Key Highlights:
- Zcash has officially activated Network Upgrade 7 (NU7) on its public testnet, reducing target block times from 75 seconds to 25 seconds.
- The upgrade introduces the Network Sustainability Mechanism (NSM) to recycle transaction fees and plans the deprecation of version 4 transactions, which will impact the legacy Sprout pool.
- A final decision on setting the mainnet activation block height is scheduled for October 20, with target production deployment slated for November 5.
Zcash Activates NU7 on Public Testnet to Accelerate Block Production
Privacy-focused cryptocurrency network Zcash has successfully deployed Network Upgrade 7 (NU7) on its public test network, launching a major testing phase aimed at drastically cutting settlement times. Under NU7, Zcash’s target block spacing drops from 75 seconds down to 25 seconds. This shift enables the protocol to produce approximately three blocks in the time frame previously reserved for just one, lowering the average wait time for an initial confirmation from 75 seconds to 25 seconds.
The Zcash Foundation released Zebra 7.0.0-rc.0 on October 2 to provide testnet operators with the necessary software, urging participants to evaluate the network modifications under real conditions.
At this stage, mainnet operators do not need to alter their nodes, as no official activation height has been determined for the production chain. The rollout follows formal alignment reached in September by Zcash engineering teams, who outlined a target mainnet activation date of November 5 pending review of testnet stability.
Shielded Limits, Fee Recycling, and Governance Approval
Alongside faster confirmation speeds, the NU7 package institutes constraints on shielded actions inside individual blocks. According to the Zcash Foundation, these capacity limits are designed to safeguard user wallets against spam during more rapid block production cycles. To maintain balanced tokenomics under three-fold block generation, NU7 recalibrates reward issuance so miners do not receive triple the amount of daily ZEC.
The technical parameters received overwhelming consensus during pre-upgrade polling. In a private governance vote accounting for nearly 2.4 million ZEC—representing about 66% of eligible Ironwood balances—approximately 99.9% of voting stake supported slashing the target block time to 25 seconds. Furthermore, roughly 98.9% voted to maintain the prevailing halving schedule, while 96.6% backed February 2031 for the initiation of reissuance under the Network Sustainability Mechanism (NSM).
The NSM establishes an economic model where a share of each transaction fee is diverted from immediate circulation into a dedicated protocol reserve, which can subsequently fund future block rewards. The Zcash Foundation characterized this framework as recycling transaction fees into future issuance.
Legacy Sprout Pool Deprecation and Node Readiness
Once deployed to mainnet, NU7 is slated to permanently disable version 4 transactions. This deprecation carries critical operational implications for users holding funds in Zcash’s original legacy Sprout shielded pool. Because spending from Sprout depends on version 4 transactions, any ZEC remaining within Sprout will become unspendable after mainnet NU7 activation unless assets are transferred out beforehand.
Infrastructure providers have concurrently tuned their software. In late September, the Zcash Foundation resolved a high-severity bug in Zebra versions 6.4.0 and 6.4.1 that could have let a remote peer crash a node; Zebra 6.4.2 fixed the vulnerability, which affected availability without jeopardizing consensus or user balances. External ecosystem participants have also adjusted node implementations: cryptocurrency exchange Gemini migrated its Zcash infrastructure to Zakura, confirming that its deployment synchronized to the chain tip in slightly over six hours—compared to nearly a day with Zebra—while deposits and withdrawals remained fully functional.
Why This Matters
NU7 comes shortly after the rapid execution of the Ironwood upgrade on July 28 at block 3,428,143. That earlier intervention mitigated a critical, theoretical vulnerability in the Orchard shielded pool that could have permitted undetectable counterfeiting. Although researchers discovered no evidence of exploitation, developers launched Ironwood to establish strict accounting limits on Orchard outflows and isolate funds within a new shielded pool.
With those emergency safeguards resolved, NU7 advances the network toward improved usability, modern transaction formats, and long-term financial sustainability. Developers will officially review public testnet performance on October 20. If testnet metrics remain stable, core teams will establish a binding mainnet block height to deliver the upgrade on November 5.
Frequently Asked Questions
Does the faster block time triple daily ZEC issuance?
No. NU7 simultaneously recalibrates block rewards alongside the shorter 25-second interval, ensuring that the total daily amount of ZEC issued to miners remains consistent with the network’s planned issuance curve rather than tripling.
What will happen to funds stored in the legacy Sprout pool?
When NU7 reaches mainnet, it will disable version 4 transactions, which are necessary to execute spends from the Sprout pool. Consequently, ZEC remaining in Sprout will become permanently unspendable unless moved to a newer pool prior to mainnet activation.
When will NU7 activate on the Zcash mainnet?
Mainnet activation is tentatively targeted for November 5. Core developers are scheduled to review testnet stability on October 20 before finalizing and locking in the official mainnet activation block height.
