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Zcash's NU7 upgrade goes live, freezing about 12,224 ZEC in the old Sprout pool
Summary
About 12,200 ZEC, worth roughly $15 million to $16 million, was still sitting in Sprout, Zcash's original 2016 privacy pool, on Thursday, and it will become unspendable when the NU7 upgrade activates at block 3,543,405, CoinDesk and Decrypt reported, citing ZecStats data.
NU7 rejects version-4 transactions, the only format that can move coins out of Sprout, so any balance left behind is frozen even for owners who still hold their private keys; both outlets said activation was expected Thursday evening U.S. time, with the exact moment depending on block production.
CoinDesk said the Sprout balance fell from about 22,263 ZEC a week earlier, most of it leaving on Sunday, but only about 40 ZEC moved out on Wednesday.
The frozen coins still count toward Zcash's issued supply, and the ZIP 2003 specification leaves open restoring access in a future upgrade while warning spending may never be re-enabled; CoinDesk reported co-founder Sean Bowe has proposed a recovery system, though none has been approved, while Decrypt said the team has not shown interest in restoring access.
The upgrade also cuts Zcash's target block time from 75 seconds to 25 seconds, which both outlets said should make first confirmations about three times faster.
Updates
- Update, : Update (Nov. 6): NU7 activated on mainnet at block 3,543,405 (about 02:34 UTC), The Block, Decrypt, CoinDesk and Cointelegraph reported. Outlets said the upgrade cut the target block interval from 75 seconds to 25, activated the Network Sustainability Mechanism that removes 60% of transaction fees into a public reserve for gradual reissuance through block rewards starting around 2031 (The Block cited reserve start block 8,939,664), and left about 12,224 ZEC in the retired Sprout pool unspendable after version-4 transactions were disallowed; Cointelegraph put the stranded value near $15 million and said a future upgrade could still restore access though ZIP 2003 warns it may never be re-enabled.
Key facts
- ZecStats, quoted by Decrypt: "NU7 (block 3,543,405) makes v4 transactions invalid, so what remains in Sprout is unspendable: frozen, not burned."
- Sprout addresses begin with "zc," which can help holders checking old wallet records see whether the deadline affects them; users of modern supported wallets do not need to migrate.
- Bowe: "I'm increasingly convinced that the store-of-value case for Zcash requires us to make these funds recoverable for as long as possible."
- CoinDesk said nobody can tell from the public pool balance who owns the remaining coins or how much belongs to wallets whose keys are already lost.