Zcash’s NU7 upgrade has gone live on testnet, putting the network’s planned protocol changes into live testing ahead of a November mainnet rollout. The move gives developers several weeks to assess 25-second blocks and other changes before deciding whether to proceed.
The upgrade reduces Zcash’s target block spacing from 75 seconds to 25 seconds. It also disables version 4 transactions and adds a Network Sustainability Mechanism that redirects part of transaction fees into future block rewards. ZecBlock, the testnet block explorer, shows block 4,465,026 — NU7’s scheduled activation point — was mined on Oct. 4 at 18:21:45 UTC. Zcash confirmed the activation in a post on X.
The Numbers Behind NU7
The block reduction is the headline, but the other changes matter just as much. Version 4 transactions are being disabled entirely, which means any ZEC held in Zcash’s legacy Sprout shielded pool will become unspendable unless users move the funds before NU7 fully activates on mainnet. That is a real deadline for anyone sitting on older balances.
The Sustainability Mechanism is the third piece. It takes part of transaction fees and redirects them into future block rewards, changing how revenue flows through the system. Developers will want to see how that redistribution behaves in practice before committing to the full rollout.
| Event | Date / Time |
|---|---|
| NU7 testnet activation | Oct. 4, 18:21:45 UTC |
| Testnet operator guidance issued | Friday |
| Final mainnet decision | Oct. 20 |
| Mainnet activation target | Nov. 5 |
What Testnet Means Now
The testnet phase is where the rubber meets the road. Developers can now assess the upgrade “under real conditions,” as the Zcash Foundation put it on Friday. That is the whole point of a testnet: catch problems before they hit the live network.
The foundation’s guidance to testnet operators is direct. Use the release candidate to test NU7 in realistic settings, not just in clean labs. The goal is to build confidence before the final call.
Zcash developers are scheduled to make a final decision on mainnet activation and set its activation height on Oct. 20, based on their experience with NU7 on testnet. Mainnet activation is targeted for Nov. 5.
The Sprout Deadline
The Sprout issue is the sleeper concern here. Because version 4 transactions are being disabled, any ZEC still sitting in the Sprout shielded pool will lose its spendable status unless owners act first. That is a practical problem for users who have not moved those funds yet.
The upgrade also changes how fees flow through the system. The Sustainability Mechanism redirects transaction fees into future block rewards.
Why This Matters
A shorter block time changes everything about how the network operates. The 25-second target means blocks confirm more quickly. It also puts pressure on nodes to keep up with the new pace, since they need to process blocks more frequently.
The fee redirection is a structural change. Developers will be watching closely to see whether the mechanism behaves as expected.
What Comes Next
The schedule is tight but clear. Testnet runs now, developers observe, and the Oct. 20 decision follows. If all goes well, mainnet activation happens on Nov. 5.
The key question is whether the testnet shows any issues that would force a delay. If developers spot problems, they can pause, fix, and try again. That is the beauty of a testnet: it exists to fail safely.
The Sprout deadline adds urgency for users. Anyone holding ZEC in the Sprout shielded pool should move it before NU7 activates on mainnet, because the version 4 disablement will render those funds unspendable otherwise.
The upgrade has already been confirmed live on testnet. The next test is whether it can run smoothly enough to pass muster before the Oct. 20 decision.
For developers, the coming weeks are a chance to watch the network under real load. The 25-second block time is new, and the fee mechanism is untested in production. Both deserve close attention before the final green light is given.
The upgrade has already passed its first test. Whether it passes the second remains to be seen.
Source material: “Zcash activates NU7 on testnet ahead of November mainnet target,” Cointelegraph.
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