[Model Runner v2] Support update_config (#42783)

Signed-off-by: mgoin <mgoin64@gmail.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

vllm/v1/worker/gpu/model_runner.py

@@ -337,6 +337,17 @@ class GPUModelRunner(LoRAModelRunnerMixin):
         self.reset_encoder_cache()
         self.reset_mm_cache()
 
+    def update_config(self, *args, **kwargs) -> None:
+        # TODO(Wentao): Use full version instead of import when fully migrated to v2
+        from vllm.v1.worker.gpu_model_runner import GPUModelRunner as GPUModelRunnerV1
+
+        GPUModelRunnerV1.update_config(self, *args, **kwargs)  # type: ignore[arg-type]
+
+        # v2 reads config via self.vllm_config (e.g. in load_model), so keep it
+        # in sync with the attributes the v1 helper just replaced.
+        self.vllm_config.model_config = self.model_config
+        self.vllm_config.load_config = self.load_config
+
     @functools.cached_property
     def main_stream(self) -> torch.cuda.Stream:
         # Cache the default CUDA stream to avoid lookup overhead.