Zcash developers are targeting November 5, 2026 for the NU7 Mainnet upgrade, which is expected to disable version-4 transactions and effectively freeze ZEC that remains in the legacy Sprout shielded pool. Sprout funds would become unspendable under the new consensus rules unless holders migrate them beforehand, creating an operational deadline for owners of old wallets, custodians and services that still control zc... addresses. A final Mainnet activation decision is scheduled for October 20, following Testnet activation on October 6.
The change is defined in ZIP-2003, which proposes disallowing v4 transactions from NU7 onward. V4 is the remaining transaction format capable of carrying Sprout JoinSplit data, because the v5 format introduced with NU5 deliberately excluded Sprout fields. The proposal does not burn, cancel or formally unissue ZEC remaining in the pool; instead, it removes the consensus path currently available to spend those funds.
Sprout Deprecation Removes Legacy Protocol Complexity
Sprout was Zcash’s original shielded protocol and was later superseded by Sapling and Orchard. ZIP-2003 argues that legacy Sprout functionality now contributes disproportionate protocol complexity and attack surface relative to its limited remaining use. Removing the ability to process Sprout transactions would allow implementations to stop supporting legacy JoinSplit logic and related verification paths. The move follows broader work to improve Zcash’s shielded infrastructure, including recent performance gains in Zakura’s cryptographic libraries.
Migration mechanics require careful distinction. Standard historical zcashd payment RPCs prevented users from manually sending directly between Sprout and Sapling addresses, instead requiring an intermediate transparent step. The dedicated migration mechanism could perform a consensus-level Sprout-to-Sapling transfer while accounting for the value through the transparent pool. That turnstile design deliberately exposes the migrated amount while avoiding disclosure of the individual shielded addresses involved.
The old official workflow used z_setmigration, but that guidance now carries an important limitation. zcashd reached End of Life on July 18, 2026, and its successor wallet Zallet explicitly does not support Sprout funds or Sprout spending keys. Zallet documentation tells users with Sprout balances to move those funds with a Sprout-capable tool before transitioning their wallet. Holders of old wallet.dat files therefore need to confirm their recovery method rather than assuming a current Zallet installation can perform the migration.
November 5 Remains a Target, Not a Final Cutoff
The current NU7 roadmap calls for Testnet activation on October 6, followed by a final Mainnet decision and activation-height selection on October 20. November 5 becomes the effective Sprout spending cutoff only if NU7 proceeds on that schedule with ZIP-2003 included. The Zcash ZIP repository still describes ZIP-2003 among the NU7 candidates, while ecosystem engineering teams said on September 17 that disabling v4 transactions is among the features agreed for the planned upgrade.
For custodians, the immediate task is therefore wallet inventory rather than market positioning. Historical cold-storage systems should be checked for Sprout addresses and corresponding spending keys before the upgrade progresses. A zc... address alone is not enough to recover funds if the underlying private key or usable legacy wallet material has been lost. The issue is particularly relevant as ZEC has seen renewed activity through cross-chain routing and shielded-wallet integrations and increased attention from large holders pursuing Zcash-focused treasury strategies.
NU7 would not directly reduce ZEC issuance or circulating supply simply because Sprout funds become inaccessible. ZIP-2003 explicitly states that the Sprout pool balance remains issued and leaves open the possibility that a future upgrade could restore v4 spending or introduce another recovery mechanism. There is currently no commitment that such recovery will ever be implemented, making migration before activation the only dependable operational path described by the proposal. The next concrete milestone is the October 6 Testnet activation, followed by the October 20 decision that will determine whether the November 5 Mainnet target becomes the actual Sprout freeze date.
