[Tests] Skip model weight download for render-only test server (#36813)

Signed-off-by: Sage Ahrac <sagiahrak@gmail.com>

tests/utils.py

@@ -144,6 +144,17 @@ class RemoteVLLMServer:
         """Subclasses override this method to customize server process launch"""
         raise NotImplementedError
 
+    def _pre_download_model(self, model: str, args) -> None:
+        """Download model weights before starting the server to avoid timeout."""
+        is_local = os.path.isdir(model)
+        if not is_local:
+            engine_args = AsyncEngineArgs.from_cli_args(args)
+            model_config = engine_args.create_model_config()
+            load_config = engine_args.create_load_config()
+
+            model_loader = get_model_loader(load_config)
+            model_loader.download_model(model_config)
+
     def __init__(
         self,
         model: str,
@@ -195,15 +206,7 @@ class RemoteVLLMServer:
             getattr(args, "show_hidden_metrics_for_version", None) is not None
         )
 
-        # download the model before starting the server to avoid timeout
-        is_local = os.path.isdir(model)
-        if not is_local:
-            engine_args = AsyncEngineArgs.from_cli_args(args)
-            model_config = engine_args.create_model_config()
-            load_config = engine_args.create_load_config()
-
-            model_loader = get_model_loader(load_config)
-            model_loader.download_model(model_config)
+        self._pre_download_model(model, args)
 
         # Record GPU memory before server start so we know what
         # "released" looks like.
@@ -515,6 +518,19 @@ class RemoteLaunchRenderServer(RemoteVLLMServer):
             start_new_session=True,
         )
 
+    def _pre_download_model(self, model: str, args) -> None:
+        """Download only the tokenizer files (no model weights needed)."""
+        is_local = os.path.isdir(model)
+        if not is_local:
+            engine_args = AsyncEngineArgs.from_cli_args(args)
+            model_config = engine_args.create_model_config()
+            get_tokenizer(
+                model_config.tokenizer,
+                tokenizer_mode=model_config.tokenizer_mode,
+                trust_remote_code=model_config.trust_remote_code,
+                revision=model_config.tokenizer_revision,
+            )
+
     def _wait_for_gpu_memory_release(self, timeout: float = 30.0):
         pass  # No GPU used