoder_layers(
     quant_config: QuantizationConfig | None = None,
 ) -> None:
     has_quantized_layers = any(
-        isinstance(module, LinearBase)
+        isinstance(module, (LinearBase, SrtLinearBase))
         and module.quant_method is not None
-        and not isinstance(module.quant_method, UnquantizedLinearMethod)
+        and not isinstance(
+            module.quant_method,
+            (UnquantizedLinearMethod, SrtUnquantizedLinearMethod),
+        )
         for module in model.modules()
     )
     if not has_quantized_layers:
@@ -345,11 +369,20 @@ def _require_quantized_encoder_layers(
             f"quantized linear layers for {component_name!r}"
         )
     if isinstance(quant_config, (ComfyFp8Config, KitchenInt8Config, KitchenW4A8Config)):
-        missing = set(quant_config.layer_markers) - set(quant_config.selected)
+        expected = set(quant_config.layer_markers)
+        selected = set(quant_config.selected)
+    elif isinstance(quant_config, QuantoInt8Config):
+        expected = quant_config.layer_prefixes
+        selected = quant_config.selected
+    else:
+        expected = set()
+        selected = set()
+    if expected:
+        missing = expected - selected
         if missing:
             raise ComponentCheckpointUnsupportedError(
                 f"The native {type(model).__name__} implementation did not consume "
-                f"Comfy quantization markers for {component_name!r}: "
+                f"serialized quantization markers for {component_name!r}: "
                 f"{sorted(missing)[:5]}"
             )
 
@@ -818,17 +851,18 @@ class TextEncoderLoader(ComponentLoader):
                 model._keep_checkpoint_mapping = True
 
             weights_to_load = {name for name, _ in model.named_parameters()}
-            loaded_weights = model.load_weights(
+            checkpoint_weights = self._get_all_weights(
-                self._get_all_weights(
                 model,
                 model_path,
                 to_cpu=component_starts_on_cpu,
             )
-            )
+            if isinstance(quant_config, QuantoInt8Config):
+                checkpoint_weights = normalize_quanto_int8_weights(checkpoint_weights)
+            loaded_weights = model.load_weights(checkpoint_weights)
 
             if quant_config is not None:
                 postprocess_device: torch.device | None = local_torch_device
-                if (
+                if isinstance(quant_config, QuantoInt8Config) or (
                     isinstance(quant_config, KitchenInt8Config)
                     and quant_config.is_checkpoint_int8_serialized
                 ):

python/sglang/multimodal_gen/runtime/models/encoders/minimax_h3_qwen3vl.py

@@ -32,6 +32,7 @@ MINIMAX_H3_QWEN3VL_HIDDEN_DIM = 5120
 _LAYER_WEIGHT_RE = re.compile(r"^model\.language_model\.layers\.(\d+)\.")
 _PARAM_NAMES_MAPPING = {
     r"^model\.(embed_tokens|layers|norm|rotary_emb)\.": r"model.language_model.\1.",
+    r"^language_model\.": r"model.language_model.",
     r"^visual\.": r"model.visual.",
     r"^(model\.visual\.blocks\.\d+\.attn\.)qkv\.": r"\1qkv_proj.",
 }

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

@@ -694,7 +694,16 @@ class Qwen3VLModel(nn.Module):
         prefix: str = "",
     ):
         super().__init__()
-        self.visual = Qwen3VLVisionTransformer(config.vision_config)
+        vision_quant_config = (
+            quant_config
+            if quant_config is not None and quant_config.supports_srt_linear_layers
+            else None
+        )
+        self.visual = Qwen3VLVisionTransformer(
+            config.vision_config,
+            quant_config=vision_quant_config,
+            prefix=add_prefix("visual", prefix),
+        )
         self.language_model = Qwen3VLTextModel(
             config.text_config,
             quant_config=quant_config,

python/sglang/multimodal_gen/runtime/models/encoders/qwen3vl_vision.py

@@ -45,22 +45,30 @@ class Qwen3VLVisionRotaryEmbedding(nn.Module):
 
 
 class Qwen3VLVisionBlock(nn.Module):
-    def __init__(self, config: Any, layer_idx: int) -> None:
+    def __init__(
+        self,
+        config: Any,
+        layer_idx: int,
+        quant_config: Any = None,
+        prefix: str = "visual",
+    ) -> None:
         super().__init__()
         parallel = get_parallel()
         self.norm1 = nn.LayerNorm(config.hidden_size, eps=1e-6)
         self.norm2 = nn.LayerNorm(config.hidden_size, eps=1e-6)
         self.attn = QwenVLVisionAttention(
             config,
-            prefix=f"visual.blocks.{layer_idx}.attn",
+            prefix=f"{prefix}.blocks.{layer_idx}.attn",
             model_name="Qwen3-VL",
+            quant_config=quant_config,
         )
         self.mlp = Qwen3_VisionMLP(
             config.hidden_size,
             config.intermediate_size,
             bias=True,
             hidden_act=config.hidden_act,
-            prefix=f"visual.blocks.{layer_idx}.mlp",
+            prefix=f"{prefix}.blocks.{layer_idx}.mlp",
+            quant_config=quant_config,
             tp_rank=parallel.tp_rank,
             tp_size=parallel.tp_size,
         )
@@ -176,7 +184,12 @@ def _vision_cu_seqlens(grid_thw: torch.Tensor) -> torch.Tensor:
 
 
 class Qwen3VLVisionTransformer(nn.Module):
-    def __init__(self, config: Any) -> None:
+    def __init__(
+        self,
+        config: Any,
+        quant_config: Any = None,
+        prefix: str = "visual",
+    ) -> None:
         super().__init__()
         parallel = get_parallel()
         self.config = config
@@ -191,7 +204,8 @@ class Qwen3VLVisionTransformer(nn.Module):
         head_dim = config.hidden_size // config.num_heads
         self.rotary_pos_emb = Qwen3VLVisionRotaryEmbedding(head_dim // 2)
         self.blocks = nn.ModuleList(
-            Qwen3VLVisionBlock(config, layer_idx) for layer_idx in range(config.depth)
+            Qwen3VLVisionBlock(config, layer_idx, quant_config, prefix)
+            for layer_idx in range(config.depth)
         )
         self.merger = Qwen3VLMoeVisionPatchMerger(
             dim=config.out_hidden_size,

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

@@ -59,7 +59,14 @@ def _apply_rotary_embedding(
 
 
 class QwenVLVisionAttention(nn.Module):
-    def __init__(self, config: Any, *, prefix: str, model_name: str) -> None:
+    def __init__(
+        self,
+        config: Any,
+        *,
+        prefix: str,
+        model_name: str,
+        quant_config: Any = None,
+    ) -> None:
         super().__init__()
         parallel = get_parallel()
         self.num_heads = config.num_heads // parallel.tp_size
@@ -70,6 +77,7 @@ class QwenVLVisionAttention(nn.Module):
             head_size=self.head_dim,
             total_num_heads=config.num_heads,
             bias=True,
+            quant_config=quant_config,
             prefix=f"{prefix}.qkv_proj",
             tp_rank=parallel.tp_rank,
             tp_size=parallel.tp_size,
@@ -78,6 +86,7 @@ class QwenVLVisionAttention(nn.Module):
             input_size=config.hidden_size,
             output_size=config.hidden_size,
             bias=True,
+            quant_config=quant_config,
             prefix=f"{prefix}.proj",
             tp_rank=parallel.tp_rank,
             tp_size=parallel.tp_size,

python/sglang/multimodal_gen/test/unit/test_quanto_int8.py

@@ -0,0 +1,85 @@
+import base64
+import json
+
+import pytest
+import torch
+import torch.nn.functional as F
+from safetensors.torch import load_file, save_file
+
+from sglang.multimodal_gen.runtime.layers.linear import ReplicatedLinear
+from sglang.multimodal_gen.runtime.layers.quantization.configs.quanto_int8_config import (
+    QuantoInt8Config,
+    inspect_quanto_int8_checkpoint,
+)
+from sglang.multimodal_gen.runtime.layers.quantization.quanto_int8 import (
+    normalize_quanto_int8_weights,
+)
+
+
+def _save_quanto_checkpoint(path, *, activations="none"):
+    prefix = "language_model.layers.0.mlp.up_proj"
+    quantization_map = {prefix: {"weights": "qint8", "activations": activations}}
+    save_file(
+        {
+            f"{prefix}.weight._data": torch.tensor(
+                [[1, -2], [3, 4], [-5, 6]], dtype=torch.int8
+            ),
+            f"{prefix}.weight._scale": torch.tensor(
+                [[0.5], [0.25], [0.125]], dtype=torch.bfloat16
+            ),
+            f"{prefix}.input_scale": torch.tensor(1, dtype=torch.bfloat16),
+            f"{prefix}.output_scale": torch.tensor(1, dtype=torch.bfloat16),
+        },
+        path,
+        metadata={
+            "quantization_format": "quanto",
+            "quantization_map_base64": base64.b64encode(
+                json.dumps(quantization_map).encode()
+            ).decode(),
+        },
+    )
+
+
+def test_quanto_checkpoint_drives_native_linear_end_to_end(tmp_path):
+    checkpoint = tmp_path / "encoder.safetensors"
+    _save_quanto_checkpoint(checkpoint)
+    config = inspect_quanto_int8_checkpoint(
+        str(checkpoint), param_name_mapper=lambda name: f"model.{name}"
+    )
+
+    assert isinstance(config, QuantoInt8Config)
+    prefix = "model.language_model.layers.0.mlp.up_proj"
+    layer = ReplicatedLinear(
+        2,
+        3,
+        bias=False,
+        params_dtype=torch.bfloat16,
+        quant_config=config,
+        prefix=prefix,
+    )
+    tensors = dict(normalize_quanto_int8_weights(load_file(str(checkpoint)).items()))
+    raw_prefix = prefix.removeprefix("model.")
+    for suffix, parameter in (
+        ("weight", layer.weight),
+        ("weight_scale", layer.weight_scale),
+    ):
+        parameter.weight_loader(parameter, tensors.pop(f"{raw_prefix}.{suffix}"))
+
+    x = torch.tensor([[2.0, -1.0]], dtype=torch.bfloat16)
+    expected_weight = layer.weight.to(torch.bfloat16) * layer.weight_scale
+    output, _ = layer(x)
+    torch.testing.assert_close(output, F.linear(x, expected_weight))
+    assert not tensors
+    assert config.selected == {prefix}
+
+
+def test_quanto_checkpoint_rejects_activation_quantization(tmp_path):
+    checkpoint = tmp_path / "encoder.safetensors"
+    _save_quanto_checkpoint(checkpoint, activations="qint8")
+    with pytest.raises(ValueError, match="activation quantization"):
+        inspect_quanto_int8_checkpoint(str(checkpoint))
+
+
+def test_quanto_weight_only_auxiliary_scales_must_be_identity():
+    with pytest.raises(ValueError, match="must equal 1"):
+        list(normalize_quanto_int8_weights([("layer.input_scale", torch.tensor(0.5))]))

python/sglang/multimodal_gen/test/unit/test_qwen3vl_vision.py

@@ -4,6 +4,9 @@ import torch
 from torch import nn
 
 from sglang.multimodal_gen.configs.models.encoders.qwen3vl import Qwen3VLArchConfig
+from sglang.multimodal_gen.runtime.layers.quantization.configs.quanto_int8_config import (
+    QuantoInt8Config,
+)
 from sglang.multimodal_gen.runtime.models.encoders.minimax_h3_qwen3vl import (
     MiniMaxH3Qwen3VLEncoder,
 )
@@ -86,6 +89,41 @@ def test_native_vision_keeps_checkpoint_parameter_names():
     }
 
 
+def test_native_vision_accepts_srt_linear_quantization():
+    config = SimpleNamespace(
+        hidden_size=16,
+        intermediate_size=24,
+        hidden_act="gelu_pytorch_tanh",
+        num_heads=2,
+        depth=1,
+        patch_size=2,
+        temporal_patch_size=1,
+        in_channels=3,
+        num_position_embeddings=16,
+        spatial_merge_size=2,
+        out_hidden_size=12,
+        deepstack_visual_indexes=[],
+    )
+    prefixes = {
+        "model.visual.blocks.0.attn.qkv_proj",
+        "model.visual.blocks.0.attn.proj",
+        "model.visual.blocks.0.mlp.linear_fc1",
+        "model.visual.blocks.0.mlp.linear_fc2",
+    }
+    quant_config = QuantoInt8Config(prefixes)
+    with get_parallel().override(tp_size=1, tp_rank=0):
+        model = Qwen3VLVisionTransformer(
+            config,
+            quant_config=quant_config,
+            prefix="model.visual",
+        )
+
+    assert quant_config.selected == prefixes
+    for name, parameter in model.blocks[0].named_parameters():
+        if name.endswith("weight") and not name.startswith("norm"):
+            assert parameter.dtype == torch.int8
+
+
 def test_native_vision_keeps_position_math_in_fp32():
     class PatchEmbed(nn.Module):
         def __init__(self):

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

@@ -186,7 +186,7 @@ class TestMiniMaxH3CheckpointFilter(unittest.TestCase):
             "model.layers.49.self_attn.q_proj.weight": True,
             "model.layers.50.self_attn.q_proj.weight": False,
             "visual.blocks.0.attn.qkv.weight": True,
-            "language_model.layers.63.mlp.down_proj.weight": True,
+            "language_model.layers.63.mlp.down_proj.weight": False,
             "module.model.language_model.layers.63.mlp.down_proj.weight": True,
         }
         self.assertEqual(
@@ -383,11 +383,11 @@ class TestTextEncoderQuantization(unittest.TestCase):
         with tempfile.NamedTemporaryFile(suffix=".safetensors") as checkpoint:
             save_file(
                 {
-                    "model.layers.0.self_attn.q_proj.weight": torch.ones(
+                    "visual.blocks.0.attn.qkv.weight": torch.ones(
                         (2, 256), dtype=torch.int8
                     ),
-                    "model.layers.0.self_attn.q_proj.weight_scale": torch.ones((2, 1)),
+                    "visual.blocks.0.attn.qkv.weight_scale": torch.ones((2, 1)),
-                    "model.layers.0.self_attn.q_proj.comfy_quant": torch.tensor(
+                    "visual.blocks.0.attn.qkv.comfy_quant": torch.tensor(
                         list(marker), dtype=torch.uint8
                     ),
                 },
@@ -411,7 +411,7 @@ class TestTextEncoderQuantization(unittest.TestCase):
         self.assertIsInstance(model_config.quant_config, KitchenInt8Config)
         self.assertEqual(
             set(model_config.quant_config.layer_markers),
-            {"model.language_model.layers.0.self_attn.q_proj"},
+            {"model.visual.blocks.0.attn.qkv_proj"},
         )
 
     def test_mixed_w4a8_weight_file_maps_embedding_and_linear_markers(self):