[diffusion] chore: fix ZMQ binding and model loading for FastWan compatibility (#13978)

Co-authored-by: Han Yu <hyu5@dt-login01.delta.ncsa.illinois.edu>
Co-authored-by: Mick <mickjagger19@icloud.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

python/sglang/multimodal_gen/runtime/entrypoints/cli/serve.py

@@ -31,7 +31,6 @@ def add_multimodal_gen_serve_args(parser: argparse.ArgumentParser):
 def execute_serve_cmd(args: argparse.Namespace, unknown_args: list[str] | None = None):
     """The entry point for the serve command."""
     server_args = ServerArgs.from_cli_args(args, unknown_args)
-    server_args.post_init_serve()
     launch_server(server_args)
 
     if server_args.webui:

python/sglang/multimodal_gen/runtime/entrypoints/diffusion_generator.py

@@ -145,12 +145,12 @@ class DiffGenerator:
         if not sync_scheduler_client.ping():
             raise ConnectionError(
                 f"Could not connect to remote scheduler at "
-                f"{self.server_args.scheduler_endpoint()} with `local mode` as False. "
+                f"{self.server_args.scheduler_endpoint} with `local mode` as False. "
                 "Please ensure the server is running."
             )
         logger.info(
             f"Successfully connected to remote scheduler at "
-            f"{self.server_args.scheduler_endpoint()}."
+            f"{self.server_args.scheduler_endpoint}."
         )
 
     def generate(

python/sglang/multimodal_gen/runtime/loader/component_loader.py

@@ -728,6 +728,7 @@ class TransformerLoader(ComponentLoader):
             param_dtype=torch.bfloat16,
             reduce_dtype=torch.float32,
             output_dtype=None,
+            strict=False,
         )
 
         total_params = sum(p.numel() for p in model.parameters())

python/sglang/multimodal_gen/runtime/loader/fsdp_load.py

@@ -79,6 +79,7 @@ def maybe_load_fsdp_model(
     fsdp_inference: bool = False,
     output_dtype: torch.dtype | None = None,
     pin_cpu_memory: bool = True,
+    strict: bool = True,
 ) -> torch.nn.Module:
     """
     Load the model with FSDP if is training, else load the model without FSDP.
@@ -138,7 +139,7 @@ def maybe_load_fsdp_model(
         weight_iterator,
         device,
         default_dtype,
-        strict=True,
+        strict=strict,
         cpu_offload=cpu_offload,
         param_names_mapping=param_names_mapping_fn,
     )
@@ -255,9 +256,15 @@ def load_model_from_full_model_state_dict(
     for target_param_name, full_tensor in custom_param_sd.items():
         meta_sharded_param = meta_sd.get(target_param_name)
         if meta_sharded_param is None:
-            raise ValueError(
+            if strict:
-                f"Parameter {target_param_name} not found in custom model state dict. The hf to custom mapping may be incorrect."
+                raise ValueError(
-            )
+                    f"Parameter {target_param_name} not found in custom model state dict. The hf to custom mapping may be incorrect."
+                )
+            else:
+                logger.warning(
+                    f"Parameter '{target_param_name}' from checkpoint not found in model; skipping. This is expected for optional parameters."
+                )
+                continue
         if not hasattr(meta_sharded_param, "device_mesh"):
             full_tensor = full_tensor.to(device=device, dtype=param_dtype)
             actual_param = param_dict.get(target_param_name)

python/sglang/multimodal_gen/runtime/managers/scheduler.py

@@ -49,7 +49,7 @@ class Scheduler:
 
         # Inter-process Communication
         self.context = zmq.Context(io_threads=2)
-        endpoint = server_args.scheduler_endpoint()
+        endpoint = server_args.scheduler_endpoint
         if gpu_id == 0:
             # router allocates identify (envelope) for each connection
             self.receiver, actual_endpoint = get_zmq_socket(

python/sglang/multimodal_gen/runtime/scheduler_client.py

@@ -70,7 +70,7 @@ class SchedulerClient:
         # 100 minute timeout for generation
         self.scheduler_socket.setsockopt(zmq.RCVTIMEO, 6000000)
 
-        scheduler_endpoint = self.server_args.scheduler_endpoint()
+        scheduler_endpoint = self.server_args.scheduler_endpoint
         self.scheduler_socket.connect(scheduler_endpoint)
         logger.debug(
             f"SchedulerClient connected to backend scheduler at {scheduler_endpoint}"
@@ -98,7 +98,7 @@ class SchedulerClient:
         ping_socket.setsockopt(zmq.LINGER, 0)
         ping_socket.setsockopt(zmq.RCVTIMEO, 2000)  # 2-second timeout for pings
 
-        endpoint = self.server_args.scheduler_endpoint()
+        endpoint = self.server_args.scheduler_endpoint
 
         try:
             ping_socket.connect(endpoint)
@@ -157,7 +157,7 @@ class AsyncSchedulerClient:
         # 100 minute timeout
         socket.setsockopt(zmq.RCVTIMEO, 6000000)
 
-        endpoint = self.server_args.scheduler_endpoint()
+        endpoint = self.server_args.scheduler_endpoint
         socket.connect(endpoint)
 
         try:
@@ -182,7 +182,7 @@ class AsyncSchedulerClient:
         ping_socket.setsockopt(zmq.LINGER, 0)
         ping_socket.setsockopt(zmq.RCVTIMEO, 2000)
 
-        endpoint = self.server_args.scheduler_endpoint()
+        endpoint = self.server_args.scheduler_endpoint
 
         try:
             ping_socket.connect(endpoint)

python/sglang/multimodal_gen/runtime/server_args.py

@@ -220,9 +220,9 @@ class ServerArgs:
     # TODO: do not hard code
     master_port: int | None = None
 
-    # http server endpoint config, would be ignored in local mode
+    # http server endpoint config
-    host: str | None = None
+    host: str | None = "127.0.0.1"
-    port: int | None = None
+    port: int | None = 30000
 
     # TODO: webui and their endpoint, check if webui_port is available.
     webui: bool = False
@@ -290,6 +290,8 @@ class ServerArgs:
         if self.attention_backend in ["fa3", "fa4"]:
             self.attention_backend = "fa"
 
+        # network initialization: port and host
+        self.port = self.settle_port(self.port)
         # Add randomization to avoid race condition when multiple servers start simultaneously
         initial_scheduler_port = self.scheduler_port + random.randint(0, 100)
         self.scheduler_port = self.settle_port(initial_scheduler_port)
@@ -306,6 +308,7 @@ class ServerArgs:
                     "Failed to load V-MoBA config from %s: %s", self.moba_config_path, e
                 )
                 raise
+
         self.check_server_args()
 
         # log clean server_args
@@ -575,12 +578,15 @@ class ServerArgs:
         else:
             return f"http://{self.host}:{self.port}"
 
+    @property
     def scheduler_endpoint(self):
         """
-        Internal endpoint for scheduler
+        Internal endpoint for scheduler.
-
+        Prefers the configured host but normalizes localhost -> 127.0.0.1 to avoid ZMQ issues.
         """
-        scheduler_host = self.host or "localhost"
+        scheduler_host = self.host
+        if scheduler_host is None or scheduler_host == "localhost":
+            scheduler_host = "127.0.0.1"
         return f"tcp://{scheduler_host}:{self.scheduler_port}"
 
     def settle_port(
@@ -623,16 +629,6 @@ class ServerArgs:
             f"(started from port {original_port})"
         )
 
-    def post_init_serve(self):
-        """
-        Post init when in serve mode
-        """
-        if self.host is None:
-            self.host = "localhost"
-        if self.port is None:
-            self.port = 3000
-        self.port = self.settle_port(self.port)
-
     @classmethod
     def from_cli_args(
         cls, args: argparse.Namespace, unknown_args: list[str] | None = None