comment

		uint64_t _handshake_pn_recv = 0;

		uint64_t _app_pn_send = 0;

		uint64_t _app_pn_recv = 0;

		uint32_t _app_unacked_count = 0;  // Delayed ACK counter

		// ACK cadence is batch-driven, not a per-packet counter/timer: one

		// ACK is sent after each recvmmsg batch is fully processed (see

		// _app_ack_pending below and pumpIncoming()'s comment on the

		// measured ~30x reduction in ACK-only sendto() calls this gives

		// vs. acking every packet). RFC 9000 §13.2.1's "at least every

		// second ack-eliciting packet" guidance is satisfied structurally

		// by that batch boundary rather than by counting.

		bool     _app_ack_pending = false; // Deferred ACK flag

		// Latest ECN counts reported by the peer via an ACK_ECN frame (RFC