Sprout Pool Funds Now Inaccessible
The Zcash network’s NU7 upgrade activated at block 3,543,405, which occurred at 02:34 UTC, marking a pivotal moment for the privacy-focused cryptocurrency. One immediate consequence: roughly 12,224 ZEC—valued between $15 million and $16 million at recent prices—are now stranded in the legacy Sprout shielded pool. This pool, introduced in 2016 as Zcash’s original privacy layer, has been closed to new deposits for years but still held a significant balance as of the upgrade.
With NU7 now live, version 4 transactions—the only type that could move funds out of Sprout—are explicitly rejected by the network. As a result, these coins are not destroyed or burned; they remain counted in circulating supply but are effectively frozen under the new protocol rules. According to decrypt.co, network specifications caution that there is no guarantee these funds will ever be accessible again.
This outcome highlights a tension: while Zcash’s technical progress continues, early users who left funds in Sprout face permanent loss of access.
Block Times Slashed, Syncing Eased
NU7 brings a dramatic reduction in block times—from 75 seconds down to just 25 seconds per block. This change means transactions confirm much faster than before and increases the network’s overall throughput. The upgrade also introduces limits on how much shielded (private) transaction data can fit into each block. By capping this activity, wallet applications now have less data to scan when searching for private payments addressed to them.
During a stress test, the orphan rate rose to 3.43% at 25-second blocks compared to 1.57% at the previous 75-second interval.
Wallets should see lighter synchronization loads and faster payment detection as a result.
However, a stress test revealed that moving to 25-second blocks increased the orphan rate (blocks discarded due to chain splits) from 1.57% up to 3.43%. Faster confirmation comes with greater technical complexity for miners and node operators.
$16 Million ZEC Frozen Indefinitely
At the time of activation, ZecStats reported that approximately 12,224 ZEC remained locked in the Sprout pool—worth between $15 million and $16 million depending on market conditions. These coins are neither spendable nor destroyed; they continue to count toward Zcash’s total supply cap of 21 million coins. Yet under current rules, there is no way to transfer or recover these funds.
The decision to freeze rather than burn these coins preserves accounting consistency but raises questions about user responsibility and protocol evolution. Developers have warned in official documentation that spending from Sprout may never be re-enabled—leaving affected holders with little recourse.
See Also
Future Mining Rewards Get a Boost
NU7 introduces what developers call the Network Sustainability Mechanism (NSM). Under this system, 60% of all transaction fees are removed from circulation after each transaction and reserved for future reissuance through mining rewards starting around February 2031. This approach ensures that while current fees help secure the network, they will eventually return as incentives for future miners—supporting long-term network health without inflating supply beyond the fixed cap.
Reissuance of these reserved fees will occur gradually along a smooth curve layered atop Zcash’s existing halving schedule. The protocol’s hard cap of 21 million ZEC remains unchanged by this mechanism.
Why it matters
The NU7 upgrade delivers tangible benefits: faster payments thanks to shorter block times and lighter wallet workloads due to stricter limits on shielded data per block. At the same time, it enforces technical discipline by retiring outdated privacy pools and introducing mechanisms like NSM to sustain miner incentives far into the future.
Yet practical impacts are mixed. While most users benefit from speedier transactions and improved wallet performance, those with assets left in Sprout face indefinite lock-up—a tradeoff between technological advancement and legacy support. The headline improvement in confirmation speeds is tempered by an uptick in orphaned blocks during stress testing, showing that every protocol change brings both gains and new challenges.
For developers and investors alike, NU7 signals a commitment to both privacy innovation and long-term economic stability within strict supply limits—though not without costs for some early adopters caught on the wrong side of progress.
Key Findings
- •The NU7 upgrade activated at block 3,543,405 on June 7, 2024, making 12,224 ZEC ($15–16 million) in Sprout unspendable.
- •NU7 reduces Zcash’s block time from 75 seconds to 25 seconds, increasing the orphan rate from 1.57% to 3.43% in tests.
- •NU7 introduces the Network Sustainability Mechanism, removing 60% of transaction fees for reissuance as mining rewards starting around February 2031.
What could shape the next move
If Zcash developers or the community propose a method to unlock the 12,224 ZEC (about $15–16 million) stranded in the Sprout pool after NU7’s activation at block 3,543,405 on June 21, it could immediately affect circulating supply and market liquidity; otherwise, these coins remain frozen with no confirmed path to recovery.