Zcash's Ironwood network upgrade activates at mainnet block 3,428,143 around 13:00 UTC on July 28. The upgrade retires the Orchard shielded pool for new deposits and outputs, replacing it with a new Ironwood shielded pool. Node operators and wallet users must upgrade to Zebra 6.0.0 or newer; the older zcashd client reached end of support on July 18 and won't work after activation.
Why the upgrade was needed
Ironwood addresses a vulnerability in the Orchard shielded pool. A turnstile mechanism — a constrained bridge — controls value leaving Orchard and entering the new pool. This enables independent supply checks after the vulnerability, ensuring the integrity of shielded transactions. The upgrade was tested on testnet starting July 4, giving wallet and tooling developers time to verify compatibility.
What users and operators must do
Anyone running a node or wallet that supports Zcash needs to update to a version that supports Ironwood before the activation block. Using outdated software after activation could result in stuck deposits to the old Orchard pool or mismatched wallet versions. The Zcash Foundation and Electric Coin Company have urged users to stop using Orchard addresses for new receipts and to update their wallets.
Custody desks and the wallet indexing issue
Some custody desks ran parallel Zebra nodes ahead of the upgrade and discovered a wallet indexing issue during testnet. The problem was identified and fixed before mainnet activation. Smaller over-the-counter desks were caught off-guard by the zcashd shutdown and scrambled to get Zebra support in time. The transition from zcashd to Zebra as the primary client has been a multi-year process, but the end-of-support deadline forced the issue.
The turnstile and supply verification
The turnstile is a key feature of Ironwood. It acts as a one-way bridge from the old Orchard pool to the new Ironwood shielded pool. This allows independent auditors and users to verify that no coins were created or destroyed during the migration, addressing the vulnerability that required the upgrade. The turnstile ensures the total supply remains consistent.
With activation just days away, node operators and wallet users should confirm they are running Zebra 6.0.0 or later. Those still on zcashd or older Zebra versions risk losing access to their funds or missing transactions. The upgrade is mandatory for continued participation in the Zcash network.
