The planned Zcash NU7 upgrade in November may make funds in the legacy Sprout shielded pool unspendable. According to Zcash Improvement Proposal-2003, the network will stop accepting version 4 transactions, which are required to spend funds from Sprout. Users are advised to move their ZEC out of this pool before the upgrade. The testnet is scheduled for October 6, the decision on the transition is set for October 20, and the target mainnet activation date is November 5.

ZIP-2003 Disables Old Transaction Format but Does Not Burn Sprout Funds

NU7 will end support for the old transaction format needed to spend from Sprout, which means any ZEC remaining in the pool will become unspendable after the upgrade. The proposal does not provide for burning the funds and leaves open the possibility of restoring access in the future, but warns that holders may never be able to spend coins left in the pool.

Community Urges Users to Check Old Wallets

A user named vaspholdings on the community forum urged ZEC holders to check old wallets before the upgrade, as they may contain both transparent funds and Sprout funds; the restriction will only affect Sprout pool funds. Zcash co-founder Zooko Wilcox also shared this warning.

NU7 Will Reduce Target Block Time to 25 Seconds

In addition to changes for Sprout, the upgrade will reduce the target block time from 75 to 25 seconds. Planned coin issuance adjustments will maintain the network's current halving schedule.