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Zcash Upgrade Set to Freeze About $16M Left in Sprout Pool
About 12,226 ZEC still sits in the 2016 Sprout pool. NU7 at block 3,543,405 turns off the only transaction format that can spend it.
Zcash's NU7 network upgrade is set to make remaining balances in Sprout, the network's original 2016 privacy pool, unspendable once block 3,543,405 arrives, under ZIP 2003.
About 12,226 ZEC was still in Sprout as of Thursday morning, ZecStats shows. At about $1,319 per ZEC near 5:57 a.m. ET Thursday, per CoinGecko, that is roughly $16 million. The coins are not burned and stay in issued supply; owners who keep their keys simply lose a consensus path to move them after activation.
How the freeze works
Sprout transfers require version-4 transactions. ZIP 2003 changes the consensus rules so that from NU7 onward the transaction version must be 5 or 6, not 4. Newer pools (Sapling, Orchard and Ironwood) use later formats and are not frozen by this change. ZecStats labels Sprout "Closing: frozen at NU7" and notes the pool has been exit-only for years.
A Zcash Foundation engineering update posted on the community forum said Zebra 7.0.0 supports NU7 on mainnet at height 3,543,405, planned for around Nov. 5. Exact wall-clock timing depends on how fast miners find blocks. CoinDesk and Crypto Briefing put activation in the Thursday evening to Friday early-Asia window if the chain keeps its prior 75-second target; NU7 also shortens the target block time to 25 seconds after activation, those outlets reported from the upgrade specs.
ZIP 2003 leaves open a future upgrade that could restore spending, and warns that spending may never be re-enabled. Holders who still have Sprout funds need to move them with software that still supports version-4 spends before the activation height. Sprout addresses begin with "zc," which can help people scanning old wallet records.
The public pool balance cannot show who owns the remaining coins or how many keys are lost. Roughly 10,000 ZEC left Sprout over the past week, with most of that move on Sunday, CoinDesk reported from ZecStats history; only a thin amount followed on Wednesday.
In our opinion: the practical check for readers is whether any old "zc" balance still shows in a wallet before block 3,543,405. The $16 million figure will fall with every successful exit, and ZIP 2003 calls later recovery only a possibility. After activation, the story shifts from a deadline to whether the community ever schedules a recovery path.
Sources: ZIP 2003 — Disallow version 4 transactions · ZecStats shielded pools · Zcash Foundation engineering update (forum) · CoinGecko · CoinDesk · Crypto Briefing
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