---
title: "Zcash Protocol Draft Outlines NU7 Upgrade With 25-Second Blocks and Sprout Deprecation"
description: "ZIP 259 schedules the NU7 network upgrade, slashing block target spacing to 25 seconds, introducing the Network Sustainability Mechanism, and invalidating legacy version 4 transactions."
url: https://basisdesk.news/news/zcash-nu7-upgrade-block-times-sprout-deprecation
published: 2026-10-21T08:11:18.009Z
modified: 2026-10-21T08:11:18.009Z
section: Altcoins
author: Basis Desk Newsroom (AI-generated, source-verified)
sentiment: bullish
tickers: [ZEC, BTC]
tags: [zcash, nu7, hard-fork, privacy-coins, consensus]
license: Quote with attribution to Basis Desk (basisdesk.news). Not financial advice.
---

# Zcash Protocol Draft Outlines NU7 Upgrade With 25-Second Blocks and Sprout Deprecation

ZIP 259 schedules the NU7 network upgrade, slashing block target spacing to 25 seconds, introducing the Network Sustainability Mechanism, and invalidating legacy version 4 transactions.

## At a glance

- **What happened:** A Zcash Improvement Proposal drafted by Dev Ojha set the technical parameters for the NU7 network upgrade, reducing block times to 25 seconds and deprecating version 4 transactions.
- **Why it matters:** The upgrade accelerates block confirmations and removes 60% of transaction fees from circulation, while permanently rendering unmigrated Sprout pool balances unspendable.
- **Who is affected:** Zcash node operators, miners, wallet developers, and holders with remaining funds in the legacy Sprout pool.
- **What's next:** Assignment and confirmation of the Mainnet activation height and NSM reissuance height.
- **Status:** proposed
- **Primary source:** [Deployment of the NU7 Network Upgrade](https://zips.z.cash/zip-0259) — zips.z.cash

## Key points

- ZIP 259 defines Zcash's NU7 upgrade, cutting block target spacing from 75 seconds to 25 seconds and removing 60% of transaction fees from circulation.
- Version 4 transactions will be invalidated upon activation, permanently rendering any remaining funds in the legacy Sprout shielded pool unspendable.
- Testnet activation is set at block height 4,465,026, while the Mainnet activation height and subsequent NSM reissuance block height remain pending.

## Editorial remark

- **Context:** Community sentiment polling conducted in August and September 2026 shaped the NU7 scope, rejecting transaction-format shifts in favor of faster block times and the Network Sustainability Mechanism.
- **Impact:** Exchanges, node operators, and custodial wallets must update client software to avoid following an unsupported branch, while users holding funds in the deprecated Sprout pool face complete loss of spendability.
- **Watch:** The assignment and publication of the Mainnet NU7 activation block height and its derived NSM reissuance height.

A draft specification for the Zcash NU7 network upgrade details substantial consensus changes, including reducing block target spacing from 75 seconds to 25 seconds, implementing the Network Sustainability Mechanism (NSM), and deprecating legacy transaction formats, according to the official proposal document [1].

Proposed under ZIP 259 by Dev Ojha, the NU7 upgrade accelerates network confirmation times via ZIP 218 while bounding validation costs with per-pool and global shielded action limits [1]. NU7 will also remove 60% of transaction fees from circulation under ZIP 235 [1]. Notably, the consensus overhaul will invalidate version 4 transactions, leaving only version 5 and version 6 formats valid post-activation [1]. Because legacy Sprout pool transfers can only be processed using version 4 structures, any funds remaining in the Sprout pool will permanently become unspendable after the upgrade executes [1].

## Halving Schedule and Upgrade Mechanics

The upgrade preserves the aggregate supply cap for $ZEC, funding reissuance strictly from the NSM Value Balance previously taken out of circulation or unclaimed by miners [1]. According to the proposal, Testnet activation is set at block height 4,465,026, while Mainnet activation height remains pending [1]. For this activation, the protocol waives the standard three-month lead time and deprecation height buffers, requiring node operators to upgrade manually before activation to avoid remaining on a split chain [1]. The upgrade proposal follows preparations by major infrastructure providers, including the [Gemini migration of Zcash infrastructure to Zakura nodes](https://basisdesk.news/news/gemini-zcash-infrastructure-migration-zakura-nu7).

At the time of writing, ZEC traded up 12.4% over 24 hours at $1,269, outpacing broader market gains as Bitcoin hovered around $83,038.

## Sources

1. [Deployment of the NU7 Network Upgrade](https://zips.z.cash/zip-0259) — zips.z.cash, 2026-10-21

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Basis Desk Newsroom · AI-generated, source-verified · https://basisdesk.news/about/how-we-use-ai