Zcash’s NU7 network upgrade activated on Friday, making approximately $15 million in ZEC held in the network’s old, ring-fenced Sprout pool no longer able to be spent.
According to blockchain tracker, the upgrade took effect at 02:34 UTC at block 3,543,405 ZecStatswhich shows the Sprout pool balance at approximately 12,224 ZEC.
The upgrade shortens Zcash’s target time between blocks from 75 seconds to 25, although the actual block intervals will adjust to the new target as mining difficulty changes.
According to the Zcash Improvement Proposal (ZIP) 2003, NU7 rejects version 4 transactions, the only format that supports the issuance of Sprout funds. The remaining coins cannot be transferred under the new rules, but have not been burned.
The specification leaves open the possibility that a future network upgrade could restore access, either by re-enabling version 4 transactions or by introducing a different mechanism for retrieving the funds. However, it warns that “the ability to spend Sprout funds may never be activated again.”
NU7 will also introduce a network sustainability mechanism starting around February 2031 that will remove 60% of transaction fees from circulation and eventually re-spend them through future mining rewards.
The upgrade maintains Zcash’s supply cap and halving schedule of 21 million ZEC while introducing limits on shielded activity to reduce the need for wallet synchronization.
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