[diffusion] feat: add --strict-ports option for predictable port assignment (#21320)

Co-authored-by: 阳虎 <yanghu@yanghudeMacBook-Pro.local>

python/sglang/multimodal_gen/registry.py

@@ -349,7 +349,10 @@ def _get_config_info(
         model_id = matched_model_names[0]
         return _CONFIG_REGISTRY.get(model_id)
     else:
-        raise RuntimeError(f"No model info found for model path: {model_path}")
+        raise RuntimeError(
+            f"No model info found for model path: {model_path}. "
+            f"Please check the model path or specify the model_id explicitly."
+        )
 
 
 # --- Part 3: Main Resolver ---

python/sglang/multimodal_gen/runtime/server_args.py

@@ -202,6 +202,9 @@ class ServerArgs:
 
     scheduler_port: int = 5555
 
+    # Strict port mode: fail if requested port is unavailable instead of auto-selecting
+    strict_ports: bool = False
+
     output_path: str | None = "outputs/"
     input_save_path: str | None = "inputs/uploads"
 
@@ -384,6 +387,24 @@ class ServerArgs:
             )
 
     def _adjust_network_ports(self):
+        if self.strict_ports:
+            # Strict mode: fail if port is unavailable
+            if not is_port_available(self.port):
+                raise RuntimeError(
+                    f"Port {self.port} is unavailable and --strict-ports is enabled. "
+                    f"Either use a different port or remove --strict-ports to allow auto-selection."
+                )
+            if not is_port_available(self.scheduler_port):
+                raise RuntimeError(
+                    f"Scheduler port {self.scheduler_port} is unavailable and --strict-ports is enabled. "
+                    f"Either use a different port or remove --strict-ports to allow auto-selection."
+                )
+            if self.master_port is not None and not is_port_available(self.master_port):
+                raise RuntimeError(
+                    f"Master port {self.master_port} is unavailable and --strict-ports is enabled. "
+                    f"Either use a different port or remove --strict-ports to allow auto-selection."
+                )
+        else:
             self.port = self.settle_port(self.port)
             initial_scheduler_port = self.scheduler_port + (
                 random.randint(0, 100) if self.scheduler_port == 5555 else 0
@@ -778,6 +799,12 @@ class ServerArgs:
             default=ServerArgs.port,
             help="Port for the HTTP API server.",
         )
+        parser.add_argument(
+            "--strict-ports",
+            action=StoreBoolean,
+            default=ServerArgs.strict_ports,
+            help="If enabled, fail when requested ports are unavailable instead of auto-selecting.",
+        )
         parser.add_argument(
             "--webui",
             action=StoreBoolean,