Reject unsupported architectures in the front end

verify_model_arch only ran from _try_load_model_cls, which the API server
does not reach: front-end resolution goes through inspect_model_cls. On
SM120 the guard therefore fired inside the worker, off the usage-stats
path in init_device(), so both TP workers spawned and dumped a traceback
before EngineCore shut them down.

Call verify_model_arch from ModelConfig once the architecture is resolved,
so an unsupported device is rejected before any worker starts. The check
in _try_load_model_cls stays as a backstop for paths that build a model
without going through ModelConfig.

Reported-by: Rawsejet <#51560>
Signed-off-by: maxim955827848 <maxim955827848@gmail.com>

Author: m4xkushnir

tests/test_config.py

@@ -611,6 +611,26 @@ def test_draft_runner(model_id, expected_runner_type, expected_convert_type):
     assert config.convert_type == expected_convert_type
 
 
+def test_platform_rejects_unsupported_arch_during_config(monkeypatch):
+    """Architectures the platform cannot run are rejected in the front end.
+
+    `_try_load_model_cls` checks this as well, but only once a worker is
+    already up and loading the model.
+    """
+    rejected = []
+
+    def verify_model_arch(model_arch: str) -> None:
+        rejected.append(model_arch)
+        raise ValueError(f"Model architecture '{model_arch}' is not supported")
+
+    monkeypatch.setattr(current_platform, "verify_model_arch", verify_model_arch)
+
+    with pytest.raises(ValueError, match="Qwen3ForCausalLM"):
+        ModelConfig("Qwen/Qwen3-0.6B", max_model_len=2048)
+
+    assert rejected == ["Qwen3ForCausalLM"]
+
+
 MODEL_IDS_EXPECTED = [
     ("Qwen/Qwen1.5-7B", 32768),
     ("mistralai/Mistral-7B-v0.1", 4096),

vllm/config/model.py

@@ -671,6 +671,11 @@ def __post_init__(
         self._architecture = arch
         logger.info("Resolved architecture: %s", arch)
 
+        # Reject architectures this platform cannot run before any worker is
+        # spawned. `_try_load_model_cls` checks this too, but that only runs
+        # once the model is being loaded inside a worker.
+        current_platform.verify_model_arch(arch)
+
         # Set default tokenizer modes based on model architecture
         if self.tokenizer_mode == "auto":
             if self.model_impl == "terratorch":