Zcash NU7 Upgrade Could Leave Legacy Sprout Pool Funds Unspendable
Key Takeaways
- •Zcash's planned NU7 upgrade in November would disable version 4 transactions, the legacy format that allows users to spend funds in the Sprout shielded pool.
- •Under Zcash Improvement Proposal-2003, Sprout funds would not be burned, but ZEC left in the pool may never be spendable again.
- •The Sprout pool dates to Zcash's 2016 launch and was superseded by the Sapling pool in 2018 and the Orchard pool in 2022, so early-era ZEC could still be sitting there.
- •NU7 is scheduled to activate on testnet on Oct. 6, with a decision on the targeted Nov. 5 mainnet activation expected on Oct. 20.
- •The upgrade would also cut Zcash's target block time from 75 seconds to 25 seconds while preserving the network's existing halving schedule.
Zcash users holding ZEC in the network's legacy Sprout shielded pool are being urged to move their funds before the planned NU7 upgrade in November, or risk losing the ability to spend them.
Under Zcash Improvement Proposal-2003, the proposed NU7 change would disable version 4 transactions — the older transaction format that allows users to spend Sprout funds — leaving any ZEC left in the pool unspendable once the upgrade activates.
The proposal would not burn Sprout funds and leaves open the possibility of restoring access at a later date. However, it warns that holders may never be able to spend funds left in the pool.
The Sprout pool dates back to Zcash's launch in 2016 and was superseded by the Sapling pool in 2018 and later by the Orchard pool, introduced with the network's NU5 upgrade in 2022. Balances in the original pool have remained spendable through the legacy transaction format that NU7 would retire, meaning ZEC from Zcash's early years could still be sitting in Sprout.
The community warning was raised on Sunday by a user posting as "vaspholdings" on the Zcash Community Forum, who urged ZEC holders to check their old wallets before the upgrade. Those wallets may contain Sprout ZEC, transparent ZEC or both, the user wrote. Only funds in the Sprout pool face the proposed restriction.
Zcash co-founder Zooko Wilcox also amplified the community warning in a post shared on X.
NU7, the network's planned November upgrade, is scheduled to activate on testnet on Oct. 6. Zcash expects to decide on Oct. 20 whether to proceed with the targeted Nov. 5 mainnet activation. For Sprout holders, proceeding on that schedule would make Nov. 5 the practical deadline to move funds out of the pool.
upgrade would also cut Zcash's target block time from 75 seconds to 25 seconds, while its planned changes to issuance would preserve the network's existing halving schedule.
ZEC traded at $1,627.82 at the time of writing, up 8% over the past 24 hours and almost 40% over the past week, according to CoinGecko.
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Source: Cointelegraph
