fix tp capture in vit cuda graph (#17255)

python/sglang/srt/multimodal/vit_cuda_graph_runner.py

@@ -17,11 +17,13 @@
 from __future__ import annotations
 
 import inspect
+from contextlib import nullcontext
 from typing import Dict, Hashable, List, Optional, Tuple
 
 import torch
 import torch.nn as nn
 
+from sglang.srt.distributed.parallel_state import get_tp_group
 from sglang.srt.layers.attention.vision import VisionAttention
 from sglang.srt.server_args import get_global_server_args
 
@@ -139,7 +141,11 @@ class ViTCudaGraphRunner:
 
         override_backend = get_global_server_args().mm_attention_backend
 
-        with torch.cuda.graph(graph):
+        tp_group = get_tp_group()
+        ca_comm = tp_group.ca_comm
+        capture_ctx = ca_comm.capture() if ca_comm is not None else nullcontext()
+
+        with capture_ctx, torch.cuda.graph(graph):
             y = None
             deepstack_outs: List[torch.Tensor] = []
             deepstack_capture_idx = 0