[Bugfix] Make compressed-tensors MoEs respect ignored layers (#28878)

Signed-off-by: HDCharles <charlesdavidhernandez@gmail.com>

.buildkite/test-pipeline.yaml

@@ -632,6 +632,7 @@ steps:
   # we can only upgrade after this is resolved
   # TODO(jerryzh168): resolve the above comment
   - uv pip install --system torchao==0.13.0 --index-url https://download.pytorch.org/whl/cu129
+  - uv pip install --system conch-triton-kernels
   - VLLM_TEST_FORCE_LOAD_FORMAT=auto pytest -v -s quantization/ --ignore quantization/test_blackwell_moe.py
 
 - label: LM Eval Small Models # 53min

tests/quantization/test_compressed_tensors.py

@@ -10,6 +10,7 @@ import torch
 from compressed_tensors.quantization import QuantizationType
 
 from tests.models.utils import check_logprobs_close
+from vllm.model_executor.layers.fused_moe import UnquantizedFusedMoEMethod
 from vllm.model_executor.layers.quantization.compressed_tensors.compressed_tensors import (  # noqa: E501
     CompressedTensors24,
     CompressedTensorsLinearMethod,
@@ -767,3 +768,50 @@ def test_compressed_tensors_fp8_block_enabled(vllm_runner):
 
         output = llm.generate_greedy("Hello my name is", max_tokens=4)
         assert output
+
+
+@pytest.mark.skipif(
+    not current_platform.is_cuda(),
+    reason="This test is not for non-CUDA platforms",
+)
+def test_compressed_tensors_moe_ignore_with_model(vllm_runner):
+    """
+    Integration test for MoE layer ignore functionality with a real model.
+
+    This test would verify that when loading a compressed-tensors quantized
+    MoE model where some MoE layers are in the ignore list, those layers
+    use UnquantizedFusedMoEMethod while non-ignored layers use the
+    quantized method.
+
+    Expected model structure:
+    - Compressed-tensors quantized MoE model (e.g., Mixtral-based)
+    - Config with ignore list containing specific MoE layers
+    - Multiple MoE layers where some are quantized and some are not
+    """
+
+    # model_path = "nm-testing/tinysmokeqwen3moe-W4A16-first-only" # CT 12.3
+    model_path = "nm-testing/tinysmokeqwen3moe-W4A16-first-only-CTstable"  # CT 12.2
+
+    with vllm_runner(model_path, enforce_eager=True) as llm:
+
+        def check_model(model):
+            from vllm.model_executor.layers.fused_moe import FusedMoE
+            from vllm.model_executor.layers.quantization.compressed_tensors.compressed_tensors_moe import (  # noqa: E501
+                CompressedTensorsMoEMethod,
+            )
+
+            # Check layer 0 MoE (should be quantized)
+            layer_quantized = model.model.layers[0].mlp.experts
+            assert isinstance(layer_quantized, FusedMoE)
+            assert isinstance(layer_quantized.quant_method, CompressedTensorsMoEMethod)
+
+            # Check layer 10 MoE (should be unquantized + ignored)
+            layer_unquantized = model.model.layers[3].mlp.experts
+            assert isinstance(layer_unquantized, FusedMoE)
+            assert isinstance(layer_unquantized.quant_method, UnquantizedFusedMoEMethod)
+
+        llm.apply_model(check_model)
+
+        # Verify the model can generate output
+        output = llm.generate_greedy("Hello, my name is", max_tokens=4)
+        assert output

vllm/model_executor/layers/fused_moe/__init__.py

@@ -18,6 +18,9 @@ from vllm.model_executor.layers.fused_moe.modular_kernel import (
     FusedMoEPrepareAndFinalize,
 )
 from vllm.model_executor.layers.fused_moe.shared_fused_moe import SharedFusedMoE
+from vllm.model_executor.layers.fused_moe.unquantized_fused_moe_method import (
+    UnquantizedFusedMoEMethod,
+)
 from vllm.model_executor.layers.fused_moe.utils import activation_without_mul
 from vllm.triton_utils import HAS_TRITON
 
@@ -41,6 +44,7 @@ __all__ = [
     "FusedMoE",
     "FusedMoEConfig",
     "FusedMoEMethodBase",
+    "UnquantizedFusedMoEMethod",
     "FusedMoeWeightScaleSupported",
     "FusedMoEPermuteExpertsUnpermute",
     "FusedMoEActivationFormat",

vllm/model_executor/layers/quantization/compressed_tensors/compressed_tensors.py

@@ -158,9 +158,23 @@ class CompressedTensorsConfig(QuantizationConfig):
         if isinstance(layer, Attention):
             return CompressedTensorsKVCacheMethod(self)
         if isinstance(layer, FusedMoE):
-            return CompressedTensorsMoEMethod.get_moe_method(self, layer)
+            return CompressedTensorsMoEMethod.get_moe_method(self, layer, prefix)
         return None
 
+    def _add_fused_moe_to_target_scheme_map(self):
+        """
+        Helper function to update target_scheme_map
+        since linear layers get fused into FusedMoE
+        targetting 'Linear' needs to also match
+        FusedMoE modules.
+        """
+        if (
+            "Linear" not in self.target_scheme_map
+            or "FusedMoE" in self.target_scheme_map
+        ):
+            return
+        self.target_scheme_map["FusedMoE"] = self.target_scheme_map["Linear"]
+
     @classmethod
     def from_config(cls, config: dict[str, Any]) -> "CompressedTensorsConfig":
         ignore: list[str] = cast(list[str], config.get("ignore", []))
@@ -655,25 +669,13 @@ class CompressedTensorsConfig(QuantizationConfig):
         to select the CompressedTensorsScheme used for inference.
         """
 
-        # Find the "target" in the compressed-tensors config
-        # that our layer conforms to.
-        # TODO (@kylesayrs): support ignore module names with ct matching utils
-        if should_ignore_layer(
-            layer_name, ignore=self.ignore, fused_mapping=self.packed_modules_mapping
-        ):
-            return None
+        # Use the new get_quant_args method to extract QuantizationArgs
+        scheme_dict = self.get_scheme_dict(layer, layer_name)
 
-        # Will be empty for models with only sparsity
-        weight_quant = input_quant = None
-        if self.target_scheme_map:
-            matched_target = find_matched_target(
-                layer_name=layer_name,
-                module=layer,
-                targets=self.target_scheme_map.keys(),
-                fused_mapping=self.packed_modules_mapping,
-            )
-
-            scheme_dict = self.target_scheme_map[matched_target]
+        weight_quant = None
+        input_quant = None
+        format = None
+        if scheme_dict:
             weight_quant = scheme_dict.get("weights")
             input_quant = scheme_dict.get("input_activations")
             format = scheme_dict.get("format")
@@ -732,6 +734,38 @@ class CompressedTensorsConfig(QuantizationConfig):
         logger.debug("Using scheme: %s for %s", scheme.__class__.__name__, layer_name)
         return scheme
 
+    def get_scheme_dict(
+        self, layer: torch.nn.Module, layer_name: str | None = None
+    ) -> dict[str, QuantizationArgs | str | None] | None:
+        """
+        Extract the QuantizationArgs for a given layer.
+
+        Returns:
+            dict with {
+                "weights": QuantizationArgs,
+                "input_activations": QuantizationArgs | None,
+                "format": str | None
+            } | None
+        """
+        # TODO (@kylesayrs): support ignore module names with ct matching utils
+        if should_ignore_layer(
+            layer_name, ignore=self.ignore, fused_mapping=self.packed_modules_mapping
+        ):
+            return None
+
+        # Will be empty for models with only sparsity
+        if self.target_scheme_map:
+            matched_target = find_matched_target(
+                layer_name=layer_name,
+                module=layer,
+                targets=self.target_scheme_map.keys(),
+                fused_mapping=self.packed_modules_mapping,
+            )
+
+            return self.target_scheme_map[matched_target]
+
+        return None
+
     def get_cache_scale(self, name: str) -> str | None:
         """
         Check whether the param name matches the format for k/v cache scales

vllm/model_executor/layers/quantization/compressed_tensors/compressed_tensors_moe.py

@@ -23,6 +23,7 @@ from vllm.model_executor.layers.fused_moe import (
     FusedMoEMethodBase,
     FusedMoEPermuteExpertsUnpermute,
     FusedMoeWeightScaleSupported,
+    UnquantizedFusedMoEMethod,
 )
 from vllm.model_executor.layers.fused_moe.config import (
     FusedMoEQuantConfig,
@@ -45,9 +46,6 @@ from vllm.model_executor.layers.quantization.compressed_tensors.schemes.compress
     WNA16_SUPPORTED_BITS,
     WNA16_SUPPORTED_TYPES_MAP,
 )
-from vllm.model_executor.layers.quantization.compressed_tensors.utils import (
-    find_matched_target,
-)
 from vllm.model_executor.layers.quantization.utils import replace_parameter
 from vllm.model_executor.layers.quantization.utils.flashinfer_fp4_moe import (
     build_flashinfer_fp4_cutlass_moe_prepare_finalize,
@@ -113,40 +111,36 @@ class CompressedTensorsMoEMethod(FusedMoEMethodBase):
     def get_moe_method(
         quant_config: "CompressedTensorsConfig",  # type: ignore # noqa E501
         layer: torch.nn.Module,
+        prefix: str,
     ) -> "CompressedTensorsMoEMethod":
-        # TODO: @dsikka: refactor this to use schemes as other kernels
-        # are supported + check if the layer is being ignored.
-        # Check if a using "Linear" to select schemes
-        if "Linear" in quant_config.target_scheme_map:
-            matched_target = "Linear"
-        else:
-            # May have instead defined the linear layers in the fused model
-
-            fused_layers = ["re:.*down_proj.*", "re:.*gate_proj.*", "re:.*up_proj.*"]
-            current_scheme = None
-            for fused_layer in fused_layers:
-                # Check if one of the fused layers are defined in quant_config
-                matched_target = find_matched_target(
-                    layer_name=fused_layer,
-                    module=layer,
-                    targets=quant_config.target_scheme_map.keys(),
-                    fused_mapping=quant_config.packed_modules_mapping,
-                )
-
-                # Only valid if down_proj, gate_proj, and up_proj
-                # are mapped to the same quant scheme in the quant_config
-                if current_scheme is None:
-                    current_scheme = quant_config.target_scheme_map.get(matched_target)
-                else:
-                    assert current_scheme == quant_config.target_scheme_map.get(
-                        matched_target
-                    )
+        # FusedMoE was made by combining multiple Linears so need to
+        # make sure quantization config for Linear can target it
+        quant_config._add_fused_moe_to_target_scheme_map()
+        unfused_names = [
+            prefix + proj_name
+            for proj_name in [".0.gate_proj", ".0.up_proj", ".0.down_proj"]
+        ]
+        # TODO: refactor this to use expert_mapping and check all layer numbers
+        all_scheme_dicts = [
+            quant_config.get_scheme_dict(layer, name) for name in unfused_names
+        ]
+        scheme_dict = all_scheme_dicts.pop()
 
-        weight_quant = quant_config.target_scheme_map[matched_target].get("weights")
-        input_quant = quant_config.target_scheme_map[matched_target].get(
-            "input_activations"
+        # multiple schemes found
+        if not all([cur_dict == scheme_dict for cur_dict in all_scheme_dicts]):
+            raise ValueError(
+                "All MoE projections need to have same "
+                "quantization scheme but found multiple"
             )
 
+        if scheme_dict is None:  # ignored layer
+            return UnquantizedFusedMoEMethod(layer.moe_config)
+
+        # TODO: @dsikka: refactor this to use schemes as other kernels
+        # are supported + check if the layer is being ignored.
+        weight_quant = scheme_dict.get("weights")
+        input_quant = scheme_dict.get("input_activations")
+
         if quant_config._is_wNa16_group_channel(weight_quant, input_quant):
             # group_size=None means channelwise
             group_size = weight_quant.group_size or -1