Zcash's NU7 puts a tentative Nov. 5 deadline on ZEC left in Sprout

Zcash activated its NU7 network upgrade on testnet at block 4,465,026.

According to Zcash testnet block data, the NU7 activation block was mined on Oct. 4 at 18:21:45 UTC, earlier than the roughly Oct. 6 timing developers had previously estimated.

Version 4 transactions would be disabled after mainnet activation, leaving ZEC in the legacy Sprout shielded pool unspendable unless holders move their funds beforehand.

Holders with funds there would need to move them before mainnet activation to retain the ability to spend them through the existing system.

NU7 retires the Sprout shielded pool, disables v4 transactions, and introduces no new transaction formats.

NU7 cuts Zcash's target block spacing from 75 seconds to 25 seconds, allowing roughly three blocks during the period currently targeted for one.

Under NU7, miners receive 40% of transaction fees, while the remaining 60% is removed from circulation and recorded in a reserve intended to fund future mining rewards.

Mainnet operators were told they did not need to make changes yet because no activation height had been established.

A service waiting for three confirmations would face a targeted wait of about 75 seconds instead of 225 if it kept its confirmation requirement unchanged.

Both major node programs support the trial: Zakura released its implementation Oct. 1, and the Zcash Foundation published a test version of Zebra the following day.

The Zcash Foundation said testnet operators should use the release candidate to test NU7 "under real conditions."

Under NU7 the scheduled reward per block falls to one-third, preserving the issuance schedule.

Actual block times vary.

A private governance poll involving nearly 2.4 million ZEC found roughly 99.9% of participating coins supported reducing the target block interval to 25 seconds; participation was roughly 66% of eligible Ironwood balances.

The testnet is the first live environment where NU7's protocol changes can be exercised.

Around 98.9% of polled coins supported keeping Zcash's existing halving schedule, and approximately 96.6% backed February 2031 for the start of reissuance under the Network Sustainability Mechanism.

The testnet features an adjusted third halving planned at block height 4,497,948, and NSM reissuance begins at testnet block height 7,305,222.

The Zcash Foundation, Project Tachyon, Valar Group, ZODL and Shielded Labs reached a unanimous agreement on the upgrade's scope after polling coinholders.

If the Nov. 5 target holds, there are 16 days between the Oct. 20 decision and mainnet activation.

NU7 introduces new limits on shielded actions that the Zcash Foundation said are intended to protect wallets from spam while block production becomes more frequent.

Retiring Sprout and disabling v4 transactions means any software still relying on those formats will need updating before mainnet activation; exchanges, wallet providers and node operators have a narrow window between the Oct. 20 decision and the Nov. 5 target.

The testnet activation block arrived about two days ahead of the developers' estimate.

Fees withheld from a Nov. 5, 2026 activation would sit in the reserve for about four and a quarter years (roughly 51 months) before reissuance begins in February 2031.

A day holds 1,152 blocks at 75-second spacing and 3,456 blocks at 25-second spacing.

At one-third of the per-block reward, 3,456 daily blocks pay the same subsidy as 1,152 blocks at the full reward, so daily issuance is unchanged.

The testnet's adjusted third halving is 32,922 blocks after activation; at the 25-second target that is about 9.5 days, putting it around Oct. 14, six days before the Oct. 20 review.