Zcash (ZEC) NU7 Upgrade to Lock 12,226 ZEC in Sprout Privacy Pool

NU7 Reaches Its Final Step Before Mainnet

Zcash (ZEC) has moved past code-complete and consensus sign-off, and NU7 now sits at its final stage: mainnet activation. The upgrade is set for block height 3,543,405, and once the chain reaches it, roughly 12,226 ZEC left in Sprout, the protocol's oldest shielded pool, become permanently immovable, even for holders who still control valid private keys. The Zcash price recorded when the balance was tallied on November 5 put the frozen sum near $16 million.

Sprout is where shielded transactions began: the pool shipped with Zcash's October 2016 launch and the trusted parameter generation known as the Zcash Ceremony. Its outputs can only be spent through v4 transactions, the oldest transaction format still accepted by consensus rules. the official deployment specification ZIP 259 fixes the activation height, and ZIP 2003, the companion mechanism, ends v4 acceptance from that block onward. Without v4, no transaction the network will confirm can draw on a Sprout balance.

Timing, per the spec and current block cadence, points to Friday morning, November 6, with the exact hour dependent on how fast blocks land between now and then. NU7 carries a second, more visible change alongside the freeze: the target block interval falls from 75 seconds to 25 seconds, roughly a third of today's wait for a first confirmation. Node infrastructure is already staged; the Zcash Foundation shipped Zebra 7.0.0, a release built to enforce the new rules from the activation block onward, and operators of other node implementations follow the same height rather than a clock. The change is one-way at the protocol level: after activation, a Sprout output that never moved is not deleted, censored or reassigned. It is simply unreachable.

12,226 ZEC Face a One-Way Lock

Twelve thousand coins is a sliver of circulating supply, but the lock is absolute and one-sided. The balance belongs to holders who never migrated to the newer Sapling or Orchard pools: keys stored in an old cold wallet, a seed phrase misplaced years ago, or dust-size remnants of early shielded transactions. None of those coins can move after Friday's height, no matter how valid the keys remain.

Three properties define the freeze. It is not a confiscation: the ZEC keeps counting toward issued supply, so nothing is burned and no on-chain record is altered. It is not a bug: the deployment spec and ZIP 2003 state the v4 cutoff plainly, and the change has moved through Zcash's standard upgrade process rather than arriving by surprise. And it is potentially reversible, but only through a future network upgrade that restores v4 processing, a decision that would have to clear the same governance path NU7 itself followed. Shielded-pool usage has shifted over the years toward newer constructions with better efficiency, which is part of why balances lingered in Sprout: small amounts, old keys, and little urgency to move them. NU7 turns that inertia into a deadline.

There is still a working exit, briefly. Any Sprout balance spent through a v4 transaction before block 3,543,405 lands normally in its destination pool. Anything not moved by then waits indefinitely for a rule change no one has scheduled. Market attention around the upgrade has been building for weeks: ZEC climbed 9% as NU7 activation neared, and the coin has since cooled after its rally, recently holding near $1,300. Against that backdrop, the Sprout freeze is a footnote in dollar terms and a precedent in kind.

One Gate Left

The stranded $16 million is a rounding error next to ZEC's market value, but the episode sets a precedent that outlasts the coins: a routine consensus upgrade, not an exploit or a custody failure, can retire a pool that has existed since launch. Holders of legacy formats elsewhere in the ecosystem now have a concrete example of what end-of-life looks like, and the burden of migration sits entirely with them before the height passes. For traders, the freeze itself is settled news; the open variable is the clock. Activation has one gate left to clear: block 3,543,405. Until the chain reaches it, blocks stay at 75 seconds, and every Sprout output remains one v4 transaction away from safety.