Zcash Schedules July 28 Hard Fork to Address Orchard Bug

Zcash Schedules July 28 Hard Fork

On July 19, 2026, Zcash founder Zooko Wilcox announced the network’s upcoming hard fork, named Ironwood, which is set to activate on July 28, 2026, at block 3,428,143. This upgrade aims to address a critical issue surrounding the Orchard shielded pool and limit the potential for excess ZEC supply.

Sealing the Orchard Pool

The Ironwood upgrade will effectively seal the old Orchard pool, restricting how much ZEC can exit after the hard fork takes effect. While this update will prevent any hidden excess supply from leaking into broader circulation, it will not identify or freeze individual counterfeit coins. Users will only be able to transfer funds through a turnstile mechanism, ensuring that more ZEC cannot leave the old pool than what has legitimately entered.

Background on the Orchard Bug

The critical flaw in the Orchard shielded system was discovered by security researcher Taylor Hornby during an audit on May 29. The vulnerability could have allowed the creation of counterfeit ZEC within the Orchard pool without leaving clear evidence of such activity. Although no unauthorized value has been detected thus far, the inherent privacy of Orchard means that verification of non-existence of counterfeits is not feasible.

Temporary Disruptions Expected

As Zcash prepares for the upgrade, temporary disruptions to services such as deposits and withdrawals may occur across various exchanges and wallets. Users are not required to take immediate action, but those relying on these platforms may experience delays while upgrades are implemented. Wallets that do not incorporate the necessary migration tools may result in temporary unavailability of funds.

Enhancing Security Across the Zcash Network

The Orchard incident prompted the Zcash development team to pursue additional security measures. An AI-assisted review using Anthropic’s Mythos system found no other significant vulnerabilities post the initial bug disclosure. Furthermore, developers are engaging in independent audits and formal verification processes to strengthen the cryptographic foundation of Zcash.

The Ironwood hard fork is primarily focused on addressing the unresolved supply concerns rather than rectifying the previous bug itself, aiming to control any theoretical counterfeit ZEC from entering circulation through the sealing of the Orchard pool.