NVRTC-compiled ISV kernels conflict with cuBLAS GEMM internal stream
scheduling when captured in the same CUDA Graph as cuBLAS ops.
Moving ISV+plan to pre-replay phase: they run BEFORE graph_mega
replay on every training step. Their outputs (gamma_mod_buf,
branch_gate_buf, gated_h_s2_buf, predicted_error_buf, plan_params_buf)
are stable device buffers consumed by the captured graph.
Same result, no deadlock. ISV updates every step (not every 50).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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