Zcash's core development team has set a precise trigger point for the next mainnet upgrade: activation block 3,428,143 is now locked, ending the era of rough estimates. Holders and node operators must prepare or risk falling behind.
Block Height Locked, Timeline Hardens
Zcash developer Sean Bowe confirmed that the Ironwood upgrade (formally known as NU6.3) has a fixed activation block height of 3,428,143, which corresponds to 8:00 AM EST on July 28, 2026 (Beijing time 20:00). The earlier soft target of "around July 21" gave way to a concrete block number, reflecting increased confidence from node operators, miners, and wallet teams in code stability. Consensus rule changes are fully implemented, related specifications and ZIPs are near final, and independent audits are running in parallel.
New Shielded Pool Replaces Orchard, Anti-Forgery and Quantum-Resistant Upgrades
Ironwood introduces a brand-new shielded pool to succeed Orchard, Zcash's current privacy pool. New shielded transactions will route into this pool, while Orchard enters a "spend-only" state via a turnstile migration: funds can exit but no new funds enter. This structural shift addresses a counterfeiting vulnerability discovered in Orchard. Rather than patching the existing pool, developers built a fresh one with stronger soundness guarantees from scratch. The upgrade also incorporates formal verification to rule out undetectable counterfeiting bugs down to the cryptographic assumptions, independent security audits, and note formats designed to resist future quantum computing threats.
A live testnet tool called CipherScan already tracks Ironwood migrations in real time, tagging each turnstile-crossing transaction with origin pool, destination pool, and verification status, all on-chain.
Node and Wallet Testing Ready, Wallet Compatibility Remains Key Question
Zebra, one of Zcash's node implementations, shipped a 6.0.0 release candidate supporting Ironwood on testnet. The bundle includes a state database upgrade that skips full resync for existing operators and expanded RPC methods exposing the new Ironwood note commitment tree. Separately, testnet.zec.rocks serves live NU6.3 transactions through an Ironwood-compatible lightwalletd branch, giving wallet developers a real test environment.
While mining hashrate reportedly signals technical readiness, wallet readiness remains the most open variable. Developers note that not every wallet needs to be ready on day one — users will have adequate alternatives if their preferred wallet lags.
Key Watchpoints: July 21-28 and Block Height Tracking
Key things to watch: July 21-28 window — wallet providers race to finish Ironwood-compatible updates; track block 3,428,143 against current height as the date nears; after activation, monitor formal verification updates confirming Zcash's 21 million ZEC supply cap holds through the migration.