Zcash has confirmed a firm activation date for its Ironwood network upgrade, with the overhaul set to go live on July 28 at approximately 8AM EST. The upgrade, formally designated NU6.3, will activate at block height 3428143 and closes the chapter on a critical vulnerability discovered in May in the network’s primary private transaction pool.
What Ironwood actually does
Announced in June, the Ironwood upgrade shuts down the existing Orchard shielded pool, blocks any new transactions from entering it, and establishes a replacement private pool. The key wrinkle: every ZEC leaving Orchard must pass through an accounting checkpoint before it can enter the new pool. That checkpoint mechanism could yield forensic evidence about whether the so-called ‘infinity’ bug was ever exploited to mint counterfeit ZEC tokens.
As Shielded Labs explained when the upgrade was first detailed: ‘As users migrate funds from the existing Orchard pool to the new pool, any hypothetical counterfeiter faces a choice: attempt to move counterfeit funds and risk exposing their existence, or leave them behind and risk being unable to move them in the future.’
Core developer confirms the date
Zcash core developer Sean Bowe confirmed the timeline on Thursday, writing: ‘Zcash’s Ironwood mainnet activation height has been set and tagged! All of the major organizations are committed to activation of NU6.3 at height 3428143, which is approximately July 28th at 8AM EST.’
The July 28 date is one week later than the previously circulated target of July 21. Shielded Labs had earlier raised the prospect of delaying the upgrade entirely, cautioning that exchanges, mining pools, and wallet providers would not have sufficient time to prepare their systems if the original late-July window was maintained. The extra week appears to be the compromise reached among ecosystem participants.
Background: the Orchard bug and ZEC price fallout
The Orchard vulnerability was disclosed on June 3. ZEC plummeted roughly 50 percent in the aftermath, dropping from approximately $602.68 to a low of $299.25. The token has staged a partial recovery since, trading at around $492.61 as of the latest data, and was up roughly 7.5 percent on the day at close to $503.72.
Supply milestone reached
Separately, Zcash crossed a notable supply threshold this week. More than 80 percent of the network’s maximum 21 million ZEC cap has now been issued, with circulating supply reaching 16,806,723 ZEC according to data shared by community account ruZCASH on Monday.
What to watch
Two points will define the upgrade. Block height 3428143 is effectively a hard deadline: if major node operators, exchanges, and miners have not upgraded their software before that point, they risk a chain split. And the accounting checkpoint at the Orchard-to-Ironwood boundary is the critical data point to watch, since any anomalous fund flows during migration would be the first concrete evidence of whether counterfeit ZEC was ever created.
