Historical report: originally published by Decrypt on November 6, 2026, at 03:46:03 UTC+8. The upgrade schedule and balances below reflect that report, not a confirmation of subsequent network events.
Zcash’s planned NU7 upgrade highlighted a hard boundary in blockchain ownership: holding private keys does not guarantee access if the network stops accepting the transactions needed to spend the coins.
According to Decrypt’s report, approximately 12,224 ZEC remained in Sprout, Zcash’s original privacy pool, based on ZecStats data updated Thursday. At the market prices cited, those holdings were worth roughly $15 million to $16 million and risked becoming inaccessible when NU7 activated.
Why retiring Sprout could freeze funds
Zcash uses zero-knowledge proofs to validate transactions without revealing private details, including amounts and the addresses involved. Sprout introduced that privacy technology at Zcash’s launch in 2016. Later systems included Sapling, Orchard and Ironwood.
Sprout had already been closed to new deposits for years, but holders could still withdraw. NU7 was set to invalidate version-4 transactions—the only transaction format capable of moving coins out of Sprout.
“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.
The rationale was technical maintenance and security: supporting the obsolete system added complexity, while Sprout’s resource-intensive privacy technology and outdated verification mechanisms presented risks developers wanted to remove.
Frozen does not mean destroyed. The coins would continue to count toward Zcash’s circulating issuance calculations. A future upgrade could theoretically restore spending, but that was not guaranteed. The report said the team had shown no interest in doing so, and the specification explicitly warned that spending might never be re-enabled.
Which holders faced the deadline?
The exposure concerned ZEC still held in Sprout, rather than all Zcash holdings. Sprout addresses begin with zc, a distinguishing feature in older wallet records.
At the time of the report, affected holders needed to use a compatible withdrawal mechanism before activation to avoid potentially indefinite loss of access. Holders using modern supported wallets did not need a Sprout migration, though keeping wallet software updated remained important.
The remaining balance also did not establish how many active users were at risk. The blockchain could not identify its owners or distinguish accessible holdings from coins whose owners had already lost their keys.
A block-based deadline, not a fixed clock time
NU7 was scheduled for block 3,543,405, expected Thursday evening in the United States. The latest available block cited at publication was 3,543,027; activation timing depended on block production.
The upgrade also aimed to reduce Zcash’s target block interval from 75 seconds to 25 seconds, which the Zcash Foundation said should make first confirmations approximately three times faster. For legacy Sprout holders, however, the central issue was whether their funds could leave the retiring pool before its transaction format became invalid.
