Zcash's Ironwood Upgrade (NU6.3): Live on Mainnet, Still a Draft ZIP

Zcash's Ironwood upgrade — a new shielded pool built in response to a vulnerability discovered in Orchard's proof circuit — activated on Zcash mainnet at block height 3,428,143, around July 28, 2026. That part is well established, reported by multiple independent outlets and confirmed by the Zcash Foundation's own node software. What's less widely reported: ZIP 258, the formal specification behind it, is still marked Draft in Zcash's own improvement-proposal repository — checked as recently as three days before this article was written. Both facts are true at the same time, and they answer two different questions, not one.

Why there's confusion

Coverage of this upgrade tends to use "Ironwood," "NU6.3," and "ZIP 258" interchangeably. For everyday reference that's reasonable shorthand — but they're three related, distinct things, and keeping them apart is what makes it possible to see that "live" and "Draft" aren't actually a contradiction.

What some reports say

Multiple outlets reported the upgrade activating on July 28, 2026: the Orchard pool, holding roughly 3.66 million ZEC at the time, was sealed to new deposits, and a new pool opened in its place. A follow-up report the next day went further, describing real on-chain movement — roughly 176,000 ZEC, about $81 million, having already moved into the new pool within the first 24 hours. That's an observation about what's happening on the network, not a repeated announcement. Separately, at least one major exchange publicly described the upgrade as already live in an operational sense. None of this coverage discusses the ZIP's formal review status one way or the other — it simply isn't what that reporting was about.

What Ironwood actually refers to

Ironwood is the name of the new shielded pool itself — the replacement for Orchard, built with formally verified circuits and a migration path (a "turnstile") that caps withdrawals from the old pool at the amount genuinely deposited there, closing the path the Orchard vulnerability had opened.

What NU6.3 refers to

NU6.3 is the network upgrade — the coordinated, height-triggered change to Zcash's consensus rules that makes Ironwood possible. It's the umbrella term for the whole coordinated change; Ironwood is what it delivers.

What ZIP 258 says

ZIP 258, "Deployment of the NU6.3 Network Upgrade," is the document that pins down the mechanics. Its own Activation Parameters section specifies:

• Mainnet activation height: 3,428,143
• Testnet activation height: 4,134,000

Its abstract states that NU6.3's consensus changes span the version-6 transaction format, an Orchard Action circuit update, ZIP 2005, and ZIP 258 itself. As of this check, ZIP 258's Status field reads Draft. Two companion documents carry the same status: ZIP 318 (the Orchard-to-Ironwood migration mechanics) and ZIP 326 (what NU6.3 means for wallets). A related document, ZIP 2005 ("Ironwood Quantum Recoverability"), has progressed one stage further, to Proposed — the stage the Zcash ZIP process defines as reached "after consideration, feedback, and rough consensus from the community." We note that difference as an observable fact; we don't have a source explaining why the other three haven't reached the same stage.

What the official repositories show

The zcash/zips repository's own index is not stale or abandoned documentation — it was substantively edited three days before this article, on work related to the upcoming NU7 upgrade. As of that same current version, its index still lists ZIP 258, 318, and 326 as Draft, and the repository's own summary text still names NU6.2, not NU6.3, as "the most recent settled Network Upgrade on Mainnet." That specific sentence has not been updated to reflect NU6.3, even though the document around it is being actively maintained.

Implementation vs. activation

This is the distinction that actually resolves the apparent conflict. Zebra, the Zcash Foundation's node implementation, shipped the NU6.3 activation rule in its 6.0.0 release on July 10, 2026 — stating plainly that "NU6.3 (Ironwood) now activates on Mainnet at block height 3,428,143." That's an unconditional consensus rule, not an experimental flag. Once the chain reached that height, the new rules took effect automatically — the same mechanism every prior Zcash network upgrade has used to activate: node software enforcing a rule at a pre-agreed height, not a separate "go live" announcement. A later Zebra release, 6.2.3 on July 27, 2026, describes following mainnet "past the NU6.3 (Ironwood) activation at block 3,428,143." Software carrying an activation rule to its target height is how Zcash upgrades activate. A ZIP's formal status, by contrast, tracks its own review process — a separate, independently-moving thing.

Timeline

• June 3, 2026 — NU6.2 activates at block height 3,364,600 — the upgrade the zips index currently names as the most recent one it calls settled.
• July 9–10, 2026 — Zebra ships the NU6.3 activation rule (height 3,428,143) and related protocol/spec updates.
• July 27, 2026 — Zebra 6.2.3 confirms tracking the chain past the NU6.3 activation height.
• ~July 28, 2026 — The chain reaches height 3,428,143; the Ironwood pool opens; media report activation.
• July 29, 2026 — A follow-up report describes roughly 176,000 ZEC already moved into the new pool.
• July 29–31, 2026 — ZIP 318 receives further technical review edits.
• September 22, 2026 — The zips README is edited again, for unrelated NU7 work; NU6.3, ZIP 258, 318, and 326 remain listed as Draft.

What we can state confidently today

Ironwood is running on Zcash mainnet, enforced by an unconditional consensus rule in the reference node implementation, and independent reporting describes real ZEC having moved into the new pool. This is corroborated across sources with different incentives to get it right — the node software's own release engineering, independent reporting on two separate days, and at least one exchange with operational infrastructure that depends on tracking the correct chain rules.

What remains uncertain

We could not directly verify the current build of the formal Zcash Protocol Specification document for this piece — it's hosted on a domain we couldn't reach while researching this article. We also did not find a direct blog post or statement from the Electric Coin Company or the Zcash Foundation addressing activation in their own editorial voice, only their code repositories and third-party reporting. And we don't have a source that explains why ZIP 258, 318, and 326 remain listed as Draft — we're describing that status, not accounting for it.

Why the distinction matters

For a wallet, an exchange, or anyone building on Zcash, "is it live" is answered by what the node software enforces at a given block height — and that's settled here. For anyone tracking Zcash's ZIP process specifically — what's been formally reviewed and advanced by the ZIP editors, versus what's already running in production — the Draft status is the separate, real signal, and it's easy to miss if the only thing you read is a headline saying an upgrade is "live."

Sources & methodology

This article is based on direct review of: the zcash/zips GitHub repository (its README index and the ZIP 258 and 318 source files, including commit history), the ZcashFoundation/zebra changelog, and cross-referenced reporting from multiple independent outlets. Where a source could not be reached directly during research, that's stated above rather than asserted as checked. Because a ZIP's status field can change, we'll revisit this page if ZIP 258 is updated — see the Zcash Network Upgrade Tracker for the current, continuously-maintained status, and Zcash Network Upgrades: A Complete Timeline for how this fits among every other Zcash upgrade. For background on the vulnerability that led to Ironwood, and on Zcash's shielded pools generally, see the Zcash Shielded Supply Tracker. Network upgrades as a mechanism, and Orchard specifically, are covered in the glossary.