Zcash NU7 has moved from development into live testing after activating on the public Zcash testnet at block 4,465,026 on Oct. 4. The block was mined at 18:21:45 UTC, bringing the upgrade into operation earlier than the previously estimated Oct. 6 testnet milestone. Zcash subsequently confirmed that NU7 was live on testnet.
The activation gives developers, node operators and infrastructure providers several weeks to examine the protocol changes before a potential Nov. 5 mainnet rollout. The mainnet date remains a target rather than a final activation, with developers scheduled to make the final decision and establish the mainnet activation height on Oct. 20.
Zebra 7.0.0-rc.0, the first release candidate supporting NU7, was prepared for testnet operators ahead of the activation. The Zcash Foundation said the testnet phase is intended to expose the upgrade to real operating conditions before any mainnet deployment.
25-Second Blocks Reshape Zcash
The most visible NU7 change is the reduction in Zcash’s target block spacing from 75 seconds to 25 seconds. That represents a threefold reduction in the target interval and could lower the waiting time for an initial confirmation. The Foundation says the change is designed to make Zcash more practical for payments, exchange deposits and other applications that depend on block confirmations.
NU7 also introduces the Network Sustainability Mechanism (NSM). Under the implementation, 60% of transaction fees are placed into a reserve for future block rewards, while miners retain the remaining 40%. The mechanism is intended to help strengthen Zcash’s long-term security budget as block rewards decline over time.
The upgrade also includes changes to older transaction infrastructure and shielded activity:
- 25-second target block spacing, down from 75 seconds.
- Version 4 transactions are disabled under NU7.
- The Network Sustainability Mechanism creates a reserve from transaction fees.
- New shielded-activity limits are included to help protect wallets from spam.
Sprout Funds Face a Key Deadline
One of the most important user-facing consequences concerns the legacy Sprout shielded pool. NU7 disables version 4 transactions, which are required to move funds from Sprout. As a result, ZEC remaining in Sprout after the mainnet upgrade could become unspendable through normal transactions. Users holding legacy Sprout funds therefore face a deadline before NU7 activates on mainnet.
The next major milestone is Oct. 20, when Zcash developers are expected to review testnet performance and determine the mainnet activation height. If testing remains satisfactory, Nov. 5 is the targeted date for NU7 to reach the production network.
Conclusion
NU7’s testnet activation at block 4,465,026 marks a significant step in Zcash’s next protocol upgrade. The shift to 25-second target blocks, the Network Sustainability Mechanism and the removal of version 4 transactions will change important parts of the network. The decisive test now is whether the upgrade performs reliably under live conditions before developers make the Oct. 20 mainnet decision. Nov. 5 remains the target, but the final rollout depends on the testnet results.
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