From 4dabfbc827d4cd4a5e1d1dd5718afeb87ffbcb6c Mon Sep 17 00:00:00 2001
From: Zaili Wang <109502517+ZailiWang@users.noreply.github.com>
Date: Fri, 12 Dec 2025 15:12:26 +0800
Subject: [PATCH] [Fix] suppress remote weight loading engine w/o mooncake
 installed (#14937)

---
 python/sglang/srt/server_args.py | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/python/sglang/srt/server_args.py b/python/sglang/srt/server_args.py
index 1782982f0..bc17db6f8 100644
--- a/python/sglang/srt/server_args.py
+++ b/python/sglang/srt/server_args.py
@@ -2226,18 +2226,25 @@ class ServerArgs:
             self.skip_server_warmup = True
 
     def _handle_remote_instance_weight_loader_support_transfer_engine(self):
-        if importlib.util.find_spec("mooncake.engine") is None:
+        try:
+            importlib.import_module("mooncake")
+            if importlib.util.find_spec("mooncake.engine") is None:
+                logger.warning(
+                    f"Failed to import mooncake.engine. Does not support using TransferEngine as remote instance weight loader backend."
+                )
+                self.remote_instance_weight_loader_support_transfer_engine = False
+            elif self.enable_memory_saver:
+                logger.warning(
+                    "Memory saver is enabled, which is not compatible with TransferEngine. Does not support using TransferEngine as remote instance weight loader backend."
+                )
+                self.remote_instance_weight_loader_support_transfer_engine = False
+            else:
+                self.remote_instance_weight_loader_support_transfer_engine = True
+        except ImportError:
             logger.warning(
-                f"Failed to import mooncake.engine. Does not support using TransferEngine as remote instance weight loader backend."
+                f"Failed to import mooncake. Does not support using TransferEngine as remote instance weight loader backend."
             )
             self.remote_instance_weight_loader_support_transfer_engine = False
-        elif self.enable_memory_saver:
-            logger.warning(
-                "Memory saver is enabled, which is not compatible with TransferEngine. Does not support using TransferEngine as remote instance weight loader backend."
-            )
-            self.remote_instance_weight_loader_support_transfer_engine = False
-        else:
-            self.remote_instance_weight_loader_support_transfer_engine = True
 
     @staticmethod
     def add_cli_args(parser: argparse.ArgumentParser):