the draft-routing patch enabling DSpark on NVFP4 checkpoints

dspark-nvfp4-draft-routing.patch

@@ -0,0 +1,43 @@
+diff --git a/vllm/models/deepseek_v4/quant_config.py b/vllm/models/deepseek_v4/quant_config.py
+index 89cf695..5918fa0 100644
+--- a/vllm/models/deepseek_v4/quant_config.py
++++ b/vllm/models/deepseek_v4/quant_config.py
+@@ -4,6 +4,7 @@
+ 
+ from __future__ import annotations
+ 
++import re
+ from typing import TYPE_CHECKING, cast
+ 
+ from vllm.config import get_current_vllm_config
+@@ -175,7 +176,7 @@ class DeepseekV4FP8Config(Fp8Config):
+             ):
+                 return UnquantizedFusedMoEMethod(layer.moe_config)
+             if self.expert_dtype == "fp4":
+-                if self.moe_quant_algo == "NVFP4":
++                if self.moe_quant_algo == "NVFP4" and not self._is_draft_layer(prefix):
+                     from vllm.model_executor.layers.quantization.modelopt import (
+                         ModelOptNvFp4FusedMoE,
+                     )
+@@ -189,7 +190,20 @@ class DeepseekV4FP8Config(Fp8Config):
+             # returns Fp8MoEMethod with block-wise float32 scales.
+         return super().get_quant_method(layer, prefix)
+ 
++    def _is_draft_layer(self, prefix: str) -> bool:
++        # NVFP4 conversions quantize only the main stack; the speculative
++        # module (runtime layer index >= num_hidden_layers) keeps its
++        # original MXFP4 experts and must load through the MXFP4 path.
++        m = re.search(r"layers\.(\d+)\.", prefix)
++        if m is None:
++            return False
++        try:
++            hf_config = get_current_vllm_config().model_config.hf_config
++        except Exception:
++            return False
++        return int(m.group(1)) >= hf_config.num_hidden_layers
++
+     def is_mxfp4_quant(self, prefix, layer):
+         if not isinstance(layer, RoutedExperts) or self.expert_dtype != "fp4":
+             return False
+-        return self.moe_quant_algo != "NVFP4"
++        return self.moe_quant_algo != "NVFP4" or self._is_draft_layer(prefix)