[Spec] Support MegaMoE for DSpark under dp attention (#34844)

Co-authored-by: weireweire <20922698+weireweire@users.noreply.github.com>

test/registered/spec/dspark/test_dspark_draft_path_default.py

@@ -5,6 +5,7 @@ from sglang.srt.arg_groups.speculative_hook import (
     _handle_dspark,
     _target_checkpoint_bundles_dspark_draft,
 )
+from sglang.srt.environ import envs
 from sglang.srt.server_args import ServerArgs
 from sglang.test.ci.ci_register import register_cpu_ci
 from sglang.test.test_utils import CustomTestCase
@@ -84,5 +85,34 @@ class TestDsparkDraftPathDefaulting(CustomTestCase):
         )
 
 
+class TestDsparkDpAttentionMoeA2aGate(CustomTestCase):
+    """Gate contract for DSpark + dp attention + MoE a2a backends."""
+
+    def _dp_server_args(self, *, moe_a2a_backend: str) -> ServerArgs:
+        server_args = _make_dspark_server_args(
+            model_path=_BUNDLED_MODEL_PATH, hf_config=_bundled_hf_config()
+        )
+        server_args.enable_dp_attention = True
+        server_args.enable_dp_lm_head = True
+        server_args.dp_size = 2
+        server_args.tp_size = 2
+        server_args.moe_a2a_backend = moe_a2a_backend
+        return server_args
+
+    def test_only_megamoe_is_admitted(self):
+        """Both sides of the allowlist: megamoe passes, others raise by name."""
+        with envs.SGLANG_RAGGED_VERIFY_MODE.override("static"):
+            _handle_dspark(self._dp_server_args(moe_a2a_backend="megamoe"))
+            for backend in ("deepep", "pplx"):
+                with self.assertRaisesRegex(ValueError, backend):
+                    _handle_dspark(self._dp_server_args(moe_a2a_backend=backend))
+
+    def test_a2a_backend_with_compact_verify_mode_raises(self):
+        server_args = self._dp_server_args(moe_a2a_backend="megamoe")
+        with envs.SGLANG_RAGGED_VERIFY_MODE.override("compact"):
+            with self.assertRaisesRegex(ValueError, "static"):
+                _handle_dspark(server_args)
+
+
 if __name__ == "__main__":
     unittest.main()