TL;DR:
- Zcash users holding ZEC in the Sprout pool should move funds before NU7 because version 4 transactions would become invalid after activation.
- ZIP 2003 would not burn or unissue Sprout balances, but access could disappear indefinitely unless the network later restores version 4 support or creates another recovery method.
- NU7 targets October 6 for testnet, an October 20 decision and November 5 mainnet activation, leaving holders limited time to act.
Zcash users with funds in the legacy Sprout shielded pool are being urged to move their ZEC before the planned NU7 network upgrade. Under ZIP 2003, NU7 would stop accepting version 4 transactions, the format required to spend Sprout funds. If the proposal activates with NU7, ZEC left in Sprout would become unspendable even though the coins would not be burned or removed from supply. The warning matters because restoring access later is possible in theory, but the proposal explicitly says holders should not assume that functionality will ever return.
NU7 Would Disable the Transaction Format Sprout Needs
Sprout was Zcash’s original shielded protocol and one of the earliest large-scale deployments of general-purpose zero-knowledge proofs. It was later superseded by Sapling and Orchard, which brought major efficiency and functionality improvements. Keeping Sprout support now adds protocol complexity and attack surface despite the pool seeing little practical use. ZIP 2003 specifically targets version 4 transactions, while newer transaction formats remain available for the rest of the network. The proposal applies the change to both mainnet and testnet and is intended to simplify future node and protocol maintenance.
The timing creates a narrow window for anyone still holding legacy funds. Zcash plans to activate NU7 on testnet on October 6, followed by a final decision on October 20 over whether to proceed with the targeted November 5 mainnet activation. Users with old wallets should therefore identify whether any ZEC remains in Sprout and move it before mainnet deployment if they want to preserve spendability. Transparent ZEC and funds held in newer shielded pools are not affected by this specific restriction, making the warning narrowly focused on the legacy Sprout balance.
Importantly, ZIP 2003 does not propose destroying or permanently confiscating Sprout funds. The balances would remain issued, leaving open the possibility that version 4 transactions could someday be re-enabled or another recovery mechanism could be created. The practical risk is access, not ownership: funds could remain recorded onchain while holders lose the ability to spend them. The change fits into the broader NU7 upgrade roadmap, which also targets 25-second blocks and other protocol changes. Zcash holders previously backed faster transactions and retiring legacy functionality, reinforcing the network’s push to simplify its architecture before the next mainnet upgrade. For users, waiting until activation creates an avoidable risk with uncertain recovery options.
