Zcash’s Ironwood upgrade to activate on July 28

Zcash will activate the Ironwood network upgrade on July 28, shutting down the existing Orchard private transaction pool and creating a new private pool. The upgrade will block new activity in Orchard and require funds leaving Orchard to pass through an accounting checkpoint before entering the new pool.

The mainnet activation height is set for block 3,428,143, which corresponds to about July 28 at 8 a.m. Eastern. The activation implements network upgrade NU6.3 and establishes a checkpoint designed to record transfers from Orchard into the new pool.

The Orchard vulnerability, disclosed in early June, was described as an “infinity” bug in the private transaction pool that could theoretically allow creation of counterfeit Zcash (ZEC). Ironwood closes the old pool and forces outbound Orchard funds through the checkpoint, which could produce evidence if any counterfeit tokens were moved into the new pool.

Some ecosystem participants warned that a late-July activation might not give exchanges, wallet providers and mining pools enough time to update their systems. One developer group proposed delaying the activation to allow more testing. Zcash core developer Sean Bowe announced the schedule and posted: “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.” He confirmed the date is one week later than an earlier July 21 target.

The disclosure of the Orchard vulnerability affected market activity: ZEC fell about 50% from roughly $602.68 to $299.25 after the issue became public on June 3, before partially recovering in the following weeks. Blockchain data show about 16,806,723 ZEC in circulation, more than 80% of the 21 million maximum supply.

Developers and node operators will monitor the July 28 activation to confirm the checkpoint functions as intended and that exchanges and wallets route funds correctly into the new private pool. The upgrade will also allow investigation into whether the Orchard bug was ever exploited.