Zcash's NU7 upgrade goes live, tripling block speed to 25 seconds and starting a fee reserve, while about 12,200 ZEC in the old Sprout pool becomes unspendable

Zcash's NU7 network upgrade has gone live on mainnet, The Block reported on Friday, at block height 3,543,405 on November 5. CoinDesk's market report said the upgrade activated early Friday. It cuts the target time between blocks from 75 seconds to 25.

Block subsidies scale down by the same factor, so new ZEC issuance stays roughly unchanged, and the number of blocks between halvings triples, which keeps the halving schedule and the 21 million coin cap intact, The Block said.

The upgrade also starts the Network Sustainability Mechanism, which removes 60% of each block's transaction fees from circulation and places them in a public reserve, while miners keep the other 40%. The reserved fees are scheduled to return through block rewards from block 8,939,664, expected in 2031. Shielded Labs, an independent group supporting Zcash development, said: "Like Bitcoin, Zcash faces a long-term challenge: how to sustain network security as block rewards decline."

The cost is on the legacy side. Version 4 transactions are now disallowed, and funds in the Sprout pool rely only on that format, so about 12,224 ZEC there became unspendable at activation, The Block said. Node operators had to upgrade before the activation height to stay on the consensus chain; most wallets need no significant changes.