Zakura syncs Zcash in four hours; Ironwood fork set July 28

Zcash will enact the Ironwood hard fork (NU6.3) at block 3,428,143, expected around 8 a.m. EST on July 28, 2026. The upgrade will stop the legacy Orchard shielded pool from accepting new deposits or internal transfers and route existing shielded funds through a verifiable checkpoint called a turnstile.

Security researcher Taylor Hornby, working with Shielded Labs, found a soundness flaw in Orchard’s cryptographic circuits in late May 2026. The bug could, in theory, have allowed counterfeit ZEC to be created inside the shielded pool without leaving observable traces. Developers applied a soft fork and then the NU6.2 hard fork to address the immediate risk before scheduling Ironwood to close the old pool permanently.

When Ironwood activates, coins already inside the legacy Orchard pool will remain spendable only if they pass through the turnstile to enter the new Ironwood pool. The turnstile enforces that outflows from the old pool do not exceed the amount legitimately deposited. If any excess supply attempts to leave the old pool, the turnstile will block those outflows and the extra coins will be removed. If no excess appears, the public record will show no exploit took place. Project Tachyon is running formal verification on the new Ironwood circuits to produce machine-checked proofs in addition to manual review.

Node operators must upgrade their software before block 3,428,143. Wallet providers connected to the Zcash Open Development Lab plan to add prompts to guide migration of shielded funds. Users holding transparent ZEC balances or funds outside the legacy Orchard pool do not need to take action. The legacy zcashd client is reaching end of life around the same time, and operators are moving to modern clients.

Zakura 1.0.0 launched on July 15, 2026, as a fork of the Zcash Foundation’s Zebra codebase. Built by Sean Bowe and Dev Ojha and funded with private ZEC donations, the client reached the chain tip in about four hours and 20 minutes in a head-to-head trace, compared with roughly 20 hours and 46 minutes for Zebra. Pruned snapshots allow a new node to bootstrap in under two minutes, and a zcashd compatibility mode aims to keep older wallets and integrations functioning during the transition.

A Zakura blog post states, “Zakura syncs mainnet from the network far faster than Zebra in this trace, reaching the chain tip while Zebra is still in the sandblasting range.” The developers of Zakura have described a long-term goal of increasing private payment throughput substantially, contingent on cryptographic upgrades and faster node software.

The Zcash Foundation welcomed the new node client and noted that multiple independent node implementations reduce the risk of a single point of failure. For market participants, Ironwood serves as a deadline-driven public audit: the turnstile will provide a short, observable window to confirm whether the May flaw produced any hidden supply. ZEC has stabilized above $500 as the July 28 activation approaches, with developers, the Foundation, Shielded Labs, Project Tachyon and Valar Group aligned on the upgrade schedule.