Author: Shenchao TechFlow
DeepChaohao summary: On November 5, 2026, Beijing time, the privacy blockchain Zcash confirmed that the network upgrade codenamed NU 7 will be officially activated at block height 3,543,405. According to report, this upgrade not only reduces the target block time from 75 seconds to 25 seconds but also completely deprecates version 4 transactions, rendering approximately 12,226 ZEC (with a total estimated value of $16 million) currently trapped in the original privacy pool, Sprout, unable to transact and indefinitely locked at the protocol level.
Final settlement of the first-generation privacy pool technology, ending version 4 transaction format
One of the core changes in the NU 7 upgrade is the removal of underlying compatibility support for version 4 (v4) transaction format. This transaction format is currently the only technical pathway for transferring funds out of the original privacy pool, Sprout, which launched in October 2016. With the arrival of the upgrade block height, full nodes will directly reject any transaction requests based on the v4 format. Even if the owner of the funded address possesses the valid private key, the system will no longer provide a valid signing and broadcast verification path for this privacy pool.
Early zero-knowledge proof technologies carried a heavy technical burden. The Sprout privacy pool relied on the original trusted setup established in 2016, whose proof generation required substantial memory and time. As subsequent privacy pools—Sapling and Orchard, which uses the trustless Halo 2 protocol—were deployed, the Zcash core development team advanced the cleanup of technical debt by directly discontinuing maintenance compatibility with the initial architecture and fully removing outdated cryptographic circuits.
Tens of millions in dormant assets have accumulated; the final window to escape the cliff is closing.
On-chain statistics show that approximately 12,226 ZEC remain locked in the Sprout privacy pool. At a market price of around $1,300 per ZEC, the total market value of these locked funds is approximately $16 million. Although the network upgrade was announced in advance, large-scale transfers of these funds have largely stalled as the deadline approaches.
Over the past week, approximately 10,037 ZEC were migrated out of the first-generation privacy pool via the emergency channel, with a single-day net outflow of 9,094 ZEC on Sunday. By Wednesday, the daily asset outflow had sharply declined to just around 40 ZEC. The steep drop in the outflow curve indicates that current holders of the remaining funds failed to respond to the upgrade window; the vast majority of the locked tokens belong to early-stage coins with lost private keys, unreachable owners, or stagnant cold storage.
Maintain the regulatory patch; assets are effectively permanently frozen.
For the frozen assets that cannot be withdrawn, the developer community has approved ZIP 2003. This specification reserves an interface within the protocol logic for potential future withdrawal mechanisms, allowing the network to potentially restore redemption of assets in the Sprout pool through a future upgrade. However, the engineering team included a clear warning in the specification, stating that this interface is only theoretically feasible and that the stranded assets are highly unlikely to ever be withdrawn again.
In the generational transition of privacy assets, Zcash has officially completed its migration from Sprout to modernized pools. The vast majority of active privacy transactions are now concentrated in the Orchard and Sapling pools, and the retirement of the old pool has fully isolated the attack surface of the legacy protocol while ensuring the security of funds for the overwhelming majority of existing users.
Block time reduced to 25 seconds, with on-chain throughput undergoing a doubled-speed reconstruction.
While cleaning up technical debt, NU 7 implemented a structural adjustment to the block time parameter across the entire Zcash network. The target block time was reduced from 75 seconds to 25 seconds, tripling the speed of block generation. This significant reduction in block time directly decreases the waiting time for users sending privacy transactions, lowering on-chain settlement latency.
The final countdown for the network upgrade is locked at block height 3,543,405, and all network nodes are awaiting the broadcast of the block at this height to complete the immediate switch of consensus rules.