Zcash Tests 25-Second Blocks as NU7 Goes Live on Testnet

NU7 testnet confirms the 25-second target

Zakura’s upgrade dashboard labels public testnet active and its earlier staging network shut down. Its saved October 4 observation, taken at 23:53 UTC, shows block 4,465,707, beyond the activation height of 4,465,026, and explicitly reports NU7 active with a 25-second target.

The page cautions that live verification is unavailable. Its displayed block tip and other measurements therefore establish the state at that recorded observation, rather than the network’s health at publication. The distinction is especially relevant when judging whether a trial is ready for production.

The deployment specification, ZIP 259, sets the same testnet activation height but leaves mainnet’s height undecided. It remains marked Draft. NU7 introduces no new transaction format: versions 5 and 6 continue, while version 4 becomes invalid after activation on the relevant network.

The shorter interval targets a lower wait for an initial confirmation. A service retaining a three-confirmation policy would have a nominal target of 75 seconds rather than 225 seconds. Actual mining times vary, and service providers may revise their confirmation policies.

ZIP 218’s timing analysis does not recommend simply reducing confirmation counts. It explains that the practical security comparison depends on the threat model, including how much mining power an attacker controls and the economic value protected by accumulated rewards.

It also sets a shared budget of 330 shielded actions per block, with separate pool limits, to constrain verification and wallet synchronization work. The authors estimate a 37% reduction in worst-case light-wallet synchronization bandwidth despite the higher block frequency. That is a modeled resource limit, not a measured improvement for every wallet.

Zcash fees enter a reserve before reissuance

Under ZIP 235’s fee-allocation rules, miners receive 40% of aggregate transaction fees in each block. The remaining 60% leaves circulation and is credited to the Network Sustainability Mechanism, or NSM, balance.

The calculation applies to the block total, with rounding performed once. It changes the destination of fees already paid by users; it does not mean each sender must add a separate 60% surcharge to a quoted transaction fee.

The reserve is public consensus accounting rather than a spendable treasury account. Nodes calculate it from the chain’s validated monetary state. No company can withdraw it as ordinary wallet funds, and it creates no direct distribution to ZEC holders.

ZIP 237 describes the later mechanism for returning a fraction of that balance through block subsidies. It retains the four-year halving structure and 21 million ZEC cap instead of replacing halvings with a continuously smoothed issuance schedule.

Collection and reissuance begin at different heights. The current testnet specification sets reissuance at block 7,305,222, well after NU7 activation. Mainnet’s corresponding height still needs to be calculated from its eventual activation height, so the trial does not imply immediate reserve-funded payments to mainnet miners.

More frequent blocks also do not triple scheduled daily coin creation. The scheduled subsidy per block is divided by the additional spacing factor, subject to integer rounding. The reserve mechanism has its own later issuance path, which must be distinguished from that timing adjustment.

These protocol-level economics are separate from investment-product payouts such as the proposed Grayscale Zcash income ETF. That filing concerns an options strategy; NU7 concerns the rules under which the underlying network processes payments and rewards miners.

Sprout spending faces a mainnet cutoff

The clearest balance-level consequence appears in ZIP 2003: Sprout requires version 4 transactions, so rejecting that format disables spending from the oldest shielded pool. Holders with funds remaining there would need to move them before mainnet adopts the rule to retain access through the existing transaction path.

The specification does not describe those balances as burned or newly transferred to an attacker. It leaves open a possible future recovery facility, but warns that spending may never be re-enabled. A potential later solution is therefore not a guaranteed exit for someone who misses the cutoff.

That warning applies specifically to Sprout balances. NU7’s version change does not mean every ZEC holder must perform a token swap or move ordinary exchange balances today. Individual providers still need to communicate their own software readiness and any service interruptions.

Zebra’s release candidate also changes its state database to version 29, according to the Foundation. Direct database consumers need compatible builds, and downgrade support is absent. Those operational checks help explain why a working testnet is only one step toward a production upgrade.

The published NU7 timeline schedules an October 20 review and mainnet activation decision, with November 5 as the intended rollout date. The testnet reached its activation height before the earlier October 6 estimate, illustrating why a block threshold and a calendar forecast are different commitments.

Ethereum’s separate Glamsterdam testnet preparation similarly leaves production readiness dependent on testing and coordination. Neither project’s testnet milestone establishes that every exchange or wallet is ready for its eventual mainnet changes.

Source: Alternative.me, whose Bitcoin-focused sentiment reading was 70, or Greed, versus 65 the previous day. It is not a Zcash-specific upgrade assessment.

As of October 5 at 13:09 UTC, the reviewed mainnet specification still lacked an activation height. The next substantive checkpoint is the October 20 decision, alongside testnet results and provider guidance for any remaining Sprout funds.