# ZIP 259: Deployment of the NU7 Network Upgrade

Status: Draft

Owners: Dev Ojha

Snapshot: a34cfc091434275120ff017c92c3b50d3cef623a

Source date: 2026-10-16T02:56:04+01:00

[Source revision](https://github.com/zcash/zips/commit/a34cfc091434275120ff017c92c3b50d3cef623a)

[Official source](https://zips.z.cash/zip-0259) · [Source file](https://github.com/zcash/zips/blob/a34cfc091434275120ff017c92c3b50d3cef623a/zips/zip-0259.md) · [Discussion](https://forum.zcashcommunity.com/t/nu7-coinholder-vote/56912)

Preamble

**ZIP**: 259

**Title**: Deployment of the NU7 Network Upgrade

**Owners**: [Dev Ojha](mailto:dev@valargroup.dev)

**Status**: Draft

**Category**: Consensus / Network

**Created**: 2026-09-15

**License**: MIT

**Discussions-To**: [https://forum.zcashcommunity.com/t/nu7-coinholder-vote/56912](https://forum.zcashcommunity.com/t/nu7-coinholder-vote/56912)

<a id="terminology"></a>

## Terminology

The key word "MUST" in this document is to be interpreted as
described in BCP 14 <a id="user-content-fnref-bcp14"></a>
[1](#user-content-fn-bcp14) when, and only when, it appears in all capitals.

The term "network upgrade" is to be interpreted as described in ZIP 200.
<a id="user-content-fnref-zip-0200"></a>
[2](#user-content-fn-zip-0200)

The character § is used when referring to sections of the Zcash Protocol
Specification. <a id="user-content-fnref-protocol"></a>
[3](#user-content-fn-protocol)

The terms "Mainnet" and "Testnet" are to be interpreted as described in
§ 3.12 'Mainnet and Testnet'. <a id="user-content-fnref-protocol-networks"></a>
[4](#user-content-fn-protocol-networks)

"Scheduled Block Subsidy" means the block subsidy determined by the existing
halving schedule, after applying the changes in ZIP 218. <a id="user-content-fnref-zip-0218"></a>
[5](#user-content-fn-zip-0218)

"NSM Value Balance" is to be interpreted as defined in ZIP 237. <a id="user-content-fnref-zip-0237"></a>
[6](#user-content-fn-zip-0237)

<a id="abstract"></a>

## Abstract

This proposal defines the deployment of the NU7 network upgrade. NU7 reduces
the block target spacing from 75 seconds to 25 seconds, introduces per-pool and
global shielded action limits, introduces the Network Sustainability Mechanism
(NSM), and removes 60% of transaction fees from circulation. It also deploys
ZIP 2008.

NU7 introduces no new transaction format. Once NU7 activates, version 4
transactions are invalid, while version 5 and version 6 transactions remain
valid. Because Sprout transfers can only be represented by version 4
transactions, funds remaining in the Sprout pool become unspendable.
<a id="user-content-fnref-zip-2003"></a>
[7](#user-content-fn-zip-2003)

The changes do not increase the ZEC supply cap. Funds issued from the NSM Value
Balance were previously removed from circulation in equal amount, or unclaimed
by miners prior to ZIP 236 <a id="user-content-fnref-zip-0236"></a>
[8](#user-content-fn-zip-0236). The NSM Value Balance is public
consensus state and introduces no new transaction-level data.

<a id="motivation"></a>

## Motivation

NU7 is deliberately limited to changes that have strong support from
coinholders, developers, and major ecosystem organizations. These changes can
be deployed without another transaction-format migration. Faster blocks reduce
confirmation latency, while the action limits in ZIP 218 bound the validation
and shielded synchronization costs enabled by the increased block frequency.

<a id="specification"></a>

## Specification

<a id="nu7-consensus-changes"></a>

### NU7 consensus changes

The primary sources of information about NU7 consensus protocol changes are:

- The Zcash Protocol Specification. <a id="user-content-fnref-protocol-2"></a>
  [3](#user-content-fn-protocol)

- ZIP 200: Network Upgrade Mechanism. <a id="user-content-fnref-zip-0200-2"></a>
  [2](#user-content-fn-zip-0200)

- ZIP 207: Funding Streams (Revision 2). <a id="user-content-fnref-zip-0207"></a>
  [9](#user-content-fn-zip-0207)

- ZIP 214: Consensus rules for a Zcash Development Fund (Revision 3).
  <a id="user-content-fnref-zip-0214"></a>
  [10](#user-content-fn-zip-0214)

- ZIP 218: 25-second Block Target Spacing. <a id="user-content-fnref-zip-0218-2"></a>
  [5](#user-content-fn-zip-0218)

- ZIP 235: Remove 60% of Transaction Fees From Circulation. <a id="user-content-fnref-zip-0235"></a>
  [11](#user-content-fn-zip-0235)

- ZIP 237: Network Sustainability Mechanism: Halving-Preserving Issuance.
  <a id="user-content-fnref-zip-0237-2"></a>
  [6](#user-content-fn-zip-0237)

- ZIP 2003: Disallow version 4 transactions. <a id="user-content-fnref-zip-2003-2"></a>
  [7](#user-content-fn-zip-2003)

- ZIP 2008: Update to `FS_FPF_ZCG_H3` address list. <a id="user-content-fnref-zip-2008"></a>
  [12](#user-content-fn-zip-2008)

The network handshake and peer management mechanisms defined in ZIP 201 also
apply to this upgrade. <a id="user-content-fnref-zip-0201"></a>
[13](#user-content-fn-zip-0201)

NU7 deploys all of the consensus changes specified in the ZIPs listed above,
including Revision 2 of ZIP 207 and Revision 3 of ZIP 214. NU7 does not deploy
ZIP 233 or ZIP 234. <a id="user-content-fnref-zip-0233"></a>
[14](#user-content-fn-zip-0233) <a id="user-content-fnref-zip-0234"></a>
[15](#user-content-fn-zip-0234)

On Testnet, ZIP 218 changes the minimum-difficulty threshold of ZIP 208
at the Testnet NU7 activation height from six to 18 block target spacings.
With the 25-second target spacing, a block time must be more than 450
seconds after the preceding block's time to qualify for minimum difficulty.
This change does not affect Mainnet. <a id="user-content-fnref-zip-0208"></a>
[16](#user-content-fn-zip-0208)

For NU7 only, the requirement in ZIP 200 <a id="user-content-fnref-zip-0200-3"></a>
[2](#user-content-fn-zip-0200) that
ACTIVATION_HEIGHT MUST exceed DEPRECATION_HEIGHT in the last software version
without support for the upgrade is waived. The recommendation to allow
approximately three months after the first supporting software release is also
waived. This exception does not change the scheduling requirements for other
network upgrades. Operators of unsupported software may therefore remain online
at activation and follow a pre-NU7 consensus branch; deployment communications
need to explicitly warn operators to upgrade before activation.

<a id="nu7-network-constants"></a>

### NU7 network constants

The following network upgrade constants are defined for NU7: <a id="user-content-fnref-zip-0200-4"></a>
[2](#user-content-fn-zip-0200)

CONSENSUS_BRANCH_ID
: `0x77190AD9`

ACTIVATION_HEIGHT (NU7)
: Testnet: 4465026
: Mainnet: TBD (To be set on OCT 20)

Each ACTIVATION_HEIGHT (NU7) MUST be a multiple of 3, as required by
Revision 3 of ZIP 214. <a id="user-content-fnref-zip-0214-2"></a>
[10](#user-content-fn-zip-0214) The Mainnet activation height MUST also
satisfy the address-list constraint in ZIP 2008 <a id="user-content-fnref-zip-2008-2"></a>
[12](#user-content-fn-zip-2008), so that the new
funding recipient is selected before the stream ends.

NSM_REISSUANCE_HEIGHT
: Testnet: 7305222
: Mainnet: $\mathsf{DEPLOYMENT\_BLOCK\_HEIGHT}$ for Mainnet, as calculated in ZIP 237 <a id="user-content-fnref-zip-0237-3"></a>
[6](#user-content-fn-zip-0237)

Each NSM_REISSUANCE_HEIGHT is $\mathsf{DEPLOYMENT\_BLOCK\_HEIGHT}$ for the
corresponding network, as calculated in ZIP 237 <a id="user-content-fnref-zip-0237-4"></a>
[6](#user-content-fn-zip-0237). The Testnet
ACTIVATION_HEIGHT (NU7) $A = 4{,}465{,}026$ lies between the second and third
pre-NU7 Testnet halvings (2,796,000 and 4,476,000). The ZIP 218 third halving
is therefore at $H_3 = 13{,}428{,}000 - 2A = 4{,}497{,}948$, and the Testnet
reissuance height is $H_3 + 2{,}807{,}274 = 16{,}235{,}274 - 2A = 7{,}305{,}222$.

MIN_NETWORK_PROTOCOL_VERSION (NU7)
: Testnet: 170180
: Mainnet: 170190

For each network, nodes compatible with NU7 activation on that network MUST
advertise a network protocol version greater than or equal to the corresponding
MIN_NETWORK_PROTOCOL_VERSION.

<a id="backward-compatibility"></a>

### Backward compatibility

Before NU7 activates on a network, NU7 and pre-NU7 nodes can connect to each
other. NU7 nodes will prefer other NU7 nodes, so pre-NU7 nodes will gradually
be disconnected approaching activation.

Once NU7 activates, NU7 nodes will disconnect peers that advertise a lower
network protocol version. Blocks produced under the pre-NU7 consensus rules
may also be rejected because of the new target spacing, subsidy calculation,
action limits, fee allocation, or transaction-version rule.

The version 4 prohibition applies to all version 4 transactions, including
transparent-only and Sapling transactions, not only Sprout transfers. Wallets
and transaction services need to stop constructing version 4 transactions for
post-activation inclusion and clearly report pending transactions that become
invalid. Where possible, users can recreate non-Sprout transactions in a
supported format; re-signing alone cannot make a version 4 transaction valid.
Saved and offline-signed transactions need the same activation checks. Sprout
transactions have no supported post-activation replacement format.

Version 5 and version 6 transactions remain structurally unchanged. This does
not imply that a transaction is valid across NU7 activation, because its
signatures commit to a consensus branch ID.

<a id="rationale"></a>

## Rationale

<a id="coinholder-and-community-polling"></a>

### Coinholder and Community polling

The August and September 2026 NU7 polls asked five scope questions: whether to
preserve halvings or smooth issuance; when NSM reissuance should begin; when
version 4 transactions should be disabled; whether to deploy ZIP 218; and
whether to ship promptly with only features ready by the September 30
deadline. The poll announcement records the complete questions and response
options. <a id="user-content-fnref-nu7-poll-questions"></a>
[17](#user-content-fn-nu7-poll-questions)

The coinholder and community poll results are available at
<a id="user-content-fnref-nu7-poll-results"></a>
[18](#user-content-fn-nu7-poll-results).

The polls did not reach a shared majority position on when NSM reissuance
should begin. NU7 uses the post-third-halving crossover of reference NSM
issuance and the scheduled block subsidy, calculated from the assigned NU7
activation height as specified in ZIP 237 <a id="user-content-fnref-zip-0237-5"></a>
[6](#user-content-fn-zip-0237).

<a id="rationale-for-no-new-transaction-format"></a>

### Rationale for no new transaction format

Avoiding a new format limits parser and wallet disruption in the upgrade
immediately following the introduction of version 6 in NU6.3. <a id="user-content-fnref-zip-0229"></a>
[19](#user-content-fn-zip-0229)
The fee contribution is a block-level consensus calculation and therefore does
not require a new field in ordinary or coinbase transactions.

<a id="open-issues"></a>

## Open issues

- Assign the Mainnet NU7 activation height.

- Publish the Mainnet NSM reissuance height calculated from the assigned
  Mainnet NU7 activation height.

- Add reference implementations and test vectors for the NSM Value Balance.

<a id="references"></a>

## References

<a id="footnote-label"></a>

### Footnotes

1. [Information on BCP 14 — "RFC 2119: Key words for use in RFCs to Indicate Requirement Levels" and "RFC 8174: Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"](https://www.rfc-editor.org/info/bcp14) [↩](#user-content-fnref-bcp14)

2. [ZIP 200: Network Upgrade Mechanism](/zip/200) [↩](#user-content-fnref-zip-0200) [↩2](#user-content-fnref-zip-0200-2) [↩3](#user-content-fnref-zip-0200-3) [↩4](#user-content-fnref-zip-0200-4)

3. [Zcash Protocol Specification, Version 2026.8.0 [NU6.3] or later](protocol/protocol.pdf) [↩](#user-content-fnref-protocol) [↩2](#user-content-fnref-protocol-2)

4. [Zcash Protocol Specification, Version 2026.8.0 [NU6.3]. Section 3.12: Mainnet and Testnet](protocol/protocol.pdf#networks) [↩](#user-content-fnref-protocol-networks)

5. [ZIP 218: 25-second Block Target Spacing](/zip/218) [↩](#user-content-fnref-zip-0218) [↩2](#user-content-fnref-zip-0218-2)

6. [ZIP 237: Network Sustainability Mechanism: Halving-Preserving Issuance](/zip/237) [↩](#user-content-fnref-zip-0237) [↩2](#user-content-fnref-zip-0237-2) [↩3](#user-content-fnref-zip-0237-3) [↩4](#user-content-fnref-zip-0237-4) [↩5](#user-content-fnref-zip-0237-5)

7. [ZIP 2003: Disallow version 4 transactions](/zip/2003) [↩](#user-content-fnref-zip-2003) [↩2](#user-content-fnref-zip-2003-2)

8. [ZIP 236: Blocks should balance exactly](/zip/236) [↩](#user-content-fnref-zip-0236)

9. [ZIP 207: Funding Streams](/zip/207) [↩](#user-content-fnref-zip-0207)

10. [ZIP 214: Consensus rules for a Zcash Development Fund](/zip/214) [↩](#user-content-fnref-zip-0214) [↩2](#user-content-fnref-zip-0214-2)

11. [ZIP 235: Remove 60% of Transaction Fees From Circulation](/zip/235) [↩](#user-content-fnref-zip-0235)

12. [ZIP 2008: Update to `FS_FPF_ZCG_H3` address list](/zip/2008) [↩](#user-content-fnref-zip-2008) [↩2](#user-content-fnref-zip-2008-2)

13. [ZIP 201: Network Peer Management for Overwinter](/zip/201) [↩](#user-content-fnref-zip-0201)

14. [ZIP 233: Network Sustainability Mechanism: Removing Funds From Circulation](/zip/233) [↩](#user-content-fnref-zip-0233)

15. [ZIP 234: Network Sustainability Mechanism: Issuance Smoothing](/zip/234) [↩](#user-content-fnref-zip-0234)

16. [ZIP 208: Shorter Block Target Spacing](/zip/208) [↩](#user-content-fnref-zip-0208)

17. [NU7 Coinholder Vote: poll questions and scope](https://forum.zcashcommunity.com/t/nu7-coinholder-vote/56912) [↩](#user-content-fnref-nu7-poll-questions)

18. [NU7 Sentiment Polls Results](https://forum.zcashcommunity.com/t/nu7-sentiment-polls-results/57590) [↩](#user-content-fnref-nu7-poll-results)

19. [ZIP 229: Version 6 Transaction Format](/zip/229) [↩](#user-content-fnref-zip-0229)

## Citation relationships

Cites: [ZIP 200](https://zips.tools/zip/200), [ZIP 201](https://zips.tools/zip/201), [ZIP 207](https://zips.tools/zip/207), [ZIP 208](https://zips.tools/zip/208), [ZIP 214](https://zips.tools/zip/214), [ZIP 218](https://zips.tools/zip/218), [ZIP 229](https://zips.tools/zip/229), [ZIP 233](https://zips.tools/zip/233), [ZIP 234](https://zips.tools/zip/234), [ZIP 235](https://zips.tools/zip/235), [ZIP 236](https://zips.tools/zip/236), [ZIP 237](https://zips.tools/zip/237), [ZIP 2003](https://zips.tools/zip/2003), [ZIP 2008](https://zips.tools/zip/2008)

Cited by: [ZIP 207](https://zips.tools/zip/207), [ZIP 214](https://zips.tools/zip/214), [ZIP 218](https://zips.tools/zip/218), [ZIP 231](https://zips.tools/zip/231), [ZIP 233](https://zips.tools/zip/233), [ZIP 234](https://zips.tools/zip/234), [ZIP 235](https://zips.tools/zip/235), [ZIP 237](https://zips.tools/zip/237), [ZIP 254](https://zips.tools/zip/254), [ZIP 2003](https://zips.tools/zip/2003), [ZIP 2008](https://zips.tools/zip/2008)