Zcash NU7 Upgrade Live, Stranding 12,224 ZEC in Sprout Pool

Zcash's NU7 network upgrade activated Friday, making roughly $15 million in ZEC held in the blockchain's legacy Sprout shielded pool unspendable. The change took effect at block 3,543,405 at 02:34 UTC, according to blockchain tracker ZecStats, which pegs the stranded Sprout balance at about 12,224 ZEC.

The activation is the latest structural shift for the privacy-focused chain, and it comes with an unusual twist: the specification deliberately leaves the door open to restoring access later, while warning it may never happen.

What does NU7 actually change?

The upgrade cuts Zcash's target time between blocks from 75 seconds to 25. Actual block intervals will drift toward the new target only as mining difficulty adjusts, so users shouldn't expect uniform 25-second spacing from day one.

Under Zcash Improvement Proposal (ZIP) 2003, NU7 rejects version 4 transactions — the only format that supports spending Sprout funds. That means the remaining coins in the oldest shielded pool cannot be transferred under the new rules.

The coins 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 introducing another retrieval mechanism. But the text is blunt about the risk, warning that "the ability to spend Sprout funds may never be re-enabled."

For holders of the roughly 12,224 ZEC still sitting in Sprout, that's the operational bottom line: their funds exist on-chain, remain visible in pool balances, and cannot move until — and unless — the community ships a future upgrade that revives a spending path. The decision effectively sunsets the protocol's first-generation shielded pool in favor of newer pool designs.

Where do transaction fees go now?

NU7 also introduces a Network Sustainability Mechanism. It removes 60% of transaction fees from circulation and routes them for eventual reissuance through future mining rewards, with that mechanism starting around February 2031.

The design is a long-horizon play for miner economics. Rather than letting all fee revenue flow immediately to miners, the network banks a majority slice and recycles it into block rewards roughly six years out — a schedule that matters for anyone modeling Zcash issuance and miner revenue beyond the current halving cycle.

The upgrade preserves two of the chain's core monetary parameters: the 21 million ZEC supply cap and the existing halving schedule. Both remain untouched despite the fee-circulation change.

NU7 also introduces limits on shielded activity, designed to reduce wallet synchronization demands — a practical constraint aimed at lighter, faster clients rather than a change to the supply or privacy model itself.

What happens to the stranded Sprout funds?

Nothing immediately. The 12,224 ZEC sits inert until a future network upgrade either re-enables version 4 transactions or builds an alternative withdrawal mechanism. ZIP 2003's own language concedes that restoration may never come, so Sprout holders should treat recovery as possible but not promised.

The context around the upgrade is already contested. A separate Zcash grants group has floated a $124 million compromise amid growing governance backlash, underscoring that the community fights over the chain's direction are far from settled.

With NU7 now live, the near-term questions are mechanical: how quickly difficulty adjustment brings block production down toward the 25-second target, and whether wallet operators handle the new shielded-activity limits without sync friction. The longer one is governance — whether a future upgrade reopens Sprout spending at all.