Zcash developers plan to activate the Ironwood hard fork (NU6.3) around July 28, 2026, at block height 3,428,143, to remediate a critical issue in one of the network’s shielded pools. A new high-performance node implementation, dubbed Zakura, is already supporting the changes and reports significantly faster initial synchronization.
Ironwood Activation Timeline
The Ironwood network upgrade is expected to go live at block height 3,428,143, which is projected to occur around July 28, 2026. As with prior Zcash consensus changes, the activation will require nodes to run Ironwood-compatible software to remain on the main chain once the fork occurs.
Vulnerability Mitigation and Pool Closure
Ironwood addresses a soundness flaw identified in the Orchard shielded pool, a component introduced to enhance Zcash’s private transactions. Developers are sealing off the affected pool as part of the upgrade to protect network integrity and prevent further use of the vulnerable circuit. The fix is designed to maintain the security assurances of shielded transfers while retiring the impacted pathway.
Performance-Focused ‘Zakura’ Node
Alongside the upgrade, the Zakura node—built for speed and quick deployment—has been introduced to support Ironwood. According to the development team, Zakura can complete an initial chain synchronization in roughly four hours, aiming to reduce operational overhead for node operators and improve resilience across the network.
What to Expect Next
- Network continuity: Post-activation, only Ironwood-ready nodes will remain in consensus, ensuring the vulnerability is fully mitigated.
- Shielded transfer integrity: Closing the affected Orchard pool is intended to preserve the soundness of private transactions going forward.
- Operational upgrades: Performance improvements from the Zakura node target faster bootstrapping and smoother maintenance for infrastructure providers.
Zcash is a privacy-focused cryptocurrency that uses zero-knowledge proofs to enable shielded transactions. The Ironwood upgrade continues the project’s cadence of network updates aimed at strengthening security and performance.