Zcash’s NU7 network upgrade is now live on the project’s public testnet, opening a production trial for 25-second blocks about a month before the change is scheduled to reach mainnet.
According to a live NU7 dashboard run by the team behind Zakura, one of the two node programs that implement Zcash, the upgrade activated at block 4,465,026 on Oct. 4. The Zcash Foundation, which maintains the other implementation, Zebra, had said in release notes for the first NU7 release candidate that activation was expected around Oct. 6. Because activation is tied to block height rather than a calendar date, the exact timing depends on chain progress.
As of early Monday UTC, the dashboard showed a 19.5-second median gap across the latest 300 blocks. It listed 17.3 seconds as the expected median when blocks average 25 seconds.
Block times move from 75 seconds to 25 seconds
NU7 reduces Zcash’s target time between blocks to 25 seconds from 75 seconds. Under the current setup, a Zcash user waits 75 seconds on average for a first confirmation. The Zcash Foundation said that creates a real obstacle at points of sale, for exchange deposits, and for cross-chain bridges.
More frequent block production does not increase new issuance. The foundation said each block’s scheduled reward will be divided by three, and the remaining halving intervals will be extended to keep the daily amount of newly issued ZEC unchanged.
Fee routing and shielded transaction limits change under NU7
The upgrade also directs 60% of transaction fees from every block into a reserve for the Network Sustainability Mechanism, leaving miners with 40%. Coinholders voted in September to begin paying that reserve back out through block rewards in February 2031.
NU7 also places caps on shielded activity in each block. Under those limits, Orchard throughput rises to more than double its current level, and the maximum slowdown a spammer can impose on light-wallet syncing falls by roughly 37%, according to the foundation.
Mainnet activation decision is scheduled for Oct. 20
Valar Group and Project Tachyon, the teams building Zakura, set the testnet activation in version 1.6.0 released on Oct. 1. The foundation released its Zebra candidate the next day.
Developers will decide on mainnet activation and set the block height on Oct. 20 based on how NU7 performs on testnet, according to a schedule posted by Zcash co-founder Sean Bowe, who also co-maintains Zakura. Nov. 5 is the planned mainnet date.
In a forum post, Bowe wrote that 「The changes in this upgrade should not affect wallets in any significant way」. He added that infrastructure such as full nodes, indexers, and block explorers may be affected.
v4 transactions will be turned off and Sprout will be suspended
NU7 also disables v4 transactions, suspending Sprout, Zcash’s original shielded pool.
A forum participant replying in the same thread said funds left in Sprout after the upgrade would effectively be stuck.
