Approximately 12,224 ZEC held in Zcash’s original Sprout privacy pool faced an indefinite freeze under the planned NU7 upgrade, according to Decrypt’s original report, published November 6, 2026, at 03:46:03 UTC+08:00.
ZecStats data updated Thursday put the balance’s value at roughly $15 million to $16 million at the market prices cited in the report. The change could make those coins inaccessible even to holders who retained their wallet passwords and private keys.
The cutoff was a block height, not a clock time
NU7 was scheduled to activate at block 3,543,405, expected Thursday evening in the United States. Its precise timing depended on block production rather than a fixed deadline. At publication, the latest available block was 3,543,027; the report did not establish that activation had already occurred.
The mechanism was the removal of version-4 transactions, the only transaction format capable of withdrawing coins from Sprout. According to the network specification cited by Decrypt, those transactions would become invalid after activation.
Sprout had already been closed to new deposits for years, but withdrawals remained possible before the upgrade.
Frozen coins would still count toward issuance
“NU7 (block 3,543,405) makes v4 transactions invalid, so what remains in Sprout is unspendable: frozen, not burned,” ZecStats stated in its Sprout information card.
That distinction matters for supply accounting: the remaining coins would continue to count toward Zcash’s circulating issuance calculations despite being unavailable to spend under the new rules.
A future upgrade could theoretically restore access, but that was not guaranteed. The specification explicitly warned that spending might never be re-enabled, and Decrypt reported no indication that the team intended to restore it.
The blockchain also could not identify the owners of the remaining balance. Consequently, it was unknown how much belonged to active holders and how much was already inaccessible because keys had been lost.
Why retire Sprout?
Zcash uses zero-knowledge proofs to verify transactions without exposing private details such as amounts and addresses. Sprout introduced that capability at Zcash’s 2016 launch; later privacy systems included Sapling, Orchard and Ironwood.
The report described Sprout’s substantial computing requirements and outdated verification mechanisms as sources of maintenance complexity and potential security risk.
Legacy holders with funds still in Sprout needed a compatible withdrawal mechanism before activation to avoid potentially indefinite loss of access. Sprout addresses begin with zc. Holders using modern supported wallets without Sprout balances did not need that migration, though keeping wallet software updated remained important.
Separately, according to the Zcash Foundation, NU7 would reduce the target block interval from 75 seconds to 25 seconds, making first confirmations approximately three times faster.
