Zcash is preparing to reduce the interval between blocks on its blockchain from 75 to 25 seconds, but the same upgrade could prevent the movement of cryptocurrencies stored in an old network protocol. The change is part of NU7, scheduled for November 2026, and advanced after developers defined, on October 20, a reference block for its activation.
The proposal establishes block 3,543,405, with activation estimated for November 5. The definition was agreed at a meeting of those responsible for Zcash technical proposals, according to information published by CoinDesk on October 21. However, the number still needed to be incorporated into the official ZIP 259 specification and into the versions of the programs responsible for operating the network.
The reduction in the interval between blocks is intended to speed up transaction confirmations. Under conditions close to the established target, three confirmations could occur in approximately 75 seconds, compared with 225 seconds previously. This does not mean, however, that all transfers will have their processing completed within that timeframe.
NU7 also provides for limits on operations protected by cryptography and changes in the distribution of fees. One of them determines that 60% of transaction fees be temporarily withdrawn from circulation, within a mechanism that provides for their future reintroduction without expanding the maximum issuance limit of ZEC.
Why funds stored in the Sprout protocol may become inaccessible
The most delicate consequence of the upgrade involves Sprout, Zcash's original private transaction system, later succeeded by the Sapling and Orchard protocols.
The ZIP 2003 specification determines that version 4 transactions will no longer be accepted after NU7 activation. Because Sprout relies exclusively on this format to move funds, balances that remain in it cannot be spent under the new rules.
The restriction does not affect only operations involving Sprout. Any service that still produces version 4 transactions will need to adopt compatible formats. Versions 5 and 6 will remain available, although transactions prepared before the upgrade will also require compatibility checks.
The technical document makes an important distinction: funds held in Sprout will not automatically be burned or eliminated from the ZEC supply. They will remain recorded on the blockchain, but without a valid mechanism for movement after the change.
Recovering these amounts would depend on a future change to the consensus rules, whether to restore compatibility with old transactions or to create another transfer procedure. The documentation stresses that this possibility is not guaranteed.
There is also a difficulty that predates the upgrade itself. The end of development of the zcashd software left the wallet functionality that offered support for Sprout without maintenance. Therefore, even before NU7, recovering and transferring old funds may require technical solutions that are not available in current wallets.
For ZEC holders, the essential distinction is in the protocol used to store the assets. Deactivating Sprout does not mean the widespread blocking of Zcash coins, but it creates a specific restriction for balances and operations dependent on old technology.
The upgrade has already been activated on the test network in October. Its deployment on the main network remains scheduled for November, subject to the finalization of the specifications and the adoption of compatible software by node operators.
