[AMD] Enable BCG on ROCm + route aiter prefill via MHA during PCG/BCG capture for Kimi-2.5 (#27833)

Co-authored-by: sogalin_codegen <39478626+sogalin@users.noreply.github.com>

python/sglang/srt/models/deepseek_common/attention_backend_handler.py

@@ -1,6 +1,9 @@
 from sglang.srt.layers.attention.tbo_backend import TboAttnBackend
 from sglang.srt.layers.utils.cp_utils import mla_use_prefill_cp
 from sglang.srt.model_executor.forward_context import get_attn_backend
+from sglang.srt.model_executor.runner_backend_utils.breakable_cuda_graph import (
+    is_in_breakable_cuda_graph,
+)
 from sglang.srt.model_executor.runner_backend_utils.tc_piecewise_cuda_graph import (
     is_in_tc_piecewise_cuda_graph,
 )
@@ -150,6 +153,11 @@ def handle_attention_tokenspeed_mla(attn, forward_batch):
 
 
 def handle_attention_aiter(attn, forward_batch):
+    # During PCG/BCG capture on ROCm, aiter fp8 MLA prefill has no capture
+    # kernels; route through the MHA path (radix_attention swaps attn_mqa for
+    # its attn_mha companion) so capture/replay use valid head/dim metadata.
+    if is_in_tc_piecewise_cuda_graph() or is_in_breakable_cuda_graph():
+        return AttnForwardMethod.MHA
     if forward_batch.forward_mode.is_extend_without_speculative():
         return AttnForwardMethod.MHA
     else: