Zcash (ZEC) Activates NU7 on Testnet at Block 4,465,026

NU7 Goes Live on Testnet

Zcash testnet operators now carry the job of proving the network's next upgrade under live conditions, after Zcash (ZEC) activated NU7 on the testnet at block 4,465,026. The activation block was produced at 18:21:45 UTC on Saturday, Oct. 4, according to ZecBlock, the network's testnet block explorer, and the protocol's official X account confirmed soon after that the upgrade was live. The block height had been fixed in advance as the upgrade's trigger point, so the mining of block 4,465,026 itself marked the switch. NU7 reaches testing roughly a month before the targeted Nov. 5 mainnet rollout, and every finding from the testnet phase now feeds a schedule with a fixed date attached.

The upgrade is substantial. NU7 trims the target interval between blocks from 75 seconds to 25 seconds, a threefold acceleration in the intended rhythm of block production across the chain. It also disables version 4 transactions, retiring a legacy transaction format outright, and introduces a Network Sustainability Mechanism that recycles part of the transaction fees users pay into future block rewards. That last piece rewires the fee market that has run since launch, giving the protocol a standing channel from current user activity to long-term security spending instead of leaving fee revenue wholly with miners.

The instruction to operators came from the Zcash Foundation, which said in a Friday announcement that testnet operators should run the release candidate, Zebra 7.0.0-rc-0, to put NU7 through real conditions rather than synthetic checks. The testnet stage exists so developers can observe how the new block cadence, the retired transaction version and the fee mechanics behave before anyone commits the same rules to the production chain. Anyone tracking the Zcash price through the upgrade window has the same calendar to weigh: a troubled testnet could shake confidence in the Nov. 5 date, while a clean pass leaves it standing as written. Testnet carries no funds at stake, which is precisely why the foundation wants failures to surface there first.

Behind the block-time change sits a direct warning for holders of the chain's oldest coins. Because NU7 disables version 4 transactions, ZEC still sitting in the legacy Sprout shielded pool becomes unspendable once the upgrade fully activates unless its owners move the funds first. Sprout is the original shielded pool Zcash launched with in 2016, the pool created through the trusted setup that preceded today's zero-knowledge proofs, and a slice of ZEC has never migrated from it to the newer Sapling and Orchard pools. The upgrade does not erase those coins. It cuts off the old transaction format they depend on for spending, so the deadline is functional rather than administrative: the funds stay in the ledger, but the route out closes.

The change also reaches into how the chain is run day to day. As a Layer 1 blockchain protocol, Zcash settles its rules in code that every node operator has to update, and its consensus mechanism is shifting on three fronts at once in NU7: block cadence, accepted transaction versions and the recycling of fees into rewards. The Zcash Foundation's testnet release candidate is the vehicle operators are being asked to run, and the foundation framed the exercise as preparation, not a verdict on mainnet timing.

The decision point is written into the calendar. Zcash developers are scheduled to make the final call on mainnet activation and to set the activation height on Oct. 20, working from what NU7 shows them on testnet between now and then. If they proceed, Nov. 5 remains the target for the production chain, and node operators would face the same software transition on mainnet that the testnet is rehearsing now.

What Stands Between Testnet and Nov. 5

The Zcash Foundation's release notes for Zebra 7.0.0-rc-0, the software version purpose-built for this testnet phase, spell out the change set in operational terms: NU7 arrives on testnet with the 25-second block target set, version 4 transactions disabled and the Network Sustainability Mechanism active, all anchored to activation block 4,465,026. Operators who stay on older releases stop following the upgraded chain once that block is crossed, which is what makes the foundation's call to test under real conditions more than routine. Two actions remain open: developers must fix the mainnet activation height on Oct. 20, and Sprout holders must move legacy funds before any activation locks the old format shut.