Records cuEventRecord between each of the 5 child graph launches. At epoch end, cuEventElapsedTime reports per-child GPU time: spectral, forward, ddqn, aux, adam. This tells us exactly which child dominates the 4s/step graph replay cost, informing Phase 2 multi-stream parallelism priorities. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>