Add PerLayerTransferManager: owns a worker thread-pool + the active per-request
contexts for the current forward batch, registered as a KV-pool notifier.
on_layer_end (forward thread) records ONE CUDA event on the compute stream and
enqueues (ctx, layer, event) per active context; workers do the event-wait +
async submit OFF the forward thread. finish(room) waits the request's transfers.
event_factory/current_stream injected for unit-testability (no CUDA needed).
Unit-tested (5 manager cases, 11 total in test_cp_per_layer_transfer.py):
per-active-ctx enqueue with the event recorded on the stream, worker-step submit +
mark-failed-on-exception, finish pop + idempotency, no-op when idle. The A3
scheduler wiring (notifier registration + setup-before-forward + finish-after +
no-double-send reconcile) is the remaining hot-path step; plan locked in
lever-a-implementation-plan.md.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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