From 983e643854f15cf9ef4370a49dfd74b6af54c3e3 Mon Sep 17 00:00:00 2001
From: ollybbmonster <42735247+ollybbmonster@users.noreply.github.com>
Date: Mon, 21 Sep 2026 07:13:59 +0800
Subject: [PATCH] [Feature] support bf16 MoE router and mxfp4 MoE for MiMo V2
 (#40448)

---
 .../attention/flashattention_backend.py       |  7 +++++-
 python/sglang/srt/models/dflash.py            |  3 ++-
 python/sglang/srt/models/mimo_v2.py           | 22 +++++++++++++++----
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/python/sglang/srt/layers/attention/flashattention_backend.py b/python/sglang/srt/layers/attention/flashattention_backend.py
index 67ba07afd..eb4204e38 100644
--- a/python/sglang/srt/layers/attention/flashattention_backend.py
+++ b/python/sglang/srt/layers/attention/flashattention_backend.py
@@ -1927,7 +1927,12 @@ class FlashAttentionBackend(AttentionBackend):
         is_swa_layer = (
             layer.sliding_window_size is not None and layer.sliding_window_size > -1
         )
-        window_size = (layer.sliding_window_size, 0) if is_swa_layer else (-1, -1)
+        if is_swa_layer and layer.attn_type == AttentionType.ENCODER_ONLY:
+            window_size = (layer.sliding_window_size, layer.sliding_window_size)
+        elif is_swa_layer:
+            window_size = (layer.sliding_window_size, 0)
+        else:
+            window_size = (-1, -1)
 
         causal = True
         if layer.is_cross_attention or layer.attn_type == AttentionType.ENCODER_ONLY:
diff --git a/python/sglang/srt/models/dflash.py b/python/sglang/srt/models/dflash.py
index 7dc69d513..5722b43d4 100644
--- a/python/sglang/srt/models/dflash.py
+++ b/python/sglang/srt/models/dflash.py
@@ -250,7 +250,8 @@ class DFlashAttention(nn.Module):
             # Per-head sink bias; each TP rank owns its slice of the
             # all-heads checkpoint tensor.
             self.attention_sink_bias = nn.Parameter(
-                torch.empty(self.num_heads, dtype=torch.float32), requires_grad=False
+                torch.empty(self.num_heads, dtype=torch.float32 if _is_npu else None),
+                requires_grad=False,
             )
             set_weight_attrs(
                 self.attention_sink_bias,
diff --git a/python/sglang/srt/models/mimo_v2.py b/python/sglang/srt/models/mimo_v2.py
index c09e54b02..1354710e7 100644
--- a/python/sglang/srt/models/mimo_v2.py
+++ b/python/sglang/srt/models/mimo_v2.py
@@ -349,7 +349,7 @@ class MoEGate(nn.Module):
     ):
         super().__init__()
         self.is_nextn = is_nextn
-        self.dtype = torch.float32
+        self.dtype = getattr(torch, getattr(config, "moe_router_dtype", "float32"))
         self.weight = nn.Parameter(
             torch.empty((config.n_routed_experts, config.hidden_size), dtype=self.dtype)
         )
@@ -359,7 +359,7 @@ class MoEGate(nn.Module):
                 if quant_config is not None
                 and quant_config.get_name() == "modelopt_fp4"
                 and get_moe_runner_backend().is_flashinfer_trtllm()
-                else self.dtype
+                else torch.float32
             )
             self.e_score_correction_bias = nn.Parameter(
                 torch.empty((config.n_routed_experts), dtype=correction_bias_dtype)
@@ -368,9 +368,15 @@ class MoEGate(nn.Module):
             self.e_score_correction_bias = None
 
     def forward(self, hidden_states):
-        logits = F.linear(hidden_states.to(self.dtype), self.weight, None)
+        if self.dtype != torch.float32 and hidden_states.is_cuda:
+            return torch.mm(
+                hidden_states.to(self.dtype),
+                self.weight.t(),
+                out_dtype=torch.float32,
+            )
 
-        return logits
+        logits = F.linear(hidden_states.to(self.dtype), self.weight, None)
+        return logits.to(torch.float32)
 
 
 class MiMoV2MoE(nn.Module):
@@ -427,6 +433,7 @@ class MiMoV2MoE(nn.Module):
             num_expert_group=config.n_group,
             topk_group=config.topk_group,
             correction_bias=self.gate.e_score_correction_bias,
+            is_fp4_experts=getattr(quant_config, "is_fp4_experts", False),
             scoring_func=config.scoring_func,
             quant_config=quant_config,
             routed_scaling_factor=1.0,
@@ -1591,6 +1598,13 @@ class MiMoV2ForCausalLM(nn.Module, AudioEncoderMixin):
                     skipped_mtp_weights = True
                 continue
 
+            if ".mlp.experts." in name and loaded_weight.dtype == torch.uint8:
+                if name.endswith(".weight_scale"):
+                    name = name + "_inv"
+                    loaded_weight = torch.exp2(loaded_weight.to(torch.float32) - 127.0)
+                elif name.endswith(".weight"):
+                    loaded_weight = loaded_weight.view(torch.int8)
+
             # Support fused qkv_proj checkpoint (Pro format)
             if "qkv_proj" in name:
                 if name in params_dict: