Zcash’s November upgrade could freeze funds in legacy Sprout pool

Zcash developers have proposed a network upgrade — labeled NU7 and formalized as Zip-2003 — that would stop the blockchain accepting version 4 transactions. Those older transaction formats are the only mechanism for spending ZEC stored in the network's legacy Sprout shielded pool, so disabling them would render funds in that pool unspendable unless access is restored later. The proposal does not destroy Sprout coins outright; instead it removes the ability to spend them under the current protocol rules while leaving open the possibility of a future fix. However, maintainers caution that holders may never regain access to any ZEC left in Sprout after NU7 activates, creating a real risk for users of older wallets. Community members and project leadership have flagged the issue publicly. A forum user posting as "vaspholdings" urged holders to inspect older wallets for balances in Sprout or transparent addresses ahead of the upgrade. Zcash co-founder Zooko Wilcox repeated the warning on X, underscoring the need for users to check wallets that might contain legacy shielded funds. NU7's schedule sets a testnet activation for Oct. 6, with a decision on whether to proceed slated for Oct. 20 and a targeted mainnet activation on Nov. 5. The upgrade would also shorten Zcash's target block time from 75 seconds to 25 seconds while keeping issuance changes aligned with the existing halving timetable.