Support V4.1 DP attention in DP-only DSpark PD

(cherry picked from commit 6ef0ebba730b3fffde4b59b953c5c9b58a35c4ed)

python/sglang/srt/arg_groups/deepseek_v4_hook.py

@@ -249,15 +249,13 @@ def validate_deepseek_v41_features(server_args: ServerArgs) -> None:
         if (
             read_ragged_verify_mode() is not RaggedVerifyMode.STATIC
             or cfg.disaggregation_transfer_backend != "mooncake"
-            or cfg.dp_size != 1
-            or cfg.enable_dp_attention
             or cfg.attn_cp_size != 1
             or cfg.dcp_size != 1
         ):
             raise ValueError(
                 "DeepSeek-V4.1 DSpark PD requires static verify, Mooncake, "
-                "DP=1 and CP=1. Both servers must enable DSpark with the same "
+                "and CP=1 on both servers. DP attention is supported when "
-                "block size and TP size."
+                "both servers use the same block size and target/draft KV layout."
             )
 
     from sglang.srt.model_executor.cuda_graph_config import Backend, Phase, with_phase

python/sglang/srt/disaggregation/common/conn.py

@@ -940,10 +940,27 @@ class CommonKVManager(BaseKVManager):
                 and self.attn_cp_size == 1
                 and info.attn_tp_size * info.attn_cp_size == self.attn_tp_size
             )
-            if info.attn_tp_size != self.attn_tp_size and not same_tp_with_prefill_cp:
+            # Combined branch (40323-series + 40177): prefill CP can also pair
+            # with a DP-attention decode server. MLA KV is replicated across
+            # prefill CP ranks, so per-rank layouts match when attn_tp matches.
+            dp_decode_with_prefill_cp = (
+                info.attn_cp_size > 1
+                and self.attn_cp_size == 1
+                and (self.is_mla_backend or self.is_hybrid_mla_backend)
+                and info.attn_tp_size == self.attn_tp_size
+            )
+            non_cp_mla_layout = info.attn_cp_size == self.attn_cp_size == 1 and (
+                self.is_mla_backend or self.is_hybrid_mla_backend
+            )
+            if info.attn_tp_size != self.attn_tp_size and not (
+                same_tp_with_prefill_cp
+                or dp_decode_with_prefill_cp
+                or non_cp_mla_layout
+            ):
                 raise RuntimeError(
-                    "DeepSeek-V4.1 DSpark PD requires the same TP size on both "
+                    "DeepSeek-V4.1 DSpark PD requires matching attention TP "
-                    "servers (including prefill CP ranks for MLA)"
+                    "unless both servers use CP=1 with an MLA KV layout, "
+                    "or prefill runs CP with an MLA KV layout"
                 )
 
         if self.dcp_size > 1: