Zcash Developers Agree NU7 Height, Cutting Block Time to 25s

Zcash's next network upgrade now has a proposed date. Developers have agreed to activate NU7 on mainnet at block 3,543,405, which Zakura's NU7 dashboard puts at around 5 November 2026.

The headline change is speed. NU7 cuts the time between blocks from 75 seconds to 25 seconds. The catch is that the height isn't final yet. It sits in a GitHub pull request that has two approvals but hasn't been merged.

The Height Is Agreed but Not Yet Merged

Sean Bowe opened pull request #1405 on 20 October, titled "Set the NU7 mainnet activation height to 3543405". He wrote that the height was "agreed at ZIP editor meeting" and that "final modifications to ZIP statuses and other changes" are needed alongside the merge.

Two reviewers, ValarDragon and str4d, approved it the same day. When we checked on 21 October, it was still open.

The spec itself hasn't caught up. The ZIP 259 deployment document still lists "Assign the Mainnet NU7 activation height" as an open issue. According to str4d, the next step is moving all NU7 ZIPs to Proposed status, and Daira has taken on that work.

The 5 November date is also an estimate. It's when block 3,543,405 is expected to arrive, not a scheduled time. No exact time has been published.

Three Times as Many Blocks

A block is the batch of transactions the network adds to its record. Each new block on top of yours counts as a confirmation. NU7 lowers the target gap between blocks from 75 seconds to 25 seconds.

If the network hits that target, any wait measured in confirmations shrinks to about a third. Three blocks would take roughly 75 seconds instead of nearly four minutes. That matters to anyone sending ZEC to an exchange that waits for several confirmations before crediting a deposit.

Fees, Limits and the Supply Cap

Speed isn't the only change. ZIP 259 says NU7 also:

• adds per-pool and global limits on shielded actions, the private transactions Zcash is known for
• introduces the Network Sustainability Mechanism, or NSM
• removes 60% of transaction fees from circulation

The pull request publishes the mainnet NSM reissuance height as block 8,939,664, calculated from the activation height under ZIP 237. It also sets block 6,132,390 as the end of the Revision 2 funding streams in ZIP 214. No calendar date for either block has been confirmed.

ZIP 259 is explicit on one point holders will ask about: the changes "do not increase the ZEC supply cap."

Old Transactions Stop Working

The quieter design decision may affect more people. Once NU7 activates, version 4 transactions become invalid. Versions 5 and 6 stay valid.

Sprout transfers can only be written as version 4 transactions. So any funds still in the Sprout pool become unspendable after activation.

The ban isn't limited to Sprout. ZIP 259 says it covers all version 4 transactions, "including transparent-only and Sapling transactions." Wallets that still build version 4 transactions will need updating.

The hardware side is moving. Ledger's device SDK has merged a change to activate NU7 on mainnet at its published height.

A Short Runway for Node Operators

Zcash usually recommends about three months between the first software release that supports an upgrade and its activation. ZIP 259 waives that for NU7.

With less time, nodes that don't upgrade could keep following a pre-NU7 branch of the chain. The spec says operators must be warned.

We couldn't confirm which node software releases already include the mainnet height. The Zakura dashboard lists a testnet build, and on testnet NU7 is already active at block 4,465,026.

The next concrete signal is the merge of #1405 and the NU7 ZIPs moving to Proposed. After that, the clock runs toward block 3,543,405.