[Bugfix] Fix DeepSeek MTP crash when using TP1ModelRunner with CUDA graph due to shape mismatch (#14237)

Signed-off-by: pyc96 <pychen96@gmail.com>

vllm/spec_decode/draft_model_runner.py

@@ -302,6 +302,11 @@ class TP1DraftModelRunner(ModelRunnerWrapperBase):
             outputs.append(output)
 
             if self.return_hidden_states and is_fallback:
+                if use_cuda_graph:
+                    indices = model_input.sampling_metadata\
+                      .selected_token_indices
+                    output.hidden_states = hidden_states[:len(indices)]
+                else:
                     output.hidden_states = hidden_states
 
             if model_input.attn_metadata.num_prefills == 0 \