Zcash’s approaching upgrade will stop spending from its oldest privacy pool

Zcash’s NU7 rules disable version-4 transactions at mainnet block 3,543,405. That also makes funds left in the old Sprout privacy pool unspendable. The deadline is a block height, not a guaranteed clock time.

Sprout is the network’s original shielded pool. Its transfers require version 4, while newer transaction formats do not support it. ZIP 2003 explains that removing the format reduces the burden of maintaining obsolete transaction-processing code.

The specification does not describe the remaining coins as burned. A later consensus change could theoretically restore access, but it explicitly warns that spending may never be re-enabled. Having the private keys would not, by itself, override the new transaction rules.

Current coverage puts activation around the US evening of 5 November, which can fall on 6 November in London. Published countdowns vary, so this edition does not turn an estimate into a firm hour. The deployment specification supplies the fixed height; holders checking old wallets should distinguish Sprout balances from balances in newer pools.

The version-4 restriction also affects other workflows that still construct that format. The upgrade is consequently relevant to wallet and transaction-service operators as well as holders of old shielded funds.