From f6cc02489fb26af8eb6704170821359b6edb91c7 Mon Sep 17 00:00:00 2001
From: Ratish P <114130421+Ratish1@users.noreply.github.com>
Date: Tue, 17 Feb 2026 15:47:46 +0530
Subject: [PATCH] [diffusion]: fix sparse video gen 2 backend being applied to
 cross-attention (#18900)

Co-authored-by: ronnie_zheng <zl19940307@163.com>
---
 .../multimodal_gen/runtime/models/dits/wanvideo.py  | 13 +------------
 .../multimodal_gen/runtime/platforms/interface.py   |  1 +
 2 files changed, 2 insertions(+), 12 deletions(-)

diff --git a/python/sglang/multimodal_gen/runtime/models/dits/wanvideo.py b/python/sglang/multimodal_gen/runtime/models/dits/wanvideo.py
index e47f72547..87db7372c 100644
--- a/python/sglang/multimodal_gen/runtime/models/dits/wanvideo.py
+++ b/python/sglang/multimodal_gen/runtime/models/dits/wanvideo.py
@@ -313,18 +313,7 @@ class WanTransformerBlock(nn.Module):
         tp_size = get_tp_world_size()
         self.local_num_heads = divide(num_heads, tp_size)
         self_attn_backends = supported_attention_backends
-        cross_attn_backends = supported_attention_backends
-        if (
-            supported_attention_backends is not None
-            and AttentionBackendEnum.SPARSE_VIDEO_GEN_2_ATTN
-            in supported_attention_backends
-        ):
-            cross_attn_backends = supported_attention_backends.copy()
-            cross_attn_backends.remove(AttentionBackendEnum.SPARSE_VIDEO_GEN_2_ATTN)
-            logger.debug(
-                "Sparse Video Gen 2 attention backend is not supported for cross-attention; "
-                "removing SPARSE_VIDEO_GEN_2_ATTN from cross-attention backends."
-            )
+
         if attention_type in ("sla", "sagesla"):
             self.attn1 = MinimalA2AAttnOp(
                 num_heads=self.local_num_heads,
diff --git a/python/sglang/multimodal_gen/runtime/platforms/interface.py b/python/sglang/multimodal_gen/runtime/platforms/interface.py
index 1dcbb7962..1623dcfe2 100644
--- a/python/sglang/multimodal_gen/runtime/platforms/interface.py
+++ b/python/sglang/multimodal_gen/runtime/platforms/interface.py
@@ -46,6 +46,7 @@ class AttentionBackendEnum(enum.Enum):
         return self in {
             AttentionBackendEnum.SLIDING_TILE_ATTN,
             AttentionBackendEnum.VIDEO_SPARSE_ATTN,
+            AttentionBackendEnum.SPARSE_VIDEO_GEN_2_ATTN,
             AttentionBackendEnum.VMOBA_ATTN,
             AttentionBackendEnum.SLA_ATTN,
             AttentionBackendEnum.SAGE_SLA_ATTN,