The Zcash Foundation has released Zebra 7.0.0-rc.0, the first release candidate supporting the NU7 network upgrade ahead of its activation on public Testnet. According to the Zcash Foundation’s official release announcement, NU7 is scheduled to activate at block 4,465,026, expected around October 6. The upgrade will cut Zcash’s target block spacing from 75 seconds to 25 seconds, reducing the average wait for a first confirmation by two-thirds.
The release is specifically intended for Testnet operators, miners, wallet developers and infrastructure providers to evaluate the new consensus rules under live network conditions before any Mainnet deployment. Mainnet operators are not being asked to adopt NU7 yet because no Mainnet activation height has been established and Zebra 7.0.0-rc.0 remains a release candidate rather than a stable production release. The sequencing follows the same broader test-before-production model seen with Ethereum’s Platåberget public testnet for Glamsterdam.
NU7 Triples Block Frequency While Preserving Issuance
NU7’s 25-second target spacing means Zcash would produce roughly three times as many blocks over the same period. To prevent that higher frequency from accelerating monetary issuance, scheduled block rewards are divided by three and the remaining halving intervals are tripled. The objective is to preserve the amount of ZEC issued over time even though individual blocks arrive substantially faster.
The difficulty-adjustment system changes alongside the shorter block interval. ZIP 218 raises the averaging window from 17 blocks to 102 after NU7 activation, extending the number of observations used to calculate mining difficulty. The move is intended to maintain a meaningful wall-clock smoothing period as blocks become more frequent rather than allowing difficulty to react to an extremely short sample of recent blocks. ZIP 218 technical specification
NU7 also introduces the Network Sustainability Mechanism. Under the planned rules, 60% of transaction fees are removed from immediate circulation and placed into a reserve, while miners retain 40%. A predictable portion of that reserve is later reissued alongside scheduled block rewards. The mechanism changes how transaction fees contribute to future network security without changing Zcash’s 21 million ZEC supply cap or its long-term issuance schedule.
Shielded Limits Target Capacity and Wallet Sync Costs
Faster blocks could substantially increase the amount of shielded data lightweight wallets need to process, so NU7 introduces explicit per-block limits. The upgrade caps Orchard or Ironwood activity at 330 actions, Sapling at 300 combined inputs and outputs, and applies a shared shielded budget of 330 across the pools. Those limits are designed to increase usable Orchard throughput while bounding the verification and synchronization burden that an attacker could impose through spam.
ZIP 218 estimates that the design can more than double Orchard throughput from roughly 2.9 to 6.6 transactions per second while cutting worst-case compact synchronization bandwidth for light wallets by about 37%. Those are protocol-capacity calculations, not evidence of current transaction demand or production throughput, and they will first be evaluated through Testnet behavior before any Mainnet activation. Similar distinctions matter when assessing other scaling projects, including Cardano Leios public-testnet development after high-throughput simulations.
The release also changes mining templates, database format and several interfaces used by wallets and indexers, which is why the Foundation is asking Testnet infrastructure providers to upgrade before activation. The Testnet phase is intended to expose compatibility, mining and network-behavior problems before NU7 becomes eligible for a Mainnet rollout. That staging mirrors other protocol transitions where public testing precedes production activation, such as BNB Chain’s Pasteur hardfork process.
For now, NU7 should therefore be described as scheduled for public Testnet activation rather than already live with 25-second blocks. If activation proceeds at block 4,465,026 as planned, the test network will provide the first live environment for evaluating faster confirmations, revised issuance mechanics and new shielded-action limits together. Mainnet timing remains a separate decision that has not yet been finalized.
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