NU7 and Future Work

Why This Chapter Exists

If you contribute today, your code may have to survive NU7. Knowing what is coming tells you which parts of the codebase are about to move under your feet.

This file dates fast. Treat it as a snapshot of the in-flight protocol work as of the file's writing date and verify each item on the zcash/zips repo, the Zcash Foundation forum, and Discord before relying on it.

What Is "nu7"

NU7 is the next-major Zcash network upgrade after NU6 (active on mainnet since November 2024). NU6.1 is a smaller cleanup upgrade that lands first or alongside.

Indicators of NU7 in this repo:

• NetworkUpgrade::Nu7 variant in zebra-chain/src/parameters/network_upgrade.rs.
• the cfg(zcash_unstable, values("nu7")) lint-allowed config flag in Cargo.toml. Code gated on nu7 is implementing-not-active.
• consensus branch IDs and activation heights pinned in zebra-chain/src/parameters/network/constants.rs. Activation heights for NU7 may be placeholders until governance ratifies.

Candidate Features

Items widely discussed for inclusion in NU7 or a follow-up upgrade. Each is a separate ZIP and may or may not actually land in NU7.

Zsas (Zcash Shielded Assets)

A scheme for issuing and transferring user-defined assets in the Orchard shielded pool. The shielded asset framework extends the Action circuit to carry an asset identifier in addition to a value. Multiple ZIPs in the ZSA family cover issuance, burn, and Action extensions.

What to read:

• ZIP-227, ZIP-228, ZIP-229 (the ZSA family; check current numbering).
• the QEDIT prototype work (the original implementation).
• the orchard-zsa branch of the orchard crate.

Crosslink

A hybrid PoW-PoS construction proposed for adding finality to Zcash without abandoning Equihash mining. The PoS layer ratifies PoW blocks, providing fast finality on top of slow probabilistic finality. Several ZIP drafts and a white-paper exist.

What to read:

• the Crosslink paper (Hopwood, et al.).
• forum discussions on PoS migration.

Transaction Version Bump (v6)

NU7 may introduce a v6 transaction format to carry ZSA support, trailing metadata, or other features. Version bumps are backward-incompatible at the consensus layer; expect implementation effort in zebra-chain/src/transaction/ and the sighash code path.

Lightclient and Mempool ZIPs

A handful of smaller ZIPs improving lightclient sync (block-data shape, treestate availability) and mempool admission rules (anti-DoS tweaks, fee tightening) are likely to land alongside NU7.

Post-quantum Exploration

Not in NU7, but expect to see early discussion of post-quantum migration paths.

Status Surfaces to Monitor

• zcash/zips PR feed: most authoritative for what is being written.
• Zcash Community Forum: for discussion and rationale.
• ZF and ECC engineering blogs: for implementation status updates.
• Zebra issue tracker, label S-needs-design: open architectural decisions in Zebra.
• ECC GitHub orgs (zcash, electriccoinco): implementation branches.
• the orchard, sapling-crypto, halo2 repos: for primitive-level changes.

How nu7 Will Land in Zebra

Based on prior upgrades, the rough sequence:

1. ZIPs reach "implementing" status.
2. ECC and ZF implementers agree on activation heights for testnet and mainnet.
3. testnet activation: first activated on testnet at an earlier height to flush out bugs.
4. interim Zebra releases gated on cfg(zcash_unstable).
5. mainnet activation height is committed in a final release.
6. operators upgrade ahead of activation; everyone watches the activation block for divergence.

Your likely role: cryptographic review of the implementing ZIP, contribution to the primitives crates (Orchard, sapling-crypto), and integration into Zebra.

Things to Do Before NU7

• finish reading files 09 through 14 of this onboarding.
• read every recently-activated ZIP (NU5 and NU6 sets) cover to cover so you understand the lifecycle in practice.
• subscribe to the zcash/zips PR feed.
• ping ZF maintainers on Discord and introduce yourself; they will steer you to current priorities.
• attend the Arborist call (or whatever its current name is, the cross-implementation weekly) if invited; this is where compat conversations happen.

See Also

• 12-protocol-history-and-governance.md.
• 14-zips-and-ceremonies.md.
• book/src/dev/ecc-updates.md for the Zebra-side update process.
• zebra-chain/src/parameters/network_upgrade.rs for the variants currently declared.

Spec Pointers

• ZIPs labelled draft or proposed for upcoming upgrades.
• The nu7 branch or feature flag in the source, when present.

Exercises

1. Identify one open ZIP intended for NU7 and find any in-progress code that references it.
2. Read the upstream NU7 tracking issue and list the three biggest open items.
3. Find one piece of dead code that an NU7 deprecation could remove. Propose a follow-up issue.